JPH0372215A - Capacitive displacement sensor - Google Patents

Abstract

PURPOSE:To obtain a highly accurate displacement detector by impressing an alternating current voltage which is shifted in phase and, analyzing the phase of a capacitor coupled signal. CONSTITUTION:A stator 10 has transmission electrodes 14 arranged with equal distance from each other and receiving electrodes 16 arranged in the shape of a belt to the electrodes 14, on the rear surface thereof. A rotor 12 has coupling electrodes 18 arranged astride the electrodes 14, 16 and opposite to the electrodes 14, 16. The rotor 12 is rotatable with the stator 10. An alternating current voltage source 20 supplies an alternating current voltage sequentially to the electrodes 14 with the phase shifted a predetermined degree. The displacement detector is provided with these stator 10, rotor 12 and voltage source 20. An alternating current voltage is introduced to electrodes 14 provided on the surface of the stator 10 by lead wires 24. The lead wires 24 are so provided that the capacity formed between one of a pair of the lead wires 24 for introducing an alternating current voltage of an opposite phase and the electrode 16 becomes approximately equal. The relative displacement amount of the stator 10 and rotor 12 can be detected by analyzing the phase of the capacitive coupled signal of the electrodes 14, 16.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention provides a capacitive displacement detector, in particular, a capacitive displacement detector which applies out-of-phase alternating current voltages and analyzes the phase of a capacitively coupled signal. This invention relates to improvements in capacitive displacement detectors that detect displacements such as rotation angles.

[Prior Art] A capacitor that detects displacement by analyzing the phase of a capacitance coupling signal between opposing electrodes, as a device for measuring the relative displacement of the angle or length of another member with respect to the other member. Mold displacement detectors are known (for example, Japanese Patent Publication No. 11883/1983)
.

This capacitive displacement detector is shown in FIG.

As shown in FIG. 3(B), regularly arranged transmitting electrodes 14 and receiving electrodes 16 arranged in a band shape relative to the transmitting electrodes 14 are on the back surface of the stator 10. On the surface of the rotor 12 that is rotatable facing the stator 10,
As shown in FIG. 4(A), the transmitting electrode 14 and the receiving electrode 16
There is a coupling electrode 18 disposed facing each other across the two sides. An AC voltage source 20 whose phase is shifted by a predetermined amount is connected to each 17 of the transmitting electrodes 14 . When the rotor 12 is rotationally displaced relative to the stake 10, the transmitting electrode 1
4 and the coupling electrode 18 facing the capacitance changes. Then, the change in capacitance coupling is transmitted to the capacitance formed by the coupling electrode 18 and the receiving electrode 16, and is detected as a capacitance coupling signal by the capacitance coupling signal detector 22. The capacitive coupling signal detector 22 compares the phase of the capacitive coupling signal with the reference phase of the AC voltage applied to the transmitting electrode 14 to detect its delay or advance, and detects the displacement of the stator 10 and rotor 12. Count the amount.

In these capacitance type displacement detectors, stray capacitance and leakage current are avoided when laying the lead wires 24 that connect the AC voltage shifted by a predetermined phase to each transmitting electrode 14 arranged on the stator 12. In order to remove defective signals such as electrostatic noise caused by such factors, the following measures have been taken.

That is, as shown in FIG. 2, the lead wire 24 is laid on the surface of the stator 10, passes through the through hole 28, and is led to the multi-conductor (g electrode 14) on the back surface of the stator 10.
At this time, the lead wires 24 connected to alternating current voltages having mutually opposite phases are laid adjacent to each other. By doing this, defective signals caused by stray capacitance, etc. formed between each lead wire 24 and other conductors are canceled out as defective signals having mutually opposite phases. .

[Problems to be Solved by the Invention] However, in laying the conventional lead wire 24,
As shown in Figure 2, two
The book leads 2424 were in a position with one inside or outside the other. For example, in FIG. 2, the lead wire 24-1 that applies an AC voltage with a phase of 0 degrees is connected from the lead electrode 26-1 to the transmitting electrodes 28 L, 28-
1-2.28--■-3, 28-1-4 and 28-1-
5, forming an approximately circle. On the other hand, a lead wire 24 that applies an AC voltage with a phase of 180 degrees, which is in the opposite phase relationship.
-2 extends from the lead electrode 26-2 to the transmitting electrode 28-2-1.28 so as to form a substantially circle inside the lead wire 24-1.
-2-2.28-2-3.28-2-4 and 28-2-
5.

Furthermore, among the various stray capacitances composed of the lead wire 24 and other conductors, the stray capacitance composed of the lead wire 24 and the receiving electrode 16 has a very large influence as a defective sign when detecting displacement. This has been experimentally investigated.

Therefore, conventionally, two sets of lead wires, for example, lead electrode 2
4-1 and 24-2 are located inside the receiving electrode 16;
There is a difference in the distance from the receiving electrode 16 because it is in an outer relationship,
It was not possible to equalize the capacitance of the stray capacitance formed by the receiving electrode 16. Therefore, there was a problem in that it was not possible to completely cancel out the defective signal by making it have an opposite phase.

The present invention has been made in view of the above circumstances, and provides a highly accurate capacitive displacement detector by making it possible to effectively cancel out the defective signal caused by the installation of the lead wire 24. The purpose is to

[Means for solving the problem] Therefore, in the present invention, the transmitting electrodes 1 arranged at equal intervals
4, a stator 10 having on its back surface a receiving electrode 16 arranged in a band shape with respect to the transmitting electrode 14, and a coupling electrode 18 disposed facing the transmitting electrode 14 and the receiving electrode 16. a rotor 12 that is rotatable with the stator, and an AC voltage source 20 that is sequentially applied to each of the transmitting electrodes 14 with a predetermined phase shift, and the capacitance between the transmitting electrode 14 and the receiving electrode 16 is In a capacitive displacement detector that detects the amount of relative displacement between the stator 10 and the rotor 12 by analyzing the phase of a coupled signal, an alternating current is applied to the transmitting electrode 14 laid on the surface of the stator 10. Of the lead wires 24 for introducing voltage, the capacitance value of the capacitance formed between each of the pair of lead wires 24 for introducing alternating current voltages having mutually opposite phases and the receiving electrode 14 is A feature is that the lead wires 24 are laid so that they are approximately equal.

Further, the pair of lead wires 24 that lead AC voltages having opposite phases to each other have substantially the same average distance between each lead wire 24 and the receiving electrode 14 over the line length of each lead wire 24. In addition, the wire lengths of the pair of J-wires 24 are made substantially the same.

Furthermore, the one set of lead wires 24 includes one lead wire 2
4 is a substantially circular shape, and the other lead wire 24 is characterized by two substantially semicircular shapes located on opposite sides of the one lead wire 24.

[Function] The capacitive coupling signal between the transmitting electrode 14 and the receiving electrode 16, which should contribute to the original displacement detection, is the capacitive coupling signal induced between the transmitting electrode 4 and the coupling electrode 18. and is transmitted to the receiving electrode 16 via the coupling electrode 18. Therefore, a signal that directly reaches the receiving electrode 6 from the transmitting electrode 14 or the lead wire 24 connected thereto without passing through the coupling electrode 18 is a defective signal that should not contribute to displacement detection.

The lead wire 24 and the receiving electrode I6 form a stray capacitance that causes a defective signal. According to the present invention, the stray capacitances formed by the receiving electrode 16 and a pair of lead wires that lead AC voltages having opposite phases to each other are approximately the same.

[Example] An example according to the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to this example.

FIG. 5 shows an overall configuration diagram of this embodiment. The alternating current voltage source 20 has eight phases that are equally phase shifted by 45 degrees,
AC voltages having phases of 0 degrees, 45 degrees, . . . 345 degrees are supplied to the transmitting electrodes 14 on the stator 10. The stator 10 and the rotor 12 are arranged opposite to each other, and the rotor 12 is supported by a bearing so as to be able to rotate opposite to the stator 10.

FIG. 3 shows a detailed configuration of the stator 10.

FIGS. 3(A), (B) and (C) each show the stator 1
0 is a diagram showing the front side, the back side, and a cross section at II OII. The stator 10 is made of a base material such as an epoxy resin.

On the surface of the stator 10 shown in FIG. 3(A),
Eight lead electrodes 26 that relay the AC voltage signal from the AC voltage source 20, eight lead wires 24 laid from each lead electrode 26 to a corresponding position of each transmitting electrode 14, and an end of each lead wire 24. Transmitting electrode 1 on the back side of stator 10
Through hole 28 for connecting to 4 and ground electrode 4
0 is provided. The eight lead electrodes 26-1, 26-2...26-8 constituting the lead electrode 26 include
0 degrees and 180 degrees, 45 degrees and 225 degrees, which are in opposite phase relationship
AC voltages of respective sets of 90 degrees and 270 degrees, and 135 degrees and 315 degrees are connected adjacently.

Regarding the installation of the lead wire 24, which is a characteristic content of the present invention, the entire installation of the lead wire 24 is shown in FIG. In Figure 1, 0 degrees and 18 degrees are in an antiphase relationship.
Only one set of 0 degrees is displayed. The lead wire 24-■ facing 0 degrees starts from the lead electrode 26-1,
Through hole 28-1-1.28-1-2...28-
Draw a approximate circle from 1 to 5. On the other hand, the lead wire 24-2 corresponding to 180 degrees starts from the lead electrode 26-2 and extends through the through holes 28-2-1, 28-2-2...28-2.
-3, a roughly semicircular lead wire 24-2-1, and a through-hole 28-2-3 starting from the vicinity of the through-hole 28-2-3.
Through hole 28-1- via 2-4 and 28-2-5
5 and a substantially semicircular lead wire 24-2-2 extending to the vicinity of 5. The portion of the lead wire 24-1 from the lead electrode 26-1 to position a is substantially orthogonal to the receiving electrode 16, so the effective area facing the receiving electrode 16 is small, and the distance from the receiving electrode 16 is also small. Since it is large, it is considered that the contribution to the floating capacitance that causes the defective signal can be almost ignored. Therefore, in this embodiment, the lead wire 2
4-1 does not include the portion from lead electrode 26-l to position a. Similarly, lead wire 2
In 4-2-1. Position C in the portion from the lead electrode 26-2 to the position C and in the lead wire 24-2-2
Lead auxiliary, lead electrode 26-2 via 1i132
The part leading to each lead wire 24-2-1.24-2-2
It is not included in The sum of the lengths of the lead wire 24-2-1 and the lead wire 24-2-2 is the lead wire 24-2-2.
The length is almost the same as that of 1. Furthermore, the lead wire 24
-2-1 and the lead wire 24-2-2, and the lead wire 24-
By laying the lead wire 24 on the opposite side to 1.
The average distance from the lead wire 24-1 to the receiving electrode 16 over the line lengths of the lead wire 24-2-1 and the lead wire 24-2-2 is approximately the same as the average distance from the lead wire 24-1 to the receiving electrode 16. Here, the average distance refers to the following. That is, the value of the product of the distance from the minute length portion of the lead wire 24 to the receiving electrode 16 and the minute length of the lead wire 24 is determined, and lead #ji
124, by dividing the sum by the total length of the lead wire 24. Although FIG. 1 shows one set of lead wires 24-1 and 24-2, the same applies to other sets.

On the back surface of the stator 10 shown in FIG. 3(B),
There is a transmitting electrode 14, a coupling electrode 16, and a grounding electrode 40.

The transmitting electrodes 14 are a set of eight electrodes 14-IL4-2, to which AC voltages having phases shifted by 45 degrees are applied.
Five sets of 14-8 are arranged in sequence. Each transmitting electrode 14
is connected to a lead wire 24 on the surface of the stator 10 by a through hole 28.

The receiving electrodes 16 are arranged in a band shape inside the transmitting electrodes 14. It is guided through a through hole 28 to a receiving lead electrode 30 on the surface of the stator 10, and from there connected to a capacitively coupled signal detector 22. Receiving electrode 16
A ground electrode 40 is disposed between the transmitter electrode 14 and the transmitter electrode 14 . The earth electrode 40 is used to eliminate direct capacitive coupling between the receiving electrode 16 and the transmitting electrode 14 as much as possible due to its shielding effect. The configuration of the rotor 12 is shown in FIG. 4 in which a ground electrode 40 on the back side is connected to a ground electrode 40 on the front side by a through hole 28. FIGS. 4(A) and 4(B) are a back view and a sectional view at IOI, respectively. low cheetah 12
The entire surface of is a ground electrode. A coupling electrode 18 and a ground electrode 40 are provided on the back surface of the rotor 12 (FIG. 4(A)). The coupling electrode 18 is composed of five electrodes arranged alternately with the ground electrode 40, and the five coupling electrodes are electrically integrated. The coupling electrode 18 is
The transmitter electrode 14 and the receiver electrode 16 on the stator 10 are disposed so as to straddle and face each other. The electrode width of this coupling electrode 18 is set to a width corresponding to four electrodes of the transmitting electrode 14.

Next, the operation of the embodiment will be explained. stator 10
When the rotor 12 is at rest, the signal detected at the capacitively coupled signal detector 22 is a capacitively coupled signal equal to the frequency of the applied AC voltage. When the rotor 12 rotates relative to the stator 10, the weighting of the capacitance coupling between the transmitting electrode and the coupling electrode 16 to which AC voltages of each phase are applied changes, and as a result, the detected AC voltage signal changes at its frequency. changes. Or in other words,
The phase of the capacitive coupling signal is delayed or advanced depending on the direction of rotational displacement of the low cheater 12 compared to before the rotational displacement. Then, the amount of displacement is counted by detecting the phase delay or advance of this capacitively coupled signal.

Next, the effects of the embodiment will be explained. As shown in FIG. 1, by installing a pair of lead wires 24 that conduct alternating current voltages that are in opposite phases to each other, stray capacitance that exists between each lead wire and the receiving electrode 16 is created. As a result, a defective signal based on the stray capacitance can be canceled out extremely effectively, and highly accurate displacement detection becomes possible.

In the above explanation, one set of lead electrode 24 and receiving electrode 16
This is an example of a case in which the average distance from the lead wires is made substantially the same, and the line lengths of one set of lead wires are made substantially the same. However, the present invention is not limited to this. Lead wire 24
It is thought that the value of the stray capacitance existing between the electrode 16 and the receiving electrode 16 is inversely proportional to the distance between the two, and proportional to the length of the lead wire 24. Therefore, when the distance between them is increased, the length of the lead wires may be increased to make the stray capacitance values of one set of lead wires 24 and the receiving electrode 6 substantially equal. Conversely, if the distance between the two is shortened, the length of the lead wire may be shortened. The present invention includes all cases where the lead wire 24 is laid with these matters in mind.

Furthermore, although this embodiment has been described with reference to a capacitive displacement detector that detects rotational displacement, the present invention can also be applied to a capacitive displacement detector that detects linear displacement.

[Effect] As described above, according to the present invention, the lead wire 24 is connected to another conductor,
In particular, the capacitance value of stray capacitance that is formed between the receiving type 116 and
It can be made almost the same as 6@. As a result, it becomes possible to effectively cancel defect No. 13 caused by the stray capacitance, and it is possible to provide a capacitive displacement detector with higher accuracy than ever before.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the installation of lead wires 24 on the surface of the stator 10 according to an embodiment of the present invention. FIG. 2 is a diagram corresponding to FIG. 1 in a conventional example. FIG. 3 is a diagram showing the stator 10 according to an embodiment of the present invention, in which (A) shows the front surface thereof, and (B) shows the back surface thereof.
(C) is a diagram showing the cross section. FIG. 4 is a diagram showing the back surface and cross section of the rotor 12. FIG. 5 is a diagram showing an outline of a capacitive displacement detector. 10... l 4... 18... 22... 24... Stator, 12... Rotor transmitting electrode, 16... Receiving electrode, coupling electrode, 20... AC voltage source, static Capacitive coupling signal detector, lead wire diagram

Claims (3)

[Claims] (1) A stator having, on its back surface, transmitting electrodes arranged at equal intervals and receiving electrodes arranged in a band shape relative to the transmitting electrodes, and a coupling disposed facing each other across the transmitting electrodes and the receiving electrodes. a rotor that is rotatable with the stator and has electrodes; and an AC voltage source that is sequentially applied to each of the transmitting electrodes with a predetermined phase shift, the phase of the capacitively coupled signal between the transmitting electrode and the receiving electrode being In a capacitive displacement detector that detects the amount of relative displacement between the stator and the rotor by analyzing the The lead wires are laid so that the capacitance values of the capacitances formed between each of the pair of lead wires that lead alternating current voltages having mutually opposite phases and the receiving electrode are approximately equal. A capacitive displacement detector characterized by: (2) In claim (1), the set of lead wires that lead alternating current voltages having opposite phases to each other has an average distance between each of the lead wires and the receiving electrode over the line length of each of the lead wires. A capacitance type displacement detector, characterized in that the wire lengths of the pair of lead wires are made substantially the same. (3) In claim (2), the one set of lead wires is
According to claim (2), one lead wire is substantially circular, and the other lead wire is two substantially semicircular shapes located on opposite sides of the one lead wire. capacitive displacement detector.