JPH0435691B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a capacitive position measuring transducer, and more particularly, to a capacitive position measuring transducer that accurately determines the absolute position between a pair of movable members that move relative to each other from changes in capacitance. The present invention relates to an improved capacitive position transducer capable of making measurements.

[Prior art] An electrical length measuring device that moves two scales relative to each other and measures the relative movement position of both scales using changes in capacitance between electrodes arranged on both scales. Length measuring devices are well known and can be used in a wide range of ways, from large length measuring devices such as three-dimensional measuring devices or NC processing machines to portable calipers, micrometers, and other small length measuring devices.

A capacitive transducer used in such a length measuring device supplies an alternating current signal, preferably a plurality of alternating current signals with different phases, to its transmitting electrode, and an electrical measuring circuit to the corresponding receiving electrode. The two electrodes are connected to each other, and a predetermined position is measured using changes in capacitance due to relative movement between both electrodes.

Conventional capacitive transducers generally perform relative measurements and are unsuitable for absolute measurements.

In other words, the relative movement between both scales of the transducer is usually electrically detected as a repeated change in capacitance, and conventionally, the amount of relative movement is usually measured by counting the number of repetitions. In such cases, it is extremely difficult to measure the absolute position itself between both scales, and relative measurement is generally performed by moving both scales relatively from the reference position to the measurement position and counting the repeated signals during this time. It was hot.

However, it is not possible to easily obtain measured values with such relative measurements, and absolute measurements have been strongly desired, especially for portable calipers and the like, in view of their operability.

Further, in the above-mentioned relative measurement, restrictions were imposed on the speed of movement between both scales, and there were also problems in that power consumption was large.

That is, according to the above-mentioned relative measurements, the measurements have to be made incrementally and always require a zero-setting of the device at the beginning of each measurement.

Therefore, conventional relative measuring devices have poor operability and
Furthermore, since the power consumption is large, a small measuring device that is powered by a battery has a problem that the battery life is short or the device becomes large.

In addition, as mentioned above, in relative measurement,
If the movement speed between both scales becomes faster, there is a problem that the processing speed cannot keep up and miscounts occur, so the movement speed is restricted or the frequency of the AC signal is made sufficiently high and the processing of the detection circuit is The problem was that the speed had to be increased sufficiently.

On the other hand, with absolute measurements, if the transducer is zeroed during assembly, there is no need to adjust it during subsequent measurements, and zeroing at each measurement value is not required at all. And since absolute measurement requires connecting the power only when obtaining the measured value,
This has the advantage that power consumption is significantly reduced, making it possible to use a battery-powered compact length measuring device, and the length measuring device can be sufficiently driven even by a battery with a small power supply capacity such as a solar cell.

Furthermore, according to absolute length measurement, since the capacitance between both scales is measured when their relative positions are determined, there is no contribution to the length measurement action during the relative movement of the scales, and as a result, the scale This has the advantage that there are no restrictions on the moving speed of the robot.

Conventionally, an absolute position measurement transducer using capacitance has been disclosed in Japanese Patent Application Laid-Open No. 54-94354 (US Patent No.
4420754), and this prior art was invented by the inventor of the present application, and its general structure is to move two pairs of transmitting/receiving electrodes relative to each other, and both pairs of electrodes are moved at their electrode pitches. The absolute position can be measured by electrically processing signals with different phases obtained from both electrode pairs or both scale pairs.

[Problems to be Solved by the Invention] However, when the conventional device is put into practical use as a length measuring device, there are several problems as described below.

The first problem is that the two pairs of scales are independent of each other and constitute separate capacitance detection circuits, and both detection outputs are processed by the measurement circuit, but there is inevitably a slight difference between the two outputs. There was a problem in that a time difference occurred, and this time difference caused a large error in the measured value.

In addition, if there is a slight measurement error between both scale pairs, that is, one scale is performing accurate phase detection, but the other scale has a slight measurement error, in principle, such a The deviation that occurs on one side will be treated as an extremely large absolute value error when the measurement circuit judges the absolute position, and the mechanical position accuracy of both scales and the independent electric circuit described above will be processed. There was a problem in that the characteristics had to be set extremely strictly.

The second problem is that the transducer requires two pairs of scales, which increases the space required for the transducer, and this has been a major impediment to the practical application of small, portable length measuring devices. .

The third problem is that, as mentioned above, in conventional devices, two pairs of scales are used as separate capacitance detection circuits, which increases power consumption. This was an unfavorable characteristic for people.

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to electrically measure the absolute position between relatively moving scales using a capacitance method, and to solve the above-mentioned problems in conventional devices. An object of the present invention is to provide an improved capacitive position transducer that eliminates all points.

According to the present invention, it is possible to perform accurate absolute value measurement with a small transducer, and there is no need for zero setting each time a measurement is made, and improvements are made in which power consumption is low and there are no restrictions on the moving speed of the scale. transducers are available.

According to the present invention, even if the frequency of the AC signal connected to the transmitting electrode is set to a relatively low frequency, sufficiently high accuracy can be ensured.
This significantly simplifies the electric circuit and allows the device to be completed at low cost.

Of course, in the present invention, if the electrodes are connected only when displaying absolute values, the desired measuring action can be performed, and the power consumption of the device is significantly reduced.

[Means for Solving the Problems] In order to achieve the above object, the present invention relates to an improvement in a transducer that measures the absolute position between two relatively moving members by measuring capacitance. The transducer includes first transducers that are movably disposed close to each other as the relatively movable members.
It has a scale and a second scale.

Generally, both scales are formed in a straight scale and move linearly relative to each other, but of course, in the present invention, the scale is formed by two coaxially arranged disks, and a rotary transformer is used. It is also suitable to obtain a deuser.

The first scale has n rows (n rows) of a first transmitting electrode to which an AC signal is supplied, and a first receiving electrode that is insulated from and close to the first transmitting electrode and is connected to a measuring circuit. is an integer greater than or equal to 1).

On the other hand, the second scale is composed of a group of electrodes arranged at a position that can face the first transmitting electrode along the relative movement direction, and a second receiving electrode capacitively coupled with the first transmitting electrode. n rows of second electrodes, each of which is capacitively coupled to the first receiving electrode;
a transmitting electrode.

Both electrodes provided on the second scale are arranged continuously over the required measurement area, and usually
An electrode row is formed that is sufficiently longer than the electrodes on the scale side.

In the present invention, each row of the second receiving electrode and the second transmitting electrode is electrically connected to each other by a coupling electrode between the transmitting and receiving electrodes, and the connected second receiving electrode and the second transmitting electrode are electrically connected to each other by a coupling electrode. Different deviations are given to the combination of the electrode groups and the electrode group along the direction of relative movement. Furthermore, the present invention is characterized in that the electrical connection between the second receiving electrode and the second transmitting electrode in a predetermined row is made through the second receiving electrode or the second transmitting electrode in another row.
A plurality of electrodes of the electrode group constituting the second transmitting electrode in the predetermined row are disposed with respect to one electrode of the electrode group constituting the transmitting electrode, and the deflection is performed with respect to one electrode of the electrode group constituting the transmitting electrode. is different for each row of the electrodes, and an absolute value measurement is performed with said excursions determined in one row of electrodes selected for each movement position.

The different deviations for each movement position described above are expressed as a predetermined function of the movement amount, and this function usually has linearity, but in the present invention, it does not necessarily have to be a linear function.
Can be given any characteristics.

In the present invention, as described above, the second receiving electrode provided on the second scale and the second transmitting electrodes in one or more rows are connected to each other by a coupling electrode. 1st scale
The AC signal supplied to the transmitting electrode is first transmitted to the second receiving electrode on the second scale side by capacitive coupling, and then this signal is electrically transmitted as it is to the second transmitting electrode of each column, and then again. The signals are returned to the first receiving electrodes of the respective opposing rows by capacitive coupling.

Therefore, according to the present invention, a change in capacitance can be detected at once through the second receiving electrode and the second transmitting electrode by one series of electric circuits for each column, and the change in capacitance can be detected at once through the second receiving electrode and the second transmitting electrode. The capacitance value detected by selecting one row of electrodes is equal to the supplied AC, since the deviation of is uniquely determined for each moving position in each row of electrodes between the required measurement areas. A single value is determined in accordance with the phase of the signal, and unlike conventional devices that use two series of electric circuits, it is possible to perform measurement with extremely high precision.

The measuring circuit compares the received signal level with the phase of the transmitted AC signal, performs a predetermined calculation operation, and can display the absolute value of the relative movement position.

In addition, when multiple rows of second transmitting electrodes are provided, different deviations are given to each row, so it is possible to obtain various absolute measurement ranges with one device, and It is also possible to perform highly accurate measurements by combining measured values.

Further, according to the present invention, by reducing the pitch of the electrode group, the connection between a predetermined deflected second transmitting electrode and the second receiving electrode can be made to one of the second receiving electrodes. On the other hand, since the second transmitting electrode is configured to have two or more electrodes, the connection between the second receiving electrode and the second transmitting electrode is a one-to-one connection for each of the constituent electrodes. As such, since there is a certain limit on the amount of deviation, it is possible to prevent the occurrence of some electrodes among the electrode group of the second transmitting electrodes that cannot be connected to the second receiving electrodes.

[Embodiments] Preferred embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows a preferred embodiment of the capacitive position detection transducer according to the present invention, which is suitable for a length measuring device such as a caliper in which a vernier scale moves linearly with respect to a main scale. 1 scale 10 and 2nd scale 2
For example, the first scale 10 is installed on the vernier side of a caliper, and the second scale 20 is installed on the main side.

Both scales 10 and 20 are disposed close to each other and movable relative to each other, and are shown at x in FIG.
The axis position indicates the movement position of the first scale 10 with respect to the second scale 20.

The first scale 10 is provided with a first transmitting electrode 12 , and an alternating current signal is supplied from an oscillator 30 to the first transmitting electrode 12 .

In the illustrated embodiment, the first transmitting electrode 12 has a first transmitting electrode structure of three pairs of two equally spaced electrodes, each pair receiving an alternating current signal of a different phase from the oscillator 30. 30a and 30b
is supplied, and the phase difference between both signals is set to 180 degrees.

The first scale 10 further includes a first receiving electrode 1.
4 are provided in n rows (n is an integer of 1 or more), and in this embodiment, one example is provided on each side of the first transmitting electrode.
A total of two rows of first receiving electrodes are provided. In the embodiment, the first receiving electrodes 14 are composed of a group of electrodes arranged at predetermined intervals in each row, and are arranged adjacent to and parallel to the first transmitting electrodes.

Each first receiving electrode 14-1, 41-2 is connected to a measuring circuit 32, respectively.

Each of the electrodes 12 and 14 is provided on the insulating substrate of the first scale 10 by vapor deposition or other means, and the two electrodes are electrically insulated.

A characteristic feature of the transducer according to the present invention lies in the electrode arrangement of the second scale 20. As is clear from the figure, the second scale 20 includes second receiving electrodes 22 arranged in alignment and second receiving electrodes 22 in two rows. A transmitting electrode 24 is provided.

The second receiving electrode 22 is composed of a group of electrodes arranged at a position facing the first transmitting electrode along the relative movement direction (x-axis), and is capacitively coupled to the first transmitting electrode.

The second receiving electrodes 22 in the embodiment are arranged at equal intervals, and the pitch is indicated by Pr2.

On the other hand, the second transmitting electrodes 24-1 to 24-2 in each column
is the first of the two rows along the relative movement direction (x-axis).
The first receiving electrode 14 is composed of a group of electrodes arranged at positions that can face the receiving electrodes 14-1 and 14-2.
are capacitively coupled to each column.

Then, the second transmitting electrodes 24-1 and 24-
2, electrode groups are arranged at equal intervals within one row, and the pitch Pt2 differs for each row.

In the present invention, the second receiving electrode 2
2 and the second transmitting electrode 24 are set to different values, and as a result, there is a sign D(x) between the two electrodes.
It is understood that the deviation shown by is given.

In the present invention, the deviation D(x)=(Pt2−Pr2)f(x)...(1) of the second transmitting electrode 24 is a constant specified value depending on the relative movement position, that is, the value of x. It is characteristic that it becomes

Further, in the present invention, the second receiving electrode 22
and the second transmitting electrodes 24 of each column are electrically connected to each other by a coupling electrode 26 for each electrode.

Therefore, according to the invention, for each relative movement position (x), the interelectrode deviation D(x) of each row coupled to each other by the coupling electrode 26 has a unique specified value for each row. It is understood that the detected capacitance value is the deviation D(x), which is a unique specified value for each column, and thereby the detected capacitance value is It is understood that the capacitance value obtained corresponds to the deviation D(x), and absolute value measurement becomes possible.

Of course, the deviation D(x) of each column increases as the measurement range of the transducer increases, but the amount of deviation D(x) increases at the transmitting pitch, in the embodiment, the first transmitting electrode. There is a restriction that the transmission wavelength pitch Wt1 on 12 cannot be exceeded.

That is, the deviation D(x) is the transmission wavelength pitch Wt1
This is because if it exceeds this, it becomes difficult to identify the received signal.

Therefore, in the embodiment shown in FIG. 1, the second scale 20 has a maximum deviation D(x) of each row of the second transmitting electrodes 24 over the entire length of the caliper, exceeding the transmitting wavelength pitch Wt1. It is set to not. More specifically, the second transmitting electrode 24- in FIG.
The deviation D(x) of 1 is set to be zero at the center of the second scale 20, and its value increases in the opposite direction as it moves left and right, and the deviation at both ends of the second scale 20 is It consists of a shape divided into negative parts.

On the other hand, the second transmitting electrode 24-2 is further pitched.
Since Pt2(2) is small and the difference from the pitch Pr2 of the second receiving electrode 22 is large, the deviation D(x) with respect to the relative movement distance also becomes large (from equation (1)).

Therefore, due to the restriction that the amount of deviation D(x) cannot exceed the transmission wavelength pitch Wt1, the deviation D(x) exceeds the transmission wavelength pitch Wt1 in a one-to-one connection between the second receiving electrode and each electrode. Therefore, there is a portion 25 of unconnected electrodes that cannot be connected.

The second transmitting electrode 24-2 corresponds to one electrode of the second receiving electrode 22, which is a characteristic part of the present invention.
This method connects multiple electrodes.

That is, if the unconnected electrode portion 25 of the second transmitting electrode 24-2 is left as is, or if no electrode is provided in the unconnectable portion, and the number of electrodes is the same as the number of electrodes of the second receiving electrode, Since measurement would not be possible in this area, the electrodes that could not be connected with a one-to-one connection on the front surface of the second scale were connected to the second electrode on the back surface of the second scale, as shown by the broken line in Figure 1. The reception electrode and the amount of deviation D(x) are the transmission wavelength pitch.
Connected so as not to exceed Wt1.

FIG. 2 is a schematic diagram showing the electrode arrangement on the second scale of this embodiment, and the second transmitting electrode 24-1 has a pitch Pt2(1) that is slightly smaller than the pitch Pr2 of the second receiving electrode 22. On the other hand, the second transmitting electrode 24-2 is arranged with an even smaller pitch Pt2(2), and the number of arranged electrodes is also smaller than that of the second receiving electrode 22-2.
The number of electrodes has also almost doubled.

Therefore, the second receiving electrode 22 and the second transmitting electrode 24
-1 can be connected over the range necessary for length measurement by one-to-one electrode connection as long as the amount of deviation D(x) does not exceed the transmission wavelength pitch Wt1. Since the difference between the electrode pitches Pr2 and Pt2(2) is larger, the connection between the receiving electrode 22 and the second transmitting electrode 24-2 is made within a range where the amount of deviation D(x) does not exceed the transmitting wavelength pitch Wt1. This is only possible within a certain narrow range.

Therefore, the unconnectable portions of the electrodes 25 are connected on the back side of the second scale 20, as shown by the broken lines in the figure, so that the deviation D(x) does not exceed the pitch Wt1.

The second scale 20 also has an insulating substrate, and includes the aforementioned second receiving electrodes 22 and two rows of second transmitting electrodes 2.
4-1, 24-2, and each coupling electrode 26 is formed on the insulating substrate by vapor deposition or other means, and is electrically connected to the second receiving electrode 22 and the second transmitting electrode 24 of each column. The electrode pairs are arranged along the relative movement direction (x-axis) so as to be electrically insulated from each other.

As described above, according to the present invention, the second receiving electrode 22 of the second scale 20 and the second transmitting electrode 2 of each column
4 has a unique specified deviation D(x) for each position along the direction of relative movement, so the capacitance value detected when the first scale 10 moves is at each position. This is the only specified value for each position, making absolute measurement possible at any position.

According to the present invention, the AC signal supplied to the first transmitting electrode 12 is transmitted to the second receiving electrode 22 by capacitive coupling, and this is immediately transmitted to the second transmitting electrode of each column by conduction of the coupling electrode. is transmitted to the first receiving electrode 14 of each corresponding row by capacitive coupling again in a state shifted in the relative movement direction (x-axis direction).
-1, returned to 14-2.

Therefore, according to the present invention, it is possible to detect signals through the electrodes having different deviations using only a single electrical system for each electrode in each row, and the position of the signal can be detected by using only a single electrical system for each electrode in each row. Absolute measurements with extremely high precision can be made without any deviation or time difference.

In FIG. 1, two rows of first receiving electrodes 14-1 are arranged adjacent to the first transmitting electrode 12.
.about.14-2 supply detection signals to the detection circuits, respectively.

In the embodiment, the first receiving electrode 14
Pitch for each block, that is, reception wavelength pitch
As described above, Wr1 is set to Wr1(2)=Wt1×Pt2(2)/Pr2 (2), corresponding to the shift amount by which the transmission signal is shifted by a predetermined amount through the second scale.

Therefore, according to such reception wavelength pitch Wr1, the AC signal transmitted from the first transmission electrode 12 has a predetermined pitch between the second reception electrode 22 of the second scale and the second transmission electrode 24 of each column. After the shift is performed, in the first receiving electrodes of each row facing each other again, the receiving electrodes 14 have a length corresponding to the shift amount.
It is understood that it can be received at

Measurement signal 32-1 output to measurement circuit 32,
32-2, one of them is selected by an analog switch in the circuit 32, and a predetermined calculation is performed.

Furthermore, the range L that can be absolutely measured by the second transmitting electrode is the pitch of the second transmitting electrode under the condition that the deviation D(x) does not exceed the transmitting wavelength pitch Wt1.
Assuming that Pt2 is smaller than the pitch Pr2 of the second receiving electrode, it is expressed as mPt2=L mPr2=L+Wr1 L=Wr1×Pt2/(Pr2−Pt2) (3) for a certain value m, and the amount of relative movement is In a range where the value exceeds the absolute measurable range L, the phase changes by more than 360°, making it impossible to identify the absolute value.

Furthermore, from equation (3), the closer the pitch Pt2 of the second transmitting electrode is to the pitch Pr2 of the second receiving electrode, that is, the smaller the deviation D(x), the wider the absolute measurable range L, but conversely, the resolution is It is understood that it will be rough.

FIG. 3 shows another example of the second scale electrode arrangement according to the present invention, in which the second receiving electrode 22
One row of arrangement of the second transmitting electrodes 24-1 to 24-n in n rows is shown, and the pitch Pt2 between each electrode of the second transmitting electrodes 24 is gradually changed from the first row to the nth row. It is arranged in a smaller size. That is, they are arranged so that the deviation Dk(x) of each column gradually increases.

By setting the second transmitting electrodes 24 in each row at different pitches in this manner, various absolute measurement ranges can be obtained on one scale.

In the case of this embodiment, the connection of the second transmitting electrode 24-n of the nth row with a small pitch Pt2 is connected to the second receiving electrode 24-n.
It is not directly connected to 2, but the n-1st
Since it is directly connected to the second transmitting electrode 24-(n-1) of the column, the one-to-multiple electrode connection is
It is shown that this is performed between the second transmitting electrodes 24 in the column and the (n-1)th column.

FIG. 4 shows another embodiment of the first scale of the present invention, in which n rows of first receiving electrodes 14 each consist of two types of electrodes for outputting signals with two different phases. The electrodes move in the direction of relative movement (x
It has a triangular wave shape that repeats at the receiving wavelength pitch Wr1 with respect to the axis).

This triangular waveform is made up of two first receiving electrodes 14a and 14b arranged in opposite phases to each other, and their detected values are subtracted from each other, thereby improving the sensitivity of the detected signal. can.

The first scale 10 of FIG. 5 is similar to the embodiment of FIG.
4a and 14b are characterized by exhibiting a sine wave shape, unlike the triangular wave shape in FIG.

Further, in the first scale 10 of FIG. 5, the AC signal supplied to the first transmitting electrode 12 is divided into eight phases, each having a phase difference of 45 degrees.

In the first scale 10 as shown in FIG.
A rectangular wave signal is selected as the AC signal supplied to the first transmitting electrode 12, and the first receiving electrode 1 of each column
Since the electrodes 4a and 14b have a sinusoidal shape, it is understood that the two types of output signals with inverted phases supplied to the measurement circuit 32 have a sinusoidal shape.

As described above, according to the present invention, the AC signal supplied to the first transmitting electrode is transmitted to the second receiving electrode by capacitive coupling, and this is immediately transferred to the second transmitting electrodes provided in n rows by a predetermined displacement. The output signal is shifted by the amount, conducts, and is returned to the first receiving electrode of each row facing each other by capacitive coupling, and this detected output signal is transferred to the second receiving electrode.
This is the deviation information for each row of the second receiving electrode and the second transmitting electrode on the school, and in the present invention, this deviation is always uniquely specified for each row with respect to the relative movement position within the required measurement area. As a result, the detected signal of one selected column contains sufficient information to calculate the relative movement position.

According to the present invention, accurate absolute measurement is possible by measuring the deviation D(x) as described above, and the zero setting, large power consumption, and scale movement speed required for each measurement in conventional relative measurement can be achieved. It is possible to provide an excellent length measuring device without any problems.

Further, according to the present invention, as described above, the second
Since there is only one electrical circuit passing through the transducer for each row of transmitting electrodes and first receiving electrodes,
Measurement accuracy can be significantly improved without considering mechanical errors in electrode arrangement or differences in electrical delay time differences, and by providing multiple rows of first receiving electrodes 14 and second transmitting electrodes 24, various absolute In addition to obtaining the measurement range, the measurement accuracy can be further increased by combining the measurement values of each column, and since the measurement is performed by a pair of scales, the transducer consumes less space and consumes less power. can be provided.

FIGS. 6 and 7 show an example of a length measuring circuit connected to the transducer according to the present invention, and FIG. 8 shows waveforms and timing charts of each part thereof.

The length measuring circuit shown in FIG. 6 is a length measuring circuit in which the first receiving electrode of each column is connected to a transducer consisting of one type of electrode, as in the embodiment shown in FIGS. 1 and 2, The above-mentioned transducer according to the present invention is indicated by the reference numeral 100, and a plurality of alternating current signals having different phases are supplied to the first transmitting electrode, and the alternating current signals are obtained from the oscillator 30 and In the present invention, the oscillation output f0 does not need to have a very high frequency, and can be set to a relatively low frequency of, for example, about 100 to 200 KHz.

The output f0 of the oscillator 30 is the transducer 10
0 is further divided by the frequency divider 60 and supplied as a signal, but it is also used as a synchronizing signal for the modulator and demodulator, and forms one factor for determining the resolution of the device. As mentioned above, in the present invention, since the fundamental frequency and the frequency of the AC signal that is then divided and supplied to the first transmitting electrode are low, sufficient resolution can be achieved by simplifying the circuit configuration and using an inexpensive device. This has the effect that the following can be obtained.

The output of the frequency divider 60 is further processed by a phase converter 34 to convert into eight desired AC signals 200-1 to 200-, each having a phase difference of 45 degrees, as shown in FIG.
Converted to 8. Therefore, such eight AC signals with different phases are, for example, the first signal in FIG. 5 mentioned above.
Preferably, it is supplied to a transmitting electrode.

The aforementioned eight AC signals are modulated by the output f0 of the oscillator 30 in the modulator 62, and these signals 200-1 to 200-8 are transmitted to the transducer 1.
00 are supplied to each of the first transmitting electrodes 12.

As described above, the transducer 100 converts the supplied AC signal 202 into signal levels corresponding to the relative movement positions of the first and second scales, and then converts the supplied AC signal 202 into electric signals from each column of the first receiving electrodes. The output of each column is output by an analog switch 65, and the output of one column selected is further demodulated by a synchronous demodulator 66.

Furthermore, in the case of a transducer in which the first receiving electrodes in each column are composed of two types of electrodes, as shown in FIG. The signal is sent to the dynamic amplifier 64 and output as a signal 204, which becomes a signal whose envelope draws a sinusoidal curve as shown in FIG. This is the only point that differs from the length measuring circuit shown in FIG. 6, and the output signal 204 is demodulated by a synchronous demodulator 66, and the circuit configuration below is the same as that shown in FIG.

The output 206 from the synchronous demodulator has a phase difference of φ compared to the reference signal 300 when both scales are at the reference position, and by determining this phase difference φ, the relative position of both scales can be determined. The absolute value determined by can be found.

Note that the output 206 of the demodulator 66 includes high frequency components as shown in FIG. 8, and in this embodiment, this high frequency component is removed by a filter 68 to obtain a signal 208 from which the high frequency component has been removed. There is.

The waveform zero-crossing position of the signal 208 is further detected by a zero-crossing circuit 70.

In the embodiment, in order to digitally calculate the phase difference φ, the device includes a counter 72 whose reset/start signal is synchronized by the control unit 80 with the trigger signals of the modulator 62 and demodulator 66 in the embodiment. The counting operation of the counter 72 is started from this point using the start of device mounting as a trigger for the reference signal. counter 7
2 counting timing is the output frequency of the oscillator 30
Controlled by f0.

The counting stop of the counter 70 is controlled by the signal from the zero cross circuit 70, and at the phase φ position in FIG. 72, and the counting operation of the counter 72 ends at this point.

Therefore, the counted value of the counter 72 indicates the phase difference by which the reference signal 300 is shifted by the transducer, and as described above, according to the present invention, this phase difference φ is the difference between both scales at the time of measurement. Corresponding to the deviation D(x) of 10 and 20, the output of the counter 72 is converted into an absolute value by an arithmetic unit 74.

The output of the arithmetic unit 74 controlled by the control unit 80 supplies a desired display signal to the display 78 via the display driver 76, so that the measured value is normally displayed digitally.

In this embodiment, the display 78 is, for example, a liquid crystal display embedded and fixed in the vernier surface of the caliper, so that the user can easily read the length measurement value.

[Effects of the Invention] As explained above, according to the present invention, the amount of phase movement between two relatively moving members, usually the first and second scales, can be measured in absolute value as a change in capacitance. This makes it possible to obtain a compact and lightweight capacitive transducer that can be driven by batteries.

Further, according to the present invention, the second scale on the second scale side
The receiving electrodes and the second transmitting electrodes in one or more rows are electrically connected to each other by coupling electrodes, and have different deviations for each row along the direction of relative movement between the two electrodes, This deviation is set to be a unique specified value for each column in the entire length measurement range, and can be determined by selecting the output signal of one column of the first transmitting electrode and performing a predetermined calculation. Therefore, it becomes possible to know the absolute value of the relative movement position of both scales from the shift value between the transmitted and received signals using a single capacitive coupling circuit that passes between both scales.

In addition, when multiple rows of second transmitting electrodes are provided, each row is given a different pitch, so it is possible to obtain various absolute measurement ranges with one scale, and the measurement values of each row can be combined. It is also possible to perform highly accurate measurements.

Furthermore, since each column uses a single capacitive coupling circuit, interference from mechanical and electrical errors can be significantly reduced, and a compact transducer with low power consumption can be obtained.

Furthermore, according to the present invention, when the electrode pitch of the second transmitting electrode is reduced in order to obtain a predetermined deviation,
Since direct or indirect electrical connection with the second receiving electrode is made by using a plurality of electrodes of the second transmitting electrode with respect to one electrode of the second receiving electrode, It is possible to avoid the occurrence of non-connected parts and prevent the occurrence of unmeasurable ranges.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a main part showing a preferred embodiment of a capacitive position measuring transducer according to the present invention, and FIG.
1 is a schematic explanatory diagram showing the second scale side of the transducer according to the embodiment of FIG. 1, and FIG. 3 is a partial schematic diagram showing another embodiment of the transducer on the second scale side according to the present invention. FIG. 4 is a schematic explanatory diagram showing another embodiment of the first scale of the transducer according to the present invention, and FIG. 5 is a plan view showing another first scale of the transducer according to the present invention. ,
6 and 7 are block diagrams of a measurement circuit suitable for a transducer according to the present invention, and FIG.
FIG. 8 is an explanatory diagram showing waveforms and timing charts in FIG. 7 and FIG. 7; 10...first scale, 12...first transmitting electrode, 1
4...first receiving electrode, 20...second scale, 22...
First receiving electrode, 24...first transmitting electrode, 26...coupling electrode, 30...oscillator, 32...measuring circuit, D(x)...deflection, x...relative movement direction.

Claims (1)

[Scope of Claims] 1. A first scale and a second scale are arranged close to each other so as to be relatively movable, and the first scale has a first transmitting electrode to which an alternating current signal is supplied, and n rows (n is an integer of 1 or more) of first receiving electrodes arranged insulated from one transmitting electrode and connected to a measuring circuit; the second scale has a relative movement direction; a second transmitting electrode that is capacitively coupled to the first transmitting electrode, and comprises a group of electrodes disposed at a position facing the first transmitting electrode along the
A receiving electrode, and n rows of second transmitting electrodes each comprising a group of electrodes disposed at a position facing the first receiving electrode along the relative movement direction and capacitively coupled to each row of the first receiving electrode. The second receiving electrode and the second transmitting electrode of each column are electrically connected to each other via a coupling electrode or via the coupling electrode and the second transmitting electrode of another column, and each connected second A different deviation is given to each row of the second transmitting electrodes along the relative movement direction between the receiving electrode and the second transmitting electrode, and the second transmitting electrode and the second transmitting electrode of a predetermined row are different from each other. The electrical connection is made by connecting a plurality of electrodes of the electrode group constituting the second transmitting electrode of the predetermined column to one electrode of the electrode group constituting the second receiving electrode or the second transmitting electrode of the other column. A capacitive position-measuring transducer, characterized in that: an absolute measurement is made by the deflection determined for each relative displacement position. 2. In the transducer according to claim 1, the electrical connection between the second receiving electrode and the second transmitting electrode in a predetermined column is such that the electrical connection between the second receiving electrode and the second transmitting electrode in the predetermined row is based on a one-to-one connection of each constituent electrode on a second scale. Connecting the constituent electrodes of the second transmitting electrodes in the predetermined row that are not connected to the second receiving electrodes or the constituent electrodes of the second transmitting electrodes in other columns on the back surface of the second scale. A capacitive position measurement transducer featuring: 3. In the device according to claim 2, the first
The pitch of the electrode group of the receiving electrode is the receiving wavelength pitch Wr1.
If the transmitting wavelength pitch is Wt1, the second receiving electrode pitch is Pr2, and the second transmitting electrode pitch is Pt2, the capacitive position measuring transducer is characterized in that Wr1=Wt1×Pt2/Pr2. Yusa. 4. In the transducer according to claim 3, each row of first receiving electrodes is composed of two types of electrodes in order to output signals with two different phases, and the electrodes have mutually inverted shapes. A capacitive position measuring transducer comprising an electrode.