JP2007060750A - Motor control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor control device that can reduce noise and vibration generated from a motor and can be manufactured more easily than before.
SOLUTION: Two terminals 11 and 12 connected to each other, a series motor 9 to which a driving force is given when a current flows between the terminals 11 and 12, and a terminal 11 when turned on, , A path connecting the terminal 12, the battery, and the ground is conducted, and when turned off, the FET 8 that cuts off this path, a random number generator 4 that obtains a random number every predetermined time, and outputs a random number signal related to the random number, A table storage unit 5 that stores frequency data for each random number, and every time a random number signal is output, frequency data corresponding to the random number signal is acquired, and the FET 8 is PWM-controlled at a frequency corresponding to the acquired frequency data. The frequency data corresponding to one random number and the frequency data corresponding to another random number correspond to different frequencies.
[Selection] Figure 1

Description

  The present invention relates to a motor control device that is mounted on a vehicle and performs PWM (Pulse Width Modulation) control.

  Patent Document 1 describes a technique for PWM control of a semiconductor switch, that is, a technique for turning on and off a semiconductor switch at a desired frequency and duty ratio. Here, the frequency is the number of times that a unit operation consisting of one on operation and one off operation is performed in unit time, and the duty ratio is one on time and one off time. Ratio. The semiconductor switch is built in the inverter. An example of the semiconductor switch is an FET (Field Effect Transistor).

  In the technique described in Patent Document 1, since the driving force is applied to the motor only when the semiconductor switch is turned on, the rotation speed of the motor (that is, the rotation speed of the rotation shaft of the motor) is determined by the duty ratio. The higher the frequency, the smoother the drive. Therefore, the rotational speed of the motor is controlled by PWM control of the semiconductor switch.

It is known that when PWM control is performed for a long time at the same frequency, noise and vibration are generated from the motor, and the technique described in Patent Document 1 reduces noise and vibration generated from the motor. That is, the technique described in Patent Document 1 calculates the maximum value and the minimum value of the frequency according to the number of rotations of the motor, and acquires a random number at regular intervals. In the technique described in Patent Document 1, one frequency is determined using a random number within a range between the maximum value and the minimum value of the frequency, and the semiconductor switch is PWM-controlled at the one frequency. Thereby, since a frequency is changed for every fixed time, the noise and vibration which generate | occur | produce from a motor reduce.
JP-A-11-220895

  However, the technique described in Patent Document 1 performs a lot of complicated processing in addition to calculating the maximum and minimum values of the frequency in order to reduce noise and vibration generated from the motor. It was necessary to prepare a CPU capable of executing processing. Furthermore, since it is necessary to detect the number of rotations of the motor when calculating the maximum value and the minimum value of the frequency, it is necessary to prepare a sensor for detecting the number of rotations of the motor. Therefore, it takes much time to manufacture the motor control device according to the technique described in Patent Document 1.

  The present invention has been made in order to solve such a conventional problem, and an object of the present invention is to reduce noise and vibration generated from a motor and to be manufactured more easily than in the past. The object is to provide a motor control device.

  In order to achieve the above object, an invention according to the present application provides a motor control device mounted on a vehicle, which includes two motor terminals connected to each other, and a current flows between one motor terminal and the other motor terminal. A motor to which driving force is applied when flowing, a semiconductor switch that conducts a path connecting one motor terminal, the other motor terminal, the battery, and the ground when turned on, and shuts off the path when turned off A random number generator that obtains a random number every predetermined time and outputs a random number signal related to the random number; a table storage unit that stores frequency data for each random number; and a random number signal that corresponds to the random number signal that is output A PWM control unit that acquires frequency data and performs PWM control of the semiconductor switch at a frequency corresponding to the acquired frequency data, and includes frequency data corresponding to one random number, and the other The corresponding frequency data to the random number, corresponding to the different frequencies.

  The invention according to the present application periodically changes the frequency of the PWM control, so that the vibration of the motor is not accumulated, and as a result, the vibration and noise generated from the motor can be reduced. The invention according to the present application can reduce vibration and noise generated from the motor by simpler processing than conventional processing, such as reading data from a table storage unit. Smaller than that. Furthermore, a rotation sensor is also unnecessary. Therefore, the motor control device according to the present application can be manufactured more easily than in the past.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing a configuration of a motor control device 1 according to the present embodiment.

  The motor control device 1 is mounted on a vehicle, and includes a speed stage output unit 2, a timer 3, a random number generation unit 4, a table storage unit 5, a table acquisition unit 6, a PWM signal output unit 7, an FET 8, A series motor 9 and a diode 10 are provided. The series motor 9 includes terminals 11 and 12 connected to each other. The motor control device 1 drives an engine cooling fan.

  The speed stage output unit 2 determines the rotational speed of the series motor 9, generates a speed stage signal related to the determined rotational speed, and outputs the speed stage signal to the table acquisition unit 6. The number of revolutions determined by the speed stage output unit 2 is divided into four stages. Hereinafter, the stage with the smallest number of revolutions is referred to as “speed stage 1”, and every time the number of revolutions increases, it is referred to as “speed stage 2,” “speed stage 3,” and “speed stage 4.”

  The timer 3 outputs a timer signal to the random number generator 4 and the PWM signal output unit 7 every 1 (div) (= 1/100 (s)).

  The random number generator 4 randomly acquires one integer as a random number from integers in the range from “1” to “8” every time the timer signal is given a predetermined number of times (for example, 10 times). Is generated and output to the table acquisition unit 6. Therefore, the random number generation unit 4 outputs a random number signal to the table acquisition unit 6 every 1/10 (s).

  The table storage unit 5 stores the table shown in FIG. The table is divided into sections “A0” to “D7”, and each section is specified by a speed stage and a random number. For example, section “B6” is specified by “speed stage 2” and random number “7”.

  Each section includes duty ratio data indicating a duty setting value and frequency data indicating a frequency setting value. The duty ratio and the frequency are calculated from these set values and the following equations (1) and (2). Hereinafter, the section is expressed by (frequency setting value, duty setting value).

(Duty ratio) (%) = (Duty setting value) / (Frequency setting value) * 100 (1)
(Frequency) (times / s) = 1 / [(1/100) (s) * (frequency setting value)] (2)
The duty ratio calculated from the section corresponding to one speed stage matches the duty ratio for realizing one speed stage. Therefore, the duty ratio data corresponding to one speed stage corresponds to the duty ratio for realizing one speed stage.

  For example, when “speed stage 1” is 10 (rotation / s) and 10 (rotation / s) is realized with a duty ratio of 50 (%), the section corresponding to “speed stage 1” is, for example, , (12, 6), (8, 4), (6, 3) are possible. It is known that noise and vibration are generated when the rotation of the motor and the PWM control of the FET 8 are synchronized, that is, when the speed stage and the frequency match. Here, “the speed stage and the frequency coincide with each other” means that these values coincide when the speed stage is represented by (number of times / s) and the frequency is represented by (times / s). . In addition, when these values are different, it can be said that “the speed stage and the frequency are different”. Therefore, (10, 5) is not included in the section corresponding to “speed stage 1”. The frequency calculated by (10, 5) is 10 (times / s), which coincides with “speed stage 1”. Therefore, if the FET 8 is PWM controlled at this frequency, vibration or noise may occur. is there.

  The frequency calculated from the section corresponding to one speed stage is different from that of one speed stage. Therefore, the frequency data corresponding to one speed step corresponds to a frequency different from that of the one speed step.

  The frequency setting value corresponding to one random number is different from the frequency setting value corresponding to another random number. That is, the frequency data corresponding to one random number is different from the frequency data corresponding to another random number.

  Each time the random number signal is given, the table acquisition unit 6 reads the duty ratio data and the frequency data from the section corresponding to the speed step signal and the random number signal, and generates a PWM control signal related to these data. , Output to the PWM signal output unit 7.

  The gate of the FET 8 is connected to the PWM signal output unit 7, the drain is connected to the terminal 12, and the source is connected to the ground. The FET 8 is turned on when an on signal is given from the PWM signal output unit 7 and is turned off when an off signal is given from the PWM signal output unit 7. The FET 8 conducts a path connecting the battery, the terminal 11, the terminal 12, and the ground when the FET 8 is on, and interrupts the path when the FET 8 is off.

  The terminal 11 of the series motor 9 is connected to the battery. The series motor 9 is given a driving force only when a current flows between the terminal 11 and the terminal 12. The series motor 9 is stopped in the initial state, and starts driving when a driving force is applied during the stop. The series motor 9 gradually decreases the rotation speed (that is, the rotation speed of the rotation shaft of the series motor 9) when driving force is not applied during driving, and stops when the speed becomes zero. The series motor 9 increases the rotation speed when a driving force is applied during driving. When the series motor 9 is driven, the engine cooling fan is driven.

  Since the driving force is applied to the series motor 9 only when the FET 8 is turned on, the PWM signal output unit 7 can control the rotational speed of the series motor 9 by PWM control of the FET 8.

  The PWM signal output unit 7 performs PWM control on the FET 8 with a duty ratio corresponding to the PWM control signal and a frequency corresponding to the PWM control signal. Specifically, the PWM signal output unit 7 performs the following processing based on the PWM control signal.

  (A) After the PWM control signal is given, the PWM signal output unit 7 sets the first timer signal as “the 0th timer signal” and starts receiving the 0th timer signal. ) Until the start of the reception of the timer signal, the ON signal is output to the FET 8, and the reception of the timer signal of (the frequency setting value) is started after the reception of the timer signal of the (duty setting value) is started. In the meantime, an OFF signal is output to the FET 8 until the start of the operation. The timer signal received next to the k-th timer signal becomes the (k + 1) -th timer signal (k is an integer equal to or greater than 0). The same applies to (b).

  (B) The PWM signal output unit 7 sets the (frequency setting value) timer signal to “0th timer signal” and starts receiving the 0th timer signal. Until the reception of the timer signal is started, the ON signal is output to the FET 8 and the reception of the (duty setting value) -th timer signal is started, and then the reception of the (frequency setting value) -th timer signal is started. Until this time, an OFF signal is output to the FET 8.

  (C) The PWM signal output unit 7 repeats the process of (b) until a new PWM control signal is given, and returns to (a) when the new PWM control signal is given.

  For example, when the section corresponding to the speed step signal and the random number signal is (100, 5), the PWM signal output unit 7 performs the 0th operation at (a) and (b) as shown in FIG. From the start of the timer signal reception until the fifth timer signal reception is started (that is, 0.05 (s)), the ON signal is output to the FET 8 to receive the fifth timer signal. The off signal is output to the FET 8 until the 100th timer signal reception is started (that is, 0.95 (s)). That is, the PWM signal output unit 7 performs PWM control of the FET 8 with a frequency of 1 (times / s) and a duty ratio of 5 (%).

  The diode 10 is provided for preventing a reverse current flow. The anode of the diode 10 is connected to the terminal 12 of the series motor 9, and the cathode of the diode 10 is connected to the terminal 11 of the series motor 9.

  Next, the operation of the motor control device 1 will be described.

  The timer 3 outputs a timer signal to the random number generator 4 and the PWM signal output unit 7 every 1 (div) while the following processing is performed. The speed stage output unit 2 determines the rotational speed of the series motor 9, generates a speed stage signal related to the determined rotational speed, and outputs the speed stage signal to the table acquisition unit 6.

  The random number generator 4 randomly acquires one integer as a random number from integers in the range from “1” to “8” every time the timer signal is given a predetermined number of times, and generates a random number signal related to this random number. To the table acquisition unit 6.

  Each time the random number signal is given, the table acquisition unit 6 reads the duty ratio data and the frequency data from the section corresponding to the speed step signal and the random number signal, and generates a PWM control signal related to these data. , Output to the PWM signal output unit 7.

  The PWM signal output unit 7 performs PWM control on the FET 8 with a duty ratio corresponding to the PWM control signal and a frequency corresponding to the PWM control signal. Specifically, the PWM signal output unit 7 performs the above-described processes (a) to (c) based on the PWM control signal. As a result, the PWM signal output unit 7 rotates the series motor 9 at the rotation speed determined by the speed stage output unit 2. The PWM signal output unit 7 changes the frequency periodically (that is, every 1/10 (s)). The frequency is different from the rotational speed of the series motor 9.

  As described above, since the motor control device 1 periodically changes the frequency of the PWM control, the vibration of the series motor 9 is not accumulated, and as a result, vibration and noise can be reduced. The motor control device 1 can reduce vibration and noise generated from the series motor 9 by processing that is simpler than conventional processing, such as reading data from a table. Smaller than that. Furthermore, a rotation sensor is also unnecessary. Therefore, the motor control device 1 can be manufactured more easily than in the past.

  The motor control device 1 can PWM control the FET 8 at a frequency different from the rotational speed of the series motor 9. Therefore, the motor control apparatus 1 can also reduce the vibration and noise of the series motor 9 in this respect.

  Note that the present embodiment can be changed without departing from the spirit of the present invention. For example, the FET 8 may be provided on the upstream side of the series motor 9, that is, between the battery and the series motor 9.

It is a circuit diagram showing a motor control device concerning one embodiment of the present invention. It is explanatory drawing which shows an example of a table.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Motor control apparatus 2 ... Speed step output part 3 ... Timer 4 ... Random number generation part 5 ... Table storage part 6 ... Table acquisition part 7 ... PWM signal output part 8 ... FET
9 ... Series motor 10 ... Diode 11, 12 ... Terminal

Claims (2)

In a motor control device mounted on a vehicle,
A motor provided with two motor terminals connected to each other, to which a driving force is applied when a current flows between the one motor terminal and the other motor terminal;
A semiconductor switch that conducts a path connecting the one motor terminal, the other motor terminal, the battery, and the ground when turned on, and shuts off the path when turned off,
A random number generator for obtaining a random number every predetermined time and outputting a random number signal related to the random number;
A table storage unit for storing frequency data for each random number;
A PWM controller that obtains frequency data corresponding to the random number signal each time the random number signal is output, and performs PWM control of the semiconductor switch at a frequency corresponding to the obtained frequency data;
A motor control device in which frequency data corresponding to one random number and frequency data corresponding to another random number correspond to different frequencies. The motor control device according to claim 1,
A speed step output unit that determines the rotation speed of the motor and outputs a speed step signal related to the rotation speed;
The table storage unit stores the frequency data and duty ratio data for each of the random number and the rotation number,
The frequency data corresponding to one rotation number corresponds to a frequency different from the one rotation number,
The duty ratio data corresponding to the one rotational speed corresponds to the duty ratio for realizing the one rotational speed,
The PWM control unit obtains frequency data corresponding to the random number signal and the speed step signal and duty ratio data corresponding to the random number signal and the speed step signal each time the random number signal is output. A motor control device that PWM-controls the semiconductor switch with a frequency corresponding to the acquired frequency data and a duty ratio corresponding to the acquired duty ratio data.

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