JPS6350717A - Apparatus for measuring moving quantity - Google Patents

Abstract

PURPOSE:To enhance the reliability of a measured value and to reduce the thickness and wt. of the title apparatus, by measuring moving quantity based on the signal informations of applied voltage and induced voltage due to two sets of electrodes. CONSTITUTION:At least two surfaces having a large number of electrodes divided so as to relatively cross with respect to a moving direction are arranged so as to be opposed to each other in a relatively movable manner through an air gap and sine wave like AC voltages different by 90 deg. in a phase are applied to electrodes 1-a, 1-b on a fixed side through coaxial cables 10-a, 10-b. The voltage induced in the electrode 2 on a rotor side is transmitted to a signal processing circuit through a rotary transformer 9 and a coaxial cable 10-c. Two signals different by 90 deg. in a phase are calculated by said signal processing circuit. Herein, the value of the phase difference between the drive AC voltage on the fixed side and the induced voltage on the rotor side corresponds to the electric angular displacement of the rotor side electrode and the fixed side electrode. By this method, the reliability of a measured value can be enhanced and the thickness and wt. of an apparatus can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a movement amount measuring device that electrically measures a movement amount.

[Prior art]

In recent years, with the spread of robots and automatic machine tools, the importance of devices that electrically measure rotation angles and travel distances has increased.

Devices conventionally used for this purpose are broadly classified into optical and magnetic devices. An optical encoder is generally used as an optical encoder, which transmits light through a disk with many slits, and detects rotation by detecting changes in the amount of light as it rotates. Optical encoders are inexpensive, but the stability of the light-emitting element is poor, the response speed of the light-receiving element is slow, and high-resolution ones are difficult to manufacture.
It has disadvantages such as being expensive and being easily affected by oil mist and dust.

There are two types of magnetic types: resolvers and magnetic encoders.

A magnetic encoder detects rotation using a large number of minute magnetic poles provided on the rotor and a magnetoresistive element provided on the fixed side. Magnetic encoders are characterized by fast response speed and high reliability, but high precision is required for back-end production, making the equipment expensive.

The resolver has two windings at positions shifted by 90 degrees in electrical angle, and supplies alternating current with a phase shifted by 70 degrees to each winding. When a winding is placed in the rotating magnetic field thus obtained, the electromotive force generated there becomes an alternating current that is out of phase by the rotation angle from the alternating current. By measuring this phase difference, the rotation angle can be determined. Although resolvers are highly reliable, they are expensive and have the disadvantage of being large and heavy because they include windings and cores.

[Problem that the invention seeks to solve]

SUMMARY OF THE INVENTION An object of the present invention has been made to solve the above-mentioned drawbacks, and it is an object of the present invention to provide a highly reliable, thin and lightweight movement measuring device capable of detecting rotation angles and displacements.

[Failure to solve the problem]

The present inventor has made a definite research effort to achieve the above object,
This led to the present invention.

That is, in the movement measuring device of the present invention, at least two surfaces having a large number of electrodes sectioned so as to be relatively intersecting with the movement direction are disposed facing each other so as to be relatively movable via an air gap, and An alternating current voltage is applied to one set of the electrodes to induce a voltage in the other set of electrodes disposed on the opposing surface, and the amount of movement of the surface is determined by a signal based on the phase difference between the applied voltage and the induced voltage. It is characterized by measuring.

Examples will be explained below.

FIG. 1 is a sectional view showing an electrostatic encoder which is an example of a movement amount measuring device of the present invention configured for the purpose of detecting a rotation angle. /-a and /-a are printed circuit boards on which the electrode pattern shown in FIG. 2a is formed by etching or other means, and are bolted to the case, r-b. Reference numeral 2 denotes a prefunded board having an electrode pattern formed on both sides as shown in FIG. 2b, and is attached to the shutter through a bushing 3. The shaft is rotatably supported by bearings a and tb, and the bearings are mounted in case ♂-a1.
Preload is applied to ♂-b by wave washer O and retaining ring 7, and it is fixed.

A coaxial cable 10 is connected to the fixed side electrodes /-a and /-b.
-a and 10-b to which a sinusoidal AC voltage with a phase difference of O is applied. ” is abbreviated as “. ). The voltage induced in the electrode on the rotor side is transmitted to the signal processing circuit through the rotating transformer and the coaxial cable 10. (abbreviated as "induced electrode").

FIG. 3 shows an example of a signal processing circuit. The oscillator // generates J sine wave signals with different phase Qo, and the trimmer /2-a.

/2-b optimizes the amplitude and supplies it to the fixed antistatic. The signal obtained from the rotor-side electrode is filtered to remove noise by the filter 13, then converted into a rectangular wave by the waveform shaping circuit/4t, which is used to convert the outputs of two oscillators with different phase shifts by θ0 into the synchronous rectifier/rectifier circuit. A, /j-b perform synchronous rectification, respectively. Furthermore, a low pass filter/A-
By removing ripples using a and /o, it is possible to obtain two signals that change sinusoidally with respect to the rotation angle and have a phase difference of 70°.

In the circuit shown in FIG. 3, a Sin, CO8 signal of /period is obtained as the rotor rotates in electrical angle /. This is the same function as a photoelectric or magnetic encoder. On the other hand, if you use a processing circuit that is generally used in magnetic resolvers, the electrical angle of the rotor! It is possible to obtain position information that subdivides the rotation.

Figure ≠ is an example of a circuit used for this purpose. An oscillator 17 and a counter /r generate a digital signal that increases in number. Sin this.

Give as the address of the read-only memory /tar a and /tar b where the COS O number table is written. By DA-exchanging this output with 20-a and 20-b, sine wave signals having phases different by 5>00 are obtained. This is boosted by amplifiers 2/-a, 2/-b and supplied to the fixed side electrode. The signal obtained on the rotor side is a zero cross detector,! 2 to detect the moment when the potential difference changes from negative to positive. The contents of the counter/♂ at this time are stored in the register, 23
By taking in the phase difference between the stationary side, drive AC, and rotor side induced voltage, it is possible to obtain.

This value corresponds to the electrical angle displacement between the rotor electrode and the stationary electrode.

Note that a similar function can also be realized by performing circuit processing using a device in which the driving alternating current is set to /phase and the detection electrodes are provided at positions 70 degrees apart in electrical angle. These are known as resolver/phase excitation systems, and their explanation here will be omitted.

As a method of arranging the application electrode and the induction electrode, FIGS. 1 and 2 show that the application electrode is (2m-/)×? in electrical angle. o
They are arranged and connected to the Hong system with a pitch of 0, and each phase is different by O! A phase AC voltage is applied, and the induced electrodes are arranged and connected in two systems at a pitch of (2n-/) x /100 in electrical angle, and the case where m, n = / is shown (however, n, m is any natural number). Although this method has the advantage of not requiring wavy lines on the electrodes and is easy to fabricate, it has the disadvantage of requiring two sets of electrodes to achieve a two-phase arrangement. The electrodes are made of double-sided printed circuit boards, resulting in a three-layer structure.

In this case, when a thrust force is applied to the shaft and the rotor electrode moves in the axial direction, the gap becomes uneven.
Outputs a signal as if it were rotating. This is particularly prone to errors when subdividing the electrical angle/rotation.

On the other hand, in another arrangement method of the present invention, the application electrodes are arranged and connected in two systems at a pitch of (2 m-/) The induced electrodes are arranged and connected in a Hong system with a pitch of (un-/) The amount of movement of the surface can be detected by a signal based on the phase difference between the applied voltage and the applied voltage (where m and n are arbitrary natural numbers).

With this arrangement method, by setting m and n to 2 or more, eliminating overlapping of the electrodes, and arranging all the electrodes facing each other in a single air gap, the above error problem can be avoided. An example of the pattern of the electrode portion on the fixed side of this reservoir is shown in FIG. The electrode pattern on the rotor side is shown in Figure tb. In this case, the applied voltage is si between A and A in Fig.
Apply n wt and cos wt to B-seeing. In this case, a crossover line (shown as a dotted line) will occur, so
It is necessary to use a double-sided through-hole board or a multilayer board.

〔Effect of the invention〕

The movement measuring device of the present invention has high stability and long life because it does not have a light receiving/emitting element. Even if an external force acts on the coater and causes inclination, eccentricity, etc., the output will not be affected because the electrodes are arranged all around the coater. Unlike magnetic encoders, it is not affected by external magnetic fields, and electric fields and electromagnetic waves can be removed by making the case made of metal.

Furthermore, since it is an alternating current type, most of the noise can be removed by using a filter that passes only the target frequency.

Furthermore, unlike resolvers, there is no need for a core or windings, making it lightweight.
It is possible to make it thinner. Furthermore, the electrodes can be manufactured at low cost and with high precision using a printed circuit board manufacturing process for which mass production methods have been established industrially.

As described above in detail, according to the present invention φ, a highly reliable, thin and lightweight rotation angle measuring device can be manufactured at low cost. Further, although the explanation has been given only for a rotary type, it goes without saying that an I-type type can also be manufactured based on the same principle.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of an electrostatic encoder which is an example of the movement measuring device of the present invention, Figs. 2a and 2b are electrode patterns, Figs. 3 and 3 are signal processing circuits, and Figs. The rb diagram is a diagram showing a pond electrode pattern.

Claims (3)

[Claims] (1) At least two surfaces having a large number of electrodes divided so as to intersect relatively to the direction of movement are disposed facing each other so as to be relatively movable via an air gap, and an alternating current voltage is applied to one set of the electrodes. is applied to induce a voltage in the other set of electrodes arranged on the opposing surface, and the amount of movement of the surface is measured by a signal based on a phase difference between the applied voltage and the induced voltage. Movement measurement device. (2) The set of electrodes to which the above voltage is applied is expressed in electrical angle (2m-1
)×90° pitch, and two-phase AC voltages with 90° different phases are applied to each system.
The above induced set of electrodes is (2n-1)×1 in electrical angle
The movement amount measuring device according to claim 1, characterized in that the device is arranged and connected in two systems at a pitch of 80°. (However, n and m are arbitrary natural numbers.) (3) The set of electrodes to be applied is (2m-1 in electrical angle)
) × 180° pitch, one-phase AC voltage is applied between them, and the above-mentioned induced set of electrodes has an electrical angle of (2n-1) × 90°. They are arranged and connected in four systems at a pitch, and among the latter electrodes, a signal based on the phase difference between the applied voltage and the voltage induced in the electrode at an electrically (2n-1) x 180° different position is used. The movement amount measuring device according to claim 1, characterized in that the movement amount measuring device measures the movement amount of the surface. (However, n, m
is any natural number. )