JPH03137568A - Device for detecting moving object electrostatically - Google Patents

Abstract

PURPOSE:To eliminate restriction of material of an attachment mounted on a moving object by providing one oscillation circuit and two tuning circuits to detect a change in electrostatic capacitance with the movement of the moving object as change in a tuning point of each of the tuning circuits. CONSTITUTION:A pair of electrodes 3 and 3' is provided facing an attachment 14 mounted on a moving object to detect movement of the attachment 14 as change in electrostatic capacitance. When the moving object moves in this arrangement, the attachment 14 moves in linkage with this, parts 16 and 17 to be detected of the attachment pass near the electrodes. As a result, the movement of the moving object is detected as change in capacitance with the electrodes 3 and 3' to apply a detection signal to corresponding first and second tuning circuits 2 and 2' from the electrodes. The tuning circuits 2 and 2' causes a change in resonance frequency according to the change in capacitance to transmit a corresponding signal. An output circuit 7 determines a difference of signals applied from the tuning circuits 2 and 2' to output a differential signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrostatic detection device for a moving object that detects changes in capacitance to detect the amount of rotational or linear physical movement of the moving object. It is something.

[Conventional technology]

Conventionally, magnetic devices, electromagnetic induction devices, and optical devices are known as rotational movement detection devices.

The magnetic device has a plurality of north and south poles magnetized on the surface of a rotating drum made of magnetic material, and this rotating drum is attached to a rotating shaft, and the rotating drum rotates integrally with the rotating shaft. A magnetic sensor is arranged nearby, and the amount of rotational movement of the rotating shaft is detected by the magnetic sensor via the rotating drum.

Also, 1! The magnetic induction type device is equipped with an mN body attachment that is attached to a rotating shaft, and a coil type detection unit is installed near this attachment to detect unevenness and rainbow current formed on the surface of the attachment.
This detects the amount of rotational movement of the rotating shaft.

Furthermore, optical devices are capable of detecting the amount of light reflected from the attachment by alternately providing parts that reflect light and surfaces that hardly reflect light on the surface of an attachment attached to a rotating body. This detects the amount of rotational movement of the rotating body.

[Problem to be solved by the invention]

However, the magnetic device has a limitation in that the rotating drum must be made of a magnetic material, and the electromagnetic induction device also has a material limitation in that the attachment must be made of a dielectric material. be.

In addition, optical devices have the problem of having to form areas of strong and weak light reflection on the surface of the attachment, and the optical system that processes the amount of reflected light also becomes complicated. .

The present invention has been made in order to solve the above-mentioned conventional problems, and its purpose is to eliminate restrictions on the material of attachments attached to moving objects (and to provide electrostatic detection for moving objects with a simple device configuration). The goal is to provide equipment.

[Means to solve the problem]

In order to achieve the above object, the present invention is configured as follows. That is, the present invention provides an attachment that is attached to a movable body and is provided with a detected part for detecting the movement of the movable body by a change in capacitance with respect to the detected part, and a movement of the attachment that moves together with the movable body. An electrostatic detection device for a moving object that includes an electrostatic sensor device that detects by a change in capacitance, the electrostatic sensor device including one oscillation circuit that oscillates and outputs a frequency signal, and the attachment. two tuning circuits, a first and a second tuning circuit whose tuning point with the frequency signal changes in response to a change in external capacitance detected by the detected section; and a signal applied from the first tuning circuit side. and an output circuit that sends out a differential output of the signal applied from the second tuning circuit side.

[Effect]

In the present invention, for example, a pair of electrodes are provided opposite to an attachment mounted on a moving body to detect movement of the attachment as a change in capacitance. In this state, when the moving object moves, the attachment moves in conjunction with this, and the detected part of the attachment passes near the electrode (as a result, the movement of the moving object is caused by capacitance between the pair of electrodes). is detected as a change in the external capacitance, and a detection signal is applied from each electrode to the corresponding first and second tuning circuits.Each tuning circuit changes the resonant frequency in accordance with this change in external capacitance. The output circuit sends out a signal corresponding to the change in capacitance.The output circuit calculates the difference between the signal applied from the first tuned circuit side and the signal applied from the second tuned circuit side, and outputs the differential signal. Output.

〔Example〕

EMBODIMENT OF THE INVENTION Hereinafter, one embodiment of the electrostatic detection device for a moving object according to the present invention will be described based on the drawings. A block diagram of an embodiment of the present invention is shown in FIG. 1. The device of this embodiment consists of an attachment 14 and an electrostatic sensor device. As shown in FIG. 3, the attachment 14 is constituted by a disk made of metal or synthetic resin having a shaft hole 15, and a plurality of convex portions 16 are formed at equal angular intervals on the side surface of the disk. The convex portion 16 and the concave portion 17 constitute a capacitance detected portion.

On the other hand, the electrostatic sensor device includes an oscillation circuit 1, a tuning circuit 2,
2', detection circuits 4 and 4', amplifier circuits 5 and 5', and a differential amplifier 7 as an output circuit. The oscillation circuit 1, the tuning circuit (first tuning circuit) 2, the detection circuit 4, and the amplifier circuit 5 constitute a first series sensor circuit 13a. A second series of sensor circuits 13b is composed of a circuit (second tuning circuit) 2', a detection circuit 4', and an amplifier circuit 5'. That is, two series of sensor circuits 13 share one oscillation circuit 1.
a, 13b are formed, and each sensor circuit 13a, 13
A differential amplifier 7 is connected to the output side of b.

In this embodiment, the first series of sensor circuits 13a and the second series of sensor circuits 13b have the same circuit configuration.

FIG. 2 shows the details of one series (first series) of sensor circuits, in which the oscillation circuit 1 uses an ultra-high frequency, which in this embodiment is 0.
A ceramic resonator IO is used as a dielectric resonator that oscillates at a fixed and constant oscillation frequency within the range of 5 GHz to 5 GHz. This oscillation circuit l oscillates the high frequency oscillation signal and converts it into the high impedance conversion section 6.
is applied to the tuning circuit 2 from the output side of the . This tuning circuit 2 is constituted by a ceramic resonator 12 as a dielectric resonator separate and independent from the dielectric resonator lO of the oscillation circuit 1, and the detection section 11 includes a pickup electrode 3 for detecting changes in external capacitance. is connected.

The detection circuit 4 is connected to the ceramic resonator 12 via a coupling capacitor 25, and this detection circuit 4 includes an inductance element 21, a diode 22, and a capacitor 23.
and a resistor 24, and the output signal from the ceramic resonator 12 is applied to the detection circuit 4 via a coupling capacitor 25. The diode 22, the capacitor 23, and the resistor 24 constitute a detection section of the detection circuit, and in this embodiment, the operating point of the diode 22 has a bias point set sufficiently deep on the negative side from 0 voltage. . The detection section performs envelope detection of the ultra-high frequency output signal output from the ceramic resonator 12, and converts it into a signal in the signal band of the detected object.

In this way, the detection section detects the ultra-high frequency signal from the ceramic resonator 12. At this time, if we consider the characteristic impedance of the diode 22, we can see that the forward impedance of the diode 22 has a large effect on the ceramic resonator 12. If the diode 22 is directly connected to the resonator 12, the Q of the resonator 12 will be lowered. In order to prevent this inconvenience, the inductance element 21 is connected to the anode side of the diode 22. In other words, the capacitor 25 and the inductance element 21 function as a high impedance circuit and prevent Q from decreasing.

The amplifier circuit 5 is constructed using elements such as a transistor 27 and a resistor, and this amplifier circuit 5 amplifies the signal applied from the detection circuit 4 and supplies it to the output circuit.

Note that the head of the symbol in the circuit of FIG. 2 indicates a grounding point.

As mentioned above, the electrostatic sensor device has two series of sensor circuits 13a and 13b configured as described above, and a high frequency signal is transmitted from the common oscillation circuit l to each sensor circuit. It is added to the tuning circuits 2, 2' of the series. The signals sent out from the amplifier circuits 5, 5' of each series are applied to a differential amplifier 7 as an output circuit.

One side of the pickup electrodes 3, 3' provided in the detection section 11 of the sensor circuits 13a, 13b is arranged to face the protrusion 16 as the detected section of the attachment 14, and the other side electrode 3' The recess 17 serving as the detection target portion of 14 is disposed opposite to the recess 17 . That is, with respect to the attachment 14, when the pick-up electrode 3 (3') on the other side has the minimum capacitance, the pick-up electrode 3 (3) on the other side is located at the position where the capacitance is the maximum. Ru.

This embodiment is configured as explained above, and the following will be explained below.
Its operation will be explained.

As shown in FIG. 10, the oscillation frequency r of the oscillation circuit 1 is set at a position slightly shifted from the resonance frequency (tuning frequency) f of the ceramic resonator 12 of the sensor circuits 13a and 13b. When the attachment attached to the rotating shaft of the device to be measured rotates together with the rotating shaft, a change in capacitance occurs between the pickup electrode 3.3' and the attachment H4 with the rotating shaft side as the ground. That is, as shown in FIG. 4(a), from a state in which the pickup electrode 3 faces the recess 17 of the attachment 14 and the pickup electrode 3' faces the projection 16, the attachment H4 rotates and moves in the direction of the arrow. Then, the fourth
As shown in Figure (b), the pickup electrode 3 has a convex portion 16
, and the pickup electrode 3' faces the recess 17. In this manner, as the attachment 14 rotates, the pickup electrodes 3.3' alternately face the convex portions 16 and the concave portions 17 of the attachment 14, and the pickup electrodes 3.3'
For example, the capacitance detected by the pickup electrode 3 is ΔC in FIG.
When the resonant frequency of the tuning circuit 2 is shifted by Δf, the output voltage change component Δ■ corresponding to the capacitance change component ΔC can be taken out from the subcircuit 2. Similarly, when the capacitance detected by the pickup electrode 3' changes by ΔC', the resonance frequency of the tuned circuit 2' shifts by Δr', and a changing component Δ■' of the output voltage is taken out from the tuned circuit 2'. In addition, in the tuned circuit 2.2', the oscillation frequency f, and the change component Δ of the resonant frequency in the tuned circuit 2.2',
Multiplication with Δf′ is performed. That is, in the first series sensor circuit 13a, the frequency signal of the oscillation frequency f,
Multiplication by the change component Δf of the resonance point is performed, and the second
In the series sensor circuit 13b, a frequency signal with an oscillation frequency f is multiplied by a variation component Δf' at the resonance point, and so-called AM modulation is obtained. 7, the modulation signal of each series becomes an ultra-high frequency signal centered on IGI (z) and corresponding to the level difference between the convex portion 16 and the concave portion 17, and this ultra-high frequency signal is transmitted to the corresponding detection circuit 4.4. '.The detection circuit 4.4' performs envelope detection on this ultra-high frequency signal to determine the signal band of the detected part (3 MHz signal in this example).
Convert to This band-converted signal is sent to the amplifier circuit 5゜5.
', and its output signal is sent to a differential amplifier 7 as an output circuit.

The differential amplifier 7 calculates the difference between the signal applied from the first series amplifier circuit 5 and the signal applied from the second series amplifier circuit 5', amplifies it, and outputs it as a single differential detection signal. It is added to a signal processing circuit, etc. not shown. This signal processing circuit is composed of, for example, a computer circuit including a comparator, and the differential detection signal applied from the differential amplifier 7 is shaped into a pulse waveform by the comparator, and the number of pulses is counted and calculated. In addition, by measuring and calculating the time between pulses, rotational acceleration can be detected.Furthermore, the voltage value of the differential detection signal applied from the differential amplifier 7 can be analyzed. By doing so, it becomes possible to detect the minute rotational position of the rotating body.

As described above, according to this embodiment, the capacitance detection signal detected by the sensor circuit 13a and the sensor circuit 1
Since a differential output with the detection signal detected by 3b is required, error factors such as runout and eccentricity of the rotating shaft are effectively removed, making it possible to detect rotation with high reliability and precision. becomes.

In addition, in this embodiment, the resonators of the oscillation circuit 1 and the tuning circuit 2゜2' are both constituted by dielectric resonators.
The device can be made smaller. Furthermore, since the dielectric resonator is constructed of a ceramic dielectric material with a high Q and the circuit is made to have a high impedance, ultra-high sensitivity detection of minute capacitance is possible. 'P
Changes in capacitance as small as F can be detected. When performing electrostatic detection using an ultra-high oscillation frequency with such an ultra-high sensitivity device, the oscillation frequency of the first series sensor circuit 13a and the oscillation frequency of the second series sensor circuit 13b may be slightly different. However, if the sensor circuits 13a and 13b are different, mutual interference occurs and accurate detection cannot be performed.However, by sharing the oscillation circuit l of the sensor circuits 13a and 13b as in this embodiment,
Such adverse effects can be completely prevented, and highly reliable and highly accurate detection is possible.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and may take various embodiments.For example, in the above-mentioned embodiments,
Although the convex portion 16 and the concave portion 17 as the detected portion are formed on the side surface of the disc, these can also be formed on the circumferential surface of the disc as shown in Fig. 5, and can also be used as a gear-shaped attachment. often,
Alternatively, as shown in FIG. 6, metal vapor deposition films 18 are formed at equal angular intervals on the circumferential surface or side surface (the side surface in FIG. 5) of an insulating disc made of glass, etc. It is also possible to configure the detected portion by utilizing the difference in dielectric constant from the metal vapor deposited film 18 portion.

Furthermore, in the above embodiment, both the resonator of the oscillation circuit 1 and the resonator of the tuning circuit 2.2' are constructed of dielectric resonators (ceramic resonators), but they can also be constructed of strip lines. It is.

Furthermore, the electrostatic sensor device of the above embodiment has an AFC (^u
tomatic Frequency Control
) Although no circuit is provided, for example, as shown in Figure 7,
An AFC circuit 8 may be provided in each series of sensor circuits. This AFC circuit 8 includes, for example, an operational amplifier 28, a capacitor 29.30, a variable resistor 31, and a resistor 32.3.
5, variable capacitance diode 33, and coupling capacitor 34
The variable capacitance diode 33 includes a capacitor 30 and a resistor 32.
The capacitance is changed according to the voltage applied from the integrating circuit configured by the coupling capacitor 34
to the ceramic resonator 12 to change the resonant frequency of the resonator 12. By providing this AFC circuit 8, it is possible to shift the oscillation frequency f1 to the left or right in FIG. 10, and therefore, the tuning point can be changed by shifting the oscillation frequency r. In other words, it becomes possible to arbitrarily vary the level of the detection voltage for capacitance change and its detection level range, and the sensitive rotation speed of the rotating shaft to be detected and its detection range can be variably adjusted as appropriate. becomes possible. In contrast, in this embodiment, which does not have an AFC circuit, the DC level (direct current level)
The advantage is that movement detection can be performed from A F
There is an advantage of not providing a C circuit), and signal processing can be facilitated.

Further, in the above embodiment, the detection example of the rotational movement of the rotating shaft was explained, but the detected portion as shown in FIGS. 2 to 5 is formed on, for example, a flat surface, and It is also possible to attach the attachment to a moving table of a machine tool, etc., and use it as a near encoder to detect the linear movement of a moving body.

Rotation detection example A polyacetal gear and a brass gear were used as attachments, and these were attached to the rotating shaft to be measured, and a rotation detection experiment was conducted with the rotating shaft on the ground side. Both the polyacetal gear and the brass gear have a module of 0.5, a number of teeth of 30, and a cutting edge diameter of 16 mm. The differential output of the detection signal of the detected capacitance was determined. FIG. 8 shows the differential output when brass gears are used, and FIG. 9 shows the waveforms of the differential output when polyacetal gears are used. Note that the horizontal axis of these figures represents time, and the vertical axis represents differential output voltage. As can be seen from these figures, changes in the differential output voltage as the gears rotate clearly appear, demonstrating that highly sensitive and highly accurate rotation detection is possible.

〔Effect of the invention〕

The present invention includes one oscillation circuit and two tuned circuits, and detects changes in capacitance caused by movement of a moving body detected by a detected part of an attachment by changes in the tuning point of each tuned circuit. Since it is configured to detect as follows, and obtain the differential output of the detection signals output from these two tuned circuits, it is possible to eliminate error factors caused by vibration and eccentricity of the moving body. This enables highly reliable and highly accurate movement detection.

Further, as described above, since the movement of the moving body is detected using a change in capacitance, there is no restriction on the material of the attachment, and the attachment can be made of any material.

In addition, since the capacitance detection part can be configured simply by arranging two pickup electrodes facing the attachment, the device manufacturing is easy, and the device exhibiting the excellent performance of the present invention can be easily constructed. can be provided at low cost.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the electrostatic detection device for a moving body according to the present invention, FIG. 2 is a circuit diagram of a series of electrostatic sensor devices constituting the device of the embodiment, and FIG. A configuration diagram of an attachment constituting the device of the same embodiment, FIG. 4 is an action explanatory diagram showing an example of electrostatic detection of a rotating moving body in the same embodiment,
5 and 6 are perspective views showing other configuration examples of the attachment, FIG. 7 is a circuit diagram of a series of electrostatic sensor devices equipped with an AFC circuit, and FIGS. 8 and 9 are the same embodiments. A waveform diagram of a differential output obtained by detecting the rotation of a rotating body using the device, and FIG. 10 are explanatory diagrams showing the principle of detecting minute capacitance of the electrostatic sensor device constituting the device of this embodiment. ■...Oscillation circuit, 2.2'...Tuned circuit, 3.3'
...Pickup electrode, 4.4'...Detection circuit, 5
゜5'...Amplification circuit, 6...High impedance conversion section, 7...Differential amplifier, 8...-AFC circuit, 10...
- Ceramic resonator, 11... Detection unit, 12... Ceramic resonator, 13a, 13b... Sensor circuit, 1
4... Attachment, 15... Shaft hole, 16...
Convex portion, 17... Concave portion, 18... Metal vapor deposited film, 21.
...Inductance element, 22...Diode, 23
... Capacitor, 24... Resistor, 25... Coupling capacitor, 27... Transistor, 28... Operational amplifier, 29.30... Capacitor, 31... Variable resistor, 32.35 ...Resistor, 33...Variable capacitance diode, 34...Coupling capacitor.

Claims (1)

[Claims] An attachment is attached to a moving body and is provided with a detected part for detecting the movement of the moving body by a change in capacitance, and the attachment that moves together with the moving body is detected by a change in capacitance with respect to the detected part. An electrostatic detection device for a movable body configured with an electrostatic sensor device that detects a signal, the electrostatic sensor device includes one oscillation circuit that oscillates and outputs a frequency signal, and a detection target portion of the attachment that detects the electrostatic signal. two tuning circuits, a first and second tuning circuit whose tuning point with the frequency signal changes in response to a change in external capacitance; and a signal applied from the first tuning circuit side and the second tuning circuit. An electrostatic detection device for a moving object, which includes an output circuit that sends out a differential output with a signal applied from the side.