JP4612458B2 - Driving method of brushless motor - Google Patents

Description

  The present invention relates to a method for driving a brushless motor, and more particularly to a method for driving a brushless motor in which a commutation timing of a stator can be optimally controlled by an energization method that drives without a sensor.

  For example, a compressor for compressing refrigerant in an in-vehicle air conditioner driven by power supplied from a battery (in addition to an electric compressor driven only by a motor, a built-in motor and other external drive source ( For example, it is known that a DC brushless motor is suitable as a drive motor or the like of a hybrid compressor configured to be drivable by both or one of the vehicle travel engines and the like.

In the energization method in which the brushless motor is driven without a sensor, for example, the induced voltage appearing in the non-energized section of the stator terminal voltage is filtered to detect the rotor position. If the motor does not rotate, no induced voltage is generated. Therefore, when starting, the stator is forcibly switched and the rotor is rotated to generate a sufficient induced voltage for position detection. The operation is switched (for example, Patent Documents 1 to 4).
Japanese Patent No. 3296636 JP-A-8-98581 JP-A-11-98884 JP-A-7-284290

  However, in the prior art as described above, if the energization switching timing and the position of the rotor are greatly deviated, the waveform after filtering is distorted, and an accurate position cannot be detected. In particular, at the time of start-up, forced energization switching is performed regardless of the detection of the position of the rotor, so that the energization switching timing and the position of the rotor are likely to deviate. As a result, accurate position detection cannot be performed and switching to sensorless operation cannot be performed.

  Therefore, an object of the present invention is to more appropriately determine the coincidence between the induced voltage (that is, the induced voltage corresponding to the position of the rotor) that appears in the non-energized section due to the rotation of the rotor and the commutation timing. An object of the present invention is to provide a driving method of a brushless motor that can be more appropriately operated without a sensor based on the determination.

In order to solve the above problems, the brushless motor driving method according to the present invention is such that when the brushless motor is driven sensorlessly, the terminal voltage appearing in the stator is filtered by the rotation of the rotor, and the commutation timing is determined to energize the brushless motor. In the driving method of the brushless motor, the terminal voltage in the non-energized section is sampled in synchronization with the PWM signal to determine whether the phase of the induced voltage that appears in the non-energized section and the commutation timing coincide with each other. After detecting the end of the spike voltage that appears at the beginning of the terminal, the terminal voltage or the difference between the power supply voltage and the terminal voltage is compared with the slope determination start threshold, and the difference between the terminal voltage or the power supply voltage and the terminal voltage is the slope determination start threshold. determined by detecting the inclination of the induced voltage appearing at least decrease count starts to non-conducting time zone of the terminal voltage when the phase is From the process commutates at the timing of the detected position of the rotor resulting from the filtering, when not coincident, wherein forced to commutation timing instruction rotational speed equivalent time to match the flow time Become. In the detection of the gradient of the induced voltage, more precisely, the direction of the gradient (for example, whether it rises to the right or falls to the right with respect to the time axis) is detected.

In this brushless motor driving method, the inclination is detected by sampling the terminal voltage in the non-energized period in synchronization with the PWM (pulse width modulation) signal and ending the spike voltage that appears at the beginning of the non-energized period. After the detection, the increase / decrease in the terminal voltage is counted to determine the inclination . The PWM control referred to here is a method in which a DC voltage from a DC power supply is applied to the motor via an inverter circuit in the motor control, and the DC voltage conduction rate is controlled by pulse width modulation.

In detecting the slope, after detecting the end of the spike voltage, the difference between the terminal voltage or the power supply voltage and the terminal voltage is compared with a predetermined slope determination start threshold, and the terminal voltage or the power supply voltage is compared. When the terminal voltage difference is equal to or greater than the inclination determination start threshold, the determination of the inclination is started . That is, when the voltage that appears first after the spike voltage ends has a certain level or more, that is, when the voltage is equal to or greater than the inclination determination start threshold, subsequent inclination detection and inclination determination are facilitated.

In the brushless motor driving method according to the present invention, it is preferable to employ the following method when starting the motor. In other words, when performing control to forcibly commutate at the start of the motor and then shift to sensorless operation, whether the energization phase of forced energization matches the phase of the induced voltage appearing in the non-energization interval Is detected by detecting the slope of the induced voltage appearing in the sensor, and if it is determined that the phases are matched one or more times, it is determined that the sensor-less rotor position detection obtained by filtering is correct, and forced commutation is performed. This is a method of switching to the sensorless operation when the timing of this and the timing of detecting the position of the rotor without the sensor match. As a result, the brushless motor can be driven more appropriately even when the motor is started.

  According to the driving method of the brushless motor according to the present invention, it becomes possible to easily and accurately detect whether the induced voltage appearing in the non-energized section due to the rotation of the rotor matches the commutation timing. It becomes possible to easily switch to the sensorless operation without causing any trouble. In addition, even when the motor is started, switching from forced commutation to sensorless operation can be performed at an appropriate timing.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a circuit diagram of a motor control device used in a brushless motor driving method according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a DC power source such as a battery, and a voltage is applied from the power source 1 to the motor control inverter circuit 3 via the power source smoothing capacitor 2. Each switching element U, V, W, X, Y, Z of the inverter circuit 3 is operated based on a signal from the inverter control circuit 5 based on a command from the main control circuit 4. From the inverter circuit 3, a voltage is applied to the brushless motor 6 (to the stator of the motor 6) in a three-phase form of U, V, and W phases, and the rotation of the brushless motor 6 is controlled.

  The waveform of the terminal voltage of the brushless motor 6 before filtering is as shown in FIG. 2, for example, for each of the U, V, and W phases. And in this invention, as shown, for example in FIGS. 3-5, the inclination of the induced voltage which appears in a non-energization area is detected. As shown in FIG. 3, for example, a spike voltage 14 is first generated in a non-energized section 13 when transitioning from an upper-phase energized section 11 to a lower-phase energized section 12, and when the spike voltage 14 ends, an induced voltage is generated. After increasing by a certain value (for example, after increasing by ΔV ≧ 20V), it decreases with a certain slope 15 and reaches the terminal voltage in the lower phase energizing section 12. When the transition from the lower phase energization section 12 to the upper phase energization section 11 occurs, a spike voltage is generated, and after the spike voltage is finished, the induced voltage is decreased by a certain value (for example, after being decreased by ΔV ≧ 20 V). It increases with a certain slope and reaches the terminal voltage in the upper-phase energization section 11. That is, as shown in FIG. No. 1 pattern and No. Two patterns of two patterns are presented.

  In detecting the slope of the induced voltage, after detecting the end of the spike voltage, the terminal voltage (that is, the induced voltage in the non-energized section) (corresponding to the No. 2 pattern) or the power supply voltage and the terminal voltage is detected. The difference (corresponding to the No. 1 pattern) is compared with a predetermined slope determination start threshold (for example, 20V), and when the difference between the terminal voltage or the power supply voltage and the terminal voltage is equal to or greater than the slope determination start threshold, It is preferable to start the determination of the inclination. For example, as shown in FIG. 4, when the ΔV is large, the number of induced voltage waveforms appearing in the non-energized section increases when detecting the gradient of the induced voltage with a pulse waveform as described later. Detection is easy and effective. On the other hand, when ΔV is small, the number of induced voltage waveforms appearing in the non-energized section is small, and it becomes difficult to detect the inclination, which is not effective.

  After detecting that the spike voltage has ended, ΔV is equal to or greater than an inclination determination start threshold (for example, 20 V), and after determining that the inclination of the induced voltage should be detected, the inclination is detected and determined. Is performed, for example, as shown in FIG. The terminal voltage (that is, the induced voltage in the non-energized period) is detected at a sampling point of 100 μsec, for example. Then, for example, every six voltage values are detected as V0 and V6, and the inclination counter is determined depending on whether V0-V6 is within a predetermined range, for example, whether it is within a range of -6V to 6V. Proceed. In other words, when it is within the range of −6V to 6V, the detected gradient is not counted as being too small, and when it is smaller than −6V or larger than 6V, as a tilt counter-1 or a tilt counter + 1, Perform the next count. In this way, counting up to the Nth time is performed, and it is determined whether the inclination is negative (inclination counter <0) (downward to the right in the illustrated example) or positive (inclination counter> 0) (upward to the right), It is assumed that the inclination determination is OK.

  The inclination detection / determination as described above is controlled by, for example, the flow shown in FIGS. In the flow shown in FIG. 6, an inclination determination flag is provided, and when the inclination determination flag is set, the flow of FIG. 7 is executed. In the flow shown in FIG. 1 pattern or No. It is determined whether there are two patterns, and Vc−Vp ≧ Va or Vp ≧ Va is determined according to each pattern (Vc: power supply voltage, Vp: terminal voltage, Va: slope determination start threshold), and each condition is satisfied Is set to the inclination determination start flag.

In the flow shown in FIG. 7, it is determined whether or not the thinned data as shown in FIG. 5 is accumulated. If the thinned data is accumulated, it is determined whether or not V0−Vm> Vb is satisfied. (Here, V0 is the latest terminal voltage, Vm is the terminal voltage with the oldest number of thinnings, and corresponds to V6 in FIG. 5, and Vb corresponds to 6V in FIG. 5). Further, it is determined whether or not V0−Vm> −Vb is satisfied, and the inclination counter is +1 or the inclination counter −1 depending on each case. At a timing after the inclination of the determination is performed, the direction by the inclination determination described above No. 1 pattern, no. It is determined which of the two patterns is No. In the case of one pattern, it is determined whether the inclination counter> 0 or not. In the case of two patterns, it is determined whether or not the inclination counter <0, and it is determined whether or not the inclination is a predetermined upward or downward inclination. If the inclination is determined to be a predetermined inclination, the counter is incremented by one as the inclination OK. If the inclination is not the predetermined inclination, the inclination OK counter is cleared. Eventually, the tilt counter is cleared in either case.

  Then, as shown in FIG. 8, a process for determining whether to shift to sensorless control is performed. For example, as shown in the figure, it is determined whether or not the inclination OK counter is 6 or more, and if it is determined that the inclination is 6 or more and a predetermined inclination or more, the forced commutation timing applied at the start and the above-described inclination detection are used. It is determined whether or not the rotor position detection timings coincide or approximately coincide with each other. If they coincide, the process proceeds to sensorless control. As described above, when the rotor position is accurately detected by detecting the gradient of the induced voltage, and the position detection timing and the commutation timing are surely coincident or approximately coincident with each other, the control is shifted to the sensorless control. It is possible to switch to the sensorless operation at the optimal timing without causing any trouble.

It is a circuit diagram of the motor control apparatus used for the drive method of the brushless motor which concerns on one embodiment of this invention. It is a wave form diagram which shows the example of the waveform of each phase of the brushless motor in the apparatus of FIG. It is explanatory drawing which shows the concept of the inclination detection of the induced voltage in this invention. It is explanatory drawing which shows the meaning which provides a threshold value in the inclination detection start of an induced voltage. It is explanatory drawing which shows an example of the inclination detection and determination method. It is a flowchart which shows an example of the inclination determination process control in this invention. It is a flowchart which shows an example of the control in case the inclination determination flag is set in the flow of FIG. It is a flowchart which shows an example of transfer determination processing control to sensorless control in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 DC power supply 2 Power supply smoothing capacitor 3 Inverter circuit 4 Main control circuit 5 Inverter control circuit 6 Brushless motor 11 Upper phase energization section 12 Lower phase energization section 13 No energization section 14 Spike voltage 15 Inclination

Claims (2)

When driving a brushless motor without a sensor, the terminal voltage that appears on the stator by the rotation of the rotor is filtered, and the method of driving the brushless motor that determines the commutation timing and energizes it. The terminal voltage in the non-energized section is sampled in synchronization with the PWM signal to determine whether the current timing matches , and the terminal voltage or power supply is detected after detecting the end of the spike voltage that appears at the beginning of the non-energized section. The difference between the voltage and the terminal voltage is compared with the slope judgment start threshold, and when the difference between the terminal voltage or the power supply voltage and the terminal voltage is equal to or greater than the slope judgment start threshold, the terminal voltage increase / decrease count is started and the induced voltage appears in the non-energized section It determined by detecting the inclination, position of the rotor resulting from the filtering process when the phase matches the commutation timing Commutated at a timing of detection, matching when not driving method of a brushless motor, wherein the forcibly be commutated at the timing of the instruction rotational speed equivalent. When performing control to forcibly commutate at the start of the motor and then shift to sensorless operation, whether the energized phase of forced energization matches the phase of the induced voltage that appears in the non-energized zone appears in the non-energized zone If it is determined by detecting the gradient of the induced voltage, and if it is determined that the phases are matched one or more times, it is determined that the sensor-less rotor position detection obtained by filtering is correct, and the forced commutation timing is determined. and When the timing of the position detection of the rotor in sensorless matches, and wherein the switching to sensorless operation, brushless motor driving method according to claim 1.

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