The foregoing and further objects, features and advantages of the invention will become apparent from the following description of preferred embodiments with reference to the accompanying drawings, wherein like numerals are used to represent like elements and wherein:
Example embodiments of the invention will now be described with reference to the accompanying drawings. Like or corresponding members in the drawings will be denoted by the same reference numerals.
Referring to
The case body 12 includes an inner peripheral surface 12c that extends around a center axis 201 which is a virtual axis. This center axis 201 is the rotational center of the UD planetary gear set 61 and the Ravigneaux type planetary gear set 64.
The friction plates 13 are fixed to the case body 12. The friction plates 14 are fixed to the planetary gear side (for example, to the outer peripheral surface of a ring gear of the planetary gear set). The friction plates 13 and the friction plates 14 are fixed to the case body 12 and the planetary gear side, respectively, so as to be able to move in the axial direction of the center axis 201 but not able to rotate in the circumferential direction around the center axis 201. The friction plates 13 and 14 are ring-shaped and extend in a circle to the inside of the inner peripheral surface 12c. The friction plates 13 and the friction plates 14 are arranged side by side alternately in the axial direction of the center axis 201.
The brake 11 also includes a brake piston 15. This brake piston 15 is arranged adjacent to the friction plates 13 and 14 in the axial direction of the center axis 201. A hydraulic pressure chamber 16 is formed inside the case body 12. This hydraulic pressure chamber 16 is formed adjacent to the brake piston 15 in the axial direction of the center axis 201. The brake piston 15 is arranged between the hydraulic pressure chamber 16 and the friction plates 13 and 14.
When hydraulic pressure is supplied to the hydraulic pressure chamber 16 (i.e. when a hydraulic pressure load is applied), the brake piston 15 moves in the axial direction of the center axis 201 and applies pressure to the friction plates 13 and 14. When pressure is applied to the friction plates 13 and 14, they engage with each other by friction. As a result, the friction plates 13 and the friction plates 14 become applied (i.e., engaged), thereby locking the planetary carrier 62 and the sun gear 65 against rotation.
The back plate 21 has a ring shape and extends in a circle around the center axis 201. The back plate 21 includes an end face 23 and an end face 24 which face in opposite directions in the axial direction of the center axis 201 and extend in a circle around the center axis 201. The end face 23 faces the friction plates 13 and 14, while the end face 24 faces the snap ring 31. The end faces 23 and 24 extend within a plane that lies orthogonal to the center axis 201.
The back plate 21 includes splines 25. These splines 25 engage with splines, not shown, formed on the inner peripheral surface 12c of the case body 12, thereby fixing the back plate 21 to the case body 12 in a manner such that the back plate 21 is able to move in the axial direction of the center axis 201 but will not rotate in the circumferential direction around the center axis 201. The back plate 21 includes a plurality of flange portions 27 (i.e., 27A, 27B, and 27C). These flange portions 27 extend in the radial direction around the center axis 201. In this example embodiment, these flange portions 27 extend to the outside in the radial direction around the center axis 201. The plurality of these flange portions 27 are formed at intervals in the circumferential direction around the center axis 201.
Each return spring 18 extends in the axial direction of the center axis 201 and includes one end 18m that is connected to the brake piston 15 and another end 18n that is connected to a flange portion 27 of the back plate 21. The return spring 18A corresponds to the flange portion 27A, the return spring 18B corresponds to the flange portion 27B, and the return spring 18C corresponds to the flange portion 27C. The plurality of return springs 18 are arranged at equidistant intervals around the center axis 201.
The snap ring 31 is positioned between the return springs 18 and the friction plates 13 and 14 in the radial direction around the center axis 201. Elastic force from the return springs 18 urges the brake piston 15 away from the back plate 21 in the axial direction of the center axis 201 and pushes the back plate 21 against the snap spring 31.
When hydraulic pressure stops being supplied to the hydraulic pressure chamber 16 (i.e. when the hydraulic pressure load has been released), the elastic force from the return springs 18 pushes the brake piston 15 away from the back plate 21. As a result, the friction plates 13 and the friction plates 14 release (i.e., disengage), thereby allowing the planetary carrier 62 and the sun gear 65 to rotate.
Referring to
The snap ring 31 is made of metal and is shaped like the letter C with a portion in the circumferential direction that has been cut. The snap ring 31 includes a pair of abutments 33p and 33q. These abutments 33p and 33q face one another across a gap 35 in the circumferential direction around the center axis 201. In
The rigidity of the snap ring 31 is relatively low at the phase where the gap 35 is formed and relatively high at the phase on the opposite side. Accordingly, the force (i.e., the constricting force) with which the snap spring 31 that is fitted in the groove 41 presses against the bottom surface 41d of the groove 41 is relatively small at the phase of the upper half in
According to these kinds of characteristics of the snap ring 31, when the snap ring 31 is fitted in the groove 41, the outer peripheral surface 31d of the snap ring 31 and the bottom surface 41d of the groove 41 fit closely at the abutments 33p and 33q, and at the phase on the opposite side of the phase where the gap 35 is formed. On the other hand, a gap 36p between the outer peripheral surface 31d and the bottom surface 41d is formed adjacent to the abutment 33p, while a gap 36q between the outer peripheral surface 31d and the bottom surface 41d is formed adjacent to the abutment 33q.
The size of the gap 36p is greatest within a range of 90° between θ=−180° and θ=−90°. In this example embodiment, the size of this gap 36p is greatest at θ=−135. The size of the gap 36q is greatest within a range of 90° between θ=+180° and θ=+90°. In this example embodiment, the size of the gap 36q is greatest at θ=+135°.
In this example embodiment, the plurality of return springs 18 are arranged so that they are axisymmetrical with respect to a straight line that connects θ=0° and θ=±180°. The invention is not limited to this kind of arrangement, however. For example, the return spring 18C may be arranged within a range from θ=0° to θ=−90°, inclusive.
Referring to
Referring to
The catching allowance between the snap ring 31 and the groove 41 initially before a hydraulic pressure load is applied is H1. When a hydraulic pressure load is applied, force applied from the hydraulic pressure chamber 16 to the friction plates 13 and 14 is transmitted to the back plate 121 and the snap ring 31. At this time, the inner peripheral side of the back plate 121 that receives the force from the friction plates 13 and 14 angles into (i.e., inclines toward) the snap ring 31. The snap ring 31 then inclines together with the back plate 121 while the corner portion E slides on the surface of the back plate 121. As a result, the position of the corner portion E seems to become displaced in the radial direction around the center axis 201 in which the snap ring 31 would slip out of the groove 41 (hereinafter this radial direction will also referred to as the “rising direction of the snap ring 31” or simply “rising direction”), as shown by arrow 211 in
After the hydraulic pressure load has been released, the back plate 121 returns from the position angled into the snap ring 31 to its original position. At this time, the snap ring 31 also returns to its original position together with the back plate 121, with the corner portion E fixed on the surface of the back plate 121 by the friction between the snap ring 31 and the back plate 121. As a result, the snap ring 31 is pulled in the rising direction when the hydraulic pressure load is released. After the hydraulic pressure has been released, the catching allowance between the snap ring 31 and the groove 41 is H2 which is smaller than H1. According to this kind of mechanism, a phenomenon occurs in which the catching allowance between the snap ring 31 and the groove 41 gradually decreases as the hydraulic pressure load is repeatedly applied and released.
Continuing on, the operation achieved by the support structure of the brake shown in
Referring to
Accordingly, the reaction force P that the snap ring 31 receives from the back plate 21 increases, thereby increasing the frictional force F generated between the back plate 21 and the snap ring 31. When a hydraulic pressure load is being applied, the corner portion E is dragged by the back plate 21 and the snap ring 31 inclines together with the back plate 21. As a result, the snap ring 31 moves in the direction opposite the rising direction.
In this way, there is a difference in the behavior of the snap ring 31 during the application of a hydraulic pressure load between the support structure of a brake for comparison shown in
The support structure of the brake 11 which is the friction apply device in this example embodiment of the invention includes the snap ring 31, the friction plates 13 and 14, the back plate 21 which serves as a plate member, and the return springs 18A and 18B which serve as the first and second elastic members. The snap ring 31 is arranged in the groove 41 that extends in a circle around the center axis 201 which is a predetermined axis. The snap ring 31 restricts the movement of the friction plates 13 and 14 in the axial direction of the center axis 201. The friction plates 13 and 14 engage together by friction when pushed toward the snap ring 31 in the axial direction of the center axis 201. The back plate 21 is arranged between the snap ring 31 and the friction plates 13 and 14. The return springs 18A and 18B push the back plate 21 against the snap ring 31. The snap ring 31 includes a pair of abutments 33q and 33p which face each other across a gap 35 in the circumferential direction. The return spring 18A is arranged between θ=−180° and θ=−90°, i.e., within a range of −90° with respect to the center of the gap 35 around the center axis 201. The return spring 18B is arranged between θ=+180° and θ=+90°, i.e., within a range of +90° with respect to the center of the gap 35 around the center axis 201.
The gap 36q is formed as a first gap between the snap ring 31 and the bottom surface 41d of the groove 41, adjacent to the abutment 33q. The gap 36p is formed as a second gap between the snap ring 31 and the bottom surface 41d of the groove 41, adjacent to the abutment 33p. The return spring 18A is arranged at θ=−135° which is the phase where the gap 36p is greatest around the center axis 201. The return spring 18B is arranged at θ=+135° which is the phase where the gap 36q is greatest around the center axis 201.
According to the support structure of the brake 11 in this example embodiment of the invention, which is structured as described above, sufficient catching allowance between the snap ring 31 and the groove 41 is able to be ensured along the entire periphery around the center axis 201. As a result, operation of the planetary gear set by the brake 11 can be ensured which improves the reliability of the automatic transmission 10.
Continuing on, a test will now be described for checking the behavior of the snap ring 31 in the support structure of a brake shown in
Referring to
In this example embodiment, the brake 11 described uses the inner diameter fitting snap ring 31 (i.e., the snap ring 31 which fits into an inner diameter groove). Alternatively, however, the invention may also be applied to a brake that uses an outer diameter fitting snap ring (i.e., a snap ring which fits into an outer diameter groove). In this case, the rising direction of the snap ring is the direction from the inner diameter side toward the outer diameter side in the radial direction around the axis around which the groove is formed. Also, the invention is not limited to being applied only to a brake, but may also be applied to a clutch of an automatic transmission. Further, the invention may also be applied to a continuously variable transmission.
The example embodiments disclosed herein are in all respects merely examples and should in no way be construed as limiting. The scope of the invention is indicated not by the foregoing description but by the scope of the claims for patent, and is intended to include all modifications that are within the scope and meanings equivalent to the scope of the claims for patent.
Number | Date | Country | Kind |
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2006-244350 | Sep 2006 | JP | national |