JPH04104063A - Acceleration sensor - Google Patents

Abstract

PURPOSE:To simplify manufacturing steps by covering the outer surface of a core comprising a permanent magnet with a synthetic resin, providing a plated part at the tip surface, and thereby manufacturing a magnetized inertial body. CONSTITUTION:A magnetized inertial body 14 is constituted of a cylindrical magnet 16, a synthetic resin layer 18 covering the outer surface of the magnet 16 and a plated layer 20 of conductor metal provided at the tip surface. In this constitution, the manufacture of the magnetized inertial body 14 which is inserted into a tube body 12 becomes easy, and the manufacturing time can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an acceleration sensor, and particularly to an acceleration sensor suitable for detecting large speed changes that occur during a vehicle collision.

[Prior art] As this type of acceleration sensor, USP 4,827,
No. 091 discloses a cylinder made of a conductive material, a magnetized inertial body inserted into the cylinder so as to be movable in the longitudinal direction of the cylinder, and the IF magnetomagnetic body at least on the longitudinal end side of the cylinder. a conductor provided on the end face of the cylindrical body, and a pair of electrodes that are arranged on one end side in the longitudinal direction of the cylinder and are electrically connected through the conductor when the conductor of the magnetized inertial body comes into contact with the conductor. and an attracting body made of a magnetic material that is disposed on the other end side in the longitudinal direction of the cylindrical body and magnetically attracts the magnetized inertial body.

In this acceleration sensor, the magnetically charged inertial body is attracted to the rigid body, and when no or almost no acceleration is applied to the acceleration sensor, the magnetically charged inertial body is stationary at the other end of the cylinder.

When a certain amount of acceleration is applied to this acceleration sensor, the magnetized inertial body moves while resisting the attraction force with the attraction body. When the magnetized inertial body is moving, an induced current flows through this cylindrical body, and a magnetic force is applied to the magnetized inertial body in the opposite direction to the direction of movement, applying a brake to the magnetized inertial body. Its movement speed is reduced.

When the acceleration is smaller than a predetermined value (threshold value), the magnetized inertial body does not reach the tip of the cylinder, stops halfway, and then is pulled back to the other end by the attraction force with the attraction body.

When the acceleration is greater than a predetermined value (threshold value) (that is, for example, when a vehicle in which this acceleration sensor is mounted collides), the magnetized inertial body reaches one end of the cylinder. Then, the conductive layer on the front end surface of the magnetically charged inertial body contacts both of the pair of electrodes to establish electrical continuity between the electrodes. If a voltage is applied between the electrodes in advance, a current will flow between the electrodes when they are short-circuited. This current detects that the vehicle has collided.

As shown in Fig. m2, the conventional magnetized inertial body 1 is a magnet assembly in which a permanent magnet 2 is enclosed in a copper case 3, and 4 is a backing made of synthetic resin. This case 3 functions to allow the magnetized inertial body 1 to smoothly slide and hang on the inner circumferential surface of the cylindrical body.

Further, in this case 3, when the magnetized inertial body 1 moves under the acceleration of a vehicle collision and comes into contact with a pair of electrodes, the effect is to conduct (short-circuit) the electrodes. Also plays.

[Invention tries to solve 3! l! ] When assembling the conventional magnetized inertial body 1 shown in FIG. 2, the magnet 2 is delivered to the case 3, and after the backing 4 is filled, the end of the case 3 is bent inward, which is a time-consuming process. Such a process was necessary.

[Means for Solving the Problems] The acceleration sensor of the present invention includes a cylinder made of a conductive material, a magnetized inertial body inserted into the cylinder so as to be movable in the longitudinal direction of the cylinder, and the magnetized inertial body. A conductor provided on at least one end face of the cylinder in the longitudinal direction; a pair of electrodes that are electrically connected through the cylindrical body, and an attracting body made of a magnetic material that is disposed on the other end side in the longitudinal direction of the cylinder and magnetically attracts the magnetized inertial body. In the acceleration sensor, the magnetized inertial body includes a cylindrical or cylindrical core made of a permanent magnet, a synthetic resin layer covering the outer surface of the core, and a conductive plating provided on the end surface of the core on the electrode side. It is characterized by comprising a layer.

[Function] In the acceleration sensor of the present invention, the magnetized inertial body is manufactured by covering the outer surface of a core made of a permanent magnet with synthetic resin and plating the tip surface,
It is extremely easy to manufacture.

Furthermore, since the outer surface of this magnetized inertial body is covered with a synthetic resin layer, this magnetized inertial body slides smoothly on the inner peripheral surface of the cylinder, and has excellent wear resistance and durability. be.

This flif! When the inertial body moves under the acceleration of a vehicle collision and comes into contact with a pair of electrodes, the conductive plating layer provided on the tip surface of the magnetized inertial body shorts the electrodes, thereby detecting a vehicle collision. Ru.

[Example] Examples will be described below with reference to the drawings.

FIG. 1 is a sectional view in the longitudinal direction of a cylinder body of an acceleration sensor according to an embodiment of the present invention.

In FIG. 1, a cylindrical bobbin 10 made of a non-magnetic material such as synthetic resin holds a cylinder 12 made of a prepared alloy, and a flip inertial body 14 is inserted into the cylinder 12. There is. This i-magnetic body 14 is a cylindrical permanent magnet (
16, a synthetic resin layer 18 covering the outer surface of the magnet 16, and a conductive metal plating layer 20 provided on the tip end surface of the magnet 16. This plating layer 20 is laminated on the synthetic resin layer 18. This magnetized inertial body 14 is fitted into the inside of the cylinder 12 so as to be freely movable in the longitudinal direction of the cylinder 12.

Examples of the synthetic resin constituting the synthetic resin 18 on the outer peripheral surface include epoxy, POM, and ABS.

Examples of the conductive metal constituting the plating layer 20 on the tip surface include gold, silver, and nickel silver, among which gold is preferred.

In this embodiment, the entire outer surface of the magnet 16 is covered with a synthetic resin layer 18. This prevents the magnet 16 from chipping.

One end of the bobbin 10 serves as a charging section 22 that enters the inside of the cylinder 12, and an opening 24 is provided at the tip of the charging section 22. At the lateral position of the tip of the loading portion 22, a pair of flanges 26 are attached to the bobbin 10.
．． 28 is provided protrudingly, and a ring-shaped attracting body (
A return washer) 30 is provided.

The bobbin 10 is further provided with another flange 32, and a coil 34 is wound between the flange 28 and the flange 32. Another flange 36 is provided at the other end of the bobbin 10, and a contact holder 38 is attached to this flange 36.

This contact holder 38 is made of synthetic resin, and has a pair of electrical contacts 8i40.42 embedded therein. electrode 40
．． The distal end side of the electrode 40.42 protrudes into the opening 44 in the center of the contact holder 38, and the distal end side of the electrode 40.42 is curved in an arc shape, and a part of the distal end side is approximately flush with the distal end surface of the cylindrical body 12. It is located so that

Although not shown, a lead wire is connected to the rear end side of the electrodes 40.42, so that a voltage can be applied between the electrodes 40.42.

In the acceleration sensor configured in this way, when no external force is applied,! The magnetic body 14 is attracted to the return washer 30, so that the rear end of the IF magnetic inertia body 14 is located at the retreat limit shown in the figure, where it abuts the front end surface of the insertion portion 22. When an external force acts in the direction of arrow A, f
The ltfi inertial body 14 moves in the direction of the arrow while resisting the attraction force with the return washer 30. Along with this movement,
An induced current flows through the cylindrical body 12 made of a tempered alloy, and the magnetic field generated by this induced current applies a magnetic force to the magnetized inertial body 14 in a direction opposite to the eight motion directions, causing the magnet assembly 14 to be braked.

When the external force applied to the acceleration sensor is small, the magnetized inertial body 14 stops when it reaches the middle of the cylinder 12,
Eventually, due to the attractive force between the return washer 30 and the magnetized inertial body 14, the f-magnetic body 14 returns to the retraction limit shown in FIG.

When a large external force is applied in the direction of arrow A, such as when a vehicle crashes, the fliii inertial body 14 moves forward to the tip of the cylindrical body 12 and comes into contact with the electric cylinder 8i40.42. Then, the plating layer 20 made of a conductive material of the magnetized inertial body 14 becomes the electrode 40.
42 is short-circuited, and a current flows between the picture electrodes 40 and 42. As a result, it is detected that a change in acceleration larger than the scheduled change has occurred, and a vehicle collision is detected.

The coil 34 is used to check the operation of this acceleration sensor. That is, when this coil 34 is energized, a magnetic field is generated from the coil 34 that urges the magnetized inertial body 14 in the direction of the arrow, and the band l inertial body 14 moves toward the cylindrical body 1.
2 and short-circuit the electrodes 40, 42. By energizing the coil 34 in this way, 11! Magnetic inertia body 14
By forcibly moving it, it is possible to check whether the magnetized inertial body 14 can move forward and backward normally and whether the electrodes 40, 42 can be short-circuited.

In the above embodiment, the cylindrical magnet 16 is lll! Although the cylindrical magnet 16A shown in FIG. 3 may be used as the F magnetic inertial body 14, the entire outer surface of this magnet 16A is covered with a synthetic resin layer 18, and the tip surface is further coated with a conductive layer. A plating layer 20 is provided. In this case as well, since the entire outer surface of the magnet 16A is covered with the synthetic resin layer 18, chipping of the magnet 16A may occur.
is prevented.

In the above embodiment, the plating layer 20 is provided on the synthetic resin layer 18 on the tip surface of the magnet 16.16A.
For example, as shown in FIG. 4, the synthetic resin layer may be omitted on this tip surface, and the conductive plating layer 20 may be formed directly on the magnet 16.16A.

[Effects] As mentioned above, the acceleration sensor of the present invention has a magnetically charged inertial body inserted into a cylinder which is extremely easy to manufacture. Therefore, the manufacturing time and manufacturing cost of the magnetically charged inertial body are reduced. can be achieved. Furthermore, the manufacturing cost of the acceleration sensor is reduced accordingly.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an acceleration sensor according to an embodiment of the present invention. FIG. 142 is a sectional view of a conventional magnetically charged inertial body, and FIGS. 3 and 4 are sectional views of a magnetically charged inertial body used in another embodiment of the present invention. 10...Bobbin, 12...Cylinder, 14...
- Magnetically charged inertial body 16... Magnet, 18... Synthetic resin layer, 20... - Conductive plating layer, 34... Coil, 40.42... Electrode.

Claims (1)

[Scope of Claims] A cylinder made of a conductive material, a magnetized inertial body inserted into the cylinder so as to be movable in the longitudinal direction of the cylinder, and at least one end side of the magnetic inertial body in the longitudinal direction of the cylinder. a conductor provided on the end face of the cylinder, and a pair of electrodes that are arranged at one end in the longitudinal direction of the cylinder and are electrically connected through the conductor when the conductor of the magnetized inertial body comes into contact with the conductor. and an attracting body made of a magnetic material that is arranged on the other end side in the longitudinal direction of the cylindrical body and magnetically attracts each other to the magnetically charged inertial body, wherein the magnetically charged inertial body is It is characterized by comprising a cylindrical or cylindrical core made of a permanent magnet, a synthetic resin layer covering the outer surface of the core, and a conductive plating layer provided on the end surface of the core on the electrode side. Acceleration sensor.