JP4269921B2 - Brushless motor drive device - Google Patents

Description

  The present invention relates to a drive device that drives a brushless motor.

Conventionally, a brushless motor having a rotor having a permanent magnet and a stator winding composed of a three-phase winding has been used in various devices, but this kind of brushless motor is opened by the rotation of the rotor. Some have position detection means for detecting the rotational position of the rotor by comparing the induced voltage (terminal voltage) generated in the stator winding of the phase (phase not energized) with the reference voltage (Patent Document 1). reference). Also, as a starting method for starting the brushless motor, when the rotor is stopped, a plurality of energization patterns with different combinations of stator windings that are energized at the same time are used regardless of the detection result of the position detecting means. The rotor is started by performing a synchronous operation that sequentially switches while gradually increasing the switching frequency (referred to as “commutation frequency”). When the commutation frequency reaches a predetermined frequency, the above-described detection is performed based on the detection result of the position detection means. There is a method of switching to brushless operation that sequentially switches a plurality of energization patterns (see Patent Document 1 and Patent Document 2). For example, in the drive device described in Patent Document 2, the applied voltage is once decreased to lower the rotational speed of the rotor so that the phase difference between the commutation timing and the rotor position during the synchronous operation is the same as that during the brushless operation. After matching the phase difference, the operation is shifted from synchronous operation to brushless operation. Also, during brushless operation, the drive device commutates at an optimal timing according to the position of the rotor, so the generated torque and acceleration can be increased, and the command speed and rotor speed given from the outside can be increased. The voltage applied to the stator winding is adjusted so as to match.
Japanese Patent Laid-Open No. 7-308092 JP 2001-178184 A

  However, in the conventional apparatus described in Patent Document 2, since the process of decreasing the applied voltage is shifted to the synchronous operation from the brushless operation, the brushless motor is started in a short time to shift from the synchronous operation to the brushless operation. It was difficult to make. In particular, as the command speed given at the time of start-up increases, the time for the synchronous operation becomes longer, and as a result, the time until the command speed is reached from the stop state must be increased.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a brushless motor driving device capable of shortening the time required to reach a command speed from a stopped state.

In order to achieve the above object, a first aspect of the present invention provides a driving apparatus for driving a brushless motor having a rotor having a permanent magnet and a stator winding composed of a three-phase winding. The position detection means that detects the rotational position of the rotor by comparing the terminal voltage of the wire with the reference voltage, and the energization state of each phase of the stator winding by switching the DC voltage supplied from the external power supply A plurality of energization patterns with different combinations of energization switching means for switching and energization switching means by controlling the energization switching means are sequentially switched and the energization amount per unit time is changed to the stator winding. And a control means for adjusting the applied voltage, the control means for synchronous operation control for sequentially switching the plurality of energization patterns irrespective of the detection result of the position detection means, and for detection of the position detection means. Based on the results, the plurality of energization patterns are sequentially switched. When the rotor is in a stopped state, brushless operation control is performed to adjust the applied voltage so that the rotational speed of the rotor matches the command speed given from the outside. In the driving device that starts the rotor by performing the synchronous operation control while gradually increasing the switching frequency of the plurality of energization patterns, and shifts to the brushless operation control after the switching frequency reaches a predetermined frequency, the control means includes: The switching frequency and the applied voltage in the synchronous operation control are changed according to the command speed, and the switching frequency and the applied voltage in the synchronous operation control are changed so as to have a positive correlation with the command speed .

According to the present invention, since the time for the synchronous operation can be shortened by changing the switching frequency and the applied voltage in the synchronous operation control according to the command speed, the time until the command speed is reached from the stop state can be shortened. . Moreover, the step-out during the synchronous operation can be prevented by increasing the switching frequency and the applied voltage in the synchronous operation control as the command speed increases.

The invention of claim 2 is characterized in that, in the invention of claim 1 , the control means changes the switching frequency and the increase rate of the applied voltage in the synchronous operation control so as to have a positive correlation with the command speed. .

  According to this invention, the step-out during the synchronous operation can be prevented by increasing the switching frequency and the increase rate of the applied voltage in the synchronous operation control as the command speed increases. Further, since the switching frequency and the initial value of the applied voltage when starting the rotor in a stopped state can be reduced, it is possible to prevent an overcurrent from flowing through the energization switching means.

According to a third aspect of the present invention, in the first or second aspect of the invention, the control means changes the predetermined frequency when shifting from the synchronous operation to the brushless operation so as to have a positive correlation with the command speed. Features.

  According to the present invention, as the command speed increases, the predetermined frequency at the time of shifting from the synchronous operation to the brushless operation increases. Therefore, the position detection of the first rotor after the completion of the synchronous operation can be reliably performed, and the brushless Even when the generated torque temporarily decreases during the transition to operation, it is possible to reduce the time required to generate the torque necessary for acceleration without stopping and reach the command speed.

According to a fourth aspect of the present invention, in any one of the first to third aspects, the control means changes the ratio of the applied voltage to the switching frequency in the synchronous operation control so as to have a positive correlation with the command speed. It is characterized by.

  According to the present invention, as the command speed increases, the torque required for acceleration also increases. Therefore, the ratio of the applied voltage to the switching frequency is increased as the command speed increases. Current can be prevented from running out of torque, and as a result, occurrence of step-out can be suppressed.

According to a fifth aspect of the present invention, in any one of the first to fourth aspects of the present invention, the control means sets the switching frequency for a predetermined time after the predetermined frequency is reached and before the transition from the synchronous operation control to the brushless operation control. And synchronous operation control is performed with the applied voltage fixed at a predetermined value.

  According to the present invention, it is possible to reliably shift to the brushless operation without being affected by the acceleration state during the synchronous operation.

According to the present invention, the time for the synchronous operation can be shortened by changing the switching frequency and the applied voltage in the synchronous operation control according to the command speed, so the time until the command speed is reached from the stop state can be shortened. There is an effect. Further, there is an effect that step-out during synchronous operation can be prevented by increasing the switching frequency and applied voltage in the synchronous operation control as the command speed increases.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the drive device according to the present invention is suitable for various electric devices (for example, electric tools) using a brushless motor as a power source.

  As shown in FIG. 1A, the brushless motor M has a rotor 50 having a permanent magnet and a stator winding 51 composed of a three-phase winding, and a U-phase, V-phase, and W-phase stator. The winding 51 is star-connected and connected to the inverter circuit 1 of the driving device A. The inverter circuit 1 has a series circuit in which two switching elements 2a and 2d, 2b and 2e, 2c and 2f, each having a diode connected in antiparallel, are connected in parallel to both ends of a DC power supply E. And a drive unit 3 for switching the six switching elements 2a to 2f, and the middle point of each series circuit in the switching element group (two switching elements 2a, 2b,. The three stator windings 51 of the brushless motor M are connected to the connection point). That is, commutation is performed by the drive unit 3 individually switching the six switching elements 2 a to 2 f based on a command given from the control unit 4. Further, the position detection unit 5 compares the voltages between the terminals of the U phase and the V phase, the V phase and the W phase, and the W phase and the U phase in the stator winding 51 with the reference voltage, thereby generating a zero cross of the induced voltage (rotor 50 position) is detected and a position detection signal is output to the control unit 4.

  The control unit 4 has a configuration shown in FIG. The speed setting circuit 41 obtains a command speed corresponding to the operation amount of the operation unit B (for example, the resistance value of the variable resistor) and outputs it to the speed control circuit 42. The speed detection circuit 43 calculates the rotation speed of the rotor 50 based on the time interval at which the position detection signal is output from the position detection unit 5 and outputs it to the speed control circuit 42. The speed control circuit 42 is a stator that is determined according to the difference between the rotation speed and the command speed so that the rotation speed of the rotor 50 input from the speed detection circuit 43 matches the command speed input from the speed setting circuit 41. The command value of the voltage applied to the winding 51 is calculated and output to the brushless energization pattern circuit 44. The brushless energization pattern circuit 44 has a condition necessary for applying an applied voltage determined by a command value input from the speed control circuit 42 to the stator winding 51 for each energization pattern of the stator winding 51, that is, a drive A switching circuit that obtains an on-duty ratio of a drive pulse that is output for switching each switching element in the unit 3 and that sends a command value of an energization pattern including the on-duty ratio after a predetermined electrical angle from the input time of the position detection signal. Output to 45.

  The command speed is also output to the synchronous control circuit 46. When the synchronous control circuit 46 confirms that the command speed has changed from zero, it outputs a control signal S for switching to synchronous operation to the switching circuit 45. The switching frequency (commutation frequency) f for switching the energization pattern is output to the synchronous energization pattern circuit 47 while gradually increasing from the initial value to the predetermined value. When the commutation frequency f reaches the predetermined value, the operation is switched from the synchronous operation to the brushless operation. A control signal S instructing the shift to is output to the switching circuit 45. The synchronous energization pattern circuit 47 obtains an on-duty ratio of a drive pulse necessary for obtaining an applied voltage corresponding to a speed command value for each energization pattern of the stator winding 51 and energization including the on-duty ratio. The pattern command value is output to the switching circuit 45 at a timing determined by the commutation frequency f. The switching circuit 45 outputs the command value input from the synchronous energization pattern circuit 47 to the drive unit 3 of the inverter circuit 1 while being switched to the synchronous operation by the control signal S, and is switched to the brushless operation by the control signal S. During this period, the command value input from the brushless energization pattern circuit 44 is output to the drive unit 3 of the inverter circuit 1. The drive unit 3 switches the energization pattern based on the command value input from the control unit 4 and changes the on-duty ratio of the drive pulse to adjust the applied voltage to the stator winding 51, so-called PWM ( (Pulse width modulation) control is performed.

  Next, with reference to the timing charts of FIGS. 2 and 3, the operation at the time of starting the brushless motor will be described in more detail.

  First, suppose that the command speed ωs output from the speed setting circuit 41 is changed from zero to ωa (> 0) by operating the operation unit B when the brushless motor M is stopped (see FIG. 2A). ), The synchronization control circuit 46 confirms the start-up when the command speed ωs changes from zero to ωa as described above, and refers to the preset data table to apply the applied voltage v, the commutation frequency f, and The elapsed time t of the synchronous operation is set to initial values v0 (> 0), f0 (> 0), and t0 corresponding to the magnitude of the command speed ωs (= ωa) (see FIGS. 2B and 2C). ), An L level control signal S is output to the switching circuit 45 to switch to synchronous operation (see FIG. 2D). Further, as shown in FIGS. 2B and 2C, the synchronous control circuit 46 reads the synchronous maximum applied voltage va, the synchronous maximum frequency fa, and the synchronous operation time ta corresponding to the set value ωa of the command speed ωs from the data table. The applied voltage v and the commutation frequency f are substantially constant so as to reach the synchronous maximum applied voltage va and the synchronous maximum frequency fa, respectively, until the elapsed time t reaches the synchronous operation time ta. Increase at an increase rate.

  When the elapsed time t reaches the synchronous operation time ta, the synchronous control circuit 46 outputs an H level control signal S to the switching circuit 45 to shift from synchronous operation to brushless operation (see FIG. 2D). ). At this time, since the speed detected by the speed detection circuit 43 does not reach the set value ωa of the command speed ωs at the time of transition to the brushless operation, the detected speed matches the set value ωa by the speed control of the speed control circuit 42. When the detected voltage and the set value ωa coincide (t = t1), the applied voltage v increases until the command speed ωs is changed or the detected speed changes. It is kept almost constant.

  On the other hand, when the command speed ωs at the start of the brushless motor M is set to a larger value ωb (> ωa), the synchronous control circuit 46 instructs the command from the data table as shown in FIGS. The synchronous maximum applied voltage vb (> va), the synchronous maximum frequency fb (> fa), and the synchronous operation time tb (<ta) corresponding to the set value ωb of the speed ωs are read, and the applied voltage v and the commutation frequency f are elapsed time. The applied voltage v and the commutation frequency f are increased at a substantially constant rate so that the maximum synchronous applied voltage vb and the maximum synchronous frequency fb are reached before t reaches the synchronous operation time tb. When the elapsed time t reaches the synchronous operation time tb, the synchronous control circuit 46 outputs an H level control signal S to the switching circuit 45 to shift from the synchronous operation to the brushless operation. When the detected voltage and the set value ωb are increased by speed control to increase the applied voltage v to accelerate, and the detected speed and the set value ωb match (t = t2), is the command speed ωs changed thereafter? Alternatively, the applied voltage v is kept substantially constant until the detection speed changes.

  When the command speed ωs is changed during the synchronous operation, for example, when the set value of the command speed ωs is changed from ωa to ωb at the elapsed time t = t3 as shown in FIG. As described above, the synchronous maximum applied voltage vb, the synchronous maximum frequency fb, and the synchronous operation time tb corresponding to the set value ωb of the command speed ωs are read from the data table, and the applied voltage v and the commutation frequency f are determined by the elapsed time t. From t = t3 to t = tb, the applied voltage v and the commutation frequency f are increased at a substantially constant rate so that the synchronous maximum applied voltage vb and the synchronous maximum frequency fb are reached, respectively, and the elapsed time t is synchronized. When the operation time tb is reached, the operation is shifted from the synchronous operation to the brushless operation.

  As described above, in this embodiment, the synchronous control circuit 46 changes the rate of increase of the commutation frequency f and the applied voltage v in the synchronous operation control so as to have a positive correlation with the command speed ωs according to the increase / decrease of the command speed ωs. Therefore, it is possible to shift from synchronous operation to brushless operation in a short time while preventing step-out due to insufficient applied voltage during synchronous operation and suppressing vibration and overcurrent of the brushless motor M due to excessive applied voltage. Since the acceleration can be increased by the speed control of the speed control circuit 42 after the transition to the brushless operation, the time until the command speed ωs is reached from the stop state can be shortened. Even if the commutation frequency f and the initial values f0 and v0 of the applied voltage v are changed according to the increase / decrease in the command speed ωs, the time from the stop state until the command speed ωs is reached can be shortened. However, if the increase rate is to be changed, the initial value f0 of the commutation frequency f and the initial value v0 of the applied voltage v when starting the rotor 50 in a stopped state can be reduced. There is an advantage that it can be prevented from flowing.

  In this embodiment, the maximum synchronous frequency when shifting from synchronous operation to brushless operation is changed so as to have a positive correlation with the command speed ωs, and the operation shifts from synchronous operation to brushless operation as the command speed ωs increases. Since the maximum synchronous frequency is increased, the position of the first rotor 50 after the synchronous operation can be reliably detected, and even when the generated torque temporarily decreases during the transition to the brushless operation. The time required to generate the torque necessary for acceleration without stopping and to reach the command speed ωs can be shortened.

  2 to 4, the ratio of the applied voltage v to the commutation frequency f in the synchronous operation control is constant regardless of the command speed ωs, but the command speed ωs is set to the set value ωb as shown in FIG. The set value of the applied voltage v is set to vc (> vb), and the ratio of the applied voltage v to the commutation frequency f (vc / fb) is changed so as to have a positive correlation with the command speed ωs. It doesn't matter. That is, as the command speed ωs increases, the torque required for acceleration also increases. At this time, if the ratio of the applied voltage v to the commutation frequency f is constant, the stator increases as the commutation frequency f increases. The impedance increases due to the inductance component of the winding 51, and the current does not increase even when the applied voltage v is increased. Therefore, the current flowing through the stator winding 51 does not increase, and therefore the torque does not increase and the step-out occurs. There is a risk of it. Therefore, if the ratio of the applied voltage v to the commutation frequency f is changed so as to have a positive correlation with the command speed ωs, a sufficient current is passed through the stator winding 51 to prevent a torque shortage. As a result, the occurrence of step-out can be suppressed.

  By the way, if the commutation frequency f, the applied voltage v, and the synchronous operation time ta and tb during the synchronous operation are changed according to the command speed ωs as described above, the acceleration state during the synchronous operation changes, and the transition to the brushless operation is performed. May be affected. Therefore, as shown in FIG. 6, after the commutation frequency f reaches the synchronous maximum frequency fb and before the transition from the synchronous operation to the brushless operation, the commutation frequency f and the application are applied until a predetermined time ts elapses from the synchronous operation time tb. If the voltage v is fixed to the synchronous maximum frequency fb and the synchronous maximum applied voltage vb, and the synchronous operation is performed and then the brushless operation is performed, the brushless operation can be reliably performed without being influenced by the acceleration state during the synchronous operation. Is desirable.

Embodiment is shown, (a) is a whole schematic block diagram, (b) is a block diagram of a control part. It is a timing chart for operation | movement description same as the above. It is a timing chart for operation | movement description same as the above. It is a timing chart for operation | movement description same as the above. It is a timing chart for operation | movement description same as the above. It is a timing chart for operation | movement description same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inverter circuit 4 Control part 41 Speed setting circuit 45 Switching circuit 46 Synchronization control circuit

Claims (5)

In a driving device for driving a brushless motor having a rotor having a permanent magnet and a stator winding composed of a three-phase winding, the terminal voltage of the stator winding of the open phase is compared with a reference voltage to thereby compare the rotor Position detection means for detecting the rotational position, energization switching means for switching the energization state of each phase of the stator winding by switching a DC voltage supplied from an external power source, and controlling the energization switching means at the same time A control means for sequentially switching a plurality of energization patterns with different combinations of stator windings to be energized and changing an energization amount per unit time to adjust a voltage applied to the stator winding; , Synchronous operation control for sequentially switching the plurality of energization patterns regardless of the detection result of the position detection means, and the plurality of energization patterns sequentially based on the detection result of the position detection means The brushless operation control is performed to adjust the applied voltage so that the rotation speed of the switching rotor matches the command speed given from the outside. When the rotor is in a stopped state, the switching frequency of a plurality of energization patterns is gradually increased. In the drive device that starts the rotor by performing synchronous operation control while increasing the frequency to shift to brushless operation control after the switching frequency reaches a predetermined frequency, the control means switches in synchronous operation control according to the command speed. A brushless motor drive device characterized by changing the frequency and applied voltage, and changing the switching frequency and applied voltage in the synchronous operation control so as to have a positive correlation with the command speed . 2. The brushless motor driving apparatus according to claim 1, wherein the control means changes the switching frequency and the increase rate of the applied voltage in the synchronous operation control so as to have a positive correlation with the command speed. 3. The brushless motor driving apparatus according to claim 1 , wherein the control unit changes the predetermined frequency when shifting from the synchronous operation to the brushless operation so as to have a positive correlation with the command speed. 4. The brushless motor driving apparatus according to claim 1, wherein the control means changes the ratio of the applied voltage to the switching frequency in the synchronous operation control so as to have a positive correlation with the command speed. The control means performs the synchronous operation control by fixing the switching frequency to the predetermined frequency and fixing the applied voltage to the predetermined value for a predetermined time before the transition from the synchronous operation control to the brushless operation control after reaching the predetermined frequency. The brushless motor drive device according to any one of claims 1 to 4 .

Images