JPH05242776A - Acceleration sensor - Google Patents

Abstract

PURPOSE:To improve detecting accuracy by eliminating noise mixed into detected output. CONSTITUTION:An acceleration sensor comprises a reed switch 2 having a contact part consisting of a couple of reed pieces 3a and 3b arranged facing to each other in a long cylindrical glass case 2a, and comprises a couple of ring magnets 5 and 6 whose mutually opposing sides are polarized in the same polarity and which are arranged on the right and the left sides separately along longitudinal direction of the glass case 2a, and at least one of which is arranged freely movable. A spacer 10 for the purpose of regulating the moving distance of a moving ring magnet (5 or 6) is provided between the couple of the ring magnets 5 and 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor used as a sensor or the like for detecting impact force and outputting information to a device for inflating an airbag when a car collides.

[0002]

2. Description of the Related Art Various air bag devices have been put into practical use as means for protecting an occupant from an impact applied when a vehicle collides. This type of airbag device
The acceleration sensor detects that a car has collided,
An airbag device is activated by the detected output to inflate the airbag.

A conventional acceleration sensor used for such a purpose is constructed as shown in the configuration diagram of FIG. 5, for example. That is, in FIG. 5, the acceleration sensor has a schematic configuration in which the reed switch 2 is supported in the main body casing 1 including the upper casing 1a and the lower casing 1b.

More specifically, the reed switch 2 is
An inert gas 4 is enclosed in a glass container 2a formed in a substantially cylindrical shape, and a switch piece connected to one lead piece 3a and a switch piece connected to the other lead piece 3b are opened with a predetermined gap. It has a structure with a switch part that is wrapped. Then, in the reed switch 2, the contact is closed when the magnet is brought close to the switch portion, so-called A-type operation is performed.

Further, the reed switch 2 thus constructed is held in the main body casing 1 with its left and right end portions supported, and the glass container 2a and the main body casing 1 are held.
A gap having a predetermined size is provided between and.

In addition, in the main body casing 1, on the peripheral surface of the glass container 2a, that is, between the glass container 2a and the main body casing 1, a first ring magnet 5 and a second ring magnet 5 are provided.
And the ring magnet 6 of the glass container 2a have the same magnetic poles on the opposite sides (in this structure, the opposite sides are N poles as shown in the explanatory diagram of the operating principle of FIG. 6). It is arranged so as to be movable along the direction. Therefore, by making the opposing surface sides have the same magnetic pole, the first and second ring magnets 5 and 6 are separated from each other in the normal state by the repulsive force of the magnetic field to open a predetermined dimension. Are facing each other. Then, in this state, as shown in the operation principle explanatory diagram of FIG. 6, one of the lead pieces 3a has the S pole on the contact portion side,
The free ends are magnetized to N poles. Further, in the other lead piece 3b, the contact side is magnetized to the N pole and the free end side is magnetized to the S pole. That is, in this case, the contact portions of the reed switch 2 are magnetized to have the same polarity,
Since the contact portions repel each other, the reed switch 2 does not operate.

Next, the operation of the acceleration sensor thus constructed will be described with reference to FIGS. First, FIGS. 5 and 6 show a state where no impact force is applied to the acceleration sensor. In this state, each ring magnet 5,
6 are arranged separately on the left and right, and the contact portion of the reed switch 2 does not operate and is off.

In this state, arrow F1 in FIGS. 7 and 8
When an impact force is applied to the acceleration sensor from the direction shown by, the first ring magnet 5 moves in the direction shown by the arrow A in FIGS. 7 and 8, that is, the direction shown by the solid line from the position shown by the dotted lines in FIGS. 7 and 8. Move to. Here, FIG. 7 shows a state in which the first ring magnet 5 is in the middle of movement, and FIG. 8 shows a state in which the first ring magnet 5 has moved to the maximum. And
As shown in FIGS. 7 and 8, when the first ring magnet 5 almost moves to the portion where the lead pieces 3a and 3b overlap, the polarity on the side connected to one lead piece 3a does not change, The polarity of the side connected to the other lead piece 3b changes to the N pole on the contact side and the S pole on the free end side. As a result, the two facing
The two lead pieces 3a and 3b are magnetized to have polarities different from each other, and these magnetically attract each other. That is, it is detected that the reed switch 2 is turned on and a shock is applied.

Next, when the impact disappears, the first ring magnet 5 returns to its original position due to the magnetic repulsive force, and the first ring magnet 5 shown in FIG.
And the rest state shown in FIG. 6, ie FIGS. 7 and 8.
And the reed switch 2 is turned off again.

[0010]

As described above, in this type of acceleration sensor, the on-operation is performed by detecting the impact force applied when a car collides, and this information is output to output the airbag device. The airbag can be activated and inflated. However, when the impact force is applied to the acceleration sensor, the first ring magnet 5
When the state where the magnetic attraction force acts on the lead pieces 3a, 3b is moved, the position where the magnetic attraction force is the strongest on the lead pieces 3a, 3b is indicated by reference numeral H2 in FIG.
When the first ring magnet 5 is arranged in the area (2), that is, in the center portion of the reed switch 2, the magnetic attraction force gradually decreases after passing through the area H2. Therefore, as shown in FIG. 8, when the first ring magnet 5 reaches the position beyond the center portion, the reed switch 2 is in the ON state, but the magnetic attraction force is considerably reduced, and at this point in time. If a shock has been entered,
As the reed switches 3a and 3b of the reed switch 2 resonate and may be turned off for a moment, noise is often mixed in the detection output to cause disturbance. As described above, in the case where the detected output is disturbed, an accurate output signal cannot be obtained, and there is a concern that the airbag device cannot be surely activated even if the automobile collides.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an acceleration sensor which can eliminate noise mixed in a detection output and can obtain an accurate output signal.

[0012]

In order to achieve the above object, an acceleration sensor according to the present invention is a reed switch having a contact portion in which a pair of reed pieces are arranged in opposition to each other in an elongated cylindrical glass container. , The main casing supporting both left and right ends of the reed switch, and the opposite sides are magnetized to have the same polarity, and at least one of them is movable along the longitudinal direction of the glass container. A pair of magnets arranged in such a state is provided, and a spacer is provided between the pair of magnets to regulate the moving amount of the moving magnet.

[0013]

According to this structure, the magnet that receives the impact force exerts the strongest magnetic attraction force on the lead piece and reaches the position where the operation after switching of the lead piece can be surely held. Once you move, don't move any more
It can be regulated by a spacer. In other words, the magnetic attraction force acts most strongly on the lead piece while the shock is being input to the magnet that has been moved under the impact force, and the operation after switching the lead piece is strongly maintained. It can be placed in a position where As a result, it is possible to prevent the reed switch reed pieces from resonating and being repeatedly turned on and off to mix noise.

[0014]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a sectional view showing the structure of an acceleration sensor according to the present invention, and FIG. 2 is an explanatory diagram of the operating principle. 1 and 2, the same reference numerals as those in FIG. 5 denote the same parts as those in FIG.

In FIG. 1, the acceleration sensor has a schematic structure in which a reed switch 2 is supported in a main body casing 1 composed of an upper casing 1a and a lower casing 1b.

More specifically, the reed switch 2 is
An inert gas 4 is enclosed in a glass container 2a formed in a substantially cylindrical shape, and a switch piece connected to one lead piece 3a and a switch piece connected to the other lead piece 3b are opened with a predetermined gap. It has a structure with a switch part that is wrapped. The reed switch 2 performs so-called A-type operation in which the contact is closed when the magnet is brought close to the switch section.

Further, the reed switch 2 thus constructed is held in the main body casing 1 with both left and right ends thereof supported, and the glass container 2a and the main body casing 1 are held.
A gap having a predetermined size is provided between and.

In addition, in the main body casing 1, on the peripheral surface of the glass container 2a, that is, between the glass container 2a and the main body casing 1, the first ring magnet 5 and the second ring magnet 5 are provided.
The ring magnet 6 of the glass container 2a has the same magnetic pole on the opposite side (in this structure, the opposite sides are N poles as shown in the explanatory diagram of the operating principle of FIG. 2). It is arranged so as to be movable along the direction. Therefore, by making the opposing surface sides have the same magnetic pole, the first and second ring magnets 5 and 6 are separated from each other in the normal state by the repulsive force of the magnetic field to open a predetermined dimension. Are facing each other. Then, in this state, as shown in the operation principle explanatory diagram of FIG. 2, one of the lead pieces 3a has an S pole on the contact portion side,
The free ends are magnetized to N poles. Further, in the other lead piece 3b, the contact side is magnetized to the N pole and the free end side is magnetized to the S pole. That is, in this case, the contact portions of the reed switch 2 are magnetized to have the same polarity,
Since the contact portions repel each other, the reed switch 2 does not operate. In the case where the ring magnets 5 and 6 are configured not to operate in a steady state as described above, the ring magnets 5 and 6 are preferably arranged symmetrically with respect to the contact portion of the reed switch 2.

In addition, on the surface of the second ring magnet 6 facing the first ring magnet 5, a ring-shaped spacer 10 is made of glass in a state of being extended from this surface to the first ring magnet 5 side. It is arranged along the longitudinal direction of the container 2a. When the first ring magnet 5 is moved to the side of the second ring magnet 6 to the maximum, the spacer 10 collides with the first ring magnet 5 and restricts further movement, and conversely, the second ring. When the magnet 6 moves to the side of the first ring magnet 5, it is moved integrally with the second ring magnet 6, and when the second ring magnet 6 is moved to the maximum, it collides with the first ring magnet 5. It has a structure that restricts further movement. Further, the length of the spacer 10 is such that when the first ring magnet 5 is moved to the second ring magnet 6 side to the maximum, the first ring magnet 5 has a symbol H1 in the operation principle explanatory view of FIG. When the second ring magnet 6 is located at the center of the reed switch 2 and is moved to the side of the first ring magnet 5 to the maximum, the second ring magnet 6 is located in the area It is set so as to be arranged at the center portion of the reed switch 2 indicated by H1. Furthermore, this spacer 1
As a material of No. 0, a soft material such as sponge or rubber is used, and by using such a soft material, it is possible to buffer the impact with the first ring magnet 5. However, it does not necessarily have to be a cushioning material.

Next, the operation of the acceleration sensor thus configured will be described with reference to FIGS. First, FIGS. 1 and 2 show a state where no impact force is applied to the acceleration sensor. In this state, each ring magnet 5,
6 are arranged separately on the left and right, and the contact portion of the reed switch 2 does not operate and is off.

In this state, when an impact force is applied to the acceleration sensor in the direction indicated by arrow F1 in FIG. 3, the first ring magnet 5 moves from the direction indicated by arrow A in FIG. It moves to the position shown by the solid line in FIG. 3 which is in the region H1 of FIG. 2 where the spacer 10 collides with and the further movement is restricted. Then, as shown by the solid line in FIG. 3, the first ring magnet 5 is connected to the lead pieces 3a, 3b.
When it is almost moved to the overlapped portion (area H1 in FIG. 2), the polarity on the side connected to one lead piece 3a does not change, but the polarity on the side connected to the other lead piece 3b is N on the contact side. To the pole, and the free end side changes to the S pole. As a result, the two lead pieces 3a and 3b facing each other are magnetized to have polarities different from each other at the contact portion, and they are magnetically attracted to each other. That is, it is detected that the reed switch 2 is turned on and a shock is applied.

Next, when the impact disappears, the first ring magnet 5 returns to its original position due to the magnetic repulsive force, and the first ring magnet 5 shown in FIG.
Then, the reed switch 2 is returned to the stationary state shown in FIG. 2, that is, the position shown by the dotted line in FIG. 3, and the reed switch 2 is turned off again.

On the other hand, when an impact force is applied to the acceleration sensor from the direction opposite to the direction shown in FIG. 3, that is, the direction indicated by arrow F2 in FIG. 4, the second ring magnet 6 together with the spacer 10 causes the arrow in FIG. A region H in FIG. 2 in which the spacer 10 collides with the first ring magnet 5 from the direction indicated by B, that is, the position indicated by the dotted line, and further movement is restricted.
It moves to the position shown by the solid line in FIG. And
As shown by the solid line in FIG. 4, the first ring magnet 5
However, when the lead pieces 3a and 3b are almost moved to the overlapping portion (region H1 in FIG. 2), the polarity of the side connected to one lead piece 3a does not change, but the side connected to the other lead piece 3b. Of the contact point side changes to the N pole, and the free end side changes to the S pole. As a result, the two lead pieces 3a and 3b facing each other are magnetized to have polarities different from each other at the contact portion, and they are magnetically attracted to each other. That is, it is detected that the reed switch 2 is turned on and a shock is applied.

Therefore, according to the acceleration sensor of this embodiment, the first ring magnet 5 or the second ring magnet 6 that has moved due to the impact force has the strongest magnetic attraction force on the lead pieces 3a and 3b. When the work moves to a position where the operation after the switching of the lead pieces 3a and 3b can be surely held, the spacer 10 regulates the movement so that it does not move further. The first or second ring magnets 5, 6 have the strongest magnetic attraction force with respect to the lead pieces 3a, 3b while the impact is input, and the lead pieces 3a, 3b
Since the lead pieces 3a and 3b of the reed switch 2 resonate and are repeatedly turned on and off, the noise is generated because the lead pieces 3a and 3b of the reed switch 2 resonate because they are arranged in a position where the operation after the switching of b can be strongly retained, that is, in the region H1. It can be prevented from being mixed. As a result, when this acceleration sensor is used as a sensor of an airbag device in an automobile, detection accuracy can be improved.

In the above embodiment, the structure in which the spacer 10 is attached to the second ring magnet 6 is disclosed, but the spacer 10 may be provided on the first ring magnet 5 side, or the first and the first ring magnets 5 may be provided. The two ring magnets 5 and 6 may be arranged so as to be freely movable. Further, the case where the invention is applied to the sensor of the air bag device has been described, but this is not limited to the air bag device and can be widely used as a general acceleration sensor.

[0026]

As described above, according to the acceleration sensor of the present invention, the magnet that receives an impact force exerts the strongest magnetic attraction force on the lead piece, and the operation after switching the lead piece is performed. After moving to a position where it can be firmly held, use spacers to prevent it from moving any further, and place it in a position where it can reliably hold the operation of this lead piece after switching. You can As a result, it can be reliably prevented that the reed piece of the reed switch resonates and is repeatedly turned on and off to mix in noise, and an effect such as an improvement in sensor accuracy can be expected.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a configuration of an acceleration sensor according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of an operation principle.

FIG. 3 is an operation state explanatory view showing a state in which an impact is applied from one side direction to operate.

FIG. 4 is an operational state explanatory diagram showing a state in which an impact is applied from the other side direction to operate.

FIG. 5 is a diagram illustrating a configuration of a conventional acceleration sensor.

FIG. 6 is an explanatory diagram of an operation principle.

FIG. 7 is an operation state explanatory view showing a state in the middle of movement in which an impact is applied from one side to operate.

FIG. 8 is an operation state explanatory diagram showing a state in which an impact is applied from one side and the apparatus operates and moves to a maximum position.

[Explanation of symbols]

 1 Main body casing 2 Reed switch 2a Glass container 3a One lead piece 3b Other lead piece 5 First ring magnet 6 Second ring magnet 10 Spacer

Claims (1)

[Claims] 1. A reed switch having a contact portion formed by arranging a pair of reed pieces in a slender cylindrical glass container so as to face each other, and a main body casing supporting substantially left and right end portions of the reed switch, In an acceleration sensor comprising a pair of magnets, which are magnetized to have the same polarity on opposite sides and are divided into left and right sides along the longitudinal direction of the glass container, at least one of which is movably arranged, An acceleration sensor, characterized in that a spacer is provided between a pair of magnets for regulating a moving amount of the moving magnet.