JP2722742B2 - Acceleration detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an acceleration detector for detecting acceleration / deceleration of a moving body such as an automobile.

[Conventional technology]

2. Description of the Related Art Among known acceleration detectors, there is one that detects the movement of a magnetic body that moves due to acceleration with a differential transformer.

FIG. 5 shows an example. When an acceleration in the direction A in the figure is applied, the differential transformer type acceleration detector 51 causes the magnetic body 54 supported by the leaf springs 53a and 53b to elastically deform each leaf spring and to move in the direction B in the figure. Moving. The movement of the magnetic material 54
In the figure, the length of the portion existing in the secondary coil 57b on the right side is longer than the length of the portion existing in the secondary coil 57a on the left side, causing a difference in the induced voltages of the secondary coils 57a and 57b. The acceleration is detected by the difference.

 In the figure, 56 is a primary coil, and 52 is a case.

As a specific conventional example of this type of detector, there is one disclosed in Japanese Utility Model Laid-Open No. 59-95266.

[Problems to be solved by the invention]

This type of detector has a drawback that the magnetic body moves only a small amount with respect to a small acceleration, so that a clear voltage difference is not generated between the secondary coils, and thus the detection sensitivity is poor.

In addition, when the magnetic body is suspended by a leaf spring, there is a problem that if an excessive acceleration is applied, the leaf spring may be permanently deformed or broken.

Further, since a voltage difference is generated due to a change in the relative position between the secondary coil and the magnetic material, a high positioning accuracy is required, and there is a problem that assembling time is reduced, assembling efficiency is reduced, and assembling cost is increased.

An object of the present invention is to provide a differential transformer type acceleration detector which eliminates these problems.

[Means for solving the problem]

In order to solve the above-mentioned problems, the present invention supports a movable magnetic body that moves in accordance with acceleration with a leaf spring between coils on both sides of a differential transformer, and further includes a case on both sides of the movable magnetic body in the movement direction. The stopper of the magnetic material supported by the above is provided with one end thereof present inside the coil of the transformer and keeping a distance at which the magnetic flux is transmitted to the movable magnetic material.

The point at which the primary coil of the transformer is installed may be either the outer peripheral portion of the stopper or the outer peripheral portion of the movable magnetic body.

It is preferable that at least a part of the case is made of a magnetic material, or that a yoke of the magnetic material is provided between the coils on both sides of the leaf spring.

[Action]

The magnetic field generated by the primary coil is transmitted from the stopper to the movable magnetic body, or from the movable magnetic body to the stopper (the relationship of the transmission order changes depending on the installation point of the primary coil), and reaches the inside of the secondary coil. A voltage is induced in the coil. The magnitude of the induced voltage at this time is determined by the amount of magnetic flux passing through the secondary coil, and the amount of magnetic flux passing through the secondary coil is determined by the magnetic resistance value of the magnetic circuit existing on both sides of the leaf spring. However, in the present invention, the detection sensitivity is improved because the stopper of the magnetic material functions to reduce the total magnetic resistance in the circuit and increase the change in magnetic flux with respect to the displacement amount of the movable magnetic material.

That is, when an acceleration is generated and the movable magnetic body moves to one stopper side, the gap between the movable magnetic body and the stopper decreases on one stopper side and expands on the other stopper side. Therefore, on one stopper side, the magnetic resistance due to the gap decreases and the amount of magnetic flux passing through the portion becomes larger as compared with the conventional structure, and on the other stopper side, the magnetic resistance due to the gap increases, which is opposite to the above. Phenomenon occurs. Due to the effect of increasing or decreasing the amount of magnetic flux passing on both sides of the leaf spring, a larger difference than before occurs in the voltage of the secondary coil induced by the passing magnetic flux. Therefore, if this difference is measured, it is possible to detect a small acceleration. .

As described above, the detection principle of the detector of the present invention is different from the conventional one in that an induced voltage difference is not generated between two secondary coils due to a change in relative position between a movable magnetic body and a secondary coil. Since a voltage difference (detector output) is generated by a gap difference between the two stoppers, it is not necessary to ensure relative positional accuracy between the coil and the movable magnetic body. In addition, since the stopper forms a magnetic path to reduce the total magnetic resistance in the two magnetic circuits, the detection sensitivity to a minute change in magnetic resistance is increased, and the output voltage relative to acceleration becomes extremely large.

In addition, since the stopper restricts excessive movement of the movable magnetic body, no excessive load is applied to the leaf spring.

〔Example〕

FIG. 1 shows an outline of the first embodiment. In the acceleration detector 1, one end of a leaf spring 3 is fixed to a case 2, and a movable magnetic body 4 having a predetermined mass is fixed to the other end of the leaf spring, that is, a free end. On both sides of the movable magnetic body 4, stoppers 5 a and 5 b made of a magnetic body are supported by the case 2, and are provided with a predetermined gap between the movable magnetic body 4 and the movable magnetic body 4. Further, primary coils 6a and 6b for generating magnetism and secondary coils 7a and 7b for detecting a change in magnetic flux are provided concentrically on the outer periphery of the movable magnetic body 4 and the stoppers 5a and 5b.
Note that each coil may be supported by a stopper or a case.

In the detector according to the first embodiment configured as described above, when the movable body 4 is accelerated or decelerated, a force of F = M · G is applied to the movable magnetic body 4 if the mass is M and the generated acceleration / deceleration is G. This force F causes the movable magnetic body 4 to be displaced by elastically deforming the leaf spring to a position where it is balanced with the elastic force of the leaf spring 3. The displacement at this time is proportional to the acceleration G if the spring constant of the leaf spring 3 and the mass M of the movable magnetic body 4 are constant.
The gap between 5b and the movable magnetic body 4 also changes in proportion to the acceleration G.

If the acceleration in the direction A in the figure is applied to the acceleration detector 1, the movable magnetic body 4 moves in the direction B, so that the gap decreases on the stopper 5 b side and increases on the stopper 5 a side. . Therefore, on the side of the stopper 5b, the movement of the magnetic flux from the stopper to the magnetic body 4 becomes smooth, and
The amount of magnetic flux transmitted from the secondary coil 6b to the secondary coil 7b increases,
A voltage larger than that at the time of acceleration 0 is induced in the secondary coil. On the other hand, on the stopper 5a side, the magnetic resistance increases due to the increase in the gap, so that the magnetic flux passing through the secondary coil 7a decreases and the output voltage also decreases. The output of the secondary coil at this time is larger than that of the conventional coil 7b by the above-described operation, and smaller than that of the conventional coil 7a.
Accordingly, the output difference between the two coils in comparison with the acceleration is naturally larger than in the conventional case, and therefore, high sensitivity detection can be expected.

Further, if the acceleration acting in the direction A in the figure is too large, the movable magnetic body 4 hits the stopper 5b and is prevented from moving any further. Therefore, excessive flexure of the leaf spring 3 due to excessive acceleration does not occur, and there is no problem of permanent deformation and breakage of the leaf spring.

FIG. 2 is a schematic configuration diagram of the second embodiment. The acceleration detector 11 has the same configuration as that of the first embodiment and operates in the same manner as the first embodiment, except that the leaf spring 13 has a double-supported structure in which the upper and lower points are fixed, and the primary coil 16a , 16b are arranged concentrically around the outer periphery of the movable magnetic body 14, and the secondary coils 17a, 17b are arranged outside (in the front and rear direction of movement), and the stoppers 15a,
The difference from the first embodiment is that 5b is integrated with the case 12. By arranging the primary coil inside (leaf spring side) and the secondary coil outside (case side), the size and weight of the movable magnetic body 14 can be increased without increasing the size of the detector. This is more advantageous in terms of increasing the sensitivity.

In addition, the movable magnetic body 14 having a large mass may cause an output voltage to change due to a movement due to not only the acceleration in the normal direction but also the acceleration in the vertical direction, etc. This has the effect that this problem can also be prevented.

In addition, in the present embodiment, not only the stopper but also the entire case is formed of a magnetic material. This is also because the magnetic resistance of the magnetic circuit around the coil is reduced and the magnetic resistance of the gap portion occupied in the total magnetic resistance. This leads to an increase in the ratio of the acceleration, thereby effectively acting on even higher sensitivity detection of acceleration.

Next, FIG. 3 shows a schematic structure of the third embodiment. The acceleration detector 21 has the same basic structure as those of the first and second embodiments, and performs the same function as these. However, the movable magnetic material 24
Are supported by two cantilevered parallel leaf springs 23a and 23b, and the secondary coils 27a and 27b are arranged concentrically on the inner circumferences of the primary coils 26a and 26b.

In the third embodiment, since two cantilevered leaf springs are used, stable movement of the movable magnetic body can be ensured in the same manner as in the double-supported structure, but the movable magnetic body has a large size as in the cantilevered structure. The displacement amount can be secured, and the opposing performances of stabilization and high output can be simultaneously satisfied.

Further, since the winding width of the coil can be reduced by laminating the primary coil and the secondary coil, it is advantageous when it is difficult to secure a space for installation in the direction in which the acceleration acts.

FIG. 4 shows a fourth embodiment of the present invention. The other structure of the acceleration detector 31 is the same as that of the first embodiment except that a magnetic yoke 8 for reducing the magnetic resistance is provided between the secondary coils 7a and 7b. The yoke 8 includes a primary coil 6a
The magnetic flux generated in step (a) returns to the stopper 5a via the movable magnetic body 4, the yoke 8, and the magnetic case 2 (the same applies to the coil 6b). Therefore, the high magnetic resistance portion in the magnetic circuit is only the gap portion between the stopper and the movable magnetic body, and the change in output due to the gap variation becomes clearer and the detection sensitivity is further improved.

〔effect〕

As described above, according to the acceleration detector of the present invention, the stoppers of the magnetic material are provided on both sides in the moving direction of the movable magnetic material, and the acceleration detector passes through the secondary coil due to the gap difference between the two stoppers and the movable magnetic material. Since the amount of magnetic flux generated is changed, unlike a conventional detector in which a voltage difference is generated by a relative position change between the movable magnetic body and the secondary coil, a change in magnetic flux with respect to the amount of displacement of the movable magnetic body, that is, a potential difference ( Output) and high sensitivity detection can be expected.

In addition, since the stoppers on both sides limit excessive movement of the movable magnetic body, excessive deformation of the leaf spring can be eliminated and permanent deformation and destruction of the leaf spring can be prevented.

Further, as described above, a voltage difference is generated by utilizing a gap difference between the stopper and the stopper, so that positioning of various components becomes easy. That is, since the coil is generally wound around a bobbin made of resin, the dimensional accuracy is poor. Therefore, according to the conventional method, the relative positional accuracy between the movable magnetic body and the coil is inevitably deteriorated. However, in the structure of the present invention, the gap accuracy is determined by a combination of metal workpieces capable of high precision processing,
Further, since the output is determined by the gap, the positioning at the time of assembly is easy as described above.

In addition, when at least the magnetic path constituting portion of the case body is formed of a magnetic material, or when a yoke is provided between the coils, the magnetic resistance in the magnetic circuit is further reduced.
Output can be measured.

Therefore, according to the present invention, high sensitivity detection is possible even with a small size, the reliability against excessive acceleration, impact, etc. is increased, and further, the effects that the manufacturing is easy and the cost can be reduced can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an acceleration detector according to the present invention, FIGS. 2 to 4 are schematic configuration diagrams of another embodiment, and FIG. 5 is a conventional differential transformer type acceleration detection device. FIG. 1, 11, 21, 31 ... acceleration detector, 2, 12, 22 ... case, 3, 13, 23a, 23b ... leaf spring, 4, 14, 24 ... movable magnetic body, 5a, 5b, 15a , 15b, 25a, 25b ... magnetic stopper, 6a, 6b, 16a, 16b, 26a, 26b ... primary coil, 7
a, 7b, 17a, 17b, 27a, 27b ... secondary coil, 8 ... yoke.

Claims (5)

(57) [Claims] An acceleration detector for detecting an acceleration by generating an output difference between secondary coils of a differential transformer by a displacement of a movable magnetic body that moves in accordance with an acceleration. A stopper of a magnetic material supported by a case is provided on both sides in the moving direction of the movable magnetic material, and one end of the stopper is present inside the coil of the transformer, and a magnetic flux is transmitted between the movable magnetic material and the movable magnetic material. An acceleration detector characterized in that the acceleration detector is provided with a distance at which the measurement is performed. 2. The transformer according to claim 1, further comprising:
The acceleration detector according to claim 1, wherein the secondary coil is arranged concentrically. 3. The acceleration detector according to claim 1, wherein a primary coil of the transformer is concentrically arranged on an outer peripheral portion of the movable magnetic body. 4. The acceleration detector according to (1), (2) or (3), wherein a part or the whole of the case is made of a magnetic material. 5. Between the coils on both sides of the leaf spring,
The acceleration detector according to any one of claims (1) to (4), further comprising a magnetic yoke.