JPH11334531A - Tension reducer for seal belt retractor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a belt tension independently of the drawing amount of the belt and eliminate a sense of oppression due to belt being fitted. SOLUTION: A tension reducer for a seat belt retractor includes a rotary damper 5 consisting of a damper case 50 filled with magnetic fluid F and locked to a frame 1 and a rotor 51 having a resistance member 52 connected to a spool 3 for winding a belt 2 and arranged in the damper case in a rotatable manner. An electromagnet 6 and a rotating direction detecting switch 7 are provided as damper control means for detecting the rotation of the spool in the belt winding direction to excite the magnetic fluid in the damper case 50.

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, and more particularly, to a tension reducer for reducing the belt winding force.

[0002]

2. Description of the Related Art In general, a seat belt retractor is structured such that a belt around which a belt is wound is always pulled into the retractor by a winding spring for urging the spool in a belt winding direction. The tension applied to the belt by the action of the winding spring causes an occupant wearing the belt to always feel pressure on the trunk. Conventionally, a technique such as a tension reducer is applied to the retractor to reduce such a feeling of oppression. The tension reducer generally includes two take-up springs having different strengths and a lock mechanism for preventing one of the strong springs from acting at a predetermined withdrawal position of the belt. In the picking range, the state where only a weak spring force is applied by the lock mechanism is maintained. As an example of such a mechanism, there is a technique disclosed in Japanese Patent Publication No. 7-47382.

A tension reducer using two take-up springs as described above requires a space for two take-up springs, which hinders a compact retractor. In addition, the complicated locking mechanism used for this hinders a reduction in the number of parts. Therefore, various proposals have been made to reduce the winding force only when the belt is mounted by using a single winding spring and a relatively simple locking mechanism. As an example of such a technique, there is a technique disclosed in Japanese Utility Model Publication No. 62-18526. In this technology, a configuration is employed in which a lock member that can move within a certain angle range while the winding shaft is locked is operated by a solenoid in conjunction with a buckle switch.

[0004]

However, these techniques follow the same idea of locking the winding shaft as in the conventional tension reducer, and the belt withdrawal amount at the time of mounting is too large to increase the belt winding amount. Does not solve the problem that the lock is released if the value exceeds a certain range. By the way, as a proposal for improving a locking mechanism of a seat belt retractor (ELR) having an emergency locking mechanism, an electrorheological fluid (for example, a substance in which electrically polarizable particles such as carbon particles are dispersed in insulating oil such as silicon oil) is used. Japanese Patent Application Laid-Open No. Hei 8-13309 discloses a method of urging the rotation of the take-up spool in the belt withdrawal direction by applying an electric charge to make the state substantially close to a solid state. In the case of this proposal, the electrorheological fluid is used to prevent the belt from being pulled out, and does not directly solve the above-mentioned problem of reducing the winding force. It is considered that application to a tension reducer is possible if the timing is devised and controlled with respect to the load.

The present invention has been devised in view of the above circumstances, and provides a tension reducer for a seat belt retractor which can surely reduce the tension applied to a belt during wearing regardless of the amount of belt withdrawal. The first purpose is to do so. Next, a second object of the present invention is to make it possible to electrically control a rotary damper used for reducing the tension. A third object of the present invention is to further reduce the resistance of the tension reducer when the belt is pulled out. Further, a fourth object of the present invention is to control the reduction of the tension electrically in accordance with the behavior of the belt. It is a fifth object of the present invention to provide a rotation direction detection switch having a simple configuration used for the electric damper control.

[0006]

In order to achieve the first object, a tension reducer according to the present invention is rotatably supported by a frame and has a spool wound with a belt and a spool retracting direction. In a seat belt retractor having a frame and a take-up spring supported by a spool so as to be able to be biased, a magnetic fluid is sealed inside and a damper case which is prevented from rotating by the frame, and a damper case connected to the spool is provided in the damper case. A rotary damper comprising a rotating body having a rotatable resistance member, and damper control means for exciting a magnetic fluid in a damper case by rotating a spool in a belt winding direction. .

Next, in order to achieve the second object, the damper control means includes an electromagnet having an exciting coil disposed in the damper case, and the damper case is fixed to the frame and is prevented from rotating. You.

Further, in order to achieve a third object, the damper control means includes a permanent magnet fixed to a frame on an outer periphery of the damper case, and an exciting coil wound around the damper case, The damper case is rotatably supported by the spool, and when the excitation coil is energized by the damper control means, the repulsive magnetic field with the permanent magnet prevents the damper case from rotating around the frame and excites the magnetic fluid in the damper case. Configuration.

Further, in order to achieve a fourth object, the damper control means includes: a rotation direction detection switch which is closed by rotation of the spool in the belt winding direction; a buckle switch which is closed by mounting the belt; And an excitation circuit for energizing the excitation coil by closing both switches.

In order to achieve the fifth object, the rotation direction detection switch includes a fixed contact provided on a frame side, and a movable contact which frictionally engages with the spool and rotates with the spool within a predetermined angle range. It is composed of

[0011]

According to the present invention, the damper control means excites the magnetic fluid in the damper case by rotation of the spool in the belt winding direction. Thereby, the viscosity of the magnetic fluid increases, the resistance applied to the resistance member increases, the rotation of the rotating body is braked, and the rotation in the belt winding direction is damped by the spool connected to the rotating body. This action reduces the belt winding force.

According to the second aspect of the present invention, the above-described action is generated by energizing the electromagnet by the damper control means.

According to the third aspect of the present invention, the excitation coil of the damper case is energized by the damper control means by the rotation of the spool in the belt winding direction. Thereby, the damper case is prevented from rotating around the frame by the repulsive magnetic field with the permanent magnet, and the magnetic fluid in the damper case is excited. As a result, the viscosity of the magnetic fluid increases, the resistance applied to the resistance member increases, the rotation of the rotating body is restricted, and the rotation in the belt winding direction is damped by the spool connected to the rotating body. This action reduces the belt winding force. Further, in this configuration, when the spool rotates in the belt withdrawing direction, the excitation coil of the damper case is not energized, so that the rotation of the damper case to the frame due to the repulsive magnetic field is released. As a result, when the spool rotates in the belt withdrawing direction, the damper case rotates together with the rotating body due to the viscosity of the magnetic fluid.

Next, in the configuration of the fourth aspect, the buckle switch is closed by mounting the belt, and the rotation direction detection switch is closed by rotating the spool in the belt winding direction after mounting. By closing these two switches, power is supplied from the excitation circuit to the excitation coil, and the belt winding force is reduced by damper control.

According to the fifth aspect of the present invention, when the spool rotates in the belt winding direction, the movable contact rotates together with the spool and comes into contact with the fixed contact. The rotation in the winding direction is detected.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 schematically show a configuration of a tension reducer of the seat belt retractor according to the first embodiment. In this device, a retractor is rotatably supported by a frame 1 and has a spool 3 around which a belt 2 is wound, and a winding mechanism which is supported by the frame 1 and the spool 3 so as to bias the spool 3 in a belt winding direction. And a spring 4. The tension reducer includes a damper case 50 in which a magnetic fluid F is sealed and is prevented from rotating by the frame 1, and a rotating body 51 having a resistance member connected to the spool 3 and rotatably disposed in the damper case 50. And damper control means 6 to 9 for exciting the magnetic fluid F in the damper case 50 by rotating the spool 3 in the belt winding direction.

Hereinafter, the above components will be described in detail. First, the damper case 50 is made of a magnetically permeable material such as plastic. In this embodiment, as shown in FIG. 2, a pair of electromagnets 6 having excitation coils are arranged on the inner peripheral surface of the damper case 50 at symmetric positions with respect to the center line. As shown in FIG. 1, it is fixed to the frame 1 via a take-up spring case 40 and is prevented from rotating. The rotator 51 has pins 52 disposed on the outer peripheral side thereof at a constant circumferential pitch as resistance members, and is fixed on the inner peripheral side to the shaft portion 30 extending from the spool 3 so as not to rotate.

A rotation direction detection switch 7 is provided outside the damper case 50. The switch 7 is fitted in an insulating disk 70 fixed to the shaft portion 30 extending from the spool 3 in a frictional engagement with the outer periphery of the disk.
It is composed of a friction plate composed of 0 and an annular conductor ring 72 that rotates. As shown in FIG. 3, the conductor ring 72 has a projection 73 projecting radially on a part of its outer periphery, and an axial projection 53 facing the projection 73.
Are provided so as to protrude from the damper case 50 as stoppers. A conductor terminal 71 is provided on the opposite side of the projection 73 from the axial projection 53.

The damper control means includes the electromagnet 6, the rotation direction detection switch 7, the power supply 8, the buckle switch 9
And an exciting circuit including: In the excitation circuit, the rotation direction detection switch 7 and the buckle 21 are connected in series with each other in a circuit connecting the power source 8 to the coil of the electromagnet 6.
A buckle switch 9 that is closed by inserting the tongue 22 into the buckle 22 is interposed.

In the apparatus having such a configuration, in a state where the tongue 22 shown in FIG. 3 is disengaged from the buckle 21, the rotation direction detection switch 7 is turned on by winding the belt 2. Since the buckle switch 9 is off, the electromagnet 6 is in a demagnetized state, and the magnetic fluid F is also in a non-excited state. Accordingly, the belt 2 can be smoothly pulled out from this state without any resistance due to an increase in the viscosity of the magnetic fluid F. When the belt is pulled out, the rotation direction detection switch 7 is also turned off.

When the tongue 22 is inserted into the buckle 21 to turn on the buckle switch 9 and the belt 2 is released, the take-up spring 4 rotates the spool 3 in the take-up direction. The switch 7 is turned on again. When the buckle switch 9 and the rotation direction detection switch 7 are turned on, the electromagnet 6 is excited,
The magnetic fluid F is also in an excited state. As a result, the magnetic fluid F in the damper case 50 is attracted to each other along the magnetic force lines created by the electromagnet 6, and the force that hinders the movement of the pin 52 that attempts to move across the magnetic force lines causes rotation resistance of the rotating body 51. . Therefore, the spool 3 fixed to the rotating body 51 receives the resistance in the belt winding direction, and the winding force is reduced.

In this state, if the belt 2 is pulled in the pulling-out direction by the operation of the occupant or the movement of the body, even if the buckle switch 9 remains on, the belt 2 is pulled in the same manner as when the belt is worn.
As a result, the rotation of the rotation direction detection switch 7 is also turned off, so that the power supply to the electromagnet 6 is cut off, the excitation is released, and the magnetic fluid F allows the belt 2 to be drawn out smoothly without resistance.

When the occupant stops pulling out the belt 2 or returns the body from the pulled-out state, the spool 3 is rotated in the winding direction by the action of the winding spring 4. Is turned on again. When the buckle switch 9 and the rotation direction detection switch 7 are both turned on, the electromagnet 6 is excited, and the magnetic fluid F
Are also excited. As a result, the magnetic fluid F in the damper case 50 is attracted to each other along the lines of magnetic force created by the electromagnet 6, and the force that hinders the movement of the pin 52 that attempts to move across the lines of magnetic force causes rotation resistance of the rotating body 51. . Therefore, the spool 3 fixed to the rotating body 51
Receives the resistance in the belt winding direction, and the winding force is reduced. Therefore, the winding of the belt 2 does not occur suddenly,
The buffered dull return results. Finally, the position is stabilized at a position where the viscous resistance and the load of the winding spring 4 are balanced. In this case, if the load of the winding spring 4 exceeds the braking load of the rotary damper 5 even when the belt 2 is along the occupant's body, the corresponding force is applied to the occupant's body as tension. If the load of the take-up spring 4 is balanced with the braking load of the damper 5 before the belt 2 moves along the occupant's body, the belt 2 is stopped in a loose state. The relationship between the winding load and the braking load can be arbitrarily adjusted by electromagnetic control of the damper 5.

Thus, according to the device of the above embodiment, unlike the conventional winding force reducing device of this type, which restricts the rotation of the spool within a fixed rotation angle range, the braking force can be continuously rotated. The rotation of the spool 3 irrespective of the magnitude of the withdrawal stroke of the belt 2, that is, the amount of rotation of the spool 3.
The same braking force can be generated at any rotational position. As a result, a stable effect of reducing the winding force can be obtained. Since the number of parts is small in terms of mechanism, it is advantageous in terms of manufacturing cost and operation stability.

Next, FIGS. 4 to 6 schematically show the structure of a tension reducer of the seat belt retractor according to the second embodiment. In this device, the tension reducer is fixed to the frame 1 around the outer periphery of the damper case 50, and the permanent magnet 6A is disposed. The damper case 50 is wound with an exciting coil 6B (see FIG. 6) instead of the electromagnet. ,
The spool 3 is rotatably supported.

Hereinafter, only differences between the second embodiment and the first embodiment will be described. First, the damper case 50
In this embodiment, as shown in FIG. 5, a pair of permanent magnets 6A are disposed on the inner peripheral surface at symmetrical positions with respect to the center line. These permanent magnets 6A are, for example, a second damper case 6 surrounding the outer periphery of a damper case 50 fixed to a cover (not shown) fixed to the frame 1 covering the entire tension reducer including the winding spring case 40.
0 is fixed to the inner peripheral surface. And damper case 5
At 0, the exciting coils 6B are wound in parallel with each other symmetrically with respect to the shaft portion 30. Further, in this embodiment, the damper case 50 is rotatable with respect to the shaft portion 30 without being fixed to the winding spring case 40.

In the case of this configuration, when the excitation coil 6B is energized by the damper control means, the repulsive magnetic field with the permanent magnet 6A causes the damper case 50 to change the winding direction of the excitation coil 6B to the magnetic field created by the two permanent magnets 6A. The magnetic fluid F in the damper case 50 is excited by the same magnetic field while being prevented from rotating around the frame 1 in a direction perpendicular to the direction.

As a feature of the above embodiment, in the case of the first embodiment, the relative rotation between the damper case 50 and the rotating body 51 occurs even when the electromagnet 6 is demagnetized when the belt is pulled out. Is generated, which is a draw resistance regardless of the magnitude of the value. According to the configuration of the second embodiment, the permanent magnet is lost due to the disappearance of the electric field due to the non-energization of the exciting coil 6B. The repulsive magnetic field against 6A is eliminated, the rotation stop of the damper case 50 to the frame 1 is released, and the damper case 50 rotates together with the rotating body 51, so that the relative rotation of the two does not occur. Viscous drag can be prevented from being applied, thereby providing an advantage that the belt 2 can be drawn out more smoothly.

As described above, the present invention has been described in detail based on the two embodiments. However, the present invention is not limited to only the disclosed contents of the above-described embodiments, and various details are included within the scope of the claims. It is needless to say that the present invention can be implemented by changing the specific configuration. For example, the resistance member provided on the rotating body 51 may be a blade having no twist extending radially from the axis or a twisted wing used in an electric fan. Further, the electromagnet in the first embodiment can be fixedly disposed on the outer periphery of the damper case.

[0030]

According to the structure of the first aspect of the present invention, the braking force by the rotary damper has a continuous resistance to the rotation of the spool only when the belt is wound.
The winding of the belt by the winding spring is damped irrespective of the looseness of the belt at the time of wearing, and the feeling of pressure on the occupant can be reduced.

Next, according to the configuration of the second aspect, the above-mentioned effect can be easily achieved by electrical control of the rotary damper.

Further, according to the configuration of the third aspect, in addition to the above-described effects, an effect of reducing the resistance when the belt is pulled out can be obtained.

Further, according to the structure of the fourth aspect, the feeling of pressure in the winding direction is automatically reduced in accordance with the operation of the belt, and the effect of reducing the resistance in the drawing direction is obtained.

According to the fifth aspect of the present invention,
The detection of the rotation direction of the spool required for controlling the rotary damper can be performed with a simple switch.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically illustrating a tension reducer of a seat belt retractor according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a circuit diagram of damper control means of the tension reducer.

FIG. 4 is a cross-sectional view schematically illustrating a tension reducer of a seat belt retractor according to a second embodiment of the present invention.

FIG. 5 is a sectional view taken along line BB of FIG. 5;

FIG. 6 is a partial perspective view of the tension reducer.

[Explanation of symbols]

 Reference Signs List 1 frame 2 belt 3 spool 4 take-up spring 5 rotary damper 6 electromagnet 6A permanent magnet 6B excitation coil 7 rotation direction detection switch 71 terminal (fixed contact) 72 conductor ring (movable contact) F magnetic fluid

Claims (5)

[Claims] 1. A seat belt retractor comprising: a spool rotatably supported by a frame and around which a belt is wound; and a winding spring supported by the frame and the spool so as to bias the spool in a belt winding direction. A rotary damper comprising: a damper case in which a magnetic fluid is sealed therein and is prevented from rotating by a frame; a rotating body having a resistance member connected to a spool and rotatably disposed in the damper case; and And a damper control means for exciting a magnetic fluid in the case by rotating the spool in a belt winding direction, the tension reducer for a seat belt retractor. 2. The seat belt retractor tension reducer according to claim 1, wherein said damper control means includes an electromagnet having an exciting coil disposed in said damper case, said damper case being fixed to a frame to prevent rotation. 3. The damper control means includes a permanent magnet fixed to a frame on the outer periphery of the damper case, and an exciting coil wound on the damper case, and the damper case is rotatably supported by a spool. The seat belt retractor according to claim 1, wherein when the excitation coil is energized by the damper control means, the damper case is prevented from rotating around the frame by a repulsive magnetic field with the permanent magnet, and the magnetic fluid in the damper case is excited. Tension reducer. 4. The damper control means includes: a rotation direction detection switch which is closed by rotation of a spool in a belt winding direction; a buckle switch which is closed by mounting a belt; and an exciting coil which is closed by closing both switches. 4. A tension reducer for a seat belt retractor according to claim 1, further comprising: an excitation circuit for supplying current to the seat belt retractor. 5. The rotation direction detection switch comprises a fixed contact provided on a frame side and a movable contact which frictionally engages with the spool and rotates with the spool within a predetermined angle range. A tension reducer for a seat belt retractor according to any one of claims 1 to 4.