JPH0260964B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an improvement in a displacement detector, particularly in a device that detects the relative displacement between a magnet and a detection head, so that the position signal can be easily adjusted with high accuracy even after fixation. Regarding.

As shown in Fig. 1, the displacement detector consisting of the magnetizing body 1, the detection head 2, and the detection circuit can detect the relative position between the magnetizing body and the detection head 2 with high precision, so it can be used as an origin detector, a limit switch, or a displacement detector. It is widely used in various fields as a quantity detection device.

However, conventional displacement detectors have the disadvantage that adjusting the position signal is inconvenient and time consuming. That is, once the magnet generator 1 and the detection head 2 are attached to a machine tool, etc., the relationship between the relative signal between them and the position signal as the detection output is fixed. If it is desired to make an adjustment such as slightly shifting the relationship, it is necessary to shift and fix the position of the magnet 1 or the detection head 2 by an amount that obtains the above relationship, and such fine mechanical adjustments must be made with high precision. It is quite difficult,
This required a large amount of time and man-hours.

Therefore, as shown in FIG. 2, a method has been proposed in which the detection circuit 3 is configured to electrically adjust the position signal. In the figure, D ₁ and D ₂ are diodes, OP is an operational amplifier, VR ₁ to _{VR 3} are variable resistors,
AC is an AC bias power supply, +E and -E are DC bias voltages, and depending on the relative position between the magnet generator 1 and the detection head 2, a position signal is generated as shown by the solid line in Fig. 3.
V ₀ is obtained. According to such a detection circuit 3,
By adjusting any of the variable resistors VR ₁ to VR ₃ , the position signal V ₀ can be adjusted as shown by the dotted line in FIG.

However, the most stable level of the detection output, that is, the position signal, is at x=0 and V ₀ =
Although the level is 0, it shifts up and down as shown by the dotted line depending on the position of the variable resistor and becomes x
= 0, V ₀ will not be 0, and a constant output will be produced, so
Because temperature drift can no longer be ignored,
The drawback is that it is difficult to have a very large adjustment range.

The present invention has been made in order to improve the drawbacks of the prior art. Two detection heads are arranged at a predetermined interval with respect to the magnet, and the detection outputs of the two detection heads are provided to a detection circuit. By obtaining position signals corresponding to the relative positions of the magnetic body and each detection head, combining the position signals, and changing the combination ratio, the origin of the combined position signal can be arbitrarily set within the range of the above-mentioned intervals. The present invention is characterized in that the position signal can be easily adjusted with high precision even after the detector is fixed.

The present invention will be described below with reference to embodiments shown in the drawings. In FIG.
If two detection heads 2, 2' are arranged for the detection heads 2, 2', and the spacing between the magnetic generators 1, 1' is L, then the detection heads 2, 2'
2' is shifted by l to provide an interval of L+l. The detection output from each detection head is given to the detection circuits 3, 3' as described above, and as described above, position signals V ₁ ,
V ₂ is obtained, and V ₁ and V ₂ are combined using, for example, resistors R ₁ and R ₂ .

The above position signals V ₁ and V ₂ are as shown in FIG.
The respective origins are separated by the distance l. The linear portion of these signals can be approximated to the relative displacement x as follows.

V ₁ =K ₀ x (1) V ₂ =K ₂ (x-l) (2) where K ₁ and K ₂ are the gains of the detection head and detection circuit.

Therefore, since the output resistance of each detection circuit can be ignored, the position signal V ₀ ' which is the composite of V ₁ and V ₂ can be expressed by the following equation, as is clear from the equivalent circuit of FIG. 4 shown in FIG. be done.

V ₀ ′=V ₁ R ₂ /R ₁ +R ₂ −V ₂ R ₂ /R ₁ +R ₂ +V ₂ =V ₁ R ₂ /R ₁ +R ₂ +V ₂ R ₁ /R ₁ +R ₂ (3) =K ₁ R ₂ +K ₂ R ₂ /R ₁ +R ₂ (x+1/1+K ₁ R ₂ /K ₂ R ₁ l
)(4) As is clear from equation (4), the synthesized position signal
By changing the ratio of K ₁ R ² and K ₂ R ₁ , that is, the composition ratio, V _{0 ′ can change its origin (V 0 ′} =0) from x=0 to
It can be set to correspond to any position within the range of l.

To change the above synthesis ratio, for example, use a synthesis resistor.
Just change the ratio of R ₁ and R ₂ . That is, since K ₁ and K ₂ can be assumed to be constant once the gap between the magnetizing body and the detection head is determined, from equation (4), the origin of V ₀ '=0 is K=
As K ₁ /K ₂ , x=1/1+KR ₂ /R ₁ l (5), and when R ₂ /R ₁ is changed from 0 to ∽, the origin of V ₀ ' can be changed from 0 to l. can.

Figure 6 shows an example of a circuit for carrying out the above variation method, in which a variable resistor R for changing the ratio of R ₂ and R ₁ is connected to the outputs of the detection circuits 3 and 3', and a detection head 2, 2' is a single AC bias power supply AC
It is connected to the.

Also, contrary to the above method, if the ratio of R ₁ /R ₂ is kept constant, the origin of V ₀ ' is given by R=R ₂ /R ₁ , and x=1/1+RR ₂ /R ₁・l (6) It is only necessary to change K ₁ /K ₂ , and an example of a circuit for this purpose is shown in FIG. In the same figure, OP ₁ and
OP ₂ is an operational amplifier, which is connected between the detection circuits 2 and 2' and the combining resistors R ₁ and R ₂ , respectively, and by changing the gain adjustment variable resistors VR ₁ and VR ₂ , K ₁ /K ₂ can be changed. In the above embodiment, two magnetic generating bodies 1 and 1' were used corresponding to two detection heads 2 and 2', but as shown in FIGS. By making the head into an integrated structure, the number of magnetizing bodies can be reduced to one. In the figure, reference numeral 4 denotes a holding member, which is structured to integrally hold cores 5, 5' and coils 6, 6' that constitute the detection heads 2, 2'.
Both detection heads are arranged so as to be spaced apart from each other by l with respect to the magnet generating body 1.

Even with this configuration, the position signal V ₀ ' synthesized by the variable resistor R for synthesis can be changed to V ₀ ' by changing the synthesis ratio R ₂ /R ₁ or K ₁ /K ₂ as in the previous embodiment. The origin of can be set arbitrarily within the range of 0 to l. In particular, in this embodiment, since the detection head has an integral structure, the clearance between the magnet and both heads can be set to be the same, and the characteristics of both heads can be easily matched.
The AC bias can be supplied from the same power supply. Therefore, since the detection sensitivities of both heads can be made almost the same, in equation (4) above, K ₁ ≒ K ₂ = K, R ₁ + R ₂ = R ₀ , and V ₀ '=K (x-R ₁ /R ₂ l ) (7) Therefore, from the point of view of the characteristics, it can be treated as one detection head.

FIG. 10 is an actual measurement diagram showing the output characteristics at each point in the above embodiment.

As explained above, according to the present invention, the position signal can be finely adjusted with high accuracy even after being fixed to the detector, and the effect is remarkable when it is put to practical use.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing the basic configuration of a displacement detector to which the present invention is applied, Fig. 2 is a circuit diagram showing an example of a conventional detection circuit in the displacement detector, and Fig. 3 is a circuit diagram thereof. Output characteristic diagram, Figure 4 is a schematic diagram showing an embodiment of the present invention, Figure 5 is its output characteristic diagram, Figure 6 is a schematic diagram showing an embodiment of the present invention.
7 and 7 are circuit diagrams respectively showing a method of changing the combination ratio of position signals in this embodiment, FIGS. 8 and 9 are diagrams showing another embodiment of the present invention, and FIG.
The figure is an actual measurement diagram of its output characteristics, and FIG. 11 is an equivalent circuit diagram of FIG. 4. 1, 1'... Magnetizing body, 2, 2'... Detection head, 3,
3'...Detection circuit, R...Variable resistance for synthesis.

Claims (1)

[Scope of Claims] 1. Two magnet generating bodies, which are arranged so as to have an interval deviated by a predetermined length with respect to the interval between these magnetic bodies, and as they approach each magnetic body, the distance between the magnetic bodies changes depending on the timing. two detection heads that generate electrical signals;
A detection circuit that generates two position signals corresponding to the relative positions of each of the magnetic generators and each detection head in response to each electric signal output from each detection head, and a variable ratio circuit that synthesizes each position signal. position signal synthesis means for synthesizing the two position signals to generate one synthesized position signal, and adjusting the synthesis ratio of the two position signals by the synthesis ratio variable circuit to generate one synthesized position signal. A displacement detector characterized in that the origin of the position signal can be set within the range of the predetermined length. 2. One magnet generating body, arranged so as to have an interval deviated by a predetermined length with respect to the length of the magnet generating body,
Two integrally held detection heads generate electrical signals in response to the magnetism as they approach each magnetic generating body, and each of the above-mentioned generators responds to the respective electrical signals output from each detection head. A detection circuit that generates two position signals corresponding to the relative position of the magnetic body and each detection head, and a position that generates one synthesized position signal by synthesizing the respective position signals via a variable synthesis ratio circuit. A signal synthesizing means is provided, and the origin of the synthesized position signal can be set within the range of the predetermined length by adjusting the synthesis ratio of the two position signals by the variable synthesis ratio circuit. A displacement detector characterized by: