JPH05264580A - Acceleration sensor - Google Patents

Abstract

PURPOSE:To provide an acceleration sensor capable of maintaining almost the same acceleration detection characteristic for all directions even in the case of tilted arrangement. CONSTITUTION:The system has a non-magnetic case 1, a moving body 5 and a magnet responding switch 3. A moving body 5 includes a magnet 51 and the magnet 51 is arranged in a case 1, supported with magnetic fluid 4 and floats on the inner surface of the bottom 101. The moving body 5 has a characteristic of space distribution that the leak magnetic field H0 caused by the magnet 51 is weak on one side and strong on the other side in the lower outside of the bottom 101 and the center of gravity is biased to the direction of weaker leak magnetic field. The magnet responding switch 3 is arranged at lower outside of the bottom 101 of the case 1 and responds to the leak magnetic field H0.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor for detecting acceleration associated with vibration or the like.

[0002]

2. Description of the Related Art As prior art similar to this type of acceleration sensor, Japanese Patent Laid-Open No. 63-21884 and Japanese Patent Laid-Open No. 6-19884 are known.
JP-A-3-317712, JP-A-63-26520, JP-A-63-141415 and JP-A-63-7.
There is a tilt sensor known from Japanese Patent No. 0017, etc. FIG. 19
Is a plan view showing its basic configuration, and FIG. 20 is a partial sectional view. In the figure, 1 is a case made of a non-magnetic material, 2 is a magnet, and 3 is a magnetically responsive switch. The case 1 has a bottom portion 101 and a side wall surface 102 continuously standing up the entire circumference thereof. The magnet 2 is disposed inside the case 1 and is supported by the magnetic fluid 4 to support the bottom portion 10.
It has emerged on the inner surface of 1. The magnetic response switch 3 is arranged outside the bottom portion 101 and responds to the position of the magnet 2.

As shown in FIG. 20, when the case 1 receives an acceleration in the horizontal direction a or b, the magnet 2 is supported by the magnetic fluid 4 due to its own inertia.
It moves on the inner surface of the bottom of the case 1, and the relative position with respect to the magnetic response switch 3 changes. The magnetic responsive switch 3 has a sensitive area S1 and a dead area S2 with respect to the position of the magnet 2. The magnetic response switch 3 is turned on in the sensitive area S1 and turned off in the insensitive area S2. This allows
The magnetic responsive switch 3 is turned on or off in response to the leakage magnetic field of the magnet 2, and the acceleration is detected.

[0004]

However, the leakage magnetic field generated from the magnet 2 has a uniform strength over the entire circumference of the magnet 2. For this reason, as shown in FIG. 21, when the acceleration sensor is attached to the object,
When the acceleration sensor tilts due to the tilting due to some reason or the mounting state of the acceleration sensor on the object is changed, the magnet 2 moves in the tilting direction, and the dead area of the magnetic response switch 3 with a small acceleration. S
2, the acceleration response characteristic in the tilt direction becomes sensitive. On the other hand, in the direction opposite to the tilt direction, the distance to the dead region S2 becomes large, and a large acceleration is required for the magnet 2 to enter the dead region S2.
It becomes insensitive. Therefore, a malfunction occurs.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned conventional problems and provide an acceleration sensor capable of maintaining substantially the same acceleration detection characteristics in all directions even when arranged in a tilted manner.

[0006]

To solve the above problems, the present invention is an acceleration sensor having a non-magnetic case, a movable body, and a magnetically responsive switch, wherein the movable body includes a magnet, The magnet is arranged in the case, is supported by a magnetic fluid, and floats above the inner surface of the bottom portion, and a leakage magnetic field generated from the magnet has a space distribution characteristic in which one side is weak outside the bottom portion and the other side is strong. The magnetic responsive switch has an eccentric center of gravity in the direction in which the leakage magnetic field is weakened, and the magnetically responsive switch is disposed outside the bottom of the bottom of the case and responds to the leakage magnetic field.

[0007]

In the movable body, the magnet is placed in the case and is supported by the magnetic fluid and floats above the inner surface of the bottom part. Since the magnetically responsive switch is located below the bottom part of the case and responds to the leakage magnetic field, When subjected to acceleration due to vibration, etc., the movable body moves on the inner surface of the bottom of the case by its own inertia while being supported by the magnetic fluid.
The relative position to the magnetically actuated switch changes. As a result, the magnetic response switch is turned on or off in response to the leakage magnetic field of the magnet, and the acceleration is detected.

When the case is arranged in a non-tilted state, the movable body is stationary at a predetermined position such as the center of the case under the action of the magnetic attraction force acting between the magnet and the magnetically responsive switch. ing. The movable body has a spatial distribution characteristic that the leakage magnetic field generated by the magnet is weaker on one side and stronger on the other side outside the bottom of the case. When it moves, it enters the dead zone within a short moving distance, and the magnetically responsive switch responds. On the contrary, when the magnetic field is moved in a direction where the leakage magnetic field is weak, the magnetically responsive switch responds by entering the dead area with a long moving distance. Of the above two-way operation, when the movable body moves in the direction in which the magnetically responsive switch responds quickly, that is, when the movable body moves in the dead zone and enters the dead zone, the signal output from the magnetically responsive switch is used as the acceleration detection signal. The acceleration can be detected by using

Next, in the case where the acceleration sensor is installed in a tilted manner because the object to which the acceleration sensor is attached is inclined due to some cause such as ground subsidence, or the attachment state of the acceleration sensor to the object is changed. State. In this case, since the center of gravity of the movable body is eccentric in the weakening direction of the leakage magnetic field, the magnetic attraction force acting between the magnet and the magnetic response switch is set so that the eccentricity direction of the center of gravity in which the leakage magnetic field becomes weak is the downside. It displaces to a position where it balances the falling force of gravity and then stands still. Therefore, the moving distance required to enter the dead zone is shortened in the eccentric direction of the center of gravity,
Increase on the other side. Therefore, the moving distance required for the movable body to enter the dead region is balanced in the eccentric direction of the center of gravity and the opposite direction, and the magnetically responsive switch can be operated with substantially the same acceleration in both directions. become.

[0010]

1 is a plan view of an acceleration sensor according to the present invention,
FIG. 2 is a partial sectional view of the same. In the figure, 1 is a non-magnetic case, 3 is a magnetic response switch, 4 is a magnetic fluid,
5 is a movable body.

The case 1 has a bottom portion 101 and a side wall surface 102 continuously standing up the entire circumference thereof.
The planar shape of 1 is substantially circular. In the illustration,
Although the inner surface of the bottom portion 101 is concave, it may be flat. The case 1 is made of a non-magnetic material such as aluminum or plastic as in the conventional case.
The magnetic fluid 4 is a magnetic powder of fine particles of cobalt, iron, nickel, etc. dispersed in a liquid having a relatively low viscosity, such as kerosene, water, etc. In general, a surfactant is adsorbed on the fine particles for stable dispersion. I am allowed to do it.

The movable body 5 includes a magnet 51, which is arranged inside the case 1 and is supported by the magnetic fluid 4 so as to float above the inner surface of the bottom portion 101. The magnet 51 is vertically or radially magnetized. As shown in FIG. 2, the movable body 5 has a spatial distribution characteristic that the leakage magnetic field H0 generated from the magnet 51 is weak on the left side (in the figure) outside the bottom portion 101 of the case 1 and is strong on the right side. .. In FIG. 2, the horizontal axis represents the spatial position and the vertical axis represents the magnetic field strength.

As a means for obtaining the above-mentioned spatial distribution characteristic, the movable body 5 shown in the figure includes a yoke 52. 3 is a perspective view of the movable body 5, and FIG. 4 is a sectional view taken along the line A4-A4 in FIG. The yoke 52 is attached so as to cover the magnet 51 from above, and one end on the A4-A4 line extends the end portion 521 to cover most of the magnet 51, and the other end shortens the end portion 522 so that the magnet 51 is It covers so as to expose a lot. Therefore, on the side where the end portion 521 is present, the leakage magnetic field generated from the magnet 51 is subjected to the converging action of the yoke 52, and on the side where the end portion 522 is present, the leakage magnetic field spreads widely. As a result, the spatial distribution characteristic shown in FIG. 2 is obtained.

Further, the movable body 5 has its center of gravity eccentric in the direction in which the leakage magnetic field is weakened. As a means for this, the movable body 5 has a yoke 52, and the yoke 52 covers most of the magnet 51 on one side on the A4-A4 line, and covers so that the magnet 51 is largely exposed on the other side. Therefore, the center of gravity of the movable body 5 is eccentric from the center O1 to the position O2 by the eccentric amount Δd (see FIG. 1). The movable body 5 shown is
The outer peripheral surfaces 523 and 524 of the yoke 52 have an arc shape having a curvature capable of overlapping with the inner peripheral surface of the side wall surface 102 of the case 1. The yoke 52 is an arc-shaped outer peripheral surface 52 in the minor axis direction.
3, 524, and the outer peripheral surfaces 523, 5 at both ends in the longitudinal direction.
It has a planar shape such that 24 is butted. Although illustration is omitted, it may have a planar shape such that both ends in the long axis direction are cut.

Referring again to FIGS. 1 and 2, description will be made.
The magnetic response switch 3 is arranged so as to have a fixed relationship with the case 1. Although it is installed vertically in the figure, it may be installed horizontally. The magnetic responsive switch 3 has sensitive areas S11, S12 and insensitive areas S21, S with respect to the leakage magnetic field H0 generated by the magnet 51.
22 and 22. In the figure, the sensitive area S11 indicates that when the movable body 5 moves in the direction of arrow a from the center line CT of the case 1 at a stationary position where the center O1 of the movable body 5 coincides with the center O of the case 1. A sensitive region is a region in which the sensitive state can be maintained, and a sensitive region S12 is a region in which the sensitive state can be maintained when the movable body 5 moves from the center line CT in the direction of the arrow b. The movable body 5 has a spatial distribution characteristic that the leakage magnetic field H0 generated from the magnet 51 is weaker on the left side and stronger on the right side outside the bottom portion 101 of the case 1 (see FIG. 2). The distance Lb0 becomes larger than the distance La0 of the sensitive area S11. The magnetic response switch 3 is turned on in the sensitive areas S11 and S12 and turned off in the insensitive areas S21 and S22.

FIG. 1 and FIG. 2 show the case where the case 1 is arranged in a non-inclined state, and the movable body 5 receives the action of the magnetic attraction force acting between the magnet 51 and the magnetic response switch 3. It is stationary at the center O of Case 1. In this stationary position, when acceleration due to vibration or the like is applied in the direction of arrow a or b, the movable body 5 floats on the inner surface of the bottom portion 101 with the magnet 51 arranged inside the case 1 and supported by the magnetic fluid 4. Therefore, as shown in FIG. 5 and FIG. 6, the movable body 5 is supported by the magnetic fluid 4 and, due to its own inertia, the bottom portion 101 of the case 1.
Of the magnetically actuated switch 3, the strength of the leakage magnetic field H0 with respect to the magnetically actuated switch 3 changes based on its spatial distribution characteristics. Since the magnetic response switch 3 is arranged below the bottom portion 101 of the case 1 and responds to the leakage magnetic field H0, the position change of the movable body 5 is detected as the ON / OFF operation of the magnetic response switch 3, and thereby the acceleration is detected. It

As shown in FIG. 2, the movable body 5 has a spatial distribution characteristic that the leakage magnetic field H0 generated from the magnet 51 is weaker on one side and stronger on the other side outside the bottom portion 101 of the case 1. Therefore, when the movable body 5 moves in the direction of the strong arrow a of the leakage magnetic field H0, the spatial distribution of the leakage magnetic field becomes Ha. The magnetically responsive switch 3 is affected by the spatial distribution characteristic Ha having a large reduction rate of the leakage magnetic field strength, and moves from the sensitive area S11 to the insensitive area S21 with only a slight movement of the movable body 5. Therefore, the short moving distance La
At 0, the magnetic response switch 3 responds. On the contrary, when the movable body 5 moves in the direction of the arrow b where the leakage magnetic field is weak, the spatial distribution of the leakage magnetic field becomes Hb. The magnetic responsive switch 3 is affected by the spatial distribution characteristic Hb having a small leakage magnetic field strength reduction rate and responds at a long moving distance Lb0. Of the two-direction operation described above, when the movable body 3 moves in the direction in which the magnetically responsive switch 3 responds quickly, that is, the movable body 3 moves in the direction of the arrow a having a strong leakage magnetic field and enters the dead zone S21, the magnetically responsive switch 3 outputs. The acceleration can be detected by using the generated signal as the acceleration detection signal.

When the movable body 5 receives an acceleration in the oblique direction a or b with respect to the line segment P1 passing through the center O1 and the center of gravity O2, the operation shown in FIG. 7 is performed. In FIG. 7, when the movable body 5 receives an acceleration in the diagonal direction b, the movable body 5 moves on the inner surface of the bottom portion 101 of the case 1 while displacing the center O1 and the center of gravity O2 on a line segment P2 parallel to the acceleration direction b. Moving. Even when the movable body 5 receives an acceleration in the direction a opposite to the direction b, the movable body 5 is displaced such that the center O1 and the center of gravity O2 of the movable body 5 are placed on the line segment P2 parallel to the acceleration direction a, and the bottom of the case 1 is displaced. It moves on the inner surface of 101. The operations of the movable body 5 and the magnetically-actuated switch 3 thereafter are as described in FIGS. 5 and 6.

FIGS. 8 and 9 are diagrams showing the operation when the acceleration sensor is tilted. In such an inclined arrangement, if the object to which the acceleration sensor is attached is
It occurs when the sensor is tilted for some reason or the mounting state of the acceleration sensor on the object changes. When the acceleration sensor is tilted, the movable body 5
Since the center of gravity is eccentric in the direction in which the leakage magnetic field weakens, the magnetic attraction force acting between the movable body 5 and the magnetic response switch 3 and the drop due to gravity are set with the center of gravity eccentric direction in which the leakage magnetic field H0 weakens as the lower side. Displaced to a position where the force balances,
And then stand still. The rest position is indicated by the solid line in FIGS. In the stationary state, the moving distance required to enter the dead zone is shortened from the distance Lb0 to the distance Lb1 in the eccentric direction of the center of gravity. On the side opposite to the eccentric direction of the center of gravity, the distance La0 increases to the distance La1. Therefore, the moving distances Lb1 and La1 required for the movable body 5 to enter the dead area S22 or S21 are balanced in the direction of eccentricity of the center of gravity and the direction opposite thereto, and the magnetically responsive switch has substantially the same acceleration in both directions. 3 can be operated.

In the above embodiment, the movable body 5 is the yoke 52.
Since the outer peripheral surfaces 523 and 524 of the movable body 5 have an arc shape having a curvature that can overlap the inner peripheral surface of the side wall surface 102 of the case 1, the outer peripheral surfaces 523 and 524 of the movable body 5 are in surface contact with the side wall surface 102 of the case 1. Then, the operation of the movable body 5 is stabilized.

Although only two directions of inclination have been described in the drawing, the case 1 has a cylindrical internal space composed of the bottom portion 101 and the side wall surface 102, and therefore the same action can be obtained in all directions.

FIG. 10 is a plan view of another embodiment of the movable body used in the acceleration sensor according to the present invention, and FIG. 11 is a sectional view of the same. The movable body 5 is a cylindrical yoke 52.
On one side, the end portion 521 is extended to cover most of the magnet 51, and on the other side, the end portion 522 is shortened to expose a large amount of the magnet 51. Therefore, on the side where the end portion 521 is present, the leakage magnetic field generated from the magnet 51 is subjected to the converging action of the yoke 52, and the end portion 5 is
On the side of 22, the leak magnetic field is widely diverged, and the center of gravity is eccentric in the direction in which the leak magnetic field is weakened.

FIG. 12 is a plan view of another embodiment of the movable body 5 used in the acceleration sensor according to the present invention, and FIG. 13 is a sectional view thereof. The movable body 5 has two half magnets 511 and 512 inside the additional member 52,
Magnets 511 and 522 are eccentrically arranged on one side of the additional member 52 in the diameter direction. The leakage magnetic field of the magnet 511 is weaker than that of the magnet 512, and the additional member 52
Is located on the eccentric side of. The additional member 52 does not need to form a yoke and can be made of a magnetic material. As a result, the movable body 5 has a spatial distribution characteristic that the leakage magnetic field generated from the magnets 511 and 512 is weaker on one side and stronger on the other side, and the center of gravity O2 is decentered from the center O1 in the direction in which the leakage magnetic field is weakened. ..

FIG. 14 shows the case where the leak magnetic fields are substantially equal as the magnets 511 and 512, and the end surface of the magnet 511 located in the eccentric direction is set to the magnet 5
It is set back from the end face of No. 12 by Δh. The movable body 5 has a spatial distribution characteristic that the leakage magnetic field generated from the magnet 511 is weak and the leakage magnetic field generated from the magnet 512 is strong, and the center of gravity O2 becomes eccentric in the direction of the magnet 511.

FIG. 15 is a plan view of another embodiment of the movable body used in the acceleration sensor according to the present invention, and FIG. 16 is its sectional view. The movable body 5 has a magnet 51 inside the additional member 52, and the magnet 51
2 is arranged eccentrically on one side in the diametrical direction. The magnet 51 has an inclined surface 510 in which the step increases as the tip end surface moves toward the eccentric direction. The additional member 52 does not need to form a yoke and can be made of a non-magnetic material. As a result, the movable body 5 has a spatial distribution characteristic that the leakage magnetic field generated from the magnet 51 gradually weakens along the inclined surface 510, and the center of gravity O2 becomes eccentric from the center O1 in the weakening direction of the leakage magnetic field.

FIG. 17 shows an example in which the tip end surface of the magnet 51 is a step surface 510 having a step Δh in the eccentric direction in the plane arrangement as shown in FIG.

FIG. 18 is a sectional view showing a more specific embodiment of the acceleration sensor according to the present invention. 7 is a holder made of a non-magnetic electric insulator such as plastic,
9 is a lead terminal, 10 is a bias magnet, 103
Is a case lid, 104 is a washer for height adjustment, 105 is a spring, and 106 is a cap. The case 1 is arranged inside the receiving portion 71 formed on the upper portion of the holder 7 after being adjusted in its height by the washer 104.
It is fixed to the holder 7 by a spring 105 and a cap 106 arranged on the top. The case lid 103 closes the upper surface of the case 1 to prevent evaporation of the magnetic fluid 4. The cap 106 covers the whole. Cap 10
6 is preferably made of a magnetic material such as iron so as to have a shielding effect.

The magnetically actuated switch 3 is inserted and arranged in a receiving portion 72 formed at the bottom of the holder 7. The lead conductors 31 and 32 of the magnetically-actuated switch are connected to the lead terminals 8 and 9. The lead terminal 8 is led to the outside through the inside of the holder 7. The lead terminal 9 has one end arranged below the magnetically-actuated switch 3 and is bent and guided along the holder 7.
The magnet 10 has a ring shape and is inserted and arranged in a ring-shaped receiving portion 73 provided around the receiving portion 72 that houses the magnetically-responsive switch 3.

[0029]

As described above, according to the present invention, the following effects can be obtained. (A) In the movable body, the magnet is arranged in the case, is supported by the magnetic fluid, and floats on the inner surface of the bottom portion.
Since the magnetically actuated switch is located outside the bottom of the case and responds to the leakage magnetic field, the movable body is supported by the magnetic fluid while the movable body is supported by the magnetic fluid while the movable body is supported by the inertia of its own. It is possible to provide an acceleration sensor that moves up and the magnetic response switch is turned on and off in response to the leakage magnetic field of the magnet to detect the acceleration. (B) The movable body has a spatial distribution characteristic that the leakage magnetic field generated from the magnet is weaker on one side and stronger on the other side outside the bottom of the case, and the center of gravity is eccentric in the direction in which the leakage magnetic field weakens. Even if the acceleration sensor is attached to the object because the object to which the acceleration sensor is attached is inclined due to some reason such as ground subsidence, or the attachment state of the acceleration sensor to the object is changed, the effect of the inclination It is possible to provide an acceleration sensor that can reliably detect the acceleration without receiving the acceleration.

[Brief description of drawings]

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

FIG. 2 is a partial cross-sectional view taken along the line A2-A2 of FIG.

FIG. 3 is a perspective view of a movable body used in the acceleration sensor shown in FIG.

4 is a cross-sectional view taken along the line A4-A4 in FIG.

5 is a plan view for explaining the operation of the acceleration sensor shown in FIG.

6 is a partial cross-sectional view taken along the line A6-A6 of FIG.

FIG. 7 is a plan view illustrating the operation of the acceleration sensor shown in FIG.

FIG. 8 is a partial cross-sectional view for explaining an operation of the acceleration sensor shown in FIG. 1 in the inclined arrangement.

FIG. 9 is a partial cross-sectional view illustrating an operation of the acceleration sensor shown in FIG. 1 in a tilted arrangement.

FIG. 10 is a plan view showing another embodiment of the movable body used in the acceleration sensor according to the present invention.

11 is a cross-sectional view of the movable body shown in FIG.

FIG. 12 is a plan view showing another embodiment of the movable body used in the acceleration sensor according to the present invention.

13 is a cross-sectional view of the movable body shown in FIG.

14 is a cross-sectional view showing another embodiment of the movable body shown in FIG.

FIG. 15 is a plan view showing another embodiment of the movable body used in the acceleration sensor according to the present invention.

16 is a sectional view of the movable body shown in FIG.

17 is a sectional view showing another embodiment of the movable body shown in FIG.

FIG. 18 is a sectional view of a specific example of the acceleration sensor according to the present invention.

FIG. 19 is a plan view of a conventional acceleration sensor.

FIG. 20 is a partial cross-sectional view of a conventional acceleration sensor.

FIG. 21 is a plan view illustrating the operation of the conventional acceleration sensor.

[Explanation of symbols]

 1 Case 101 Bottom 3 Magnetic Response Switch 4 Magnetic Fluid 5 Movable Body 51 Magnet 52 Yoke or Additional Member

Claims (3)

[Claims] 1. An acceleration sensor having a non-magnetic case, a movable body, and a magnetically responsive switch, wherein the movable body includes a magnet, and the magnet is disposed in the case and supported by a magnetic fluid. Leakage magnetic field generated from the magnet floats on the inner surface of the bottom portion and has a spatial distribution characteristic in which one side is weaker outside the bottom portion and the other side is stronger, and the center of gravity is eccentric in the weakening direction of the leakage magnetic field. The magnetically responsive switch is an acceleration sensor arranged outside the bottom of the case below the case and responsive to the leakage magnetic field. 2. The acceleration sensor according to claim 1, wherein the movable body includes a yoke, the yoke is attached to the magnet to cause the eccentricity, and the leakage magnetic field is converged on the eccentric side. 3. The acceleration sensor according to claim 1, wherein the movable body has a curvature such that an outer peripheral surface thereof can overlap an inner peripheral surface of the side wall surface.