JP2001103779A - Method of driving seat belt driving motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of actuating a seat belt driving motor that prevents unpleasant beats even when the motor is driven by a pulse control. SOLUTION: When given external signal such as the rotational direction and speed of a motor M, a CPU outputs pulses P1 to P4 accordingly. By changing the control pulses that are turned on or off and their frequency, duty ratio, etc., the rotational direction and speed of the motor M can be changed. At this time, the beat caused by driving the motor M can be made inaudible to human ears by setting the frequency of the pulses P1 to p2 to a level higher than audio frequency range to human beings. This setting prevents unpleasant feeling.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD OF THE INVENTION

2. Description of the Related Art Seat belts used in passenger cars are provided with tension by a seat belt winder. That is, when a seat belt is used, a person pulls out a seat belt wound by a spring in a seat belt winder, and engages the other seat belt fixed to the seat with a buckle. Thereafter, when the user relaxes his hand, the loosened seat belt is wound up by the action of the spring of the seat belt winder, and the tension determined by the spring is applied to the seat belt to restrain the occupant to the seat.

However, in such a spring-type winding mechanism, a force is applied only in the direction of tightening the seat belt. Therefore, if a person tries to loosen the seat belt, the user must pull the seat belt against this force. There was a problem that it did not become. Further, since the elastic force of the spring is used, the operation is unstable, and winding failure may occur.

[0003]

SUMMARY OF THE INVENTION In order to solve such a problem, a colleague of the inventor has found that a human being can easily relax a restraining force by pulling a seat belt, and is flexible. An invention relating to a seat belt driving device capable of coping with winding control was made, and a patent application was filed as Japanese Patent Application No. 126242 in 1999. That is, a DC motor is used to drive a seat belt, and PWM control or pulse width constant / cycle variable control is performed to control the rotation direction and rotation speed of the DC motor. According to the present invention, since the seat belt can be driven at a required speed in a required direction, a highly flexible driving of the seat belt can be realized.

In such control of the seat belt driving motor, since the motor does not need to rotate at a high speed, the cycle of the control pulse is usually set to about 1 kHz. However, as a result of our prototype production,
It has been found that when the motor is driven at such a low frequency, a humming sound such as a boon is generated, giving uncomfortable feeling to human beings, and generating vibration.

[0005] The present invention has been made in view of such circumstances, and even when a seat belt is driven by a motor and the motor is controlled by pulse control, unpleasant growls and vibrations do not occur. An object of the present invention is to provide a method for driving a motor for use.

[0006]

A first means for solving the above-mentioned problem is a method of driving a seat belt driving DC motor by pulse control, wherein the frequency of a current pulse flowing through the motor is controlled by a human. A method for driving a seat belt driving motor, wherein the driving frequency is set higher than an audible frequency (claim 1).

In this means, the frequency of the current pulse flowing through the motor is set higher than the human audible frequency. The frequency of the current pulse is a repetition frequency in the case of PWM control, and a frequency corresponding to a variable period in the case of constant pulse width / variable cycle control. In any case, since this frequency is higher than the audible frequency of a human, even when the vibration of the motor is generated due to the ripple, the vibration is not heard by the human and does not give any discomfort.

[0008] A second means for solving the above problems is as follows.
A driving method of a motor for driving a seat belt according to the first means, wherein a frequency of a current pulse supplied to the motor is set higher than a mechanical resonance frequency of the seat belt retractor. ).

In this means, the frequency of the current pulse flowing through the motor is set higher than the mechanical resonance frequency of the seat belt retractor, which is a mechanical system to which the motor is coupled, so Even when the vibration of the motor occurs, it does not resonate with the mechanical system and the vibration does not increase. Therefore, generation of large vibration can be suppressed.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of the present invention.
It is a figure showing the outline of the motor control system of the seat belt drive for carrying out the example. Although not shown, a seat retractor is coupled to the motor M, and the rotation of the motor M causes the seat belt to be wound or unwound.

The noise filter is formed by the capacitors C1 and C2 and the reactance L, and prevents the noise from the switching element from flowing back to the DC power supply. C
Control pulses P1 to P4 are supplied from the PU to the gate circuit GAT.
Via E, they are given as P1 'to P4' to the gates of switching transistors Q1 to Q4, which are switching elements. On the other hand, the voltage from the DC power supply that has passed through the noise filter is connected to the collectors of the switching transistors Q1 and Q2, and the motor terminal A is connected to the transistor Q1.
And the motor terminal B is connected to the emitter of the transistor Q2 and the collector of the transistor Q3. Further, the emitters of the switching transistors Q3 and Q4 are grounded.

For example, when the buckle of the seat belt is engaged, the CPU inputs this information as external information,
A voltage is applied to the coil of the relay RL so that the relay R
When the contact of L is closed, the switching transistor Q
1. A voltage is applied to the collector of Q2. When external information such as the rotation direction and the rotation speed of the motor M is input to the CPU, the CPU outputs control pulses P1 to P4 in response thereto.

FIG. 2 shows an example of an output method of the control pulses P1 to P4 when rotating the motor M in the forward direction. (a)
In, the control pulse P3 is kept at a high level, and the control pulse P1 is turned on and off (hereinafter, ON is set to a high level,
OFF is set to low level). As a result, the switching transistors Q2 and Q4 are turned off, Q3 is turned on, and Q
1 repeats on / off. Therefore, the current from the DC power supply flows in the order of Q1 → motor terminal A → motor terminal B → Q3 → ground in synchronization with the on / off of the switching transistor Q1, and the winding current flowing from the terminal A side to the B side to the motor M Given. As a result, the motor M rotates forward.

In (b), the control pulse P1 is kept at a high level, and the control pulse P3 is turned on and off. As a result, the switching transistors Q2 and Q4 are turned off and Q1
Is turned on, and Q3 repeats on / off. Therefore, the current from the DC power supply flows in the order of Q1 → motor terminal A → motor terminal B → Q3 → ground in synchronization with the on / off of the switching transistor Q3, and the winding current flowing from the terminal A side to the B side flows to the motor M. Given. Thereby, the motor M
Turns forward.

In (c), the control pulses P1 and P3 are turned on and off in synchronization. As a result, the switching transistors Q2 and Q4 are turned off, and Q1 and Q3 are repeatedly turned on and off. Therefore, the current from the DC power supply is synchronized with the on / off of the switching transistors Q1 and Q3,
Q1 → motor terminal A → motor terminal B → Q3 → ground, and a winding current flowing from terminal A to terminal B is applied to motor M. As a result, the motor M rotates forward.

FIG. 3 shows an example of an output method of the control pulses P1 to P4 when rotating the motor M in the reverse direction. (a)
In, the control pulse P4 is kept at a high level, and the control pulse P2 is turned on and off. As a result, the switching transistors Q1 and Q3 are turned off, Q4 is turned on, and Q
2 repeats on / off. Therefore, the current from the DC power supply flows in the order of Q2 → motor terminal B → motor terminal A → Q4 → earth in synchronization with the on / off of the switching transistor Q2, and the winding current flowing from the terminal B side to the A side to the motor M Given. As a result, the motor M rotates in the reverse direction.

In (b), the control pulse P2 is maintained at a high level, and the control pulse P4 is turned on and off. As a result, the switching transistors Q1 and Q3 are turned off and Q2
Is turned on, and Q4 repeats on / off. Thus, the current from the DC power supply flows in the order of Q2 → motor terminal B → motor terminal A → Q4 → ground in synchronization with the on / off of the switching transistor Q4, and the winding current flowing from the terminal B side to the A side to the motor M Given. Thereby, the motor M
Turns forward.

In (c), the control pulses P2 and P4 are turned on and off in synchronization. Thus, the switching transistors Q1 and Q3 are turned off, and Q2 and Q4 are repeatedly turned on and off. Therefore, the current from the DC power supply is synchronized with the on / off of the switching transistors Q2 and Q4,
Q2 → motor terminal B → motor terminal A → Q4 → ground, and a winding current flowing from the terminal B side to the A side is given to the motor M. As a result, the motor M rotates in the reverse direction.

When changing the rotation speed of the motor, as shown in FIG. 4, the pulse width (T2) of the pulse to be turned on / off is fixed and the pulse rate (period corresponding to T1) is changed or the pulse rate is fixed ( The cycle is T1), and the duty ratio (T2 / T1) is changed.

When the motor M is not driven, in order to make it difficult for the motor M to rotate due to an external force, as shown in FIG.
Leave 2) on. As a result, the voltage from the DC power supply is not applied to the motor M, but when the motor M tries to rotate by an external force, a regenerative current flows through the switching transistors Q3 and Q4 due to the electromotive force, and the motor M is regenerated by the regenerative braking. It is difficult to rotate.

Conversely, when the motor M is easily rotated by an external force, the control pulse is turned off. As a result, the regenerative current of the motor M does not flow and regenerative braking is not applied, so that the seat belt can be moved lightly.

In FIG. 1, the thermistor TH is
It is provided to monitor the temperature of the motor M, input the information to the CPU when the motor M is overloaded and the temperature rises, and stop the driving of the motor M by the CPU. The flywheel diode connected in parallel to the motor M is not shown.

In the present embodiment, T1 shown in FIG.
Is set to about 30 kHz, which is set higher than the human audible frequency and the resonance frequency of the seat retractor. Therefore, even if vibration occurs in the motor M due to the ripple due to the pulse drive, the vibration sound is not audible to humans, so that it does not cause discomfort, and
Large vibration does not occur due to resonance with the seat retractor.

[0024]

As described above, according to the first aspect of the present invention, even when the vibration of the motor is generated due to the ripple due to the pulse driving, the vibration is not heard by the human. No discomfort.

According to the second aspect of the present invention, even when the vibration of the motor occurs due to the ripple due to the pulse drive, the vibration does not resonate with the mechanical system and the vibration does not increase. Can be suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a circuit configuration of a motor drive circuit for implementing an example of an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a method of outputting a control pulse when rotating a motor in a forward direction.

FIG. 3 is a diagram illustrating an example of a method of outputting a control pulse when rotating a motor in a reverse direction.

FIG. 4 is a diagram showing a duty ratio of a control pulse.

FIG. 5 is a diagram illustrating an example of a state of a control pulse when the motor is hardly rotated by an external force.

[Explanation of symbols]

 CPU: microcomputer P1 to P6, P1 'to P4': control output (pulse) GATE: gate circuit Q1 to Q4: switching transistor M: motor C1, C2: capacitor L: reactance RL, RL2: relay TH: thermistor SW: CPU switch

Claims (2)

[Claims] 1. A method of driving a seat belt driving DC motor by pulse control, wherein a frequency of a current pulse supplied to the motor is set higher than a human audible frequency. Drive method. 2. The driving method of a seat belt driving motor according to claim 1, wherein a frequency of a current pulse supplied to the motor is set higher than a mechanical resonance frequency of the seat belt retractor. Driving method of the seat belt driving motor.