JPH0358447B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a capacitive displacement detector that precisely detects the amount of relative displacement between two members using a variable capacitance transducer.

2. Description of the Related Art Conventionally, as a detector for detecting the position of one relatively displaced member with respect to the other by capacitance, there is known a detector as described in, for example, Japanese Patent Laid-Open No. 54-94354. In this device, a plurality of groups of supply electrodes are arranged on one side of the member in the measurement direction, and the electrodes are arranged in n groups for each group.
further comprising at least one receiving electrode connected to a signal processing circuit on said one member, connected to the output of each phase of the phase oscillator to supply voltage to all supply electrodes in a periodic pattern; An electrode pattern consisting of a plurality of mutually insulated electrodes is provided on the other side of the member, and each of these electrodes is constituted by two electrode parts connected to each other, one electrode part serving as a detection electrode. , the sensing electrode is disposed near a circular area of the other member over which the supply electrode on the one member moves, and the other electrode portion constitutes a transmission electrode;
The transmitting electrode is disposed proximate an area of the other member over which the receiving electrode of the one member moves, and the transmitting electrode is arranged in the vicinity of an area of the other member over which the receiving electrode of the one member moves. The receiving electrode generates a signal based on signals from at least two adjacent electrodes of the supply electrode, and the signal processing circuit detects a displacement amount of one of the members relative to the other based on an amplitude ratio of the signal. This is what I did. However, such a device has a problem in that the output fluctuates depending on the surrounding environmental conditions, such as humidity and temperature, resulting in a large detection error. Furthermore, since the output is an analog quantity, an A/D converter must be provided in the signal processing circuit for direct reading, which poses the problem that the overall structure becomes complicated and expensive.

This invention was made in view of the above-mentioned problems, and utilizes the invention described in Japanese Patent Application Laid-Open No. 149911/1983 to provide a highly accurate, simple, and inexpensive capacitive displacement detector. The purpose is to

Such a purpose is to provide a large number of main electrodes spaced apart from each other by an equal distance P ₁ in the direction of displacement of one member that is relatively displaced, and to arrange the main electrodes on the other member so that they can face the main electrodes in the same direction. n separated from each other by a distance P 2 given by the formula (a±1/n)×P ₁ [where n is a positive integer greater than or equal to ₂ , and a is a positive integer greater than or equal to 1]
A first capacitor comprising: a main sensing electrode, a sub-sensing electrode on one or the other member, the one main sensing electrode serving as one electrode plate, and the main sensing electrode and the main electrode. n with each
a first delay circuit, and a second capacitor with the sub-sensing electrode as one plate, respectively.
n second delay circuits that form a pair with the delay circuit; a pulse generation circuit that sends pulses to the first and second delay circuits; and first and second capacitors in the first and second delay circuits that form the pair. Discriminate the phase difference between pulses delayed by an amount corresponding to the capacitance value of n
a phase discrimination circuit, and the phase discrimination circuit detects which main detection electrode is opposed to the main electrode, thereby detecting the amount of relative displacement of the one member and the other member. This can be achieved by

This capacitive displacement detector operates as follows. That is, in the initial state, one or more of the main sensing electrodes face the main electrode, and the remaining main sensing electrodes do not face the main electrode. The first capacitor having the remaining main sensing electrode has a small capacitance, and therefore the amount of pulse delay in the first delay circuit is small. On the other hand, since the second delay circuit paired with the first delay circuit has a larger delay amount than the first delay circuit, the phase discrimination circuit does not output any output.
In this way, the phase discrimination circuit connected to the main detection electrode that does not face the main electrode does not output any output. On the other hand, since the first capacitor having the main sensing electrode facing the main electrode has a large capacitance,
The amount of pulse delay in the first delay circuit having this first capacitor is large, and as a result, this first delay circuit has a large delay amount.
The amount of pulse delay increases due to the amount of delay in the second delay circuit paired with the delay circuit, and the phase of the pulse from the first delay circuit and the phase of the pulse from the second delay circuit are reversed, and the phase discrimination circuit Output.
In this way, the phase discrimination circuit connected to the main sensing electrode facing the main electrode provides an output. Next, when one and the other members are relatively displaced by a predetermined amount, the main sensing electrode different from the initial state faces the main electrode, and the remaining main sensing electrodes do not face the main electrode. At this time, as described above, there is an output from the phase discrimination circuit connected to the main detection electrode facing the main electrode, and the phase discrimination circuit connected to the main detection electrode not opposed to the main electrode. There is no output from . In this way, the amount of relative displacement between one member and the other member is detected depending on which phase discrimination circuit has an output in the initial state and which phase discrimination circuit has an output in the state after displacement. However, in this case, as mentioned above, there are n main sensing electrodes, and they are separated from each other by a distance P ₂ given by the formula (a ± 1/n) × P ₁ , so the Vernier principle Accordingly, the amount of displacement can be detected with an accuracy of 1/n of the distance P ₁ between the main electrodes. Also, during this detection, temperature,
Even if there is a change in environmental conditions such as humidity, the first and second capacitors forming the pair are affected in the same way, so these effects cancel each other out. Moreover, at the time of detection, each phase discrimination circuit has two outputs or non-outputs.
Since the value (digital quantity) is obtained, an A/D converter is not required to display the detection result numerically.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

Figures 1 and 2 show an example in which the present invention is applied to a caliper, which is a length measuring device.
is the main scale as one member, and this main scale 1
has a main body 2 made of metal and a support 3 made of an insulating material fixed to the surface of the main body 2, and a jig 4 is fixed to one end of the main scale 1. On the surface side of the support body 3, P ₁ are spaced equidistantly from each other,
A large number of main electrodes 5 are buried, for example, 1 mm apart, and these main electrodes 5 are lined up in the longitudinal direction of the main scale 1, and in the displacement direction of the vernier scale as described later. These main electrodes 5 are insulated from the main body 2 by the support 3 and have the same width and length. Further, all the main electrodes 5 are connected by a connecting band 6 buried in the support body 3, as shown in FIG. 1, and this connecting band 6 is grounded. These main electrodes 5 serve as the other plate of the first capacitor, which will be described later. Although not shown, a thin film made of synthetic resin is attached to the surface of the support 3, the main electrode 5, and the connecting band 6, and this thin film allows the main electrode 5 to come into direct contact with a main sensing electrode to be described later. This prevents short circuits. 7 is main scale 1
The vernier scale 7 and the main scale 1 are relatively movable in the longitudinal direction of the main scale 1. This vernier measure 7 has a metal main body 8
and a mounting body 9 fixed to the inner surface of the main body 8 and facing the support 3, and the mounting body 9 is made of an insulating material. The vernier scale 7 is provided with a jaw 10 that faces the jaw 4, and the object to be measured is held between these jaws 4 and 10. A thin plate 1 made of an insulating material is provided on the surface side of the mounting body 9.
1 is buried, and a main electrode 5 is buried on the surface of this thin plate 11.
n pieces (10 pieces in this example) arranged in the same direction as
A main sensing electrode 12 is buried therein. These main sensing electrodes 12 can face the main electrode 5,
Further, each main sensing electrode 12 has the same width and length. These main sensing electrodes 12 serve as one plate of a first capacitor to be described later, and together with the main electrode 5 constitute n first capacitors. Although not shown, a thin film made of synthetic resin is attached to the surfaces of the main sensing electrode 12 and the thin plate 11. The main sensing electrodes 12 are spaced apart from each other by an equal distance P ₂ , and this distance P ₂ is given by one of the following equations (A) and (B) representing the Vernier principle.

P ₂ = (a+1/n)×P ₁ ………(A) P ₂ = (a-1/n)×P ₁ ………(B) Here, P ₁ is the distance between the main electrodes 5. can be,
n is the number of main sensing electrodes 12, and is a positive integer of 2 or more. Further, a is a positive integer of 1 or more, and when a is 1, the main sensing electrode 12 is the main electrode 5.
When a is 2, the main sensing electrodes 12 correspond to approximately every other main electrode 5. In this example, formula (A) is used, P ₁ is 1 mm as described above, and n is
10 pieces, a is 1, and as a result, P ₂ is 11/
It will be 10mm. Thereby, if this vernier measure 7 is used, the relative displacement between the main measure 1 and the vernier measure 7 can be detected with an accuracy of 1/10 mm. In addition, in the well-known caliper, a zero scale is also provided on the vernier scale at a distance of (n+1)×P ₁ , that is, 11 mm from the zero scale, and the main detection electrode 12 is located at this zero scale position.
may be provided. Reference numeral 13 designates a belt-shaped sub-sensing electrode that is buried in the back surface of the thin plate 11 and overlaps with the main detecting electrode 12.
This becomes one plate of the capacitor. 14 is the mounting body 9
This shield plate 14 covers the back side of the main sensing electrode 12 and the sub-sensing electrode 13. The shield plate 14 is grounded, and as a result, the main sensing electrode 12 and the sub-sensing electrode 13 are electrostatically shielded from surrounding charges. 15 are n first delay circuits (only three are shown in FIG. 2), and each first delay circuit 15 is connected to a first capacitor 16.
have. Each first capacitor 16 has one main sensing electrode 12 serving as one plate, as described above.
and one main electrode 5 which serves as the other electrode plate (always interchanged depending on the relative displacement between the main scale 1 and the vernier scale 7).
Each first capacitor 16 has a minimum capacitance when the main sensing electrode 12 reaches the midpoint of two adjacent main electrodes 5, and the main sensing electrode 12 overlaps the main electrode 5. When they face each other, their capacitance is maximum. 17 is n (second
Only three of them are shown in the figure), and these second delay circuits 17 form a pair with the first delay circuit 15. Each of the second delay circuits 17 has a second capacitor 18, and these second capacitors 18 have a sub-detection electrode 13 serving as one common plate, and a shield plate 14 serving as the other common plate. , and as a result, the capacitance of the second capacitor 18 is always constant. 19 is a pulse generation circuit, and this pulse generation circuit 19 is connected to the first and second delay circuits 15 and 1.
Send a pulse to 7. Reference numeral 20 denotes n phase discrimination circuits, and these phase discrimination circuits 20 are connected to a pair of first and second delay circuits 15 and 17, respectively. Discriminate phase difference. 21 is a counting circuit, and this counting circuit 21 is connected to the phase discrimination circuit 20. This counting circuit 21 performs counting, carry-up, carry-down, etc., and outputs a display signal to the display 22.

Next, the operation of one embodiment of the present invention will be explained.

First, the magnitude of the capacitance of each first capacitor 16 is adjusted, and when the main sensing electrode 12 is not facing the main electrode 5, the phase of the pulse from the first delay circuit 15 including the main sensing electrode 12 is adjusted. is slightly advanced by the phase of the pulse from the paired second delay circuit 17, and on the other hand, when the main sensing electrode 12 faces the main electrode 5, the pulse from the first delay circuit 15 including the main sensing electrode 12 is slightly advanced. The phase of the pulse from the paired second delay circuit 17 is delayed. Such adjustment may be performed, for example, by the first delay circuit 1
This is done by adjusting the resistance value of a variable resistance element built in 5. When such an adjustment is made, the main sensing electrode 1 that is not facing the main electrode 5
There is no output from the phase discrimination circuit 20 connected to the main sensing electrode 1 , which is connected to the main sensing electrode 5 .
There is an output from a phase discrimination circuit 20 connected to 2. Next, the vernier scale 7 is displaced toward one end of the main scale 1 to bring the jaws 4 and 10 into contact with each other. At this time, the first main sensing electrode 12a is the first main sensing electrode 5.
The remaining main sensing electrodes 12 overlap and face a.
b, 12c, 12d... are main electrodes 5b, 5c, 5
d... and not facing each other. As a result, the capacitance of the first first capacitor 16 increases, and the amount of delay of the pulse in the first delay circuit 15a increases. As a result, the phase of the pulse from the first delay circuit 15a lags behind the phase of the pulse from the second delay circuit 17a, and an output is sent from the first phase discrimination circuit 20a to the counting circuit 21. . Meanwhile, the remaining first
Since the capacitance of the capacitor 16 remains small, the amount of pulse delay in these first delay circuits 15b, 15c, . . . is the same as that of the paired second delay circuit 17.
b, 17c..., and as a result, the first delay circuits 15b, 15c...
The phase of the pulse from the second delay circuit 17b, 17
The remaining phase discrimination circuits 20b, 20c... remain slightly ahead of the phase of the pulse from c...
There is no output from .... In this way, when the output from only the first phase discrimination circuit 20a is sent to the counting circuit 21, 0 is displayed in the 1/10 digit of the display 22. Next, the vernier scale 7 is displaced toward the other end of the main scale 1 to sandwich the object to be measured between the jaws 4 and 10. At this time, as shown in FIG. 2, for example, the first main sensing electrode 12a is connected to the thirteenth main electrode 5
If the remaining main detection electrodes 12 are offset from the main electrode 5, only the first phase discrimination circuit 20a will output, and the display 22 will be 1/1
The tens place indicates 0. Note that when the vernier scale 7 is displaced, the first main detection electrode 12a is connected to the main electrode 5b,
A carry is carried out in the counting circuit 21 every time 5c, 5d... is faced, and the 1 digit on the display 22 is
, and the tens place indicates 1. Therefore,
By directly reading the display on the display 22, one can easily know that the length of the object to be measured is 12.0 mm. Further, for example, the first main sensing electrode 12a
is located between the 13th and 14th main electrodes 5m and 5n, and the 3rd main sensing electrode 12c faces the 16th main electrode 5p, the 3rd phase discrimination It is output only from the circuit 20c, and the display 2
The 1/10th digit of 2 represents 8, the 1s digit represents 2, and the tens digit represents 1. That is, the display 22 indicates that the length of the object to be measured is 12.8 mm.

In the above-mentioned embodiment, the case where the present invention was applied to a caliper which is a length measuring device was explained, but the present invention can also be applied to other length measuring devices such as a height gauge, a micrometer, a dial gauge, and a linear length measuring device. It can also be applied to Further, the present invention can also be applied to an angle detector such as a rotary encoder shown in FIG. 3, for example.
In the figure, 28 is a motor, 29 is a rotating shaft of the motor, and a disk 30 as one member is fixed to this rotating shaft 29. A large number of main electrodes 31 are attached to the surface of this disk 30, aligned in the rotation direction (displacement direction) of the disk 30, and these main electrodes 31 are spaced apart from each other by an equal distance _P1 . 32 is a fixed block as the other member, and this fixed block 32 is provided with n main detection electrodes 33 which are arranged in the same direction as the main electrode 31 and can face the main electrode 31. These main sensing electrodes 33 are separated by a distance P ₂ given by the above formula.
only apart from each other. Furthermore, the fixed block 32 is provided with a sub-detection electrode 34 and a shield plate 35 as described above. Furthermore, although not shown, a pulse generation circuit, first and second delay circuits, a phase discrimination circuit, a counting circuit, and a display are connected to the main and sub-sensing electrodes 33 and 34 as described above. With such a rotary encoder, the angle of adjacent main electrodes 31 can be read with an accuracy of 1/n. In addition, in the above embodiment, the case where n is 10 was explained, but n may be a positive integer of 2 or more. For example, when n is 20, the distance
P ₁ can be detected with an accuracy of 1/20, and when n is 100, the distance P ₁ can be detected with an accuracy of 1/100. Also,
In the above embodiment, 1 was used as a in the formula (a±1/n)×P ₁ , but a may be a positive integer of 2 or more, for example, 5. In this case, the fourth
As shown in the figure, each main sensing electrode 41 is formed into a comb-teeth shape, and the five tooth portions 42 of this main sensing electrode 41,
If the distance Q between the main electrodes 43, 44, 45, and 46 is made equal to the distance _P1 between the main electrodes 5, each main sensing electrode 41 can face the main electrode 5 at five locations simultaneously, so that the measurement is reliable. Also, the first and second
Between the delay circuits 15, 17 and the phase discrimination circuit 20, there is an offset circuit constructed of a known one-shot multivibrator or the like, which delays the output pulses of the first and second delay circuits 15, 17 by an arbitrary amount and outputs the delayed pulses. A delay adjustment circuit for adjustment may be inserted. Furthermore, in the embodiment described above, the main sensing electrode 12
When the electrodes 12 and 5 completely overlap the main electrode 5, these electrodes 12 and 5 are said to be facing each other, but in this invention, when the electrodes 12 and 5 overlap each other at a certain ratio or more, They may be facing each other. In such a case, a plurality of main sensing electrodes 12 will simultaneously face the main electrode 5, respectively. Furthermore, in the above-described embodiment, a case was explained in which the sub-sensing electrode 13 was placed apart from the main detecting electrode 12 with respect to the upper main electrode 5 integrated in a series, but in this invention, the sub-sensing electrode The upper main electrode may be placed at the same position and at the same pitch as the electrodes, but may be placed apart from the main sensing electrode.

As described above, according to the present invention, it is possible to detect the amount of displacement of a relatively displaced member with high accuracy without being affected by the surrounding environment.
Furthermore, since the output is a digital quantity, an A/D converter is not required, making the overall structure simple and inexpensive.

[Brief explanation of drawings]

Fig. 1 is a schematic perspective view showing an embodiment in which the present invention is applied to a caliper, and Fig. 2 is a -
3 is a partially cutaway plan view showing another embodiment of the present invention, and FIG. 4 is a main electrode and main sensing electrode showing still another embodiment of the present invention. FIG. DESCRIPTION OF SYMBOLS 1... One member (main scale), 5... Main electrode, 7... Other member (vernier scale), 12... Main detection electrode, 13... Sub-detection electrode, 15... First delay circuit, 16... First capacitor, 17...Second delay circuit, 18...Second capacitor, 19...Pulse generation circuit, 20...Phase discrimination circuit.

Claims (1)

[Claims] 1. A plurality of main electrodes are provided on one member that is relatively displaceable, spaced apart from each other by an equal distance P ₁ in the direction of displacement, and the other member is provided with a number of main electrodes so that they can face the main electrodes in the same direction. n main sensing electrodes separated from each other by a distance P ₂ given by the arrangement formula (a±1/n)×P ₁ [where n is a positive integer of 2 or more, a is a positive integer of 1 or more] , a sub-sensing electrode is provided on the one or the other member, the one main sensing electrode is one of the electrode plates, and a first electrode is formed of the main sensing electrode and the main electrode.
n first delay circuits each having a capacitor; n second delay circuits each having a second capacitor having the sub-sensing electrode as one plate and forming a pair with the first delay circuit; A pulse generation circuit that sends pulses to the first and second delay circuits, and the pulses that are delayed by an amount corresponding to the capacitance values of the first and second capacitors in the pair of first and second delay circuits. n phase discrimination circuits for discriminating phase differences between the two members, and the phase discrimination circuit detects which main sensing electrode is opposed to the main electrode, thereby determining the relative displacement of the one and the other member. A capacitive displacement detector characterized by detecting a quantity.