JPH0682475A - Acceleration sensor - Google Patents

Abstract

PURPOSE:To enhance the accuracy of detection of acceleration and to reduce the manufacturing cost of an acceleration sensor. CONSTITUTION:The permanent magnet 16 of a magnetic inertia body 14 for insertion into a cylinder 12 is enclosed in a metallic case 18 and a metallic plate 20 made from a gold-plated panel or a clad material of gold alloy is connected to an end face of the case 18 by welding or calking. Since the gold or gold alloy is provided only at an end face of the magnetic inertia body 14 inserted into the cylinder 12, the coefficient of friction between the magnetic inertia body 14 and the cylinder 12 is stabilized over a long period of time. Therefore, the accuracy of detection of acceleration is stabilized. Since the amount of gold used is small, the manufacturing cost of the acceleration sensor is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor, and more particularly to an acceleration sensor suitable for detecting a large speed change that occurs when a vehicle collides.

[0002]

2. Description of the Related Art As an acceleration sensor of this type, USP 4,82
No. 7,091 discloses a tubular body made of a conductive material, a magnetized inertial body inserted inside the tubular body so as to be movable in the longitudinal direction of the tubular body, and at least one end side of the magnetized inertial body in the longitudinal direction of the tubular body. A conductor provided on the end face, and a pair of electrodes disposed on one end side in the longitudinal direction of the cylindrical body and brought into conduction through the conductor when the conductor of the magnetic inertia body contacts. , And an attracting member which is disposed on the other end side in the longitudinal direction of the cylindrical member and which is made of a magnetic material that magnetically attracts the magnetizing inertial member.

A similar acceleration sensor is disclosed in Japanese Patent Application No. 2-221.
No. 996, No. 2-221997, No. 2-221998.
No. 2-221999 (JP-A-4-104062)
No. 4-221997, No. 4-104064, No. 4-104065).

In this type of acceleration sensor, the magnetized inertial body is attracted to the attracting body, and when no acceleration or almost no acceleration is applied to the acceleration sensor, the magnetized inertial body rests on the other end side of the cylinder. is doing.

When a somewhat large acceleration is applied to this acceleration sensor, the magnetized inertial body moves while resisting the attractive force with the attractive body. Then, when the magnetized inertial body is moving, an induced current flows in this cylindrical body, a magnetic force is applied to the magnetized inertial body in a direction opposite to the moving direction, and the magnetized inertial body is braked. And its moving 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 cylindrical body, stops at a midpoint, and is then pulled back to the other end side by the suction force with the suction body. Be done.

When the acceleration is greater than a predetermined value (threshold value) (that is, when a vehicle equipped with this acceleration sensor collides, for example), the magnetized inertial body reaches one end of the cylinder. . Then, the conductive layer on the tip end surface of the magnetized inertial body comes into contact with both of the pair of electrodes to conduct the electrodes.
When a voltage is applied between the electrodes in advance, a current flows between the electrodes when the electrodes are short-circuited. This current detects that the vehicle has collided.

As shown in FIG. 10, the conventional magnetized inertial body 1 is
This is a magnet assembly (magnet assembly) in which a permanent magnet (magnet core) 2 is covered with a case 3 made of copper or a copper alloy such as brass. The entire front surface and outer peripheral surface of the case 3 are gold-plated through a Ni-plated underlayer. 4 is a synthetic resin packing. The case 3 has a function of allowing the magnetized inertial body 1 to smoothly slide on the inner peripheral surface of the cylindrical body. Also, this case 3
Also has the effect of electrically connecting (short-circuiting) the electrodes when the magnetized inertial body 1 moves under the acceleration of a vehicle collision and comes into contact with a pair of electrodes.

[0009]

In the conventional magnetized inertial body 1 shown in FIG. 10, the gold plating layer is easily worn when the magnetized inertial body 1 slides in the cylinder. When the gold plating is peeled off, the frictional resistance between the magnetized inertial body and the cylinder increases. Moreover, since the entire surface of the case 3 is plated with gold, the amount of gold used is large and the cost is high.

[0010]

According to another aspect of the present invention, there is provided an acceleration sensor comprising: a cylindrical body made of a conductive material; a magnetic inertial body inserted inside the cylindrical body so as to be movable in a longitudinal direction of the cylindrical body; The conductor provided on at least one end face in the longitudinal direction of the cylinder and the conductor arranged in the longitudinal direction of the cylinder are contacted by the conductor of the magnetized inertial body. A pair of electrodes that are conducted through the body, and an attracting body that is disposed on the other end side in the longitudinal direction of the tubular body and that is made of a magnetic material that magnetically attracts the magnetized inertial body. In the acceleration sensor, the magnetized inertial body includes a cylindrical case made of metal, a permanent magnet housed in the case, and a metal plate coupled to an end surface of the case on the electrode side. ,
Only the front surface of the metal plate is made of gold or a gold alloy.

According to a second aspect of the present invention, in the acceleration sensor according to the first aspect, the metal plate is a metal plate having only a front surface plated with gold, or a metal plate having a front surface clad with gold or a gold alloy.

An acceleration sensor according to a third aspect is the acceleration sensor according to the first or second aspect, wherein the metal plate is joined to the case by welding or caulking.

[0013]

In the acceleration sensor of the present invention, the magnetized inertial body is not provided with gold plating on the outer peripheral surface of the case, and even if the outer peripheral surface of the magnetized inertial body slides on the inner peripheral surface of the cylindrical body. The frictional resistance between the magnetized inertial body and the cylinder does not change. Further, since the amount of gold used is small, the cost of the magnetized inertial body can be reduced.

[0014]

Embodiments will be described below with reference to the drawings.

FIG. 1 is a sectional view in the longitudinal direction of the cylinder of the acceleration sensor according to the embodiment of the present invention, and FIG. 2 is an enlarged sectional view of the front end portion of the magnetized inertial body 16.

In FIG. 1, a cylindrical bobbin 10 made of a non-magnetic material such as synthetic resin is provided inside a cylindrical body 12 made of copper alloy.
Is held, and the magnetized inertial body 14 is
Is installed slidably. The magnetized inertial body 14 is joined by a cylindrical permanent magnet (magnet) 16, a cylindrical metal case 18 accommodating the magnet 16 and a synthetic resin packing 17, and spot welding to the tip end surface of the case 18. And a metal plate 20.

This metal plate 20 comprises a base material 20A and gold 20B.
And clad. That is, this metal plate 20
Is a clad material in which a base material plate and a gold alloy plate are superposed and rolled to bond the two. The metal plate 20 is joined to the front end surface of the case 18 by spot welding. The case 18 is processed by drawing into a container shape with its tip sealed. After the permanent magnet 14 and the packing 17 are inserted into the case 18, the rear edge of the case 18 is bent inward to fix the permanent magnet 14 and the packing 17.

The base material 20A is made of a metal (including alloy) having good corrosion resistance other than gold. Such metals include:
Examples include copper alloys such as phosphor bronze and stainless steel.

As a gold alloy, 2 to 20% of silver, especially about 1
A gold-silver alloy containing about 0% is preferable. It is preferable to interpose a base layer of silver alloy between the base material 20A and the gold alloy layer 20B. As this silver alloy, 40 to 7 palladium is used.
Silver-palladium alloys containing 0%, especially about 60%, are preferred.

The thickness of the gold alloy layer and the thickness of the underlayer are each preferably 1 to 20, especially 2 to 6 μm. The base material 20A has a thickness of 50 to 500 μm, especially 100 to 300 μm.
The degree is suitable.

As the case 18, nickel silver (German Silver)
. Ni5 to 33 wt%, Cu50 to 70 wt%, Zn
13-35 wt% Ni-Cu-Zn alloy. ) Are preferred.

The bobbin 10 has an insertion portion 22 which is inserted into the inside of the cylindrical body 12 at one end thereof, and an opening 24 is provided at a tip portion of the insertion portion 22. This insertion part 22
A pair of flanges 26 and 28 are provided on the bobbin 10 at a position in the lateral direction of the tip end of the ring-shaped suction member (return member) made of a magnetic material such as iron and sandwiched between the flanges 26 and 28. A washer) 30 is provided.

The bobbin 10 has a further flange 32.
Is provided, and the flange 28 and the flange 32 are provided.
A coil 34 is wound between and. A further flange 36 is provided on the other end side of the bobbin 10, and a contact holder 38 is attached to the flange 36.

The contact holder 38 is made of synthetic resin and has a pair of electrodes 40 and 42 embedded therein. The tip ends of the electrodes 40, 42 project into the opening 44 at the center of the contact holder 38, and the electrodes 40, 4
The distal end side of 2 is curved in an arc shape, and a part thereof is positioned so as to be substantially flush with the distal end surface of the cylindrical body 12.

Although not shown, a lead wire is connected to the rear ends of the electrodes 40 and 42 so that a voltage can be applied between the electrodes 40 and 42.

In the acceleration sensor constructed as described above, when the external force is not applied, the magnetized inertial body 1
4 is positioned at the illustrated retracted limit where the rear end of the magnetized inertial body 14 comes into contact with the front end surface of the insertion portion 22 by attracting the return washer 30. When an external force acts in the arrow A direction, the magnetized inertial body 14 moves in the arrow A direction while resisting the attraction force with the return washer 30. Along with this movement, an induced current flows in the copper alloy cylindrical body 12, and the magnetic field generated by this induced current gives a magnetic force to the magnetized inertial body 14 in the direction opposite to the moving direction, and the magnet assembly 1
The brakes on 4 are applied.

When the external force applied to the acceleration sensor is small, the magnetized inertial body 14 is stopped when it reaches the middle of the cylindrical body 12, and eventually the attraction force of the return washer 30 and the magnetized inertial body 14 causes the magnetized inertial body. 14 returns to the backward limit of FIG.

When a large external force generated in a vehicle collision or the like is applied in the direction of arrow A, the magnetized inertial body 14 advances to the tip of the cylindrical body 12 and contacts the electrodes 40 and 42. Then, the metal plate 20 of the magnetized inertial body 14 short-circuits the electrodes 40 and 42, and a current flows between the electrodes 40 and 42. As a result, it is detected that the acceleration change is larger than the predetermined threshold value, and the vehicle collision is detected.

The coil 34 is used to check the operation of the acceleration sensor. That is, when the coil 34 is energized, a magnetic field for urging the magnetized inertial body 14 in the direction of arrow A is generated from the coil 34, the magnetized inertial body 14 advances to the tip of the cylindrical body 12, and the electrodes 40 and 42 are short-circuited. To do. In this way, by energizing the coil 34 and forcibly moving the magnetized inertial body 14, whether the magnetized inertial body 14 can normally move back and forth, and the electrodes 40, 4
It can be checked if 2 can be shorted.

In the above embodiment, the base material 20A is formed by the clad.
Although the gold alloy layer 20B is provided on the surface of, the gold alloy layer 20B may be provided on the surface of the base material 20A by plating.

In the above embodiment, the metal plate 20 is joined to the case 18 by welding, but as shown in FIG. 3, an opening 18a is provided in the tip surface of the case 18A, and the opening 18a is formed.
The convex portion 13a of the metal plate 13 is inserted into a and the convex portion 13a
By crimping, the metal plate 13 may be joined to the case 18A as shown in FIG.

In the embodiment shown in FIGS. 1 and 2, the permanent magnet 16 and the packing 17 are fixed in the case 18 by bending the rear end portion of the case 18 inward. The back cover 52 may be attached to the case 50 as shown in FIGS.

A plurality of (for example, 3
L) -shaped claw 54 is provided, and an elastic piece 56 is cut and raised from this claw 54. A groove 58 into which the claw 54 fits is provided at the rear end edge of the case 50.

When the lid 52 is inserted into the rear end of the case 50 so that the claw 54 is engaged with the groove 58, as shown in FIG.
The elastic piece 56 presses the inner peripheral surface of the case 50, whereby the lid 52 is fixed to the case 50.

Since the lid 52 is provided with the step portion 60, the lid 52 has high rigidity and is less likely to warp and deform.

[0036]

As described above, the acceleration sensor of the present invention is
Since gold or a gold alloy is provided only on the tip end surface of the magnetized inertial body inserted in the cylinder, the friction coefficient between the magnetized inertial body and the cylinder is stable for a long period of time. Therefore, the accuracy of acceleration detection is stable.

Since the amount of gold used is small, the manufacturing cost of the acceleration sensor is reduced.

[Brief description of drawings]

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

FIG. 2 is an enlarged cross-sectional view of a tip end portion of a magnetized inertial body.

FIG. 3 is a cross-sectional view showing a method of joining a case and a metal plate.

FIG. 4 is a cross-sectional view showing a method of connecting the case and the metal plate.

FIG. 5 is a perspective view showing a method of connecting the case and the back cover.

FIG. 6 is a front view of the back cover.

7 is a sectional view taken along line VII-VII of FIG.

FIG. 8 is a perspective view of a claw portion of the back cover.

FIG. 9 is a cross-sectional view showing a combined structure of a case and a back cover.

FIG. 10 is a cross-sectional view of a conventional magnetized inertial body.

[Explanation of symbols]

 10 Bobbin 12 Cylindrical Body 14 Magnetized Inertial Body 16 Magnet 18 Case 20 Metal Plate 34 Coil 40, 42 Electrode 52 Back Cover

Claims (3)

[Claims] 1. A tubular body made of a conductive material, a magnetized inertial body inserted inside the tubular body so as to be movable in the longitudinal direction of the tubular body, and at least one end side of the magnetized inertial body in the longitudinal direction of the tubular body. An electric conductor provided on the end face, and a pair of electrodes arranged on one end side in the longitudinal direction of the cylindrical body and electrically connected through the electric conductor of the magnetized inertial body An acceleration sensor that is disposed on the other end side of the cylindrical body in the longitudinal direction and that is made of a magnetic material that magnetically attracts the magnetic field inertial body, and the magnetic field inertial body is a metal. A cylindrical case made of metal, a permanent magnet housed in the case, and a metal plate joined to the end surface of the case on the electrode side, and only the front surface of the metal plate is made of gold or An acceleration sensor, which is made of a gold alloy. 2. The acceleration sensor according to claim 1, wherein the metal plate is a metal plate having only a front surface plated with gold, or a metal plate having a front surface clad with gold or a gold alloy. 3. The acceleration sensor according to claim 1, wherein the metal plate is joined to the case by welding or caulking.