JP5766222B2 - Brushless fan motor driving device and starting method - Google Patents

Description

  The present invention relates to a brushless fan motor driving apparatus and a starting method.

  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.

  As another method for detecting the rotor stop position, a short pulse current that does not cause the rotor to move is simultaneously supplied from one coil to the other two coils to conduct three-phase energization. There is one that determines the rotor stop position by detecting the pulse width of the generated square wave pulse voltage (see, for example, Patent Document 2). Since the pulse widths of the two square wave pulse voltages generated simultaneously in the two coils slightly change depending on the difference in the rotor stop position, the rotor stop position is specified by comparing the two.

Also, as a conventional method for starting the brushless motor, the open pulse forced energization for forcibly switching the energization is performed without detecting the rotor position, and when the rotor position can be detected, the pulse signal described above is used. There is one in which the energization switching is controlled based on (see, for example, Patent Document 3).
In addition to this, the first energization pattern for positioning the rotor at a specific position is energized to suck the rotor position to the specific position to be in a locked state, and the second energization pattern advanced by 60 ° is energized for a short time. Thereafter, there is a method of starting the brushless motor by energizing a third energization pattern advanced by 60 ° from the second energization pattern (see, for example, Patent Document 4).

  Here, as a starting method in the case where the brushless motor rotates in reverse by an external load, for example, there is one disclosed in Patent Document 5. First, after the rotor rotation speed is reduced by three-phase energization, the energization is repeatedly turned ON / OFF during the three-phase energization, and the position where the phase current becomes zero and the phase difference are examined. The direction of rotation is determined from the phase difference of the current, and when it is determined that the motor is in the reverse rotation state, the reverse rotation frequency is obtained from the zero point generation cycle of each phase. After pulling in by supplying an alternating current of reverse rotation frequency, the frequency is gradually changed from the reverse rotation direction to the frequency in the normal rotation direction, and the rotational speed of the rotor is increased to a desired rotational speed and started.

JP 2004-40943 A JP 2002-335691 A Japanese Utility Model Publication No. 6-25224 JP 2001-211684 A JP 2001-128485 A

However, when detecting the rotor stop position, the method disclosed in Patent Document 1 must add a transistor, a resistor, a comparator, and the like that constitute a stop position detection circuit for detecting the rotor stop position. This has become a factor that complicates the device configuration. Also, since the difference in voltage rise time is small, the difference in inductance is also very small, making it difficult to make a precise determination.
The method as disclosed in Patent Document 2 has an advantage that a special circuit is not required. However, since the difference in inductance due to applied voltage is small in three-phase energization, the difference in pulse width of the square wave pulse voltage is small. As a result, accurate detection was difficult.
In addition, when the open-loop forced energization is performed by the conventional method of starting the brushless motor, it is difficult to set parameters because it is vulnerable to disturbance and the parameter dependence of the brushless motor is large. Further, since the rotor starts to rotate gradually by continuing the forced energization, it takes a long time to start and the torque at the start is small. Note that if forced energization switching is performed many times, it will be more susceptible to disturbances.
Even when the rotor is locked with a predetermined energization pattern or when measuring the inductance, it is necessary to perform forced open-loop energization until the rotor position can be detected after the brushless motor starts rotating. So it has a similar problem. Furthermore, when the rotor is locked, a long inertia time is required for a motor having a large inertia until the rotor is positioned.
When starting from the reverse rotation state, the rotation direction and the frequency of rotation are calculated after checking the position where the phase current becomes zero, so that complicated processing is required. In addition, since the frequency is gradually changed from the reverse direction to the normal direction, it takes a long time to start.
The present invention has been made in view of such circumstances, and a main object thereof is to start a motor in a short time by a simple method and to obtain a large torque at the time of starting.

The invention according to claim 1 of the present invention for solving the above-mentioned problems is a brushless fan motor drive device that drives a brushless fan motor that is provided for a radiator in an engine room and is used for a rotation mechanism of a radiator fan. And energizing the brushless fan motor for an initial energization time with an excitation pattern that matches the rotor stop position of the brushless fan motor when starting the brushless fan motor, and then de-energizing the rotor of the brushless fan motor. Among the energization pattern determining means for free-running and the time interval of the signal of the induced voltage generated at the terminal of the brushless fan motor during the free-running, the signal of the second to third induced voltage after the brushless fan motor is started The rotor position is detected based on the time interval of Possess the excitation switch timing calculating means for determining the timing and the and 2-3 times of signal, when the time interval of 3 to 4 times of signal are equal, the time interval of the signal 2-3 th induced voltage The excitation timing is determined by detecting the position of the rotor based on the above, and when the time interval between the second and third signals and the third and fourth signals changes, the next time interval is determined. The brushless fan motor drive device is characterized in that the excitation timing is calculated by estimation .
In this brushless motor drive device, after accelerating, it is put into a free-run state and the rotor position is detected from the induced voltage generated during the free-run so that the rotational position of the rotor can be correctly detected when it is started. Since the induced voltage at this time is not affected by the pulse width modulation signal or the like, the rotor position is correctly detected. After detecting the rotor position, normal energization switching is performed.

According to a second aspect of the present invention, in the brushless fan motor drive device according to the first aspect, the initial energization time is equal to or less than the time from the start of rotation of the rotor to the first energization switching timing. It is characterized by being.
In this brushless motor drive device, acceleration is performed within a range in which the rotor is not attracted to the stator and reverse torque is generated, so that the free-running can be performed at a rotational speed sufficient to detect the rotor position .

According to a third aspect of the present invention, there is provided a brushless fan motor starting method for starting a brushless fan motor disposed on a radiator in an engine room and used for a rotating mechanism of a radiator fan, wherein the rotor of the brushless fan motor is used. After energizing the brushless fan motor for an initial energization time with an excitation pattern that matches the stop position of the brushless fan motor, freeing the energization and free-running the rotor of the brushless fan motor; A step of detecting the position of the rotor based on the time interval of the second to third induced voltage signals after the start of the brushless fan motor, among the time intervals of the induced voltage signals generated at the terminals; Switching the excitation pattern based on the position of the rotor , Have a, wherein the 2-3 th signal, if the time interval of 3 to 4 times of signal are equal, based on the time interval of the signal 2-3 th induced voltage, detects the position of the rotor On the other hand, when the time interval between the second and third signals and the third and fourth signals changes, the next time interval is estimated to calculate the excitation timing. The starting method of the characteristic brushless fan motor was used.
In this brushless motor starting method, when the rotor starts to rotate, the energization is stopped and a free-run state is set. The position of the rotating rotor is detected from the induced voltage generated at this time. Thereafter, normal energization switching is performed based on the detected rotor position to control the drive of the brushless motor.

According to a fourth aspect of the present invention, in the brushless fan motor starting method according to the third aspect , the initial energization time is equal to or less than the time from the start of rotation of the rotor to the first energization switching timing. And the step of detecting the position of the rotor is performed until a signal of an induced voltage generated at a terminal of the brushless fan motor when the rotor is rotated is generated for the fourth time. .
In this brushless motor starting method, at the time of starting, acceleration is performed until a time corresponding to the first energization switching timing, free running is performed, and the position of the rotor is detected by a time corresponding to the fourth energization switching timing .

According to the present invention, an induced voltage generated at a motor terminal can be detected without being affected by a pulse width modulation signal or the like by creating a free-run state at the time of starting. This makes it possible to correctly detect the rotor position without being affected by disturbance. Further, since the rotor position is detected during free running, it is possible to detect the rotor position in a short time and shift to normal operation.
If it is determined that the brushless motor is not rotating in the forward direction at the start, the energization control is performed to stop the rotor and then the start process is performed again. Can be started. This eliminates the need for complicated processing for determining the reverse direction.

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 illustrates typically that a process changes with the rotational speed at the time of a start. It is a flowchart explaining the outline | summary of the process at the time of starting. It is a figure which illustrates typically the flow of the magnetic flux when it supplies with the excitation pattern at the time of a start, and the excitation pattern. It is a graph explaining the procedure and timing which measure the square wave pulse voltage width with respect to each excitation pattern. It is a graph for demonstrating the relationship between a rotor position and a starting excitation pattern. 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. 4 is a timing chart when starting from a region R2 in FIG. 3. 4 is a timing chart when starting from a region R3 in FIG. 3. It is a figure explaining the procedure and timing in the case of measuring a square wave pulse voltage width twice. It is a flowchart explaining the outline | summary of the process at the time of starting. It is a flowchart explaining the outline | summary of the process at the time of starting. It is a flowchart explaining the outline | summary of the process at the time of starting. It is a figure which shows concretely the method of determining the energization time in the case of performing the open loop control to the method of determining initial energization time, and three energization switching.

  The best mode for carrying out the invention will be described in detail with reference to the drawings. Note that the same reference numerals are given to the same components in each embodiment. Moreover, the description which overlaps between embodiment is abbreviate | omitted.

(First embodiment)
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.
The brushless motor 1 has a rotor having a permanent magnet and a stator, and three-phase (U, V, W) coils are wound around the stator in order in the circumferential direction. This brushless motor system is a sensorless type system that does not have a sensor for detecting the rotor position.

  The driving device 2 includes a control device 11 constituted by a microcomputer, an induced voltage I / F (interface) circuit 12 for detecting a voltage applied to a current line forming a three-phase coil of the brushless motor 1, an inverter 13 and a voltage dividing circuit 14 that is a level conversion circuit that converts the level of the voltage applied to the energization line of the brushless motor 1, and between the control device 11 and the inverter 13, pre-drivers 37A and 37B, An overcurrent detection circuit 38 and overcurrent protection means 39 are provided.

  As shown in FIG. 2, the induced voltage I / F circuit 12 receives a voltage (analog signal) of each of the three-phase motor terminals and divides the voltage into a voltage that can be input to the comparators 17A to 17C (resistor R1 and resistor R2) and low-pass filter circuits 15A, 15B, and 15C composed of a primary CR filter (resistor R2 and capacitor C1) for removing noise of the pulse width modulation signal, and a circuit 16 for detecting an equivalent neutral point potential Comparators 17A, 17B, and 17C that generate pulse signals from the equivalent neutral point potential and the analog signal of the induced voltage that appears in the non-energized phase (open period), and a low-pass filter that cuts chattering components from the outputs of the comparators 17A to 17C ( Primary CR filters) 18A, 18B, 18C.

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 composite signal generation circuit 19 through the low-pass filter circuits 18A to 18C.

The inverter 13 is a circuit formed by connecting six switching elements by two bridges between the positive and negative terminals of the power supply 20, and the DC voltage supplied from the power supply 20 is a pulse input from the control device 11. It is converted into an AC voltage based on a width modulation signal (drive signal) and applied to each phase of the brushless motor 1. A shunt resistor 13A is provided between the inverter 13 and the ground level. The current flowing through the inverter 13 using the shunt resistor 13A, that is, the current input to the brushless motor 1 can be detected using the overcurrent detection circuit 38.
The voltage dividing circuit 14 divides a terminal voltage (for example, 12V or 36V) generated in each energization line of the brushless motor 1 by two resistors and can be used by the control device 11 (for example, 3V or 5V). ).

  The control device 11 includes a separation unit 21 connected to the induced voltage I / F circuit 12, an excitation switching timing calculation unit 22, a rotation direction determination unit 23, a rotation direction detection logic selection unit 24, and a brake stop unit 25. , Energization pattern determination means 26, excitation voltage output means 27, and PWM duty determination means 28. The control device 11 is connected to the voltage dividing circuit 14 and includes a square wave pulse voltage width detection means 29, a square wave pulse voltage width comparison means 30, and a rotor position estimation means 31 that are used at the time of starting. Furthermore, it has an overcurrent protection means 32 connected to the overcurrent detection circuit 38.

The separation means 21 performs processing for separating the edge of the pulse signal input from the induced voltage I / F circuit 12 into an edge of the induced voltage and an edge of the square wave pulse voltage. 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. Calculate timing. The excitation switching timing calculation means 22 is provided with a delay phase correction unit 22A that corrects the excitation switching timing.
The rotation direction determination unit 23 determines the rotation direction from the excitation switching timing, and outputs a predetermined command to the rotation direction detection logic selection unit 24 and the brake stop unit 25. The rotation direction detection logic selection unit 24 is used when the logic used by the separation unit 21 can be selected depending on the rotation direction of the brushless motor 1. The brake stop means 25 is used when energizing a current energization pattern that stops the brushless motor 1.

  The energization pattern determination unit 26 includes a steady-state excitation unit 33, a stop position detection unit 34, a free-run control unit 35, and a start-up excitation unit 36. The constant excitation means 33 determines an excitation pattern corresponding to the rotor position at the excitation switching timing calculated by the excitation switching timing calculation means 22. The stop position detecting means 34 receives a start command from the outside and causes the excitation voltage output means 27 to generate a pulse width modulation signal for detecting the rotor stop position. The starting excitation means 36 determines an excitation pattern corresponding to the rotor stop position corresponding to the square-wave pulse voltage width determined to be the minimum by the rotor position estimation means 31. The free-run control means 35 performs a process of detecting the rotor position by causing the brushless motor 1 to free-run after energizing the starting excitation pattern for a predetermined initial energization time Ts1. Details of these processes will be described later.

  The excitation voltage output means 27 outputs a signal for applying an excitation current to the coil of the brushless motor 1 to each of the pre-drivers 37A and 36B. 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 a signal is input from the overcurrent protection means 39 when an overcurrent flows through the inverter 13. When an overcurrent is detected, a signal is input to the overcurrent protection means 32 and a software reset is applied.

  The square wave pulse voltage width detection unit 29 performs a process of detecting the square wave pulse voltage width from the signal input from the voltage dividing circuit 14. The square wave pulse voltage width detection means 29 has a storage means 29A such as a memory, and can store the detected square wave pulse voltage width data in association with the excitation pattern at that time. The square wave pulse voltage width comparison means 30 compares data of a plurality of square wave pulse voltage widths stored in the storage means 29A of the square wave pulse voltage width detection means 29 and determines the smallest one. The rotor position estimation means 31 estimates the rotor position at a stop or at a low speed based on the comparison result of the square wave pulse voltage width.

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 rotated by an external load. Furthermore, when the brushless motor 1 is rotated, there are a case where the brushless motor 1 is rotating forward and a case where the brushless motor 1 is rotating reversely. 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 rotates in reverse with an external load, control at the time of starting is performed assuming that the rotation speed and torque are small.

  FIG. 3 schematically shows the classification of the starting method according to the rotational speed of the brushless motor 1 at the time of starting. 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 in the forward rotation direction is greater than the region R1, the rotor position is detected by detecting the induced voltage and the rotation is controlled. When the rotational speed in the reverse rotation direction is larger than the region R1, reverse rotation state determination processing, rotor stop processing, and start start processing by inductance detection are 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.

Further, in a region R3 that is smaller than the region R1, that is, the rotational speed is high in the reverse rotation direction, the rotor position is detected after the brushless motor 1 is braked, as will be described later. 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 brushless motor 1 is regarded as being in the region R3, and the processing corresponding to the region R3 is repeated. A specific example of such a starting method will be described with reference to the flowchart of FIG.

  When a start start command is input to the stop position detection means 34, overcurrent detection is performed (step S101). The overcurrent is monitored by the current value flowing through the shunt resistor 13A of the inverter 13. When the current flowing through the shunt resistor 13A exceeds a predetermined value, it is determined as an overcurrent, that is, an overload state (Yes in step S101), and all phases are turned off and stop processing is performed (step S102). Exit. If no overcurrent is detected (No in step S101), a rotor position detection process based on inductance detection is performed (step S103). The overcurrent check is constantly monitored by another program that is processed in parallel. If an overcurrent is detected during the processing after step S103, the processing is stopped at that point.

When the rotor stop position is detected by the inductance detection, the starting excitation means 36 determines a starting excitation pattern having a phase capable of generating the maximum torque with respect to the rotor position, and the excitation voltage output means 27 outputs the starting excitation pattern. (Step S104). The initial energization counter is activated, and the aforementioned phase is energized until a preset initial energization time Ts1 elapses (step S105). When the initial energization time Ts1 elapses (Yes in step S105), the free-run control means 35 turns off the energization of all phases and free-runs (step S106). From the induced voltage generated while the rotor 41 is free running due to inertia, the position of the rotor 41 is detected using the forward rotation exclusive logic (step S107). When the rotor position has been detected a predetermined number of times (Yes in step S108), the process shifts to sensorless driving (steady driving mode) by the induced voltage using the steady state excitation means 33 (step S109).
If the rotor position cannot be detected a predetermined number of times (No in step S108), the process waits until the counter for measuring the edge interval of the induced voltage overflows a preset number of times (step S110). When the counter overflows a predetermined number of times (Yes in step S110), the rotation direction determination means 23 determines that the brushless motor 1 is reversely rotated. As a result, as a brake process by the brake stop means 25, a two-phase energization lock process is performed with a low duty (step S111). The brake process is performed for a predetermined time, and when this time has elapsed (step S112), the process returns to step S101.

Here, Step S103 to Step S105 are processes when the initial rotational speed is within the range of the region R1 and the region is accelerated from here to the region R2.
Details of step S103 will be described. Here, 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 by focusing on the fact that the permeability of the magnet core increases and the inductance decreases.

  When starting the brushless motor 1 in a stopped state, a start command is input from the outside to the stop position detecting means 34 of the control device 11. The stop position detection means 34 issues a command to the excitation voltage output means 27 so that six predetermined excitation patterns for stop position determination 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 voltage output means 27 outputs a pulse width modulation signal corresponding to the excitation pattern to the inverter 13, and the switching element is turned on / off in response to the pulse width modulation signal to energize any two of the three phases. .

Here, the excitation pattern for stop position determination commanded by the stop position detecting means 34 is shown in FIG. These excitation patterns # 1 to # 6 are patterns that can drive the brushless motor 1.
In excitation pattern # 1, a current flows from a U-phase coil (hereinafter referred to as U-phase) to a V-phase coil (hereinafter referred to as U-phase). The U phase is N pole magnetized and the V phase is S pole magnetized. When the arrangement of the U, V, and W phases and the stop position of the rotor 41 are as shown in the figure, as shown by the arrows, the U-phase passes through the S pole and N pole of the permanent magnet 42 of the rotor 41 in order, A magnetic flux toward the V phase is formed.
In excitation pattern # 2, a current flows from the U phase to the W phase. The U phase is N pole magnetized and the W phase is S pole magnetized. As indicated by the arrow, a magnetic flux is formed from the U phase through the S pole and the N pole of the permanent magnet of the rotor 41 in that order toward the W phase.
In excitation 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. As indicated by the arrow, a magnetic flux is formed from the V-phase to the S-phase and N-pole of the permanent magnet of the rotor 41 in that order and toward the W-phase.
In excitation 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. As indicated by the arrow, a magnetic flux is formed from the V phase through the S pole and the N pole of the permanent magnet of the rotor 41 in that order and toward the U phase.
In excitation 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. As indicated by the arrow, a magnetic flux is formed from the W phase through the S pole and the N pole of the permanent magnet of the rotor 41 in that order toward the U phase.
In excitation 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 indicated by the arrow, a magnetic flux is formed from the W phase through the S pole and the N pole of the permanent magnet of the rotor 41 in this order and toward the V phase.

As shown in FIG. 6, the stop position inspection of the rotor 41 in this embodiment performs energization control with steps 0 to 11 as one set. Each step is incremented every time the value of the counter in the control device 11 reaches a predetermined value. When incrementing a step, the counter is reset each time.
In step 0, the excitation pattern # 1 is selected and energization is performed with the duty of the pulse width modulation signal being 100%. The remaining W phase is released. In step 1, the duty is set to 0% and neither phase is energized. When Step 0 ends and the process proceeds to Step 1, the electrical energy stored in the coil at the moment when the switching element of the inverter 13 is turned off flows as a current through the return diode of the switching element. At this time, a square wave pulse voltage is generated at the V-phase terminal. This terminal voltage is taken as a square wave pulse voltage into the voltage dividing circuit 14 and divided and input to the square wave pulse voltage width detecting means 29. The square wave pulse voltage width detecting means 29 checks the count value when the falling edge of the pulse is detected. Since the count value corresponds to the elapsed time from the step switching timing, this count value is stored in the storage means 29A as the square wave pulse voltage width for the excitation pattern # 1 (UV energization).

In step 1, processing such as the square wave pulse voltage width detecting means 29 is executed and the counter is counted up. When the count value reaches the same predetermined value as in step 0, the counter is reset and the process proceeds from step 1 to step 2. In step 2, excitation pattern # 2 is used, and the duty of the pulse width modulation signal is set to 100%. The remaining V phase is opened. In step 3, the duty is set to 0%, and neither phase is energized, and the count value when the edge of the square wave pulse voltage generated in the W phase falls is examined, and the excitation pattern # 2 (UW energization) The square wave pulse voltage width is stored in the storage means 29A.
In step 4, the U phase is released by energizing with excitation pattern # 3. In Step 5, without energizing any phase, the pulse width of the square wave pulse voltage generated in the W phase is examined and stored in the storage means 29A as the square wave pulse voltage width for the excitation pattern # 3 (VW energization).
In Step 6, the W phase is released by energizing with excitation pattern # 4. In step 7, without energizing any phase, the pulse width of the square wave pulse voltage generated in the U phase is checked and stored in the storage means 29A as the square wave pulse voltage width for excitation pattern # 4 (VU energization).
In step 8, energization is performed with excitation pattern # 5 to release the V phase. In step 9, without energizing any phase, the pulse width of the square wave pulse voltage generated in the U phase is checked and stored in the storage means 29A as the square wave pulse voltage width for excitation pattern # 5 (WU energization).
In step 10, the U phase is released by energizing with excitation pattern # 6. In step 11, without energizing any phase, the pulse width of the square wave pulse voltage generated in the V phase is examined and stored in the storage means 29A as the square wave pulse voltage width for the excitation pattern # 6 (WV energization).

Then, at the timing of step 12 following step 11, the rotor position estimation unit 31 has the respective square wave pulse voltages of the excitation patterns # 1 to # 6 stored in the storage unit 29 </ b> A of the square wave pulse voltage width detection unit 29. The excitation pattern having the minimum value is checked from the width, and the rotor position where the inductance is minimized by the excitation pattern is set as the stop position of the rotor 41. In the example of FIG. 5, since the magnetic flux flows most easily in the excitation pattern # 6, the pulse width of the square wave pulse voltage of the excitation pattern # 6 is the smallest. The position of the rotor 41 at this time is the stop position.
The details of the processing of the rotor position estimating means 31 will be specifically described. When it is known in advance that the count value of the square wave pulse voltage width is 1000 or less, the initial value is set to 1000 in the memory storing the minimum value. A larger value is stored and compared with the count value of the square wave pulse voltage width of excitation pattern # 1. When the count value is small, the data stored in the minimum value memory is replaced with the count value of the excitation pattern # 1 from the initial value. The data of the minimum value memory and the count values of all the square wave pulse voltage widths are compared in order, and the smaller count value is stored in the minimum value memory. Finally, the stored count value becomes the minimum value, and the excitation pattern at that time becomes the excitation pattern in which the square wave pulse voltage width is minimized.

  Details of step S104 will be described. The starting excitation means 36 selects an excitation pattern delayed by 120 ° in the rotation direction from the excitation pattern having the smallest square wave pulse voltage width as the excitation pattern at the start. This will be described with reference to a specific example in FIG. In FIG. 7, the horizontal axis is the phase (electrical angle) and the vertical axis is the torque. Line L1 indicates cogging torque, and lines L2 to L4 indicate the relationship between phase and torque in energization patterns # 6, # 1, and # 2, respectively. For example, if the square wave pulse voltage width is the smallest in the excitation pattern # 6 energized from the W phase to the V phase, and the excitation pattern # 6 is the starting excitation pattern, the torque at the electrical angle of 0 ° is zero, so the brushless motor 1 cannot be rotated. When the electrical angle is 0 °, the positive torque is large in the excitation pattern # 1 (60 ° phase-lag energization) advanced by 1 and the excitation pattern # 2 (120 ° phase-lag energization) advanced by two. However, when starting with the excitation pattern # 1 shown in the line L3, the torque decreases thereafter, so that the force for rotating the rotor 41 is small. On the other hand, when starting with the excitation pattern # 2 shown in the line L4, since the torque increases thereafter, the rotor 41 can be rotated with a large force.

Each process so far will be described in more detail with reference to FIG. In FIG. 8, the horizontal axis indicates the passage of time, and various types of information are arranged in the vertical direction. The hall sensor combined 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 (step S104). 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 has elapsed at time t3, the free-run control means 35 turns off the energization of all phases (corresponding to step S106). 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. Therefore, the first signal SL1 is generated as the excitation switching timing signal corresponding to the rising edge of the three-phase composite signal. 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 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 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 excitation switching timing is determined based on the three-phase composite signal generated from the comparison result of the motor terminal voltage and the equivalent neutral point potential, and the energization pattern switching control is performed, thereby synchronizing the brushless motor 1. Driving is performed. 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. 9, at the time of start-up, the duty of the pulse width modulation signal (PWM) is set to 50%, the current is suppressed, and then the rotational speed is increased. After the initial energization time Ts1 has elapsed, the duty is once set. Set to 0% and free run. When the free run is completed, the duty is again set to 50%, and then the duty is gradually increased so that the rotational speed reaches the target value (for example, the maximum rotational speed) when the duty finally reaches 100%. . 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.

Details of the sensorless drive (steady drive mode) by the induced voltage in step S109 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 1 and a square wave pulse voltage end edge determination logic shown in Table 2.
Note that the forward rotation dedicated logic is referred to by the separation unit 21 in response to a command from the rotation direction detection logic selection unit 24 when the rotation direction determination unit 23 illustrated in FIG. 1 determines that the brushless motor 1 is rotating forward.

  FIG. 10 shows signal waveforms when energization control is performed in the steady drive mode. In FIG. 10, the horizontal axis represents the electrical angle, and the vertical axis represents the energized state from the upper side to each of the stator windings U, V, W and the actual induced voltage waveform Uv of each stator winding U, V, W. , Vv, Wv (analog signals) and induced voltage signals Ud, Vd, Wd (digital signals) of the respective stator windings U, V, W are shown. The energization state of the uppermost stator windings U, V, W is such that the stator windings U, V, W added with “+” in the upper stage are on the high potential side, and “−” is in the lower stage. It shows that the added stator windings U, V, W are on the low potential side. That is, “W +” and “V−” between the electrical angles of 0 ° and 60 ° indicate that the stator winding W is energized to the stator winding V (equivalent to the energization pattern # 6 in FIG. 5). . 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. 11 is a diagram schematically showing a mask signal generation process and a position detection signal generation process. In FIG. 11, 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. 10) of the stator windings U, V, W from the upper side, and the stator winding. Position detection signals Us, Vs, Ws of lines U, V, W, position detection signals Uss, Vss, Wss after phase shift of electrical angle 30 °, square wave pulse voltage signal Um of stator winding U, fixed A square wave pulse voltage signal Vm of the child winding V and a square wave pulse voltage signal Wm of the stator winding W are illustrated in order.

  The induced voltage waveforms Uv, Vv, and Wv of the stator windings U, V, and W shown in FIG. 10 are input to the induced voltage I / F circuit 12 (see FIG. 1) and divided by the low-pass filter circuits 15A to 15C. 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, and Ws made up of information on the induced voltage generated by the rotation of the rotation are generated and passed 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 voltage output means 27 controls the inverter 13 in accordance with these 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. .

Here, the excitation voltage output means 27 is provided with 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 voltage output means 27 outputs an energization pattern to the inverter. To do.
For example, in the example of FIG. 11, the mask signal Wm of the stator winding W is set to the H (High) level immediately before the occurrence timing of the edge of the position detection signal Uss of the stator winding U. Similarly, the mask signal Um of the stator winding U is set to H (High) level immediately before the occurrence timing of the edge edge of the position detection signal Vss of the stator winding V. Immediately before the edge generation timing of the position detection signal Wss of the stator winding W, the mask signal Vm of the stator winding V is set to 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 brushless motor 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. 12, 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 induced voltage of the stator winding U. 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. 13, 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 separation means 21 refers 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 and determines the induced voltage edge. The position detection signals Us, Vs, and Ws are created.

  In FIG. 13, 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 1 and 2 are used. It is checked whether or not the condition of the above is satisfied. In this case, since the condition for the induced voltage signal Ud of the falling edge in Table 2 is satisfied, it is regarded as the edge of the square wave pulse voltage Ps, and the position detection signal Us is created after removing this signal. 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 2. 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 1 and 2 are obtained. 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. 14 shows a delay phase to be corrected. FIG. 14 schematically shows excitation timing and delay phases θ1 and θ2 in the U phase. The delay phase θ1 varies depending on the rotation speed caused by the low-pass filter circuits 15A to 15C of the induced voltage I / F circuit 12. The delay phase θ2 is the sum of the delayed component θ2a of the induced voltage I / F circuit 12 from the comparators 17A to 17C, that is, the comparators 17A to 17C and the low-pass filters 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 R4 shown in FIG. 15 is a 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 R4. FIG. 15 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 filters 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 filters 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)

  (Equation 6) shows that since the delay time T2 is constant, the value of T2 / Ta increases and the delay phase θ2 increases as the rotation 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. 16, the state before starting is the same as the above-described free-run state. Even if the processing from step S103 to step S106 is performed according to the flowchart of FIG. 4, there is little influence on the free running rotational state, and the free running state can be maintained. Therefore, the process proceeds from step S108 to step S109 to shift to the steady drive mode.

A case where the rotational speed is in the region R3 at the start will be described.
Even if step S101 to step S107 of FIG. 4 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 (equivalent to step S110), it is determined that the rotation direction determination means 23 is in the reverse rotation state.
In this case, the control device 11 shown in FIG. 1 causes the brake stop means 25 to apply the two-phase lock energization to the brushless motor 1 with a low duty that does not cause an overcurrent for a certain period of time. The radiator fan acts as a brake, and the rotation speed of the radiator fan is reduced to approach the stop state. As shown in FIG. 17, 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 S103 to S108 are performed, and the routine shifts to the steady drive mode.

According to this embodiment, it is possible to examine the magnitude of the inductance from the square wave pulse voltage width by performing two-phase energization. The pulse width is easier to measure than in the case of measuring the voltage rise time as in the prior art, and it is not necessary to add a special circuit. The apparatus configuration can be simplified and the manufacturing cost can be reduced.
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. In addition, the rotor stop position can be detected stably.
When changing from N-pole magnetization to S-pole magnetization in the order of excitation patterns for generating square-wave pulse voltage, that is, the search order of the rotor stop position, an excitation pattern that is not energized during that time is executed. Since the switching order is adopted, it is difficult to be affected by the residual magnetization of the iron core around which the coil is wound, and the inductance detection accuracy can be improved.

  The rotor position estimating means 31 may check the maximum value instead of checking the minimum value of the square wave pulse voltage width. In this case, the square-wave pulse voltage width detection unit 29 stores the largest pulse width in the storage unit 29A in association with the excitation pattern at that time. The starting excitation unit 36 starts the brushless motor 1 by selecting the energizing pattern delayed by 60 ° in the rotation direction from the excitation pattern giving the maximum pulse width by the starting excitation unit 36. For example, in the example shown in FIG. 5, the excitation pattern # 3 has the smallest square wave pulse voltage width because the magnetic flux hardly flows, so the previous excitation pattern # 2 is determined as the starting excitation pattern.

  Further, the square wave pulse voltage width may be measured a plurality of times. For example, a process when measuring twice is described with reference to FIG. In the stop position inspection in this case, the energization control is performed with 24 steps 0 to 23 as one set, and the stop position is estimated in the 25th step 24. In Step 0 and Step 1, the excitation pattern # 1 is energized and then released, and the pulse width of the square wave pulse voltage generated in the W phase is counted. In step 2 and step 3, the same processing as in step 0 and step 1 is repeated. Steps 4 and 5 and steps 6 and 7 perform the same processing for the excitation pattern # 2. Thereafter, until the step 23, the same square wave pulse voltage width is counted twice in order for each of the excitation patterns # 3 to # 6.

At this time, the square wave pulse voltage width detection means 29 has the entire square wave pulse voltage width (count value) measured twice in the storage means 29A or only the square wave pulse voltage width (count value) measured second time. Are stored in association with the excitation pattern. In the stop position estimation process of step 24, the square wave pulse voltage width measured for the second time is compared in the same manner as described above. The excitation pattern having the smallest square wave pulse voltage width is determined as the starting excitation pattern.
In this way, when the brushless motor 1 is configured to be easily affected by the residual magnetization of the coil core, the influence of the residual magnetization can be further reduced and the inductance detection accuracy can be improved.

  Here, the stop position estimation process may calculate an average value of square wave pulse voltage widths (count values) measured a plurality of times for the same excitation pattern, and compare the magnitudes of the average values in the same manner as described above. . By performing the averaging process, the inductance detection accuracy can be further improved. Even when the square wave pulse voltage width is acquired a plurality of times, the rotor stop position and the start excitation pattern may be determined by examining the maximum value instead of the minimum value.

Further, in this embodiment, since the free-run state is created when the brushless motor 1 is started, the position detection of the rotor 41 which has started to rotate with all phases opened can be performed without noise. It becomes possible. For this reason, the rotor position can be detected promptly and accurately.
Since the energization time (Ts1) until free running is within a range where no reverse torque is generated, the rotor 41 is not greatly decelerated during free running, and the rotor position can be detected correctly.
If the second and subsequent signals SL2 to SL4 are used without using the first signal SL1 generated at the time of free-running, correct detection is possible even when a signal due to the square wave pulse voltage is generated the first time. .

  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. As described above, the method for detecting the rotor stop position and the method for determining the starting excitation pattern are not limited to the method based on the inductance, and various methods can be used.

  Further, according to this embodiment, when starting the brushless motor 1, even when the rotor 41 is rotating in the reverse direction, it is possible to detect the rotor position using the coil inductance by performing the braking process. . From here, the brushless motor 1 can be started, and it is possible to promptly shift to a steady operation by 120 ° energization. When the brushless motor 1 is not energized, the brushless motor 1 is reliably started by performing start-up control corresponding to the state in which the rotor 41 is rotating forward / reversely due to the influence of wind or the like and the state where it is stopped. it can. For example, when the brushless motor 1 is used for driving a radiator fan of an engine cooling system such as an automobile, the reliability of the system can be improved.

(Second Embodiment)
This embodiment is characterized in that reverse rotation dedicated logic is used in addition to forward rotation dedicated logic. The apparatus configuration is the same as that of the first embodiment.
FIG. 19 shows a flowchart of the operation at the start. The process from step S101 to step S108, that is, when the rotation speed of the brushless motor 1 at the start of the start is in the region R1 or the region R2 in FIG. 3, is the same as that in the first embodiment. When the rotation speed at the start is in the region R3, the process proceeds from step S108 to step S110A.

  In step S110A, the induced voltage is detected and the rotor position is detected using the reverse 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 2 and the square wave pulse voltage shown in Table 1 are selected. It consists of end edge determination logic and is registered in the separation means 21. Using such reverse rotation dedicated logic, 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 switching pulse and detect the rotor position. . The processing here is the same as in the steady drive mode in the first embodiment, except that the logic used is different.

When the rotor position detection process is performed and a rotor position detection signal is actually obtained (Yes in step S110B), the processes after step S111 are performed. The rotor position detection signal only needs to be generated once or more as long as it can be confirmed that the rotation is reverse. The processes after step S111 are the same as those in the first embodiment.
On the other hand, when the rotor position detection signal is not obtained (No in step S110B), after waiting for a certain time (Yes in step S110C), the process proceeds to step S111.

  In this embodiment, the reverse rotation state can be reliably detected by using the reverse rotation dedicated logic. Other effects are the same as those of the first embodiment.

(Third embodiment)
This embodiment is characterized in that the brake processing is first performed.
As shown in FIG. 20, after performing an overcurrent detection process (step S101), a two-phase energization lock process with a low duty is performed (step S102A). The brake time is a fixed time (step S102B). These processes are processes corresponding to steps S111 and S112 in the first embodiment. Even when the rotational speed of the brushless motor 1 is in any of the regions R1 to R3 at the time of starting, it is forcibly controlled to the region R1 by the brake process. Subsequent processing is the same as in the first embodiment.
Further, as shown in FIG. 21, even when using the reverse rotation dedicated logic (corresponding to step S110A), the rotational speed of the brushless motor 1 is set to any region R1 by first performing the brake processing in steps S102A and S102B. Even in the case of ˜R3, the region is forcibly controlled to the region R1 by the brake process.

Note that the present invention can be widely applied without being limited to the above-described embodiment.
For example, when the terminal voltage fluctuates, such as when the power supply voltage fluctuates, it is desirable to use a level conversion circuit instead of the voltage dividing circuit 14. The level conversion circuit uses transistors, FETs, comparators, and the like, and is configured so that the terminal voltage can be lowered according to the power supply voltage.
The energization control at the start is not limited to the duty of 50% as long as the current value is monitored from the shunt resistor 13A and controlled so as not to exceed a predetermined value.
The initial energization time Ts1 may be obtained by substituting predetermined physical constants into the voltage / current equation and the position / torque equation, or may be determined by simulation.

If the initial energization time Ts1 alone cannot be used to accelerate to a rotational speed sufficient for rotor position detection, forced energization by several open loops may be performed to sufficiently accelerate and then shift to a free-run state. For example, as shown in FIG. 22, the first energization switching timing (initial energization time Ts1) is determined using the Hall sensor, and the second energization switching timing (energization time Ts2) and the third energization are performed. The switching timing (energizing time Ts3) is also measured, and these energizing times Ts1 to Ts3 are stored in the control device 11 as programs. At the start, the start excitation pattern is continued for the initial energization time Ts1, the next excitation pattern for the start excitation pattern is continued for the time Ts2, and the next excitation pattern is continued for the time Ts3. Free run.
In FIG. 7, when the brushless motor 1 is reversely rotated at the start, an excitation pattern advanced by 120 ° is selected as an excitation pattern at the start.

DESCRIPTION OF SYMBOLS 1 Brushless motor 2 Drive apparatus 11 Control apparatus 14 Voltage dividing circuit 15A, 15B, 15C Filter 22 Excitation switching timing calculation means 22A Delay phase correction | amendment part (Filter delay phase correction means, Circuit delay phase correction means)
26 energization pattern determination means 27 excitation voltage output means 29 square wave pulse voltage width detection means 31 rotor position estimation means 41 rotor SL2, SL3, SL4 signal Ts1 initial energization time

Claims (4)

A brushless fan motor drive device that drives a brushless fan motor that is disposed with respect to a radiator in an engine room and is used in a rotation mechanism of a radiator fan,
When the brushless fan motor is started, the brushless fan motor is energized for the initial energization time with an excitation pattern that matches the stop position of the rotor of the brushless fan motor, and then the energization is stopped to free run the rotor of the brushless fan motor. Energization pattern determination means to be
Of the time interval of the induced voltage signal generated at the terminal of the brushless fan motor during the free run, the time interval of the signal of the induced voltage of the second time after the start of the brushless fan motor is determined based on the time interval of the rotor. Excitation switching timing calculating means for detecting the position and determining the excitation timing;
I have a,
When the time interval between the second to third signals and the third to fourth signals are equal, the excitation timing is determined by detecting the position of the rotor based on the time intervals of the second to third induced voltage signals. Decide
On the other hand, when the time interval between the second and third signals and the third and fourth signals changes, the excitation timing is calculated by estimating the next time interval, and the driving of the brushless fan motor apparatus. 2. The brushless fan motor drive device according to claim 1, wherein the initial energization time is equal to or shorter than a time from the start of rotation of the rotor to a first energization switching timing. A brushless fan motor starting method for starting a brushless fan motor which is disposed with respect to a radiator in an engine room and used for a rotating mechanism of a radiator fan,
Energizing the brushless fan motor for an initial energization time with an excitation pattern matched to the stop position of the brushless fan motor rotor, and then stopping energization to free run the rotor of the brushless fan motor;
Of the time interval of the induced voltage signal generated at the terminal of the brushless fan motor during the free run, the time interval of the signal of the induced voltage of the second time after the start of the brushless fan motor is determined based on the time interval of the rotor. Detecting the position;
Switching the excitation pattern based on the detected position of the rotor;
I have a,
When the time interval between the second to third signals and the third to fourth signals are equal, the excitation timing is determined by detecting the position of the rotor based on the time intervals of the second to third induced voltage signals. Decide
On the other hand, when the time interval between the second and third signals and the third and fourth signals changes, the next time interval is estimated and the excitation timing is calculated. Method. The initial energization time is a length equal to or shorter than the time from the start of rotation of the rotor to the first energization switching timing,
Detecting a position of said rotor, according to claim 3, characterized in that it is carried out until the signal of the induced voltage generated at the terminals of the brushless fan motor generates fourth time when rotating the rotor The start method of the brushless fan motor as described in 2.

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