Drive unit

Abstract

To suppress a driving feeling from lowering at the time of deceleration.SOLUTION: A drive unit 100 includes an electric motor 2, an electromagnetic brake 3 and a controlling unit 4. The electromagnetic brake 3 is mounted on the electric motor 2. The controlling unit 4 is configured to control the electromagnetic brake 3. The controlling unit 4 is configured to control the electromagnetic brake 3 according to a vehicle speed when determining that deceleration operation is performed.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a drive unit.

Background Art

[0002] Ride-on work vehicles such as ride-on lawn mowers or golf carts have an engine and an HST (Hydraulic Static Transmission). Since this ride-on work vehicle can decelerate using the HST, it does not have a foot brake for the purpose of deceleration.

[0003] In recent years, electric-type ride-on work vehicles using an electric motor as a drive source have been proposed. This electric-type ride-on work vehicle does not have an HST and is decelerated by the regenerative brake of the electric motor.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the electric-type ride-on work vehicle as described above, when decelerating by the regenerative brake during low-speed running, there is a problem that torque fluctuation becomes large and the driving feeling deteriorates.

[0006] An object of the present invention is to suppress the deterioration of the driving feeling during deceleration.

Means for Solving the Problems

[0007] The drive unit according to the first embodiment is configured to be mounted on a passenger work vehicle. This drive unit comprises an electric motor, an electromagnetic brake, and a control unit. The electromagnetic brake is attached to the electric motor. The control unit is configured to control the electromagnetic brake. When the control unit determines that a deceleration operation has been performed, it is configured to control the electromagnetic brake according to the vehicle speed.

[0008] With this configuration, when deceleration is performed at low speeds, deceleration can be achieved by activating the electromagnetic brake without using the regenerative braking of the electric motor. As a result, torque fluctuations due to deceleration at low speeds can be suppressed, thus preventing a deterioration in the driving feel during deceleration.

[0009] The drive unit according to the second embodiment is configured as follows in the drive unit according to the first embodiment. The control unit is configured to activate the electromagnetic brake when it is determined that a deceleration operation has been performed and the vehicle speed is below a threshold.

[0010] The drive unit according to the third embodiment is configured as follows in the drive unit according to the first or second embodiment: The control unit is configured to calculate the excitation current supplied to the electromagnetic brake based on the manipulated amount input to the operating unit.

[0011] The drive unit according to the fourth embodiment is configured as follows in the drive unit according to the third embodiment. The control unit is configured to supply the upper limit excitation current to the electromagnetic brake when it determines that the calculated excitation current is greater than the upper limit excitation current. The upper limit excitation current is predetermined for each vehicle speed.

[0012] The drive unit according to the fifth embodiment is configured as follows in the drive unit according to any of the first to fourth embodiments: When the control unit determines that the passenger work vehicle is in a stopped state, it activates the electromagnetic brake. With this configuration, the stopped state of the passenger work vehicle can be maintained with less power consumption than if the stopped state of the passenger work vehicle were maintained by an electric motor.

[0013] The drive unit according to the sixth embodiment is configured as follows in the drive unit according to any of the first to fifth embodiments: The control unit activates the electromagnetic brake when it determines that the required deceleration torque is greater than the regenerative deceleration torque. The required deceleration torque is calculated based on the amount of operation input to the operation unit. The regenerative deceleration torque is the deceleration torque generated by the regenerative braking of the electric motor. [Effects of the Invention]

[0014] According to the present invention, it is possible to suppress the deterioration of driving feel during deceleration. [Brief explanation of the drawing]

[0015] [Figure 1] Block diagram of the drive unit. [Figure 2] A flowchart illustrating the control method for the control unit. [Figure 3] A flowchart to explain the shutdown process. [Figure 4] A flowchart illustrating the first deceleration process. [Figure 5] A flowchart illustrating the second deceleration process of the control unit in a modified example. [Figure 6] A flowchart illustrating the second deceleration process of the control unit in a modified example. [Modes for carrying out the invention]

[0016] The drive unit 100 according to this embodiment will be described below with reference to the drawings. The drive unit 100 is mounted on a ride-on work vehicle that does not have a foot brake. A ride-on work vehicle is, for example, a ride-on lawnmower or a golf cart. A foot brake is a brake operated by a brake pedal to decelerate a ride-on work vehicle. The ride-on work vehicle may have a parking brake to maintain a parked state. Also, the ride-on work vehicle does not have an engine or an HST.

[0017] [Drive Unit] As shown in FIG. 1, the drive unit 100 has an electric motor 2, an electromagnetic brake 3, and a control unit 4. The drive unit 100 also has a battery 5, an inverter 6, a drive circuit 7, and the like.

[0018] [Electric Motor] The electric motor 2 is connected to the battery 5. Specifically, the electric motor 2 is connected to the battery 5 via the inverter 6. The electric motor 2 is driven by power supplied from the battery 5. Also, the electric motor 2 can function as a generator. The power generated by the electric motor 2 is charged into the battery 5.

[0019] [Electromagnetic Brake] The electromagnetic brake 3 is attached to the electric motor 2. For example, the electromagnetic brake 3 is attached to the output shaft of the electric motor 2. The electromagnetic brake 3 is connected to the battery 5. Specifically, the electromagnetic brake 3 is connected to the battery 5 via the drive circuit 7.

[0020] The electromagnetic brake 3 is configured to decelerate the vehicle speed of the riding work vehicle. Specifically, the electromagnetic brake 3 is configured to decelerate the rotational speed of the electric motor 2. Also, the electromagnetic brake 3 is configured to maintain the stopped state of the riding work vehicle.

[0021] The electromagnetic brake 3 is an excitation-operated brake. The electromagnetic brake 3 brakes the rotation of the output shaft of the electric motor 2 when an excitation current is supplied from the battery 5. The electromagnetic brake 3 generates a braking force (deceleration torque) corresponding to the supplied excitation current. By increasing the excitation current supplied to the electromagnetic brake 3, the braking force (deceleration torque) by the electromagnetic brake 3 can be increased. Note that the deceleration torque is a torque for decelerating the riding work vehicle.

[0022] [Control Unit] The control unit 4 is configured to control the electromagnetic brake 3. The control unit 4 controls the electromagnetic brake 3 by controlling the excitation current supplied to the electromagnetic brake 3. The control unit 4 also controls the excitation current supplied to the electromagnetic brake 3 by controlling the drive circuit 7.

[0023] Furthermore, the control unit 4 is configured to control the electric motor 2. Specifically, the control unit 4 controls the electric motor 2 by controlling the inverter 6. Note that the control unit 4 performs speed control rather than torque control on the electric motor 2.

[0024] The control unit 4 is composed of a computer (e.g., a microcomputer) equipped with, for example, a CPU (Central Processing Unit) and ROM (Read Only Memory). The ROM stores programs for performing various calculations. The CPU executes the programs stored in the ROM.

[0025] The control unit 4 is connected to the speed sensor 11 and the forward / reverse operation unit 12 (hereinafter also referred to as "operation unit 12") via wired or wireless communication. The control unit 4 acquires data related to the vehicle speed of the riding work vehicle from the speed sensor 11. The control unit 4 receives deceleration operation signals and data related to the operation amount from the operation unit 12.

[0026] The operating unit 12 is, for example, an operating lever or operating pedal. The operating unit 12 is operated by the driver when deceleration or acceleration is requested. The operating unit 12 is operated forward and backward around the neutral position. By operating the operating unit 12 forward or backward from the neutral position, the driver can accelerate the passenger work vehicle in the forward or reverse direction. This operation of the operating unit 12 forward or backward from the neutral position is called acceleration operation. On the other hand, by operating the operating unit 12 from the front or rear toward the neutral position, the driver can decelerate the passenger work vehicle. This operation of the operating unit 12 from the front or rear toward the neutral position is called deceleration operation. When this deceleration operation is performed, the control unit 4 receives the deceleration operation signal and determines that a deceleration operation has been performed. Furthermore, by holding the operating unit 12 in the neutral position, the passenger work vehicle can be maintained in a stationary state. In the following description, unless otherwise specified, the amount of operation refers to the amount of operation when the operating unit 12 is decelerated.

[0027] The control unit 4 stores an excitation current map and an upper limit current map. The excitation current map and the upper limit current map are created in advance and stored in the control unit 4. The excitation current map is a map that associates the manipulated amount with the excitation current supplied to the electromagnetic brake 3. This excitation current map shows how much excitation current should be supplied to the electromagnetic brake 3 for each manipulated amount when the driver operates the control unit 12. In the excitation current map, the excitation current increases as the manipulated amount increases. That is, the larger the manipulated amount, the greater the deceleration torque from the electromagnetic brake 3. When the driver operates the control unit 12, the control unit 4 calculates the excitation current corresponding to that manipulated amount based on the excitation current map and supplies the calculated excitation current from the battery 5 to the electromagnetic brake 3.

[0028] The control unit 4 may also have a deceleration torque map and a second excitation current map instead of this excitation current map. The deceleration torque map is a map that associates the manipulated variable with the deceleration torque. The second excitation current map is a map that associates the deceleration torque with the excitation current. In this case, the control unit 4 first calculates the deceleration torque corresponding to the manipulated variable based on the deceleration torque map. Then, the control unit 4 calculates the excitation current necessary to generate that deceleration torque in the electromagnetic brake 3 based on the second excitation current map.

[0029] The upper limit current map is a map that correlates vehicle speed with excitation current. In this upper limit current map, the excitation current represents the maximum allowable deceleration at a given vehicle speed when deceleration is performed. In other words, the upper limit current map shows the preset upper limit of excitation current for each vehicle speed. Note that in the upper limit current map, the excitation current increases as the vehicle speed increases.

[0030] The control unit 4 is configured to perform a stop process and a first deceleration process. When the control unit 4 determines that the passenger work vehicle is in a stopped state, it performs the stop process. In the stop process, the control unit 4 controls the drive circuit 7 so that a constant excitation current is supplied to the electromagnetic brake 3.

[0031] The control unit 4 controls the electromagnetic brake 3 according to the vehicle speed. Specifically, when the control unit 4 receives a deceleration operation signal and determines that the vehicle speed at that time is below a threshold, it executes a first deceleration process. In the first deceleration process, the control unit 4 supplies the excitation current calculated based on the excitation current map to the electromagnetic brake 3. Note that the control unit 4 does not activate the regenerative braking by the electric motor 2 in the first deceleration process.

[0032] [Control Method] Next, the control method of the electromagnetic brake by the control unit 4 will be explained. Figure 2 is a flowchart for explaining the control method of the control unit 4, Figure 3 is a flowchart for explaining the stopping process, and Figure 4 is a flowchart for explaining the first deceleration process.

[0033] As shown in Figure 2, the control unit 4 determines whether the passenger vehicle is stopped or not (step S1). For example, the control unit 4 determines whether the passenger vehicle is stopped or not based on speed data obtained from the speed sensor 11.

[0034] When the control unit 4 determines that the passenger work vehicle is stopped (Yes in step S1), it executes a stop process (step S2). That is, the control unit 4 controls the drive circuit 7 so that a constant excitation current is supplied to the electromagnetic brake 3.

[0035] In detail, as shown in Figure 3, the control unit 4 supplies a constant excitation current (stop-holding current) to the electromagnetic brake 3 (step S21). Next, the control unit 4 determines whether or not there has been a request to release the stop (step S22). For example, the control unit 4 determines that there has been a request to release the stop if an acceleration operation has been performed.

[0036] If the control unit 4 determines that a release request has been received (Yes in step S22), it stops supplying excitation current to the electromagnetic brake 3 (step S23). This releases the braking force applied by the electromagnetic brake 3. On the other hand, if the control unit 4 determines that there is no release request (No in step S22), it returns to the process in step S21.

[0037] As shown in Figure 2, when the control unit 4 determines that the passenger car is not stopped (No. in step S1), it then determines whether or not a deceleration operation has been performed (step S3). When the control unit 4 determines that no deceleration operation has been performed (No. in step S3), it returns to the process of step S1.

[0038] When the control unit 4 determines that a deceleration operation has been performed (Yes in step S3), it then determines whether the vehicle speed is below a threshold (step S4). When the control unit 4 determines that the vehicle speed is below a threshold (Yes in step S4), it executes the first deceleration process (step S5).

[0039] In detail, as shown in Figure 4, the control unit 4 first outputs a regenerative braking prohibition instruction (step S51). Specifically, the control unit 4 controls the inverter 6 so that the regenerative braking by the electric motor 2 does not activate.

[0040] Next, the control unit 4 calculates the excitation current based on the manipulated variable and the excitation current map (step S52). Specifically, the control unit 4 determines the excitation current corresponding to the manipulated variable for deceleration operation based on the excitation current map.

[0041] Next, the control unit 4 determines whether the calculated excitation current is equal to or greater than the upper limit excitation current (step S53). Specifically, the control unit 4 calculates the upper limit excitation current based on the vehicle speed and the upper limit current map. That is, the control unit 4 determines the upper limit excitation current corresponding to the vehicle speed at that time based on the upper limit current map.

[0042] If the control unit 4 determines that the calculated excitation current is greater than or equal to the upper limit excitation current (Yes in step S53), it controls the drive circuit 7 so that the upper limit excitation current is supplied to the electromagnetic brake 3 (step S54).

[0043] On the other hand, if the control unit 4 determines that the calculated excitation current is less than the upper limit excitation current (No. in step S53), it controls the drive circuit 7 so that the excitation current calculated in step S52 is supplied to the electromagnetic brake 3 (step S55).

[0044] As shown in Figure 2, when the control unit 4 determines that the vehicle speed is greater than a threshold (No. in step S4), it executes the second deceleration process (step S6). In the second deceleration process, the control unit 4 does not activate the electromagnetic brake 3. That is, the control unit 4 controls the inverter 6 so that the regenerative braking of the electric motor 2 is activated.

[0045] [Differentiation] Although embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications are possible without departing from the spirit of the invention. Furthermore, the following modifications can basically be applied simultaneously.

[0046] (a) In the above embodiment, the control unit 4 controls the electromagnetic brake 3 not to activate during the second deceleration process, but is not limited to this. That is, the control unit 4 may activate the electromagnetic brake 3 during the second deceleration process. The second deceleration process in this modified example will be described below.

[0047] As shown in Figure 5, the control unit 4 calculates the required deceleration torque based on the manipulated amount (step S101). For example, the control unit 4 has a deceleration torque map, which is a map that associates the manipulated amount with the deceleration torque. Based on the deceleration torque map, the control unit 4 calculates the required deceleration torque according to the manipulated amount.

[0048] Next, the control unit 4 determines whether the required deceleration torque is less than or equal to the regenerative deceleration torque due to the regenerative braking of the electric motor 2 (step S102). The control unit 4 calculates the regenerative deceleration torque based on the motor performance of the electric motor 2, the state of charge (SOC) of the battery 5, and the motor speed.

[0049] If the control unit 4 determines that the required deceleration torque is less than or equal to the regenerative deceleration torque (Yes in step S102), it decelerates using only the regenerative braking of the electric motor 2 (step S103). In other words, the control unit 4 does not activate the electromagnetic brake 3.

[0050] On the other hand, if the control unit 4 determines that the required deceleration torque is greater than the regenerative deceleration torque (No. in step S102), the control unit 4 activates the electromagnetic brake 3 in addition to the regenerative brake of the electric motor 2 (step S104). Specifically, the control unit 4 generates the insufficient deceleration torque, which is the required deceleration torque minus the regenerative deceleration torque, using the electromagnetic brake 3. Based on the second excitation current map, the control unit 4 supplies an excitation current to the electromagnetic brake 3 that corresponds to the insufficient deceleration torque.

[0051] (b) In the second deceleration process, the control unit 4 may operate the electromagnetic brake 3 as follows, depending on the conditions.

[0052] As shown in Figure 6, the control unit 4 determines whether the conditions are unfavorable for regenerative braking (step S201). That is, the control unit 4 determines whether the conditions are such that the regenerative braking by the electric motor 2 does not operate sufficiently. .Ma Furthermore, the control unit 4 determines that a deceleration operation has been performed while driving uphill, based on the vehicle speed and the input, and also determines that a regenerative braking unfavorable condition exists. In addition, the control unit 4 determines that a regenerative braking unfavorable condition exists when it determines that the state of charge (SOC) of the battery 5 is above a threshold.

[0053] If the control unit 4 determines that the conditions are unfavorable for regenerative braking (Yes in step S201), it activates the electromagnetic brake 3 in addition to the regenerative braking of the electric motor 2 (step S202). On the other hand, if the control unit 4 determines that the conditions are not unfavorable for regenerative braking (No in step S201), it decelerates using only the regenerative braking of the electric motor 2 (step S203). In other words, the control unit 4 does not activate the electromagnetic brake 3.

[0054] (c) In the above embodiment, the control unit 4 calculates the excitation current based on the manipulated variable, but the method of calculating the excitation current by the control unit 4 is not limited to this. For example, the control unit 4 may calculate the excitation current by considering not only the manipulated variable but also the operating speed. For example, the control unit 4 may calculate the excitation current such that the excitation current increases as the operating speed increases. [Explanation of Symbols]

[0055] 2: Electric motor 3: Electromagnetic brake 4: Control Unit 12:Operation section 100: Drive unit

Claims

1. A drive unit configured to be mounted on a passenger work vehicle, Electric motor and, An electromagnetic brake attached to the aforementioned electric motor, A control unit configured to control the electromagnetic brake, Equipped with, The control unit is configured to control the electromagnetic brake according to the vehicle speed when it determines that a deceleration operation has been performed. The control unit is configured to activate the electromagnetic brake without activating the regenerative brake by the electric motor when it determines that a deceleration operation has been performed and the vehicle speed is below a threshold. The control unit is configured to calculate the excitation current supplied to the electromagnetic brake based on the operation amount input to the operation unit. The control unit is configured to supply the upper limit excitation current to the electromagnetic brake when it determines that the calculated excitation current is greater than a predetermined upper limit excitation current for each vehicle speed. Drive unit.

2. The control unit activates the electromagnetic brake when it determines that the passenger vehicle is stopped. The drive unit according to claim 1.

3. When the control unit determines that the required deceleration torque calculated based on the input amount to the operation unit is greater than the regenerative deceleration torque due to the regenerative braking of the electric motor, it activates the electromagnetic brake. The drive unit according to claim 1.

4. A drive unit configured to be mounted on a passenger work vehicle, Electric motor and, An electromagnetic brake attached to the aforementioned electric motor, A control unit configured to control the electromagnetic brake, Equipped with, The control unit is configured to control the electromagnetic brake according to the vehicle speed when it determines that a deceleration operation has been performed. The control unit is configured to activate the electromagnetic brake when it determines that a deceleration operation has been performed and the vehicle speed is below a threshold. The control unit is configured to calculate the excitation current supplied to the electromagnetic brake based on the operation amount input to the operation unit. The control unit is configured to supply the upper limit excitation current to the electromagnetic brake when it determines that the calculated excitation current is greater than a predetermined upper limit excitation current for each vehicle speed. Drive unit.

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