JPS62198764A - Reduced speed sensor - Google Patents

Abstract

PURPOSE:To generate a signal for a long period by fitting a cushion material to the front end surface of a guide path that a sensing mass contacts. CONSTITUTION:A reduced speed sensor 1 is fitted to a vehicle body so that a cap 4 is in the front in the running direction of the vehicle; and the sensing mass 10 is held by a magnet 11 during a normal run in contact with the rear end surface 9 of a guide path 6. If the car body is reduced greatly in speed owing to a collision, etc., an inertial force in the running direction operates on the mass 10, which moves forth when the speed reduction exceeds a specific value. At this time, the gap between the mass 10 and the inner peripheral surface 3a of the guide path 6 is small, so air is compressed in the space in front of the mass 10 and the pressure in the space behind it becomes negative. Consequently, the forward motion of the mass 10 is reduced in speed and when the mass 10 abuts on the cushion material 8, the forward moving speed of the mass 10 decreases. Thus, the time from the contacting of the mass 10 with contacts 15 and 16 to its leaving is held sufficiently long. Therefore, the signal is generated for a long period.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a deceleration sensor mounted on a vehicle such as an automobile, and particularly relates to a deceleration sensor that uses a sensing mass that moves when deceleration of a predetermined value or more occurs. , relates to a deceleration sensor in which an output contact is closed and a signal is generated.

(Conventional technology) For vehicles such as automobiles, as an occupant protection device.

It is equipped with airbags and seat belts.

Many of these airbags and seat belts are designed to be activated in response to the deceleration that occurs in the vehicle body during a vehicle collision. A sensor is installed.

Generally, such deceleration sensors include 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 configured to move toward the front end along the guideway when the vehicle body decelerates to a predetermined value or more. An output contact is provided at the front end of the guideway.

By the way, in such a deceleration sensor, when a large deceleration occurs in the vehicle body, the sensing mass that has moved along the guide path is bounced back 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 air pack etc., the signal output from the deceleration sensor is required to continue for about 2 seconds.

Therefore, a deceleration sensor that damps the motion of a sensing mass has been devised, as disclosed in, for example, Japanese Patent Laid-Open No. 57-813. This deceleration sensor includes a housing having a tubular guideway that is sealed from the outside, and the sensing mass has a diameter slightly smaller than the guideway. Further, the sensing mass is formed of a magnetic material and is attracted to the rear by a magnet attached to the rear end of the housing. Further, the front end of the guide path has a large cross-sectional area, so that when the sensing mass contacts the contact point, the space in front of the mass and the space behind the mass communicate with each other through a relatively large gap. There is.

In such deceleration sensors, the sensing mass is usually held at the rear end of the guideway by the magnetic force of a magnet, and when the housing decelerates beyond a predetermined value, it is released from the restraint by the magnetic force of the magnet. Leave and move forward. At that time, the sensing mass is subjected to a damping force due to the flow resistance of the fluid flowing through the small gap between the sensing mass and the guide path and the magnetic force of the magnet. In addition, 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 if the sensing mass is bounced back by the front end face of the guideway. ,
The fluid applies 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 make the time from when the vehicle body decelerates until the output contact is closed as short as possible. Therefore, the forward movement of the sensing mass until it contacts the contact point cannot be damped too much; however, if the damping force is made too small, the mass will be strongly bounced back by the front end face of the guideway. For this reason, in the deceleration sensor as shown in the above-mentioned publication, if the contact is to be closed for a predetermined period of time, the length and inner diameter of the guide path, the mass and outer diameter of the sensing mass, the magnet's It is necessary to set 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 increase the opening time of the contact.

The present invention has been made in view of such problems, and its purpose is to provide a deceleration sensor as described above.
The contact time between the sensing mass and the output point ta should be kept sufficiently long.

(Means for Solving the Problems) In order to achieve this object, in the present invention, when the sensing mass moves forward due to inertial force, the sensing mass is applied to the front end face of the sealed tubular guide path. I try to attach cushioning material that touches it.

(Function) With this configuration, the sensing mass that moves forward comes into contact with the cushion material before contacting the front end surface of the guide path. Therefore, the cushioning material absorbs the kinetic energy of the sensing mass, and the forward movement speed of the mass is reduced. Also,
The cushioning material reduces the coefficient of repulsion of the sensing mass by the front end surface of the guide path.

As a result, the speed at which the sensing mass bounces back and moves backward is also reduced, and the time it is in contact with the output contact becomes sufficiently long.

(Example) Hereinafter, the present invention will be explained in detail using the drawings.

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

As is clear from these figures, this deceleration sensor 1 has a cylindrical housing 2. This housing 2 includes a cylindrical sleeve 3, a cap 4 which has a larger diameter than the sleeve 3 and seals one end surface of the sleeve, and a case 5 into which the sleeve 3 and cap 4 are fitted and which seals the other end surface of the sleeve 3. It is designed to be installed facing the longitudinal direction of the vehicle body, with the cap 4 located at the front in the direction of travel of the vehicle.

Inside the cap 4, a pair of arc-shaped guide surfaces 4a, 4a are provided on the left and right sides, which are connected to the inner circumferential surface 3a of the sleeve 3. , a linearly extending tubular guide path 6 is formed. In this way, the guide path 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 cushioning material 8 is adhered to the front end surface 7. The impact receiving surface 8a of the cushion material 8 is a concave surface.

Further, a vertical groove 8b is formed in the impact receiving surface 8a. Rear end surface 9 of guideway 6. That is, the surface of the case 5 exposed to the guide path 6 is also a concave surface.

Inside the guide path 6, a spherical sensing mass IO having a diameter slightly smaller than the inner diameter of the guide path 6 is housed. This sensing mass IO is made of a metal with high specific gravity that has magnetism and conductivity. A cylindrical magnet 11 is attached to the rear end surface of the housing 2 . Therefore, the sensing mass 10 is
As shown in FIG. 1, the guideway 6 is normally held in close contact with the rear end surface 8 of the guideway 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. Also, the cap 4
A sleeve 3 is provided on the outer periphery between the left and right guide surfaces 4a, 4a.
A vertical groove 12 is provided that extends to the abutting surface. Therefore, the sensing mass 10 is
When it moves close to the front end face 7 of
The spaces before and after the groove 12 communicate with each other through a relatively large gap formed by the groove 12.

A pair of terminals 13 and 14 are attached to the bottom surface of the groove 12 of the cap 4, that is, to the front end surface 7 of the guide path 6, and extend through the front end wall of the housing 2 to the outside. One terminal 13 is connected to a power source such as a battery, and the other terminal 1
4 is connected to an actuating device such as an air bag. The inner ends of these terminals 13, 14 are bent towards the guideway 6, thereby forming a pair of output contacts 15, 16. These contacts 15, 16 are made to have sufficient elasticity, and their tips 15a, 16a face each other with a small distance between them, and are connected to the guide path 6.
It is located at a central portion slightly behind the cushioning material 8 attached to the front end surface 7 of. In this way, when the sensing mass 10 moves forward, the mass lO
However, before contacting the impact receiving surface 8a of the cushioning material 8, the contact points 15 and 16 are contacted, and the contacting state is maintained while contacting the cushioning material 8.

Next, the operation of the deceleration sensor 1 configured as described above will be explained.

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

As mentioned above, this deceleration sensor 1 is attached to the vehicle body in the longitudinal direction with the cap 4 facing forward in the direction of travel of the vehicle.6 During normal driving, the sensing mass lO is guided by the magnetic force of the magnet 11. It is held in close contact with the rear end surface 9 of the channel 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 l.

On the other hand, an inertial force in the direction of movement is acting on the sensing mass IO. As a result, when the deceleration is greater than a predetermined value, the inertial force of the sensing mass 10 becomes greater than the holding force due to the magnetic force of the magnet 11, and the sensing mass 10 begins to move forward. At this time, since the gap between the mass 10 and the inner circumferential surface 3a of the guide path 6 is small, the gas flowing through the gap is subjected to large flow resistance. Therefore, the gas is compressed in the space in front of the mass IO, and the pressure in the space behind the mass 10 becomes negative. As a result, the forward movement of mass 10 is damped. Also, a magnet 11 is placed in the square 10.
Since a force is applied to pull the mass 10 backward, the forward movement of the mass 10 is also attenuated by this force.

When the inertia of mass IO is greater than these damping forces, mass IO moves forward and contacts contact point 15.16, as shown in FIG. 4A. Since the mass 10 is electrically conductive, when it contacts the contacts 15.18 in this way, the contacts 15.16 become electrically conductive. 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 within the cap 4. As a result, the gas compressed in the space in front of the mass 10 flows through the groove 12 into the space behind the mass 10 through the large gap between the mass 10 and the mass 10. Therefore, the damping force of the mass IO due to the gas in the guide path 6 no longer works. Therefore, mass lO moves further forward. During this time, contacts 15 and 16
are deformed by mass 10, but the contact between them is maintained.

When the mass 10 moves further forward, the contact points 15 and 16 enter the groove 8b of the cushioning material 8, and as shown in FIG. comes into contact with. As a result, the cushioning material 8 is compressed and the kinetic energy of the mass 10 is absorbed. Therefore, the forward movement speed of the square 10 decreases. During this time, the contact state between the mass 10 and the contact points 15 and 16 is maintained.

When the cushion material 8 is compressed to the maximum limit as shown in FIG. 4(C), the mass 10 receives a repulsive force from the front end surface 7 of the guide path 6.

However, since the coefficient of repulsion is reduced by the cushioning material 8, the speed at which the mass lO is rebounded is low. Moreover, when the mass 10 is bounced back and moves backward, just before the mass 1O leaves the contact point 15°16, the mass 10
Since the gap between the inner circumferential surface 3a of the guide path 6 is narrowed, the rearward movement of the mass 10 is resisted by the gas in the inner space of the sleeve 3.

In this way, a sufficiently long time is ensured between when the mass 10 contacts and leaves the contact 15.16. During this time, a signal is output from the deceleration sensor 1, so that the occupant protection device etc. can operate reliably.

Furthermore, the time it takes for the mass IO to come into contact with the contacts 15 and 16 can be made as short as the setting.

Note that, as in the above embodiment, if a material having a concave impact receiving surface 8a is used as the cushioning material 8, the area in contact with the sensing mass 10 can be increased, and a large buffering force can be obtained. However, the cushioning material 8 may have a convex impact receiving surface 8a as shown in FIG. By doing so, the buffering force acting on the mass 0 gradually increases, so that the mass 10 is gradually decelerated, and the speed at which it is bounced back by the front end surface 7 of the guide path 6 becomes even smaller.

Further, in the above embodiment, the sensing mass IO is electrically conductive, but it can also be formed of a non-conductor. In that case, the pair of contacts 15 and 16 may be arranged in an overlapping manner. Furthermore, as a holding means for holding the sensing mass 10 at the initial position, the housing 2 may be decelerated by a predetermined value or more. The mass 10 can also be made of a non-magnetic material by using a protrusion or the like that the mass IO can climb over when the mass IO is exposed.

(Effects of the Invention) As is clear from the above description, according to the present invention, since the cushioning material is attached to the front end surface of the guide path that the sensing mass contacts, the kinetic energy of the sensing mass is absorbed. Its forward movement speed will now be reduced. This also reduces the speed at which the sensing mass is bounced off the front end surface of the guide path. Therefore, the time from when the sensing mass comes into contact with the output contact to when it leaves can be increased, and it is possible to obtain a deceleration sensor that generates a signal over a long period of time.

Moreover, since the cushioning material only needs to be provided in front of the output contact, the time it takes for the sensing mass to come into contact with the output contact can be shortened, and a deceleration sensor with excellent responsiveness can be achieved.

[Brief explanation of drawings]

FIG. 1 is a horizontal longitudinal sectional view showing one embodiment of the deceleration sensor according to the present invention, FIG. 2 is a vertical longitudinal sectional view of the deceleration sensor, and FIG. 3 is a first embodiment of the deceleration sensor. 4(A) to (C) are explanatory diagrams for explaining the action of the deceleration sensor, and FIG. 5 is a vertical cross-sectional view taken along line m-■ in the figure. It is a horizontal longitudinal cross-sectional view which shows another Example. 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: A housing 2 having a sealed tubular guideway 6; When the deceleration of the housing 2 exceeds a predetermined value, the sensing mass 10 moves forward along the guide path 6 and comes into contact with the front end surface 7 of the housing 2; output contacts 15 and 16 that are closed when the sensing mass 10 comes into contact with the deceleration sensor; A deceleration sensor is installed.