GB2231926A

GB2231926A - Continuously variable friction transmission

Info

Publication number: GB2231926A
Application number: GB9007554A
Authority: GB
Inventors: Takashi Takahashi
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-04-19
Filing date: 1990-04-04
Publication date: 1990-11-28
Anticipated expiration: 2010-04-04
Also published as: GB2231926B; DE4012060A1; GB9007554D0; JPH02278048A

Description

CONTINUOUS VARIABLE TRANSMISSION This invention relates to a continuous

variable transmission, and particular, to a continuous variable transmission of traction system capable of transmitting a large power equivalent to that of a gear system.

A continuous variable transmission of traction system is to generate traction force by bringing rollers into pressure-contact with rotary discs and using frictional force based on the product F x p of pressure-contact force P between the rollers and the rotary discs and the frictional coefficients - p. Such continuous variable transmission has an advantage that the mechanism is simpler than a gear mechanism and can transmit the power smoothly without pulsation. This system, on the other hand, has had a disadvantage that it is more liable to generate slipping at the pressure- contact faces as the transmitted power becomes larger since frictional force obtained from the product of the frictional coefficients p and the pressurecontact force F at the pressure contact faces is traction force, and that this system can, as a result, not been used for transmitting large power.

An object of the present invention is to provide a continuous variable transmission capable of transmitting smooth power by the adoption of a traction system.

Another object of the invention is to provide such continuous variable transmission of a traction system capable of generating a large traction force in spite of its traction feature, and also of transmitting a large power.

To attain the above objects, this invention provides a construction in which at least one roller is sandwitched in the presence of oil between at least two sheets of rotary discs facing each other with a distance therebetween in the axial directions thereof and the roller is pressurized by a pressurizing mechanism from the outside of the rotary discs, wherein the roller is interconnected to one of input and output shafts through an intermediate gear group, and the two sheets of rotary discs are interconnected to the other of the input and output shafts through another intermediate gear group. In the above construction, when the rollers sandwitched between the rotary discs through oil are pressurized strongly by the pressurizing mechanism, an extreme pressure is generated on narrow contact faces between is the rotary discs and the rollers to generate a large frictional force, thereby generating a large traction force to transmit a large power to the output shaft from the input shaft.

A continuous variable transmission according to this invention is obtained by utilizing the results of research on a recent tribology. Namely, according to a recent tribology, especially to elastohydrodynamic lubrication, it is apparent that the frictional coefficient increases to 3 - 4 times instantaneously when an extreme pressure is given between two faces in contact with each other in the presence of special lubrication oil. It is possible to transmit a large power in spite of its traction feature by combining the property of such lubrication oil with the above construction. As the lubrication oil having the above function and effect, for example, "SANTOTRAC"nYade by NIPPON OIL CO., LTD. may be used.

Fig. 1 is a vertical sectional view of a continuous variable transmission according to an embodiment of the invention; Fig. 2 is a sectional view taken on line II - II in Fig. 1; Fig. 3 is a vertical sectional view of a continuous variable transmission according to another embodiment of the invention; and Fig. 4 is a schematic view of a continuous variable transmission according to another embodiment of the invention.

In the continuous variable transmission shown in Figs. 1 and 2, numeral 1 denotes a casing, in which an input shaft 2 and an output shaft 3 are supported to rotate freely with their axial directions aligned with each other. Inside this casing 1, rotary discs 4a, 4b each having a flat annular face are arranged in a coaxial manner with the shafts 2, 3. The disc 4a is supported on the input shaft 2 to rotate freely through a bearing 31 and to move freely in the axial direction, while the disc 4b is spline-fitted directly to the output shaft 3 to move freely in the axial direction.

Two rollers 5, 5 are sandwitched between the above two rotary discs 4a, 4b via the lubrication oil such as "SANTOTRAC" 10 entioned before. These two rollers are disposed at an equal interval of 180 degree in a circumferential direction around the rotary axis of the discs. Though two rollers 5, 5 are provided in the embodiment shown in Figs. 1 and 2, three rollers 5 may tl be disposed at equal intervals of 120 degree, and otherwise four or more rollers 5 may be disposed similarly.

Ring type bellows 20a, 20b are arranged as a pressurizing mechanism via pressurizing plates 21a, 21b outside both the rotary discs 4a, 4b. The bellows 20a, 20b elongate in an axial direction due to a work oil supplied from an oil pressure source 9 to apply opposing loads in an axial direction to the two rotary discs 4a, 4b, thereby strongly pressurizing the rollers 5 sandwitched by the rotary discs 4a, 4b. Since the rollers 5 and the rotary discs 4a, 4b are in contact with each other at extremely small areas resembling a line contact, when the load of the pressurizing mechanism is applied thereto as mentioned in the above, an extreme pressure is generated at the contact faces in the presence of oil to increase the frictional coefficients widely, generating a large traction force.

The rollers 5 are spline-fitted to the rotary shaft 6, respectively, while the shaft 6 extends in a radial direction so as to cross the rotary shafts of the rotary discs 4a, 4b orthogonally. As shown in Fig. 2, a ball screw 11 is provided in parallel with the rotary shaft 6. Holders 10 are threadably fitted, respectively, to two screwed portions on the ball screw 11, while the rollers 5 are retained by the holders 10, respectively. The screwed directions of two screwed portions are opposite to each other, and therefore, when the ball screw 11 is operated to rotate by means of a handle 12, the holders 10 are moved in the opposite directions to each other in an axial direction, whereby the rollers 5 are moved in the opposite direction to each other along the rotary shaft 6.

The rotary shaft 6 is interconnected with the input shaft 2-via gears 13, 14 to allow a power to be inputted from this input shaft 2. The power inputted to the rotary shaft 6 from the input shaft 2 drives the rollers 5 to rotate the two rotary discs 4a, 4b in contact with the rollers 5 in opposite directions to each other by-a large frictional force based on the tribology theory mentioned before. The power transmitted to one rotary discs 4a is transmitted to a gear 15 fixed to the rotary disc 4a and further transmitted to the output shaft 3 via gears 16, 17. on the other hand, the power transmitted to the other rotary disc 4b is transmitted to the output shaft 3 directly and outputted to the output shaft 3 after being integrated with the power from the rotary disc 4a.

In such a power transmission as mentioned above, the output from the output shaft 3 changes in A speed steplessly since the rotation ratio of the rollers 5 to the rotary discs 4a, 4b changes when the rollers 5 are moved along the rotary shaft 6 in the radial direction of the rotary discs 4a, 4b through operation 5 of the handle 12.

As in the above, in the above continuous variable transmission, an extreme pressure is generated between the rotary discs 4a, 4b and the rollers 5 due to the pressurization by the bellows 20a, 20b, and thus, an extremely large traction force is generated in combination with the property of oil mentioned before. This traction force is generated at both surfaces of the rollers 5 and it will be doubled if integrated at the output shaft 3. It is therefore possible to transmit an extremely large power even with a traction system.

In this invention, a pressurizing mechanism is not limited to only bellows and a means using pistons 20a, 20b actuated by a work oil as in Fig. 3 may be used. An embodiment in Fig. 3 is different from the first embodiment in that the mechanism of bellows in the first embodiment is replaced with the mechanism of pistons, the rotary disc 4a and a rotary shaft 7 are meshed with each other through a spline and the rotary shaft 7 and the gear 15 are integrated with each other. Other than these, the construction of the embodiment in Fig. 3 is the same as the first embodiment substantially.

As the pressurizing mechanism used in the invention, belleville springs, coil springs, leaf springs, and the like may be used.

Fig. 4 is a continuous variable transmission showing another embodiment of the invention.

in this embodiment, three rotary discs 4a, 4b, 4c are provided, and between the rotary discs 4a, 4b adjacent to each other and between the rotary discs 4b, 4c, a plurality of rollers 5 are interposed in the presence of oil, respectively. in this way the mechanism of the first embodiment is arranged in the form of continuous two stages. These three sheets of rotary discs 4a, 4b, 4c generate a large traction force at each stage according to the tribology theory when the load is applied by means of the bellows 20a, 20b from both outsides. Since the forces are merged into one at the output shaft 3 via the gear 15, gears 16 and 17, an extreme large power can be transmitted.

Namely, in this embodiment, if the number of rollers arranged at portions between the rotary discs in each stage is determined to be three, each roller will have two contact points, resulting in that there will be 3 x 2 x 2 = 12 in total as a whole. The traction forces based on the 12 contact points are combined into one at one output shaft. It is thus possible to transmit an extremely large motive power.

According to the invention, four or more rotary discs may also be combined, and with the multistage structure of mechanism by the increase of the number of such rotary discs, the power transmission capacity can be improved.

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Claims

A continuous variable transmission comprising at least two rotary discs which face each other with a space therebetween in the axial direction and are supported to move freely; at least one roller which is sandwitched between said rotary discs adjacent to each other in the presence of oil, has a rotary shaft in the direction perpendicular to the axial direction of said rotary discs, and is supported to move freely in the direction of the rotary shaft; a pressurizing mechanism applying its load to said rotary discs so as to compress said roller strongly; is an input shaft; and an output shaft, said rotary discs being interconnected with one of said input and output shafts, said roller being interconnected with the other of said input and output shafts.
2. A continuous variable transmission according to claim 1, wherein the number of said rotary discs is two.
3. A continuous variable transmission according to claim 1, wherein the number of said rotary discs is three or more.

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4. A continuous variable transmission according to claim 1, wherein the number of said rollers sandwitched between said two rotary discs adjacent to each other is two which are arranged at an equal angular interval around the rotary axis of said rotary discs.
5. A continuous variable transmission according to claim 1, wherein the number of said rollers sandwitched between said two rotary discs adjacent to each other is three which are arranged at equal angular intervals around the rotary axis of said rotary discs.
6. A continuous variable transmission according to claim 1, wherein said pressurizing mechanism is composed of bellows to which a work oil is supplied.
7. A continuous variable transmission according to claim 1, wherein said pressurizing mechanism is composed of a piston mechanism actuated by work oil.
8.

A continuous variable transmission substantially as hereinbefore described with reference to and as shown in Figures 1 and 2 or Figure 3 or Figure 4 of the accompanying drawings.
9. Any novel integer or step, or combination of integers or steps, hereinbefore described and/or shown in the accompanying drawings, irrespective of whether the present claim is within the scope of, or relates to the same or a different invention from that of, the preceding claims.

Published 1990 at The Pa-entOfice.S.aleHousc-66 71 High Rolborn, LondorWC1R4TP.F-arther copies maybe obtained from The Patent Office Sales Branch. St May Cray. Orpington. Kent BR5 3RD Printed bY Multiplex techniques ltd. St Mary Cray. Kent. Con. 1 87