JP2008310977A - Shock sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shock sensor having long ON duration and a simple and highly reliable structure. <P>SOLUTION: The shock sensor includes a reed switch 1, a tube 3 disposed around the reed switch 1 at the center of a case 2, a magnet 4 moving along the outer periphery of the tube 3 to drive the reed switch 1, a spring 5 supporting the magnet 4, a back stopper 6 setting the initial position of the magnet 4 moving from shock, and a front stopper 7 defining a moving range of the magnet 4 from the back stopper 6. An end face (an oblique end 4a) of the cylindrical magnet 4 on the side of the front stopper 7 is obliquely formed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an impact sensor, and more particularly to an impact sensor suitable for activating an occupant protection device such as a seat belt pretensioner or an airbag in the event of a vehicle collision.

  An impact sensor using a reed switch is used as a switch for operating an occupant protection device (such as a seat belt pretensioner or an air bag) such as an automobile. That is, it is an application for detecting a large acceleration force due to a collision or a sudden brake and energizing a circuit for operating the occupant protection device by this detection.

  Conventionally, this type of impact sensor uses a reed switch with a contact made of a ferromagnetic material built in a glass tube, and a non-magnetic tube is provided around the reed switch so that the magnet can move along the tube. Is inserted into the tube, a spring is inserted on one side of the magnet, and the magnet is normally pressed against the other side of the housing. When a large acceleration force generated by an impact or the like is applied, the magnet moves on the tube and the reed switch contact is closed. In addition, the magnet is pushed back to the other side by the repulsive force of the spring due to the absorption of the impact force and the acceleration disappearing, and the repulsive force due to the collision with the front stopper, and the contact opens by the restoring force of the contact support part to be in the OFF state. .

  In this impact sensor, the ON duration is greatly influenced by the repulsion state when the magnet collides with the front stopper. Generally, when the impact force exceeds a certain value, the ON duration is shortened and the operation of the sensor circuit is unstable. May be.

  Patent Document 1 discloses an impact sensor in which an ON duration time is extended by using a spring constituted by portions having two different spring constants.

  Further, Patent Document 2 discloses an impact sensor in which the ON duration is extended by forming the end face of the moving member obliquely.

JP-A-5-250969 Japanese Patent Laid-Open No. 9-43265

  The techniques of Patent Document 1 and Patent Document 2 solve the problem that the ON duration time is shortened by limiting the repulsive force at the time of the collision between the magnet and the front stopper. With the impact sensor of Document 1, it is not easy to control the variation in spring characteristics. Moreover, the impact sensor of Patent Document 2 has a problem of durability due to the end face structure of the moving member. Therefore, it is demanded from the production of a product to obtain the same effect with a simpler and more reliable structure.

  That is, an object of the present invention is to provide an impact sensor having a simple and reliable structure with a long ON duration.

  In order to solve the above-described problem, in the impact sensor of the present invention, an impact sensor having a long ON duration time is obtained by making the end surface on the front stopper side of the magnet oblique.

  The present invention relates to a reed switch, a tube formed or arranged in the center of a sensor case and provided around the reed switch, and a magnet for driving the reed switch by moving along the outer periphery of the tube. An impact sensor comprising a spring that supports the magnet, a back stopper that sets an initial position of the magnet that is moved by impact, and a front stopper that defines a moving range of the magnet from the back stopper. The impact sensor is characterized in that the ON duration time is increased by making the stopper side end surface oblique.

  That is, the impact sensor of the present invention has a reed switch, a tube provided in the center of the sensor case and disposed so as to contain the reed switch, and a cylindrical shape in which at least one of end faces is formed obliquely. A magnet that is arranged concentrically with the tube and drives the reed switch by moving along the outer periphery of the tube, and the magnet is moved to the tube while one end is in a fixed position and the other end presses the inclined end surface of the magnet. A coiled spring that supports the outer periphery of the magnet, a back stopper that sets the initial position of the magnet before the impact is applied, and the magnet by contacting the inclined end surface of the magnet after the impact is applied And a front stopper for defining a moving range of the head.

  The inclination angle of the end surface on the front stopper side is preferably in the range of 5 ° ± 2 °.

  You may form both the end surfaces of the said magnet diagonally and in parallel with each other.

  As described above, the present invention provides a reed switch, a tube formed or disposed in the center of a sensor case and provided around the reed switch, and moving along the outer periphery of the tube. An impact sensor comprising: a magnet for driving the magnet; a spring that supports the magnet; a back stopper that sets an initial position of the magnet that moves by impact; and a front stopper that defines a moving range of the magnet from the back stopper. In this case, there is an effect that the ON duration time can be lengthened by making the front stopper side end surface of the magnet slant.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows an impact sensor according to Embodiment 1 of the present invention. 1A is a cross-sectional view before applying an impact, FIG. 1B is a cross-sectional view when the magnet collides with the front stopper after the impact is applied, and FIG. 1C is after the magnet collides with the front stopper. It is sectional drawing when a magnet absorbs an inclination impact. That is, the reed switch 1 is disposed along the center line of the tube 3, the movable magnet 4 is provided between the back stopper 6 and the front stopper 7 along the outer periphery of the tube 3, and one end of the spring 5 is a magnet inclined end. It has been shown that an ON signal is generated by an impact sensor that presses the portion 4a.

  The impact sensor of the present embodiment is formed concentrically with the reed switch 1 as the center, and the end surface of the magnet 4 on the front stopper 7 side is slanted. As shown in the front view of FIG. 2, the magnet 4 has a substantially cylindrical shape with a predetermined thickness, and one of its end faces is inclined by an angle θ as a magnet inclined end 4a.

  The operation will be described. Before the impact is applied, referring to FIG. 1 (a), the right end of the coiled spring 5 is in contact with the magnet inclined end 4a, and the right end of the magnet 4 is in contact with the back stopper 6, so that the magnet 4 Is set to the initial position, and the contact of the reed switch 1 is in the OFF state.

  Next, when an impact is applied, the spring 5 contracts, and one point of the magnet inclined end 4a comes into contact with the surface of the front stopper 7 as shown in FIG. Thereafter, the magnet 4 rotates, and the entire surface of the magnet inclined end 4 a comes into contact with the surface of the front stopper 7. As a result, the magnet 4 returns to the initial position by the repulsive force of the front stopper 7 and the spring 5. During this time, when a magnetic field in the longitudinal direction is applied to the lead of the reed switch 1, the reed switch is kept in the ON state. In other words, the ON duration of the reed switch 1 changes depending on the time from when the magnet 4 receives an impact, leaves the initial position, and returns to the initial position again.

  By the way, if the end surface of the magnet 4 on the front stopper 7 side is parallel to the surface of the front stopper 7, that is, when a magnet as shown in FIG. 4 is used, the repulsive force when the magnet 4 collides with the front stopper 7. Becomes larger and the ON duration time becomes shorter. On the other hand, in the impact sensor of the present embodiment, it can be said that when the magnet collides with the front stopper, the end face of the magnet is inclined, so that the impact with the front stopper is reduced. That is, the force at the time of the collision between the magnet 4 and the front stopper is temporally dispersed.

  In this embodiment, the front stopper 7 made of PBT (polybutylene terephthalate) is used, but when the inclination angle θ of the magnet inclined end 4a shown in FIG. 2 is in the range of 5 ° ± 2 °. Compared with the case of using a cylindrical magnet whose end is not inclined as shown in the front view of FIG. 4, the ON duration time can be extended by 5 ms or more.

  Next, an impact sensor according to Embodiment 2 of the present invention will be described. FIG. 3 is a front view of a magnet used in Embodiment 2 of the present invention.

  In the magnet of the present embodiment, both end surfaces are formed obliquely and parallel to each other. The present embodiment and the first embodiment are common except that this magnet is used in place of the magnet 4 of the first embodiment (see FIG. 2).

  Although the ON duration time can be extended also by this embodiment, the magnet of this embodiment does not have the directionality related to the end face shape, so the step of determining the directionality when incorporating the magnet is not necessary. .

  In the first and second embodiments of the present invention, the surface of the magnet inclined end portion 4a has a certain inclination angle, so that it is almost uniformly pressed by the spring 5 in the initial state before the impact force is applied. Has been.

1 shows an impact sensor according to Embodiment 1 of the present invention, FIG. 1 (a) is a sectional view before impact application, FIG. 1 (b) is a sectional view at the moment when a magnet collides with a front stopper after impact application, FIG. 1 (c) is a cross-sectional view when the magnet absorbs an impact after the magnet collides with the front stopper. The front view of the magnet used in Embodiment 1 of this invention. The front view of the magnet used in Embodiment 2 of this invention. The front view of the cylindrical magnet which an edge part does not incline.

Explanation of symbols

1 Reed Switch 2 Case 3 Tube 4 Magnet 4a Magnet Inclined End 5 Spring 6 Back Stopper 7 Front Stopper

Claims (3)

A reed switch,
A tube provided at the center of the sensor case and arranged to contain the reed switch;
A magnet having at least one end face formed in a slanted cylindrical shape, arranged concentrically with the tube and moving along the outer periphery of the tube, and one end at a fixed position and the other end A coiled spring that supports the magnet along the outer periphery of the tube while pressing the inclined end surface of the magnet,
A back stopper for setting the initial position of the magnet before an impact is applied;
A front stopper that determines the moving range of the magnet by contacting the inclined end surface of the magnet after an impact is applied;
An impact sensor comprising:   2. The impact sensor according to claim 1, wherein an inclination angle of an end surface on the front stopper side is in a range of 5 [deg.] ± 2 [deg.].   The impact sensor according to claim 1 or 2, wherein both end faces of the magnet are formed obliquely and in parallel with each other.

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