JP4686903B2 - Automatic transmission - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a horizontal automatic transmission having a three-axis configuration, and more particularly to a brake arrangement structure in an automatic transmission in which a counter gear pair is arranged at an intermediate portion in the axial direction of a main shaft.
[0002]
[Prior art]
As one form of automatic transmission, a torque converter and a speed change mechanism are arranged on a main shaft coaxial with the engine shaft, and three shafts transmit power to the main shaft and a differential shaft parallel to the counter shaft via a counter shaft parallel to the torque converter. There is a horizontal automatic transmission with configuration. In such an automatic transmission, the counter gear pair for transmitting power from the main shaft to the counter shaft is located at the rear end of the transmission mechanism, that is, on the non-engine side (hereinafter referred to as “rear out”). Or a differential-side gear pair consisting of a differential drive pinion gear and a differential ring gear that is arranged in the middle part (also abbreviated as “centering”) and transmits power from the counter shaft to the differential shaft. The transmission mechanism is disposed closest to the torque converter.
[0003]
Since the brake attached to the speed change mechanism locks the rotating member of the speed change mechanism to the transmission case, the friction member is different from the clutch that connects the rotating members to each other. In particular, in the automatic transmission having the three-axis parallel shaft configuration as described above, when the brake is a multi-plate disk type, there is interference on the outer diameter between the friction member and the differential gear pair. It becomes a problem. In general, in the later arrangement, a sufficient axial space is ensured between the counter gear pair and the differential gear pair because of the arrangement positional relationship described above. It is easy to avoid interference on the outer diameter between the friction member and the differential gear pair by devising the arrangement of the friction member.
[0004]
[Problems to be solved by the invention]
However, in the centering configuration, since the axial space between the counter gear pair and the differential gear pair is significantly restricted, in general, in order to avoid the interference, the distance between the main shaft and the differential shaft is The above interference cannot be avoided without taking measures such as increasing the distance or extending the shaft length of the transmission to dispose the friction member, but such measures are undesirable because they increase the size of the transmission. With respect to this point, there is not a measure to dispose the brake in the same axial position as the differential gear pair as a band brake type in which the radial thickness can be extremely reduced. However, since the band brake generally has a rotational directionality in the engagement force, it is difficult to control, and the braking force is also defined by the band winding angle. Therefore, when considering changing the brake engagement force in order to cope with different engine outputs, it is possible to change the engagement force simply by changing the number of friction members, such as a disc type, to change the braking force. Adopting a band brake is not necessarily a versatile measure because it is disadvantageous in that it cannot be performed. Therefore, the present invention provides a frictional member for a disc-type brake of a transmission mechanism in an automatic transmission having a three-axis configuration and a centering configuration, and an increase in the distance between the main shaft and the differential shaft and an increase in the shaft length of the transmission. It is a first object to enable the arrangement without the need.
[0005]
Further, the multi-plate friction member of the disc type brake is generally configured such that the outer peripheral side thereof is supported directly and axially movable by the transmission case. Since the counter gear pair in the conventional rear-out configuration is disposed outside the transmission case, the brake friction member disposed inside the counter gear pair extends forward from the rear end of the transmission case. It is arranged to support the case peripheral wall. On the other hand, in the center-out configuration, the axial portion of the peripheral wall from the counter gear pair to the differential gear pair of the transmission case is continuous for meshing of the counter gear pair and meshing of the differential gear pair. Since there is no effective support means in this part, there is no effective support means, so the brake friction member should be placed in the axial space between the counter gear pair and the differential gear pair It is difficult. Therefore, a second object of the present invention is to enable the friction member to be arranged on the notch portion of the transmission case.
[0006]
By the way, in such an automatic transmission, since the differential device is disposed at a substantially central portion of the shaft length of the engine shaft length and the shaft length of the speed change mechanism, the differential gear pair is positioned on the main shaft at the axial position. It is located closer to the engine of the transmission mechanism. When the brake is arranged at an axial position that overlaps the position of the differential gear pair on the transmission mechanism side, not only the outer diameter of the brake and the outer diameter of the differential drive pinion gear, but also the outer diameter of the differential ring gear is different from the main shaft and the differential shaft. Because of the distance between the two shafts, the counter shaft and the differential shaft cannot be modified to increase the gear ratio to accommodate different engine output models due to the interference in the radial direction between the counter shaft and the differential shaft. It becomes. The present invention provides a brake device structure capable of reducing the outer diameter of the overlapping portion on the axial position of the brake with the differential ring gear as much as possible so as to cope with such a change in the outer diameter of the differential ring gear. The third purpose is to obtain the above.
[0007]
[Means for Solving the Problems]
As described in claim 1, the first object is to provide a main shaft provided with a speed change mechanism, a brake attached to the speed change mechanism, a counter shaft parallel to the main shaft, and a main shaft and a counter shaft in parallel. And a counter drive gear that transmits power from the main shaft to the counter shaft is disposed in the axial middle portion of the main shaft, and the brake friction member on the main shaft is disposed on the counter shaft Is arranged at an axial position between a counter driven gear meshing with a counter drive gear on the main shaft and a differential drive pinion gear meshing with a differential ring gear on the differential shaft, and the sum of the radius of the brake and the radius of the differential drive pinion gear is This is achieved by a configuration characterized by being larger than the distance between the main shaft and the counter shaft .
[0009]
A second object is as described in claim 2, wherein the brake has a brake drum of the transmission case and the separate friction member of the brake, the axial moving its outer peripheral side to the brake drum The brake drum is achieved by a configuration in which the brake drum is supported by the transmission case.
[0010]
In the above-described configuration, as described in claim 3 , it is effective that the brake drum has an end wall that supports the end portion of the friction member without interruption throughout the entire circumference.
[0011]
In the above-described configuration, as described in claim 4 , the brake drum has splines formed on the peripheral wall so as to be substantially uniformly distributed in the circumferential direction, and the friction member has an outer peripheral side of the brake drum. It is further effective to adopt a configuration in which the spline is engaged so as to be movable in the axial direction.
[0012]
In the above-described configuration, as described in claim 5 , the brake drum is pressed against the transmission case by a load load of a return spring stretched between the brake drum and a hydraulic servo piston of the brake. It is also effective.
[0013]
Furthermore, a third object is as set forth in claim 6 , wherein in any of the configurations described above, the hydraulic servo of the brake is built in the front wall of the transmission case, and the apply tube portion of the hydraulic servo piston is The return spring of the hydraulic servo piston extends in the same axial position as the diff ring gear, and the return spring of the hydraulic servo piston is arranged in a distributed manner in the circumferential direction of the apply tube portion, avoiding the circumferential position facing the diff ring gear side. Achieved.
[0014]
Regarding the achievement of the second object, as described in claim 7 , a main shaft provided with a transmission mechanism and a brake attached to the transmission mechanism, a counter shaft parallel to the main shaft, the main shaft and the counter In an automatic transmission having a differential drive shaft parallel to the shaft and having a counter drive gear for transmitting power from the main shaft to the counter shaft arranged in an intermediate portion in the axial direction of the main shaft, a predetermined rotation element of the speed change mechanism is provided on the main shaft. has a locking to brake, the brake has a brake drum of the transmission case and the separate friction member of the brake is supported axially movable on said brake drum, said brake drum, transmission are detent supported by the case Rutotomoni, it is also possible to adopt a structure characterized by having an end wall which supports seamless across the ends of the friction member on the entire circumference.
[0016]
[Action and effect of the invention]
In the configuration according to claim 1, the counter shaft side radial direction portion of the friction member on the main shaft is disposed so as to enter a space inevitably formed between the counter driven gear and the differential drive pinion gear on the counter shaft. since it is, without extension of the axial length of the expansion and transmission center distance between the main shaft and the differential shaft, it is possible to allow placing the friction member of the brake of the speed change mechanism. Further, it is possible to employ a differential drive pinion gear diameter and a brake diameter that are relatively large with respect to the distance between the main shaft and the differential shaft. Therefore, the mechanism utilizing this can be made compact and the brake torque capacity can be increased.
[0018]
According to a second aspect of the present invention, the brake friction member is supported by the brake drum separate from the transmission case, and the outer peripheral side thereof is supported in an axially movable manner, and is supported by the transmission case via the brake drum. Therefore, the friction member can be arranged on the transmission case missing circle.
[0019]
Furthermore, in the configuration according to claim 3 , by engaging the end portion of the friction member with the end wall of the brake drum that supports the entire end of the friction member without a break, the engagement force applied to the friction member during the brake engagement is circumferential. Therefore, the pressing force of the hydraulic servo piston can be efficiently used for generating the braking torque. As a result, the number of friction members can be reduced or the outer diameter can be reduced in order to obtain the same torque capacity, compared to the configuration in which the friction member is intentionally supported directly on the transmission case having a missing circle. The member itself can be made compact.
[0020]
According to the fourth aspect of the present invention, since the outer peripheral side of the friction member can be supported on the spline of the brake drum substantially uniformly in the circumferential direction, the friction member is less likely to be eccentric when the brake is engaged. Thus, the pressing force of the hydraulic servo piston can be efficiently used for generating the braking torque. Therefore, according to this configuration, it is possible to always obtain a stable braking force against the pressing force of the hydraulic servo piston.
[0021]
Furthermore, in the configuration of claim 5 , since the brake drum as a separate part is pressed against the transmission case by the load load of the return spring, it is not necessary to provide additional retaining means such as a snap ring, It is possible to reduce the number of parts and assembly man-hours of the automatic transmission.
[0022]
Furthermore, in the configuration of claim 6 , the outer diameter of the ring gear of the differential device is about to contact the apply tube portion without changing the axial distance between the main shaft on which the brake is disposed and the differential shaft on which the differential device is disposed. Therefore, the gear ratio setting between the counter shaft and the differential shaft can be easily changed.
[0023]
Next, in the configuration of claim 7 , the friction member of the brake is supported by the brake drum separate from the transmission case so as to be movable in the axial direction, and is supported by the transmission case via the brake drum. The restriction of the arrangement position due to the shape of the transmission case as in the case where the brake friction member is directly supported by the transmission case can be eliminated, and the degree of freedom of the brake arrangement position is increased. Compactness is possible. Furthermore, since the end of the friction member is brought into contact with the end wall of the brake drum that supports the entire circumference continuously without any break, the engagement force applied to the friction member during brake engagement can be made uniform in the circumferential direction. The pressing force of the hydraulic servo piston can be efficiently used for generating the braking torque. As a result, a sufficient torque capacity can be obtained even when the brake is disposed at a position where the entire circumference cannot be supported on the transmission case.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an axial sectional view of three axes of an automatic transmission to which the present invention is applied developed on a common plane, and FIG. 2 is a front view of the automatic transmission as viewed in the axial direction from the opening side to which a converter housing is connected. As shown in the figure, the automatic transmission includes a main shaft X provided with a transmission mechanism M and a brake B-1 associated with a predetermined rotation element of the transmission mechanism M, a counter shaft Y parallel to the main shaft X, and a main shaft. A counter drive gear 11 that includes X and a differential shaft Z that is parallel to the counter shaft Y and that transmits power from the main shaft X to the counter shaft Y is disposed in an intermediate portion in the axial direction of the main shaft X.
[0026]
According to the features of the present invention, the friction member 21 of the brake B-1 on the main shaft X is disposed on the counter shaft Y and meshes with the counter drive gear 11 on the main shaft X, and the diff ring gear on the differential shaft Z. 14 is disposed at an axial position between the differential drive pinion gear 13 and the differential drive pinion gear 13.
[0027]
Referring to FIG. 3 showing an enlarged detailed configuration, the brake B-1 has a brake drum 22 that is separate from the transmission case C, and the friction member 21 of the brake B-1 has an outer peripheral side thereof. The brake drum 22 is supported by the brake drum 22 so as to be movable in the axial direction, and the brake drum 22 is supported by the transmission case C so as not to rotate. The brake drum 22 has an end wall 22a that supports the end of the friction member 21 over the entire circumference without any breaks, and has splines 22b that are substantially uniformly distributed in the circumferential direction on the peripheral wall. The member 21 is supported so as to be movable in the axial direction with its outer peripheral side engaged with a spline 22 b of the brake drum 22. The brake drum 22 is prevented from coming off the transmission case C by a load of a return spring 23b stretched between the brake drum 22 and the hydraulic servo piston 23a of the brake B-1. The hydraulic servo 23 of the brake B-1 is built in the front wall P of the transmission case, and the apply tube portion 23c of the hydraulic servo piston 23a is connected to the diff ring gear 14 (actually with respect to the member on the main shaft X in the imaginary line in FIG. 2 and the maximum diameter position where the diameter can be further expanded is extended in the direction of the friction member 21 at the same axial position as the broken line in FIGS. 1 to 3, and the return spring 23b of the hydraulic servo piston 23a is as shown in, are arranged also urchin matter Na cause interference, it is dispersed in the circumferential direction of the applied tube portion 23c to avoid circumferential position facing the ring gear side in the differential ring gear 14 'of maximum diameter.
[0028]
Further, in relation to the outer diameter of the differential ring gear 14, the sum of the radius of the brake B-1, specifically, the outer diameter of the brake drum 22 and the radius of the maximum diameter differential drive pinion gear 13 is shown in FIG. As shown in the upper half cross section of the axis Y, the distance between the main axis X and the counter axis Y is made larger than the inter-axis distance. That is, when viewed in the axial direction, the brake drum 22 and the differential drive pinion gear 13 overlap in a part of their circumferential direction. The outer diameter of the differential drive pinion gear 13 shown in FIG. 1 in the lower half section of the counter shaft Y and shown in FIG. 3 is the same as the diameter of the differential drive pinion gear 13 that meshes with it. The case where the diameter is reduced is shown.
[0029]
Hereinafter, each part will be further described in detail. The automatic transmission includes a torque converter T, a transmission mechanism M, and a counter drive gear 11 as an output member thereof on a main shaft X, a counter driven gear 12 as an input member, and an output member as an output member. A differential drive pinion gear 13 is provided, and a differential ring 14 as an input member and a differential device D are provided on the differential shaft Z.
[0030]
The speed change mechanism M decelerates between the center support S disposed at the center in the axial direction of the transmission case C and the front wall of the transmission case C constituted by the oil pump body P on the front side thereof. Planetary gear G1 (referenced only in FIG. 3), two reduction-rotation input clutches C-1 and C-3 arranged so as to surround the front and rear and outer circumference thereof, and further arranged so as to surround the outer circumference thereof. A sun gear locking brake B-1 between the rear casing of the transmission case behind the center support S and a Ravigneaux type planetary gear set G, and a carrier locking brake B-2 surrounding the outer periphery thereof. The one-way clutch F-1 and the non-decelerated rotation input clutch C-2 arranged so as to surround the outer periphery and the rear side are provided, and the center support S and the planetary gear set G , The counter drive gear 11 from the center support S by support boss portion extending rearward is disposed.
[0031]
The counter shaft Y is a shaft extending from the front wall of the transmission case C to a substantially intermediate portion between the center support S and the rear wall, and the front and rear shaft end portions are respectively supported by both walls, and between the center support S and the front wall. The differential drive pinion gear 13 integral with the counter shaft Y, the parking gear 12a extending to the center support S side, having a width exceeding approximately half of the axial direction, and the counter drive gear 11, and the counter shaft Y The counter driven gear 12 integrated with the counter shaft Y by spline engagement is disposed separately from the counter shaft Y.
[0032]
The differential device D on the differential shaft Z is disposed in the vicinity of the rear end of the torque converter T, is bolted to the rear end of the differential case 31, and has a substantially same width as the differential drive pinion gear 13. Is arranged at the same axial position as the differential drive pinion gear 13.
[0033]
The brake B-1 includes a brake drum 22, a brake hub 24 that also serves as the drum of the clutch C-3, a friction member 21 that supports the inner and outer periphery thereof, and a hydraulic servo 23 that is built in the oil pump body P. Has been.
[0034]
The brake drum 22 as a support means for the friction member 21 has a radial flange portion 22c extending in the inner diameter direction on one end side, and is formed in a cylindrical shape with the other end side opened. As shown in FIG. A spline 22b extending outward from the outer diameter of the shape portion is provided. In the present embodiment, the splines 22b are divided into three groups with four strips as one group, and are arranged substantially evenly in the circumferential direction. Inner peripheral teeth 22d are formed on the inner peripheral side of the radial flange portion 22c, and these inner peripheral teeth 22d are fitted into protrusions formed on the wall surface of the center support S that is bolted and fixed to the transmission case C. Is fixed.
[0035]
The friction member 21 forms spline teeth on the inner peripheral surface (in FIG. 1, the upper cross section sandwiching the main shaft X indicates a tooth root portion, and the lower cross section indicates a tooth crest portion), and friction is formed on both surfaces. Separator plate on which a disc 21b with a material attached and spline teeth on the outer peripheral surface (in FIG. 1, the upper cross section sandwiching the main shaft X indicates a tooth crest portion and the lower cross section indicates a tooth root portion) 21a are arranged alternately in the axial direction, a backing plate 21c is disposed on one end side, and a disc spring-like pressure plate 21d is disposed on the other end side. The friction member 21 engages the spline teeth of the separator plate 21a and the backing plate 21c with the brake drum 22 and the brake hub 24 disposed on the inner peripheral side thereof, with the spline 22b on the brake drum 22 side, The spline teeth of the disc 21b are engaged with the splines on the brake hub 24 side.
[0036]
The hydraulic servo 23 includes an annular cylinder formed in the oil pump body P, an annular piston 23a that is fitted in the cylinder so as to be slidable in the axial direction, and whose inner and outer peripheral surfaces are sealed with an O-ring against the cylinder wall. , An apply tube portion (hereinafter referred to as an apply tube in the description of the embodiment) 23c extending in the axial direction from the piston 23a, and a return spring 23b supported by the apply tube 23c.
[0037]
The return spring 23b is a plurality of cylindrical coil springs, and the piston-side end portions thereof are axially formed window holes formed in the apply tube at intermediate portions of the apply tube 23c extending from the piston 23a toward the friction member 21. The brake drum side end is supported by a retainer fitted in 23c 'and the end surface of the brake drum 22 is brought into contact with and supported by a retainer fitted in the window hole 23c' along the apply tube 23c. It is arranged. As shown in FIG. 2, the arrangement pitch circle of each return spring 23b along the apply tube portion 23c is equal to the outer circle of the diff ring gear 14 'having the maximum diameter of the differential device D when viewed from the axial end direction of the automatic transmission. In the present embodiment, 12 return springs 23b are dispersedly arranged so as to avoid the overlapping portion of the pitch circle and the outer circle disposed in the circumferential direction of the apply tube portion 23c. The retainer that supports the piston side end of the return spring 23b is formed with a part of the circumferential notch so as to avoid interference with the diff ring gear 14 'having the maximum outer diameter.
[0038]
According to the automatic transmission configured as described above, the radial direction portion of the counter shaft Y side of the friction member 21 on the main shaft X is inevitably formed between the counter driven gear 12 and the differential drive pinion gear 13 on the counter shaft Y. The arrangement in which the friction member 21 of the brake B-1 of the transmission mechanism is arranged can be obtained without increasing the distance between the main shaft X and the differential shaft Y or extending the shaft length of the transmission. The friction member 21 of the brake B-1 is supported by the brake drum 22 that is separate from the transmission case C, and the outer peripheral side thereof is movable in the axial direction. The friction drum 21 is supported by the center support S of the transmission case C via the brake drum 22. The arrangement of the friction member 21 on the transmission case missing circle portion is realized by the structure in which the rotation is supported.
[0039]
Furthermore, the end of the friction member 21 is brought into contact with the end wall 22a of the brake drum 22 that supports the entire circumference without any breaks, so that the engagement force applied to the friction member 21 at the time of brake engagement is made uniform in the circumferential direction. Therefore, the pressing force of the hydraulic servo piston 23a can be efficiently used for generating the braking torque. As a result, in order to obtain the same torque capacity as compared with the configuration in which the friction member 21 is directly supported by the transmission case C having a missing circle portion, the number of components of the friction member 21 can be reduced or the outer diameter can be reduced. Therefore, the friction member 21 itself can be made compact.
[0040]
Further, the configuration in which the outer peripheral side of the friction member 21 is supported to be substantially non-rotatably supported by the spline 22b of the brake drum 22 in the circumferential direction can prevent the friction member 21 from being eccentric when the brake is engaged. The pressing force of the hydraulic servo piston 23a can be efficiently used for generating the braking torque. Therefore, with this configuration, a stable braking force can always be obtained with respect to the pressing force of the hydraulic servo piston 23a.
[0041]
Further, since the separate brake drum 22 is pressed against the center support S of the transmission case C by the load of the return spring 23b, there is no need to provide additional retaining means such as a snap ring. It is possible to reduce the number of transmission parts and assembly man-hours.
[0042]
Further, when looking at the positional relationship between the apply tube 22 and the diff ring gear 14, in this embodiment, the tooth tip position of the diff ring gear 14 shown by a solid line in FIG. 1 is outside the outer diameter position of the brake drum 22. A sufficient margin is maintained between the outer diameter of the apply tube 23c having a small diameter. Therefore, the tooth tip diameter of the diff ring gear 14 can be expanded to the maximum diameter position indicated by a broken line in the drawing. In this state, the arrangement pitch circle passing through the center of each return spring 23b is formed with the tip diameter of the maximum diameter diff ring gear 14 ′ as shown in FIG. 2 when the transmission is viewed from the end side. Although it overlaps with a part of the outer circle in the circumferential direction, it can be seen that there is room for expanding the diff ring gear diameter to this lapped state by avoiding the arrangement of the return spring 23b at this position. Therefore, with this configuration, the outer diameter of the differential ring gear 14 is brought into contact with the apply tube 23c without changing the axial distance between the main shaft X provided with the brake B-1 and the differential shaft Z provided with the differential device D. The outer diameter of the diff ring gear 14 is reduced from the dimensional relationship of the outer diameter of the brake drum 22 and the differential drive pinion gear 13 with respect to the distance between the main shaft and the counter shaft. Since the outer diameter of the differential drive pinion gear 13 that engages with this can be increased to the outer diameter just before contacting the apply tube 23c, the gear ratio setting between the counter shaft Y and the differential shaft Z can be set to the engine output. It can easily be changed accordingly.
[0043]
As mentioned above, for convenience of understanding the technical idea of the present invention, the description has been made based on one embodiment. However, the present invention is not limited to the illustrated embodiment, and individual claims in the scope of claims. Various specific configurations can be changed and implemented within the scope of the matters described in.
[Brief description of the drawings]
FIG. 1 is an axial sectional view of three axes of an automatic transmission to which the present invention is applied developed on a common plane.
FIG. 2 is a front view of the automatic transmission as viewed in an axial direction from an opening side to which a converter housing is connected.
FIG. 3 is an axial cross section showing an enlarged main shaft portion of the automatic transmission.
FIG. 4 is a front view of the brake drum as viewed from the hydraulic servo side in the axial direction.
[Explanation of symbols]
M Transmission mechanism B-1 Brake X Main shaft Y Counter shaft Z Differential shaft C Transmission case P Oil pump body (transmission case front wall)
11 counter drive gear 12 counter driven gear 13 differential drive pinion gear 14 differential ring gear 21 friction member 22 brake drum 22a end wall 22b spline 23 hydraulic servo 23a piston 23b return spring 23c apply tube

Claims (7)

A main shaft provided with a speed change mechanism, a brake attached to the speed change mechanism, a counter shaft parallel to the main shaft, and a differential shaft parallel to the main shaft and the counter shaft, and transmits power from the main shaft to the counter shaft In the automatic transmission in which the counter drive gear is arranged in the axial middle portion of the main shaft,
The friction member of the brake on the main shaft is disposed at an axial position between the counter driven gear that is disposed on the counter shaft and meshes with the counter drive gear on the main shaft and the differential drive pinion gear that meshes with the diff ring gear on the differential shaft. It is,
The automatic transmission characterized in that the sum of the radius of the brake and the radius of the differential drive pinion gear is larger than the distance between the main shaft and the counter shaft . The brake has a brake drum that is separate from the transmission case, and the friction member of the brake is supported on the outer periphery of the brake drum so as to be axially movable, and the brake drum is supported by the transmission case in a non-rotating manner. The automatic transmission according to claim 1 . The automatic transmission according to claim 2 , wherein the brake drum has an end wall that supports the end portion of the friction member without interruption throughout the entire circumference. The brake drum has splines formed substantially uniformly distributed in the circumferential direction on the peripheral wall, and the friction member is supported so as to be movable in the axial direction with the outer peripheral side engaged with the spline of the brake drum. The automatic transmission according to claim 2 or 3 . 5. The automatic transmission according to claim 2 , wherein the brake drum is pressed against the transmission case by a load applied by a return spring stretched between the brake drum and a hydraulic servo piston of the brake. The hydraulic servo of the brake is built in the front wall of the transmission case, the apply tube portion of the hydraulic servo piston extends in the direction of the friction member at the same axial position as the diff ring gear, and the return spring of the hydraulic servo piston is The automatic transmission according to any one of claims 1 to 5, wherein the automatic transmission is arranged in a distributed manner in a circumferential direction of the apply tube portion while avoiding a circumferential position facing the ring gear side. A main shaft provided with a speed change mechanism, a brake attached to the speed change mechanism, a counter shaft parallel to the main shaft, and a differential shaft parallel to the main shaft and the counter shaft, and transmits power from the main shaft to the counter shaft In the automatic transmission in which the counter drive gear is arranged in the axial middle portion of the main shaft,
A brake for locking a predetermined rotating element of the speed change mechanism on the main shaft;
The brake has a brake drum separate from the transmission case,
Friction members of the brake is supported axially movable on said brake drum,
The brake drum, automatic transmission and having Rutotomoni supported detent in the transmission case, the end walls for supporting seamless across the ends of the friction member on the entire circumference.

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