Background Art Generally, a pulley type CVT, in which a rubber cr metal V-belt is connected between two pulleys so as to variously control a transmission ratio, is widely used. Further, there is proposed and commercialized a CVT using sliding friction of various metal members. In the pulley type CVT, an efficient diameter is controlled using a hydraulic control device, thereby controlling the transmission ratio in an extent of 0. 5 to 2. 5 in a continuously variable speed changing method.

However, in the conventional CVT, as described above, since a driving pulley and a driven pulley are connected using a rubber belt, a chain or a metal belt, it is difficult to scale up the CVT due to a limitation of frictional force between the belt and the pulley. Further, there is a problem that a centrifugal force

is generated when the belt is rotated and thus the frictional force between the belt and the pulley is reduced, thereby increasing a slipping phenomenon.

In addition, the hydraulic device for controlling the transmission ratio increases a weight of the CVT. Therefore, loss of power is occurred, and it is also difficult to reduce a size and a weight of the CVT.

Detailed description of the invention Accordingly, it is a technical object of the invention to provide a CVT in which power loss due to a slipping phenomenon is prevented and also the power is precisely transmitted.

It is another object of the invention to provide a CVT in which a structure of a controlling unit for mechanically controlling a transmission ratio using centrifugal force of a rotational pendulum is simplified.

To accomplish the technical object and other advantages, there is a CVT, comprising first and second rotation center maintaining unit for receiving rotational power from a power generating device, and controlling a rotational radius of a rotational bar, and maintaining a center of mass so as to control a transmission ratio using centrifugal force ; two pairs of I type racks disposed at the rotational bar to be twisted by at least 90 degrees, for converting the rotational force transmitted from the first and second rotation center maintaining unit into liner

reciprocations respectively having a phase difference of 45 degrees ; two rotational cylinders coupled to the two pairs of I type racks respectively interposing a one-way clutch therebetween, for changing a torque and a speed of each linear reciprocation and then uniting the linear reciprocations; a ring gear for transmitting the rotational force united in the two rotational cylinders to an output shaft ; and an elastic means interposed between the rotational cylinder and the ring gear, for absorbing a torsional shock when driving.

Preferably, each of the rotational cylinder has four one-way clutches having a same locking direction so as to selectively transmit a desired directional component of the linear reciprocation transmitted from one pair of the I type racks to the ring gear, and a center portion of the rotational cylinder is empty so as not to obstruct rotation of the rotational bar.

Preferably, the two rotation center maintaining unit is comprised of a male type rotational pendulum and a female type rotational pendulum so as to maintain the center of mass even in a case that the rotational radiuses of the rotational pendulums are changed.

Selectively, the pair of I type racks are disposed at both ends of a bar so as to be linearly moved, and one of the pair of I type racks has a teeth portion near to the bar, and the other has a teeth portion apart from the bar.

As described above, the CVT is provided with a rotation

center maintaining unit for transmitting the rotational force generated from the power generating device to the rotational bar, the two pairs of I type racks twisted by 90 degrees, and a one-way clutch for converting a linear motion of the two pairs of I type racks into a rotational motion and then transmitting the rotational motion to the rotational cylinder so as to control a transmission ratio of the rotational force generated from the power generating unit in a continuously variable speed changing method and then to transmit the power to a driving shaft.

As the result, the CVT is interposed between the power generating unit and the driving shaft so as to control the power in the continuously variable speed changing method, thereby preventing loss of the power due to a slipping phenomenon. Further, since the transmission ratio is mechanically controlled using the centrifugal force, a sudden acceleration phenomenon is also prevented. Further, the CVT has a simple structure, thereby reducing a size and a weight thereof.

Brief Description of the Drawings Figs. 1-14 are views showing a CVT according to embodiments of the present invention, in which: Fig. 1 is a side view of the CVT in a status that a housing is removed; Fig. 2 is a front view of a rotation center maintaining unit of Fig. 1;

Fig. 3 is a side view of the rotation center maintaining unit of Fig. 2 ; Fig. 4 is a cross-sectional view taken along the line A-A' of Fig. 2; Fig. 5 is a cross-sectional view taken along the line B-B' of Fig. 2 ; Fig. 6 is rear view of the rotation center maintaining unit of Fig. 2 Fig. 7 is a cross-sectional view taken along the line C-C' of Fig. 3; Fig. 8 is a cross-sectional view taken along the line D-D' of Fig. 3; Fig. 9 is a cross-sectional view taken along the line E-E' of Fig. 1 ; Fig. 10 is a cross-sectional view of a rotational cylinder mounted in the housing interposing a thrust bearing therebetween ; Fig. 11 is a perspective view of an I type rack of Fig. 1 ; Fig. 12a is a front view showing an operation state of the CVT at a maximum speed in a status that a ring gear is removed ; Fig. 12b is a front view showing an operation state of the CVT at a minimum speed in a status that a ring gear is removed; Fig. 13a is a cross-sectional view taken along the line G-G' of Fig. 1 ; Fig. 13b is a cross-sectional view taken along the line F-F' of Fig. 1 in a status that a rotational bar is rotated at an angle

of 180° ; and Fig. 14 is a schematic view showing a motion of the I-type rack of Fig. 1.

Best Mode for Carrying Out the Invention Hereinafter, there are in detail described preferred embodiments of the present invention with reference to the accompanying drawings. In the drawings, like elements having the same function are designated by identical reference numerals, and their repeated descriptions are intentionally omitted.

Figs. 1 to 11 are views showing a construction of a CVT according to the present invention. Fig. 1 is a side view of the CVT in a status that a housing is removed. In the CVT, a first helical gear 4 is fixedly coupled to an input shaft 1, which is connected with a power generation device such as an engine (not shown) so as to receive rotational power, in a spline method. An end of the input shaft is connected to a first rotation center maintaining unit 40.

The first helical gear 4 is engaged with a second helical gear 5, which is fixed to a transmission shaft, so as to transmit the rotational power received from the power generating device to a second rotation center maintaining unit 40'.

As shown in Figs. 2 and 3, the first and second rotation center maintaining unit 40 and 40'includes two horseshoe-shaped rotational pendulums 41 and 43 overlapped with each other. One

of the two horseshoe-shaped rotational pendulums 41 and 43 is formed in a male type and the other is formed in a female type.

The male type rotational pendulum 41 is coupled in the female type rotational pendulum 43 so as to be horizontally movable.

Further, the female type rotational pendulum 43 has a first rack 20 at a right side of a groove contacted with the input shaft 1. As shown in Fig. 4, the first rack 20 is engaged with a spur gear 23 formed at the input shaft 1. The male type rotational pendulum 41 has a second rack 21 at a left side of a groove contacted with the input shaft 1. The second rack 21 is engaged with a second spur gear 24 formed at the input shaft 1.

As shown in Fig. 5, the male type rotational pendulum 41 is formed with a radial journal opposite to the input shaft 1.

The journal is enclosed with a slide bearing interposing a bearing metal 27 therebetween. As shown in Fig. 9, the slide bearing 37 is connected with four rollers 36. The four rollers 36 transmit power to the first rack 20.

As shown in Fig. 7, in the female type rotational pendulum 43, there is provided a shock absorber 44 comprised of a lobe rotary so as to absorb shock due to rapid speed change. As shown in Fig.

8, the second rack 21 of the male rotational pendulum 41 is meshed with a fourth spur gear 46. The fourth spur gear 46 is engaged with a third spur gear 45 fixed to a rotary shaft.

In addition, as shown in Fig. 6, at a rear portion of the female type rotational pendulum 43, there is provided an elastic

member such as a leaf spring 48 so as to compensate centrifugal force in a case that a rotational radius of the female type rotational pendulum 43 is small.

Fig. 10 is a partial sectional view of a rotational cylinder 19 mounted in a transmission housing 70 interposing a thrust bearing 18 therebetween.

According to the present invention, there are provided two the rotational cylinders 19. As shown in Fig. 10, in each of the rotational cylinders 19, there are provided four sprag one-way clutches 11 and 12. Sprags are arranged so that all of clutching directions of the eight clutches are the same. At each outer race 11', 12'of the clutches, there are formed helical teeth so as to engaged with the first and second racks 20 and 21.

Further, between the rotational cylinder 19 and a ring gear 15 as an output portion, there is provided an elastic member such as a spring 16 so as to absorb torsional shock.

As shown in Fig. 10, a center portion of the rotational cylinder 19 is empty so as not to obstruct rotation of the rotational bar 60. The rotational bar 60 passes through the two rotational cylinders 19 to be connected with the first and second rotation center maintaining units 40 and 40'at both ends of the transmission, as shown in Fig. 1, respectively interposing the slide bearing 37 therebetween.

Fig. 11 is a perspective view of an I-type rack of Fig. 1.

In the I-type rack, a bar 31 is disposed to be linearly moved by

the four rollers 36. At both ends of the bar 31, there are respectively provided the third and fourth racks 32 and 33. The third and fourth racks 32 and 33 are disposed to be not opposite to each other. That is, the third rack 32 is formed to be near to the bar 31 and the fourth rack 33 is formed to be apart from the bar 31.

Further, at both ends of the bar 31 of the I type rack, there are respectively rollers 35 so that the I type rack can be linearly moved without large friction with respect to a housing 70. As shown in Fig. 9, at the housing, there is formed a groove 71 so that the roller 35 can be moved along a constant track.

In Fig. 1, reference symbols Rl, R2, R3 and R4 designate the I-type racks as described above. The I-type racks are disposed at the rotational bar 60 through the rollers 36 so that RI and R3, and R2 and R4 are respectively twisted by 90 degrees with respect to each other, and Rl and R2 are twisted by 45 degrees.

The third rack 32 having the teeth near to the bar 31 is engaged with the outer race 11'of the clutch near to the bar 31.

The fourth rack 33 having the teeth apart from the bar 31 is engaged with the outer race 12'of the clutch.

Meanwhile, as shown in Fig. 1, two ring gears 15, which are respectively fixed to each rotational cylinder 19 interposing an elastic member such as a spring 16, are connected to an output shaft 2.

Hereinafter, the CVT of the present invention will be fully

described with reference to Figs. 1 to 14.

First, if the CVT is run, the rotational force is generated from the power generating unit such as the engine. The rotational force is transmitted through the input shaft 1 to the male and female type rotational pendulums 41 and 43. At this time, the rotational force, i. e., a torque transmitted to the male and female type rotational pendulums 41 and 43 moves the first and second rack 20 and 21 of the each rotational pendulums 41 and 43, so as to rotate the rotational bar 60 on the smallest rotational radius rO, as shown in Fig. 12a. After a short time, as shown in Fig. 12b, while a load applied to the rotational cylinder 19 is reduced and the centrifugal force of the male and female type rotational pendulums 41 and 43 is increased, the first and second rotation center maintaining units 40 and 40'are rotated on a rotational radius r in which a torque T applied to the input shaft 1 and a centrifugal force f meet an equation"T=f (rl+r2)". Then, the first and second rotation center maintaining unit 40 and 40' transmits the rotational force to the rotational bar 60. The transmitted rotational force is distributed into linear reciprocations showing four sine waves, each of which has a phase difference of 45°, by the four I type racks 32 and 33, i. e., R1, R2, R3 and R4 which are twisted by 90°. As shown in Figs. 13a and 13b, a torque and a speed of the rotational force converted into the sine wave pulse are changed and then united in the rotational cylinder 19 by the one-way clutches 11 and 12. At this

time, the outer races 11' and 12' of the one-way clutches 11 and 12 are respectively rotated in an opposite direction. When the rotational bar 60 passes regions a and a', the one-way clutches are locked and the rotational force is transmitted to the two rotational cylinders 19. At other region except the region a and a', as shown in Fig. 10, the rest three I type racks transmit the power to the two rotational cylinders 19, thereby providing an output indicated by a thick solid line, as shown in Fig. 14.

The rotational force united by the two rotational cylinders 19 is transmitted to the output shaft in a status that a torsional shock component is removed by an elastic member like the spring 16 interposed between the rotational cylinder 19 and the ring gear 15.

Meanwhile, in a conventional CVT as a comparison example, when a belt for connecting a driving pulley and a driven pulley is rotated, centrifugal force is generated. Frictional force between the belt and pulleys is reduced, so that a slipping phenomenon is increased and a load of the transmission is also increased by a hydraulic device for controlling a transmission ratio. Thus, loss of the power is occurred. On the contrary, <BR> <BR> <BR> the CVT comprises a rotation center maintaining unit for receiving the rotational force from the power generating device like an engine and controlling a rotational radius of a rotational bar, two pairs of I type rack, and a one-way clutch for converting a liner reciprocation of the I type racks into a rotational motion

and transmitting the rotational force to a rotational cylinder.

The CVT controls the transmission ratio of the power in a continuously variable speed changing method, and transmits the power to a driving shaft.

According to the present invention, therefore, the slipping phenomenon generated between the belt and the pulleys of the conventional CVT is not occurred. Since the transmission ratio is mechanically controlled using the centrifugal force, there is an advantage in that a sudden acceleration phenomenon is not occurred.

According to the CVT of the present invention, as described above, the CVT is disposed between the power generating device like an engine and the driving shaft so as to control the power in the continuously variable speed changing method and also to precisely transmit the power. Therefore, the slipping phenomenon is prevented between the existing belt and the pulleys.

Since the transmission ratio is mechanically controlled using the centrifugal force, a sudden acceleration phenomenon is also prevented. Further, the CVT has a simple structure, thereby reducing a size and a weight thereof.

While the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art will appreciate that various modifications and substitutions can be made thereto without departing from the spirit and scope of the present invention as set forth in the appended claims.