electric work vehicle

Abstract

To provide an electric work vehicle capable of reducing heat generation and abrasion caused by friction occurring during brake operation, facilitating maintenance of a stop state of the vehicle, and reducing the number of electric actuators for a brake which stops the vehicle.SOLUTION: An electric work vehicle comprises: an electric motor; wheels driven by the electric motor; a power transmission mechanism configuring at least a part of a power transmission path between the electric motor and the wheels and transmitting rotating power of the electric motor to the wheels; an operation part operated by an operator; an electromagnetic brake for stopping rotation of the electric motor; and a control part for executing the process to set a control value of the rotation speed of the electric motor to 0 on the basis of information from the operation part. The control part forces the electromagnetic brake to operate by maintaining the control value of the rotation speed of the electric motor to 0 when the vehicle speed is a specified value or below which is near 0, and the electromagnetic brake, which is disposed on an output shaft of the electric motor, has a rotating portion and a fixing portion facing the rotating portion.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an electric vehicle (electric utility vehicle) driven by an electric motor. [Background technology]

[0002] Conventionally, an electric vehicle driven by an electric motor is known, for example, as disclosed in Patent Document 1. This electric vehicle includes an electric motor, wheels driven by the electric motor, and brakes capable of braking the wheels. The brakes are friction brakes. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-223681 Summary of the Invention [Problem to be solved by the invention]

[0004] In the case of electric vehicles such as those described above, applying the brakes to stop a moving vehicle generates heat due to friction and causes wear on the brake pads. Furthermore, to maintain the vehicle in a stopped state, the driver must either continue to depress the brake pedal or manually activate the parking brake. Furthermore, in the case of a four-wheel vehicle that applies pressure to the brake discs with an electric actuator to brake the wheels, two or more electric actuators are required.

[0005] In view of these problems, the present invention aims to provide an electric vehicle that can reduce heat generation and wear caused by friction when the brakes are applied, make it easier to maintain a stopped state, and reduce the number of electric actuators used to brake the vehicle. [Means for solving the problem]

[0006] The technical means adopted by the present invention to solve the above problems are characterized as follows.

[0007] An electric vehicle (electric work vehicle) includes an electric motor, wheels driven by the electric motor, a power transmission mechanism that forms at least a part of a power transmission path between the electric motor and the wheels and transmits the rotational power of the electric motor to the wheels, an operation unit operated by a driver, an electromagnetic brake that stops the rotation of the electric motor, and a control unit that executes processing to set the control value of the rotation speed of the electric motor to 0 based on information from the operation unit. a transmission shaft that transmits the rotational power of the electric motor to an operating unit other than the wheels; wherein the control unit maintains a control value of the rotation speed of the electric motor at 0 and activates the electromagnetic brake when the vehicle speed becomes equal to or less than a predetermined value close to 0, and the electromagnetic brake is provided on an output shaft of the electric motor and has a rotating portion and a fixed portion facing the rotating portion. A clutch that allows or blocks the transmission of the rotational power is provided between the output shaft of the electric motor and the transmission shaft, and when the control unit stops the operation of the operating unit, the control value is maintained at 0 to activate the electromagnetic brake, and the transmission of the rotational power is blocked by the clutch, thereby stopping both the wheel and the operating unit.

[0008] The electromagnetic brake may have a coil, and may bring the fixed part into contact with the rotating part by energizing the coil.

[0009] The electromagnetic brake may be provided on a power transmission path between the electric motor and the power transmission mechanism. [Effects of the Invention]

[0013] According to the electric vehicle (electric work vehicle) of the present invention, when the vehicle speed drops below a predetermined value close to zero, the control value of the electric motor's rotation speed is maintained at zero and the electromagnetic brake is activated, thereby stopping the vehicle and maintaining the stationary state. This minimizes deceleration due to friction in the brake (electromagnetic brake), making it possible to reduce heat generation and wear associated with friction generated when the brake is activated. Furthermore, the vehicle can be maintained stationary without having to continuously depress the brake pedal or manually activate the parking brake. Furthermore, because the electric actuator (electromagnetic brake) is used to stop the rotation of the electric motor rather than to apply pressure to the brake disc, the number of electric actuators for braking can be reduced. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a side view showing an embodiment of an electric vehicle according to the present invention. [Figure 2] FIG. 1 is a configuration diagram of a drive system of an electric vehicle. [Figure 3] FIG. 4 is a diagram showing an example (first example) of an operation flow when an electric vehicle is stopped from a traveling state. [Figure 4] FIG. 10 is a diagram showing another example (second example) of the operation flow when the electric vehicle is brought to a stop from a traveling state. [Figure 5] FIG. 10 is a diagram showing yet another example (third example) of the operation flow when the electric vehicle is brought to a stop from a traveling state. [Figure 6] FIG. 10 is a configuration diagram of another example of a drive system of an electric vehicle. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, preferred embodiments of an electric vehicle (electric work vehicle) according to the present invention will be described.

[0016] FIG. 1 is a side view showing an embodiment of an electric vehicle 1 according to the present invention.

[0017] In Fig. 1, a work vehicle is shown as the electric vehicle 1. The work vehicle shown in Fig. 1 is a tractor. However, the electric vehicle 1 according to the present invention is not limited to tractors, and may be a work vehicle such as a backhoe, a loader work machine (wheel loader, compact track loader, skid steer loader, etc.), a utility vehicle (multipurpose work vehicle), or a freight vehicle, or may be a vehicle other than a work vehicle.

[0018] The electric vehicle 1 includes a vehicle body 2 and a traveling device 3 that supports the vehicle body 2 so that the vehicle can travel.

[0019] The vehicle body 2 is provided with a seat 4 on which a driver sits. The traveling device 3 is provided with wheels 5. The wheels 5 include front wheels 5F provided at the front of the vehicle body 2 and rear wheels 5R provided at the rear of the vehicle body 2. The front wheels 5F and rear wheels 5R are provided on the left and right sides of the vehicle body 2, respectively.

[0020] The vehicle body 2 is equipped with an electric motor 6 that drives the wheels of the traveling device 3. The electric vehicle 1 of this embodiment is a rear-wheel drive type electric vehicle in which the rear wheels 5R are driven by the electric motor 6. However, the electric vehicle 1 may also be a front-wheel drive type in which the front wheels 5F are driven by the electric motor 6, or a four-wheel drive type in which the front wheels 5F and the rear wheels 5R are driven by the electric motor 6.

[0021] FIG. 2 is a configuration diagram of the drive system of the electric vehicle 1. As shown in FIG.

[0022] As shown in FIG. 2, the electric vehicle 1 includes a power transmission mechanism 7, wheel brakes 8, an electromagnetic brake 9, and a control unit 10 as components of its drive system.

[0023] The power transmission mechanism 7 is a mechanism that transmits the rotational power of the electric motor 6 to the wheels 5 that serve as drive wheels (in this embodiment, the rear wheels 5R). The power transmission mechanism 7 constitutes at least a part of the power transmission path between the electric motor 6 and the wheels 5. In the example shown in FIG. 2, the power transmission path between the electric motor 6 and the wheels 5 is made up of the power transmission mechanism 7 and an electromagnetic brake 9.

[0024] The power transmission mechanism 7 has a reduction gear 7A and a differential gear (differential gear) 7B. The rotational power of the electric motor 6 is input to the reduction gear 7A and transmitted to the wheels 5 via the differential gear 7B. The reduction gear 7A reduces the rotational speed of the electric motor 6 by meshing multiple gears 70 and transmits the rotational power to the differential gear 7B. The differential gear 7B is connected to the axles 15 of the wheels 5 and transmits the rotational power transmitted from the reduction gear 7A to the left and right wheels 5.

[0025] The wheel brakes 8 are provided on the wheels 5. It is preferable to provide the wheel brakes 8 on at least the drive wheels of the front wheels 5F and rear wheels 5R. In the present embodiment, the wheel brakes 8 are provided on the rear wheels 5R. However, the wheel brakes 8 may be provided on the front wheels 5F, or on both the front wheels 5F and the rear wheels 5R. The wheel brakes 8 are brakes that stop the rotation of the wheels 5 by friction braking force. The wheel brakes 8 have, for example, a brake disc that rotates together with the wheels 5, and brake pads that are pressed against the brake disc by driving a hydraulic cylinder or the like. The wheel brakes 8 are activated by depressing a brake pedal provided on the electric vehicle 1.

[0026] The electromagnetic brake 9 stops the rotation of the electric motor 6. The electromagnetic brake 9 is provided on the power transmission path between the electric motor 6 and the wheels 5 (midway along the path that transmits power from the electric motor 6 to the wheels 5).

[0027] In this embodiment, the electromagnetic brake 9 is provided on the power transmission path between the electric motor 6 and the power transmission mechanism 7 (midway along the path that transmits power from the electric motor 6 to the power transmission mechanism 7). Specifically, the electromagnetic brake 9 is provided on the power transmission path between the electric motor 6 and the reduction gear device 7A (midway along the path that transmits power from the electric motor 6 to the reduction gear device 7A).

[0028] The electromagnetic brake 9 stops the rotation of the output shaft 6a of the electric motor 6 (the shaft that transmits the rotational power of the electric motor 6 to the power transmission mechanism 7). In this embodiment, the electromagnetic brake 9 is attached to the output shaft 6a of the electric motor 6. However, the electromagnetic brake 9 may also be attached to another shaft 6b that rotates in conjunction with the output shaft 6a of the electric motor 6. In FIG. 2, the other shaft 6b is shown as a shaft that protrudes on the opposite side to the output shaft 6a of the electric motor 6.

[0029] The electromagnetic brake 9 has a rotating part 9a attached to the output shaft 6a (or another shaft 6b) of the electric motor 6, and a fixed part 9b facing the rotating part 9a. The electromagnetic brake 9 brings the rotating part 9a and the fixed part 9b into contact with each other using electromagnetic force generated by passing current through a coil, thereby generating a braking force (a force that stops the rotation of the rotating part 9a and the output shaft 6a) due to friction and magnetic force.

[0030] The electromagnetic brake 9 operates under the control of a control unit 10. The control unit 10 is composed of a CPU, an electric and electronic circuit, a memory unit, etc. The memory unit is composed of RAM, ROM, etc. A predetermined control program is stored in the memory unit. The CPU controls the operation of the electric motor 6 and the electromagnetic brake 9 based on the control program.

[0031] FIG. 3 shows an example (first example) of the operation flow when the electric vehicle 1 is stopped from a traveling state.

[0032] When the electric vehicle 1 is stopped from a traveling state, first, the control unit 10 sets the control value of the rotation speed of the electric motor 6 to 0 (S1). "Setting the control value of the rotation speed of the electric motor 6 to 0" means controlling the value of the current supplied to the electric motor 6 so that the rotation speed of the electric motor 6 becomes 0. When the control value of the rotation speed of the electric motor 6 is set to 0 while the electric vehicle 1 is not stopped, a current is supplied to the electric motor 6 to set the rotation speed to 0 (a current that causes the electric motor 6 to rotate in the opposite direction to the direction of rotation). The electric motor 6 remains in a state in which it is forcibly rotated in conjunction with the rotation of the wheels 5 until the rotation speed becomes 0 (until the electric vehicle 1 stops). As a result, the electric motor 6 enters a regenerative state in which it functions as a generator, and the regenerative brake is activated (S2). As a result, the electric vehicle 1 begins to decelerate.

[0033] The operation of the control unit 10 to set the control value of the rotation speed of the electric motor 6 to 0 is started by stopping the accelerator pedal provided on the electric vehicle 1, or by stopping the accelerator pedal and depressing the brake pedal.

[0034] After the regenerative brake is applied, the wheel brake 8 is applied by stepping on the brake pedal (S3). Since the electric vehicle 1 is decelerated by the regenerative brake, the wheel brake 8 is applied in a decelerated state due to the regenerative brake.

[0035] The wheel brakes 8 are activated in addition to the regenerative brakes, thereby further decelerating the electric vehicle 1. When the vehicle speed of the electric vehicle 1 reaches a predetermined value close to 0 (S4: Yes), the control unit 10 maintains the control value of the rotation speed of the electric motor 6 at 0 (S5), and activates the electromagnetic brake 9 while maintaining this control value at 0 (S6). This causes the electric vehicle 1 to stop traveling (S7). When the vehicle speed of the electric vehicle 1 has not reached the predetermined value close to 0 (S4: No), the control unit 10 does not activate the electromagnetic brake 9 until the vehicle speed reaches the predetermined value close to 0.

[0036] The above-mentioned "predetermined value close to 0" is, for example, "5 km / h", but is not limited to this value and may be a value greater than this value (for example, "10 km / h") or a value smaller than this value (for example, "3 km / h").

[0037] Even after the electric vehicle 1 stops traveling (S7), the control unit 10 can maintain the stopped state of the electric vehicle 1 by maintaining the control value of the rotation speed of the electric motor 6 at 0 and maintaining the operating state of the electromagnetic brake 9.

[0038] The control unit 10 releases the stopped state of the electric vehicle 1 when an operation unit 16 (see FIG. 2 ) for releasing the stopped state is operated. The operation unit 16 can be operated by a driver seated in the seat 4, and is, for example, an accelerator pedal or an operation button. When a release operation (depressing the accelerator pedal, pressing an operation button, etc.) is performed using the operation unit 16, the control unit 10 stops maintaining the control value of the rotation speed of the electric motor 6 at 0 and stops operation of the electromagnetic brake 9. As a result, the stopped state of the electric vehicle 1 is released and it becomes possible to travel.

[0039] As described above, when the vehicle speed of the electric vehicle 1 falls below a predetermined value close to 0, the control unit 10 maintains the control value of the rotation speed of the electric motor 6 at 0 and activates the electromagnetic brake 9.

[0040] In detail, the control unit 10 sets the control value of the rotation speed of the electric motor 6 to 0 and activates the regenerative brake of the electric motor 6, and then, when the vehicle speed of the electric vehicle 1 becomes equal to or lower than a predetermined value close to 0, maintains the control value of the rotation speed of the electric motor 6 at 0 and activates the electromagnetic brake 9.

[0041] More specifically, the control unit 10 sets the control value of the rotation speed of the electric motor 6 to 0 and activates the regenerative brake of the electric motor 6, and after the wheel brake 8 is activated, when the vehicle speed of the electric vehicle 1 becomes equal to or less than a predetermined value close to 0, maintains the control value of the rotation speed of the electric motor 6 at 0 and activates the electromagnetic brake 9.

[0042] As described above, in the electric vehicle 1 according to the present invention, when the vehicle speed falls below a predetermined value close to 0, the control value of the rotation speed of the electric motor 6 is maintained at 0 and the electromagnetic brake 9 is activated to stop the electric vehicle 1, thereby minimizing deceleration due to friction of the electromagnetic brake 9. This makes it possible to reduce heat generation and wear associated with friction that occurs when the electromagnetic brake 9 is activated.

[0043] Furthermore, after the electric vehicle 1 has stopped traveling, the control unit 10 maintains the control value of the rotation speed of the electric motor 6 at 0 and maintains the operating state of the electromagnetic brake 9, thereby maintaining the stopped state of the electric vehicle 1. Therefore, the stopped state can be maintained without having to continue to depress the brake pedal or manually operate the parking brake, as in conventional electric vehicles.

[0044] 4 shows another example (second example) of the operation flow when the electric vehicle 1 is stopped from a traveling state. S1 to S5 are the same as the operation flow of the first example.

[0045] When the electric vehicle 1 is stopped from a traveling state, first, the control unit 10 sets the control value of the rotation speed of the electric motor 6 to 0 (S1). When the control value of the rotation speed of the electric motor 6 is set to 0 in a traveling state, the electric motor 6 is forced to rotate in accordance with the rotation of the wheels 5. This causes the electric motor 6 to function as a generator, and regenerative braking is activated (S2).

[0046] After the regenerative brake is activated, the wheel brake 8 is activated by stepping on the brake pedal (S3). Since the electric vehicle 1 is decelerated by the regenerative brake activation, the wheel brake 8 is activated in a state where the vehicle is slower than before the regenerative brake activation.

[0047] The wheel brakes 8 are activated in addition to the regenerative brakes, thereby further decelerating the electric vehicle 1. When the vehicle speed of the electric vehicle 1 reaches a predetermined value close to 0 (S4: Yes), the control unit 10 maintains the control value of the rotation speed of the electric motor 6 at 0 (S5), and activates the electromagnetic brake 9 while maintaining this value (S7). This causes the electric vehicle 1 to stop traveling (S8). When the vehicle speed of the electric vehicle 1 has not reached the predetermined value close to 0 (S4: No), the control unit 10 does not activate the electromagnetic brake 9 until the vehicle speed reaches the predetermined value close to 0.

[0048] In the second example of the operation flow, the temperature of the electric motor 6 or the electrical equipment electrically connected to the electric motor 6 is taken into consideration as a condition for activating the electromagnetic brake 9. The electrical equipment electrically connected to the electric motor 6 is electrical equipment that is electrically connected to the electric motor 6 directly or indirectly, such as a battery that stores the power supplied to the electric motor 6, or an inverter interposed between the battery and the electric motor 6. These batteries and inverters are mounted on the electric vehicle 1. Hereinafter, "the electric motor 6 or the electrical equipment electrically connected to the electric motor 6" will be referred to as "the electric motor 6, etc."

[0049] 4, when the temperature of the electric motor 6 or the like reaches or exceeds a predetermined temperature (S6: Yes) while the control value of the rotation speed of the electric motor 6 is maintained at 0, the control unit 10 activates the electromagnetic brake 9. On the other hand, when the temperature of the electric motor 6 or the like is below the predetermined temperature (S6: No), the control unit 10 does not activate the electromagnetic brake 9.

[0050] If the control value of the rotation speed of the electric motor 6 is maintained at 0 while the electric vehicle 1 is not stopped, a current for setting the rotation speed to 0 continues to be supplied to the electric motor 6 while the electric motor 6 is being forcibly rotated. Therefore, if time passes while the control value of the rotation speed of the electric motor 6 is maintained at 0, the temperature of the electric motor 6 and the like will rise due to the continued supply of current.

[0051] As a countermeasure, by activating the electromagnetic brake 9 when the temperature of the electric motor 6 etc. reaches or exceeds a predetermined temperature while maintaining the control value of the rotation speed of the electric motor 6 at 0, the amount of current supplied to make the rotation speed of the electric motor 6 0 can be reduced, making it possible to prevent the electric motor 6 etc. from overheating.

[0052] The above-mentioned predetermined temperature can be set to, for example, 100° C. However, the predetermined temperature is not limited to 100° C., and may be less than 100° C. (for example, 80° C.) or may be a temperature greater than 100° C. (for example, 120° C.).

[0053] The predetermined temperature can be changed depending on the type of the electric motor 6, etc., which is considered as a condition for activating the electromagnetic brake 9. If the electric motor 6, etc. is an electric motor 6, the predetermined temperature is set to, for example, 100°C. If the electric motor 6, etc. is a battery, the predetermined temperature is set to, for example, 60°C. If the electric motor 6, etc. is an inverter, the predetermined temperature is set to, for example, 80°C. However, the predetermined temperature is not limited to these temperatures.

[0054] The temperature of the electric motor 6 etc. can be detected by a temperature measuring device such as a temperature sensor provided in the electric vehicle 1. The control unit 10 receives information about the temperature of the electric motor 6 etc. from the temperature measuring device, and determines whether the temperature of the electric motor 6 etc. has reached a predetermined temperature or higher based on the information.

[0055] 5 shows yet another example (third example) of the operation flow when the electric vehicle 1 is brought to a stop from a traveling state. S1 to S5 are the same as the operation flow of the first example.

[0056] When the electric vehicle 1 is stopped from a traveling state, first, the control unit 10 sets the control value of the rotation speed of the electric motor 6 to 0 (S1). When the control value of the rotation speed of the electric motor 6 is set to 0 in a traveling state, the electric motor 6 is forced to rotate in accordance with the rotation of the wheels 5. This causes the electric motor 6 to function as a generator, and regenerative braking is activated (S2).

[0057] After the regenerative brake is activated, the wheel brake 8 is activated by stepping on the brake pedal (S3). Since the electric vehicle 1 is decelerated by the regenerative brake activation, the wheel brake 8 is activated in a state where the vehicle is slower than before the regenerative brake activation.

[0058] The wheel brakes 8 are activated in addition to the regenerative brakes, thereby further decelerating the electric vehicle 1. When the vehicle speed of the electric vehicle 1 reaches a predetermined value close to 0 (S4: Yes), the control unit 10 maintains the control value of the rotation speed of the electric motor 6 at 0 (S5), and activates the electromagnetic brake 9 while maintaining this value (S7). This causes the electric vehicle 1 to stop traveling (S8). When the vehicle speed of the electric vehicle 1 has not reached the predetermined value close to 0 (S4: No), the control unit 10 does not activate the electromagnetic brake 9 until the vehicle speed reaches the predetermined value close to 0.

[0059] In the case of the operation flow of the third example, the condition for activating the electromagnetic brake 9 is considered to be the time during which the control value of the rotation speed of the electric motor 6 is maintained at 0.

[0060] Specifically, the control unit 10 activates the electromagnetic brake 9 when a predetermined time has elapsed with the control value of the rotation speed of the electric motor 6 maintained at 0 (S6: Yes). On the other hand, the control unit 10 does not activate the electromagnetic brake 9 when the predetermined time has not elapsed with the control value of the rotation speed of the electric motor 6 maintained at 0 (S6: No).

[0061] As described above, if time passes while the control value of the rotation speed of the electric motor 6 is maintained at 0, the temperature of the electric motor 6 rises due to the continued supply of current.

[0062] Therefore, by activating the electromagnetic brake 9 after a predetermined time has elapsed while the control value of the rotation speed of the electric motor 6 is maintained at 0, the amount of current supplied to make the rotation speed of the electric motor 6 0 can be reduced, thereby preventing the electric motor 6 from overheating.

[0063] The predetermined time can be set to, for example, 30 seconds. However, the predetermined time is not limited to 30 seconds, and may be less than 30 seconds (for example, 20 seconds) or more than 30 seconds (for example, 60 seconds).

[0064] The time during which the control value of the rotation speed of the electric motor 6 is maintained at 0 can be measured by a timing device such as a timer provided in the electric vehicle 1. The control unit 10 receives information relating to the time during which the control value of the rotation speed of the electric motor 6 is maintained at 0 from the timing device, and determines based on the information whether a predetermined time has elapsed while the control value of the rotation speed of the electric motor 6 is maintained at 0.

[0065] In the first to third examples described above, the wheel brakes 8 are actuated by depressing the brake pedal, but the wheel brakes 8 may be actuated by operating a brake operation unit different from the brake pedal (for example, a brake button provided on the electric vehicle 1) instead of depressing the brake pedal. Also, the control unit 10 may be configured to actuate the wheel brakes 8.

[0066] FIG. 6 is a diagram showing another example of the configuration of the drive system of the electric vehicle 1. In FIG.

[0067] Below, differences between the configuration of the drive system shown in FIG. 6 and the configuration of the drive system shown in FIG. 2 will be explained, and explanations of the same configurations will be omitted.

[0068] The drive system shown in FIG. 6 includes a transmission shaft 11 that transmits the rotational power of the electric motor 6 to an operating unit 13 other than the wheels 5. The transmission shaft 11 is, for example, a PTO (Power Take-Off) shaft. In this case, the operating unit 13 is a working device that is driven by the power transmitted from the PTO shaft. When the electric vehicle 1 is a tractor, the operating unit 13 is a working device that performs work on a field. Specifically, the working device is, for example, a tilling device that tills a field, a spraying device that sprays fertilizer or chemicals on a field, a seeding device that sows seeds on a field, etc.

[0069] The output shaft 6a of the electric motor 6 is provided with a power branching section 14 that branches the rotational power of the output shaft 6a and transmits it to the transmission shaft 11. The power branching section 14 is configured by, for example, a gear mechanism, a belt transmission mechanism, or the like.

[0070] A clutch 12 is provided between the output shaft 6a of the electric motor 6 and the transmission shaft 11 to allow or block the transmission of rotational power from the electric motor 6 to the transmission shaft 11. The clutch 12 is provided midway along the power transmission path from the output shaft 6a to the transmission shaft 11. The clutch 12 is, for example, an electric clutch. When the transmission shaft 11 is a PTO shaft, a one-way clutch is preferably used as the clutch 12.

[0071] When stopping the operation of the operating unit 13, the control unit 10 maintains the control value of the rotation speed of the electric motor 6 at 0 to activate the electromagnetic brake 9, and also causes the clutch 12 to interrupt the transmission of rotational power from the electric motor 6 to the transmission shaft 11. This allows the control unit 10 to stop both the wheels 5 and the operating unit 13. Furthermore, the clutch 12 can stop the operation of the operating unit 13 before the wheels 5 stop. Therefore, the operating unit 13 can be stopped quickly and reliably.

[0072] It should be noted that the clutch 12 is not limited to being operated by the control unit 10. The clutch 12 may be one that can be operated (to perform an operation to cut off the transmission of rotational power from the electric motor 6 to the transmission shaft 11) by operating an operating tool such as an operating button, rather than being operated by the control unit 10. In this case, the operation of the operating tool can be stopped independently of the operation of the wheels 5. In other words, the operation of the operating tool can stop the operation of the operating unit 13 without stopping the wheels 5.

[0073] The electric vehicle 1 according to the above embodiment has the following advantages.

[0074] The electric vehicle 1 includes an electric motor 6, wheels 5 driven by the electric motor 6, a power transmission mechanism 7 that forms at least a part of the power transmission path between the electric motor 6 and the wheels 5 and transmits the rotational power of the electric motor 6 to the wheels 5, wheel brakes 8 provided on the wheels 5, an electromagnetic brake 9 that stops the rotation of the electric motor 6, and a control unit 10 that maintains the control value of the rotation speed of the electric motor 6 at 0 and activates the electromagnetic brake 9 when the vehicle speed falls below a predetermined value close to 0.

[0075] According to this configuration, when the vehicle speed of the electric vehicle 1 falls below a predetermined value close to zero, the control value of the rotation speed of the electric motor 6 is maintained at zero and the electromagnetic brake 9 is activated, thereby stopping the electric vehicle 1 and maintaining the stationary state. This minimizes deceleration due to friction of the brake (electromagnetic brake 9), making it possible to reduce heat generation and wear associated with friction generated when the brake is activated. Furthermore, unlike conventional electric vehicles, the stationary state can be maintained without having to continuously depress the brake pedal or manually activate the parking brake. Furthermore, because the electric actuator (electromagnetic brake 9) is used to stop the rotation of the electric motor 6 rather than to apply pressure to the brake disc, the number of electric actuators for braking can be reduced.

[0076] In addition, the control unit 10 sets the control value of the rotation speed of the electric motor 6 to 0 and activates the regenerative brake of the electric motor 6, and then, when the vehicle speed becomes equal to or less than a predetermined value close to 0, maintains the control value at 0 and activates the electromagnetic brake 9.

[0077] According to this configuration, regardless of whether the wheel brakes 8 are activated, the vehicle speed of the electric vehicle 1 can be reduced to a predetermined value close to 0 by the regenerative braking of the electric motor 6, and then the electromagnetic brake 9 can be activated.

[0078] Furthermore, after the wheel brakes 8 and the regenerative brake are activated, when the vehicle speed falls below a predetermined value close to 0, the control unit 10 maintains the control value of the rotation speed of the electric motor 6 at 0 and activates the electromagnetic brake 9.

[0079] According to this configuration, the electromagnetic brake 9 can be activated after the vehicle speed of the electric vehicle 1 is quickly reduced to a predetermined value close to 0 by operating the wheel brakes 8 and the regenerative brake.

[0080] Furthermore, the control unit 10 activates the electromagnetic brake 9 when the temperature of the electric motor 6 reaches or exceeds a predetermined temperature while the control value of the rotation speed of the electric motor 6 is maintained at 0.

[0081] According to this configuration, the control value of the rotation speed of the electric motor 6 is continuously maintained at 0 while the electric motor 6 is rotating (current is continuously flowing to keep the rotation speed at 0), thereby preventing the electric motor 6 from overheating.

[0082] In addition, the control unit 10 activates the electromagnetic brake 9 when the temperature of the electrical equipment electrically connected to the electric motor 6 reaches or exceeds a predetermined temperature while maintaining the control value of the rotation speed of the electric motor 6 at 0.

[0083] According to this configuration, by continuously maintaining the control value of the rotation speed of the electric motor 6 at 0 while the electric motor 6 is rotating (continuing to flow current to make the rotation speed 0), it is possible to prevent electrical equipment (e.g., a battery, an inverter, etc.) electrically connected to the electric motor 6 from overheating.

[0084] Furthermore, the control unit 10 activates the electromagnetic brake 9 when a predetermined time has elapsed while the control value of the rotation speed of the electric motor 6 is maintained at 0.

[0085] According to this configuration, the time for which the control value of the rotation speed of the electric motor 6 is maintained at 0 (current is continued to flow to make the rotation speed 0) while the electric motor 6 is rotating can be reduced, thereby preventing the electric motor 6 from overheating.

[0086] The electromagnetic brake 9 is provided on the power transmission path between the electric motor 6 and the wheels 5.

[0087] According to this configuration, the rotation of the electric motor 6 can be stopped by the electromagnetic brake 9 midway along the path that transmits power from the electric motor 6 to the wheels 5.

[0088] The electromagnetic brake 9 is provided on the power transmission path between the electric motor 6 and the power transmission mechanism 7.

[0089] According to this configuration, the electromagnetic brake 9 can stop the rotation of the electric motor 6 midway along the path that transmits power from the electric motor 6 to the power transmission mechanism 7. Therefore, the electromagnetic brake 9 can be provided at a position away from the wheels 5.

[0090] The vehicle also includes a transmission shaft 11 that transmits the rotational power of the electric motor 6 to an operating unit 13 other than the wheels 5, and a clutch 12 that allows or blocks the transmission of the rotational power of the electric motor 6 is provided between the output shaft of the electric motor 6 and the transmission shaft 11. When the control unit 10 stops the operation of the operating unit 13, it maintains the control value of the rotation speed of the electric motor 6 at 0, activates the electromagnetic brake 9, and blocks the transmission of the rotational power using the clutch 12.

[0091] According to this configuration, it is possible to stop both the wheels 5 and the operating unit 13 by the control unit 10. Furthermore, it is possible to stop the operation of the operating unit 13 by the clutch 12 before the wheels 5 stop. Therefore, it is possible to stop the operating unit 13 quickly and reliably.

[0092] Furthermore, the electric vehicle 1 is provided with an operating unit 16 that is operated by the driver, and the control unit 10 stops the operation of the electromagnetic brake 9 when the operating unit 16 is operated.

[0093] According to this configuration, the driver can operate the operation unit 16 to release the stopped state of the electric vehicle 1 and allow it to travel.

[0094] Although the embodiments of the present invention have been described above, the embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0095] 1. Electric vehicles (electric work vehicles) 5 wheels 6 electric motor 7 Power transmission mechanism 8 Wheel Brakes 9 Electromagnetic Brake 9a Rotational Part 9b Fixation site 10 Control Unit 11 Transmission shaft 12 Clutch 16 Control section

Claims

1. An electric motor; a wheel driven by the electric motor; a power transmission mechanism that constitutes at least a part of a power transmission path between the electric motor and the wheels and transmits rotational power of the electric motor to the wheels; an operating unit operated by a driver; an electromagnetic brake that stops the rotation of the electric motor; a control unit that executes a process of setting a control value of the rotation speed of the electric motor to 0 based on information from the operation unit; a transmission shaft that transmits the rotational power of the electric motor to an operating unit other than the wheels; Equipped with the control unit maintains a control value of the rotation speed of the electric motor at 0 and activates the electromagnetic brake when the vehicle speed becomes equal to or less than a predetermined value close to 0; the electromagnetic brake is provided on an output shaft of the electric motor and has a rotating portion and a fixed portion facing the rotating portion, a clutch that allows or interrupts transmission of the rotational power is provided between the output shaft of the electric motor and the transmission shaft; When stopping the operation of the operating unit, the control unit maintains the control value at 0, activates the electromagnetic brake, and cuts off the transmission of the rotational power using the clutch, thereby stopping both the wheels and the operating unit.

2. 2. The electric work vehicle according to claim 1, wherein the electromagnetic brake has a coil, and when current is applied to the coil, the fixed part is brought into contact with the rotating part.

3. 2. The electric work vehicle according to claim 1, wherein the electromagnetic brake is provided on a power transmission path between the electric motor and the power transmission mechanism.

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