JPH0455266B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a sensor that detects acceleration, inclination, and the like.

(Prior art) For example, as a sensor for detecting acceleration,
60-233564 has been developed by the present applicant. In this sensor, a magnetic fluid is sealed inside a bobbin, and a magnetic field generating member such as a permanent magnet for attracting the magnetic fluid to a predetermined position and a detection coil are arranged outside the bobbin. The above sensor is installed on a moving object, and when the moving object accelerates and the magnetic fluid is displaced and deformed against the magnetic force of the magnetic field generating member, this is detected as a change in the inductance of the detection coil. be.

The above-mentioned magnetic fluid is a colloidal liquid in which fine ferromagnetic particles are dispersed in a solvent, and even when a magnetic field is applied, the fine ferromagnetic particles do not precipitate or aggregate, and the liquid itself appears to be magnetic. It behaves as if it has.

(Problem to be solved by the invention) However, in the magnetic fluid of the above sensor, ferromagnetic fine particles are dispersed in a solvent and the amount of magnetic material contained is small, so the number of magnetic fluxes generated is small, and the displacement of this magnetic fluid , the change in inductance of the detection coil due to deformation was small. For this reason, it has been difficult to increase detection accuracy. Further, there were problems such as poor responsiveness due to resistance due to adhesion of the magnetic fluid to the bobbin, and poor reproducibility due to residual adhesion.

Therefore, the applicant has developed a sensor that uses magnetic balls such as iron balls instead of magnetic fluid. A patent application was filed for this sensor on October 28, 1985, but it is not publicly known. The present invention further improves this technique to improve the reproducibility of detection.

(Means for Solving the Problems) The gist of the present invention is to store magnetic balls in a storage space formed inside a cylindrical bobbin with play in the radial direction of the bobbin, and to , a ring-shaped magnetic field generating member that has multiple locations with large magnetic field gradients in the circumferential direction to attract magnetic balls, and a coil that detects the position of the magnetic balls in the axial direction of the bobbin are arranged, and the magnetic field caused by the play is The sensor is characterized in that the center axis of the radially movable region of the sphere is offset from the center axis of the magnetic field generating member.

(Function) When the sensor is used to measure acceleration, for example, during acceleration, the magnetic sphere receives an inertial force in a direction opposite to the direction of acceleration, and tends to be displaced from a predetermined position against the attractive force of the magnetic field generating member. The position of this magnetic ball is detected by a coil and the acceleration is measured.

In the above operation, in the case of a magnetic sphere, the amount of magnetic material contained is more than 10 times that of a magnetic fluid, so the number of magnetic fluxes generated increases, large changes in coil inductance can be detected, and detection accuracy improves. Furthermore, since the magnetic sphere has less resistance during movement and does not adhere to the bobbin like magnetic fluid, responsiveness and reproducibility can be improved.

The above magnetic balls have play in the radial direction of the bobbin, and due to this play they can also move in the radial direction; The central axis of the possible region is offset from the central axis of the magnetic field generating member. For this reason, in the magnetic sphere, the magnetic force from a specific location selected among multiple locations with large magnetic field gradients in the magnetic field generating member is always stronger than the magnetic force from other locations. As a result, the magnetic sphere is always in contact with the inner surface of the bobbin at a position close to the above-mentioned specific point, and there is no change in the grounding position, so even if there is an error in the strength of the magnetic field at a place with a large magnetic field gradient, it will not be detected. The output is stable without being affected by this error, and the reproducibility of detection can be improved.

(Example) An example of the present invention will be described below with reference to FIGS. 1 and 2. The illustrated sensor has a bobbin 1 . This bobbin 1 has a cylindrical portion 1a and a closed end portion 1b, has a bottomed cylindrical shape, is closed by a stopper 3 fitted with an O-ring 2, and has a storage space 4 inside. In this storage space 4, a magnetic ball, for example, an iron ball 5 is stored. This iron ball 5 has a diameter slightly smaller than the inner diameter of the cylindrical portion 1a of the bobbin 1, and has a play 6 in the radial direction of the bobbin 1.
have.

The magnetic sphere 5 is movable in the radial direction of the bobbin 1 due to this play 6. When the cross-sectional shape of the storage space 4 is a perfect circle as in this embodiment, the movable range A in the radial direction is equal to the cross-section of the storage space 4.

Two transformers 10, 10 are arranged around the outer periphery of the cylindrical portion 1a of the bobbin 1 in a state where they are wound around a cylindrical frame 13. These transformers 10,10
The border is located at the center of the storage space 4 of the bobbin 1 in the axial direction. Each transformer 10 includes an outer primary coil 11 and an inner secondary coil 12.

An annular permanent magnet 15 (magnetic field generating member) magnetized in the radial direction is provided on the outside of the transformers 10, 10.
is arranged, and its axial center is located at the boundary between the transformers 10, 10. The center axis O of this annular permanent magnet 15 coincides with the center axis of the outer circumferential circle of the bobbin 1. As shown in FIG. 2, the permanent magnet 15 has a plurality of magnetized regions 1 in the circumferential direction,
It is divided into 6 to 19. Adjacent magnetized regions 1
6 to 19, the positions of the north and south poles are different from each other; for example, in magnetized regions 16 and 18, the south pole is on the inside and the north pole is on the outside, and the opposite is true for magnetized regions 17 and 19. . Such a permanent magnet 15
Then, the four boundaries Pa to Pd of magnetization regions 16 to 19
is the location where the magnetic field gradient is large.

The cylindrical portion 1a of the bobbin 1 has a thick upper wall and a thin lower wall, and the central axis of the storage space 4, that is, the central axis O' of the movable area A, is
The central axis of the outer circumferential circle of the bobbin 1, that is, the permanent magnet 15
This point is an important feature of the present invention.

The bobbin 1, transformers 10, 10, and magnet 15 are housed in a housing 20 having a cylindrical shape with a bottom. A lid 21 is attached to the housing 20, and the above-mentioned components are movably housed by spacers 22.

A connector 25 is inserted and fixed into the lid 21, and a spacer 22 is inserted into the terminal of the connector 25.
The transformers 10, 10 are connected to each other via a lead wire (not shown) passing through a hole 22a formed in the. Further, the connector 25 is connected to a connector (not shown) of a control unit 26 that includes an AC constant voltage generating circuit, a signal processing circuit, and the like. A display 27 is connected to the control unit 26. The primary coils 11, 11 of the transformers 10, 10 are connected to the AC constant voltage generating circuit of the control unit 26, and the operating output of the secondary coils 12, 12 is detected by the signal processing circuit. .

The above bobbin 1, plug 3, frame 13, housing 2
0, the lid 21, and the spacer 22 are made of nonmagnetic material.

A case will be described in which a sensor configured as described above is attached to a moving body and its acceleration is detected. When the moving object is not accelerated, the iron ball 5 is a permanent magnet 1
Attracted by the magnetic force of 5, the transformer 10,
It is located on the border of 10. Therefore, the operating output of the secondary coils 12 of both transformers 10 is zero. The signal processing circuit of the control unit 26 converts the operation output into a digital signal and sends it to the display 27, which digitally displays the zero value.

When the moving body is accelerated to either the left or right in the first illustration, the iron ball 5 receives an inertial force in the direction opposite to the acceleration direction, and moves against the magnetic force of the permanent magnet 15. Due to this change in the position of the iron ball 5, the transformer 1
The inductance of 0,10 changes and an actuation output is generated between the secondary coils 12,12. As a result, the display 27 digitally displays the acceleration as a positive value or a negative value.

In the above operation, since the entire iron ball 5 is made of magnetic material and generates a large number of magnetic fluxes, the transformer 1
The change in inductance between 0 and 10 is large, and the differential output can be increased. As a result, detection accuracy can be increased.

Further, since the iron ball 5 can move without being subjected to adhesion resistance as in the case of magnetic fluid, it can be quickly displaced and responsiveness can be improved.

Furthermore, unlike magnetic fluid, there is no residual adhesion, so
This eliminates variations in detection output and improves reproducibility.

By the way, the magnetic sphere 5 and the cylindrical portion 1a of the bobbin 1
Since there is play 6 between the magnetic ball 5 and the inner circumferential surface of the
As mentioned above, this play 6 allows the magnetic balls 5 to move in the radial direction of the bobbin 1.

If the central axis of the storage space 4, that is, the central axis O' of the movable area A, coincides with the central axis O of the permanent magnet 15, the iron ball 5 will be moved by the magnetic field gradient in the permanent magnet 15. Large boundary Pa~Pd
It is possible to land on any of the upper, left, right, and lower portions of the inner circumferential surface of the cylindrical portion 1a. In this way, when the ground contact position changes,
This poses a problem in improving the reproducibility of acceleration detection. This is because when the above-mentioned grounding positions differ, the boundary parts Pa to Pd that act most strongly on the iron ball 5 differ, but each boundary part Pa to Pd
Since there is an error in the strength of the magnetic field, the resultant magnetic force varies, and as a result, even if the same acceleration is applied, the position of the iron ball 5 where the resultant magnetic force should be in equilibrium with the inertial force due to acceleration is This is because it will change.

In particular, the acceleration is small and the iron ball 5 becomes a permanent magnet 15.
If the bobbin 1 is not displaced greatly in the axial direction from As a result, the detection output fluctuates even more.

However, in the present invention, the above-mentioned fluctuation in detection output does not occur. To be more specific, since the central axis O' of the movable area A is biased downward from the central axis O of the permanent magnet 15, the iron ball 5 cannot be moved to any position within the radial movable range A due to vibration etc. However, the boundary between the magnetized regions 17 and 18 located below the bobbin 1
The magnetic force from Pc acts on the iron ball 5 more strongly than the magnetic forces from other boundaries Pa, Pb, and Pc. As a result, since the iron ball 5 always touches the lower part of the inner peripheral surface of the cylindrical part 1a, the detection output corresponding to the acceleration is
It is stable regardless of errors in the magnetic field strength between Pa and Pd, and can improve reproducibility.

The above sensor can be used not only for detecting acceleration but also for detecting inclination. In this case, when the sensor is tilted, the iron ball 5 is displaced in the tilt direction.

In the embodiment shown in FIG. 3, two
There are two protrusions 7, 7, and upward movement of the iron ball 5 is restricted by these protrusions 7, 7. Therefore, the circle where the tips of the protrusions 7 and the lower part of the inner circumferential surface of the bobbin 1 are in contact, that is, the inscribed circle, becomes the radially movable area A of the iron ball 5, and the central axis of this movable area A O' is offset downward from the central axis of the outer circumferential circle of the bobbin 1', that is, the central axis O of the permanent magnet 15.

The present invention is not limited to the above embodiments, and various embodiments are possible. For example, the magnetic field generating member may be configured by arranging a plurality of arc-shaped permanent magnets in a ring shape. Further, instead of the permanent magnet, a plurality of electromagnetic coils may be arranged along the circumferential direction of the bobbin to constitute the magnetic field generating member. The electromagnetic coil may generate a constant magnetic field or a variable magnetic field. In addition, when the electromagnetic coil generates a variable magnetic field, for example, the supply voltage of the electromagnetic coil is controlled by feedbacking the differential output of the detection coil so that the output becomes zero, and the supply voltage of this electromagnetic coil is It is also possible to measure acceleration and inclination by detecting .

Further, the magnetic field generating member may be arranged inside the detection coil.

Further, although two transformers are used in the above embodiment, changes in self-inductance of the two coils may be detected as a differential output. Further, if there is no need to detect the direction of acceleration or inclination, only one detection coil may be arranged around the bobbin.

(Effects of the Invention) As explained above, in the present invention, since magnetic spheres are used, detection accuracy, responsiveness, and reproducibility are improved. Moreover, by making the central axis of the area where the magnetic sphere can move in the radial direction due to play deviate from the central axis of the magnetic field generating member, the grounding position of the magnetic sphere on the inner circumferential surface of the bobbin is kept constant. The reproducibility of detection can be further improved.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a sensor according to an embodiment of the present invention, FIG. 2 is a sectional view along the stopper showing the relationship between the magnetic field generating member, bobbin, and magnetic sphere in FIG.
The figure is a diagram corresponding to FIG. 2 showing another embodiment. 1...Bobbin, 5...Magnetic ball (iron ball), 11,
12... Coil, 15... Magnetic field generating member (permanent magnet), Pa~Pd... Location with large magnetic field gradient (boundary of magnetized region).

Claims (1)

[Claims] 1. In the storage space formed inside the cylindrical bobbin,
The magnetic balls are stored with play in the radial direction of the bobbin,
On the outer periphery of the bobbin, an annular magnetic field generating member having multiple locations with large magnetic field gradients in the circumferential direction to attract magnetic balls, and a coil for detecting the position of the magnetic balls in the axial direction of the bobbin are arranged. A sensor characterized in that the center axis of a region in which the magnetic sphere can move in the radial direction due to play is offset from the center axis of the magnetic field generating member. 2. The storage space has a circular cross section, the entire area of which is an area in which the magnetic sphere can move in the radial direction, and the central axis of the magnetic field generating member coincides with the central axis of the outer circumferential circle of the bobbin, and the storage space has a circular cross section. The sensor according to claim 1, wherein the central axis of the bobbin is offset from the central axis of the outer circumferential circle of the bobbin. 3. The central axis of the magnetic field generating member coincides with the central axis of the outer circumferential circle of the bobbin, and a protrusion is formed on the inside of the bobbin, and the protrusion restricts the movement of the magnetic sphere in the radial direction, allowing it to move. The sensor according to claim 1, wherein the central axis of the region is offset from the central axis of the outer circumferential circle of the bobbin.