JP5756542B2 - Brushless motor control device and control method - Google Patents

Description

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

  A brushless motor of a type in which the rotor has a permanent magnet may perform drive control without a position sensor without providing a position sensor for detecting the rotational position of the rotor. In this case, the rotational position of the rotor is detected from the edge interval of the pulse signal obtained by inputting the induced voltage and the equivalent neutral point potential appearing at the motor terminal in the open section (non-energized phase) to the comparator. However, when the number of rotations is zero or when the number of rotations is extremely low, such as when a brushless motor is started, an induced voltage is not generated or is extremely small, so that a signal sufficient for detecting the rotation position cannot be obtained.

  As a conventional method for detecting the stop position of the rotor, the voltage applied to the three-phase coil is detected, the inductance of the coil is detected from the difference in the rise time of the voltage, and is opposed to the magnetic pole of the permanent magnet. The coil is judged (see Patent Document 1). When the direction of the magnetic flux by the coil and the direction of the magnetic flux of the iron core do not match, the impedance changes before and after the current is passed due to the residual magnetization of the iron core when the current is passed. Therefore, in the driving device disclosed in Patent Document 1, a current is continuously supplied twice or more in the same phase, and a coil having a minimum voltage rise time after the second time is detected.

JP 2004-40943 A

However, when detecting the rotor stop position, the method disclosed in Patent Document 1 has a problem that the rotor stop position may not be detected accurately.
The present invention has been made in view of such circumstances, and a main object thereof is to detect and control the rotor stop position with high accuracy.

The invention according to claim 1 of the present invention for solving the above-mentioned problem is a control device for a brushless motor comprising a stator and a stator around which coils of a plurality of phases are wound, the current flowing through the coils of a plurality of phases, Position signal generating means for generating a signal for instructing a plurality of predetermined energization patterns, an inverter circuit for supplying current to the coil by a signal from the position signal generating means, and for measuring the current flowing in the coil Current measuring means used in the above, current comparing means for outputting a detection signal when a current value measured using the current measuring means exceeds a preset threshold, and a signal for instructing an energization pattern are output. wherein a counter detection signal to count the energization time to be output for each energization pattern, the plurality of energization pattern from, sequentially through A difference of the energization time of the energization pattern, and a position estimation means for determining a rotor stop position and a rotor stop position in accordance with the difference from the related with the map, the control of the brushless motor, characterized in that The device.
When the coil is energized, the ease with which the magnetic flux flows depends on the rotor stop position. This brushless motor control device detects the rotor stop position by checking the time until the current flowing through the coil exceeds a predetermined threshold value for each energization pattern, so that the rotor stop position can be accurately measured. it can. Further, with this configuration, a complicated circuit is not required and the apparatus configuration can be simplified.

    According to a second aspect of the present invention, in the brushless motor control apparatus according to the first aspect, the predetermined number is two to four, and the energization pattern is estimated from a combination of signs of differences between the respective energization patterns. It is characterized by controlling. This brushless motor control device uses the fact that the change in the count value due to the ease of flow of the magnetic flux changes to a sine wave shape or a trapezoidal wave shape depending on the energization pattern, and estimates the rotor stop position based on two to four energization patterns To do.

According to a third aspect of the present invention, in the brushless motor driving apparatus according to the first or second aspect, the current comparing means is an overcurrent detection circuit that detects an overcurrent flowing through the inverter circuit. And
This brushless motor control device determines the rotor stop position using an overcurrent detection circuit provided so as not to allow overcurrent to flow through the coil.

The invention according to claim 4 is a control method of a brushless motor including a stator and a stator around which coils of a plurality of phases are wound, wherein a plurality of predetermined energization patterns of currents flowing through the coils of a plurality of phases are provided. A step of generating a command signal, a step of stopping current supply when a current flowing through the coil exceeds a predetermined threshold value, and a current flowing through the coil from an output of a signal commanding an energization pattern exceeding the threshold value a step of counting the current time until the counter, the plurality of energization patterns, and the energization time of the energization pattern is energized continuously difference, associations and a rotor stop position corresponding to the difference Determining the rotor stop position from the map, and a control method for the brushless motor.

  The invention according to claim 5 is the brushless motor control method according to claim 4, wherein the step of counting by the counter is performed for two to four energization patterns. This method of detecting the rotor stop position of the brushless motor uses the fact that the change in the count value due to the ease of flow of the magnetic flux changes to a sine wave shape or a trapezoidal wave shape depending on the energization pattern, and counts from 2 to 4 energization patterns. To detect the rotor stop position.

  According to the present invention, the rotor stop position can be accurately detected and controlled.

It is a block diagram which shows schematic structure of the drive device of the brushless motor which concerns on embodiment of this invention. It is a figure which illustrates the specific circuit structure of an induced electric power I / F circuit. It is a figure which shows the structure of an inverter circuit and an overcurrent detection circuit in detail. It is a figure which illustrates typically that a process changes with the rotational speed at the time of a start. It is a flowchart of a fixed time interruption process. It is a figure explaining the magnetic flux and torque which generate | occur | produce with an electricity supply pattern. It is a chart explaining the detection method of a rotor stop position. It is a figure which shows the generated torque at the time of applying two-phase electricity according to a rotor stop position. It is a figure which shows the relationship between the two-phase electricity supply pattern in the rotor stop position P6, an inductance, and generated torque. It is a figure explaining the relationship between a rotor stop position and energization time. It is a flowchart of a stop position detection process. 7 is a flowchart of a stop position detection subroutine A. 7 is a flowchart of a stop position detection subroutine B. 7 is a flowchart of a stop position detection subroutine B. It is a flowchart of a start excitation process. It is a flowchart of a free run process. It is a flowchart of a brake stop process. It is a timing chart for explaining processing at the time of starting concretely. It is a figure which shows the duty control in the case of carrying out a soft start, and a rotational speed. It is a figure explaining the signal processing of the induced voltage waveform of a stator winding, Comprising: It is a timing chart which shows the procedure which produces a digital signal from an analog signal. It is a figure explaining the signal processing of the induced voltage waveform of a stator winding, Comprising: It is a timing chart which shows the preparation procedure of a mask signal, and the preparation procedure of the position detection signal after a mask process. It is a timing chart explaining the determination process of an induced voltage edge, Comprising: It is a figure which shows the case where the pulse width of a square wave pulse voltage is below the pulse width of a mask signal. It is a timing chart explaining the determination process of an induced voltage edge, Comprising: It is a figure which shows the case where the pulse width of a square wave pulse voltage exceeds the pulse width of a mask signal. It is a figure which shows the excitation timing of a U phase. It is a figure which shows the delay phase of the motor terminal voltage waveform with respect to a frequency. 5 is a timing chart when starting from a region R2 in FIG. 4. 6 is a timing chart when starting from a region R3 in FIG.

The best mode for carrying out the invention will be described in detail with reference to the drawings.
As shown in FIG. 1, the brushless motor system includes a brushless motor 1 and a drive device 2 that controls the rotational drive of the brushless motor 1. This brushless motor system is a sensorless type system that does not have a sensor for detecting the rotor position.
The brushless motor 1 has a rotor having a permanent magnet and a stator, and three-phase (U, V, W) coils U, V, W are wound around the stator in order in the circumferential direction.

  The drive device 2 includes a control device 11 constituted by a microcomputer, an induced voltage I / F (interface) circuit 12 that detects the voltages of the three-phase U, V, and W motor terminals of the brushless motor 1, and an energization switching device. And an inverter circuit 13 that is a drive circuit including the switching elements, and between the control device 11 and the inverter circuit 13, a predriver (Hi side predriver 37 </ b> A, Lo side predriver 37 </ b> B) and overcurrent detection means 38. And overcurrent protection means 39 are provided.

  As shown in FIG. 2, the induced voltage I / F circuit 12 receives the voltages (analog signals) of the motor terminals of the three phases U, V, and W, and divides them into voltages that can be input to the comparators 17A to 17C. Low-pass filter circuits 15A, 15B and 15C composed of a voltage dividing circuit (resistor R11 and resistor R12) and a primary CR filter (resistor R11 and capacitor C11) for removing noise of the pulse width modulation signal, and an equivalent neutral point potential A chattering component is generated from the output of the comparators 17A, 17B, and 17C, and the comparators 17A to 17C that generate a pulse signal from the analog signal of the induced voltage appearing in the circuit 16 to detect, the equivalent neutral point potential and the non-energized phase (open period). And low-pass filter circuits (primary CR filters) 18A, 18B, and 18C for cutting.

Here, the circuit 16 that detects the equivalent neutral point potential employs a two-phase comparison method that detects the equivalent neutral point potential from the motor terminal voltages of the V phase and the W phase for the U phase, for example. ing. In this way, a substantially flat voltage is obtained as the equivalent neutral point potential. It should be noted that a three-phase comparison method for obtaining an equivalent neutral point potential using all three-phase signals of U, V, and W may be employed.
In this case, the potential at the equivalent neutral point is a substantially triangular wave centered at 1/2 of the power supply voltage.
The comparators 17A to 17C output a low level signal when the induced voltage analog signal is higher than the equivalent neutral point potential, and output a high level signal when the induced voltage analog signal is lower than the equivalent neutral point potential. A pulse signal is generated. In each of the comparators 17A to 17C, a pulse signal having a resolution of 120 electrical degrees is created. These signals are respectively input to the separation means 21 through the low-pass filter circuits 18A to 18C.

  As shown in FIG. 3, the inverter circuit 13 is a circuit configured by bridge-connecting six switching elements 40UH, 40UL, 40VH, 40VL, 40WH, and 40WL each between the positive and negative terminals of the power supply 20. Thus, the DC voltage supplied from the power supply 20 is converted into an AC voltage based on a pulse width modulation signal (drive signal) input from the control device 11 and applied to each phase U, V, W of the brushless motor 1. Each of the switching elements 40UH to 40WL has a configuration in which a field effect transistor (FET) and a free wheel diode are connected in parallel.

  A shunt resistor 13A as current measuring means is provided between the inverter circuit 13 and the ground level. By using the shunt resistor 13 </ b> A, the current flowing through the inverter circuit 13, that is, the current input to the brushless motor 1 can be detected using the overcurrent detection means 38.

The overcurrent detection unit 38 is a current comparison unit having a comparator. The reference voltage is input to the positive input terminal of the comparator, and the voltage of the shunt resistor 13A is input to the negative terminal. That is, when the voltage generated by the current flowing through the shunt resistor 13A reaches the reference potential, a signal (overcurrent detection signal) is output from the overcurrent detection means 38. The output of the overcurrent detection means 38 is connected to the overcurrent protection means 32 that is software means via the falling edge detection port of the control device 11 and is also protected by hardware. Connected to means 39.
The overcurrent protection unit 39 is configured such that when an overcurrent detection signal is input, a current flows through the diode, and an output signal from the PWM duty determination unit 28 is not input to the Hi side pre-driver 37A.

The control device 11 includes a CPU (central processing unit), a memory, and the like, and includes a separation unit 21 connected to the induced voltage I / F circuit 12, an excitation switching timing calculation unit 22, a rotation direction detection logic selection unit 24, and the like. , Mode selection means 40, energization pattern determination means 26, excitation signal output means 27, PWM duty determination means 28, overcurrent protection means 32, current application time measurement means 29, and current application time comparison means 30 The rotor position estimating means 31 and the overcurrent flag setting means 41 are provided.
The energization pattern determination means 26 includes a stop position detection mode 26A, a start excitation mode 26B, a free run control mode 26C, a steady excitation mode 26D, a brake stop mode 26E, and a stop mode 26F.

  The rotation direction detection logic selection unit 24 determines a logic to be used in the separation unit 21 according to a rotation direction signal from the outside and outputs the logic to the separation unit 21. The separation means 21 performs processing for separating the edge of the pulse signal input from the induced voltage I / F circuit 12 into the edge of the induced voltage and the edge of the square wave pulse voltage using the selected rotation direction detection logic. . The excitation switching timing calculation means 22 generates one pulse signal with a resolution of 60 ° electrical angle from three pulse signals with a resolution of 120 ° electrical angle in order to calculate the excitation phase according to the induced voltage edge, and switches the excitation switching. The timing is calculated and output to the mode selection means 40. The mode selection means 40 determines the rotation direction based on whether or not the excitation switching timing signal is input from the excitation switching timing calculation means 22 and selects the mode of the energization pattern determination means 26. When the excitation switching timing signal is input, the steady excitation mode 26D is set. Similarly, when the excitation switching timing signal is not input, it is considered that the brushless motor 1 is rotating in reverse, the brake stop mode 26E is set, and an energization pattern for stopping the brushless motor 1 is output to the excitation signal output means 27. .

The energization pattern determination means 26 has a stop position detection mode 26A, a start excitation mode 26B, a free run control mode 26C, a steady excitation mode 26D, a brake stop mode 26E, and a stop mode 26F.
In the stop position detection mode 26A of the energization pattern determination means 26, a pulse width modulation signal for detecting the rotor stop position is generated in the excitation signal output means 27 in response to a start command from the outside.
The start excitation mode 26B determines an energization pattern corresponding to the rotor stop position determined by the rotor position estimating means 31.
In the free-run control mode 26C, after the start energization pattern is energized for a predetermined initial energization time Ts1, the brushless motor 1 is free-runned, and the rotor position is detected by the free-run mode 22C of the excitation switching timing calculation means 22. To implement.
In the steady excitation mode 26D, an energization pattern corresponding to the rotor position is determined at the excitation switching timing calculated by the steady mode 22D of the excitation switching timing calculation means 22 when the brushless motor 1 is rotating.
Details of these processes will be described later.

  The excitation signal output means 27 outputs a signal for applying an excitation current to the coil of the brushless motor 1 to each pre-driver (Hi-side pre-driver 37A, Lo-side pre-driver 37B). The Hi-side pre-driver 37A is a driver that switches ON / OFF of the high-potential side switching element at the duty ratio determined by the PWM duty determining means 28. The Lo-side pre-driver 37B is a driver that switches ON / OFF of the switching element on the low potential side. The Hi-side pre-driver 37A has a function of turning off each switching element when an overcurrent flows through the inverter circuit 13 and a signal is input from the overcurrent protection means 39. When an overcurrent is detected, a signal is input to the overcurrent protection means 32 and a software reset is applied.

The current application time measurement means 29 is connected to the stop position detection mode 32A of the overcurrent protection means 32, the stop position detection mode 26A of the energization pattern determination means, and the current application time comparison means 30, and stores the storage means 29A and the counter 29B. Prepare. The counter 29B starts counting upon receiving a command from the stop position detection mode 26A. The storage unit 29A stores the count value of the counter 29B when the overcurrent detection signal output from the overcurrent detection unit 38 is input via the stop position detection mode 32A of the overcurrent protection unit 32. The counter 29B is reset after a predetermined time has elapsed, and at the same time, outputs a signal to the stop position detection mode 26A.
The current application time comparison unit 30 receives the count value stored in the storage unit 29A of the current application time measurement unit 29 and performs data processing to be described later. The output is connected to the rotor position estimating means 31 and constitutes a position estimating means for determining the rotor position together with the rotor position estimating means 31.
The rotor position estimating means 31 estimates the rotor position at a stop or at a low speed based on the calculation result of the current application time comparing means 30.

Next, the operation of the drive device 2 will be described.
When the brushless motor 1 is started, there are a case where the brushless motor 1 is stopped and a case where the brushless motor 1 is started from a state where the brushless motor 1 is rotated by an external force. For example, when the brushless motor 1 is used as a radiator fan rotation mechanism, when the wind is blowing in the direction from the radiator toward the engine room, the brushless motor 1 is rotated forward according to the rotation of the radiator fan without being energized. It is done. On the other hand, the case where the brushless motor 1 is rotating in reverse is considered when the wind is blowing in the direction of the radiator from the engine side or when negative pressure is generated in the reverse direction with respect to the radiator fan. .

  When it is assumed that the drive device 2 is used as a radiator fan, the radiator fan has a structure that easily rotates in the forward rotation direction, and a large wind force is required to rotate in the reverse rotation direction. However, there is little possibility that large wind power is generated in the reverse direction from the structure of the vehicle, and even when the radiator fan rotates in reverse, the rotation speed is considered to be low. Therefore, in this drive device 2, even when the brushless motor 1 is reversely rotated by an external load, control at the time of starting is performed assuming that the rotation speed and torque are small.

FIG. 4 schematically shows a classification of the starting method according to the rotational speed of the brushless motor 1 at the time of starting. In this embodiment, three cases are divided according to the rotation speed.
If the rotational speed of the brushless motor 1 shown on the horizontal axis includes a region R1 that includes zero, the driving device 2 executes a start-start process based on inductance detection.
If the rotational speed of the brushless motor 1 is in the positive rotation direction in the region R2 larger than the region R1, the rotor position is detected by detecting the induced voltage and the rotation is controlled. When the rotational speed is in the region R3 larger than the region R1 in the reverse rotation direction, the process proceeds to the region R1 by the reverse rotation state determination process and the rotor stop process, and the start start process by inductance detection is executed. The region R1 and the region R2 overlap each other at a rotation speed near N1 (rpm). The rotational speed N1 corresponds to a low rotational speed at which the rotor position cannot be detected by detecting the induced voltage. If the rotational speed is zero or low, the rotor position can be detected with a resolution of an electrical angle of 60 ° by inductance detection, and energization can be performed at a phase that can generate the maximum torque in the forward rotation direction. On the other hand, as the rotational speed increases, the detection result of the rotor position by inductance detection is out of phase from the electrical angle of 60 ° and the detection accuracy becomes worse, so the starting torque decreases compared to the stopped state. Because.

If the rotation speed of the brushless motor 1 is in the reverse rotation direction and in the region R3 larger than the region R1, the brushless motor 1 is braked and moved to the region R1, as described later, and the rotor position is detected. The region R1 and the region R3 overlap with each other when the rotation speed is near -N1 (rpm).
Note that the region R1 and the region R2 may be divided with the rotation speed N1 as a boundary without overlapping. The region R1 and the region R3 may be divided with the rotation speed −N1 as a boundary without overlapping.

  The driving device 2 first executes processing assuming that the rotational speed of the brushless motor 1 is in the region R1, and then shifts to steady driving through processing corresponding to the region R2. If the rotor position cannot be detected when the processing corresponding to the region R2 is performed, the rotation state of the brushless motor 1 is regarded as being in the region R3, and the processing corresponding to the region R3 is repeated.

Such a process at the time of start-up is carried out as an interrupt process at a fixed time shown in FIG.
The mode selection means 40 confirms the rotation speed signal and the overcurrent flag signal. The overcurrent flag monitors the value of the current flowing through the shunt resistor 13A of the inverter circuit 13, and when the current flowing through the shunt resistor 13A exceeds a predetermined value, it is determined to be ON, that is, an overload state. If the overcurrent flag is ON when the rotation speed signal is turned ON (Yes in step S101), all phases are turned OFF, stop processing is performed (step S102), and the processing here ends. At this time, the PWM duty is set to 0% and various parameters are also initialized.
On the other hand, when the rotation speed signal is ON but the overcurrent flag signal is OFF (No in step S101), the energization pattern determination means 26 is set to the stop position detection mode 26A (step S103), and the brushless motor 1 A stop position detection process for detecting the inductance and detecting the rotor position is performed (step S104).

When the mode selection unit 40 detects the rotor stop position, the process proceeds from step S103 to step S105, and the energization pattern determination unit 26 is set to the start excitation mode 26B (Yes in step S105). The energization pattern determination means 26 performs a start excitation process (step S106).
When the start excitation process is performed, the process proceeds from step S107 to step S108, and the free run process is performed. In this free-run processing, the rotor position is detected from the induced voltage generated while the rotor of the brushless motor 1 is free-running due to inertia, using a forward rotation dedicated logic.
When the rotor position can be detected using the induced voltage, the routine proceeds from step S109 to step S110, where steady excitation processing is performed (step S110). When the rotor position cannot be detected using the induced voltage, the process proceeds from step S111 to step S112, and the brake stop process is performed (step S112).

  Here, in the stop position detection process in step S104, paying attention to the fact that the magnetic permeability of the magnet core increases and the inductance decreases when the direction of the magnetic flux generated by the coil is the same as the direction of the magnetic flux of the magnet. The stop position is determined. Below, the principle at the time of determining an energization pattern by a stop position detection process is demonstrated.

  When starting the brushless motor 1 in a stopped state, a rotation speed signal (a signal for changing the rotation speed stepwise from zero to a certain rotation speed) is input to the mode selection means 40 of the control device 11 from the outside. Thereby, the mode selection means 40 sets the energization pattern determination means 26 to the stop position detection mode 26A. The stop position detection mode 26A of the energization pattern determination means 26 issues a command to the excitation signal output means 27 so that six predetermined stop position determination energization patterns are continued for a period of time that the rotor does not rotate. The time that the rotor does not rotate varies depending on the inertia of the brushless motor 1, but is, for example, between several μs and several milliseconds and is counted by a counter included in the control device 11. The excitation signal output means 27 outputs a pulse width modulation signal corresponding to the energization pattern to the inverter circuit 13, and the switching elements 40UH to 40WL are turned on and off in response to the pulse width modulation signal, and any two of the three phases. Is energized.

FIG. 6 shows a stop position determination energization pattern commanded by the stop position detecting means 34. These energization patterns # 1 to # 6 are patterns that can drive the brushless motor 1.
In the energization pattern # 1, a current flows from the U-phase coil U to the V-phase coil V. The U phase is N pole magnetized and the V phase is S pole magnetized.
In the energization pattern # 2, a current flows from the U phase to the W phase coil W. The U phase is N pole magnetized and the W phase is S pole magnetized.
In the energization pattern # 3, a current flows from the V phase to the W phase. The V phase is N pole magnetized and the W phase is S pole magnetized.
In the energization pattern # 4, a current flows from the V phase to the U phase. The V phase is N pole magnetized and the U phase is S pole magnetized.
In the energization pattern # 5, a current flows from the W phase to the U phase. The W phase is N pole magnetized and the U phase is S pole magnetized.
In the energization pattern # 6, a current flows from the W phase to the V phase. The W phase is N pole magnetized and the V phase is S pole magnetized.

As shown in FIG. 7, the stop position inspection of the rotor 41 in this embodiment is performed corresponding to the energization patterns # 1 to # 6.
In the energization pattern # 1, energization from the U phase to the V phase is performed, and then a regeneration period is provided. That is, a PWM signal with a duty of 100% is input to the switching element 40UN and the switching element 40VL, and the N pole magnetization and the S pole magnetization are performed respectively. A current flows from the coil U to the coil V, and a current corresponding to the current flows to the shunt resistor 13A. The current flowing through the shunt resistor 13A is an applied current that is applied to the brushless motor 1 through the power supply 20, and gradually increases as time passes.

  When the applied current reaches a predetermined overcurrent threshold, the energization interval is terminated and the regeneration period is started. Specifically, the overcurrent detection unit 38 that monitors the voltage value of the shunt resistor 13A corresponds to the applied current flowing through the shunt resistor 13A because the reference voltage is set to a voltage corresponding to the overcurrent threshold. When the voltage reaches the reference voltage, a low level signal is output as an overcurrent detection signal. As a result, the potential of the overcurrent protection means 39 falls to the Low level, and all the switching elements 40UH to 40WH on the High side are turned off (hardware limit). Further, at the same time, when detecting the falling edge of the overcurrent detection signal, the control device 11 executes an interrupt process to end the energization of the energization pattern # 1 (software limit). Thereby, the electric current which flows into the brushless motor 1 becomes zero. Since the software limit generation is delayed, the current is quickly made zero by using the hardware limit together.

  The stop position detection mode 26A of the energization pattern determining means 26 selects the stop position detection mode 32A of the overcurrent protection means 32, and at the same time, the counter 29B starts counting up. Thereafter, when an overcurrent detection signal is input from the overcurrent detection unit 38 to the counter 29B via the stop position detection mode 32A of the overcurrent protection unit 32, the count value of the counter 29B is stored in the storage unit 29A. The The storage unit 29A stores the count value at this time as the energization time T1 for the energization pattern # 1.

  Note that all the FETs of the inverter circuit 13 are turned off in order to make the current flowing through the brushless motor 1 zero. At this time, the electric power accumulated in the coil becomes a negative current because it becomes a regenerative current flowing through the body diode of the FET, the power source 20, and the circuit returning to the coil via the shunt resistor 13A. The regenerative current becomes zero with time as shown in the current waveform of the shunt resistor 13A.

  In the stop position detection mode 26A of the energization pattern determining means 26, the energization of the energization pattern # 2 is performed when a signal indicating that a predetermined time has elapsed from the output of the signal for instructing energization of the energization pattern # 1 is received. Outputs a command signal. The predetermined time is set to a sufficient value as the time required until the applied current reaches the overcurrent threshold and the regenerative current flowing thereafter becomes zero. In the counter 29B, a count value corresponding to the predetermined time is set as a counter clearing threshold value. For this reason, the value of the counter 29B is reset at the timing of switching the energization pattern.

  The predetermined time is set to a sufficient value as the time required until the applied current reaches the overcurrent threshold and the regenerative current flowing thereafter becomes zero. The time until the time is reached (measurement result of the storage unit 29A) may be set as the predetermined time. In this case, every time the storage unit 29A measures the energization time, data for a predetermined time for resetting the counter 29B is passed to the counter 29B. That is, a predetermined time signal is sent from the storage means 29A to the counter 29B.

Thereafter, when the energization patterns # 2 to # 6 are performed in the same manner, the applied current and the regenerative current sequentially flow through the shunt resistor 13A corresponding to the respective energization patterns. The current application time measuring unit 29 stores the count value from the start of energization in the storage unit 29A as energization times T2 to T6 corresponding to the energization patterns # 2 to # 6.
The count value stored in the storage unit 29A varies depending on the rotor stop position. In the energization pattern corresponding to the rotor stop position, the magnetic flux flows most easily, and the time until the overcurrent threshold is reached is shortened. In the example of FIG. 7, the energization pattern # 3 is the largest, the adjacent energization patterns # 2 and # 4 are the next largest, and the energization pattern # 6 is the smallest. Therefore, the rotor is stopped at a position corresponding to the energization pattern # 6. Thus, if the magnitude of the count value is examined by the current application time comparison means 30, the rotor position estimation means 31 can estimate the rotor stop position.

The start excitation mode 26B of the energization pattern determining means 26, which is performed after the rotor stop position is estimated, starts an energization pattern in which the phase is advanced by 120 ° in the rotation direction from the energization pattern that becomes the minimum among the six energization times. Select as the current conduction pattern. This will be described with reference to FIG.
When a current is passed between the two phases of the three-phase brushless motor 1 to rotate the rotor, a sine wave (or trapezoid wave) torque out of phase is generated as shown in FIG. For example, when trying to rotate the rotor from the outside in the energization pattern # 3 in the VW energization state, the torque is zero when the rotor position phase is ± 0 °, and the rotor position phase is + 60 °. A torque of 86.6% of the maximum torque on the plus side can be obtained. Hereinafter, when the phase of the rotor position is + 120 °, the torque is 86.6% of the maximum torque on the positive side, zero when the phase of the rotor position is 180 °, and negative when the phase of the rotor position is + 210 °. A torque of 86.6% of the maximum torque can be obtained.
Therefore, in order to rotate so that a large torque is always obtained on the plus side according to the rotor position, when the energization pattern # 3 is performed when the rotor position is P1, the torque increases thereafter, so the rotor 41 is driven with a large force. Can be rotated.

As described above, in the 120 ° rectangular wave driving in which the two-phase energization pattern is switched every 60 ° of electrical angle, the driving is performed using the 86.6% torque to the 100% torque.
When the rotor position is P1, the lock energization pattern is UV energization. Therefore, if a VW energization pattern whose phase is advanced by 120 ° from the UV energization pattern is used, it is started with high torque. When the lock energization state is established, the rotor magnet magnetic flux and the coil magnetic flux are in a magnetized state, so that the coil inductance is reduced. For this reason, a lock energization pattern at an arbitrary rotor position can be specified by searching for an energization pattern with the smallest coil inductance at an arbitrary rotor position. Therefore, if an energization pattern whose phase is advanced by 120 ° from the specified lock energization pattern is used, the engine can be started with high torque. When the torque waveform becomes a trapezoidal wave, almost 100% torque can always be obtained even with 120 ° rectangular wave driving. The lock energization pattern corresponds to the rotor stop position.

Here, the behavior when six energization patterns are output for one rotor position will be described assuming that the rotor position is at P6 in FIG.
The energization pattern that increases the magnetism most with respect to the rotor position of P6 in FIG. At this time, it is the energization pattern # 2: UW energization advanced by 120 ° that the rotor is rotated in the plus direction with the plus side maximum torque. This is because, when energization of the energization pattern # 2 is performed on the rotor position P6, a force (torque) that rotates in the plus direction is generated in the rotor from the relationship of the attractive repulsion due to the magnetic flux of the stator coil and the magnetic flux of the rotor magnet. Because it can.
This is equivalent to the state shown in FIG. 6B. When the direction of the N pole of the rotor magnet is d-axis and the direction orthogonal to the d-axis is q-axis, the q-axis component of the magnetic flux by the stator coil is −86. When the rotor is rotated in the plus direction, the absolute value of the q-axis component magnetic flux increases.
Further, in order to rotate the rotor at P6 in the negative direction with the maximum negative torque, the energization pattern # 4: VU energization may be performed. If energization of the energization pattern # 4 is performed on the rotor position of P6, a force (torque) that rotates in the negative direction is generated in the rotor due to the relationship of attraction and repulsion due to the magnetic flux of the stator coil and the magnetic flux of the rotor magnet is there. In this case, this is equivalent to the state of FIG. 6D, and the q-axis component of the magnetic flux by the stator coil is 86.6%. When the rotor is rotated in the minus direction, the absolute value of the magnetic flux of the q-axis component is The value increases.

  In the energization pattern # 1 in FIG. 6A, UV energization is performed. The magnet magnetic flux vector overlaps the d-axis, but the coil magnetic flux vector is deviated from the d-axis and the q-axis. Specifically, the d-axis component is 50% and the q-axis component is −86.6%. For this reason, the torque generated instantaneously becomes -86.6%. When the rotor (rotating magnetic field) rotates in the plus direction (forward rotation direction), torque is generated that reduces the absolute value of the q-axis component magnetic flux. At this time, the second largest torque is obtained. On the other hand, when the rotor rotates in the-direction (reverse direction), the absolute value of the q-axis component magnetic flux increases, but cannot be rotated in this positional relationship.

  In the energization pattern # 2: UW energization in (b), the coil magnetic flux vector has a d-axis component of −50% and a q-axis component of −86.6%. A torque is generated that increases the absolute value of the magnetic flux of the q-axis component that rotates the rotor (rotating magnetic field) in the + direction. At this time, the largest torque is obtained in the + rotation direction. On the other hand, when the rotor rotates in the-direction, the absolute value of the magnetic flux of the q-axis component increases, but cannot be rotated in this positional relationship.

  In the energization pattern # 3: (c), in the VW energization, the coil magnetic flux and the magnet magnetic flux are in a reverse relationship. For this reason, the attraction force is zero and the rebound is maximized. The coil magnetic flux vector has a d-axis component of −100% and a q-axis component of 0%. The instantaneous generated torque becomes 0%, and the absolute value of the q-axis component magnetic flux increases regardless of which of the rotors rotates, but the generated torque is small and almost zero. At this time, the magnetic flux penetrating the stator core is minimized, and magnetic saturation is difficult. The magnetic permeability of the core is maximized, and the inductance of the stator coil is also maximized.

  In energization pattern # 4: VU energization in (d), the coil magnetic flux vector has a d-axis component of −50% and a q-axis component of 86.6%. For this reason, the torque generated instantaneously is 86.6%. When the rotor rotates in the + direction, the absolute value of the q-axis component magnetic flux decreases, but it cannot be rotated in this positional relationship. When the rotor rotates in the-direction, torque is generated that increases the absolute value of the q-axis component magnetic flux. At this time, the largest torque is obtained in the negative direction.

  In energization pattern # 5: WU energization in (e), the coil magnetic flux vector has a d-axis component of 50% and a q-axis component of 86.6%. When the rotor rotates in the + direction, the absolute value of the q-axis component magnetic flux increases, but cannot be rotated in this positional relationship. When the rotor rotates in the-direction, torque is generated that reduces the absolute value of the q-axis component magnetic flux. At this time, the second largest torque is obtained in the negative direction.

In energization pattern # 6: WV energization in (f), the coil magnetic flux and the magnet magnetic flux coincide.
For this reason, the suction force becomes maximum and the repulsive force becomes zero. The coil magnetic flux vector has a d-axis component of 100% and a q-axis component of 0%. The instantaneous generated torque becomes 0%, and the absolute value of the q-axis component magnetic flux increases regardless of which of the rotors rotates, but the generated torque is small and almost zero. In this state, the magnetic flux penetrating the stator core is maximized, and magnetic saturation is likely to occur. The magnetic permeability of the core is minimized, and the inductance of the stator coil is also minimized.

Regarding inductance, changing the rotating magnetic field (stator coil magnetic flux) with respect to the stopped rotor position changes the amount of magnetic flux that penetrates the core in a sine wave form in principle, so the change in inductance is also a sine wave form. become. FIG. 9 shows a two-phase energization pattern, an inductance change, and a generated torque change when the rotor position is P6.
In FIG. 9, the broken line indicates the change in generated torque, and the solid line indicates the change in inductance. The energization pattern # 3 that maximizes the inductance is the energization pattern that maximizes the energization time. Therefore, the energization pattern immediately before this energization pattern # 3 or the energization pattern two ahead of the energization pattern # 6 that minimizes the energization time is the energization pattern capable of generating the maximum torque in the forward rotation direction. Becomes energization pattern # 2.
Similarly, the energization pattern that is the next energization pattern of the energization pattern # 3 that maximizes the energization time, or the energization pattern that is two before the energization pattern # 6 that minimizes the energization time is the energization pattern that can generate the maximum torque in the reverse direction It is. By setting the energization pattern capable of generating the maximum torque determined in this way to the activation energization pattern, it is possible to start with high torque.

Further, the relationship between each energization pattern and the energization time is as shown in FIG. The energization time waveform shown in the line L6 indicates a change in the energization time when the rotor is at the position P6. The energization time waveform of the line L1 shows a change in the energization time when the rotor is at a position P1 advanced by π / 3 (60 °) in the forward rotation direction from P6. Hereinafter, the lines L2, L3, L4, and L5 are energization time waveforms when they are at positions P2, P3, P4, and P5 advanced by π / 3 (60 °) in the forward rotation direction, respectively. Thus, since it becomes six types of sine waves depending on the rotor position, the activation energization pattern can be estimated from the sine waves.
As shown in FIG. 10B, when each energization time waveform is regarded as a triangular wave and each of the triangular waves is differentiated (difference ΔT is obtained) to obtain the sign of the slope, as shown in FIG. 10C. become. For example, in the energization time waveform of the line L4, since it tends to decrease from the energization time T1 to the energization time T2, the sign of the difference ΔT between the energization time T1 and the energization time T2 is “−”.

Here, it is possible to check the energization time for all six energization patterns and store it in the storage means 29A. In this embodiment, however, by providing the current application time comparison means 30 with a map 30A, 3 The rotor stop position is estimated by one or four energization patterns. That is, as shown in FIG. 10B, since peaks always appear in the four energization patterns # 1 to # 4, the difference T12 (= T2-T1), the difference T23 (= T3-T2), the difference From the combination of the signs of T34 (= T4-T3), the maximum or minimum peak of the triangular wave can be obtained, and the activation energization pattern can be estimated.
The configuration of the map 30A is shown below.

As can be seen from the map 30A, the two rotor stop positions P5 and P2 can be estimated only by T12 and T23 without performing T34.
As described above, a map 30A as shown in Table 1 is prepared in advance, and by searching for the difference between the energization times of the two energization patterns energized before and after, the energization can be performed three or four times. The rotor rotational position can be estimated. In all cases, the rotor stop position may be determined after energization four times.

Here, FIG. 11 shows a flow of the stop position detection process in step S104.
First, the stop position detection mode 32A of the overcurrent protection means 32 is selected (step S121), and the stop position detection subroutine A is executed (step S122). The stop position detection subroutine A carries out determination of the energization pattern (step S122A) and determination of whether or not the mode can be shifted to the next mode (step S122B).
When the starting excitation pattern is not fixed, the process proceeds from step S122B to step S123. This process is an interrupt process that occurs when the falling of the overcurrent detection signal is detected. The process waits while the current is flowing through the brushless motor 1 (step S123), and when overcurrent detection is detected (step S124). ), The stop position detection subroutine B is executed (step S125). Thereafter, the process returns to the stop position detection subroutine A.
On the other hand, when the starting excitation pattern is confirmed, the process proceeds from step S122B to step S126, and the counter 29B is stopped. Thereafter, the mode is shifted to the start excitation mode (step S127), and the overcurrent detection mode 32B of the overcurrent protection means 32 is set (step S128). Specifically, when the overcurrent detection means 38 detects an overcurrent (step S128A), the overcurrent flag is set to “1” (step S128B).

As shown in FIG. 12, in the stop position detection subroutine A, the energization number (energization No) counter is incremented (step S201). In the first processing, the energization No counter is set to 1. The threshold for clearing the counter 29B is set to the maximum value (step S202), the counter 29B is reset once (step S203), and the PWM duty is set to 100% (step S204).
If the energization No counter is “1” (Yes in step S205), energization pattern # 1 is performed (step S206). Then, the process ends here.
Similarly, if the energization No counter is “2” (Yes in step S207), energization pattern # 2 is performed (step S208).
If the energization No counter is “3” (Yes in step S209), energization pattern # 3 is performed (step S210).

  On the other hand, if the energization No counter is “4” (Yes in step S211), the difference T12 <0 and the difference T23> 0 (Yes in step S212), or the difference T12> 0 and the difference If T23 <0 (Yes in step S213), the PWM duty is set to 0% (step S214), and the process proceeds to the next mode (starting excitation mode 26B) (step S215). In other cases (both step S212 and step S213 are No), the energization pattern # 4 is performed (step S216).

  If the energization No counter is “5” (Yes in step S217), the difference T12> 0, the difference T23> 0, and the difference T34> 0 (Yes in step S218), the difference T12> 0, If difference T23> 0 and difference T34 <0 (Yes in step S219), difference T12 <0, difference T23 <0, and difference T34 <0 (Yes in step S220), difference T12 < If 0, difference T23 <0, and difference T34> 0 (Yes in step S221), the PWM duty is set to 0% (step S222), and the process proceeds to the next mode (starting excitation mode 26B) (step S22). S223).

Details of the stop position detection subroutine B are shown in FIGS. The stop position detection subroutine B shows details of processing of the current application time measuring means 29, the current application time comparing means 30, and the rotor position estimating means 31. First, the energization counter is checked, and if the counter number is “1” (Yes in step S251), the storage unit 29A stores the count value of the counter 29B as the energization time T1 (step S252).
If the counter number is “2” (Yes in step S253), the storage unit 29A stores the count value of the counter 29B as the energization time T2 (step S254). Further, the difference T12 is calculated (step S255).
If the counter number is “3” (Yes in step S256), the count value of the counter 29B is stored in the storage unit 29A as the energization time T3 (step S257). Further, the difference T12 is calculated (step S258).

Here, if the difference T12 <0 and the difference T23> 0 (Yes in step S259), if it is forward rotation (No in step S260), the activation energization pattern is set to the energization pattern # 1 (step S261). If it is reverse (Yes in step S260), the activation energization pattern is set to energization pattern # 3 (step S262).
On the other hand, when the difference T12> 0 and the difference T23 <0 (step S263) and during normal rotation (No in step S264), the activation energization pattern is set to the energization pattern # 4 (step S265). If it is during reverse rotation (Yes in step S264), the activation energization pattern is set to energization pattern # 6 (step S266).

If the counter number is “4” (Yes in step S267), the storage unit 29A stores the count value of the counter 29B as the energization time T4 (step S268). Further, the difference T34 is calculated (step S269).
Here, when the differences T12> 0, T23> 0, and T34> 0 (Yes in step S270), if it is forward rotation (No in step S271), the start energization pattern is set to the energization pattern # 6 (step S272). If it is during reverse rotation (Yes in step S271), the activation energization pattern is set to energization pattern # 2 (step S273).

If the differences T12> 0, T23> 0, and T34 <0 (Yes in step S274), if it is forward rotation (Yes in step S275), the activation energization pattern is set to the energization pattern # 5 (step S276). If it is during reverse rotation (No in step s275), the activation energization pattern is set to energization pattern # 1 (step S277).
If the differences T12 <0, T23 <0, and T34 <0 (Yes in step S278), if it is forward rotation (No in step S279), the activation energization pattern is set to the energization pattern # 3 (step S280). If it is during reverse rotation (Yes in step S279), the activation energization pattern is set to energization pattern # 5 (step S281).
If the difference is T12 <0, T23 <0, T34> 0 (Yes in step S282), if it is forward rotation (No in step S283), the activation energization pattern is set to energization pattern # 2 (step S284). If it is during reverse rotation (Yes in step S283), the activation energization pattern is set to energization pattern # 4 (step S285).

Next, details of the start excitation process in step S106 of FIG. 5 will be described.
As shown in FIG. 15, in the start excitation mode 26B of the energization pattern determining means 26, a start energization pattern having a phase capable of generating the maximum torque for the rotor position is determined, and the start energization pattern is supplied to the excitation signal output means 27. Is output (step S131). The initial energization counter is activated, and the aforementioned phase is energized until a predetermined initial energization time Ts1 has elapsed (step S132). When it is confirmed that the predetermined energization time Ts1 has elapsed, the mode selection means 40 sets the energization pattern determination means 26 to the free-run control mode 26C (step S133).

Details of the free-run control process in step S108 of FIG. 5 will be described.
As shown in FIG. 16, first, the energization pattern for turning off energization of all phases is output as the free-run control mode 26C of the energization pattern determining means 26 (step S141).
From the induced voltage generated while the rotor of the brushless motor 1 is free-running due to inertia, the rotor position is detected using the forward rotation dedicated logic (step S142). When the rotor position has been detected a predetermined number of times (Yes in step S143), the energization pattern determination means 26 is set to the steady excitation mode 26D, and the process shifts to sensorless drive (steady drive mode) based on the induced voltage (step S144).
If the predetermined number of times the rotor position has not been detected in step S143 (No in step S143), step S142 is repeated until the number of times of measuring the edge interval of the induced voltage has elapsed (step S145). . If the rotor position cannot be detected a predetermined number of times after a predetermined number of times (Yes in step S145), it is determined that the brushless motor 1 is reversely rotated, and the mode selection means 40 brakes the energization pattern determination means 26. The mode 26E is set (step S146).

Details of the brake stop process in step S112 in FIG. 5 will be described.
As shown in FIG. 17, as a brake stop process in the brake stop mode 26E, a two-phase energization lock process is performed with a low duty (step S151). The two-phase energization lock process is performed for a predetermined time, and when this time has elapsed (step S152), the stop position detection mode 26A is set (step S153).

Next, the entire process at the start including the detection of the stop position will be described in more detail with reference to FIG. In FIG. 18, the horizontal axis indicates the passage of time, and various types of information are arranged in the vertical direction. The hall sensor signal shown on the uppermost side is a signal assumed as an output of the hall sensor when the hall sensor is attached.
When the start signal is input at time t1, the rotor stop position detection process (step S103) is performed until time t2. The rotation speed during this time is zero.

When the rotor stop position is determined at time t2, as shown in the current waveform of the shunt resistor 13A, the starting excitation means 36 continuously energizes the starting excitation pattern only during the initial energization time Ts1. During this time, the rotational speed of the rotor 41 gradually increases.
Here, the initial energization time Ts1 is such that the rotor 41 can be free-runned at a rotational speed of N1 or more until the edge of the induced voltage is generated a plurality of times, for example, four times or more after the energization is turned off. This is the time during which 41 can be accelerated. From this viewpoint, it is desirable that the initial energization time Ts1 is long. However, if the initial energization time Ts1 is too long and the same excitation pattern is continued beyond the excitation pattern switching position during normal operation, reverse torque is generated and the rotor 41 is decelerated. Therefore, it is preferable that the initial energization time Ts1 is as long as possible within a range where no reverse torque is generated. As an example of a method for determining the initial energization time Ts1, the brushless motor 1 is started with a hall sensor at the design stage or the manufacturing stage, and the time until the signal of the hall sensor is switched first is measured. A shorter time can be stored in the control device 11 as the initial energization time Ts1.

  When the initial energization time Ts1 elapses at time t3, the energization pattern determining means 26 shifts to the free-run control mode 26C and turns off energization to all phases. The current value measured by the shunt resistor 13A becomes zero, and the rotor 41 free-runs. Thereafter, the rotational speed gradually decreases with time. At time t3, a pulse appears in each position signal. For this reason, the first signal SL1 is generated as the excitation switching timing signal corresponding to the rising edges of the three-phase signals. At this time, the pulse signal is generated due to the fact that square wave pulse voltages are generated in the motor terminal voltages of all three phases when the energy accumulated in the stator coil is released as a flywheel pulse. In the case of normal driving, these square wave pulse voltages can be ignored by the separating means 21, but since the logic turns off all phases at time t3, the square wave pulse voltage can be ignored because it becomes an exceptional state that cannot exist during normal driving. Without false detection. For this reason, the first signal SL1 after starting is not used for detecting the rotor position.

  Furthermore, when the rotor 41 is free-running, an induced voltage is generated at a motor terminal of a predetermined phase of the brushless motor 1 according to the rotational position of the rotor 41. In this case, rising edges or falling edges occur in the order of the W-phase position signal, the U-phase position signal, and the V-phase position signal. As a result, the excitation switching timing signal includes the second signal SL2 caused by the W-phase edge, the third signal SL3 caused by the U-phase edge, and the fourth signal SL4 caused by the V-phase edge. Will occur. By turning off all phases, the intersection of the induced voltage and the equivalent neutral point potential can be measured in the absence of unnecessary signal components such as a pulse width modulation signal input from the inverter circuit 13 to the brushless motor 1. Therefore, the rotor position can be accurately detected.

  During this time, the excitation switching timing calculation means 22 measures the time interval between the second signal SL2 and the third signal SL3 to calculate an electrical angle of 60 °. Furthermore, an electrical angle of 60 ° is calculated by measuring the time interval between the third signal SL3 and the fourth signal SL4. Based on these time intervals, the excitation switching timing is calculated by, for example, advancing the electrical angle by 30 ° from the fourth signal SL4. Thereafter, the brushless motor 1 is operated by determining the excitation switching timing based on the signal generated from the comparison result of the motor terminal voltage and the equivalent neutral point potential and performing the switching control of the energization pattern. . Driving with a performance equivalent to that of a rectangular wave driving with an electrical angle of 120 ° in the case of having a Hall sensor is possible, and the rotation speed is controlled.

Note that in a brushless motor with a large inertia, the fifth and subsequent signals may be acquired, and the excitation energization timing may be similarly calculated from the time interval. Stability and accuracy at start-up can be further improved.
In a brushless motor having a large inertia, the time interval between the second and third signals SL2 and SL3 is substantially equal to the time interval between the third and fourth signals SL3 and SL4. For this reason, you may transfer to sensorless drive only in the time interval of the 2nd to 3rd signals SL2 and SL3. In this way, steady operation can be started in a shorter time. Alternatively, only the time interval between the first signal SL1 and the second signal SL2 may be acquired to shift to sensorless driving. Effective for brushless motors with low inertia. In this case, the initial energization time SL1 uses a preset value, and when the SL2 timing is detected, the time interval between SL1 and SL2 can be calculated and used as the rotor position signal. It becomes possible to shift to sensorless driving up to the second signal SL2.
Further, in a brushless motor with small inertia, the deceleration is increased and the time interval between the third and fourth signals SL3 and SL4 is larger than the time interval between the second and third signals SL2 and SL3. In this case, the excitation energization timing may be calculated by calculating the acceleration from the change in the time interval and estimating the next time interval using this acceleration.

  Further, in this starting method, a method of starting while suppressing the current at the time of starting the motor (hereinafter referred to as soft start) is implemented. For example, as shown in FIG. 19, at the time of start-up, the duty of the pulse width modulation signal (PWM) is set to, for example, 50%, the current is suppressed, the rotational speed is then increased, and once the initial energization time Ts1 has elapsed, the duty is once set. Set to 0% and free run. When the free run is completed, set the duty to about 50% again, gradually increase the duty from there, and finally reach the target value (for example, maximum speed) when the duty reaches 100%. To do. Thereby, it is possible to prevent an overcurrent from flowing at the time of starting, and to improve the stability of the entire system in which the brushless motor 1 is mounted.

Next, the details of the sensorless drive (steady drive mode) by the induced voltage shown in step S110 of FIG. 5 will be described.
In the steady drive mode, the rotor position is detected by detecting the induced voltage at the motor terminal. However, since the square-wave switching pulse (square wave pulse voltage) is superimposed on the induced voltage waveform, it is necessary to remove such noise. There is. In this embodiment, when an edge corresponding to the rotor position signal of each phase is detected, the level of the other phase is detected to distinguish the rotor position signal from the square wave pulse voltage. The forward rotation dedicated logic used at this time includes an induced voltage signal detection logic shown in Table 2 and a square wave pulse voltage end edge determination logic shown in Table 3.
Note that the forward rotation exclusive logic is referred to by the separation unit 21 in accordance with a command from the rotation direction detection logic selection unit 24 when it is determined that the brushless motor 1 is rotating forward.

  FIG. 20 shows signal waveforms when energization control is performed in the steady drive mode. In FIG. 20, the horizontal axis represents the electrical angle, the vertical axis represents the energized state from the upper side to each phase U, V, W, and the actual induced voltage waveforms Uv, Vv, Wv (analogue) of each phase U, V, W. Signal) and induced voltage signals Ud, Vd, Wd (digital signals) for phases U, V, W are shown. The energization state of the uppermost phases U, V, W is such that the phases U, V, W added with “+” in the upper stage are on the high potential side, and the phases U, “-” added in the lower stage, V and W are on the low potential side. That is, “W +” and “V−” between the electrical angles of 0 ° and 60 ° indicate that the W phase is energized from the W phase (equivalent to the energization pattern # 6 in FIG. 6). Further, for example, in the induced voltage waveform Uv, a pulse that rises at an electrical angle of 0 ° and a pulse that falls at an electrical angle of 180 ° are square wave pulse voltages Ps, and these square wave pulse voltages Ps are to be removed in this embodiment. Is a signal.

  FIG. 21 is a diagram schematically showing a mask signal generation process and a position detection signal generation process. In FIG. 21, the horizontal axis represents the electrical angle, and the vertical axis represents the induced voltage signals Ud, Vd, Wd (the same signals as in FIG. 20) of the phases U, V, W from the upper side, and the induced voltage signal Ud, Mask signals Um, Vm, Wm for separating the square wave pulse voltage signal Ps superimposed on Vd, Wd, respectively, and square wave pulse voltage signals Ups, Vps separated from Ud, Vd, Wd by the mask signal. , Wps, position detection signals Us, Vs, Ws of each phase U, V, W, and position detection signals Uss, Vss, Wss after a phase shift of 30 electrical degrees are illustrated in order.

  The induced voltage waveforms Uv, Vv, and Wv of the phases U, V, and W shown in FIG. 20 are input to the induced voltage I / F circuit 12 (see FIG. 1) and divided by the low-pass filter circuits 15A to 15C in FIG. The circuit divides the voltages into voltages Uv2, Vv2, and Wv2 that can be input to the comparators 17A to 17C. Thereafter, the induced voltage signals Uv3, Vv3, and Wv3 after the PWM noise is removed by the low-pass filter circuits 18A to 18C are generated, and an equivalent neutral point voltage is obtained from these voltage values. When this equivalent neutral point voltage and the induced voltage waveform Uv3 are input to the comparator, an induced voltage signal Ud is obtained. Similarly, the induced voltage signals Vd and Wd of the digital signal are obtained from the induced voltage waveforms Vv3 and Wv3 of the analog signal. These induced voltage signals Ud, Vd, Wd are input to the separating means 21 of the control device 11, and the energization switching timing is generated by the following processing.

  The separating means 21 separates the edge of the square wave pulse voltage Ps and the edge of the induced voltage generated by the rotation of the rotor 41 from the pulse signals of the induced voltage signals Ud, Vd, and Wd. Position detection signals Us, Vs, Ws comprising information on the induced voltage generated by the rotation of the rotation are generated and transferred to the excitation switching timing calculation means 22. The excitation switching timing calculation means 22 counts the intervals Te between the edges (induced voltage edges) of the position detection signals Us, Vs, Ws shown in FIG. Specifically, measurement by the counter is started using all edges of the position detection signals Us, Vs, and Ws as triggers, and the count value is cleared when any edge of the position detection signals Us, Vs, and Ws is detected next. At the same time, the next count is started. Here, when the brushless motor 1 is rotating, the induced voltage edge interval Te is generated at every electrical angle of 60 °. Therefore, the rotational speed and acceleration of the rotor 41 are calculated from the count value indicating the induced voltage generation interval. In response to this, the timing to switch the energization next is corrected, and the phase of the position detection signals Us, Vs, Ws is shifted by that amount to generate the phase detection signals Uss, Vss, Wss. The excitation signal output means 27 controls the inverter circuit 13 in accordance with the phase detection signals Uss, Vss, Wss, and switches the energization to the stator windings U, V, W to rotate the rotor 41 of the brushless motor 1. Let

Here, the excitation signal output means 27 includes a mask signal generation means 27A. The mask signal generation means 27A outputs a mask signal to the separation means 21 immediately before the excitation signal output means 27 outputs an energization pattern to the inverter circuit 13. Output.
For example, in the example of FIG. 21, the W-phase mask signal Wm is set to the H (High) level immediately before the occurrence timing of the edge of the U-phase position detection signal Uss. Similarly, the U-phase mask signal Um is set to the H (High) level immediately before the edge generation timing of the V-phase position detection signal Vss. Immediately before the occurrence timing of the edge of the W-phase position detection signal Wss, the V-phase mask signal Vm is set to the H (High) level. The signal levels of these mask signals Um, Vm, Wm are changed to L (Low) level after being maintained for a predetermined electrical angle.

  Note that the electrical angle that determines the pulse width of the mask signals Um, Vm, and Wm is always calculated in advance from the measured value of Te. Specifically, the intersection of the induced voltage waveforms Uv, Vv, Wv and the equivalent neutral point voltage is masked by the pulse of the mask signal, which is larger than the pulse width of the square wave pulse voltage Ps when rotated by a normal load. A value such that 0 ° <θ <30 ° is used.

  Thereafter, with respect to the induced voltage signals Ud, Vd, Wd input from the induced voltage I / F circuit 12, the pulses of the square wave pulse voltage Ps are removed by the mask signals Um, Vm, Wm, and the position detection signals Us, Vs and Ws are created, and energization control of the plural parallel motors 1 is performed.

  Here, the pulse width of the square wave pulse voltage Ps varies depending on the size of the load and the rotation speed. On the other hand, since the mask signals Um, Vm, and Wm have a constant pulse width, there are cases where the mask signal Um, Vm, and Wm can completely mask the pulse of the square wave pulse voltage Ps and cases where the mask signal cannot be completely masked. Arise.

  First, when the pulse width of the square wave pulse voltage Ps is equal to or smaller than the mask width, both the start edge and the end edge of the square wave pulse voltage Ps can be masked as shown in FIG. In this case, the separating unit 21 creates the position detection signals Us, Vs, Ws from the induced voltage signals Ud, Vd, Wd according to the induced voltage signal detection logic as shown in Table 1.

  In FIG. 22, the rising edge and falling edge of the square wave pulse voltage Ps starting from the electrical angle θ1 are ignored because the mask signal Um is at the H level. Since the rising edge at the electrical angle θ2 satisfies the condition for the induced voltage signal Ud of the rising edge in Table 1, it is regarded as the rising edge of the U-phase induced voltage. Similarly, the falling edge and rising edge of the square wave pulse voltage Ps starting from the electrical angle θ3 are ignored because the mask signal Um is at the H level. Since the falling edge of the induced voltage signal Ud at the electrical angle θ4 satisfies the conditions for the induced voltage signal Ud of the falling edge in Table 1, it is regarded as the falling edge of the induced voltage of the stator winding U. Similarly, with respect to the other induced voltage signals Vd and Wd, the rising edge and the falling edge of the induced voltage are determined according to the induced voltage signal detection logic shown in Table 1, and the position detection signals Us, Vs, and Ws are created.

  On the other hand, as shown in FIG. 23, when the pulse width of the square wave pulse voltage Ps exceeds the mask width, the start edge of the square wave pulse voltage Ps can be masked, but the end edge of the square wave pulse voltage Ps. Can not be masked. In such a case, the separating means 21 separates the induced voltage edge with reference to the square wave pulse voltage end edge determination logic as shown in Table 2 in addition to the induced voltage signal detection logic as shown in Table 1. The position detection signals Us, Vs and Ws are generated.

  In FIG. 23, the rising edge of the square wave pulse voltage Ps starting from the electrical angle θ1 is masked, but the falling edge of the same square wave pulse voltage Ps cannot be masked. Therefore, the falling edges shown in Tables 2 and 3 are used. It is checked whether or not the condition of the above is satisfied. In this case, since the conditions for the induced voltage signal Ud of the falling edge in Table 3 are satisfied, the position detection signal Us is created after removing the signal, considering the edge of the square wave pulse voltage Ps. The edge of the electrical angle θ2 satisfies the conditions in Table 1 as described above, and is therefore an induced voltage edge. Similarly, the falling edge of the square wave pulse voltage Ps starting from the electrical angle θ3 is removed by the mask signal Um, and the rising edge of the same square wave pulse voltage Ps is the condition for the induced voltage signal Ud of the rising edge in Table 3. Since it satisfies, it is removed. In this way, when there is a pulse of the square wave pulse voltage Ps that cannot be removed by the mask signal Um, the level of the voltage levels of the other induced voltage signals Vd and Wd is examined and the conditions shown in Tables 2 and 3 are satisfied. To determine whether or not it is necessary to remove the signal, and a signal based on the square wave pulse voltage Ps is removed to generate the position detection signal Us. Further, similarly, the position detection signals Vs and Ws are created.

  Here, a process for correcting the timing of switching energization when generating the phase detection signals Uss, Vss, Wss will be described. The correction is performed by a delay phase correction unit 22A provided in the excitation switching timing calculation unit 22. FIG. 23 shows the delay phase to be corrected. FIG. 24 schematically shows excitation timing and delay phases θ1 and θ2 in the U phase. The delay phase θ1 is caused by the low-pass filter circuits 15A to 15C of the induced voltage I / F circuit 12, and changes depending on the rotation speed. The delay phase θ2 is the sum of the induced voltage I / F circuit 12 at the subsequent stage from the comparators 17A to 17C, that is, the delay component θ2a by the comparators 17A to 17C and the low-pass filter circuits 18A to 18C, and the processing delay time θ2b of the microcomputer of the control device 11. (Θ2 = θ2a + θ2b), which is a value unique to the driving device 2. Therefore, the delay phase correction unit 22A functions as a filter delay phase correction unit that corrects the delay phase θ1 and a circuit delay phase correction unit that corrects the delay phase θ2.

First, the processing of the delay phase correction unit 22A as the filter delay phase correction means will be described.
When the range R5 shown in FIG. 25 is the control range of the rotational speed of the brushless motor 1, the low-pass filter circuits 15A to 15C have the cutoff frequency fc set in a frequency region higher than the range R5. FIG. 25 is a Bode diagram in which the horizontal axis represents logarithm of frequency and the vertical axis represents phase. A delayed phase θ1 is generated in the induced voltage signal that has passed through the low-pass filter circuits 15A to 15C having the cutoff frequency fc. The delay phase θ1 increases as the frequency increases.

The transfer function G (s) of the low-pass filter circuits 15A to 15C can be expressed by the following equation using τ (= C × R).
G (s) = 1 / (τs + 1) (1)
From equation (1), the delay phase θ1 [rad] is
θ1 = −arctan (ωτ) (2)

Here, the angular acceleration ω can be expressed as a function of the fundamental frequency f of the motor terminal voltage corresponding to the rotational speed.
θ1 = −arctan (2πτ × f) (3)
It becomes. If you change the unit to [°] and take the delay,
θ1 = arctan (2πτ × f) × 360 / 2π (4)
It becomes. Assuming that the time required to rotate the electrical angle of 60 ° is Ta, 1 / f = 6Ta, so θ1 = arctan (2πτ / 6Ta) × 360 / 2π (5)
The delay phase θ1 by the low-pass filter circuits 15A to 15C can be calculated from Expression (5). The delay phase θ1 may be calculated each time from the equation (5), but in this embodiment, the map is registered in the delay phase correction unit 22A, and the delay phase θ1 is obtained by searching at the time Ta.

Next, processing of the delay phase correction unit 22A as circuit delay phase correction means will be described.
The delay phase θ2 is generated by other circuits other than the low-pass filter circuits 15A to 15C and software processing. This delay phase θ2 is generated due to comparators 17A to 17C, low-pass filter circuits 18A to 18C, a microcomputer, and the like. The delay time T2 at this time is a constant value regardless of the rotation speed. Therefore, the delay phase θ2 can be calculated from the ratio of the delay time T2 to the time Ta required to rotate the electrical angle of 60 °.
θ2 = (T2 / Ta) × 60 [°] (6)

  From equation (6), it can be seen that since the delay time T2 is constant, the value of T2 / Ta increases and the delay phase θ2 increases as the rotational speed increases and the time Ta decreases. If equation (6) is also mapped, the calculation can be performed smoothly.

From the above, the timing Ew for switching excitation is
Ew = 30− (θ1 + θ2) (7)
become. By correcting the timing Ew using the map, the timing Ew can be quickly calculated. Further, by using the corrected timing Ew, the excitation can be switched with high accuracy regardless of the rotation speed.

Next, the case where the rotational speed is already in the region R2 at the start will be described.
As shown in FIG. 26, the state before starting becomes the same as the above-described free-run state. Even if the processing from step S103 to step S108 is performed according to the flowchart of FIG. 5, the free running state is hardly affected and the free running state can be maintained. Accordingly, the process proceeds from step S109 to step S110 to shift to the steady drive mode.

The case where the rotation speed is in the region R3 shown in FIG. 4 at the start will be described.
Even if steps S101 to S108 in FIG. 5 are performed, the rotor position signal cannot be extracted by the forward rotation dedicated logic in the induced voltage waveform of the rotor 41 rotating in the reverse direction. Therefore, when the rotor position signal cannot be detected for a predetermined time of, for example, about 1 to 9 seconds, the excitation switching timing signal from the free run mode 22C of the excitation switching timing calculation unit 22 is not sent to the mode selection unit 40. Therefore, it is determined that the mode selection means is in the reverse rotation state.
In this case, the control device 11 shown in FIG. 1 applies the two-phase lock energization to the brushless motor 1 with a low duty that does not cause overcurrent for a certain period of time in the brake stop mode 26E (brake stop mode 26E). The radiator fan acts as a brake, and the rotation speed of the radiator fan is reduced to approach the stop state.

  FIG. 27 shows the change in the rotational speed when the engine rotates in reverse at the start. The time for which the two-phase lock energization is continued is a preset brake energization time, for example, about 1 to 9 seconds. As a result, the rotational speed of the brushless motor 1 approaches -N1 to zero. This is because, as described above, the radiator fan has a small number of rotations and torque when it is rotating in the reverse direction.

  When the brake energization time has elapsed, start processing using inductance detection is performed. Since the radiator fan is a system with high friction, the mechanical time constant is large, and if it is forcibly stopped during reverse rotation, it takes time to start rotating in the reverse direction again due to the wind force. This is because it stays at R1. Thereafter, the above-described steps S102 to S108 are performed, and the routine shifts to the steady drive mode.

According to this embodiment, when the magnetic flux generated by the coil and the magnetic flux generated by the magnet are in the same direction, that is, the rotor position where the magnetic flux easily flows between the coil and the magnet, the inductance is reduced. Compared with this method, the rotor stop position can be detected with high accuracy and stability.
Since a special circuit for detecting inductance is not required, the circuit configuration can be simplified.

  Here, the brushless motor 1 is, for example, a motor having a large inertia such as a fan motor or a fuel pump motor, a slotless motor having no cogging torque, and a low loss motor having a small loss due to friction or cogging torque. It is done. In a slotless motor, the rotor stop position cannot be detected by inductance detection because there is no slot core. However, since the inertia is extremely small, it can be easily sucked to the predetermined rotation position by energization when detecting the stop position of the rotor. Therefore, the stop position is determined by such a method, and the electric angle 120 is determined therefrom. ° Energization pattern with delayed phase may be selected as starting excitation pattern.

Note that the present invention can be widely applied without being limited to the above-described embodiment.
For example, a reverse rotation dedicated logic may be used in addition to the forward rotation dedicated logic. The reverse rotation dedicated logic is selected by the rotation direction detection logic selection unit 24 when the rotation direction determination unit 23 determines that the rotation is reverse. The induced voltage signal detection logic shown in Table 3 and the square wave pulse voltage shown in Table 2 are selected. It consists of end edge determination logic and is registered in the separation means 21. By using the reverse rotation dedicated logic, it is possible to reliably detect the reverse rotation state.

The brake stop process in step S112 may be performed first. Even when the rotational speed of the brushless motor 1 is in any of the regions R1 to R3 at the start, the control is forcibly controlled to the region R1 by the brake stop process.
The rotor stop position may be determined by counting the count values for all six energization patterns.
A plurality of brushless motors 1 may be connected in parallel.
The starting method after detecting the rotor stop position and the driving method during steady rotation are not limited to the embodiment.

DESCRIPTION OF SYMBOLS 1 Brushless motor 2 Drive apparatus 11 Control apparatus 13 Inverter circuit 13A Shunt resistance (current measurement means)
29A Storage means 29B Counter 30 Current application time comparison means (position estimation means)
30A map 31 rotor position estimating means (position estimating means)
38 Overcurrent detection means (current comparison means)
41 Rotor U, V, W Coil

Claims (5)

A control device for a brushless motor comprising a rotor and a stator around which coils of a plurality of phases are wound,
Position signal generating means for generating a signal for instructing a plurality of predetermined energization patterns of currents flowing through the coils of a plurality of phases;
An inverter circuit for supplying a current to the coil by a signal from the position signal generating means;
Current measuring means used for measuring the current flowing in the coil;
A current comparison means for outputting a detection signal when a current value measured using the current measurement means is equal to or greater than a preset threshold; and
A counter for counting the current time from the signal instructing the energization pattern is outputted to said detection signal is output for each energization pattern,
Among the plurality of energization pattern, the position estimating means for determining and said energization time of the energization pattern is energized continuously difference, the rotor stop position and a rotor stop position from the related with the map corresponding to the difference Comprising
A control device for a brushless motor. The number of energization patterns that are energized continuously is two to four, and the energization patterns are estimated and controlled from combinations of signs of differences between the energization patterns. The brushless motor control device described. The brushless motor control device according to claim 1, wherein the current comparison unit is an overcurrent detection circuit that detects an overcurrent flowing through the inverter circuit. A control method of a brushless motor including a stator and a stator around which coils of a plurality of phases are wound,
Generating a signal for instructing a plurality of predetermined energization patterns of currents flowing through the coils of a plurality of phases;
Stopping the current supply when the current flowing through the coil is equal to or greater than a predetermined threshold;
Counting the energization time from the output of the signal that commands the energization pattern until the current flowing through the coil becomes equal to or greater than the threshold;
Among the plurality of current patterns, and the energization time of the energization pattern is energized continuously difference, determining a rotor stop position from the related with maps and a rotor stop position in accordance with the difference,
A method for controlling a brushless motor, comprising: The brushless motor control method according to claim 4, wherein the step of counting by the counter is performed for two to four energization patterns.

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