JP2008005683A - Drive unit for brushless dc motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive unit for a brushless DC motor capable of normally operating, even when a rotation speed changes. <P>SOLUTION: A selection circuit 20 selects a 120° conduction type, a 180° conduction type or a sine-wave conduction type based on a speed signal detected on the base of a position signal from a hall IC 30, to perform PWM control of the brushless DC motor 10 being a driving source of an automatic door based on the conduction type thus selected. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a drive device for controlling a brushless DC motor with an inverter circuit, and particularly to an automatic door.

  A brushless DC motor (hereinafter simply referred to as a motor) detects the rotational position of a rotor by using a position signal such as a Hall IC or an induced voltage, performs PWM control according to the detected rotational position, and performs stator winding. The drive current is controlled to flow through the line from the inverter circuit (see, for example, Patent Document 1).

  In the motor driving apparatus as described above, the drive current is output from the inverter circuit and driven for a certain energization time (energization width) according to the position signal output from the Hall IC or the like. In a conventional motor driving device, the motor is started, stopped, and rotated forward and backward by one type of driving method.

In particular, a motor used as a drive source for an automatic door employs a 120-degree energization method in order to start or stop an inertial load.
JP 2004-23823 A

  In the driving method in which the next energization pattern is estimated from the change period of the position signal of the Hall IC or the like as described above, the energization to be estimated for a sudden speed change such as starting the motor from the stop. An error may occur in the pattern and the normal operation may not be performed.

  In particular, there is a problem that an automatic door may have a rapid speed change, an error is likely to occur in the energization pattern, and the opening / closing control cannot be performed well with only one type of the 120-degree energization method.

  Therefore, in view of the above problems, the present invention provides a brushless DC motor driving device capable of performing normal operation even when the rotational speed changes.

  The invention according to claim 1 is a three-phase brushless DC motor, an inverter circuit that supplies a drive current to a stator winding of each phase of the brushless DC motor, and a speed detection that detects a rotational speed of the brushless DC motor. A drive circuit for controlling the inverter circuit based on the detected rotation speed and a speed command signal from the outside, wherein the control circuit is configured so that the detected rotation speed is A selection means for selecting a 120-degree energization method or a 180-degree energization method when earlier than one threshold, and a sine wave energization method when the detected rotational speed is slower than the first threshold; A brushless DC motor drive device comprising: control means for controlling the inverter circuit based on the selected energization method.

  In the invention according to claim 2, the selecting means selects a 180-degree energization method when the detected rotational speed is earlier than the first threshold value and slower than the second threshold value, and the detected rotational speed is 2. The brushless DC motor driving apparatus according to claim 1, wherein the 120-degree energization method is selected when it is earlier than the second threshold value.

  According to a third aspect of the present invention, the selecting means sets the first threshold value when the detected rotational speed is accelerating to the first threshold value when the detected rotational speed is decelerating. 2. The brushless DC motor driving device according to claim 1, wherein the driving device is a value higher than the value.

  According to a fourth aspect of the present invention, the selecting means sets the second threshold value when the detected rotational speed is accelerating to the second threshold value when the detected rotational speed is decelerating. 3. The brushless DC motor driving device according to claim 2, wherein the driving device is higher than the value.

  According to a fifth aspect of the present invention, the speed detection circuit includes a position detection element in the vicinity of the rotor of the brushless DC motor, and detects the rotation speed based on a position signal from the position detection element. 5. The brushless DC motor driving device according to claim 1, wherein the driving device is a brushless DC motor.

  The invention according to claim 6 is characterized in that the speed detection circuit detects an induced voltage of each stator winding and detects the rotational speed based on the detected induced voltage of each phase. 5. The brushless DC motor driving device according to at least one of Items 1 to 4.

  The invention according to claim 7 is the brushless DC motor drive device according to at least one of claims 1 to 4, wherein the brushless DC motor is a drive source of an automatic door.

  In the brushless DC motor driving device according to the first aspect, when the detected rotational speed is faster than the first threshold value, the 120-degree energization method or the 180-degree energization method is selected, and the detected rotational speed is When it is slower than the first threshold value, the sine wave energization method is selected. Therefore, even if there is a sudden change in the rotational speed, the energization method is in accordance with the rotational speed and the brushless DC motor operates normally.

  In the brushless DC motor drive device according to the second aspect of the present invention, when the detected rotational speed is higher than the first threshold value and lower than the second threshold value, the 180-degree energization method is selected, and the detected rotational speed is Since the 120-degree energization method is selected when it is earlier than the second threshold value, energization according to the rotation speed can be performed more.

  In the brushless DC motor drive device according to the third aspect, the first threshold value when the detected rotational speed is accelerating is set to a value higher than the first threshold value when decelerating. As a result, hunting in the vicinity of the threshold when switching the driving method can be eliminated.

  In the brushless DC motor drive device according to the fourth aspect of the invention, the second threshold value when the detected rotational speed is accelerating is set to a value higher than the second threshold value when decelerating. Thus, hunting near the threshold can be eliminated.

(First embodiment)
Hereinafter, a driving device 12 for a brushless DC motor (hereinafter simply referred to as a motor) 10 according to a first embodiment of the present invention will be described with reference to FIGS. 1 and 2. The motor 10 is a drive source for the automatic door.

(1) Configuration of Drive Device 12 The configuration of the drive device 12 will be described based on the block diagram of FIG.

  The drive device 12 includes an inverter circuit 14, a control circuit 16, a speed detection circuit 18, a selection circuit 20, a first drive circuit 22, a second drive circuit 24, and a third drive circuit 26.

  The inverter circuit 14 is a full bridge inverter circuit composed of six switching elements (for example, MOS-FETs) connected in parallel with a diode. A three-phase drive current is supplied from the inverter circuit 14 to the three-phase Y-connection stator winding 28 of the motor 10. The inverter circuit 14 is driven by a motor current supplied from a DC power source.

  Based on the energization method selected by the selection circuit 20, the control circuit 16 compares a speed command signal input from the outside with a detected speed signal, which will be described later, and the rotational speed of the motor 10 is compared with this speed command signal. The feedback control is performed so as to match, and the PWM control is performed so that the PWM signal is output to the gate terminal of each switching element of the inverter circuit 14 based on the difference signal subjected to the feedback control.

  The speed detection circuit 18 calculates the rotational speed of the motor 10 based on position signals from the three Hall ICs 30 provided to detect the rotational position of the rotor of the motor 10. Then, a speed signal indicating the calculated rotation speed is output to the control circuit 16 and the selection circuit 20.

  The selection circuit 20 selects one drive method from the three drive methods based on the speed signal input from the speed detection circuit 18 and outputs the selected drive method to the control circuit 16.

  There are three types of driving methods selected by the selection circuit 20; a 120-degree energization method, a 180-degree energization method, and a sine wave energization method. The circuit 24 outputs an energization drive signal based on the 180-degree energization method, and the third drive circuit 26 outputs a drive signal based on the sine wave energization method. Then, the drive signal of the selected energization method is output to the control circuit 16.

  FIG. 2 shows the drive current supplied to the three-phase Y-connected stator winding 28 in each energization method. The upper stage is a 120-degree energization system, the middle stage is a 180-degree energization system, and the lower stage is a sine wave. It is an energization method. In FIG. 2, the hatching with the lower left and the right rising indicates a state in which a current enters, and the left upper and lower right indicates a state in which a current is output.

  For example, in the diagram of the 120-degree energization method, the upper stage is the U phase, the middle stage is the V phase, and the lower stage is the W phase. The rightmost waveform shows a state in which drive current flows from the W-phase stator winding 28 to the V-phase stator winding 28.

  In the 180-degree energization method, the rightmost waveform of the W phase shows a state in which drive current enters from the W-phase stator winding 28 and drive current exits from the U-phase and V-phase stator windings 28. ing.

  The waveform on the right side in the sine wave energization method shows a state in which the drive current enters from the W-phase stator winding 28 and the drive current exits from the U-phase and V-phase stator windings 28.

  In this selection circuit 20, the first threshold value A1 and the second threshold value A2 are stored as a reference for selecting three kinds of energization methods. When the speed signal is slower than A1, the sine wave energization method is selected. When the speed signal is between A1 and A2, the 180 degree energization method is selected, and when the speed signal is faster than A2, the 120 degree energization method is selected. That is, the energization method changes in the order of the sine wave energization method, the 180-degree energization method, and the 120-degree energization method in accordance with the speed.

  The selection of the driving method will be described in view of the actual automatic door control method.

  In the automatic door, the door does not move when the door is closed and the door is open, but the motor 10 presses the door against the door frame in order to hold the door in the closed state and the open state. Therefore, the door 10 is loaded even though the rotational speed is zero. When the door is going to be opened from the closed state, the rotational speed of the motor 10 is gradually accelerated and the door is opened. On the contrary, even when the open state is changed to the closed state, the motor 10 is gradually accelerated, and then the speed is decreased to be in the closed state.

  As described above, the rotational speed of the motor 10 changes in many steps when the automatic door is opened and closed.

  Therefore, the first threshold value A1 is set when the speed signal is 0, that is, when the motor 10 is not rotating but the drive current is flowing. As the second threshold value A2, the speed in the middle of the door being accelerated is set.

  Then, when the door is in the closed state or the open state, the motor 10 stops by pressing the door against the door frame by a sine wave driving method. On the other hand, when the open signal or the close signal is input and the motor 10 starts to rotate, the motor 10 rotates by the 180-degree energization method, and when the second threshold A2 is exceeded, the 120-degree energization method is switched. When the door starts decelerating and becomes slower than the second threshold value A2, the 120-degree energization method changes to the 180-degree energization method.

  In this way, by using a three-stage energization method, an energization method according to the rotation speed can be selected, and energy can be used without being wasted and noise reduction can be achieved.

(Second Embodiment)
Next, the drive device 12 of the second embodiment will be described with reference to FIG.

  The difference between the present embodiment and the first embodiment is that an FV conversion circuit 32, a switching circuit 34, and a threshold setting circuit 36 are provided instead of the speed detection circuit 18.

  In the driving device 12 according to the first embodiment, when the door state changes near the first threshold value or near the second threshold value, that is, near the rotational speed at which the driving method is switched, the door moving speed is high. When it becomes slow or slow, the driving method in the selection circuit 20 is finely switched, which may cause hunting. Therefore, in the present embodiment, the first threshold value and the second threshold value when the rotation speed of the motor 10 is accelerating, and the first threshold value when the rotation speed is decelerating are second. The threshold is set to a different value to prevent this hunting.

  The position signals from the three Hall ICs 30 are converted into speed signals by the FV conversion circuit 32 and output to the switching circuit 34. The switching circuit 34 outputs a switching signal indicating which driving method is selected to the selection circuit 20. In this case, the switching circuit 34 determines the switching based on the threshold signal from the threshold setting circuit 36. For example, when a speed signal is input to the switching circuit 34 and the rotational speed indicated by the speed signal is accelerating, the switching circuit 34 outputs a change signal to the threshold value setting circuit 36, so Instruct to output 1 threshold. Based on this change signal, the threshold setting circuit outputs a threshold signal indicating the first threshold value during acceleration to the switching circuit 34. Then, the first threshold value at the time of acceleration and the speed signal are compared, and a switching signal is output based on the comparison. On the other hand, when the rotational speed is decelerated by the speed signal, the switching circuit 34 instructs the threshold setting circuit 36 to output the first threshold value during deceleration based on the change signal, and sets the threshold value. In the circuit 36, a threshold value signal circuit indicating the first threshold value during deceleration is shown in the switching circuit 34. Here, by making the value of the first threshold value during acceleration higher than the value of the first threshold value during deceleration, the fluctuation range can be absorbed by that amount and hunting can be prevented.

  That is, even when the speed signal changes near the first threshold value, the first threshold value at the time of acceleration and the first threshold value at the time of deceleration are different from each other. Stable switching can be performed without switching.

  Similarly, for the second threshold value, hunting can be prevented by making the second threshold value during acceleration higher than the second threshold value during deceleration.

(Example of change)
The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist thereof.

(1) Modification 1
In the above embodiment, the rotational speed is detected using a position detecting element such as a Hall IC. Instead, the induced voltage of the three-phase stator winding 28 is detected, and the detected induced voltage of each phase is detected. A so-called sensorless method may be used in which the rotational speed is detected based on the above.

(2) Modification example 2
In the above embodiment, the 120 degree energization method, the 180 degree energization method, and the sine wave energization method are selected, but instead of this, four types of 120 degree energization method, 150 degree energization method, 180 degree energization method, and sine wave energization method are selected. You may make it the structure which selects one type of electricity supply system from the inside.

  With such a configuration, more stable control can be performed.

  The brushless DC motor drive device of the present invention is suitable for a drive source of an automatic door.

It is a block diagram of the drive device which shows the 1st Embodiment of this invention. It is a graph of the induced voltage of a 120 degree energization system, a 180 degree energization system, and a sine wave energization system. It is a block diagram of the drive device of 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Motor 12 Drive apparatus 14 Inverter circuit 16 Control circuit 18 Speed detection circuit 20 Selection circuit 22 1st drive circuit 24 2nd drive circuit 26 3rd drive circuit 28 Stator winding 30 Hall IC

Claims (7)

A three-phase brushless DC motor;
An inverter circuit for supplying a drive current to the stator winding of each phase of the brushless DC motor;
A speed detection circuit for detecting the rotational speed of the brushless DC motor;
A drive circuit for controlling the inverter circuit based on the detected rotation speed and an external speed command signal;
In the drive device of the brushless DC motor having
The control circuit includes:
When the detected rotational speed is faster than the first threshold, a 120-degree energization method or a 180-degree energization method is selected, and when the detected rotational speed is slower than the first threshold, a sine wave energization method A selection means for selecting
Control means for controlling the inverter circuit based on the selected energization method;
A drive device for a brushless DC motor. The selection means includes
When the detected rotation speed is earlier than the first threshold and slower than the second threshold, the 180 degree energization method is selected, and when the detected rotation speed is faster than the second threshold, the 120 degree energization method is selected. The brushless DC motor driving device according to claim 1, wherein: The selection means includes
The first threshold value when the detected rotational speed is accelerating is higher than the first threshold value when the detected rotational speed is decelerating. 2. A brushless DC motor drive device according to 1. The selection means includes
The second threshold value when the detected rotational speed is accelerating is higher than the second threshold value when the detected rotational speed is decelerating. 3. A brushless DC motor drive device according to 2. The speed detection circuit includes:
A position detection element in the vicinity of the rotor of the brushless DC motor;
5. The brushless DC motor driving device according to claim 1, wherein the rotational speed is detected based on a position signal from the position detection element. 6. The speed detection circuit includes:
5. The brushless according to claim 1, wherein an induced voltage of each stator winding is detected, and the rotational speed is detected based on the detected induced voltage of each phase. 6. DC motor drive device. The brushless DC motor drive device according to at least one of claims 1 to 4, wherein the brushless DC motor is a drive source of an automatic door.

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