JPH0545569U - Acceleration sensor - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide an acceleration sensor with a simple structure that prevents the chattering phenomenon. In an acceleration sensor of a type that is attached to a moving body, and a magnet 3 that is an inertial body compresses a coil spring 4 and closes a reed switch 5 by deceleration of the moving body, a plurality of different pitch groups 13 and 14 are used. It is characterized in that a coil spring 4 is provided which is formed and whose spring constant changes stepwise by displacement.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an acceleration sensor used for moving bodies such as vehicles, ships, and aircraft.

[0002]

[Prior Art]

 A conventional acceleration sensor of this type is shown in FIG. As shown in the figure, in this acceleration sensor, a ring-shaped magnet 3 as an inertial body is fitted in a housing 1 provided in a moving body (not shown), and one end of the magnet 3 is arranged in the housing 1. One end of the coil spring 4 abuts on the lid 2 of the housing 1 so as to surround the reed switch 5 of the normally open contact type, and one end of the magnet 3 is attached to the coil spring 4 during deceleration of the moving body. It is possible to contact the abutting body 11 provided in the housing 1 while moving while compressing. Due to the movement of the magnet 3, the reed switch 5 is closed and a collision is detected.

[0003]

[Problems to be solved by the device]

 However, in the acceleration sensor using the reed switch 5 as described above, the load with respect to the displacement of the coil spring 4 constantly changes linearly as shown in FIG. 6, so that when a large acceleration is applied, the magnet 3 is There is a problem of a chattering phenomenon in which the contact body 11 collides with the abutting body 11 at a high speed, and the contact vibrates back and forth to temporarily separate the contacts 15 and 16 of the reed switch 5.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and prevents the occurrence of chattering phenomenon when a magnet, which is an inertial body, collides with the butting body. An object is to provide an acceleration sensor having a simple structure.

[0005]

[Means for Solving the Problems]

 In order to achieve the above object, the present invention is an acceleration sensor of a type that is attached to a moving body, and a deceleration of the moving body causes an inertial magnet to compress a coil spring and close a reed switch. It is characterized in that a coil spring whose spring constant changes is provided in the.

[0006]

[Action]

 According to the above configuration, by using the coil spring whose spring constant changes stepwise, the spring force at the abutting position is increased without changing the initial biasing force, that is, the force for keeping the inertial body at the initial position. Therefore, the speed of the inertial body that collides with the abutting body can be reduced and the impact force can be reduced without slowing the operability for small acceleration. This can prevent the occurrence of chattering at the time of hitting.

[0007]

【Example】

 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same components as those of the conventional one will be designated by the same reference numerals.

FIG. 1 is a longitudinal sectional view of an acceleration sensor according to the present invention, in which 1 is a housing, 2 is a lid, 3 is a magnet, 4 is a coil spring, 5 is a reed switch, and 6 is a filler. ..

The housing 1 is formed in a bottomed tubular shape and is integrated with a moving body such as a vehicle, and a hole 8 is formed in the center of the bottomed portion 7.

The lid body 2 has a shaft cylinder 9 having an outer diameter substantially equal to the diameter of the hole 8 and having a tip fitted in the hole 8 at the center of one side, and also the one side of the housing 1 on the one side. Ring-shaped abutting bodies 11 each having an outer diameter substantially equal to the inner diameter on the open end 10 side and allowing contact and separation of the magnet 3 which moves along the shaft tube 9 and which is inertially moved are projected and respectively A flange 12 that abuts the open end 10 of the housing 1 is provided on the outer periphery of the base end of the abutment body 11 and is integrally configured.

The magnet 3 is formed in a ring shape, one end of which can be brought into contact with and separated from the inside of the bottomed portion 7, and the other end (free end) of which is in contact with one end of the coil spring 4 near the central axis. 9 is slidably fitted.

The coil spring 4 is made of a coil body having the same wire diameter, and a dense pitch group 13 having a small pitch interval and a rough pitch group 14 having a large pitch interval are continuously formed with the same winding diameter. The ends of the dense pitch group 13 are abutted and fixed on the free end side of the magnet 3, and the ends of the rough pitch group 14 are abutted and fixed on the lid 2 side. The pitch of the length of the dense pitch group 13 is set so that the coil portions of the dense pitch group 13 are completely brought into close contact with each other when the magnet 3 contacts the butting body 11.

The portion where the ends of the dense pitch group 13 are fixed in contact with each other is near the central axis of the free end surface of the magnet 3, and the portion of the free end surface near the outer peripheral surface is the abutting body 11. It is possible to collide with.

In the reed switch 5, a switch chamber 17 having contact blades 15 and 16 that are normally open is formed, and the chamber 17 is arranged in a substantially central portion of the housing 1. The conductors 18 and 19 respectively connected to 16 are fixed in the shaft cylinder 9 with a resin 6 as a filler.

Next, the operation of the embodiment configured as described above will be described.

First, as shown in FIGS. 1 and 2, a state in which the deceleration force acting on the moving body, that is, the acceleration sensor is zero will be described. At this time, the magnet 3 is in the initial position, that is, the inertial force in the arrow direction is not generated, and the effective number of turns of the coil spring 4 is the total amount in which the dense pitch group 13 and the rough pitch group 14 both effectively act. Is a value n ₁ . Since this effective number of turns n ₁ is large, the spring constant of the coil spring 4 is small, and the load against displacement is small as shown in FIG.

Next, when the deceleration force acting on the acceleration sensor increases, the coil spring 4 is compressed by the inertial force of the magnet 3 in the direction of the arrow, and the pitch interval between the dense pitch group 13 and the rough pitch group 14 is narrowed. As shown in FIG. 3, the dense pitch groups 13 are completely in close contact with each other, and the effective number of turns is the value n ₂ which occurs only in the rough pitch groups 14. In this way, the effective number of turns of the coil spring 4 decreases from n ₁ to n ₂ , so that the spring constant increases and the load for displacement increases as shown in FIG.

According to the coil spring 4 having such a structure, since the spring constant changes stepwise, the force for keeping the magnet 3 at the initial position, that is, the initial biasing force of the magnet 3 does not change. The spring biasing force increases as it approaches the position (Fig. 4).

Therefore, the speed of the magnet 3 colliding with the abutting body 11 can be reduced and the impact force can be reduced without deteriorating the operability for a small acceleration.

As a result, the reed switch 5 is closed to the ON position in the initial stage of the compression stroke of the coil spring 4 by the magnet 3 at the time of a small acceleration, and further in the latter stage of the compression stroke as the acceleration increases. The impact of the magnet 3 hitting the butting body 11 is mitigated, the contact blades 15 and 16 held on are not separated, and the chattering phenomenon is prevented.

In the above-described embodiment, the coil springs having the same winding diameter are continuously formed into the coil springs having the close pitch intervals and the rough groups made of the wire material having the same wire diameter. It is also possible to form a coil spring having the same winding diameter by adjoining a coil portion having a small wire diameter and a coil portion having a large wire diameter by using wire rods with equal pitch intervals.

Also in this modified embodiment, the initial effective winding number n ₁ is generated in the portion where the coil portion with the thin wire diameter and the coil portion with the thick wire diameter are combined, and the spring constant of the coil spring is small. As shown in, the load against displacement is small at the initial position of the magnet 3, but as the inertial force of the magnet increases in the direction of the arrow, the coil portion with the thin wire diameter first comes into close contact with the coil portion with the thick wire diameter. It was found that the value n _{2 of the} effective number of turns changed and the Bane constant of the coil spring increased, and the load against the displacement increased as shown in FIG.

Also according to this modification, an acceleration sensor having a simple structure that prevents the chattering phenomenon can be obtained.

[0024]

[Effect of the device]

 As described above, in short, according to the present invention, in the acceleration sensor of the type that is attached to the moving body and the magnet, which is an inertial body, compresses the coil spring by the deceleration of the moving body to close the reed switch, Since a coil spring whose spring constant changes stepwise is provided, the spring constant of the coil spring changes stepwise with respect to displacement, and by using this coil spring, the acceleration sensor The structure can be simplified and the load when displaced to the abutting position can be made larger than before, and the impact force at the time of an abutting collision can be reduced.

[Brief description of drawings]

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

FIG. 2 is an operation explanatory diagram of an initial position of a main part of the above acceleration sensor.

FIG. 3 is a diagram for explaining the operation of the abutting collision position of the main part of the acceleration sensor.

FIG. 4 is a graph showing the action of the acceleration sensor in the same manner as the relationship between load and displacement.

FIG. 5 is a vertical sectional view of a conventional acceleration sensor.

FIG. 6 is a graph showing the action of a conventional acceleration sensor in the relationship between load and displacement.

[Explanation of symbols]

 1 Housing 2 Lid 3 Magnet 4 Coil Spring 5 Reed Switch 6 Filling Resin 7 Bottom 8 Hole 9 Shaft Cylinder 10 Open End 11 Abutment 12 Flange 13 Dense Pitch Group 14 Rough Pitch Group 15 Contact Blade 16 Contact Blade 17 Switch Room 18 Conductor 19 Conductor

Claims (1)

[Scope of utility model registration request] 1. An acceleration sensor of a type which is attached to a moving body and in which a magnet, which is an inertial body, compresses a coil spring by a deceleration of the moving body to close a reed switch,
An acceleration sensor comprising a coil spring whose spring constant changes stepwise by displacement.