JPS63289417A - Pulse encoder - Google Patents

Abstract

PURPOSE:To obtain absolute position data within a reduced moving range by a simple means, by employing A- and B-phase incremental systems having predetermined phase difference and generating Z-phase pulses having pulse widths different in the width equal to or more than several pulses of each of A- and B-phases with the movement of a moving body. CONSTITUTION:A rotary disc 2 is mounted to the shaft 1 rotating with the movement of a moving body. 90 slits each 3A and 3B for A- and B-phase 3A, 3B and Z-phase slits 3Z (Z1-Z6) are respectively provided to said disc 2 by drilling. The pulse widths of the slits Z1-Z6 are different from each other and respectively correspond to the moving position (angle of rotation) of the moving body. Light emitting elements 4A-4Z correspond to A-Z-phase slits 3A-3Z and the photoreceptors 5A-5Z are arranged in opposed relation to the elements 4A-4Z through the disc 2. Therefore, by one revolution of the disc 2, 90 pulses each for A- and B-phase having 90 deg. phase difference are outputted from the photoreceptors 5A, 5B and 6 Z-phase pulses different in a pulse width are outputted from the photoreceptor 5Z.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a pulse encoder suitable for a position detector of a device that uses a servo motor to move, such as a machine tool.

[Conventional Technique #I] Pulse encoders have traditionally been used to detect the position of machine tools and the rotation angle of robot arms.

Such pulse encoders include a rotary type that is attached to a servo motor shaft or the like and detects a rotation angle, and a linear type that detects a moving distance on a linear axis.

Here, the principle of the optical rotary pulse encoder is shown in FIG. As shown in the figure, opposing light emitting elements 4
A rotating disk 2 with a slit 3 cut therein is arranged between the light receiving element 5 and the light receiving element 5 . Therefore, when the rotating disk 2 rotates around the axis 1, the light generated by the light emitting element 4 reaches the light receiving element 5 in the slit 3 portion and generates an electric signal, and the light is emitted by the disk 2 in the non-slit portion. Being blocked, the light receiving element 5 does not generate an electrical signal. In this way, when the rotating disk 2 makes one revolution, the same number of electric pulse signals as the number of slits 3 passing through the rotation are obtained.

In order to also detect the direction of movement, as shown in FIG. 6, an A-phase slit 3A and a B-phase slit 3B are provided so that their rotation angles overlap each other by half (90 degrees in electrical angle). A phase and B arranged on the same straight line Ω from the center of rotation
There is a method of generating electric pulse signals using the optical elements 5A and 5B.

This method is commonly called a 90° phase difference A phase B phase method incremental type. In this method, the obtained A phase and B phase
When the phase pulses are processed by a predetermined logic circuit, the number of pulses per rotation in the rotational direction is outputted as four times the number of A-phase pulses (or B-phase pulses).

Furthermore, as the origin signal within one rotation, a slit and generator called a two-phase slit that generates only one pulse within one rotation,
There are also commercially available pulse encoders that are equipped with a light-receiving element and generate three types of pulses: A, B, and Z phases.

In addition, as shown in Fig. 7, multiphase slits are provided in the radial direction of the rotating disk 2, and the combination of the presence and absence of slits in the radial direction is made to correspond to a code such as a binary number, so that the absolute position within one rotation is Absolute value encoders that output digital values are also commercially available.

[Problems to be solved by the invention] However, since the incremental type shown in Fig. 6 has a simple configuration, high-performance products can be manufactured at low cost. Since the system does not support this, there is a problem in that information is lost when the power is turned off or moves during a power outage, making the current location unknown. In this case, if the device also has a Z-phase slit, absolute position information can be recovered by rotating a servo motor and detecting two-phase pulses, but with this method, the disk 2
had to be rotated a maximum of one revolution.

On the other hand, the absolute value type encoder shown in FIG. 7 has a problem in that it is expensive due to its complicated configuration. In particular, when the resolution is improved, the number of output bits increases, making it even more complex and expensive.

It is an object of the present invention to provide a pulse encoder that is less complex and expensive than the incremental type, but that is capable of obtaining absolute position information by simple means and within a small movement range. It is in.

[Means for Solving the Problems] The present invention employs an incremental type A-phase and B-phase system with a predetermined phase difference, and additionally includes: Z-phase pulses with different pulse widths are generated as the moving body moves.

[Function] As described above, if the pulse widths of the two-phase pulses are made different, each pulse width of the Z-phase pulse is made to correspond to the absolute position, and from a certain stationary position of the moving body to one of the adjacent Z-phase pulses, it is possible to By measuring the number of detected A-phase or B-phase pulses up to the edge of the phase pulse and between both edges of the Z-phase pulse sandwiching the above-mentioned stationary position, the current position (stationary position) of the moving object can be determined as absolute position information. can be obtained as Furthermore, the movement range of the moving body required to obtain this absolute position is approximately one pulse width of the two-phase pulse.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 2 is a side view showing an embodiment of the pulse encoder according to the present invention, in which 1 is a shaft that rotates as a moving body (not shown) moves (rotation of a rotating body here), and 2 is this shaft 1. It is a rotating disk attached to the As shown in FIG. 1, this disk 2 has A-phase and B-phase slits 3A similar to those in FIG. 6.

3B and a Z-phase slit 3Z are bored. Here, there are 90 each of A-phase and B-phase slits 3A and 3B, and 6 Z-phase slits 3Z (indicated by Z1 to Z6). The slit widths of the Z-phase slits Z1 to Z6 are different from each other, and their positions are associated with the movement position of the moving body (here, the rotation angle of the rotating body). 4A, 4B and 4Z are A phase, B phase and Z phase slits 3A, 3B and 3Z of the disk 2 near the disk 2.
This is a light emitting element disposed at a position corresponding to the drilling position. 5A, 5B and 5z are connected to the light emitting element 4A via the disk 2.
, 4B and 4z, and each of the light receiving elements 5A and 5B receives 90
pulses (A phase) (Rus.

B-phase pulses) are output with a phase difference of 90 degrees in electrical angle. Also, from the light receiving element 5Z, six pulses (two-phase pulses) each having a different pulse width are generated for one rotation of the disk 2.
is output.

FIG. 3 is a block diagram showing an example of a servo mechanism to which the above-mentioned pulse encoder is applied. In the figure, 11 is a servo motor, and 12 is its rotating shaft. A rotating body (not shown) whose position (rotation angle) is to be detected is attached to one end of the rotating shaft 12, here the left end.

13 is a coupling, which connects the rotating shaft 12 of the servo motor 11.
The right end is connected to the rotation shaft 1 of the pulse encoder 14 mentioned above. Reference numeral 15 denotes a control device for controlling the rotation angle of the servo motor 11, which includes a quadrupling circuit (not shown) that quadruples the number of A-phase and B-phase pulses, and controls the rotation of the rotating body, in other words, the servo motor. 360 A-phase and B-phase pulses are measured in one rotation of the motor 14. The control device 15 also performs drive control of the pulse encoder 14 to obtain the absolute position of the rotating body using the pulse encoder 14, which will be described later.

Next, the operation will be explained. Immediately after the above-mentioned servo mechanism is powered on, the rotation angle (current position) of the pulse encoder 14
Information is lost. From this state, the control device 15
First, the Z-phase pulse from the light receiving element 5Z is detected, and then the motor 11 is slightly moved. When the reversal of the Z-phase pulse (adjacent edge on one side) is detected, the motor 11 is slightly rotated in the reverse direction, and when the other adjacent edge of the Z-phase pulse is detected, it is stopped. During this time, the light receiving elements 5A and 5B
Accordingly, at least one of the A-phase and B-phase pulses is measured, and therefore, the pulse width of the Z-phase pulse can be determined from the measured value. Since the pulse widths of the two-phase pulses are different, if the pulse widths are known, it is possible to know in which region the two-phase pulse is located in terms of absolute angle. Then, based on the measured value of the A-phase or B-phase pulse until the edge of the above-mentioned titer of the two-phase pulse is detected, the pulse at the time of power-on is determined.
The absolute angle of the encoder 14 is known, and the current position (rotation angle) during subsequent rotation is also known.

A specific example will be described below with reference to FIG.

FIG. 4 shows the Z phase slit 3Z (Z1 to Z
6) in relation to the absolute angle shown on the horizontal axis, where Z-phase slits Z1 to Z correspond to each pulse width of the Z-phase pulse (or each pulse width of the inverted pulse of the two-phase pulse).
The central angle of 6 is 5° in order.

They are different at 10°, 15°, 20', 25°, and 300, respectively.

Also, the non-slit portions between them are also 55°.

Each has a different angular width of 50°, 45°, 40°, 35°, and 30°. As a result, while rotating the motor 11 as described above, a change in the state of the two-phase slit 3Z (or the non-slit portion between them) is detected by Z-phase pulse detection, and the Z-phase slit 3Z (or the non-slit portion) is detected.
Measure the angular width. As a result, the detected Z-phase slit 3Z (or non-slit portion) is specified, and the current position (absolute angle) is detected. Here, up to 55
The absolute angle can be determined within a rotation range of about 6° (if the absolute angle at the time of power-on was about 6°).

In the above embodiment, the present invention is applied to a rotary type pulse generator.
Although the case where the present invention is applied to an encoder has been described, it is of course applicable to other types of pulse encoders such as linear pulse encoders.

Further, in the above embodiment, an optical type is used as a means for generating each phase pulse, but various types such as a magnetic type can be used.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide a pulse encoder that has a relatively inexpensive configuration and can obtain absolute position information within a small movement range.

[Brief explanation of the drawing]

FIG. 1 is a front view showing an example of a rotary disk used in the encoder of the present invention, FIG. 2 is a side view showing an example of the encoder of the present invention equipped with the disk shown in FIG. 1, and FIG. FIG. 4 is a block diagram showing an example of a servo mechanism to which the encoder of the present invention is applied. FIG. 4 is a diagram for explaining a specific example of the absolute angle determination operation in the encoder of the present invention. FIGS. It is an explanatory diagram. 1...Axis, 2...Rotating disk, 3A...A phase slit, 3B...B phase slit, 3Z, Zl~Z6...Z
Phase slit, 4A, 4B, 4Z... Light emitting element, 5A,
5B, 5Z... Light receiving element. Patent applicant Hitachi Seiko Co., Ltd. Agent Patent attorney Aki, Tadashi Moto Figure 1

Claims (1)

[Claims] In a pulse encoder that outputs information on the current position of a moving object as it moves linearly or rotationally, a pulse encoder outputs information on the current position of the moving object as the moving object moves, in order to detect the direction and amount of movement of the moving object. A-phase pulse and B-phase pulse generation means for periodically generating A-phase pulses and B-phase pulses each having a phase difference; and at least several pulses of the A-phase pulse and B-phase pulse as the moving body moves 1. A pulse encoder comprising: Z-phase pulse generating means for generating Z-phase pulses having the above pulse width and each having a different pulse width.