JPH0611304A - Displacement measuring instrument - Google Patents

Abstract

PURPOSE:To obtain an absolute type displacement measuring instrument which is reduced in average current consumption. CONSTITUTION:The title instrument is provided with an ABS sensor 1, demodulation circuits 3-5 which measure the absolute displacement of the mobile element of the sensor 1 against the fixed element of the sensor by processing the output of the sensor 1, phase detection circuits 6-8, synthesization circuit 10, and arithmetic circuit 12. In addition, the instrument is provided with a control circuit 9 which performs intermittent measuring operations by controlling the signal processing circuit section composed of the circuits 3-5, 6-8, 10, and 12 and a moving/stopping state detection circuit 16 which detects the movement or stoppage of the mobile element of the sensor 1. The circuit 9, variably controls the measuring interval of the intermittent measuring operations in accordance with the output of the circuit 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a displacement measuring device applied to a small measuring instrument such as a digital caliper, and more particularly to measuring an absolute displacement amount based on a relative positional relationship of a movable element to a fixed element of a displacement sensor. The present invention relates to a so-called absolute type displacement measuring device capable of performing.

[0002]

2. Description of the Related Art As a small measuring instrument such as a digital caliper, a digital micrometer or a height gauge for displaying a measured value on a liquid crystal display device or the like, it is promising to use a capacitance type displacement sensor. In a capacitance type displacement sensor, a large number of electrodes are arranged on a fixed element such as a main scale and a movable element such as a slider which moves relative to the fixed element, and the electrodes are moved along with the movement of the movable element with respect to the fixed element. The displacement amount is detected by extracting a signal of periodic capacitance change generated between patterns.

Such displacement sensors are classified into two types, an incremental type and an absolute type, depending on the form of the output signal. The former measures the displacement amount by continuously measuring the periodic signal generated by the movement of the slider from the reference position. The latter is capable of obtaining the absolute displacement amount (position) of the movable element with respect to the fixed element without performing the continuous counting operation. For example, depending on the shape of the electrode pattern, a coarse pitch, an intermediate pitch, or a fine pitch can be obtained. By making it possible to output a periodic signal of a pitch and combining the phase information of these periodic signals of each pitch, it is possible to detect the absolute displacement amount of the movable element.

Since the incremental displacement sensor continuously measures the amount of movement of the slider from an arbitrarily determined origin, the measurement operation cannot be stopped even if the movable element is stopped. This is because if the movable element moves during the measurement stop period, the movement amount cannot be detected by restarting the measurement. On the other hand, in the absolute displacement sensor, the absolute position can be known by measuring for a short time, and therefore intermittent measurement is possible, and the measurement cycle can be set by the control circuit. For example, with a digital caliper using an absolute displacement sensor, the measurement time is 4
The measurement of 0 msec is an intermittent operation of 10 times in 1 sec. By performing such an intermittent operation, the average current consumption can be reduced and the battery life can be extended as compared with the case of the incremental type.

[0005]

However, in the absolute displacement sensor, if the life of the built-in battery can be further extended, the battery can be downsized and the battery replacement work can be reduced.
It is preferable for resource saving. The present invention has been made in consideration of such circumstances, and an object of the present invention is to provide an absolute displacement measuring device in which the average current consumption of the system is reduced.

[0006]

DISCLOSURE OF THE INVENTION The present invention relates to a displacement sensor which outputs an output signal according to a relative positional relationship of a movable element to a fixed element, and the movable element relative to the fixed element by processing the output signal of the displacement sensor. In an absolute displacement measuring device having a signal processing means for measuring the absolute displacement amount of, and a control means for controlling the signal processing means to intermittently perform a measuring operation, the movable element of the displacement sensor is moved or stopped. Providing moving / stopped state detection means for detecting,
It is characterized in that the control means variably controls the interval of the intermittent measuring operation according to the output of the moving / stopped state detecting means.

[0007]

In the present invention, the state of movement or stop of the movable element with respect to the fixed element of the displacement sensor (hereinafter, simply referred to as movement or stop of the displacement sensor) is detected, and the intermittent measurement operation is performed according to the state. The measurement time per unit time of is variably controlled. Specifically, for example, when the displacement sensor is stopped for a certain period, the measurement cycle (measurement interval) is extended as compared with the case of normal measurement. When a longer stop period has elapsed, the power is turned off. Thus, by reducing the measurement frequency when the displacement sensor is stopped, the average power consumption of the system is reduced. For example, considering a digital caliper, the time when the sensor is stopped is overwhelmingly longer than the time when the sensor is actually moving. Therefore, when an absolute displacement sensor is used, the measurement frequency should be controlled as in the present invention. Thus, the average current consumption can be effectively reduced.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a system configuration of a displacement measuring device according to an embodiment of the present invention, and FIG. 2 is a configuration of an absolute capacitance displacement sensor (hereinafter referred to as ABS sensor) 1 used here. . In the ABS sensor 1, a slider 21, which is a movable element, is arranged to face a main scale 22, which is a fixed element, with a slight gap therebetween, and is movable in the measurement axis x direction. Slider 21
, The transmission electrodes 23 are arranged at a predetermined pitch Pt0. The transmission electrode 23 has a pitch Pr on the main scale 22.
First receiving electrode 24a and second receiving electrode 24 arranged in
It is capacitively coupled with b. The receiving electrodes 24a and 24b are
The first pitches Pt1 and Pt2 adjacent to each other along the arrangement direction
The transmission electrodes 25a and the second transmission electrodes 25b are connected one-to-one. The transmission electrodes 25a and 25b are the first detection electrodes 26a and 26 provided on the main scale 21 side, respectively.
b and the second detection electrodes 27a and 27b are capacitively coupled.

The transmission electrodes 23 are commonly connected to every other eight electrodes to form a plurality of electrode groups each having eight electrodes. In the measurement mode, the eight-phase periodic signals a, b, ...
Is being supplied as. More specifically, these drive signals Sd are signals chopped with high frequency pulses, and are generated and output from the transmission waveform generating circuit 2 in FIG.

The pitch Wt of the electric field pattern generated by supplying the drive signal Sd to the transmission electrode 23 is eight times the pitch Pt0 of the transmission electrode 23, and this pitch Wt is
It is set to N times the pitch Pr of the receiving electrodes 24a and 24b. Here, N is preferably an odd number such as 1, 3, 5 or the like, and is set to 3 in this embodiment. Therefore, three to four receiving electrodes 24a and 24b are always capacitively coupled to the eight continuous transmitting electrodes 23. The receiving electrodes 24a and 24b are formed by sandwiching triangular or sinusoidal electrode pieces. The phase of the signal received by each of the receiving electrodes 24a and 24b is determined by the capacitive coupling area between the transmitting electrode 23 and the receiving electrodes 24a and 24b, which changes depending on the relative position between the slider 21 and the main scale 22. .

Receiving electrodes 24a, 24b and transmitting electrode 25
If a and 25b are formed at the same pitch, the detection electrodes 26a, 26b, 27a, and 27b simply detect a periodic signal that is repeated each time the position of the main scale 21 in the x direction changes by the pitch Pr. However, in the ABS sensor 1 of this embodiment, a coarse displacement amount (coarse scale),
In order to detect the displacement amount of three levels of the intermediate displacement amount (medium scale) and the fine displacement amount (fine scale), the transmission electrodes 25a and 25b are actually the reception electrodes 24a and 24b.
On the other hand, the pitch is changed to deviate by D1 and D2 respectively. The deviation amounts D1 and D2 are functions of the distance x in the measuring direction from the reference position x0, and can be expressed as in the following formula 1.

[0012]

## EQU1 ## D1 (x) = (Pr-Pt1) x / Pr D2 (x) = (Pr-Pt2) x / Pr

The transmitting electrodes 25a and 25b are thus displaced relative to the receiving electrodes 24a and 24b, and the detecting electrode 26
a, 26b, 27a, 27b with a pitch Wr1 (= 3Pt
1) and Wr2 (= 3Pt2), the deviation amounts D1 (x) and D2 from the detection electrodes 26 and 27 are set.
Detection signals B1, B2, C1 in which a small period of the detection electrodes 25a, 25b is superimposed on a large period corresponding to (x)
, C2 can be obtained. The signals B1 and B2 have a large period in opposite phase and a small period in phase. Therefore, a signal with a large period can be obtained from the difference between both signals, and a signal with a small period can be obtained from the sum of both signals. The same applies to the detection signals C1 and C2. Here, the electrode pattern is set so that the large cycle of the detection signals B1 and B2 is several tens of times the small cycle and the large cycle of the detection signals C1 and C2 is tens of times the large cycle of the detection signals B1 and B2. Thus, the displacement of each level can be obtained by the calculation of the following Expression 2.

[0014]

[Equation 2] C1-C2 (coarse scale) B1-B2 (medium scale) (B1 + B2)-(C1 + C2) (fine scale)

These operation output signals C1-C2, B1-
B2 and (B1 + B2)-(C1 + C2) are processed by the coarse scale demodulation circuit 3, the medium scale demodulation circuit 4, the fine scale demodulation circuit 5 and the phase detection circuits 6, 7 and 8, respectively. The demodulation is specifically a rectangular wave phase signal CM that carries phase information at the edges through processing such as sampling at the chop frequency of the transmission waveform, mixing, low-pass filtering, and binarization.
This is done by generating P. Phase detection circuit 6,
0 ° output from the transmission waveform generation circuit 2 from 7 and 8
The phase of each input signal is output as a digital value using the drive signal Sd of 1 as a reference signal.

The digital values output from these phase detection circuits 6 to 8 are weighted and synthesized by the synthesis circuit 10. The offset value stored in the offset storage unit 11 including an EEPROM or the like is also supplied to the synthesis circuit 10, and the offset amount of the synthesis value can be adjusted. In the arithmetic circuit 12, the output of the synthesizing circuit 10 is converted into, for example, an electrode array pitch into an actual dimension value. The arithmetic circuit 12 is connected to a control circuit 9 that outputs an ON / OFF control signal for supplying power to each circuit, a clock signal, a reset signal, and the like. The actual dimension value obtained by the arithmetic circuit 12 is displayed on the LCD display 13.
Reference numeral 14 denotes a built-in small battery, the output of which is stabilized by a voltage regulator 15 and supplied to the entire system.

Also in this embodiment, a sensor movement / stop detection circuit 16 for monitoring the output signal to the LCD display 13 to detect the movement or stop of the ABS sensor 1 is provided, and its output is sent to the control circuit 9. Is being supplied. That is, the control circuit 9 has a function of setting the measurement cycle of the intermittent measurement operation, but the output of the movement / stop detection circuit 16 causes the intermittent measurement according to the movement or stop state of the ABS sensor 1 as described below. The operation measurement cycle is variably controlled.

FIG. 3 shows how the control circuit 9 receives the output of the movement / stop detection circuit 16 and controls the measurement interval. The normal measurement is, for example, intermittent measurement of 10 times per 1 second (measurement time for one time is 40 msec). ABS sensor 1
When stops, the control circuit 9 measures the stop time,
When 1 minute has passed after the stop, the measurement is switched to the thinning measurement of 5 times in 1 second. When the ABS sensor 1 starts moving again, it returns to the normal measurement. ABS sensor 1 stop time is 3
Turn off the power after a lapse of minutes. Thus, according to this embodiment, by controlling the measurement frequency and controlling the power supply according to the state of movement of the ABS sensor 1, it is possible to reduce the average current consumption of the system and extend the battery life. be able to.

The control circuit 9 is provided with a Zero / ABS switch and an OFF switch. When the Zero / ABS switch is pressed from the power-off state, the control circuit 9 operates and the LCD display 13 displays the measured value.
When this switch is pressed again, the LCD display becomes zero (zero set operation). That is, the Zero / ABS switch serves to alternately switch the measured value and the zero value.
The OFF switch is unnecessary when the power source is a solar cell.

The control circuit 9 supplies an ON / OFF signal, a reset signal, a clock signal, etc. to all other circuits, and not only the output of the sensor movement / stop detection circuit 16 but also
The output of the voltage detection circuit 17 that monitors the power supply output is also input. Then, when the power output is lower than the reference value, the control circuit 9 supplies a measurement-off signal to each circuit.

In the embodiment, the movement / stop state of the displacement sensor is detected, and the control is performed such that the measurement interval, that is, the measurement cycle is doubled by stopping for 1 minute. It can be set to an appropriate value.
Further, the measurement cycle may be switched to a plurality of stages according to the stop time, and generally, the same effect can be obtained by controlling the measurement time per unit time. Further, the movement / stop state of the sensor can be detected using not the output signal to the LCD display but the direct output of the displacement sensor or the signal of an appropriate node of another signal processing circuit unit. The present invention is also effective when a secondary battery or a solar cell is used as the battery, in addition to a normal primary battery.
Others The present invention can be variously modified and implemented without departing from the spirit thereof.

[0022]

As described above, according to the present invention, in the intermittent type absolute displacement measuring apparatus, the average current consumption of the system can be reduced by variably controlling the measuring interval according to the moving / stopped state of the displacement sensor. It can be effectively reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a block configuration of a capacitance type displacement measuring device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of an ABS sensor of the example.

FIG. 3 is a control flow of a measurement operation of the same embodiment.

[Explanation of symbols]

1 ... ABS sensor, 2 ... Transmission signal waveform generation circuit, 3,
4, 5 ... Demodulation circuit, 6, 7, 8 ... Phase detection circuit 9 ... Control circuit, 10 ... Synthesis circuit, 11 ... Offset storage section, 12
... arithmetic circuit, 13 ... LCD display, 14 ... battery, 15 ...
Voltage regulator, 16 ... Sensor movement / stop state detection circuit, 17 ... Voltage detection circuit.

Claims (1)

[Claims] 1. A displacement sensor that outputs an output signal according to a relative positional relationship of a movable element to a fixed element, and a signal that processes an output signal of the displacement sensor to measure an absolute displacement amount of the movable element with respect to the fixed element. Processing means; moving / stop state detecting means for detecting movement or stop of a movable element relative to a fixed element of the displacement sensor; and controlling the signal processing means to intermittently perform a measurement operation, and the moving / stop state. A displacement measuring device comprising: a control unit that variably controls an interval between intermittent measurement operations according to an output of the detection unit.