JPH0760098B2 - Position sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention is configured to cause a sensor coil to detect as an electric signal that a magnetic field from a field coil changes in accordance with a moving amount of an object to be measured. It relates to a position sensor.

[Conventional technology]

In this type of position sensor, by changing the degree of coupling of the secondary winding to the primary winding in accordance with the displacement of the movable iron piece, an AC signal of the corresponding amplitude is applied to the secondary winding as a sensor coil. Differential transformers that are adapted to induce induction are well known.

[Problems to be solved by the invention]

Although such a differential transformer is widely used as a position sensor, since the frequency of the AC signal cannot be increased because the iron core is used, it is difficult to miniaturize it, and in principle, the amplitude is detected as the displacement amount. Therefore, if the amplitude of the input signal to the primary winding as a field coil fluctuates,
There was a drawback that led to a detection error.

Therefore, an object of the present invention is to provide a position sensor that can detect the moving position of a measurement target as a phase change.

[Means for solving problems]

In order to achieve this object, the present invention arranges the field coils 1 and 2 on both sides so as to be spaced apart from each other and relatively moves along a line A connecting these field coils, as shown in FIG. Sensor coil 3 is inserted, and a magnetic field having a strength corresponding to sin ωt is applied to one of the field coils 1 by the line A.
To the other side, and cosω to the other field coil 2.
By generating a magnetic field having a strength corresponding to t toward the line A and causing the sensor coil 3 to detect the combined magnetic field of both, the phase θ changes according to the moving distance of the sensor coil sin (ωt + θ) The voltage signal corresponding to is induced.

[Action]

The mutual phases generated by the field coils 1 and 2 are 90.
AC magnetic field DEG maximum H _O each intensity of the magnetic field, depending on the line A to change the distance l from the one, namely the strength depending on the approach to and separate from for the field coils 1 The sensor coil 3 is caused to generate the next combined magnetic field H that changes so as to increase or decrease.

That is, if l → large, f (l) → small, f ′ (l) →
Larger, θ → larger.

As a result, the AC magnetic flux φ corresponding to the H is induced in the sensor coil 3, and the following voltage signal E in which the phase θ changes according to the distance 1 is induced.

Embodiment of the Invention FIG. 2 shows a position sensor according to an embodiment of the present invention.

In the drawing, ring-shaped concentric field coils 11 and 12 having an average radius r and separated by a distance L are arranged coaxially around a central axis B by an average distance L. Between these field coils 11 and 12, there is a ring-shaped concentric winding sensor coil 13 which is similarly slidable around the central axis B along with this object in conjunction with the measurement object and has a larger inner diameter. Has been inserted.

As shown in principle in FIG. 3, the strength of the magnetic field generated from the field coil 11 at the position P corresponding to l ₁ on the central axis B.
H _P, when that generates a magnetic field of up to H _O sin .omega.t the position of l ₁ = 0, as follows.

Therefore, the magnetic fields H ₁ and H ₂ generated by the field coils 11 and 12 at the position of the sensor coil 13 in FIG. ₂ are as follows.

As a result, in response to the combined magnetic flux of H ₁ and H ₂ in the sensor coil 13, as is clear from the above equations (1) and (2), a sinusoidal wave whose θ increases with changes in l ₁ A voltage signal is generated. Therefore, the position of the measuring object to which the sensor coil 13 is fixed is detected by converting θ into the distance.

FIG. 4 shows that L = 100, 20, and 10 m in this embodiment.
According to the equations (1) and (2) for m and r = 10 mm, l ₁
The change curve of θ with respect to is obtained. That is, the linearity changes depending on the coil structure, and the sensor coil
The linearity also changes depending on the shape of 13, but in any case, θ changes corresponding to l ₁ . In particular, when the linearity of θ is required, it may be possible to limit the detection range to the central portion for use.

It should be noted that in the above-described embodiment, both types of coils may be solenoids wound around a straight bobbin, or other coil structures such as a sensor coil fixed and a field coil movable. In order to improve the linearity, it is possible to adjust the shape such as bending the field coil instead of simply flattening it.

〔The invention's effect〕

As described above, according to the present invention, it is possible to realize a position sensor that detects a relative distance between sensor coils between field coils as a phase angle. In addition, since it is not necessary to intentionally use the iron core, it is possible to use a high frequency signal, so that the size can be reduced and a printed coil or the like can be used.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a configuration of a position sensor of the present invention, FIG. 2 is a schematic side view of a position sensor according to an embodiment of the present invention, and FIG.
FIG. 4 is a diagram for explaining the principle of the same embodiment and FIG. 4 is a diagram for explaining the operation of the same embodiment. 1, 2, 11, 12 ... Field coil, 3, 13 ... Sensor coil.

Claims (1)

[Claims] 1. A field coil is arranged so as to be spaced apart from each other on both sides, and a sensor coil that moves relatively to the field coil along a line connecting the field coils is inserted between the field coils, and one of the field coils is provided. In the coil, a magnetic field whose strength changes corresponding to sin ωt is generated toward the line, and in the other field coil, the strength changes corresponding to cos ωt which is 90 ° out of phase with the magnetic field. Corresponding to sin (ωt + θ) in which the phase θ changes in accordance with the moving distance of the sensor coil by similarly generating a changing magnetic field toward the line and causing the sensor coil to detect both the magnetic fields. A position sensor characterized by inducing an electric signal.