JPS62159002A - Digital display type measuring instrument - Google Patents

Abstract

PURPOSE:To obtain an instrument which is small in size and has a high accuracy by constituting it so that its main scale is formed by an electric insulating material, and a receiving electrode and a coupling electrode are placed on one surface and the other surface side, respectively. CONSTITUTION:A main scale 110 is formed from a ceramics material, and a receiving electrode 126 and a coupling electrode 128 are formed on its right and left side faces, respectively. Also, a slider 112 is formed to a rectangular cylindrical shape having a square-shaped section, the main scale 110 is inserted through its cylinder, and also a transmitting electrode substrate part 132 and an output electrode substrate part 134 are stuck and placed to its right and left side walls, respectively. These substrate parts 132, 134 consist of an electric insulating material, formed in parallel to each other, and on their inside surfaces, a transmitting electrode 122 and an output electrode 124 are formed and placed in accordance with the electrodes 126, 128, respectively. In this way, a relative moving position of the slider 112 and the main scale 110 is detected from an electrostatic capacity signal having a periodic variation corresponding to a moving displacement quantity of the electrode 122 and 126. In this state, unless a variation is generated in a parallelism of the substrate part 132 and 134, D1+D2 is always constant, and the detection accuracy is not changed even by looseness, etc., between the main scale 110 and the slider 112.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a digital display type measuring instrument, and particularly to a digital display type measuring instrument having a capacitive encoder and detecting a linear movement displacement amount.

[Prior Art] In recent years, digital display type measuring instruments such as calipers, micrometers, and hide gauges, which electrically read measured values and display them digitally, have become popular in place of conventional mechanical reading methods.

Typically, such a digital display type measuring instrument includes a movable body movably installed in the main body of the device, and an encoder that detects the amount of movement of the movable body and converts it into electrical signal pulses. The output electrical signal pulses are counted by a counting circuit, and the counted value is digitally displayed on a digital display section.

Incidentally, as encoders used in this type of apparatus, photoelectric encoders, contact encoders, capacitive encoders, and the like are conventionally well known.

A photoelectric encoder includes slits provided at equal intervals on the surface of a scale, and a light emitter and a light receiver that form an optical path through the slits of the scale, and moves the scale according to the amount of displacement of a moving body. By turning on and off the optical path formed between the light emitting and receiving devices, electric signal pulses are obtained and the amount of displacement of the moving object is detected.

However, this photoelectric encoder has the drawbacks that the light emitting device consumes a large amount of power, the number of battery replacements required increases, and if a large capacity battery is used, the weight of the device increases. was.

Furthermore, in order to improve measurement accuracy, it is necessary to provide slits on the scale at intervals of several microns, which is difficult to manufacture, and moreover, there are problems in that miscounts are likely to occur due to clearance changes during operation.

Furthermore, since the contact type encoder uses slits, brushes, etc. to detect the amount of displacement of a moving body, there are problems in that these slits and brushes are subject to severe wear and noise is likely to be mixed into the measurement signal.

On the other hand, capacitive encoders do not consume as much current as photoelectric encoders, and they do not have the problems of wear of brushes, slits, etc. or noise contamination like contact encoders. Widely used in equipment.

Capacitive encoders used in such measuring instruments have multiple pairs of electrode plates arranged opposite each other to form a capacitor.
Both electrode plates are moved relative to each other in accordance with the amount of displacement of the moving body, and the amount of mechanical displacement at this time is electrically detected as a change in capacitance of the capacitor.

This type of capacitive encoder includes voltage comparison type, phase discrimination type, etc., but the phase discrimination type has particular advantages such as small size, light weight, high precision, and low power consumption.
Widely used.

FIG. 5 shows a digital caliper as a digital display type measuring instrument using such a phase-discriminative capacitive encoder.

In the figure, a main scale 10a, on which a receiving electrode and a coupling electrode are arranged, is integrally adhered to a main scale 10 as a second member. A reading unit 12a composed of a capacitive encoder and a digital display section is attached to the slider 12 as a first member that is slidably attached to the main scale 10, and the reading unit 12a includes the following: After the battery 14 is installed, the cover 12b is placed over the battery 14.

Further, the slider 12 is attached with a depth spar 16 for measuring depth and a leaf spring 18 that provides an appropriate sense of moderation to the sliding movement of the slider 12.

The receiving electrode and slider 12 provided on the main scale 10 are
The arrangement of the transmitter electrodes provided in the transmitter electrodes is shown in detail in FIG.

An electrode substrate 20 made of an insulating material is attached to the leading unit 12a of the slider 12, and a plurality of transmitting electrodes 22 arranged at equal intervals are arranged on the side of the electrode substrate 20 that faces the main scale 10. ．． An output electrode 24 is provided below the transmitting electrode group.

The main scale 10a on the main scale 10 is made of an electrically insulating material, and on the side of the main scale 10a facing the leading unit 128, there is a position corresponding to the transmitting electrode 22 along the longitudinal direction of the main scale 10. The receiving electrode 26 is
Further, a coupling electrode 28 is provided below the receiving electrode 26. In the illustrated example, a plurality of receiving electrodes 26 are provided on the main scale 10a, and a ground electrode 30 is arranged between each receiving electrode 26.

Then, an alternating current voltage of a sine wave or a rectangular wave with a predetermined phase, for example, a phase shifted by π/4, is sequentially applied to the transmitting electrode 22 from a detection circuit to be described later, and a unit electrode group 40 having eight phase electrodes as one unit is applied. It is formed. Here, continuous predetermined transmitting electrodes 2 included in each unit electrode group 40
The receiving electrodes 26 are arranged so as to face each other. That is, in the illustrated example, four consecutive transmitting electrodes 2
2) That is, the transmitting electrode to which the reference voltage V1 is applied and the reference voltage V2. V3. One receiving electrode 26 is disposed opposite to the transmitting electrodes to which each voltage of V4 is applied.

In the illustrated example, the detection circuit is generally configured as shown in FIG.

In the figure, an 8-phase transmission signal generator 50 generates 8-phase voltages with a phase shift of π/4 to be applied to the transmission electrode 22 in a trapezoidal waveform using pulses.

Then, the voltage induced in the receiving electrode 26 is transferred to the coupling electrode 2
8 and the output electrode 24 to the input section 52 .

The input section 52 performs synchronization with a pulse voltage from an oscillator 54 and performs rectification.

The output from the input section 52 is input to a phase difference detector 56, and the phase difference detector 56 always uses the phase when the slider 12 is stopped as a reference, and calculates the phase according to the subsequent movement of the slider. Capture phase changes.

Then, the direction of movement is determined and outputted as a voltage level, as well as a number of pulses corresponding to the amount of movement.

The output of the phase difference detector 56 is input to the counter 58 of the LSI 2, and the amount of displacement is displayed on the LCD 60.

In addition, the counter 62 in LSI 1 is used, and its output (
It is also suitable to connect the BCD signal to the LSI 3 and display it on the LCD 64, and this type is provided with a terminal 66 for outputting display data to an external device.

With the above configuration, when the slider 12 is moved relative to the main scale 10, the receiving electrode 26 and the transmitting electrode 22 are moved relative to each other, and the receiving electrode 26 becomes static with a periodic change according to the amount of displacement of the slider 12. A capacitance signal is obtained. The capacitance signal detected in this manner is transmitted to the coupling electrode 28 via the coupling electrode 28 electrically coupled to the receiving electrode 26.
8 is taken out by the output electrode 24 which is electrostatically coupled to the main scale 8, and is supplied to a digital display unit etc. via the detection circuit, so that the relative movement displacement amount of the slider 12 and the main scale 10 can be accurately measured with a simple configuration. can do.

[Problem to be solved by the invention] By the way, the phase-discriminative capacitive encoder used in such digital display type measuring instruments has a problem in that the clearance between the transmitting electrode and the receiving electrode is small. Compared to other types of encoders, it can be larger than other encoders, so it has the advantage of being easy to manufacture. However, on the other hand, the distance between the transmitting electrode and receiving electrode directly affects the electrostatic capacitance. Parallelism is required to be constant at all times.

However, the relative position of the first and second members on which each electrode is arranged changes due to slight play or backlash due to wear due to sliding, and the gap between the two members, that is, the transmitting electrode and the receiving electrode The clearance between them will fluctuate.

As a result, there is a problem in that the capacitance signal from the output electrode fluctuates, resulting in an error in measuring the amount of displacement.

In addition, capacitive encoders used in digital display measuring instruments are required to be more compact, and as a result, the width of the first and second members is particularly regulated, and as a result, the area of each electrode I have no choice but to make it narrower. Therefore, there is a problem in that the detected capacitance signal value becomes small and the S/N ratio deteriorates.

This problem will be explained in more detail with reference to FIG.

FIG. 8 is an enlarged view of the capacitive encoder part of the caliper shown in FIG. situation,
FIG. 6B shows the main scale 10 viewed from the receiving electrode installation side, and the same parts as in FIG. 6 are given the same reference numerals.

As is clear from the figure, the length of the main scale 10, that is, the length L of the digital caliper, is determined according to the length measurement range that the encoder is intended to measure, and is simply a matter of miniaturization. It is impossible to plan.

Therefore, the issue of miniaturization of the caliper here is the width W of the main scale 10 or the electrode substrate 20.

This width W is regulated in terms of the mechanical conditions of the caliper, ease of handling, etc., but generally it is required to be as small as possible.

Here, in a conventional caliper, it is necessary to install a transmitting electrode 22 and an output electrode 24 on the electrode substrate 20, and a receiving electrode 26 and a coupling electrode 28 on the main scale 10. Since each electrode is installed on the same surface, the area of each electrode inevitably becomes small.

Of course, by increasing the width A of the transmitting electrode 22, it is possible to increase the area of each electrode, but on the other hand, this transmitting electrode width A
Enlarging the image will reduce the resolution.

As described above, in capacitive encoders used in conventional digital display measuring instruments, the area of each electrode must be set small, which results in a decrease in the output of capacitance signals.
This directly leads to deterioration of measurement accuracy.

Furthermore, as shown in FIG. 8, as a result of having the transmitting electrode 22 and the output electrode 24 adjacent to each other on the same plane, crosstalk occurs between the two, which also deteriorates measurement accuracy and makes wiring to each electrode difficult. This has also caused problems in that it is complicated and extremely difficult to manufacture.

The present invention has been made in view of the problems of the prior art described above, and its purpose is to provide a compact and highly accurate digital display type measuring instrument.

[Means for Solving the Problems] In order to achieve the above object, the digital display type measuring instrument according to the present invention has a second strip-shaped member made of an electrically insulating material, and a receiving electrode on one side of the second member. However, a coupling electrode is arranged on the other side. The first member also includes a transmitting electrode substrate portion facing the receiving electrode arranging surface of the second member and having the transmitting electrode arranged thereon, and an output type @ facing the coupling electrode arranging surface of the second member and having the output electrode arranged thereon. It is characterized by having a substrate.

[Function] As is clear from the above-described configuration, according to the digital display type measuring instrument according to the present invention, AC voltages having different phases are applied to the plurality of transmitting electrodes provided on the transmitting electrode substrate portion of the first member. As a result, a capacitance signal is detected at the receiving electrode on the second member that is capacitively coupled to the transmitting electrode.

This capacitance signal is taken out from an output electrode that is capacitively coupled to the coupling electrode via a coupling electrode provided on the other surface of the second member.

Then, based on this capacitance signal, the relative displacement amount of both members is calculated, and the display section provided on the first member displays the following:
The amount of relative displacement is digitally displayed.

Here, since the second member itself is made of an electrically insulating material, there is no need to attach an electrode substrate made of an insulating material onto the second member as in the conventional case.

Therefore, the second member can be formed thinly, and the step of attaching the electrode substrate is not necessary, so that manufacturing is also facilitated.

In addition, the capacitance signal taken out from the output electrode is affected only by the distance between the transmitting electrode and the output electrode that are arranged in parallel, that is, the transmitting electrode substrate portion and the output electrode substrate portion of the first member. It is independent of the distance between the receiving electrodes and between the coupling electrode and the output electrode.

As a result, even if there is a slight change in the relative positional relationship between the first member and the second member, as long as there is no change in the relative positional relationship between the transmitting electrode substrate section and the output electrode substrate section of the first member, the output electrode It does not have any effect on the capacitance signal taken out.

Therefore, it is possible to reliably eliminate a decrease in measurement accuracy due to relative positional fluctuations, inclination, backlash, etc. between the first member and the second member.

Moreover, since the receiving electrode and the coupling electrode are separately arranged on each surface of the strip-like second member, it is possible to form the respective electrodes simultaneously on the upper and lower sides of each surface.

Furthermore, in accordance with this, it is possible to form the respective electrodes on the transmitting electrode substrate portion and the output electrode substrate portion of the first member at the same time on the upper and lower sides.

As a result, the area of each electrode can be approximately doubled without changing the widths of the first member and the second member, and the detection efficiency of the capacitance signal taken out from the output electrode can be improved. It becomes possible to significantly improve the measurement accuracy of the encoder, especially the S/N ratio.

Further, since the transmitting electrode and the output electrode are not adjacent to each other, crosstalk does not occur between the two electrodes, and from this point as well, measurement accuracy can be improved.

Note that although the thickness of the first member becomes slightly larger, even when considering the output electrode substrate parts and the clearance between the coupling electrode and the output electrode, the thickness is only a few millimeters and does not pose a practical problem. .

As described above, according to the present invention, it is possible to obtain a highly accurate digital display type measuring instrument without increasing the size at all.

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

1 to 3 show a preferred embodiment of a capacitive encoder portion of a digital caliper according to the present invention, and FIG. 1 is a partially cutaway external perspective view; 2 is a side view of FIG. 1 viewed from the direction of the arrow ``2'', and FIG. 3 is a cross-sectional view taken along the line m--'' of FIG. 1.

Note that the same parts as those in FIG. 6 are designated by the reference numeral 100, and their explanation will be omitted.

The characteristic feature of the present invention is that the second member in the form of a strip is formed from an electrically insulating material, and a receiving electrode and a coupling electrode are separately arranged on each surface of the second member, and the first member is
The second member has a transmitting electrode substrate portion facing the receiving electrode arranging surface and an output electrode substrate portion facing the coupling electrode arranging surface.

For this purpose, in this embodiment, the main scale 110 constituting the second member is formed from a ceramic material, and a receiving electrode 126 is provided on the right side of the main scale 110, and a coupling electrode 128 is provided on the left side of the main scale 110. The top and bottom are formed at the same time. Further, the slider 112 constituting the first member is formed into a cylindrical shape with a cross section, and the main scale 110 is inserted into the cylinder.

A transmitting electrode substrate section 132 is attached to the right side wall of the slider 112, and an output electrode substrate section 134 is attached to the left side wall thereof.

Both electrode substrate parts 132 and 134 are made of an electrically insulating material and are formed parallel to each other.
A transmitting electrode 122 is located on the inner surface of the output electrode substrate section 134, that is, a surface facing the receiving electrode 126, and an output electrode 124 is located on the inner surface of the output electrode substrate section 134, that is, the surface facing the coupling electrode 128, corresponding to the receiving electrode 126 and the coupling electrode 128, respectively. The top and bottom are arranged together.

In this embodiment, a plurality of receiving electrodes 126 are provided, and a ground electrode 130 is arranged between each receiving electrode 126 to eliminate mutual interference.

In this embodiment, as described above, the main scale 110 is made of ceramic material, and on top of it are a receiving electrode 126, a coupling electrode 128, and so on. Although the ground electrodes 130 are directly arranged, the receiving electrode 126 and the coupling electrode 128 are electrically coupled through a conductive portion 136 passing through the main scale 110@'774.

The digital caliper according to this embodiment is configured as described above, and its operation will be explained below.

The digital caliper according to this embodiment, like the conventional example shown in FIG. It is detected from a capacitance signal having .

Here, the transmitting electrode substrate section 132 and the output electrode substrate section 13
4 are formed in parallel, and as a result, the transmitting electrodes 122
The distance between the output electrode 124 and the output electrode 124 is also always constant. and,
The main scale 110 inserted between the transmitting electrode substrate section 132 and the output electrode substrate section 134 moves relative to the slider 112, but at this time, the transmitting electrode 122 and the receiving electrode 1
26 and the coupling electrode 128 and output electrode 124
It is conceivable that the distance D2 between them varies depending on the backlash or inclination of the main scale 110.

Conventionally, changes in the relative positional relationship between the main scale 110 and the slider 112 directly affected the capacitance signal, but in this embodiment, the change in the relative positional relationship between the main scale 110 and the slider 112 directly affected the capacitance signal. DI unless there is a change in the degree
D2 is always constant, and as a result, the sum of the capacitance between the transmitting electrode 122 and the receiving electrode 126 and the capacitance between the coupling electrode 128 and the output electrode 124 is always constant.

Therefore, the detection accuracy is not affected by relative position fluctuations such as backlash or inclination between the main scale 110 and the slider 112, and high accuracy can be maintained.

Further, as is clear from FIG. 4, since the area of each electrode can be increased, measurement accuracy can be improved.

That is, FIG. 4 (A) shows the transmitting electrode substrate section 132 viewed from the surface where the transmitting electrode 122 is formed, and FIG. 4 (B) shows the main scale 11.
0 as seen from the surface where the coupling electrode 128 is formed, and FIG.

As is clear from the figure, even if the width W is the same as that of the conventional digital caliper as shown in FIG. is carried out extremely efficiently.

Furthermore, since the transmitting electrode 122 and the output electrode 124 are arranged opposite to each other with a distance between them, and are not arranged adjacently on the same plate as in the conventional case, the influence of crosstalk can be reliably eliminated.

In this embodiment, the main scale 110 is made of a ceramic material which is an electrically insulating material, and each electrode is arranged on the main scale 110. Therefore, as in the conventional case, an electrode substrate is pasted on the main scale. It is no longer necessary, the main thickness can be reduced, and
Manufacturing is also easier.

It is also preferable to provide a shielding electrode on the outer surface of the output electrode substrate section to further improve the S/N ratio.

Further, in this embodiment, a digital caliper is used as an example of a digital display type measuring instrument, but the present invention is not limited to this, and it goes without saying that it can also be applied to a hide gauge or a micrometer.

[Effects of the Invention] As explained above, according to the digital display type measuring instrument according to the present invention, the strip-like second member is formed of an electrically insulating material, and a receiving electrode and a coupling electrode are provided on each surface of the second member. were arranged separately, and the first member was configured to have a transmitting electrode substrate section facing the receiving electrode arrangement surface of the second member, and an output electrode substrate section facing the coupling electrode arrangement surface of the second member. Therefore, it is possible to perform a compact and highly accurate length measurement operation.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway external perspective view of a digital caliper according to a preferred embodiment of the present invention, FIG. 2 is a side view of the digital caliper according to FIG. 1, and FIG. 3 is a side view of the digital caliper according to FIG. 1. A cross-sectional view of the digital caliper taken along the line III-III, Figure 4 is an explanatory diagram of the main scale and slider of the digital caliper according to Figure 1, Figure 5 is an exploded explanatory diagram of the conventional digital caliper, and Figure 6 is an explanatory diagram of the conventional digital caliper. A perspective view of the main parts of a conventional digital caliper, Fig. 7 is an explanatory diagram of the detection circuit of a general digital caliper, and Fig. 8 is an explanation of the first and second members of the capacitive encoder shown in Fig. 6. It is a diagram. 10.110 Main scale (second member) 12.11
2... Slider (first member) 22, 122
... Transmitting electrode 24.124 ... Output electrode 26.126 ... Receiving electrode 28.128 ... Coupling electrode.

Claims (2)

[Claims] (1) A plurality of transmitting electrodes arranged in a row on a first member and to which alternating current voltages of different phases are applied; and a second strip-shaped member formed to be movable relative to the first member along the longitudinal direction. , a receiving electrode disposed corresponding to the transmitting electrode; a coupling electrode provided on the second member and electrically coupled to the transmitting electrode; and a coupling electrode provided on the first member and electrostatically coupled to the coupling electrode. an output electrode, and a capacitive encoder that detects the amount of relative movement displacement between the first member and the second member based on a capacitance signal from the output electrode that changes due to the relative movement of the first member and the second member. In a digital display type measuring device that digitally displays the amount of relative displacement on a display section provided on a member, the second strip-like member is formed of an electrically insulating material, and a receiving electrode is provided on one side of the second member, and a receiving electrode is provided on the other side of the second member. A coupling electrode is arranged on the side, and the first member faces a receiving electrode arrangement surface of the second member and a transmitting electrode substrate part on which a transmitting electrode is arranged, and a transmitting electrode substrate part facing a coupling electrode arrangement surface of the second member. A digital display type measuring instrument comprising: an output electrode substrate portion on which an output electrode is disposed. (2) A digital display type measuring instrument according to claim (1), wherein the second member is made of a ceramic material.