JPH07294546A - Acceleration sensor - Google Patents

Abstract

PURPOSE:To provide an acceleration sensor having an automatic restoring mechanism of a movable member equipped with a permanent magnet and small in size. CONSTITUTION:The acceleration sensor 1 comprises a movable member 2A consisting of a permanent magnet 20 and a holder member 21, a vessel body made of a non-magnetic material and a Hall device IC5. A specific shape of spherical concave surface 3c is formed in the inner bottom section 3b of the vessel body and a spherical convex surface 21a is formed on the under face side of the holder member 21. When a condition is changed from a stationary state wherein acceleration is not applied, to a non-stationary state wherein acceleration is applied, the movable member 2A moves from a reference axis 6 (stationary position) and when the condition is changed to the stationary state again, the movable member 2A automatically restores to the reference axis because of its specific shape. The Hall device IC5 detects the variation of the flux due to the movement of the movable member 2A equipped with the permanent magnet 20.

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 vibrations, impacts, tilts, falls, etc., and more particularly to an acceleration sensor having an automatic return mechanism for a movable member provided with a permanent magnet.

[0002]

2. Description of the Related Art As an acceleration sensor of this type, various sensors using a reed switch, a magnetic fluid application switch, a mercury switch, etc. have been known.

FIG. 15 is a sectional view showing an example of a conventional sensor using the reed switch. This sensor 10
When the sensor 10 is displaced due to inclination or the like (unsteady state), the movable permanent magnet 11 moves from the steady position magnetically held by the magnetic member 12 and the sensor 10 returns to its original state (steady state). ), The movable permanent magnet 11 is provided with an automatic return mechanism for returning to a steady position, and changes in the magnetic flux caused by the movement of the movable permanent magnet 11 are detected by the reed switch 13 to detect tilting, overturning, etc. 4-96003).

In the magnetic fluid application switch, a permanent magnet wrapped with a magnetic fluid is placed in a container made of a non-magnetic material, and a reed switch is placed vertically directly below the container, and the whole container and reed switch are placed. When is tilted, the permanent magnet moves to a position off the axis of the reed switch, so that the contact of the reed switch is opened, and tilting, vibration, etc. are detected.

In the mercury switch, mercury is interposed between a pair of conductors in a steady state to make them conductive. When acceleration due to vibration, shock, etc. is applied, the mercury moves and the pair of conductors becomes non-conductive. As a result, vibration or the like is detected.

[0006]

However, as shown in FIG.
The automatic return mechanism of the sensor 10 shown in FIG.
Since the magnetic member 12 for magnetically holding the sensor is required at a steady position, the structure of the container 14 side becomes complicated and the sensor 10 becomes large. Also, the reed switch 1
Since No. 3 is arranged so as to be long in the vertical direction, the height of the container 14 must be increased, and there is a problem that the entire sensor 10 becomes large.

Further, when the magnetic fluid application switch is used, the structure is complicated because the sealing with an inert gas is required and the magnetic fluid itself is expensive, so that the cost of the switch is increased. .

Further, when the mercury switch is used, there is a problem that the environment of the earth is polluted by mercury.

Therefore, the present invention has been made in view of the above circumstances, and an object of the present invention is to provide an acceleration sensor which is provided with an automatic return mechanism for a movable member provided with a permanent magnet and which is downsized. .

[0010]

According to another aspect of the present invention, there is provided an acceleration sensor, wherein a movable member at least a part of which is provided with a permanent magnet, a non-magnetic container movably accommodating the movable member in an internal space, and Hall IC that is arranged to face a movable member and detects a change in magnetic flux caused by the movement of the movable member.
And the movable member moves from the steady position when the steady state changes to the unsteady state, and the movable member returns to the steady state when the steady state is restored. It is characterized in that the mechanism is constituted by a specific shape.

According to another aspect of the acceleration sensor of the present invention, the movable member provided with the permanent magnet is composed of a holding member that comes into contact with the inner surface of the bottom of the container, and a rod-shaped permanent magnet held by the holding member. It is what

According to another aspect of the acceleration sensor of the present invention, the specific shape is such that a concave curved surface is formed on the inner surface of the bottom of the container, and a radius of curvature is larger than that of the concave curved surface on the lower surface side of the holding member constituting the movable member. A small convex curved surface is formed.

According to another aspect of the acceleration sensor of the present invention, the specific shape is such that a concave spherical curved surface is formed on the inner surface of the bottom of the container, and a radius of curvature is larger than the concave spherical curved surface on the lower surface side of the holding member constituting the movable member. A small convex spherical curved surface is formed.

[0014]

According to the acceleration sensor of the first aspect, when the steady state changes to the unsteady state, the movable member moves from the steady position, and when it returns to the steady state again, the movable member automatically moves to the steady position according to the specific shape. Return to. The Hall IC detects a change in magnetic flux caused by the movement of a movable member provided with a permanent magnet.

According to the acceleration sensor of the second aspect, the holding member holds the permanent magnet so that the magnetic flux corresponding to the acceleration is supplied to the Hall IC.

According to the acceleration sensor of the third aspect, when the steady state is changed to the unsteady state, the movable member rolls on the concave curved surface of the inner surface of the bottom to move from the steady position, and then returns to the steady state. The movable member rolls on the concave curved surface of the inner surface of the bottom portion by gravity and automatically returns to the steady position. The Hall IC detects a change in magnetic flux caused by the movement of a movable member provided with a permanent magnet.

According to the acceleration sensor of the fourth aspect, by forming the concave spherical curved surface on the container and the convex spherical curved surface on the holding member as specific shapes, it is possible to detect acceleration in all directions in the horizontal direction.

[0018]

Embodiments of the present invention will now be described in detail with reference to the drawings.

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

The acceleration sensor 1 includes a movable member 2A having a permanent magnet 20 at least partially provided therein, and a container body 3A for movably accommodating the movable member 2A in an internal space.
And a printed circuit board 4A disposed on the opening side of the upper portion 3a of the container body 3A and a printed circuit board 4A disposed below the printed circuit board 4A so as to face the movable member 2A, and detect changes in magnetic flux caused by movement of the movable member 2A. The Hall IC 5 as a magnetic detecting means and a mechanism for automatically returning the movable member 2A are provided.

The container body 3A has a bottomed box shape made of a non-magnetic material, a concave spherical curved surface 3c of a specific shape is formed on the inner surface of the bottom portion 3b, and a mounting hole 3d is provided around the bottom portion 3b. The flange portion 3e is provided so as to project, and a step portion 3f for positioning the printed circuit board 4A is provided on the upper portion 3a. This step 3
Hall IC 5 arranged on printed circuit board 4A by f
Can be easily positioned on a reference axis (steady position) 6 described later.

As shown in the perspective views of FIGS. 1 and 2, the movable member 2A comprises a rod-shaped permanent magnet 20 and a holding member 21 for holding the permanent magnet 20, and the bottom portion 3b of the container body 3A. It is placed in contact with the inner surface. Movable member 2
By configuring A by the permanent magnet 20 and the holding member 21, it becomes easy to hold the permanent magnet 20 so that the magnetic flux corresponding to the acceleration is supplied to the Hall IC 5.

The permanent magnet 20 may be isotropic or anisotropic, and any material including ferrite type, neodymium type, rare earth type, alnico type and the like can be selected.

The holding member 21 is made of a non-magnetic metal such as brass or aluminum or a non-magnetic material such as plastic, and has a substantially hemispherical shape with a convex spherical curved surface 21a of a specific shape.
The convex spherical curved surface 21a has a radius of curvature smaller than that of the concave spherical curved surface 3c. Further, in the holding member 21, in the steady state described later, the magnetic pole, for example, the S pole, has the Hall IC 5
The permanent magnet 20 is held so as to face to. In addition, the magnetic pole is the opposite magnetic pole (N
It may be a pole.

Next, the automatic return mechanism of the movable member 2A will be described.

In this embodiment, the "automatic return mechanism" is used.
The movable member 2A is located on the reference axis (steady position) 6 in the steady state, and the movable member 2A is in the unsteady state.
When A moves from the reference shaft 6 and returns to the steady state again, the movable member 2A automatically returns to the reference shaft 6. In addition, “steady state” means that the sensor 1 vibrates,
A state in which acceleration due to impact or the like is not applied or a state in which the sensor 1 is not displaced due to tilting, falling, or the like is "non-steady state". Acceleration due to vibration or impact is applied to the sensor 1. Condition or inclination to this sensor 1,
It refers to the state of displacement caused by a fall or the like.

In order to realize this automatic return mechanism, it is necessary that the center of gravity of the entire movable member 2A is on the reference axis 6 in the steady state. Further, in order to stably detect the change of the magnetic flux by the Hall IC 5, it is necessary that the center of gravity of the permanent magnet 20 is on the reference axis 6 in the steady state. Therefore, the permanent magnet 20 has a symmetrical shape such as a cylindrical shape or a prismatic shape with respect to the reference axis 6, the holding member 21 also has a symmetrical shape with respect to the reference axis 6, and the movable member 2A as a whole also has the reference axis. 6 has a completely or substantially symmetrical structure. Also,
The center of curvature of the convex spherical curved surface 21a is aligned with the reference axis 6. The concave spherical curved surface 3c of the container body 3A has a symmetrical shape with respect to the reference axis 6, and the center of curvature thereof coincides with the reference axis 6.

As a result, not only can the automatic return mechanism be realized, but in the steady state, the movable member 2A will not tilt or fall due to its own weight, and the magnetic poles of the permanent magnet 20 will be Hall I.
It becomes completely oriented to C5, and as shown in FIG. 2, the acceleration in all directions in the horizontal direction A can be detected uniformly.

The printed circuit board 4A is provided with a lead wire 8 having a connector 7 at its end for supplying power to the Hall IC 5 and outputting a signal from the Hall IC 5. Further, the printed circuit board 4A regulates the movable member 2A from rolling and reversing due to vibration, inclination, etc., as shown by an imaginary line in FIG. 6, and is set at such a height position. Moreover, the printed circuit board 4A is set at a height position such that the permanent magnet 20 does not come into contact with the Hall IC 5 to prevent the movable member 2A from rolling.

As shown in the perspective views of FIGS. 1 and 3, the Hall IC 5 has a case 5a having a substantially rectangular shape,
A hose element 50 described later is provided inside the case 5a, and a magnetic detection surface 5b is provided on the upper surface of the case 5a.
The Hall IC 5 is for detecting a change in magnetic flux from the movable member 2A, and the Hall IC 5 has a magnetic detection surface 5b.
Is arranged on the lower surface side of the printed circuit board 4A so that the center of the is aligned with the reference axis 6.

As shown in the block diagram of FIG. 4, this Hall IC 5 comprises a Hall element 50, an amplifier 51, a Schmitt trigger 52, a power supply circuit 53, a temperature compensation circuit 54, an output transistor 55 and an output resistor 56. There is. As shown in the output characteristic diagram of FIG. 5, the Hall IC 5 is a one-way magnetic field operation type that performs a switching operation with respect to a magnetic field strength of a certain level or more of either the N pole or the S pole toward the magnetic detection surface 5b. belongs to. In the steady state, the permanent magnet 20 has one of the determined polarities (S pole or N pole) directed toward the magnetic detection surface 5b of the Hall IC 5 in the steady state, so that this permanent magnet 20 serves as a magnetic detection means. It is possible to use the directional magnetic field type Hall IC 5. Then, the strength of the magnetic field to the Hall IC 5 is constant (B
₂ ) Above, the output transistor 55 is turned on and the output voltage becomes low level L. On the other hand, when the magnetic field strength becomes constant (B ₁ ) or less, the output transistor 55 is turned off and the output voltage becomes the high level H. By using such a Hall IC 5, an input power supply is required, but since the output signal can be obtained at a low level (on) / high level (off), it is easy to handle and any lead wire, pin terminal, etc. can be used. It is possible to extract the signal by the method. Depending on the circuit, the output transistor 55
It is also possible to reverse the relationship between ON / OFF of L and H of output voltage.

Next, the operation of this embodiment will be described with reference to FIGS. 6 and 7. FIG. 6 is a sectional view showing an unsteady state, and FIG. 7 is a magnetic flux B supplied to the Hall IC 5 and the Hall IC 5.
It is a figure which shows the signal S which is output by. Note that, in the unsteady state, a case where acceleration in one direction A in the horizontal direction is applied to the sensor 1 will be described.

First, in a steady state in which no acceleration is applied to the sensor 1, the movable member 2A has a convex spherical curved surface 21a of the movable member 2A due to its own weight as shown in FIG. 1 and a concave spherical curved surface of the container body 3A. 3c is in contact with the reference axis 6, and the magnetic pole of the permanent magnet 20, for example, the S pole, faces the magnetic detection surface 5b of the Hall IC 5, and supplies a sufficient magnetic flux to the Hall IC 5. Therefore, in the Hall IC 5, the output transistor 55 is turned on by the sufficient magnetic flux and outputs the low level L voltage.

As shown in FIG. 6, when a certain acceleration or more is applied to the present sensor 1 in the horizontal direction A, the movable member 2A causes the concave spherical surface 3 of the container body 3A to move.
It rolls on c and moves from the reference axis 6. As a result, the magnetic flux is no longer supplied from the permanent magnet 20 to the Hall IC 5,
The output transistor 55 of the Hall IC 5 is turned off, and the output voltage becomes the high level H.

Next, when the acceleration is not applied and the steady state is restored again, the movable member 2A rolls on the concave spherical curved surface 3c by gravity and automatically returns to the reference axis 6, as shown in FIG. To do. The magnetic pole (S pole) of the permanent magnet 20 is the hall I.
Again facing the magnetic detection surface 5b of C5, a sufficient magnetic flux is supplied to the Hall IC 5, and the Hall IC 5 turns on the output transistor 55 due to the sufficient magnetic flux, so that the low level L
Output the voltage.

The magnetic flux supplied to the magnetic detection surface 5b of the Hall IC 5 by the movement and return of the movable member 2A about the reference axis 6 as described above depends on the vibration like a sine wave as shown in FIG. Change from Hall IC5 to Fig. 7
The pulse waveform signal S as shown in is output and the acceleration is detected.

Next, a modification of the sensor 1 shown in FIG. 1 is shown in FIG.
It will be described with reference to FIGS.

8 and 9 are sectional views showing modified examples of the container body 3A and the printed circuit board 4A.

As shown in FIG. 8, the container body 3B is formed only within the range in which the holding member 21 of the movable member 2A actually contacts without forming the concave spherical curved surface 3c on the entire inner surface of the bottom portion 3b. You may. This facilitates the manufacture of the container body 3B.

Further, the printed circuit board 4B is shown in FIGS.
As shown in, the lead pin 8B may be used instead of the lead wire 8. Since the lead pin 8B can also serve as the fixing of the substrate 4B, the assembly becomes easy.

Further, as shown in FIG. 9, the container body 3C has a substantially flat surface 3g in the vicinity of the reference axis 6 as shown in FIG. 9, even if the entire concave spherical curved surface 3c does not have the same radius of curvature as shown in FIG. The curved surface 3h may be formed around the substantially flat surface 3g. The curved surface 3h in this case may have a smaller radius of curvature than the convex spherical curved surface 21a of the movable member 2A. Figure 9
With the configuration shown in (3), the container body 3C can be easily manufactured.

10 to 14 show the movable member 2 shown in FIG.
It is sectional drawing which shows the modification of A.

As in the movable member 2B shown in FIG. 10, a flat surface 21b may be provided on a part of the convex spherical curved surface 21a of the holding member 21 that intersects with the reference axis 6 in the steady state. As a result, in the steady state, the permanent magnet 20 surely faces upward, and it becomes easy to increase the magnitude of acceleration to be detected.

Further, as in the movable member 2C shown in FIG. 11, an inclined surface 21c may be provided on the upper peripheral edge of the holding member 21. This can prevent the upper peripheral edge from being caught during rolling.

Further, as in the movable member 2D shown in FIG. 12, an inclined surface 20a may be provided on the upper peripheral edge of the permanent magnet 20. As a result, the magnetic flux to the Hall IC 5 is sharply reduced due to the acceleration, so that high speed and high sensitivity can be achieved.

The permanent magnet 20 may be embedded in the holding member 21 as in the movable member 2E shown in FIG.
As a result, when rolling, the permanent magnet 20 hits the Hall IC 5 or the container body 2A, etc.
Can be prevented from being damaged.

Further, like the movable member 2F shown in FIG. 14, a center of gravity position adjusting member 23 for adjusting the center of gravity position may be added. The actuation acceleration can be adjusted by selecting the position where the center-of-gravity position adjusting member 23 is arranged, its specific gravity, and the thickness to adjust the position of the center of gravity. The center-of-gravity position adjusting member 23 in the figure is arranged below the permanent magnet 20, and by selecting, for example, one having a specific gravity larger than that of the permanent magnet 20, the position of the center of gravity can be lowered, and the specific gravity is smaller than that of the permanent magnet 20. By selecting one, the position of the center of gravity can be raised. In this way, after manufacturing the permanent magnet 20 and the holding member 21, the center of gravity position adjusting member 23
It is possible to easily adjust the position of the center of gravity in the height direction by selecting the specific gravity and thickness of the. In addition to this, without using the center-of-gravity position adjusting member 23, it is also possible to change the depth of the hole for housing the permanent magnet 20 to move the center-of-gravity position of the entire movable member 2 to adjust the operating acceleration. Further, the magnitudes of acceleration and displacement that can be detected by the sensor 1 of the present embodiment include the outer diameter of the holding member 21, the magnetic force of the permanent magnet 20, the position of the center of gravity of the movable member 2, the weight of the movable member 2, and the convex sphere. The radius of curvature of the curved surface 21a and the concave spherical curved surface 3c, the permanent magnet 20 and the Hall IC
It can be changed by changing the distance between the 5 and the like.

The movable member 2A may be made of a permanent magnet. In this case, for example, it can be easily manufactured by integral molding.

According to this embodiment, the following effects can be obtained.

(1) Concave spherical curved surface 3c and convex spherical curved surface 21
Since the automatic return mechanism is configured by the specific shape of a,
Since it is not necessary to provide a magnetic member for magnetically holding the movable member 2 on the container body 3 side, and the structure of the container body 3 can be simplified, the sensor 1 can be downsized.

(2) Since the movable member 2A rolls with a slight acceleration, it is possible to detect a slight vibration, and therefore it is suitable as a seismic device for a safety device for earthquake detection.

(3) Since the acceleration and displacement to be detected are determined by the size, weight, position of the center of gravity, the characteristics of the permanent magnet 20 and the like of each part, it is possible to suppress variations in characteristics basically with dimensional accuracy. Since the reproducibility is also good, it is possible to manufacture products with small variations.

(4) Since the Hall IC 5 is used as the magnetic detection means, the following effects can be obtained.

(I) Since the height of the container body 3 can be reduced as compared with the case where a reed switch is used, the sensor 1 can be downsized.

(Ii) High reliability can be obtained because there is no contact failure due to dirt on the contact such as a reed switch.

(Iii) It is possible to detect a micro-vibration of an earthquake without using toxic substances polluting the environment such as mercury.

(Iv) Since an expensive magnetic fluid application switch is not used, the structure is simple and the cost can be reduced.

The present invention is not limited to the above embodiment,
Various modifications can be made without changing the gist of the invention.
For example, as a specific shape, a concave semi-columnar curved surface may be formed on the container and a convex semi-columnar curved surface may be formed on the movable member. In this case, the reciprocal acceleration and displacement along one axis in the horizontal direction can be detected. Further, in the present embodiment, the detection of the acceleration is mainly described, but it goes without saying that the displacement due to the inclination, the fall, etc. can be detected in the same manner.

[0059]

According to the present invention described in detail above, the following effects can be obtained.

According to the first aspect of the invention, since the movable member is returned to the steady position by the specific shape without using a magnetic member or the like, an automatic return mechanism for the movable member provided with a permanent magnet is provided. It is possible to provide an acceleration sensor that is equipped with and is downsized. Further, by using the Hall IC as the magnetic detection means, a highly reliable detection signal can be obtained without polluting the global environment, variation in detection characteristics is small, and the size of the container in the height direction can be reduced. It is possible to achieve the excellent effects of the Hall IC that other magnetic detection means do not have, such as simplification and miniaturization.

According to the second aspect of the invention, the permanent magnet can be held by the holding member so that the magnetic flux corresponding to the acceleration is supplied to the Hall IC.

According to the third aspect of the present invention, the holding member forming the movable member is provided with the convex curved surface, and the inner surface of the bottom of the container is provided with the concave curved surface. It is possible to provide an acceleration sensor that is equipped with an automatic return mechanism and is downsized.

According to the fourth aspect of the invention, since the concave spherical curved surface and the convex spherical curved surface are formed as the specific shapes, it is possible to detect acceleration and displacement in all directions in the horizontal direction.

[Brief description of drawings]

FIG. 1 is a sectional view of the present embodiment.

FIG. 2 is a perspective view of a movable member.

FIG. 3 is a perspective view of a Hall IC

[Figure 4] Hall IC block diagram

[Figure 5] Hall IC output characteristic diagram

FIG. 6 is a sectional view showing an unsteady state of the present embodiment.

FIG. 7 is a diagram showing a magnetic flux supplied to the Hall IC and a signal output from the Hall IC.

FIG. 8 is a sectional view showing a modified example of the container body and the printed circuit board.

FIG. 9 is a sectional view showing a modified example of the container body and the printed circuit board.

FIG. 10 is a sectional view showing a modified example of the movable member.

FIG. 11 is a cross-sectional view showing a modified example of the movable member.

FIG. 12 is a sectional view showing a modified example of the movable member.

FIG. 13 is a sectional view showing a modified example of the movable member.

FIG. 14 is a cross-sectional view showing a modified example of the movable member.

FIG. 15 is a cross-sectional view showing an example of a conventional sensor using a reed switch.

[Explanation of symbols]

 1 Acceleration Sensor 2A, 2B, 2C, 2D, 2E, 2F, Movable Member 3A, 3B, 3C Container Body 3b Container Bottom 3c Concave Spherical Curved Surface (Specific Shape) 5 Hall IC 6 Reference Axis (Steady Position) 20 Permanent Magnet 21 Holding member 21a Convex spherical curved surface (specific shape)

Claims (4)

[Claims] 1. A movable member, at least a part of which is provided with a permanent magnet, a non-magnetic container that movably accommodates the movable member in an internal space, and a movable member that is disposed so as to face the movable member and that moves. An acceleration having a Hall IC that detects a change in magnetic flux, and an automatic return mechanism that moves the movable member from a steady position when the steady state changes to a non-steady state and returns to the steady position when the movable member returns to the steady state. An acceleration sensor, wherein the automatic return mechanism has a specific shape. 2. The movable member provided with the permanent magnet,
The acceleration sensor according to claim 1, comprising a holding member that comes into contact with the inner surface of the bottom of the container, and a rod-shaped permanent magnet held by the holding member. 3. The specific shape is such that a concave curved surface is formed on the inner surface of the bottom of the container, and a convex curved surface having a smaller radius of curvature than the concave curved surface is formed on the lower surface side of the holding member constituting the movable member. The acceleration sensor according to claim 1 or 2, which is obtained by 4. The specific shape is such that a concave spherical curved surface is formed on the inner surface of the bottom of the container, and a convex spherical curved surface having a smaller radius of curvature than the concave spherical curved surface is formed on the lower surface side of the holding member constituting the movable member. The acceleration sensor according to any one of claims 1 to 3, which is obtained.