JP2010196854A - Piston mechanism for automatic transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent outbreaks of buckling of a wave spring in a piston mechanism for an automatic transmission using a wave spring as a return spring. <P>SOLUTION: This piston mechanism for an automatic transmission includes: a ring-like piston 20 for pushing a friction fastening element 7; a spring retainer 30 locked with a transmission case 1 as a fixed member relative to the piston 20 and facing the piston 20; and a return spring interposed between the piston 20 and the spring retainer 30 and formed of an annular wave spring 15 formed by spirally winding a plate spring formed into a corrugated shape. A washer 17 having a friction coefficient smaller than a friction coefficient in the case wherein the wave spring 15 and the piston 20 are brought into direct contact with each other is interposed between the wave spring 15 and the piston 20 so that one end of the wave spring 15 on a piston 20 side is formed as a free end. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a piston mechanism of an automatic transmission, and more particularly to a return spring support structure in the piston mechanism.

  Conventionally, a piston mechanism of an automatic transmission has been provided with a return spring that returns a piston that presses a frictional engagement element (friction engagement element) in the axial direction. A piston mechanism has been proposed in which a wave spring is used in which a plate spring is spirally wound so that wave peaks contact each other (for example, Patent Document 1).

JP-A-9-10091

  FIG. 5A is a view showing a return spring support structure in a piston mechanism in which a wave spring 150 according to a conventional example as disclosed in Patent Document 1 is adopted as a return spring, and FIG. It is a figure explaining 150 buckling. 6A is a view schematically showing the wave spring 150 disposed between the spring retainer 140 and the piston 120, and FIG. 6B is a view schematically showing the buckled wave spring 150. FIG. It is a figure.

  In the transmission case 100, a plurality of drive plates 110a and a plurality of driven plates 110b are alternately stacked in the axial direction, and the drive plate 110a and the driven plate 110b constitute a frictional engagement element 110. Yes.

The piston 120 that presses the frictional engagement element 110 is disposed in the ring-shaped cylinder 131 of the partition wall 130 fixed to the transmission case 100 so as to be able to stroke in the axial direction.
A spring retainer 140 is provided between the frictional engagement element 110 and the partition wall 130, and a wave spring 150 is disposed between the piston 120 and the spring retainer 140.

  The spring retainer 140 includes a disk part 141 and a cylindrical part 142 extending in the axial direction from the inner diameter side of the disk part 141, and the outer peripheral edge of the disk part 141 is fitted in a groove 102 formed in the spline 101 of the transmission case 100. The axial direction is positioned by being locked by the snap ring 103 inserted.

As shown in FIG. 6A, the wave spring 150 is formed by spirally winding a single leaf spring formed into a corrugated shape so that the wave peaks 151 are in contact with each other.
When the wave spring 150 is compressed in the axial direction by the stroke of the piston 120, the wave crests 151 that are in contact with each other are stuck together to obtain a spring force. 120 (see FIG. 5A) can be returned to the original position before the frictional engagement element 110 is pressed.

  The wave spring 150 is provided in a state in which a wave peak 151 a and a wave peak 151 h located outside in the axial direction are in contact with the spring retainer 140 and the piston 120, respectively. Here, the stress due to the spring force of the wave spring 150 is concentrated at the contact point between the wave peak 151a and the spring retainer 140 and the contact point between the wave peak 151h and the piston 120, so The friction coefficient becomes very large at the crest of the crest, and the crests 151a and 151h of the wave spring 150 are in surface contact with the spring retainer 140 and the piston 120 so that they do not slide in the circumferential direction. .

  For this reason, the wave spring 150 repeats expansion and contraction in a state where both ends 151a and 151h are fixed and the degree of freedom in the torsional direction is hindered, and the wave peaks that are in contact with each other are relatively displaced. It tends to be easy. Accordingly, the wave spring 150 has a particularly low radial rigidity.

  When the wave spring 150 repeatedly expands and contracts in a state where the degree of freedom in the torsional direction is hindered, the positional deviation of the wave peaks 151 (151b to 151g) that are in contact with each other advances, and for example, The wave peaks 151b to 151g (see FIG. 6A) that are in contact with each other may be shifted in a staggered direction across the straight line X (see FIG. 6B).

The amount of deviation at this time tends to be the largest between the wave peaks 151a and 151h at the fixed ends and the wave peaks 151b and 151g adjacent to them in the axial direction. The amount of change in the diameter of the wave spring 150 between the wound portions 150A and 150B and between 150G and 150H increases.
Therefore, for example, when the amount of change in diameter at the winding portions 150A and 150B increases and exceeds the plate width of the wave spring 150, the winding portions 150A and 150B are shifted by the plate width and remain engaged with each other. A so-called buckling state is obtained (see FIG. 5B).

  The wound portion in the buckled state interferes with the cylindrical portion 142 of the piston 120 and the spring retainer 140, or causes a decrease in the spring constant of the wave spring 150, and the smooth pressing of the frictional engagement element 110 is obstructed. As a result, the transmission performance is deteriorated.

  Therefore, an object of the present invention is to prevent the wave spring from buckling in a piston mechanism of an automatic transmission that uses a wave spring as a return spring.

  The present invention includes a piston for pressing a frictional engagement element, a spring retainer that is locked to a fixed member and opposed to the piston, and a leaf spring that is interposed between the piston and the spring retainer and formed into a corrugated shape. In a piston mechanism of an automatic transmission comprising a return spring composed of an annular wave spring formed by spirally winding, at least one of a wave spring and a piston, and a wave spring and a spring retainer. On the other hand, a low friction coefficient member lower than the friction coefficient when the wave spring and the piston or the spring retainer are in direct contact is interposed, and one end of the wave spring is in contact with the piston and the other end is in contact with the spring retainer. At least one of these is supported so as to be displaceable in the circumferential direction.

According to the present invention, since at least one of the one end and the other end in the axial direction of the wave spring is a free end, the wave spring repeatedly expands and contracts in a state in which the degree of freedom in the twisting direction is ensured.
Therefore, when the free end side is twisted in one direction when the wave spring is contracted, the entire wave spring is twisted in the same direction, so that it is possible to prevent the wave peaks that are in contact with each other from being shifted in a staggered direction.
Thereby, since the change of the diameter of each spring winding (winding part) of a wave spring is suppressed, buckling of a wave spring can be prevented.

It is a figure which shows the support structure of a return spring. It is the figure which looked at a part of piston in FIG. 1 from the friction fastening element side. It is the sectional view on the AA line in FIG. It is the figure which looked at the center side from the circumferential direction of the wave spring. It is a figure which shows the support structure of the return spring concerning a prior art example. It is a figure explaining the buckling of the return spring in a prior art example.

Embodiments of a return spring support structure according to the present invention will be described below.
FIG. 1 is a cross-sectional view illustrating a return spring support structure according to an embodiment. FIG. 2 is a partially enlarged view of the piston 20 in FIG. 1 as viewed from the frictional engagement element 7 side, and FIG. 3 is a partially enlarged view of the AA cross section in FIG. FIG. 4 is a schematic view showing a state in which the return spring in FIG. 1 is viewed from the outside in the radial direction.

  A spline 2 is formed on the inner wall of the transmission case 1, and a hub portion 5 having a spline 6 on the outer periphery facing the spline 2 extends from a rotating member (not shown) and engages with the spline 6 of the hub portion 5. A plurality of drive plates 7a and a plurality of driven plates 7b engaged with the splines 2 of the transmission case 1 are alternately arranged in the axial direction to constitute the frictional engagement element 7.

A piston 20 for pressing these frictional engagement elements 7 is disposed in the ring-shaped cylinder 11 of the partition wall 10 fixed to the transmission case 1 so as to be capable of stroke in the axial direction, and between the piston 20 and the cylinder 11. An oil chamber 13 is formed in the upper part.
As shown in FIG. 2A, the piston 20 has a ring shape corresponding to the cylinder 11, and a pressing portion 21 that extends in the axial direction toward the frictional fastening element 7 is provided in the vicinity of the outer peripheral edge. Are provided at equal intervals in the circumferential direction. These pressing portions 21 are provided in the same number as the passage holes 33 at positions aligned with passage holes 33 (see FIG. 3) of the spring retainer 30 described later.

  As shown in FIG. 1, a spring retainer 30 is provided between the frictional engagement element 7 and the partition wall 10, and the wave spring 15 is disposed between the piston 20 and the spring retainer 30.

As shown in FIGS. 1 and 3, the spring retainer 30 includes a disk part 31 and a cylindrical part 32 extending in the axial direction from the inner diameter side of the disk part 31, and has a ring shape when viewed from the axial direction. .
The outer peripheral side of the disk portion 31 is engaged with a snap ring 4 fitted in the groove 3 of the spline 2 of the transmission case 1 on the side opposite to the surface with which the wave spring 15 abuts, and the spring retainer 30 is The axial direction is positioned by the snap ring 4.

  The disc part 31 is provided with the passage hole 33 which penetrates the press part 21 of the piston 20, and as shown in FIG. 3, the passage hole 33 is provided at equal intervals in the circumferential direction. The circumferential length of the passage hole 33 is set to be slightly larger than the circumferential width of the pressing portion 21 (see FIG. 2) to suppress the gap between the two and restrict the relative rotation of the piston 20 and the spring retainer 30 within a predetermined range. It is like that.

As shown in FIG. 3, on the outer peripheral edge of the disk portion 31, fitting portions 31 c that fit into the spline grooves 2 a of the splines 2 of the transmission case 1 are provided at equal intervals in the circumferential direction.
The fitting portion 31 c has a radial length that can be engaged with the spline groove 2 a of the transmission case 1, and is formed with a length that extends radially outward from the snap ring 4.
As shown in FIG. 1, the surface 4a on the partition wall 10 side of the snap ring 4 is in contact with the disk portion 31 (outer half portion 31b, fitting portion 31c) of the spring retainer 30 over the entire surface, and the wave spring 15 The snap ring 4 is prevented from falling down due to the stress received from the spring retainer 30 biased by. This is to prevent the spring retainer 30 from falling off the support by the snap ring 4.

  As shown in FIGS. 1 and 3, in the spring retainer 30, the outer half portion 31 b including the passage hole 33 of the disk portion 31 is slightly in the extending direction of the cylindrical portion 32 than the inner half portion 31 a on the inner diameter side. When the spring retainer 30 is viewed from the partition wall 10 side, the inner half portion 31a is recessed. The inner half portion 31 a is a contact (sitting) portion of one end of the wave spring 15.

As shown in FIG. 4, the wave spring 15 is formed by spirally winding a single leaf spring formed into a corrugated shape so that the wave peaks 16 are in contact with each other, and is not normally buckled. In this state, the contact point between the wave peak 16a and the disk portion 31 of the spring retainer 30, the contact point between the wave peak 16h and the washer 17, and the contact points between the wave peaks 16b to 16g are the center of the wave spring. On the straight line (axis line) X that passes, the contact points of the wave peaks 16a ′ to 16h ′ also match on the straight line X ′ parallel to the straight line X.
In this wave spring 15, a row of wave peaks 16 a to 16 h and a row of wave peaks 16 a to 16 h ′ arranged in the axial direction are alternately arranged in the circumferential direction, and the piston 20 (see FIG. 1). When the wave spring 15 is compressed in the axial direction by the stroke, the wave peaks 16 (16b to 16g, 16a ′ to 16h ′) that are in contact with each other are thrust together to obtain a spring force.

The wave spring 15 includes a wave peak 16a protruding outward in the axial direction of the winding portion 15A and a wave peak 16h protruding outward in the axial direction of the winding portion 15H, respectively, and a disk portion 31 of the spring retainer 30; It is provided in contact with a washer 17 which will be described later.
As shown in FIG. 1, the wave spring 15 urges the piston 20 in the initial position direction (direction of the partition wall 10). FIG. 1 shows a state where the piston 20 is in the initial position, and in this state, the clutch is in a released state.

  As shown in FIG. 1, the piston 20 has a recess 22 on the side opposite to the oil chamber 13, and a washer 17 having a shape matching the bottom wall 22a is provided on the bottom wall 22a.

  The washer 17 has a ring shape when viewed from the axial direction, is formed with a uniform thickness over the entire circumference, and serves as a contact (seat) portion at the other axial end of the wave spring 15.

  The washer 17 includes PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer), FEP (tetrafluoroethylene / hexafluoropropylene copolymer), PCTFE (polychlorotrifluoroethylene), ETFE (tetrafluoroethylene / ethylene copolymer). Is a washer made of a fluororesin such as a polymer, and has a small coefficient of friction (μ) (preferably 0.3 or less) and excellent slidability.

Here, the friction coefficient of the washer 17 is smaller than the friction coefficient of the material constituting the piston 20 and the spring retainer 30, and when the wave spring 15 contracts, the wave peak 16h of the wave spring 15 (FIG. 4). The contact position of the washer 17 and the washer 17 can be displaced in the circumferential direction, and is not particularly limited as long as the degree of freedom in the twisting direction of the wave spring 15 can be secured.
In the embodiment, the friction coefficient is set to be smaller than the friction coefficient when the wave spring 15 and the piston 20 or the spring retainer 30 are in direct contact.

According to the support structure of the wave spring 15 having such a configuration, when hydraulic oil is supplied to the oil chamber 13 (see FIG. 1) and the piston 20 strokes in the left direction in the drawing while the wave spring 15 is contracted, FIG. As described above, the contact position between the wave peak 16h of the wave spring 15 and the washer 17 can be displaced in the circumferential direction by the washer 17 having a smaller friction coefficient than that when the wave spring 15 and the piston 20 are in direct contact. Therefore, it moves in the circumferential direction (for example, the direction indicated by arrow A in the figure) according to the contraction amount of the wave spring 15.
Then, since the wave spring 15 is formed by spirally winding a single leaf spring, the wave peaks 16b to 16g also move in the direction of arrow A in the figure following the movement of the wave peak 16h. Then, the entire wave spring 15 is twisted in the circumferential direction with the wave peak 16a as a fixed end (see FIG. 4B).

That is, with the washer 17 interposed, the wave spring 15 repeats expansion and contraction with one end on the wave peak 16a side as a fixed end and the other end on the wave peak 16h side as a free end. Since the both ends are not fixed like the wave spring 150, the wave peaks 16b to 16g do not move in the alternate direction as shown in FIG. The same applies to the wave peaks 16a 'to 16h'.
Therefore, the amount of change in the diameter of each winding portion 15A to 15H of the wave spring 15 does not exceed the plate width, and the wave spring 15 is not buckled.

  Further, as shown in FIG. 4 (b), the displacement amount L of the contact position at the adjacent wave crest when the wave spring 15 is twisted is greatly different in each of the winding portions 15A to 15H. Therefore, the expansion / contraction tendency of each winding portion can be kept substantially the same.

  Here, the transmission case 1 in the embodiment corresponds to a fixed member in the invention, and the washer 17 corresponds to a low friction coefficient member.

As described above, in the embodiment, the ring-shaped piston 20 for pressing the frictional engagement element 7, the spring retainer 30 that is locked to the transmission case 1 that is a stationary member with respect to the piston 20 and faces the piston 20, An automatic transmission comprising a return spring composed of an annular wave spring 15 formed by spirally winding a single leaf spring interposed between a piston 20 and a spring retainer 30 and formed into a corrugated shape. In the piston mechanism, the wave spring 15 is contracted by interposing a ring-shaped washer 17 having a friction coefficient smaller than that when the wave spring 15 and the piston 20 are in direct contact between the wave spring 15 and the piston 20. When it is applied, the wave peak 16h on the piston 20 side of the wave spring 15 and the washer 1 Contact position between has to be displaced in the circumferential direction.
Accordingly, the wave spring 15 has one end (wave peak 16a) on the spring retainer 30 side as a fixed end, and the other end (wave peak 16h) on the piston 20 side as a free end displaceable in the circumferential direction. The expansion and contraction is repeated with the degree of freedom secured.
Therefore, when the wave spring 15 is contracted and the contact position between the wave peak 16h of the wave spring 15 and the washer 17 is displaced in the circumferential direction, the entire wave spring 15 has the wave peak 16a as a fixed end. Since they are twisted in the same direction (see FIG. 4B), it is possible to prevent the wave peaks 16b to 16g and 16a ′ to 16h ′ adjacent in the axial direction from moving in the alternate direction.
Thereby, since the variation | change_quantity of the diameter of each spring winding (winding part 15A-15H) of the wave spring 15 can be suppressed, buckling of the wave spring 15 can be prevented.
Further, since the amount of deviation of the contact position between the wave peaks in the adjacent winding portions is substantially the same in each winding portion, the same expansion and contraction tendency is obtained for each winding.
Furthermore, unlike the automatic transmission according to the conventional example in which a plurality of coil springs are provided for one piston, it is only necessary to provide one coil spring for one piston, which significantly reduces the number of parts. Assembly is also easy.

In particular, since the washer 17 is a resin washer made of any one of PFA, FEP, PCTFE, and ETFE, a washer with a small friction coefficient can be easily provided. Further, the buckling of the wave spring 15 can be prevented with a simple configuration in which the washer 17 is attached to the recess 22 of the piston 20.
Furthermore, by preparing a plurality of resin washers having different friction coefficients in advance, the resin spring washer having an appropriate friction coefficient can be selected according to the spring force of the wave spring 150, and the wave spring 15 can be buckled simply by attaching it. Can be prevented.

Further, a fitting portion 31c that fits into the spline groove 2a of the spline 2 formed on the inner wall of the transmission case 1 is provided on the outer periphery of the spring retainer 30, and the snap ring 4 that positions the spring retainer 30 in the axial direction is provided. The surface 4a on the partition wall 10 side is in contact with the disk portion 31 (the outer half portion 31b and the fitting portion 31c) of the spring retainer 30 over the entire surface.
As a result, compared to the case where the outer peripheral edge of the spring retainer shown in FIG. 5 is locked to only a part of the snap ring, the snap ring 4 is caused by the stress received from the spring retainer 30 biased by the wave spring 15. It can prevent suitably falling down and can prevent the spring retainer 30 from falling off from the support by the snap ring 4.

In the embodiment, the washer 17 is interposed between the wave spring 15 and the bottom wall 22a of the piston 20. However, the washer 17 is provided between the wave spring 15 and the inner half portion 31a of the spring retainer 30. Also good.
In this case, a ring-shaped washer having a smaller friction coefficient than that when the wave spring 15 and the spring retainer 30 are in direct contact is provided.
The washer 17 may be provided both between the wave spring 15 and the bottom wall 22 a of the piston 20 and between the wave spring 15 and the inner half portion 31 a of the spring retainer 30.
Also by doing in this way, when the wave spring 15 is contracted, the wave spring 15 is twisted, so that the wave peaks 16b to 16g and 16a 'to 16h' adjacent in the axial direction are greatly shifted in the staggered direction. Can be prevented.
Thereby, since the variation | change_quantity of the diameter of each spring winding (winding part 15A-15H) of the wave spring 15 can be suppressed, the buckling of the wave spring 15 can be prevented.

In the embodiment, the case where a fluororesin washer is employed is exemplified, but a metal washer that has been treated so that the coefficient of friction of the surface becomes small may be employed instead of the fluororesin washer. In this case, it is possible to easily create a metal washer with a reduced surface friction coefficient by performing a surface treatment such as a plating treatment for forming a manganese phosphate coating on the surface or a deflick treatment.
In addition, a thrust bearing is provided instead of the washer, and at least one end of the wave spring. Displacement in the circumferential direction may be possible.
By doing so, buckling of the wave spring 15 can be prevented.

1 Transmission case (fixed side member)
2 Spline 3 Groove 4 Snap ring 5 Hub part 6 Spline 7 Friction fastening element (friction engagement element)
7a Drive plate 7b Driven plate 10 Bulkhead 11 Cylinder 13 Oil chamber 15 Wave spring 16a to 16h, 16a 'to 16h' Wave peak 17 Washer (low friction coefficient member)
20 piston 21 pressing portion 22 recess 22a bottom wall 30 spring retainer 31 disk portion 31a inner half portion 31b outer half portion 31c fitting portion 32 cylinder portion 33 passage hole 100 transmission case 102 groove 103 snap ring 110 friction fastening element 120 piston 130 Bulkhead 131 Cylinder 140 Spring retainer 141 Disc part 142 Tube part 150 Wave spring 151 Wave mountain

Claims (4)

A piston for pressing the frictional engagement element, a spring retainer that is locked to the fixed side member and faces the piston, and a leaf spring that is interposed between the piston and the spring retainer and formed into a corrugated shape is spirally formed. In a piston mechanism of an automatic transmission having a return spring composed of an annular wave spring formed by winding in a shape,
Low friction lower than the friction coefficient when the wave spring and the piston or the spring retainer are in direct contact with at least one of the wave spring and the piston or between the wave spring and the spring retainer. An automatic device characterized in that a coefficient member is interposed and at least one of the one end of the wave spring contacting the piston and the other end contacting the spring retainer is supported displaceably in the circumferential direction. The piston mechanism of the transmission.   The piston mechanism for an automatic transmission according to claim 1, wherein the low friction coefficient member is a resin washer made of a fluororesin.   2. The piston mechanism for an automatic transmission according to claim 1, wherein the low friction coefficient member is a metal washer having a friction coefficient of a predetermined value or less.   The piston mechanism of an automatic transmission according to claim 1, wherein the low friction coefficient member is a thrust bearing.

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