阅读说明：本技术 电动工具的控制装置 (Control device for electric tool ) 是由 米田文生 于 2018-04-17 设计创作，主要内容包括：本发明是用于使用了电池和DC无刷电动机的电动工具的控制装置,该装置具备：电流检测部,其检测在所述DC无刷电动机中流动的瞬时电流；电流计算部,其计算由所述电流检测部检测出的电流的平均值或有效值；电流控制部,其将所述电流计算部的结果作为检测值来利用；速度控制部,其生成所述电流控制部的目标值,其中,在所述速度控制部的输出级具备限制所述电流控制部的目标值的限制器。(The present invention is a control device for an electric power tool using a battery and a DC brushless motor, the device including: a current detection unit that detects an instantaneous current flowing in the DC brushless motor; a current calculation unit that calculates an average value or an effective value of the current detected by the current detection unit; a current control unit that uses the result of the current calculation unit as a detection value; and a speed control unit that generates a target value of the current control unit, wherein a limiter that limits the target value of the current control unit is provided at an output stage of the speed control unit.)

1. A control device for an electric power tool, which is used for the electric power tool using a battery and a DC brushless motor, is characterized by comprising:

a current detection unit that detects an instantaneous current flowing through the dc brushless motor;

a current calculation unit that calculates an average value or an effective value of the current detected by the current detection unit;

a current control unit that uses the result of the current calculation unit as a detection value; and

a speed control unit that generates a target value of the current control unit,

wherein the output stage of the speed control unit includes a limiter that limits a target value of the current control unit.

2. A control method for an electric power tool using a battery and a dc brushless motor, the control method comprising:

a current detection step of detecting an instantaneous current flowing in the dc brushless motor;

a current calculation step of calculating an average value or an effective value of the current detected in the current detection step;

a current control step of using a result of the current calculation step as a detection value;

a speed control step of generating a target value for the current control step; and

a limiter provided at an output stage of the speed control step limits a target value of the current control step.

3. An electric power tool using a battery and a DC brushless motor, the electric power tool being characterized in that,

a control device provided with the electric power tool according to claim 1.

Technical Field

The present disclosure relates to a control device and a control method for an electric power tool using, for example, a DC (direct current) brushless motor, and an electric power tool.

Background

In recent years, a DC brushless motor is often used in an electric power tool.

This DC brushless motor has a longer life than a conventional DC motor without replacing a brush, but uses a switching element instead of a brush, and needs to protect both the battery and the switching element from a large current flowing at the time of motor stalling, overload, or the like.

As an example of a method for solving this problem, patent document 1 proposes one of the following methods: two filters having different cutoff frequencies are provided in one current detection circuit to protect both the battery (average current) and the switching element (instantaneous current).

Disclosure of Invention

Problems to be solved by the invention

However, in the method of patent document 1, even if overcurrent protection of the battery and the switching element is possible, improvement of controllability of the electric power tool itself is not involved. In addition, from the viewpoint of the durability of the electric power tool, it is important to perform control for avoiding the overcurrent at a stage before the overcurrent is detected.

The present disclosure is directed to solving the above-described problems and to providing a control device and a control method for an electric power tool, and an electric power tool, which are capable of performing control to avoid an overcurrent at a stage before the overcurrent is detected.

Means for solving the problems

A control device for an electric power tool according to a first aspect of the present disclosure is a control device for an electric power tool using a battery and a DC brushless motor, the control device including:

a current detection unit that detects an instantaneous current flowing in the DC brushless motor;

a current calculation unit that calculates an average value or an effective value of the current detected by the current detection unit;

a current control unit that uses the result of the current calculation unit as a detection value; and

a speed control unit that generates a target value of the current control unit,

wherein the output stage of the speed control unit includes a limiter that limits a target value of the current control unit.

A control method for an electric power tool according to a second aspect of the present disclosure is a control method for an electric power tool using a battery and a DC brushless motor, the control method including:

a current detection step of detecting an instantaneous current flowing in the DC brushless motor;

a current calculation step of calculating an average value or an effective value of the current detected by the current detection unit;

a current control step of using a result of the current calculation step as a detection value;

a speed control step of generating a target value for the current control step; and

a limiter provided at an output stage of the speed control step limits a target value of the current control step.

The electric power tool according to the third aspect of the present disclosure is an electric power tool using a battery and a DC brushless motor,

the control device is provided with the electric tool.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the control device, the control method, and the like of the present disclosure, overcurrent protection of the battery, the switching element, and the circuit can be performed by one current detection unit, and since the limiter of the current control operates before the overcurrent protection operation is performed, overcurrent can be prevented in advance. In addition, by setting the current control unit as a minor loop (minor loop) of the speed control unit, control for avoiding an overcurrent can be performed at a stage before the overcurrent is detected while improving the control performance of the entire electric power tool.

Drawings

Fig. 1 is a block diagram showing a configuration example of an electric power tool according to an embodiment of the present disclosure.

Detailed Description

Fig. 1 is a block diagram showing a configuration example of an electric power tool according to an embodiment of the present disclosure. In fig. 1, the electric power tool according to the embodiment is configured to include, for example, a DC brushless motor (hereinafter, referred to as a motor) 1, a PWM inverter circuit 2, a gear 3, a chuck 4, a rechargeable battery 5, a capacitor 6, a current detection resistor 7, and a motor control device 10. Here, the motor control device 10 is configured to include a current detection unit 11, a current calculation unit 12, an overcurrent detection unit 51, a speed control unit 52, a current control unit 53, and a gate (gate) control unit 20.

The motor control device 10 according to the present embodiment is characterized in that an instantaneous current and an average current of a current supplied to the PWM inverter circuit 2 are detected to protect a switching element, a circuit, and a battery, the detected average current is controlled, and a current limiter 24 that limits a target value of the average current is provided at an output stage of a speed control unit 52 as a current controller, thereby preventing an overcurrent in advance. In addition, the speed control unit 52 is disposed near the current control unit 53, and the speed control is a local loop of the speed control, thereby improving the speed response and stability of the speed control of the electric power tool.

In fig. 1, a DC voltage from a rechargeable battery 5 is supplied to a PWM inverter circuit 2 via a capacitor 6 and a current detection resistor 7. The PWM inverter circuit 2 modulates the supplied DC voltage with 6 gate drive signals G1 to G6 from the gate control unit 20, converts the DC voltage into an ac voltage, and outputs the ac voltage to the motor 1. Here, the rotation of the motor 1 is transmitted to a chuck 4 of the electric tool via a gear 3. The gate control unit 20 generates speed detection values and gate drive signals G1 to G6 based on motor rotational position signals from hall elements 41 to 43 provided in the motor 1, a PWM signal from the current control unit 53, and a gate block signal from the overcurrent detection unit 51.

The voltage detected by the current detection resistor 7 is output to the current detection unit 11, and the current detection unit 11 converts the voltage into a corresponding current value and outputs the voltage to the non-inverting input terminal of the comparator 13 and the current calculation unit 12. The current calculating unit 12 calculates an average value of the current values by adding the current values for a predetermined period using an adder, for example, and outputs the average value to the subtractor 25. Alternatively, the current calculation unit 12 may calculate an effective value of the current for a predetermined period instead of the average value of the current for the predetermined period.

The overcurrent detection unit 51 is configured to include the comparator 13 and the maximum current signal generator 14. The comparator 13 compares the instantaneous current signal from the current detection unit 11 with the maximum current signal indicating the maximum current value from the maximum current signal generator 14, generates a gate block signal based on the comparison result, and outputs the gate block signal to the gate control unit 20. When the instantaneous current exceeds the maximum current value, the gate control unit 20 immediately stops the driving of the PWM inverter circuit 2, thereby protecting the switching elements.

The speed control unit 52 includes an absolute value arithmetic unit 30, a speed target value generator 21, a subtractor 22, a PI controller 23 that performs proportional-integral control of the motor speed, and a current limiter 24. The absolute value calculator 30 calculates the absolute value of the speed detection value from the gate control unit 20 and outputs the calculated value to the subtractor 22. The subtractor 22 subtracts the absolute value of the speed detection value from the speed target value generator 21, and outputs the subtraction result to the PI controller 23. The PI controller 23 performs proportional-integral control on the motor speed based on the input subtraction result, and outputs a target current value for performing the control to the subtractor 25 via the current limiter 24. Here, the current limiter 24 limits the current target value corresponding to the speed target value to within a predetermined value, thereby preventing an overcurrent in advance and protecting the circuit and the battery.

The current control unit 53 is configured to include a subtractor 25, a PI controller 26, a limiter 27, a comparator 28, and a triangular wave generator 29. The subtractor 25 subtracts the average current signal from the current calculation unit 12 from the current target value signal indicating the current target value, and outputs a signal of a current control value as a subtraction result to the PI controller 26. The PI controller 26 performs proportional-integral control on the current control value, and outputs the control signal to the non-inverting input terminal of the comparator 28 via the limiter 27. Here, the limiter 27 controls the amplitude value of the PWM signal output from the comparator 28 to be within a predetermined value. The comparator 28 compares the control signal from the limiter 27 with the triangular wave from the triangular wave generator 29 to generate a PWM signal for driving the motor 1 by PWM modulation, and outputs the PWM signal to the gate control unit 20.

The gate control unit 20 generates 6 gate drive signals G1 to G6 based on the PWM signal and the gate block signal, and outputs the signals to the PWM inverter circuit 2, thereby controlling the operation of the PWM inverter circuit 2.

In the control device 10 for the electric power tool according to the embodiment configured as described above, the switching elements and circuits in the PWM inverter circuit 2 and the battery 5 can be protected from overcurrent by the single current detection unit 11. In addition, since the current limiter 24 for current control operates before the overcurrent protection operation is performed, overcurrent can be prevented in advance. In addition, the speed control unit 52 provides the current target value to the current control unit 53 that generates the PWM signal to form the local loop of the speed control unit 52, thereby providing a unique effect of improving the control performance of the electric power tool itself.

In the above embodiments, for example, the rotary electric tool of the drill has been described, but the present disclosure is not limited thereto, and can be applied to an impact electric tool.

In the above embodiment, the rechargeable battery 5 is provided as a secondary battery, but the present disclosure is not limited thereto, and other types of batteries such as a primary battery may be used.

In the above embodiment, the motor control device 10 may be configured as a main body by hardware, or may be configured as a main body by software.

Description of the reference numerals

1: an electric motor; 2: a PWM inverter circuit; 3: a gear; 4: a chuck; 5: a rechargeable battery; 6: a capacitor; 7: a current detection resistor; 10: a motor control device; 11: a current detection unit; 12: a current calculation unit; 13: a comparator; 14: a maximum current signal generator; 20: a gate control section; 21: a speed target value generator; 22: a subtractor; 23: a PI controller; 24: a current limiter; 25: a subtractor; 26: a PI controller; 27: a limiter; 28: a comparator; 29: a triangular wave generator; 30: an absolute value calculator; 41-43: a Hall element; 51: an overcurrent detection unit; 52: a speed control unit; 53: a current control unit.