JPS648286B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a capacitively coupled displacement detection device.

A capacitively coupled displacement detection device generally has a plurality of fixed electrodes arranged in a row and a movable electrode arranged to face them, and adjacent fixed electrodes have the same amplitude and a phase difference of 90°. The amount of displacement of the movable electrode is detected by applying a sinusoidal voltage shifted by a degree and utilizing the fact that the phase of the voltage induced therein changes in accordance with the displacement of the movable electrode. Conventionally, in this type of displacement detection device, in order to improve detection accuracy, one in which the fixed electrode is segmented has been proposed. however,
The detection accuracy of the device is not determined only by the structure of the electrodes, but also greatly depends on the accuracy of the electric circuit that detects the phase of the induced voltage. Therefore, in order to improve the detection accuracy of the device, In addition to improving the accuracy of the phase detection circuit, it is also necessary to improve the phase stability of an amplifier or the like used between the movable electrode and the phase detection circuit.

The present invention eliminates the drawbacks of conventional devices as described above, and provides a simple displacement detection device that can detect displacement with high accuracy without being affected by the phase stability of amplifiers used in the middle of the detection circuit. The purpose is to realize this through configuration.

In the displacement detection device of the present invention, two movable electrodes are arranged for one fixed electrode, and these movable electrodes are used as a reference side and a measurement side in displacement detection, respectively. By detecting the displacement on the measuring side with respect to the reference side from the difference in displacement amount, displacement can be detected with high accuracy without being affected by the phase stability of amplifiers, etc. used in the middle of the detection circuit. .

Hereinafter, the displacement detection device of the present invention will be explained using the drawings.

FIG. 1 is a block diagram showing an embodiment of the displacement detection device of the present invention, and here, a case where it is applied to the detection of angular displacement is illustrated. In the figure, S ₁ to S ₄ are fixed electrodes, P ₁ and P ₂ are movable electrodes, and the fixed electrodes S ₁ to _{S 4} are arranged in the circumferential direction, and the movable electrodes P ₁ and P ₂
are arranged to face each other from both sides so as to sandwich the fixed electrodes S ₁ to _{S 4} . Here, movable electrode P ₁ is used as the measurement side in displacement detection, and movable electrode P ₂ is used as _the reference side, and the movable electrode
The amount of displacement of P ₁ is detected. e ₁ to e ₄ are sinusoidal voltages applied to the fixed electrodes S ₁ to S ₄ , respectively, and e _P1 and e _P2 are voltages induced in the movable electrodes P ₁ and P ₂ , respectively. In addition, 1 is an oscillator, 2 is a frequency divider that divides the output o of oscillator 1 and generates a reference frequency signal e _g , and 3 is a phase shifter of 90 degrees based on the reference signal e _g . This is a phase shift circuit that generates sinusoidal voltages _e1 to _e4 . The sinusoidal voltage e ₁ to e ₄ generated here
is applied to the fixed electrodes S ₁ to S ₄ described above. 4
₅ is an amplifier, ₆ is a _waveform shaping circuit, 7 is _a gate that opens and closes using a reference signal e _g synchronized with the sine wave voltage e ₁ ; A gate circuit 8 generates a pulse width signal S _P according to the phase difference between the induced voltages e _P1 and e _P2 , and 8 calculates the displacement amount of the movable electrodes P ₁ and P ₂ from this pulse width signal S _P , and calculates the difference between them. 9 is a display that displays the output of the data processing circuit 8.

The operation of the displacement detection device of the present invention configured as described above is as follows. movable electrode
P ₁ and P ₂ are capacitively coupled with fixed electrodes S ₁ to S ₄ ,
The degree of coupling depends on the positions of the movable electrodes P ₁ and P ₂ , that is, the amount of angular displacement. Here, the fixed electrode
Since sinusoidal voltages e ₁ to _{e 4} with the same amplitude and 90 degrees of phase shift between adjacent electrodes are applied to S ₁ to S ₄ , movable electrodes P ₁ and P ₂ are connected to fixed electrode S ₁ If the position opposite to is set as the reference position, the movable electrode P ₁ ,
Voltages e _P1 and e P2 whose phase difference with respect to the sinusoidal voltage e ₁ is proportional to the angular displacements _{θ 1} and θ ₂ are induced in _{P 2} .

In the device shown in the figure, the circumference is divided by four fixed electrodes S ₁ to _{S 4} , so the angular displacements θ ₁ and θ ₂ of the movable electrodes P ₁ and P ₂ expressed in mechanical angles are This coincides with the phase difference between the induced voltages e _P1 and e _P2 expressed in electrical angle. Therefore, the induced voltages e _P1 and e _P2 can be expressed as follows.

e _P1 = k ₁ E _sio (〓t-ψ ₁ ) e _P2 = k ₂ E _sio (〓t-ψ ₂ ) k ₁ , k ₂ are constants As is clear from the above equation, the induced voltage e _P1 , e _P2 By measuring _the phase difference ψ _{1 ,} ψ ₂ with respect to _the sinusoidal voltage e _{1 at}
can be detected.

The induced voltages e _P1 and e _P2 are alternately switched by a switch SW and sent to a waveform shaping circuit 6 via an amplifier 5.
is applied to In the waveform shaping circuit 6, it is converted into a pulse signal synchronized with this, and the gate circuit 7
is applied to Since the reference signal e _g applied to the other input of the gate circuit 7 is synchronized with the sine wave voltage e ₁ , in the gate circuit 7, the sine wave voltage e ₁ (reference signal e _g ) and the induced voltage e _P1 , _e Pulse width signal with pulse width according to phase difference ψ ₁ , ψ ₂ with P2
_SP is obtained. This situation is shown in FIG. In addition,
The switch 1 described above switches the induced voltages e _P1 and e _P2 at a sufficiently long period with respect to the reference signal e _g .
The error at the time of switching is caused by the data processing circuit 8, which will be described later.
are averaged and removed.

In the data processing circuit 8, the output of the oscillator 1 is counted according to each pulse width signal S _P obtained by the gate circuit 7, and the pulse width proportional to the angular displacement amounts θ ₁ and θ ₂ is quantified. , calculates the difference between the angular displacements θ ₁ and θ ₂ from these data, and displays it on the display 9.
to be displayed. Here, in the displacement detection device of the present invention, one of the two movable electrodes P ₁ and P ₂ (P ₂ ) is used as the reference side in displacement detection, and the other (P ₁ ) is used as the measurement side. , the displacement θ to be measured is the movable electrode obtained as above.
It is obtained as the difference between the displacement amounts θ ₁ and θ ₂ at P ₁ and P ₂ .

In this way, the movable electrodes on the reference side and measurement side
Measure the positions of P ₁ and P ₂ with fixed electrode S ₁ as a reference,
If these measured values are calculated to determine the displacement θ between the movable electrodes P ₁ and P ₂ , the displacement θ between the movable electrodes P 1 and P ₂ is calculated.
It is possible to cancel out the error that is mixed into the measured value when measuring the position of P ₂ and to detect the displacement θ with high accuracy. That is, the displacement amount θ ₁ of the movable electrodes P ₁ , P ₂ ,
Assuming that δ ₁ and δ ₂ are the errors caused by the drift of the amplifier 5 and the hysteresis of the waveform shaping circuit 6 that are mixed in when measuring θ ₂ , the actual measured values θ ₁ ′ and θ ₂ ′ are as follows: θ ₁ ′= θ ₁ +δ ₁ θ ₂ ′=θ ₂ +δ ₂ . Here, if the voltage levels of the induced voltages e _P1 and e _P2 are almost equal, including the time factor, δ ₁
= δ ₂ , so the displacement θ obtained by the data processing circuit 8 is θ=θ ₁ ′−θ ₂ ′=θ ₁ +δ ₁ −(θ ₂ +δ ₂ )=θ ₁ −θ ₂ , and will not be affected by the errors δ ₁ and δ ₂ .

In the above description, the displacement detection device of the present invention is applied to detect angular displacement. However, if the fixed electrodes are arranged linearly, linear displacement can be detected. In addition, if the movable electrode on the reference side is also displaced as an input signal, the amount of relative displacement between the two movable electrodes can be detected. Also, in the above explanation, the circumference (360 degrees) is divided into four equal parts of 90 degrees each using four fixed electrodes S ₁ to S ₄ .
The fixed electrodes can be divided arbitrarily, and the phase difference between the voltages applied to adjacent fixed electrodes is not limited to 90 degrees. Furthermore, the voltage applied to the fixed electrodes does not have to be a sine wave. For example, a similar operation can be achieved by applying a square wave to the fixed electrode and extracting a sine wave component from the induced voltage using a filter.

As explained above, in the displacement detection device of the present invention, two movable electrodes are arranged for one fixed electrode, and these movable electrodes are used as the reference side and measurement side in displacement detection, respectively. Since the displacement amount on the measurement side with respect to the reference side is detected from the difference in the displacement amount measured for the electrode, it is not affected by the phase stability of the amplifier used in the middle of the detection circuit, and the displacement can be accurately measured. A displacement detection device capable of detecting well can be realized with a simple configuration.

[Brief explanation of drawings]

FIGS. 1 and 2 are configuration diagrams showing one embodiment of the displacement detection device of the present invention. _S1 to _S4 ...Fixed electrode, _P1 , _P2 ...Movable electrode, 1...
Oscillator, 2... Frequency divider, 3... Phase shift circuit, 4... Switch, 5... Amplifier, 6... Waveform shaping circuit, 7... Gate circuit, 8... Data processing circuit, 9... Display.

Claims (1)

[Claims] 1 A fixed electrode to which voltages having the same amplitude and a phase shift are applied to adjacent electrodes, and two movable electrodes arranged oppositely on both sides of the fixed electrode so as to sandwich the fixed electrode, the movable electrode The amount of displacement of each movable electrode from the reference position is detected using the phase change of the voltage induced in each movable electrode according to the displacement of the two movable electrodes. A displacement detection device is used for detecting the displacement on the measurement side with respect to the reference side from the difference in the amount of displacement of each movable electrode determined as described above.