JP2006166564A - Motor control apparatus and image forming apparatus - Google Patents

Abstract

A motor for generating a detection timing for the other two phases by arithmetic processing using a magnet rotor position detection sensor for one phase in a DC brushless motor and generating a switching timing with a simple configuration and high accuracy. A control device is provided.
A plurality of changes in the outputs of switches S1 to S6 for performing switching control of an excitation current of a DC brushless motor 2 and a single hall sensor HU installed in the DC brushless motor 2 for detecting a rotational position. Is provided, and a switching timing arithmetic circuit for generating signals SW1 to SW6 that serve as a reference for switching by the switches S1 to S6 is provided.
[Selection] Figure 1

Description

  The present invention relates to a motor control device suitable for use in controlling a motor such as a DC brushless motor and an image forming apparatus configured using the motor control device.

  As a polygon mirror motor for controlling the rotation of a polygon mirror mounted on an image forming apparatus or the like, a DC brushless motor is often used. Here, the polygon mirror is a rotating polygon mirror used in a beam scanning system or the like. In a polygon mirror motor composed of a DC brushless motor, the rotation of the magnet rotor is controlled by controlling the three-phase excitation current that flows through the fixed (stator) yoke. Further, switching of each phase of the excitation current is performed based on the position information of the magnet rotor. Rotational speed (rotational speed) control is achieved by PWM (Pulse Width Modulation) control that directly varies the time to chop the applied voltage of the stator yoke, or PAM (Pulse) that indirectly controls the DC applied voltage of the stator yoke itself by PWM control. (Amplitude Moduration) control.

  Conventionally, position information detection by a polygon mirror motor has been performed by arranging three Hall sensors on the rotational position of the magnet rotor and detecting changes in the magnetic poles of the magnet by the Hall sensor. In addition, in a DC brushless motor for AV (Audio Visual) equipment, the induced voltage of each phase is compared with a reference voltage without using a sensor, and the comparison result is used as a position detection signal to perform arithmetic processing to generate an excitation current switching timing signal. In some cases, the position detection signal is created by analog circuit processing in which the induced voltage of each phase is integrated and compared with a reference voltage.

  As described above, in the rotation control of the conventional holgon mirror motor, the excitation current of the stator yoke has been switched based on the position information of the magnet rotor with respect to the position of the three-phase stator yoke. Since this position detection information is required for three phases, the configuration of the control circuit is complicated, and it is difficult to reduce the cost and size. On the other hand, in recent years, a motor control device has been developed that reduces the number of sensors for position detection information. For example, Patent Document 1 or 2 describes a motor control device in which the number of Hall sensors is one (or two).

In the motor control device described in Patent Document 1 or 2, for example, the switching period between the N pole and the S pole of the rotor detected by one Hall sensor is measured, and each phase is calculated based on the result of calculating the period. The switching pattern of the excitation current to be passed through is determined.
JP-A-9-163787 JP-A-10-290592

  In the devices described in Patent Literature 1 and Patent Literature 2, processing for calculating outputs of two other sensors omitted from the output of one Hall sensor is performed. At that time, the timing of the change of the other two sensors is obtained by a predetermined calculation process (ie, estimated) based on the cycle of the change of one Hall sensor. On the other hand, when the number of poles of the DC brushless motor is increased, the rotation angle measured by one change in the output of the Hall sensor is about a fraction (for example, 60 °) of a fraction of one rotation (360 °) of the motor. turn into. That is, in one measurement, the time corresponding to one part (angle) of one rotation is repeatedly measured. In such a case, if a change occurs in the rotation of the motor within one rotation, it is considered that the influence of the change affects the timing at which the change is made, and the accuracy may be reduced.

  In addition, when the change in the number of rotations of the motor at the time of start-up is large, a relatively large difference may occur between the current measured value and the next actual value. It is conceivable that a large error occurs in the change timing of the other two sensors.

  The present invention has been made in consideration of the above circumstances, and the detection timing for the other two phases is created by arithmetic processing using the magnet rotor position detection sensor for one phase in the DC brushless motor, An object of the present invention is to provide a motor control device and an image forming apparatus that can create a switching timing of a DC brushless motor with high accuracy with a simple configuration.

  According to the first aspect of the present invention, in the control device for the DC brushless motor, the output of the driving means for performing switching control of the driving current of the DC brushless motor, and one sensor for detecting the rotational position installed in the DC brushless motor. Calculating means for measuring the time of the plurality of changes and determining the time of the next change based on the time, and signal generating means for generating a signal serving as a reference for switching by the driving means based on the output of the calculating means. It is characterized by providing.

  According to a second aspect of the present invention, the calculation means measures a plurality of changes in the output of one sensor for detecting the rotational position installed in the DC brushless motor, and calculates the next change from the average value thereof. It is characterized in that the time is determined.

  According to a third aspect of the present invention, the calculation means measures the time of a plurality of changes in the output of one sensor for detecting the rotational position installed in the DC brushless motor, and the predicted value obtained based on them. And the time of the next change from the time of the last change.

  According to a fourth aspect of the present invention, the calculating means measures a plurality of changes in the output of one sensor for detecting the rotational position installed in the DC brushless motor, while the rotational speed of the DC brushless motor is measured. Is within the predetermined range, the time of the next change is obtained from the average value thereof, while when it is not within the predetermined range, the next value is calculated from the predicted value obtained based on them and the time of the last change. It is characterized by obtaining the time of change.

  According to a fifth aspect of the present invention, when the signal generating means changes the output of the sensor, the driving means is based on a preset switching pattern regardless of the output of the calculating means. A signal serving as a reference for switching is created.

  According to a sixth aspect of the present invention, in the image forming apparatus provided with the polygon mirror, the polygon mirror motor that rotates the polygon mirror is a DC brushless motor, and the control device switches the drive current of the DC brushless motor. A driving means for performing control, an arithmetic means for measuring a plurality of changes in the output of one sensor for detecting a rotational position installed in the DC brushless motor, and obtaining a time for the next change; Signal generating means for generating a signal that becomes a reference for switching by the driving means based on the output.

  According to the present invention, the time of a plurality of changes in the output of one sensor is measured, and the time of the next change is obtained based on them, so that it is easy to cope with the rotation state of the motor. In the configuration where the detection timing for the other two phases is created by calculation processing using the magnet rotor position detection sensor for one phase in the DC brushless motor, and the switching timing is determined, the configuration is simplified and highly accurate Can be achieved.

  Embodiments of a motor control device according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the present embodiment. The motor control device 1 shown in FIG. 1 performs rotational speed control (rotational speed control) by switching and controlling the excitation current flowing in the three-phase winding 21 of the DC brushless motor 2 using the DC power supply 3 as a power supply. The motor control device 1 and the DC brushless motor 2 are mounted on the same substrate, for example.

  In this case, the DC brushless motor 2 in FIG. 1 is a three-phase 12-pole DC brushless motor, as shown in a cross-sectional view in FIG. 2, and includes a stator yoke 22 around which a three-phase winding 21 of UVW is wound, The rotor 23 is composed of 6-pole N-pole magnets 23N and S-pole magnets 23S, and one Hall sensor HU disposed on the outer periphery of the rotor 23. The DC brushless motor 2 can be used as a polygon mirror motor by attaching a polygon mirror (not shown) to the rotor 23, for example.

  The motor control device 1 in FIG. 1 includes a switching timing calculation circuit 10, a PWM control rotation speed control circuit 11, six switches S1 to S6, and three AND gates G1 to G3. Here, the switches S1 to S6 are semiconductor switching elements such as bipolar transistors and FETs (Field-Effect Transistors). The switches S <b> 1 to S <b> 6 constitute a three-phase inverter circuit, generate a three-phase AC voltage by chopping control of the DC voltage supplied from the DC power supply 3, and apply it to the three-phase winding 21.

  The PWM control rotation speed control circuit 11 detects the rotation speed based on the output signal of the hall sensor HU, and outputs a control signal to the AND gates G1 to G3 so that the DC brushless motor 2 rotates at a predetermined constant speed. To do. As a result, the ON time widths of the switches S2, S4 and S6 are controlled.

  The switching timing arithmetic circuit 10 generates switching control signals for the six switches S1 to S6. The switching timing calculation circuit 10 obtains 60-degree rotation time information of the rotor 23 from the output signal of the position detection hall sensor HU of the magnet rotor 23 for one phase in the DC brushless motor 2, and based on the obtained information, the other 2 The detection timing of the phase is created by calculation processing. Then, the on / off signals SW1 to SW6 of the switches S1 to S6 are set in correspondence with the detection timing of one phase directly detected and the detection timing of two phases created by calculation processing based on the detection timing. Output.

  FIG. 3 is a timing chart showing a basic relationship between the output signal of the hall sensor HU and the on / off signals SW1 to SW6 of the switches S1 to S6. The hall sensor HU inverts an output signal (that is, a magnet rotor position detection signal) every time the rotor 23 rotates 60 degrees. The switching timing calculation circuit 10 measures the rise and fall times (60 degree rotation time) of the output signal of the Hall sensor HU, and divides it into six times (10 degree rotation time; 5 wavy lines within 60 ° The switches S1 to S6 are turned on / off at the timing shown in FIG. Here, the switching timing calculation circuit 10 of the present embodiment has the following characteristics in the switching timing calculation processing.

(1) When the DC brushless motor 2 is controlled to a predetermined constant speed (with a specified rotational speed), when the rotational speed of the DC brushless motor 2 is within a predetermined error range from the specified rotational speed (see FIG. 4), a switching timing is created based on an average value of a plurality of 60-degree rotation times (a plurality of sets of rise and fall changes of the output signal of the Hall sensor HU). That is, within a predetermined error range, an average value (moving average value) of a plurality of 60-degree rotation times is obtained, detection timings for the other two phases are created, and excitation current switching timings are created. As a result, the rotation angle of the DC brushless motor 2 corresponding to one measurement cycle can be increased, and the switching timing can be created while suppressing the influence of rotation fluctuation.

(2) On the other hand, when the DC brushless motor 2 is controlled to a predetermined constant speed (with a specified rotational speed), the rotational speed of the DC brushless motor 2 is out of a predetermined error range from the specified rotational speed at the time of startup or the like. (See FIG. 4), a plurality of 60-degree rotation times (a plurality of sets of rise and fall changes in the output signal of the Hall sensor HU) are measured, and a 60-degree rotation time obtained based on them is measured. The next switching timing is created based on the predicted value of the change in time and the time of the last change. That is, the switching timing is created by calculating a plurality of movement change amounts for 60 ° rotation time and correcting the previous 60 ° rotation time.

(3) In order to deal with a case where the rotational speed fluctuates due to a load fluctuation or the like with respect to the calculated predicted value, the rise and rise of the output signal (magnet rotor position detection signal) of the actually detected hall sensor HU. At the time of going down, control is performed to forcibly change to a preset excitation current switching pattern of the stator yoke.

  In other words, the switching timing calculation circuit 10 uses different processing algorithms to calculate the excitation current switching timing when rotating within the specified rotation speed range and when rotating outside the specified rotation speed range. It is processing. FIG. 4 shows the change characteristics of the rotational speed with respect to the time axis from the start of the DC brushless motor 2 until the specified rotational speed is reached and from when the specified rotational speed is reached until the motor 2 is stopped (energization OFF). Yes.

  Next, a configuration (logic) for realizing the algorithms (1) to (3) will be described.

  FIG. 5 is a block diagram showing a first configuration example for realizing the algorithm (1), and FIG. 6 is a timing chart for explaining the operation thereof. The moving average value calculation circuit 50 is a circuit that calculates an average 60-degree rotation time from 60-degree rotation times T1 to T4 for four cycles. In this case, the moving average value calculation circuit 50 includes an n-bit counter 51, a counter enable circuit 52 that controls the operation of the counter 51, an n / 4 operation circuit 53 that performs an operation of dividing the n-bit output of the counter 51 by 4, And an n / 4 arithmetic circuit 54 that performs an operation of dividing the output of the n / 4 arithmetic circuit 53 by six. FIG. 6 is a timing chart showing changes in the output signal (HU) of the hall sensor HU, the on / off signals SW1 to SW6 of the switches S1 to S6, and the count value of the counter 51. Note that the same reference numerals are used for the same signals in the following timing charts.

  The counter enable circuit 52 outputs an enable signal corresponding to four cycles from T1 to T4 of the output signal (HU) of the hall sensor HU every four cycles. As a result, the counter 51 resets the counter value when the enable signal changes, then counts the number of clocks (predetermined system clock CLOCK) for four cycles from T1 to T4, and holds the result. The n / 4 arithmetic circuit 53 divides the count value by 4 and outputs a predicted time To_60 with a rotation angle of 60 °. The 1/6 arithmetic circuit 54 further divides this value by 6 to calculate and output an estimated time To_10 at a rotation angle of 10 °. This process is repeated every four cycles to update the prediction times To_60 and To_10.

  FIG. 7 is a block diagram showing a configuration example for realizing the algorithm (2), and FIG. 8 is a timing chart for explaining the operation. 7 includes a counter group 71 composed of five counters, a counter enable circuit 72 that controls the counter group 71, and a variation calculation circuit group 73 composed of four variation calculation circuits. An adder circuit 74, a 1/4 arithmetic circuit 75, an arithmetic circuit 76 that subtracts the output of the 1/4 arithmetic circuit 75 from the output of the counter 71a that counts the latest value in the counter group 71, and a 1/6 arithmetic circuit 77. It is composed of In FIG. 8, signals C1 to C5 represent the count values (outputs) of the counters of the counter group 71 (for example, the signal C5 is the output of the counter 71a).

  In the movement change amount average value calculation circuit 70, the number of clocks for five cycles from the HU signals T1 to T5 is counted by each counter (COUNTER1 to 5) of the counter group 71, and the four change amount calculation circuit group 73 are counted. The difference between the count values is calculated by the change amount calculation circuit. Then, the results are added by the adder circuit 74 and divided by 4 by the ¼ arithmetic circuit 75 to obtain the average value of the movement change amount. Further, the calculation circuit 76 subtracts the movement change amount average value from the value of the count value (COUNTER5) of the immediately preceding counter 71a to calculate the predicted time To_60 for the rotation angle 60 ° of the next cycle. Then, the 1/6 arithmetic circuit 77 further divides this value by 6 to calculate a predicted time To_10 at a rotation angle of 10 °.

  In the moving change amount average value calculation circuit 70 shown in FIG. 7, the moving average value of the change amount (difference) of each count value is calculated from the count values n1 to n5 of the five counters in the circuit in the block indicated by the wavy line. Looking for. That is, the movement change amount average value (predicted change) is obtained by {(n1-n2) + (n2-n3) + (n3-n4) + (n4-n5)} / 4. Then, the arithmetic circuit 76 calculates the predicted value of the next 60-degree rotation time To_60 by subtracting this movement change amount average value (predicted change) from the latest count value n5. That is, the predicted value is obtained by subtracting the moving average of the amount of change in each past count value from the latest count value. In this calculation, when the 60-degree rotation time To_60 changes, the predicted value is obtained on the assumption that the movement change amount is substantially constant. When the DC brushless motor is started up or the like, it is possible to obtain a relatively highly accurate predicted value even when the amount of change in each 60-degree rotation time To_60 is considered to be substantially constant.

  It should be noted that the equation {(n1-n2) + (n2-n3) + (n3-n4) + (n4-n5)} / 4 for obtaining the change amount in the circuit within the wavy line block shown in FIG. n5) / 4. That is, the predicted value of the next 60-degree rotation time To_60 can be obtained by the equation n5- (n1-n5) / 4. Therefore, the configuration of FIG. 7 can be simplified to a form corresponding to this equation.

  Further, in the configuration of FIG. 7, it is assumed that the movement change amount is constant (the difference between the current and next counter values is substantially constant). It is also possible to adopt a prediction method that can cope. For example, the predicted value of the 60-degree rotation time To_60 can be obtained while obtaining the inclination of the movement change amount and predicting the change of the movement change amount. That is, when Δ1 = (n1−n2), Δ2 = (n2−n3), Δ3 = (n3−n4), and Δ4 = (n4−n5), the predicted value of the change amount is, for example, Δ4 − {(Δ1− Δ2) + (Δ2-Δ3) + (Δ3-Δ4)} / 3. In this case, the predicted value of the 60-degree rotation time To_60 can be obtained as n5- [Δ4-{(Δ1-Δ2) + (Δ2-Δ3) + (Δ3-Δ4)} / 3].

  Next, a configuration for realizing the algorithm (3) will be described with reference to FIGS. FIG. 9 is a block diagram showing a configuration example for realizing the algorithm (3), and FIGS. 10 to 12 are timing charts for explaining the operation.

  9 includes a counter 901, a comparator 902, a 2-bit counter 903, a decoder 904 that generates an output in accordance with a decoder output table 90T, D flip-flop circuits 905, 906, and 912, an inverter circuit 907, and 908, AND gates (AND circuits) 909 and 910, and an OR circuit 911. The excitation current switching signal creation circuit 90 creates an excitation current switching signal using the predicted time To_10 with the rotation angle of 10 ° calculated above and the output (HU signal) of the hall sensor HU for U-phase stator detection.

  10 shows a circuit operation timing chart when the estimated time To_60 at the rotation angle 60 ° is substantially equal to the detection signal of the actual Hall sensor HU, and FIG. 11 shows the estimated time To_60 at the rotation angle 60 ° of the actual Hall sensor HU. FIG. 12 shows a circuit operation timing chart when the predicted time To_60 at a rotation angle of 60 ° becomes smaller than the detection signal of the actual Hall sensor HU.

  The operation of the excitation current switching signal creation circuit 90 will be described. First, the number of clocks is counted by a counter 901 (COUNTER_A), and the count value and To_10 are compared by a comparator 902 (COMPARATOR). When they become equal, the comparator 902 generates a COMP_OUT signal that becomes an output of Hi level. The counter 901 is reset (cleared to 0) in synchronization with the COMP_OUT output and the rising / falling detection signal UP / DOWN_EDGE of the HU signal.

  Next, since the COMP_OUT signal is input to the 2-bit counter 903 (COUNTER_B), the count is incremented by one every time the count value of the counter 901 (COUNTER_A) becomes equal to To_10. Here, the counter 903 (COUNTER_B) is reset (cleared to 0) in synchronization with the rising / falling edge detection signal UP / DOWN_EDGE of the HU signal.

  The HU signal is subjected to clock synchronization delay processing by the D flip-flop circuit 905 (DFF1) and the D flip-flop circuit 906 (DFF2), and a rising / falling edge detection signal UP / DOWN_EDGE is created. The D flip-flop circuit 912 (DFF3) becomes Hi (“1”) level at the rising edge of the HU signal and becomes Low (“0”) level at the falling edge. By inputting the output of the counter 903 (COUNTER_B) and the output of the D flip-flop circuit 912 (DFF3) to a decoder 904 (DECODER) that outputs in accordance with the decoder output table 90T, an excitation current switching control signal shown in FIGS. Is created.

  As described above, according to the present embodiment, in the DC brushless motor, the detection timings for the other two phases are generated by calculation processing based on the magnet rotor position detection information for one phase and the 60-degree rotation time information. As a result, it is possible to provide a rotation control circuit technology that is inexpensive, corresponds to downsizing, and is highly accurate.

  In the above description, for example, the circuit for detecting the number of rotations in FIG. 4 and switching is not specifically illustrated and described. However, the output interval of the Hall sensor HU is measured by a counter and compared with a predetermined value by a comparator. It is possible to cope with such a configuration. Further, the embodiment of the present invention is not limited to the above, and it is possible to make a change such as further increasing or decreasing the counter, each arithmetic circuit, and the like.

It is a block diagram for demonstrating one embodiment (motor control apparatus 1) of this invention. Sectional drawing which shows the structure of the DC brushless motor 2 of FIG. The timing chart for demonstrating the basic operation | movement aspect in the structure of FIG. The timing chart which shows the rotation change of the DC brushless motor 2 for demonstrating the processing content of the structure of FIG. The block diagram which shows the structure of the moving average value calculation circuit 50 provided in the switching timing calculating circuit 10 of FIG. The timing chart for demonstrating the processing content of the moving average value calculation circuit 50 of FIG. FIG. 2 is a block diagram showing a configuration of a movement change amount average value calculation circuit 70 provided in the switching timing calculation circuit 10 of FIG. 1. The timing chart for demonstrating the processing content of the movement variation | change_quantity average value calculation circuit 70 of FIG. FIG. 2 is a block diagram showing a configuration of an exciting current switching signal generation circuit 90 provided in the switching timing arithmetic circuit 10 of FIG. The timing chart for demonstrating the processing content of the exciting current switching signal preparation circuit 90 of FIG. The timing chart for demonstrating the processing content of the exciting current switching signal preparation circuit 90 of FIG. The timing chart for demonstrating the processing content of the exciting current switching signal preparation circuit 90 of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Motor control apparatus 2 DC brushless motor 10 Switching timing calculation circuit 11 PWM control rotation speed control circuit 50 Moving average value calculation circuit 70 Moving change amount average value calculation circuit 90 Excitation current switching signal generation circuit HU Hall sensor (or Hall sensor HU Output signal)
S1-S6 switch

Claims (6)

In a DC brushless motor control device,
Driving means for performing switching control of the driving current of the DC brushless motor;
Calculating means for measuring a plurality of changes in the output of one sensor for detecting a rotational position installed in the DC brushless motor, and obtaining a next change based on the measured times;
A motor control device comprising: a signal generating unit that generates a signal that serves as a reference for switching by the driving unit based on an output of the calculating unit. The calculation means measures the time of a plurality of changes in the output of one sensor for detecting the rotational position installed in the DC brushless motor, and obtains the time of the next change from the average value thereof. The motor control device according to claim 1. The calculation means measures a plurality of change times of the output of one sensor for detecting the rotational position installed in the DC brushless motor, and based on the predicted value obtained based on them and the last change time. The motor control device according to claim 1, wherein a time for the next change is obtained. The arithmetic means measures the time of a plurality of changes in the output of one sensor for detecting the rotational position installed in the DC brushless motor, while the rotational speed of the DC brushless motor is within a predetermined range. Finds the time of the next change from the average value of them, and calculates the time of the next change from the predicted value obtained based on them and the time of the last change when they are not within the predetermined range. The motor control device according to claim 1. When the signal generating means changes in the output of the sensor, the signal generating means generates a signal serving as a reference for switching by the driving means based on a preset switching pattern regardless of the output of the calculating means. The motor control device according to claim 1, wherein the motor control device is a motor control device. In an image forming apparatus provided with a polygon mirror,
The polygon mirror motor that rotates the polygon mirror is a DC brushless motor, and
The control unit is
Driving means for performing switching control of the driving current of the DC brushless motor;
A calculation means for measuring a plurality of changes in the output of one sensor for detecting a rotational position installed in the DC brushless motor and obtaining a next change time;
An image forming apparatus comprising: a signal generation unit that generates a signal that serves as a reference for switching by the driving unit based on an output of the calculation unit.

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