JP4203268B2 - Motor control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for a brushless DC motor (hereinafter simply referred to as a motor) used in an electric tool such as an electric driver or an electric impact driver.
[0002]
[Prior art]
In the conventional electric impact driver, a strong torque is generated in the striking mechanism, but the torque is too large depending on the application, and thus the screw or the like may be tightened or damaged. Therefore, in order to solve this problem, there is a type in which a mechanical clutch mechanism is added and the striking mechanism and the clutch mechanism can be switched according to the application.
[0003]
And when setting torque, it sets using this clutch mechanism.
[0004]
[Problems to be solved by the invention]
However, the electric impact driver of this type has a problem that the structure becomes complicated because the clutch mechanism is provided, the number of parts increases, and the cost increases.
[0005]
In addition, there is a problem that the external dimensions of the electric impact driver are large and heavy, which is disadvantageous for workability.
[0006]
In view of the above problems, the present invention provides a motor control device that can facilitate torque control.
[0007]
[Means for Solving the Problems]
The invention of claim 1 includes an inverter circuit that outputs a drive signal to a brushless DC motor that drives an electric tool such as an electric driver or an electric impact driver, a gate drive circuit that controls the inverter circuit, and the gate drive circuit A motor control device having an arithmetic circuit for PWM control, a speed command circuit for outputting a speed command signal to the arithmetic circuit by a signal from a trigger switch for operating the electric tool, and the motor A torque control switch for setting so as not to rotate more than a set torque value, wherein the torque control switch is connected to the speed command circuit, and the speed command circuit is in an ON state. Output a speed command signal exceeding the set torque value to the arithmetic circuit. A control apparatus for a motor, wherein the motor is PWM controlled so as not to rotate more than the set torque value.
[0010]
[Operation]
In the motor control device of the present invention, the arithmetic circuit performs PWM control so that the motor does not rotate beyond the set torque value when the torque control switch is in the ON state. When tightening, it will not be damaged by overtightening.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIGS.
[0012]
FIG. 1 is a front view of an electric impact driver showing an embodiment of the present invention, and FIG. 2 is a block diagram showing a control device 18 of the electric impact driver 11.
[0013]
(1) Configuration of Electric Impact Driver 11 The configuration of the electric impact driver 11 will be described with reference to FIG.
[0014]
The electric impact driver 11 includes a main body 12 having a substantially cylindrical outer shape, which is a body, a chuck portion 13 on which a tool is mounted on the tip of the main body 12, and a gripping portion 14 formed to be a pistol type. I have.
[0015]
A brushless DC motor (hereinafter simply referred to as a motor) 15 and a striking portion 16 that also serves as a striking mechanism are incorporated in the rear portion of the main body 12.
[0016]
The grip portion 14 is formed so that an operator can grip it with a hand, and a trigger-like trigger switch 17 is disposed at a position where a finger is positioned in the grip state.
[0017]
A circuit board of a control device 18 that controls the motor 15 with a predetermined rotational speed and torque by the operation of the trigger switch 17 is disposed below the motor 15.
[0018]
A battery 19 and a large-capacity power supply voltage smoothing capacitor 20 electrically connected in parallel with the battery 19 are accommodated in the gripping part 14.
[0019]
(2) Configuration of Control Device 18 Next, the control device 18 that controls the electric impact driver 11 will be described with reference to FIG.
[0020]
The motor 15, which is a brushless DC motor, has three phases, and U-phase, V-phase, and W-phase drive signals are supplied from the inverter circuit 21. That is, the bipolar switching is performed by using the six switching transistors constituting the inverter circuit 21 and driving the motor 15 by flowing a bidirectional current through the Y-connected three-phase coils. Examples of the bipolar driving method include a 120 ° energization rectangular wave driving method.
[0021]
Three Hall elements H1, H2, and H3 (hereinafter collectively referred to as H) are provided to detect the rotational position of the rotor of the motor 15, and respond to changes in the magnetic pole for each phase due to the rotation of the rotor. The rotation signals S1, S2, and S3 (hereinafter, collectively referred to as S) are output to the position detection circuit 23, respectively.
[0022]
The inverter circuit 21 is supplied with DC power as a battery 19, and the power supply voltage smoothing capacitor 20 is connected in parallel with the battery 19 between the inverter circuit 21 and the battery 19.
[0023]
A gate drive circuit 28 that sends a gate signal to the gate terminal of each switching transistor of the inverter circuit 21 is provided, and an arithmetic circuit 22 that supplies a PWM (pulse width modulation) signal to the gate drive circuit 28 is provided. The arithmetic circuit 22 sends the PWM signal to the gate drive circuit 28 based on the position signal from the position detection circuit 23, the speed command signal from the speed command circuit 24, and the rotation direction command signal from the rotation direction command circuit 25. Output.
[0024]
The speed command circuit 24 that outputs a speed command signal is connected to the trigger switch 17 described above, and the speed command circuit 24 outputs a speed command signal to the arithmetic circuit 22 according to a pressing state of the trigger switch 17 by an operator. . That is, a speed command signal is output so as to rotate faster by pulling a large number of trigger switches 17.
[0025]
The main body 12 is provided with a rotation direction changeover switch 26. When the rotation direction changeover switch 26 is switched to normal rotation or inversion, the rotation direction command circuit 25 outputs a rotation direction command signal corresponding to the rotation direction.
[0026]
A lock protection circuit 27 is provided between the gate drive circuit 28 and the arithmetic circuit 22. This lock protection circuit 27 is operated when the position detection circuit 23 detects that the rotation of the motor 15 is not detected by the rotation signal S from the Hall element H even though the drive signal is output to the motor 15. This circuit forcibly cuts off the signal from the circuit 22 to the gate drive circuit 28.
[0027]
A resistor 32 for detecting the drive current output from the battery 19 is connected, and a current control circuit 29 for detecting the drive current flowing through the resistor 32 is provided. The current control circuit 29 has two purposes.
[0028]
The first purpose is to output a control signal that instructs the arithmetic circuit 22 to reduce the rotational speed or torque by determining that the current is an overcurrent when the drive current flowing through the resistor 32 exceeds a set value. When this control signal is output, the arithmetic circuit 22 forcibly narrows the pulse width of the PWM waveform and decreases the output of the motor 15. Thereby, the further heat generation of the motor 15 is suppressed, the temperature rise does not occur, and the control device 18 can be prevented from being damaged by heat.
[0029]
The second purpose is to perform torque control when a small screw or the like is tightened.
[0030]
That is, the torque control switch 31 is connected to the current control circuit 29. The torque control switch 31 is a switch provided in the main body 12. When the torque control switch 31 is turned on, the current control circuit 29 outputs a threshold signal to the arithmetic circuit 22. When this threshold signal is input to the arithmetic circuit 22, the pulse width of the PWM waveform is controlled so as not to exceed the set torque value regardless of the speed command signal from the speed command circuit 24. The torque is determined by the electric power applied to the motor, and this electric power is a product of current and voltage. When the voltage value is increased, the rotational speed is increased, and when the current value is increased, the electric power value is increased and the torque is also increased. Therefore, the arithmetic circuit 22 narrows the pulse width of the PWM waveform so that the current value is adjusted so as not to exceed the set torque value.
[0031]
As a result, if the torque control switch 31 is turned on when a small screw or the like is tightened, the operator does not output more than the set value even when the trigger switch 17 is pushed deeply, so that the small screw is not crushed. .
[0032]
In this way, a certain degree of torque control is possible even during the hit operation. And since it is not necessary to provide the mechanism for adjusting torque control in the striking part 16, since the striking part 16 can be produced inexpensively and compactly, the electric impact driver 11 itself can be reduced in size and weight. Excellent workability when working.
[0033]
(Modification 1)
Although the electric impact driver 11 has been described in the above embodiment, torque control can be performed by using this control device 18 in a normal electric driver that does not have a striking mechanism instead.
[0034]
(Modification 2)
In the above embodiment, the torque control switch 31 is provided in the current control circuit 29. Instead, the torque control switch 31 is connected to the speed command circuit 24. When the torque control switch 31 is in the ON state, the speed command circuit 31 is connected. No. 24 may output a speed command signal to the arithmetic circuit 22 so that the rotational speed and torque are not more than the set values.
[0035]
【The invention's effect】
As described above, in the motor control device of the present invention, it is possible to prevent a torque exceeding a certain value from being output by the torque control switch, so that these screws are not crushed when a small screw or the like is tightened.
[Brief description of the drawings]
FIG. 1 is a front view of an electric impact driver showing an embodiment of the present invention.
FIG. 2 is a block diagram of a control device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Electric impact driver 15 Motor 17 Trigger switch 18 Controller 21 Inverter circuit 22 Arithmetic circuit 23 Position detection circuit 24 Speed command circuit 25 Rotation direction command circuit 26 Rotation direction switch 28 Gate drive circuit 29 Current control circuit 31 Torque control switch

Claims (1)

An inverter circuit that outputs a drive signal to a brushless DC motor that drives an electric tool such as an electric driver or an electric impact driver, a gate drive circuit that controls the inverter circuit, and an arithmetic circuit that performs PWM control on the gate drive circuit A motor control device having
A speed command circuit that outputs a speed command signal to the arithmetic circuit by a signal from a trigger switch for operating the electric tool;
A torque control switch for setting the motor not to rotate more than a set torque value;
Have
The torque control switch is connected to the speed command circuit, and the speed command circuit does not output a speed command signal equal to or higher than a set torque value to the arithmetic circuit when the torque control switch is in an ON state, and the motor sets A motor control device that performs PWM control so as not to rotate more than a torque value .

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