Power transmission device of small electric vehicle

Abstract

To provide a power transmission device of a small electric vehicle which can inhibit increase of a travel speed by generating the brake force when the travel speed of the small electric vehicle increases in a state where a clutch mechanism is disengaged.SOLUTION: In a small electric vehicle 1, a centrifugal brake 41 is provided coaxially with a clutch mechanism 33. The centrifugal brake 41 rotates in conjunction with rotation of rear wheels 4L, 4R and generate brake force to provide resistance to the rotation of the rear wheels 4L, 4R when the rear wheels 4L, 4R rotate at high rotation speed.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Compact electric vehicles have been known for some time for use by people with weak legs and backs, such as the elderly. Some compact electric vehicles are equipped with a clutch that connects and disconnects the power transmission between a motor, which is the drive source, and the drive wheels (see Patent Document 1).

[0003] The clutch is operated by a clutch lever, and in the normal state where the clutch lever is not operated, the clutch is in an engaged state, connecting the motor and drive wheels, transmitting the motor's power to the drive wheels and causing the small electric vehicle to run.

[0004] On the other hand, when the clutch lever is operated, the clutch is disengaged. When the clutch is disengaged, the drive wheels are disconnected from the motor, eliminating the load on the motor and allowing the small electric vehicle to be easily pushed around by hand. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-346833 Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, in the case of small electric vehicles, it would be preferable to suppress an increase in the running speed of the small electric vehicle so that the vehicle does not reach an unintended speed when the clutch is disengaged and the vehicle is pushed by hand, in order to further improve the performance of the small electric vehicle.

[0007] The present invention has been made in light of the above-mentioned circumstances, and aims to provide a power transmission device for a small electric vehicle that can generate braking force to suppress an increase in the driving speed when the driving speed of the small electric vehicle increases with the clutch mechanism disengaged. [Means for solving the problem]

[0008] The present invention is a power transmission device for a small electric vehicle comprising an input shaft to which power is transmitted from an electric motor, a differential device that transmits the power of the input shaft to drive wheels, a reduction mechanism that is provided between the input shaft and the differential device and that reduces the power of the input shaft before transmitting it to the differential device, and a clutch mechanism that interrupts the transmission of power between the electric motor and the drive wheels, wherein a brake mechanism is provided coaxially with the clutch mechanism, and the brake mechanism rotates in conjunction with the rotation of the drive wheels, and when the drive wheels reach a high rotational speed, generates a braking force that acts as a resistance to the rotation of the drive wheels. [Effects of the Invention]

[0009] As described above, according to the present invention, when the traveling speed of the small electric vehicle increases with the clutch mechanism disengaged, a braking force can be generated to suppress the increase in traveling speed. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a right side view of a small electric vehicle equipped with a power transmission device according to one embodiment of the present invention. [Figure 2] FIG. 2 is a configuration diagram of a power transmission device for a small electric vehicle according to one embodiment of the present invention, showing a state in which the sleeve is located at the clutch engagement position. [Figure 3] FIG. 3 is a rear view of a seat back of a small electric vehicle equipped with a power transmission device according to one embodiment of the present invention. [Figure 4] FIG. 4 is a configuration diagram of a power transmission device for a small electric vehicle according to one embodiment of the present invention, and is a front view (view from the right) of a centrifugal brake. [Figure 5]FIG. 5 is a configuration diagram of a power transmission device for a small electric vehicle according to one embodiment of the present invention, showing a state in which the sleeve is positioned at the clutch disengagement position. [Figure 6] FIG. 6 is a diagram showing the configuration of a centrifugal brake of a power transmission device for a small electric vehicle according to one embodiment of the present invention, illustrating a state when the brake lever is not operated by the driver. [Figure 7] FIG. 7 is a diagram showing the configuration of a centrifugal brake of a power transmission device for a small electric vehicle according to one embodiment of the present invention, and shows a state when the brake lever is operated by the driver. DETAILED DESCRIPTION OF THE INVENTION

[0011] A power transmission device for a small electric vehicle according to one embodiment of the present invention comprises an input shaft to which power is transmitted from an electric motor, a differential device that transmits the power of the input shaft to the drive wheels, a reduction mechanism that is provided between the input shaft and the differential device and that reduces the power of the input shaft before transmitting it to the differential device, and a clutch mechanism that interrupts the transmission of power between the electric motor and the drive wheels, and a brake mechanism is provided coaxially with the clutch mechanism, which rotates in conjunction with the rotation of the drive wheels and generates a braking force that acts as resistance to the rotation of the drive wheels when the drive wheels reach a high rotational speed.

[0012] As a result, the power transmission device of a small electric vehicle according to one embodiment of the present invention can generate braking force to suppress the increase in driving speed when the driving speed of the small electric vehicle increases while the clutch mechanism is disengaged. [Example]

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A power transmission device for a small electric vehicle according to an embodiment of the present invention will now be described with reference to the drawings.

[0014] 1 to 7 are diagrams showing a power transmission device for a small electric vehicle according to one embodiment of the present invention. In Fig. 1 to 7, the up / down, front / rear, left / right directions are based on the small electric vehicle, and the front / rear direction of the small electric vehicle is the front-rear direction, the left / right direction of the small electric vehicle (vehicle width direction) is the left / right direction, and the up / down direction of the small electric vehicle (vehicle height direction) is the up / down direction.

[0015] First, the configuration will be described. In Figure 1, a small electric vehicle 1 has a body frame 2, and the body frame 2 rotatably supports left and right front wheels 3R ​​(only the right front wheel is shown) and left and right rear wheels 4L, 4R (see Figure 2) via suspensions not shown.

[0016] The body frame 2 is covered with a resin cover including a front cover 5, a leg shield 6, a floor 7, a rear cover 8, and the like.

[0017] The rear cover 8 is formed in a roughly box shape and is provided at the rear of the small electric vehicle 1, bulging upward from the body frame 2. The space inside the rear cover 8 accommodates the drive motor 21 shown in FIG. 2, a power transmission device 22 that transmits the power of the drive motor 21 to the rear wheels 4L, 4R as drive wheels via drive shafts 10L, 10R, a battery (not shown) that supplies power to the drive motor 21, a controller (not shown) that controls the small electric vehicle 1, and the like.

[0018] As shown in Figure 1, a seat 11 on which a driver sits is provided above the rear cover 8, and the seat 11 is attached to the vehicle body frame 2 via a bracket 12. The seat 11 has a seat cushion 13 and a seat back 14.

[0019] Arm supports 15 are provided on both sides of the seat back 14, and the arm supports 15 are supported by the seat back 14 so as to be rotatable about fulcrums 15a.

[0020] The leg shield 6 protrudes upward from the body frame 2 at the front of the small electric vehicle 1, and protects the driver seated in the seat 11 from wind or the like blowing against the driver's legs.

[0021] A steering shaft 16 for steering the left and right front wheels 3R ​​is provided inside the leg shield 6, and a handle unit 17 is attached to the upper end of the steering shaft 16.

[0022] The driver sits on the seat 11 and turns the handle unit 17 left and right to steer the left and right front wheels 3R.

[0023] The handle unit 17 includes a switch box 17A, semicircular operating handles 17B provided on both the left and right sides of the switch box 17A, and an accelerator lever and a brake lever (not shown) provided in correspondence with the operating handles 17B.

[0024] The switch box 17A is provided with switches such as a power switch 17a for starting the small electric vehicle 1, a maximum speed setting switch (not shown), and a forward / reverse switch.

[0025] 2, the power transmission device 22 includes a reducer case 23. The reducer case 23 is covered with a rear cover 8 and attached to the body frame 2.

[0026] A motor housing chamber 23A is formed in the reducer case 23, and the motor housing chamber 23A houses a drive motor 21 as an electric motor and an electromagnetic clutch 25. When the driver operates the accelerator lever in the traveling direction, the drive motor 21 rotates to generate power (driving force).

[0027] When the electromagnetic clutch 25 is engaged, it prevents the drive motor 21 from rotating and maintains the stationary state of the small electric vehicle 1. Furthermore, the electromagnetic clutch 25 is in an engaged state when not energized.

[0028] In other words, the electromagnetic clutch 25 acts as a parking brake for the small electric vehicle 1, and when the accelerator lever is released and the speed becomes almost zero, it is engaged and works to maintain the small electric vehicle 1 in a stopped state.

[0029] When the small electric vehicle 1 is running with the main power supply turned on, or when the driver operates the accelerator lever with the main power supply turned on, the electromagnetic clutch 25 is released to enable rotation of the drive motor 21. Note that deceleration when the accelerator lever is released as usual is performed by regenerative braking of the drive motor 21.

[0030] When the clutch mechanism 33 described later is not disconnected, the drive motor 21 and the rear wheels 4L and 4R, which are the drive wheels, are connected, so when the electromagnetic clutch 25 is engaged, the small electric vehicle 1 can be maintained in a stopped state.

[0031] Furthermore, the electromagnetic clutch 25 allows the drive motor 21 to rotate when energized, and is engaged when de-energized to prevent the drive motor 21 from rotating. In other words, the electromagnetic clutch 25 is engaged when the main power supply is turned off, and therefore functions as a parking brake to maintain the small electric vehicle 1 in a parked state.

[0032] A gear accommodating chamber 23B is formed to the right of the motor accommodating chamber 23A in the reducer case 23. A partition wall 23C is disposed between the motor accommodating chamber 23A and the gear accommodating chamber 23B, and the gear accommodating chamber 23B is separated from the motor accommodating chamber 23A by the partition wall 23C.

[0033] An input shaft 26, which will be described later, is disposed to pass through the partition wall 23C, and an oil seal 18A is provided between the partition wall 23C and the input shaft 26. Lubricating oil is filled in the gear accommodating chamber 23B, and the gear accommodating chamber 23B is liquid-tightly separated from the motor accommodating chamber 23A by the oil seal 18A.

[0034] A centrifugal brake accommodating chamber 23D that accommodates a centrifugal brake 41, which will be described later, is formed to the right of the gear accommodating chamber 23B in the reducer case 23. A partition wall 23E is disposed between the gear accommodating chamber 23B and the centrifugal brake accommodating chamber 23D, and the centrifugal brake accommodating chamber 23D is separated from the gear accommodating chamber 23B by the partition wall 23E.

[0035] A counter shaft 30, which will be described later, is disposed to pass through the partition wall 23E, and an oil seal 18B is provided between the partition wall 23E and the counter shaft 30. The oil seal 18B prevents the lubricating oil in the gear accommodating chamber 23B from leaking into the centrifugal brake accommodating chamber 23D, and the gear accommodating chamber 23B and the centrifugal brake accommodating chamber 23D are separated liquid-tightly.

[0036] The gear accommodating chamber 23B accommodates an input shaft 26, a reduction gear mechanism 27, and a differential gear 28. The input shaft 26 has an input gear 26A, and is rotatably supported by bearings 29A and 29B in the reducer case 23. The input shaft 26 is connected to the drive motor 21, and power is transmitted from the drive motor 21 to the input shaft 26.

[0037] The reduction mechanism 27 includes a counter shaft 30, a counter gear 30A, and a sleeve 31. The left end of the counter shaft 30 is rotatably supported by the partition wall 23C via a bearing 29C.

[0038] The right end of the countershaft 30 penetrates the partition wall 23E and protrudes into the centrifugal brake housing chamber 23D. That is, the countershaft 30 has a protruding end portion 30r at its right end that protrudes from the gear housing chamber 23B into the centrifugal brake housing chamber 23D, and the starting end of the protruding end portion 30r of the countershaft 30 is rotatably supported on the partition wall 23E by a bearing 29D.

[0039] That is, the countershaft 30 is rotatably supported by the partition walls 23C and 23E via the bearings 29C and 29D. In the partition wall 23E, the bearing 29D and the oil seal 18B are provided side by side, and the oil seal 18B is attached to an oil seal attachment portion that protrudes from the partition wall 23E toward the centrifugal brake housing chamber 23D.

[0040] The centrifugal brake housing chamber 23D of the reducer case 23 is composed of a cylindrical peripheral wall 23F that protrudes rightward from the partition wall 23E and a cover 37 that closes the open end of the peripheral wall 23F. The peripheral wall 23F extends from the partition wall 23E in the axial direction of the countershaft 30 to a length greater than the countershaft 30, and surrounds the protruding end 30r with its right end open.

[0041] A cover 37 is fastened to the open end of the peripheral wall 23F by bolts 20A, and the centrifugal brake accommodating chamber 23D is closed by the cover 37.

[0042] A counter gear 30A is attached to the counter shaft 30 so as to be rotatable relative to the counter shaft 30. The left end of the counter shaft 30 is inserted into the counter gear 30, which is rotatably supported. The counter gear 30A is attached to the counter shaft 30 so as to be connectable with the counter shaft 30 by a sleeve 31 (described later) so as to rotate integrally with the counter shaft 30, and meshes with the input gear 26A.

[0043] The input gear 26A has a smaller diameter than the counter gear 30A, and the power of the drive motor 21 is transmitted from the input shaft 26 via the input gear 26A and the counter gear 30A to the counter shaft 30 at a reduced speed. In other words, the rotational speed of the drive motor 21 is reduced by the input gear 26A and the counter gear 30A and then transmitted to the counter shaft 30.

[0044] The sleeve 31 is disposed to the right of the counter gear 30A so as to be able to engage with the counter gear 30A. The counter shaft 30 is inserted into the sleeve 31, and the sleeve 31 is supported by the counter shaft 30. The sleeve 31 is spline-fitted to the counter shaft 30, so that the sleeve 31 rotates integrally with the counter shaft 30 and is movable in the axial direction of the counter shaft 30.

[0045] A final drive gear 31A is formed on the outer periphery of the sleeve 31, and the final drive gear 31A is constantly meshed with the final driven gear 28A. The final drive gear 31A is formed to have a smaller diameter than the final driven gear 28A.

[0046] A return spring 36 is provided between the sleeve 31 and the bearing 29D, and the return spring 36 biases the sleeve 31 toward the counter gear 30A.

[0047] An inner peripheral gear portion 30a is formed on the inner peripheral portion of the counter gear 30A. The sleeve 31 is biased by a return spring 36, so that its left end enters between the counter shaft 30 and the inner peripheral gear portion 30a, and the final drive gear 31A formed on the sleeve 31 is fitted into the inner peripheral gear portion 30a of the counter gear 30A.

[0048] In other words, in this embodiment, a final drive gear 31A is provided on the outer peripheral surface of the sleeve 31 all the way to the left end in the axial direction, and when the sleeve 31 moves to the left, the final drive gear 31A immediately engages with the inner peripheral gear portion 30a of the counter gear 30A, causing the sleeve 31 to rotate integrally with the counter gear 30A.

[0049] The differential device 28 includes a final driven gear 28A and a differential case 28B. The final driven gear 28A is attached to the outer periphery of the differential case 28B and rotates integrally with the differential case 28B.

[0050] The power of the drive motor 21 is reduced in speed by the input gear 26A and the counter gear 30A, and then transmitted from the final drive gear 31A to the differential case 28B via the final driven gear 28A.

[0051] The differential case 28B is rotatably supported on the partition walls 23C, 23E by bearings 29E, 29F. The differential device 28 includes a pair of pinion gears 28C, 28D, a pinion shaft 28E that rotatably supports the pinion gears 28C, 28D, and a pair of side gears 28F, 28G.

[0052] The pinion gears 28C, 28D are disposed opposite each other across the central rotation axis C of the differential case 28B. When the differential case 28B rotates, the pinion gears 28C, 28D revolve around the central rotation axis C of the differential case 28B and rotate about the axis of the pinion shaft 28E.

[0053] The side gears 28F, 28G mesh with the pinion gears 28C, 28D. One end of the left and right drive shafts 10L, 10R is fitted to the inner peripheries of the side gears 28F, 28G, respectively, and the drive shafts 10L, 10R rotate integrally with the side gears 28F, 28G.

[0054] The rear wheels 4L, 4R are connected to the other ends of the drive shafts 10L, 10R, and rotate integrally with the drive shafts 10L, 10R.

[0055] When power is transmitted from the final drive gear 31A to the final driven gear 28A, the differential case 28B of the differential device 28 rotates integrally with the final driven gear 28A.

[0056] At this time, the side gears 28F, 28G rotate differentially relative to each other via the pinion gears 28C, 28D, and transmit the power of the drive motor 21 to the left and right drive shafts 10L, 10R and the rear wheels 4L, 4R in a differentially rotatable manner.

[0057] The power transmission device 22 includes a clutch mechanism 33, which is disposed on the counter shaft 30. The clutch mechanism 33 includes a sleeve 31 and a slide fork 34 attached to the sleeve 31.

[0058] The final drive gear 31A protrudes radially outward from the sleeve 31 and is formed from the left end of the sleeve 31 toward the right end.

[0059] A flange portion 31B is provided at the right end portion of the sleeve 31, and the return spring 36 is disposed between the flange portion 31B and the bearing 29D.

[0060] An annular groove 31C is formed between the final drive gear 31A and the flange portion 31B, and a slide fork 34 is fitted into the annular groove 31C.

[0061] A clutch lever 35 (see FIG. 3) is connected to the slide fork 34 via an operation force transmission member (not shown).

[0062] As shown in FIG. 3, a recess 14a is formed on the rear surface of the seat back 14, and a clutch lever 35 is housed in the recess 14a.

[0063] The recess 14a is formed to be large enough for a person's finger to fit inside so that the user can operate it, and the clutch lever 35 is attached to the seat back 14 so that it can rotate freely between a clutch connection lever position where it is housed in the recess 14a and a clutch disconnection lever position where it is operated by the user and is positioned above the clutch connection lever position and protrudes from the recess 14a.

[0064] The clutch lever 35 is biased to the clutch connection lever position by a spring member (not shown) so that the clutch lever 35 is housed in the recess 14a and is in the clutch connection lever position. When the clutch lever 35 is in the clutch connection lever position, the slide fork 34 moves to move the sleeve 31 to the clutch connection position 61 (see Figure 2).

[0065] At this time, the counter gear 30A is connected to the counter shaft 30 via the final drive gear 31A, and the power of the drive motor 21 can be transmitted to the rear wheels 4L, 4R.

[0066] When the clutch lever 35 is rotated from the clutch engagement lever position to the clutch disengagement lever position, the operation force transmission member moves the slide fork 34, and moves the sleeve 31 to the clutch disengagement position 62 against the biasing force of the return spring 36 (see Figure 5).

[0067] At this time, the counter gear 30A and the final drive gear 31A are separated, the connection between the counter gear 30A and the counter shaft 30 is released, the braking force of the electromagnetic clutch 25 cannot be transmitted to the rear wheels 4L and 4R, and the small electric vehicle 1 becomes pushable by hand.

[0068] In other words, the clutch lever 35 allows the clutch mechanism 33 to manually connect and disconnect the power transmission path from the drive motor 21 to the rear wheels 4L, 4R.

[0069] Here, intermittent means mechanically disconnecting and connecting the power transmission path between the drive motor 21 and the rear wheels 4L, 4R. When the clutch mechanism 33 is disconnected, the power transmitted from the drive motor 21 (electromagnetic clutch 25) to the rear wheels 4L, 4R is cut off, and when the clutch mechanism 33 is connected, power can be transmitted from the drive motor 21 (electromagnetic clutch 25) to the rear wheels 4L, 4R.

[0070] For example, after getting off the small electric vehicle 1, the user holds the operating handle 17B with one hand and rotates the clutch lever 35 from the clutch engagement lever position to the clutch disengagement lever position with the other hand, thereby moving the sleeve 31 to the clutch disengagement position 62 via the operation force transmission member. This allows the user to move the small electric vehicle 1 with a light force. Here, the user refers to the driver, a caregiver who cares for the driver, or a maintenance technician.

[0071] When the user or the like releases the clutch lever 35 after the small electric vehicle 1 has moved, the spring member rotates the clutch lever 35 from the clutch disengagement lever position to the clutch engagement lever position, and the operating force transmission member moves, causing the sleeve 31 to move to the clutch engagement position 61 due to the biasing force of the return spring 36.

[0072] As a result, the rear wheels 4L, 4R are connected to the drive motor 21, and the resistance force of the drive motor 21 and the braking force of the electromagnetic clutch 25 act as a parking brake, thereby keeping the small electric vehicle 1 stopped.

[0073] In this way, the clutch mechanism 33 of the small electric vehicle 1 of this embodiment mechanically connects and disconnects the transmission of power between the drive motor 21 and the rear wheels 4L, 4R.

[0074] The operating force transmission member is composed of a cable member having one end connected to the clutch lever 35, a member connected to the cable member, which rotates with the movement of the cable member and converts this rotational movement into the axial direction (linear direction) of the sleeve 31, and a slide fork 34 which receives force from the converting member and moves in the axial direction of the sleeve 31.

[0075] However, the configuration of the operation force transmission member is not limited to this, and any member that transmits the operation force from the clutch lever 35 to the sleeve 31 may be used.

[0076] 2 and 4, the small electric vehicle 1 has a centrifugal brake 41, which constitutes a braking mechanism, attached to the protruding end 30r of the counter shaft 30. The centrifugal brake 41 is provided coaxially with the counter shaft 30, to which the sleeve 31, which constitutes the clutch mechanism 33, is attached, and is actuated by the rotation of the counter shaft 30.

[0077] That is, the centrifugal brake 41 is provided coaxially with the clutch mechanism 33 and is disposed inside the centrifugal brake housing chamber 23D.

[0078] The centrifugal brake 41 includes a disk-shaped plate 42, brake weights 43A, 43B, and 43C, a return spring 44, and a cylindrical member 48.

[0079] Plate 42 is disposed closer to partition wall 23E in the left-right direction than brake weights 43A, 43B, and 43C. A cylindrical portion 42A is provided at the center of plate 42 as an attachment portion for protruding end portion 30r, and cylindrical portion 42A protrudes from plate 42 to the side opposite partition wall 23E.

[0080] The protruding end 30r of the countershaft 30 is inserted into the cylindrical portion 42A and spline-fitted, so that the plate 42 rotates integrally with the countershaft 30.

[0081] Three shaft portions 42B are provided on the peripheral edge of the plate 42 outside the cylindrical portion 42A, and the shaft portions 42B protrude from the plate 42 in parallel with the axial direction of the counter shaft 30 on the side opposite to the partition wall 23E.

[0082] A shaft 42B is inserted into one end of brake weights 43A, 43B, and 43C arranged along the periphery of the disk-shaped plate 42, and the brake weights 43A, 43B, and 43C are able to swing around the shaft 42B as a swing axis.

[0083] A snap ring 45 is fitted to the protruding end of the shaft portion 42B, and the brake weights 43A, 43B, and 43C are prevented from coming off the shaft portion 42B by the snap ring 45.

[0084] One end of a return spring 44 is engaged with the brake weights 43A, 43B, and 43C, and the other end of the return spring 44 is engaged with the adjacent brake weights 43A, 43B, and 43C. In other words, the return spring 44 elastically connects the adjacent brake weights 43A, 43B, and 43C.

[0085] The return spring 44 biases the brake weights 43A, 43B, and 43C radially inward with the shaft portion 42B as a pivot axis. In other words, the return spring 44 biases the brake weights 43A, 43B, and 43C so that they are positioned closer to the axis of the counter shaft 30 and have a reduced diameter.

[0086] A brake shoe 43D is provided on the outer periphery of each of the brake weights 43A, 43B, and 43C. The brake shoe 43D faces the peripheral wall 23F in the radial direction. The brake shoe 43D in this embodiment constitutes a friction member.

[0087] The cylindrical member 48 is provided inside the centrifugal brake housing chamber 23D radially inward of the peripheral wall 23F, and is disposed radially between the peripheral wall 23F and the brake weights 43A, 43B, and 43C. In other words, the cylindrical member 48 covers the radially outer sides of the brake weights 43A, 43B, and 43C.

[0088] 6 and 7, cylindrical member 48 is a bowl-shaped part that is open at the right end and has a disk portion 48A that is attached to partition wall 23E and a cylindrical portion 48B that extends from disk portion 48A to the side opposite partition wall 23E. Cylindrical portion 48B covers the radially outward sides of brake weights 43A, 43B, and 43C.

[0089] A plurality of boss portions 23a are provided around the oil seal attachment portion of partition wall 23E where oil seal 18B is attached. Boss portions 23a are formed so as to protrude from partition wall 23E toward centrifugal brake 41.

[0090] A central hole is formed in the center of the disk portion 48A, through which the countershaft 30 passes, and the oil seal 18B and the oil seal mounting portion fit into this central hole. Bolt holes are formed around the central hole, and the disk portion 48A is fixed to the boss portion 23a with bolts 20D.

[0091] The cylindrical portion 48B has an open end opposite the partition wall 23E, and brake weights 43A, 43B, 43C and return spring 44 integral with the plate 42 can be attached to the inside of the cylindrical member 48 from the open end side.

[0092] When the rotational speed of the counter shaft 30 is less than a predetermined speed, the brake weights 43A, 43B, and 43C of the centrifugal brake 41 are in a state in which they are contracted in diameter by the force of the return spring 44, and the brake shoe 43D faces the inner surface of the cylindrical portion 48B in the radial direction without abutting against it.

[0093] In other words, the centrifugal brake 41 does not generate a braking force unless the rotational speed of the countershaft 30 reaches a predetermined speed. In contrast, when the rotational speed of the countershaft 30 reaches or exceeds the predetermined speed, the centrifugal force of the centrifugal brake 41 overcomes the biasing force of the return spring 44, causing the brake weights 43A, 43B, and 43C to move radially outward, and the brake shoe 43D comes into sliding contact with the inner surface of the cylindrical portion 48B, generating a braking force.

[0094] In other words, in the small electric vehicle 1, when the rotation speed of the counter shaft 30 increases, the brake weights 43A, 43B, 43C swing radially outward around the shaft portion 42B as the swing center against the biasing force of the return spring 44, and the brake shoes 43D of the brake weights 43A, 43B, 43C are pressed against the inner circumferential surface of the cylindrical portion 48B, generating a frictional force.

[0095] This contact pressure depends on the centrifugal force acting on the brake weights 43A, 43B, and 43C, and increases as the rotational speed of the countershaft 30 increases. As a result, the centrifugal brake 41 does not generate braking force up to a certain speed, but generates braking force according to the rotational speed once the certain speed is exceeded.

[0096] 4 and 6, each of the brake weights 43A, 43B, and 43C has a protrusion 43a that protrudes from the inner end of each of the brake weights 43A, 43B, and 43C toward the central axis of the countershaft 30 so as to approach the cylindrical portion 42A.

[0097] A slope 43b is formed on the surface of the protrusion 43a facing the cover 37, which slopes inward (toward the partition wall 23E) as it approaches the central axis of the countershaft 30. In detail, the slope 43b is inclined in the axial direction of the countershaft 30 so that the inner end side is positioned closer to the sleeve 31 (left side) than the outer end sides of the brake weights 43A, 43B, and 43C (see FIG. 2).

[0098] 6, a cam member 46 is attached to the cover 37 at the central axis position of the countershaft 30. A female threaded hole 37a is formed in the cover 37 at the central axis position of the countershaft 30, and a cam member 46 having a male thread 46a formed on the outer circumferential surface thereof is screwed into this female threaded hole 37a.

[0099] When the cam member 46 rotates, the cam member 46 moves in the axial direction of the countershaft 30 due to the action of the female screw hole 37 a of the cover 37 and the male screw 46 a of the cam member 46 .

[0100] A tapered surface 46b is formed on the left end of the cam member 46. The tapered surface 46b is a truncated cone-shaped surface having a center line coaxial with the center axis of the countershaft 30, and is inclined so that the inner end side is located closer to the sleeve 31 (left side) than the outer end side in the axial direction of the countershaft 30, and the generatrix of the inclined surface 43b and the tapered surface 46b are formed parallel to each other and are in contact with each other without any gap in the inclined direction.

[0101] A recess 46c is formed in the center of the left end face of the cam member 46, and the protruding end 30r of the counter shaft 30 is inserted into the recess 46c.

[0102] An operating lever 47 is attached to the cam member 46 by bolts 20B and 20C. Specifically, an operating member such as a wire cable (not shown) is connected to one end of the operating lever 47, and the other end of the operating lever 47 is connected to the cam member 46 by bolts 20B and 20C. The swinging of the operating lever 47 rotates the cam member 46, causing the cam member 46 to advance and retreat in the axial direction.

[0103] Bolt 20B is attached to the rotation center of cam member 46. Bolt 20C has a smaller diameter than bolt 20B and is attached radially outward of bolt 20B, and prevents rotation of operating lever 47 so that it does not rotate relative to cam member 46 around bolt 20B when cam member 46 is rotated by operating lever 47.

[0104] When the brake lever is returned to the brake release position by the driver's operation, a return spring (not shown) presses one end of the operating lever 47 to one side around the axis of the counter shaft 30. This pressure causes the operating lever 47 to swing, and the cam member 46 rotates and moves to the right in the axial direction.

[0105] At this time, the cam member 46 moves away from the counter shaft 30 so that the gap between the bottom surface 46d of the recess 46c of the cam member 46 and the protruding end portion 30r becomes larger (see FIG. 6).

[0106] As a result of the movement of the cam member 46, which had been acting to spread the brake weights 43A, 43B, and 43C, the return spring 44 brings the brake weights 43A, 43B, and 43C into a reduced diameter position closer to the axis of the countershaft 30, so that the brake shoe 43D is no longer in contact with the cylindrical portion 48B and the countershaft 30 becomes rotatable.

[0107] On the other hand, when the driver grips the brake lever and operates the brake lever from the brake release position to the brake operation position, the wire cable pulls one end of the operation lever 47 to the other side around the axis of the counter shaft 30.

[0108] At this time, the cam member 46 rotates and approaches the counter shaft 30 so that the gap between the bottom surface 46d of the recess 46c and the protruding end portion 30r becomes smaller, and as the cam member 46 approaches the counter shaft 30, the contact surface of the tapered surface 46b with the inclined surface 43b shifts from the inner end side of the tapered surface 46b to the outer end side (see Figure 7).

[0109] As a result, the brake weights 43A, 43B, and 43C move away from the axis of the counter shaft 30 (to an expanded diameter) against the force of the return spring 44, and the brake shoe 43D slides against the cylindrical portion 48B.

[0110] As a result, the centrifugal brake 41 prevents the counter shaft 30 from rotating. In other words, the centrifugal brake 41 functions as a brake when the small electric vehicle 1 is being pushed and moves, and functions as a parking brake when the small electric vehicle 1 is parked.

[0111] Next, the operation will be described. When the clutch lever 35 is operated by a user or the like from the clutch engagement lever position to the clutch disengagement lever position, the sleeve 31 moves from the clutch engagement position 61 to the clutch disengagement position 62 against the biasing force of the return spring 36, and the drive motor 21 and the electromagnetic clutch 25 are disconnected from the rear wheels 4L and 4R.

[0112] This eliminates the load and braking force of the drive motor 21 and the electromagnetic clutch 25, making it possible to easily move the small electric vehicle 1 by pushing it manually without using the driving force of the drive motor 21.

[0113] Here, if an attempt is made to manually push the small electric vehicle 1 on a slope and the clutch is disengaged to disconnect the drive motor 21 from the rear wheels 4L, 4R, and the brake function is then released by the cam member 46, there is a risk that the small electric vehicle 1 will travel at an unintended speed.

[0114] Once the small electric vehicle 1 starts moving and gains speed, it cannot be easily stopped even if the driver operates the cam member 46 to generate braking force.

[0115] The small electric vehicle 1 of this embodiment is decelerated along the power transmission path from the drive motor 21 to the rear wheels 4L, 4R as it approaches the rear wheels 4L, 4R.

[0116] In other words, since the diameter of the final driven gear 28A is larger than the diameter of the final drive gear 31A, the rotational speed of the counter shaft 30, to which power is transmitted from the final driven gear 28A via the final drive gear 31A, becomes the highest when the small electric vehicle 1 is pushed by hand.

[0117] The small electric vehicle 1 of this embodiment has a centrifugal brake 41 provided coaxially with the clutch mechanism 33. The centrifugal brake 41 rotates in conjunction with the rotation of the rear wheels 4L, 4R, and generates a braking force that acts as resistance to the rotation of the rear wheels 4L, 4R when the rear wheels 4L, 4R reach a high rotational speed.

[0118] In other words, when the centrifugal brake 41 reaches a high rotational speed, the brake weights 43A, 43B, and 43C spread apart from the axis of the countershaft 30 due to centrifugal force against the force of the return spring 44, and the brake shoe 43D slides against the cylindrical portion 48B, generating a braking force against the rotation of the countershaft 30 and suppressing an increase in the rotational speed.

[0119] Here, the high rotation speed is a rotation speed that exceeds the rotation speed expected when the small electric vehicle 1 is pushed by hand, and is a rotation speed of the counter shaft 30 that exceeds the rotation speed during normal driving by the drive motor 21.

[0120] As the rotational speed of the counter shaft 30 increases, the centrifugal force acting on the brake weights 43A, 43B, and 43C increases, and the force that spreads radially outward with the shaft portion 42B as the center of oscillation against the biasing force of the return spring 44 increases, causing the brake shoes 43D of the brake weights 43A, 43B, and 43C to come into strong frictional contact with the inner surface of the cylindrical portion 48B.

[0121] This contact pressure increases as the rotation speed of the countershaft 30 increases, so that an increase in the vehicle speed of the small electric vehicle 1 can be effectively suppressed.

[0122] Furthermore, the brake shoes 43D of the plurality of brake weights 43A, 43B, 43C come into uniform contact with the inner peripheral surface of the cylindrical portion 48B, so that a large contact pressure can be generated.

[0123] As a result, the centrifugal brake 41 generates a braking force that acts as resistance to the rotation of the counter shaft 30 by the brake weights 43A, 43B, 43C, and can suppress an increase in the vehicle speed of the small electric vehicle 1.

[0124] In this way, when the running speed of the small electric vehicle 1 increases while the clutch mechanism 33 is disconnected, the centrifugal brake 41 generates a braking force to suppress the increase in the running speed of the small electric vehicle 1, thereby improving the performance and usability of the small electric vehicle 1 and further increasing the safety of the small electric vehicle 1.

[0125] On the other hand, when the user or the like releases the operation of the clutch lever 35 and the clutch lever 35 returns from the clutch disengagement lever position to the clutch engagement lever position, the sleeve 31 moves from the clutch disengagement position 62 to the clutch engagement position 61 in the axial direction of the countershaft 30.

[0126] As a result, the clutch mechanism 33 is engaged and the drive motor 21 is connected to the rear wheels 4L, 4R by the power transmission device 22, making it possible to transmit power from the drive motor 21 to the rear wheels 4L, 4R.

[0127] The power transmission device 22 of the small electric vehicle 1 of this embodiment also has a reducer case 23 that houses an input shaft 26, a reduction mechanism 27, a differential device 28, and a centrifugal brake 41.

[0128] The reduction mechanism 27 is composed of a counter shaft 30 and a counter gear 30A that is provided on the counter shaft 30 and meshes with an input gear 26A that is provided on the input shaft 26, and the centrifugal brake 41 is arranged coaxially with the counter shaft 30.

[0129] Here, if the counter gear 30A, sleeve 31 and centrifugal brake 41 are arranged coaxially on the counter shaft 30 and housed in the reducer case 23 (i.e., if the clutch mechanism 33 and centrifugal brake 41 are arranged coaxially), both ends of the counter shaft 30 must be supported on the reducer case 23 via bearings, which may reduce the support rigidity of the long counter shaft 30.

[0130] According to the power transmission device 22 of this embodiment, the right end of the countershaft 30 forms a protruding end portion 30r that penetrates the partition wall 23E of the reducer case 23 and protrudes outward from the partition wall 23E.

[0131] In addition, the counter shaft 30 is rotatably supported by the partition wall 23E via a bearing 29D, and a centrifugal brake 41 is provided on the protruding end 30r of the counter shaft 30.

[0132] This allows the countershaft 30 to be supported by the partition wall 23E located between the left and right ends of the countershaft 30 via the bearing 29D.

[0133] In other words, by arranging the counter gear 30A and sleeve 31 on the counter shaft 30 between the partition walls 23C and 23E and arranging the centrifugal brake 41 on the counter shaft 30 to the right of the partition wall 23E, even when the counter gear 30A, sleeve 31 and centrifugal brake 41 are arranged coaxially on the counter shaft 30, the support rigidity of the counter shaft 30, which rotates at high speed, can be improved and the centrifugal brake 41 can be stably supported on the partition wall 23E via the counter shaft 30.

[0134] Furthermore, according to the power transmission device 22 of the small electric vehicle 1 of this embodiment, the centrifugal brake 41 has brake weights 43A, 43B, 43C that are movable radially, a brake shoe 43D provided on the outer periphery of the brake weights 43A, 43B, 43C, and a cylindrical member 48 that is attached to the partition wall 23E and covers the radially outward side of the brake weights 43A, 43B, 43C, and when the brake weights 43A, 43B, 43C move radially outward, the brake shoe 43D comes into sliding contact with the inner circumferential surface of the cylindrical portion 48B.

[0135] As a result, after the counter shaft 30 and the reduction mechanism 27 are housed in the reducer case 23, the centrifugal brake 41 can be attached to the protruding end 30r of the counter shaft 30 that protrudes from the partition wall 23E outside the reducer case 23. As a result, the workability of attaching the centrifugal brake 41 to the reducer case 23 can be improved.

[0136] Furthermore, the power transmission device 22 of the small electric vehicle 1 of this embodiment has a cam member 46 that presses the brake shoe 43D against the cylindrical portion 48B in response to operation by the driver, and the cam member 46 moves the brake weights 43A, 43B, and 43C radially outward to press the brake shoe 43D against the cylindrical portion 48B.

[0137] This allows the centrifugal brake 41 to function as a parking brake. Therefore, by adding the parking brake function to the centrifugal brake 41, the cost required for using a dedicated parking brake can be reduced, and the manufacturing cost of the power transmission device 22 can be reduced.

[0138] Furthermore, according to the power transmission device 22 of the small electric vehicle 1 of this embodiment, the differential device 28 has a final driven gear 28A.

[0139] The clutch mechanism 33 has a sleeve 31 attached to the counter shaft 30 so as to be movable in the axial direction of the counter shaft 30, and is configured so that the counter shaft 30 and the counter gear 30A are connected or disconnected in conjunction with the movement of the sleeve 31.

[0140] The sleeve 31 is formed to have a smaller diameter than the final driven gear 28A and has a final drive gear 31A that meshes with the final driven gear 28A.

[0141] This allows the rotation (driving force) of the drive motor 21 to be transmitted from the counter gear 30A via the final drive gear 31A to the final driven gear 28A after being reduced in speed.

[0142] Furthermore, when the small electric vehicle 1 is being pushed by hand, the counter shaft 30 can be rotated at the highest speed, and by providing the centrifugal brake 41 on the counter shaft 30 which rotates at high speed, braking force can be generated effectively.

[0143] In this embodiment, the brake mechanism is configured from the centrifugal brake 41, but is not limited to this, and a centrifugal governor with a multi-plate clutch, a viscous clutch, or the like may also be used.

[0144] While an embodiment of the present invention has been disclosed, it will be apparent to one skilled in the art that modifications may be made thereto without departing from the scope of the present invention, and it is intended that all such modifications and equivalents be included in the following claims. [Explanation of symbols]

[0145] 1. Small electric vehicles 4L, 4R rear wheels (drive wheels) 21 Drive motor (electric motor) 23 Reducer case 23F Peripheral wall 26 Input shaft 26A input gear 27 Reduction mechanism 28 Differential device 28A Final driven gear 29D bearing 30 Counter shaft 30A counter gear 30r protruding end 31 Sleeve 31A Final drive gear 33 Clutch mechanism 41 Centrifugal brake (brake mechanism) 43A, 43B, 43C brake weights 43D Brake shoe (friction material) 46 Cam member

Claims

1. an input shaft to which power is transmitted from the electric motor; a differential device that transmits power from the input shaft to drive wheels; a reduction mechanism provided between the input shaft and the differential device, which reduces the power of the input shaft and transmits it to the differential device; a clutch mechanism that interrupts the transmission of power between the electric motor and the drive wheels, a brake mechanism is provided coaxially with the clutch mechanism, The brake mechanism rotates in conjunction with the rotation of the drive wheels, and generates a braking force that resists the rotation of the drive wheels when the drive wheels reach a high rotational speed.

2. the power transmission device has a reducer case that houses the input shaft, the differential device, the reduction mechanism, and the brake mechanism, the reduction mechanism includes a counter shaft and a counter gear provided on the counter shaft and meshing with an input gear provided on the input shaft, the brake mechanism is configured by a centrifugal brake that is disposed coaxially with the counter shaft and is actuated by rotation of the counter shaft, one end of the counter shaft constitutes a protruding end portion that penetrates a partition wall of the reducer case and protrudes outward from the partition wall, the counter shaft is rotatably supported by the partition wall via a bearing, 2. The power transmission device for a small electric vehicle according to claim 1, wherein the centrifugal brake is attached to the protruding end of the counter shaft.

3. The centrifugal brake is a plurality of brake weights that are movable in the radial direction, friction members provided on outer peripheries of the brake weights, and a cylindrical member that is attached to the partition wall and covers the radially outer sides of the brake weights, 3. The power transmission device for a small electric vehicle according to claim 2, wherein the friction member comes into sliding contact with the cylindrical member when the plurality of brake weights move radially outward.

4. a cam member that presses the friction member against the cylindrical member in response to an operation by a driver; 4. The power transmission device for a small electric vehicle according to claim 3, wherein the cam member moves the brake weight radially outward to press the friction member against the cylindrical member.

5. the differential device has a final driven gear, the clutch mechanism has a sleeve attached to the counter shaft so as to be movable in the axial direction of the counter shaft, and is configured so that the counter shaft and the counter gear are connected or disconnected in conjunction with the movement of the sleeve, 5. The power transmission device for a small electric vehicle according to claim 2, wherein the sleeve has a final drive gear formed to have a smaller diameter than the final driven gear and meshing with the final driven gear.

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