JPH1144706A - Acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acceleration sensor with a simpler structure. SOLUTION: This acceleration sensor is provided with a wound coil 1, a pendulum 2 made of a flexible magnetic material and cantilever-supported at the base end section 2a, two magnetic pieces 3, 4 having facing sections 3b, 4b facing both side faces of the tip section 2c of the pendulum 2 at the prescribed voids 3a, 4a respectively and inserted into the inner space la of the coil 1 respectively, a permanent magnet 5 magnetizing two magnetic pieces 3, 4 to different poles respectively, a detector 6 detecting the warp displacement quantity when acceleration is applied based on the change quantities of the electrostatic capacities existing in the prescribed voids 3a, 4a at two positions, and a readout section 8 reading the value of the exciting current for exciting the coil 1 so that the pendulum 2 is magnetized to negate the displacement of the pendulum 2 via feedback control based on the signal of the detector 6 and both magnetic attractions between the prescribed voids 3, 4 at two positions are equilibrated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called servo type acceleration sensor for detecting the acceleration by performing feedback control so as to cancel the displacement of a pendulum due to an applied acceleration.

[0002]

2. Description of the Related Art Conventionally, there is an acceleration sensor of this type having a configuration shown in FIG. This is a pendulum A,
Coil B, permanent magnet C, detector D, amplifier E, reading unit F
And a base G.

The pendulum A is formed in a rod shape from a flexible magnetic material, and its base end is cantilevered by a base G.

The coil B is fixed to the pendulum A with its central axis in a direction perpendicular to the longitudinal direction of the pendulum A and both open ends located on both sides of the pendulum A.

The permanent magnet C is disposed on each side of the pendulum A with one end inserted into both open ends of the coil B. The magnetic fluxes of the two permanent magnets C, C Are generated so as to intersect each coil wire of the coil B in a direction orthogonal to the central axis of the coil B.

The detector D is connected to two detection coils D, D provided on both sides of the tip of the pendulum A, respectively. The two detection coils D and D pass through the pendulum A
The magnetic fluxes of the permanent magnets C are separated from the tip of the pendulum A and flow so as to form closed magnetic paths in a balanced state. When the tip of the pendulum A bent by the application of the acceleration is displaced in either direction of the two detection coils D, D, the equilibrium state of the two detection coils D, D is lost. When the magnetic velocity flowing through each increases or decreases, a voltage proportional to the amount of displacement is generated, and the voltage is detected by the detector D.

After the detection signal of the detector D is amplified by the amplifier E, it is fed back to the coil B, and an exciting current proportional to the amount of displacement flows through the coil B. Then, the magnetic fluxes of the permanent magnets C, C cross each coil wire of the coil B in which the exciting current flows in a direction orthogonal to the center axis of the coil B, so that the coil fixed to the pendulum A
B is moved in a direction to cancel the displacement of the pendulum A by the Lorentz force, and the pendulum A returns to the equilibrium state.

At this time, the value of the exciting current flowing through the coil B is proportional to the applied acceleration.
The acceleration is read as a voltage generated by passing the exciting current through the resistor.

[0009]

In the above-described conventional acceleration sensor, the acceleration can be detected by performing feedback control so as to cancel the displacement of the pendulum A due to the applied acceleration.

However, since the coil B through which the exciting current for feedback control flows is fixed to the pendulum A, it moves together with the pendulum A. Therefore,
When wiring to the coil B, it is necessary to take into consideration the prevention of disconnection due to movement, and the structure becomes complicated accordingly.

The present invention has been made in view of the above points, and an object of the present invention is to provide an acceleration sensor having a simpler structure.

[0012]

Means for Solving the Problems In order to solve the above-mentioned problems, the invention according to claim 1 comprises a wound coil,
The coil includes a pendulum made of a flexible magnetic material and having a cantilevered base end, and opposing portions that oppose each other with a predetermined gap with respect to both side surfaces of the tip of the pendulum. Two magnetic pieces respectively inserted into the two spaces, a permanent magnet that magnetizes the two magnetic pieces to different polarities, and a deflection displacement amount when acceleration is applied exists in the two predetermined gaps. A detector that detects the amount of change in capacitance,
In order to perform feedback control to cancel the displacement of the pendulum based on the signal of the detector, magnetize the pendulum and excite the exciting current for exciting the coil so that both magnetic attractive forces of the two predetermined gaps are balanced. A reading unit for reading a value.

According to a second aspect of the present invention, in the first aspect of the present invention, the magnetic piece has a structure in which the facing portion is locally formed to be wide.

According to a third aspect of the present invention, in the first aspect of the present invention, the pendulum has a structure in which a thin portion is provided near a base end thereof.

According to a fourth aspect of the present invention, in the third aspect of the invention, a plurality of the thin portions are provided, and the plurality of the thin portions are formed at a base end and a tip end of the pendulum. It is configured to be provided substantially symmetrically with respect to a line connecting the centers.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the reading section also reads a direction in which the exciting current flows.

According to a sixth aspect of the present invention, in the first aspect, the pendulum and the two magnetic pieces are supported by a coil frame around which the coil is wound. I have to.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

Reference numeral 1 denotes a coil, which is wound around a winding drum 11a of a coil frame 11. Reference numeral 2 denotes a pendulum, which is made of a flexible magnetic material and is formed in a square shape in plan view, and has a base end 2a that is cantilevered by an extension 11c that extends from the one flange 11b of the coil frame 11. It is fixed. In FIG. 2, the coil frame 11 is omitted. Near the base end 2a of the pendulum 2, thin portions 2b, 2b are provided. For details, see the thin section 2b, 2b
Are provided substantially symmetrically with respect to a line connecting the centers of the base end 2a and the tip 2c of the pendulum 2.

Reference numerals 3 and 4 denote two magnetic pieces.
It has a T-shape in a plan view, and has a predetermined gap 3a, 4a with respect to both side surfaces of the tip 2c of the pendulum 2, and the tip portions which become the opposing portions 3b, 4b opposing each other are locally widened. I have. The magnetic pieces 3 and 4 are inserted into the coil 1, more specifically, into the inner space 1 a of the winding body 11 a of the coil frame 11, and are connected to one of the flange 11 b and the extension 11 c of the coil frame 11. It is fixed in between.

Reference numeral 5 denotes a permanent magnet which is sandwiched between the two magnetic pieces 3 and 4 and is fixed in the space inside the winding drum portion 11a of the coil frame 11. In the permanent magnet 5, both magnetic pieces are magnetized to different polarities, for example, one magnetic piece 3 is magnetized to the N pole and the other magnetic piece 4 is magnetized to the S pole.

Reference numeral 6 denotes a detector, two magnetic pieces 3, 4 and a pendulum.
2 are connected to the base end 2a of the second predetermined gap 3a, 4a
The difference between the capacitances existing in the two is detected.
That is, when acceleration is applied and the pendulum 2 bends, the tip 2c of the pendulum 2 is displaced in any direction from the equilibrium state at the center position between the two magnetic pieces 3 and 4,
Since there is a difference between the capacitances existing in the two predetermined gaps 3a and 4a, the difference is detected as a signal of the amount of bending displacement of the pendulum 2 according to the acceleration.

Reference numeral 7 denotes an amplifier, which is connected to the detector 6 and one end of the coil, and amplifies a detection signal from the detector 6. The amplified detection signal is fed back to the coil 1 so that the excitation current is proportional to the applied acceleration and a power supply (not shown) connected to the amplifier 7 so as to cancel the displacement of the tip 2a of the pendulum 2. And flows through the coil 1.

More specifically, for example, if the tip 2c of the pendulum 2 which has been in an equilibrium state due to acceleration is displaced in a direction approaching one of the magnetic pieces 3, the two predetermined gaps 3 are provided.
In a and 4a, as described above, a difference occurs in the capacitance, and a permanent magnet is formed in proportion to the difference in the capacitance.
The two magnetic pieces 3 and 4 magnetized in different polarities in step 5 also cause the two magnetic attraction forces acting on the tip 2c of the pendulum 2 to be stronger in one of the magnetic pieces 3 but based on the detection signal of the detector 6. When the exciting current proportional to the amount of displacement of the pendulum 2 flows through the coil 1 and the tip 2c of the pendulum 2 is magnetized to the N pole, the tip 2c of the pendulum 2 generates a repulsive force by one magnetic piece 3. , The other magnetic piece
4 receives the suction force. Then, pendulum 2
Is moved toward the center position between the two magnetic pieces 3 and 4 in the direction to cancel the displacement, and returns to the equilibrium state.
As a result, both capacitances and both magnetic attractive forces in the two predetermined gaps 3a and 4a are balanced. When the acceleration application direction is opposite to the above, the exciting current of the coil 1 also flows in the opposite direction.

Reference numeral 8 denotes a reading unit. A resistor is connected to the other end of the coil 1, a current of the coil 1 proportional to the applied acceleration is passed through the resistor, and a voltage generated at both ends of the resistor is read to read the acceleration. The value is detected. At this time, the direction in which the acceleration current is applied is also detected by reading the direction in which the exciting current flows.

In such an acceleration sensor, two coils 1 each of which passes an exciting current for feeding back so as to cancel the displacement of the pendulum 2 when the acceleration is applied are inserted into the wound inner space. Since the opposing portions 3b, 4b of the magnetic pieces 3, 4 have predetermined gaps 3a, 4a on both side surfaces of the tip 2c and are not fixed to the opposing pendulum 2,
When the pendulum 2 is flexed and displaced, it does not move together and is fixed, and the coil 1 is hardly disconnected.Therefore, it is possible to adopt a simple structure that does not require wiring to prevent disconnection due to movement. it can.

Further, the facing portion 3 formed locally and widely.
Since the areas b and 4b increase in area as compared with those having a uniform width, the amount of change in the capacitance existing in the predetermined gaps 3a and 4a also increases with the increase in the area, and the amount of deflection displacement increases. , The detection accuracy of the acceleration becomes higher, and thus the detection accuracy of the acceleration can be increased.

The pendulum 2 has a thin portion 2b near the base 2a.
Is provided, even if the acceleration is smaller, the sensor is bent, so that the accuracy of detecting the acceleration is higher.

The plurality of thin portions 2b, 2b are substantially symmetrical with respect to a line connecting the center of the cantilevered base end 2a of the pendulum 2 and the center of the tip 2c where the capacitance changes. Is provided, the only one thin portion 2b side does not bend significantly, and the pendulum 2 does not bend in a twisted state, so that it faces the opposing portions 3b, 4b of the magnetic pieces 3, 4. The tip 2c is no longer twisted, and an error in detecting acceleration can be reduced.

By reading the direction in which the exciting current flows for feedback control, it is possible to detect not only the value of the acceleration but also the direction in which it is applied.

Further, since the pendulum 2 and the two magnetic pieces 3 and 4 are both supported by the coil frame 11 around which the coil 1 is wound, the two magnetic pieces 3 and 4 are attached to the tip of the pendulum 2. The predetermined intervals 3a and 4a provided on both side surfaces of the portion 2c can be set with high accuracy, and the acceleration detection accuracy can be improved accordingly.

In the present embodiment, the opposing portions 3b and 4b of the magnetic pieces 3 and 4 are locally formed to be wide. However, for example, when the accuracy of detecting the acceleration is sufficiently high, the width is uniform. May be formed.

In this embodiment, the pendulum 2 has a base end portion.
The thin portion 2b which is easily bent is provided in the vicinity of 2a. However, this is not necessary when, for example, the amount of bending displacement necessary for detecting the applied acceleration can be sufficiently ensured.

In this embodiment, a plurality of thin portions 2
Although b and 2b are provided substantially symmetrically with respect to a line connecting the centers of the base end 2a and the tip 2c of the pendulum 2, for example, there is a possibility that only one of the thin portions 2b is largely bent. When there is no, there is no need to provide such.

In the present embodiment, the reading unit 8 reads the direction in which the exciting current flows. For example, when the direction in which the applied acceleration is applied is determined, That is not needed.

In this embodiment, the pendulum 2 and the two magnetic pieces 3 and 4 are supported by the coil frame 11 around which the coil 1 is wound. For example, the mechanical strength of the coil frame 11 is reduced. In a case where the strength is not so strong, the support may be supported by a member provided separately such as a strong base or the like, and there is no limitation.

In this case, the pendulum 2 has opposed portions 3b, 4b having predetermined gaps 3a, 4a with respect to both side surfaces of the tip 2c of the pendulum 2, and is inserted into the inner space 1a of the coil 1 respectively. If so, the coil may be wound in a hollow shape by the coil 1 itself without using the coil frame 11 as in the present embodiment.

[0038]

According to the first aspect of the present invention, two coils, each of which is provided with an exciting current for feeding back so as to cancel the displacement of the pendulum when an acceleration is applied, are inserted into the wound inner space, respectively. The two sides of the tip end of the opposing portion of the magnetic piece do not have a predetermined gap and are not fixed to the opposing pendulum, so when the pendulum is bent and displaced, it does not move together and remains in a fixed state. Since the coil is hardly disconnected, it is possible to provide a simple structure that does not require wiring in consideration of prevention of disconnection due to movement.

According to the second aspect of the present invention, in addition to the effect of the first aspect of the present invention, the opposed portion formed locally wide has an increased area as compared with the case where the width is formed uniformly. Accordingly, the amount of change in the capacitance existing in the predetermined gap also increases with an increase in the area, and the accuracy of detecting the amount of bending displacement increases, so that the accuracy of detecting the acceleration can be increased.

According to the third aspect of the present invention, in addition to the effects of the first or second aspect, the pendulum is provided with a thin portion near the base end, so that even a smaller acceleration can be obtained. Due to the bending, the accuracy of detecting the acceleration becomes higher.

According to a fourth aspect of the present invention, the plurality of thin portions are substantially symmetrical with respect to a line connecting the center of the cantilevered base end of the pendulum and the center of the tip end where the capacitance changes. Since only one of the thin-walled portions does not bend significantly, and the pendulum does not bend in a twisted state, the tip end of the magnetic piece facing the opposing portion is not twisted, An error in detecting the acceleration can be reduced.

According to a fifth aspect of the present invention, in addition to the effect of the first aspect of the present invention, by reading the direction of the exciting current flowing for feedback control, the value of the acceleration together with the value of the acceleration can be obtained. The direction of application can also be detected.

According to a sixth aspect of the present invention, in addition to the effect of the first aspect, the pendulum and the two magnetic pieces are all supported by the coil frame around which the coil is wound. Since the two magnetic pieces are provided on both side surfaces of the tip of the pendulum, predetermined intervals can be accurately set.
Accuracy of acceleration detection is also improved accordingly.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention together with a circuit diagram.

FIG. 2 is a partial perspective view of the same.

FIG. 3 is a cross-sectional view showing a conventional example together with a circuit diagram.

[Explanation of symbols]

 1 Coil 1a Inner space 11 Coil frame 2 Pendulum 2a Base 2b Thin part 2c Tip 3 Magnetic piece 3a Predetermined interval 3b Opposing part 4 Magnetic piece 4a Predetermined interval 4b Opposing part 5 Permanent magnet 6 Detector 8 Reading unit

Claims (6)

[Claims] 1. A pendulum having a wound coil, a pendulum made of a flexible magnetic material and having a base end cantilevered, and a predetermined gap with respect to both side surfaces of a tip end of the pendulum. Two magnetic pieces each having an opposing portion facing each other and inserted into the inner space of the coil, permanent magnets for magnetizing the two magnetic pieces to different polarities, and bending when acceleration is applied A detector for detecting the amount of displacement based on the amount of change in the capacitance existing in the two predetermined gaps; and magnetizing the pendulum for feedback control to cancel the displacement of the pendulum based on a signal from the detector. A reading unit for reading a value of an exciting current for exciting the coil so that both magnetic attractive forces in the predetermined gap are balanced. 2. The acceleration sensor according to claim 1, wherein the opposing portion of the magnetic piece is locally wide. 3. The acceleration sensor according to claim 1, wherein the pendulum is provided with a thin portion near a base end thereof. 4. The thin-walled portion is provided with a plurality of thin-walled portions, and the plurality of thin-walled portions are provided substantially symmetrically with respect to a line connecting centers of a base end and a tip end of the pendulum. The acceleration sensor according to claim 3, wherein: 5. The acceleration sensor according to claim 1, wherein the reading unit reads a direction in which the exciting current flows. 6. The acceleration sensor according to claim 1, wherein the pendulum and the two magnetic pieces are supported by a coil frame around which the coil is wound.