JPH06230158A - Ultrasonic meter - Google Patents

Abstract

PURPOSE:To downsize a meter by converting positional information detected at a rotational angle detecting section into a signal having frequency low enough to be processed by an operational amplifier. CONSTITUTION:A rotary disc 22 constituting a rotational angle detecting section 20 rotates as an ultrasonic motor 10 rotates. A current collecting electrode 22 takes out a rotating electric field which is the sum of electric fields generated by electrodes 21a-21c. The rotating electric field having a frequency fc is applied to the gate electrode of a FET 55 having a drain electrode applied with a signal having frequency fL from a frequency divider 54. A band-pass amplifier 57 amplifies a converted signal having a low frequency representative of phase difference information and outputs the amplified signal. A phase detector 58 detects the phase of an output from the amplifier 57 with reference to a reference value and outputs a pulse. An integrator 60 compares the pulse with an input pulse 40 and performs switching control of the phase of driving signal. When a motor 10 rotates forward and reversely and the output from the integrator 60 goes zero, rotation of the motor 10 is stopped and the rotary position is read out from a pointer 30. The pointed value represents the magnitude of an input 40 to be measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic meter which measures an amount of electricity to be measured by using an ultrasonic motor.

[0002]

2. Description of the Related Art For example, a moving magnet type meter is currently the mainstream as a meter for measuring the speed of an automobile, engine rotation, etc., but this is largely due to the fact that automatic production is possible. However, the movable magnet type meter has the following drawbacks. Since the outer circumference coil is large, we cannot expect a significant cost reduction. Since the fixed coil requires a certain amount of power, it is difficult to reduce the size of the electric circuit, and it is difficult to reduce the weight and size of the electric circuit as a whole. In order to eliminate these drawbacks of the movable magnet type meter, an ultrasonic meter has recently been proposed as a meter for automobiles. It uses an ultrasonic motor as a drive source and is suitable for automobile meters that can be used in a narrow instrument panel and under harsh conditions such as ultra-miniaturization, high-speed response and large static friction. The meter using an ultrasonic motor is one in which the above-mentioned drawbacks are eliminated, such as automatic production with stronger torque is possible.

[0003]

When the ultrasonic motor is used as a meter, it is necessary to have a position control means for controlling the position of the rotary shaft to stop the pointer at a position corresponding to the quantity to be measured. This position control means is composed of an electric circuit.
An object of the present invention is to improve the position control means constituted by an electric circuit so as to be downsized, and to provide an ultrasonic meter which is further downsized and is inexpensive and suitable for automobiles. is there.

[0004]

SUMMARY OF THE INVENTION The present invention has an ultrasonic motor having a rotary shaft and a pointer attached to the rotary shaft,
A capacitance type rotation angle detection unit that outputs a rotating electric field whose phase is shifted corresponding to the rotation angle of the ultrasonic motor, and a phase angle detector that detects the phase angle of the output frequency of the rotation angle detection unit, And a position control means comprising a drive circuit for comparing the pulse corresponding to the signal to be measured with the output pulse of the phase angle detector and controlling the switching of the phase of the drive signal for driving the ultrasonic motor according to the comparison result. It is equipped.

[0005]

According to the present invention as described above, while operating the rotation angle detector constituting the position control means at a frequency of about 100 KHz, the phase information is converted to a frequency of 1 KHz which can be handled by a general-purpose operational amplifier.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings.
FIG. 1 is an exploded perspective view showing an embodiment of the present invention, and FIG. 2 is an enlarged sectional configuration diagram. In FIGS. 1 and 2, reference numeral 10 is an ultrasonic motor. This ultrasonic motor is composed of an electrostrictive element, an elastic body, and a moving body. When the electrostrictive element vibrates the surface of the elastic body, an elastic wave is generated, and the elastic wave propagates on the surface of the elastic body. Therefore, when the moving body is brought into pressure contact with the surface of the elastic body, the surface of the moving body makes point contact with the surface of the elastic body due to the elastic wave, and the moving body moves in the direction opposite to the elastic wave due to the frictional force between the moving body and the elastic body. This is the principle of operation, and such an ultrasonic motor itself is already known, for example, from Japanese Patent Laid-Open No. 59-122385. Reference numeral 11 is a substrate of the ultrasonic motor 10.

Reference numeral 20 denotes an electrostatic capacitance type rotation angle detection section (rotary encoder) which constitutes a position control means. The overall configuration of the position control means will be described later. In the rotation angle detection unit 20, 21 is a rotating electric field electrode, 22 is a collecting electrode, and 23 is a rotating disk. The rotating electric field electrode 21 and the current collecting electrode 22 are formed by disks having the same diameter, and the rotating disk 23 is formed by a disk having a diameter smaller than that. 24 and 25 are spacers, and 26 is a metal ring. The electrode 21 is divided into three parts (120 ° each) as shown in FIG. 3A to detect the position by a three-phase rotating electric field, and a through hole 21 'is formed in the center thereof. The electrode 22 is entirely composed of a conductor piece, and a through hole 22a is formed in the center thereof. The electrode 21 is formed by printing on one surface of the printed board 27. In the embodiment, the rotary disk 23 has a thickness of 1.6 mm, and as shown in FIG.
3 is a conductor part and 1/3 is an insulator part, and a rotary shaft 23a is provided so as to penetrate the center part thereof.

A rotation angle detecting section 20 including the above-mentioned respective sections.
The rotating disk 23 is arranged inside the ring 26, the upper part of the rotating shaft 23a of the rotating disk freely penetrates the through hole 22a of the electrode 22, and the lower part of the rotating shaft 23a is the through hole of the electrode 21. The electrode 22 and the electric plate 21 are integrated with each other through a ring 26 by a screw so as to freely penetrate through 21 ′. In the example, the electrodes 21 and 22 are at regular intervals,
There is a very small gap between the electrode 21 and the rotary disc 23 and between the electrode 22 and the rotary disc 23, and spacers 24 and 25 are inserted between them. The board 11 and the printed board 27 are vertically attached via studs 13 and 14. Rotating shaft 23a of rotating disk 23 that freely penetrates electrode 21 printed board 27
Is attached to the rotary shaft portion 12 of the ultrasonic motor 10 described above. Thereby, the electrostatic capacitance type rotation angle detection unit 20 is configured.

Reference numeral 30 is a pointer, 31 is a mounting portion thereof, and 32 is a scale plate. The base portion of the pointer 30 is attached to the attachment portion 31, and the attachment portion 31 is attached to the rotary shaft 23a of the rotary disk 23 that freely penetrates the electrode 22. The scale plate 32 is fixedly arranged between the pointer 30 and the rotation angle detection unit 20. Incidentally, the chain line in FIG. 2 indicates a shield.

FIG. 4 is an electric circuit diagram of the entire ultrasonic meter according to the present invention including the position control means. In FIG. 4, 10 is the ultrasonic motor described in FIG. 1, 20 is also a rotation angle detection unit, and the rotating electric field electrode 21, the collecting electrode 22,
It consists of a rotating disk 23. 40 is a signal input terminal,
From this input terminal, a pulsed electric signal corresponding to the traveling speed of the automobile is input. Reference numeral 41 is a conversion circuit for converting the input pulse signal to be measured into a constant pulse width related to the frequency fc.

Reference numeral 50 is an oscillator for oscillating a square wave of frequency fo, and 51, 52 and 53a to 53c are frequency dividers. In the embodiment, fo is 18.240 MHz, the frequency divider 51 divides fo by 1/64, and the frequency divider 52 has the frequency divider 5.
The output frequency of 1 is divided into 1/32. Each of the frequency dividers 53a to 53c further divides the output of the frequency divider 52 into 1/6. As a result, the frequency dividers 53a-5
When the output frequency of 3c is fc, fc is 95 KHz. The frequency dividers 53b and 53c have a frequency shift function and a phase shift function. When the output of the frequency divider 53a is the reference phase (0 °), the frequency divider 53b outputs the frequency of the frequency divider 53a ( 2/3) π phase shift, and the frequency divider 53b outputs (4 /
3) π phase shift. The outputs of the frequency dividers 53a to 53c thus phase-shifted by (2/3) π are applied to the rotating electric field electrode 21 constituting the above-described rotation angle detecting unit 20. That is, the electrode 21 is divided into three parts 21a to 21c for position detection by the three-phase rotating electric field, and the frequency divider 5
The output end of 3a is connected to one of the three divided electrodes 21a,
The output terminal of the frequency divider 53b is connected to the electrode 21b, and the frequency divider 53c is also connected.
The output ends of are connected to the electrodes 21c, respectively. It should be noted that the value of the frequency is one example and is not particularly limited.

A frequency divider 54 divides the oscillation frequency fo of the oscillator 50 into 1/190. If the output frequency of the frequency divider 54 is fL, then fL will be 96 KHz. 55 is a field effect transistor used as a heterodyne detector, the gate electrode of which is connected to the collector electrode 22 of the rotation angle detector 20, the drain electrode of which is connected to the output terminal of the frequency divider 54, and the source electrode of which is connected. Is connected to the common potential point COM via the resistance element 56. Reference numeral 57 is a band pass amplifier, 58 is a phase detector, and 59 is a frequency divider. The input terminal of the bandpass amplifier 57 is the heterodyne detector 55.
Is connected to the connection point of the resistance element 56 and the output terminal is connected to the phase detector 58. The frequency divider 59 is the frequency divider 53a.
This frequency signal is fR when the output frequency of 1KHz is fR.
Is added to the phase detector 58 as a reference phase. The band pass amplifier 57 may be a digital filter.

Reference numeral 60 is an integrator, and 61 is a pointer 3 shown in FIG.
A zero bias circuit for adjusting the mechanical position of 0 to the zero position, the input terminal of which is connected to the frequency divider 59.
The integrator 60 receives the input pulse 40 to be measured, which has passed through the conversion circuit 41, the output of the phase detector 58, and the output of the zero bias circuit 61, and adds and integrates these three signals. Reference numeral 70 denotes a motor drive circuit, which receives an output frequency fM of 285 KHz obtained from the frequency divider 51, supplies the ultrasonic motor 10 with the output frequency, receives an output signal of the integrator 60, and changes the polarity of the output signal. The ultrasonic motor 10 is provided with a switching control signal for rotating the motor in the normal direction or in the reverse direction.

The operation of the ultrasonic meter according to the present invention having such a configuration will be described below. The oscillation output fo of the oscillator 50 is the frequency dividers 51, 52, 53a-5.
It is added to 3c and 54 and divided into predetermined frequencies fc and fL. Frequency divider 53a whose phases are shifted from each other by 120 °
Outputs fc of to 53c are added to the respective electrodes 21a to 21c of the electrodes 21 constituting the rotation angle detection unit 20. As a result, the electrodes 21a to 21c generate an electric field with a phase difference of 120 ° as shown in (a) to (c) of FIG. 5, and the combined electric field is the phase difference as shown in (d) of FIG. Is a rotating disk 2
The rotating electric field changes from 0 ° to 360 ° depending on the rotation angle of 3. The electrode 21 is divided into three phases because the rotating disk 23
Is to operate as a space electrode for removing the third harmonic by operating as a conductor electrode.

On the other hand, by applying a pulse input to be measured from the input terminal 40, this pulse input is applied to the integrator 60. This input pulse has a constant pulse width T1 as shown in FIG. 6C, and its period T2 changes according to the magnitude of the input to be measured. In the embodiment, the pulse input is a full scale value, for example, 400 pps.
In the integrator 60, the input pulse 40, the output of the phase detector 58 whose pulse width T changes by 0 to 360 ° as shown in (b) of FIG. 6, and the zero pulse as shown in (a) of FIG.
The output of the bias circuit 61 is added. A drive signal fM of 285 KHz is applied to the ultrasonic motor 10 via the drive circuit 70.

The integrator 60 adds and integrates the above three signals. When the value of the integration result is positive, the drive circuit 70 delays the phase of the drive signal by π / 2 to generate a drive signal for rotating the ultrasonic motor 10 in the reverse direction. When the integrator output is positive, the drive circuit 70 outputs the drive signal A drive signal is generated which advances the phase by π / 2 and rotates the ultrasonic motor 10 in the forward direction. As a result, the ultrasonic motor 10 rotates in the forward or reverse direction. When the output of the integrator 60 becomes zero, the rotation of the motor 10 stops.

A rotary disc 22 constituting a rotation angle detecting section 20 is attached to the rotary shaft of the ultrasonic motor 10.
The rotating disk rotates as the ultrasonic motor 10 rotates. In this case, since the electrode 21 and the collector electrode 22 are capacitively coupled, each electrode 21a to
The rotating electric field, which is a combined value of the electric fields generated by 21c, is taken out from the collector electrode 22. This rotating electric field is shown in FIG.
As shown by, depending on the rotation angle of the ultrasonic motor 10,
It will change 360 °. Frequency fc (9 in the embodiment)
This rotating electric field of 5 KHz) is taken out from the collector electrode 22 and then applied to the gate electrode of the field effect transistor 55. On the other hand, the frequency force fL obtained from the frequency divider 54
A signal (96 KHz in the embodiment) is applied to the drain electrode of the field effect transistor 55. This frequency force f
The signal of L and the signal of frequency fc applied to the gate are heterodyne-detected by the field effect transistor 55 (multiplication in this case), and fc + fL (= 191 KHz + harmonic), fc at the source electrode of the field effect transistor 55. , FL, and fL-fc = fs (= 1K
(Hz + harmonic) signal is output. These four signals are applied to the bandpass amplifier 57, and the bandpass amplifier 5
7 amplifies and outputs only the fS signal, that is, the signal of 1 KHz. That is, the bandpass amplifier 57
Outputs a signal converted to a low frequency of 1 KHz having phase difference information. This signal is applied to the phase detector 58. A signal of fR (= 1 KHz) obtained by the frequency divider 59 is added to the phase detector 58 as a reference signal, and the phase detector 58 outputs the phase of the output of the bandpass amplifier 57 with respect to this reference value. Is detected, and a pulse whose pulse width T changes from 0 to 360 ° is output as shown in FIG. This pulse is compared with the input pulse 40 in the integrator 60, as described above, and when the input pulse 40 is greater than the output pulse of the phase detector 58, the drive circuit 70.
A reverse rotation signal is given to the ultrasonic motor 10 via
When it is small, the phase of the drive signal is switched and controlled so that a positive rotation signal is sometimes given. When the ultrasonic motor 10 rotates in the normal or reverse direction and the output of the integrator 60 becomes zero, the rotation of the ultrasonic motor 10 stops. The rotational position of the ultrasonic motor 10 is read by the pointer 30 and the scale plate 32. The indicated value is the size of the measured input 40.

In this way, the circuit including the rotation angle detector 20 and the heterodyne detector 55 has the ultrasonic motor 10
The position control means required when the is used for the meter is configured.

FIG. 8 is an electric circuit diagram of another embodiment of the present invention. In the embodiment shown in FIG. 4, heterodyne detection is performed at a frequency fL different from the frequency fc obtained by frequency-dividing the output of the oscillator, the frequency of the difference between the frequencies fc and f is extracted, and the phase of the frequency of this difference is extracted. I tried to detect the corner,
In the embodiment shown in FIG. 8, the switch 55 is driven by the rotating electric field obtained from the collector electrode 22, and the output thereof is detected by the phase detector 58 via the band pass amplifier 57.

The circuit of FIG. 8 having such a configuration has an advantage that the frequency dividers 54 and 59 used in the circuit of FIG. 4 can be omitted, and the circuit configuration can be simplified as compared with the circuit of FIG. . The drive frequency fc of the circuit in FIG.
It is necessary to set it to about 0 KHz.

In the embodiments of FIGS. 4 and 8 described above, since the rotation angle detecting section 20 used as the position control means uses capacitive coupling, the structure of the rotation angle detecting section 20 can be simplified and downsized. Moreover, in general, since the detection of the rotation angle by such capacitive coupling takes out the change of the absolute capacitance, the rotation angle that can be obtained as the capacitance is at most 180 °, but in the present invention, the rotating electrostatic field is And the rotation angle is extracted as a phase change, a rotation angle of 360 ° can be detected.
Further, as shown in FIG. 7, as long as the distance g between the electrode 21 and the collector electrode 22 constituting the rotation angle detector 20 is constant, the position of the rotary disc 23 may be any position in the thickness direction. The capacity itself does not change. Therefore, there is an advantage that the axial mechanical dimension of the rotary disc 23 does not require high precision. In addition, between the electrode 21 and the rotating disk 23, and the collector electrode 2
2, a spacer (film) 24, between the rotary disk 23 and
By inserting 25, slippage of the rotary disk 23 is improved, and by increasing ε of the spacer, the coupling capacity can be increased and the operation can be stabilized.

Although the present invention has been described above mainly for an automobile, the present invention is not particularly limited to an automobile.

[0023]

According to the first embodiment of the present invention, while the rotation angle detecting section constituting the position control means is operated at a frequency of about 100 KHz, the phase information is set to a frequency of 1 KHz which can be handled by a general-purpose operational amplifier. Since the conversion is performed, the configuration of the rotation angle detection unit is small,
Since the path amplifier or the phase detector portion can be handled by a general operational amplifier, it is possible to obtain a compact and inexpensive device. As a result, a very suitable meter can be obtained as a meter using an ultrasonic motor that can be miniaturized.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing an embodiment of the present invention.

FIG. 2 is an enlarged sectional configuration diagram showing an embodiment of the present invention.

FIG. 3 is a configuration diagram of a rotating electric field electrode and a collecting electrode that constitute a rotation angle detecting unit according to the present invention.

FIG. 4 is an electrical circuit diagram showing an embodiment of the present invention including position control means.

FIG. 5 is a waveform diagram for explaining the operation of the rotation angle detection unit of the present invention.

FIG. 6 is a waveform diagram for explaining the operation of the present invention.

FIG. 7 is an explanatory diagram of a rotation angle detection unit according to the present invention.

FIG. 8 is an electric circuit diagram of another embodiment of the present invention.

[Explanation of symbols]

 10 Ultrasonic Motor 20 Rotation Angle Detector 21 Rotating Electric Field Electrode 22 Current Collector Electrode 23 Rotating Disc 30 Pointer 55 Heterodyne Detector 57 Band Pass Amplifier 58 Phase Detector 60 Integrator 70 Drive Circuit

Claims (3)

[Claims] 1. An ultrasonic motor having a rotary shaft and a pointer attached to the rotary shaft, and a capacitance type rotary angle for outputting a rotary electric field having a phase shift corresponding to the rotary angle of the ultrasonic motor. A detection unit, a phase angle detector that detects the phase angle of the output frequency of the rotation angle detection unit, and a pulse corresponding to the signal under measurement and the output pulse of the phase angle detector are compared, and the comparison result indicates that An ultrasonic meter, comprising: position control means including a drive circuit that controls switching of a phase of a drive signal that drives an ultrasonic motor. 2. An ultrasonic motor having a rotating shaft, and an output frequency fc of an ultrasonic motor having an indicator attached to the rotating shaft, and an output frequency fc of the oscillator being given to the rotating electric field having a phase shift corresponding to a rotating angle of the ultrasonic motor. After detecting the electrostatic capacitance type rotation angle detection unit and the output frequency of the rotation angle detection unit at a frequency fL different from the frequency fc and extracting the frequency fs of the difference between the frequencies fc and fL, A phase angle detector for detecting the phase angle of the frequency fs is compared with a pulse corresponding to the signal under measurement and the output pulse of the phase angle detector, and the comparison result shows the drive signal for driving the ultrasonic motor. An ultrasonic meter comprising: a position control unit including a drive circuit for controlling phase switching. 3. The electrostatic capacitance type rotation angle detecting section is fixed to a disc-shaped electrode for a rotating electric field having a plurality of divided electrodes, and fixed to the rotating electric field electrode at a constant interval. A disk-shaped collecting electrode arranged, and mounted between the rotating electric field electrode and the collecting electrode and attached to the rotating shaft of the ultrasonic motor, and a part of the rotating disk was made of a conductor. The ultrasonic meter according to claim 1 or 2, characterized in that.