JP2015027120A - Control device for brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress processing other than processing of sensorless control from being stagnant while suppressing a processing capability of a control device (a processor), in a control device for a brushless motor switching a phase applied with a pulse voltage depending on a pulse width modulation signal depending on position information based on a pulse induction voltage induced to a non-energization phase to perform sensorless control for driving the brushless motor.SOLUTION: Processing of sensorless control including processing of receiving an A/D conversion data, processing of setting a voltage threshold, processing of comparing the A/D conversion data with the threshold and processing of deciding a PWM output pattern is executed at the rate of every N times (e.g., twice) of PWM output cycles. In a PWM output cycle in which the sensorless control is halted, processing other than the sensorless control, such as failure diagnosis processing, fail-safe processing based on the failure diagnosis result, communication processing with the other unit, is progressed to suppress the processing other than the sensorless control from being stagnant.

Description

  The present invention relates to a control device that controls a brushless motor sensorlessly by rectangular wave driving.

  In Patent Document 1, in a three-phase synchronous motor, an induced voltage (pulse induced voltage) of a non-energized phase induced by application of a pulse voltage in rectangular wave driving is detected, and the induced voltage is compared with a reference voltage. A sensorless drive system for a synchronous motor that sequentially switches energization modes according to the result of the comparison is disclosed.

JP 2009-189176 A

In sensorless control that detects the switching timing of the energization mode based on the pulse induced voltage of the non-energized phase, it is necessary to detect the voltage of the non-energized phase during the period in which the pulse voltage is applied (in other words, while the PWM is on). is there.
However, in the control device (processor) of the brushless motor, if the sensorless control processing based on the voltage of the non-energized phase is performed every PWM output cycle, the processing load of the sensorless control is large and other processing is delayed. there were.

Note that sensorless control processing includes, for example, voltage data (AD conversion output) reception processing, motor position estimation calculation, PWM output pattern calculation, and the like, and other processing includes, for example, diagnostic control, fail This includes safe processing and communication processing with other units.
Here, if the processing capability of the control device (processor) is increased, processing stagnation can be suppressed, but the cost of the control device increases.

  The present invention has been made in view of the above problems, and provides a brushless motor control device capable of suppressing processing other than sensorless control processing while suppressing processing capacity of the control device (processor). Objective.

  Therefore, in the present invention, the execution frequency of the sensorless control process at the process timing synchronized with the output period of the pulse width modulation is changed.

  According to the above invention, by having the function of changing the execution frequency of the sensorless control process, it is possible to set the processing timing for pausing (thinning out) the sensorless control process. When the sensorless control process is paused In addition, processes other than the sensorless control process can be performed.

It is a block diagram which shows the structure of the hydraulic pump system in embodiment. It is a circuit diagram which shows the structure of the motor control apparatus and brushless motor in embodiment. It is a functional block diagram of a control unit in an embodiment. It is a time chart which shows the electricity supply pattern in embodiment. It is a time chart which shows A / D conversion and processing timing in an embodiment. It is a time chart for demonstrating a problem at the time of implementing low speed sensorless control each time. It is a flowchart which shows 1st Embodiment of the thinning-out function of low speed sensorless control. It is a time chart which shows the implementation timing of the process of the low speed sensorless control in 1st Embodiment. It is a time chart which shows the correlation with the process timing and process content in 1st Embodiment. It is a flowchart which shows 2nd Embodiment of the thinning-out function of low speed sensorless control. It is a time chart which shows the implementation timing of the process of the low speed sensorless control in 2nd Embodiment. It is a time chart which shows the execution timing of the process of low speed sensorless control in 2nd Embodiment, and the execution timing of the process of low speed sensorless control when the frequency | count of thinning-out n is made constant. It is a time chart which shows the execution timing of the process of the low speed sensorless control at the time of changing the frequency switching threshold value Vfc according to the motor rotational speed in 2nd Embodiment. It is a flowchart which shows 3rd Embodiment of the thinning-out function of low speed sensorless control. It is a time chart which shows the implementation timing of the process of the low speed sensorless control in 3rd Embodiment. It is a time chart for demonstrating the setting method of frequency switching time Tfc in 3rd Embodiment. It is a time chart for demonstrating a problem when the step-out of a brushless motor generate | occur | produces. It is a flowchart which shows 4th Embodiment of the thinning-out function of low speed sensorless control.

Embodiments of the present invention will be described below.
FIG. 1 shows an example applied to a hydraulic pump system of an automatic transmission for an automobile as an example of a brushless motor control device according to the present invention.
The hydraulic pump system shown in FIG. 1 includes a mechanical oil pump 6 driven by the output of an engine (internal combustion engine) (not shown) and a motor as an oil pump that supplies oil to the transmission mechanism (TM) 7 and the actuator 8. And an electric oil pump 1 to be driven.

The electric oil pump 1 is operated, for example, when the engine is stopped by an idle stop, supplies oil to the transmission mechanism 7 and the actuator 8, and suppresses a decrease in hydraulic pressure during the idle stop.
The electric oil pump 1 is driven by a brushless motor (three-phase synchronous motor) 2, and the brushless motor 2 is controlled by a motor control unit (MCU) 3.
The motor control device 3 controls the brushless motor 2 based on a command from the AT control device (ATCU) 4.

The electric oil pump 1 driven by the brushless motor 2 supplies the oil in the oil pan 10 to the speed change mechanism 7 and the actuator 8 via the oil pipe 5.
During the engine operation, the mechanical oil pump 6 driven by the engine is operated, and oil is supplied from the mechanical oil pump 6 to the transmission mechanism 7 and the actuator 8. At this time, the brushless motor 2 is in an off state (stopped) State), and the check valve 11 blocks the oil flow toward the electric oil pump 1.

On the other hand, when the engine is temporarily stopped by the idle stop, the mechanical oil pump 6 is stopped and the oil pressure in the oil pipe 9 is reduced. Therefore, when the engine is stopped by the idle stop, the AT control device 4 is activated by the motor. The command is transmitted to the motor control device 3.
Upon receiving the motor activation command, the motor control device 3 activates the brushless motor 2 to rotate the electric oil pump 1 and starts the oil pumping by the electric oil pump 1.

  When the discharge pressure of the mechanical oil pump 6 decreases while the discharge pressure of the electric oil pump 1 exceeds the set pressure, the check valve 11 is opened, and the oil is supplied to the oil pipe 5, the electric oil pump 1, It circulates through the path of the check valve 11, the speed change mechanism 7, the actuator 8, and the oil pan 10.

The above-described hydraulic pump system for an automatic transmission for automobiles is an example of a system to which a brushless motor is applied, and the control device according to the present invention can be applied to various systems using the brushless motor as an actuator.
For example, the brushless motor can be a brushless motor that drives an electric water pump used to circulate engine cooling water in a hybrid vehicle or the like, and the device that the brushless motor drives is not limited to an oil pump, The brushless motor is not limited to a motor mounted on an automobile.

FIG. 2 is a circuit diagram illustrating an example of the brushless motor 2 and the motor control device 3.
The motor control device 3 includes a motor driving circuit 212 and a control unit 213 including a microcomputer (microcomputer) 213b including an A / D converter 213a and a microprocessor (CPU, MPU, etc.). Communication is performed with the AT control device 4.
The brushless motor 2 is a three-phase DC brushless motor (three-phase synchronous motor) and includes U-phase, V-phase, and W-phase three-phase windings 215u, 215v, and 215w in a cylindrical stator (not shown), A permanent magnet rotor (rotor) 216 is rotatably provided in a space formed in the center of the stator.

The motor drive circuit 212 includes a circuit in which switching elements 217 a to 217 f including anti-parallel diodes 218 a to 218 f are connected in a three-phase bridge, and a power supply circuit 219. The switching elements 217a to 217f are composed of, for example, FETs.
The control terminals (gate terminals) of the switching elements 217a to 217f are connected to the control unit 213, and the control unit 213 controls on / off of the switching elements 217a to 217f by the pulse width modulation signal PWM.

The drive control of the brushless motor 2 by the control unit 213 is performed without using a sensor that detects the position information of the rotor, and further switches between sine wave driving and rectangular wave driving according to the motor rotation speed.
The sine wave drive is a method of driving the brushless motor 2 by applying a sine wave voltage to each phase. In this sine wave drive, while the rotor position information is obtained from the induced voltage (speed electromotive voltage) generated by the rotation of the rotor, the motor rotational speed is adjusted during the detection period of the rotor position by the speed electromotive voltage. The rotor position is estimated based on the calculated rotor position and the PWM duty, the three-phase output set value is calculated, and the direction and strength of the current are controlled by the difference in the interphase voltage to flow the three-phase alternating current. .

Further, the rectangular wave driving is a method of driving the brushless motor 2 by sequentially switching a selection pattern (energization mode) of two phases to which a pulse voltage is applied among the three phases according to a predetermined switching timing.
In this rectangular wave drive, the position information of the rotor is obtained from the voltage (transformer electromotive voltage, pulse induced voltage) induced in the non-conduction phase by applying a pulsed voltage to the conduction phase, and the switching timing of the conduction mode is detected. To do.
Here, since the output level of the speed electromotive voltage detected for position detection in the sine wave drive decreases as the motor rotation speed decreases, the accuracy of position detection decreases in the low rotation range. On the other hand, the pulse induced voltage detected for position detection in the rectangular wave drive can detect position information even in a low rotation range including the motor stop state.

Therefore, the control unit 213 controls the brushless motor 2 by sine wave drive in a high rotation region (region where the motor rotation speed is higher than the set value) where position information can be detected with sufficient accuracy by sine wave drive.
In addition, the control unit 213 controls the brushless motor 2 by rectangular wave drive in a low rotation region where the position information cannot be detected with sufficient accuracy by sine wave drive (a region where the motor rotation speed is lower than the set value, including during startup). Control.
Further, in the PWM control of the brushless motor 2, the control unit 213 determines the actual motor rotation speed by determining the duty ratio of the PWM control according to the deviation between the detected value of the motor rotation speed and the target motor rotation speed. Move closer to the motor speed.

Below, the rectangular wave drive control of the brushless motor 2 which the control unit 213 implements is explained in full detail.
FIG. 3 is a functional block diagram of the control unit 213 in the rectangular wave drive control.
The control unit 213 includes a PWM generation unit 251, a gate signal switching unit 252, an energization mode determination unit 253, a comparison unit 254, a voltage threshold switching unit 255, a voltage threshold learning unit 256, and a non-energization phase voltage selection unit 257.

The PWM generator 251 generates a pulse wave-modulated PWM wave based on an applied voltage command (command voltage).
The energization mode determination unit 253 is a device that sequentially outputs a mode command signal for determining the energization mode (switching mode) of the motor drive circuit 212, and has six energization modes triggered by the mode switching trigger signal output from the comparison unit 254. Switch to.
The energization mode is a two-phase selection pattern in which a pulse voltage is applied among the three phases (U phase, V phase, and W phase) of the brushless motor 2.

The gate signal switching unit 252 determines how the switching elements 217a to 217f of the motor drive circuit 212 are switched based on the mode command signal output from the energization mode determination unit 253, and follows the determination. Six gate pulse signals are output to the motor drive circuit 212.
The voltage threshold value switching unit 255 sequentially switches and outputs the threshold values in the energization mode switching control based on the comparison between the pulse induced voltage of the non-energized phase and the threshold value, and the threshold switching timing is determined by the output of the energization mode determination unit 253. It is determined based on a certain mode command signal.

The non-conduction phase voltage selection unit 257 selects a detection value of the non-conduction phase voltage from the three-phase terminal voltages Vu, Vv, and Vw of the brushless motor 2 in accordance with the mode command signal, and compares the comparison unit 254 and the voltage threshold learning unit. 256 is a circuit to output to 256.
The terminal voltage of the non-energized phase is strictly a voltage between the ground GND and the terminal, but in this embodiment, a neutral point voltage is separately detected, and the neutral point voltage and the GND-terminal are detected. The terminal voltages Vu, Vv, and Vw are obtained by obtaining the difference from the voltage.

The comparison unit 254 compares the threshold value output from the voltage threshold value switching unit 257 with the voltage detection value (detected value of the pulse induced voltage) of the non-conduction phase voltage output from the non-conduction phase voltage selection unit 257, thereby The switching timing is detected, and a mode switching trigger is output to the energization mode determination unit 253 based on the detection result.
The voltage threshold learning unit 256 is a device that updates and stores a threshold used for determination of switching timing of the energization mode.

Since the pulse induced voltage of the non-energized phase detected for the determination of the switching timing varies depending on the manufacturing variation of the brushless motor 2, the detection variation of the voltage detection circuit, and the like, a fixed value is set as a threshold for the variation of the induced voltage. If is used, the switching timing of the energization mode is erroneously determined.
Therefore, the voltage threshold learning unit 256 detects the pulse induced voltage at the magnetic pole position corresponding to the switching timing of the energization mode, thereby correcting the threshold to be close to the induced voltage generated at the actual switching timing. The threshold value stored in the unit 257 is rewritten to the correction result.

FIG. 4 shows an example of a voltage application state to each phase in each energization mode.
The energization mode is composed of six energization modes (1) to (6) which are sequentially switched every electrical angle of 60 deg. With respect to two phases selected from three phases in each energization mode (1) to (6). A pulse voltage (pulse voltage) is applied.
When the angular position of the U-phase coil is the reference position (angle = 0 deg) of the rotor (magnetic pole) and the angular position (magnetic pole position) of the rotor is 30 deg. ) To the energization mode (4), when the rotor angular position is 90 deg, the energization mode (4) is switched to the energization mode (5), and when the rotor angular position is 150 deg. The energization mode (5) is switched to the energization mode (6). When the rotor angular position is 210 deg, the energization mode (6) is switched to the energization mode (1), and the rotor angular position is 270 deg. Is switched from the energization mode (1) to the energization mode (2), and when the rotor angular position is 330 degrees, the energization mode (2) is switched to the energization mode (3).

Here, the voltage threshold value switching unit 255 of the control unit 213 stores the voltage (pulse induced voltage) of the non-energized phase at the angle at which the energization mode is switched as a threshold value, and the threshold value according to the energization mode at that time Is output.
The comparison unit 254 outputs a signal indicating that the angle for switching to the next energization mode is detected when the voltage of the non-energization phase (pulse induced voltage) reaches a threshold value, and the energization mode is based on the signal. The determination unit 253 executes switching of the energization mode.

In the energization mode (1), the control unit 213 (gate signal switching unit 252) applies the voltage V to the U-phase by turning on the switching elements 217a and 217d and turning off all others. A voltage −V is applied to the V phase, and a current is passed from the U phase to the V phase.
In the energization mode (2), the control unit 213 applies the voltage V to the U phase and the voltage −V to the W phase by turning on the switching elements 217a and 217f and turning off all others. Is applied to flow current from the U phase to the W phase.

In the energization mode (3), the control unit 213 applies the voltage V to the V phase and the voltage −V to the W phase by turning on the switching elements 217c and 217f and turning off all others. Is applied, and a current flows from the V phase toward the W phase.
In the energization mode (4), the control unit 213 applies the voltage V to the V phase and the voltage −V to the U phase by turning on the switching elements 217b and 217c and turning off all others. Is applied, and a current flows from the V phase toward the U phase.

In the energization mode (5), the control unit 213 applies the voltage V to the W phase and the voltage −V to the U phase by turning on the switching elements 217b and 217e and turning off all others. Is applied, and a current flows from the W phase toward the U phase.
Further, in the energization mode (6), the control unit 213 applies the voltage V to the W phase and the voltage −V to the V phase by turning on the switching elements 217e and 217d and turning off all others. Is applied, and current flows from the W phase to the V phase.

In the energization control, for example, in the energization mode (1), the control unit 213 applies the voltage V to the U phase by turning on the switching elements 217a and 217d and turning off all others. A voltage −V is applied to the V phase, and a current flows from the U phase to the V phase.
On the other hand, when the control unit 213 drives the upper switching element 217c with a PWM wave having a phase opposite to that of the PWM wave driven by the lower switching element 217d, and the lower switching element 217d is on, the upper switching element When the element 217c is turned off and the lower switching element 217d is turned off, the energization control in each of the energization modes (1) to (6) can be performed by a complementary control system in which the upper switching element 217c is turned on.

As described above, each of the switching elements 217a to 217f is energized for 120 deg every 240 deg by switching the six energization modes (1) to (6) every 60 deg electrical angle, as shown in FIG. This energization method is called a 120 degree energization method.
Further, the AT control device 4 determines the command value of the applied voltage of the brushless motor 2 as follows, for example.

For example, the AT control device 4 calculates a target motor rotation speed (rpm) of the brushless motor 2 based on the oil temperature and the like, and applies an applied voltage (input voltage) based on the target rotation speed and the actual motor rotation speed (rpm). ) Command value.
Specifically, the AT control device 4 determines the command value of the applied voltage (input voltage) according to the following equation by proportional-integral control (PI control) based on the deviation between the target motor speed and the actual motor speed.
Applied voltage = rotational speed deviation * proportional gain + rotational speed deviation integrated value * integral gain rotational speed deviation = target rotational speed-actual rotational speed

However, the method for determining the command value of the applied voltage is not limited to the method based on the target motor rotation speed, and for example, based on the deviation between the target discharge pressure of the electric oil pump 1 and the actual discharge pressure, A known determination method such as a method of determining a value or a method of determining a command value of an applied voltage based on a required torque can be appropriately employed.
Further, the calculation processing of the applied voltage for bringing the actual value closer to the target value is not limited to proportional integral control, and a known calculation processing method such as proportional integral differentiation control (PID control) can be appropriately employed.

Next, the AD conversion timing of the voltage (pulse induced voltage) of the non-conduction phase by the A / D converter 213a will be described.
The A / D converter 213a of the control unit 213 converts the analog signal of the non-energized phase voltage into a digital signal, and the microcomputer 213b of the control unit 213 outputs the voltage as a digital signal output from the A / D converter 213a. The value is compared with the threshold value, and the energization mode switching control is performed.

FIG. 5 shows an example of the sampling timing of the A / D converter 213a.
FIG. 5 shows an energization mode (3) in which the rotor angular position is 330 deg to 30 deg, an energization mode (4) in which the rotor angular position is 30 deg to 90 deg, and a rotor angular position from 90 deg to 150 deg. The voltage of each phase in each energization mode (5) during is shown. In the example shown in FIG. 5, the output frequency (PWM output frequency) in the pulse width modulation control is 12 kHz.

For example, in the energization mode (3), the voltage V corresponding to the instruction voltage is applied to the V phase by the pulse width modulation operation, the voltage −V is applied to the W phase, and the current flows from the V phase toward the W phase. The voltage detection phase (non-energized phase) is the U phase, and this U phase terminal voltage is subjected to AD conversion during the ON period of the switching element 217f in the upper stage of the V phase.
That is, it is necessary to perform sampling in the A / D converter 213a while the PWM output is on, and the sampling period of the A / D converter 213a is synchronized with the PWM output period of 83.3 μs (12 kHz).

FIG. 6 is a diagram showing in detail an example of the sampling timing of the A / D converter 213a.
In the example shown in FIG. 6, in the PWM control, the valley of the PWM counter that repeats increase / decrease for each carrier cycle, in other words, the point where the PWM counter value changes from decrease to increase and near the center of the pulse width of the pulse applied voltage (time Let t1, t3, t5, t7) be A / D conversion timing of voltage (start timing of A / D conversion).

  In the example shown in FIG. 6, the A / D conversion timing when the PWM output is on is set near the center of the pulse width. However, the timing is not limited to this timing. For example, the delay time elapses from the rising edge of the pulse. The point in time can be used as the A / D conversion timing. The delay time is provided for A / D conversion after the voltage fluctuation period immediately after the pulse rises.

By the way, in the example shown in FIG. 6, the A / D converter 213a A / D converts the voltage of the non-conduction phase at that time for each valley of the PWM counter and holds the digital output until the next conversion timing.
Then, the control unit 213 performs digital processing of the voltage detection value of the latest non-conduction phase by, for example, interrupt processing for each peak (time t2, t4, t6) of the PWM counter that is half a PWM output cycle after the conversion timing. Data is read and rectangular wave drive control without sensor (hereinafter referred to as low speed sensorless control) is performed.
In this case, the ratio of the processing time of the low speed sensorless control to the processing cycle (83.3 μs = PWM output cycle) is high, and processing other than the processing of the low speed sensorless control (hereinafter referred to as other processing) may be delayed.

  The low-speed sensorless control processing includes A / D conversion data reception processing (voltage measurement processing), voltage threshold setting processing, A / D conversion data (actual pulse induced voltage) and threshold comparison processing (rotor). A series of processes in PWM control of the brushless motor 2 such as position estimation process), PWM output pattern (energization mode, pulse width) determination process, PWM output process, and the like. The other processing is processing other than PWM control, such as failure diagnosis processing, fail-safe processing based on the failure diagnosis result, communication processing with other units, and the like.

The control unit 213 has a function of changing the execution frequency of the low-speed sensorless control process at the processing timing synchronized with the PWM output cycle (hereinafter referred to as a thinning function), and performs the low-speed sensorless control process synchronized with the PWM output cycle. By thinning out, it is possible to prevent other processing from being delayed.
That is, the control unit 213 sets the case where the low-speed sensorless control process is not performed even when the process timing is synchronized with the PWM output cycle, so that the control unit 213 performs the execution frequency more than when the low-speed sensorless control is performed at each processing timing. To reduce the burden for the low-speed sensorless control process, and to perform other processes accordingly.

Therefore, it is possible to suppress delays in detecting the occurrence of a failure or delaying the implementation of fail-safe based on the occurrence of a failure due to the delay in other processing.
In addition, signal transmission to other units is delayed due to delay in other processes, control unit 213 failure is erroneously detected in other units, or signal reception from other units is delayed, resulting in control delays. It can be suppressed from occurring.

The flowchart of FIG. 7 shows a first embodiment in which the thinning function of the control unit 213 is embodied. In the routine shown in the flowchart of FIG. 7, the control unit 213 executes an interrupt at a processing timing for each PWM output cycle (for example, every peak of the PWM counter).
First, in step S101, the control unit 213 detects whether or not it is the low-speed sensorless control processing timing based on the thinning counter CT (thinning counter CT ≧ 0).

Here, when the thinning counter CT = 0, the control unit 213 detects the processing timing of the low speed sensorless control, and when detecting the processing timing of the low speed sensorless control, the control unit 213 executes the low speed sensorless control after step S103.
On the other hand, the control unit 213 detects the thinning timing for stopping the low-speed sensorless control when the thinning counter CT ≠ 0, and if it is the thinning timing, the control unit 213 decreases the value of the thinning counter CT by 1 in step S102. Implement the process.

When performing decimation to perform low-speed sensorless control at a rate of once every N (N ≧ 2) PWM output cycles, decimation count n = N−1 is set in decimation counter CT every time low-speed sensorless control is performed. , N indicates the number of times to stop the low-speed sensorless control.
Note that the number of thinnings n ≧ 0, and the number of thinnings n = 0 indicates that low-speed sensorless control is performed at each processing timing synchronized with the PWM output cycle, and this state is a state in which thinning is canceled. The frequency of performing the low speed sensorless control decreases as the number of thinning out n increases.

For example, when the number of thinnings n = 1, the control unit 213 sets the thinning counter CT = 1 when the low-speed sensorless control is performed, and the thinning counter CT = 1 at the next processing timing. In step S101, the decimation counter CT is updated to 0, and if it is detected in step S101 that the decimation counter CT = 0 at the next next processing timing, the process proceeds to step S103 and subsequent steps, and low speed sensorless control is performed.
That is, when n = 1, when low-speed sensorless control is performed, the low-speed sensorless control is paused (decimated) in the next PWM output cycle, and the low-speed sensorless control is repeatedly performed in the next PWM output cycle. The low-speed sensorless control is performed at a rate of once every two PWM output cycles (processing timing).

Similarly, when the number of thinning-out n = 2, when the low-speed sensorless control is performed, the control unit 213 repeatedly performs the low-speed sensorless control after pausing the low-speed sensorless control twice (thinning out). The low-speed sensorless control is performed at a rate of once every three PWM output cycles (processing timing).
In other words, when the control unit 213 performs the thinning function, the execution period of the low-speed sensorless control extends N times the PWM output period.

Here, as the value of the number of thinnings n is increased, the execution frequency of the low-speed sensorless control is reduced and the execution period is extended. As the value of the number of thinnings n is increased, the low-speed sensorless control within the switching period of the energization mode. On the other hand, as the value of the number of thinning-out n is increased, the processing load of the control unit 213 is suppressed and the time during which other processing can be performed becomes longer.
Therefore, the control unit 213 can reduce the influence on the controllability of the low-speed sensorless control of the brushless motor 2 sufficiently, and the number of thinning-out times n (control request frequency) that can secure a sufficient time for performing other processes. Set.

In addition, when the motor rotation speed is high, the switching interval time of the energization mode is shortened, and the number of PWM outputs at the switching interval is reduced. Therefore, in order to perform low-speed sensorless control more than a certain number of times at the switching interval of the energization mode, n can be changed smaller as the motor rotation speed is higher.
When the control unit 213 detects the thinning counter CT = 0 in step S101, in step S103, the control unit 213 performs reception processing (voltage measurement processing) of A / D conversion data that is the detected voltage value of the non-conduction phase at that time. Then, in step S104, A / D conversion data (actual pulse induced voltage) is compared with a threshold value (rotor position estimation process). In step S105, the PWM output pattern (energization mode, pulse Width) is determined.

The processes in steps S103 to S105 described above correspond to the low speed sensorless control.
When the low-speed sensorless control is performed in steps S103 to S105, the control unit 213 performs a process of resetting the value of the thinning counter CT from 0 to the number of thinnings n in step S106.

Hereinafter, the correlation between the number of thinning-out n and the motor rotation speed will be described in detail.
For example, assuming that the maximum rotation speed (rpm) of the brushless motor 2 is 3000 rpm, the number of motor pole pairs is 3, and the energization mode is 6 patterns, the energization mode switching interval Tmc (μs) at the maximum rotation speed is Tmc. = 60 ÷ 3000 ÷ 6 ÷ 3 = 1111.1 (μs).
If the PWM output cycle is 83.3 μs, the number of PWM outputs (processing timing) at the switching interval Tmc of the energization mode at the maximum rotation speed is 13.3 times, and when thinning is not performed, the low-speed sensorless control process Can be carried out 13 times.

Here, in order that the thinning function does not affect the controllability of the brushless motor 2, for example, low-speed sensorless control is performed before and after the non-energized phase voltage reaches the threshold value, and noise effects are suppressed. In addition, if the energization mode is switched when it is detected that the voltage of the non-energized phase has reached the threshold value twice continuously, the low-speed sensorless control is performed at least four times at the energization pattern switching interval Tmc. Is required.
If the low-speed sensorless control is executed only four times among the 13 PWM output times at the maximum rotation speed, the low-speed sensorless control is executed at a rate of once every three PWM output cycles. In this case, the thinning-out number n is 2. That is, the number of thinning-out n = 2 indicates a request for the frequency of execution of low-speed sensorless control at 3000 rpm (control request frequency). If the number of thinning-out is n or less, the low-speed sensorless control is executed more than the minimum necessary number. Can do.

As described above, if the low-speed sensorless control is performed at the minimum necessary number of times (control request frequency) at the energization pattern switching interval Tmc, the motor rotation speed decreases and the energization pattern switching interval Tmc becomes longer, and the switching interval Tmc. As the number of PWM outputs increases, the number of thinnings n can be increased accordingly.
Table 1 shows a setting example of the number of thinning-out times n (control request frequency) with respect to the motor rotation speed based on the above setting method.

If the number of thinning-out n is set to be equal to or less than the number of thinning-out n for each rotation speed range shown in Table 1, even if the rotation speed of the brushless motor 2 is changed, the necessary number of times (4 times) or more is required at the conduction pattern switching interval Tmc. The low-speed sensorless control can be performed as many times as possible.
By setting the motor rotation speed used for setting the number of thinnings n to the higher of the actual motor rotation speed and the target motor rotation speed, low-speed sensorless control is performed for the minimum number of times required even in a transient state of the motor rotation speed. Can be implemented.

  When the brushless motor 2 is started up and the actual motor rotational speed is uncertain, the target motor rotational speed can be used to set the thinning number n, and the maximum rotational speed of the brushless motor 2 can be set. If the number of thinning-out n is set based on this, the necessary minimum number of executions can be secured.

The time chart of FIG. 8 shows an example in which the correlation between the voltage of the non-energized phase and the execution timing of the low-speed sensorless control process when the process shown in the flowchart of FIG. Show.
In the decimation with n = 1 as shown in FIG. 8, the control unit 213 performs the low-speed sensorless control at a rate of once every two PWM output cycles, and the cycle (time t1) at which the low-speed sensorless control is performed. When the angular position at which the energization mode is switched is detected, a process for switching the energization mode to the next energization mode is executed, and the PWM output pattern is determined according to the energization mode after switching.

The time chart of FIG. 9 shows the correlation between the PWM counter, the A / D conversion state, and the processing contents in the processor of the control unit 213 when the control unit 213 performs the processing shown in the flowchart of FIG. The case where = 1 is shown as an example.
The A / D converter 213a performs voltage sampling (A / D conversion) based on the conversion trigger signal output from the microcomputer 213b for each valley (time t1, t3, t5, t7) of the PWM counter.

On the other hand, the low speed sensorless control by the microcomputer 213b is performed at a rate of once every two PWM output cycles. In the case of FIG. 9, time t2 and t6 are processing timings for performing the low speed sensorless control, and time t4 is a low speed. This is the processing timing for pausing sensorless control.
For example, when the low speed sensorless control is performed with the PWM counter peak (time t2, t6) as the start timing, the PWM counter peak is next detected from the timing when the low speed sensorless control is ended (time t3A). During the time (time t3A to time t4), other processing is performed.

On the other hand, at the processing timing (time t4) when the low-speed sensorless control is paused and thinned out, processing for the thinning function that is completed in a short time, such as updating of the thinning counter (step S102), is performed initially. By shifting, it is possible to obtain a processing time during which other processing can be sufficiently performed.
In other words, by performing low-speed sensorless control at a rate of once every two PWM output cycles, other processing can be performed at a sufficient processing time at a rate of once every two PWM output cycles. Therefore, it is possible to prevent other processing from being delayed.

The flowchart in FIG. 10 shows a second embodiment in which the thinning function for low-speed sensorless control is implemented. The routine shown in the flowchart in FIG. 10 is executed by the control unit 213 (microcomputer 213b) every PWM output cycle (for example, PWM It is executed by interruption every counter mountain).
The second embodiment is different from the first embodiment in that the execution frequency of the low-speed sensorless control at the processing timing, that is, the value of the number of thinning-outs n is changed during the switching period of the energization mode.

That is, in the second embodiment, after switching the energization mode, when the next energization mode switching timing approaches, that is, when the voltage of the non-energization phase approaches the threshold value, the frequency of performing the low-speed sensorless control increases. (Decrease the value of the number of thinning-out n).
Thereby, before approaching the switching timing of the energization mode, the processing load of the control unit 213 can be reduced and other processing can proceed, and when the switching timing of the energization mode approaches, the execution period of the low-speed sensorless control is shortened. Therefore, the detection delay of the switching timing of the energization mode can be suppressed.

In the flowchart of FIG. 10, the control unit 213 performs the same processes as steps S101 to S105 in steps S201 to S205.
On the other hand, when the control unit 213 performs the low-speed sensorless control in steps S203 to S205, the control unit 213 performs processing that is a feature of the second embodiment after step S206.

In step S206, the control unit 213 determines whether or not the non-energized phase voltage has reached the frequency switching threshold value Vfc for changing the execution frequency of the low-speed sensorless control (thinning number n) after switching the energization mode. Is detected.
The frequency switching threshold Vfc is set to a voltage lower than the threshold Vmc by a predetermined value if the threshold Vmc used for detecting the switching timing of the energization mode is a positive voltage, and if the threshold Vmc is a negative voltage, the threshold Vmc. The voltage is set higher than the predetermined value. In other words, the absolute value of the frequency switching threshold Vfc is smaller than the absolute value of the threshold Vmc used for detecting the switching timing of the energization mode, and the voltage reached before the non-energized phase voltage reaches the threshold Vmc after the energization mode is switched. It is.

Here, in the case where the voltage of the non-energized phase reaches the frequency switching threshold Vfc after switching the energization mode, in step S207, the control unit 213 stores the decimation count n1 (n1 ≧ n1) in the decimation counter CT. 1) is set. The number of thinning-out times n1 can be the number of thinning-out times n shown in Table 1 in which low-speed sensorless control can be performed at the control request frequency.
On the other hand, when the non-energized phase voltage has reached the frequency switching threshold Vfc and until the energization mode switching determination threshold Vmc is reached (Vfc ≦ non-energized phase voltage <Vmc or Vmc). <Voltage of non-energized phase ≦ Vfc), the control unit 213 sets the thinning number n2 to the thinning counter CT in step S208. Here, n1> n2 ≧ 0, for example, n1 = 2 and n2 = 0.

That is, when the non-energized phase voltage approaches the energization mode switching determination threshold Vmc and the energization mode switching timing approaches, the low-speed sensorless control is performed more frequently (decreasing the number of thinnings n) and energized. The detection delay of the mode switching timing is suppressed.
Also, before the energization mode switching timing is approached, detection of the energization mode switching timing is not delayed even if the low-speed sensorless control is performed at low frequency, and other processing can proceed.

Therefore, in the second embodiment, it is possible to obtain a sufficient time for performing other processes and to reduce the detection delay of the switching timing of the energization mode as much as possible.
Note that the number of thinning-out times n2 is set as a value that can sufficiently reduce the detection delay of the switching timing of the energization mode, and the number of thinning-out times n1 is a value that can sufficiently advance other processing without affecting motor control. Set as

In the time chart of FIG. 11, when the control unit 213 performs the processing shown in the flowchart of FIG. 10, the correlation between the voltage of each phase and the execution timing of the low-speed sensorless control is n1 = 1 and n2 = 0. The case is shown as an example.
In the example shown in FIG. 11, when the energization mode is switched (time t1, time t3), if the number of thinnings n is set to n = n1 = 1 and the low-speed sensorless control is performed, the following processing cycle is performed. Repeatedly pauses the low-speed sensorless control. Here, in the PWM output cycle in which the low-speed sensorless control is paused, the processing load on the control unit 213 is reduced, and other processing can proceed.

On the other hand, when it is detected at time t2 and t4 that the energization mode switching timing is approaching based on the comparison between the voltage of the non-energization phase and the frequency switching threshold Vfc, the number of thinning-out n is n = n1 = Since 1 is changed to n = n2 = 0 and the execution frequency of the low-speed sensorless control at the rate of once every two processing timings is switched to the execution every time, the detection delay of the switching timing of the energization mode can be suppressed.
Further, the time chart of FIG. 12A shows the correlation between the voltage of the non-energized phase and the execution timing of the low-speed sensorless control when the control unit 213 performs the processing shown in the flowchart of FIG. A case where n2 = 0 is shown as an example.

In the example shown in FIG. 12A, when the energization mode is switched (time t1), when the number of thinning-out n is set to n = n1 = 2 and the low-speed sensorless control is performed, the next cycle and the next cycle The low-speed sensorless control is repeatedly paused at the next cycle. Here, in the PWM output cycle in which the low-speed sensorless control is paused, the processing load on the control unit 213 is reduced, and other processing can proceed.
FIG. 12A shows an example in which the switching timing is detected when the voltage of the non-energized phase decreases as it approaches the switching timing of the energizing mode, and decreases to the threshold Vmc. Is set to a value higher than the threshold value Vmc for switching determination.

In the example shown in FIG. 12A, when it is detected that the voltage of the non-conduction phase has reached the frequency switching threshold Vfc in the state where the number of thinnings n = 2 (time t2), the number of thinnings n is n = n2. = 0 so that the low-speed sensorless control is repeated every PWM output cycle. That is, detection of the switching timing of the energization mode by the control unit 213 is performed in a state where the low-speed sensorless control is repeated every PWM output cycle, and it is possible to suppress delay in detection of the switching timing of the energization mode.
On the other hand, FIG. 12B illustrates a case where the thinning-out number n is fixed to n = n1 = 2 without changing the thinning-out number n based on the comparison between the voltage of the non-energized phase and the frequency switching threshold Vfc. It is.

When the number of thinnings n = 2 is fixed, the switching timing of the energization mode by the control unit 213 is detected in the state of the number of thinnings n = 2, and the next PWM output cycle (time of the low speed sensorless control) Even if the voltage of the non-energized phase sampled at t3) reaches the threshold Vmc for determining whether to switch the energization mode, the energization mode is switched until the next low speed sensorless control is performed (until time t4). Will be delayed.
On the other hand, as shown in FIG. 12A, if the number of thinning-out n is decreased to approach the energization mode switching timing, for example, the number of thinning-out n = 0, the voltage of the non-conduction phase is sampled. Since the low speed sensorless control is performed every time, it is possible to suppress a delay in the switching timing of the energization mode, and to switch the energization mode at time t3.

Further, the difference between the frequency switching threshold Vfc, in other words, the difference between the frequency switching threshold Vfc and the energization mode switching determination threshold Vmc can be a fixed value, and can be set variably according to the motor rotation speed. Can do.
When the motor rotation speed is high, the voltage change speed of the non-energized phase is increased, and when the frequency switching threshold is constant, the threshold for determining the switching of the energized mode after the voltage of the non-energized phase reaches the frequency switching threshold Vfc. The time to reach Vmc is shorter than when the rotation speed is low, and the low-speed sensorless control cannot be performed a sufficient number of times with the frequency increased, and the controllability of the brushless motor 2 may be reduced. is there.

Here, when the frequency switching threshold Vfc is set so that the low-speed sensorless control can be performed a sufficient number of times when the frequency is high when the rotation speed is high, the motor rotation speed is low, and the voltage change of the non-energized phase When the speed becomes low, the number of times of low speed sensorless control in the state where the frequency is increased becomes excessive, and the time that can be used for other processing is unnecessarily used for the low speed sensorless control. .
Therefore, as the motor rotation speed increases, the difference ΔV between the frequency switching threshold Vfc and the energization mode switching determination threshold Vmc is increased, in other words, the absolute value of the frequency switching threshold Vfc is changed to be smaller, and the motor rotation Even if the speed is increased, the number of times of low-speed sensorless control after the voltage of the non-energized phase reaches the frequency switching threshold Vfc exceeds the predetermined number.

  As described above, if the frequency switching threshold Vfc is variably set according to the motor rotation speed, when the motor rotation speed is low, the processing load of the control unit 213 can be reduced and other processing can be performed sufficiently. In addition, when the motor rotation speed is increased, it is possible to suppress a decrease in controllability due to an excessive number of low-speed sensorless controls.

FIG. 13 shows an example in which the correlation between the voltage of the non-energized phase and the execution timing of the low-speed sensorless control is n1 = 2 and n2 = 0 in the configuration in which the frequency switching threshold Vfc is changed according to the motor rotation speed. FIG. 13A shows a state where the motor rotation speed is low, and FIG. 13B shows a state where the motor rotation speed is high.
In the state where the motor rotation speed in FIG. 13A is low, after switching the energization mode at time t1, the voltage of the non-energized phase reaches the frequency switching threshold Vfc for low rotation at time t4, and the number of thinnings n is Switching from n1 to n2 and then switching to the energization mode is performed when the voltage of the non-energized phase reaches the threshold value Vmc for switching determination of the energization mode at time t5 thereafter.

On the other hand, in the state where the motor rotation speed in FIG. 13B is high, the motor rotation speed is higher than in the case of 13A, and thus the speed at which the voltage of the non-conduction phase changes is faster than in FIG. . When the motor rotation speed is high, the switching timing of the number of thinning-out times n is detected based on the frequency switching threshold value Vfc for high rotation whose absolute value is smaller than the frequency switching threshold value Vfc for low rotation.
Here, in the example of FIG. 13B, the voltage of the non-energized phase reaches the frequency switching threshold Vfc for high rotation at time t2, the number of thinnings n is switched from 2 to 0 at time t2, and the time At t3, it is detected that the voltage of the non-energized phase has reached the threshold value Vmc for determining whether to switch the energization mode, and the energization mode is switched.

  In FIG. 13B, assuming that the number of thinning-out times n is switched based on the low-rotation frequency switching threshold Vfc, which is the same as the state where the motor rotation speed is low, the change in the decreasing direction of the number of thinning-out times n is delayed. By approaching the energization mode switching timing, the time until the energization mode switching timing is reduced after the decimation number n is decreased, and the number of times of low-speed sensorless control after the decimation number n is decreased is reduced. turn into.

On the other hand, if the change timing of the thinning number n is detected using the high rotation frequency switching threshold value Vfc whose absolute value is smaller than the low rotation frequency switching threshold value Vfc, the energization is performed after decreasing the thinning number n. A sufficient time can be obtained as the time until the mode switching timing, and the number of times of low-speed sensorless control after the thinning-out number n is reduced can be set to a sufficient number for controllability.
Note that the values of the number of thinning-outs n1 and n2 can be constant values, and can be variably set according to the motor rotation speed as in the first embodiment.

The flowchart of FIG. 14 shows a third embodiment in which the thinning function is embodied, and the routine shown in the flowchart of FIG. 14 is executed by the control unit 213 (microcomputer 213b) every PWM output cycle (for example, every mountain of the PWM counter). ) Is executed by interruption.
As in the second embodiment, the third embodiment increases the execution frequency of the low-speed sensorless control (the value of the number of thinning-out n) when switching to the next energization mode after switching the energization mode. However, the third embodiment is different in that the approaching timing of the next energization mode is detected based on the elapsed time from the previous energization mode switch.
Thereby, another process can be advanced, suppressing the detection delay of the switching timing of energization mode.

In the flowchart of FIG. 14, the control unit 213 performs the same processes as steps S101 to S105 in steps S301 to S305.
On the other hand, when the low-speed sensorless control is performed in steps S303 to S305, the control unit 213 performs processing that is a feature of the third embodiment after step S306.

In step S306, the control unit 213 reaches a frequency switching time Tfc in which the elapsed time T from the previous energization mode switching timing is shorter by the set time ΔT than the predicted time Tmc until the next energization mode switching timing. Detect whether or not.
The predicted time Tmc from the switching timing of the previous energization mode to the switching timing of the next energization mode can be calculated from the motor rotation speed at that time and the rotation angle of the switching cycle of the energization mode. A time shorter than the switching cycle time Tmc by a predetermined time ΔT is set as a frequency switching time Tfc.

Thus, it is possible to detect that the next energization mode switching timing is approaching based on the elapsed time T from the previous energization mode switching timing.
When the control unit 213 detects that the elapsed time T from the previous switching timing of the energization mode has not reached the frequency switching time Tfc in step S306, the control unit 213 performs non-operation after switching the energization mode in step S307. It is detected whether the voltage of the energized phase has reached the frequency switching threshold value Vfc for changing the execution frequency of the low speed sensorless control (the value of the number of thinnings n).

Here, when the voltage of the non-energized phase reaches the frequency switching threshold value Vfc after switching the energization mode, the control unit 213 sets the decimation number n3 in the decimation counter CT in step S308. .
On the other hand, when the voltage of the non-energized phase has reached the frequency switching threshold value Vfc, the control unit 213 sets the thinning-out count CT to the thinning-out counter CT in step S309. Here, n3> n4 ≧ 1, and for example, n3 = 2 and n4 = 1 can be set.

The processing from step S307 to step S309 is the same as the processing from step S206 to step S208 in the second embodiment, but the number of thinning-out times n4 after the voltage of the non-energized phase reaches the frequency switching threshold Vfc is set to 1. This is different from the second embodiment. This is because, when it is detected that the elapsed time T from the switching timing of the previous energization mode has reached the frequency switching time Tfc after the non-energized phase voltage has reached the frequency switching threshold Vfc, This is to obtain a reduction allowance for reducing n.
On the other hand, when the control unit 213 detects that the elapsed time T from the previous switching timing of the energization mode has reached the frequency switching time Tfc in step S306, the control unit 213 sets the thinning counter CT to the thinning counter CT in step S310. set. Here, n3>n4> n5 ≧ 0, for example, n3 = 2, n4 = 1, and n5 = 0.

  That is, immediately after switching the energization mode, the control unit 213 sets the thinning number n to the largest n3, thereby reducing the execution frequency of the low-speed sensorless control to reduce the processing load and proceed with other processes. Next, when the voltage of the non-energized phase reaches the frequency switching threshold Vfc, the frequency of low-speed sensorless control is increased by lowering the number of thinnings n to the intermediate value n4 so as to be prepared for switching control of the energization mode. To. Further, when the elapsed time T from the switching timing of the previous energization mode reaches the frequency switching time Tfc and the switching timing of the energization mode is approaching, the frequency of performing the low-speed sensorless control by decreasing the number of thinnings n to the minimum value n5 By maximizing, the detection delay of the switching timing of the energization mode is suppressed.

In the third embodiment described above, it is possible to shorten the period of the number of thinning-out times n (for example, n = 0) that can suppress the detection delay of the switching timing of the energization mode as much as possible. As compared with the first and second embodiments, it is possible to further reduce the frequency of performing the low-speed sensorless control between the energization mode switching cycles.
In the third embodiment, the values of n3, n4, and n5 and the frequency switching threshold value Vfc can be variably set according to the motor rotation speed.

The time chart of FIG. 15 shows the correlation between the voltage of the non-energized phase and the execution timing of the low-speed sensorless control when the control unit 213 performs the processing shown in the flowchart of FIG. 14, with n3 = 2, n4 = 1, A case where n5 = 0 is shown as an example.
In the example shown in FIG. 15, when the energization mode is switched (time t1), the number of thinnings n is set to n = n3 = 2, and when the low-speed sensorless control is performed, the next cycle and the next next Repeatedly pauses the low-speed sensorless control in a cycle. Here, in the PWM output cycle in which the low-speed sensorless control is suspended, the processing load of the control unit 213 is reduced and other processing can proceed.

FIG. 15 shows an example in which the switching timing is detected when the voltage of the non-energized phase decreases as it approaches the switching timing of the energizing mode and falls to the threshold value. The frequency switching threshold Vfc is the switching determination of the energizing mode. It is set to a value higher than the threshold value Vmc for use.
When it is detected that the voltage of the non-energized phase has reached the frequency switching threshold Vfc in the state where the number of thinnings n = n3 = 2 (time t2), the number of thinnings n is switched to n = n4 = 1 and PWM output The low-speed sensorless control is repeatedly executed and paused every cycle, and the low-speed sensorless control is executed more frequently to prepare for switching of the energization mode.

  Further, when the elapsed time T from the switching timing of the previous energization mode reaches the frequency switching time Tfc in the state where the number of thinnings n = n4 = 1 (time t3), the number of thinnings n is switched to n = n5 = 0. By executing the low speed sensorless control every PWM output cycle, the execution frequency of the low speed sensorless control is maximized, and the detection delay of the switching timing of the energization mode is suppressed.

Note that the processing in step S307 and step S308 in the flowchart of FIG. 14 is omitted, and the control unit 213 performs the processing in step S308 when the frequency switching time Tfc is reached, and after the frequency switching time Tfc is reached. In some cases, the process of step S310 may be performed.
That is, switching of the thinning-out number n can be performed based on the frequency switching time Tfc without using the frequency switching threshold Vfc, and a plurality of times having different lengths are set as the frequency switching time Tfc. As the elapsed time T from the switching timing of the energization mode becomes longer, the switching in the decreasing direction of the thinning-out number n can be performed twice or more.

Here, the setting according to the motor rotation speed of the frequency switching time Tfc will be described in detail.
For example, when the motor rotation speed (rpm) is 1000 rpm and the number of motor pole pairs is 3 and the energization mode is 6 patterns, the energization pattern switching interval Tmc (μs) is Tmc = 60 ÷ 3000 ÷ 6 ÷. 3 = 3333.3 (μs).
If the PWM output period is 83.3 μs, the number of PWM outputs at the energization pattern switching interval Tmc at 1000 rpm is 40 times, and the energization mode is switched at the PWM output period 40 times after the previous energization mode switching. It's time.

Here, the number n of thinnings satisfying the minimum number of times of low-speed sensorless control in the switching period of the energization mode is, for example, 5 times at 1000 rpm as shown in Table 1, and the number of thinnings n = 5 is set as the frequency switching time Tfc. An example in which the number of thinnings before reaching n is shown in the time chart of FIG.
In this case, in order to detect that the frequency switching time Tfc has been reached before the energization mode switching timing in the state where the number of thinnings n = 5, the low speed at the number of thinnings n = 5 from the switching timing of the energization mode. It is necessary to set the point before the sensorless control execution cycle (PWM output cycle × (n + 1)) as the time when the frequency switching time Tfc has elapsed.

That is, the control unit 213 subtracts, from the switching interval Tmc of the energization pattern calculated from the motor rotation speed, a time that is equal to or longer than the execution period of the low-speed sensorless control at the number of thinnings n at that time, to the frequency switching time Tfc Set.
As a result, the elapse of the frequency switching time Tfc can be detected before the energization mode switching timing is detected, and the energization mode switching timing can be detected after reducing the number of thinning-out times n. It is possible to carry out thinning out of the low-speed sensorless control while suppressing it.

Note that the motor rotation speed data used in the setting of the frequency switching time Tfc uses the higher one of the actual motor rotation speed and the target motor rotation speed, so that the frequency switching is performed before the switching timing of the energization mode is detected. By detecting the passage of time Tfc, it is possible to reduce the number of thinning-out times n even in a transient state of the motor rotation speed.
In addition, when the deviation between the actual motor rotation speed and the target motor rotation speed is large, or when the prediction accuracy of the time until the switching time of the next energization mode is greatly reduced, such as when the brushless motor 2 is started, the frequency is switched erroneously. If the time Tfc is set to be excessively short, the reduction setting of the number of thinnings n is excessively advanced, so that a high processing load state in which other processing does not proceed in the low-speed sensorless control processing continues for a long time.

  Therefore, the frequency switching time Tfc is set to a significantly long time when priority is given to securing an opportunity to perform other processing under the condition that the prediction accuracy of the time until the next energization mode switching timing is greatly reduced. By doing so, it is possible to cancel the switching in the decreasing direction of the number of thinnings n by the frequency switching time Tfc. Thereby, it can suppress that the state where the frequency | count n of thinning | decimation decreased was continued excessively long.

By the way, when a step-out occurs due to a sudden change in the load of the brushless motor 2 or a motor lock, the control unit 213 stops the motor based on the fact that the energization mode has not been switched for a predetermined time. The predetermined time is set to a long time of about several hundred ms, for example.
Therefore, as in the third embodiment, when the number of thinnings n is reduced based on the passage of the frequency switching time Tfc, the time from when the number of thinnings n is reduced until the motor stop (step out) is detected. In the meantime, the low-speed sensorless control is repeatedly performed in a short cycle, so that a state in which the other processing does not proceed and the processing load is high continues.

The time chart of FIG. 17 shows a state in which the low-speed sensorless control is repeated in a short cycle (a high processing load state) due to the occurrence of the step-out of the brushless motor 2.
FIG. 17 shows an example in which the thinning-out number n is set to 2 immediately after switching the energization mode, and the step-out occurs at time t1 in the state where the thinning-out number n = 2.

Even if a step-out occurs at time t1, it takes time for the control unit 213 to detect a motor stop (step out), and before the motor stop (step out) is detected, the control unit 213 By detecting that the frequency switching time Tfc has been reached at time t2, the thinning-out count n is reduced to zero.
Here, the motor is stopped due to step-out, and the voltage of the non-energized phase does not change and does not reach the threshold value Vmc even after the number of thinnings n is reduced to 0. Therefore, the energization mode is not switched. The process of returning the thinning-out number n to 2 is not performed. As a result, until the motor stop (step out) is detected, the state where the number of thinnings n is 0 is continued.

The flowchart of FIG. 18 is a fourth embodiment that embodies the thinning function, and shows an embodiment that includes a measure for suppressing a high processing load from continuing due to the occurrence of step-out described above. The routine shown in the flowchart of FIG. 18 is executed by the control unit 213 (microcomputer 213b) by interruption every PWM output cycle (for example, every peak of the PWM counter).
In the flowchart of FIG. 18, in steps S401 to S405, processing similar to that in steps S301 to S305 of the flowchart of FIG. 14 is performed. In steps S407 to S411, steps S306 to S310 of the flowchart of FIG. Similar processing is performed.

Then, as a countermeasure when a step-out occurs, a difference is that steps S406 and S412 are added to the routine shown in the flowchart of FIG.
In the routine shown in the flowchart of FIG. 18, each time the low speed sensorless control (steps S403 to S405) is performed, the control unit 213 performs a predetermined time after the predicted switching timing of the energization mode in step S406. Detect whether or not it has passed.

The control unit 213 predicts the time Tes from the motor rotation speed at that time to the next switching timing from the timing at which the previous energization mode was switched, and at step S406, the predicted time Tes + predetermined time Tα is the previous time. It is detected whether or not the switching timing has elapsed.
Even if there is a fluctuation in the motor rotation speed or a delay in detection of the switching timing, if the brushless motor 2 rotates without being stepped out, based on the voltage of the non-conduction phase before the time Tes + the predetermined time Tα elapses. The predetermined time Tα is set so that the switching timing of the energization mode is detected.

Therefore, when time Tes + predetermined time Tα has not elapsed, it can be estimated that the brushless motor 2 has not stepped out. In this case, the control unit 213 proceeds to step S407 and subsequent steps to switch the next energization mode. Control for reducing the number of thinnings n as the timing approaches, that is, control for changing the number of thinnings n similar to that in the third embodiment is performed.
On the other hand, if the switching timing of the energization mode is not detected based on the voltage of the non-energized phase even after time Tes + predetermined time Tα has elapsed from the previous switching timing, the control unit 213 sets the thinning number n to n3 in step S412. (In the example shown in FIG. 17, n3 = 2), that is, control is performed to return to the number of thinning-out n immediately after switching of the energization mode.
Thereby, until the control unit 213 detects the motor stop (step out), the processing load of the control unit 213 is held in the state of the thinning-out number n = n3, and the processing load is kept high. It is possible to prevent the state in which the process is not continued from continuing.

The technical ideas described in the above embodiments can be used in appropriate combination as long as no contradiction arises.
Although the contents of the present invention have been specifically described with reference to preferred embodiments, it is obvious that those skilled in the art can take various modifications based on the basic technical idea and teachings of the present invention. It is.
For example, when the motor rotation speed exceeds a predetermined speed, the low-speed sensorless control thinning is stopped (the number of thinnings n is set to 0 in the entire energization mode switching cycle), and the low-speed sensorless control is performed every PWM output cycle. When the motor rotation speed is lower than the predetermined speed, the low-speed sensorless control can be thinned out.

In addition, when switching the thinning number n based on the frequency switching threshold Vfc, the frequency switching time Tfc, or the predetermined time Tα, the number of thinnings between intermediate values between the thinning number n before switching and the thinning number n after switching is transitively. It is possible to perform decimation with n.
Further, for example, when the number of thinnings n is 2, the low-speed sensorless control can be performed at a rate of once every three PWM output cycles as an average. For example, the low-speed sensorless control is performed twice continuously. After that, the low-speed sensorless control can be stopped four times continuously.
In addition, when the number of thinnings n is set to 0 before the switching timing of the energization mode, a plurality of processing timings immediately after the switching of the energization mode is set as an execution period of other processing, and regardless of the setting of the number of thinnings n, The low speed sensorless control can be stopped.

Here, technical ideas other than the claims that can be grasped from the above embodiment will be described together with effects.
(I)
The brushless motor control device according to any one of claims 1 to 3, wherein an execution frequency of the sensorless control is changed according to a rotation speed of the brushless motor.
According to the above invention, when the rotational speed of the brushless motor is increased, the number of processing timings in the switching period of the phase to which the pulse voltage is applied is reduced, and when the execution frequency of the sensorless control process is constant, The number of sensorless control processes is reduced. Therefore, the execution frequency is changed according to the rotation speed of the brushless motor, and the number of times of the process of the sensorless control in the switching cycle is adjusted.

(B)
The brushless motor control device according to claim 3, wherein an increase timing of the execution frequency based on an elapsed time after switching a phase to which the pulse voltage is applied is changed according to a rotation speed of the brushless motor.
According to the above invention, since the time required to perform the sensorless control process a predetermined number of times changes due to the change in the rotation speed of the brushless motor, the increase frequency of the execution frequency based on the elapsed time is set as the rotation speed of the brushless motor. By changing according to the above, it becomes possible to hold the sensorless control processing after the execution frequency is increased a predetermined number of times or more.

(C)
The brushless motor control device according to claim 3, wherein an increase timing of the execution frequency based on the pulse induced voltage is changed according to a rotation speed of the brushless motor.
According to the above invention, since the speed of change of the pulse induced voltage is increased by increasing the rotational speed of the brushless motor, the increase timing of the execution frequency based on the pulse induced voltage is changed according to the rotational speed of the brushless motor. Thus, the sensorless control process after increasing the execution frequency can be held a predetermined number of times or more.

(D)
The brushless motor control device according to claim 2 or 3, wherein when the phase to which the pulse voltage is applied is not switched over for a predetermined time, the execution frequency is reduced.
According to the above invention, when the brushless motor steps out and the brushless motor stops, it is not possible to detect the switching timing of the phase to which the pulse voltage is applied, and the state in which the frequency of performing the sensorless control process is increased is maintained. Therefore, when the phase to which the pulse voltage is applied is not switched over for a predetermined time, it is assumed that there is a possibility of step-out, and the execution frequency is reduced and the processing load of sensorless control is reduced. .

DESCRIPTION OF SYMBOLS 1 ... Electric oil pump, 2 ... Brushless motor, 3 ... Motor control apparatus, 212 ... Motor drive circuit, 213 ... Control unit, 213a ... A / D converter, 213b ... Microcomputer, 215u, 215v, 215w ... Winding, 216 ... Permanent magnet rotor, 217a to 217f ... Switching element

Claims (3)

A control device for a brushless motor that performs sensorless control for driving a brushless motor by switching a phase to which a pulse voltage according to a pulse width modulation signal is applied according to position information based on a pulse induced voltage induced in a non-energized phase. There,
A brushless motor control apparatus that changes a frequency of execution of the sensorless control process at a processing timing synchronized with an output period of the pulse width modulation.   The brushless motor control device according to claim 1, wherein the sensorless control processing frequency is increased as the timing at which the phase to which the pulse voltage is applied is switched is approached.   The brushless motor control device according to claim 2, wherein the execution frequency is increased based on at least one of an elapsed time after switching the phase to which the pulse voltage is applied and the pulse induced voltage.