JP2001315618A - Retractor for seat belt with pretensioner - Google Patents

Abstract

(57) Abstract: A compact retractor for a seat belt with a pretensioner that can effectively use gas pressure of a driving means and smoothly transmit a winding driving force to a winding shaft. SOLUTION: A rack 25 capable of transmitting a rotational torque in a belt tightening direction to a winding shaft 4 of a retractor via a pinion gear 21 is pressed and driven by gas pressure at the time of a vehicle collision. A rack 25 integrated with the piston is provided with a guide recess 34 formed in a rack gear case 22 mounted outside the base side wall 11a, and a plate disposed in the rack gear case 22 so as to cover the pinion gear 21 and the rack 25. The slide is guided by.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a retractor for a seat belt provided with a pretensioner for removing slack of a seat belt by winding webbing around a winding shaft of the retractor 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.

In order to remove the slack by winding up the seat belt in an emergency, there is a retractor in which a pretensioner for instantly rotating the winding shaft of the retractor in the winding direction is incorporated in the retractor. As the pretensioner as described above, for example, as disclosed in Japanese Patent Application Laid-Open No. 5-162614, a belt is wound by rotating a driving member such as a pulley by tension by operation of a driving means such as a tension cable driving device. Some types are tightened. The driving member of such a pretensioner is disengaged when the pretensioner is not operated, and is connected to the winding shaft when the pretensioner is operated so as not to interfere with the rotation of the winding shaft of the retractor during normal use. The rotation torque is transmitted to the take-up shaft via an engagement means so as to transmit the rotational torque to the take-up shaft. By using a meshing means such as a gear as the engaging means, the driving member can efficiently transmit the rotational torque to the winding shaft.

A pretensioner disclosed in, for example, Japanese Utility Model Publication No. 55-21696 is a piston rod which can slide instantaneously in a cylinder by gas pressure, and accompanies the operation of the piston rod. Then, it can be engaged with a gear fixed to a winding shaft of the seat belt, thereby rotating the winding shaft in a seat belt retracting direction, and thereafter, a rack rod which can be locked. Therefore,
When the rack rod moves together with the piston rod due to gas pressure during a vehicle collision, the rack rod and the gear mesh with each other to rotate the gear,
The seat belt is pulled into the retractor.

[0005]

However, in the configuration of the pretensioner disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 5-162614, the driving force by the piston of the driving means is transmitted to the transmission means for transmitting the driving force as the rotational force of the winding shaft. In the case of using a rope such as a wire rope, in addition to the required amount of seat belt tightening, it is necessary to consider a loss in a winding amount by which the driving member is engaged with the winding shaft. The piston stroke is required, the pretensioner becomes large, and the mountability of the retractor to the vehicle decreases. In addition, the high-pressure gas generated from the gas generator leaks from the gap between the wire rope sliding hole of the manifold case and the wire rope, so that the gas pressure cannot be effectively used for the driving force of the driving means.

Further, in the configuration of the pretensioner disclosed in Japanese Utility Model Publication No. 55-21696, a rack stroke is required as much as the seat belt is tightened. The size increases, and the mountability of the retractor on the vehicle decreases. Furthermore, in these pretensioner configurations, the pulley and the rack rod after the belt winding operation is completed are:
Because movement in the belt extension direction is not regulated,
The belt extension cannot be suppressed until the winding shaft is prevented from rotating in the belt extension direction by the emergency lock mechanism. Further, when the pulley and the winding shaft, or the rack rod and the gear, which are the engaging means, are gear-engaged with each other in a vehicle emergency, the teeth are not meshed in an initial state. When the tooth tips collide with each other during operation, the teeth may be damaged.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems, and it is possible to effectively use the gas pressure of the driving means and to smoothly transmit the driving force for winding to the winding shaft, thereby achieving belt winding. An object of the present invention is to provide a compact seatbelt retractor with a pretensioner that can prevent extension after the operation is completed.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a retractor winding shaft which is rotatably supported by a retractor base and is constantly biased in a webbing winding direction, and which is driven when a vehicle collides. A gas generator that generates gas, a cylinder into which a driving gas generated from the gas generator flows, and a piston housed slidably in the cylinder and driven to be pressed by the gas pressure of the driving gas, A pinion gear that is always meshed with a rack and is rotated by the rack; a rotation drive member that is rotated by rotation of the pinion gear; and a rotation drive member that is provided between the rotation drive member and the winding shaft. A clutch that disconnects the member from the winding shaft and connects the rotation driving member and the winding shaft when the rotation driving member rotates. A retractor for a seat belt with a shocker, wherein the rack integrated with the piston covers a guide formed on a rack gear case attached to the retractor base, and covers the pinion gear and the rack. The present invention is achieved by a seat belt retractor with a pretensioner, which is slidably guided by a plate disposed on a rack gear case.

According to the above configuration of the present invention, when the driving gas generated from the gas generator at the time of a vehicle collision flows into the cylinder and the piston slidably housed in the cylinder is pressed and driven by the gas pressure, Since the rack integrated with the piston is also pressed and driven to rotate the pinion gear, the rotation drive member can rotate the winding shaft in the webbing winding direction via the clutch mechanism.

In this case, the rack having a rectangular cross section is disposed on the rack gear case so as to cover the guide formed on the rack gear case attached to the retractor base and the pinion gear and the rack. The rack is prevented from rotating and oscillating around the longitudinal axis even when the rack is driven to expand rapidly by the expansion pressure of the driving gas, so that the rack and the pinion gear can be mutually moved. The state in which the teeth are engaged can be reliably maintained.

Further, preferably, as a return preventing mechanism for preventing the rack from moving in a direction opposite to the pressing drive direction,
A cam surface of the rack gear case forming a substantially wedge-shaped space between the sliding contact surface of the rack, a meshing element provided in the wedge-shaped space, and an elastic biasing of the meshing element in a meshing direction. A one-way clutch is used.

In this case, since the relative movement of the rack in the return direction is restricted, the pinion gear is prevented from rotating in the reverse direction. Therefore, even immediately after the completion of the belt tightening operation by the pretensioner, the rack and the pinion gear can suppress the belt from extending.

[0013]

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 seatbelt retractor 1 with a pretensioner according to an embodiment of the present invention, and FIGS. 2 to 4 are exploded main parts of the seatbelt retractor 1 with a pretensioner shown in FIG. FIG. 5 is a perspective view, FIG. 5 and FIG. 6 are an AA sectional view and a BB sectional view of the seat belt retractor 1 with a pretensioner shown in FIG. 1, and FIG. It is CC sectional view taken on the arrow of the shown pretensioner.

The retractor 1 for a seat belt with a pretensioner is provided with a take-up reel 7 on which a webbing 20 is wound so as to be able to be wound up or pulled out. Like the conventional retractor, the take-up reel 7 is provided with the same. The webbing 2 is moved by the winding spring device 5 connected to the winding shaft 4.
It is always biased in the direction in which 0 is wound. When the webbing 20 is to be pulled out at an acceleration equal to or larger than a predetermined magnitude, the rotation of the winding shaft 4 is prevented by the emergency lock mechanism 2, so that the webbing 20 is not pulled out further.

Further, in the retractor 1 for a seat belt with a pretensioner, the winding shaft 4 is used to remove slack of the seat belt on one base side wall 11a of the retractor base 11 formed in a substantially U-shape. A pretensioner 3 having a driving means for rotating in the direction is provided. 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 gas pressure generated by a gas generator 29. A driving means 6 for rotationally driving the clutch outer ring 12 by a pinion gear 21 constantly meshed with the pinion gear 21 is disposed between the pinion gear 21 and the clutch outer ring 12 to rotate the clutch outer ring 12 at a higher speed by the rotation of the pinion gear 21. The vehicle includes a planetary gear device 35 that is a speed increasing gear transmission device, and a control device (not shown) that operates the gas generator 29 at the time of a vehicle collision.

The clutch outer race 12 is provided on the base side wall 11.
a is rotatably disposed around the axis of the clutch ring 14 fitted to one end of the take-up shaft 4 penetrating through a, and is rotationally driven by the driving means 6 via a planetary gear device 35 described later. A cylindrical member having a planetary gear set 3
The outer teeth 12a for forming a sun gear that meshes with the planetary gears 15 of the fifth embodiment are formed, and a wedge-shaped space is formed between the outer peripheral surface of the clutch ring 14 and the hollow inner peripheral surface. Four cam surfaces 12b are formed at equal intervals along the circumferential direction. In each of the wedge-shaped spaces, a cylindrical roller pin 10 which is a meshing element that is movable in a clutch ring engaging direction so as to enable torque transmission between the clutch outer ring 12 and the clutch ring 14 is disposed. And a clutch mechanism 30 together with a 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 substrate portion 8a having a circular hole through which the winding shaft 4 is inserted. There are provided four pairs of roller pin holding pieces 9a and 9b which are provided vertically along the axial direction of the substrate portion 8a. Then, the roller pin holding pieces 9a,
9b is projected toward the base side from the roller pin holding piece locking portions 13a, 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. Is arranged in the retractor in this way. Therefore, the roller pin holding pieces 9a,
9b is inserted into each wedge-shaped space of the clutch outer ring 12 disposed outside the base side wall 11a,
The roller pin 10 is held so as not to be engaged 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 held 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. On the other hand, it has clearance. That is, the roller pin 1
0 is securely held by the holder 8 in a state where 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 vibrations, so that the webbing 20 can be pulled out and retracted from the retractor and the emergency lock mechanism 2 functions. It is less likely to affect or generate abnormal noise.
The roller pin holding pieces 9a, 9
b pinch the roller pins 10 so as to face each other along the circumferential direction of the substrate portion 8a.
However, its radial portion facing the clutch ring 14 and the clutch outer ring 12 is open. Therefore, even when the rotational driving force in the webbing winding direction acts on the clutch outer ring 12 and the clutch outer ring 12 rotates rapidly, the roller pin 10 can be reliably stopped at the base side wall 11a. Therefore, the roller pin holding pieces 9a,
9b can restrict the movement of the roller pin 10 in the circumferential direction until the roller pin 10 is securely bitten.

In addition, 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 prevented. The roller pin holding pieces 9a and 9b can be easily deformed so as not to be caused. Then, when the clutch outer ring 12 is further driven to rotate in the webbing winding direction, the roller pin holding pieces 9a and 9b are broken from the substrate portion 8a, and the roller pin 10 biting into the clutch ring 14 is integrated with the clutch outer ring 12 together. To the webbing winding direction. The clutch ring 14
Is made of a material harder than the roller pin 10, and has a knurling process on its outer peripheral surface to facilitate biting.

That is, the webbing winding direction (arrow X _{1 in} FIG. 2) is applied to the clutch outer ring 12 by the driving means 6 described later.
Direction), the roller pin 10
Are the cam surface 12b of the clutch outer ring 12 and the clutch ring 1
The clutch ring 14 and the clutch outer ring 12 are connected by biting between the outer peripheral surface of the clutch 4 and the clutch outer ring 12, and the rotational torque of the clutch outer ring 12 is transmitted to the winding shaft 4.

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

The driving means 6 includes the pinion gear 21
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 for communicating and connecting the distal end of the cylinder 24 and the gas ejection part of the gas generator 29. The base end of the cylinder 24 is located outside the planetary gear case 16. The rack gear case 22 is fixed to the rack gear case 22. The rack gear case 22 has a central opening 33 in which the pinion gear 21 is rotatably housed.
And a guide concave portion 34 as a guide portion that slides and guides the rack 25 in partial communication with the central opening 33, and the tip of the winding shaft 4 penetrates outside the rack gear case 22. A plate 23 having an opening 23 a is formed so as to cover the pinion gear 21 and the rack 25.

At the end of the rack 25 on the side of the gas generator case 28, a piston 27 slidable in the cylinder 24 together with a cushioning material 26 made of a material such as synthetic resin, rubber, or foamed metal is provided integrally. Gas generator 29
The generated high-pressure gas is transmitted to the piston 27 via a gas generator case 28. Further, depending on the design, the cushioning material is not required, and the piston and the rack can be manufactured integrally. Further, it is also possible to obtain an effect of gas sealing by using an O-ring for the cushioning material.

A cam surface 32 forming a wedge-shaped space is formed on the side wall of the guide concave portion 34 on the side facing the back surface 25b of the rack 25, and the rack gear case 22 is formed in the wedge-shaped space. (in FIG. 5, the arrow Y ₂ direction) return direction of the rack 25 relative to the inner wall of the guide recess 34 and cylindrical roller pin 36 is a mating element of one clutch for restricting the relative movement of the rack engaging the roller pin 36 A coil spring 31 that urges the rack 25 in the direction is provided to constitute a mechanism for preventing the rack 25 from returning. Then, the rack 25 moves in the webbing take-up driving direction (in FIG. 5,
When moving in the arrow Y ₁ direction), the roller pin 36 is movable against the biasing force of the coil spring 31 to the non-intermeshing direction, it does not prevent the movement of the rack 25.

In order to improve the assemblability of the rack 25 and the planetary gear unit 35, an initial positioning pin 37 for regulating an initial mounting position of the rack 25 is inserted into the bottom wall of the guide recess 34. Is being worn. The initial positioning pins 37 are made of resin, and can be easily broken when the rack 25 is pressed and driven. Note that the initial positioning pins 37 are not always necessary.

Next, the operation of the seat belt retractor 1 with a pretensioner will be described. In the normal running state of the vehicle, as shown in FIG. 6, the clutch outer ring 12 and the roller pin 10 are not engaged with the clutch ring 14, so that the winding shaft 4 is freely rotatable.
Therefore, the webbing 20 can be wound by the urging force of the winding spring device 5, and the webbing 2 can be wound against the spring force.
0 can be pulled out freely.

When a certain degree of deceleration such as sudden braking occurs in the vehicle, the occupant moves forward and tries to pull out the webbing 20 at a certain acceleration. At this time,
The retractor's emergency lock mechanism 2 is activated and the winding shaft 4
Lock the rotation of. This prevents the webbing from extending, but the control device (not shown) controls the gas generator 2.
Since the rack 9 is not operated, the rack 25 is not pressed and driven.

On the other hand, when an extremely large predetermined deceleration occurs at the time of a vehicle collision or the like, a control device (not shown) detects this deceleration and ignites the gas generator 29. The ignited gas generator 29 injects the driving gas into the gas generator case 28. Then, the expansion pressure of the driving 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 via the buffer material 26 in the webbing winding driving direction. At this time, the buffer member 26 can suppress a sudden pressurization of the gas pressure to the rack 25.

Here, since the piston 27 is configured to press and drive the rack 25, there is no need to provide an opening in the gas generator case 28 through which a piston rod or the like for transmitting a driving force is inserted. Therefore, almost all the gas pressure acts on the piston 27 without leaking, and the rack 2
5 can be used effectively. The rack 25 shown in FIG.
When press drive the arrow Y ₁ direction shown in, the rack 25
Gear 2 meshed with the rack teeth 25a of the
1 (In FIG. 5, the direction of arrow X ₁₎ webbing winding direction is rotated to. Then, the rotational circular plate 17 rotates integrally with the pinion gear 21 is rotated in the direction of arrow X _1.

A planetary gear 15 rotatably supported by a pin 19 is held on the rotary disk 17. As shown in FIG. 6, the planetary gear 15 is an internal tooth 16 a of the planetary gear case 16. And meshes with the external teeth 12a of the clutch outer ring 12. Therefore, by rotating disk 17 is rotated in the arrow X ₁ direction, the planetary gear 15 is caused to revolve in the arrow X ₁ direction, arrow clutch outer ring 12 to rotate while meshing with the internal teeth 16a of the planetary gear case 16 X Rotate in _one direction. Therefore, the arrow X _{1 of the} pinion gear 21
The rotation in the direction is transmitted at an increased speed by the planetary gear set 35.

[0032] When the clutch outer ring 12 is rotated in the direction of arrow X _1, the roller pin 10 is urged to the winding shaft center direction by the cam surface 12b. At this time, the roller pin holding pieces 9a and 9b do not move toward the center of the winding shaft until the roller pin 10 bites between the outer peripheral surface of the clutch ring 14 and the cam surface 12b. Enabled by deformation.

When the roller pin 10 moves to a position where the roller pin 10 is securely engaged 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
4 and since the roller pin 10 rotates in integrally direction of arrow X ₁ and the clutch outer ring 12, as shown in FIG. 8, the roller pin holding pieces 9a, 9b is broken.

Further, the pinion gear 2 is driven by the driving force of the rack 25 pressed and driven by the expansion pressure of the driving gas.
1 when rotated in the webbing winding direction, the clutch outer ring 12 is rotated accelerated rotates driven integrally arrow X ₁ direction clutch ring 14 via the roller pin 10, winding the webbing 20 By rotating the winding shaft 4 in the direction, the webbing 20 is tightened and the play of the seat belt is eliminated.

That is, the rack 25 of the driving means 6 capable of transmitting the increased rotation to the winding shaft 4 via the planetary gear unit 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 made compact. A clutch mechanism that constitutes the planetary gear device 35 and connects the clutch outer ring 12 that is rotated at an increased speed and the clutch ring 14 that is fixed to the take-up shaft 4 when the pretensioner is not operated. The gears constituting the pinion gear 21, the rack 25, and the planetary gear device 35 are in a state where their teeth are meshed in advance in an initial state when the pretensioner is not operated. Therefore, when the rack 25 is rapidly pressed and driven by the expansion pressure of the driving gas, the tooth tips of the gears do not collide with each other, so that damage to the teeth can be prevented and the driving force by the driving means 6 can be prevented. Can be smoothly transmitted to the winding shaft 4.

Further, as shown in FIGS. 5 and 7, the rack 25 having a rectangular cross section has a guide recess 34 formed in the rack gear case 22 attached to the outside of the base side wall 11a. Since the slide guide is provided by the plate 23 provided on the rack gear case 22 so as to cover the pinion gear 21 and the rack 25, the rack 25 can be rapidly pressed and driven by the expansion pressure of the driving gas. Rotational movement and lateral runout around the longitudinal axis are prevented, and the state in which the pinion gear 21 and the teeth mesh with each other can be reliably maintained.

Then, when the pressing of the rack 25 by the expansion pressure of the driving gas stops, the take-up shaft 4 is pulled out by the tension of the webbing 20 in the webbing withdrawing direction (arrow X in FIG. 8).
₂ ), and the clutch outer ring 12 and the pinion gear 21 also start reverse rotation. Then, the rack 25 (in FIG. 5, the arrow Y ₂ direction) return direction with respect to the inner wall of the guide recess 34 tries to move relative to the cam surface of the back 25b and the guide recesses 34 of the roller pin 36 is a rack 25 32, the relative movement of the rack 25 in the return direction is restricted, so that the pinion gear 21 is prevented from rotating in the reverse direction.

Therefore, immediately after the completion of the belt winding operation by the pretensioner 3, the driving means 6 can suppress the belt from extending. The mechanism for preventing the return of the rack 25 may be set at any position as long as the surface of the rack 25 and the rollers (meshing elements) contact each other at the initial position. Incidentally, the shapes of the guide portion and the plate of the rack gear case, the return preventing mechanism, and the like in the present invention are not limited to the configuration of the above-described embodiment, and it goes without saying that various forms can be adopted.

[0039]

According to the seat belt retractor with a pretensioner of the present invention, the driving gas generated from the gas generator at the time of vehicle collision flows into the cylinder, and the piston slidably accommodated in the cylinder is removed. When pressed by the gas pressure, the rack integrated with the piston is also pressed and driven to rotate the pinion gear, so that the rotation drive member can rotate the winding shaft in the webbing winding direction via the clutch mechanism. .

At this time, the rack having a rectangular cross-sectional shape is disposed on the rack gear case so as to cover the guide formed on the rack gear case attached to the retractor base and the pinion gear and the rack. The rack is prevented from rotating and oscillating around the longitudinal axis even when the rack is driven to expand rapidly by the expansion pressure of the driving gas, so that the rack and the pinion gear can be mutually moved. The state in which the teeth are engaged can be reliably maintained.

Further, as a return preventing mechanism for preventing the movement of the rack in the direction opposite to the pressing drive direction, a cam surface of the rack gear case which forms a substantially wedge-shaped space between the rack and the sliding contact surface of the rack. The relative movement of the rack in the return direction is restricted by using a one-way clutch comprising a meshing element disposed in the wedge-shaped space and a biasing means for elastically biasing the meshing element in the meshing direction. Therefore, reverse rotation of the pinion gear is prevented. Therefore, even immediately after the completion of the belt tightening operation by the pretensioner, the rack and the pinion gear can suppress the belt from extending.

Accordingly, the gas pressure of the driving means can be effectively used, the driving force for tightening can be smoothly transmitted to the winding shaft, and extension after completion of the belt tightening operation can be prevented. It is possible to provide a seat belt retractor with a pretensioner.

[Brief description of the drawings]

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

FIG. 2 is a partial exploded view of the essential part of the retractor for a seat belt with a pretensioner shown in FIG. 1;

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

4 is an exploded view of a main part of the retractor for a seat belt with a pretensioner shown in FIG.

5 is a sectional view of the retractor 1 for a seat belt with a pretensioner shown in FIG.

6 is a cross-sectional view of the retractor 1 for a seat belt with a pretensioner shown in FIG.

7 is a cross-sectional view of the pretensioner shown in FIG. 5 taken along the line CC.

FIG. 8 is a cross-sectional view of a main part for describing an operation state of the clutch mechanism shown in FIG.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 seat belt retractor with pre-tensioner 3 pre-tensioner 4 take-up shaft 5 take-up spring device 6 drive means 7 take-up 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 (3)

[Claims] 1. A retractor winding shaft rotatably supported by a retractor base and constantly urged in a webbing winding direction; a gas generator for generating a driving gas upon a vehicle collision; A cylinder into which the driving gas generated from the generator flows, a piston housed slidably in the cylinder and driven to be pressed by the gas pressure of the driving gas, and constantly engaged with a rack, and rotated by the rack. A pinion gear, a rotation drive member that is rotated by the rotation of the pinion gear, and a rotation drive member provided between the rotation drive member and the winding shaft, and in normal use, the rotation drive member and the winding shaft are disconnected. A seat belt lith with a pretensioner, comprising a clutch mechanism for connecting the rotary drive member and the winding shaft when the rotary drive member rotates. A tractor, wherein the rack integrated with the piston is disposed on the rack gear case so as to cover a guide formed on a rack gear case attached to the retractor base, the pinion gear and the rack. A seat belt retractor with a pretensioner, wherein the retractor is guided by a sliding motion with a plate. 2. A cam surface of the rack gear case, which forms a substantially wedge-shaped space between the rack and a sliding contact surface of the rack, as a return prevention mechanism for preventing movement of the rack in a direction opposite to a pressing drive direction. 2. A pretensioner according to claim 1, wherein a one-way clutch comprising a meshing element disposed in said wedge-shaped space and a biasing means for elastically biasing said meshing element in a meshing direction is used. With seat belt retractor. 3. A cam, wherein the clutch mechanism is fixed to the take-up shaft and has a circular outer periphery, and a cam formed on the rotary drive member and defining a wedge-shaped space between the clutch ring outer peripheral surface. 3. The device according to claim 1, further comprising: a surface, a meshing element disposed in the wedge-shaped space, and holding means supported by the retractor base and holding the meshing element in a predetermined position. 4. A retractor for a seat belt with a pretensioner as described.