Vehicle power transmission unit

Abstract

To provide a vehicle power transmission unit in which a brake unit is arranged on the opposite side from an electric motor in a housing, the vehicle power transmission unit having a high mountability to a vehicle.SOLUTION: A power transmission unit 41 includes an electric motor 30, an input shaft 60, a gear mechanism 80a, and a housing 44. Power from the electric motor is transmitted to the input shaft, the gear mechanism, and an axle in order. The housing accommodates the input shaft, the gear mechanism, and the axle. A brake unit 90 is arranged on the opposite side from the electric motor in the housing. A shaft spline hole 61 provided with a female spline part is formed by hollowing a bearing end surface of the input shaft on the electric motor side. An end portion of a motor shaft 32 on the input shaft side is inserted to the shaft spline hole in a spline engagement state.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a power transmission unit for a vehicle. [Background technology]

[0002] It has been known for some time that vehicles such as lawn mowers equipped with a working unit such as a lawn mower have wheels driven by an electric motor to enable travel. Patent Document 1 describes a lawn mower in which both left and right wheels are driven by a common electric motor. Patent Document 2 describes a lawn mower in which the left and right wheels can be driven independently of each other, with the left wheel driven by a left electric motor and the right wheel driven by a right electric motor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2009 / 0069964 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-117026 Summary of the Invention [Problem to be solved by the invention]

[0004] As described above, vehicles that use one or two motors to drive left and right wheels use a power transmission unit that transmits the power of the electric motor to the wheels. In this power transmission unit, the power of the electric motor is transmitted in this order to an input shaft, a gear mechanism, and an axle, and a brake unit for braking the wheels may be located on the opposite side of the housing from the electric motor. Alternatively, the motor shaft of the electric motor and the input shaft to which the brake rotor is fixed may be arranged so that their respective axes coincide with each other, and a sleeve may be splined to connect the opposing ends of the motor shaft and input shaft to each other.

[0005] However, in this case, the fitting portion between the motor shaft and the input shaft is divided into two in the axial direction via the sleeve, which increases the length from the housing-side end face of the electric motor to the outer surface of the brake unit, leaving room for improvement in terms of increasing the mountability of the vehicle power transmission unit on the vehicle.

[0006] The present invention aims to improve the mountability of a vehicle power transmission unit in which a brake unit is disposed on the opposite side of a housing from an electric motor. [Means for solving the problem]

[0007] The vehicle power transmission unit of the present invention comprises an electric motor, an input shaft, a gear mechanism, an axle, and a housing, wherein power from the motor shaft of the electric motor is transmitted in that order to the input shaft, the gear mechanism, and the axle, and the housing accommodates the input shaft, the gear mechanism, and the axle, and a brake unit is disposed on the side of the housing opposite the electric motor, and an axial spline hole with a female spline portion is formed by recessing the end face of the bearing portion of the input shaft on the electric motor side, and the input shaft side end of the motor shaft is inserted in a spline-engaged state into the axial spline hole. [Effects of the Invention]

[0008] In a power transmission unit for a vehicle according to the present invention, in a configuration in which the brake unit is disposed on the opposite side of the housing from the electric motor, the length from the housing-side end face of the electric motor to the outer surface of the brake unit can be shortened, thereby improving the mountability of the power transmission unit for a vehicle. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view of a vehicle equipped with a vehicle power transmission unit according to an embodiment of the present invention; [Figure 2] FIG. 2 is a schematic configuration diagram of the vehicle of FIG. 1 as seen from above. [Figure 3] 3 is a top view of a power transmission structure for left and right wheels including the left and right power transmission units shown in FIG. 2. FIG. [Figure 4A] FIG. 4 is a cross-sectional view of the left power transmission unit shown in FIG. 3. [Figure 4B] FIG. 4B is an enlarged view of the front portion of FIG. 4A. [Figure 5] 4C is a cross-sectional view taken along the line AA in FIG. 4B. [Figure 6] FIG. 4C is a diagram showing the brake unit and spacer separated from the other components in FIG. 4B. [Figure 7] FIG. 7 is a view corresponding to FIG. 6 in another embodiment of the present invention. [Figure 8] FIG. 7 is a view corresponding to FIG. 6 in another embodiment of the present invention. [Figure 9] 6 is a view corresponding to the cross section BB in FIG. 5 in another embodiment of the present invention. [Figure 10] FIG. 4B is a view corresponding to FIG. 4B in another embodiment of the present invention. [Figure 11] FIG. 10 is a view corresponding to FIG. 9 in another embodiment of the present invention. [Figure 12] FIG. 10 is a view corresponding to FIG. 9 in another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present invention will be described in detail below with reference to the drawings. In the following, a vehicle power transmission unit will be described as being mounted on a lawnmower, which is a work vehicle. However, the vehicle on which the vehicle power transmission unit is mounted is not limited to this. It may be another work vehicle having a working section for performing one or more of snow removal, excavation, civil engineering, and agricultural work, an off-road utility vehicle having a loading platform and traveling on rough terrain, an all-terrain vehicle (ATV) known as a buggy, a recreational vehicle (RV), or a recreational off-highway vehicle (ROV). In addition, in the following, a vehicle in which two rear wheels are driven by two motors will be described, but the vehicle may also be configured so that two front wheels are driven by two motors. In addition, the following description will be given of a case where a left-right lever-type operator having two operating levers, one on the left and one on the right, is used, but this is merely an example, and the steering wheel may be used as a turning instruction tool, and the accelerator pedal provided in front of the seat may be used as a driving instruction tool. In the following, similar elements will be given the same reference numerals in all drawings, and duplicate explanations will be omitted or simplified.

[0011] (First embodiment) 1 to 6 show a first embodiment. In the drawings described below, the front-rear direction is indicated by X, the left-right direction is indicated by Y, and the up-down direction is indicated by Z. Furthermore, the front side is indicated by Fr, the left side is indicated by Lh, and the up side is indicated by Up. X, Y, and Z are perpendicular to each other.

[0012] FIG. 1 is a perspective view of a vehicle 10 incorporating a vehicle power transmission unit according to an embodiment. FIG. 2 is a schematic diagram of the vehicle 10. FIG. 3 is a top view of the power transmission structure for left and right wheels 12, 13 including the left and right power transmission units shown in FIG. 2. In the following description, the vehicle power transmission unit will be referred to as a power transmission unit. The vehicle 10 is a riding self-propelled lawnmower suitable for mowing lawns. The vehicle 10 includes two left and right wheels (left wheel 12 and right wheel 13) (FIGS. 2 and 3), two front wheels (left and right caster wheels 15, 16), a lawnmower 18 serving as a working unit, and a left traveling motor 30 and a right traveling motor 31 (FIGS. 2 and 3). The vehicle 10 also includes three deck motors 63 (FIG. 2) serving as working motors, two left and right operating levers 22, 23, a battery 34 (FIG. 2), and a control device (not shown). The left traveling motor 30, the right traveling motor 31, and the deck motor 63 are each an electric motor.

[0013] The left wheel 12 and the right wheel 13 are rear wheels supported on both the left and right rear sides of a main frame 20, which is the vehicle body, and are also main drive wheels. The main frame 20 is formed into a beam structure or the like using metal such as steel. The main frame 20 includes side plate portions 20a, 20b extending substantially in the front-to-rear direction at both left and right ends, and a connecting portion 20c connecting the left and right side plate portions 20a, 20b. A driver's seat 21, where the driver sits as a user, is fixed to the upper side between the rear ends of the left and right side plate portions 20a, 20b.

[0014] Left and right operating levers 22, 23 are arranged separately on the left and right sides of the driver's seat 21, and each moves forward and backward to control the rotation direction and rotation speed of the corresponding left wheel 12 or right wheel 13. Specifically, two guide panels 26, 27 are fixed to the main frame 20 on both the left and right sides of the driver's seat 21, and the two left and right operating levers 22, 23 are supported on the main frame 20 so that they protrude upward from each of the two guide panels 26, 27. The left operating lever 22 corresponds to a driving indicator that controls the acceleration / deceleration, stopping, and forward / reverse rotation of the left traveling motor 30, and the right operating lever 23 corresponds to a driving indicator that controls the acceleration / deceleration, stopping, and forward / reverse rotation of the right traveling motor 31. The tip of each operating lever 22, 23 is grasped by the driver to control the rotation direction and rotation speed of the left wheel 12 and right wheel 13. The left operating lever 22 is operated to control the drive state of the left wheel 12. The right operating lever 23 is operated to specify the drive state of the right wheel 13. Each operating lever 22, 23 is substantially L-shaped, and has a grip portion 24 formed at the upper end thereof that extends in the left-right direction. The grip portion 24 is grasped and operated by the driver. Each operating lever 22, 23 is swingable at the lower end about an axis that runs along the left-right direction. When each operating lever 22, 23 is tilted forward with reference to the N position, which is a neutral position close to the upright position, the operating lever 22 (or 23) controls the travel motor 30 (or 31) on the same side as the operating lever 22 (or 23) to a target number of rotations per unit time (rpm) as a target rotation speed corresponding to forward movement. -1 ) as the target rotation speed. -1 ) can also be set.

[0015] The operating levers 22, 23 indicate that the target rotation speed increases as the amount of tilt increases. When the operating levers 22, 23 are tilted rearward relative to the N position, they indicate that the traveling motor 30 (or 31) on the same side as the operating lever 22 (or 23) should be driven at the target rotation speed corresponding to reverse, and the target rotation speed increases as the amount of tilt increases. When the operating levers 22, 23 are moved to the N position, they indicate that the driving of the traveling motor 30 (or 31) on the same side as the operating lever 22 (or 23) should be stopped. Thus, each operating lever 22, 23, when operated by the user, indicates the target rotation speed of the corresponding traveling motor 30, 31, thereby indicating whether the vehicle should move forward, backward, or stop.

[0016] The tilt positions of the two left and right operating levers 22, 23 in the front-rear direction are detected by left and right lever position sensors (not shown). Each lever sensor includes, for example, a potentiometer. The detection signals of each lever sensor are sent to a control device.

[0017] The two left and right caster wheels 15, 16 are steering wheels supported on the front end of the main frame 20 and are also front wheels. Each caster wheel 15, 16 is provided spaced apart in the longitudinal direction of the vehicle 10 from the left wheel 12 and the right wheel 13. Each caster wheel 15, 16 can freely rotate 360 ​​degrees or more around an axis in the vertical direction (the up and down direction in FIG. 1). The number of caster wheels is not limited to two per vehicle, and only one, or three or more, may be provided per vehicle.

[0018] As shown in FIG. 2, the left traveling motor 30 is connected to the left wheel 12 via a left gear mechanism 80a supported on the rear side of the main frame 20 and a left axle 120. The right traveling motor 31 is connected to the right wheel 13 via a right gear mechanism 80b supported on the rear side of the main frame 20 and a right axle 121. The left traveling motor 30 and the right traveling motor 31 are supported on the left and right sides, respectively, at the rear side of the main frame 20. The drive of each traveling motor 30, 31 is controlled by a control device in response to the operation of the corresponding operating levers 22, 23. As a result, the two left and right traveling motors 30, 31 are connected to the two left and right wheels 12, 13, respectively, and are driven independently of each other.

[0019] The left traveling motor 30 is connected to a battery 34 (FIG. 2) via a traveling inverter (not shown) and is supplied with power from the battery 34. The right traveling motor 31 is connected to a battery 34 via a right traveling inverter (not shown) and is supplied with power from the battery 34. The left traveling motor 30 and the right traveling motor 31 are, for example, three-phase motors. As shown in FIG. 2, the battery 34 is fixed to the upper or lower surface of the main frame 20 behind the driver's seat 21.

[0020] As shown in Figures 1 and 2, the lawnmower 18 is supported on the lower side of the main frame 20 in the longitudinal middle. This positions the lawnmower 18 between the caster wheels 15, 16 and the left and right wheels 12, 13 in the front-to-rear direction. The lawnmower 18 includes three lawnmower blades 18a, 18b, and 18c (Figure 2), which are rotary lawnmower tools and are located inside a mower deck 19, which serves as a cover. The upper sides of the lawnmower blades 18a, 18b, and 18c are covered by the mower deck 19. Each of the lawnmower blades 18a, 18b, and 18c has multiple blade elements that rotate around an axis oriented vertically (the direction from the front to the back of the paper in Figure 2). This allows the blade elements to rotate and cut the grass to cut it. The cut grass is discharged from an exhaust duct 18d located on either the left or right side of the mower deck 19.

[0021] Each of the three lawnmower blades 18a, 18b, 18c is connected to a corresponding one of three deck motors 63, which are work motors. Each deck motor 63 is connected to a battery 34 via a deck inverter (not shown), which is an inverter for the corresponding deck motor 63, and is supplied with power from the battery 34. The driving of each deck inverter is controlled by a control device in response to the operation of a deck switch (not shown). This drives each deck motor 63. Each deck motor 63 is, for example, a three-phase motor.

[0022] The lawnmower may be configured as a lawnmower rotary tool having, for example, a spiral blade arranged on a rotating shaft parallel to the ground surface, and having the function of mowing grass, etc., and including a lawnmower reel driven by a deck motor.

[0023] Furthermore, the two operating levers 22, 23 are configured to be tiltable from an upright neutral position so as to open outward in the vehicle width direction, and the tilted position is the parking brake position. The two operating levers 22, 23 have the function of instructing the operation of the parking brake by moving to the parking brake position. A T-shaped guide hole may be formed in guide panels 26, 27 provided on the top of the vehicle, so that the two operating levers 22, 23 can be opened outward in the vehicle width direction only when the operating levers 22, 23 are in the upright position. The lower ends of the left and right operating levers 22, 23 are connected to brake units 90 (described below) of the left and right power transmission units 41, 42 by a link mechanism. When the operating levers 22, 23 are opened outward, the brake units 90 are activated to brake the left and right wheels 12, 13.

[0024] The above is the overall configuration of the vehicle 10. Next, the power transmission units 41, 42 (FIGS. 2 and 3) mounted on this vehicle 10 will be described. The left power transmission unit 41 is connected to the left wheel 12, and the right power transmission unit 42 is connected to the right wheel 13. The structure of the right power transmission unit 42 is similar to the structure of the left power transmission unit 41, except that it is symmetrical with respect to the center in the vehicle width direction. For this reason, the left power transmission unit 41 will be described in detail below. Hereinafter, the left traveling motor 30 will be referred to as traveling motor 30.

[0025] Fig. 4A is a cross-sectional view of the left power transmission unit 41. Fig. 4B is an enlarged view of the front portion of Fig. 4A. Fig. 5 is a cross-sectional view taken along line AA in Fig. 4B. Fig. 6 is a view showing the brake unit 90 and spacer 110 in Fig. 4B separated from the other components. The power transmission unit 41 is formed by integrally combining a housing 44 which is a transmission case, a traveling motor 30, a gear mechanism 80a and an axle 120, the brake unit 90 and spacer 110.

[0026] The housing 44 accommodates the input shaft 60, the axle 120, and the gear mechanism 80a inside. The gear mechanism 80a is a mechanism that transmits power between the input shaft 60 and the axle 120, and transmits the power from the input shaft 60 to the axle 120 after reducing the speed. The input shaft 60 and the axle 120 are arranged in parallel. The input shaft 60 is connected to the motor shaft 32 of the travel motor 30, and rotates in synchronization with the motor shaft 32.

[0027] The housing 44 is integrated by fastening a first member 46, which forms one axial side, that is, the inner side in the vehicle width direction (the right side of the paper in FIG. 4A), to a second member 47, which forms the other axial side, that is, the outer side in the vehicle width direction (the left side of the paper in FIG. 4A), with a plurality of bolts. Here, the axial direction of the power transmission unit 41 is a direction parallel to the input shaft 60 and the axle 120, and coincides with the vehicle width direction.

[0028] The first member 46 is a gear case having an opening 46a on the front side on the inner side in the vehicle width direction and an opening 46b on the outer side in the vehicle width direction from the front side to the rear side. The second member 47 is open on the inner side in the vehicle width direction, and a cylindrical portion 49 extends axially from a rear portion of the outer surface in the vehicle width direction. The axle 120 penetrates this cylindrical portion 49. The first member 46 and the second member 47 are joined so that the outer peripheral edges of their widthwise ends abut each other, thereby closing the opening 46b on the outer side in the vehicle width direction of the first member 46 with the second member 47. This forms a gear chamber S1 inside the housing 44, in which the gears of the gear mechanism 80a are arranged. Meanwhile, the opening 46a on the inner side in the vehicle width direction of the first member 46 is closed by the motor case 30a of the travel motor 30. The motor shaft 32 of the travel motor 30 and the input shaft 60 are arranged so that their respective axes coincide with each other. The input shaft 60 is rotatably supported by the first member 46 and the second member 47 via bearings 50 and 51. For this reason, the end of the input shaft 60 on the travel motor 30 side serves as a bearing portion to which the inner ring of the bearing 50 is fixed.

[0029] The bearing end face of the input shaft 60 on the traveling motor 30 side is recessed to form an axial spline hole 61, which is a recess with a female spline portion 62 on the inner peripheral surface. The end of the motor shaft 32 on the input shaft 60 side is inserted in a spline-engaged state into the axial spline hole 61. For this reason, the outer peripheral surface of the end of the motor shaft 32 on the input shaft 60 side is formed with a male spline portion 33 that is spline-engaged with the female spline portion 62.

[0030] A brake rotor 91 (FIGS. 4A, 4B, and 6) constituting a brake unit 90 (described below) is fitted to a second end 60a of the input shaft 60 opposite the travel motor 30, and is disposed so as to be unable to rotate relative to the input shaft 60. A brake case 92 constituting the brake unit 90 is screwed to the outer side of the second member 47 in the vehicle width direction with a plurality of bolts 64 so as to cover the second end 60a of the input shaft 60 and the brake rotor 91. As a result, the brake unit 90 is disposed on the opposite side of the housing 44 from the travel motor 30. A brake chamber S2 (FIGS. 4A and 4B) is formed inside the brake case 92.

[0031] As shown in Fig. 4A, the outer end of the axle 120 in the vehicle width direction protrudes from the tip of the cylindrical portion 49, and a hub 52 is fixed to this protruding portion. A left wheel 12 is fixed to the hub 52. An output gear 84 that constitutes the gear mechanism 80a is fitted onto the outer peripheral surface of the axle 120 on the inner side in the vehicle width direction so as to be able to rotate relative to the outer peripheral surface. Power that drives the wheels is input to the output gear 84 from the traction motor 30 via the gear mechanism 80a. A clutch sleeve 71 that constitutes the clutch mechanism 70 is fitted onto the outer peripheral surface of the middle part of the axle 120 at a position adjacent to the inner end of the output gear 84 in the vehicle width direction.

[0032] The clutch mechanism 70 includes an output gear 84, an axle 120, a clutch sleeve 71, and a lever member 74. A male spline portion 120a is formed on the outer peripheral surface of the middle portion of the axle 120. Meanwhile, the clutch sleeve 71 has a cylindrical portion 71a and a pair of flanges 71b, 71c provided on the outer peripheral surfaces of both ends of the cylindrical portion 71a. A locking groove 72 is formed around the entire circumference in a region surrounded by the side surfaces of the pair of flanges 71b, 71c and the outer peripheral surface of the cylindrical portion 71a. Furthermore, a female spline portion formed on the inner peripheral surface of the cylindrical portion 71a is spline-engaged with the male spline portion 120a of the axle 120. As a result, the clutch sleeve 71 is fitted to the axle 120 so as to be non-rotatable relative to the axle 120 but slidable in the axial direction. Protrusions 71d are formed at multiple positions in the circumferential direction on the outer end surface of the flange 71b of the clutch sleeve 71 on the output gear 84 side. The plurality of protrusions 71d can be engaged with through holes formed at a plurality of positions in the circumferential direction of the output gear 84 by the axial movement of the clutch sleeve 71.

[0033] The lever member 74 has a lever shaft 75 extending in the vertical direction, and an arm portion (not shown) extending from the lower end of the lever shaft 75 in a direction perpendicular to the lever shaft 75. A roller (not shown) is rotatably supported at the tip of the arm portion. The lever shaft 75 is rotatably supported by the first member 46, and its upper end protrudes from the outer surface of the first member 46. The roller is engaged in an engaging groove 72 of the clutch sleeve 71, and is rotatable within the clutch sleeve 71.

[0034] An operating arm 76 is fixed to a portion of the lever shaft 75 that protrudes from the first member 46, extending in a direction perpendicular to the lever shaft 75. The tip of the operating arm 76 is connected via a wire or link to a clutch shift command unit (not shown), such as a lever, provided near the driver's seat of the vehicle. When the clutch shift command unit is operated, the clutch sleeve 71 moves outward in the vehicle width direction relative to the axle 120, causing the multiple protrusions 71d to engage with the multiple through-holes of the output gear 84, and the clutch mechanism 70 enters an engaged state. In this state, the power of the travel motor 30 is transmitted from the motor shaft 32 to the input shaft 60, reduced by the gear mechanism 80a, and transmitted to the axle 120 via the clutch mechanism 70. This causes the left wheel 12 to rotate. As a result, the power from the travel motor 30 is transmitted in this order from the motor shaft 32 to the input shaft 60, the gear mechanism 80a, and the axle 120.

[0035] On the other hand, when the clutch sleeve 71 moves inward in the vehicle width direction relative to the axle 120 in response to operation of the clutch switching instruction unit, the multiple protrusions 71d are pulled out of the multiple through-holes of the output gear 84, and the clutch mechanism 70 is disengaged. A coil spring 76 is provided between the clutch sleeve 71 and a retaining ring engaged with the inner end of the axle 120 in the vehicle width direction, and the coil spring 76 biases the clutch mechanism in the direction of engagement.

[0036] The traction motor 30 has a motor rotor fixed to the outer circumferential surface of a motor shaft 32, a stator core facing the outer circumferential surface of the motor rotor, and a three-phase stator coil wound around the stator core. The motor rotor has, for example, permanent magnets arranged at multiple positions around the rotor core. The stator core is fixed to the inside of a motor case 30a. The motor shaft 32 is rotatably supported by bearings (not shown) in the motor case 30a. When three-phase AC power is supplied from a battery to the stator coil, the motor shaft 32 rotates due to the interaction between a rotating magnetic field generated in the stator core and a magnetic field generated by the motor rotor.

[0037] The gear mechanism 80a includes a first helical gear 81 provided on the input shaft 60 by being formed directly on the input shaft 60, an intermediate gear shaft 82 disposed between the input shaft 60 and the axle 120 and having a second helical gear 83 engaged on its outer circumferential surface, and the output gear 84. The second helical gear 83 meshes with the first helical gear 81, and the output gear 84 meshes with teeth on one side of an intermediate gear portion 82a formed directly on the intermediate gear shaft 82. The internal teeth of the second helical gear 83 mesh with teeth on the other side of the intermediate gear portion 82a. The intermediate gear shaft 82 and the axle 120 are rotatably supported inside the housing 44 via bearings.

[0038] Next, the brake unit 90 will be described with reference to FIGS. 4A to 6. As described above, the brake rotor 91 is non-rotatably mounted on the second end 60a of the input shaft 60. The second end 60a is a protruding end that protrudes outward in the vehicle width direction from the housing 44 of the input shaft 60. A cylindrical member 77 is fixed to the outside of the second end 60a so as to be non-rotatable relative to the input shaft 60. A female spline portion 91b is formed on the inner periphery of a rotor spline hole 91a formed in the center of the brake rotor 91. The female spline portion 91b of the brake rotor 91 is spline-engaged with the male spline portion 77a formed on the outer circumferential surface of the sleeve 77. As a result, the male spline portion 77a is inserted into the rotor spline hole 91a in a spline-engaged state. The brake rotor 91 is mounted on the input shaft 60 so as to be non-rotatable relative to the input shaft 60 but movable in the axial direction.

[0039] The brake unit 90 is an electromagnetic brake unit that performs braking by releasing the electromagnetic attraction of an electromagnet. Specifically, the brake unit 90 includes the above-mentioned brake rotor 91, a brake case 92, an armature 93 that is arranged to sandwich the brake rotor 91 between a fixed plate 95 (described later), and an electromagnet 94. In Figures 4A, 4B, and 6, the electromagnet 94 is shown simplified by a diagonal grid portion.

[0040] The brake case 92 includes a cylindrical case body 96 with a bottom that is open at the inner end in the vehicle width direction, and a fixing plate 95 that is connected to the inner end of the case body 96 in the vehicle width direction so as to cover the opening of the case body 96. The case body 96 has a first recess 97 formed in the center of the inner surface of the bottom, into which the second end 60a of the input shaft 60 is inserted. A ring-shaped second recess 98 is formed around the first recess 97 at the bottom of the case body 96, and an electromagnet 94 is disposed in the second recess 98. The electromagnet 94 is an electromagnetic solenoid and a coil. The fixing plate 95 has an annular plate shape and is formed from a metal plate such as a steel plate.

[0041] The armature 93 is annular and formed from a metal plate made of a magnetic material such as a steel plate, and is disposed inside the brake case 92, facing the electromagnet 94. The brake rotor 91 is disposed inside the brake case 92, facing the inner surface of the armature 93 in the vehicle width direction.

[0042] The fixing plate 95 faces an inner end surface 96a of the case main body 96 in the vehicle width direction. The fixing plate 95, together with a spacer 110 adjacent to the fixing plate 95 on the inner side in the vehicle width direction, is sandwiched between the inner end surface 96a and the outer end surface 47a, which is the outer end surface of the second member 47 in the vehicle width direction, and is screw-fastened with bolts 64. The fixing plate 95 is provided to appropriately manage the gap between the armature 93 and the brake rotor 91 when not braking, which affects the effectiveness of the brake. The fixing plate 95 is formed from a metal material such as a steel plate, and is an annular plate-shaped member whose both axial end surfaces are parallel flat surfaces. Furthermore, while the outer diameter of the fixing plate 95 is approximately the same as the outer diameter of the case main body 96, the outer diameter of the spacer 110 is larger than the outer diameter of the fixing plate 95, and the spacer 110 protrudes radially outward from the outer peripheral surface of the fixing plate 95 over the entire circumference.

[0043] As shown in FIG. 6 , through holes 95a for passing the flat head screws 65 are formed at multiple positions around the circumferential surface of the fixing plate 95. The through holes 95a have a conical surface on the spacer side of the circular hole, and the conical surface engages with the head of the screw 65. Furthermore, multiple through holes 93a for fitting with cylindrical sleeves 66 are formed at multiple positions around the circumferential surface of the armature 93 that face the multiple through holes 95a. The armature 93 is axially slidable relative to the sleeves 66. The screws 65 pass through the inside of the sleeves 66 and are threadedly coupled to multiple threaded holes formed on the inner bottom surface of the case body 96 of the brake case 92. At this time, the heads of the screws 65 engage with the through holes, thereby fixing the fixing plate 95 to the case body 96. At this time, multiple bolts 64 that penetrate axially from the outside of the bottom of the brake case 92 penetrate axially through the armature 93 and the fixing plate 95. As a result, the brake unit 90 can be separated from the input shaft 60 with the electromagnet 94 , armature 93 , and brake rotor 91 housed and supported in the brake case 92 .

[0044] In the power transmission unit 41 of this embodiment, the components excluding the brake unit 90 and spacer 110 can be used in combination with any of three types of brake units: two types of electromagnetic brake units of different sizes and a mechanical brake unit, as will be described in detail later. In this example, the brake unit 90, which is a small electromagnetic brake unit, is used in combination with the spacer 110.

[0045] As shown in FIG. 5 , a first group of holes 100 and a second group of holes 102 are formed in the transversely outer end surface of the second member 47 of the housing 44. Specifically, at the transversely outer end of the front portion of the second member 47, the outer end surface 47a is formed around the central tubular portion 49 through which the input shaft 60 passes. The outer end surface 47a has an annular portion 47b against which the outer periphery of the transversely inner surface of the spacer 110 can abut, and a plurality of first ribs 47c and a plurality of second ribs 47d connected to the inner periphery of the annular portion 47b. The first ribs 47c extend radially toward the inner diameter of the annular portion 47b, and the second ribs 47d protrude into a semicircular cross section toward the inner diameter of the annular portion 47b. The first ribs 47c and the second ribs 47d protrude from the transversely outer surface of a wall portion 48 that separates the second member 47 into the transversely inner and outer sides. In FIG. 5, the number of the first ribs 47c is three, but it may be two or four or more.

[0046] Furthermore, a substantially rectangular connecting rib 47e that connects the second rib 47d and the tubular portion 49 is also formed on the inner diameter side of the annular portion 47b. The connecting rib 47e also protrudes from the outer surface of the wall portion 48 of the second member 47 in the vehicle width direction. A retaining recess 99 for retaining a fixed brake pad is formed on the outer end surface of the connecting rib 47e. The fixed brake pad is used when combined with a mechanical brake unit.

[0047] A plurality of first holes 101 are formed on the outer end surfaces of the first ribs 47c and the second ribs 47d on a circumference having the same diameter and centered on the central axis of the annular portion 47b. One first hole 101 is formed in each of the first ribs 47c and the second ribs 47d. The first holes 101 constitute a first hole group 100. Each of the first holes 101 is a threaded hole and is used when assembling a large electromagnetic brake unit or a mechanical brake unit. Note that each of the first holes 101 is not a threaded hole, but rather a simple cylindrical hole before forming a female thread. When combining with a large electromagnetic brake unit or a mechanical brake unit, a female thread can be formed in the cylindrical hole as a post-processing step.

[0048] A plurality of second holes 103 are formed on the outer end surfaces of the plurality of first ribs 47c, on a circumference having the same diameter centered on the central axis of the annular portion 47b, inside the first hole group 100. One second hole 103 is formed in each of the plurality of first ribs 47c. The plurality of second holes 103 constitute a second hole group 102. Each of the plurality of second holes 103 is a screw hole, and is used when assembling a small electromagnetic brake unit as in this example.

[0049] The brake unit 90 is screw-coupled to the second member 47 using the inner second hole group 102 of the first hole group 100 and the second hole group 102, and a plurality of bolts 64 screwed into the second hole group 102. At this time, the bolts 64 that pass through through holes provided at multiple positions in the brake case 92 axially penetrate the armature 93, the fixing plate 95, and the spacer 110, and are screw-coupled to the second hole group 102. At this time, of the bolts 64, an intermediate shaft portion 64a whose outer circumferential surface is a cylindrical surface penetrates the armature 93 so as to be slidable in the axial direction.

[0050] Furthermore, an annular seal groove 104 is formed in the radially middle portion of the annular portion 47b, and a seal member 105 made of an elastic material such as an O-ring, made of resin or rubber, is disposed in the seal groove 104. The seal member 105 is compressed between the vehicle width direction inner surface of the spacer 110 and the bottom surface of the seal groove 104. As a result, the seal member 105 surrounding the first hole group 100 and the second hole group 102 is provided between the vehicle width direction inner end surface of the fixing plate 95, which is the inner end surface of the brake case 92, and the end surface of the housing 44 on the brake unit 90 side. Furthermore, the first hole group 100 is disposed inside the seal member 105 along the circumferential direction, and the second hole group 102 is disposed inside the first hole group 100 along the circumferential direction. As a result, the gap between the brake case 92 and the second member 47 is sealed by the seal member 105. The gaps between both end faces of the fixed plate 95 and the case body 96 and the spacer 110 are sealed by seal members 106, 107 fitted in the seal grooves of the case body 96 and the spacer 110, respectively.

[0051] When the electromagnet 94 is energized, it can attract the armature 93. In addition, a spring (not shown) is provided in the case main body 96 to bias the armature 93 toward the brake rotor 91 so that the armature 93 cooperates with the fixed plate 95 to sandwich and press the brake rotor 91 when the electromagnet 94 is not energized.

[0052] In the brake unit 90, the electromagnet 94 generates an electromagnetic force when energized by the battery 34 (FIG. 2), thereby attracting the armature 93 against the biasing force of the spring. When the two operating levers 22, 23 are operated to the parking brake position or a main switch (not shown) for turning on the vehicle's system power is turned off, for example, and thus the power supply from the battery 34 to the electromagnet 94 is cut off, the armature 93 is pressed against the brake rotor 91 by the biasing force of the spring. As a result, the brake rotor 91 is sandwiched between the armature 93 and the fixed plate 95, thereby braking the corresponding left wheel 12. In this case, the brake unit 90 on the right wheel 13 side acts in the same way, thereby braking the right wheel 13 as well. The control device receives a detection signal that the two operating levers 22, 23 have been operated to the parking brake position, and energizes the electromagnet 94 to brake the wheels 12, 13.

[0053] On the other hand, when the main switch is turned on and the two operating levers 22, 23 are operated to a position other than the parking brake position, current is applied from the battery 34 to the electromagnet 94, causing the armature 93 to move away from the brake rotor 91 against the biasing force of the spring, thereby releasing the braking of the left wheel 12. In this case, the brake unit 90 on the right wheel 13 side also acts in the same way, so the braking of the right wheel 13 is also released, allowing the vehicle to travel.

[0054] A brake pedal (not shown) that can be operated by the driver's foot is provided in front of the driver's seat 21 of the vehicle. When the brake pedal is operated, regenerative braking is performed in the left and right travel motors 30, 31, and the rotation of each travel motor 30, 31 is stopped. On the other hand, a configuration may also be adopted in which, when depression of the brake pedal is detected, the control device cuts off the power supply to the electromagnet 94, and the brake unit 90 brakes the left and right wheels 12, 13.

[0055] According to the power transmission unit 41 described above, the bearing end face of the input shaft 60 on the traveling motor 30 side is recessed to form an axial spline hole 61 with a female spline portion 62, and the end of the motor shaft 32 on the input shaft 60 side is inserted in a splined state into the axial spline hole 61. This allows the length L1 (FIG. 4A) from the end face of the traveling motor 39 on the housing 44 side to the outer surface of the brake unit 90 to be shortened in a configuration in which the brake unit 90 is disposed on the opposite side of the housing 44 from the traveling motor 30. Therefore, as shown in FIG. 3, even if the lateral gaps d1 and d2 between the wheels 12 and 13 and the power transmission units 41 and 42 on the wheels 12 and 13 side are small, the power transmission units 41 and 42 can be easily mounted on a vehicle. This increases the variety of vehicles on which the power transmission units 41 and 42 can be mounted. Furthermore, since the length L1 can be shortened, when the left and right power transmission units 41, 42 are arranged so that the two left and right travel motors 30, 31 are arranged facing each other as shown in Fig. 3, even if the left and right lengths of the travel motors 30, 31 increase due to higher output, the necessary spacing between the travel motors 30, 31 can be ensured. This makes it easier to realize a vehicle equipped with a high-output travel motor.

[0056] The brake unit 90 is an electromagnetic brake unit and includes an electromagnet 94, an armature 93, a brake rotor 91, and a brake case 92. The brake unit 90 is separable from the input shaft 60 with the electromagnet 94, armature 93, and brake rotor 91 housed and supported in the brake case 92. A male spline portion 77a is provided on the outer side of the second end 60a of the input shaft 60 protruding from the housing 44 and is inserted in a spline-engaged state into a rotor spline hole 91a provided in the brake rotor 91. At least a first hole group 100 and a second hole group 102 are formed in the end face of the housing 44 facing the brake unit 90, and the brake unit 90 is screwed together using the second hole group 102. This eliminates the need to previously manufacture and prepare dedicated housings 44 for each different size corresponding to the capacity of the brake unit 90. It is possible to assemble, by screw connection, a brake unit 90 selected from a plurality of brake units 90 of different sizes to the common housing 44. In the above, a case where a small brake unit 90 is assembled to the housing 44 has been described, but a configuration may also be used in which a brake unit 90a larger than the brake unit 90 used in the configuration of this example is assembled to the housing 44, as in a second embodiment which is another example of the embodiment shown in Figure 7 described later.

[0057] Furthermore, in the configuration of this example, a seal member 105 that surrounds the first hole group 100 and the second hole group 102 is provided between the inner end surface of the brake case 92 and the end surface of the housing 44 on the brake unit 90 side. This improves the sealing performance between the housing 44 and the brake case 92 in a configuration in which a brake unit 90 selected from a plurality of brake units 90 of different sizes can be assembled to the common housing 44 by screw connection.

[0058] Furthermore, the first hole group 100 is arranged circumferentially inside the seal member 95, and the second hole group 102 is arranged circumferentially inside the first hole group 100. Furthermore, when the brake unit 90 is a brake unit 90 that is threadedly coupled to the second hole group 102, a spacer 110 that contacts the seal member 95 is provided between the brake case 92 of the brake unit 90 and the end face of the housing 44 on the brake unit 90 side, and the seal member 95 is compressed between the housing 44 and the spacer 110. As a result, in a configuration in which brake units 90 of different sizes can be threadedly coupled to the housing 44, when assembling a small brake unit 90, the seal between the housing 44 and the brake case 92 can be ensured by the seal member 95 outside the first hole group 100 using the simple plate-shaped spacer 110. Therefore, the seal between the housing 44 and the brake case 92 can be improved while suppressing an increase in parts costs.

[0059] In the configuration of this example, as shown in Fig. 5, an air breather device 112 is provided on the upper part of the front portion of the second member 47. The air breather device 112 is attached to a vertical through-hole (not shown) in the second member 47 that communicates with the brake chamber S2 (Fig. 4A). The air breather device 112 is provided to prevent liquids such as water and dust from entering from above, and to enable air inside the brake chamber S2 to be sucked and discharged to the outside of the housing 44 when the lubricating oil in the brake chamber S2 expands. When the internal pressure of the brake chamber S2 increases, air is discharged to the outside of the housing 44 through the air breather device 112, thereby preventing an excessive increase in internal pressure.

[0060] The first member 46 and the second member 47 are symmetrical about the center in the up-down direction. For example, as shown in Fig. 5, the second member 47 has a second through-hole (not shown) formed at a position that is aligned in the up-down direction with the through-hole to which the air breather device 112 is attached. A plug is attached to the lower end of the second through-hole to prevent oil from leaking from the brake chamber.

[0061] As shown in FIG. 5 , the second member 47 has two retaining recesses 99 formed on its outer surface, which is covered by the brake case 92, at symmetrical positions relative to the center in the vertical direction to retain the fixed brake pads. The retaining recesses 99 correspond to retaining holes. When combined with a mechanical brake unit, only the upper retaining recess 99 retains the fixed brake pads. Therefore, for each of the first member 46 and the second member 47, components with the same structure can be used for both the right and left wheels by reversing their up-down orientation. When the second member 47 for the left wheel 12 is used for the right wheel 13, a plug is attached to the outer end of the lower through-hole, and an air breather device 112 is attached to the upper second through-hole. Furthermore, of the two retaining recesses 99 in the second member 47, only the upper retaining recess 99 retains the fixed brake pads. Instead of retaining recesses, the retaining holes may be through-holes that penetrate the second member 47 in the axial direction.

[0062] (Second embodiment) Figure 7 is a diagram of a second embodiment corresponding to Figure 6. In the configuration of this example, a brake unit 90a, which is an electromagnetic brake unit larger than the brake unit 90 used in the configurations of Figures 1 to 6, is used in combination with other elements of the power transmission unit 41a. In this example, a spacer 110 (Figure 4B, etc.) is not used.

[0063] Specifically, the brake unit 90a includes a brake rotor 118, an armature 132 arranged inside a brake case 122 so as to sandwich the brake rotor 118 between the armature 132 and a fixed plate 130 (described later), and an electromagnet 94a. The outer diameters of the brake case 122, the brake rotor 118, the armature 132, and the electromagnet 94a are larger than the outer diameters of the brake case 92, the brake rotor 91, the armature 93, and the electromagnet 94 in the configurations shown in Figures 1 to 6, respectively. The outer diameter of the brake case 122 is approximately the same as the outer diameter of the annular portion 47b of the outer end surface 47a of the housing 44.

[0064] The brake unit 90a is screw-coupled using the first hole group 100 formed in the plurality of first ribs 47c and a plurality of bolts 64 screwed into the first hole group 100, which is farthest from the central axis of the annular portion 47b, out of the first hole group 100 and the second hole group 102 of the housing 44. At this time, the plurality of bolts 64 pass through through holes provided at multiple positions in the case main body 126 of the brake case 122, the armature 132, and the fixing plate 130, and are screwed into the first hole group 100. At this time, the seal member 105 attached to the seal groove 104 of the housing 44 is compressed between the end face of the fixing plate 130 of the brake case 122 and the bottom surface of the seal groove 104. 1 to 6, the configuration of this example does not require a spacer to be connected between the brake case 122 and the housing 44 in order to connect the brake case 122 and the housing 44 while ensuring internal sealing. In this example, the other configurations and operations are the same as those of the configurations of FIGS. 1 to 6.

[0065] (Third embodiment) Fig. 8 is a view of the third embodiment corresponding to Fig. 6. Fig. 9 is a view of the third embodiment corresponding to the cross section BB of Fig. 5. In the configuration of this example, unlike the configurations of the above examples, a brake unit 90b, which is a mechanical brake unit, is used in combination with other elements of the power transmission unit 41b. In this example, as with the configuration of Fig. 7, no spacer is used between the brake case 140 and the housing 44.

[0066] Brake unit 90b is a brake unit separate from the electromagnetic brake unit and is a mechanical brake unit for mechanically braking the wheels. Brake unit 90b includes a brake rotor 146, a movable brake pad 150 ( FIG. 9 ) disposed opposite the outer surface, which is one axial side surface, of brake rotor 146, a brake shaft 152, and a brake case 140. Brake rotor 146 corresponds to the mechanical brake rotor, and brake case 140 corresponds to the mechanical brake case. Brake shaft 152 presses movable brake pad 150 against brake rotor 146. The movable brake pad 150, brake rotor 146, and brake shaft 152 are housed and supported in brake case 140, and can be separated from input shaft 60.

[0067] The brake case 140 is generally disc-shaped, having a flat, disc-shaped rotor arrangement space 140a that is open at its inner end in the vehicle width direction. A recess 143 is formed in the center of the inner surface of the bottom 142, into which the second end 60a of the input shaft 60 is inserted. A generally cylindrical protrusion 144 is formed in the center of the outer surface of the bottom 142 so as to include the recess 143 inside. As shown in FIG. 9 , a protrusion 145 that has a generally semicircular cross section and extends in the front-rear direction so as to be connected to the upper side of the protrusion 144 is formed on the outer surface of the bottom 142. A brake shaft arrangement space 140b that communicates with the rotor arrangement space 140a is formed inside the protrusion 145. The outer diameter of an inner end surface 140c, which is the inner end surface of the brake case 140 in the vehicle width direction and abuts against the outer end surface 47a of the second member 47 of the housing 44, is generally the same as the outer diameter of the outer end surface 47a.

[0068] The brake rotor 146 has a cylindrical tubular portion 147 and a disk-shaped rotor body 148 formed on the outer peripheral surface of the end of the tubular portion 147 facing the housing 44. A male spline portion 60b provided on the outside of a second end portion 60a, which is the protruding end portion of the input shaft 60 protruding from the housing 44, is inserted in a spline-engaged state into a rotor spline hole 149 that is on the inner peripheral surface of the tubular portion 147 and has a female spline portion 149a. The rotor spline hole 149 corresponds to a machine rotor spline hole.

[0069] The cylindrical portion 147 is disposed in a recess 143 of the brake case 140 together with the second end 60a of the input shaft 60, and the rotor body 148 is disposed in the rotor arrangement space 140a. As shown in Fig. 9, when the brake case 140 is coupled to the housing 44, the recess 143, the rotor arrangement space 140a, and the brake shaft arrangement space 140b form a brake chamber S2a.

[0070] As shown in Figure 9, the movable brake pad 150 is in the shape of a block with an L-shaped cross section. In the brake shaft arrangement space 140b of the brake case 140, a retaining recess 140d for retaining the movable brake pad 150 is formed inside the protrusion 145 on the outer surface (left side surface in Figure 9) of the rotor body 148, in a portion facing the front portion of the upper part. The retaining recess 140d is formed by a pair of recesses with rectangular cross sections facing each other in the vertical direction. The movable brake pad 150 is movable in the axial direction of the brake rotor 146 while held in the retaining recess 140d.

[0071] The brake shaft 152 is rotatably supported relative to the brake case 140 in a state extending in the front-to-rear direction of the vehicle so that its tip end portion is disposed in the brake shaft arrangement space 140b of the brake case 140. For this purpose, a through-hole 140e is formed in the front side of the upper portion of the brake case 140, through which the brake shaft 152 passes and which rotatably supports the passed-through portion. A brake lever 154 is fixed to the front end of the brake shaft 152 that protrudes outward from the brake case 140. The tip end of the brake lever 154 is connected via a wire or link to the lower end of the left operating lever 22 corresponding to the brake unit 90b, of two operating levers 22, 23 provided around the driver's seat.

[0072] A protrusion (not shown) having a retaining recess is formed on the inner surface of brake case 140 at a position facing the tip of brake shaft 152, and the tip of brake shaft 152 is rotatably supported in the retaining recess. A cam portion 153 having a substantially semicircular cross section is formed on the tip side portion of brake shaft 152, including the part facing movable brake pad 150. Movable brake pad 150 is held in retaining recess 140d between cam portion 153 and the outer surface of rotor body 148 so as to be movable in the axial direction of brake rotor 146.

[0073] The fixed brake pad 155 has a flat rectangular parallelepiped shape and is pressed against the brake rotor 146 during braking. In the second member 47 of the housing 44, a retaining recess 99 is provided in a portion of the inner surface (the right side surface in FIG. 9) of the rotor body 158 that faces the front portion of the upper part. The fixed brake pad 155 is fixed in this retaining recess 99.

[0074] The brake unit 90b is screw-connected to the housing 44 using all of the first hole groups 100 and second hole groups 102 of the housing 44 that are farthest from the center axis of the annular portion 47b, and a plurality of bolts 64 (FIGS. 8 and 9) that are screw-connected to the first hole groups 100. As a result, when combining a mechanical brake unit 90b, a greater number of bolts 64 are used to connect the brake unit 90b to the housing 44 than when combining an electromagnetic brake unit, thereby improving the connection strength between the brake unit 90b and the housing 44. At this time, the inner end surface 140c of the brake case 140 compresses the seal member 105 attached to the seal groove 104 of the housing 44 between itself and the bottom surface of the seal groove 104. As a result, unlike the configurations of FIGS. 1 to 6, there is no need to connect a spacer between the brake case 140 and the housing 44 to connect the brake case 140 and the housing 44.

[0075] 5, of the two retaining recesses 99 formed on the end surface of the housing 44 on the brake unit side, the upper retaining recess 99 retains a fixed brake pad 155 to be pressed against the brake rotor 146. This makes it possible to replace the electromagnetic brake unit with brake unit 90b as a different mechanical brake unit using a configuration that is common to part of the configuration that uses the electromagnetic brake unit. Furthermore, in place of brake unit 90b, another brake unit such as an electromagnetic brake unit can be screwed together using the first hole group 100 or the second hole group 102, and the male spline portion 60b provided on the outside of the input shaft 60 can be inserted in a spline-engaged state into the rotor spline hole formed in the brake rotor of that different brake unit.

[0076] The above describes the brake unit 90b provided on the left-side power transmission unit 41b, but the brake unit provided on the right-side power transmission unit has the same configuration as the left-side brake unit 90b, except that the left-right relationship is reversed.

[0077] Furthermore, a second through-hole (not shown) is formed in the rear portion of the upper portion of the brake case 140, at a position aligned with the front through-hole 140e in the front-rear direction, so as to be symmetrical with the through-hole 140e about the center in the front-rear direction. A plug is attached to the outer end of the second through-hole to prevent leakage of oil sealed inside the brake case 140. The brake case 140 also has a symmetrical shape about the center in the front-rear direction. For example, in the brake case 140, a retaining recess 140d for retaining the movable brake pad 150 is also formed in the outer surface (left side surface in FIG. 9) of the rotor body 148, in a portion facing the upper rear portion. Therefore, components with the same structure for the brake case 140 can be used for both right and left wheels by reversing the front-rear direction while maintaining the vertical relationship. In addition, by supporting the brake shaft 152 in the second through-hole for the right wheel and attaching a plug to the outer end of the through-hole 140e, the brake case 140 can be used commonly for both the right and left wheels by leaving the front-to-rear relationship as is and reversing only the left-to-right relationship.

[0078] When the two operating levers 22, 23 are operated to the parking brake position, the brake lever 154 rotates in a first direction. This causes the cam portion 153 provided on the brake shaft 152 to rotate as well, so that the cam portion 153 pushes the movable brake pad 150 out of the retaining recess 140d toward the rotor body 148 and presses the movable brake pad 150 against the rotor body 148. As a result, the rotor body 148 is sandwiched between the movable brake pad 150 and the fixed brake pad 155, so that the left wheel 12 is braked. In this case, the brake mechanism on the right wheel 13 side acts in the same way, so that the right wheel 13 is also braked.

[0079] On the other hand, when the two operating levers 22, 23 are operated to a position other than the parking brake position, the brake lever 154 rotates in the second direction, causing the cam portion 153 provided on the brake shaft 152 to also rotate, and the flat portion of the cam portion 153 becomes parallel to the outer surface of the movable brake pad 150. As a result, the movable brake pad 150 moves away from the rotor body 148, and the braking of the left wheel 12 is released. In this case, the brake mechanism on the right wheel 13 side also acts in the same way, and the braking of the right wheel 13 is also released. This allows the vehicle to travel.

[0080] As shown in Fig. 8, a coil spring 156 is provided between the outer surface of the brake case 140 and the brake lever 154. The coil spring 156 biases the brake lever 154 to rotate in the second direction. In this example, the other configurations and functions are the same as those in Figs. 1 to 6.

[0081] (Fourth embodiment) Fig. 10 is a view of the fourth embodiment corresponding to Fig. 4B. Fig. 11 is a view of the fourth embodiment corresponding to Fig. 9. In the configuration of this example, similar to the configurations of the examples shown in Figs. 1 to 7, a brake unit 90c, which is an electromagnetic brake unit, is used in combination with other elements of a power transmission unit 41c.

[0082] In this example, the brake case 160 of the brake unit 90c has the same configuration as the brake case 92 shown in Fig. 4B, except that the vehicle width direction inner portion of the case main body 96 is omitted and the left-right length is reduced. For this reason, the brake case 160 has a first recess 97 that opens to the center of the vehicle width direction inner surface and a second recess 98 in which the electromagnet 94 is disposed around the first recess 97, but does not have a cylindrical portion that accommodates the brake rotor 91 and armature 93.

[0083] Meanwhile, on the vehicle width direction outer surface of the second member 162 constituting the housing 44a, a wall portion 164 is provided around a through hole 163 through which the input shaft 60 passes, and the thickness in the left-right direction is increased. A recess 165 that opens at the vehicle width direction outer end is formed inside the wall portion 164. The recess 165 accommodates the armature 93, the brake rotor 91, and a support plate 170. The support plate 170 is provided to appropriately manage the gap between the armature 93 and the brake rotor 91 when braking is not being applied. The support plate 170 is in the shape of an annular plate and is formed from a metal plate such as a steel plate. The outer diameter of the support plate 170 is approximately the same as that of the armature 93. The outer surface of the support plate 170 does not abut against the brake case 160. The support plate 170 is connected to the brake case 160 by a plurality of screws 65, with the inner diameter portion of the outer surface of the support plate 170 facing the outer surface of the brake rotor 91 in the vehicle width direction, so that the brake rotor 91 can be clamped between the armature 93 and the support plate 170.

[0084] The brake case 160 is fitted into a cylindrical portion 166 formed on the outer surface of a wall portion 164 of the second member 162, and is directly abutted against the outer surface of the wall portion 164 in the vehicle width direction. In this state, a plurality of bolts 64 passing through the brake case 160 are screwed into threaded holes formed in the second member 162. This fixes the brake case 160 to the housing 44a. In this state, a seal member 167 made of an elastic material such as rubber, resin, or an O-ring is fitted into an annular seal groove 161 formed on the outer peripheral surface of the brake case 160, sealing the interior of the brake chamber S2b from the outside.

[0085] Furthermore, the power transmission unit 41c of this example is provided with a malfunction brake release mechanism 172 for mechanically releasing the braking state of the brake unit 90c in the event of a malfunction in the electrical system. The malfunction brake release mechanism 172 includes a pressure plate 173, a brake release pad 174 disposed opposite to the inner surface, which is one axial side surface of the pressure plate 173, a brake release shaft 175, and a brake release lever 177, and is provided within the second member 162. The brake release shaft 175 presses the brake release pad 174 against the pressure plate 173, separating the armature 93, which is in contact with the pressure plate 173, from the brake rotor 91.

[0086] The pressing plate 173 is disk-shaped with a circular center hole, and is provided around the second end 60a of the input shaft 60. The pressing plate 173 is supported rotatably or non-rotatably with respect to the second end 60a of the input shaft 60. Meanwhile, pillar portions 93b protrude parallel to the center axis of the input shaft 60 from a plurality of positions around the circumference of the inner surface of the armature 93 in the vehicle width direction, and the tips of these pillar portions 93b face the outer surface of the pressing plate 173.

[0087] As shown in Fig. 11, the brake release pad 174 is in the shape of a block with an L-shaped cross section. On the inner surface of the second member 162 facing the brake chamber S2b, a holding recess 162a for holding the brake release pad 174 is formed in a portion of the inner surface (right side surface in Fig. 11) of the pressing plate 173 that faces the front portion of the upper part. The holding recess 162a is formed by a pair of recesses with rectangular cross sections that face each other in the vertical direction. The brake release pad 174 is movable in the axial direction of the pressing plate 173 while held in the holding recess 162a.

[0088] The brake release shaft 175 is rotatably supported on the second member 162 in a state extending in the front-to-rear direction of the vehicle so that its tip end portion is disposed in the brake chamber S2b. For this purpose, a through-hole (not shown) is formed in the front side of the upper portion of the second member 162, through which the brake release shaft 175 passes and which rotatably supports the passed-through portion. A brake release lever 177 is fixed to the front end of the brake release shaft 175 that protrudes outward from the second member 162. A brake release operating device provided near the driver's seat is connected to the tip end of the brake release lever 177 via a wire or link.

[0089] A protrusion (not shown) having a retaining recess is formed on the inner surface of the second member 162 at a position facing the tip of the brake release shaft 175. The tip of the brake release shaft 175 is rotatably supported in this retaining recess. A cam portion 176 having a substantially semicircular cross section is formed on the tip side portion of the brake release shaft 175, including the portion facing the brake release pad 174. As a result, the brake release pad 174 is held in the retaining recess 162a between the cam portion 176 and the inner surface of the pressing plate 173 so as to be movable in the axial direction of the pressing plate 173.

[0090] 10, a coil spring 178 is provided between the outer surface of the second member 162 and the brake release lever 177. The coil spring 178 is biased so that the brake release lever 177 rotates in the direction opposite to the brake release direction. As a result, under normal circumstances, the pressure plate 173 and the support plate 170 are separated from each other, as shown in FIG.

[0091] The above describes the malfunction brake release mechanism 172 provided in the left power transmission unit 41c, but the malfunction brake release mechanism provided in the right power transmission unit has the same configuration as the left malfunction brake release mechanism 172, except that the left-right relationship is reversed.

[0092] When the brake release operating device around the driver's seat is operated in the direction to release the brake, the brake release lever 177 rotates in the brake release direction. This causes the cam portion 176 provided on the brake release shaft 175 to rotate, and the cam portion 176 pushes the brake release pad 174 out of the retaining recess 162a toward the pressure plate 173. As a result, the brake release pad 174 is pressed against the pressure plate 173, and the pressure plate 173 pushes the armature 93 outward via the pillar portion 93a, causing the armature 93 to move away from the brake rotor 91. This releases the brake on the left wheel 12. In this case, the malfunction brake release mechanism on the right wheel 13 side also operates in the same way.

[0093] According to the configuration of this example, the spring 180 provided in the brake case 160 applies a biasing force to the armature 93 in a direction that clamps the brake rotor 91 between the armature 93 and the support plate 170, thereby braking the left and right wheels. In this configuration, the braking force of the left and right wheels can be released by a brake release operation. Therefore, in the event of a malfunction in the electrical system, the braking state by the brake unit 90c can be mechanically released. In this example, the other configurations and operations are the same as those of the configurations of Figures 1 to 6.

[0094] Although the above describes a case where the brake release lever 177 is connected to a brake release operating tool by a link or the like, the brake release lever 177 may be configured not to be connected to an operating tool around the driver's seat. In this case, if a malfunction occurs in the electrical system, the user can release the braking force on the wheels by operating the brake release lever 177 attached to the power transmission unit 41c on the underside of the vehicle to the brake release side.

[0095] (Fifth embodiment) Fig. 12 is a diagram of the fifth embodiment corresponding to Fig. 9. The configuration of this example uses a common configuration with part of the configuration using the electromagnetic brake unit shown in Figs. 10 and 11, but replaces the electromagnetic brake unit with a brake unit 90d, which is a mechanical brake unit.

[0096] 10 and 11 constitutes a brake unit 90d. Specifically, a cylindrical portion 147 of a brake rotor 146 is spline-engaged with a male spline portion 60b provided on the outer peripheral surface of the second end portion 60a of the input shaft 60. Furthermore, a fixed brake pad 185 is held in a holding recess 184 formed on the front side of the upper portion of the inner surface of the brake case 182 in the vehicle width direction.

[0097] The movable brake pad 186 is held in the retaining recess 162a of the second member 162 so as to be movable in the axial direction of the brake rotor 146, such that the brake rotor 146 can be sandwiched between the fixed brake pad 185 and the movable brake pad 186. A cam portion 189 is provided on a brake shaft 188 that is rotatably supported on the second member 162, and the cam portion 189 faces the inner surface of the movable brake pad 186. A brake lever 190 is fixed to a portion of the brake shaft 188 that is positioned outside the second member 162. The configurations of the brake lever 190, brake shaft 188, retaining recess 162a, and movable brake pad 186 are similar to the configurations of the brake release lever 177, brake release shaft 175, retaining recess 162a, and brake release pad 174 of the malfunction brake release mechanism 172 shown in Figures 10 and 11, respectively.

[0098] As a result, according to the configuration of this example, it is possible to easily realize a configuration incorporating a mechanical brake unit 90d while utilizing the configuration of the malfunction brake release mechanism 172. In this example, other configurations and operations are similar to those of the configurations in Figures 8 and 9 or the configurations in Figures 10 and 11.

[0099] In the above examples, the left and right wheels are independently driven, with the left wheel driven by the left electric motor and the right wheel driven by the right electric motor. However, the present invention can also be applied to a vehicle in which both wheels are driven by a common electric motor. [Explanation of symbols]

[0100] 10 vehicle, 12 left wheel, 13 right wheel, 15, 16 caster wheel, 18 lawn mower device, 18a to 18c lawn mower blade, 18d exhaust duct, 19 mower deck, 20 main frame, 20a, 20b side plate portion, 20c connecting portion, 21 driver's seat, 22, 23 operation lever, 24 grip portion, 26, 27 guide panel, 30 left travel motor, 31 right travel motor, 32 motor shaft, 33 male spline portion, 34 battery, 41, 42, 41a, 41b, 41c, 41d power transmission unit, 44, 44a housing, 46 first member, 47 second member, 48 wall portion, 49 cylindrical portion, 50, 51 bearing, 60 input shaft, 61 shaft spline hole, 62 female spline portion, 63 deck motor, 64 Bolt, 65 Screw, 66 Sleeve, 70 Clutch mechanism, 71 Clutch sleeve, 72 Locking groove, 73 Coil spring, 74 Lever member, 75 Lever shaft, 76 Coil spring, 77 Sleeve, 78 Main body, 80a, 80b Gear mechanism, 81 First helical gear, 82 Intermediate gear shaft, 83 Second helical gear, 84 Output gear, 90, 90a, 90b, 90c, 90d Brake unit, 91 Brake rotor, 92 Brake case, 93 Armature, 94, 94a Electromagnet, 95 Fixing plate, 96 Case main body, 97 First recess, 98 Second recess, 99 Retaining recess, 100 First hole group, 101 First hole, 102 Second hole group, 103 Second hole, 104 Seal groove, 105, 106, 107 Seal member, 110 spacer, 112 air breather device, 118 brake rotor, 120, 121 axle, 122 brake case, 126 case body, 130 fixed plate, 132 armature, 140 brake case, 142 bottom, 143 recess, 144 protrusion, 145 protrusion portion, 146 brake rotor, 147 cylindrical portion, 148 rotor body, 149 rotor spline hole, 150 movable brake pad, 152 brake shaft, 153 cam portion, 154 brake lever, 155 fixed brake pad, 156 coil spring, 160 brake case, 162 second member, 164 wall portion, 165 recess, 166 cylindrical portion, 167 seal member, 170 support plate, 172 malfunction brake release mechanism, 180 spring, 182 Brake case.

Claims

1. An electric motor, an input shaft, a gear mechanism, an axle, and a housing, a power transmission unit for a vehicle, wherein power from a motor shaft of the electric motor is transmitted to the input shaft, the gear mechanism, and the axle in this order, and the input shaft, the gear mechanism, and the axle are housed in the housing, a brake unit is disposed on the housing opposite to the electric motor; an end surface of a bearing portion of the input shaft on the electric motor side is recessed to form a shaft spline hole provided with a female spline portion; The input shaft side end of the motor shaft is inserted into the shaft spline hole in a splined engagement state. Power transmission unit for vehicles.

2. the brake unit is an electromagnetic brake unit, the electromagnetic brake unit includes an electromagnet, an armature, a brake rotor, and a brake case, and is separable from the input shaft with the electromagnet, the armature, and the brake rotor housed and supported in the brake case, a male spline portion provided on the outside of a protruding end portion of the input shaft protruding from the housing is inserted in a spline-engaged state into a rotor spline hole provided in the brake rotor, At least a first group of holes and a second group of holes are formed in an end surface of the housing on the electromagnetic brake unit side, the electromagnetic brake unit is screwed together using either the first hole group or the second hole group; 2. The power transmission unit for a vehicle according to claim 1.

3. a seal member surrounding the first hole group and the second hole group is provided between an inner end surface of the brake case and an end surface of the housing on the electromagnetic brake unit side; 3. The power transmission unit for a vehicle according to claim 2.

4. the first hole group is arranged along a circumferential direction inside the seal member, and the second hole group is arranged along a circumferential direction inside the first hole group, When the electromagnetic brake unit is the electromagnetic brake unit that is screw-coupled to the second hole group, a spacer that comes into contact with the seal member is provided between the brake case of the electromagnetic brake unit and the end face of the housing on the electromagnetic brake unit side, and the seal member is compressed between the housing and the spacer.

4. The power transmission unit for a vehicle according to claim 3.

5. the first hole group is arranged along a circumferential direction inside the seal member, and the second hole group is arranged along a circumferential direction inside the first hole group, When the electromagnetic brake unit is the electromagnetic brake unit that is screw-coupled to the first hole group, the seal member is compressed by an end surface of the brake case of the electromagnetic brake unit.

4. The power transmission unit for a vehicle according to claim 3.

6. one of the first hole group and the second hole group is used to enable attachment of a mechanical brake unit, which is another brake unit for mechanical braking; a retaining hole for retaining a fixed brake pad to be pressed against a brake rotor constituting the mechanical brake unit is formed in an end surface of the housing on the electromagnetic brake unit side; 3. The power transmission unit for a vehicle according to claim 2.

7. the brake unit is a mechanical brake unit, the mechanical brake unit includes a mechanical brake rotor, movable brake pads arranged opposite to a side surface of the mechanical brake rotor, a brake shaft that presses the movable brake pads against the mechanical brake rotor, and a mechanical brake case, and is separable from the input shaft with the movable brake pads, the mechanical brake rotor, and the brake shaft housed and supported in the mechanical brake case, a male spline portion provided on a protruding end portion of the input shaft protruding from the housing is inserted in a spline-engaged state into a mechanical rotor spline hole provided in the mechanical brake rotor, At least a first group of holes and a second group of holes are formed in an end surface of the housing on the mechanical brake unit side, the mechanical brake unit is screwed together using either the first hole group or the second hole group, a retaining hole is formed in an end surface of the housing on the mechanical brake unit side, and a fixed brake pad that is pressed against the mechanical brake rotor is held in the retaining hole; 2. The power transmission unit for a vehicle according to claim 1.

8. The brake shaft is supported in a state in which it extends in the front-rear direction of the vehicle relative to the mechanical brake case.

8. The power transmission unit for a vehicle according to claim 7.

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