JPH03282328A - Encoder - Google Patents

Abstract

PURPOSE:To realize detection with high resolution on a scale where position information is stored with specific wavelength by making a pi/4 phase difference between a 1st and 2nd relatively movable sensor along the time base of the scale. CONSTITUTION:The scale 1 is magnetized with the position information corresponding to a sine wave along the direction of displacement to be detected. The 1st sensor 4 moves relatively along the scale 1 to output signals sintheta and costheta based upon the intervals of graduations 3, and is constituted by forming, for example, a resistance circuit on a substrate with a pi/4 phase difference in the direction of the relative movement. The 2nd sensor 5 has the same constitution with the sensor 4 and is arranged having the pi/4 phase difference from the sensor 4. Then the sine wave and cosine wave corresponding to the position information are outputted from the sensors 4 and 5 while having the specific phase difference as the sensors move relatively, and they are multiplied by the sensors to obtain a sine wave and a cosine wave with a period of resolution twice as high as that of the position information from a multiplier.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an encoder used for detecting the amount of displacement, velocity, etc. of an object.

[Conventional technology]

An example of an encoder that converts the displacement of an object into an electrical signal is disclosed in Japanese Patent Application No. 157062/1983 filed by the present applicant. This encoder has a sensor that is movable relative to a scale on which position information corresponding to a sine wave of a predetermined wavelength λ is magnetically recorded along the time axis of the position information. The sensor generates a sine wave (si
nθ) and a cosine wave (COSθ).

[Problem to be solved by the invention]

By the way, the period θ of the output signal of the sensor is uniquely determined depending on the wavelength λ of the position information recorded on the scale, so to increase the resolution of the encoder, the wavelength λ of the magnetic information should be shortened. However, in order to shorten the wavelength λ and make the magnetization period of the positional information finer, high accuracy is required in writing the positional information on the scale. That is, there is a problem in that the resolution of the encoder is limited depending on the cycle of position information that can be written on the scale. Therefore, s in2θ is calculated based on the sine law from the sine wave and cosine wave obtained from the magnetic sensor, and further,
It is possible to increase the resolution by calculating cos2θ, but since cos2θ is calculated based on 5in2θ obtained from sinθ and cosθ, its accuracy is poor, and it is also sensitive to fluctuations in the original signal, such as amplitude fluctuations. There is a problem in that the occurrence of errors due to this cannot be avoided. The present invention has been made in view of the above circumstances, and an object of the present invention is to realize detection with higher resolution from a scale in which position information is stored at a predetermined wavelength.

[Means to solve the problem]

To achieve the above object, the present invention includes a scale on which sine wave position information is recorded, and a scale that is movable relative to the scale along the time axis of the position information and corresponds to the position information. first and second sensors that output a sine wave and a cosine wave, and a sine wave and a cosine wave output from the first sensor, and a sine wave and a cosine wave output from the second sensor, respectively. first and second multipliers that multiply each other, and the first and second sensors are spaced apart from each other along the time axis direction and with a phase difference of π/4. This is an arranged configuration.

[Effect]

With the above configuration, sine waves and cosine waves corresponding to position information are output from both sensors with a predetermined phase difference as the relative movement occurs, and by multiplying these for each sensor, the multiplier From this, it is possible to obtain a sine wave and a cosine wave with a period of resolution twice that of the position information.

【Example】

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. Reference numeral 1 is a scale, and this scale 1 is a base 2.
The structure is such that position information corresponding to a sine wave is magnetized on the surface of the sensor along the direction of the displacement to be detected. Note that the scale indicated by reference numeral 3 in the figure schematically indicates the position of the positive peak and the position of the negative peak in the magnetic information (sine wave). A first sensor 4 and a second sensor 5 are arranged near the scale 1. These sensors 4 and 5 are
They are provided so as to be movable relative to the scale 1 along the time axis of the position information recorded on the scale 1, and are spaced apart from each other along the time axis. By moving relative to the scale 1, the first sensor 4 is configured to
It outputs signals θ and COSθ, for example,
JP-A-62-289722, JP-A-62-28927
As described in various publications such as No. 3 and Japanese Patent Application Laid-open No. 62-289724, a resistance circuit including an MR element (an element whose electrical resistance changes due to changes in a magnetic field) is moved by π/4 in the direction of the relative movement. The scale 1 may be formed on a substrate with a phase difference of 1, or may be formed by a magnetic node for reproducing the recorded position information of the scale 1. Further, the second sensor 5 is a magnetic sensor having the same configuration as the first sensor 4, and is arranged with a phase difference of π/4 with respect to the first sensor 4. . By disposing the phase difference with respect to the first sensor 4, 5 inches (θ+π/4) and c
It is designed to output a signal os(θ+π/4). In addition, the output sin θ of the first sensor 4 and CO
Sθ are multiplied by each other in a multiplier 6. That is, by performing the calculation sin θ x cos θ = 1/2 x sin 2 θ, it is possible to obtain a signal with a cycle with twice the resolution of the original signal. Further, the outputs 5 inches (θ+I/4) and C05 (θ+g/4) of the second sensor 5 are multiplied by each other in a multiplier 7. That is, 5irl(θ10g/4)X cos(θ+l/4
) = t/zX sin (2θ + r/2) = 1/2X
cos 2θ, and a signal with a period twice the resolution of the original signal can be obtained. Then, 5i outputted from the multipliers 6 and 7, respectively.
By using n2θ and cos2θ, the conventional (
It is possible to obtain higher resolution than the encoder (with period θ). In other words, for a period of 2π of the position information recorded on the scale, outputs with a period of π can be obtained from each of the multipliers 6 and 7. In the above embodiment, the position information was magnetically written on the scale, but instead of this, the position information is written optically (by changing the degree of transmission and reflection of the light beam), and this position information is written on the scale. Of course, the technology of the present invention can also be applied to an encoder that optically reads the information. Furthermore, since the first and second sensors need to be maintained at a constant interval in the direction of the scale time axis, it is desirable to mechanically connect them to each other by mounting them on the same frame, etc. .

【Effect of the invention】

As is clear from the above description, in the present application, a phase difference of π/4 is provided between the first and second sensors that are relatively movable along the time axis of the scale on which position information is recorded. Because it is a product, it has the following effects. ■From a scale on which position information is written at a predetermined period,
Position information can be read with a resolution that exceeds the period of this position information. Since the sine wave and cosine wave are calculated using the signals obtained from both sensors, the accuracy of both signals is equal. Since both sensors use position information read at the same position with a predetermined phase difference, it is unlikely to be affected by changes in the amplitude of the original signal.

[Brief explanation of drawings]

The drawing is a plan view of one embodiment of the present invention. 2...-scale, 4.5...sensor,
6.7・Multiplier.

Claims (1)

[Claims] a scale on which sine wave position information is recorded; and a first scale that is movable relative to the scale along the time axis of the position information and outputs a sine wave and a cosine wave corresponding to the position information, respectively. and a second sensor, and first and second multipliers that multiply the sine wave and cosine wave output from the first sensor, and the sine wave and cosine wave output from the second sensor, respectively. The encoder is characterized in that the first and second sensors are arranged at intervals along the time axis and with a phase difference of π/4.