JPS63293413A - Encoder - Google Patents

Abstract

PURPOSE:To detect the absolute quantity of displacement such as the rotation and movement of a body to be detected with high resolution by arranging a track for the least significant digit bit and a track for a 2nd following lower- order bit at a maximum distance. CONSTITUTION:The outermost peripheral track 21 of a code part 1C for absolute signal generation is used as the track for the least significant digit bit which generates a least-significant digit bit signal and the track 22 for the 2nd following lower-order digit bit which generates a following lower-order digit bit signal is provided at the innermost periphery so that they are at the maximum distance from each other. Consequently, the incidence deviation of luminous flux when luminous flux is made incident linearly on the code part 1C to generate the absolute signal, i.e. the inclination from the direction crossing the rotating direction of a rotary disk at right angles, e.g. an error in readout timing when the luminous flux is incident slantingly is reduced to minimize a decrease in detection accuracy. Consequently, the absolute quantity of the displacement such as the rotation and movement of the object body is detected with high resolution.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an encoder for measuring the displacement of an object to be measured such as its rotational state or moving state, and particularly relates to an encoder for measuring the displacement of an object to be measured, such as a rotating state or a moving state. By appropriately setting the arrangement of the tracks of a track section having a plurality of tracks consisting of a base-coded coat, electrical data can be obtained from the light beam incident on the track section, and from this, especially the object to be measured can be obtained. The present invention relates to an encoder suitable for obtaining the absolute displacement state of a with high accuracy.

(Prior Art) Rechargeable encoders have conventionally been widely used as measuring devices for detecting the rotation, movement, position, etc. of an object to be measured, and for detecting the rotation amount, rotation speed, etc. of a rotating mechanism.

FIG. 4 is a schematic diagram showing an example of a conventional absolute type encoder for measuring the absolute amount of the displacement state of an object to be measured. In the same figure, 51 is a rotating disk that rotates around the rotation axis 50, and on the rotating disk 51, binary data elements are generated according to arbitrary (quantized) angular positions. A plurality of tracks 56 are provided concentrically. Each track 56 is provided with optically binarized data, for example, a plurality of slits 52 each consisting of a transparent area and a non-transparent area.

A fixed slit array 53 has a plurality of openings for selectively passing the light beam from the slits provided on each track 56. 54 is a light projecting means having a plurality of light projecting elements, and 55 is a light receiving means having a plurality of light receiving elements. They are arranged so as to correspond to each opening of the fixed slit row 53, respectively.

In the configuration shown in the figure, the light receiving means 55 includes a light projecting means 54.
The luminous flux emitted from each light projecting element passes through the slit 52 and the fixed slit 53 and enters. At this time, the absolute rotational position of the rotating disk 51 is determined from the combination of output signals of each light receiving element.

Generally, when the light beam from the light projecting means 54 is linearly irradiated onto the track 56 on the rotating disk 51 directly or via an optical system, it is linearly irradiated in a direction perpendicular to the direction of rotation of the rotating disk 51. is preferable in terms of accuracy.

However, if the light beam is irradiated at an angle for some reason, the timing of reading information between the two tracks that are farthest apart from each other will be most deviated.

In general, the so-called gray binary code pattern of tracks in rotary encoders, linear encoders, etc.
) signal from the track that generates the lower bit (Lea
They are arranged sequentially from the inner circumference to the outer circumference or from one side to the other, or vice versa, from the track that generates the st51gn1ficant Bit ) signal. That is, both ends of the track are a track for the least significant bit and a track for the most significant bit.

In this case, since the bit signal of the track for the most significant bit changes little per revolution, it becomes extremely difficult to determine whether or not the timing of reading information is off, which is one of the causes of a large drop in measurement accuracy. It becomes.

(Problems to be Solved by the Invention) When the present invention provides a track portion consisting of a plurality of tracks provided with a bit signal generation pattern on an object to be inspected, by appropriately setting the arrangement of the tracks, An encoder that can detect with high resolution the absolute amount of displacement such as rotation or movement of an object to be detected even if the linear light beam incident on the track section is incident in a direction somewhat orthogonal to the direction of movement of the object to be detected. The purpose is to provide.

(Means for solving the problem) A light beam is made incident on a track section having a plurality of tracks that generate bit signals connected to the object to be measured, and an optical signal from the track section is obtained. In an encoder that detects a displacement state, among a plurality of tracks of the track unit, a least significant bit track generates a least significant bit signal, and a second least significant bit track generates the next least significant bit signal.
The reason is that the lower bit track is placed farthest away from the lower bit track.

(Embodiment) FIG. 1 is a schematic diagram of an optical system of an embodiment when the present invention is applied to a rotary encoder. In the figure, reference numeral 1 denotes a rotating chart plate connected to an object to be measured (not shown). IA is a grid section for generating incremental signals, and is regularly arranged radially around the rotation axis 10 on the outer periphery of the chart board 1. 2A is a reading device which obtains incremental signals via the grid section IA.

Reference numeral 1B denotes a reference position grid section for obtaining a reference position signal, which is provided as needed, and is provided adjacent to the inside of the grid section IA. 2B is a reading device which obtains a reference position signal via the reference position grid section IB. The IC is a code section for obtaining an absolute signal, and is composed of a binary code formed by a transmitting section and a light shielding section, and is provided adjacent to the inside of the reference position grid section IB. 2C is a reading device, which obtains an absolute signal via the code section IC. L is a luminous flux, and 3A is a reflecting means, which reflects the diffracted light that is incident on the grating section IA on the chart board 1 and diffracted so as to be incident on the original position.

In this embodiment, each predetermined signal is obtained by detecting the directly reflected light, the directly transmitted light, or the reflected or transmitted diffracted light of the light beam incident on each grating portion on the chart board 1 using each reading device. ing.

For example, a light beam from a light source is made incident on the grating part IA on the chart board 1, a transmitted light beam from the grating part IA is detected, and the number of periods at this time is counted, or two diffracted lights generated from the grating part IA are detected. They interfere with each other to form interference fringes, and the rotational state of the object to be measured is determined by counting the brightness and darkness of the interference fringes.

FIG. 2 is an explanatory diagram showing only the code part IC portion of FIG. 1. In this embodiment, the outermost track 21 is used as the least significant bit track that generates the least significant bit signal, and the second least significant bit track 22 that generates the next least significant bit signal is provided on the innermost circumference. Tracks are placed farthest apart. As a result, when the luminous flux is linearly incident on the code part IC and an absolute signal is obtained, the incidence deviation of the luminous flux, that is, the inclination from the direction perpendicular to the rotating direction of the rotating disk, for example, the inclination of the luminous flux as shown by the dotted line in the same figure. This reduces the read timing error when the light is incident on the sensor, thereby minimizing the drop in detection accuracy.

FIGS. 3A and 3B are explanatory diagrams of output signals when the least significant bit track 21 and the second least significant bit track 22 are read by the reading device 2C, respectively. The figure (A) shows the output signal from the least significant bit track 21,
FIG. 2B shows an output signal from the second lower bit track.

In Figures 3 (A) and (B), the solid lines indicate the normal state;
That is, this is an output signal when the light beam is incident perpendicularly to the rotational direction of the code section IC and no light beam from an adjacent track is mixed. Moreover, the broken line is an output signal when the light beam is incident obliquely from a direction perpendicular to the rotation direction of the code section IC.

The one-dot chain line is a reference level value when converting the output signal into a binary number of 1.0, and the output signal value is inverted at the timing of crossing this reference level value to obtain the binary number.

As shown in FIGS. 3(A) and 3(B), the reading timing difference between the outermost track for the least significant bit and the innermost track for the second least significant bit occurs in opposite directions as shown by the arrows. The deviation between the two is maximum.

For this reason, in this embodiment, by making use of the deviation between the two sides that have a large change in reading timing, and adjusting the incident state of the light flux to the code section IC so as to minimize the deviation at this time, other bits can be read at the same time. The deviation from the signal generation track and the mutual difference between other tracks are suppressed to less than this, thereby enabling highly accurate detection.

In this embodiment, the least significant bit track 21 may be placed on the innermost circumference, and the second least significant bit track 21 may be placed on the outermost circumference.

Further, this embodiment can be applied as is to a linear encoder.

(Effects of the Invention) According to the present invention, the track for the least significant bit and the track for the second least significant bit, which is the next lower order, are arranged farthest among the plurality of tracks, and the output signal values from both tracks are simply By adjusting, mutual assembly of the devices becomes easy and errors in the incident position of the light beam on the object to be measured can be reduced, and a highly accurate and high resolution encoder, especially a highly accurate absolute encoder, can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an embodiment when the present invention is applied to a rotary encoder, FIG. 2 is an explanatory diagram of a part of FIG. 1, and FIGS. 3 (A) and (B) are implementations of FIG. 1. FIG. 3 is an illustration of the output signal obtained from the example. FIG. 4 is an explanatory diagram of a conventional encoder. In the figure, 1 is a chart board, IA is a grid section for generating incremental signals, IB is a reference position grid section, IC is a code section for generating absolute signals, 2A, 2B, and 2C are reading devices, 3A is a reflecting means, and 10 is a rotating shaft, 21 is a track for the lowest bit, 22 is a track for the second lower pit,
23 is an incident light beam. Figure 1 (A) (B) 夷 4 口

Claims (1)

[Claims] (1) In an encoder that makes a light beam enter a track section having a plurality of tracks that generate bit signals connected to the object to be measured, obtains an optical signal from the track section, and detects the displacement state of the object to be measured. , characterized in that among the plurality of tracks of the track section, a least significant bit track that generates the least significant bit signal and a second least significant bit track that generates the next least significant bit signal are arranged most apart. encoder.