HOUSING METHOD OF MANUFACTURING THE CLUTCH HOUSING AND

SYSTEM FOR THE FRICTION CLUTCH HAVING MULTI FRICTION

PLATES

Technical Field

The present invention relates to a multi-frictional plate type friction clutch, and more particularly, to a multi-frictional plate type friction clutch for preventing deformation due to expansion of a clutch housing of the clutch.

Background Art

In general, a multi-frictional plate type friction clutch (hereinafter, referred to as "multi-friction clutch") refers to a shaft coupling member for determining whether to transmit power via a spacing between multi-frictional plates. A small-sized multi- friction clutch is characterized in that, after a rotary hub and a clutch housing have been disposed internally and externally, respectively, two different kinds of frictional plates are engageably mounted between the rotary hub and the clutch housing to be alternately arranged with each other. The movement of the clutch housing and the rotary hub determines the contact or separation between the frictional plates. The rotary force can be transmitted from the clutch housing to the rotary hub or vice versa by means of the frictional force between the frictional plates. Generally, the small-sized multi-friction clutch is formed in a small size and can be used to control a large power. The small- sized multi-friction clutch is mainly used in a wet environment rather than a dry environment. FIG. 1 is a cross-sectional view illustrating a conventional multi-friction clutch according to a conventional art.

Referring to FIG. 1, conventional multi-friction clutch includes a clutch housing 10, a rotary hub 20, a plurality of first frictional plates 30 and a plurality of second frictional plates 40. The clutch housing 10 is formed in a generally hollow cylindrical shape, and is connected at an end to a first rotary shaft 1 so as to receive a rotational force from the first rotary shaft 1. The clutch housing 10 has three to four guide grooves 12 formed on a circumferential side wall thereof so as to transmit the rotational force and guide the first frictional plates 30 therethrough. In addition, the clutch

housing 10 is internally provided with the rotary hub 20. The rotary hub 20 has a plurality of splines 22 formed on an outer circumferential surface thereof so as to engage the second frictional plates 40 thereto.

The plurality of second frictional plates 40 are arranged to be slidably moved on the splines 22 of the rotary hub 20. In this case, different kinds of first and second frictional plates are alternately arranged so that one first frictional plate 30 is located between two adjacent second frictional plates 40. Each of the second frictional plates 40 centrally defines a spline hole for engaging with the spline 22 whereas each of the first frictional plates 30 internally defines a rotary hole having a diameter larger than that of the maximum outer diameter of the rotary hub 20. Accordingly, the first frictional plate 30 can rotate on the outer circumference of the rotary hub 20 in a state where the first frictional plate is not engaged with the rotary hub 20, and can rotate along with the rotary hub 20 only in a state where the first frictional plate is indirectly engaged with the rotary hub 20 via the second frictional plate 40. In this case, the first frictional plate 30 is formed on the outer circumferential surface thereof with a guide piece corresponding to the guide groove 12 of the clutch housing 10, and can always rotate along with the clutch housing 10 while maintaining the engagement with the clutch housing 10.

As shown in FIG. 1, a spring 50 can be interposed between the clutch housing 10 and the rotary hub 20. Since the spring 50 resiliently supports the rotary hub 20, it can allow the distance between the first frictional plate 30 and the second frictional plate 40 to be kept large, but can hinder the transmission of power between the first frictional plate 30 and the second frictional plate 40 at ordinary times. Since a wet-type clutch is generally submerged in oil, the rotational force of the clutch housing 10 can affect the rotary hub 20 via the mutually adjacent frictional plates. In order to prevent the rotary hub 20 from unexpectedly rotating, a brake (not shown) is mounted at the rotary hub or a shaft connected to the rotary hub, so that it is also possible to control the rotary hub 20 to no longer rotate in a state where the first frictional plate 30 and the second frictional plate 40 are spaced apart from each other. An external pedal, a shaft or other intermittent transmission device 3 can move the rotary hub 20 toward the clutch housing 10. At this time, the first frictional plate 30 and the second frictional plate 40 approach each other to engage with each other. The engaged frictional plates can transmit the rotational force of the clutch housing 10

to the rotary hub 20.

The conventional multi-friction clutch can be used in a power take-off (PTO), etc., of agricultural machines and can typically transmit a larger torque when compared to its dimension. However, since the conventional multi-friction clutch transmits a larger toque, deformation or damage of the clutch may frequently occur during its use. For example, in the case where the clutch rotates at high speed, the clutch housing 10 may be expanded at a side wall thereof due to a centrifugal force thereof. Further, in the process of transmitting power through the clutch, the guide piece of the first frictional plate 30 may push outwardly against the surrounding portion of the guide groove 12 to expand a circumferential side wall of the clutch housing 10. The expansion of the circumferential side wall of the clutch housing 10 makes it impossible to normally transmit power, which may result in a problem that a snap ring escapes from the inside wall of the clutch housing to thereby damage the clutch.

As such, since the conventional clutch housing 10 is applied with a large load, it is manufactured by means of a casting or founding process. However, in the case where the housing processed by the casting also rotates at a high speed or is applied with a large toque, it may be expanded or impaired. When the clutch housing 10 receives an impact from an outside force, it may be deformed or damaged. Of course, in order to address or solve these problems, there has been proposed an improvement in which a ring-shaped fixture 60 is securely fixed to the outer circumference of the clutch housing by means of welding. But also in this case, as a process of engaging/disengaging the clutch is repeatedly performed, the fixture 60 may become detached from the clutch housing 10. In addition, the fixture 60 and peripheral components are thermally deformed to thereby cause a failure of balance in the clutch.

Disclosure of Invention Technical Goals

Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the conventional art, and it is an objective of the present invention to provide a multi-friction clutch which can stably maintain a clutch housing in an original state without any deformation.

Another objective of the present invention is to provide a multi-friction clutch which can structurally maintain durability of the clutch so that a clutch housing can be

manufactured not in a complicated and expensive casting process, but in a simple and inexpensive pressing process, thereby securing improved stability.

Still another objective of the present invention is to provide a multi-friction clutch which can be simply and easily assembled, without any deformation of components when assembling, and allows for easy replacement and repair thereof even during its use.

Yet another objective of the present invention is to provide a clutch housing which can easily maintain horizontality of frictional plates even in the case where the clutch housing is manufactured by a process method using pressing or other plastic deformation, and a multi-friction clutch including the clutch housing.

A further objective of the present invention is to provide a multi-friction clutch which can be easily assembled and can reduce a number of components.

A still further objective of the present invention is to provide a brake system for a multi-friction clutch which can include a brake device which adjusts a spacing between a clutch housing and a transmission case and controls the rotation of the clutch housing so that a drag torque is prevented when releasing the clutch to restrict rotation of the clutch housing, and which can be stably maintained for a long period of time even in a state where the clutch housing is stopped.

Technical solutions

To accomplish the above objectives, a multi-friction clutch according to one aspect of the present invention includes a clutch housing connected to a first rotary shaft and a rotary hub connected to a second rotary shaft, wherein the clutch housing and the rotary hub can transmit or interrupt the power depending on the contact or separation of frictional plates alternately arranged. Guide grooves are formed on a circumferential side wall of the clutch housing, in parallel with an axial direction for guiding frictional plates or facilitating inflow/outflow of oil therethrough. When the clutch rotates at a high speed, a centrifugal force can be exerted to a circumferential side wall of the clutch housing, at which time the circumferential side wall may be expanded by the presence of guide grooves formed thereon.

However, the multi-friction clutch according to the present invention includes a fixing ring mounted on the top circumferential edge of the clutch housing to surround the top circumferential edge of the clutch housing, retaining pieces of the fixing ring

protrude inwardly from the clutch housing through the guide grooves or retaining grooves of the clutch housing, a fixing member such as a snap ring presses the top surface of the retaining pieces so that the fixing ring can be prevented from becoming detached from the clutch housing. The clutch can be completed through a simple process in which an assembly of the rotary hub and the frictional plates are mounted inside the clutch housing, the fixing ring is placed on the assembly, and the snap ring is snap-fit into a ring groove formed on an inner circumferential wall surface of the clutch housing. A separate work such as welding does not need to be performed in order to protect the circumferential side wall of the clutch housing using the fixing ring. Despite the repeated engaging/releasing of the clutch, the fixing ring can be maintained in its original state without any deformation.

As mentioned above, the clutch housing, etc., of the conventional multi-friction clutch is manufactured by means of casting. The casting process is complicated and requires high cost, whereas a pressing process is simple and requires low cost. However, the clutch housing manufactured by the pressing is weak in rigidity and can be easily inflated at a side wall thereof. Also, the snap ring easily detaches from the clutch housing to thereby damage the clutch. In the meantime, the circumferential side wall of the clutch housing can be prevented from being expanded or deformed outwardly using the fixing ring, and the fixing ring can be adjusted to be movable only within a certain travel range from the clutch housing using the retaining pieces of the fixing ring and the snap ring.

The multi-friction clutch of the present invention includes a clutch housing connected to a first rotary shaft and a rotary hub connected to a second rotary shaft. The clutch housing and the rotary hub can transmit or interrupt the power depending on frictional plates which are alternately arranged therebetween. The relative movement between the clutch housing and the rotary hub can adjust a spacing between the frictional plates, and when the clutch housing and the rotary hub approach each other to cause the frictional plates to come into close contact with each other, the frictional plates form an integral unit to transmit the rotational force. In addition, the clutch housing can be provided with support pieces bent inwardly from the circumferential side walls thereof. The support pieces are intended to stably support bottom surfaces of the frictional plates. When the frictional plates comes into close contact with each other to rotate, the frictional plates supported by the

support pieces can be arranged to be oriented vertically with respect to a longitudinal axis of the clutch housing. Thus, the clutch including the frictional plates can rotate while maintaining its stable balance, and partial abrasion can be maximally prevented from occurring in the frictional plates or the rotary hub. As a result, transmission efficiency of the rotational force can be improved and a lifespan of the clutch can be extended to be over average when compared to a conventional clutch.

According to the present invention, the clutch housing can be manufactured by means of pressing, and a limitation in precision due to the pressing process can be overcome through the use of the support pieces formed on the circumferential side wall of the clutch housing. More specifically, in order to manufacture the clutch housing, first a hollow housing body is formed by pressing. Thereafter, the guide grooves and support pieces prior to being bent are simultaneously or separately formed in the housing body by pressing. A portion corresponding to the support pieces are bent inwardly from the circumferential side wall of the clutch housing so as to form a structure of supporting the frictional plates. Further, for a more precise adjustment, the top surfaces of the bent support pieces are machined by a cutting machine or grinding machine so that the support pieces can have a common horizontal plane. This method is different from a conventional one in which a separate annular support ring is fit between the rotary hub and the clutch housing. It is not required to manufacture such a separate annular support ring, and an assembling process for the support ring can be eliminated.

As mentioned above, the clutch housing, etc., of the conventional multi-friction clutch is manufactured by casting. The casting process is complicated and requires high cost, whereas a pressing process is simple and requires low cost. However, the clutch housing manufactured by the pressing is weak in rigidity so that it can be deformed, and may be deteriorated in dimensional precision due to the use of plastic deformation. But it is possible to form a structure of supporting the frictional plates using the support pieces in the pressing process, and a number of components can be reduced, thereby achieving temporal and economical benefit. According to one aspect of the present invention, there is provided a multi- friction clutch system adapted to control the rotation of a multi-friction clutch for functionally interconnecting a driving shaft and a driven shaft, the multi-friction clutch comprising: a clutch housing adapted to receive a power from the driving shaft and

rotate, the clutch housing having a plurality of guide grooves axially formed on a circumferential side wall thereof to be spaced apart equiangularly from one another; a plurality of plates each having a plurality of guide pieces formed outwardly from an outer circumferential surface thereof to be spaced apart equiangularly from one another to correspond to the plurality of guide grooves, respectively; a plurality of discs arranged alternately between the plurality of first frictional plates so that one first frictional plate is located between two adjacent second frictional plates; a rotary hub engaged with the discs to rotate along with the discs and adapted to transmit the power to the driven shaft; a brake unit for controlling a spacing between the clutch housing and a transmission case as well as the rotation of the clutch housing; and a spring mounted between a spring seat of the rotary hub and the clutch housing for causing the clutch housing to return to its original position when the clutch is disengaged.

According to another aspect of the present invention, the brake unit may include a brake disc mounted on a front surface of the transmission case to correspond to a rear surface of the clutch housing, and a brake lining mounted on a front surface of the brake disc.

According to another aspect of the present invention, the brake lining may come into direct contact with the rear surface of the clutch housing so as to put the brake unit on. According to another aspect of the present invention, the brake unit may further include a brake plate mounted on the rear surface of the clutch housing.

According to another aspect of the present invention, the transmission case may include a fixing groove for receiving the brake disc therein and a fixture.

According to another aspect of the present invention, an oil circulating hole may be formed at a boss spline and a bearing holder part of the driving shaft, respectively, so that oil is circulatingly supplied between the plates and the discs via a circulation pump.

Brief Description of Drawings

FIG. 1 is a cross-sectional view illustrating a conventional multi-friction clutch according to a conventional art;

FIG. 2 is a cross-sectional view illustrating a power apparatus using a multi- friction clutch according to one embodiment of the present invention;

FIG. 3 is a perspective view illustrating the multi-friction clutch of FIG. 2;

FIG. 4 is a front view illustrating the multi-friction clutch of FIG. 3;

FIG. 5 is a perspective view illustrating a clutch housing of FIG. 3;

FIG. 6 is an exploded perspective view illustrating a state where first frictional plates, second frictional plates and a rotary hub of FIG. 3 are disassembled; FIG. 7 is an exploded perspective view illustrating a process in which an assembly of the rotary hub and the frictional plates of FIG. 6 is mounted in a clutch housing;

FIG. 8 is an exploded perspective view illustrating a process in which an assembly of the rotary hub and the frictional plates of FIG. 7 is fixed in a clutch housing;

FIG. 9 is a perspective view illustrating a fixing ring of FIG. 8;

FIG. 10 is a cross-sectional view illustrating a state where the power is not transmitted in the multi-friction clutch of FIG. 2;

FIG. 11 is a cross-sectional view illustrating a state where the power is transmitted in the multi-friction clutch of FIG. 2;

FIG. 12 is a cross-sectional view illustrating a multi-friction clutch according to another embodiment of the present invention;

FIG. 13 is a cross-sectional view illustrating a power apparatus using the multi- friction clutch according to still another embodiment of the present invention; FIG. 14 is a perspective view illustrating the multi-friction clutch of FIG. 13 ;

FIG. 15 is a front view illustrating the multi-friction clutch of FIG. 14;

FIG. 16 is a perspective view illustrating a clutch housing of FIG. 14;

FIG. 17 is a top view illustrating the clutch housing of FIG. 14;

FIG. 18 is a perspective view illustrating a state before support pieces of the clutch housing of FIGs. 16 and 17 are bent;

FIG. 19 is an exploded perspective view illustrating a state where first frictional plates, second frictional plates and a rotary hub of FIG. 14 are disassembled;

FIG. 20 is an exploded perspective view illustrating a process in which an assembly of the rotary hub and the frictional plates of FIG. 19 is mounted in a clutch housing;

FIG. 21 is an exploded perspective view illustrating a process in which an assembly of the rotary hub and the frictional plates of FIG. 20 is fixed in a clutch housing;

FIG. 22 is a cross-sectional view illustrating a state where the power is not transmitted in the multi-friction clutch of FIG. 13;

FIG. 23 is a cross-sectional view illustrating a state where the power is transmitted in the multi-friction clutch of FIG. 13 FIG. 24 is a perspective view illustrating a clutch housing according to still another embodiment of the present invention;

FIG. 25 is a perspective view illustrating a state before support pieces of the clutch housing of FIG. 24 are bent;

FIG. 26 is a cross-sectional view illustrating a multi-friction clutch according to a yet another embodiment of the present invention;

FIG. 27 is a cross-sectional view illustrating a power apparatus using the multi- friction clutch including a brake system according to a further embodiment of the present invention;

FIG. 28 is a view illustrating a state where an actuation lever and a manipulation load-limiting spring are mounted in the multi-friction clutch of the present invention;

FIG. 29 is an enlarged view illustrating a portion "A" of FIG. 27;

FIG. 30 is a cross-sectional view illustrating a power apparatus using a multi- friction clutch including a brake system according to still another embodiment of the present invention; FIG. 31 is a cross-sectional view illustrating a power apparatus using a multi- friction clutch including a brake system according to still another embodiment of the present invention; and

FIG. 32 is an enlarged view illustrating a portion "B" of FIG. 31.

Best Mode for Carrying Out the Invention

FIG. 2 is a cross-sectional view illustrating a power apparatus using a multi- friction clutch according to one embodiment of the present invention, FIG. 3 is a perspective view illustrating the multi-friction clutch of FIG. 2, and FIG. 4 is a front view illustrating the multi-friction clutch of FIG. 3. Referring to FIG. 2, the multi-friction clutch 100 is mounted on a power take-off

(PTO) of tractors or other agricultural machines. The power take-off of the tractors includes a first power gear 40 connected to an engine (not shown), a second power gear 45 meshed with the first power gear 40, and a first rotary shaft 10 acting as a central

axis of the second power gear 45. One end of a multi-friction clutch 100 is mounted to an end of the first rotary shaft 10. Another end of the multi-friction clutch 100 is connected to a second rotary shaft 20 so as to transmit a rotational force transferred from the first rotary shaft 10 to the second rotary shaft 20. A spline of the first rotary shaft 10 is engaged with a boss spline of the second power gear, and the first rotary shaft 10 can transmit the rotational force to the multi-friction clutch 100 via the spline. An actuation lever 30 is mounted at a position adjacent to the second rotary shaft 20. The actuation lever 30 controls the operation of the multi-friction clutch 100 so that the transmission of the power between the first rotary shaft 10 and the second rotary shaft 20 can be controlled.

As shown in FIGs. 2 to 4, the multi-friction clutch 100 includes a clutch housing 110, a rotary hub 120, first frictional plates 130, second frictional plates 140, a spring 150 (shown in FIG. 10), a fixing ring 160 and a first snap ring 170. The clutch housing 110 is engaged with the first rotary shaft 10 by means of the spline, so that the rotational force of the first rotary shaft 10 can be transmitted to the clutch housing 110. At this time, the rotation force of the clutch housing 110 can be transmitted to the rotary hub 120 via the first and second frictional plates 130 and 140, and then to the second rotary shaft 20 so as to drive an external apparatus.

The rotary hub 120 is supported by the actuation lever 30. When the actuation lever 30 pressurizes the rotary hub 120 through a pressing plate 32, the rotary hub 120 is moved toward the clutch housing 110 so that the first frictional plates 130 and the second frictional plates 140 approach each other to come into close contact with each other. As a result, the rotational force of the clutch housing 110 is transmitted to the rotary hub 120 via the frictional plates. Now, the constitutional element of the multi-friction clutch according to the present invention will be described sequentially hereinafter pursuant to the assembling order.

FIG. 5 is a perspective view illustrating a clutch housing of FIG. 3.

Referring to FIG. 5, the clutch housing 110 is formed in a generally hollow cylindrical shape. The clutch housing 110 can be manufactured by means of casting or pressing. The clutch housing 110 has four guide grooves 112 formed on a circumferential side wall thereof to be spaced apart equiangularly from one another. The guide grooves 112 are substantially formed in an axial direction of the clutch

housing 110. Guide pieces 132 (shown in FIG. 6) of the first fractional plates 130 are guided through the guide grooves 112 to be movable vertically, which will be described later. In the case of a wet-type clutch, it is possible to allow oil to smoothly flow into or out of the clutch housing. The clutch housing 110 has a hole 116 formed on a bottom surface thereof to correspond to the spline of the first rotary shaft 10. The clutch housing 110 and the first rotary shaft 10 are engaged with each other via the spline so as to rotate together.

In addition, the clutch housing 110 has a first ring groove 114 formed on an inner circumferential surface of an upper end portion of each of four equally spaced apart circumferential side walls thereof. The first ring groove 114 is intended to allow a first snap ring 170 to be snap-fit to the clutch housing 110.

The clutch housing 110 is internally mounted with the rotary hub 120 which is engaged with the first frictional plates 130 and the second frictional plates 140.

FIG. 6 is an exploded perspective view illustrating a state where first frictional plates, second frictional plates and a rotary hub of FIG. 3 are disassembled.

Referring to FIG. 6, the first frictional plates 130 and the second frictional plates 140 are alternately arranged on the outer circumferential surface of the rotary hub 120, at which time, the first frictional plates 130 and the second frictional plates 140 are securely fastened to the rotary hub 120 by means of a second snap ring 175. The rotary hub 120 can be divided into an upper portion and a lower portion based on a stepped portion. As shown in FIG. 2, the lower portion of the rotary hub 120 corresponds to the first and second frictions 130 and 140, and the upper portion of the rotary hub 120 corresponds to a brake. The lower portion of the rotary hub 120 includes an outer circumferential surface on which a first spline 122 is formed. The first spline 122 formed on the lower portion of the rotary hub 120 corresponds to a concavo-convex portion 142 of the second frictional plates 140, and the second frictional plates 140 are securely fastened to the rotary hub 120 by means of the engagement between the concavo-convex portion 142 and the first spline 122 so that the second frictional plates 140 and the rotary hub 120 rotate together. The second frictional plates 140 can be slidably moved along an axial direction of the rotary hub 120. Also, the rotary hub 120 has a second ring groove 124 formed on the outer circumferential surface thereof for fitting the second snap ring 175 therearound.

The upper portion of the rotary hub 120 is located at a position exposed to the

outside from an inlet of the clutch housing 110, and is formed thereon with a second spline 126 similar to the lower portion of the rotary hub 120. A pair of disc plates 70 and a brake plate 75 are fit around the upper portion of the rotary hub 120 on which the second spline 126 is formed. As shown in FIG. 2, the brake plate 75 is interposed between the disc plates 70, and the movement of the rotary hub 120 can determine whether the disc plates 70 and the brake plate 75 come into close contact with each other. As the rotary hub 120 is moved toward the clutch housing 110, the spacing between the brake plate 75 and the disc plates 70 becomes larger, whereas as the rotary hub 120 is moved away from the clutch housing 110, the spacing between the brake plate 75 and the disc plates 70 becomes smaller to come into close contact with each other, which results in a prevention of the undesired rotation of the rotary hub 120.

Moreover, the upper portion of the rotary hub 120 has a third spline 128 formed on an inner circumferential surface thereof. The third spline 128 formed on the inner circumferential surface of the upper portion of the rotary hub 120 is engaged with the second rotary shaft 20, and the second rotary shaft 20 is partially formed on an outer circumferential surface thereof with a spline so as to maintain an engagement relation with an end of the rotary hub 120. Although the rotary hub 120 is linearly moved along an axial direction by means of the actuation lever 30, the second rotary shaft 20 and the rotary hub 120 are slidably moved rotatably while being brought into an engagement with each other by means of the third spline 128.

The first frictional plates 130 and the second frictional plates 140 are alternately arranged on the outer circumferential surface of the lower portion of the rotary hub 120. The second frictional plates 140 include a spline hole formed with the concavo-convex portion 142. When the second frictional plates 140 are fit around the rotary hub 120, the concavo-convex portion 142 and the first spline 122 are brought into an engagement with each other. The first frictional plates 130 centrally define a rotary hole 134 which is not formed on an inner circumferential surface thereof with a concavo-convex portion. In this case, the diameter of the rotary hole 134 is larger than the maximum diameter of the rotary hub 120. Thus, the first frictional plates 130 can rotate on the outer circumferential surface of the rotary hub 120. Each of the first frictional plates 130 has a plurality of guide pieces 132 formed outwardly from an outer circumferential surface thereof to be spaced apart equiangularly from one another. The guide pieces 132 are engaged with the guide grooves 112 of the clutch housing 110. Thus, the first

frictional plates 130 rotate along with the clutch housing 110, and the first frictional plates 130 can be vertically moved along the guide grooves 112.

After the first frictional plates 130 and the second frictional plates 140 have been fit around the rotary hub 120, it is possible to limit the vertical movement range of the first frictional plates 130 and the second frictional plates 140 using a second snap ring 175. The second snap ring 175 is securely fit around the second ring groove 124 of the rotary hub 120, and can define the top end boundary of the first frictional plates 130 or the second frictional plates 140. The second snap ring 175 can prevent the frictional plates from escaping from the rotary hub 120. Even when the rotary hub 120 approaches the clutch housing 110, the second snap ring 175 presses the top end of the first and second frictional plates 130 and 140 to allow the first and second frictional plates 130 and 140 to come into close contact with each other.

FIG. 7 is an exploded perspective view illustrating a process in which an assembly of the rotary hub 120 and the frictional plates of FIG. 6 is mounted in a clutch housing.

Referring to FIG. 7, an assembly of the rotary hub 120 and the frictional plates 130 and 140 is inserted into the clutch housing 110, at which time the guide pieces 132 (shown in FIG. 6) of the first frictional plates 130 are adjusted in position to correspond to the guide grooves 112 of the clutch housing 110. Also, an annular support ring 118 is interposed between the assembly of the rotary hub 120 and the clutch housing 110. The annular support ring 118 can horizontally support the frictional plates 130 and 140 from the bottom surface of the clutch housing 110. The clutch housing 110 which is generally manufactured by casting process can be machined to a precise dimension via lathe machining or grinding, and the bottom end of the guide grooves can be machined horizontally in the lathe machining or grinding. Since the clutch housing 110 manufactured by pressing is susceptible to being deformed by pressing, it is unrealistic to assume a precise dimension. Particularly, it may frequently occur that the bottom ends of the four guide grooves 112 are not kept in a horizontal state. A failure of balance in the clutch and a partial abrasion in the frictional plates or the rotary hub 120 may be caused when the bottom ends of the guide grooves 112 are not maintained in the horizontal state. Accordingly, in the case of using the clutch housing 110 manufactured by the pressing, a separately manufactured annular support ring 118 can be interposed between the

clutch housing 110 and the assembly of the rotary hub 120. The annular support ring 118 may allow the frictional plates to be disposed vertically with respect to a rotary shaft in a state where the frictional plates are in close contact with one another.

In the process of mounting the assembly of the rotary hub 120 and frictional plates 130 and 140 at the clutch housing 110, a thrust ball bearing (not shown) can be installed at the inner circumferential wall of the hole 116 formed on the bottom surface of the clutch housing 110. A spring may be mounted above the thrust ball bearing so as to allow the spring and the clutch housing to smoothly rotate.

FIG. 8 is an exploded perspective view illustrating a process in which an assembly of the rotary hub and the frictional plates of FIG. 7 are fixed in a clutch housing, and FIG. 9 is a perspective view illustrating a fixing ring 160 of FIG. 8.

Referring to FIGs. 8 and 9, in a state where the assembly including the rotary hub 120 is pressed, a fixing ring 160 is placed on the assembly and the fixing ring 160 can be fixed inwardly from the clutch housing 110 using the first snap ring 170. The body of the fixing ring 160 is formed in a ring shape, and can surround the outer circumference of the clutch housing 110. In addition, the fixing ring 160 includes retaining pieces 162 formed inwardly from the top circumferential edge thereof to be spaced apart equiangularly from one another to correspond to the guide grooves 12 of the clutch housing 110. When the fixing ring 160 is mounted on the top circumferential edge of the clutch housing 110, the retaining pieces 162 can protrude inwardly from the clutch housing 110 through the guide grooves 112.

After the fixing ring 160 has been fit around the clutch housing 110, the first snap ring 170 can be securely fit into the first ring groove 114 of the clutch housing 110. The first snap ring 170 abuts against the top surface of the fixing ring 160 at ordinary times to prevent the separation of the fixing ring 160 from the clutch housing 110. The fixing ring 160 surrounds the top circumferential edge of the clutch housing 110 so as to prevent the four equally spaced apart circumferential side walls from being expanded outwardly.

As mentioned above, the clutch housing 110 manufactured by casting or pressing may generate a centrifugal force from the circumferential side walls thereof while rotating at a high speed. In this case, the circumferential side walls of the clutch housing 110 is deformed so that the first snap ring 170 can escape from the first ring groove 114, thereby damaging the clutch. In order to protect the circumferential side

walls of the clutch housing 110 from deforming, there has been proposed a method of fixing a separate protecting ring to the outer circumferential surface of the clutch housing 110 by welding. But in the case of such a method, the welding process is complicated, and the welding can cause the clutch to be deformed. Also even during the normal use of the clutch, a welding portion may nevertheless become separated so that even a normal function may not be performed.

However, the fixing ring 160 according to this embodiment can be assembled so that the fixing ring 160 is placed on the clutch housing 110 and then is easily fixed by means of the first snap ring 170 so that the retaining pieces 162 can be seated in the guide grooves without any separate welding process. Also, since the fixing ring 160 does not possess any deformation factor such as in heat, a failure in balance or a damage of components does not occur, and although the clutch is frequently engaged/disengaged, no cracks between the fixing ring 160 and the clutch housing 110 are generated. Furthermore, even in the case of using the clutch housing 110 manufactured by the pressing and having a poor durability, the fixing ring 160 can securely protect the clutch housing 110, and hence a simple and inexpensive pressing method can be applied to the manufacture of the clutch.

FIG. 10 is a cross-sectional view illustrating a state where the power is not transmitted in the multi-friction clutch of FIG. 2, and FIG. 11 is a cross-sectional view illustrating a state where the power is transmitted in the multi-friction clutch of FIG. 2.

Referring to FIG. 10, the rotary hub 120 is internally supported by a spring 150, and is prone to move in a direction away from the clutch housing 110 by means of a resilient force of the spring 150. Thus, the spacing between the first frictional plates 130 and the second frictional plates 140 can also become large and does not allow a frictional force to act on each other so that a rotational force is not transmitted.

Referring back to FIG. 2, as the rotary hub 120 is moved toward the brake, the brake plate 75 and the disc plates 70 can come into close contact with each other and a frictional force acts between the brake plate 75 and the disc plates 70 so as to prevent an undesired rotation of the rotary hub 120. On the contrary, when the rotary hub 120 is moved toward the clutch housing

110 by means of the actuation lever 30, etc., the clutch is operated interconnectivley so that the brake is separated into an opened state. Referring to FIG. 11 , as the rotary hub 120 is moved downwardly, the spring is contracted, and the second snap ring 175

presses the first and second frictional plates 130 and 140 and causes them to come into close contact with each other. At this time, the annular support ring 118 horizontally supports the bottom end of the frictional plates so that the multi-frictional clutch 100 including the frictional plates 130 and 140 can be wholly maintained in balance to be rotatable.

During the rotation of the clutch housing 110, a centrifugal force can be exerted to the circumferential side walls of the clutch housing 110. But, since the fixing ring 160 supports the clutch housing 110 from the outside against the centrifugal force, the clutch housing 100 can be prevented from being deformed or expanded. As shown in FIG. 11, when the rotary hub 120 and the frictional plates 130 and 140 are moved downwardly, the fixing ring 160 is also moved downwardly.

FIG. 12 is a cross-sectional view illustrating a multi-friction clutch according to another embodiment of the present invention. For reference, the multi-friction clutch 200 according to this embodiment will be described hereinafter with reference to the description and the drawing for the conventional friction clutch and the multi-friction clutch 100 of the previous first embodiment.

Referring to FIG. 12, the multi-friction clutch 200 includes a clutch housing 210, a rotary hub 220, first frictional plates 230, second frictional plates 240, a spring 250, a fixing ring 260 and a first snap ring 270. The clutch housing 210 is engaged with the first rotary shaft 1, so that the rotational force of the first rotary shaft 1 can be transmitted to the clutch housing 210. At this time, the rotation force of the clutch housing 110 can be transmitted to the rotary hub 120 via the first and second frictional plates 230 and 240, and then to the second rotary shaft 2. Also, an intermittent transmission device 3 can move the rotary hub 220 in an axial direction using a pedal unit, a lever unit, a hydraulic unit, etc. The actuation of the intermittent transmission device 3 allows the first frictional plates 230 and the second frictional plates 240 to be engaged with or disengaged from each other.

The clutch housing 210 has guide grooves 212 formed on a circumferential side wall thereof to be spaced apart equiangularly from one another. Each of the first frictional plates 230 has a plurality of guide pieces 132 formed on an outer circumferential surface thereof to correspond to the guide grooves 212 of the clutch housing 210 to be spaced apart equiangularly from one another. Since the guide grooves 212 support the guide pieces, it can restrict the rotation of the first frictional

plates 230 and can guide the vertical movement of the first frictional plates 230. On the other hand, the second frictional plates 240 are separated from the inner circumferential surface of the clutch housing 210, and maintains an engagement relation with the rotary hub 220 by means of a spline or other engagement structure. Thus, the rotational force of the first rotary shaft 1 can be transmitted to a second rotary shaft 2 in a state where the first and second frictional plates 230 and 240 are engaged with each other, but the rotational force of the first rotary shaft 1 may not be transmitted to the second rotary shaft 2 in a state where the first and second frictional plates 230 and 240 are disengaged from each other. As shown in FIG. 12, the fixing ring 260 is mounted on the top circumferential edge of the clutch housing 210, retaining pieces 262 (shown in FIGS. 8 and 9) formed on the fixing ring 260 can protrude inwardly from the clutch housing 210 through the guide grooves 212. In a state where an assembly of the rotary hub 220 and the frictional plates 230 and 240 is pressed, the fixing ring 260 is placed on the assembly and the fixing ring 260 can be fixed inwardly from the clutch housing 210 using the first snap ring 270. In this case, since the retaining pieces 262 are supported by the first snap ring 270, the fixing ring 260 can be stably engaged with the clutch housing 210.

Alternatively, the retaining pieces 262 formed on the fixing ring 260 can protrude inwardly from the clutch housing 210 through separately formed retaining grooves, but not the guide grooves 212. As described above in the previous embodiment, the retaining pieces 262 are advantageously engaged with the clutch housing 210 through the guide grooves 212, but the present invention is not limited thereto and separate retaining grooves are formed in separate circumferential side walls to engage the fixing ring 260 with the clutch housing 210. Referring to FIG. 12, the body of the fixing ring 260 is formed in a ring shape, and can accommodate the outer circumference of the clutch housing 210. When the fixing ring 260 is mounted on the top circumferential edge of the clutch housing 210, the retaining pieces 262 can protrude inwardly from the clutch housing 210 through the guide grooves 212. The first snap ring 270 abuts against the top surface of the fixing ring 260 at ordinary times to prevent the separation of the fixing ring 260 from the clutch housing 210. The fixing ring 260 surrounds the top circumferential edge of the clutch housing 210 so as to prevent the equally spaced apart circumferential side walls from being expanded outwardly.

In particular, the clutch housing 210 manufactured by pressing may deform the circumferential side walls thereof by a centrifugal force generated while rotating at a high speed due to a poor rigidity. However, the fixing ring 260 according to this embodiment can be easily and simply fixed to the clutch housing 210 using the first snap ring 270 without a separate welding process. Further, since the fixing ring 260 does not possess any deformation factor such as in heat, a failure in balance or a damage of components does not occur, and although the clutch is frequently turned engaged/disengaged, no cracks between the fixing ring 260 and the clutch housing 210 are generated. FIG. 13 is a cross-sectional view illustrating a power apparatus using the multi- friction clutch according to still another embodiment of the present invention, FIG. 14 is a perspective view illustrating the multi-friction clutch of FIG. 13, and FIG. 15 is a front view illustrating the multi-friction clutch of FIG. 14.

Referring to FIG. 13, the multi-friction clutch 300 is mounted on a power take- off (PTO) of tractors or other agricultural machines. The power take-off of the tractors includes a first power gear 40 connected to an engine (not shown), a second power gear 45 meshed with the first power gear 40, and a first rotary shaft 10 acting as a central axis of the second power gear 45. One end of a multi-friction clutch 300 is mounted to an end of the first rotary shaft 10. Another end of the multi-friction clutch 300 is connected to a second rotary shaft 20 so as to transmit a rotational force transferred from the first rotary shaft 10 to the second rotary shaft 20. A spline of the first rotary shaft 10 is engaged with a boss spline of the second power gear, and the first rotary shaft 10 can transmit the rotational force to the multi-friction clutch 300 via the spline. An actuation lever 30 is mounted at a position adjacent to the second rotary shaft 20. The actuation lever 30 controls the operation of the multi-friction clutch 300 so that the transmission of the power between the first rotary shaft 10 and the second rotary shaft 20 can be controlled.

As shown in FIGs. 13 to 15, the multi-friction clutch 300 includes a clutch housing 310, a rotary hub 320, first frictional plates 330, second frictional plates 340, a spring, a fixing ring 360 and a first snap ring 370. The clutch housing 310 is engaged with the first rotary shaft 10 by means of the spline, so that the rotational force of the first rotary shaft 10 can be transmitted to the clutch housing 310. At this time, the rotation force of the clutch housing 310 can be transmitted to the rotary hub 320 via the

first and second frictional plates 330 and 340, and then to the second rotary shaft 20 so as to drive an external apparatus.

The rotary hub 320 is supported by the actuation lever 30. When the actuation lever 30 pressurizes the rotary hub 320 through a pressing plate 32, the rotary hub 320 is moved toward the clutch housing 310 so that the first frictional plates 330 and the second frictional plates 340 approach each other to come into close contact with each other. As a result, the rotational force of the clutch housing 310 is transmitted to the rotary hub 320 via the frictional plates.

Now, the constitutional element of the multi-friction clutch according to the present invention will be described sequentially hereinafter pursuant to the assembling order.

FIG. 16 is a perspective view illustrating a clutch housing of FIG. 14, FIG. 17 is a top view illustrating the clutch housing of FIG. 14, and FIG. 18 is a perspective view illustrating a state before support pieces of the clutch housing of FIGs. 16 and 17 are bent.

Referring to FIGs. 16 and 17, the clutch housing 310 is formed in a generally hollow cylindrical shape. The clutch housing 310 can be manufactured by means of a process method using pressing or other plastic deformation. The clutch housing 310 has four guide grooves 312 formed on a circumferential side wall thereof to be spaced apart equiangularly from one another. The guide grooves 312 are substantially formed in an axial direction of the clutch housing 310. Guide pieces 332 (shown in FIG. 19) of the first frictional plates 330 are guided through the guide grooves 312 to be movable vertically, which will be described later. In the case of a wet-type clutch, it is possible to allow oil to smoothly flow into or out of the clutch housing. The clutch housing 310 has a hole 316 formed on a bottom surface thereof to correspond to the spline of the first rotary shaft 10. The clutch housing 310 and the first rotary shaft 10 are engaged with each other via the spline so as to rotate together.

In addition, the clutch housing 310 has a first ring groove 314 formed on an inner circumferential surface of an upper end portion of each of four equally spaced apart circumferential side walls thereof. The first ring groove 314 is intended to allow a first snap ring 370 to be snap-fit to the clutch housing 310.

Each of the guide grooves 312 is provided with a support piece 318 bent inwardly from the bottom end thereof. The support piece 318 is formed integrally with

the clutch housing 310, and may be formed in each circumferential side wall positioned between the guide grooves 312 by means of pressing or pressing/punching. As mentioned above, the top surfaces of the support pieces 318 have a common plane which must be oriented to be perpendicular to a longitudinal axis of the clutch housing 310. Thus, after the support pieces 318 have been bent, the top surfaces of the support pieces 318 may be adjusted to form a horizontal plane via cutting machining or grinding.

FIG. 18 is a perspective view illustrating a state before support pieces 318 of the clutch housing 310 of FIGs. 16 and 17 are bent.

Referring to FIG. 18, there is shown a body of a clutch housing 310 manufactured by pressing or pressing/punching. Portions corresponding to the support pieces 318 are bent inwardly so as to provide the clutch housing 310. In this embodiment, each of four support pieces 318 is formed on the bottom surface of each of the guide grooves 312, but at least two support pieces 318 may be arranged appropriately. The clutch housing 310 is internally mounted with the rotary hub 320 which is engaged with the first frictional plates 330 and the second frictional plates 340.

FIG. 19 is an exploded perspective view illustrating a state where the first frictional plates 330, the second frictional plates 340 and the rotary hub 320 of FIG. 14 are disassembled. Referring to FIG. 19, the first frictional plates 330 and the second frictional plates 340 are alternately arranged on the outer circumferential surface of the rotary hub 320, at which time, the first frictional plates 330 and the second frictional plates 340 are securely fastened to the rotary hub 320 by means of a second snap ring 375.

The rotary hub 320 can be divided into an upper portion and a lower portion based on a stepped portion. As shown in FIG. 13, the lower portion of the rotary hub 320 corresponds to the first and second frictions 330 and 340, and the upper portion of the rotary hub 320 corresponds to a brake. The lower portion of the rotary hub 320 includes an outer circumferential surface on which a first spline 322 is formed. The first spline 322 formed on the lower portion of the rotary hub 320 corresponds to a concavo-convex portion 342 of the second frictional plates 340, and the second frictional plates 340 are securely fastened to the rotary hub 320 by means of the engagement between the concavo-convex portion 342 and the first spline 322 so that the second frictional plates 340 and the rotary hub 320 rotate together. The second

frictional plates 340 can be slidably moved along an axial direction of the rotary hub 320. Also, the rotary hub 320 has a second ring groove 324 formed on the outer circumferential surface thereof for fitting the second snap ring 375 therearound.

The upper portion of the rotary hub 320 is located at a position exposed to the outside from an inlet of the clutch housing 310, and is formed thereon with a second spline 326 similar to the lower portion of the rotary hub 320. A pair of disc plates 70 and a brake plate 75 are fit around the upper portion of the rotary hub 120 on which the second spline 326 is formed. As shown in FIG. 13, the brake plate 75 is interposed between the disc plates 70, and the movement of the rotary hub 320 can determine whether the disc plates 70 and the brake plate 75 come into close contact with each other. As the rotary hub 320 is moved toward the clutch housing 310, the spacing between the brake plate 75 and the disc plates 70 becomes larger, whereas as the rotary hub 320 is moved away from the clutch housing 310, the spacing between the brake plate 75 and the disc plates 70 becomes smaller to come into close contact with each other, which results in a prevention of the undesired rotation of the rotary hub 320.

Moreover, the upper portion of the rotary hub 320 has a third spline 328 formed on an inner circumferential surface thereof. The third spline 328 formed on the inner circumferential surface of the upper portion of the rotary hub 320 is engaged with the second rotary shaft 20, and the second rotary shaft 20 is partially formed on an outer circumferential surface thereof with a spline so as to maintain an engagement relation with an end of the rotary hub 320. Although the rotary hub 320 is linearly moved along an axial direction by means of the actuation lever 30, the second rotary shaft 20 and the rotary hub 320 are slidably moved rotatably while being brought into an engagement with each other by means of the third spline 328. The first frictional plates 330 and the second frictional plates 340 are alternately arranged on the outer circumferential surface of the lower portion of the rotary hub 320. The second frictional plates 340 include a spline hole formed with the concavo-convex portion 342. When the second frictional plates 340 are fit around the rotary hub 320, the concavo-convex portion 342 and the first spline 322 are brought into an engagement with each other. The first frictional plates 330 centrally define a rotary hole 134 which is not formed on an inner circumferential surface thereof with a concavo-convex portion. In this case, the diameter of the rotary hole 334 is larger than the maximum diameter of the rotary hub 320. Thus, the first frictional plates 330 can rotate on the outer

circumferential surface of the rotary hub 320. Each of the first frictional plates 330 has a plurality of guide pieces 332 formed outwardly from an outer circumferential surface thereof to be spaced apart equiangularly from one another. The guide pieces 332 are engaged with the guide grooves 312 of the clutch housing 310. Thus, the first frictional plates 330 rotate along with the clutch housing 310, and the first frictional plates 330 can be vertically moved along the guide grooves 312.

After the first frictional plates 330 and the second frictional plates 340 have been fit around the rotary hub 320, it is possible to limit the vertical movement range of the first frictional plates 330 and the second frictional plates 340 using a second snap ring 375. The second snap ring 375 is securely fit around the second ring groove 324 of the rotary hub 320, and can define the top end boundary of the first frictional plates 330 or the second frictional plates 340. The second snap ring 375 can prevent the frictional plates from escaping from the rotary hub 320. Even when the rotary hub 320 approaches the clutch housing 310, the second snap ring 375 presses the top end of the first and second frictional plates 330 and 340 to allow the first and second frictional plates 330 and 340 to come into close contact with each other.

FIG. 20 is an exploded perspective view illustrating a process in which an assembly of the rotary hub 320 and the frictional plates of FIG. 19 is mounted in a clutch housing. Referring to FIG. 20, an assembly of the rotary hub 320 and the frictional plates

330 and 340 is inserted into the clutch housing 310, at which time the guide pieces 332 (shown in FIG. 19) of the first frictional plates 330 are adjusted in position to correspond to the guide grooves 312 of the clutch housing 310.

Also, each of the guide grooves 312 of the clutch housing 310 is provided with a support piece 318 bent inwardly from the bottom end thereof to horizontally support an assembly of the rotary hub 320 and the first and second frictional plates 330 and 340. The support pieces 318 horizontally support the first and second frictional plates 330 and 340 from a bottom surface of the clutch housing 310. The clutch housing 310 which is generally manufactured by a casting process can be machined to a precise dimension via lathe machining or grinding. Since the clutch housing 310 manufactured by pressing is susceptible to being deformed by pressing, it is unrealistic to assume a precise dimension. Particularly, it may frequently occur that the bottom ends of the four guide grooves 312 are not kept in a horizontal state. Accordingly, in the case of

using the clutch housing 310 manufactured by the pressing, an annular support ring can be interposed between the clutch housing 320 and the assembly of the rotary hub 310. However, in this embodiment, the annular support ring may be replaced by support pieces bent by a simple process. The top surfaces of the support pieces can be adjusted horizontally through the adjustment or cutting/grinding of the support pieces 318. Accordingly, the clutch housing 310, the frictional plates and the rotary hub 320 are oriented to be perpendicular to the rotary shaft to thereby maintain stable balance.

In the process of mounting the assembly of the rotary hub 320 and frictional plates 330 and 340 at the clutch housing 310, a thrust ball bearing (not shown) can be installed at the inner circumferential wall of the hole 316 formed on the bottom surface of the clutch housing 310. A spring 350 is mounted above the thrust ball bearing so as to allow the spring 350 and the clutch housing 310 to smoothly rotate.

FIG. 21 is an exploded perspective view illustrating a process in which an assembly of the rotary hub and the frictional plates of FIG. 20 is fixed in a clutch housing, and

Referring to FIG. 21, in a state where the assembly including the rotary hub 320 is pressed, a fixing ring 360 is placed on the assembly and the fixing ring 160 can be fixed inwardly from the clutch housing 110 using the first snap ring 370.

The body of the fixing ring 360 is formed in a ring shape, and can accommodate the outer circumference of the clutch housing 310. In addition, the fixing ring 360 includes retaining pieces 362 formed to be bent inwardly from the top circumferential edge thereof to be spaced apart equiangularly from one another to correspond to the guide grooves 312 of the clutch housing 110. When the fixing ring 160 is mounted on the top circumferential edge of the clutch housing 110, the retaining pieces 162 can protrude inwardly from the clutch housing 110 through the guide grooves 112.

After the fixing ring 360 has been fit around the clutch housing 310, the first snap ring 370 can be securely fit into the first ring groove 314 of the clutch housing 310. The first snap ring 370 abuts against the top surface of the fixing ring 360 at ordinary times to prevent the separation of the fixing ring 360 from the clutch housing 310. The fixing ring 360 surrounds the top circumferential edge of the clutch housing 310 so as to prevent the four equally spaced apart circumferential side walls from being expanded outwardly.

FIG. 22 is a cross-sectional view illustrating a state where the power is not

transmitted in the multi-friction clutch of FIG. 13, and FIG. 23 is a cross-sectional view illustrating a state where the power is transmitted in the multi-friction clutch of FIG. 13.

Referring to FIG. 22, the rotary hub 320 is internally supported by the spring

350, and is prone to move in a direction away from the clutch housing 310 by means of a resilient force of the spring 350. Thus, the spacing between the first frictional plates

330 and the second frictional plates 340 can also become large and does not allow a frictional force to act on each other so that a rotational force is not transmitted.

Referring back to FIG. 13, as the rotary hub 310 is moved toward the brake, the brake plate 75 and the disc plates 70 can come into close contact with each other and a frictional force acts between the brake plate 75 and the disc plates 70 so as to prevent an undesired rotation of the rotary hub 320.

On the contrary, when the rotary hub 320 is moved toward the clutch housing

310 by means of the actuation lever 30, etc., the clutch is operated interconnectivley so that the brake is separated into an opened state. Referring to FIG. 23, as the rotary hub 320 is moved downwardly, the spring 350 is contracted, and the second snap ring 375 presses the first and second frictional plates 330 and 340 and causes the first and second frictional plates 330 and 340 to come into close contact with each other. At this time, the support pieces 318 horizontally supports the bottom end of the frictional plates so that the multi-frictional clutch 300 including the first and second frictional plates 330 and 340 can be wholly maintained in balance to be rotatable.

FIG. 24 is a perspective view illustrating a clutch housing according to still another embodiment of the present invention, and FIG. 25 is a perspective view illustrating a state before support pieces of the clutch housing of FIG. 24 are bent.

Referring to FIGs. 24 and 25, the clutch housing 410 is formed in a generally hollow cylindrical shape. The clutch housing 410 can be manufactured by means of a process method using pressing or other plastic deformation. The clutch housing 410 has four guide grooves 412 formed on a circumferential side wall thereof to be spaced apart equiangularly from one another so as to vertically guide guide pieces of first frictional plates therethrough. In the case of a wet-type clutch, it is possible to allow oil to smoothly flow into or out of the clutch housing 410.

The clutch housing 410 has a hole 416 formed on a bottom surface thereof to correspond to the spline of the first rotary shaft. In addition, the clutch housing 410 has a first ring groove 414 formed on an inner circumferential surface of an upper end

portion of each of four equally spaced apart circumferential side walls thereof. The first ring groove 414 is intended to allow a snap ring to be snap-fit to the clutch housing 410.

An opening 417 for forming a support piece 418 is formed in each circumferential side wall of the clutch housing positioned between the guide grooves 412. The support piece 418 is bent inwardly from the bottom end of the opening 417 to protrude inwardly from the circumferential side wall of the clutch housing 410. As shown in FIG. 24, the support piece 418 may be formed at a position beside the guide groove 412, and may have the top surface horizontally supporting the frictional plates via cutting/grinding.

FIG. 25 is a perspective view illustrating a state before support pieces of the clutch housing of FIG. 24 are bent.

Referring to FIG. 25, there is shown a body of a clutch housing manufactured by pressing or pressing/punching. Portions corresponding to the support pieces 418 are bent inwardly by incising so as to provide the clutch housing 410. In this embodiment, each of four support pieces 418 is formed on each of four circumferential side wall positioned between the guide grooves 412 of the clutch housing 410. But at least two support pieces 318 may be arranged appropriately, and formed on the bottom end of the guide groove 412 and in the circumferential side wall positioned between the guide grooves 412 in a combination manner.

FIG. 26 is a cross-sectional view illustrating a multi-friction clutch according to yet another embodiment of the present invention. For reference, the multi-friction clutch 500 according to this embodiment will be described hereinafter with reference to the description and the drawing for the conventional friction clutch and the multi- friction clutch 100 of the previous first embodiment.

Referring to FIG. 26, the multi-friction clutch 500 includes a clutch housing 510, a rotary hub 520, first frictional plates 530, second frictional plates 540, a spring 550, a fixing ring 560 and a first snap ring. The clutch housing 510 is engaged with the first rotary shaft 1, so that the rotational force of the first rotary shaft 1 can be transmitted to the clutch housing 510. At this time, the rotation force of the clutch housing 510 can be transmitted to the rotary hub 520 via the first and second frictional plates 530 and 540, and then to the second rotary shaft 2. Also, an intermittent transmission device 3 can move the rotary hub 520 in an axial direction using a pedal unit, a lever unit, a

hydraulic unit, etc. The actuation of the intermittent transmission device 3 allows the first frictional plates 530 and the second factional plates 540 to be engaged with or disengaged from each other.

The clutch housing 510 has guide grooves 512 formed on a circumferential side wall thereof to be spaced apart equiangularly from one another. Each of the first frictional plates 530 has a plurality of guide pieces formed outwardly from an outer circumferential surface thereof to correspond to the guide grooves 512 of the clutch housing 510 to be spaced apart equiangularly from one another. Since the guide grooves 512 support the guide pieces, it can restrict the rotation of the first frictional plates 530 and can guide the vertical movement of the first frictional plates 530. On the other hand, the second frictional plates 540 are separated from the inner circumferential surface of the clutch housing 510, and maintains an engagement relation with the rotary hub 520 by means of a spline or other engagement structure. Thus, the rotational force of the first rotary shaft 1 can be transmitted to a second rotary shaft 2 in a state where the first and second frictional plates 530 and 540 are engaged with each other, but the rotational force of the first rotary shaft 1 may not be transmitted to the second rotary shaft 2 in a state where the first and second frictional plates 530 and 540 are disengaged from each other.

As shown in FIG. 26, the fixing ring 560 is mounted on the upper circumferential edge of the clutch housing 510 by welding, and prevents deformation of the clutch housing 510 during the rotation of the circumferential side wall of the clutch housing 510.

In particular, the clutch housing 210 manufactured by pressing may not support the frictional plates 530 and 540 only on the bottom surface of the guide groove 512 due to a poor precision in dimensions. Particularly, the unstable balance of the clutch housing 510 and the frictional plates 530 and 540 caused by the high speed rotation thereof may hinder smooth transmission of the power, and shorten a lifespan of components. However, a support piece 518 according to this embodiment can stably support the frictional plates 530 and 540 and help to maintain a stable balance. FIG. 27 is a cross-sectional view illustrating a power apparatus using the multi- friction clutch including a brake system according to a further embodiment of the present invention, FIG. 28 is a view illustrating a state where an actuation lever and a manipulation load-limiting spring are mounted in the multi-friction clutch of the present

invention, FIG. 29 is an enlarged view illustrating a portion "A" of FIG. 27, FIG. 30 is a cross-sectional view illustrating a power apparatus using a multi-friction clutch including a brake system according to still another embodiment of the present invention, FIG. 31 is a cross-sectional view illustrating a power apparatus using a multi-friction clutch including a brake system according to still another embodiment of the present invention, and FIG. 32 is an enlarged view illustrating a portion "B" of FIG. 31.

First, the constitutional elements and the operation relationship of the multi- friction clutch as shown in FIG. 27 will be described hereinafter

Referring to FIG. 27, the multi-friction clutch 300 includes a clutch housing 310, a rotary hub 320, frictional plates 330, discs 340, a snap ring 355, a restring spring 370, an actuation lever 380 and a manipulation load-limiting spring 390.

The clutch housing 310 is formed in a generally hollow cylindrical shape. The clutch housing 310 can be manufactured by means of a process method using pressing or other plastic deformation. The clutch housing 310 has four guide grooves formed on a circumferential side wall thereof to be spaced apart equiangularly from one another.

The guide grooves 312 allow guide pieces 332 of the frictional plates 330 to be guided therealong to be movable vertically. In the case of a wet-type clutch, it is possible to allow oil to smoothly flow into or out of the clutch housing 310. The clutch housing 310 has a hole formed on the bottom surface thereof to correspond to a spline shaft 630 of a driven shaft 311, and has a first ring groove formed on an upper inner circumferential surface of four equally spaced apart circumferential sidewalls thereof.

The first ring groove is intended to allow a first snap ring to be snap-fit to the clutch housing 310.

An opening 319 for forming the support piece 318 is formed in each circumferential side wall positioned between the guide grooves 312. The support piece 318 is bent inwardly from a bottom end of the opening 319 to protrude inwardly from the circumferential side wall of the clutch housing 310. As shown in FIG. 27, the support piece 318 may be formed at a position beside the guide groove 312, and may have a top surface horizontally supporting the frictional plates 330 and the discs 340 via cutting/grinding.

Here, the clutch housing 310 is engaged with the spline shaft 630 of the driven

shaft 311 via the hole thereof so that the rotational force of a driving shaft 316 is transmitted to the driven shaft 311.

The clutch housing 310 rotates when the rotational force of the driving shaft 316 is transmitted to the rotary hub 320 to rotate the discs 340 and the frictional plates 330. Thereafter, the rotational force of the clutch housing 310 is transmitted to the driven shaft 311 via the hole corresponding to the spline shaft 630 to thereby drive the driven shaft 311.

That is, in order to switch the multi-friction clutch 300 into a connection state, when the manipulation load-limiting spring 390 is pulled in an arrow direction as shown in FIG. 27, the actuation lever 380 is actuated to cause the shift fork 385 to press a collar thrust 620. Then, the spline shaft 630 of the driven shaft 311 operated in cooperation with the collar thrust 620 is moved to the left, and simultaneously the clutch housing

310 is also moved to the left so that the plates 330 and the discs 340 comes into close contact with each other to be switched into a friction state. As a result, the rotational force of the driving shaft 316 is transmitted to the clutch housing 310 via the rotary hub 320 and then the frictional plates 330 and the discs 340 to rotate the clutch housing 310 so that the rotational force of the clutch housing 310 is transmitted to the driven shaft 311.

At this time, the manipulation load-limiting spring 390 as shown in FIG. 28 acts to allow the plates 330 and the discs 340 to come into close contact with other in a connection state of the multi-friction clutch. In the meantime, over-pressure is applied to the collar thrust 620 while an excessive pressing pressure is exerted to the actuation lever 380 and the shift fork 385 via the manipulation load-limiting spring 390, and then the over-pressure is again transferred to the frictional plates 330 and the discs 340 so that the clutch housing may be broken. Thus, the manipulation load-limiting spring

390 also functions to offset such an excessive pressing pressure.

That is, when the plates 330 and the discs 340 come into close contact with each other to transmit the rotational force of the clutch, if the rotational force is in excess of a force necessary for the frictional rotation, the manipulation load-limiting spring 390 is extended to offset the excess force so as to prevent the over-pressure from being transmitted.

In the meantime, in a state where the clutch is engaged, the frictional plates 330 and the discs 340 are engaged with each other to rotate, at which time, high heat is

generated due to a frictional force for rotation.

In order to prevent such a phenomenon, an oil circulating hole 315 is preferably formed at a bearing holder part 317 and a boss spline 313, respectively, so that oil is circulating, continuously supplied to the clutch through a circulation pump 610. The reason why new oil is continuously supplied to a frictional engagement portion between the frictional plates 330 and the discs 340 using the circulation pump

610 is that oil is discharged to the outside by a centrifugal force during the rotation of the clutch, resulting in a lack of remaining oil, and high heat is generated from the frictional plates 330 and the discs 340 so that the outer surface of the frictional plates 330 and the discs 340 are expanded, which may cause structural deformation of the clutch, and thereby requiring frequent replacement of a broken clutch with new one.

Accordingly, new oil is supplied to the frictional engagement portion between the frictional plates 330 and the discs 340 to thereby prevent a deficiency of oil at a corresponding portion, and any deformation due to high heat which may occur at the corresponding portion, so that the frictional plates 330 and the discs 340 can be used for an extended period of time without frequent replacement.

Now, an explanation on the constituent elements of a brake system for a multi- friction clutch according to one embodiment of the present invention for braking the multi-friction clutch driven as described above will be given hereinafter. As shown in FIG. 27, in one embodiment for controlling the rotation of the clutch housing 310, the brake system for the multi-friction clutch is composed of a brake disc 360, a brake lining 600, and a restoring spring 370.

The brake disc 360 is mounted on a front surface of the transmission case 314 to correspond to a rear surface of the clutch housing 310, and the brake lining 600 is mounted on a front surface of the brake disc 360.

In this case, the clutch housing 310 can serve as a brake plate 350 as shown in FIG. 30.

A state where the brake disc 360 is mounted at the transmission case 314 will be described hereinafter. As shown in FIGs. 27 and 29, the brake disc 360 may be fit into a fixing groove

314-1 formed on the transmission case 314, or may be fit into the fixing groove 314-1 and then securely fixed to the transmission case by means of a fixture 365.

The fixing groove 314-1 is formed in the same shape as that of a fixing piece

363 of the brake disc 360 to allow the fixing piece 363 to be fit into the fixing groove 314-1.

In addition, if the fixture 365 is fixed using a fastening means such as a bolt 367, etc., after the fixture 365 mounted at the transmission case 314 has been placed on the fixing piece 363, even though a braking force is exerted to the clutch housing 310, the brake disc 360 may not be moved.

The fixture 365 is preferably engaged with the fixing piece 363 to be protrudingly placed on the fixing piece 363 enough not to hinder the rotation of the clutch housing 310. In the meantime, in such a brake system for the multi-friction clutch, as shown in FIG. 30, the clutch housing 310 may further comprise a brake plate 350 formed on the rear surface thereof.

At this time, the brake plate 350 can be formed to a predetermined thickness. The brake plate 350 functions to double a capability preventing movement or rotation of the clutch housing 310 in addition to a brake force due to the brake disc 360 mounted to the transmission case 314 and the brake lining 600 during disengagement of the clutch to thereby prevent any rotation of the driven shaft 311. Moreover, only a small restoring force of the manipulation load-limiting spring 390 can sufficiently control the rotation of the clutch housing 310. Here, the thickness of the brake plate 350 mounted at the clutch housing 310 and the thickness of the brake disc 360 mounted at the transmission case 314 can be variously modified depending on an intention of the user.

The restoring spring 370 is installed between a spring seat mounted to the rotary hub 320 and the clutch housing 310. The restoring spring 370 is compressed by means of a restoring force of the manipulation load-limiting spring 390 and the actuation lever

380 in a state where the clutch is engaged and acts to return the clutch housing 310 to its original position in a state where the clutch is disengaged.

The clutch housing 310 is returned to its original position by means of the restoring force of the restoring spring 370 to be forced to stop its rotation in a state where the clutch housing 310 is in close contact with the brake lining 600.

That is, the restoring force of the restoring spring 370 allow the clutch housing 310 to induce a brake operating force to control the rotation of the clutch housing when the clutch is disengaged. In this case, a drag toque of a clutch disc due to a rotation of

120° of the clutch housing 310 is prevented so as to stop the rotation of the clutch housing 310.

The operation state of the brake system of the multi-friction clutch including the above-mentioned constituent elements will be described in brief hereinafter. When a user pulls the manipulation load-limiting spring 390 to interconnect the friction clutch so as to operate a tractor or a power take-off (PTO), etc., of other agricultural machines, the actuation lever 380 connected to the manipulation load- limiting spring 390 presses the collar thrust 630.

Next, the driven shaft 311 operated cooperatively with the collar thrust 620 is moved to the left, and simultaneously the clutch housing 310 is moved forward to be switched into a frictional contact between the frictional plates 330 and the discs 340.

Accordingly, the rotational force of the driving shaft 316 is transmitted to the rotary hub 320 and then to the clutch housing 310 via the discs 340 and the plates 330 to cause the clutch housing 310 to rotate along with the driven shaft 311. When the driven shaft 311 rotates, the power take-off operating in cooperation with the driven shaft 311 is operated to cause the working machine to start to work.

When the user disengages the clutch to stop the operation of the working machine after the work has been completed, the multi-friction clutch returns to its original position to stop its rotation. As a result, the restoring spring 370 which had been compressed returns to its original position to push the clutch housing 310 to its original position to cause the clutch housing 310 itself or the brake plates 350 separately mounted to the clutch housing to come into close contact with the brake disc 360 mounted to the transmission case 314 and the brake lining 600 to brake the clutch housing 310. Therefore, the braking force due to the contact between the brake plate 350 and the brake lining attached on the brake disc 360 stops the rotation of the clutch housing 310, and simultaneously stops the rotation of the driven shaft 311, thereby preventing a drag torque caused by viscosity of oil and a risk of an unexpected accident due to an undesired operation of a work machine.

Industrial Applicability

A multi-friction clutch according to the present invention can stably maintain a clutch housing in an original state without any deformation since the outer

circumferential side wall of the clutch housing is protectively supported by using a fixing ring.

Further, since the escape of the fixing ring is easily prevented by using the retaining pieces formed on the fixing ring, it is possible to overcome the damage of a welding portion, thermal deformation due to welding, and complication and difficulty of welding, etc., which are involved in the problems of the prior conventional art.

In addition, the inventive multi-friction clutch can structurally resolve durability of the clutch so that a clutch housing can be manufactured in a simple and inexpensive pressing process, but not in a complicated and expensive casting process, thereby remarkably reducing the manufacturing cost and purchase cost of the clutch as well as securing improved stability even in the case of the clutch manufactured by casting.

The inventive multi-friction clutch can be simply and easily assembled without any deformation of components, and allows for easy replacement and repair thereof even during its use. While the present invention has been described with reference to the particular illustrative embodiments, it is not to be restricted by the embodiments but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present invention.