Automatic transmission

Abstract

A first multi-plate brake device and a second multi-plate brake device are arranged along the inner circumferential surface of the transmission case in the direction of the rotation axis X. In the second multi-plate brake device, a retaining ring is formed on the first multi-plate brake device side of the retaining ring and is supported by a support portion protruding from the inner circumferential surface of the transmission case toward the radial inner side of the rotation axis X. The piston retainer of the first multi-plate brake device has an abutment portion that protrudes toward the second multi-plate brake device side and abuts against the support portion from the opposite side of the retaining ring of the second multi-plate brake device. The abutment portion has a wall thickness portion having a radially increased thickness compared to the upper side in the vertical direction on the lower side in the vertical direction based on the mounting state of the automatic transmission on the vehicle.

Description

Technical Field

[0001] The invention relates to an automatic transmission. Background Art

[0002] In the automatic transmission disclosed in JP2000-104810A, two multi-plate brake devices are arranged side by side in the rotation axis direction along the inner peripheral surface of the transmission case. Summary of the invention

[0003] Problems to be solved by the invention

[0004] The multi-plate brake device includes a plurality of friction engagement plates and a piston that performs a stroke relative to the plurality of friction engagement plates to switch between engagement and release of the plurality of friction engagement plates.

[0005] A snap ring is provided on the side of the friction engagement plates opposite to the piston to restrict the movement of the piston in the rotation axis direction. The snap ring is supported on the side opposite to the friction engagement plates by a support portion formed by protruding the inner peripheral surface of the transmission case radially inward.

[0006] If the support part is deformed by being pressed by the piston through the snap ring, the snap ring will tilt, affecting the stable engagement of the friction engagement plate. Therefore, it is desirable to prevent the support part from deforming. However, since the support part is provided between two multi-plate brake devices, it is not easy to make the support part thicker to increase the rigidity due to layout constraints.

[0007] In an automatic transmission, it is required to reduce deformation of a support portion and stably support a snap ring.

[0008] Technical solutions to solve problems

[0009] According to one aspect of the present invention, there is provided an automatic transmission, wherein a first multi-plate brake device and a second multi-plate brake device are arranged in a row along the inner circumference of a transmission case in a direction of a rotation axis, wherein:

[0010] The first multi-plate brake device and the second multi-plate brake device respectively have:

[0011] Multiple friction snap-on plates;

[0012] A piston, which is disposed on one end side of the plurality of friction engagement plates in the direction of the rotation axis and travels along the direction of the rotation axis;

[0013] a snap ring provided on the other end side of the plurality of friction engagement plates in the direction of the rotation axis and restricting movement of the friction engagement plates in the direction of the rotation axis,

[0014] In the first multi-plate brake device,

[0015] The piston is held on a piston holder, which is arranged on the second multi-plate brake device side of the piston and is fixed to the inner peripheral surface of the transmission case.

[0016] In the second multi-plate brake device,

[0017] The snap ring is supported by a support portion, which is formed on the first multi-plate brake device side of the snap ring and protrudes from the inner peripheral surface of the transmission case toward the radial inner side of the rotating shaft.

[0018] The piston holder of the first multi-plate brake device has an abutment portion that protrudes toward the second multi-plate brake device and abuts against the support portion from the opposite side of the retaining ring of the second multi-plate brake device.

[0019] The contact portion has a thick portion having a greater radial thickness than an upper portion in the vertical direction on a lower side in a vertical direction based on a state in which the automatic transmission is mounted on the vehicle.

[0020] According to the above scheme, the supporting part pressed on the piston via the retaining ring can be pushed back by the abutting part abutting the supporting part from the opposite side of the retaining ring, thereby reducing deformation. In addition, a thick wall portion is formed on the abutting part at the lower side of the vertical line direction of the transmission case where the supporting part is easily deformed, thereby increasing the contact area between the abutting part and the supporting part. In this way, the deformation of the supporting part can be reduced, and the retaining ring can be stably supported. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1A It is a diagram showing an automatic transmission according to an embodiment.

[0022] Figure 1B It is a diagram showing an automatic transmission according to an embodiment.

[0023] Figure 2 It is along Figure 1A A cross-sectional view of the transmission case taken along line II-II.

[0024] Figure 3 It is a diagram for explaining the pressure applied to the support part.

[0025] Figure 4 It is a diagram showing the contact portion of the piston retainer.

[0026] Figure 5 It is a diagram showing the correspondence between the support portion of the transmission case and the piston retainer. DETAILED DESCRIPTION

[0027] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0028] Figure 1A, Figure 1B It is a diagram showing an automatic transmission according to an embodiment. Figure 1A The figure shows the periphery of the multi-plate brake device on the lower side of the rotation axis X of the transmission case 1 in the vertical direction, with the automatic transmission mounted on the vehicle as a reference. Figure 1B The figure shows the periphery of the multi-plate brake device located above the rotation axis X in the vertical direction.

[0029] Figure 2 It is along Figure 1A A cross-sectional view of the transmission housing 1 taken along line II-II. Figure 2 In the embodiment, the parts contained in the transmission case 1 are removed. Figure 2 The support portion 23 and the annular groove 24 are shown in an exaggerated manner.

[0030] like Figure 1A As shown, in the automatic transmission of the embodiment, the multi-disc brake device 3 and the multi-disc brake device 5 are arranged side by side along the rotation axis X direction along the inner peripheral surface 1 a of the transmission case 1 .

[0031] The multi-plate brake device 3 and the multi-plate brake device 5 are respectively arranged on a step portion 10 and a step portion 20 that extend radially inward of the rotation axis X from the inner peripheral surface 1a of the transmission case 1. The step portions 10 and 20 are stepped, and the step portion 20 extends radially inward from the step portion 10. Spline portions 11 and 21 are formed on the step portion 10 and the step portion 20, respectively.

[0032] like Figure 2 As shown in FIG. 1 , the spline portion 21 is composed of a plurality of axial grooves 210 extending in the direction of the rotation axis X. The plurality of axial grooves 210 are arranged at intervals in the circumferential direction of the rotation axis X on the inner peripheral surface 1a of the transmission housing 1. Each axial groove is formed by digging the step portion 20 from the upper surface to the bottom side. Figure 2 The middle figure shows the spline portion 21 of the step portion 20 , and the spline portion 11 of the step portion 10 is not shown in the figure, but is also composed of a plurality of axial grooves.

[0033] like Figure 1A As shown, the multi-plate brake device 3 includes a friction engagement plate 31 and a piston 32 arranged in a row with respect to the friction engagement plate 31 in the direction of the rotation axis X. The friction engagement plate 31 is composed of an annular driving plate 31a and a driven plate 31b alternately arranged in the direction of the rotation axis X. A disc spring 38 is arranged on the piston side of the friction engagement plate 31, and an end plate 39 is arranged on the opposite side of the piston side.

[0034] A clutch drum 33 as a rotating body is arranged on the inner peripheral side of the drive plate 31a. A spline 33a is provided on the outer peripheral portion of the clutch drum 33, and the drive plate 31a is fitted with the spline 33a of the clutch drum 33 in a manner that can slide along the rotation axis X direction. The driven plate 31b is fitted with the spline portion 11 provided on the step portion 10 in a manner that can slide along the rotation axis X direction. The disc spring 38 is provided on the spline portion 11 in a manner that can slide along the rotation axis X direction similarly to the driven plate 31b.

[0035] The end plate 39 is fitted to the spline portion 11 and is positioned by the snap ring 34 on the side opposite to the friction engagement plate 31. The end plate 39 and the snap ring 34 restrict the friction engagement plate 31 from sliding in the rotation axis X direction.

[0036] A spring holder 35 is disposed between the piston 32 and the friction engagement plate 31. An arm 32a that presses the friction engagement plate 31 protrudes from the piston 32, penetrates the spring holder 35, and extends toward the friction engagement plate 31 side.

[0037] The spring holder 35 is positioned in the rotation axis X direction by the snap ring 36 .

[0038] The spring Sp is held by the spring holder 35 and the piston 32. One end of the spring Sp is held by the spring holder 35, and the other end is held by the piston 32. The spring Sp urges the piston 32 in a direction away from the friction engagement plate 31 (rightward in the figure).

[0039] The piston 32 is held by the piston holder 37 so as to be able to slide in the direction of the rotation axis X. The piston holder 37 has a holding portion 372 for the piston 32 formed on one end side of the annular wall portion 371, and a cylindrical abutment portion 373 formed on the opposite side. A hydraulic chamber R for sliding the piston 32 is formed in the holding portion 372. When hydraulic pressure is supplied to the hydraulic chamber R, the piston 32 slides toward the friction engagement plate 31 along the direction of the rotation axis X, and the arm 32a presses the friction engagement plate 31, so that the drive plate 31a and the driven plate 31b engage. As a result, the rotation of the clutch drum 33 splined with the drive plate 31a is restricted.

[0040] When the hydraulic pressure is exhausted from the hydraulic chamber R, the arm 32a of the piston 32 moves away from the friction engagement plate 31 due to the urging force of the spring Sp, and the piston 32 returns to the initial position. As a result, the engagement between the drive plate 31a and the driven plate 31b is released, and the rotation of the clutch drum 33 is allowed.

[0041] The piston holder 37 is positioned in the direction of the rotation axis X by the front end of the abutment portion 373 of the piston holder 37 coming into contact with the end surface 22 of the step portion 20 .

[0042] like Figure 1A and Figure 1BAs shown in FIG. 1 , the radial thickness of the abutment portion 373 of the piston holder 37 is not constant, and is set such that the radial thickness Ha below the vertical line direction of the rotation axis X is greater than the radial thickness Hb above the vertical line direction. That is, a wall thickness portion 374 is provided below the abutment portion 373 of the piston holder 37 in the vertical line direction. The details and function of the wall thickness portion 374 will be described later.

[0043] The multi-plate brake device 5 is also similar to the multi-plate brake device 3, and includes a friction engagement plate 51 composed of a driving plate 51a and a driven plate 51b, and a piston 52 arranged in a row with respect to the friction engagement plate 51 along the direction of the rotation axis X. A disc spring 58 is arranged on the piston 52 side of the friction engagement plate 51, and an end plate 59 is arranged on the opposite side of the piston side.

[0044] In the multi-plate brake device 5, a clutch drum 53 as a rotating body is arranged on the inner peripheral side of the drive plate 51a, and a spline 53a is provided on the outer peripheral portion of the clutch drum 53. The drive plate 51a is engaged with the spline 53a on the inner peripheral side. The driven plate 51b is engaged with the spline portion 21 provided on the step portion 20. The drive plate 51a is engaged with the spline 53a of the clutch drum 53 in a manner that allows sliding along the rotation axis X direction.

[0045] Although not shown in the figure, the piston 52 is held by a piston holder and is provided to be slidable in the direction of the rotation axis X by hydraulic pressure supplied to a hydraulic chamber formed between the piston holder and the piston holder. The piston 52 is urged away from the friction engagement plate 51 by a spring (not shown).

[0046] When hydraulic pressure is supplied to the hydraulic chamber (not shown), the piston 52 slides toward the friction engagement plate 51 along the rotation axis X direction, pressing the friction engagement plate 51 via the disc spring 58, engaging the drive plate 51a and the driven plate 51b. This restricts the rotation of the clutch drum 53 spline-fitted with the drive plate 51a.

[0047] When the hydraulic pressure is exhausted from the hydraulic chamber (not shown), the piston 52 moves away from the friction engagement plate 51 due to the biasing force of the spring (not shown) and returns to the initial position. As a result, the engagement between the drive plate 51a and the driven plate 51b is released, and the rotation of the clutch drum 53 is allowed.

[0048] The end plate 59 is fitted to the spline portion 21 and is positioned by the snap ring 54 on the side opposite to the friction engagement plate 51. The end plate 59 and the snap ring 54 restrict the friction engagement plate 51 from sliding in the rotation axis X direction.

[0049] The snap ring 54 is fitted into the annular groove 24 formed near the end surface 22 of the step portion 20. That is, the portion of the step portion 20 divided by the end surface 22 and the annular groove 24 functions as the support portion 23 that supports the snap ring 54. As described above, since the abutment portion 373 of the piston retainer 37 of the multi-plate brake device 3 abuts against the end surface 22, the support portion 23 also functions as a positioning member of the piston retainer 37.

[0050] like Figure 2 As shown, the annular groove 24 is formed in an annular shape so as to be orthogonal to the axial groove 210 constituting the spline portion 21 and to cross the step portion 20 in the circumferential direction.

[0051] The dimensions of the axial groove 210 and the annular groove 24 are appropriately set according to the dimensions of the engaged driven plate 51 b and the snap ring 54, but in the illustrated example, the radial depth Hd of the axial groove 210 is set smaller than the radial thickness Hc of the step portion where the axial groove 210 is formed. Furthermore, the radial depth He of the annular groove 24 is set smaller than the radial depth Hd of the axial groove 210.

[0052] A plurality of oil holes H1, H2, and H3 are formed in the step portion 20. The oil holes H1, H2, and H3 are through holes formed to discharge lubricating oil supplied into the transmission case 1 to an oil pan (not shown) provided at the bottom of the transmission case 1.

[0053] The oil supplied to the interior of the transmission case 1 is gathered up by the rotating body constituting the speed change mechanism, and then falls downward in the vertical direction due to gravity. Therefore, oil holes H1, H2, and H3 are formed in the portion of the transmission case 1 that is downward in the vertical direction relative to the rotation axis X, for discharging the fallen oil to the oil pan. The number or position of the oil holes is not limited, but in the example shown in the figure, the oil hole H1 is provided at the lowest portion in the vertical direction of the transmission case 1, and the oil holes H2 and H3 are provided at two locations that are upward in the vertical direction relative to the oil hole H1. The portion of the transmission case 1 where the oil holes H1, H2, and H3 are formed is cut off from the support portion 23.

[0054] Figure 3 This is a diagram for explaining the pressure applied to the support portion 23 .

[0055] like Figure 3 As shown, when the friction engagement plate 51 is engaged with the snap ring 54 of the multi-plate brake device 5, the pressure P1 is applied to the multi-plate brake device 3 side in the direction of the rotation axis X by the pressing force of the piston 52. Since the snap ring 54 is engaged with the annular groove 24, the pressure P1 is applied to the support portion 23 via the snap ring 54.

[0056] The support portion 23 is expected to have increased rigidity in order to prevent it from tipping over toward the multi-plate brake device 3 due to the pressure P1. However, in recent years, there has been a trend to use a blank such as a magnesium alloy in the transmission case 1 for weight reduction, and it is sometimes difficult to increase the rigidity of the support portion 23 from the blank aspect. Furthermore, the support portion 23 is formed between the multi-plate brake device 3 and the multi-plate brake device 5, and from the perspective of layout constraints, it is difficult to provide a thick wall in the direction of the rotation axis X or in the radial direction to ensure rigidity.

[0057] Furthermore, as described above, since the support portion 23 is cut off at the oil holes H1 to H3 provided below the vertical line direction of the transmission case 1, stress caused by the influence of the pressure P1 is likely to be concentrated on the support portion 23 around it. If the support portion 23 is deformed by the pressure P1 and tilted toward the multi-plate brake device 3, the snap ring 54 may be tilted, affecting the stable engagement of the friction engagement plate 51. In addition, cracks may occur in the support portion 23 around the oil holes H1 to H3 of the transmission case 1.

[0058] Here, as described above, the contact portion 373 of the piston holder 37 of the multi-plate brake device 3 contacts the end surface 22 of the step portion 20. That is, the contact portion 373 of the piston holder 37 contacts the support portion 23 from the side opposite to the snap ring 54.

[0059] Furthermore, when the friction engagement plate 31 is released and engaged, pressures P2 and P2 ′ are applied to the piston holder 37 of the multi-plate brake device 3 , respectively.

[0060] First, when the engagement of the friction engagement plate 31 is released, the pressure P2 is applied to the multi-plate brake device 5 side in the direction of the rotation axis X by the urging force of the spring Sp. Since the abutting portion 373 of the piston retainer 37 abuts against the support portion 23, the pressure P2 is applied to the support portion 23 via the abutting portion 373. Since the pressure P2 is a force in the opposite direction to the pressure P1, the support portion 23 tilted toward the multi-plate brake device 3 side by the pressure P1 is pushed back to the multi-plate brake device 5 side. In this way, the pressures P1 and P2, which are forces in opposite directions from both ends, act on the support portion 23, thereby reducing the tilting of the support portion 23.

[0061] When the friction engagement plate 31 is engaged, a pressure P2' is generated in the hydraulic chamber R. When the piston 32 is moved toward the retaining ring 34 and the engagement of the friction engagement plate 31 is completed, the piston holder 37 of the multi-plate brake device 3 is pushed back to the support portion 23 side by the pressure P2'. Since the abutment portion 373 of the piston holder 37 abuts against the support portion 23, the pressure P2' is applied to the support portion 23 via the abutment portion 373. Since the pressure P2' is a force in the opposite direction to the pressure P1, the support portion 23 tilted toward the multi-plate brake device 3 side by the pressure P1 is pushed back to the multi-plate brake device 5 side. In this way, the pressures P1 and P2', which are forces in opposite directions from both ends, act on the support portion 23, and the tilting of the support portion 23 is reduced.

[0062] In the embodiment, a thick wall portion 374 is provided on the abutment portion 373 of the piston retainer 37 at a location where cracks are easily generated due to the provision of the oil holes H1 to H3, specifically, at the lower side of the transmission case 2 in the vertical direction relative to the rotation axis X, to further reduce tipping.

[0063] Figure 4 1 and 2 are diagrams showing the contact portion 373 of the piston holder 37 , and are diagrams of the piston holder 37 as viewed from the multi-disc brake device 5 side in the direction of the rotation axis X. FIG.

[0064] Figure 5 It is a diagram showing the correspondence relationship between the contact portion 373 and the support portion 23 . Figure 5 In with Figure 2 Similarly, in the cross-sectional view of the transmission case 1 , the abutment portion 373 of the piston holder 37 is indicated by an imaginary line.

[0065] like Figure 4 As shown, the abutment portion 373 is formed in an annular shape along the outer periphery of the wall portion 371 of the piston retainer 37. A semicircular wall thickness portion 374 is formed at a portion of the abutment portion 373 that is lower than the rotation axis X in the vertical direction. The radial thickness Ha of the wall thickness portion 374 is set to be larger than the radial thickness Hb at the upper side in the vertical direction. The wall thickness portion 374 is cut off at the lowest part of the wall thickness portion 374 in the vertical direction to form an oil drain portion 375 so that oil does not accumulate on the inner periphery of the abutment portion 373. Figure 5 As shown, the oil drain portion 375 is formed at a position corresponding to the oil hole H1 formed in the transmission case 1 .

[0066] like Figure 3 As shown, the radial thickness Ha of the wall thickness portion 374 is set to be equal to or higher than the radial thickness Hc of the support portion 23. As a result, the contact area between the abutment portion 373 and the support portion 23 is larger on the lower side of the rotation axis X in the vertical direction than on the upper side in the vertical direction (see Figure 1B), the pressures P2 and P2′ for pushing back the pressure P1 are easily transmitted from the abutting portion 373 to the supporting portion 23.

[0067] like Figure 5 As shown, the thick wall portion 374 overlaps the oil holes H2 and H3 when viewed from the rotation axis X. Thus, the thick wall portion 374 can easily apply pressures P2 and P2' to the support portion 23 around the oil holes H2 and H3 where cracks are likely to occur due to the concentration of pressure P1, thereby reducing the possibility of tilting.

[0068] In addition, when viewed from the direction of the rotation axis X, the thick wall portion 374 is formed so as to straddle the plurality of axial grooves 210 constituting the spline portion 21. If the support portion 23 is deformed, cracks are likely to occur starting from between the axial grooves 210 and the support portion 23. Therefore, by forming the thick wall portion 374 so as to straddle the plurality of axial grooves 210, it is possible to effectively prevent the tilting and easily prevent the occurrence of cracks.

[0069] As described above, with respect to the automatic transmission of the embodiment,

[0070] (1) The multi-disc brake device 3 (first multi-disc brake device) and the multi-disc brake device 5 (second multi-disc brake device) are arranged side by side along the rotation axis X direction along the inner peripheral surface 1 a of the transmission case 1 .

[0071] The multi-plate brake device 3 and the multi-plate brake device 5 respectively have:

[0072] A plurality of friction engaging plates 31, 51;

[0073] The piston 32, 52 is provided at one end side of the plurality of friction engagement plates 31, 51 in the direction of the rotation axis X and travels along the direction of the rotation axis X;

[0074] The snap rings 34 and 54 are provided on the other end side of the plurality of friction engagement plates 31 and 51 in the direction of the rotation axis X, and restrict movement of the friction engagement plates 31 and 51 in the direction of the rotation axis X.

[0075] In the multi-plate brake device 3,

[0076] The piston 32 is arranged on the multi-plate brake device 5 side of the piston 32 and is held by a piston holder 37 fixed to the inner peripheral surface 1a of the transmission case 1.

[0077] In the multi-plate brake device 5,

[0078] The snap ring 54 is formed on the multi-plate brake device 3 side of the snap ring 54 and is supported by a support portion 23 that protrudes from the inner peripheral surface 1a of the transmission case 1 toward the radial inner side of the rotation axis X.

[0079] The piston holder 37 of the multi-disk brake device 3 has a contact portion 373 that protrudes toward the multi-disk brake device 5 and contacts the support portion 23 from the side opposite to the retaining ring 54 of the multi-disk brake device 5.

[0080] The contact portion 373 has a thick portion 374 having a greater radial thickness than that of the upper portion in the vertical direction, on the lower side in the vertical direction based on the mounting state of the automatic transmission on the vehicle.

[0081] The abutment portion 373 of the piston holder 37 of the multi-plate brake device 3 abuts against the support portion 23 from the opposite side of the snap ring 54, and the pressure P2 or P2' that pushes back the pressure P1 input to the support portion 23 via the snap ring 54 is input to the support portion 23. As a result, the support portion 23 can be prevented from being deformed and tilted toward the multi-plate brake device 3 side due to the pressure P1, and because the support portion 23 can stably support the snap ring 54, the stable engagement of the friction engagement plate 51 can be maintained.

[0082] Moreover, since the support portion 23 is easily deformed on the lower side in the vertical direction, by forming a thick wall portion 374 on the lower side in the vertical direction of the abutment portion 373, the contact area between the abutment portion 373 and the support portion 23 can be increased, thereby improving the stability of the support portion 23.

[0083] (2) The multi-plate brake device 5 is disposed on a step portion 20 formed by extending the inner peripheral surface 1a of the transmission case 1 inwardly in the radial direction of the rotation axis X.

[0084] An annular groove 24 (groove portion) into which the snap ring 54 of the multi-disk brake device 5 fits is formed near the end surface 22 (end portion) of the step portion 20 on the multi-disk brake device 3 side.

[0085] The support portion 23 is a portion of the step portion 20 divided by the end surface 22 and the annular groove 24. The abutment portion 373 of the piston holder abuts against the end surface 22 to be positioned.

[0086] The thick portion 374 of the contact portion 373 has a radial thickness Ha that is equal to or greater than the radial thickness Hc of the support portion 23 with which the thick portion 374 contacts.

[0087] By setting such a structure, the support portion 23 can take into account both the support of the snap ring 54 and the positioning of the piston retainer 37, and can achieve space saving and reduction in the number of parts in the transmission housing with strict layout constraints. In addition, by setting the radial thickness Ha of the wall thickness portion 374 to be greater than the radial thickness Hc of the support portion 23, the abutment portion 373 is in full contact with the support portion 23, so that the pressure P2 or P2' is easily and evenly transmitted to the support portion 23, pushing back the pressure P1, and easily reducing the tilting of the support portion 23.

[0088] (3) The support portion 23 is partially cut away on the inner peripheral surface 1a of the transmission case 1 below the rotation axis X in the vertical direction to provide oil holes H2 and H3 for discharging the lubricating oil inside the transmission case 1.

[0089] The thick portion 374 is formed at a position corresponding to the oil holes H2 and H3 when viewed from the rotation axis X direction.

[0090] By providing the thick wall portion 374 of the contact portion 373 at the position corresponding to the oil holes H2 and H3 , the pressure P2 or P2 ′ that pushes back the pressure P1 can be input to the portion where the support portion 23 is likely to collapse, thereby reducing the collapse.

[0091] (4) When viewed from the rotation axis X direction, the thick portion 374 is formed so as to overlap with the oil holes H2 and H3.

[0092] By providing the thick wall portion 374 so as to overlap the oil holes H2 and H3 , the pressure P2 or P2 ′ that pushes back the pressure P1 can be input to a portion where the support portion 23 is likely to collapse, thereby reducing the collapse.

[0093] (5) A plurality of axial grooves 210 extending in the direction of the rotation axis X are formed at intervals in the circumferential direction of the rotation axis X in the step portion 20 where the multi-plate brake device 5 is arranged on the inner circumferential surface 1a of the transmission case 1.

[0094] The support portion 23 is formed between the axial grooves 210.

[0095] When viewed from the rotation axis X direction, the thick portion 374 is formed across the plurality of axial grooves 210 .

[0096] Since the support portion 23 is formed between the axial grooves 210, if the support portion 23 is deformed, cracks are likely to occur starting from between the axial grooves 210 and the support portion 23. Therefore, by forming the thick wall portion 374 across a plurality of axial grooves 210, it is possible to effectively prevent the collapse and easily prevent the occurrence of cracks.

[0097] This application claims priority based on Japanese Patent Application No. 2019-214323 filed with the Japan Patent Office on November 27, 2019, the entire contents of which are incorporated into this specification by reference.

Claims

1. An automatic transmission, comprising a first multi-plate brake device and a second multi-plate brake device arranged in a row along the inner circumferential surface of a transmission case in a direction of a rotation axis, wherein: The first multi-plate brake device and the second multi-plate brake device respectively have: Multiple friction snap-on plates; A piston, which is disposed on one end side of the plurality of friction engagement plates in the direction of the rotation axis and travels along the direction of the rotation axis; a snap ring provided on the other end side of the plurality of friction engagement plates in the direction of the rotation axis and restricting movement of the plurality of friction engagement plates in the direction of the rotation axis, In the first multi-plate brake device, The piston is held on a piston holder, which is arranged on the second multi-plate brake device side of the piston and is fixed to the inner peripheral surface of the transmission case. In the second multi-plate brake device, The snap ring is supported by a support portion, which is formed on the first multi-plate brake device side of the snap ring and protrudes from the inner peripheral surface of the transmission case toward the radial inner side of the rotating shaft. The piston holder of the first multi-plate brake device has an abutment portion that protrudes toward the second multi-plate brake device and abuts against the support portion from the opposite side of the retaining ring of the second multi-plate brake device. The contact portion has a thick portion having a greater radial thickness than an upper portion in the vertical direction on a lower side in a vertical direction based on a state in which the automatic transmission is mounted on the vehicle.

2. The automatic transmission according to claim 1, wherein: The second multi-plate brake device is arranged on a step portion formed by extending the inner peripheral surface of the transmission case inwardly in the radial direction of the rotating shaft. A groove portion into which the snap ring of the second multi-disc brake device is fitted is formed near the end portion of the step portion on the first multi-disc brake device side. The support portion is a portion of the step portion divided by the end portion and the groove portion, and the abutment portion of the piston holder abuts against the end portion to be positioned. The wall thickness portion of the abutment portion has a radial thickness that is equal to that of the support portion, or has a radial thickness that is greater than that of the support portion.

3. The automatic transmission according to claim 1 or 2, wherein: The support portion is partially cut away and an oil hole for discharging lubricating oil for lubricating the inside of the transmission case is provided on the inner peripheral surface of the transmission case below the rotation axis in the vertical direction. The thick portion is formed at a position corresponding to the oil hole when viewed from the rotation axis direction.

4. The automatic transmission according to claim 3, wherein: The thick portion is formed to overlap the oil hole when viewed from the rotation axis direction.

5. The automatic transmission according to claim 1 or 2, wherein: A plurality of axial grooves extending in the direction of the rotating shaft are formed at intervals in the circumferential direction of the rotating shaft in the region of the inner circumferential surface of the transmission case where the second multi-plate brake device is arranged. The support portion is formed between the axial grooves, The thick portion is formed across the plurality of axial grooves when viewed from the rotation axis direction.

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