JPH0980073A - Acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an acceleration sensor which can respond to high acceleration in the horizontal direction and applicable to an apparatus of low response speed. SOLUTION: A disc-like supporting member 12 is secured, at the outer circumferential end part thereof, to the intermediate part on the inner circumferential surface of the side wall 11a of a tubular housing 11. A through hole 12a is made in the center of the supporting member 12 and the upper surface 12b thereof is inclined upward toward the radial outside and a spherical body 13 is set on the supporting member 12. Only when the acceleration of housing 11 in the horizontal direction exceeds a predetermined level, the spherical body 13 ascends on the upper surface 12b of supporting member 12 toward the radial outside and then descends the upper surface 12b before being reset on the through hole 12a. A switch 15 is built in under the through hole 12a of supporting member 12 in order to decide whether the spherical body 13 is seated on the through hole 12a or not thus detecting an acceleration in the horizontal direction higher than a predetermined level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor for detecting a horizontal acceleration larger than a predetermined value and for continuously generating a detection signal for a predetermined time or longer in response to the detection.

[0002]

2. Description of the Related Art Conventionally, as this type of acceleration sensor,
For example, as disclosed in Japanese Patent Application Laid-Open No. 6-52763, it is incorporated in a fan heater, a stove, etc., and a pair of switch contacts are arranged facing each other at the bottom of the recess in the housing. A conductive metal ball is seated on a pair of switch contacts, and the acceleration due to a fall, earthquake, etc. is detected by the conduction / non-conduction between the pair of switch contacts and used for automatic fire extinguishing of fan heaters, stoves, etc. Things are known.

[0003]

There is no problem when the conventional acceleration sensor is applied to a device which responds to a fall, an earthquake and the like and has a fast response speed like the above-mentioned automatic fire extinguishing device such as a fan heater and a stove. However, when applied to a device that responds to a large horizontal acceleration and has a slow response speed, such as a device for deploying an air bag of a vehicle, there are the following problems. That is, although the metal ball of the conventional acceleration sensor momentarily switches the pair of switch contacts to the non-conducting state with respect to the horizontal acceleration, it returns to the recess in a short time, and repeatedly sits and leaves the recess. Therefore, the operation of the applied device cannot be stabilized.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problem, and an object of the present invention is to provide an acceleration sensor which responds to a large horizontal acceleration and can be applied to a device having a slow response speed. is there.

[0005]

In order to achieve the above object, a structural feature of the present invention is to provide a housing having a side wall and an upper wall and forming a space therein, and an inner circumference of the side wall of the housing. It has a circular through hole that is horizontally fixed at the outer peripheral end in the middle part of the surface and vertically penetrates in the central part, and part or all of the upper surface is inclined upward as it goes radially outward from the through hole. A support member, a sphere having a diameter larger than that of the through hole and incorporated into the housing and placed on the upper surface of the support member, and the sphere incorporated into the housing below the through hole of the support member and penetrating the same sphere. It is provided with a switch for discriminating between a seated state and a non-seated state on the hole. Then, when the acceleration of the housing in the direction opposite to the direction in which the upper surface of the support member is inclined with respect to the through hole is less than or equal to a predetermined value, the sphere is seated on the through hole, and in the opposite direction. When the acceleration of the housing becomes larger than a predetermined value, the spherical body moves up the upper surface of the supporting member inclined away from the through hole, and then descends on the upper surface to return to the through hole.

[0006]

As described above, according to the acceleration sensor of the present invention, when the acceleration of the housing in the direction opposite to the direction in which the upper surface of the supporting member is inclined with respect to the through hole is larger than a predetermined value. Only, the sphere goes up on the upper surface of the supporting member inclined away from the through hole, and then descends on the upper surface to return to the through hole. Then, the switch determines the state in which the sphere is separated from the through hole. As a result, even when the acceleration sensor according to the present invention is applied to a device that responds to large horizontal acceleration and has a slow response speed, such as a device for deploying an airbag of a vehicle, the sphere is on the upper surface of the support member. In the meantime, the operation of the applicable device can be ensured, and the operation control of the device can be accurately performed.

Further, by changing the inclination angle of the upper surface of the support member, it is possible to adjust the time during which the sphere is separated from the through hole, and the response time of the device to which the acceleration sensor according to the present invention is applied can be easily adjusted. Can be adapted. Furthermore, by changing the size of the diameter of the through hole, it is possible to change the size of the acceleration of the sphere separating from the through hole, and it is possible to easily correspond to the size of the response acceleration in the applied device. it can.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of the present invention will be described below. FIG. 1 is a vertical cross-sectional view of an acceleration sensor showing the first embodiment of the present invention.

This acceleration sensor is provided with a housing 11 integrally formed of synthetic resin, which is composed of a cylindrical side wall 11a and an upper wall 11b covering the upper end surface of the side wall 11a. A cylindrical space is formed inside the housing 11, and a conical portion 11c provided at the center of the inner surface of the upper wall 11b projects downward in the space.

A support member 12 formed of a synthetic resin in a circular shape is horizontally fixed at its outer peripheral end to a step formed intermediately on the inner peripheral surface of the side wall 11a of the housing 11. A circular through hole 12a penetrating vertically is formed in the central portion of the support member 12, and the upper surface 12b is inclined upward from the through hole 12a toward the radially outer side over the entire circumference of the through hole 12a. is there. A sphere 13 is incorporated in the space inside the housing 11 and above the support member 12. The sphere 13 is made of a metal material or the like, has a predetermined mass, has a diameter larger than that of the through hole 12a, and is movably placed on the upper surface 12b of the support member 12.

A circular bottom plate 14 made of synthetic resin is mounted on the inner peripheral surface of the lower end portion of the side wall 11a of the housing 11, and the bottom plate 14 is fixed by deforming the lower end of the side wall 11a inward by heat. . The bottom plate 14 has a pair of electrically conductive metal pieces 15a and 15b which penetrate through the metal pieces 15a and 15b at positions opposite to each other.
The upper portions of 15b are bent inward toward each other and are in contact with the lower surface of the support member 12 at their upper surfaces. The lower surfaces of the upper portions of the metal pieces 15a and 15b form fixed contacts of the switch 15, and lead wires are connected to the lower ends of the metal pieces 15a and 15b, respectively.

A circular conductive metal plate 15c is incorporated in the space between the support member 12 and the bottom plate 14, and the outer peripheral end of the metal plate 15c is opposed to the upper and lower surfaces of the metal pieces 15a and 15b. An annular projection 15d is formed on the. The annular protrusion 15d constitutes a movable contact of the switch 15, and the metal plate 15c is biased upward by a spring 16 assembled between the bottom surface of the annular protrusion 15d and the bottom plate 14. A circular protrusion 15e is formed in the center of the metal plate 15c immediately below the through hole 12c,
The upper surface of the circular protrusion 15e is formed in a spherical shape, and is pressed downward by the spherical body 13.

The acceleration sensor configured as described above is fixed to a device to which the side wall 11a of the housing 11 is made vertical, for example, a vehicle body of a vehicle. When the housing 11 is stationary, the sphere 13 is seated on the through hole 12 a of the support member 12. In this state, the metal plate 15c is displaced downward by the weight of the spherical body 13 against the spring 16, and the annular projection 1 that constitutes the movable contact is formed.
The upper surface of 5d is a metal piece 15a, 15b that constitutes a fixed contact.
The switch 15 is off, apart from the lower surface of the upper part of the.

When a horizontal force acts on the housing 11 and the horizontal acceleration of the housing 11 is not "0", the spherical body 13 is moved toward the support member 12 in the opposite direction to the acceleration. The force to displace works.
However, when the magnitude of the acceleration is small, the sphere 1
3 cannot get over the annular projection at the upper end of the through hole 12a of the support member 12, and the switch 15 is kept off.

On the other hand, the acceleration increases and the sphere 13
When the force for displacing the sphere 13 becomes large and the force acting on the sphere 13 becomes larger than the force required for the sphere 13 to get over the annular projection at the upper end of the through hole 12a, the sphere 13 becomes
The inclined upper surface 12 of the support member 12 as shown by the chain double-dashed line
Roll b outward in the radial direction and start climbing. Then, when the acceleration decreases, the sphere 13 is supported by the support member 1 by its own weight.
The seat 2 is seated on the through hole 12a while rolling down the inclined upper surface 12b toward the through hole 12a. As described above, while the sphere 13 is on the upper surface 12b of the support member 12 leaving the through hole 12a, the metal plate 15c is urged upward by the spring 16 to form the annular protrusion 15d forming the movable contact.
The switch 15 is turned on by the contact between the upper surface of the metal plate and the upper and lower surfaces of the metal pieces 15a and 15b forming the fixed contact. As a result, the fact that the horizontal acceleration of the housing 11 has become larger than a predetermined value is detected by the change of the switch 15 to the ON state, and the sphere 13 is placed on the upper surface 12b of the support member 12 when the switch 15 is in the ON state. It is maintained for a certain period of time.

As can be understood from the above description, according to the acceleration sensor of the first embodiment, when the acceleration of the housing in any horizontal direction becomes larger than the predetermined value, the spherical body 13 is separated from the through hole 12a. Support member 12
The switch 15 discriminates the state in which the spherical body 13 is separated from the through hole 12a by going up the upper surface 12b and then down the upper surface 12b.
As a result, even if the acceleration sensor is applied to a device that responds to a large horizontal acceleration and has a slow response speed such as a device for deploying an airbag of a vehicle, the sphere 13 is placed on the upper surface 12b of the support member 12. The operation of the applicable apparatus can be ensured during a certain period of time, and the operation control of the apparatus can be accurately performed.

In the detection of such acceleration, by changing the diameter of the through hole 12a of the support member 12, the magnitude of the acceleration by which the spherical body 13 gets over the annular projection at the upper end of the through hole 12a is changed. Further, by changing the inclination angle of the upper surface 12b of the support member 12, it is possible to change the time during which the spherical body 13 is separated from the through hole 12a. Since the support member 12 is integrally molded of synthetic resin and is configured as a single unit separately from other components, the acceleration sensor according to the first embodiment can reduce the support member 12 By simply changing the shape, it is possible to easily respond to the magnitude of response acceleration and response time of various devices to which the sensor is applied.

Further, according to the acceleration sensor of the first embodiment, the conical portion 11c is provided on the upper wall 11b of the housing 11, and the upper surface 12b of the support member 12 inclined with the conical portion 11c. A path of the sphere 13 having a substantially constant width is formed between the and. As a result, sphere 1
Even if the device to which this acceleration sensor is applied vibrates up and down, the spherical body 13 is less likely to vibrate up and down, and the accuracy of horizontal acceleration detection is improved. Further, according to this acceleration sensor, the sphere 13 is seated on the through hole 12a of the support member 12 when the acceleration is small, and the spring 16 is in contact with the sphere 13 during the seating.
Since only a small amount is compressed by the weight of, the spring 16 has little secular change and is excellent in durability.

Next, a second embodiment of the acceleration sensor of the present invention will be described with reference to the drawings. FIG. 2 shows a longitudinal sectional view of the acceleration sensor according to the same embodiment. In this acceleration sensor, the sphere 13 is made of a magnetic metal material, and the bottom plate 1 is located below the through hole 12a.
A magnet 17 is fixed on the upper surface of the center of 4. According to this, since the magnet 17 urges the sphere 13 downward due to the magnetic force, the sphere 13 moves through the through hole 1 against the horizontal acceleration.
It becomes difficult to get over the annular projection at the upper end of 2a. Therefore, only a large acceleration can be detected, and the acceleration sensor can be applied to a device that requires a large response acceleration. Further, since the magnetic force of the magnet 17 also contributes to suppressing the vertical vibration of the sphere 13, the displacement of the sphere 13 on the upper surface 12b of the support member 12 is stabilized, and the accuracy of horizontal acceleration detection is improved. Become.

Further, a third embodiment of the acceleration sensor of the present invention will be described with reference to the drawings. FIG. 3 is a longitudinal sectional view showing the acceleration sensor according to the same embodiment.
In this acceleration sensor, only the upper surface 12b in one direction out of the entire circumference of the through hole 12a of the support member 12 is inclined upward in the radial direction, and the inclined upper surface 12b is also formed.
The inner surface of the upper wall 11b is cut away to face the space sandwiched between the two as a passage of the sphere 13. The other points are similar to those of the first embodiment.

Therefore, according to this acceleration sensor,
Only when the acceleration of the housing 11 in a direction opposite to the direction in which the upper surface 12b of the support member 12 is inclined with respect to the through hole 12a becomes larger than a predetermined value, the sphere 13 moves away from the through hole 12a and accelerates. Is detected and the same detection state is maintained for a predetermined time. As a result, if this acceleration sensor is applied to a device that responds only to acceleration in one horizontal direction, the acceleration can be detected accurately.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an acceleration sensor according to a first embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view of an acceleration sensor showing a second embodiment of the present invention.

FIG. 3 is a longitudinal sectional view of an acceleration sensor showing a third embodiment of the present invention.

[Explanation of symbols]

11 ... Housing, 11a ... Side wall, 11b ... Upper wall, 12
... Support member, 12a ... Through hole, 12b ... Top surface, 13 ... Sphere, 15 ... Switch, 15a, 15b ... Metal piece, 15c
... metal plate, 16 ... spring, 17 ... magnet.

Claims (1)

[Claims] 1. A housing having a side wall and an upper wall forming a space therein, and a housing which is horizontally fixed to an upper middle portion of an inner peripheral surface of the side wall at an outer peripheral end and vertically penetrates a central portion. A supporting member having a circular through hole, and a part or all of the upper surface of which is inclined upward as it goes radially outward from the through hole; and a support member having a diameter larger than that of the through hole. A sphere incorporated and placed on the upper surface of the support member, and a state in which the sphere is incorporated into the housing below the through hole of the support member and the sphere is seated on the through hole and not seated. And a switch for discriminating between the through-hole and the upper surface of the supporting member inclined relative to the direction in which the acceleration of the housing in a direction opposite to the predetermined direction is below a predetermined value Seated on When the acceleration of the housing in the opposite direction becomes larger than a predetermined value, the sphere moves away from the through hole and goes up the upper surface of the inclined supporting member, and then goes down the same upper surface and onto the through hole. An acceleration sensor characterized by being designed to return.