JPS6352067A - Revolution indicator - Google Patents

Abstract

PURPOSE:To obtain a small-sized, high-accuracy, and fast-response revolution indicator which easily detects information on a rotating direction in addition to a rotating speed by composing a sensor part of a couple of electrode plates and a dielectric plate as a variable capacitor. CONSTITUTION:The sensor part 2 is formed by providing the couple of electrode plates 2a and 2b or dielectric plate 2c sandwiched between them to a rotating shaft 3 for measurement and setting the shapes of the electrode plates 2a and 2b or dielectric plate 2c so that the electrostatic capacity between the electrode plates varies by the rotation of the rotating shaft asymmetrically about the center of one cycle in the time base direction, thus constituting the variable capacitor. An electrostatic capacity detection part 5 obtains a detection signal S0 corresponding to variation in the electrostatic capacity by using a charge amplifier which can measure even fine electrostatic capacity accurately. Then a signal processing part 6 finds and displays 12 the rotating speed of the rotating shaft 3 by using the number of times of the asymmetric variation in the electrostatic capacity and displays and also decides and displays 14 the rotating direction by using the shape of the asymmetric variation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a tachometer using a capacitance detection method using a charge amplifier.

[Conventional technology]

BACKGROUND ART Conventionally, as a method for detecting the number of rotations of a rotating functional unit in various devices, a pulse conversion method in which the number of rotations is processed by converting it into pulses has been widely used.

This method uses a rotational speed sensor that outputs a repetitive signal (pulse signal) to the rotating shaft that is consistent with or proportional to the rotational speed, and the rotating shaft and sensor are generally in mechanical contact with the rotating speed sensor. There are contact methods and non-contact methods in which the rotating shaft and sensor are not in contact; in the latter case, electromagnetic, photoelectric, and electrostatic types are known.

[Problem that the invention seeks to solve]

However, the conventional pulse conversion method simply obtains a pulse signal that matches or is proportional to the rotational speed, and calculates the rotational speed by counting the number of pulses. The problem is that the elements cannot be detected.

Furthermore, when focusing on the principles of rotational speed sensors, electromagnetic and photoelectric sensors have the problem of being large in size and cannot be attached to equipment that requires miniaturization. On the other hand, the electrostatic type can in principle be installed even in a relatively narrow space. However, as the size of the sensor is reduced, the detection capacitance also becomes smaller, resulting in a problem of lower reliability such as lower detection accuracy and increased susceptibility to malfunction.

Furthermore, both sensors are insufficient in terms of high-speed response, and there is a problem in that they become undetectable especially when the rotational speed becomes large.

[Means for solving problems]

The purpose of the present invention is to provide a tachometer that is compact, highly accurate, and highly responsive, and can easily detect information other than the rotational speed, such as the direction of rotation, which solves the problems that exist in the prior art described above. This is achieved by the tachometer shown in .

That is, the tachometer (1) according to the present invention is characterized by a pair of electrode plates (2a), (2b) or each electrode plate (2a), (2
One of the dielectric plates (2c) sandwiched between the electrodes (2c) is installed on the rotating shaft (3) to be measured, and the rotation of the rotating shaft (3) changes the capacitance between the electrode plates relative to the center of one cycle on the time axis. A sensor unit (2) in which the shape of the electrode plate (2a), (2b) or dielectric plate (2c) is set so as to change asymmetrically in the direction.
and a charge amplifier (4) that measures the change in capacitance.
) and processes the detection signal corresponding to the capacitance change from the capacitance detector (5) to determine the rotation speed and rotation direction of the rotating shaft (3). The present invention also includes a signal processing unit (6) for obtaining rotation information such as the following.

[For production]

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

The tachometer (1) according to the present invention has a sensor section (2) configured as a variable capacitor by a pair of electrode plates (2a), (2b) and a dielectric plate (2c). ), the capacitance between the electrode plates changes, and this change is asymmetrical in the time axis direction with respect to the center of one cycle as shown in FIG. On the other hand, the capacitance detection section (5) obtains a detection signal corresponding to a change in capacitance using a charge amplifier (4) that can accurately measure even minute capacitances. Then, the signal processing unit (6) determines the rotation speed of the rotating shaft (4) based on the number of repetitions of the asymmetric change in capacitance, and determines the rotation direction based on the shape of the asymmetric change.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described in detail based on the drawings.

Fig. 1 is a block circuit diagram of a tachometer according to the present invention, Fig. 2 is an external perspective view of a sensor section in the tachometer, and Fig. 3 is a characteristic diagram showing rotation angle versus capacitance change in the sensor section. Figure 4 is a circuit diagram of the capacitance detection section in the same tachometer.
Figure 5 is a block circuit diagram of the signal conversion circuit in the tachometer, Figure 6 is a time chart of signals in the conversion circuit, and Figure 7 is a block circuit of the rotation speed detection circuit and rotation speed display section in the tachometer. 8 is a time chart of signals in the detection circuit, and FIG. 9 is an electric circuit diagram of the rotation direction detection circuit and rotation direction display section.

First, the overall configuration of the present tachometer (1) will be explained with reference to FIG.

(2) is the sensor section, which itself is the rotating shaft to be measured (
3) constitutes a variable capacitor whose capacitance changes with rotation. In addition, the sensor section (2) is equipped with a charge amplifier (
4) is connected to the capacitance detection section (5) using the capacitance detection section (5). This detection section (5) detects the magnitude of the capacitance and outputs a detection signal (So) proportional to this magnitude. and,
This detection signal (SO) is supplied to a signal processing section (6). This processing unit (6) includes a signal conversion circuit (10) that converts the signal (So) into pulses, and a rotation speed detection circuit (11) that counts the pulses of this pulsed pulse signal (Sl) to determine the rotation speed. ), a rotation speed display section (12) that displays the rotation speed obtained by this circuit (11), a rotation direction detection circuit (13) that determines the rotation direction based on the shape of the pulse in the signal (Sl), and this circuit. It consists of a rotation direction display section (14) that displays the rotation direction obtained in (13).

Next, the configuration of each part will be specifically explained.

First, the configuration and function of the sensor section (2) will be explained with reference to FIGS. 2 and 3.

The sensor unit (2) consists of a dielectric plate (2c) attached perpendicularly to the rotating shaft (3) for measurement of equipment, etc.;
) consists of a pair of electrode plates (2a) and (2b) sandwiching both end surfaces of the electrode plate (2a) and (2b).

The dielectric plate (2c) is formed in a shape (a kind of spiral curve) in which the length in the radial direction increases successively as the rotation angle position of the rotation shaft (3) advances. By this, the electrode plate (2
The capacitance (Cx) between a) and (2b) changes asymmetrically in the time axis direction with respect to the center of the period, that is, as shown in Figure 3 (a), the rotation angle of the rotation axis (3) (e.g. to the left) (speed rotation), it becomes saw-blade shaped (asymmetrical triangle). Note that when the rotating shaft (3) rotates in the opposite direction (to the right), the capacitance changes also in the opposite direction as shown in FIG. 3(b).

Next, the capacitance detection section (5) will be explained with reference to FIG.

This detection 1i! The IK (5) is constituted by a charge amplifier (4), and a minute capacitance detection circuit using such a charge amplifier (4) has already been proposed by the present inventor (Japanese Patent Application No. 60-203798). . The same amplifier (4
), (20) is an operational amplifier, and the sensor section (20) is connected to the inverting input terminal (20a) of this operational amplifier (20).
) is connected to one electrode plate (2a), and an AC power source (21) is connected in series to the other electrode plate (2b). In this case, the voltage of the AC power supply (21) is (Ei) and the frequency is (f), which are set according to the conditions described later. Note that the non-inverting input terminal (20b) of the operational amplifier (20) is grounded. Further, (22) and (23) are the electrode plate (2a
) and (2b) are shown.

On the other hand, there is a standard capacitance ffi (Cf) between the inverting input terminal (20a) and the output terminal (20c) of the operational amplifier (20).
A parallel circuit of a capacitor having a resistance value (Rr) and a negative feedback resistor having a resistance value (Rr) is connected, and the magnitudes of (Cr) and (Rf) are also set according to the conditions described later. Note that (C1) is the stray capacitance that exists when there is a direct connection between the connecting wires connecting the power supply (21) and the amplifier (20) to the sensor section (2), and (C2) and (C3) are the stray capacitances that exist when there is a direct connection between the connecting conductors that connect the power supply (21) and the amplifier (20) to the sensor section (2). ) capacitance f
The stray capacitances generated between each terminal and ground at both terminals of fi (Cx) are shown, but they can be ignored at a practical level. Further, (25) and (26) are output terminals of the detection section (5).

Therefore, the output terminals (25) and (26) have an output voltage (Eo) that is directly proportional to the capacitance (Cx) of the sensor section (2).
) can be obtained.

Here, it is desirable that the circuit constants of the charge amplifier (4) be set according to the following conditions.

(a) Set r ≧ 10 kHz.

Further, the value of (cr) which becomes the standard capacity is set in the range of Gmax Gm1n. Note that Cxmin=Cxmax is the capacitance range to be detected, GffIin≧(readable output voltage Eo/Ei), and G11ax≧(Cx/Cr).

On the other hand, the value of (Rf) is set to . In addition, Ao: DC oven gain of operational amplifier (-order characteristic), To: effective time constant of operational amplifier, eO
: Target measurement relative error [t].

Furthermore, (Cf) and (Rf) are A.

(d) Cr-Rf=-To(2πr)2 and within the range of both (C) and (d) above
Select a combination of f) and (Rf). Note that in this case, it is desirable to set (cr) to a minimum value so that the output voltage becomes large.

Therefore, under the above conditions, the frequency of the input terminal (Ei) (
r) at 40 dB or higher than the hum noise frequency, i.e. 1QkHz
The settings above facilitate the removal of hum noise, and the circuit elements of the peripheral circuit connected to the operational amplifier (20), especially the values of (cr) and (Rf), are set to finite (Ao) and (T
o) is optimally set using the value of It is most suitable for use in detection targets such as (2).

Next, with reference to FIGS. 5 and 6, the signal conversion circuit (10
) will be explained.

The circuit (10) includes a bypass filter (30) from the Moe stage,
Amplifier (31), detector (32), capacitor (C
d), low-pass filter (33), comparator (34)
) to connect and configure. Note that (35) is an input terminal to which the output voltage (Eo) of the capacitance detection section (5) is supplied, and (36) is an output terminal of the same circuit (10). The operation of the circuit (10) is as follows. First, the output voltage (Eo) becomes an amplitude modulated wave shown in FIG. 6 (Sl) in which the variation of (Cx) is used as a modulation signal and the input signal (Ei) is used as a carrier wave.

Therefore, the amplitude modulated wave (S
l) (Output voltage (Eo)) is a bypass filter (30)
This removes the hum mixed in at the input end of the charge amplifier (5), etc., and further amplifies it to a required size by the amplifier (31). Then, the detector (32) performs linear detection and removes the carrier wave, and the capacitor (32)
The DC component is removed by Cd), and the low frequency signal shown in the figure (Sl) is further passed through a low pass filter (33).
In other words, the signal is proportional to the magnitude of the capacitance (Cx). In addition, the comparator (34) has a hysteresis characteristic with Vr as a threshold value on a constant voltage, and has z
It has a margin of xlvrl. Therefore, the comparator (3
The output signal of 4) has a threshold value ±Vr as shown in the same figure (S3).
It becomes a pulse signal that is turned on and off by. In this case, the output signal (S3) has a relationship between the non-pulse period (TI) and the pulse period (T2) such that (TI) > (T2), so the area occupied by the negative voltage on the time axis is larger than that of the positive voltage. It's also big. In addition, in the case of reverse rotation, (T2) > (Tl
), and thereby the rotation direction, which will be described later, is determined.

Next, referring to FIGS. 7 and 8, the rotation speed detection circuit (1
1) and the rotation speed display section (12) will be explained.

The configuration of the detection circuit (11) first includes a reference clock generation circuit (40), and the output pulse signal of this circuit (40) is converted into a clock signal (3) with a period of 1 second by a divider (41).
4X Fig. 8) and a clock signal with a period of 2 seconds (S5) (
(Fig. 8). Then, the signal (S4) is directly supplied, and the signal (S5) is inverted and supplied to a NANDAND circuit (NANDAND circuit), and the latch signal shown in FIG. 8 (S6) is obtained at its output. In addition, the signals (S4) and (S5) are both inverted and supplied to the AND circuit (43), whose output is
7) Obtain the reset signal. On the other hand, (44) is a counter, which includes the latch signal (S6) and the reset signal (S6).
7) is input. On the other hand, (46) represents the signal conversion circuit (
This is an input terminal to which the output signal (S3) of IO) is supplied, and is connected to the input terminal of the AND circuit (45). Further, the pulse signal (S4) is supplied to the other input terminal of the circuit (45), and the output terminal of the circuit (45) is supplied to the counter (4).
4) Connect to. Therefore, since the pulse signal (S5) has an interval of 1 second, the output signal (S5)
3) The number of pulses is counted and the number of rotations is determined. This number of revolutions is displayed on the number of revolutions display section (1) connected to the counter (44).
2) is displayed digitally, for example. Note that the contents of the counter (44) are latched at the falling edge of the latch signal (S6) and displayed on an LED, etc., and the counter contents after latching are cleared every time at the rising edge of the reset signal (S7), and are used in the next cycle. Be prepared.

Next, the rotation direction identification circuit (13) and its display section (14) will be explained with reference to FIG.

First, the rotation direction identification circuit (13) mainly uses a time constant τ0=c
OR circuit (50) with o-RO, FET (5
1), inverters (52) to (56), and D-type flip-flops (57) and (58). In the circuit (13), the input terminal (59) is connected to the comparator (34).
) is supplied, and (Co) is charged according to the time constant τ0 of the OR circuit (50). Therefore, F
The gate of E T (51) has a positive (
A voltage is applied that causes clockwise rotation) or negative (counterclockwise rotation), and F
E T (51) is turned on or off depending on the direction of rotation. Therefore, for example, in the case of counterclockwise rotation, the data input terminals (D
I) and (D2) become "1" and "0", respectively.

Furthermore, the clock input terminals (CLI) and (Cl3) of the flip-flops (57) and (58) are connected to the output signal (S).
3) A pulse signal (Pc) synchronized with the rising edge is manually input. This concentration causes outputs (Ql) and (Q2) of flip-flops (57) and (58) in synchronization with the pulse signal (Pc).
) are respectively “1° to 0”, and the rotation direction display section (1°
4) The light emitting diode (60) constituting the light emitting diode (60) is turned on and the light emitting diode (61) is turned off. In addition, the flip-flop (5
7) and (58) are initialized. In addition, in the case of clockwise rotation, the output (Ql) of the flip-flop (57), (5g),
(Q2) becomes "0" and "lo", respectively, and the diode (60) goes out and the diode (61) lights up.In other words, the rotation direction can be identified and displayed.
If it is not rotating, the flip-flop (57), (
The levels of the input terminals (Dl) and (D2) of the flip-flop (58) are undefined, but since the pulse signal (Pc) is not input and only the reset operation is performed by the pulse signal (Pr), the output terminal (D2) of the flip-flop Ql) and (Q2) both become "0" level, and the light emitting diodes (60) and (61
) are both turned off.

With this circuit configuration, this tachometer (1) has linearity,
Obtained extremely good results in terms of accuracy and data dispersion,
The measurable upper limit rotation speed can be stably measured up to approximately 5X 103 rps. Furthermore, if the system uses an MO3FET element, directly connects a roller to the rotating shaft (3), and incorporates a battery as a power source, it can be configured as a small portable sensor.

Although the embodiments have been described above, the present invention is not limited to these embodiments. For example, the sensor part (2
), it is sufficient that the capacitance changes asymmetrically, and the electrode plate,
The shape of the dielectric plate is arbitrary. In addition, the signal processing section (6)
This circuit can also be replaced with another circuit having the same function, and another circuit capable of phase detection may be added. Furthermore, although the present invention is named as a tachometer, it can also be used as a vibrometer that can measure the frequency of any object.

In this case, it is only necessary to change the shape of the sensor section (2).

Other changes may be made in the detailed structure, shape, arrangement, material, etc., without departing from the gist of the present invention.

〔Effect of the invention〕

As described above, the tachometer according to the present invention is provided with a sensor section using a capacitance detection method, and the capacitance detection is performed by a detection section using a charge amplifier, thereby achieving the following significant effects. .

■Due to extremely high responsiveness, it is possible to accurately measure capacitance that fluctuates over time, and for tachometers, it is possible to significantly expand the detectable range of rotational speed and improve detection accuracy.

■Since complex changes in capacitance can be detected accurately, not only the number of rotations but also other information such as rotation direction and phase can be easily detected through signal processing, resulting in excellent functionality.

■Because of its high accuracy, the sensor part can be easily miniaturized, so when it is used as a tachometer attached to equipment, the sensor part can be easily attached to small equipment, making it possible to miniaturize the equipment, and at the same time In the case of a single portaple type, the tachometer can be made more compact, contributing to smaller size, lighter weight, and lower cost.

[Brief explanation of the drawing]

Fig. 1.2 Block circuit diagram of the tachometer according to the present invention. Fig. 2: External perspective view of the sensor section in the tachometer. Fig. 3: Characteristic diagram showing changes in rotation angle versus P% electric power amount in the sensor section. , Figure 4: Circuit diagram of the capacitance detection section in the tachometer, Figure 5: Block circuit diagram of the signal conversion circuit in the tachometer, Figure 6: Time chart of signals in the conversion circuit, 7 Figure: Block circuit diagram of the rotation speed detection circuit and rotation speed display section in the same tachometer, Figure 8: Time chart diagram of signals in the same detection circuit, Figure 9: Electric circuit of the rotation direction detection circuit and circuit direction display section In the drawing, (1) Double tachometer (2): Sensor part (2a)
, (2b): Electrode plate (3): Rotating shaft to be measured (4): Charge amplifier (5): Capacitance detection section (6): Signal processing section

Claims (1)

[Claims] A pair of electrode plates or one of the dielectric plates sandwiched between each electrode plate is provided on the rotating shaft to be measured, and due to the rotation of the rotating shaft, the capacitance between the electrode plates is asymmetrical in the time axis direction with respect to the center of one cycle. A sensor section in which the shape of the electrode plate or dielectric plate is set to change, a capacitance detection section using a charge amplifier that measures a change in the capacitance, and a capacitance detection section that uses static electricity from the capacitance detection section. A tachometer comprising: a signal processing section that processes a detection signal corresponding to a change in capacitance to obtain rotation information such as the rotation speed and rotation direction of the rotation shaft.