GB2273647A

GB2273647A - Vehicle deceleration sensor for releasing an ignition pin, e.g. in a seat belt pretensioner

Info

Publication number: GB2273647A
Application number: GB9326268A
Authority: GB
Inventors: Teruhiko Koide; Shinji Mori
Original assignee: Tokai Rika Co Ltd
Current assignee: Tokai Rika Co Ltd
Priority date: 1992-12-28
Filing date: 1993-12-23
Publication date: 1994-06-29
Anticipated expiration: 2013-12-23
Also published as: JPH06199204A; DE4344399A1; GB9326268D0; GB2273647B

Description

2273647 TITLE MECHANICAL IGNITION SYSTEM SENSOR

The present invention relates to a mechanical ignition system sensor for sensing a state of a sudden deceleration of a vehicle, etc. Description of the Related Art:

As a seat belt system mounted to a vehicle, there is known, for example, one provided with a socalled pretensioner wherein a webbing applied to an occupant is retracted a predetermined amount when the vehicle suddenly decelerates. The looseness of the webbing applied to the occupant is thus forcibly removed so as to tighten the webbing to thereby improve occupantrestraining characteristics.

With this type of pretensioner, there is known one wherein a take-up shaft of a webbing retractor is forcibly rotated so as to tighten a webbing and one wherein a buckle is forcibly pulled so as to tighten a webbing. For example, the latter pretensioner is provided with a cas generator having a mechanical ignition system sensor. A cylinder is attached to the gas generator and coupled to a buckle via a wire or the like.

When the vehicle suddenly decelerates, a state of a sudden deceleration is detected by the mechanical ignition system sensor and the gas generator is operated to instantaneously generate gas. As a result, the cylinder which generated the gas is moved and the resultant moving force is transmitted to the buckle via the wire so as to forcibly move the buckle, thereby tightening the webbing.

The mechanical ignition system sensor employed in the conventional pretensioner referred to above basically comprises an ignition pin for igniting a detonator, an inertial body inertially moved by a rapid acceleration and a trigger member such as a ball or the like, which is interposed between the ignition pin and the inertial body so as to prevent the ignition pin from moving (see Japanese Patent Application Publication No. 52-13104, for example). Since the trigger member is simply interposed between the inertial body and the ignition pin and serves to prevent the movement of the ignition pin in a normal state, the direction in which the trigger member is pressed by the ignition pin is different from that in which the inertial body is pressed by the trigger member. Thus, the pressing force applied to the trigger member by the ignition pin is increased owing to the difference in pressing direction and applied to the trigger member. As a result, the so-raised pressing force acts on the inertial body. Thus, the frictional force between the trigger member and the inertial body becomes greater and variations in operating sensitivity or the like of the mechanical ignition system sensor are produced.

When the mass of the inertial body is simply increased to reduce any influence received from the frictional force between the trigger member and the inertial body, the mechanical ignition system sensor is increased in shape and becomes heavy in weight as a whole.

Further, the conventional mechanical ignition system sensor is constructed such that the trigger member such as the ball is simply interposed between the inertial body and the ignition pin and the ignition pin is normally prevented from moving. Therefore, after the trigger member is once separated from between the inertial body and the ignition pin so as to release the ignition pin from a state in which the ignition pin has been prevented from moving, it was very difficult to reset the ignition pin to such a movement-preventing state again.

Thus, for example, when one attempts to confirm the operating sensitivity or the like of the mechanical ignition system sensor and make an operation check as to whether or not the mechanical ignition system sensor is reliably operated, only the operation check can be carried out. However, the mechanical ignition system sensor cannot be normally assembled into the gas generator so as to be placed (reset to) in a state of being capable of being actuated after completion of theoperation check. Further, the operation check of the mechanical ignition system sensor cannot be omitted.

With the foregoing in view, it is an object of the present invention to provide a mechanical ignition system sensor which is capable of reducing negative influence received from frictional force and ensuring stable operating characteristics in a simple structure and which can be easily reset even after an operation check for confirming sensitivity or the like has been carried out.

According to one aspect of the present invention, a mechanical ignition system sensor according to the present invention comprises an ignition pin movably disposed along an axial direction thereof and moved in the axial direction by an urging force of a firing spring so as to ignite a detonator, an inertial mass body normally urged by a trigger spring and moved by the inertial force against the urging force of the trigger spring when a predetermined load acts on the inertial mass body, and a trigger lever for normally holding the ignition pin in a state of being separated from the detonator and releasing the ignition pin from being held in the separated state when the inertial mass body is moved a predetermined distance or more.

According to another aspect of the present invention as well, the trigger lever is supported by a support shaft so as to be rotatable in a direction of approaching and moving away from the ignition pin. Further. the trigger lever has an engaging portion which engages the ignition pin and a roller which is located at a position farther than the position where the engaging portion is separated from the support shaft and which is normally held in rolling contact with the inertial mass body. The roller is normally pressed by the inertial mass body so as to bring the engaging portion into engagement with the ignition pin and prevent the trigger lever from being rotated about the support shaft. Thus, the trigger lever holds the ignition pin against an urging force of the firing spring in a state in which the trigger lever has been pressed by the ignition pin in the direction of moving away from the ignition pin. When the inertial mass body is moved, the trigger lever is released from the prevention of its rotation by the inertial mass body so as to rotate in the direction of moving away from the ignition pin while the roller is being held in rolling contact with the inertial mass body, thereby enabling the ignition pin to move.

Further, according to a further aspect of the present invention, the trigger lever has an engaging portion engaged with the ignition pin, a roller held in contact with the inertial mass body and an elongated hole for slidably supporting the roller. The engaging portion is normally brought into engagement with the ignition pin so as to hold the ignition pin. The roller rolls while being slidingly moved along the elongated slot when the inertial mass body is moved, thereby releasing the ignition pin from being held by the engaging portion.

In the mechanical ignition system sensor according to the present invention, the ignition pin is normally located at a position where it is separated from the detonator against the urging force of the firing spring. The inertial mass body enters a locus of swinging movement of the trigger lever by the trigger spring. Further, the trigger lever holds the ignition pin in a state in which it has been turned in a direction of approaching the ignition pin. The trigger lever is prevented from rotating by contact between the roller and the inertial. mass body, so that the trigger lever is placed in a state in which the ignition pin has been held.

When a rapid acceleration acts on the mechanical ignition system sensor, the inertial mass body is inertially moved so as to be separated from the locus of the swinging movement of the trigger lever. As a result, the inertial- mass body can be rotated about the support shaft of the trigger lever. Therefore, the trigger lever pressed in the direction of moving away from the ignition pin by the ignition pin which has been urged by the firing spring, is rotated in the direction of moving away from the ignition pin while the roller is being held in rolling contact with the inertial mass body. Thus, the ignition pin is released from the state in which it has been held by the engaging portion of the trigger lever. Therefore, the ignition pin is moved in its axial direction by the urging force of the firing spring so as to ignite the detonator.

Since the roller is located at a position farther than the position where the engaging portion is separated from the support shaft even if the direction in which the trigger lever is pressed by the ignition pin, differs from the direction in which the inertial mass body is pressed by the trigger lever (roller), the pressing force applied to the trigger lever by the ignition pin is reduced and applied to the trigger lever. The reduced pressing force acts on the inertial mass body. Thus, the frictional force between the trigger lever (roller) and the inertial. mass body is reduced so that the operational sensitivity of the mechanical ignition system sensor is stabilized.

Further, when the inertial mass body is inertially moved so that the trigger lever is rotated about the support shaft, the roller of the trigger lever is rotated while being held in rolling contact with the inertial mass body. Therefore, a further reduction in frictional force is made and a more effective result is obtained.

Thus, a reduction in negative influence received from the frictional force between the trigger lever and the inertial mass body and stable operating characteristics can be ensured without an increase in mass of the inertial mass body.

Once the ignition pin is moved, the trigger lever is pressed in the direction of approaching the ignition pin by the inertial mass body which has been urged by the trigger spring.

Next, when the mechanical ignition system sensor, which has been operated once, is brought into a state of being capable of being actuated again (i. e., when it is reset), the ignition pin is moved in the axial direction thereof against the urging force of the firing spring.

Since the trigger lever is pressed in the direction of approaching the ignition pin by the inertial mass body which has been urged by the trigger spring, the trigger lever is rotated in the above approaching direction when the ignition pin has reached an initial position. As a result, the trigger lever is brought into engagement with the ignition pin so that the ignition pin is held at the initial position separated from the detonator.

Thus, when the ignition pin is simply moved to the initial position along an axis of the ignition pin, the trigger lever can be rotated so as to return to an initial state in which the ignition pin is held. Accordingly, the mechanical ignition system sensor can be easily brought into a state of being capable of being actuated (i.e., it can be reset) by normally assembling the mechanical ignition system sensor into a gas generator after completion of an operation check of the mechanical ignition system sensor.

In the mechanical ignition system sensor according to another aspect, the ignition pin is normally disposed at the position where it is separated from the detonator against the urging force of the firing spring. The inertial mass body enters the locus of the swinging movement of the trigger lever by the trigger spring. Further, when the engaging portion is engaged with the ignition pin so as to hold the ignition pin and the roller is brought into contact with the inertial mass body, the trigger lever is prevented from rotating so that the trigger lever is placed in a state in which the ignition pin has been held.

When a rapid acceleration acts on the mechanical ignition system sensor, the inertial mass body is inertially moved so that the trigger lever is moved in the direction of moving away from the ignition pin while the roller of the trigger lever is being held in rolling contact with the inertial mass body. Thus, the ignition pin is released from being held by the engaging portion of the trigger lever so that the ignition pin is moved in the axial direction by the urging force of the firing spring, thereby igniting the detonator.

Now, the roller of the trigger lever, which contacts the inertial mass body, is slidably supported by the elongated hole. Therefore, when the inertial mass body is inertially moved so as to rotate the trigger lever, the roller rolls while being slidingly moved along the elongated hole by simply moving the inertial mass body an extremely short distance after the inertial mass body has passed over a position where the prevention of the trigger lever from rotating is switched or released. That is, when the roller is slid along the elongated hole, the trigger lever is rotated so as to reliably release the ignition pin from being held by the engaging portion. Thus, further reliable and stable operating characteristics can be ensured.

The mechanical ignition system sensor according to the present invention as described above has an excellent advantageous effect in that a reduction in negative influence received from frictional force and stable operating characteristics can be ensured in a simple structure and the sensor can be easily reset even after an operation check for confirming sensitivity and the like has been effected.

The invention will now be described by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a cross-sectional view showing an initial state of a mechanical ignition system sensor according to a first embodiment of the present invention; FIG. 2 is a partly enlarged view of FIG. 1, illustrating the state of a roller attached to a trigger lever of the mechanical ignition system sensor shown in FIG. 1; FIG. 3 is an enlarged view showing the state of the roller at the time of operation of the mechanical ignition system sensor shown in FIG. 1 and corresponding to FIG. 2; FIG. 4 is a cross-sectional view showing the state after the mechanical ignition system sensor shown in FIG. 1 has been operated; and FIG. 5 is a cross-sectional view illustrating a mechanica 1 ignition system sensor according to a second embodiment of the present invention.

FIG. 1 is a cross-sectional view of a mechanical ignition system sensor 10 according to a first sensor cover 12, the ignition pin 24 protrudes outwards through the aperture 16 defined in the bottom wall 14. on the other hand, a collar portion 28 is formed on the other end of the ignition pin 24. The outside diameter of the collar portion 28 corresponds to the inside diameter of the guide 18. Thus, the ignition pin 24 is held so as to be slidable within the guide 18.

A firing spring 30 is disposed between the ignition pin 24 and the plate 20 and normally urges the ignition pin 24 in the direction of the aperture 16.

On the other hand, an inertial mass body 32 is disposed between the sensor cover 12 and the guide 18. The inertial mass body 32 is shaped substantially in the form of a fan and is rotatably supported by a shaft 33. A step 34 is formed in one side wall of the inertial mass body 32. Further, a trigger spring 36 is disposed between the inertial mass body 32 and the bottom wall 14 of the sensor cover 12 and normally urges the inertial mass body 32 in the direction of the bottom wall 14.

A trigger lever 38 is disposed between the inertial. mass body 32 and the guide 18. The trigger lever 38 is shaped substantially in the form of the letter L and has an L-shaped corner rotatably supported by a shaft 40. One leading end portion of the L-shaped embodiment of the present invention.

The mechanical ignition system sensor 10 has a sensor cover 12. The sensor cover 12 is shaped in the form of a cylinder having a bottom wall 14 at one end thereof. The bottom wall 14 has a through hole or aperture 16 defined therein along the axis of the sensor cover 12. A guide 18 is coaxially disposed inside the sensor cover 12. The guide 18 is also shaped substantially in the form of a cylinder. Further, the guide 18 has one end connected and fixed to the bottom wall 14 of the sensor cover 12 and the other end blocked by a plate 20 and integrally connected and secured to the sensor cover 12. A through hole or aperture 22 is formed in an axiallyextending intermediate portion of a side wall of the guide 18 and provided so as to correspond to a trigger lever to be described later.

A ignition pin 24 is disposed inside the guide 18. As a whole, the ignition pin 24 is shaped substantially in the form of a column as a whole and is slidable within the guide 18 along an axial direction thereof. A convex portion 26 projects from a leading end portion (corresponding to an end on the left side in FIG. 1) of the ignition pin 24. When the ignition pin 24 is moved to the leftmost bottom wall 14 of the trigger lever 38 serves as an engaging portion 42 and is provided so as to correspond to the aperture 222) of the guide 18. Further, the leading end portion can extend through the aperture 22 so as to be projectable into the guide 18. That is, when the trigger lever 38 is rotated about the shaft 40, the engaging portion 42 can pass through the aperture 22 of the guide 18 so as to approach or be separated from the ignition pin 24. When the trigger lever 38 is turned and the engaging porti.on 42 penetrates the aperture 22 of the guide 18 so as to project into the guide 18, the engaging portion 42 engages the collar portion 28 of the ignition pin 24 so that the ignition pin 24 which is urged by the firing spring 30 is held or fixed at the position where the convex portion 26 of the ignition pin 24 is separated from the aperture 16.

A roller 44 is mounted to the other leading end portion of the trigger lever 38. The roller 44 is provided at a position farther than the position where the engaging portion 42 is spaced away from the center of rotation of the trigger lever 38, i.e., the shaft 40 (i.e., a distance L1 between the shaft 40 and the roller 44 is set so as to be longer than a distance L2 between the shaft 40 and the engaging portion 42). Further, the roller 44 is slidably supported by an elongated hole 45 defined in the trigger lever 38 as shown in FIG. 2. The roller 44 is provided so as to correspond to a lower wall 35 of the aforementioned inertial mass body 32 and the step 34. When the trigger lever 38 is rotated so that the engaging portion 42 is withdrawn from the aperture 22 of the guide 18 (i.e., when the ignition pin 24 is released from being held by the engaging portion 42), the roller 44 is brought into sliding contact with the step 34 while rolling along the lower wall 35.

Further, the inertial mass body 32 is located at a position closest to the bottom wall 14 of the sensor cover 12 by the trigger spring 36. In this condition, the lower wall 35 of the inertial mass body 32 contacts the roller 44 of the trigger lever 38. Further, the engaging portion 42 of the trigger lever 38 penetrates the aperture 22 of the guide 18 so as to project into the guide 18. Thus, the engaging portion 42 is brought into engagement with the collar portion 28 of the ignition pin 24 so that the ignition pin 24 is held at the position where the convex portion 26 thereof is separated from the aperture 16.

The mechanical ignition system sensor lo constructed as described above is incorporated into a gas generator 50 for a pretensioner, for example.

The gas generator 50 has a cylindrical main body 52 in which a gas generating material 54 is accommodated and a detonator 56 for igniting and combusting the gas generating material 54 is disposed. The detonator 56 is disposed at the axial position of the main body 52. The -mechanical ignition system sensor 10 is assembled into the main body 52 in an opposing relationship to the detonator 56 inclusive of a shield ring 58 and sealed and fixed by a plate 60. Thus, when the mechanical ignition system sensor 10 has been assembled into the main body 52, the aperture 16 of the sensor cover 12 opposes the detonator 56 and the convex portion 26 of the ignition pin 24, which is projectable from the aperture 16, can strike against the detonator 56.

Operation of the present embodiment will- now be described below.

In the mechanical ignition system sensor 10 according to the present embodiment, which has been constructed as described above, the ignition pin 24 is provided at a position separated from the detonator 56 (the aperture 16 of the sensor cover 12) against the urging force of the firing spring 30. The engaging portion 42 extends through the aperture 22 of the guide 18 so as to project into the guide 18, thereby engaging with the collar portion 28 of the ignition pin 24. As a result, the trigger lever 38 holds the ignition pin 24. Further, the inertial mass body 32 enters the position closest to the bottom wall 14, i.e., a locus of swinging movement of the trigger lever 38 by the trigger spring 36. Thus, the lower wall 35 is brought into contact with the roller 44 of the trigger lever 38 so as to prevent the trigger lever 38 from rotating, so that the trigger lever 38 is placed in a state in which the ignition pin 24 has been held.

When a rapid acceleration now acts on the mechanical ignition system sensor 10, the inertial mass body 32 is inertially moved in the direction indicated by arrow A in FIG. 1 so as to be separated from the locus of the swinging movement of the trigger lever 38. As a result, the inertial mass body 32 can be rotated about the shaft 40 of the trigger lever 38. Therefore, the trigger lever 38 pressed in a direction of moving away from the ignition pin 24 by the ignition pin 24 which has been urged by the firing spring 30, is rotated in the direction of moving away from the ignition pin 24 while the roller 44 is being held in rolling contact with the lower wall 35 of the inertial mass body 32. Thus, the engaging portion 42 of the trigger lever 38 is separated from the collar portion -18 28 of the ignition pin 24 so as to be drawn out from the aperture 22 of the guide 18, thereby releasing the ignition pin 24 from being held. Therefore, the ignition pin 24 is moved in the axial direction by the urging force of the firing spring 30 so that the convex portion 26 protrudes from the aperture 16. As a result, the ignition pin 24 strikes against the detonator 56 so as to ignite it.

Thus, the gas generating material 54 of the gas generator 50 is ignited so as to combust thereby actuating the pretensioner, for example.

Since the roller 44 is located at a position farther than the position where the engaging portion 42 is separated from the center (shaft 40) of rotation of the trigger lever 38 even if the direction in which the trigger lever 38 is pressed by the ignition pin 24, differs from the direction in which the inertial mass body 32 is pressed by the trigger lever 38 (roller 44), the pressing force applied to the trigger lever 38 by the ignition pin 24 is reduced and applied to the trigger lever 38 in the ratio of the distance between the roller 44 and the shaft 40 to the distance between the roller 44 and the engaging portion 42 (i.e., in the ratio of L,/L2). The reduced pressing force acts on the inertial mass body 32. Thus, the frictional force between the trigger lever 38 (roller 44) and the inertial mass body 32 is reduced so that the operational sensitivity of the mechanical ignition system sensor 10 is stabilized.

Further, when the inertial mass body 32 is inertially moved so that the trigger lever 38 is rotated about the shaft 40, the roller 44 of the trigger lever 38 is rotated while being held in rolling contact with the lower wall 35 of the inertial mass body 32. Therefore, a further reduction in frictional force is made and a more effective result is obtained. Moreover, since the roller 44 is slidably supported by the elongated hole 45 defined in the trigger lever 38, the roller 44 rolls while being slidingly moved along the elongated hole 45 by simply moving the inertial mass body 32 an extremely short distance (up to the state indicated by the solid line in FIG. 3) after the inertial mass body 32 has been moved a predetermined distance from the original or initial position (i.e., the position indicated by the broken line in FIG. 2) and has reached a switching position (i.e., each of positions indicated by the solid line in FIG. 2 and indicated by the broken line in FIG. 3). Thus, the inertial mass body 32 is inertially moved so as to rotate the trigger lever 38, thereby enabling the engaging portion 42 to reliably release the ignition pin 24 from being held. As a result, the mechanical ignition system sensor 10 can be reliably operated.

Thus, a reduction in negative influence received from the frictional force between the trigger lever 38 and the inertial mass body 32 and stable operating characteristics can be ensured without an increase in the mass of the inertial mass body 32.

Once the mechanical ignition system sensor 10 is operated and the ignition pin 24 is moved, the step 34 of the inertial mass body 32 is brought into sliding contact with the roller 44 of the trigger lever 38. Thus, the trigger lever 38 is pressed in a direction of approaching the ignition pin 24 by the inertial mass body 32 which has been urged by the trigger spring 36 (see the state shown in FIG. 4).

Next, when the operated mechanical. ignition system sensor 10 is brought into a state of being actuated again (i.e., when it is reset), the mechanical ignition system sensor 10 can be reset by moving the ignition pin 24 in the axial direction against the urging force of the firing spring 30.

That is, as shown in FIG. 4, the ignition pin 24 whose convex portion 26 has protruded from the aperture 16, is pr essed by a jig X from the outside of the sensor cover 12 so as to move into the guide 18.

Since, in this case, the trigger lever 38 is pressed in the direction of approaching the ignition pin 24 by the inertial mass body 32 which has been urged by the trigger spring 36 as described above., the trigger lever 38 is rotated in the above approaching direction when the ignition pin 24 has reached the initial position. Thus, the engaging portion 42 of the trigger lever 38 passes through the aperture 22 of the guide 18 again so as to project into the guide 18. As a result, the engaging portion 42 is brought into engagement with the collar portion 28 of the ignition pin 24-so that the ignition pin 24 is held at the initial position separated from the aperture 16. Further, the roller 44 moves from the step 34 of the inertial mass body 32 to the lower wall 35 according to the swinging movement of the trigger lever 38, so that the inertial mass body 32 approaches the bottom wall 14 again. That is, the inertial mass body 32 enters into the locus of the swinging movement of the trigger lever 38 so as to be returned to the initial state in which the trigger lever 38 is prevented from rotating.

In the mechanical ignition system sensor 10 as described above, the reduction in the negative influence received from the frictional force between -22 the trigger lever 38 and the inertial mass body 32 and stable operating characteristics can be ensured. Further, the trigger lever 38 can be rotated so as to return to the initial state for holding the ignition pin 24 by simply pressing the ignition pin 24 from the outside so as to move to the initial position. Thus, even when an operation check is carried out before the mechanical ignition system sensor 10 is assembled into the gas generator 50, for example, the mechanical ignition system sensor 10 can be easily brought into a state of being capable of being actuated (i. e., it can be reset) by normally assembling the mechanical ignition system sensor 10 into the gas generator 50 after completion of the operation check.

A second embodiment of the present invention will next be described below. Components which are basically identical to those employed in the first embodiment are identified by like reference numerals and their description will therefore be omitted.

FIG. 5 is a cross-sectional view of a mechanical ignition system sensor 70 according to the second embodiment of the present invention. In the mechanical ignition system sensor 70, a roller 72 is disposed

coaxially with a shaft 40 of a trigger lever 38. On the other hand, an inertial mass body 74 is disposed immediately above the trigger-lever 38. Further, a roller 76 is provided immediately above the inertial mass body 74. The inertial mass body 74 is shaped in the form of a block. The inertial mass body 74 has a lower portion supported by the aforementioned roller 44 and the roller 72 and an upper portion supported by the roller 76. Thus, the inertial mass body 74 can slide in its axial direction.

In the mechanical ignition system sensor 70 similarly to the mechanical ignition system sensor according to the first embodiment, an engaging portion 42 is normally brought into engagement with a collar portion 28 of an ignition pin 24 so that a trigger lever 38 holds the ignition pin 24. Further, the inertial mass body 74 enters the position clos.est to a bottom wall 14, i.e., a locus of swinging movement of the trigger lever 38 due to a trigger spring 36. Thus, the lower portion of the inertial mass body 74 is brought into contact with the roller 44 of the trigger lever 38 so as to prevent the trigger lever 38 from rotating, thereby maintaining an ignition pin holding state.

When a rapid acceleration now acts on the mechanical ignition system sensor 70, the inertial mass body 74 is inertially moved in the axial direction so as to be separated from the locus of the swinging movement of the trigger lever 38. As a result, the inertial mass body 74 can be rotated about a shaft 40 of the trigger lever 38. Therefore, the trigger lever 38 pressed in a direction of moving away from the ignition pin 24 by the ignition pin 24 which has been urged by a firing spring 30, is rotated in the direction of moving away from the ignition pin 24 while the roller 44 is in rolling contact with the lower portion of the inertial mass body 74. Thus, the engaging portion 42 of the trigger lever 38 releases the ignition pin 24 from being held. Therefore, the ignition pin 24 is moved in the axial direction by the urging force of the firing spring 30 to thereby strike against a detonator 56 so as to ignite it.

Since the roller 44 is located at a position farther than the position where the engaging portion 42 is separated from the center (shaft 40) of rotation of the trigger lever 38 even if the direction in which the trigger lever 38 is pressed by the ignition pin 24, differs from the direction in which the inertial mass body 74 is pressed by the trigger lever 38 (roller 44), the pressing force applied to the trigger lever 38 by the ignition pin 24 is reduced and applied to the trigger lever 38 in the ratio of the distance between the roller 44 and the shaft 40 to the distance between the roller 44 and the engaging portion 42. The reduced pressing force acts on the inertial mass body 74. Thus, the frictional force between the trigger lever 38 (roller 44) and the inertial mass body 74 is reduced so that the operational sensitivity of the mechanical ignition system sensor 70 is stabilized.

Further, when the inertial mass body 74 is inertially moved so that the trigger lever 38 is rotated about the shaft 40, the roller 44 of the trigger lever 38 is rotated while being held in rolling contact with the lower portion of the inertial mass body 74. Therefore, a further reduction in frictional force is made and a more effective result is obtained. Moreover, since the roller 44 is slidably supported by an elongated hole 45 defined in the trigger lever 38, the roller 44 rolls while being slidingly moved along the elongated hole 45 by simply moving the inertial mass body 74 an extremely short distance after the inertial mass body 74 has been moved a predetermined distance from the original or initial position and has reached a switching position. Thus, the inertial mass body 74 is inertially moved so as to allow the engaging portion 42 of the trigger lever 38 to reliably release the ignition pin 24 from being held. As a result, the mechanical ignition system sensor 70 can be reliably operated.

Thus, a reduction in the negative influence received from the frictional force between the trigger lever 38 and the inertial mass body 74 and stable operating characteristics can be ensured without an increase in mass of the inertial mass body 74 even in the case of the second embodiment.

When the operated mechanical ignition system sensor 70 is brought into a state of being capable of being actuated again (i.e., when it is reset) in the same manner as described above, the mechanical ignition system sensor 70 can be reset by moving the ignition pin 24 in the axial direction against the urging force of the firing spring 30.

That is, when the ignition pin 24 is pressed by a jig X from the outside of a sensor cover 12 so as to move into the guide 18 in a manner similar to the first embodiment, the trigger lever 38 is rotated in the direction of approaching the ignition pin 24 when the ignition pin 24 has reached the initial position, thereby holding the ignition pin 24 at the initial position and moving the roller 44 from a side wall portion of the inertial mass body 74 to the lower portion thereof according to the swinging movement of the trigger lever 38. As a result, the inertial mass body 74 is returned to the initial state in which the trigger lever 38 is prevented from rotating.

In the mechanical ignition system sensor 70 as described above, the negative influence received from the frictional force between the trigger lever 38 and the inertial mass body 74 can be reduced and stable operating characteristics can be ensured. Further, the trigger lever 38 can be rotated so as to be returned to the initial state in which the ignition pin 24 is held, by simply pressing the ignition pin 24 from the outside so as to move to the initial position.

Incidentally, each mechanical ignition system sensors 10 and 70 according to the above embodiments can be employed in the gas generator 50 for the pretensioner. However, they are not necessarily limited to the gas generator 50. It is needless to say that the mechanical ignition system sensors can be applied to other devices which are actuated due to the collision of the ignition pin 24.

Having now fully described the invention, it will be apparent to those skilled in the art that many changes and modifications can be made without departing from the spirit or scope of the invention as set forth herein.

Claims

1. A mechanical ignition system sensor comprising: an ignition pin movably disposed in an axial direction thereof and moved in the axial direction by an urging force of a firing spring so as to ignite a detonator; an inertial mass body normally urged by a trigger spring and moved by the inertial force against the urging force of the trigger spring when a predetermined load acts on said inertial mass body; and a trigger lever for normally holding said ignition pin in a state of being separated from the detonator and releasing said ignition pin from being held in said separated state when said inertial mass body is moved a predetermined distance or more.

2. A mechanical ignition system sensor according to claim 1, wherein said trigger lever has an engaging portion engaged with said ignition pin, a roller held in contact with said inertial mass body and an elongated hole for slidably supporting said roller, said engaging portion is normally brought into engagement with said ignition pin so as to hold said ignition pin, and said roller rolls while being slidingly moved along said elongated slot when said inertial mass body is moved, thereby releasing said ignition pin from being held by said engaging portion.

3. A mechanical ignition system sensor according to claim 1, wherein said trigger lever is shaped substantially in the form of an L letter.

4. A mechanical ignition system sensor according to claim 1, wherein said inertial mass body is shaped in the form of a rectangular parallelopiped.

5. A mechanical ignition system sensor according to claim 1, further comprising supporting means for movably supporting said inertial mass body when the predetermined load acts on said inertial mass body.

6. A mechanical ignition system sensor according to claim 5, wherein said supporting means comprises a first shaft mounted to a cover and said inertial mass body is shaped substantially in the form of a fan and has a step formed in one side wall thereof and an upper end portion thereof pivotably supported on said first shaft.

7. A mechanical ignition system sensor according to claim 5, wherein said supporting means comprises a plurality of rollers disposed with said inertial mass body interposed thereamong.

8. A mechanical ignition system sensor according to claim 1, wherein said trigger lever is supported by a support shaft so as to be rotatable in a direction of approaching and moving away from said ignition pin and has an engaging portion engaged with said ignition pin and a roller which is located at a position farther than the position where said engaging portion is separated from said support shaft and which is normally held in rolling contact with said inertial mass body, said roller is normally pressed by said inertial mass body so as to bring said engaging portion into engagement with said ignition pin and prevent said trigger lever from being rotated about said support shaft, whereby said trigger lever holds said ignition pin against an urging force of the firing spring in a state in which said trigger lever has been pressed by said ignition pin in the direction of moving away from said ignition pin and when said inertial mass body is moved, said trigger lever is released from the prevention of its rotation by said inertial mass body so as to rotate in the direction of moving away from said ignition pin while said roller is being held in rolling contact with said inertial mass body, thereby enabling said ignition pin to move.

9. A mechanical ignition system sensor according to claim 8, wherein said roller provided at a leading end portion of said trigger lever is located at the position farther than the position where said engaging portion is separated from said support shaft, the distance between said support shaft and said roller is set so as to be longer than that between said support shaft and said engaging portion and said roller is slidably supported by an elongated hole defined in said trigger lever.

10. A mechanical ignition system sensor according to claim 8, wherein said roller is provided so as to correspond to said inertial mass body and when said trigger lever is rotated so that said ignition pin is released from being held, said trigger lever is separated from said ignition pin while said roller is being held in rolling contact with said inertial mass body.

11. A mechanical ignition system sensor according to claim 1, further comprising: a cover formed in the shape of a cylinder; a first aperture defined in the bottom of said cover and formed on the axis of said cover so that said ignition pin is capable of striking said detonator; a guide coaxially provided inside said cover and shaped substantially in the form of a cylinder; and a second aperture defined in a substantially intermediate portion of a side wall of said guide, and wherein said trigger lever is mounted in said second aperture.

12. A mechanical ignition system sensor according to claim 11, wherein said ignition pin is shaped substantially in the form of a column, disposed so as to be slidable along the axial direction thereof within said guide and has a convex portion formed so as to protrude from a leading end portion of said ignition pin and a collar portion formed at the other end thereof and having an outside diameter set so as to correspond to an inside diameter of said guide, and when said ignition pin is moved to the bottom of said cover, said convex portion protrudes from said first aperture and the engaging portion of said trigger lever engages said collar portion.

13. A mechanical ignition system sensor according to claim 11, wherein said trigger lever has a support shaft which is attached to said guide and rotatably supports said trigger lever and an engaging portion formed at an end of said trigger lever, said trigger lever is disposed so as to correspond to said second aperture defined in said guide and is capable of penetrating said second aperture so as to project into said guide, when said trigger lever is rotated about said support shaft, said engaging portion is capable of penetrating said second aperture so as to approach or be separated from said ignition pin, and when said trigger lever is rotated to allow said engaging portion to penetrate said second aperture defined in said guide so that said engaging portion projects into said guide, said engaging portion is brought into engagement with the collar portion of said ignition pin to thereby hold said ignition pin at a position where said convex portion has been separated from said first aperture.

14. A mechanical ignition system sensor substantially as herein described with reference to and as illustrated in any one of Figures 1 to 4 or Figure 5 of the accompanying drawings.