JP3402161B2 - Brushless DC motor control method and device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless DC motor control method and apparatus, and more particularly, to a brushless DC motor by applying an output voltage of each phase of an inverter to a stator winding of each phase of a brushless DC motor. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for controlling a DC motor and driving a load in which a load applied to an output shaft fluctuates cyclically during one rotation.

[0002]

2. Description of the Related Art As a motor having a higher efficiency than an AC motor, by installing a permanent magnet in the rotor instead of the rotor winding, a secondary copper loss caused by a current flowing through the rotor winding. There is known a brushless DC motor that eliminates the above. It is known that this brushless DC motor has a particularly large efficiency improvement effect in the small and medium capacity range of several tens kW or less as compared with the AC motor.

Focusing on this advantage, it has been proposed or put into practical use to drive various loads by a brushless DC motor. Of these, when a compressor is used as the load, torque control technology can be applied to suppress speed fluctuations of the compressor and reduce vibrations due to speed fluctuations. Here, in the torque control, as is conventionally known, the magnetic pole position of the rotor of the brushless DC motor is detected, the inverter is controlled based on the magnetic pole position detection signal, and the output voltage of each phase of the inverter is brushless. The control is to obtain a desired generated torque by applying to the stator winding of each phase of the DC motor. Also,
The magnetic pole position of the rotor can be detected based on the terminal voltage of the motor, the neutral point voltage, and the like, and can also be detected using a sensor such as a Hall element. However, for cost-oriented applications such as home appliances, it is not necessary to provide a special sensor to detect the magnetic pole position. It is necessary to adopt a configuration based on the motor terminal voltage, neutral point voltage, etc. Is preferred.

Therefore, by adopting the above-mentioned configuration, it is considered that the compressor can be driven with a low-cost system configuration while suppressing the speed fluctuation and reducing the vibration caused by the speed fluctuation.

[0005]

However, as described above, the torque control technique is applied to suppress the speed fluctuation of the compressor and to reduce the vibration due to the speed fluctuation, and the brushless method is also adopted. A one-cylinder compressor is adopted which detects the magnetic pole position of the rotor of the DC motor based on the terminal voltage of the motor, the neutral point voltage, and the like, and has less loss due to unnecessary gas leakage during the compression process. In this case, it becomes impossible to detect the magnetic pole position of the rotor during the period when the load torque is large (the period when the motor current increases) during one rotation of the compressor. In the worst case, the compressor is driven. There is an inconvenience that it becomes impossible to do.

This inconvenience can be generally avoided by appropriately selecting the design constant of the brushless DC motor. In such a case, however, the amount of iron core, copper wire, magnet, etc. constituting the brushless DC motor can be reduced. There is a new inconvenience that the number of brushless DC motors increases (for example, the size of the brushless DC motor becomes large or the inductance becomes small), and the cost of the brushless DC motor increases.

This inconvenience occurs not only when a one-cylinder compressor is used as a load, but also when a load with a large torque fluctuation is used. FIG. 14 shows a system configuration for driving a brushless DC motor without a position sensor. In this configuration, the conduction period of each phase transistor of the inverter circuit connected to the brushless DC motor is set to 120 °, the speed electromotive voltage of the brushless DC motor appearing in the terminal voltage during the remaining 60 ° period in which the open state is maintained is detected, and the zero cross comparator is detected. To obtain the position signal.

However, even if the transistor is turned off, the current is not immediately cut off due to the inductance of the motor winding,
Motor current continues to flow through the diode connected in parallel with the transistor (see waveform diagram in FIG. 15). This time toff is, if the initial current when the transistor is turned off is I0, the speed electromotive voltage of the brushless DC motor is E0, the DC voltage of the inverter is Vdc, and the winding inductance of each phase is L, then toff = I0.2・ It can be approximated to L / (Vdc + E0). That is, it can be seen that the diode current is cut off in proportion to the initial current I0 when the transistor is off, and the time until the motor terminal is opened becomes longer.

FIG. 16 shows a one-cylinder compressor with a brushless D
The waveform of each part when torque control is driven by the C motor is shown. As can be seen from this figure, when the torque control for controlling the motor torque (motor current) according to the load torque fluctuation is performed by the brushless DC motor drive system of FIG. 14, the motor current becomes large near the peak of the load torque, and When the initial current I0 in the equation becomes a predetermined value or more, to
Although ff becomes long and is within the allowable operating range of the motor (the motor torque is sufficient), the current cannot be cut off, so that the speed electromotive voltage cannot be detected and the brushless DC motor cannot be operated.

FIG. 17 shows another system configuration for driving a brushless DC motor without a position sensor. In this configuration, the voltage difference between the neutral point potential of the motor and the neutral point potential of the resistor Y-connected to the inverter output terminal is passed through the integrator and binarized by the zero-cross comparator to output the position detection signal. As a result, the position can be detected even if the motor current is continuous (even if the motor current is not cut off) (see Republication 7-827328). Therefore, in FIG.
As in the system configuration of
Although the inconvenience of not being able to detect the position can be prevented in advance, as a result of the experiment, as shown in FIG.
When the motor current increases as the load increases, a beat phenomenon occurs in the integrated signal (“PM Brushless”).
Motor Drives: A Self-Com
mutating System without R
otor-Position Sensors ",
P. Ferraris et al., Ninth Annua
l Symposium-Incremental M
motion Control System and
Devices, pp. 305-312, 1980
See, this seems to be because the impedance of each phase of the brushless DC motor does not necessarily match in the actual machine. ), A malfunction of position detection (zero-cross detection error) is caused, and it is found that there is a problem that the brushless DC motor is stalled.

As described above, when the torque control is performed by the brushless DC motor using the simple position detection circuit using the motor terminal voltage, the torque output range originally allowed by the brushless DC motor is restricted due to the restriction of the position detection. However, there is an inconvenience that the operating range becomes narrow.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is intended to detect a magnetic pole position of a rotor without using a sensor and to drive a load having a large torque fluctuation. Another object of the present invention is to provide a brushless DC motor control method and device capable of driving a load without any inconvenience.

[0013]

A brushless D according to claim 1.
In the C motor control method, the output terminal of each phase of the inverter is connected to the stator winding of each phase of the brushless DC motor to control the brushless DC motor, and the load applied to the output shaft during one rotation has a periodicity. When driving a fluctuating load, the drive period of the load is divided based on the magnitude of the load torque based on a predetermined threshold value. In the small load torque, the terminal voltage of the brushless DC motor is set. The magnetic pole position of the rotor is detected based on the magnetic pole position detection signal, and the inverter is controlled to set the output voltage waveform or the output current waveform to be applied to the brushless DC motor based on the magnetic pole position detection signal. A pseudo magnetic pole position signal is generated based on the cycle of the magnetic pole position detection signal, and an output voltage waveform or a waveform to be applied to the brushless DC motor is generated based on the pseudo magnetic pole position signal. A method for controlling the inverter so as to set the output current waveform.

A brushless DC motor control method according to a second aspect of the present invention is a method of detecting the magnetic pole position of the rotor by using the phase voltage of the brushless DC motor. The brushless DC motor control method according to claim 3, wherein one terminal is connected to the neutral point voltage of the stator winding of the brushless DC motor and the output terminal of each phase of the brushless DC motor to detect the magnetic pole position of the rotor. And the difference voltage from the neutral point voltage obtained by the resistors having the other terminals connected to each other.

According to another aspect of the brushless DC motor control device of the present invention, the output terminals of each phase of the inverter are connected to the stator windings of each phase of the brushless DC motor to control the brushless DC motor, and the output shaft is rotated during one rotation. The load applied to drive a fluctuating load with a periodicity, and the load torque is divided into a drive unit and a drive unit that divides the drive period of the load based on the magnitude of the load torque based on a predetermined threshold. In a small section, the magnetic pole position of the rotor is detected based on the terminal voltage of the brushless DC motor, and the inverter is used to set the output voltage waveform or the output current waveform to be applied to the brushless DC motor based on the magnetic pole position detection signal. First to control
In the control means and in the section where the load torque is large, a pseudo magnetic pole position signal is generated based on the cycle of the magnetic pole position detection signal, and an output voltage waveform or an output current to be applied to the brushless DC motor based on the pseudo magnetic pole position signal. Second control means for controlling the inverter to set the waveform.

The brushless DC motor control device according to a fifth aspect of the present invention employs, as the first control means, one for detecting the magnetic pole position of the rotor by using the phase voltage of the brushless DC motor. The brushless DC motor control device according to claim 6 detects, as the first control means, the magnetic pole position of the rotor by detecting the neutral point voltage of the stator winding of the brushless DC motor and the output terminals of each phase of the brushless DC motor. One of the terminals is connected to the other terminal, and the other terminal is connected to each other.

[0017]

According to the brushless DC motor control method of the first aspect, the output terminals of each phase of the inverter are connected to the stator windings of each phase of the brushless DC motor to control the brushless DC motor, and the brushless DC motor is controlled during one rotation. When driving a load in which the load applied to the output shaft fluctuates with periodicity, the drive period of the load is classified based on the magnitude of the load torque based on a predetermined threshold, and the load torque is small. , The magnetic pole position of the rotor is detected based on the terminal voltage of the brushless DC motor, and the brushless D is detected based on the magnetic pole position detection signal.
The inverter is controlled to set an output voltage waveform or an output current waveform to be applied to the C motor, and in a section where the load torque is large, a pseudo magnetic pole position signal is generated based on the cycle of the magnetic pole position detection signal. Since the inverter is controlled to set the output voltage waveform or output current waveform to be applied to the brushless DC motor based on the position signal, it is possible to reliably detect the magnetic pole position detection signal due to torque fluctuation. Even if there is, a pseudo magnetic pole position signal can be generated to control the output voltage waveform or the output current waveform of the inverter, and as a result, the load applied to the output shaft during one rotation surely drives the load that varies in the same pattern. be able to.

According to the brushless DC motor control method of the second aspect, since the magnetic pole position of the rotor is detected by using the phase voltage of the brushless DC motor, in addition to the same operation as the first aspect, the rotor is also added. The detection of the magnetic pole position can be easily achieved. According to the brushless DC motor control method of claim 3, for detecting the magnetic pole position of the rotor, one terminal is used as the neutral point voltage of the stator winding of the brushless DC motor and the output terminal of each phase of the brushless DC motor. Is connected,
And since it is performed by using the voltage difference between the other terminal and the neutral point voltage obtained by the resistors connected to each other, in addition to the same operation as in claim 1, the rotor current is maintained even when the motor current is continuous. Detection of the magnetic pole position of the can be achieved.

According to another aspect of the brushless DC motor control device of the present invention, the output terminals for each phase of the inverter are brushless D.
Brushless DC by connecting to the stator winding of each phase of the C motor
When the motor is controlled to drive a load in which the load applied to the output shaft fluctuates with a periodicity during one rotation, the load drive torque is divided by the dividing means with the drive period of the load based on a predetermined threshold value. In the classification in which the load torque is small, the first control means detects the magnetic pole position of the rotor based on the terminal voltage of the brushless DC motor and the brushless DC motor based on the magnetic pole position detection signal. The inverter is controlled so as to set an output voltage waveform or an output current waveform to be applied to, and in a section where the load torque is large, the second control means generates a pseudo magnetic pole position signal based on the cycle of the magnetic pole position detection signal. Then, the inverter is controlled to set the output voltage waveform or the output current waveform to be applied to the brushless DC motor based on the pseudo magnetic pole position signal.

Therefore, even if the magnetic pole position detection signal cannot be reliably detected due to torque fluctuation, the output voltage waveform or output current waveform of the inverter can be controlled by generating the pseudo magnetic pole position signal. Therefore, it is possible to reliably drive the load in which the load applied to the output shaft fluctuates in the same pattern during one rotation. According to the brushless DC motor control device of the fifth aspect, the first control means employs a device for detecting the magnetic pole position of the rotor by using the phase voltage of the brushless DC motor. In addition to the operation similar to, detection of the magnetic pole position of the rotor can be achieved with a simple configuration.

According to another aspect of the brushless DC motor control device of the present invention, the first control means detects the magnetic pole position of the rotor by detecting the neutral point voltage of the stator winding of the brushless DC motor and the brushless DC motor. One of the terminals is connected to the output terminals of each phase, and the other terminal is connected to each other is adopted by using the voltage difference with the neutral point voltage obtained by the resistor is connected, In addition to the effect similar to that of 4, the detection of the magnetic pole position of the rotor can be achieved even when the motor current is continuous.

Further description will be made. As shown in FIGS. 16 and 18, when the pulsating load is driven by the torque control motor, (1) the load torque and the motor current are small for a predetermined period during one rotation.
Position detection can be reliably performed in any of the systems shown in FIG. 17, and (2) Further, if torque control is performed, the operation can be performed with a small fluctuation in rotation speed (constant speed operation). Focusing on the fact that the rotation position of the rotor can be predicted, one rotation of the brushless DC motor is divided into large and small load torques by a predetermined threshold value, and the position signal is detected during the period when the load torque is small. The present invention has been completed by performing speed calculation based on a signal, predicting the rotational position of the rotor during a period when the load torque is large, and controlling the brushless DC motor.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing an embodiment of the brushless DC motor drive device of the present invention, in which the output voltage of the inverter 2 is used as a load in which the load applied to the output shaft fluctuates cyclically during one rotation. The voltage is applied to the brushless DC motor 3 that drives the compressor 6. Then, a first neutral point obtained by Y-connecting a resistor between the second neutral point voltage obtained by Y-connecting the stator windings of each phase of the brushless DC motor 3 and the output terminal of each phase of the inverter 2. An output signal from the motor position detection circuit 4, which receives the difference voltage from the neutral point voltage, is supplied to the control circuit 5, and the control circuit 5 controls the electrical energization width to be, for example,
A control command is generated and supplied to the inverter 2 so as to have a predetermined width of more than 120 ° and 180 ° or less. In addition, “having periodicity” means that the basic waveform does not change, for example, although the waveform itself and the amplitude of the second neutral point voltage, the difference voltage, and the like change due to the load. To do.

Therefore, the motor position detection circuit 4 obtains the magnetic pole position detection signal of the motor rotor based on the difference voltage between the neutral point voltages, and the control circuit 5 generates the control command based on the magnetic pole position detection signal. Set the switch (not shown) of the inverter 2 to, for example, over 120 ° and 180 °
Control is performed so that the following predetermined energization width is achieved. FIG. 2 is a diagram schematically showing the structure of a brushless DC motor having a surface magnet structure, in which a permanent magnet 3b is mounted at a predetermined position on the surface of the rotor 3a. Further, the stator 3c has a large number of slots 3d around which a stator winding (not shown) is wound.
The d-axis indicated by the arrow in the figure is an axis that indicates the direction of the magnetic flux generated by the permanent magnet 3b, and the q-axis is an axis that is electrically deviated from the d-axis by 90 °.

FIG. 3 is a diagram schematically showing the structure of a brushless DC motor having an embedded magnet structure, in which a permanent magnet 3f is mounted on the surface of the rotor 3e so as not to be exposed. However, the non-magnetic body 3g is mounted between the adjacent permanent magnets 3f to prevent a magnetic flux short circuit between the adjacent permanent magnets 3f. Since the structure of the stator 3c is the same as that of the brushless DC motor of FIG. 2, the description will be omitted.

FIG. 4 is a diagram schematically showing the configuration of the brushless DC motor driving device, and FIG. 5 is a diagram showing the internal configuration of the microprocessor 18 of FIG. 4, in which three pairs of switching transistors are provided between the terminals of the DC power supply 11. 12u1, 12u
2, 12v1, 12v2, 12w1, 12w2 are respectively connected in series to configure the inverter 12, and the Y-connected phases of the brushless DC motor 13 that drives the compressor 6 with the connection point voltage between the switching transistors of each pair. Is applied to each of the stator windings 13u, 13v, and 13w. Then, the resistors 14u, 14v, 14w, which are Y-connected to the connection point voltage between the switching transistors of each pair,
Is also applied to each. The switching transistors 12u1, 12u2, 12v1, 12v2, 12w
Protective diodes 12u1d, 12u2d, 12v1 between collector and emitter terminals of 1 and 12w2, respectively.
d, 12v2d, 12w1d, 12w2d are connected. Further, 13e indicates a rotor of the brushless DC motor 13. Further, the subscripts u, v, w correspond to the u phase, v phase, and w phase of the brushless DC motor 13, respectively.

The above Y-connected stator windings 13u, 13
The voltage at the neutral point 13d of v and 13w is supplied to the inverting input terminal of the amplifier 15 via the resistor 15a, and the voltage at the neutral point 14d of the Y-connected resistors 14u, 14v, and 14w is the non-inverted state of the amplifier 15 as it is. It is supplied to the input terminal. The resistor 15b is connected between the output terminal and the inverting input terminal of the amplifier 15 so that the amplifier 15 operates as a differential amplifier.

The output signal output from the output terminal of the amplifier 15 is supplied to the integrator 16 in which the resistor 16a and the capacitor 16b are connected in series. The output signal from the integrator 16 (the voltage at the connection point between the resistor 16a and the capacitor 16b) is supplied to the non-inverting input terminal of the zero-cross comparator 17 whose voltage at the neutral point 13d is supplied to the inverting input terminal.

Therefore, the zero cross comparator 17
A magnetic pole position detection signal is output from the output terminal of. In other words, the differential amplifier, the integrator 16, and the zero-cross comparator 17 constitute a magnetic pole position detector that detects the magnetic pole position of the rotor 13e of the brushless DC motor 13. Further, the voltage commands for the three phases output from the microprocessor 18 are supplied to the base drive circuit 20, which generates a switch command and supplies the switch command to the inverter 12.

The magnetic pole position detection signal output from the magnetic pole position detector is supplied to the external interrupt terminal of the microprocessor 18. The microprocessor 18 uses the magnetic pole position detection signal supplied to the external interrupt terminal to interrupt the phase correction timer 18a, the cycle measurement timer 18b, and the compensation voltage amplitude mode selection unit 19g (interrupt processing 1 in FIG. See). Here, the phase correction timer 18a
, The timer value is set by the timer value calculator 19a described later. The cycle measuring timer 18b measures the cycle of the magnetic pole position detection signal to obtain a timer value, and the timer value is stored in the CPU.
It is supplied to the position signal cycle calculator 19b included in 19.
The position signal cycle calculator 19b is used by the cycle measurement timer 18
In response to the timer value from b, the stator windings 13u, 13u
The cycle of the voltage patterns of v and 13w is calculated, and the position signal cycle signal indicating the cycle is output. Phase correction timer 18a
Supplies a count-over signal to the inverter mode selection unit 19c included in the CPU 19 to perform an interrupt process (see FIG. 5).
(See middle and interrupt processing 2). Further, the phase correction timer 18a supplies a count-over signal to the energization width control timer 18f to start the timer operation of the energization width control timer 18f. This energization width control timer 18f is set with a timer value by a timer value calculator 19a described later. The energization width control timer 18f also supplies a countover signal to the inverter mode selection unit 19c included in the CPU 19 to perform an interrupt process (see interrupt process 3 in FIG. 5). The inverter mode selection unit 19c reads out the corresponding voltage pattern from the memory 18c and outputs it. In the CPU 19, the position signal cycle calculator 19b
Performs a calculation based on the timer value to output a position signal cycle signal, and the timer value calculation unit 19a and the speed calculation unit 19
e and the period storage table 19k. The phase amount command is also supplied to the timer value calculation unit 19a, and the timer value to be set in the phase correction timer 18a is calculated based on the phase amount command and the position signal cycle signal from the position signal cycle calculation unit 19b. The speed calculator 19e calculates the current speed based on the position signal cycle signal from the position signal cycle calculator 19b, and the speed controller 19f and the coefficient generator 19
supply to i. The coefficient generation unit 19i includes a speed calculation unit 19e.
A predetermined coefficient (0
Output a value of ~ 1). A speed command is also supplied to the speed control unit 19f, and the speed command and speed calculation unit 19e is also supplied.
The average voltage amplitude is output based on the current speed from. The average voltage amplitude, the coefficient output from the coefficient generation unit 19i, and the pattern output from the compensation voltage amplitude mode selection unit 19g are supplied to the multiplier 19j, and the compensation voltage amplitude pattern is output. Then, the average voltage amplitude output from the speed controller 19f and the compensation voltage amplitude pattern output from the multiplier 19j are supplied to the adder 19h, and the sum of the two is output as a voltage command. Then, the voltage pattern output from the inverter mode selection unit 19c and the voltage command output from the adder 19h are supplied to the PWM (pulse width modulation) unit 18d, and the voltage commands for three phases are output. This voltage command is supplied to the base drive circuit 20, and the base drive circuit 20 causes the switching transistor 1 to operate.
2u1, 12u2, 12v1, 12v2, 12w1, 1
It outputs a control signal to be supplied to each base terminal of 2w2.

The previous speed stored in the cycle storage table 19k is supplied to the next position calculating unit 19m, and the next position (timer value corresponding to the next magnetic pole position) is calculated and output. The calculated timer value is supplied to the pseudo position signal generation timer 19n, which generates a pseudo position signal corresponding to the count-over and supplies it to the switching determination unit 19p. The magnetic pole position detection signal supplied to the external interrupt terminal is also supplied to the switching determination unit 19p, and the phase correction timer 1 is selected by selecting the pseudo position signal or the magnetic pole position detection signal.
8a, the period measurement timer 18b. The switching determination unit 19p increments the index iPOS every time the position signal period signal from the position signal period calculation unit 19b is supplied to the period storage table 19k, and selects the pseudo position signal according to the value of the index iPOS. , Or whether to select the magnetic pole position detection signal.

In the above description, the constituent parts included in the CPU 19 only show the functional parts for achieving the corresponding functions as constituent parts.
These components do not exist in a clearly identifiable manner inside the. 6 to 9 are flowcharts for explaining the processing of the microprocessor 18. 6 and 7 illustrate the interrupt processing 1, FIG. 8 illustrates the interrupt processing 2, and FIG. 9 illustrates the interrupt processing 3.

FIGS. 6 and 7 are flowcharts for explaining the processing contents of the interrupt processing 1, and the switching determination unit 19
It is performed every time an interrupt signal is output from p. In step SP1, the cycle measuring timer 18b is stopped, in step SP2, the timer value of the cycle measuring timer 18b is read, and in step SP3, the cycle measuring timer 18b is immediately reset and started for the next cycle measurement. .

In step SP4, the cycle of the position signal is calculated based on the read timer value (for example, calculation of the number of counts per 1 ° of electrical angle), and step SP
In 5, the position signal cycle is stored in the cycle storage table using the signal iPOS output from the switching determination unit 19p as an index, and in step SP6, for example, 0 is stored.
Index iP held in the ring counter of ~ 11
The OS is incremented, and in step SP7 it is determined whether the index iPOS is equal to the constant n1. Then, if the index iPOS is equal to the constant n1, a flag indicating that the pseudo position signal should be used in step SP8 (pseudo position signal use flag).
Is set to "1", and in step SP9, a timer value for generating a pseudo position signal (pseudo position signal generation timer value) is calculated from the values of the cycle storage tables n1 and n2.

In step SP7, the index iP
If it is determined that the OS is not equal to the constant n1, or if the process of step SP9 is performed, step S
In P10, it is determined whether the index iPOS is equal to the constant n2. And index iPOS
Is equal to the constant n2, the pseudo position signal use flag is set to "0" in step SP11.

In step SP10, the index i
If it is determined that POS is not equal to the constant n2, or if the process of step SP11 is performed, the pseudo position signal use flag is set to "1" in step SP12.
Or not. When the pseudo position signal use flag is "1", in step SP13,
The switching determination unit 19p is controlled to prohibit the external interruption, the timer value is set in the pseudo position signal generation timer 19n in step SP14, the interruption by the pseudo position signal generation timer 19n is permitted in step SP15, and the step SP16 is performed. , The pseudo position signal generation timer 19n is started.

On the contrary, if it is determined in step SP12 that the pseudo position signal use flag is not "1",
In step SP17, the pseudo position signal generation timer 1
9n is stopped, the interruption by the pseudo position signal generation timer 19n is prohibited in step SP18, and the external interruption is permitted in step SP19. When the processing of step SP16 or the processing of step SP19 is performed, based on the phase signal (phase correction angle) command from the outside and the position signal cycle signal obtained by the position signal cycle calculator 19b in step SP20. Calculating the correction timer value to be set in the phase correction timer 18a, and in step SP21, the phase correction timer 18a
The correction timer value is set to and the phase correction timer 18a is started in step SP22.

Specifically, for example, the period measuring timer 18
If the count value corresponding to the interval of the magnetic pole position detection signals is 360, the inverter output voltage 1
The count value of the cycle is 360 × 6 = 2160 because the number of rising edges and falling edges of the position detection signal is 6. Since this value 2160 corresponds to 360 °, the count value for 1 ° is 2160/360 = 6. Here, if the phase amount command is 30 °, the count value (timer value) corresponding to the phase amount command is 6 × (60-3
0) = 180. Therefore, this value 180 is set in the phase correction timer 18a as a correction timer value, and the phase correction timer 18a is started.

Then, in step SP23, the current rotation speed of the brushless DC motor is calculated from the position signal cycle calculation result, in step SP24, the pattern is read based on the compensation voltage amplitude mode, and in step S24.
In P25, the compensation voltage amplitude pattern mode is advanced by one step, in step SP26, speed control is performed based on the speed command, the average voltage amplitude command is calculated, and in step SP27, the coefficient is read based on the current speed, and in step SP28. , The pattern is multiplied by the coefficient times the average voltage amplitude to calculate the compensation voltage,
In P29, the compensation voltage is added to the average voltage amplitude and output, and the process returns to the original process.

Therefore, for example, taking the time chart shown in FIG. 10 as an example, the constant n1 is 3 and the constant n2 is 11.
If it is, the index i shown in FIG.
When the POS is in the range of 3 or more and less than 11, the timer value of the pseudo position signal generation timer 19n changes as shown in FIG. 10B, and during this period, the pseudo position signal is generated every time the pseudo position signal generation timer 19n counts over. An interrupt based on is generated. On the contrary, if the index iPOS is out of the above range, the magnetic pole position detection signal is selected as shown in FIG. 10A, and an interrupt is generated at the rising and falling edges of each magnetic pole position detection signal. The both interrupts are as shown in FIG. Also,
The constants n1 and n2 determine which index iPOS should switch both interrupts when the brushless DC motor 13 is actually installed.
By setting the index iPOS determined in this way in the switching determination unit 19p, the interrupt process based on the magnetic pole position detection signal and the interrupt process based on the pseudo position signal are selected, and the brushless DC motor 13 is inconvenient. Can be operated without. Of course, instead of adopting the pseudo position signal, the structure required for detecting the magnetic pole position in these periods is also complicated (because noise is mixed in the third harmonic detected in the steep current portion,
This noise can be eliminated to eliminate the complication of the configuration for accurately detecting the third harmonic, and the configuration for torque control can be simplified as a whole.

FIG. 8 is a flow chart for explaining the processing contents of the interrupt processing 2 in detail. When the phase correction timer 18a started in the interrupt processing 1 counts over, the interrupt processing 2 is accepted. In step SP1, the inverter mode set in advance in the memory 18c is advanced by one step, in step SP2 a voltage pattern corresponding to the advanced inverter mode is output, and in step SP3 the position signal cycle (energization width command) to the energization width Calculate the timer value of the control timer 18f,
In step SP4, the timer value obtained by the calculation is set in the energization width control timer 18f, the energization width control timer 18f is started in step SP5, and the process returns to the original processing.

FIG. 9 is a flow chart for explaining the processing contents of the interrupt processing 3 in detail, and the interrupt processing 3 is accepted when the energization width control timer 18f started in the interrupt processing 2 counts over. Step SP1
At step SP2, the inverter mode preset in the memory 18c is advanced by one step. At step SP2, the voltage pattern corresponding to the advanced inverter mode is output, and the process directly returns to the original process.

Therefore, the inverter mode is set to, for example, "4", "6", "8" ... "10" by the interrupt processing 2.
"0", "2", "4" ... are selected in order, and interrupt processing 3
Depending on the inverter mode, for example, "3""5""7"
... "11", "1", "3" ... are selected in this order.
Since the interrupt processing 2 and the interrupt processing 3 occur alternately, the inverter mode is "3", "4", "5" ...
“11” “0” “1” “2” “3” ... As a result, the torque control operation of the brushless DC motor 13 can be performed to drive the compressor 6.

FIG. 11 shows the u-phase current when the brushless DC motor 13 is controlled by using the magnetic pole position detection signal and the pseudo position signal {(A) in FIG. 11} and the pseudo position signal use flag {(in FIG. 11 ( B)}, an integrated signal {(C) in FIG. 11}, and FIG. 12 shows the u-phase current when the brushless DC motor 13 is controlled using only the magnetic pole position detection signal {(A) in FIG. 12). }, Pseudo position signal use flag {(B) in FIG. 12}, integrated signal {(C) in FIG. 12}
FIG.

Referring to FIG. 11, since the magnetic pole position detection signal is used only when the u-phase current is small and the pseudo position signal is used when the u-phase current is large, the magnetic pole position detection signal is used when the u-phase current is large. It can be seen that the brushless DC motor 13 can be stably controlled, although it may not be accurately detected. On the other hand, referring to FIG. 12, when the u-phase current is large, the disturbance of the u-phase current is large due to the fact that the magnetic pole position detection signal cannot be accurately detected, and the state immediately before the brushless DC motor 13 stops. It turns out that

Therefore, by adopting the above-described embodiment, the brushless DC motor 13 can be stably controlled regardless of whether or not the magnetic pole position detection signal can be accurately detected. In the above embodiment, the stator windings 13u, 1
The magnetic pole position is detected based on the voltage of the neutral point 13d of 3v and 13w and the voltage of the neutral point 14d of the Y-connected resistors 14u, 14v and 14w, but as shown in FIG. The integrator circuit 16 'is connected to each phase terminal of the brushless DC motor, and the output voltage from the integrator circuit 16' is supplied to the zero-cross comparator 17 'to obtain a magnetic pole position detection signal whose level is inverted at each zero-cross. You may When this configuration is adopted, since the motor induced voltage is detected during the current off period, the brushless DC motor 13 is operated by using the pseudo position signal during the period when the motor current becomes large and the current cannot be cut off. It can be controlled stably.

[0047]

According to the first aspect of the present invention, even if the magnetic pole position detection signal cannot be reliably detected due to torque fluctuation, the pseudo magnetic pole position signal is generated to output the output voltage waveform or output of the inverter. It is possible to control the current waveform, and thus it is possible to reliably drive a load in which the load applied to the output shaft changes in the same pattern during one rotation.

The invention of claim 2 has a unique effect that the detection of the magnetic pole position of the rotor can be easily achieved in addition to the effect of claim 1. According to the invention of claim 3, in addition to the effect similar to that of claim 1, there is a unique effect that the detection of the magnetic pole position of the rotor can be achieved even when the motor current is continuous.

According to the fourth aspect of the present invention, even if the magnetic pole position detection signal cannot be reliably detected due to the torque fluctuation, the pseudo magnetic pole position signal is generated to output the output voltage waveform or the output current waveform of the inverter. Can be controlled
As a result, it is possible to reliably drive the load in which the load applied to the output shaft changes in the same pattern during one rotation.

In addition to the same effect as the fourth aspect, the invention of the fifth aspect has a unique effect that the detection of the magnetic pole position of the rotor can be achieved with a simple structure. The invention of claim 6 has a unique effect that the detection of the magnetic pole position of the rotor can be achieved even when the motor current is continuous, in addition to the effect similar to that of claim 4.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of a brushless DC motor drive device of the present invention.

FIG. 2 is a diagram schematically showing a configuration of a brushless DC motor having a surface magnet structure.

FIG. 3 is a diagram schematically showing a configuration of a brushless DC motor having an embedded magnet structure.

FIG. 4 is a diagram schematically showing an example of the configuration of a brushless DC motor drive device.

5 is a diagram showing an internal configuration of the microprocessor of FIG.

FIG. 6 is a flowchart illustrating a part of interrupt processing 1.

FIG. 7 is a flowchart illustrating the remaining part of interrupt processing 1.

FIG. 8 is a flowchart illustrating interrupt processing 2.

FIG. 9 is a flowchart illustrating interrupt processing 3.

FIG. 10 is a time chart illustrating interrupt processing 1.

FIG. 11 u in the case where a brushless DC motor is controlled using a magnetic pole position detection signal and a pseudo position signal
It is a figure which shows a phase current, a pseudo position signal use flag, and an integral signal.

FIG. 12: Brushless D using only magnetic pole position detection signals
It is a figure which shows the u-phase current and the integrated signal when controlling a C motor.

FIG. 13 is a diagram schematically showing another example of the configuration of the brushless DC motor drive device.

FIG. 14 is an electric circuit diagram showing an example of a conventional brushless DC motor drive device.

15 is a waveform diagram showing a motor current, a detected voltage, an integrator output, and a position detection signal in the brushless DC motor drive device of FIG.

FIG. 16 is a diagram showing changes in load torque and motor current during one rotation.

FIG. 17 is an electric circuit diagram showing another example of a conventional brushless DC motor drive device.

FIG. 18 is a waveform diagram showing motor current and integrator output during torque control operation.

[Description of Reference Signs] 6 compressor 12 inverter 13 brushless DC motor 13e rotors 13u, 13v, 13w stator windings 14u, 14
v, 14w resistor 15 differential amplifier 16, 16 'integrator 17, 17' zero cross comparator 18 microprocessor 19p switching determination unit

─────────────────────────────────────────────────── --- Continuation of front page (56) Reference JP-A-7-322679 (JP, A) JP-A-8-237987 (JP, A) JP-A-9-182485 (JP, A) JP-A-8- 163888 (JP, A) International publication 95/027328 (WO, A1) (58) Fields investigated (Int.Cl. ⁷ , DB name) H02P 6/18

Claims (6)

(57) [Claims] 1. An output terminal of each phase of an inverter (12) is connected to a stator winding (1) of each phase of a brushless DC motor (13).
3u) (13v) (13w) connect to brushless DC
A method of controlling a motor (13) to drive a load (6) in which a load applied to an output shaft fluctuates with a periodicity during one rotation, wherein a drive period of the load is based on a predetermined threshold value. Based on the magnitude of the load torque to be applied, in the low load torque category, the magnetic pole position of the rotor (13e) is detected based on the terminal voltage of the brushless DC motor (13), and based on the magnetic pole position detection signal. The inverter (12) is controlled to set an output voltage waveform or an output current waveform to be applied to the brushless DC motor (13), and in a section where the load torque is large, the pseudo magnetic pole position is determined based on the cycle of the magnetic pole position detection signal. Brushless DC motor (13) that generates a signal and is based on the pseudo magnetic pole position signal
A method for controlling a brushless DC motor, comprising controlling an inverter (12) to set an output voltage waveform or an output current waveform to be applied to the inverter. 2. The brushless DC motor control method according to claim 1, wherein the magnetic pole position of the rotor (13e) is detected by using the phase voltage of the brushless DC motor (13). 3. A stator winding (13u) of a brushless DC motor (13) for detecting a magnetic pole position of a rotor (13e).
(13v) (13w) neutral voltage and brushless DC
A resistor (14u) having one terminal connected to the output terminal of each phase of the motor (13) and the other terminal connected to each other.
The brushless DC motor control method according to claim 1, wherein the brushless DC motor control method is performed by using a voltage difference from the neutral point voltage obtained by (14v) and (14w). 4. An output terminal of each phase of the inverter (12) is connected to a stator winding (1) of each phase of the brushless DC motor (13).
3u) (13v) (13w) connect to brushless DC
A device for controlling a motor (13) to drive a load (6) in which a load applied to an output shaft fluctuates with a periodicity during one rotation, wherein a drive period of the load is based on a predetermined threshold value. The classification means (19p) for classifying based on the magnitude of the load torque, and the classification of the load torque is small, the magnetic pole position of the rotor (13e) is detected based on the terminal voltage of the brushless DC motor (13), and the magnetic pole is detected. First control means (15) (16) (16 ') (17) for controlling the inverter (12) to set an output voltage waveform or an output current waveform to be applied to the brushless DC motor (13) based on the position detection signal. )
(17 ') and (18) In the section where the load torque is large, the pseudo magnetic pole position signal is generated based on the cycle of the magnetic pole position detection signal, and the brushless DC motor (13) is generated based on the pseudo magnetic pole position signal.
Second control means (1) for controlling the inverter (12) to set an output voltage waveform or an output current waveform to be applied to the
8) A brushless DC motor control device comprising: 5. The first control means (16 ') (17') (1
The brushless DC motor control device according to claim 4, wherein 8) is for detecting the magnetic pole position of the rotor (13e) by using the phase voltage of the brushless DC motor (13). 6. First control means (15) (16) (17)
(18) is for detecting the magnetic pole position of the rotor (13e) by detecting the stator winding (13u) of the brushless DC motor (13).
(13v) (13w) neutral voltage and brushless DC
A resistor (14u) having one terminal connected to the output terminal of each phase of the motor (13) and the other terminal connected to each other.
5. The brushless DC motor control device according to claim 4, wherein the brushless DC motor control device is performed by using a voltage difference with a neutral point voltage obtained by (14v) and (14w).