JPS59187203A - Digital display micrometer - Google Patents

Abstract

PURPOSE:To make a device compact and to make it possible to measure the amount of displacement of a spindle highly accurately, by applying AC voltages, whose phases are different, to transmitting electrodes of an electrostatic encoder, and detecting the output signals of receiving electrodes, which are changed by the rotation of a rotary body. CONSTITUTION:A fixed cylindrical body 40 is coupled to a rotary body 28, which is rotated in association with a spindle 14 with a specified gap being provided. A plurality of transmitting electrodes 44 are provided on the cylindrical body 40 at an equal interval. Receiving electrodes 46 in a ring shape is provided in parallel with said electrodes 44. A combining electrode 48 and a grounding electrode 50 are attached to the rotary body 28. Thus an electrostatic encoder is formed. The rotary body 28 is rotated under the state AC voltages having the different phases are applied to the transmitting electrodes 44. Then, the outputs, whose phases correspond to the amount of the displacement of rotation of the rotary body 28, are obtained by the receiving electrodes 46. Based on said signals, the amount of displacement of the spindle is accurately detected. Therefore, the device can be made compact, and the amount of displacement can be measured highly accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a digital display micrometer, and more particularly to a digital display micrometer using an electrostatic encoder.

BACKGROUND ART Conventionally, digital display micrometers that digitally display measured values of an object to be measured have been well known, and this digital display micrometer can eliminate individual errors in reading measured values and Because it can perform reading quickly, it is widely used for measurements in various manufacturing departments.

In general, this type of measuring device 1d1 includes a spindle that is movably provided in the main body of the device and contacts the object to be measured, and an encoder that detects the amount of movement of the spindle and converts it into electrical signal pulses, and outputs the output of the encoder. Electric signal pulses are counted by a counting circuit, and the counted value is digitally displayed on a digital display.

By doing so, the measured value of the object to be measured can be obtained instantaneously by reading the displayed value displayed on the display.

Incidentally, photoelectric encoders, contact encoders, electrostatic encoders, and the like are conventionally known as encoders used in this type of measuring device.

A photoelectric encoder includes slits provided at equal intervals on the surface of a rotating disk, and a light emitter and a light receiver that form an optical path through the slits of the rotating disk, and the encoder has slits provided at equal intervals on the surface of a rotating disk, and a light emitter and a light receiver that form an optical path through the slits of the rotating disk. The amount of displacement of the object to be measured is detected by rotating the disk and turning on and off the optical path formed between the light emitter and receiver.

However, the photoelectric encoder has disadvantages in that the power consumption of the light emitter is large, the number of battery replacements required increases, and when a large capacity battery is used, the entire device becomes large. Furthermore, in order to improve measurement accuracy, it is necessary to provide slits at intervals of several microns on the rotating disk, which is difficult to manufacture and is prone to miscounts due to clearance changes during operation. Ta.

In addition, since the contact type encoder uses slits, brushes, etc. to detect the displacement amount of the probe, there is a problem 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, electrostatic encoders do not consume as much power as photoelectric encoders, and do not have the problems of wear and tear of brushes, slits, etc. and noise contamination like contact encoders, so in recent years they have been used for various digital display measurements. It is proposed to be adopted in the device.

Prior Art In an electrostatic encoder used in such a proposed digital display micrometer, at least a pair of electrode plates are arranged facing each other to form a capacitor, and both electrode plates are arranged relative to each other in accordance with the amount of displacement of the spindle. The structure is such that the amount of mechanical displacement at this time is electrically detected as a change in capacitance of the capacitor.

For example, one electrode plate is arranged at regular intervals on a stator fixed to the micrometer body, and the other electrode plate is placed on a rotor facing the stator at a certain distance. The spindle is rotated parallel to the stator in accordance with the displacement of the spindle, and at this time, the amount of displacement of the spindle is detected by the change in capacitance of the capacitor formed by both electrode plates.

However, in the electrostatic encoder in the proposed device, a voltage dividing circuit is formed using a capacitor made of the moving electrode plate, and the amount of displacement of the spindle is detected by detecting a voltage dividing ratio that changes according to the capacitance of the capacitor. Therefore, the proposed measurement device can be used in cases where the distance between the surfaces of the movable electrode plates that form the capacitor changes for some reason and the capacitance of the capacitor changes, or when the power supply voltage applied to the voltage divider circuit changes. In such a case, there is a drawback that the partial pressure output no longer corresponds accurately to the amount of displacement of the spindle, and accurate measurement cannot be performed.

In addition, in recent years, there has been a demand for smaller devices from the viewpoint of portability and operability, and in response to this demand, when downsizing devices, electrodes disposed on the stator and rotor are required. The pole area of the plate becomes smaller, and as a result, if the electrode plate becomes slightly misaligned, the amount of displacement of the spindle cannot be detected with high precision. There is a problem in that the manufacturing process is extremely complicated, as the incorporation of the electrode plate must be done extremely precisely, and ultra-precision machining is required to improve the machining accuracy of the electrode plate. Meters have not yet been put into practical use.

Purpose of the Invention The present invention has been made in view of the above-mentioned problems, and its purpose is to easily miniaturize the device and to measure the object to be measured with high precision. Our objective is to provide a digital display micrometer.

Structure of the Invention In order to achieve the above object, the present invention includes a spindle that is movably provided in a main body and comes into contact with an object to be measured, and an encoder that detects the amount of displacement of the spindle and converts it into an electrical signal. In a digital display micrometer that digitally displays an electrical signal output by a rotating body that rotates in accordance with the movement of the spindle, and a plurality of transmitting electrodes arranged at equal intervals on one circumferential wall where the fixed cylindrical body and the rotating body face each other, and a plurality of transmitting electrodes arranged in parallel with the transmitting electrodes. A strip-shaped receiving electrode is provided.

and on the other circumference q, a coupling electrode which is arranged facing across the transmitting electrode and the receiving electrode and electrostatically feeding between the two electrodes;
A receiving electrode is provided with a grounding electrode disposed facing each other across the transmitting electrode and the receiving electrode along the circumferential direction, and AC voltages having different phases are applied to each of the transmitting electrodes, and the receiving electrode changes with the rotation of the rotating body. The spindle displacement amount is detected based on the output signal of the spindle.

Example Next, preferred embodiments of the present invention will be described based on the drawings.

FIG. 1 shows the mechanical configuration of a digital display micrometer according to the present invention, and the device of this embodiment is installed on the inner surface of one end of a U-shaped frame IO with its measuring surface 12a facing inward. a spindle 4 disposed on the other end side of the U-shaped frame 1O facing the measurement surface 12a of the anvil 12;
The spindle 14 is moved forward and backward toward the anvil 12 by rotating a simple 16 provided coaxially with the anvil 4.

That is, the simple 16 is formed integrally with the spindle 14, and a screw is formed on the inner peripheral surface of the simple 16, and this screw is fitted into the spindle 14 and fixed to the frame 10 via the holding member 18. sleeve 2
It is screwed to 0.

Therefore, by rotating the simple 16, the spindle j4 will rotate the anvil 1 in conjunction with the rotation of the simple 16.
We will advance and retreat towards 2.

The device of the embodiment uses an encoder to detect the amount of mechanical displacement of the spindle 14, and inputs an electric signal pulse corresponding to the detected amount of displacement to the counting circuit. The counting circuit counts the electrical signal pulses output by the encoder and digitally displays the counted value on a digital display 22 provided on the side surface of the frame 10.

Therefore, according to the apparatus of the embodiment, both sides constant surfaces 1211, 14 of the anvil 12 and the spindle 14! It becomes possible to digitally display the dimensions of the object to be measured held between the two positions on the display 22.

A characteristic feature of the present invention is that an electrostatic encoder having a predetermined electrode structure is used as the encoder, and the spindle 14
The object of the present invention is to enable accurate measurement of mechanical displacement with a simple configuration.

For this reason, the encoder used in the device of the present invention has a holding cylinder 26 that is slidably fitted onto the spindle 14, and a cylindrical rotating body 28 is fitted and fixed to this holding cylinder 26. There is. The holding cylinder 26 is urged in the axial direction by a spring 30, thereby preventing the rotating body 28 from wobbling.

Note that the holding cylinder 26 is attached to the spindle 1 by the bottle 32.
It is connected to 4. That is, a key groove 34 is formed in the spindle 14, and a bottle hole is provided in the force holding cylinder 26, and by inserting the bottle 32 into the pin hole, the lower end of the bottle 32 is inserted into the key groove. 34 to connect the spindle 14 and the holding cylinder 26, that is, the rotating body 28.

Therefore, in conjunction with the rotation of the spindle 14, the rotating body 28
will perform the rotation.

In this case, in order to smoothly rotate the rotating body 28, the holding cylinder 26 is supported by a bearing 38 on the base 24 of the main body.

On the other hand, in this embodiment, the fixed cylindrical body 40 is
It is fixed at 4.

That is, the fixed cylindrical body 40 is fitted onto the rotating body 28 at a constant interval, one end of the fixed cylindrical body 40 is locked to the base 24, and the other end is attached to the base 24. It is securely fixed to a holding arm 42 fixed to the wall.

In this embodiment, electrodes for detecting displacement of the spindle 14 are arranged on the circumferential surfaces of the rotating body 28 and the fixed cylindrical body 40.

FIG. 2 shows a developed view of the electrode-arranged circumferential surfaces of the rotating body 28 and the fixed cylindrical body 40, and the fixed cylindrical body 40 has an insulating section 41
A plurality of transmitting electrodes 44 are arranged circumferentially and at equal intervals, and a ring-shaped receiving electrode 46 is provided in parallel with the transmitting electrodes. Further, on the rotating body 28, a coupling electrode 48 is disposed facing across the transmitting electrode 44 and the receiving electrode 46 and electrostatically couples the two electrodes.
A ground electrode 50 is provided facing the transmitting electrode 44 and the receiving electrode 46 with an insulating portion 49 interposed therebetween along the circumferential direction thereof.

With the above configuration, according to the present invention, if the rotating body 28 is rotated while applying an alternating current voltage consisting of a rectangular wave or a sine wave with different phases to each of the transmitting electrodes 44,
An output signal having a phase corresponding to the amount of rotational displacement of the rotating body 28 is obtained from the receiving electrode 46 . be able to.

Therefore, by comparing the phase of the signal output from the receiving electrode 46 with a predetermined reference phase, it is possible to accurately measure the amount of displacement of the spindle 14 without being affected by fluctuations in the power supply voltage or the like.

In the embodiment, the transmitting electrodes 44 are arranged on the fixed cylindrical body 40 in two or more unit electrode sets each having n pieces, and in this embodiment, two or more unit electrode sets each having eight pieces. The receiving electrodes 46 are arranged in a ring band shape in parallel with the transmitting electrodes 44. And that of the transmitting electrode 44 of each group 360° 3
60° and □, that is, alternating current voltages whose phases differ by 7 = 45° are applied. Further, the coupling electrode 4
Two sets of ground electrodes 8-1, 48-2 and 50-1, 50-2 are provided, and are arranged symmetrically and alternately along the circumferential direction of the rotating body 28. These coupling electrodes 48 and 50 earth electrodes are provided on the fixed cylindrical body 40 in a quarter area of the transmitting electrodes 44 and receiving electrodes 46, that is, the four transmitting electrodes 44 and the receiving electrodes formed in a ring band shape. It is arranged so as to face a quarter range of 46.

With the above structure, the device of this embodiment can accurately detect the amount of displacement of the spindle 14 based on the output signal of the receiving electrode 46 that changes with the rotation of the rotating cylindrical body 28.

FIG. 3 shows an electric circuit of an encoder that detects the amount of displacement of the spindle 14 using each of the electrodes. a pulse modulation generator 54 that applies 8-phase AC voltages having phases different by 45 degrees to each transmitting electrode 44 in synchronization with a clock pulse;
The output signal of the receiving electrode 46, which changes with the rotation of the receiving electrode 8, is inputted to a phase comparator 58 via an integrating circuit 56.

The phase comparator 58 compares the phase of the signal thus inputted with the reference phase, and detects the amount of relative rotational displacement of the rotating body 28 with respect to the fixed cylindrical body 40 as a phase shift of the input signal with respect to the reference phase. Then, the detection signal is input to the counting circuit 60. The counting circuit 60 counts the clock pulses output from the oscillator 52 based on the detection signal input in this way, and displays the spindle 1 on the display 22.
Digitally displays the displacement amount of 4.

The apparatus of this embodiment has the above-mentioned configuration.The operation thereof will now be explained.

In the apparatus of the embodiment, when the simple 16 is rotated to move the spindle 14 forward or backward, the rotating body 28 is moved in synchronization with this.
The receiving electrode 4 rotates and is electrostatically coupled by the coupling electrode 48.
6 and the transmitting electrode 44 change.

In the embodiment, two sets of eight transmitting electrodes 44 are provided, and voltages having a 45° phase difference are applied to each of these electrodes 44, so that when the rotating body 28 rotates once, the receiving electrode 46 outputs voltages. The signal is 45° x 16 = 720
°When the phase changes, it becomes . Therefore, for example, the rotating body 28
If the screw pitch for advancing and retracting the spindle 14 is set so that the spindle 14 is displaced by 500 microns per rotation, the output signal of the receiving electrode 46 will change by lc500/720 #0.7 micron every time the phase angle changes by 10. Displacement can be detected.

Therefore, according to the device of this embodiment, the spindle 14 has a simple structure in which two sets of eight transmitting electrodes 44 are arranged in the fixed cylinder 4δ and voltages having different phases are applied to each of the transmitting electrodes 44. In other words, it becomes possible to accurately measure the displacement of the object to be measured.

In addition, in a micrometer with a spindle feed pitch of 500 microns, if we compare the conventional contact type encoder with a two-row arrangement or two-brush type structure and the encoder of this embodiment, we can see that the conventional encoder is formed on a rotating body. The number of slits n is - Jn per column = s OO/4 = 12
5, that is, it is necessary to form 9125 slits across 360 degrees of electrical angle, and it is understood that the structure is extremely precise and complicated compared to this embodiment.

Similarly, when comparing the device of this embodiment with a conventional photoelectric 4-segment encoder, it is found that in this conventional device, the number n of slits provided on the rotating body is n= It is understood that it is necessary to provide 125 slits per 5oo/4=125, that is, 36 electrical angles (1'), and the structure is extremely precise and complicated.

In this way, with the device of the present invention, it is possible to detect the amount of displacement of the spindle 14 with a device having an extremely simple structure.

Furthermore, in this embodiment, each electrode is arranged on the circumferential surface of the rotating body 28 and the fixed cylindrical body 40, so that the electrode area can be made relatively large even though the entire device is downsized. This makes it possible to improve measurement accuracy compared to conventional devices in which each electrode is arranged on a disk. In this embodiment, as described above, each electrode is disposed on the circumferential surface, and as a result, the device parts can be processed and assembled using the axis reference mechanism, which makes it easy to assemble the device. It is possible to improve the accuracy of assembly of these parts.

In this embodiment, the holding cylinder 26 is constantly urged in the axial direction by the spring 30, and as a result of preventing the rotating body 28 from wobbling, the distance between the rotating body 28 and the fixed cylindrical body 40 is reduced.
In other words, the distance between the transmitting/receiving electrodes 44, 46 and the coupling electrode 48 is kept constant, allowing highly accurate measurement.

In the above embodiment, two sets of eight transmitting electrodes 44 are arranged on the fixed cylindrical body 40, and each of these transmitting electrodes is tilted at an angle of 45 degrees.
Although the explanation has been given by taking as an example a device that applies alternating current voltages with different phases, the device of this embodiment is not limited to this, and the fixed cylindrical body 40
An arbitrary number n of transmitting electrodes 44 may be arranged on the top, and different AC voltages of predetermined phases 360' may be applied to each of these @poles 44, respectively.

Further, in the embodiment of the present invention, the receiving electrode 46 of the fixed cylindrical body 40 is not formed into a ring band shape, but instead is formed into a ring band shape.
As shown in the figure, there is a strip-shaped receiving electrode 4 whose length corresponds to the width of the plurality of transmitting electrodes, in FIG. 4, the width of four transmitting electrodes.
6 are arranged in parallel on the transmitting electrode 44, and each receiving electrode 46
It is also possible to adopt a configuration in which the amount of displacement of the spindle 14 is determined by processing the signals from the.

Furthermore, in this embodiment, a transmitting electrode 44 and a receiving electrode 46 are arranged on the rotating body 28, and a coupling electrode 4 is arranged on the fixed cylindrical body 40.
8 and a ground electrode 50, but
A coupling electrode 48 and a ground electrode 50 are provided on the rotating body 28,
By arranging the transmitting electrode 44 and the receiving electrode 46 on the fixed cylindrical body 40, it is only necessary to connect lead wires etc. to the transmitting electrode 44 and the receiving electrode 46 provided on the fixed cylindrical body 40 side. Since the coupling electrode 48 and the ground electrode 50 provided on the rotating body 28 do not require connection of lead wires, etc., all the wiring for electric circuits etc. can be done on the fixed side, and the entire fruiting device can be It becomes possible to have a simple structure and a small size. Furthermore, the rotating body 28
Since electrical wiring is often required on the movable side of the device, the entire device can be made extremely reliable.

As described in detail, according to the present invention, a signal having a phase corresponding to the amount of displacement of the spindle is output from the receiving electrode, and the dimensions of the object to be measured can be accurately measured based on this output signal. be able to.

As a result of arranging each electrode for measurement on the circumferential surface, it is possible to make the electrode area relatively large even when downsizing the device, and it is possible to prevent a decrease in measurement accuracy due to downsizing of the device. It becomes possible to prevent this.

Furthermore, as mentioned above, as a result of arranging the electrodes on the circumferential surface,
It is possible to process and assemble each part of the device using an axis reference method, and it is possible to improve the processing accuracy of the parts and facilitate the device assembly.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of the digital display micrometer of the present invention, Fig. 2 is a developed explanatory diagram of the rotating body and fixed cylindrical body used in the device of the present invention, and Fig. 3 is an illustration of the electric circuit used in the device of the present invention. A block diagram showing an example. FIG. 4 is a modified explanatory diagram of FIG. 3 showing a case where the receiving electrodes are formed in an intermittent band shape in the device of the present invention. 14... Spindle, 28... Rotating body, 40...
- Fixed cylindrical body, 44... Transmitting electrode, 46...
Receiving electrode, 48... Coupling electrode, 50... Earth electrode. Agent: Patent attorney Yoshi 1) Kenji (and 1 other person)

Claims (1)

[Claims] (1) A spindle which is movably provided on the main body and comes into contact with the object to be measured; A digital display micrometer that includes an encoder that detects the amount of displacement of a spindle, converts it into an electrical signal, and digitally displays the electrical signal output from the encoder, wherein the encoder is a fixed cylindrical body provided on the base side of the device. and a rotating body that is fitted onto the inner or outer periphery of the fixed cylindrical body at a constant interval and rotates according to the movement of the spindle, and the fixed cylindrical body and the rotating body are attached to one of the opposing circumferential walls. is provided with a plurality of transmitting electrodes arranged at equal intervals and a band-shaped receiving electrode parallel to the transmitting electrodes, and on the other circumferential wall, the transmitting electrodes and the receiving electrodes are disposed opposite to each other, and between the two electrodes. A coupling electrode for electrostatically feeding the electric current, and a ground electrode facing each other across the transmitting electrode and the receiving electrode are arranged in a circumferential direction, and alternating current voltages with different phases are applied to each of the transmitting electrodes. A digital display micrometer, characterized in that the amount of displacement of a spindle is detected based on an output signal of a receiving electrode that changes due to rotation of a rotating body. (2. In the device described in claim (1), the transmitting electrodes are composed of two or more units', each set of n pieces, in a pole 360
1. A digital display micrometer, characterized in that it is divided into .degree. groups and that an alternating current voltage having an equal phase shift of -bar is sequentially applied to the transmitting electrodes of each electrode group.