JPH04313060A - acceleration detector - Google Patents

Abstract

PURPOSE:To achieve downsizing, simplification, cost reduction and the like of a servo- type acceleration detector which detects the changing amount of a mass piece that is moved in response to acceleration with a displacement detecting part, amplifies the electric signal from the displacement detecting part, feeds back the signal to torquer coils, returns the mass piece to the balance point at the zero displacement by the electromagnetic force generated in the torquer part, and obtains the input acceleration based on the current flowing through the torquer coil at this time. CONSTITUTION:A differential-transformer type displacement detecting part is formed of a movable magnetic body 4 which is fixed to a plate spring 3, primary coils 5a and 5b and secondary coils 6a and 6b. A torquer part is formed of torquer coils 7a and 7b and permanent magnets 8a and 8b which are bonded to the end parts of the movable magnetic body 4 in the moving direction. The torquer part makes the magnetic fluxes of the torquer coils act on the permanent magnets so as to return the movable magnetic body to the balance point. Thus, the displacement detecting part and the torquer part form a unitary body, and simplification of the structure, downsizing and cost reduction are achieved. Since the airtight sealing is not indispensable in the differential transformer type displacement detecting part, the cost becomes advantageous also in this point.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration detector for detecting acceleration and deceleration of a moving body such as an automobile, and particularly to a servo type acceleration detector.

0002

[Prior Art] A conventional servo-type acceleration detector has a torquer coil in its pendulum, detects the swing of the pendulum due to the application of acceleration by a change in the amount of light or a change in capacitance, and a torquer section consisting of a permanent magnet and a torquer coil. Some devices return the pendulum to an equilibrium point with zero swing and measure the current flowing through the torquer coil at this time to detect acceleration. An example is shown in FIG. In this servo type acceleration detector 51,
When acceleration is applied in the direction, the pendulum 53 moves in the B direction. This displacement is converted into an electrical signal by an optical or capacitive displacement detection unit 55 shown in a dotted line frame, and this electrical signal is amplified by an electric circuit and returned to the torquer coils 57a and 57b, and is permanently connected to the torquer coil. The pendulum is returned to the equilibrium point by the electromagnetic force generated in the torquer section composed of magnets 58a and 58b. Note that specific examples of this type of acceleration detector include:
There is one shown in Japanese Patent Application Laid-Open No. 58-90173.

0003

[Problems to be Solved by the Invention] Conventional acceleration detectors of this type have a structure in which the torquer part and the displacement detection part are separated, which increases the number of parts, complicates the structure, and increases assembly costs. There are challenges.

[0004]Moreover, those employing an optical or capacitance type displacement detection section have poor environmental resistance, and the displacement detection section may be exposed to water or water.
Affected by adhesion of dust, etc. Therefore, it is necessary to hermetically seal the case of the acceleration detector, which requires high processing accuracy and increases processing costs.

[0005]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention supports a movable magnetic body that moves according to acceleration with a leaf spring or the like, and arranges the movable magnetic body and the outer periphery of the movable magnetic body. A displacement detection section is formed by a primary coil and a secondary coil of a differential transformer. In addition, the torquer section that amplifies and returns the electric signal from this displacement detection section has a permanent magnet attached to the end of the movable magnetic body in the direction of movement, and has a torquer coil through which a current according to the feedback signal flows, and is fixed at a fixed position. The magnetic flux generated by the torquer coil fixed to the magnet generates an attractive force or a repulsive force between the magnet and the permanent magnet, and this force acts as a return force to the equilibrium point and is integrated with the displacement detecting section. Note that, as described later, the torquer coil may be arranged on the outer periphery of the movable magnetic body, or may be disposed at a position facing both ends of the movable magnetic body in the moving direction.

Furthermore, in the first solution, the displacement detecting section is provided with a primary coil and a secondary coil on the outer periphery of the movable magnetic body.
Two sets of the next coils may be arranged symmetrically, and one set of the torquer coils may be arranged on the left and right sides corresponding to the displacement detecting section. In this second solution, the polarity of the pair of permanent magnets provided at both ends of the movable magnetic body in the moving direction is set in the same direction with respect to the movable magnetic body, and the left and right primary coils are set in opposite phases to each other. The left and right secondary coils are wound and connected so that they are in phase with each other, and the frequency of the alternating current applied to the primary coil is sufficiently larger than the natural frequency of the mechanical system, and the direct current component is It is recommended that it not be included.

Alternatively, the polarities of a pair of permanent magnets provided at both ends of the movable magnetic body in the moving direction are set in opposite directions with respect to the movable magnetic body, and the left and right primary coils are wound so as to be in phase with each other. The left and right secondary coils are wound and connected so that they are in opposite phases to each other, and the frequency of the alternating current applied to the primary coil is sufficiently higher than the natural frequency of the mechanical system,
And it may be one that does not contain a direct current component.

[0008]

[Operation] When an alternating current is passed through the primary coil to generate an alternating magnetic field, the magnetic flux generated by the primary coil induces a voltage in the secondary coil via the movable magnetic body. The magnitude of the induced voltage at this time is determined by the amount of magnetic flux passing through the secondary coil, while the amount of magnetic flux passing through the secondary coil is determined by the amount of displacement of the movable magnetic body. Therefore, an output corresponding to the acceleration can be obtained from the displacement detection section.

[0009] The output signal from the displacement detecting section which is proportional to this acceleration is amplified and fed back to the torquer coil. When current flows through the torquer coil, a magnetic field proportional to the amount of current flowing through the torquer coil is generated, and a torque corresponding to the magnetic field strength is applied to the permanent magnet at the end of the movable magnetic body placed in this magnetic field. This torque becomes a tensile force or a repulsive force depending on the direction of the current flowing through the torquer coil. Therefore, if the current is made to flow through the torquer coil in a direction in which the direction of the torque generated by the magnetic field generated by the torquer coil is opposite to the direction in which the movable magnetic body is displaced in response to acceleration, the movable magnetic body will always have the output of the displacement detector. It is returned to the zero position (the equilibrium point of zero displacement), and a current corresponding to the acceleration flows through the torquer coil, and input acceleration can be detected from this current.

[0010] As described above, in the present invention, since a differential transformer is used in the displacement detecting section, it has excellent environmental resistance and does not necessarily require airtight sealing. Furthermore, since the displacement detection part and the torquer part are integrated, the shape is not large, and the structure is simple and inexpensive, resulting in a servo-type acceleration detector. However, in the first and second solution means, since permanent magnets are joined to both ends of the movable magnetic body, the alternating current applied to the primary coil of the differential transformer exerts an electromagnetic force on the permanent magnets.
Forces other than the force due to input acceleration may be applied to the movable magnetic body.

Furthermore, since the displacement of the movable magnetic body is the displacement of the permanent magnet, it results in a change in magnetic flux and induces a voltage in the secondary coil. Due to the principle of a differential transformer, an induced voltage proportional to the displacement of the movable magnetic body is generated in the secondary coil, and there is a possibility that the induced voltage due to the displacement of the permanent magnet will be added to this induced voltage, which serves as a signal. be.

[0012] Such a phenomenon may lead to deterioration of the performance of the acceleration detector and instability of the servo system. Therefore, in the third and fourth solutions, the primary coil is provided with a vibration frequency that is sufficiently higher than the natural frequency of the mechanical system. The occurrence of the above phenomenon is prevented by applying an alternating current that has a frequency and does not contain a direct current component, and by specifying the polarity of the permanent magnet and the winding connection method of the primary coil and secondary coil.

According to the third solution, the electromagnetic force generated by the alternating current applied to the left and right primary coils is in the same direction with respect to the permanent magnet, but the frequency of the alternating current is equal to the natural frequency of the mechanical system. Since it is sufficiently larger and does not contain a direct current component, no mechanical vibration occurs and the electromagnetic force exerted on the movable magnetic body via the permanent magnet can be ignored.

When the permanent magnet is displaced, the magnetic flux generated by the permanent magnet increases in one of the secondary coils, and an induced voltage is generated in the secondary coil in a direction that reduces this magnetic flux. In the other secondary coil, the magnetic flux generated by the permanent magnet is reduced, and an induced voltage is generated in a direction that increases this magnetic flux. Since the polarities of the permanent magnets provided at both ends of the movable magnetic body are in the same direction, the magnetic fluxes generated by the two permanent magnets are in the same direction. Therefore, as described above, an induced voltage is generated in one secondary coil in the direction of increasing the magnetic flux in the same direction, and an induced voltage is generated in the other secondary coil in the direction of decreasing it. In other words, induced voltages with opposite phases are generated in the left and right secondary coils. Therefore, by winding and connecting the secondary coils in the same phase, the induced voltages cancel each other out, and the displacement of the permanent magnet does not affect the secondary coils.

Similar to the third solution, the fourth solution applies alternating current having a frequency sufficiently larger than the natural frequency of the mechanical system and no direct current component to the primary coil, so that the primary coil remains permanently The influence of electromagnetic force exerted on the movable magnetic body via the magnet can be ignored. In the fourth solution, the polarities of the permanent magnets provided at both ends of the movable magnetic body are opposite, so the magnetic fluxes generated by the two permanent magnets are opposite. Therefore, an induced voltage is generated in one secondary coil in a direction that increases the magnetic fluxes in opposite directions, and in the other secondary coil, an induced voltage is generated in a direction that decreases the magnetic fluxes. In other words, induced voltages of the same phase are generated in the left and right secondary coils. Therefore, by winding and connecting the secondary coils in opposite phases to each other, the induced voltages cancel each other out, and the secondary coil is not affected by changes in the permanent magnet.

[0016]

Embodiment FIG. 1 shows a schematic configuration diagram of a first embodiment. In this acceleration detector 1, one end of a leaf spring 3 is fixed to a case 2 made of a magnetic material, and a movable magnetic material 4 of a predetermined mass is fixed to the other end, that is, the free end of the leaf spring 3. And the movable magnetic body 4
Permanent magnets 8a and 8b are connected to both ends of the magnet. Also,
On the outer periphery of the movable magnetic body 4, there are primary coils 5a, 5b, secondary coils 6a, 6b that detect changes in magnetic flux, and torquer coils 7a, 7b that generate torque to return the movable magnetic body 4 to a predetermined position. are arranged in layers on concentric circles. In this case, since the direction of the torque can be changed by changing the direction of the current flowing through the torquer coil, the torquer coil and the permanent magnet can operate with either 7a, 8a or 7b, 8b. The non-magnetic displacement stoppers 9a and 9b supported by the case 2 include permanent magnets 8a,
Excessive movement of the movable magnetic body 4 is restricted without being affected by the force 8b, thereby preventing permanent deformation and damage of the leaf spring 3. Furthermore, since the case 2 is made of a magnetic material, it has a magnetic shielding effect, and has a structure in which the influence of an external magnetic field does not reach the torquer portion, and also leads to an increase in the output of the secondary coil due to the configuration of the magnetic circuit. Note that a pendulum may be substituted for the illustrated leaf spring 3.

The acceleration detector 1 of this first embodiment now has the following features:
Assuming that acceleration is applied in the direction A in the figure, the feedback signal output from the displacement detection section and amplified by the electric circuit is directed to the torquer coil 7b in the direction in which a magnetic attraction force is generated between the torquer coil 7a and the permanent magnet 8a. Permanent magnet 8 for
Since the current flows in the direction in which magnetic repulsion is generated between the coils and B (the direction of the current is reversed in both coils when acceleration is applied in the B direction), a torque acts on the movable magnetic body 4 in the A direction. , this force balances the moving force due to acceleration, and the movable magnetic body 4 returns to the equilibrium point of zero displacement. The return torque to the equilibrium point can also be generated by making the forces acting on both ends of the movable magnetic body both attractive or repulsive. That is, if the currents of the two torquer coils are made to increase in one and decrease in the other in response to the feedback signal, the movable magnetic body is returned to the equilibrium point by the difference in the forces acting on both ends. Furthermore, as described above, it is also possible to arrange the permanent magnet and the torquer coil on only one side, and to generate a return torque by changing the direction of the current flowing through the torquer coil when the direction of acceleration is reversed.

FIG. 2 is a schematic diagram of the second embodiment. This acceleration detector 11 has a configuration similar to that of the first embodiment and functions similarly. However, this embodiment differs from the first embodiment in that two leaf springs 13a and 13b are used, and that the primary coil 15 is integrated into one and separated from the secondary coil and torquer coil. In this embodiment, since two leaf springs are used, there is an effect of reducing the influence of displacement of the movable magnetic body 14 due to acceleration input in directions other than directions A and B in the figure. Also, 1
Since the next coil is separated from other coils, there is sufficient space in the winding width direction of the coil, but it is suitable when there is no space available in the radial direction of the coil.

FIG. 3 is a schematic diagram of the third embodiment. This acceleration detector 21 also has the same basic structure as the former two, and functions similarly to them. However, the point that the leaf spring 23 has a double-sided structure, and the primary coils 25a, 25b
This is different from the former two in that the secondary coils 26a and 26b are arranged in parallel, and the torquer coils 27a and 27b are stacked on the outer periphery thereof. Similarly to the second embodiment, in this embodiment, stable movement of the movable magnetic body 24 can be ensured by the double-sided structure of the leaf spring, and the space in the coil radial direction can be reduced.

FIG. 4 is a schematic diagram of the fourth embodiment. This acceleration detector 31 also has the same basic structure as the previous three, and functions similarly to them. However, Torca coil 3
It differs from the former three in that 7a and 37b are arranged at positions facing both ends of the movable magnetic body 34 in the moving direction. Incidentally, in each of the embodiments, damper liquid can be sealed in the case in order to improve vibration resistance.

Next, FIGS. 5 and 6 show the polarity of the permanent magnet bonded to the movable magnetic body of the embodiments shown in FIGS. 1, 3, and 4, and the relationship between the primary coil and secondary coil provided on the outer periphery of the permanent magnet. The specified example will be explained. In the embodiments of FIGS. 1, 3 and 4,
Although the direction of the permanent magnet and the winding connection method of the primary coil and secondary coil are not clearly mentioned, the permanent magnet, 1
Depending on the configuration of the secondary coil and the secondary coil, the alternating current applied to the primary coil may exert an electromagnetic force on the permanent magnet, and a force other than the force due to input acceleration may be applied to the movable magnetic body. Further, an induced voltage due to displacement of the permanent magnet may be added to the induced voltage generated in the secondary coil. these are,
This may lead to a decline in the performance of the acceleration detector and destabilization of the servo system.

In order to avoid such a problem, in FIG. 5, permanent magnets 8a and 8b are provided at both ends of the movable magnetic body 4 so that the same polarity of the magnetic poles are directed in the same direction. The secondary coils 5a, 5b are connected by winding so that they are in opposite phases, and the left and right secondary coils 6a, 6b are connected by winding so that they are in phase. And in this case, 1
An AC power source having a frequency sufficiently higher than the natural frequency of the mechanical system of the acceleration detector and containing no DC component is applied to the secondary coils 5a and 5b.

Although not shown, the structure of the permanent magnet and the method of connecting the primary coil and secondary coil of this embodiment can of course be applied to the embodiments shown in FIGS. 3 and 4. Therefore, although the symbols in FIG. 1 are used in the embodiment of FIG. 5, when applied to FIGS. 3 and 4, the symbols are replaced with corresponding parts.

In this embodiment with such a configuration, 1
Next, when an alternating current is applied to the coils 5a, 5b, electromagnetic force in the same direction acts on the left and right permanent magnets 8a, 8b, and they momentarily try to move in either the left or right direction. However, in this case, the current applied to the primary coils 5a, 5b has a frequency sufficiently larger than the natural frequency of the mechanical system and does not contain a DC component, so the permanent magnets 8a, 8b
does not respond to the switching of the alternating current, and is not displaced to the left or right by the electromagnetic force. Therefore,
The influence of electromagnetic force on the movable magnetic body 4 can be ignored.

On the other hand, when acceleration is applied to the acceleration detector and the movable magnetic body 4 and the permanent magnets 8a and 8b try to move, the permanent magnets 8a and 8b are provided on the movable magnetic body 4 with their polarities in the same direction. Therefore, the magnetic flux changes due to the displacement of the permanent magnets 8a and 8b are in opposite directions on the left and right (if one increases, the other decreases). Since the secondary coils 6a and 6b are connected in the same phase, the induced voltages in the secondary coils cancel each other out. Therefore, the influence of the induced voltage in the secondary coil caused by the displacement of the permanent magnets 8a, 8b can be ignored.

In the embodiment shown in FIG. 6, permanent magnets 8a and 8b are provided at both ends of the movable magnetic body 4 so that the polarities of the magnetic poles are directed in opposite directions, and the left and right primary coils 5a and 5b are in phase with each other. The left and right secondary coils 6a and 6b are wound and connected in opposite phases to each other. Note that this embodiment can also be applied to the embodiments shown in FIGS. 3 and 4.

[0027] Also in this case, the primary coils 5a, 5b
By applying an alternating current with a frequency sufficiently higher than the natural frequency of the mechanical system and containing no direct current component to
The effect of electromagnetic force on is negligible.

[0028] Also, due to the change in magnetic flux caused by the displacement of the permanent magnets 8a, 8b when acceleration is applied, the secondary coils 6a, 6
Since the secondary coils 6a and 6b are connected in opposite phases, the induced voltage generated in the permanent magnets 8a, 6b is also canceled out by each other.
The influence of the induced voltage in the secondary coil caused by the displacement of 8b can also be ignored. As described above, according to the embodiments shown in FIGS. 5 and 6, the influence of the electromagnetic force generated by the alternating current flowing through the primary coil on the movable magnetic body through the permanent magnet can be ignored, and the electromagnetic force that is bonded to the movable magnetic body can be ignored. The influence of the voltage induced in the secondary coil by the displacement of the permanent magnet can be ignored, so the performance of the acceleration detector is not degraded, and the cause of instability of the servo system can be eliminated.

[0029]

[Effects of the Invention] As explained above, since the acceleration detector of the present invention integrates the differential transformer type displacement detection section and the torquer section, it can be expected to be miniaturized. In addition, the integration simplifies the structure, reducing assembly costs, and since a differential transformer is used in the displacement detection section, it has excellent environmental resistance, eliminating the need for airtight sealing, etc. Therefore, the processing cost can be reduced, and the effect of being advantageous in terms of cost can be obtained.

Furthermore, when the displacement detection section is composed of a primary coil and a secondary coil arranged symmetrically,
The effect of the electromagnetic force generated by the alternating current flowing through the primary coil on the movable magnetic body can be ignored, and the displacement of the permanent magnet connected to the movable magnetic body cancels out the voltage induced in the secondary coil. The primary coil and secondary coil are wound. Therefore, it does not cause performance deterioration of the acceleration detector,
An advantage is obtained that the operation of the servo system is stable.

[Brief explanation of drawings]

[FIG. 1] A schematic configuration diagram showing an example of an acceleration detector of the present invention.

[Figure 2] Schematic configuration diagram of another embodiment

[Figure 3] Schematic configuration diagram of another embodiment

[Figure 4] Schematic configuration diagram of another embodiment

[Figure 5] Schematic diagram of a circuit showing the winding connection of the primary coil and secondary coil to the permanent magnets at both ends of the movable magnetic body

[Figure 6]
Schematic diagram of a winding connection circuit different from Figure 5

[Figure 7] Schematic configuration diagram of a conventional servo-type acceleration detector

[Explanation of symbols]

1, 11, 21, 31, 51 Acceleration detector 2, 12
, 22, 32, 52 Case 3, 13a, 13b, 2
3, 33 Leaf springs 4, 14, 24, 34 Movable magnetic bodies 5a, 5b, 15, 25a, 25b, 35a, 35b
Primary coils 6a, 6b, 16a, 16b, 26a, 26b, 36a
, 36b Secondary coils 7a, 7b, 17a, 17b, 27a, 27b, 37a
, 37b, 57a, 57b Torca coil 8a, 8b
, 18a, 18b, 28a, 28b, 38a, 38b,
58a, 58b Permanent magnets 9a, 9b, 19a, 19
b, 29a, 29b, 39a, 39b Displacement stopper 50 Hinge 53 Pendulum 54a, 54b Yoke 55 Displacement detection section

Claims (7)

[Claims] Claim 1: A movable magnetic body that moves in accordance with acceleration, a permanent magnet that is joined to an end of the movable magnetic body in the direction of movement, and a primary coil that detects displacement of the movable magnetic body and generates an electrical signal. A differential transformer type displacement detection section consisting of a secondary coil, and a torquer that amplifies the electric signal from this displacement detection section to a torquer coil fixed at a fixed position and returns it to return the movable magnetic body to an equilibrium point of zero displacement. The torquer section has a magnetic flux generated by the torquer coil to generate an attractive force or a repulsive force with the permanent magnet, and this force acts as a return force to the equilibrium point. A servo-type acceleration detector characterized by: 2. The acceleration detector according to claim 1, wherein a torquer coil is arranged around the outer periphery of the movable magnetic body. 3. The acceleration detector according to claim 1, wherein the torquer coil is disposed at a position facing the permanent magnet. 4. The acceleration detector according to claim 1, wherein the case is made of a magnetic material, and the case is provided with a non-magnetic displacement stopper for regulating the amount of movement of the movable magnetic material. 5. The displacement detecting section includes two pairs of a primary coil and a secondary coil arranged symmetrically around the outer periphery of the movable magnetic body, and the torquer coil is arranged horizontally and horizontally in correspondence with the displacement detecting section. The acceleration detector according to claim 1, characterized in that one set is arranged. 6. A pair of permanent magnets provided at both ends in the moving direction of the movable magnetic body have polarities in the same direction with respect to the movable magnetic body, and the left and right primary coils are wound in opposite phases to each other. The left and right secondary coils were connected by winding so that they were in phase with each other, and the frequency of the alternating current applied to the primary coil was made sufficiently larger than the natural frequency of the mechanical system and did not contain a direct current component. The acceleration detector according to claim 5, characterized in that: 7. A pair of permanent magnets provided at both ends in the moving direction of the movable magnetic body have polarities opposite to each other with respect to the movable magnetic body, and the left and right primary coils are wound so as to be in phase with each other. The left and right secondary coils are wound and connected so that they are in opposite phase to each other, and the frequency of the alternating current applied to the primary coil is sufficiently higher than the natural frequency of the mechanical system and does not contain a direct current component. The acceleration detector according to claim 5, characterized in that: