JP5384908B2 - Brushless motor starting method and control device - Google Patents

Description

  The present invention relates to a brushless motor starting method and a control device for starting a sensorless brushless motor.

  Conventionally, as a brushless motor, a sensor is not used to detect the magnetic pole position (rotor position) of the magnet rotor with respect to the stator. Instead, the voltage (induced voltage) induced in the stator coil when the magnet rotor rotates is used. A sensorless drive system that detects and generates a motor energization signal based on the detection signal, that is, performs “induced drive” is known. However, the voltage is induced in the stator coil only when the magnet rotor is rotating. When the brushless motor is stopped, the magnet rotor does not rotate and no induced voltage is generated in the coil. I can't get location information. For this reason, at the time of starting the brushless motor, for example, “forced driving” for forcibly rotating the magnet rotor is performed.

Here, the following Patent Document 1 describes a control method capable of properly starting a brushless motor without forcibly driving it and without rotating it in reverse. In this control method, when a three-phase four-pole brushless motor is started, two coils are energized for a predetermined time, and then one coil that is energized and two coils that are not energized are predetermined. Time energization is performed so that the rotor of the brushless motor is fixed at a predetermined position. That is, in this control method, energization switching is performed twice when the brushless motor is started.
Normally, when starting up a three-phase, four-pole brushless motor, when two coils are energized for a predetermined time, depending on the initial rotor position, there is a dead point where the force generated by the coil is balanced against the rotor. This is because the energization switching needs to be performed twice or more.
On the other hand, Patent Document 2 describes a method of performing a synchronous motor operation when starting and performing a sensorless brushless motor operation after starting. According to this method, three-phase energization is performed as the first excitation, and two-phase energization and three-phase energization are sequentially repeated.

JP-A-8-205579 Japanese Patent No. 3284201

However, the conventional method for starting a brushless motor has the following problems.
(1) In the method described in Patent Document 1, when energization for positioning is performed, if the inertia of the magnet rotor is small, depending on the initial position of the magnet rotor, it is rapidly accelerated and thus stopped. There is a problem that vibration is sometimes generated and it takes time to converge. In a product in the electrical industry where brushless motors are widely used, a delay in start-up time is not a big problem, but in the automobile industry, there is a problem that drivability deteriorates due to a short time delay.
Moreover, in the starting method of patent document 1, at the time of starting of a brushless motor, the rotor is moved to a specific position by energizing two coils, and the energized one coil and the energizing are not performed thereafter. Since energization is performed on the two coils of the coil, the start-up time tends to increase by the amount that requires two energizations.

(2) The starting method described in Patent Document 2 does not have the technical idea of moving the rotor to a specific position. However, three-phase energization is disclosed as the first excitation. Even if the three-phase energization described in Patent Document 2 is performed as a method of moving the rotor to a specific position, there are the following problems.
That is, when the three-phase energization is performed as the first excitation, the probability of occurrence of a dead point can be reduced compared to the case where the first excitation is performed by the two-phase energization.
When the first excitation is a two-phase energization, as shown in FIG. 10 as an initial state of a three-phase four-pole outer rotor brushless motor, the rotor rotates in the cases (A) to (D). In the case of (E) and (F), it becomes a dead point and the rotor cannot rotate.
When the first excitation is three-phase energization, as shown in FIG. 9 as an initial state of a three-phase four-pole outer rotor brushless motor, the rotor rotates in the cases (A) to (E). In the case of (F), it becomes a dead point and the rotor cannot rotate. Compared with the method in which the first excitation is performed with two-phase energization, the probability of occurrence of dead points is reduced, but the dead points are not completely eliminated, and at least two energizations are required. Had the same problem.

  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 starting method and a control device capable of reliably starting a brushless motor and shortening the starting time. It is in.

The brushless motor starting method and control device according to the present invention made to solve the above problems have the following configuration.
(1) A brushless motor activation method for activating a sensorless brushless motor including a stator having a three-phase coil and a magnet rotor provided corresponding to the stator, and when the brushless motor is activated, after the energization to the three-phase coils of the three phases of coils, the forced driving is performed to perform forcibly energized to the coil of the two-phase of the coil of the three-phase, of the 3-phase Of the energization to the coil, the two-phase energization is controlled with different duty by the PWM signal, and the duty is gradually increased.

(2) A brushless motor control device that activates a sensorless brushless motor including a stator having a three-phase coil and a magnet rotor provided corresponding to the stator, and when the brushless motor is activated, after the energization to the three-phase coils of the three phases of coils, the forced driving is performed to perform forcibly energized to the coil of the two-phase of the coil of the three-phase, of the 3-phase Of the energization to the coil, the two-phase energization is controlled with different duty by the PWM signal, and the duty is gradually increased.

  Next, the operation and effect of the brushless motor starting method and control device of the present invention having the above-described configuration will be described.

(1) According to the brushless motor activation method and control apparatus of the present invention, a brushless motor that activates a sensorless brushless motor including a stator having a three-phase coil and a magnet rotor provided corresponding to the stator. a starting method, upon activation of the brushless motor, after the energization to the three-phase coils of the three-phase coils, the forcibly energized to the coil of the two-phase of the three-phase coils Even when using a magnet rotor with a small inertia, the forced drive is performed and the two-phase energization is controlled with different duty by the PWM signal and the duty is gradually increased. Since a force is gradually applied to move the rotor to the positioning position, an excessive speed is applied to the magnet rotor. It is no, it is possible to reduce the vibration when stopping, it is possible to shorten the time to stop. In addition, among the three-phase energization, the two-phase energization is controlled with different duty by the PWM signal, so that a difference occurs in the magnetic force generated by the two-phase energization and the balance of the magnetic force is lost, so that the rotor is at the dead point position However, the rotor can be rotated, and the rotor can always be stopped at a predetermined position.
(2) Here, since the duty is gradually increased, even in the case of a rotor having a small inertia, the rotor can be rotated by giving a magnetic force little by little, so that the vibration of the rotor can be reduced. The time for stopping at a predetermined position can be shortened.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a most preferred embodiment embodying a brushless motor starting method and a control device of the present invention will be described in detail with reference to the drawings.
In this embodiment, a brushless motor activation method and a control device used for an engine cooling device water pump or a fuel pump will be described. FIG. 1 is an electric circuit diagram showing the configuration of a brushless motor 11 and its controller 10 used in a water pump or a fuel pump. The controller 10 includes a control circuit 12 and a drive circuit 13. In this embodiment, the brushless motor 11 is of a three-phase, four-pole sensorless type, and a three-phase drive system circuit is adopted as the drive circuit 13. The brushless motor 11 includes a stator 14 including three-phase (U-phase, V-phase, W-phase) coils 14A, 14B, and 14C, and a magnet rotor 15 that is a four-pole outer rotor. Since the brushless motor 11 is of a sensorless type, it is generated in the coils 14A to 14C of each phase of the stator 14 without using a Hall element in order to detect the magnetic pole position (rotor position) of the magnet rotor 15 with respect to the stator 14. An induced voltage is used. Then, when the magnet rotor 15 rotates, the rotor position is detected based on the induced voltage generated in the coils 14A to 14C of each phase, and the coil 14A of each phase to be energized based on the detected rotor position. “Induced drive” is performed to determine ˜14C.

As shown in FIG. 1, the drive circuit 13 includes PNP-type first, third, and fifth transistors Tr1, Tr3, Tr5 as switching elements, and NPN-type second, fourth, and sixth transistors. Each of Tr2, Tr4, and Tr6 is configured by a three-phase bridge connection. The emitters of the first, third, and fifth transistors Tr1, Tr3, Tr5 are each connected to a power supply (+ B), and the emitters of the second, fourth, and sixth transistors Tr2, Tr4, Tr6 are grounded. One terminal of the coils 14A to 14C of each phase of the brushless motor 11 is connected to a common connection point, the other terminals are common connection points of the first and second transistors Tr1 and Tr2, and the third and fourth transistors Tr3. , Tr4, and the common connection point of the fifth and sixth transistors Tr5, Tr6, respectively. The bases of the transistors Tr1 to Tr6 are connected to the control circuit 12. Both terminals of the control circuit 12 are connected to the power source (+ B) and grounded. In this embodiment, the control circuit 12 is configured by a custom IC.

  Since the brushless motor 11 of this embodiment is a sensorless type, no induced voltage is generated in the coils 14A to 14C of each phase when stopped. Therefore, in this embodiment, when the brushless motor 11 is started, the magnet rotor 15 is rotated by forcibly energizing the two-phase coils among the three-phase coils 14A to 14C in a predetermined energization sequence. “Forced drive” is performed. However, even if the rotor position is ignored at startup and the coils 14A to 14C of each phase are forcibly started to energize in a predetermined energization order, the magnet rotor 15 may or may not rotate. For this reason, the brushless motor 11 can be activated, cannot be activated, or it takes more time than necessary to complete the activation. Therefore, in this embodiment, when the brushless motor 11 is started, predetermined “startup control” is executed to energize the coils 14A to 14C of each phase, thereby moving the rotor of the brushless motor 11 to a fixed position. After that, “forced driving” is performed. After a predetermined induced voltage is generated by this “forced driving”, the above-described “induced driving” is switched.

  Here, the “induced drive” will be described in detail. FIG. 2 is a time chart showing each phase energization timing and each phase coil terminal voltage change executed by the control circuit 12 during induction driving. The control circuit 12 controls energization of the U-phase, V-phase, and W-phase coils 14A to 14C by controlling energization of the bases (gates) of the transistors Tr1 to Tr6 of the drive circuit 13. In FIG. 2, “UH, VH, and WH” indicate Hi-side gates that set the U phase, V phase, and W phase to high levels, and “UL, VL, and WL” indicate U phase, V phase, and W phase, respectively. A low-side gate that is at a low level is shown. As shown in FIG. 2, by controlling the energization of the Hi-side gate and the Low-side gate, the U-phase, V-phase, and W-phase coils 14A to 14C are energized, and a coil terminal voltage is generated in each phase. I understand.

  FIG. 3 is a time chart showing changes in the terminal voltages of the coils 14A to 14C in each phase of the U phase, the V phase, and the W phase. As can be seen from this chart, the coils 14A to 14C of the respective phases alternately receive “120 ° energization” and “60 ° non-energization”. In FIG. 3, when switching to non-energization at time t1, a positive counter electromotive force is first generated as a pulsed voltage, and then the induced voltage increases. Next, a transition is made by a positive constant voltage from when switching to energization at time t2 to when switching to non-energization at time t3. And when it switches to a non-energization at the time t3, a negative back electromotive force will arise as a pulse-like voltage, and an induced voltage will reduce after that. And when it switches to electricity supply at the time t4, it changes with a negative constant voltage. The control circuit 12 detects the rotor position using an induced voltage generated after the back electromotive voltage. The control circuit 12 controls energization of the coils 14A to 14C of the U-phase, V-phase, and W-phase based on the rotor position detected as described above. In other words, the control circuit 12 rotates the magnet rotor 15 by sequentially switching energization to the coils 14A to 14C of each phase, and detects the rotor position based on the induced voltage generated in the coils 14A to 14C of each phase. And the control circuit 12 controls electricity supply with respect to the coils 14A-14C of each phase based on the detected rotor position. In this way, “induced drive” is performed.

4, the stop position of the magnet rotor 15 with respect to the scan tape over data 14 (initial position), per be convenient to start the brushless motor 11, and a change in current phase, the magnetic pole position of the magnet rotor 15 relative to stator 14 (rotor (Position) change is shown by a conceptual diagram.
In FIG. 5, when the stop position (initial position) of the magnet rotor 15 with respect to the stator 14 is inconvenient for starting the brushless motor 11, the change of the energized phase and the magnetic pole position (rotor position) of the magnet rotor 15 with respect to the stator 14 are shown. The change is shown by a conceptual diagram.
FIG. 9 is a conceptual diagram showing all possible patterns for the initial position of the magnet rotor 15. As shown in FIGS. 9A to 9F, there are six initial positions “pattern 1” to “pattern 6”.

When the initial positions are (A) to (E) in FIG. 9, as shown in FIG. 4 (A), energization is performed so that the W phase and the V phase are N poles, and the U phase is the S poles. The magnet rotor 15 can be rotated to the position (A) of FIG. 4 and positioned at the position (A) of FIG. 4 and 5, the W phase and the V phase that are N poles are represented by dark shading, and the U phase that is an S pole is represented by thin shading.
In this embodiment, the three-phase energization for positioning is energized for 32 milliseconds. Since the energization time in each switching at the time of induction driving is on the order of 0.1 msec, energization is performed for a considerably longer time than that. Thus, by energizing for a long time, in the case of (A) to (E) in FIG. 9 , the positioning is all performed at the position of (A) in FIG. 4 after 32 milliseconds.
Next, as shown in FIG. 4B, two-phase energization for forced driving is performed. Energization is performed so that the W phase becomes the N pole, and energization is performed so that the U phase becomes the S pole. The two-phase energization for forced driving is energized for 16 msec in this embodiment. As a result, the magnet rotor 15 positioned at the position (A) in FIG. 4 rotates 15 degrees in the forward rotation direction (counterclockwise direction) to the position shown in (B). As a result, an induced voltage is generated, and normal induction driving is switched from (C). By switching the energization phase in a predetermined energization sequence of “W → V”, “U → V”, “U → W”, “V → W”, “V → U”, “W → U”, a brushless motor 11 is inductively driven.

On the other hand, when the brushless motor 11 is in a stopped state, when the magnet rotor 15 is at an initial position as shown in FIG. 9F with respect to the stator 14, as shown in FIG. In addition, even if energization is performed so that the W phase and the V phase are N poles and the U phase is the S pole, the N poles of the magnet rotor 15 and the W phase constituting the N pole on the stator side At the boundary of the V phase, the S pole of the magnet rotor 15 faces the U phase constituting the S pole on the stator side, so that the repulsive forces are balanced and the magnet rotor 15 does not rotate. Therefore, it remains at the position shown in FIG. 5A, which is different from the regular positioning position shown in FIG.
Next, as shown in FIG. 5B, two-phase energization for forced driving is performed. Energization is performed so that the W phase becomes the N pole, and energization is performed so that the U phase becomes the S pole. The two-phase energization for forced driving is energized for 16 msec in this embodiment.
However, the magnet rotor 15 positioned at the position (A) in FIG. 5 rotates in the reverse direction (clockwise direction) when the forced drive is energized. As a result, a normal induced voltage is not generated and switching to normal induced driving cannot be performed. That is, even if 32 msec + 16 msec is spent, it is impossible to switch to induction driving.
In addition, when the inertia of the magnet rotor 15 is small when the positioning drive is performed, the magnet rotor 15 continues to vibrate indefinitely at the stop position, so that it cannot be quickly changed to the induction drive, which is a problem.

In this embodiment, in order to solve the above problem, in the three-phase energization for positioning the magnet rotor 15, the energization duty for setting the V phase to the N pole and the energization for setting the W phase to the N pole The duty is a different value. Further, in the three-phase energization for positioning, control is performed so that the energization duty for setting the V phase to the N pole and the energization duty for setting the W phase to the N pole are gradually increased. These will be described below.
FIG. 8 shows an energization pattern. The horizontal axis indicates the time course, and the vertical axis indicates the coil that is energized. The length of the horizontal axis does not represent the exact time.
T1 is an activation control pattern for positioning. Of T2, only the first T2 is a drive control pattern. Subsequent T3 to T7 and the return to T2 to T7 are induced drive patterns. In this embodiment, the activation control pattern T1 is 32 milliseconds, the drive control pattern T2 (only the first) is 16 milliseconds, and the induction driving T2 to T7 are each in the order of 0.1 milliseconds.

FIG. 6 shows an enlarged view of the T1 pattern (an enlarged view of a portion A in FIG. 8). In the energization to the V phase, the duty is increased in six steps from B1 to B6 by PWM control. Further, in the energization to the W phase, the duty is increased in six stages from C1 to C6 by PWM control. Here, C1 = B1, C2 = B2,... C6 = B6.
In FIG. 8, some of the control patterns from T2 to T7 are also subjected to PWM control. However, these PWM controls always have a constant duty and are not gradually increased.
By giving a positioning control pattern as shown in FIG. 6, even when using a magnet rotor with a small inertia, a force is gradually applied to move the brushless motor to the positioning position. It can be reduced and the time to stop can be shortened. That is, by gradually increasing the duty, the occurrence of vibration of the magnet rotor 15 can be reduced, and the time until stopping at a predetermined position can be shortened. The feature of this embodiment, only the positioning control patterns T1 at startup is to have gradual change torque to be applied to the magnet rotor 15.

FIG. 7 shows a positioning control pattern T1 of another embodiment. In the energization to the V phase, the duty is increased in six steps from B1 to B6 by PWM control. Further, in the energization to the W phase, the duty is increased in six stages from C1 to C6 by PWM control. Here, the duty of C1 is larger than the duty of B1, and the duty of C2 is larger than the duty of B2. The same applies to C5 below. C6 and B6 are both the maximum duty and the same size.
By giving a positioning control pattern as shown in FIG. 7, a difference occurs in the magnetic force generated by the two-phase energization and the balance of the magnetic force is lost. Therefore, even when the rotor is at the dead point position, the rotor can be rotated. The rotor can always be stopped at a predetermined position.

As described above in detail, according to the brushless motor starting method and the control device of the present embodiment, the stator 14 having a three-phase coil and the four-pole magnet rotor 15 provided corresponding to the stator 14 are provided. A three-phase four-pole brushless motor activation method or control device for activating a sensorless brushless motor 11 provided, and energizing a three-phase coil among the three-phase coils when the brushless motor 11 is activated, Of the three-phase energization, the two-phase energization is controlled by the duty that gradually increases by the PWM signal, so even when using a magnet rotor with a small inertia, force is gradually applied to move the magnet rotor to the positioning position. As a result, excessive speed is not applied to the magnet rotor, and vibration when stopped is reduced. It is possible to shorten the time to.
Further, according to the brushless motor starting method and the control device of the present embodiment, the sensorless brushless motor 11 including the stator 14 having three-phase coils and the four-pole magnet rotor 15 provided corresponding to the stator 14 is provided. A three-phase four-pole brushless motor activation method or control device to be activated, wherein when the brushless motor 11 is activated, the three-phase coil is energized and the three-phase coil is energized. Since the energization is controlled with different duty by the PWM signal, a difference occurs in the magnetic force generated by the two-phase energization, and the balance of the magnetic force is lost. Therefore, even when the rotor is at the dead point position, the rotor can be rotated, The rotor can always be stopped at a predetermined position.

The present invention can be applied to various applications in addition to the above embodiments.
For example, in the present embodiment, the outer rotor type has been described, but the same applies to the inner rotor type.
In this embodiment, the three-phase four-pole type has been described, but the same applies even when a multi-pole magnet rotor is used.

1 is an electric circuit diagram showing a configuration of a brushless motor 11 and a controller 10 according to an embodiment of the present invention. It is a time chart which shows each phase energization timing and each phase coil terminal voltage change which are performed by the control circuit 12 at the time of induction drive. It is a time chart which shows the change of the terminal voltage of the coils 14A-14C of each phase of U phase, V phase, and W phase. Stop position of the magnet rotor 15 with respect to the scan tape over data 14 (initial position), the change in per be convenient to start the brushless motor 11, and a change in current phase, the magnetic pole position of the magnet rotor 15 relative to stator 14 (rotor position) FIG. A concept indicating a change in energized phase and a change in the magnetic pole position (rotor position) of the magnet rotor 15 relative to the stator 14 when the stop position (initial position) of the magnet rotor 15 with respect to the stator 14 is inconvenient for starting the brushless motor 11. FIG. FIG. 9 is an enlarged view of the positioning control pattern T1 (an enlarged view of a portion A in FIG. 8). It is the positioning control pattern T1 of another Example. It is a figure which shows the electricity supply pattern to the stator. 4 is a conceptual diagram showing all possible patterns for the initial position of the magnet rotor 15. FIG. It is a conceptual diagram which shows the initial state of a 3 phase 4 pole outer rotor type brushless motor.

Explanation of symbols

11 Brushless motor 12 Control circuit 13 Drive circuit 14 Stator 15 Magnet rotor T1 Positioning control pattern

Claims (2)

A brushless motor starting method for starting a sensorless brushless motor including a stator having a three-phase coil and a magnet rotor provided corresponding to the stator,
Wherein upon activation of the brushless motor, after the energization to the three-phase coils among the coils of the three phases, the forced driving of performing forcibly energized to the coil of the two-phase of the coil of the 3-phase Is done,
2. A brushless motor starting method comprising: controlling energization of two phases among energizations of the three-phase coils with different duties according to a PWM signal, and gradually increasing the duty. A brushless motor control device for starting a sensorless brushless motor including a stator having a three-phase coil and a magnet rotor provided corresponding to the stator,
Wherein upon activation of the brushless motor, after the energization to the three-phase coils among the coils of the three phases, the forced driving of performing forcibly energized to the coil of the two-phase of the coil of the 3-phase Is done,
A brushless motor control device, wherein, among energizations to the three-phase coils, two-phase energizations are controlled with different duties according to PWM signals, and the duty is gradually increased.

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