JP2005304145A - Motor drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor drive in which the efficiency of a motor is enhanced inexpensively while ensuring safety of the motor drive, and mounting space can be ensured. <P>SOLUTION: A fuse resistor 40 is connected with a wiring path from a battery 30 to an inverter circuit 14, and an overcurrent detection circuit 26 outputs a stop signal to a control circuit 20 when a current flowing through the fuse resistor 40 exceeds a predetermined level. The control circuit 20 stops rotation of a motor 12 upon receiving a stop signal. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a motor drive device that is designed to provide overcurrent protection.

  In conventional brushless DC motor driving devices, inverter control is widely adopted. In this case, DC power is supplied to the inverter circuit, and a fuse is provided in the middle of the supply path to prevent smoke and fire on the wiring board of the drive circuit.

In order to prevent overcurrent due to a high load during motor rotation, a resistance element is connected in the middle of the supply path to the inverter circuit, and the current flowing through this resistance element is measured. An overcurrent protection device is provided that adjusts the output of the brushless DC motor when the value exceeds a predetermined value (see, for example, Patent Document 1).
JP 2003-199382 A

  In the conventional motor driving apparatus as described above, since it is necessary to connect a fuse and a resistance element for current detection on the circuit, the work is complicated and the parts cost is high. is there.

  Further, there is a problem in that the efficiency of the motor is lowered due to a drop in the voltage of the DC power supply caused by the fuse and the resistance element.

  Furthermore, there is a problem that it is necessary to secure a mounting space for the fuse and the resistance element.

  Accordingly, in view of the above problems, the present invention provides a motor driving device that can secure the safety of the motor driving device, reduce the cost, improve the efficiency of the motor, and secure the mounting space.

  The invention according to claim 1 is an inverter circuit that supplies a drive current to a stator winding of each phase of a motor, a control unit that controls the inverter circuit, a power source unit that supplies a DC power to the inverter circuit, A fuse resistor is connected to a wiring path from the power supply means to the inverter circuit, and a stop signal is output to the control means when a current flowing through the fuse resistor exceeds a predetermined value. The motor driving device includes a current detection unit, and the control unit stops or decelerates the rotation of the motor when the stop signal is input.

  The invention according to claim 2 is the motor drive device according to claim 1, wherein the motor is a brushless DC motor.

  The invention according to claim 3 is the motor drive device according to claim 1, wherein the motor is a drive source of an electric tool.

  The invention according to claim 4 is the motor driving apparatus according to claim 1, wherein the power supply means is a battery.

  In the motor driving apparatus according to the first aspect of the present invention, when the current flowing through the fuse resistor exceeds a predetermined value, the overcurrent detection means outputs a stop signal, and when the stop signal is input, the control signal is output from the motor. As a result, the inverter circuit can be protected from overcurrent and the motor safety can be ensured. When an abnormally large current flows to the inverter circuit, the fuse resistor element is melted to protect the inverter circuit and the entire motor drive device.

  Since this fuse resistor plays the role of a conventional fuse and the role of a resistance element, the cost can be reduced, the voltage drop is reduced, the motor efficiency is increased, and the mounting space is also one component. It ’s just that.

  A motor drive device 10 according to an embodiment of the present invention will be described below with reference to FIG.

  The driving device 10 is a driving device for a three-phase brushless DC motor (hereinafter simply referred to as a motor) 12 and is a driving source for an electric tool.

(1) Configuration of Drive Device 10 The configuration of the drive device 10 will be described with reference to FIG.

  The drive device 10 includes an inverter circuit 14, a logic circuit 16, a PWM circuit 18, a control circuit 20, a rotor position detection circuit 22, a speed adjustment circuit 24, an overcurrent detection circuit 26, a noise filter circuit 28, and a battery 30. ing. The logic circuit 16, the PWM circuit 18, the control circuit 20, the rotor position detection circuit 22, and the load current detection circuit 26 are integrated on one IC chip.

  The inverter circuit 14 is supplied with a direct current from a battery 30 composed of a rechargeable battery, and is supplied with a predetermined direct current from which noise has been removed by the noise filter circuit 28. The inverter circuit 14 is formed of six switching elements 32 made of MOSFETs and six diodes 34, and each of the three switching elements 32 connected in three stages in the upper and lower stages, respectively, three-phase stator windings of the motor 12. A drive current is supplied to the line 36.

  The rotor position detection circuit 22 outputs a position signal of the rotor of the motor 12 to the control circuit 20 based on the position detection signals from the three Hall ICs 38. The three Hall ICs 38 are attached in the vicinity of the rotor of the motor 12 and detect its rotation.

  The speed adjustment circuit 24 outputs a speed command signal to the control circuit 22 based on a trigger switch attached to the frame of the electric tool.

  Based on the position detection signal from the rotor position detection circuit 22 and the speed command signal from the speed adjustment circuit 24, the control circuit 20 adjusts the current rotation speed of the motor 12 to a rotation speed corresponding to the speed command signal. A control signal is output to the PWM circuit 18.

  The PWM circuit 18 outputs a PWM signal to the logic circuit 16 based on the control signal from the control circuit 20.

  The logic circuit 16 outputs a drive signal for turning on / off the six switching elements 32 of the inverter circuit 14 based on the PWM signal from the PWM circuit 18.

  A fuse resistor 40 is connected between the noise filter circuit 28 and the inverter circuit 14. “Fuse resistor” functions as a resistor when the current is less than the specified value. When an overcurrent exceeding the specified value flows, the element of the resistance element melts within the specified time, preventing the current flow. An element that has a function that does not return to its original value.

  The overcurrent detection circuit 26 measures the voltage difference between both ends of the fuse resistor 40 to calculate the current value flowing through the fuse resistor 40. If the current value exceeds a predetermined value, the overcurrent detection circuit 26 stops the control circuit 20. Output a signal. The overcurrent detection circuit 26 is configured by a comparator, for example.

(2) Operating state of the driving device 10 In the driving device 10 having the above-described configuration, when the user of the electric tool turns on the power switch and adjusts the trigger switch to rotate the motor 12, the motor 12 is rotated based on the adjusted speed. As a result, the motor 12 rotates.

  When the motor 12 rotates and a load is applied to the tool portion of the electric power tool, and an overcurrent of a predetermined value or more flows through the inverter circuit 14 and the fuse resistor 40, the overcurrent detection circuit 26 detects this, and the control circuit 20 Output a stop signal. When the stop signal is output, the control circuit 20 stops or decelerates the rotation of the motor 12.

  When a large current flows instantaneously in the inverter circuit 14 and the fuse resistor 40 due to a disturbance or the like, the element of the resistance element of the fuse resistor 40 is blown, and the DC power supply to the inverter circuit 14 is prevented. The motor 12 is stopped. Therefore, it is possible to prevent smoke and ignition.

  In the case of the present embodiment, the fuse resistor 40 has two configurations of the role of a conventional fuse and a current detection resistor element. Space can be secured.

  A fuse resistor 40 is provided on the output side of the noise filter circuit 28, and it is possible to prevent a reduction in motor efficiency due to a voltage drop.

(Example of change)
In addition, this invention is not limited to said embodiment, It can implement in various changes in the range which does not deviate from a summary.

(1) Modification 1
The motor is not limited to a brushless DC motor, and may be another motor.

(2) Modification example 2
The drive device 10 may be used not only for electric tools but also for home appliances such as air conditioners.

(3) Modification 3
In this embodiment, the Hall IC 38 is provided to detect the position of the rotor. Instead of this, the position of the rotor is detected based on the drive current flowing from the inverter circuit 14 to the three-phase stator winding 36. A so-called sensorless driving device may be used.

(4) Modification 4
In the present embodiment, the battery 30 is used as the DC power supply. However, instead of this, an AC power supply may be used, the AC power supply may be smoothed by a rectifying and smoothing circuit, and the DC power supply may be supplied to the inverter circuit 14. . In this case, the fuse resistor 40 is provided on the output side of the rectifying / smoothing circuit, that is, between the inverter circuit 14 and the rectifying / smoothing circuit.

  The present invention is suitable as a driving device for motors such as electric tools and air conditioners.

It is a block diagram of the drive device of the motor which shows one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Drive apparatus 12 Motor 14 Inverter circuit 16 Logic circuit 18 PWM circuit 20 Control circuit 22 Rotor position detection circuit 24 Speed adjustment circuit 26 Overcurrent detection circuit 28 Noise filter circuit 30 Battery

Claims (4)

An inverter circuit that supplies drive current to the stator windings of each phase of the motor;
Control means for controlling the inverter circuit;
Power supply means for supplying DC power to the inverter circuit;
In a motor drive device having
A fuse resistor is connected to the wiring path from the power supply means to the inverter circuit,
Overcurrent detection means for outputting a stop signal to the control means when the current flowing through the fuse resistor exceeds a predetermined value;
When the stop signal is input, the control means stops or decelerates the rotation of the motor. The motor driving apparatus according to claim 1, wherein the motor is a brushless DC motor. The motor drive device according to claim 1, wherein the motor is a drive source of an electric tool. The motor driving apparatus according to claim 1, wherein the power supply means is a battery.

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