JPH0840204A - Seat belt taking-up device - Google Patents

Abstract

PURPOSE:To arbitrarily adjust belt taking-up force by composing a motor driving circuit from a constant current driving circuit and a regenerative braking circuit and setting the torque direction of a motor which is generated in the constant current driving circuit in the reverse direction to the generated torque of a spiral spring. CONSTITUTION:A belt 2 is wound on a winding core 3, and a shaft 4 is allowed to penetrate through the winding core 3. Further, at the end part of the shaft 4, a spur gear 5 having a spiral spring laying part A formed integrally is inserted. The spur gear 5 is connected with a small gear 8 press-fitted on the shaft of a motor 9 through an intermediate gear 7. Further, the inside and outside of the spiral spring 6 are laid on the spring laying parts A and B of the spur gear 5 and a spring case 10. The motor 9 is connected to a driving circuit 13, which forms a constant electric current driving circuit and a regenerative brake circuit integrally. At this time, the torque direction of the motor 9 which is generated in the constant electric current driving circuit is set in the reverse directiond to the generated torque of the spiral spring 6. Accordingly, the winding-up force for the belt 2 can be adjusted arbitrarily.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seat belt retractor for an automobile.

[0002]

2. Description of the Related Art A seat belt for an automobile has a belt wound around a winding device when the seat belt is not worn, and an occupant pulls out and wears the belt when using the seat belt. The retracting force required for the seat belt retractor at this time is that the buckle is firmly retracted with a relatively strong retracting force when not worn and a weak retracting force that fits the body moderately when worn. It has been demanded.

However, in the case of the system in which the belt is wound by a generally used spring, as the amount of pulling out the belt increases, the spring is wound more and the generated torque becomes stronger. In addition, since the amount of winding of the belt is reduced, the moment acting on the winding core of the belt is reduced, and a larger pulling force is required. This is weak at first, and when pulled out to the mounting position, it has a winding force characteristic contrary to the requirement of being strong. In order to make up for this drawback, a winding device has been put into practical use that utilizes an auxiliary spring and a clutch mechanism that electromagnetically operates to reduce the tension during mounting. This method has the drawback of increasing the number of parts and complicating the structure. In this case, the take-up force when not attached is
It can be stronger than the winding force when it is attached, but the retracting speed of the belt will be faster, and the buckle of the seat belt will bounce and hit the window glass.

[0004]

SUMMARY OF THE INVENTION According to the present invention, a winding force of a strength that generates a weak winding force that does not give a feeling of pressure to a human body when worn, and a strength that pulls a buckle securely when not worn, Another object of the present invention is to provide a seat belt retractor that generates a retracting force with an appropriate speed limitation.

[0005]

According to the present invention, there is provided a mainspring as a driving force for winding a belt, a motor as means for suppressing the torque of the spring, a constant current drive circuit for the motor, and a belt when the belt is wound. It is composed of a regenerative braking circuit of a motor as a speed suppressing means.

[0006]

In the above structure, by turning on the power supply to the constant current drive circuit of the motor, the motor generates torque in the direction of suppressing the torque of the main spring, and the belt winding force is reduced. If the belt is wound while the power to the constant current drive circuit of the motor is cut off, regenerative braking will be applied to the motor and the winding speed will be limited.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a front view of a seat belt retractor embodying the present invention, a part of which is shown in section. Second
The drawing is a left side view of FIG. 1 and is shown with the cover 10 cut open. The lock mechanism 12 on the right side of FIG.
It has a built-in lock mechanism that detects acceleration and prohibits belt extension. Since this portion is outside the essential points of the present invention, details are omitted.

The belt 2 shown in FIG. 1 is wound around a winding core 3. A shaft 4 penetrates the winding core 3. The shaft is supported by both side plates of the frame 1. Shaft 4
The core 3, and the end of the belt 2 are fixed to each other. At the left end of the shaft 4, a spur gear 5 integrally formed with a spiral spring hook portion A is inserted. This spur gear is connected via an intermediate gear 7 to a small gear 8 press-fitted into the shaft of a motor 9. The mainspring 6 is housed in the spring case with the outer hook hooked on the spring hook B provided on the spring case 10, and the inner hook is assembled with the spring hook hooked on the spring hook A of the spur gear 5. It is attached. The motor 9 is a small DC motor and is connected to the drive circuit 13. Drive circuit 13
Has an integrated constant current drive circuit and regenerative braking circuit.
Generally, a DC motor does not have a constant torque characteristic, but if it is driven by a constant current drive circuit as described later, a substantially constant torque characteristic can be obtained regardless of the number of rotations. With the above configuration, the torque of the main spring 6 and the torque of the motor 9 always act in parallel on the shaft 4. Therefore, when no torque is generated in the motor 9, the belt 2 is wound by the torque of the main spring 6 and the torque of the motor 9 is applied in a direction to cancel the torque of the main spring 6, whereby the winding force can be reduced.

Next, the drive circuit 13 for the motor 9 will be described. FIG. 3 shows details of the drive circuit shown in FIG. CP1 and CP2 in the figure are comparators, which are open collector outputs. TR1 is a switching transistor that drives the motor 9. D1 is a flywheel diode. VR1 is a variable resistor for supplying the current setting signal Si. RI is a resistance for current detection.
In the configuration shown in the figure, when the power switch SW1 is turned on, there is no current feedback signal Mi because the output transistor is initially in the off state, and the output of the comparator CP1 becomes high level. As a result, the capacitor C1 is charged through the resistor R2, and when the threshold value determined by the voltage division ratio of the resistors R3 and R4 is exceeded, the output of CP2 becomes high level, the transistor TR1 is turned on, and the current flows to the motor 9. The motor current excessively increases due to the reactance of the motor itself, and when the target current value is reached, the current setting signal Mi becomes larger and the output of the comparator CP1 becomes low level. At the same time, the charge of the capacitor C1 is rapidly discharged, the output of CP2 also becomes low level, and the switching transistor TR1 is turned off. The electric current of the motor circulates through the flywheel diode D1 for a while and is gradually attenuated. When the current value becomes lower than the target current value, the comparator CP1 operates again, and the circuit operation described above is repeated thereafter to supply a constant current to the motor 9. At this time, the resistor R2 and the capacitor C1 operate as a time constant circuit for the purpose of limiting the switching frequency. As described above, this circuit operates so that a constant current is always supplied to the motor when the power is turned on. As a result, the motor produces a substantially constant torque regardless of the rotation speed.

Next, in this circuit, since the flywheel diode D1 is always connected to the motor 9 even when the power switch SW1 is off, a regenerative current flows when the motor 9 is rotated in the counter torque direction by the spring. The current at this time begins to flow when the electromotive force of the motor 9 exceeds the forward voltage drop of the fly hold diode D1, and its magnitude can be adjusted by the resistance value of the current detection resistor RI.

When the above-described structure is mounted on an actual vehicle, the power switch SW1 is wired so as to interlock with a seat belt wearing confirmation switch incorporated in the buckle of the seat belt. As a result, when the user pulls out the belt and inserts the buckle, the power switch SW1 is turned on and the winding force is reduced. Further, by arranging the current setting variable resistor VR1 at a position where the user can operate, it is possible to adjust the winding force to a desired one according to the body shape of the user.

[0012]

As described above, the seat belt retractor of the present invention adjusts the belt retracting force by the method of canceling the torque of the mainspring by the torque of the motor. As a result, there is an unprecedented advantage that the user can arbitrarily adjust the winding force of the belt at the time of wearing. Also, since the winding force when not attached can be set to a higher level,
The buckle can be rolled up firmly so that it does not drip, and the buckle does not bounce because the winding speed is too fast, which gives a good usability.

[0013]

[Brief description of drawings]

FIG. 1 is a front view of an embodiment of the present invention, which is partially sectioned.

FIG. 2 is a left side view of FIG. 1, partly in section.

FIG. 3 is a circuit diagram of a drive circuit of the motor shown in FIG.

[Explanation of symbols]

 1 frame 2 belt 3 core 4 shaft 5 spur gear 6 spiral spring 7 intermediate gear 8 small gear 9 motor 10 cover 11 seat plate 12 lock mechanism 13 drive circuit A spring hooking part B spring hooking part BT battery SW1 power switch C1 condenser C2 smoothing Capacitor CP1-2 Comparator R1-R5 Resistance RI Current detection resistance VR1 Variable resistor D1 Flywheel diode TR1 Switching transistor

Claims (2)

[Claims] 1. A seat belt retractor having a structure in which a belt is wound by a mainspring, comprising a motor arranged in parallel with a mainspring for generating a winding force, a constant current drive circuit for the motor, and a regenerative braking circuit for the motor. The seat belt retractor is characterized in that the direction of torque of the motor generated by the constant current drive circuit is opposite to the direction of torque generated by the mainspring. 2. The seat belt retractor according to claim 1, wherein the seat belt retractor is composed of a switching transistor connected in series to the motor and a drive circuit for the motor composed of flywheel diodes connected in parallel.