Abstract:
The toroidal-type continuously variable transmission comprises a hydraulic loading mechanism of an oil pressure type for pushing an input disk toward the disposition side of an output disk to thereby transmit the rotation power of the input disk to the output disk, and a countersunk spring incorporated in a hydraulic chamber formed in the loading mechanism for elastically pushing the input disk toward the disposition side of the output disk. In the toroidal-type continuously variable transmission, there are formed a plurality of slits in the countersunk spring and, when oil is supplied into the inside area of the countersunk spring within the hydraulic chamber by and from a hydraulic pump, the oil in the inside area of the countersunk spring is allowed to flow through the slits into the outside area of the countersunk spring.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a toroidal-type continuously variable transmission that is used, for example, as a transmission mechanism of a vehicle. 
     Conventionally, as a transmission mechanism of a vehicle, there has been developed and used practically a toroidal-type continuously variable transmission. 
     Now, FIG. 6 shows the structure of a half-toroidal-type continuously variable transmission of a double cavity type. This toroidal-type continuously variable transmission comprises, within a housing  1 , a first input disk  2   a  and a first output disk  3   a  respectively forming a first cavity la as well as a second input disk  2   b  and a second output disk  3   b  respectively forming a second cavity  1   b.    
     A pair of power rollers  5  is interposed between the first input and output disks  2   a  and  3   a.  The outer peripheral surfaces of the power rollers  5  are respectively contacted with the traction surfaces  4  of the respective disks  2   a,    3   a.  Between the second input and output disks  2   b,    3   b  as well, there are interposed a pair of power rollers  5 , while the outer peripheral surfaces of these power rollers  5  are also respectively contacted with the traction surfaces  4  of the respective disks  2   b,    3   b.    
     These power rollers  5  are rotatably mounted on their respective trunnions  7  by power roller bearings  6 . The respective trunnions  7  can be swung about their associated trunnion shafts  8 . 
     The traction surfaces  4  of the respective disks  2   a,    2   b,    3   a,    3   b  are each formed as a concave-shaped surface which can be obtained by rotating an arc, the center of which is the trunnion shaft  8 , about an axis extending at right angles to the trunnion shaft  8 . 
     The first input disk  2   a  is mounted on an input shaft  10  in such a manner that it can be moved in the axial direction of the input shaft  10  with respect to the input shaft  10  while it is prevented against rotation by a ball spline  11 . 
     The second input disk  2   b  is mounted on the input shaft  10  by a loading nut in such a manner that it is prevented against rotation by an involute spline  12 . Therefore, the input disks  2   a,    2   b  can be rotated integrally with the input shaft  10 . This input shaft  10  can be driven or rotated by a drive source such as an engine. 
     The output disks  3   a,    3   b  are interposed between the input disks  2   a  and  2   b.  The first output disk  3   a  is disposed opposed to the first input disk  2   a,  while the second output disk  3   b  is disposed opposed to the second input disk  2   b.    
     These output disks  3   a,    3   b  are respectively supported on the input shaft  10  through bearings  13 ,  14  in such a manner that they can be rotated with respect to the input shaft  10 . And, the output disks  3   a,    3   b  are connected to each other by a connecting member  15  and can be rotated in synchronization with each other. On the connecting member  15 , there is disposed an output gear  16 . 
     On the back surface side of the first input disk  2   a,  there is disposed a hydraulic loading mechanism  20  of an oil pressure type. The loading mechanism  20  includes a hydraulic cylinder  21  that is mounted on the input shaft  10  in such a manner that it is opposed to the back surface of the input disk  2   a.  The peripheral wall  21   a  of the hydraulic cylinder  21  is fitted with the outer periphery of the input disk  2   a  in a liquid-tight manner through a seal member  22  in such a manner that it can be slid in the axial direction thereof. Between the hydraulic cylinder  21  and input disk  2   a,  there is formed a hydraulic chamber  25  having a closed structure. 
     The hydraulic cylinder  21  includes a fit cylinder  26  that is disposed in the center portion of the hydraulic cylinder  21  integrally therewith, while the input shaft  10  is fitted into the fit cylinder  26 . And, there is formed an oil supply passage  27  which extends from an inner hole  10   a  formed in the input shaft  10  to the hydraulic chamber  25  within the hydraulic cylinder  21 . That is, by means of the oil supply passage  27 , oil can be pressure fed into the hydraulic chamber  25  through a control valve  29  from a hydraulic pump  28  serving as an oil supply member. 
     In addition, within the hydraulic chamber  25 , there is disposed a countersunk spring  30  serving as pre-load applying means. When the countersunk spring  30  is viewed from the side surface thereof, it has a flat trapezoid shape. When it is viewed from the plane surface thereof, it has a circular ring shape. 
     This countersunk spring  30  is fitted with the outer periphery of the fit cylinder  26  of the hydraulic cylinder  21  and is interposed between the back surface of the input disk  2   a  and the inner surface of the hydraulic cylinder  21  with the plate section thereof inclined such that the inner peripheral edge thereof can be contacted with the back surface of the input disk  2   a  and the outer peripheral edge thereof can be contacted with the inner surface of the hydraulic cylinder  21 . By the way, the countersunk spring  30  may also be disposed in such a manner that the inner peripheral edge thereof can be contacted with the back surface of the hydraulic cylinder  21  and the outer peripheral edge thereof can be contacted with the back surface of the input disk  2   a.  Due to the elastic force of the countersunk spring  30 , there is applied such a preload that allows the respective disks  2   a,    2   b,    3   a,    3   b  and their respective power rollers  5  to be elastically contacted with each other. 
     And, when the input shaft  10  and input disks  2   a,    2   b  are rotated in linking with a drive source such as an engine, oil is supplied from the hydraulic pump  28  into the hydraulic chamber  25  through the control valve  29 . Due to the oil pressure of the thus supplied oil, the first input disk  2   a  is pushed toward the first output disk  3   a.  Since a reaction force which the hydraulic cylinder  21  receives is applied to the input shaft  10 , the second input disk  2   b  is pushed toward the second output disk  3   b.    
     The rotation power of the input disks  2   a,    2   b  is transmitted through the power rollers  5  to the output disks  3   a,    3   b  and, in linking with the output disks  3   a,    3   b,  the output gear  16  is rotated. 
     To change the rotation speed ratio between the input shaft  10  and output gear  16 , the respective power rollers  5  may be swung about their associated trunnion shafts  8 . The swinging movements of the power rollers  5  change the contact positions between the peripheral surfaces of the power rollers  5  and the traction surfaces  4  of the disks  2   a,    2   b,    3   a,    3   b,  thereby changing the rotation speed ratio between the input disks  2   a,    2   b  and output disks  3   a,    3   b,  that is, the rotation speed ratio between the input shaft  10  and output gear  16 . 
     In order to enhance the power transmission efficiency of a transmission, it is important to secure a sufficient contact-pressure between the disks  2   a,    2   b,    3   a,    3   b  and power rollers  5 . In the present transmission, such contact pressure is secured by the oil pressure within the hydraulic chamber  25  as well as by the elastic force of the countersunk spring  30  within the hydraulic chamber  25 . 
     The structure, in which, as described above, the countersunk spring  30  is incorporated into the hydraulic chamber  25  and the contact pressure between the disks  2   a,    2   b,    3   a,    3   b  and power rollers  5  is secured by the oil pressure and the elastic force of the countersunk spring  30 , is long known; for example, such structure is disclosed in U.S. Pat. No. 3,823,613. 
     In case where the countersunk spring  30  is incorporated in the hydraulic chamber  25 , there is an advantage that the wear resistance of the countersunk spring  30  is enhanced, but there arises a problem that the presence of the countersunk spring  30  obstructs the flow of the oil within the hydraulic chamber  25 . 
     That is, the circular-ring-shaped countersunk spring  30  is disposed within the hydraulic chamber  25  in the following manner that the inner peripheral edge of the countersunk spring  30  is contacted with the back surface of the input disk  2   a  and the outer peripheral edge thereof is contacted with the inner surface of the hydraulic cylinder  21 , or, the inner peripheral edge of the countersunk spring  30  is contacted with the inner surface of the hydraulic cylinder  21  and the outer peripheral edge thereof is contacted with the back surface of the input disk  2   a,  while the plate section of the countersunk spring  30  is inclined between the inner surface of the hydraulic cylinder  21  and the back surface of the input disk  2   a;  and, in this state, the countersunk spring  30  presses against the input disk  2   a  elastically. 
     And, oil is supplied through the oil supply passage  27  into the inside area of the countersunk spring  30  within the hydraulic cylinder  21 , and the oil then flows out into the outside area of the countersunk spring  30  within the hydraulic cylinder  21 , thereby generating a given level of oil pressure. 
     However, since the inner peripheral edge of the spring  30  is contacted with the back surface of the input disk  2   a  and the outer peripheral edge thereof is contacted with the inner surface of the hydraulic cylinder  21 , or, the inner peripheral edge of the spring  30  is contacted with the inner surface of the hydraulic cylinder  21  and the outer peripheral edge thereof is contacted with the back surface of the input disk  2   a,  there is formed only a slight clearance between them, so that the oil supplied into the inside area of the countersunk spring  30  is hard to flow out therefrom. As a result of this, the oil supplied into the interior of the hydraulic cylinder  21  suffers from a so called damping action, which delays the response characteristic between a hydraulic force to be controlled by the control valve  29  and a pressing force to be actually applied to the input disk  2   a.  Therefore, in case where torque is caused to vary suddenly, there is a fear that the pressing force can increase excessively to thereby degrade the oil flow efficiency or the pressing force can be short to thereby cause the input disk  2   a  to slip. 
     SUMMARY OF THE INVENTION 
     The present invention aims at eliminating the drawbacks found in the above-mentioned conventional toroidal-type continuously variable transmissions. Accordingly, it is an object of the invention to provide a toroidal-type continuously variable transmission in which, when oil is supplied into a hydraulic chamber, oil in the inside area of a countersunk spring can be made to flow smoothly into the outside area of the countersunk spring to thereby be able to raise the oil pressure of the whole of the hydraulic chamber up to a given level of oil pressure. 
     The above object can be attained by a toroidal-type continuously variable transmission according to the invention. The transmission comprises: an input disk and an output disk disposed such that they are disposed opposed to each other and are concentric with each other; power rollers swingably interposed between the input and output disks; and, a hydraulic loading mechanism of an oil pressure type for pushing the input disk toward the disposition side of the output disk to thereby transmit the rotation power of the input disk through the power rollers to the output disk, wherein the loading mechanism comprises: a hydraulic cylinder disposed on the back surface side of the input disk for defining a hydraulic chamber between the input disk and itself; an oil supply member for supplying oil into the hydraulic chamber to thereby push the input disk; a countersunk spring disposed in the hydraulic chamber and interposed between the back surface of the input disk and the inner surface of the hydraulic cylinder for elastically pushing the input disk toward the disposition side of the output disk; and, an oil flow passage which, when oil is supplied to the inside area of the countersunk spring disposed in the hydraulic chamber by the oil supply member, allows the oil in the inside area of the countersunk spring to flow smoothly into the outside area of the countersunk spring. 
     According to the invention, the oil flow passage may consist of a plurality of slits formed in the countersunk spring. 
     In addition, according to the invention, the oil flow passage may also consist of a plurality of circular-shaped through holes formed in the countersunk spring. 
     Further, according to the invention, the oil flow passage may also consist of a plurality of recessed grooves formed in the portion of the inner surface of a hydraulic cylinder that is to be contacted with the outer peripheral edge of a countersunk spring incorporated into the hydraulic chamber. 
     Furthermore, according to the invention, the oil flow passage may also consist of a plurality of recessed grooves formed in the portion of the inner surface of a hydraulic cylinder that is to be contacted with the inner peripheral edge of the countersunk spring incorporated into the hydraulic chamber. 
     Moreover, according to the invention, the oil flow passage may also consist of a plurality of recessed grooves formed in the portion of the back surface of the input disk that is to be contacted with the outer peripheral edge of a countersunk spring incorporated into the hydraulic chamber. 
     In addition, according to the invention, the oil flow passage may also consist of a plurality of recessed grooves formed in the portion of the back surface of the input disk that is to be contacted with the inner peripheral edge of the countersunk spring incorporated into the hydraulic chamber. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a section view of a first embodiment of a toroidal-type continuously variable transmission according to the invention; 
     FIG. 2 is a section view taken along the line A-A shown in FIG. 1; 
     FIG. 3 is a section view of a second embodiment of a toroidal-type continuously variable transmission according to the invention; 
     FIG. 4 is a section view taken along the line B-B shown in FIG. 3; 
     FIG. 5A is a section view of a third embodiment of a toroidal-type continuously variable transmission according to the invention, FIG. 5B is a sectional views of a main portion according to a modification of the embodiment, FIG. 5C is a sectional views of a main portion according to an another modification of the embodiment, and FIG. 5D is a sectional views of a main portion according to an another modification of the embodiment; and, 
     FIG. 6 is a section view of the structure of a conventional toroidal-type continuously variable transmission. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Now, description will be given below of the preferred embodiments of a toroidal-type continuously variable transmission according to the invention with reference to FIGS. 1 to  5 D. By the way, in these figures, the parts thereof corresponding to those employed in the above-mentioned conventional toroidal-type continuously variable transmission are given the same designations and thus the description thereof is omitted here. 
     FIGS. 1 and 2 respectively show a first embodiment of a toroidal-type continuously variable transmission according to the invention. In the present embodiment, between a hydraulic cylinder  21  and an input disk  2   a,  there is formed a hydraulic chamber  25 ; in the hydraulic chamber  25 , there is disposed a countersunk spring  30 ; and, in the countersunk spring  30 , there are formed a plurality of slits  30   a  which serve as oil flow portions. 
     These slits  30   a,  as shown in FIG. 2, are formed on the plate surface of the countersunk spring  30  in such a manner that they extend in the radial direction of the countersunk spring  30  with the center axis of the countersunk spring  30  as their centers and, through these slits  30   a,  the inside and outside areas of the countersunk spring  30  are allowed to communicate with each other. Each of the slits  30   a  is formed into a U-shape that is opened at the inner periphery of the countersunk spring  30 . By the way, in FIG. 2, the inner peripheral edge of the countersunk spring  30  is contacted with the back surface of the input disk  2   a  and the outer peripheral edge thereof is contacted with the inner surface of the hydraulic cylinder  21 . However, alternatively, the inner peripheral edge of the spring  30  may be contacted with the inner surface of the hydraulic cylinder  21  and the outer peripheral edge thereof may be contacted with the back surface of the input disk  2   a.    
     In the above structure, when oil is supplied from a hydraulic pump  28  into the hydraulic chamber  25  through a control valve  29  and an oil supply passage  27 , oil existing in the inside area of the countersunk spring  30  is allowed to flow smoothly through the slits  30   a  into the outside area of the countersunk spring  30 , thereby being able to quickly increase the oil pressure of the whole of the interior of the hydraulic chamber  25  up to a given level of oil pressure. Therefore, the input disk  2   a  can be pushed with a good response characteristic in accordance with the control of the oil supply by the control valve  29 . Thus, even in case where torque happens to change suddenly, the input disk  2   a  can be pushed properly and accurately with a good response characteristic in accordance with the control by the control valve  29 . 
     The countersunk spring  30  is incorporated in the interior of the hydraulic chamber  25  and, due to this, when it is expanded and contracted, the friction thereof is small, thereby being able to obtain good wear resistance. The direction, in which the input disk  2   a  is pushed out by the oil pressure of the oil within the hydraulic chamber  25 , is a direction in which the flexed condition of the countersunk spring  30  is released. Therefore, there is no possibility that the countersunk spring  30  can be flexed further than the initially set condition thereof, which is advantageous in enhancing the durability of the countersunk spring  30 . 
     The countersunk spring  30  including the slits  30   a,  when compared with a countersunk spring including no slit, is easy to flex, which makes it possible to reduce variations in a load to be generated by variations in the flex amount of the countersunk spring  30 . Therefore, even in case where the oil pressure within the hydraulic chamber  25  rises to thereby move the input disk  2   a  in a direction where it is pushed out from the hydraulic cylinder  21 , a decrease in the pushing force by the countersunk spring  30  is small and thus the hydraulic pump  28  can be driven with correspondingly lowered pressure. 
     Also, since the countersunk spring  30  including the slits  30   a  is small in variations in a load to be generated by variations in the flex amount of the countersunk spring  30 , the countersunk spring  30  can also provide another advantage in facilitating the control of a clearance which is formed between the hydraulic cylinder  21  and input disk  2   a  for incorporation of the countersunk spring  30 . 
     Now, FIGS. 3 and 4 show a second embodiment of a toroidal-type continuously variable transmission according to the invention. In the present embodiment, between a hydraulic cylinder  21  and an input disk  2   a,  there is formed a hydraulic chamber  25 ; in the hydraulic chamber  25 , there is disposed a countersunk spring  30 ; and, in the countersunk spring  30 , there are formed a plurality of circular-shaped through holes  30   b  which serve as oil flow portions. 
     These through holes  30   b  are formed on the plate surface of the countersunk spring  30 , more specifically, on a circumference with the center axis of the countersunk spring  30  as its center in such a manner they are spaced at regular intervals and, through these through holes  30   a,  the inside and outside areas of the countersunk spring  30  are allowed to communicate with each other. By the way, in FIG. 4, the inner peripheral edge of the countersunk spring  30  is contacted with the back surface of the input disk  2   a  and the outer peripheral edge thereof is contacted with the inner surface of the hydraulic cylinder  21 . However, alternatively, the inner peripheral edge of the spring  30  may be contacted with the inner surface of the hydraulic cylinder  21  and the outer peripheral edge thereof may be contacted with the back surface of the input disk  2   a.    
     In the present structure, similarly to the structure employed in the first embodiment, when oil is supplied from a hydraulic pump  28  into the hydraulic chamber  25  through a control valve  29  and an oil supply passage  27 , oil existing in the inside area of the countersunk spring  30  is allowed to flow smoothly through the through holes  30   b  into the outside area of the countersunk spring  30 , thereby being able to quickly increase the oil pressure of the whole of the interior of the hydraulic chamber  25  up to a given level of oil pressure. Therefore, the input disk  2   a  can be pushed with a good response characteristic in accordance as the oil supply is controlled by the control valve  29  and thus, even in case where torque happens to change suddenly, the input disk  2   a  can be pushed properly and accurately with a good response characteristic in accordance with the control by the control valve  29 . 
     Now, FIG. 5A shows a third embodiment of a toroidal-type continuously variable transmission according to the invention In the present embodiment, in the inner surface of a hydraulic cylinder  21 , more specifically, in the portion thereof to be contacted with the outer peripheral edge of a countersunk spring  30  incorporated into a hydraulic chamber  25 , there are formed a plurality of recessed grooves  21   c  which serve as oil flow portions. 
     These recessed grooves  21   c  are disposed in such a manner that they extend from the inside area of the countersunk spring  30  to the outside area thereof as well as are arranged in parallel to each other at a given pitch along the outer peripheral edge of the countersunk spring  30 . 
     However, in this case, as shown in FIG. 5B recessed grooves  2   c  serving as the oil flow passages may be formed in the portion of the back surface of the input disk that is to be contacted with inner peripheral edge of the countersunk spring  30  incorporated into the hydraulic chamber  25 . Note that an outer peripheral surface of the fit cylinder  26  of the hydraulic cylinder  21  is provided with a plurality of slits  26   a  that extending in the axial direction. 
     In the present structure, when oil is supplied from a hydraulic pump  28  into the hydraulic chamber  25  through a control valve  29  and an oil supply passage  27 , oil existing in the inside area of the countersunk spring  30  is allowed to flow smoothly through the recessed grooves  21   d  into the outside area of the countersunk spring  30 , thereby being able to quickly increase the oil pressure of the whole of the interior of the hydraulic chamber  25  up to a given level of oil pressure. Therefore, the input disk  2   a  can be pushed with a good response characteristic in accordance as the oil supply is controlled by the control valve  29  and thus, even in case where torque happens to change suddenly, the input disk  2   a  can be pushed properly and accurately with a good response characteristic in accordance with the control by the control valve  29 . 
     Also, in the present embodiment, the countersunk spring  30  is disposed such that the inner peripheral edge of the countersunk spring  30  is contacted with the back surface of the input disk  2   a  and the outer peripheral edge thereof is contacted with the inner surface of the hydraulic cylinder  21 . However, alternatively, the countersunk spring  30  may also be disposed such that the inner peripheral edge of the countersunk spring  30  is contacted with the inner surface of the hydraulic cylinder  21  and the outer peripheral edge thereof is contacted with the back surface of the input disk  2   a.    
     In this case, as shown in FIG. 5C recessed grooves  21   c  serving as the oil flow passages may be formed in the portion of the inner surface of the hydraulic cylinder  21  that is to be contacted with the outer peripheral edge of the countersunk spring  30  incorporated into the hydraulic chamber  25 , or, as shown in FIG. 5D recessed grooves  2   d  serving as the oil flow passages may be formed in the portion of the back surface of the input disk  2   a  that is to be contacted with inner peripheral edge of the countersunk spring  30  incorporated into the hydraulic chamber  25 . 
     By the way, according to the invention, there may be formed recessed grooves in the portion of the back surface of an input disk that is to be contacted with the inner peripheral edge of a countersunk spring, and oil in the inside area of the countersunk spring may be allowed to flow into the outside area of the countersunk spring through the thus formed recessed grooves. The essential thing is that oil flow portions to allow the oil existing in the inside area of a countersunk spring to flow smoothly therethrough into the outside area of the countersunk spring are formed in any proper portion of the input disk. 
     Also, it goes without saying that the present invention can be applied not only to a toroidal-type continuously variable transmission of a double cavity type but also to a toroidal-type continuously variable transmission of a single cavity type. 
     As has been described heretofore, according to the invention, when oil is supplied into the hydraulic chamber by the oil supply means, the oil in the inside area of the countersunk spring is allowed to flow smoothly into the outside area of the countersunk spring through the oil flow portions and, therefore, the whole of the interior of the hydraulic chamber can be raised up to a given level of oil pressure and thus the input disk can be pushed properly and accurately. 
     While there has been described in connection with the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is aimed, therefore, to cover in the appended claim all such changes and modifications as fall within the true spirit and scope of the invention.