Power transmission unit

Abstract

To provide a power transmission unit capable of realizing a more stable brake.SOLUTION: A power transmission unit 41 contains: a motor including a motor shaft housed in a case 42; a gear shaft; and an output shaft. A power of the motor shaft is transmitted to the output shaft via a gear mechanism. The power transmission unit forms a brake chamber at a position where the gear shaft and the motor shaft, constructing the gear mechanism are opposite. In the brake chamber, the power transmission unit is fitted to the outside of a shaft member as one or both of the gear shaft and the motor shaft. The power transmission unit contains: a brake rotor 76 in which a relative rotation to the shaft member is blocked; a friction material that is arranged on one side of the brake rotor, can be pressed to the brake rotor by a cam surface provided to a rotatable brake shaft 94; and a brake holder 102 that is arranged onto the side opposite to the friction material of the brake shaft, is fixed to a case, or receives a reaction force in response to the friction material that is one part of the case or the brake shaft.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a power transmission unit.

Background Art

[0002] Conventionally, in a vehicle such as a lawn mowing vehicle equipped with a lawn mowing device, it has been known that wheels can be driven by an electric motor to run. Patent Document 1 describes a lawn mowing vehicle that commonly drives left and right wheels with an electric motor. Patent Document 2 describes a lawn mowing vehicle that can drive left and right wheels 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

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a vehicle that drives left and right wheels with one or two motors as described above, a power transmission unit that transmits the power of the motor to the wheels is used. In this power transmission unit, it is conceivable to provide a brake rotor on an internal shaft member and brake the wheels by sandwiching the brake rotor between friction materials such as brake pads from both sides. At this time, it is conceivable to provide a cam surface on a rotatable brake shaft disposed on one side of the brake rotor, and to press the friction material against the brake rotor by the cam surface. However, there is room for improvement in terms of enabling stable braking by simply rotating the brake shaft rotatably supported by the case to press the friction material against the brake rotor.

[0005] The objective of this invention is to enable more stable braking in a power transmission unit. [Means for solving the problem]

[0006] The power transmission unit according to the present invention comprises a motor having a motor shaft housed in a case, a gear mechanism, and an output shaft, wherein the power of the motor shaft is transmitted to the output shaft via the gear mechanism, and a brake chamber is formed at a position where the gear shaft constituting the gear mechanism and the motor shaft face each other, and the brake chamber comprises a brake rotor fitted to the outside of a shaft member which is one or both of the gear shaft and the motor shaft, and which prevents relative rotation with respect to the shaft member, a friction material disposed on one side of the brake rotor and which can be pressed against the brake rotor by a cam surface provided on a rotatable brake shaft, and a brake holder disposed on the opposite side of the brake shaft from the friction material, fixed to the case or being part of the case, and which receives the reaction force of the brake shaft against the friction material. [Effects of the Invention]

[0007] According to the power transmission unit of the present invention, the brake holder is positioned on the side of the brake shaft opposite to the friction material, and the brake holder is fixed to the case and receives the reaction force of the brake shaft against the friction material. This makes it possible to achieve a configuration in which the friction material can be stably pressed against the brake rotor by a rotatable brake shaft. This makes it possible to achieve more stable braking.

[0008] In the power transmission unit described above, the brake rotor is integrally provided on the outer circumference of a cylindrical portion fitted to the outside of the shaft member, and is arranged in a brake rotor housing formed by a recess larger than the outer diameter and thickness of the brake rotor, which is formed on one side wall surface of the brake chamber, and oil is contained in the brake chamber, and the brake holder has a through hole in its substantially central portion that penetrates the cylindrical portion, and is mounted on the one side wall surface so as to cover the brake rotor housing, a gap is formed between the through hole and the cylindrical portion, and the recess may be configured to be open from the brake rotor housing to the motor side portion of the brake chamber through an opening for inserting the brake shaft formed on the one side wall surface.

[0009] With the above configuration, the brake rotor housing is covered by the brake holder, thus limiting the amount of oil that comes into contact with the brake rotor. This reduces the amount of oil stirred up, thereby decreasing the resistance to oil agitation by the brake rotor, and thus reducing energy loss in the power transmission unit. Furthermore, when the brake rotor rotates, the surrounding oil is blown out by centrifugal force through the opening for inserting the brake shaft, which is an open position in the brake rotor housing, into the motor-side portion of the brake chamber. The oil blown out into this portion merges with the oil already present in this portion. The oil blowing out creates a slight negative pressure in the brake rotor housing, drawing oil from the motor-side portion into the brake rotor housing through the gap between the through-hole and the cylindrical portion near the center of the brake holder. This makes it easier for the oil to circulate while in contact with the brake rotor, thus promoting heat dissipation from the brake rotor.

[0010] In the power transmission unit described above, the brake chamber may have a case through-hole that penetrates from the inside to the outside, and an air breather device may be attached to the outer end opening of the case through-hole, with a portion of the brake holder facing the inner end of the case through-hole with a gap in between.

[0011] With the above configuration, it is possible to prevent oil from the brake chamber from splashing into the inside of the case through-hole and penetrating deep inside. Therefore, the reliability of the air breather device can be ensured over the long term.

[0012] In the power transmission unit described above, the case includes a transmission case that houses the gear mechanism and a motor case that houses the motor and is fixed to the transmission case, the transmission case is provided with a mounting surface for the motor case that faces the same direction as one side wall surface of the brake chamber, and the brake holder may be formed by a portion of the motor case that faces the brake shaft and faces into the brake chamber.

[0013] According to the above configuration, the brake holder is formed from a part of the motor case. This eliminates the need for a separate brake holder, which is a separate component from the motor case, thus reducing the number of parts and lowering the manufacturing cost of the power transmission unit. [Brief explanation of the drawing]

[0014] [Figure 1] This is a perspective view of a vehicle equipped with a power transmission unit according to an embodiment of the present invention. [Figure 2] Figure 1 is a perspective view of the power transmission unit of the embodiment for the left wheel of the vehicle. [Figure 3] Figure 2 is a diagram showing a partial cross-section of the power transmission unit. [Figure 4] This is an enlarged view of section A in Figure 3. [Figure 5] This is a parts drawing of the first case that makes up the transmission case. [Figure 6] Figure 4 is a cross-sectional view of BB. [Figure 7] Figure 6 is a cross-sectional view of CC. [Figure 8] Figure 4 is a cross-sectional view of the DD. [Figure 9] This is a diagram from Figure 8 with the brake holder omitted. [Figure 10] It is a sectional view taken along the line E-E of FIG. 4. [Figure 11] It is a sectional view taken along the line F-F of FIG. 4. [Figure 12] It is a perspective view seen from the motor side with the motor and the motor case removed from FIG. 2. [Figure 13] It is an exploded perspective view of FIG. 12. [Figure 14] In the power transmission unit of another example of the embodiment according to the present invention, it is a figure corresponding to FIG. 4. [Figure 15] In the power transmission unit of another example of the embodiment according to the present invention, it is a figure corresponding to FIG. 3. [Figure 16] It is a sectional view taken along the line G-G of FIG. 15. [Figure 17] It is a sectional view taken along the line H-H of FIG. 16.

Mode for Carrying Out the Invention

[0015] Embodiments of the present invention will be described in detail below with reference to the drawings. In the following description, the power transmission unit will be described as being mounted on a work vehicle, specifically a lawnmower. However, the vehicle on which the power transmission unit is mounted is not limited to this, and may be other work vehicles equipped with work implements that perform one or more of the following tasks: snow removal, excavation, civil engineering, or agricultural work; or it may be an off-road utility vehicle (Utility Vehicle) with a cargo bed that travels on rough terrain; or an All Terrain Vehicle (ATV) called a buggy; or a recreational vehicle (RV); or a recreational off-highway vehicle (ROV). Furthermore, in the following description, the vehicle will be described as having two rear wheels driven by two motors. However, the vehicle may also be configured to have two front wheels driven by two motors. Furthermore, the following description explains the use of a left and right lever type control with two operating levers, but this is an example, and the steering wheel may be used as a steering device, and the accelerator pedal located in front of the seat may be used as an accelerator device. In the following drawings, similar elements will be denoted by the same reference numerals.

[0016] (First embodiment) Figures 1 to 10 show the first embodiment. In the drawings described below, the front-to-back direction is indicated by X, the left-to-right direction by Y, and the up-to-down direction by Z. The front side is indicated by Fr, the left side by Lh, and the top side by Up. X, Y, and Z are orthogonal to each other.

[0017] First, the overall configuration of a lawnmower vehicle 10 as an example of a vehicle equipped with the power transmission unit of the present invention will be described, and then the power transmission unit 41 (Figure 2) mounted on the lawnmower vehicle 10 will be described in detail. The engine-less ride-on lawnmower vehicle 10 comprises a main frame 16 that constitutes the vehicle body, two front wheels 18, 20 which are caster wheels, two rear wheels 24 which are left and right, a lawnmower device 25 which is a work implement, two operating levers 34, 36 which are left and right, and a power supply unit 40 including a battery. The left wheel is not shown in Figure 1.

[0018] The driver's seat 17 is fixed to the upper part of the main frame 16 in the middle section in the front-rear direction. The left and right caster wheels 18 and 20 are supported on the front side of the main frame 16. Each caster wheel 18 and 20 is capable of free steering of more than 360 degrees around its vertical axis. The left and right wheels 24 are supported on the rear side of the main frame 16. The left and right wheels 24 are the main drive wheels and are driven by the left and right electric motors, which are the driving motors 70 (Figure 3), described later.

[0019] The caster wheels 18 and 20 can be installed on the lawnmower vehicle 10 in any configuration other than two, for example, just one, or three or more. The caster wheels and drive wheels can also be reversed in the front-to-back position compared to the configuration in this example.

[0020] The mower 25 is supported from below at the midpoint in the front-to-rear direction of the main frame 16. The mower 25 includes a mower deck 26 and three mowing blades (not shown) which are rotating tools for mowing grass, each rotatable about a vertical axis inside the mower deck 26. The rotation of the mowing blades cuts and cuts the grass, etc. Each mowing blade is driven by a motor 28 for the mower.

[0021] The grass can be cut by the rotation of the mowing blade, and the cut grass is discharged from the inside of the mower deck 26 to one side in the width direction of the vehicle.

[0022] The lawn mowing device 25 may be configured to include a lawn mowing reel driven by a motor for a mower, which has a rotating shaft parallel to the ground surface and, for example, a spiral blade arranged on the cylinder to grip and cut grass and the like.

[0023] The two operating levers 34 and 36 are mounted on both the left and right sides of the driver's seat 17 so as to be able to swing in the forward and backward directions around a horizontal axis oriented in the left-right direction. When the lower part of each operating lever 34 or 36 is in an upright, neutral position, the drive motor 70 stops rotating. By operating the levers to swing, the corresponding drive motor 70 is instructed to rotate according to the direction and amount of swing.

[0024] The forward and backward swing positions of the operating levers 34 and 36 are detected by lever sensors (not shown). The detection signal from the lever sensors is input to a control device (not shown) mounted on the vehicle as a signal indicating a rotation instruction for the motor 70 for driving, and the control device rotates the motor 70 in the direction of rotation according to the instruction. The power of each motor 70 is transmitted to the left and right wheels 24 via the gear mechanism 80 (Figure 3) of the power transmission unit 41 (Figure 2), which will be described later. As a result, the vehicle moves forward or backward in response to the operation of the operating levers 34 and 36, and by changing the amount of operation of the left and right operating levers 34 and 36, a difference in rotational speed is created between the left and right wheels 24, causing the vehicle to turn. Furthermore, by tilting one of the two operating levers 34 and 36 forward and the other operating lever backward, the left and right wheels 24 rotate in opposite directions, reducing the turning radius and causing the vehicle to make a sharp turn. The motors 70 are equipped with rotation sensors and position sensors (not shown), which feed back the motor rotation signals to the control device.

[0025] Furthermore, the two operating levers 34 and 36 are configured to be tiltable from an upright neutral position so as to open outward in the vehicle width direction, with the tilted position being the parking brake position. The two operating levers 34 and 36 have the function of instructing the operation of the parking brake by moving to the parking brake position. A T-shaped guide hole (not shown) is provided on the upper part of the vehicle to guide the movement of the operating levers 34 and 36, so that the outward opening of the two operating levers 34 and 36 in the vehicle width direction is possible only from the upright position. The lower ends of the operating levers 34 and 36 are connected to the brake device 90 of the power transmission unit 41, which will be described later, by a link mechanism, and when the operating levers 34 and 36 are opened outward, the brake device 90 is activated and the corresponding wheels 24 are braked.

[0026] The above describes the overall configuration of the lawnmower vehicle 10. Next, the power transmission unit 41 (Figure 2) mounted on this lawnmower vehicle 10 will be explained. The right power transmission unit is connected to the right wheel 24, and the left power transmission unit 41 is connected to the left wheel. The structure of the right power transmission unit is the same as that of the left power transmission unit 41, except that it is symmetrical with respect to the center in the vehicle width direction.

[0027] Figure 2 is a perspective view of the power transmission unit 41 for the left wheel. Figure 3 is a cross-sectional view. Figure 2B is an enlarged view of the rear portion of Figure 2A. Figure 3 is a diagram showing a partial cross-section of the power transmission unit 41 of Figure 2. Figure 4 is an enlarged view of part A of Figure 3. The power transmission unit 41 is formed by integrally combining a case 42, a motor 70 for driving, a gear mechanism 80, and an output shaft 120. The case 42 is formed by combining a transmission case 43 and a motor case 50.

[0028] The transmission case 43 houses an input shaft 60, an output shaft 120, and a gear mechanism 80 inside. The input shaft 60 corresponds to a gear shaft. The gear mechanism 80 is a mechanism that transmits power between the input shaft 60 and the output shaft 120, and also transmits power from the input shaft 60 to the output shaft 120 at a reduced speed. The input shaft 60 and the output shaft 120 are arranged in parallel. As will be described later, the input shaft 60 is connected to the motor shaft 72 of the motor 70 and rotates in sync with the motor shaft 72.

[0029] The transmission case 43 is formed by connecting a first case 44, which forms the inner side in the vehicle width direction (right side of the paper in Figure 4) on one axial side, and a second case 48, which forms the outer side in the vehicle width direction (left side of the paper in Figure 4) on the other axial side, with a number of bolts 58. Here, the axial direction of the power transmission unit 41 is the direction parallel to the input shaft 60 and the output shaft 120, and coincides with the vehicle width direction.

[0030] Figure 5 is a parts diagram of the first case 44. As shown in Figure 5, the first case 44 is a gear case having an opening 44a on the front side on the inside in the vehicle width direction, and an opening 44b on the outside in the vehicle width direction extending from the front to the rear. As shown in Figures 3 and 4, the second case 48 has an opening on the inside in the vehicle width direction, and a cylindrical portion 49 extends axially from the rear part of the outer surface in the vehicle width direction. The output shaft 120 passes through this cylindrical portion 49. The first case 44 and the second case 48 are joined so that their outer peripheral edges at the ends in the vehicle width direction abut, and the opening 44b on the outside in the vehicle width direction of the first case 44 is closed by the second case 48. This forms a gear chamber S1 in which each gear of the gear mechanism 80 of the transmission case 43 is arranged. On the other hand, the front opening 44a on the inside in the vehicle width direction of the transmission case 43 is closed by the motor case 50, which will be described later. As a result, the brake rotor and brake holder described later are positioned, and a brake chamber S2 is formed that includes one end of the input shaft 60 and one end of the motor shaft 72 facing this end, and includes the position where both shafts 60 and 72 face each other. As shown in Figures 4 and 5, of the two bearings 51 and 52 that support the input shaft 60 in the transmission case 43, bearing 51 is held by a partition wall 47 (Figure 5) extending inward from the peripheral wall of the first case 44, and bearing 52 is held on the inner surface of the vertical wall of the second case 48.

[0031] The gear chamber S1 houses the input shaft 60, the gear mechanism 80, and the output shaft 120. The transmission case 43 is filled with an appropriate amount of oil, and an oil level is formed at the boundary with the air layer. As will be described later, the gear chamber S1 and the brake chamber S2 are designed to allow oil to flow freely between them, and the oil is contained in the lower part of both chambers S1 and S2. As a result, the gear mechanism 80 is lubricated in the gear chamber S1, and the brake rotor, as will be described later, is cooled in the brake chamber S2. In Figures 6, 8 to 10 described later, the oil level is shown by the solid line La. An air layer is formed above each of the chambers S1 and S2.

[0032] The input shaft 60 and the output shaft 120 are rotatably supported by the transmission case 43. The outer end of the output shaft 120 in the vehicle width direction protrudes from the tip of the cylindrical portion 49, and a hub 62 is fixed to this protruding portion. The left wheel is fixed to the hub 62.

[0033] Meanwhile, the motor shaft 72 of the motor 70 is connected to one end of the input shaft 60, which is the inner end in the vehicle width direction, by a connecting member 74 acting as a coupling. As a result, the power of the motor 70 is transmitted from the motor shaft 72 to the input shaft 60. The power of the input shaft 60 is reduced by the gear mechanism 80 and transmitted to the output shaft 120. As a result, the wheels 24 rotate and the vehicle moves.

[0034] The motor case 50 houses the motor 70 inside and is bolted to the first case 44, thereby closing the inner opening 44a of the transmission case 43 in the vehicle width direction. The motor case 50 has a bottomed cylindrical case body 50a, and the inner end opening in the vehicle width direction is closed by a cover 50b. The bottom plate portion 50a1 of the case body 50a has a stepped cylindrical portion 50a2 near the center, and the motor shaft 72 passes through the inside of this cylindrical portion 50a2. A bearing 53 and a seal 54 for sealing to prevent circulating oil from the transmission case 43 from entering the motor case 50 are fixed to the inner circumferential surface of the cylindrical portion 50a2. The input shaft 60 is rotatably supported inside the cylindrical portion 50a2 by the bearing 53.

[0035] As shown in Figure 4, the motor 70 is, for example, a permanent magnet type three-phase motor. The motor 70 has a motor rotor fixed to the outer circumference of the motor shaft 72, a stator core facing the outer circumference of the motor rotor, and three-phase stator coils wound around the stator core. The motor rotor has, for example, permanent magnets arranged at multiple positions in the circumferential direction of the rotor core. The stator core is fixed inside the motor case 50. One end of the motor shaft 72, which is the inner end in the vehicle width direction, is rotatably supported by a bearing (not shown) in the motor case 50. When three-phase AC power is supplied to the stator coils from a battery, the motor shaft 72 rotates due to the interaction between the rotating magnetic field generated in the stator core and the magnetic field generated by the motor rotor.

[0036] The motor shaft 72 is positioned on the same axis as the input shaft 60 of the gear mechanism 80, and their respective end faces are spaced apart and connected by a connecting member 74. Specifically, male splines are formed on the outer circumferential surface of one end of the motor shaft 72 and on the outer circumferential surface of the opposite end of the input shaft 60. The axial sides of the cylindrical portion 75 of the connecting member 74 are fitted to the outside of one end of the motor shaft 72 and the outside of one end of the input shaft 60, respectively. A female spline is formed on the inner circumference of the cylindrical portion 75 along the axial length, and engages with the male splines on the outer circumferential surface of one end of the motor shaft 72 and the outer circumferential surface of one end of the input shaft 60, respectively. As a result, the motor shaft 72 and the input shaft 60 rotate as a single unit but cannot rotate relative to each other, and the connecting member 74 and the input shaft 60 are configured to move relative to the motor shaft 72 in the axial direction. Note that the connection between the motor shaft 72 and the input shaft 60 to the cylindrical portion 75 can be made to function similarly by using a key instead of the splines described above.

[0037] Furthermore, a brake rotor 76 is integrally formed on the outer circumference of one end of the cylindrical portion 75 of the connecting member 74. This makes it possible to suppress the increase in size of the power transmission unit 41 in a configuration in which a brake rotor 76 is provided around the input shaft 60. This will be explained in more detail later.

[0038] The gear mechanism 80 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 positioned between the input shaft 60 and the output shaft 120 with a second helical gear 83 locked to its outer circumferential surface, and an output gear 84 fixed to the output shaft 120.

[0039] The intermediate gear shaft 82 has an inner shaft 82a fixed to the transmission case 43 and an outer shaft 82b fitted to the outer circumference of the inner shaft 82a, with the outer shaft 82b being supported so as to be rotatable relative to the inner shaft 82a. An intermediate gear portion 82c, which is axially wide and spur gear shaped, is formed on the outer circumference of the outer shaft 82b, and the output gear 84 meshes with the teeth on the right side of the intermediate gear portion 82c. The internal teeth 83a formed on the inner circumference of the second helical gear 83 mesh with the teeth on the left side of the intermediate gear portion 82c, so as to be non-rotatable relative to each other.

[0040] The second helical gear 83 is positioned relative to the intermediate gear section 82c in the axial direction. To allow for this relative displacement, no protrusions or retaining rings are provided on the outer circumference of the intermediate gear section 82c. Instead, the relative axial displacement of the second helical gear 83 is restricted by a pair of thrust bearing members 121 and 124, as described later. The intermediate gear section 82c is made of sintered material, which allows for low-cost mass production. Since its outer circumference does not have the stepped portion described above, the density distribution of the sintered material can be made uniform, maintaining manufacturing quality such as hardness and strength.

[0041] The second helical gear 83 meshes with the first helical gear 81 to form a helical gear mechanism. The number of teeth of the output gear 84 is greater than the number of teeth of the intermediate gear section 82c, and the number of teeth of the second helical gear 83 is greater than the number of teeth of the first helical gear 81. As a result, the rotation of the input shaft 60 is reduced in two stages by the gear mechanism 80 and transmitted to the output shaft 120.

[0042] The input shaft 60 and the output shaft 120 are rotatably supported by multiple bearings provided in the transmission case 43. The left end of the inner shaft 82a of the intermediate gear shaft 82 is fitted into a recess 48a formed in the vertical wall of the second case 48. The right end of the inner shaft 82a is non-rotatably inserted into a through hole 45 formed in the wall of the first case 44. The right tip of the inner shaft 82a is machined to form a flat portion on its outer circumferential surface, so that the inner shaft 82a cannot rotate when fitted into the flat portion of the through hole 45.

[0043] The first helical gear 81, mounted on the input shaft 60, is sandwiched between the inner rings of two bearings 51 and 52 from both sides. When the first helical gear 81 is rotationally driven, the input shaft 60 experiences an axial displacement (thrust force) equal to the inherent play of the bearings 51 and 52. However, this axial displacement is absorbed by the relative slippage of the spline engagement point of the connecting member 74 and is not transmitted to the motor shaft 72. Therefore, the motor shaft and motor rotor are not moved axially, and there is no risk of detection failures in the various detection sensors (not shown) equipped on the motor shaft and motor rotor, thus maintaining good motor accuracy during operation.

[0044] On the other hand, the second helical gear 83 is configured to be able to move relative to the intermediate gear shaft 82 in the axial direction. In the helical gear mechanism, when each helical gear 81,83 is driven to rotate by the meshing of the first helical gear 81 and the second helical gear 83, a thrust force is applied in the axial direction. As a result, only the second helical gear 83 moves in the axial direction, and the direction of its movement changes according to the rotation direction of the first helical gear 81, i.e., the rotation direction of the motor shaft 72. The second helical gear 83 is made of a hard material such as iron or steel. On the other hand, the transmission case 43 is made of aluminum or an aluminum alloy to reduce weight, and its hardness is lower than that of the second helical gear 83. Therefore, if the second helical gear 83 moves in the axial direction and comes into contact with the transmission case 43, causing friction, the transmission case 43 may be worn down.

[0045] In this embodiment, to prevent such inconveniences, a pair of thrust bearing members 121 and 124 are provided in the transmission case 43 on the case portions facing one axial end face and the other end face of the second helical gear 83. The pair of thrust bearing members 121 and 124 are each supported non-rotatably by the transmission case 43. Specifically, one of the thrust bearing members 121 on the outer side in the vehicle width direction has a plate-shaped body portion and is fitted to one end of the intermediate gear shaft 82, interposed between the second case 48 and the second helical gear 83.

[0046] Figure 5 shows the die sets 201 and 202 used when forming the first case 44 by forging. By applying pressure to the metal material constituting the first case 44 from both the left and right sides of Figure 5 and causing plastic deformation, the first case 44 is formed with openings 44a and 44b on both sides. At this time, a stepped surface 44c is formed on the mating surface between the die sets 201 and 202.

[0047] Figures 6 and 7 are cross-sectional views BB of Figure 4 and CC of Figure 6, respectively. Of the pair of thrust bearing members 121a and 124 facing both end faces of the second helical gear 83, one thrust bearing member 121a has a disc-plate shaped main body portion 121b, as shown in Figure 4, and its central hole is fitted to one end of the intermediate gear shaft 82, interposed between the second case 48 and the second helical gear 83. The arm portion 121c, which is integral with the thrust bearing member 121a, extends in a direction that does not interfere with the first helical gear 81, and its width gradually decreases toward the outside in the direction of extension, with the width remaining constant at the outer end in the direction of extension. The peripheral portion that extends outward from the outer circumference of the second helical gear 83, which is the outer end in the direction of extension of the arm portion 121c, has a bent portion 121d that is bent parallel to the tooth width of the second helical gear 83. The bent portion 121d is fitted into and locked within notches 134a and 135a formed in parts of the partition walls 134 and 135, which are formed in the gear chamber S1 of the first case 44 and the second case 48 to prevent oil agitation. As a result, one of the thrust bearing members 121a is supported in a way that prevents rotation relative to the case 42a, and does not rotate together with the second helical gear 83 even when it comes into contact with it. This eliminates the need for special processing or dedicated parts to support one of the thrust bearing members 121 in the case 42.

[0048] The other thrust bearing member 124 is pad-shaped and fits into a recess 46 formed on the side of the first case 44 on the second case 48 side. A portion of it protrudes from the open end of the recess 46 toward the second helical gear 83 and faces the side of the second helical gear 83. Each thrust bearing member 121, 124 is made of a material with a higher hardness than the material forming the transmission case 43, such as iron or steel. This prevents the second helical gear 83 from coming into contact with the case 42 that houses the second helical gear 83 and causing frictional contact, thus preventing the case 42 from being worn down.

[0049] Next, the connecting member 74 that connects the motor shaft 72 and the input shaft 60 will be described. The connecting member 74 has a cylindrical portion 75 with a female spline on its inner circumference, as described above. A single-plate-shaped brake rotor 76 that protrudes diametrically over its entire circumference is integrally provided on the outer circumference of one end of the cylindrical portion 75. In this example, shaft members 30 are formed on both the input shaft 60 and the motor shaft 72. As a result, the brake rotor 76 is fitted to the outside of the shaft members 30, 30 via the cylindrical portion 75, preventing the brake rotor 76 from rotating relative to the shaft members 30.

[0050] The connecting member 74 is formed by sintering to integrally form the brake rotor 76. On both axial sides of the brake rotor 76, the brake shoes 92 and brake pads 93, which are friction materials and constitute the braking force generating section 91 of the brake device 90, are arranged opposite each other. The brake rotor 76 is pressed against by the brake shoes 92 and brake pads 93 from both axial sides, applying braking torque and stopping the rotation of the input shaft 60 and motor shaft 72.

[0051] Specifically, the brake device 90 comprises a brake rotor 76 and a braking force generating unit 91. The brake rotor 76 is arranged in a brake rotor housing S3 partitioned within the brake chamber S2. The brake rotor housing S3 has a circular recess 101 formed in one side wall T1 of the partition wall 47 forming the brake chamber S2, which is slightly larger than the outer diameter and thickness of the brake rotor 76, and the brake rotor 76 is arranged in this recess.

[0052] Braking force is applied to the brake rotor 76 from the braking force generating unit 91. The braking force generating unit 91 comprises a brake shaft 94, a brake shoe 92, a brake pad 93, and a brake arm 95 (Figure 8). The brake pad 93 is held in a pocket on one side wall surface T1 located within the recess 101.

[0053] Figure 8 is a cross-sectional view of the DD section of Figure 4. Figure 9 is a view of Figure 8 with the brake holder omitted. Figures 10 and 11 are cross-sectional views of the EE section and the FF section of Figure 4, respectively.

[0054] The brake shaft 94 extends vertically from the upper part of the first case 44 and is rotatably supported by the transmission case 43. As shown in Figures 10 and 11, the upper portion of the brake shaft 94 protrudes outward from the upper surface of the first case 44 on the transmission case 43. Specifically, as shown in Figure 11, a through hole 110 for fitting the brake shaft 94 is formed at the upper end of the first case 44 at a position that coincides with a portion of the circumferential direction of the brake rotor 76 in the longitudinal direction. The upper portion of the through hole 110 has a larger diameter than the lower portion and is provided with an O-ring 98 inside to maintain oil tightness.

[0055] On the other hand, a semicircular portion in cross-section having a cam surface 97 is formed on the lower part of the brake shaft 94 that has passed through the brake chamber S2 and reached the brake rotor housing S3. For this reason, openings 150a and 150b (Figure 9) for inserting the lower part of the brake shaft 94 are formed on the one side wall surface T1, separated into upper and lower sections. Each opening 150a and 150b extends in the same direction as the longitudinal direction of the brake shaft 94 and leads to the recess 101. Of the openings 150a and 150b, the brake shaft 94 passes through only the upper opening 150a. The lower opening 150b is used when the transmission case is used in common for both the left and right sides, as described later, by reversing its orientation so that the opening 150b is on the upper side for the right wheel. The cam surface 97 faces the brake shoe 92 which is movable in the axial direction of the transmission case 43. The brake shoe 92 is positioned between the brake shaft 94 and the brake rotor 76, with the surface facing the brake rotor 76 serving as the braking surface. As shown in Figure 13, which will be described later, the brake shoe 92 has a plate-shaped body portion 92a with two legs 92b and 92c protruding from both ends in the front-rear direction, opposite to the brake rotor 76, and is guided by the brake holder 102, which will be described later.

[0056] As shown in Figure 11, the brake pad 93 is mounted on the partition wall 47 of the first case 44. When the cam surface 97 is positioned parallel to the brake shoe 92, the brake shoe 92 moves away from the brake rotor 76 and becomes non-braked. On the other hand, when the brake shaft 94 rotates and the cam surface 97 is tilted relative to the brake shoe 92, the cam surface 97 is pressed against the brake shoe 92, the brake shoe 92 is guided by the brake holder 102, and the braking surface pops out from the brake holder 102. As a result, the brake rotor 76 is pressed towards the brake pad 93 and sandwiched from both sides by the brake shoe 92 and the brake pad 93, so that the brake rotor 76 and the transmission system leading to the wheel 24 to which power is transmitted from the input shaft 60 are braked.

[0057] As shown in Figure 11, the brake arm 95 is attached and fixed to the upper end of the brake shaft 94 in a direction perpendicular to the brake shaft 94. The lower ends of the operating levers 34 and 36 (Figure 1) are connected to the tip of the brake arm 95 via a link mechanism (not shown). A spring 99 is positioned between the brake shaft 94 on the outer surface of the transmission case 43 and the brake arm 95. Both ends of the spring 99 engage with a first engagement pin 100a fixed to the brake arm 95 and protruding downward, and a second engagement pin 100b fixed to the transmission case 43 and protruding upward. As a result, the brake shaft 94 is biased in a first rotational direction via the spring 99 and the brake arm 95 so that the cam surface 97 and the brake shoe 92 are parallel and no braking occurs.

[0058] When the operating levers 34 and 36 of the lawnmower vehicle 10 are operated to the parking brake position, the tip of the brake arm 95 moves against the biasing force of the spring 99, causing the brake shaft 94 to rotate in a second rotational direction, with the cam surface 97 tilted relative to the brake shoe 92 and pressing the brake shoe 92 against the brake rotor 76. The second rotational direction is opposite to the first rotational direction. As a result, the brake device 90 enters a braking state, stopping the rotation of the brake rotor 76 and the wheel 24, and this state is maintained.

[0059] On the other hand, a brake holder 102 fixed to the transmission case 43 is positioned on the opposite side of the brake shoe 92 from the brake shaft 94. The brake holder 102 is provided to enable more stable braking by allowing the brake shoe 92 and brake pad 93 to be pressed more stably against the brake rotor 76.

[0060] Figure 12 is a perspective view from the motor side, with the motor and motor case removed from Figure 2. Figure 13 is an exploded perspective view of Figure 12. As shown in Figures 12 and 13, the brake holder 102 is made of a metal material such as iron, steel, or aluminum alloy. The brake holder 102 has a central opening 102a, which is a through hole through which the cylindrical portion of the connecting member 74 passes, in its approximate central portion. As shown in Figure 13, a guide surface 103 with an arc-shaped cross-section is formed vertically on the front portion of one side of the thickness direction of the brake holder 102, allowing a part of the brake shaft 94 to enter from above. Grooves 104 are also formed at two vertically separated positions on the guide surface 103, which can lock and hold each leg of the brake shoe 92.

[0061] As shown in Figures 4 and 12, the brake holder 102 has a central opening 102a in the center of its front surface for inserting the motor shaft 72 and the cylindrical portion 75. The brake holder 102 is fixed to the transmission case 43 by screwing a bolt 111, which passes through one of the two extensions extending vertically from the rear end and the front end, into a screw hole 112 formed in the one side wall surface T1. The brake holder 102 is positioned on the opposite side of the brake shoe 92 with respect to the brake shaft 94 and is fixed to the transmission case 43. Furthermore, the brake holder 102 has a guide surface 103 that receives the lower end of the brake shaft 94 and abuts against the semi-circular surface opposite the cam surface 97. This guide surface 103 is configured to receive the reaction force of the brake shaft 94 against the brake shoe 92 when the brakes are applied.

[0062] To configure the above disc brake mechanism as a durable wet type, the oil in the gear chamber S1 is allowed to enter the brake chamber S2 through a first oil flow port 113 (Figures 8-10) formed in the partition wall 47 in a long, narrow shape that spans the oil level La and runs vertically, and a second oil flow port 114 (Figure 11) located below the oil level La. As a result, the brake chamber S2 is also filled with oil, the brake rotor 76 is bathed in oil, and the heat generated during brake operation is dissipated through the oil.

[0063] When the motor shaft 72 rotates, the brake rotor 76 also rotates, and if it stirs up the oil in the brake chamber S2, this creates stirring resistance, leading to energy loss in the power transmission unit 41. Therefore, in this embodiment, the brake holder 102 is positioned so that its flat back surface abuts against the opening edge of the recess 101 and covers the front surface of the recess 101, thereby partitioning the motor-side portion S2a of the brake chamber S2, which is the part other than the brake rotor housing portion S3, from the brake rotor housing portion S3. This limits the amount of oil that comes into contact with the brake rotor 76, thereby reducing the amount of oil stirred up. As a result, the stirring resistance of the oil by the brake rotor 76 can be reduced, and thus the energy loss in the power transmission unit 41 can be reduced.

[0064] As described above, the recess 101 is open to the motor-side portion S2a of the brake chamber S2 through openings 150a and 150b formed vertically to allow the lower end of the brake shaft 94 to pass through. As a result, when the brake rotor 76 rotates, the surrounding oil is blown out by centrifugal force from the open position of the brake rotor housing S3 into the motor-side portion S2a of the brake chamber S2, for example, in the directions of arrows α1 and α2 in Figure 8, or arrows β1 and β2 in Figure 11. The blown-out oil merges with the oil in the motor-side portion S2a. The blown-out oil creates a negative pressure in the brake rotor housing S3, which draws the oil in the motor-side portion S2a into the brake rotor housing S3 through the gap between the inner surface of the central opening 102a and the outer surface of the connecting member 74. This makes it easier for the oil to circulate while in contact with the brake rotor 76, thus promoting heat dissipation of the brake rotor 76. In this example, as described later, openings 150a and 150b are formed on both the upper and lower sides so that the transmission case can be reversed vertically and used interchangeably for the left and right power transmission units. However, if interchangeability is not considered, one of the openings 150b may be omitted.

[0065] Furthermore, in this example, the transmission case 43 is symmetrical with respect to its vertical center so that it can be used upside down. As a result, as shown in Figure 10, in the first case 44, a lower through-hole 110a is formed at the lower end position, which is aligned vertically with the upper through-hole 110 into which the brake shaft 94 is fitted, and which is in the longitudinal and vehicle width directions. This lower through-hole 110a is symmetrical with respect to the vertical center of the transmission case 43, and this through-hole 110a is sealed with a plug 115. The shapes of the upper and lower ends of the first case 44, which have the through-holes 110, 110a, are also symmetrical with respect to the vertical center. When the vertical orientation of the transmission case 43 is reversed, the lower through-hole 110a in Figure 10 becomes the upper side, allowing the brake shaft 94 to be inserted in that position, and the upper through-hole 110 in Figure 10 becomes the lower side, allowing the plug 115 to be attached. As shown in Figure 11, the partition wall 47 has a second oil flow port 114 above the oil level La, symmetrically positioned above the second oil flow port 114 below the oil level La. The retaining holes for the brake pads 93 and brake shoes 92 are also provided in symmetrical positions on one side wall T1 and the brake holder 102, respectively, and are swapped when the transmission case 43 is inverted. This allows a single power transmission unit 41 to be used for driving the left and right wheels by simply reversing the orientation of the transmission case 43 vertically.

[0066] Furthermore, in the brake chamber S2 of the first case 44, two vertically penetrating case through-holes 116 and 116a are formed at the upper and lower ends located behind the through-hole 110, at positions aligned vertically and symmetrically with respect to the vertical center. An air breather device 117 is inserted and installed at the outer end opening of the upper case through-hole 116. The air breather device 117 is provided to prevent liquids such as water and dust from entering the transmission case 43, and to allow air to be drawn in and out of the transmission case 43. When the internal pressure rises due to oil expansion in the transmission case 43, the air breather device 117 discharges air to the outside of the transmission case 43, preventing an excessive rise in internal pressure. The lower case through-hole 116a is closed by a plug 115a. The two case through-holes 116 and 116a are also symmetrically shaped with respect to the vertical center of the transmission case 43. As a result, when the vertical orientation of the transmission case 43 is reversed, the lower through-hole 116a in Figure 10 becomes the upper side, allowing the air breather device 117 to be installed, and the upper through-hole 116 in Figure 10 becomes the lower side, allowing the plug 115a to be installed.

[0067] Furthermore, the brake holder 102 is symmetrical with respect to its vertical center, and the portion that protrudes upward at its rear end faces the inner end of the case through-hole 116 with a gap in between. This prevents oil from the brake chamber S2 from splashing into the inside of the case through-hole 116 and penetrating deep inside. This ensures the reliability of the air breather device 117 over the long term. In preparation for the inversion of the transmission case 43, the portion that protrudes downward at its rear end also faces the inner end of the case through-hole 116a with a gap in between.

[0068] When installing the brake holder 102 in the brake chamber S2, the first case 44 shown in Figure 13 is positioned with its motor case joining surface facing upwards, the input shaft 60 and brake pad 93 are assembled, and the cylindrical portion 75 of the connecting member 74 is fitted onto one end of the input shaft 60 through the motor-side opening of the first case 44. Next, the brake shoe 92 is temporarily placed on the brake rotor 76, and the side of the brake shaft 94 inserted into the brake chamber S2 opposite to the cam surface 97 is fitted onto the brake shoe 92. After that, the brake holder 102 is assembled so that it sandwiches the brake rotor 76 between the first case 44. At this time, a plurality of positioning pins 118 protrude in the vehicle width direction from one side wall surface T1 facing the brake holder 102. The positioning pins 118 are fitted into circular recesses 119 formed on the transmission case 43 side surface of the brake holder 102 at positions that align with the tips of the plurality of positioning pins 118, thereby temporarily fixing the brake holder 102. In this state, the brake holder 102 is fixed to the transmission case 43 by screwing multiple bolts 111 that pass through the brake holder 102 into the screw holes 112 of the transmission case 43.

[0069] According to the power transmission unit 41 described above, a helical gear mechanism can be formed by the first helical gear 81 provided on the input shaft 60 and the second helical gear 83 that meshes with this gear, thereby improving the quietness of the gear mechanism 80. In addition, a brake rotor 76 is integrally provided on the outer circumference of the connecting member 74 fitted to the motor shaft 72 and the input shaft 60. This prevents the overall length of the part connecting the motor shaft 72 and the input shaft 60 from increasing. This prevents the power transmission unit 41 from becoming larger when the brake rotor 76 is provided around the input shaft 60. Furthermore, it prevents a significant decrease in machinability compared to a configuration in which a helical gear is formed on a configuration in which the motor shaft and input shaft are integrally formed.

[0070] Furthermore, the gear mechanism 80 includes a second helical gear 83 that meshes with the first helical gear 81, and an intermediate gear shaft 82 that engages with the inner circumference of the second helical gear 83, is capable of axial relative displacement with respect to the second helical gear 83, and prevents relative rotation with respect to the second helical gear 83. A pair of thrust bearing members 121 and 124 are provided on the case portion facing one axial end face and the other end face of the second helical gear 83, formed from a material with higher hardness than the material forming the case 42, and supported so as to be non-rotatable relative to the case 42. This prevents the second helical gear 83 from coming into contact with the case 42 housing the second helical gear 83 and frictional contact when the second helical gear 83 is displaced axially with respect to the intermediate gear shaft 82 due to the meshing of the helical gear mechanism, thus preventing the case 42 from being worn down.

[0071] Furthermore, one end of the intermediate gear shaft 82 is inserted and supported in the wall of the case 42, and one of the pair of thrust bearing members 121, 124 has a plate-shaped main body that is fitted to one end of the intermediate gear shaft 82 and interposed between the case 42 and the second helical gear 83. This eliminates the need for special processing or dedicated parts to support one of the thrust bearing members 121 in the case 42.

[0072] Furthermore, the brake chamber S2 is provided with a brake rotor 76, brake shoes 92, and a brake holder 102 which is positioned on the opposite side of the brake shaft 94 from the brake shoes 92, fixed to the case 42, and receives the reaction force of the brake shaft 94 against the brake shoes 92. This makes it possible to achieve a configuration in which the brake shoes, which are friction material, can be stably pressed against the brake rotor 76 by the rotatable brake shaft 94. As a result, more stable braking can be achieved.

[0073] Furthermore, since the brake holder 102 and the transmission case 43 are symmetrical with respect to the vertical center, parts of the same structure can be used interchangeably for both the right and left wheels. The configuration is the same for both the right and left wheels, except that the vertical positional relationship is reversed. The brake shaft 94 and air breather device 117 are mounted on the upper end of the transmission case 43, and the plug is mounted on the lower end of the transmission case 43. This allows for a reduction in manufacturing costs through the commonality of parts.

[0074] (Another example of an embodiment) Figure 14 is a diagram corresponding to Figure 4, showing a power transmission unit 41a of another embodiment. In this example, the brake holder is configured such that a part of the motor case 130, which constitutes the case 42a, also performs the function of the brake holder. Specifically, the transmission case 43 is provided with a mounting surface T2 for the motor case 130 that faces the same direction as one side wall surface T1 of the brake chamber S2.

[0075] The motor case 130 has a thick cylindrical portion 130a2 that protrudes axially toward the transmission case 43 near the center of the spigot portion 130a1 of the case body 130a. The amount of protrusion is such that, as shown in Figure 11, when the motor case 130 is joined to the first case 44, the tip of the cylindrical portion 130a2 abuts against the mounting surface T2. The mounting surface T2 may be the same surface as one side wall surface T1 of the brake chamber S2. In this state, the tip surface of the cylindrical portion 130a2 is provided with a guide surface 131 into which the lower end of the brake shaft 94 can enter and which abuts against the semicircular surface opposite the cam surface 97, similar to the brake holder 102 in the embodiment shown in Figure 4, and a groove 132 formed at the open end of the guide surface 131 that locks the brake shoe 92 and guides its axial movement. As a result, the brake holder is formed by the portion of the tip surface of the cylindrical portion 130a2 of the motor case 130 that faces the brake chamber S2 and is opposite to the brake shaft 94.

[0076] In this example, the brake holder is formed by the cylindrical portion 130a2 of the case body 130a of the motor case 130. This eliminates the need for a separate brake holder, which is a separate part from the motor case 130, thus reducing the number of parts and lowering the manufacturing cost of the power transmission unit 41a. In this example, the other configurations and operations are the same as those in Figures 1 to 13.

[0077] Figure 15 is a diagram corresponding to Figure 3 in a power transmission unit 41c of another embodiment. Figure 16 is a cross-sectional view GG of Figure 15. Figure 17 is a cross-sectional view HH of Figure 16. In this example, the power transmission unit 41c is incorporated into a vehicle in which one motor 70 drives the two left and right rear wheels of the vehicle. In this vehicle, the two left and right front wheels of the vehicle are steered by a steering mechanism including a steering wheel. In this case, the steering wheel is used as a turning indicator, and an accelerator pedal located in front of the driver's seat is used as an acceleration indicator. The motor 70 is controlled so that its rotational speed increases in response to the operation of the accelerator pedal.

[0078] In the power transmission unit 41c, power from the motor shaft 72 of the motor 70 is transmitted to the first axle 151 and the second axle 152, which extend to the left and right, respectively, via the input shaft 60, the gear mechanism 80, and the differential gear mechanism 140. In the differential gear mechanism 140, power is transmitted to the side bevel gears 153 and 154 fixed to the two output shafts, axles 151 and 152, respectively, causing the wheels fixed to axles 151 and 152 to rotate. Due to this structure, the power transmission unit 41c is not used upside down.

[0079] In this example, case 42b is constructed by sandwiching and fixing the first case 157 between a first axle case 155 that houses the first axle 151 and a second axle case 156 that houses the second axle 152, and then fixing the motor case 50 to the first case 157. The first axle case 155 is constructed in the same way as the second case 48 in the configurations of the above examples. The first case 157 has a through hole 158 formed therein for fitting and fixing one end of the second axle case 156.

[0080] Furthermore, of the pair of thrust bearing members 160 and 124 facing both end faces of the second helical gear 83, one thrust bearing member 160, as shown in Figures 16 and 17, has a disc-plate shaped main body portion 161 that extends diametrically toward the outer circumference of the second helical gear 83 from the portion fitted to the intermediate gear shaft 82, and has two extended portions 162 and 163. One extended portion 162 extends diagonally upward, and the other extended portion 163 extends diagonally downward. Similar to one thrust bearing member 121a in the configuration of Figures 1 to 13, one extended portion 162 has a bent portion 162a at its outer end in the extension direction, and this bent portion 162a is locked to a part of the case 42b.

[0081] The other extended portion 163 is fan-shaped, with its width increasing outward in the direction of extension. The peripheral portion of the other extended portion 163 that extends outward from the outer circumference of the second helical gear 83, which is the outermost end in the direction of extension, has a second bent portion 163a that is bent along the tooth width of the second helical gear 83. The second bent portion 163a is positioned opposite a part of the outer circumferential surface of the second helical gear 83. Therefore, the second bent portion 163a has a greater circumferential length than the bent portion 162a on the side of the other extended portion 162, and extends in the gear chamber S1 where the oil is contained, from the bottom of the case to near the oil surface.

[0082] In this example, the second bent portion 163a of the anti-rotation thrust bearing member 160 is positioned opposite a portion of the outer circumferential surface of the second helical gear 83 on its lower side. This suppresses the increase in energy loss in the power transmission unit 41c caused by the resistance exerted by the oil on the second helical gear 83 and other gears when the oil is agitated by the rotation of the second helical gear 83, when oil is contained in the case 42b. In this example, the other configurations and operations are the same as those in Figures 1 to 13.

[0083] Furthermore, the configuration of one of the thrust bearing members 160 used in this example can also be applied to the configurations shown in Figures 1 to 13, or the configuration shown in Figure 14.

[0084] Furthermore, in the configurations of the above examples, the brake rotor may be fitted to the outside of only one of the gear shaft and the motor shaft, with the gear shaft or motor shaft serving as the shaft member, thereby preventing relative rotation with respect to the shaft member. Alternatively, the gear shaft and motor shaft may be integrated into a single shaft member, with the brake rotor fitted to the outside of this shaft member, thereby preventing relative rotation with respect to the shaft member. [Explanation of Symbols]

[0085] 10 Lawn mowing vehicle, 16 Main frame, 17 Driver's seat, 18, 20 Caster wheels, 24 Wheels, 25 Lawn mowing device, 26 Mower deck, 28 Motor, 30 Shaft member, 40 Power supply unit, 41 Power transmission unit, 42 Case, 43 Transmission case, 44 First case, 45 Through hole, 46 Recess, 47 Partition wall, 48 Second case, 49 Cylinder section, 50 Motor case, 51, 52, 53 Bearings, 54 Seal, 58 Bolt, 60 Input shaft, 62 Hub, 70 Motor, 72 Motor shaft, 74 Connecting member, 75 Cylinder section, 76 Brake rotor, 80 Gear mechanism, 81 First helical gear, 82 Intermediate gear shaft, 83 Second helical gear, 84 Output gear, 90 Brake device, 91 Braking force generation mechanism, 92 Brake shoe, 93 94 Brake pad, 95 Brake shaft, 98 O-ring, 99 Spring, 101 Recess, 102 Brake holder, 103 Recess, 104 Groove, 110, 110a Through hole, 111 Bolt, 112 Screw hole, 113 First oil flow port, 114 Second oil flow port, 115, 115a Plug, 116, 116a Case through hole, 117 Air breather device, 118 Positioning pin, 119 Recess, 120 Output shaft.

Claims

[Claim 1] The motor has a motor shaft housed in a case, and the gear mechanism and output shaft are included. A power transmission unit in which the power of the motor shaft is transmitted to the output shaft via the gear mechanism, A brake chamber is formed at a position where the gear shaft and the motor shaft constituting the gear mechanism are facing each other, and in the brake chamber, A brake rotor is fitted to the outside of one or both of the gear shaft and the motor shaft, such that relative rotation with respect to the shaft is prevented. A friction material is positioned on one side of the brake rotor and can be pressed against the brake rotor by a cam surface provided on a rotatable brake shaft, The brake shaft is positioned on the opposite side of the brake shaft from the friction material and receives the reaction force of the brake shaft against the friction material, The brake rotor is positioned within a brake rotor housing formed by a recess larger than the outer diameter and thickness of the brake rotor, which is formed on one side wall surface of the brake chamber. Oil is contained in the aforementioned brake chamber. The brake holder is a power transmission unit mounted on one side wall so as to cover the brake rotor housing.

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