JP4249761B2 - Pretensioner - Google Patents

Description

  The present invention relates to a pretensioner constituting a seat belt device that restrains a vehicle occupant by a webbing belt.

  In a so-called seat belt device that restrains a vehicle occupant by a long belt-like webbing belt, a webbing belt forcing a winding shaft with one end in the longitudinal direction of the webbing belt locked in a predetermined state such as a sudden vehicle deceleration state. A pretensioner is provided which rotates in the winding direction to wind up and improves the binding force.

  Hereinafter, a general configuration of the pretensioner will be briefly described.

  The pretensioner has a bottomed cylindrical cylinder. A piston is accommodated inside the cylinder. A rack bar is integrally formed at the end of the piston on the opening end side of the cylinder. A pinion gear that meshes with the rack bar is disposed on the side of the rack bar. The pinion is mechanically connected to the take-up shaft via a one-way clutch, and the take-up shaft is forcibly moved in the take-up direction when the piston moves to the opening end side of the cylinder and the rack bar rotates the pinion. It can be rotated.

  On the other hand, a generator accommodating portion is formed integrally with the main body portion of the cylinder on the side of the main body portion that accommodates the piston of the cylinder, and forms a cylinder together with the main body portion. The generator accommodating portion has a cylindrical shape with both ends open, and one end thereof communicates with the inside of the cylinder near the bottom of the main body. On the other hand, a gas generator is inserted from the other end. The gas generator has a cylindrical shape whose outer diameter is slightly smaller than the inner diameter of the generator housing, and a gas generating agent that instantaneously generates a predetermined amount of gas when burned, An ignition device for igniting the gas generating agent is housed, and the gas when the gas generating agent burns is instantaneously supplied between the bottom of the cylinder (main body portion) and the piston, and the gas pressure at this time is The piston is pushed out.

  The ignition device is connected to a separately provided acceleration sensor directly or indirectly through a control device such as a computer, and the ignition device is activated when the acceleration sensor detects a vehicle sudden deceleration state. .

  By the way, in the conventional pretensioner described above, the axial direction of the generator accommodating portion is orthogonal to the axial direction of the main body portion of the cylinder. For this reason, even if the inner diameter of the cylinder main body is reduced, the entire cylinder cannot be reduced due to the axial length of the generator housing. In addition, since the pretensioner becomes larger as a whole in this way, when the cylinder is attached to the vehicle, the generator housing may interfere with the vehicle structure, making it difficult to install the cylinder. The degree of freedom of position selection was small.

On the other hand, when the gas generator is accommodated in the generator accommodating portion, a stopper having a large outer diameter with respect to the main body portion of the gas generator is formed in the gas generator for positioning the gas generator. On the other hand, a large-diameter portion is formed at the other end of the generator accommodating portion so that the inner diameter dimension is larger than the inner diameter dimension at the portion accommodating the main body portion of the gas generator and the stopper can be inserted. The stopper is accommodated in the large diameter portion, and the stopper is brought into contact with the bottom portion of the large diameter portion (that is, the boundary portion between the large diameter portion and the main body portion of the gas generator), thereby Was positioned.

However, in this case, the outer diameter dimension of the generator housing portion must be made sufficiently larger than the outer diameter size of the stopper. As a result, the generator housing portion becomes large, and the pretensioner is also enlarged.

In consideration of the above facts, the present invention has an object to obtain an overall small pretensioner.

  According to the embodiment of the present invention, the winding shaft in which one end of the webbing belt is locked and the piston that rotates the winding shaft in the direction of winding the webbing belt by moving toward one end in the axial direction are housed inside. In addition, the thickness on the bottom side is increased so that the thickness on the opening end side on the one end side in the axial direction is thinner than the bottom side on the other end side in the axial direction, and an increase in internal pressure causes the piston to move in the axial direction. A cylinder main body pushed out to one end side, one end opened between the bottom of the cylinder main body and the piston, a cylindrical generator accommodating portion formed integrally with the cylinder main body, and accommodated in the generator accommodating portion; A pretensioner comprising: a gas generator that generates gas under a predetermined condition and supplies the gas to the cylinder body.

  According to an embodiment of the present invention, there is provided a pretensioner that applies a rotational force in a direction in which the webbing belt is wound under a predetermined condition to the winding shaft on which one end of the webbing belt is locked. The piston that rotates the winding shaft in the direction of winding the webbing belt by moving to the inside is housed inside, and the wall thickness is greater on the opening end side on the one axial end side than on the bottom side on the other axial end side. The thickness on the bottom side is increased so as to be thinner, and the opening end on one end side in the axial direction is located around the housing portion where the one-way clutch is disposed inside, and the piston is moved in the axial direction by increasing the internal pressure. A cylinder main body pushed out to one end side, and a cylindrical generator accommodating portion integrally formed in the cylinder main body, one end opening between the bottom of the cylinder main body and the piston; A gas generator fitted into the generator housing portion from the other end side of the generator housing portion to generate gas under the predetermined condition and to supply the generated gas to the cylinder body. A pretensioner is provided.

  According to the pretensioner having the above configuration, when gas is generated in the gas generator under a predetermined condition and this gas is supplied into the cylinder body, the internal pressure of the cylinder body rises to push up the piston, thereby Move the piston to one end in the direction. By this movement of the piston, the winding shaft is rotated in the winding direction. Thereby, the force which restrains the passenger | crew's body by a webbing belt rises.

  By the way, in this pretensioner, the thickness of the cylinder body is thinner at the opening end side than at the bottom side. For this reason, the cylinder body can be reduced in size and weight, which contributes to the reduction in size and weight of the pretensioner.

  Here, mechanical strength due to thinning of the cylinder body becomes a problem, but when the pressure of the gas supplied to the cylinder body is maximum, the piston is basically in the initial position. It only works near the bottom of the body. On the other hand, when the piston rises as the internal pressure rises, the internal space of the cylinder body expands compared to the volume of the generated gas, so that the internal pressure becomes low and the cylinder body opens to the initial bottom side. The gas pressure does not work.

  Therefore, in this pretensioner, at the beginning, the thickness is secured near the bottom where a large gas pressure acts to secure the mechanical strength, and the thickness is reduced at the opening end side where only a relatively small gas pressure acts. Therefore, the necessary mechanical strength can be ensured as a whole.

  According to the pretensioner having the above-described configuration, when the internal pressure of the cylinder body increases and the piston moves, the rack bar provided at one end of the piston in the axial direction rotates the pinion that meshes with the rack bar. The rotation of the pinion at this time is transmitted to the take-up shaft, and the take-up shaft is rotated in the direction in which the webbing is taken up.

  According to the present invention, the pretensioner can be reduced in size and weight as a whole.

  FIG. 1 is a sectional view showing a configuration of a pretensioner 10 according to an embodiment of the present invention. As shown in this figure, the pretensioner 10 includes a housing 12. The housing 12 is formed of a metal or a hard synthetic resin material, and is fixed to a leg plate (not shown) of the frame of the webbing take-up device. The housing 12 is formed with an accommodating portion 14, and a one-way clutch 16 having a disc shape or a columnar shape having a relatively short axial dimension is disposed inside the housing portion 14.

  The one-way clutch 16 does not transmit the rotational force on one axial end side (the bottom side of the housing 12) to the other axial end side, but transmits the rotational force on the other axial end side to the one axial end side.

  One end of the one-way clutch 16 in the axial direction is mechanically connected to a take-up shaft (not shown) that passes through a circular hole formed in the bottom of the housing portion 14 of the housing 12. A base end portion of a long strip webbing belt (not shown) is locked to the outer periphery of the winding shaft, and the webbing belt is rotated by rotating the winding shaft in one winding direction around the shaft. Wind around the outer periphery.

  A pinion 18 is coaxially fixed to the other axial end of the one-way clutch 16.

  On the side of the pinion 18, there is disposed a square bar-shaped rack bar 22 in which a disk-shaped piston 20 is integrally formed at one end in the longitudinal direction. The rack bar 22 is formed with rack teeth that can mesh with the pinion 18 at one end in the width direction, and the rack teeth can be meshed with the pinion 18 by sliding toward the other end in the longitudinal direction. ing.

  As shown in FIG. 1, the pretensioner 10 includes a cylinder 28 including a cylinder body 24 and a generator housing portion 26. The cylinder body 24 has a cylindrical shape with a bottom, and an inner diameter of the cylinder main body 24 is a piston housing portion 30 having an inner diameter that is substantially the same (strictly, slightly larger than the outer diameter) of the piston 20. Accommodates part or all of the piston 20 and cylinder 28 described above. Here, as shown in FIG. 1, the thickness of the cylinder body 24 on the bottom side is thicker than the thickness on the opening end side.

  On the other hand, the generator accommodating portion 26 is provided in the vicinity of the bottom portion of the cylinder body 24. The generator accommodating portion 26 has a cylindrical shape that is axially oriented along a direction inclined in the direction perpendicular to the axial direction of the cylinder body 24 (that is, the radial direction of the piston accommodating portion 30). However, as shown in FIG. 1, the axial direction of the generator housing portion 26 does not extend along the direction perpendicular to the axis of the cylinder body 24, and the axial direction of the generator housing portion 26 is a cylinder relative to the direction perpendicular to the axis of the cylinder body 24. The main body 24 is inclined at a predetermined angle in the axial direction.

  The generator housing 26 is integrally connected to the cylinder body 24 at one end in the axial direction in the vicinity of the bottom of the cylinder body 24, and the generator housing 26 and the cylinder are connected to each other through the opening 32 (see FIG. 2). The inside of the main body 24 (that is, the piston housing portion 30) communicates with the inside.

  Here, as shown in FIG. 2, the generator accommodating portion 26 has a central axis that is orthogonal to the axial direction of the generator accommodating portion 26 and also orthogonal to the axial direction of the cylinder body 24. The position displaced in the direction, that is, the central axis of the generator housing 26 is connected to the cylinder body 24 so as not to pass through the center of the cylinder body 24.

  On the other hand, as shown in FIG. 1, a gas generator 34 is accommodated in the generator accommodating portion 26. The gas generator 34 as a whole has a cylindrical shape with an outer diameter that is slightly smaller than the inner diameter of the generator housing 26, and generates a predetermined amount of gas instantaneously by burning inside the gas generator 34. A gas generating agent that ignites, an ignition device that ignites the gas generating agent, and the like (both not shown) are accommodated.

  The ignition device is connected to a separately provided acceleration sensor directly or indirectly through a control device such as a computer (both not shown), and the ignition device is activated when the acceleration sensor detects a vehicle sudden deceleration state. Then, the gas generating agent burns and gas is instantaneously generated, and is supplied from the axial end of the gas generator 34 (end on the cylinder body 24 side) into the cylinder body 24 through the opening 32.

  Further, the other end side in the axial direction of the gas generator 34 protrudes from the other end portion in the axial direction of the generator accommodating portion 26. A stopper 36 is integrally formed on the protruding portion of the gas generator 34. The stopper 36 has an outer diameter that is smaller than the outer diameter of the generator housing 26 and larger than the inner diameter of the generator housing 26, and the stopper 36 is in contact with the other end of the generator housing 26. Thus, the movement of the gas generator 34 into the generator housing 26 is restricted.

  A cap 38 is attached to the other end portion of the generator housing portion 26. The cap 38 has a bottomed cylindrical shape, and a female screw is formed on the inner peripheral portion on the opening end side. Correspondingly, a male screw is formed on the outer peripheral portion of the other end portion of the generator housing portion 26, and the bottom portion of the cap 38 prevents the gas generator 34 from coming off by screwing the male screw and the female screw. ing.

  Here, both the male screw of the generator accommodating portion 26 and the female screw of the cap 38 are left-handed screws.

  Further, connection means such as a cable (not shown) is drawn out from the gas generator 34. This connecting means is directly connected to the acceleration sensor of the vehicle or indirectly via a control means such as a computer, and a signal from the acceleration sensor or the control means is ignited in the gas generator 34 via the connecting means. The ignition device is activated by being sent to.

  Next, the operation and effect of the present embodiment will be described.

  In the present pretensioner 10, when the acceleration sensor detects a sudden deceleration state of the vehicle and a signal from the acceleration sensor is sent directly or indirectly to the ignition device of the gas generator 34 via the control means, the gas generator 34 The gas generating agent burns and gas is generated instantly. The gas generated in the gas generator 34 is supplied from the inside of the generator housing portion 26 into the piston housing portion 30 of the cylinder body 24 through the opening 32. By supplying gas into the piston housing part 30, the internal pressure in the piston housing part 30 rises, and the piston 20 is pushed out toward the opening end side of the cylinder body 24 by this internal pressure. As the piston 20 moves in this way, the rack bar 22 integral with the piston 20 meshes with the pinion 18 and rotates the pinion 18. The rotation of the pinion 18 is transmitted to the take-up shaft via the one-way clutch 16 and rotates the take-up shaft. By rotating the winding shaft, the webbing belt is wound around the winding shaft, thereby increasing the restraining force of the occupant's body by the webbing belt and restraining the occupant's body more strongly than before.

  By the way, as described above, the cylinder body 24 of the pretensioner 10 has a wall thickness at the opening end side of the cylinder body 24 that is thinner than a wall thickness at the bottom side. Sufficient mechanical strength is required on the bottom side of the cylinder body 24 where the gas pressure acts greatly, but the opening of the cylinder body 24 where the internal pressure acts after the piston 20 moves and the internal pressure of the piston housing 30 decreases. It does not require the same mechanical strength at the end as it is at the bottom. Therefore, as in the present embodiment, the thickness of the cylinder body 24 on the opening end side is made thinner than that on the bottom side, whereby the weight and size of the cylinder 28 can be reduced.

  Further, since the axial direction of the generator accommodating portion 26 is inclined in the axial direction of the cylinder main body 24 with respect to the axial orthogonal direction of the cylinder main body 24, the entire pretensioner 10 can be reduced in size. That is, for example, when the direction dimensions of the generator accommodating portion 26 are the same, the axial direction of the generator accommodating portion 26 is set with respect to the axis orthogonal direction of the cylinder main body 24 rather than being provided along the axis orthogonal direction of the cylinder main body 24. When the cylinder body 24 is inclined in the axial direction, the other end of the generator housing 26 (that is, the end opposite to the cylinder body 24) is closer to the cylinder body 24, and the cylinder body 24 is perpendicular to the axis direction. Since the overall dimension of the pretensioner 10 along is small, the pretensioner 10 is generally small.

  Further, as described above, the axial direction of the generator accommodating portion 26 is inclined in the axial direction of the cylinder main body 24 with respect to the direction perpendicular to the axis of the cylinder main body 24, thereby lowering the generator accommodating portion 26 (that is, the generator accommodating portion 26. When the axial direction is along the direction orthogonal to the axis of the cylinder body 24, a space having no generator housing portion 26) can be formed. Therefore, even if there is a structural member on the vehicle body side corresponding to this space portion, the assembly of the pretensioner 10 is not hindered. Therefore, the assembling property can be improved, and the assembling property can be improved to improve the workability in the assembling work, and as a result, the assembling cost can be reduced.

  On the other hand, in the present pretensioner 10, the central axis of the generator accommodating portion 26 is displaced in a direction orthogonal to the axial direction of the generator accommodating portion 26 and also in a direction orthogonal to the axial direction of the cylinder body 24. The position, that is, the central axis of the generator housing portion 26 is connected to the cylinder body 24 so as not to pass through the center of the cylinder body 24. For this reason, the opening radius of the opening portion 32 can be made larger than the inner diameter dimension of the generator housing portion 26.

  That is, when the center axis of the generator housing portion is set so as to pass through the center of the cylinder body, the opening radius of the opening portion is the same as the opening radius of the generator housing portion at the maximum. In addition, the gas generated by the gas generator must be supplied between the piston and the bottom of the cylinder body, and the piston cannot be pushed out by gas pressure.Therefore, the opening must be opened closer to the bottom of the cylinder body than the piston. If the outer periphery of the generator housing is located at the same position as the outer bottom of the cylinder body, it will not be possible to secure a sufficient opening area, and in order to ensure a sufficient opening area. If the generator accommodating portion is installed further below the outer bottom portion of the cylinder body (that is, the side opposite to the opening end of the cylinder body), the entire pretensioner is increased in size.

  However, as described above, since the center axis of the generator housing portion 26 is connected to the cylinder body 24 so as not to pass through the center of the cylinder body 24, the opening radius direction of the opening portion is the opening radius of the generator housing portion 26. Since it is inclined with respect to the direction, the opening radius of the opening portion 32 is larger than the opening radius of the generator housing portion 26, and as a result, the opening area of the opening portion 32 is increased. As a result, a sufficient opening area of the opening 32 can be ensured even if the outer peripheral portion of the generator accommodating portion 26 is not positioned further below the outer bottom portion of the cylinder body 24. For this reason, the pretensioner 10 can be reduced in size.

  Furthermore, in the present embodiment, since the stopper 36 provided in the gas generator 34 is in contact with the other end of the generator housing portion 26 to limit the displacement of the gas generator 34, the generator housing portion 26 is configured to be a gas generator. It is only necessary to have an inner diameter dimension of the main body portion 34 and a thickness that can maintain this. Thereby, the outer diameter dimension of the generator accommodating part 26 can be made small, and it contributes to size reduction of the pretensioner 10 as a result.

  Further, in the present embodiment, since the connection between the cap 38 and the generator accommodating portion 26 is made by screwing a male screw and a female screw which are left screws, a general screw having a concept that a screw is usually a right screw. There is also an advantage that the user cannot remove the cap 38.

It is a longitudinal cross-sectional view of the pretensioner which concerns on one embodiment of this invention. FIG. 2 is a cross-sectional view taken along line 2-2 in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Pretensioner 18 Pinion 20 Piston 22 Rack bar 24 Cylinder main body 26 Generator accommodating part 34 Gas generator 36 Stopper

Claims (2)

A winding shaft on which one end of the webbing belt is locked;
A piston that rotates the take-up shaft in a direction to take up the webbing belt by moving toward the one end side in the axial direction is housed inside, and the open end side on the one end side in the axial direction rather than the bottom side on the other end side in the axial direction A cylinder body that is thickened on the bottom side so that the wall thickness is reduced, and pushes the piston toward the one end side in the axial direction due to an increase in internal pressure;
One end is opened between the bottom of the cylinder body and the piston, and a cylindrical generator housing part formed integrally with the cylinder body,
A gas generator housed in the generator housing section for generating gas under predetermined conditions and supplying the gas to the cylinder body;
A pretensioner characterized by comprising: A pretensioner that applies a rotational force in a direction of winding the webbing belt under a predetermined condition to a winding shaft on which one end of the webbing belt is locked;
A piston that rotates the take-up shaft in a direction to take up the webbing belt by moving toward the one end side in the axial direction is housed inside, and the open end side on the one end side in the axial direction rather than the bottom side on the other end side in the axial direction The bottom side wall is thickened so that the wall thickness is reduced, and the opening end on the one axial end side is positioned around the housing housing portion where the one-way clutch is disposed inside, and the piston is increased by increasing the internal pressure. A cylinder body for pushing
One end is opened between the bottom of the cylinder body and the piston, and a cylindrical generator housing part formed integrally with the cylinder body,
A gas generator that is inserted into the generator housing portion from the other end side of the generator housing portion, generates gas under the predetermined condition, and supplies the generated gas to the cylinder body;
A pretensioner characterized by comprising:

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