JP2004015986A - Control device of motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device capable of facilitating torque control and driving a brushless DC motor at small torque. <P>SOLUTION: The control device comprises an inverter circuit 21 that outputs a drive signal to the brushless DC motor 15 for driving a motor-driven impact driver 11, a gate drive circuit 28, a PWM-controlling operating circuit 22, a speed command circuit 24 that outputs a speed command signal to the operating circuit 22 by using a signal from a trigger switch 17, and a torque control switch 31 that sets the motor not to rotate exceeding a set torque value. When the torque control switch 31 is in an on-state, the operating circuit 22 controls the motor 15 not to rotate exceeding the set torque value. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a control device for a brushless DC motor (hereinafter, simply referred to as a motor) used for an electric tool such as an electric driver or an electric impact driver.
[0002]
[Prior art]
In a conventional electric impact driver, a strong torque is generated in a striking mechanism, but depending on the application, the torque is too large, which may cause overtightening or breakage of a small screw or the like. Therefore, in order to solve this problem, there is a type in which a mechanical clutch mechanism is added and the impact mechanism and the clutch mechanism can be switched according to the application.
[0003]
When setting the torque, the setting is performed using this clutch mechanism.
[0004]
[Problems to be solved by the invention]
However, such an electric impact driver has a problem that the structure is complicated and the number of parts is increased due to the provision of the clutch mechanism, and the cost is increased.
[0005]
Further, there is a problem that the external dimensions of the electric impact driver are large and heavy, which is disadvantageous to 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 according to claim 1 is 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 speed command circuit that outputs a speed command signal to the arithmetic circuit by a signal from a trigger switch for operating the power tool; and A torque control switch for setting so as not to rotate more than a set torque value, wherein the arithmetic circuit is configured to perform PWM so that the motor does not rotate more than the set torque value when the torque control switch is ON. It is a motor control device characterized by controlling.
[0008]
The invention according to claim 2 has a current control circuit that detects a drive current flowing from the DC power supply to the inverter circuit, and outputs a control signal to the arithmetic circuit when the detected drive current is equal to or greater than a set value. The torque control switch is connected to the current control circuit, and the current control circuit outputs a threshold signal to the arithmetic circuit when the torque control switch is in an ON state, so as to prevent the torque control switch from rotating beyond a set torque value. The motor control device according to claim 1, wherein:
[0009]
According to a third aspect of the present invention, the torque control switch is connected to the speed command circuit, and the speed command circuit outputs a speed command signal equal to or larger than a set torque value to the arithmetic circuit when the torque control switch is ON. The motor control device according to claim 1, wherein the motor control device does not perform the control.
[0010]
[Operation]
According to 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 it is tightened, it is not damaged due to excessive tightening.
[0011]
BEST MODE FOR CARRYING OUT 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 one 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 section 13 on which a tool is mounted at a tip end of the main body 12, and a grip section 14 formed to be a pistol type. Have.
[0015]
At the rear of the main body 12, a brushless DC motor (hereinafter simply referred to as a motor) 15 and a striking section 16 which also functions as a gearbox and a striking mechanism are incorporated.
[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 arranged at a position where a finger is located in the grip state.
[0017]
A circuit board of a control device 18 that controls the motor 15 with a predetermined rotation speed and torque by operating the trigger switch 17 is disposed below the motor 15.
[0018]
A battery 19 and a large-capacity power supply voltage smoothing capacitor 20 that is electrically connected in parallel with the battery 19 are housed inside the holding unit 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, bipolar driving is performed using six switching transistors forming the inverter circuit 21 and driving the motor 15 by passing a bidirectional current through the three-phase coils connected in a Y-connection. As a bipolar driving method, a 120 ° energized rectangular wave driving method may be used.
[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 correspond to the magnetic pole change 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 between the inverter circuit 21 and the battery 19 in parallel with 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 above-described trigger switch 17 is connected to the speed command circuit 24 that outputs the speed command signal. The speed command circuit 24 outputs the speed command signal to the arithmetic circuit 22 according to the pressing state of the trigger switch 17 by the operator. . That is, the speed command signal is output so as to rotate faster by pulling the trigger switch 17 many times.
[0025]
The main body 12 is provided with a rotation direction switch 26. By switching the rotation direction switch 26 between normal rotation and reverse rotation, 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. 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, the lock protection circuit 27 This is a circuit for forcibly blocking a signal from the circuit 22 to the gate drive circuit 28.
[0027]
A resistor 32 for detecting a drive current output from the battery 19 is connected, and a current control circuit 29 for detecting a drive current flowing through the resistor 32 is provided. This current control circuit 29 has two purposes.
[0028]
The first object is that when the drive current flowing through the resistor 32 exceeds a set value, it is determined that the current is overcurrent, and a control signal is output to the arithmetic circuit 22 to instruct the arithmetic circuit 22 to reduce the rotation speed or torque. When this control signal is output, the arithmetic circuit 22 forcibly narrows the pulse width of the PWM waveform and lowers the output of the motor 15. As a result, further generation of heat of the motor 15 is suppressed, and the control device 18 can be prevented from being damaged by heat without causing a temperature rise.
[0029]
A second object is to perform torque control when tightening a small screw or the like.
[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 on 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. Note that the torque is determined by the power applied to the motor, and this power is a product of the current and the voltage. When the voltage value is increased, the rotation speed is increased, and when the current value is increased, the power value is increased, and the torque is also increased. Therefore, the arithmetic circuit 22 reduces the pulse width of the PWM waveform so that the current value is adjusted so as not to exceed the set torque value.
[0031]
Accordingly, if the torque control switch 31 is turned on when a small screw or the like is to be tightened, the operator will not output the set value or more even if the trigger switch 17 is pushed deep, so that the small screw will not be crushed. .
[0032]
By doing so, it is possible to control the torque to some extent even during the striking operation. Since it is not necessary to provide a mechanism for adjusting the torque control in the hitting portion 16, the hitting portion 16 can be manufactured inexpensively and in a small size. Excellent workability when working.
[0033]
(Modification 1)
Although the electric impact driver 11 has been described in the above embodiment, the torque control can be performed by using the control device 18 in a normal electric driver having no impact 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, and when the torque control switch 31 is in the ON state, the speed command circuit 31 is turned on. 24 may output a speed command signal to the arithmetic circuit 22 so that the rotation speed and torque do not exceed the set values.
[0035]
【The invention's effect】
As described above, according to the motor control device of the present invention, it is possible to prevent the torque control switch from outputting a torque that is equal to or more than a certain value. Therefore, when a small screw is tightened, the screw is not crushed.
[Brief description of the drawings]
FIG. 1 is a front view of an electric impact driver according to an embodiment of the present invention.
FIG. 2 is a block diagram of a control device.
[Explanation of symbols]
Reference Signs List 11 electric impact driver 15 motor 17 trigger switch 18 control device 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 (3)

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 of 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 power tool;
A torque control switch for setting the motor so as not to rotate more than a set torque value,
Has,
The motor control device, wherein the arithmetic circuit performs PWM control so that the motor does not rotate beyond a set torque value when the torque control switch is ON. A current control circuit that detects a drive current flowing from the DC power supply to the inverter circuit, and outputs a control signal to the arithmetic circuit when the detected drive current is equal to or greater than a set value,
The torque control switch is connected to the current control circuit, and the current control circuit outputs a threshold signal to the arithmetic circuit when the torque control switch is in an ON state, so as to prevent the operation circuit from rotating beyond a set torque value. The motor control device according to claim 1, wherein: The torque control switch is connected to the speed command circuit, and the speed command circuit does not output a speed command signal having a set torque value or more to the arithmetic circuit when the torque control switch is in an ON state. Item 2. A motor control device according to Item 1.

Images