JPH092207A - Retractor for seat belt with pretensioner - Google Patents

Abstract

PURPOSE: To provide a compact retractor for a seat belt with a pretensioner which smoothly engages with a rack and a pinion and can effectively use the gas pressure of driving means. CONSTITUTION: A rack 25 which can transmit rotating torque in a belt coiling direction to the coiling shaft 4 of a retractor via a pinion gear 21 is pressed and driven by gas pressure. Rack teeth 25a of a rack 25 engaging with gear teeth 21a of a pinion gear 21 have a pitch Px set at a pitch which is equal to or wider than the elastic and plastic deformation to be produced at an engaging part 31 where the rack 25 engages with the pinion gear 21 when the rack 25 rotates the pinion gear 21, or a lager pitch P than a standard pitch.

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 having a pretensioner for removing looseness of a seat belt by winding a webbing around a retractor winding shaft in an emergency.

[0002]

2. Description of the Related Art Conventionally, in a seat belt device for holding a vehicle occupant's body safely in a seat, in order to reduce the occupant's feeling of wearing the seat belt, the retractor has to reduce the force of winding the seat belt. Tend to. This increases the slack of the seatbelt worn on the occupant's body, increasing the amount of extension of the seatbelt when a large force is applied to the seatbelt in an emergency such as a vehicle collision, effectively restraining the occupant's body. There was something I could not do.

Therefore, there is a retractor in which a pretensioner for instantly rotating the retracting shaft of the retractor in the retracting direction is incorporated in order to remove the slack by retracting the seat belt in an emergency. For example, Jitsuko Sho 55-
The pretensioner disclosed in Japanese Patent No. 21696 discloses a piston rod that can be momentarily slid in a cylinder by a gas pressure, and a pre-tensioner that is fixed to a take-up shaft of a seat belt along with the operation of the piston rod. The rack rod is capable of meshing with a gear that is provided, thereby rotating the winding shaft in the seat belt retracting direction and then locking it. Therefore, when the rack rod moves together with the piston rod due to the gas pressure in a vehicle collision, the rack rod and the gear mesh with each other, the gear rotates, and the seat belt is pulled into the retractor.

[0004]

However, in the configuration of the pretensioner disclosed in Japanese Utility Model Publication No. 55-21696, the rack rod is moved by the high pressure gas generated from the gas generator to rotate the gear. At this time, a sudden force acts on the meshing part of the engaged rack rod and gear, so that the meshed part of the rack rod and gear is elastically and plastically deformed, and the phase of the rack tooth and the gear tooth is changed. It may shift. Particularly, since the rack rod and the gear do not mesh with each other in the initial state, when the rack rod is moved, the tooth tips collide with each other and are easily deformed.

Therefore, the following rack teeth and gear teeth do not mesh well with each other, or the rack teeth and gear teeth interfere with each other to prevent smooth rotation. There is a problem that the pressure transmission efficiency decreases. Therefore, an object of the present invention is to solve the above problems, and to provide a compact seat belt retractor with a pretensioner in which the rack and the pinion gear are smoothly engaged and the gas pressure of the drive means can be effectively utilized. Is to provide.

[0006]

SUMMARY OF THE INVENTION The above object of the present invention is to drive a rack capable of transmitting rotational torque to a retractor take-up shaft via a pinion gear by gas pressure at the time of a vehicle collision, thereby making the take-up shaft move. In a seat belt retractor having a pretensioner that rotates in a direction in which the slack of the seat belt is removed, at least in the initial stage of driving, the rack teeth of the rack that mesh with the pinion gear have a pitch wider than a reference pitch. And a seat belt retractor with a pretensioner.

[0007]

According to the above configuration of the present invention, even if the rack tooth and the gear tooth are out of phase due to elastic and plastic deformation at the meshing portion of the rack and the pinion gear when the rack rotationally drives the pinion gear during a vehicle collision. Since the pitch of the rack teeth is widened with respect to the reference pitch in advance in anticipation of this amount of deformation, the next rack tooth and gear tooth that follow it do not mesh well, or the rack teeth and gear teeth interfere with each other. While it does not rotate.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a front view of a seat belt retractor 1 with a pretensioner according to a first embodiment of the present invention, and FIGS. 2 to 4 are main parts of the seat belt retractor 1 with a pretensioner shown in FIG. FIG. 5 is an exploded perspective view, FIG. 5 and FIG. 6 are an AA sectional arrow view and a BB sectional arrow view of the seat belt retractor 1 with a pretensioner shown in FIG. 1, and FIG. FIG. 6 is a cross-sectional view of the pretensioner shown in FIG.

The seatbelt retractor 1 with a pretensioner is equipped with a take-up reel 7 on which the webbing 20 can be taken up or taken out freely. Like the conventional retractor, the take-up reel 7 has its own take-up reel 7. By the winding spring device 5 connected to the winding shaft 4, the webbing 2
It is always urged in the direction of winding 0. Further, when the webbing 20 is to be pulled out at an acceleration of a predetermined magnitude or more, the emergency lock mechanism 2 prevents the winding shaft 4 from rotating, and the webbing 20 is prevented from being further pulled out.

Further, in the seat belt retractor 1 with a pretensioner, one side wall 11a of the retractor base 11 formed in a substantially U-shape has the winding shaft 4 removed from the seat belt slack. A pretensioner 3 provided with a driving means for rotating in the direction is arranged. The pretensioner 3 includes a clutch outer ring 12 which is a rotary driving member capable of intermittently transmitting torque to the winding shaft 4 via a clutch mechanism 30, and a rack 25 which is pressed and driven by a gas pressure generated by a gas generator 29. A drive means 6 for rotating the clutch outer ring 12 by means of a pinion gear 21 that is constantly meshed with the pinion gear 21, and a driving means 6 arranged between the pinion gear 21 and the clutch outer ring 12 for increasing the speed of the clutch outer ring 12 by the rotation of the pinion gear 21. A planetary gear unit 35, which is a speed-increasing gear transmission unit, and a control unit (not shown) that operates the gas generator 29 in the event of a vehicle collision.

The clutch outer ring 12 has a base side wall 11
The clutch ring 14 is fitted to one end of the winding shaft 4 penetrating a and is rotatable relative to the shaft center of the clutch ring 14, and is rotationally driven by the driving means 6 via a planetary gear device 35 described later. It is a cylindrical member, and the planetary gear unit 3 is provided on the outer peripheral surface.
5, outer teeth 12a for forming a sun gear that meshes with the planetary gear 15 are formed, and a wedge-shaped space is formed between the outer peripheral surface of the clutch ring 14 and the thinned inner peripheral surface. The four cam surfaces 12b are formed at equal intervals along the circumferential direction. A cylindrical roller pin 10, which is a meshing element movable in the clutch ring engaging direction so as to enable torque transmission between the clutch outer ring 12 and the clutch ring 14, is disposed in each wedge-shaped space. And the clutch mechanism 30 together with the holder 8 which is a holding means locked to the base side wall 11a to prevent the roller pin 10 from moving in the clutch ring engaging direction.
(See FIG. 6).

The holder 8 is made of a synthetic resin material such as polyacetal and nylon, or a metal material such as aluminum and zinc, and has an annular base plate portion 8a having a circular hole through which the winding shaft 4 is inserted, and It is provided with four pairs of roller pin holding pieces 9a and 9b vertically provided along the axial direction of the substrate portion 8a. Then, the roller pin holding piece 9a,
9b are projected to the side of the base from the roller pin holding piece engaging portions 13a and 13b formed on the base side wall 11a, respectively, and the substrate portion 8a is sandwiched between the flange portion of the take-up reel 7 and the base side wall 11a. Thus, it is arranged in the retractor. Therefore, the roller pin holding piece 9a,
The tip portion of 9b is inserted into each wedge-shaped space of the clutch outer ring 12 arranged outside the base side wall 11a,
The roller pin 10 is held in a disengaged state with the outer peripheral surface of the clutch ring 14.

Further, the inner diameter of the clutch outer ring 12 is larger than the outer diameter of the clutch ring 14, and the roller pin 10 sandwiched by the roller pin holding pieces 9a and 9b of the holder 8 is provided on the outer peripheral surface of the clutch ring 14. In contrast, it has clearance. That is, roller pin 1
0 is securely held by the holder 8 in a state in which torque cannot be transmitted.

Therefore, during normal use, the roller pin 10 held by the holder 8 comes into contact with the clutch ring 14 due to factors such as vibration, so that the webbing 20 is pulled out from the retractor and wound up, and the function of the emergency lock mechanism 2 is achieved. It is unlikely that it will affect or cause abnormal noise.
Further, the roller pin holding pieces 9a, 9 forming a pair, respectively.
b holds the roller pin 10 so as to face each other along the circumferential direction of the substrate portion 8a.
The radial portion of the clutch facing the clutch ring 14 and the clutch outer ring 12 is open. Therefore, even if the rotational driving force in the webbing take-up direction acts on the clutch outer ring 12 and the clutch outer ring 12 suddenly rotates, the roller pin 10 can be reliably kept stationary with respect to the base side wall 11a. Therefore, the roller pin holding piece 9a,
9b can regulate the movement of the roller pin 10 in the circumferential direction until the roller pin 10 is securely bitten.

Moreover, when the clutch outer ring 12 rotates by a predetermined angle and the roller pin 10 is urged toward the center of the winding shaft by the cam surface 12b, the movement of the roller pin 10 in the biting direction may be hindered. The roller pin holding pieces 9a and 9b can be easily deformed so as not to exist. When the clutch outer ring 12 is further driven to rotate in the webbing take-up direction, the roller pin holding pieces 9a and 9b are broken from the base plate portion 8a, and the roller pin 10 biting into the clutch ring 14 is integrated with the clutch outer ring 12. The webbing rotates in the winding direction. The clutch ring 14
Is made of a material harder than the roller pin 10, and the outer peripheral surface thereof is knurled to facilitate biting.

That is, the webbing winding direction (indicated by arrow X _{1 in} FIG. 2) around the clutch outer ring 12 by the drive means 6 described later.
Direction), the roller pin 10
Is the cam surface 12b of the clutch outer ring 12 and the clutch ring 1
By engaging with the outer peripheral surface of the clutch 4, the clutch ring 14 and the clutch outer ring 12 are connected, and the rotational torque of the clutch outer ring 12 is transmitted to the winding shaft 4.

The planetary gear unit 35 has the internal teeth 1 of the planetary gear case 16 fixed to the outside of the base side wall 11a.
6a and the outer ring 12 of the clutch, and a planetary gear 15 and a rotating disk 17 that is a carrier member that rotatably supports the planetary gears 15. The rotating disk 17 is formed with a through hole 17a into which a pin 19 that rotatably supports the planetary gear 15 is press fitted, and a central hole 18 into which a pinion gear 21 is fitted. It is revolved by a rotating disc 17 that rotates integrally with the pinion gear 21. Therefore, the clutch outer wheel 12 is rotated at an increased speed by the rotation of the pinion gear 21.

The drive means 6 includes the pinion gear 21.
Rack 2 having rack teeth 25a meshed with the rack 2
5 and a cylinder 2 for movably receiving the rack 25
4 and a gas generator case 28 that connects the tip of the cylinder 24 and the gas jetting portion of the gas generator 29 to each other. The base end of the cylinder 24 is located outside the planetary gear case 16. It is connected to the rack gear case 22 fixed to. The rack gear case 22 has a central opening 33 in which the pinion gear 21 is rotatably accommodated.
And a guide recess 34 that partially communicates with the central opening 33 and slides and guides the rack 25. An opening 23a through which the tip of the winding shaft 4 penetrates is formed outside the rack gear case 22. The formed plate 23 is arranged so as to cover the pinion gear 21 and the rack 25.

Here, the gear teeth 2 of the pinion gear 21
As shown in FIG. 8, the rack teeth 25a of the rack 25 that mesh with 1a have a pitch Px that is appropriately wider than the reference pitch P shown by the chain double-dashed line. The pitch Px is presumed to be elastic or plastically deformed at the meshing portion 31 of the rack 25 and the pinion gear 21, which mesh with each other when the rack 25 drives the pinion gear 21 to rotate. It is set wider than the reference pitch P.

The gas generator case 2 of the rack 25 is also provided.
A piston 27 slidable in a cylinder 24 is provided at the end on the 8 side together with a buffer material 26 made of a material such as synthetic resin, rubber, or foam metal, and a high pressure generated by a gas generator 29 is provided. The gas is transmitted to the piston 27 via the gas generator case 28. Further, depending on the design, it is possible to integrally manufacture the piston and the rack without using a cushioning material. Furthermore, it is also possible to use an O-ring as the cushioning material to obtain the effect of gas sealing.

Next, the operation of the seat belt retractor 1 with a pretensioner will be described. In the normal traveling state of the vehicle, as shown in FIG. 6, since the clutch outer ring 12 and the roller pin 10 are not engaged with the clutch ring 14, the winding shaft 4 can freely rotate.
Therefore, the webbing 20 can be wound by the biasing force of the winding spring device 5, and the webbing 2 can be resisted against the spring force.
0 can be withdrawn freely.

When a certain amount of deceleration such as sudden braking occurs in the vehicle, the occupant moves forward and tries to pull out the webbing 20 with a certain acceleration. This time,
The retractor's emergency lock mechanism 2 operates and the winding shaft 4
Lock the rotation of. This prevents the webbing from extending, but the control device (not shown) causes the gas generator 2 to operate.
The rack 25 is not pushed because the 9 is not operated.

On the other hand, when an extremely large predetermined deceleration occurs such as during a vehicle collision, a control device (not shown) detects this deceleration and ignites the gas generator 29. The ignited gas generator 29 ejects the driving gas into the gas generator case 28. Then, the expansion pressure of the drive gas flowing into the cylinder 24 from the gas generator case 28 acts on the piston 27, and the piston 27 presses the rack 25 in the webbing winding drive direction via the buffer material 26. At this time, the shock absorbing material 26 can prevent the gas pressure from being rapidly applied to the rack 25.

Since the piston 27 is configured to press and drive the rack 25, it is not necessary to provide the gas generator case 28 with an opening through which a piston rod or the like for transmitting the driving force is inserted. Therefore, the gas pressure acts on the piston 27 almost without leaking, and can be effectively used for the driving force of the rack 25. When the rack 25 is pressed and driven in the arrow Y ₁ direction shown in FIG. 5, the pinion gear 21 meshed with the rack teeth 25a of the rack 25 rotates in the webbing winding direction (the arrow X ₁ direction in FIG. 5). Driven. Then, the rotary disk 17 that rotates integrally with the pinion gear 21 also rotates in the direction of arrow X ₁ .

At this time, a sudden force suddenly acts on the meshing portion 31 between the rack 25 and the pinion gear 21 by the rack 25 that is pressed and driven by the high-pressure gas generated from the gas generator 29. Therefore, as shown in FIG. 9, the rack teeth 25a and the gear teeth 21a of the meshing portion 31 are elastically and plastically deformed, and the rack teeth 25a and the gear teeth 21a are out of phase with each other.

However, since the pitch Px of the rack teeth 25a is widened with respect to the reference pitch P in consideration of the deformation amount of the meshing portion 31, the meshing portion 31 is formed.
The rack 25 and the pinion gear 21 can be smoothly engaged with each other without the next rack tooth 25a and the gear tooth 21a meshing well or the rack tooth 25a and the gear tooth 21a not interfering with each other and rotating. .

Here, in order to clarify the above effect in the present embodiment, FIG. 10 illustrates the engagement state of the rack 25 and the pinion gear 21 when the pitch of the rack teeth 25a is set to the reference pitch P as in the conventional case. . That is, when the rack 25 pressed and driven by the high-pressure gas momentarily exerts a sudden force on the meshing portion 31, and the rack teeth 25a and the gear teeth 21a of the meshing portion 31 are elastically and plastically deformed,
The rack teeth 25a and the gear teeth 21a are out of phase with each other. Therefore, the tooth tips of the next gear tooth 21a following the meshing portion 31 are caught in the middle of the rack tooth 25a, and the tooth tips of the rack tooth 25a and the gear tooth 21a bite into each other at the tooth bottom. Therefore, as shown in FIG. 10, when the pitch of the rack teeth 25a is set to the standard pitch P as in the conventional case, the rack teeth 25a and the gear teeth 21a do not mesh well and the rack teeth 25a and the gear teeth 21a are not meshed with each other. It will rotate while interfering with each other.

A planetary gear 15, which is rotatably supported by a pin 19, is held on the rotary disk 17.
As shown in FIG. 6, the planetary gear 15 includes inner teeth 16 a of the planetary gear case 16 and outer teeth 1 of the clutch outer ring 12.
It meshes with 2a. Then, the rotating disk 17 is indicated by the arrow X.
_The planetary gear 15 revolved in the direction of the arrow X ₁ by rotating in _one direction is the inner tooth 16 of the planetary gear case 16.
Rotate while engaging with a and rotate the clutch outer ring 12 to the arrow X
Rotate in _one direction. Therefore, the rotation of the pinion gear 21 in the arrow X ₁ direction is transmitted by being accelerated by the planetary gear device 35.

When the clutch outer ring 12 is rotated in the direction of arrow X ₁ , the roller pin 10 is urged by the cam surface 12b toward the center of the winding shaft. At this time, the roller pin holding pieces 9a, 9b are moved in the direction of the winding shaft center until the roller pin 10 bites securely between the outer peripheral surface of the clutch ring 14 and the cam surface 12b. Enabled by deformation.

Therefore, when the roller pin 10 moves to a position where it bites securely between the outer peripheral surface of the clutch ring 14 and the cam surface 12b, the rotation of the clutch outer ring 12 is transmitted to the clutch ring 14 and the clutch ring 1
Since the roller 4 and the roller pin 10 rotate integrally with the clutch outer ring 12 in the direction of the arrow X ₁ , the roller pin holding pieces 9a and 9b are broken as shown in FIG.

Further, the pinion gear 2 is driven by the driving force of the rack 25 which is pressed by the expansion pressure of the driving gas.
When 1 is rotationally driven in the webbing winding direction, the clutch outer ring 12 that has been rotated at an increased speed drives the clutch ring 14 to rotate integrally in the arrow X ₁ direction via the roller pin 10 to wind the webbing 20. Since the winding shaft 4 is rotated in the direction, the webbing 20 is tightened and the play of the seat belt is removed.

That is, the rack 25 of the drive means 6 capable of transmitting the increased rotation speed to the winding shaft 4 via the planetary gear device 35.
Can sufficiently rotate the winding shaft 4 in the webbing winding direction even with a short rack stroke. Therefore,
The rack 25 and the cylinder 24 may be short, and the pretensioner can be constructed compactly. Further, between the clutch outer ring 12 that constitutes the planetary gear device 35 and is rotated at an increased speed, and the clutch ring 14 that is fixedly installed on the winding shaft 4, the clutch mechanism that disconnects these when the pretensioner is not operating. The pinion gear 21, the rack 25, and the gears forming the planetary gear device 35 are in a state in which their teeth are meshed with each other in the initial state when the pretensioner is not operating.

Therefore, when the rack 25 is abruptly pressed by the expansion pressure of the driving gas, the tooth tips of the rack teeth 25a and the gear teeth 21a do not collide with each other, preventing damage to the teeth. be able to. Further, even if the rack teeth 25a and the gear teeth 21a of the meshing portion 31 are elastically and plastically deformed and the rack teeth 25a and the gear teeth 21a are out of phase with each other, the next rack tooth 25a following the meshing portion 31 is formed.
The gear teeth 21a and the gear teeth 21a do not mesh well, and the rack teeth 25a and the gear teeth 21a do not rotate while interfering with each other.

That is, the rack 25 and the pinion gear 21
Can be smoothly engaged with each other, and the rack 25 can smoothly transmit the driving force by the drive means 6 to the winding shaft 4. Therefore, the transmission efficiency of the gas pressure of the gas generator 29 to the winding shaft 4 can be increased. Does not decrease, and the expansion pressure of the driving gas can be effectively used to drive the winding shaft 4.
Therefore, as the gas generator 29, a compact gas generator that generates a small amount of gas can be used.

FIG. 12 is an enlarged view of an essential part showing the engaged state of the rack 55 and the pinion gear 51 according to the second embodiment of the present invention. The same components as those in the first embodiment are designated by the same reference numerals. And detailed description is omitted. The rack teeth 55a of the rack 55 that mesh with the gear teeth 51a of the pinion gear 51 have the same pitch as the rack teeth 55a of the rack 55 and the pinion gear 51, as in the first embodiment. Px is formed appropriately wider than the reference pitch P shown by the chain double-dashed line. Further, the pinion gear 51 is provided with rounded portions 52 and 53 at the tips and bottoms of the gear teeth 51a, and the rack 55 is provided with rounded portions 56 and 57 at the tops and bottoms of the rack teeth 55a.
Is provided.

Therefore, a sudden force is instantaneously applied by the rack 55 that is pressed and driven by the high-pressure drive gas.
When acting on the meshing portion 58 of the gear tooth 5a with the gear tooth 5a, the actual amount of deformation is larger than the amount of deformation of the meshing portion 31 which is estimated in advance, and the phases of the rack tooth 55a and the gear tooth 51a are deviated more than expected. Also in this case, the tooth tips of the next gear tooth 51a following the meshing portion 58 are caught in the middle of the rack tooth 55a, or the rack tooth 55a and the gear tooth 51a.
It is possible to reduce the possibility that the tooth tips of the two will bite into each other.

FIG. 13 is an enlarged view of an essential part showing the engaged state of the rack 65 and the pinion gear 61 according to the third embodiment of the present invention. The same components as those in the first embodiment are designated by the same reference numerals. And detailed description is omitted. The rack tooth 65a of the rack 65 that meshes with the gear tooth 61a of the pinion gear 61 changes from the pitch Px at the meshing position at the initial stage of driving to the pitch Px at the meshing position after the completion of the pressing drive.
Up to _n , each rack tooth 65a is formed wider than the reference pitch P. These pitches Px _n may be at least the reference pitch P or more, and the length of each pitch is appropriately set.

That is, the rack 2 is affected by the performance characteristics of the gas generator 29 and the influence of the cylinder 24, etc., in which the space as the pressure container becomes large due to the movement of the rack 65.
Since the pressure of the driving gas acting on 5 changes, the same force is not applied to all the meshing portions with which the rack 65 meshes while moving from the meshing position at the initial stage of driving to the meshing position after the completion of the pressing drive. Not exclusively. Therefore, the amount of elasticity and plastic deformation generated at the meshing portions of the rack teeth 65a and the gear teeth 61a may differ depending on the meshing position.

Therefore, by changing the pitch Px _n of each rack tooth 65a according to the specifications of each retractor, the rack 65 and the pinion gear 61 can always be smoothly engaged. Needless to say, the pitch Px at the meshing position in the initial stage of driving needs to be wider than the reference pitch P, but depending on the load conditions, the pitch Px thereafter may be larger.
_n may be the same as the reference pitch P.

Needless to say, the structure of the pretensioner driving means, the clutch mechanism, the speed increasing gear transmission, the rotary driving member, and the like in the above-described embodiments can take various known forms. For example, the drive means of the pretensioner may be a drive means of the type that pulls and drives the rack.

[0041]

According to the seat belt retractor with a pretensioner of the present invention, when the rack rotationally drives the pinion gear in the event of a vehicle collision, elastic and plastic deformation occurs in the meshing portion between the rack and the pinion gear, and the rack teeth and the gear. Even if the phase of the tooth is deviated, the pitch of the rack tooth is widened with respect to the reference pitch in anticipation of this amount of deformation in advance, so the next rack tooth and gear tooth following this will not mesh well, or the rack tooth will not mesh well. And gear teeth do not rotate while interfering with each other.

That is, the rack and the pinion gear can be smoothly engaged with each other, and the rack can smoothly transmit the driving force by the driving means to the winding shaft, so that the gas pressure of the gas generator with respect to the winding shaft is increased. The transmission efficiency of the drive gas does not decrease, and the expansion pressure of the driving gas can be effectively used for the winding drive of the winding shaft. Therefore, the pretensioner can be made compact.

Therefore, it is possible to provide a compact seat belt retractor with a pretensioner in which the rack and the pinion gear are smoothly engaged and the gas pressure of the drive means can be effectively utilized.

[Brief description of drawings]

FIG. 1 is a front view of a seat belt retractor with a pretensioner according to a first embodiment of the present invention.

FIG. 2 is a part of an exploded arrow view of essential parts of the seat belt retractor with a pretensioner shown in FIG.

FIG. 3 is a remaining part of an exploded arrow view of a main part of the seat belt retractor with a pretensioner shown in FIG. 1.

FIG. 4 is the remaining part of the main part exploded arrow view of the seat belt retractor with pretensioner shown in FIG. 1.

5 is a sectional view taken along the line AA of the seat belt retractor 1 with a pretensioner shown in FIG.

6 is a cross-sectional view taken along the line BB of the seat belt retractor 1 with a pretensioner shown in FIG.

7 is a cross-sectional view taken along the line CC of the pretensioner shown in FIG.

8 is an enlarged view of essential parts of the rack and pinion gear shown in FIG.

9 is an enlarged view of a main part for explaining an engaged state of the rack and the pinion gear shown in FIG.

FIG. 10 is an enlarged view of a main part illustrating an engaged state of a conventional rack and a pinion gear.

11 is a sectional view of relevant parts for explaining an operating state of the clutch mechanism shown in FIG.

FIG. 12 is an enlarged view of a main part of a rack and a pinion gear according to a second embodiment of the present invention.

FIG. 13 is an enlarged view of a main part of a rack and a pinion gear according to a third embodiment of the present invention.

[Explanation of symbols]

1 Seat belt retractor with pretensioner 3 Pretensioner 4 Winding shaft 5 Winding spring device 6 Driving means 7 Winding reel 8 Holder 9a Roller pin holding piece 9b Roller pin holding piece 10 Roller pin 11 Retractor base 12 Clutch outer ring 14 Clutch Ring 15 Planetary Gear 16 Planetary Gear Case 17 Rotating Disk 19 Pin 21 Pinion Gear 22 Rack Gear Case 24 Cylinder 25 Rack 27 Piston 29 Gas Generator

Claims (1)

[Claims] Claim: What is claimed is: 1. A rack capable of transmitting rotational torque to a retractor take-up shaft via a pinion gear is driven by gas pressure when the vehicle collides to drive the take-up shaft in a direction in which slack of the seat belt is removed. In a seat belt retractor having a rotating pretensioner, the rack teeth of the rack meshing with the pinion gear at least in an initial stage of driving have a pitch larger than a reference pitch. Seat belt retractor.