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Title:
CONTINUOUSLY VARIABLE TRANSMISSION
Document Type and Number:
WIPO Patent Application WO/2015/105424
Kind Code:
A1
Abstract:
Device for providing a variable transmission ratio between an input shaft and an output shaft, wherein the device comprises a cone-shaped first revolving body (I). Also provided are coupling means for connecting the input shaft and/or the output shaft at variable positions to the surface of the cone-shaped first revolving body (I). The coupling means comprise a cylindrical second revolving body (II) in combination with a third revolving body (III) placed operatively between the first revolving body and the second revolving body. Positioning means (P) are provided for positioning the third revolving body (III) at any desired position relative to the outer surfaces of the cone-shaped first revolving body (I) and the cylindrical second revolving body (II).

Inventors:
VAN DER HOEVEN WILLEM (NL)
Application Number:
PCT/NL2015/050017
Publication Date:
July 16, 2015
Filing Date:
January 12, 2015
Export Citation:
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Assignee:
HOWEVA B V (NL)
International Classes:
F16H15/18; F16H3/42; F16H15/40
Foreign References:
JPH1163140A1999-03-05
Other References:
DANIEL H: "IST EIN STUFENLOSES ECHT FORMSCHLUESSIGES GETRIEBE MOEGLICH?", ANTRIEBSTECHNIK, VEREINIGTE FACHVERLAGE, MAINZ, DE, vol. 23, no. 5, 1 January 1984 (1984-01-01), pages 49/50, XP001160734, ISSN: 0722-8546
JAHR A: "ES IST KEIN FORMSCHLUESSIGES STUFENLOSES GETRIEBE MOEGLICH", ANTRIEBSTECHNIK, VEREINIGTE FACHVERLAGE, MAINZ, DE, vol. 28, no. 1, 1 January 1989 (1989-01-01), pages 45/46, XP001160727, ISSN: 0722-8546
Attorney, Agent or Firm:
JILDERDA, Anne Ayolt (Postbus 13363, LJ Utrecht, NL)
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Claims:
Claims

1. Device for providing a continuously or stepwise variable transmission ratio between a rotatable input shaft and a rotatable output shaft, comprising a first revolving body which is connected to a one of the input shaft and output shaft and which is rotatable about a first longitudinal axis and comprises a cone-shaped surface, a second revolving body which is connected to another of the input shaft and the output shaft and which is rotatable about a second longitudinal axis, a third revolving body which is in engagement with the first revolving body at the position of the cone-shaped outer surface and with the second revolving body in order to provide a transmission therebetween, and comprising positioning means able and configured to displace the third revolving body at least in axial direction relative to the cone-shaped surface of the first revolving body in order to mutually connect the input shaft and the output shaft at a variable position on the cone- shaped surface of the first revolving body, characterized in that the second revolving body comprises a cylindrical surface with an at least substantially constant diameter, and that the third revolving body is in engagement with the second revolving body at the position of the cylindrical surface.

2. Device as claimed in claim 1, characterized in that the cylindrical surface of the second revolving body, as seen in longitudinal direction, runs parallel to a direction of the cone-shaped surface of the first revolving body, likewise as seen in longitudinal direction, and that the third revolving body engages on the one side on the cone-shaped surface of the first revolving body and on the other on the cylindrical surface of the second revolving body.

3. Device as claimed in claim 1 or 2, characterized in that the cylindrical surface of the second revolving body maintains an at least substantially fixed distance to the cone- shaped surface of the first revolving body.

4. Device as claimed in claim 3, characterized in that the longitudinal axis of the first revolving body and the longitudinal axis of the second revolving body lie at an angle in a common plane, this angle being roughly equal to half an apex angle of the cone-shaped surface of the first revolving body, and that the third revolving body is placed between the first revolving body and the second revolving body.

5. Device as claimed in claim 2, 3 or 4, characterized in that the second revolving body has a constant diameter and a rotation axis thereof runs parallel to the direction of the cone-shaped outer surface, as seen in longitudinal direction, of the first revolving body.

6. Device as claimed in any of the claims 1 to 5, characterized in that the third revolving body, positionable by said positioning means, is situated in an area substantially between the first revolving body and the second revolving body and engages here on the first revolving body on one side relative to its rotation axis and engages on the second revolving body on the other side relative to its rotation axis.

7. Device as claimed in any of the claims 1 to 5, characterized in that the third revolving body, positionable by said positioning means, is situated in an area substantially on the same side of the first revolving body and the second revolving body, and on said side engages on both the first revolving body and the second revolving body.

8. Device as claimed in one or more of the foregoing claims, characterized in that the first revolving body and the third revolving body engage each other by means of mutually engaging gears.

9. Device as claimed in claim 8, characterized in that the first revolving body and the third revolving body each comprise a bevel gear, particularly in the form of a cone-shaped or hypoid gear or in the form of a worm and worm wheel configuration.

10. Device as claimed in one or more of the foregoing claims, characterized in that the second revolving body and the third revolving body engage each other by means of mutually engaging gears. 1 1. Device as claimed in claim 10, characterized in that the second revolving body and the third revolving body each comprise a bevel gear, in particular in the form of a cone- shaped or hypoid gear or in the form of a worm and worm wheel configuration.

12. Device as claimed in one or more of the foregoing claims, characterized in that the first revolving body and the second revolving body each comprise a bevel gear, in particular in the form of a cone-shaped or hypoid gear or in the form of a worm and worm wheel configuration.

13. Device as claimed in claim 12, characterized in that the bevel gear of the first revolving body and/or of the second revolving body is oriented at an angle relative to the longitudinal axis thereof, in particular at an angle of about 45 degrees.

14. Device as claimed in claim 13, characterized in that a gearing angle of the gear of the first revolving body and a gearing angle of the gear of the second revolving body either each make a corresponding acute angle relative to the respective longitudinal axis thereof or an acute angle and a corresponding obtuse angle.

Description:
CONTINUOUSLY VARIABLE TRANSMISSION

The present invention relates to a device for providing a continuously or stepwise variable transmission ratio between a rotatable input shaft and a rotatable output shaft, comprising a first revolving body which is connected to a one of the input shaft and output shaft and which is rotatable about a first longitudinal axis and comprises a cone-shaped surface, a second revolving body which is connected to another of the input shaft and the output shaft and which is rotatable about a second longitudinal axis, a third revolving body which is in engagement with the first revolving body at the position of the cone-shaped outer surface and with the second revolving body in order to provide a transmission therebetween, and comprising positioning means able and configured to displace the third revolving body at least in axial direction relative to the cone-shaped surface of the first revolving body in order to mutually connect the input shaft and the output shaft at a variable position on the cone-shaped surface of the first revolving body.

Such a transmission device is also referred to as a continuously variable transmission (CVT) and provides the option of varying a transmission ratio between the input shaft and output shaft in continuous or stepwise manner in order to thus enable optimal adjustment of a drive torque or rotation speed of the output shaft to a power and rotation speed of a drive, in particular a drive motor, of the input shaft. Such a transmission device is known from Tnternational patent application WO 95/33146. This known transmission device comprises two revolving bodies oriented in opposite directions relative to each other and each having a cone-shaped surface, between which a third revolving body is displaceable so as to provide a transmission between the two revolving bodies at a variable position between the two surfaces. A ratio between a diameter of the first and second revolving body at the chosen position here defines a transmission ratio between an input shaft and an output shaft of the known transmission device. Although this provides per se a transmission device with a particularly wide transmission range, it has been found problematic in practice to realize the known transmission device. It is important to keep tolerance and friction in the transmission device as low as possible in order to limit transmission losses to a minimum. The present invention therefore has for its object, among others, to provide a transmission device in which transmission losses are counteracted.

In order to achieve the stated object a device of the type described in the preamble has the feature according to the invention that the second revolving body comprises a cylindrical surface with an at least substantially constant diameter, and that the third revolving body is in engagement with the second revolving body at the position of the cylindrical surface. For the second revolving body use is thus simply made of a cylinder surface for the transmission with the first revolving body. It has been found that the transmission device in this form can be constructed in relatively simple manner and also results in relatively small transmission losses.

According to the invention the device comprises in a particular embodiment a cone-shaped first revolving body which is rotatable around its longitudinal axis and which is on the one side connected directly or indirectly to the input shaft and on the other side connected directly or indirectly to the output shaft, wherein coupling means are also provided which are configured to connect the input shaft and/or the output shaft at variable positions to the surface of the cone-shaped first revolving body.

A preferred embodiment of the device according to the invention is characterized here in that the cylindrical surface of the second revolving body, as seen in longitudinal direction, runs parallel to a direction of the cone-shaped surface of the first revolving body, likewise as seen in longitudinal direction, and that the third revolving body engages on the one side on the cone-shaped surface of the first revolving body and on the other on the cylindrical surface of the second revolving body. According to another further development, the second revolving body has a constant diameter and the rotation axis thereof runs parallel to the direction of the outer surface, as seen in longitudinal direction, of the cone-shaped first revolving body.

In a further particular embodiment the device according to the invention has the feature that the third revolving body, positionable by said positioning means, is situated in an area substantially between the first revolving body and the second revolving body and engages here on the first revolving body on one side relative to its rotation axis and engages on the second revolving body on the other side relative to its rotation axis. With a view hereto a further preferred embodiment of the device according to the invention has the feature that the cylindrical surface of the second revolving body maintains an at least substantially fixed distance to the cone-shaped surface of the first revolving body. A third revolving body with a fixed diameter can thus be applied in particularly practical manner in order to bridge the thus likewise fixed distance between the first and second revolving bodies. This latter can be realized in particularly effective manner in a further preferred embodiment of the device which is characterized according to the invention in that the longitudinal axis of the first revolving body and the longitudinal axis of the second revolving body lie at an angle in a common plane, this angle being roughly equal to half an apex angle of the cone-shaped surface of the first revolving body, and that the third revolving body is placed between the first revolving body and the second revolving body. This is particularly achieved in a further embodiment of the device according to the invention wherein the second revolving body has a constant diameter and a rotation axis thereof runs parallel to the direction of the cone-shaped surface of the first revolving body as seen in longitudinal direction.

As alternative a particular embodiment of the device according to the invention is characterized in that the third revolving body, positionable by said positioning means, is situated in an area substantially on the same side of the first revolving body and the second revolving body, and on said side engages on both the first revolving body and the second revolving body. This embodiment has the advantage that, despite the cone-shaped surface of the first revolving body on the one side and a cylindrical surface of the second revolving body on the other, the two revolving bodies can nevertheless be oriented with their longitudinal axes parallel to each other. A drive line in which the device is incorporated thus retains the same direction at the position thereof.

The different co-acting revolving bodies can engage each other by means of for instance outer surfaces with sufficient friction pressing against each other with sufficient pressure, whereby the relative slip is minimized, although particularly when greater forces have to be transmitted by the device it is preferably envisaged that the different co-acting revolving bodies engage each other by means of mutually engaging gears, preferably bevel gears, for instance in the form of a cone-shaped or hypoid gear or in the form of a worm and worm wheel configuration.

A particular embodiment of the device according to the invention has in this latter respect the feature that the first revolving body and the third revolving body engage each other by means of mutually engaging gears, and more particularly that the first revolving body and the third revolving body each comprise a bevel gear, particularly in the form of a cone- shaped (conical) or hypoid gear or in the form of a worm and worm wheel configuration. A further particular embodiment of the device according to the invention is characterized in that the second revolving body and the third revolving body engage each other by means of mutually engaging gears, and more particularly that the second revolving body and the third revolving body each comprise a bevel gear, in particular in the form of a cone-shaped (conical) or hypoid gear or in the form of a worm and worm wheel configuration.

In a further preferred embodiment the device according to the invention has the feature that the first revolving body and the second revolving body each comprise a bevel gear, in particular in the form of a cone-shaped or hypoid gear or in the form of a worm and worm wheel configuration, particularly such that the bevel gear of the first revolving body and/or second revolving body is oriented at an angle relative to the longitudinal axis thereof, in particular an angle of about 45 degrees. It is possible here that a gearing angle of the gear of the first revolving body and a gearing angle of the gear of the second revolving body either each make a corresponding acute angle relative to the respective longitudinal axis thereof or an acute angle and a corresponding obtuse angle. The bevel gears thus lie either mutually in line or are oriented in more or less opposite directions.

The invention will now be further discussed with reference to figures 1-15B, in which different practical implementations are shown schematically. The figures are purely schematic here and not drawn to scale. Some dimensions in particular may be exaggerated to greater or lesser extent for the sake of clarity.

The field of application of the device according to the invention comprises mechanical driving of vehicles including racing cars, all-terrain vehicles, trucks and passenger cars, agricultural vehicles, ships, aircraft, trains and the like. The device can however also be utilized to realize a continuously or stepwise variable transmission ratio between an optionally motorized drive and an output operating shaft.

Mounting the transmission device on for instance a motor which provides a constant rotation speed here, for instance an electric motor or combustion engine, makes it possible by means of such a transmission device to control an output rotation speed and speed of revolution without interrupting the driving. By increasing the rotation speed of the motor a rapid driving can thus be realized, or a high drive torque can be transmitted.

An important part of the transmission device - see figure 1 - is a first revolving body A which tapers partially in cone-shaped or conical manner, referred to separately and jointly in the present application as cone-shaped, and which thus has a cone-shaped engaging surface I, designated in the figures with both the letter A and with reference numeral I. Due to the difference in diameter at left and right there is a difference in circumference, and so a difference in circumferential speed. When - as figure 2 illustrates - A is driven in a rotating movement, B, designated here as the third revolving body III, begins to rotate and B in turn drives C, designated here as the second revolving body II. The third revolving body B is for instance covered with a hard rubber roll. When the third revolving body B is displaced by means of a selector fork, part of the above-mentioned positioning means P, toward the relatively wide outer end of conical surface A, the rotation speed of C will increase; if the third revolving body B is displaced (shifted) toward the relatively narrow outer end of conical surface A, the rotation speed will then decrease. This results in a variable transmission. The more oblique the angle of inclination (gearing angle) of the cone-shaped revolving surface A becomes - as illustrated in figures 3A-3C - the wider the range over which the transmission ratio can be varied. The same applies for a longer revolving surface A at a given gearing angle.

Figure 4 illustrates that B is displaceable to the left or right over a gear shaft. The rotating movement of A is transmitted by B to the shaft. The shaft will rotate more quickly or slowly by displacing B forward or rearward on the shaft (i.e. moving it to the left or the right). The shaft can conversely also be driven, and the rotation thereof transmitted by means of B to A as subsequently driven part.

In foregoing examples the mutual engagement of the revolving bodies is imparted wholly or partially by means of friction. Use will be made in the following, of a complete gear transmission, the principle of which is otherwise the same as that of a flat (non-toothed), optionally tapering friction roller as illustrated in the foregoing.

Figures 5 and 6 show embodiments with toothed revolving bodies A (I), B (III) and C (II). A conical gear A is rotated. This results in a rotating movement on gear shaft B. This drives gear shaft C. It is possible to opt to also drive C2 in order to thus realize a twin drive. This is another uniform rotating movement. A difference in circumference and circumferential speed is transmitted from A to B and subsequently to C I and/or C2 by displacing gear shaft B in a linear movement, see arrows in the drawing. A higher or lower rotation speed of gear shaft C I and/or C2 can hereby be realized. CI can also be driven (omit C2), so that shaft A will be the output drive shaft.

Figures 7A-7C illustrate that a range of the transmission ratio will be greater or smaller with a greater or smaller gearing angle (angle of inclination). The same applies for a longer or shorter cone-shaped surface on the first revolving body.

Figure 8 shows an exemplary embodiment with a twin drive. Figures 9A-9C illustrate that in this embodiment the deceleration or acceleration will also be greater or smaller at a greater or smaller gearing angle (angle of inclination) due to the choice then made. It is also possible to change the length of the bevel gear.

In the embodiments of figures 5, 6 and 8 the elongate, more or less shaft-like third revolving body B (III), always positionable by the positioning means (P), is situated in an area substantially on the same side (for instance on the upper side) of the first revolving body A (I) and the second revolving body C (II), and engages here on one side relative to its rotation axis (for instance on the underside) on the first revolving body A (I) and engages on the same side relative to its rotation axis on the second revolving body C (II).

Figures 10- 13 show embodiments wherein the (for instance pinion-like) third revolving body B (III), always positionable by said positioning means (P), is situated in an area substantially between the first revolving body A (I) and the second revolving body C (II) and engages here on one side relative to its rotation axis on the first revolving body A (I) and engages on the other side relative to its rotation axis on the second revolving body C (II).

When gear A (tapering form) begins to rotate, gear B will co-rotate. This then drives gear shaft C. The rotation speed of C increases or decreases by moving gear B linearly forward or rearward (i.e. to the left or right) in the groove. The rotation speed of C can thus be varied continuously in relation to A. Gear B here rotates without (its own) drive and serves only as satellite wheel for transmitting the rotating movement between A and B. It is also possible to realize more shafts C in the drive. Gear shaft C can also drive, whereby A becomes the driven gear via B. It is also possible to have a combustion engine or electric motor operate at uniform or constant speed and to move gear B to the left or right, whereby a varying rotation speed results and hereby a likewise varying travel speed of a vehicle driven thereby.

Figure 1 1 illustrates a right-angled drive comprising a transmission device according to the invention. In the case of a motorbike or scooter this is for instance the drive by means of a motor, and in the case of a cycle the crankshaft. When C is set into rotation and gear B is moved downward from the top, the rotating movement of A will increase. A drives the wheel shown on the right in the drawing via the right angle gear.

Figure 12 shows a twin drive. Gear CI and gear C2 are driven independently of each other here by A. When gear B l or B2 is shifted, the circumferential speed of gear C I and C2 changes. When gear A (tapering form) is set into rotation, gear B will co-rotate and then in turn drive gear shaft C. The rotation speed of C also becomes greater or smaller than A by moving gear B linearly to the left or right in the groove form. A higher or lower circumferential speed is hereby obtained. Gear B also rotates here without its own drive, and B serves only to transmit the rotating movement between A and B. It is also possible to realize more shafts C in the drive, and gear shaft C can also drive, whereby A becomes the driven output gear via B.

Figure 13 illustrates an embodiment in which the device is used for a stepwise change of the transmission ratio, here for instance in five steps. When A is set into rotation, B is driven and subsequently drives C. A changed rotation speed is obtained when gear B is displaced in the groove running parallel to the oblique side of A and C. As figure 13 illustrates, it is also possible to displace B (free-rotating gear) to fixed positions, for instance in the positions 1 -2-3-4-5. Fixed gear ratios are hereby obtained, just as in the case of a traditional gearbox, but without interruption of the clutch and drive. It is thus possible to change gear directly and maintain the rotation speed. It is possible to realize this movement automatically, whereby a variable automatic gearbox is created.

Figure 14 once again illustrates that, when A begins to rotate with a uniform rotating movement, this is transmitted to B. This transmits the rotation to rotation shaft C. Rotation shaft C will begin to rotate more quickly or slowly by moving B - see direction arrows P - due to the difference in circumference.

It is noted that in the devices as shown in the figures the second revolving body II has a constant diameter and the rotation axis thereof runs parallel to the direction of the outer surface, as seen in longitudinal direction, of the cone-shaped first revolving body I.

A gear on the cylindrical outer surface of the second revolving body can take a right- angled form, as for instance shown in figure 10. A bevel gear can instead also be applied on the second revolving body. This is shown by way of illustration in figures 15A and 15B. A bevel gear, in particular a spiral (screw) gear, can be applied here on the second revolving body substantially corresponding to that on the first revolving body, as shown in figure 1 A. It is however also possible to provide bevel gears on both revolving bodies which conversely have more or less opposite directions, as shown in figure 1 B. A gearing angle of the gear of about 45 degrees relative to the respective longitudinal axis is found in both cases to produce good results.

Although the invention has been further elucidated above solely on the basis of a finite number of embodiments, it will be apparent that the invention is by no means limited thereto. On the contrary, many variations and embodiments are still possible within the scope of the invention for a person with ordinary skill in the art.