JPH0769344B2 - Deceleration sensor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deceleration sensor mounted on a vehicle such as an automobile, and particularly to a sensing mass that moves when a deceleration of a predetermined value or more occurs. The present invention relates to a deceleration sensor in which an output contact is closed and a signal is generated.

(Prior Art) Vehicles such as automobiles are equipped with airbags and seat belts as occupant protection devices. Many of such airbags and seat belts are adapted to be actuated according to the deceleration that occurs in the vehicle body at the time of a vehicle collision or the like. In that case, the vehicle is equipped with a deceleration sensor that detects the deceleration.

Generally, such a deceleration sensor includes a sensing mass that moves due to inertial force, and an output contact that is closed by the movement of the mass. The sensing mass is normally held at the rear end of the guideway, and is moved along the guideway to the front end side when the vehicle body is decelerated by a predetermined value or more. The output contact is provided at the front end of the guide path.

By the way, in such a deceleration sensor, when a large deceleration occurs in the vehicle body, the sensing mass moved along the guide path is repelled by the front end surface of the guide path. Therefore, the closing time of the output contact provided at the front end of the guide path is extremely short. On the other hand, in order to activate the airbag, the signal output from the deceleration sensor is required to continue for about 2 msec.

Therefore, as shown in, for example, Japanese Unexamined Patent Publication No. 57-813, a deceleration sensor that damps the motion of the sensing mass has been considered. This deceleration sensor includes a housing having a tubular guide passage that is sealed from the outside. The sensing mass has a diameter slightly smaller than that of the guideway. The sensing mass is made of a magnetic material and is attracted rearward by a magnet attached to the rear end of the housing. Further, the front end portion of the guide path has a large cross-sectional area so that when the sensing mass comes into contact with the contact point, the space on the front side of the mass and the space on the rear side of the mass communicate with each other through a relatively large gap. There is.

In such a deceleration sensor, the sensing mass is usually held at the rear end of the guide path by the magnetic force of the magnet, and when the deceleration of the housing exceeds a predetermined value,
It moves away from the constraint due to the magnetic force of the magnet and moves forward. At that time, the sensing mass receives a damping force due to the flow resistance of the fluid flowing through the small clearance between the sensing mass and the magnetic force of the magnet. Also, when the sensing mass reaches the state where it comes into contact with the output contact, the fluid compressed on the front side flows into the guideway on the rear side, so even when the sensing mass is bounced back by the front end face of the guideway. , The fluid adds a damping force to the motion of the sensing mass.

(Problems to be Solved by the Invention) In such a deceleration sensor, it is necessary to shorten the time from the deceleration of the vehicle body until the output contact is closed. Therefore, the forward movement of the sensing mass before coming into contact with the contact cannot be damped too much. However, if the damping force is made too small, the mass will be strongly repelled by the front end face of the guideway. Therefore, in the deceleration sensor as disclosed in the above publication, when the contacts are closed for a predetermined time, the length and inner diameter of the guide path, the mass and outer diameter of the sensing mass, and the magnet It is necessary to set the magnetic force etc. extremely accurately. Moreover, since the rebound of the sensing mass tends to be promoted by the magnetic force of the magnet, it is difficult to make the contact closing time longer.

The present invention has been made in view of such a problem, and an object thereof is to provide a deceleration sensor as described above,
The purpose is to keep the contact time between the sensing mass and the output contact sufficiently long.

(Means for Solving Problems) In order to achieve this object, in the present invention, an output contact is
Place the sensing mass, which moves forward by inertial force, in contact with the front end face of the guideway before it comes into contact with it. So that
It is made deformable, and a cushion material having a groove for receiving an output contact that is deformed as the sensing mass moves is attached to the front end face of the guide path.

(Operation) With this configuration, the sensing mass that has moved forward contacts the output contact before contacting the front end face of the guide path, and contacts the cushion material while maintaining the contact state. It will be. In that case, the cushion material is provided with a groove that receives the output contact that deforms as the sensing mass moves, so that the output contact does not get caught on the cushion material, and the contact moves the sensing mass. Is not disturbed. Therefore, the cushion material effectively absorbs the kinetic energy of the sensing mass, and the forward moving speed of the mass is reduced. Further, the cushion material reduces the coefficient of repulsion of the sensing mass by the front end face of the guide path. As a result, the speed at which the sensing mass bounces and moves backward is also reduced, and the contact time with the output contact is sufficiently long.

(Examples) Examples of the present invention will be described below with reference to the drawings.

1 to 3 are a horizontal vertical sectional view, a vertical vertical sectional view, and a vertical horizontal sectional view showing an embodiment of a deceleration sensor according to the present invention.

As is clear from these figures, this deceleration sensor 1
Has a cylindrical housing 2. The housing 2 has a cylindrical sleeve 3, a cap 4 having a diameter larger than that of the sleeve 3 and sealing one end surface thereof, and a case 5 into which the sleeve 3 and the cap 4 are fitted to seal the other end surface of the sleeve 3. The cap 4 is disposed in the front-rear direction of the vehicle body so that the cap 4 is located in front of the traveling direction of the vehicle.

Inside the cap 4, a pair of arc-shaped guide surfaces 4a, 4a continuous with the inner peripheral surface 3a of the sleeve 3 are provided on the left and right,
Inner peripheral surface 3a of the sleeve 3 and guide surface 4a of the cap 4
Thereby forming a tubular guide path 6 that extends linearly. In this way, the guide passage 6 is hermetically sealed from the outside, and the inside thereof is filled with a gas such as an inert gas or air.

The front end surface 7 of the guide path 6, that is, the inner bottom surface of the cap 4 is a flat surface, and a disk-shaped cushion member 8 is bonded to the front end surface 7. The impact receiving surface 8a of the cushion member 8 is a concave surface. Further, the receiving surface 8a has a vertical groove 8b.
Are formed. The rear end surface 9 of the guide path 6, that is, the surface of the case 5 exposed in the guide path 6 is also a concave surface.

A spherical sensing mass 10 having a diameter slightly smaller than the inner diameter of the guide passage 6 is accommodated inside the guide passage 6. The sensing mass 10 is formed of a metal having a large specific gravity having magnetism and conductivity. A cylindrical magnet 11 is attached to the rear end surface of the housing 2. Therefore, as shown in FIG. 1, the sensing mass 10 is normally held in close contact with the rear end face 8 of the guide path 6 by the magnetic force of the magnet 11. That is, in this embodiment, the magnet 11 constitutes a holding means for the sensing mass 10.

The guide surface 4a of the cap 4 is slightly longer than the radius of the sensing mass 10. A vertical groove 12 extending to the abutting surface with the sleeve 3 is provided on the outer peripheral portion between the left and right guide surfaces 4a, 4a of the cap 4.
Therefore, when the sensing mass 10 moves to the vicinity of the front end face 7 of the guide path 6, the space in front of and behind the mass 10 communicates with each other through a relatively large gap formed by the groove 12.

The bottom surface of the groove 12 of the cap 4, that is, the front end surface 7 of the guide path 6.
A pair of terminals 13 and 14 extending through the front end wall of the housing 2 and extending to the outside are attached thereto. One terminal 13
Is connected to a power source such as a battery, and the other terminal 14 is connected to an actuator such as an airbag. The inner ends of these terminals 13 and 14 are bent toward the guide path 6 to form a pair of output contacts 15 and 16. These contacts 15 and 16 are supposed to have sufficient elasticity,
The tips 15a and 16a are located at a central portion slightly rearward of the cushion material 8 attached to the front end surface 7 of the guide path 6 so as to face each other with a small gap. Thus, when the sensing mass 10 moves forward, the mass 10 contacts the contact points 15 and 16 before contacting the impact surface 8a of the cushion member 8, and the cushion member 8 is maintained with the contact state maintained. It is designed to abut.

Next, the operation of the deceleration sensor 1 thus configured will be described.

FIG. 4 is an explanatory diagram for explaining the operation.

The deceleration sensor 1 is attached to the vehicle body in the front-rear direction so that the cap 4 is located in front of the traveling direction of the vehicle as described above. During normal driving, the sensing mass
The magnetic force of the magnet 11 holds 10 in close contact with the rear end surface 9 of the guide path 6.

When a large deceleration occurs in the vehicle body due to a collision or the like, the deceleration is transmitted to the housing 2 of the deceleration sensor 1.
On the other hand, an inertial force in the traveling direction acts on the sensing mass 10. As a result, when the deceleration is larger than the predetermined value, the inertial force of the sensing mass 10 becomes larger than the holding force by the magnetic force of the magnet 11, and the sensing mass 10 starts to move forward. At this time, since the clearance between the mass 10 and the inner peripheral surface 3a of the guide path 6 is small, the gas flowing through the clearance receives a large flow resistance. Therefore, the gas is compressed in the space in front of the mass 10 and has a negative pressure in the space behind the mass 10. As a result, the forward movement of the mass 10 is damped. Further, since the magnet 11 applies a force to pull it back to the rear by the magnet 11, the forward movement of the mass 10 is also damped.

When the inertial force of the mass 10 is larger than these damping forces,
The mass 10 moves forward and contacts the contacts 15, 16 as shown in FIG. 4 (A). Since the mass 10 has conductivity, when the contacts 15 and 16 are contacted in this manner, the contacts 15 and 16 are electrically connected. Therefore, a current flows from the terminal 13 to the terminal 14, and a signal for operating the occupant protection device or the like is output.

At this time, more than half of the mass 10 is located inside the cap 4. As a result, the gas compressed in the space in front of the mass 10 flows into the space in the rear of the mass 10 through the groove 12 through the large gap with the mass 10. Therefore, the damping force of the mass 10 due to the gas in the guide path 6 does not work. Therefore, the cell 10 moves further forward. During this time, the contacts 15, 16 are deformed by the mass 10, but the contact state between them is maintained.

When the mass 10 moves further forward, the contacts 15 and 16 enter the groove 8b of the cushion material 8, and the mass 10 contacts the receiving surface 8a of the cushion material 8 as shown in FIG. 4 (B). Abut. As a result, the cushion material 8 is compressed and the mass
Ten kinetic energies are absorbed. Therefore, the moving speed of the mass 10 to the front is reduced. During this time, the mass
The contact state between 10 and the contacts 15 and 16 is maintained.

When the cushioning material 8 is compressed to the maximum extent as shown in FIG. 4 (C), the mass 10 is moved to the front end face 7 of the guide path 6.
Receive repulsive force by. However, the cushion material 8
Since the coefficient of restitution is reduced by
The bounce speed is small. Moreover, when the mass 10 is bounced back and moved rearward, the clearance between the mass 10 and the inner peripheral surface 3a of the guide path 6 is narrowed just before the mass 10 separates from the contact points 15 and 16, so that the internal space of the sleeve 3 is reduced. Depending on the gas on the side,
Movement of square 10 to the rear will be resisted.

In this way, the time from the contact of the mass 10 with the contacts 15 and 16 to the separation thereof is sufficiently long. Then, during that time, since the signal is output from the deceleration sensor 1, the occupant protection device and the like can be reliably operated. Moreover, the time until the mass 10 contacts the contacts 15 and 16 can be set to a short time.

If the cushioning member 8 has a concave surface 8a as in the above embodiment, the area where the sensing mass 10 contacts can be increased and a large cushioning force can be obtained. However, as the cushion member 8, it is also possible to use the cushion member 8 having the convex receiving surface 8a as shown in FIG. By doing so, the buffering force acting on the mass 10 gradually increases, so that the mass 10 is gradually decelerated, and the speed at which the front end surface 7 of the guide path 6 bounces is further reduced.

Further, although the sensing mass 10 has conductivity in the above-mentioned embodiment, it may be formed of a non-conductor. In that case, the pair of contacts 15 and 16 may be arranged in an overlapping manner. Further, as a holding means for holding the sensing mass 10 in the initial position, if a projection or the like that can be overcome by the mass 10 when a deceleration of a predetermined value or more occurs in the housing 2 is used, the mass 10 is made of a non-magnetic material. Can also consist of

(Effect of the invention) As is apparent from the above description, according to the present invention, since the cushion material is attached to the front end face of the guide path with which the sensing mass abuts, the kinetic energy of the sensing mass is absorbed, The speed of movement in the forward direction is reduced. Moreover, the speed at which the sensing mass is bounced off by the front end face of the guideway is also reduced. Therefore, it is possible to lengthen the time from when the sensing mass contacts the output contact to when it separates from the output contact, and it is possible to obtain a deceleration sensor that generates a signal for a long time.

Moreover, since the cushion material is provided with the groove for receiving the output contact that is deformed with the movement of the sensing mass, the output contact is not caught by the cushion material and is deformed. Therefore, the contact state between the output contact and the sensing mass can be reliably maintained. On the other hand, since only the sensing mass comes into contact with the cushion material, the sensing mass receives the damping force set for the cushion material. Therefore, the kinetic energy of the sensing mass can be effectively absorbed, and the contact time between the sensing mass and the output contact can be reliably lengthened. Further, since the cushion material may be provided in front of the output contact, the time until the sensing mass comes into contact with the output contact can be shortened, and the deceleration sensor having excellent responsiveness can be obtained.

[Brief description of drawings]

FIG. 1 is a horizontal vertical sectional view showing an embodiment of a deceleration sensor according to the present invention, FIG. 2 is a vertical vertical sectional view of the deceleration sensor, and FIG. A vertical cross-sectional view taken along the line III-III in the figure, FIGS. 4A to 4C are explanatory views for explaining the action of the deceleration sensor, and FIG. 5 is a deceleration sensor according to the present invention. It is a horizontal longitudinal cross-sectional view showing another embodiment. DESCRIPTION OF SYMBOLS 1 ... Deceleration sensor, 2 ... Housing 6 ... Guideway, 7 ... Front end surface of guideway 8 ... Cushion material 10 ... Sensing mass 11 ... Magnet (holding means) 15, 16 ... Output contact

Claims (1)

[Claims] 1. A housing 2 having a closed tubular guide passage 6, and a housing 2 housed in the guide passage 6 and usually held at a rear end portion of the guide passage 6 by a holding means 11. When a deceleration of a predetermined value or more occurs in the housing 2, the sensing mass 10 that moves forward along the guide path 6 until it comes into contact with the front end surface 7 of the guide path 6, and the front side of the sensing mass 10. Of the guideway 6 when moving
A deceleration sensor having output contacts 15 and 16 which are provided at a position where the sensing mass 10 comes into contact with the front end face 7 before contacting the front end face 7 and are closed by the contact; 16, while the sensing mass 10 is in contact with the output contacts 15 and 16 thereof, and while moving further forward,
The groove 8b is deformable so that the contact state is maintained, and the front end surface 7 of the guide path 6 receives the output contacts 15 and 16 which deform with the movement of the sensing mass 10.
The deceleration sensor is provided with a cushioning material 8 which has a cushioning member 8 and which absorbs the kinetic energy of the sensing mass 10 when the sensing mass 10 comes into contact with the cushioning material 8.