Drive unit

Abstract

To provide a drive unit that is able to appropriately control output torque of a motor.SOLUTION: A drive unit 100 includes a motor 3, a first detection unit 4, and a control unit 6. The first detection unit 4 detects vehicle speed information relating to a vehicle speed of a moving body. The control unit 6 performs PWM control on the motor 3. The control unit 6 controls a duty ratio of a PWM signal according to the vehicle speed information detected by the first detection unit 4.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] It has been proposed to improve the performance of a moving body such as a hand lift, a dolly, or a wheelchair by attaching a drive unit to the moving body. The drive unit has a motor for rotating the wheels (see Patent Document 1). The motor has a characteristic that the maximum output torque decreases as the rotation speed increases, and the maximum output torque increases as the rotation speed decreases. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2014-512307 Summary of the Invention [Problem to be solved by the invention]

[0004] The above-mentioned drive unit outputs high torque at start-up when the motor is driven at maximum capacity, which may cause sudden acceleration or drive wheel slip at start-up. If the drive voltage value (or the resulting current value) is uniformly limited to prevent this and suppress the motor torque, the maximum value of the motor rotation speed will also decrease, which is a problem. For this reason, there is a demand for more appropriate control of the motor output torque.

[0005] An object of the present invention is to provide a drive unit capable of appropriately controlling the output torque of a motor. [Means for solving the problem]

[0006] A drive unit according to an aspect of the present invention is a drive unit attached to a moving body, and includes a motor, a first detector, and a controller. The first detector detects vehicle speed information related to the vehicle speed of the moving body. The controller performs PWM control of the motor. The controller controls the duty ratio of the PWM signal according to the vehicle speed information detected by the first detector.

[0007] According to this configuration, since the control unit controls the duty ratio of the PWM signal according to the vehicle speed information, for example, the duty ratio can be controlled so that the duty ratio increases as the rotation speed of the motor increases. Therefore, when the rotation speed of the motor is low, the duty ratio is small, and the output torque is also small. Therefore, problems such as sudden acceleration at start-up and slipping of the drive wheels can be suppressed. In addition, when the rotation speed of the motor is high, the duty ratio is large, and therefore a decrease in the maximum value of the rotation speed of the motor can also be suppressed. As described above, the above-mentioned drive unit can appropriately control the output torque of the motor.

[0008] Preferably, the control unit increases the duty ratio as the rotation speed of the motor increases.

[0009] Preferably, the first detection unit detects a rotation speed of the motor as the vehicle speed information.

[0010] Preferably, the control unit selectively executes a first mode and a second mode. In the first mode, the control unit controls the duty ratio to increase or decrease according to the vehicle speed information. In the second mode, the control unit controls the duty ratio to be constant regardless of the vehicle speed information.

[0011] Preferably, the drive unit further includes a second detector configured to detect a current of the motor, and the controller corrects the duty ratio in response to the current of the motor detected by the second detector.

[0012] Preferably, the drive unit further includes a third detector configured to detect a temperature of the motor, and the controller corrects the duty ratio in response to the temperature of the motor detected by the third detector.

[0013] Preferably, the drive unit further includes a fourth detector configured to detect a weight of an object placed on the moving body, and the control unit corrects the duty ratio in response to the weight detected by the fourth detector.

[0014] Preferably, the drive unit further includes a correction value input device that is operated by a user, and the control unit corrects the duty ratio in accordance with an amount of operation of the correction value input device.

[0015] Preferably, the drive unit further includes a motor driver. The control unit controls the motor via the motor driver. Effect of the Invention

[0016] According to the present invention, the output torque of the motor can be appropriately controlled. [Brief description of the drawings]

[0017] [Figure 1] FIG. [Diagram 2] 6 is a graph showing the relationship between rotation speed and duty ratio. [Diagram 3] 10 is a flowchart showing an example of processing of a control unit. [Figure 4] 10 is a flowchart showing an example of processing of a control unit. [Diagram 5] 4 is a graph showing the relationship between rotation speed and torque. [Figure 6] 10 is a flowchart showing an example of a process of a control unit according to a modified example. [Figure 7] FIG. 11 is a block diagram of a drive unit according to a modified example. [Figure 8] FIG. 11 is a block diagram of a drive unit according to a modified example. [Figure 9] FIG. 11 is a block diagram of a drive unit according to a modified example. [Figure 10] FIG. 11 is a block diagram of a drive unit according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, the drive unit 100 according to this embodiment will be described with reference to the drawings. The drive unit 100 is attached to a moving body. Examples of the moving body include a hand lift, a dolly, an unmanned transport vehicle, a wheelchair, and a kickboard. The moving body is configured to transport an object. The object is a concept that also includes a person. The moving body includes, for example, wheels.

[0019] <Drive unit> 1, the drive unit 100 includes an input device 2, a motor 3, a first detector 4, a motor driver 5, and a controller 6. The drive unit 100 also includes a battery 7 and drive wheels (not shown).

[0020] <Input device> The input device 2 is, for example, an on-off switch. When a user operates the input device 2, the input device 2 outputs an on-off signal to the control unit 6. As a result, the motor 3 is driven or stopped.

[0021] <Motor> The motor 3 is configured to rotate and drive the drive wheels of the drive unit 100. The motor 3 is supplied with power from a battery 7 via a motor driver 5. The motor 3 is driven in response to the voltage and current output from the motor driver 5.

[0022] <First detection unit> The first detection unit 4 is configured to detect vehicle speed information related to the vehicle speed of the moving object. The first detection unit 4 detects, for example, the rotation speed of the motor 3. The first detection unit 4 is configured, for example, by a rotary encoder. The first detection unit 4 outputs the vehicle speed information to the control unit 6. The first detection unit 4 may output the vehicle speed information to the control unit 6 via a motor driver 5. The first detection unit 4 may be built into the motor 3.

[0023] <Motor driver> The motor driver 5 is electrically connected to the motor 3, the control unit 6, and the battery 7. The motor driver 5 outputs a current and a voltage from the battery 7 to the motor 3. The motor driver 5 drives the motor 3 based on an instruction signal from the control unit 6. In detail, the motor driver 5 receives an instruction signal from the control unit 6, and outputs a voltage and a current according to the instruction signal to the motor 3.

[0024] <Control Unit> The control unit 6 performs PWM control of the motor 3. The control unit 6 controls the duty ratio of the PWM signal in accordance with the vehicle speed information detected by the first detection unit 4. Specifically, the control unit 6 increases the duty ratio as the rotation speed of the motor 3 increases.

[0025] The control unit 6 executes the first mode when it receives an on signal from the input device 2. In the first mode, the control unit 6 controls the duty ratio to increase or decrease according to vehicle speed information.

[0026] The control unit 6 calculates the duty ratio of the PWM signal based on the vehicle speed information. The control unit 6 can set the duty ratio so that it increases as the rotation speed of the motor 3 increases, for example, as shown in FIG. 2. The increase rate of the duty ratio is, for example, constant. That is, the duty ratio increases linearly. The increase rate of the duty ratio does not have to be constant. For example, the increase rate of the duty ratio may increase as the rotation speed increases, or may decrease as the rotation speed increases.

[0027] 1, the control unit 6 calculates the duty ratio as described above, and outputs the calculation result as an instruction signal to the motor driver 5. The motor driver 5 outputs a voltage and a current to the motor 3 based on the duty ratio calculated by the control unit 6.

[0028] When the control unit 6 receives the off signal from the input device 2, it stops the electrical driving of the motor 3. That is, the control unit 6 stops the output of voltage and current from the motor driver 5 to the motor 3.

[0029] The control unit 6 is configured by, for example, a computer (for example, a microcomputer) including a CPU (Central Processing Unit) and a ROM (Read Only Memory). The ROM stores a program for calculating the duty ratio of the PWM signal. The CPU executes the program stored in the ROM.

[0030] <Control unit operation> Next, an example of processing executed by the control unit 6 will be described with reference to the flowcharts of FIGS.

[0031] First, the control unit 6 acquires an on / off signal from the input device 2 (step S1). Then, the control unit 6 determines whether the signal from the input device 2 is an on signal or not (step S2).

[0032] When the control unit 6 determines that the signal from the input device 2 is not an ON signal, that is, that the signal from the input device 2 is an OFF signal (No in step S2), it stops the electrical drive of the motor 3 (step S3). In detail, the control unit 6 stops the output of voltage and current from the motor driver 5 to the motor 3. Note that if the motor 3 has already stopped, the control unit 6 keeps it stopped.

[0033] On the other hand, when the control unit 6 determines that the signal from the input device 2 is an ON signal (Yes in step S2), it executes the first mode (step S4).

[0034] 4, in the first mode, the control unit 6 executes the following process. First, the control unit 6 acquires vehicle speed information detected by the first detection unit 4 (step S41). The control unit 6 may acquire the vehicle speed information directly from the first detection unit 4, or may acquire the vehicle speed information via the motor driver 5.

[0035] Next, the control unit 6 calculates the duty ratio based on the acquired vehicle speed information (step S42). Specifically, the control unit 6 calculates the duty ratio according to a function or a table that represents the relationship between the rotation speed of the motor 3 and the duty ratio.

[0036] Then, the control unit 6 outputs an instruction signal to the motor driver 5 so that the motor driver 5 outputs a voltage and a current to the motor 3 based on the calculated duty ratio (step S43).

[0037] According to the drive unit 100 configured as above, the following effects can be obtained, as shown in Fig. 5. Note that Fig. 5 is a graph showing the relationship between the rotation speed of the motor 3 and the output torque of the motor 3.

[0038] The dotted line in Figure 5 shows the relationship between rotation speed and torque when the motor 3 is driven with a constant duty ratio (for example, a duty ratio of 100%) without controlling the duty ratio. When the rotation speed is low, i.e., at start-up, the motor rotates with maximum torque. This can cause problems such as sudden acceleration and slipping.

[0039] Therefore, if the duty ratio is uniformly reduced (for example, to a duty ratio of 50%), the relationship between rotation speed and torque will be as shown by the two-dot chain line in Figure 5. By reducing the duty ratio in this way, the torque at start-up can also be reduced, making it possible to prevent sudden acceleration and slipping at start-up. However, this creates the problem of a reduction in the maximum rotation speed.

[0040] In contrast, in the drive unit 100 according to this embodiment, the control unit 6 controls the duty ratio according to the rotation speed of the motor 3. Therefore, when the rotation speed of the motor 3 is low, the duty ratio is reduced to reduce the output torque, thereby making it possible to suppress sudden acceleration and slippage of the drive wheels at the time of starting. In addition, since the duty ratio can be increased as the rotation speed of the motor 3 increases, it is also possible to prevent a decrease in the maximum value of the rotation speed of the motor 3. That is, in the drive unit 100 according to this embodiment, the relationship between the rotation speed of the motor 3 and the output torque of the motor 3 is as shown by the solid line in FIG. 5.

[0041] [Variations] Although the embodiments of the present invention have been described above, the present invention is not limited to these, and various modifications are possible without departing from the spirit of the present invention. The following modifications may be appropriately combined.

[0042] Variation 1 The control unit 6 may selectively execute the first mode and the second mode. The user selects the mode via the input device 2. For example, the user selects the off mode, the first mode, and the second mode. When the user operates the input device 2, the input device 2 outputs a mode selection signal to the control unit 6. Note that when the off mode is selected, the electric drive of the motor 3 is stopped.

[0043] When the user selects the first mode, the control unit 6 executes the first mode in the same manner as in the above embodiment.

[0044] On the other hand, when the user selects the second mode, the control unit 6 executes the second mode. In the second mode, the control unit 6 controls the duty ratio to be constant regardless of the vehicle speed information. In other words, the control unit 6 does not execute a duty ratio calculation as in the first mode. The control unit 6 outputs an instruction signal to the motor driver 5 so that the duty ratio is constant regardless of the vehicle speed information. The motor driver 5 outputs a voltage and a current to the motor 3 at a constant duty ratio (for example, 100%) based on an instruction from the control unit 6.

[0045] Fig. 6 is a flowchart showing an example of the process of the control unit 6 in Modification 1. As shown in Fig. 6, the control unit 6 acquires a mode selection signal from the input device 2 (step S11).

[0046] The control unit 6 determines whether or not the mode selection signal indicates the off mode (step S12). If the control unit 6 determines that the mode selection signal indicates the off mode (Yes in step S12), it stops the motor 3 (step S13).

[0047] When the control unit 6 determines that the mode selection signal does not indicate the off mode (No in step S12), the control unit 6 determines whether or not the mode selection signal indicates the first mode (step S14).

[0048] When the control unit 6 determines that the mode selection signal indicates the first mode (Yes in step S14), it executes the first mode (step S15).

[0049] On the other hand, when the control unit 6 determines that the mode selection signal does not indicate the first mode (No in step S14), the control unit 6 executes the second mode (step S16). That is, the control unit 6 outputs an instruction signal to the motor driver 5 to output a voltage and a current at a predetermined duty ratio without performing any calculation.

[0050] In addition to the first and second modes, the control unit 6 may selectively execute a third mode. In the third mode, the control unit 6 executes the same process as in the second mode. In the third mode, the duty ratio is smaller than that in the second mode.

[0051] Variation 2 In the above embodiment, the control unit 6 controls the duty ratio based only on the rotation speed of the motor 3, but the configuration of the drive unit 100 is not limited to this. For example, as shown in FIG. 7, the drive unit 100 may further include a second detection unit 8. The second detection unit 8 is configured to detect the current of the motor 3. Second detection unit 8 The controller 6 outputs information relating to the detected current of the motor 3 to the controller 6.

[0052] The control unit 6 corrects the duty ratio according to the current of the motor 3 detected by the second detection unit 8. In detail, the control unit 6 first calculates a duty ratio according to the rotation speed of the motor 3. Then, the control unit 6 corrects the calculated duty ratio according to the current of the motor 3.

[0053] For example, the control unit 6 can correct the duty ratio so that the duty ratio increases as the current of the motor 3 decreases. Alternatively, the control unit 6 may correct the duty ratio to be larger only when the current of the motor 3 is equal to or smaller than a predetermined threshold value.

[0054] Variation 3 8, the drive unit 100 may further include a third detector 9. The third detector 9 is configured to detect the temperature of the motor 3. The third detector 9 outputs information relating to the detected temperature of the motor 3 to the control unit 6.

[0055] The control unit 6 corrects the duty ratio in accordance with the temperature of the motor 3 detected by the third detection unit 9. In detail, the control unit 6 first calculates a duty ratio in accordance with the rotation speed of the motor 3. Then, the control unit 6 corrects the calculated duty ratio in accordance with the temperature of the motor 3.

[0056] For example, the control unit 6 can correct the duty ratio so that the duty ratio becomes smaller as the temperature of the motor 3 decreases. Alternatively, the control unit 6 may correct the duty ratio so that the duty ratio becomes larger as the temperature of the motor 3 decreases.

[0057] Alternatively, the control unit 6 may correct the duty ratio to be smaller only when the temperature of the motor 3 is equal to or higher than a predetermined threshold value. Also, the control unit 6 may correct the duty ratio to be larger only when the temperature of the motor 3 is equal to or lower than a predetermined threshold value.

[0058] Variation 4 As shown in Fig. 9, the drive unit 100 may further include a fourth detection unit 10. The fourth detection unit 10 is configured to detect the weight of an object placed on the moving body. The fourth detection unit 10 outputs information related to the detected weight of the object to the control unit 6. Note that the concept of an object placed on the moving body includes not only an object transported by a hand lift or a dolly, but also a person riding a wheelchair or a kickboard.

[0059] The control unit 6 corrects the duty ratio according to the weight of the object detected by the fourth detection unit 10. In detail, the control unit 6 first calculates a duty ratio according to the rotation speed of the motor 3. Then, the control unit 6 corrects the calculated duty ratio according to the weight of the object.

[0060] For example, the control unit 6 can correct the duty ratio so that the duty ratio increases as the weight of the object increases.

[0061] Variation 5 10, the drive unit 100 may further include a correction value input device 11. The correction value input device 11 may be, for example, a lever. A user can correct the duty ratio by operating this correction value input device 11 and adjusting the amount of operation.

[0062] In detail, the control unit 6 first calculates a duty ratio according to the rotation speed of the motor 3. Then, the control unit 6 corrects the duty ratio according to the operation amount of the correction value input device 11. For example, when the operation amount of the correction value input device 11 is large, the control unit 6 corrects the duty ratio so that the duty ratio becomes large. Note that the correction value input device 11 may be configured to increase and decrease the operation amount continuously, or may be configured to increase and decrease the operation amount stepwise.

[0063] Variation 6 The vehicle speed information detected by the first detection unit 4 does not have to be the rotation speed of the motor 3. For example, the first detection unit 4 may be an acceleration sensor. The control unit 6 may calculate the vehicle speed based on the acceleration of the moving object detected by this acceleration sensor, and control the duty ratio according to the calculated vehicle speed. [Explanation of symbols]

[0064] 2 Input Devices 3 Motor 4 First detection section 5 Motor Driver 6 Control section 8 Second detection section 9. Third detector 10 Fourth detection unit 11 Correction value input device 100 Drive Unit

Claims

1. A drive unit attached to a moving body, A motor; A first detection unit that detects vehicle speed information related to a vehicle speed of the moving object; A control unit that PWM controls the motor; an input device for outputting an on / off signal to the control unit; Equipped with When the control unit determines that the signal from the input device is an ON signal, the control unit controls a duty ratio of a PWM signal in accordance with vehicle speed information detected by the first detection unit; The control unit increases the duty ratio as the rotation speed of the motor increases. Drive unit.

2. The first detection unit detects a rotation speed of the motor as the vehicle speed information.

2. A drive unit according to claim 1.

3. The control unit selectively executes a first mode and a second mode, The control unit controls the duty ratio so as to increase or decrease in accordance with the vehicle speed information in the first mode, and controls the duty ratio so as to be constant regardless of the vehicle speed information in the second mode. A drive unit according to claim 1 or 2.

4. A second detection unit that detects a current of the motor is further provided, The control unit corrects the duty ratio in response to the current of the motor detected by the second detection unit. A drive unit according to any one of claims 1 to 3.

5. A third detection unit that detects a temperature of the motor is further provided. The control unit corrects the duty ratio in response to the temperature of the motor detected by the third detection unit. A drive unit according to any one of claims 1 to 4.

6. A fourth detection unit that detects a weight of an object placed on the moving body, The control unit corrects the duty ratio in accordance with the weight detected by the fourth detection unit. A drive unit according to any one of claims 1 to 5.

7. A correction value input device operated by a user is further provided, The control unit corrects the duty ratio in accordance with an amount of operation of the correction value input device. A drive unit according to any one of claims 1 to 6.

8. Further comprising a motor driver; The control unit controls the motor via the motor driver. A drive unit according to any one of claims 1 to 7.

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