JPS6052715A - Incremental encoder - Google Patents

Abstract

PURPOSE:To set a reference value without hindrance even if the width of a reference signal is relatively wide, by measuring the width of the reference signal and setting the reerence value in accordance with the measured result and the output of a direction discriminating part. CONSTITUTION:When a collimating telescope 1 has passed a horizontal reference position, the reference signal is generated in a light receiving part. This reference signal becomes a sqaure wave signal in a reference signal generating part 200 and is given to an entry number operating part 230. The entry number operating part 230 is cleared by the rise of the square wave signal. Simultaneously with this clearing, a pulse counting part 170 receives a signal from a sqaure wave converter 220 and is cleared. Thereafter, the entry number operating part 230 receives the output from the pulse counting part 170 and counts it and performs an operation according as the output of a direction discriminating part 160 to determine an entry value.

Description

TECHNICAL FIELD The present invention relates to incremental encoders. In particular, the invention relates to a reference position setting device for incremental encoders.

(Prior art) An incremental encoder has two relatively displaceable members, namely a main slit plate and a sub-slit plate, and the main slit plate has regular slits arranged at a constant pitch in the direction of relative displacement between the two plates. A main slit grating is formed on the sub-slit plate, and two sub-slit gratings having the same pinch as the main slit grating are formed with a phase difference of A pitch and overlapping with the main slit grating. Displacement signal generating means is provided to generate two displacement signals that change in accordance with changes in the overlap of the main and sub slit gratings that occur when the main and sub slit plates are displaced relative to the reference position. The displacement signal from the displacement signal generating means is converted into counting pulses in the pulse forming section, and by counting these pulses, the relative displacement of the main and sub slit plates from the reference position is measured. The reason why two sub-slit gratings are formed on the sub-slit plate is to determine the direction of relative displacement between the positive and sub-slit plates, and to increase the number of counting pulses to obtain high resolution. By arranging the slit gratings with a phase difference of A pitch, the displacement signals obtained by these sub-slit gratings are shaped into rectangular waves, and pulses having rising points at the rising and falling edges of the rectangular waves are formed. High pitch counting pulses can be obtained.

In this manner, since the incremental encoder counts the relative displacement from the reference position as the number of pulses corresponding to the displacement, it is necessary to set a reference position that is the starting point of counting. In order to indicate the same reference position for both forward and reverse relative displacements of both slit plates, the signal that determines this reference position must be within the pinch of the counting pulse, and that the position must be within the pinch of the two adjacent slit plates. It must fall between the counting pulses.

Conventionally, in order to set this reference position, the main slit plate is provided with a main reference slit, and the sub-slit plate is provided with a sub-reference slit that overlaps the main reference slit at the reference position. A reference position signal with a required timing is obtained by comparing this reference signal with a voltage at a predetermined level.

(Problems with the prior art) The above-mentioned reference position setting device of the conventional incremental encoder is sensitive to fluctuations in the level of the reference signal caused by fluctuations in circuit constants due to extreme changes in temperature, or fluctuations in the power supply voltage. This variation in the comparison voltage level changes the inside of the reference position signal, and therefore the timing of the reference position, so that the reference position signal no longer falls between two adjacent count pulses, making it difficult to set the reference value properly. The problem is that it cannot be done.

(Object of the Invention) An object of the present invention is to provide a reference value setting device for an incremental encoder, which is capable of setting a reference value at a constant timing even if the level of a reference signal varies.

(Structure of the Invention) In order to achieve the above object, the present invention provides a main slit plate having a regular main slit lattice with a constant pitch, and a main slit plate having a main slit lattice arranged in a direction relative to the main slit plate. A sub-slit plate that is movable and has two sub-slit gratings formed at the same pitch as the main slit grating and displaced from each other by the pinch of x, and from the reference position of the main slit plate and the sub-slit plate. displacement signal generating means for generating two displacement signals representing the relative displacement according to a change in the overlap between the main slit grating and the sub-slit grating due to the relative displacement of the main slit grating; and a pulse forming section that forms a pulse according to the relative displacement based on the output of the two displacement signals and the direction discrimination section, In an incremental encoder that has come to know the amount of displacement of a target, both of the slit plates are formed with reference slint gratings that overlap each other at a reference position, and a reference signal that generates a reference signal according to the overlapping state of the reference slit gratings is formed. The present invention is characterized in that a generating means and a reference value setting means for measuring the inside of the reference signal and setting a reference value from the measurement result and the output of the direction discriminator are formed.

As a pulse forming section, there is a device that forms two rectangular wave signals of x pitch phase difference based on two displacement signals, and forms a constant pitch counting pulse having rising and falling points of the rectangular wave signals. It is well known and it is desirable to adopt such a pulse forming method in the present invention. In that case, counting pulses included in 11 of the reference signal are counted, and based on the counted value, By knowing the width of the reference signal, for example, the center position of the reference signal may be calculated and set as the reference position. By the time the counting of the counting pulses included in the reference signal has finished, the reference position has already been passed, but the reference value can be set by setting the count value A at the time of the counting completion. Become.

In the present invention, the slit grating includes not only optical slits but also magnetic and other slits.

(Effects of the Invention) As described above, the present invention measures the width of the reference signal and sets the reference value from the measurement result and the output of the direction discriminator. Even if the target is large, the reference value can be set without any problem.

(Description of Embodiments) Fig. 1 is a perspective view showing a transit using the incremental encoder of the present invention.

The transshift includes a reference telescope 1, a holder 2 having supports 2a and 2b that rotatably support the reference telescope 1, and a base 3 that supports the holder 2 rotatably around a vertical axis. A photoelectric encoder 4 for reading horizontal degrees is built in between the stand 2 and the base 3. This encoder 4 has a main slit plate 4a fixed to the base part 3.
, a sub slit plate 4b fixed to the mount part 2 and rotating together with the mount part 2, a light emitting part 4C for illuminating the main slit plate 4a and the sub slit plate 4b, and a light emitting part 4C for receiving the illumination light. It is composed of a light receiving section 4d.

The main slit plate 4a has a main slit lattice 14a regularly formed with a constant pitch, and the sub-slit plate 4b has two sub-slit lattices 14b and 24blr of the same pitch as the main slit lattice 14a. The main slit grating 14a and the sub-slit gratings 14b and 24b have a conventionally known configuration and function to detect the rotation angle of the support section 2 with respect to the base section 3. For this reason, the pillar 2a has
A signal processing unit 6 for processing the read signal from the encoder 4 into an angle value, and a display 7 for digitally displaying the angle value from the signal processing unit 6 as a horizontal minute angle are arranged.

An encoder 5 for reading the elevation angle from the amount of rotation of the reference telescope 1 is attached to the support 2b. The encoder 5 has a main slit plate 5a that is attached to the rotation axis (not shown) of the reference telescope 1 and rotates together with the telescope 1, and a sub-slit plate 5b that is fixed to the support 2b. is a main slit grating 15 regularly with a constant pitch.
A is formed on the sub-slit plate 5b, and two sub-slit gratings 15b, 2 are formed at the same pitch as the main slit grating 15a.
5b is formed. Sub-slit gratings 15b, 25b
are arranged so as to overlap with the main slit grating 15a, and are formed with a phase difference of x pitch.

As shown in FIG. 2, a main reference slit grating 35a is formed on the main slit plate 5a in line with the main slit grating 15a, and a sub-slit grating 35a is formed on the sub-slit plate 5b at a position overlapping with the main reference slit grating 35a at the reference position. A reference slit grating 35b is formed. In this example, each slit grating is an optical slit consisting of transparent slits formed in an opaque part, and includes a main slit grating 15a and a sub-slit grating 15a.
a light source section 15C and a light receiving section 15d for reading the overlap between the main slit grating 15a and the sub slit grating 25b and generating a 0° signal; and a light source section 25c and the light receiving section for reading the overlap between the main slit grating 15a and the sub slit grating 25b and generating a 90° signal. A light source section 35c and a light receiving section 3 for reading the overlap between the section 25d and the main and sub reference slit gratings 35a and 35b to generate a reference signal.
5d is provided. The signal processing section 6 includes an encoder 5
It has an elevation angle calculation circuit for processing the signals from the elevation angle and obtaining reading values for the elevation and low angles, and the calculation results are displayed on the display 7.
will be displayed.

Arithmetic circuit FIG. 3 shows a height/low degree angle arithmetic circuit, which is comprised of a displacement detecting section 100 and a reference signal forming section 200.

The displacement detection section 100 has amplifiers 110 and 120 for receiving signals from the light receiving sections 15d and 25d, respectively. When the reference telescope 1 is moved upward from the horizontal position, that is, the reference position, the light receiving sections 15d and 25d generate a 0° signal as shown in FIG.
) generates a 90° signal as shown in When the telescope 1 is moved in the opposite direction, the phase relationship of these signals is reversed. These signals are amplified by amplifiers 110 and 120.
J and manually input to square wave converters 130 and 140, respectively. The square wave converters 130, 140 have a 0° signal and a 9
The outputs of the converters 130 and 140 are both input to the pulse generator 150 and the direction discrimination circuit 160. The pulse generator 150 generates pulses in response to the rising and falling edges of its input rectangular wave, and its output waveform is equally spaced pulses as shown in FIG. 4 (6). The direction discrimination circuit 160 discriminates the displacement direction from the phase relationship of the two input rectangular waves, and generates a signal indicating normal rotation or reverse rotation. Pulse generator 150 and direction discrimination circuit 1
60 are both input to a pulse counting section 170, and the pulse counting section 170 increases or decreases the output pulses of the pulse generator 150 according to the output of the direction discrimination circuit 160.

The output of this pulse counting section 170 is given to a displacement amount converting section 180, and the conversion result is displayed on the display 7.

Reference Signal 0 Forming Section 200 The reference signal forming section 200 has an amplifier 210 that receives the signal from the light receiving section 35d. The light receiving part 35d is raised when the telescope 1 is in the horizontal reference position as shown in FIG. 4 (3).
) is generated, and the reference signal is amplified by an amplifier 210.

The output of the amplifier 210 is converted into a rectangular wave shown in FIG. 4 (7) by a rectangular wave converter 220 and output. The output of the rectangular wave converter 220 is directly converted into a signal shown in FIG. At the same time, the output of the rectangular wave converter 220 is also input to the pulse stitch number section 170 as a clear signal. In addition, the position value calculation section 23 is
The output of the pulse counting section 170 is received and counted as the number of stitches.

In operation, when measuring an upward altitude angle, the reference telescope 1 is moved upward from below the horizontal reference position across the reference position and stopped at a position where the target is referenced. In this process, when the reference telescope 1 passes the horizontal reference position, a reference signal shown in FIG. 4(3) is generated in the light receiving section 35d. This reference signal is converted into a rectangular wave signal shown in FIG. The input value calculation section 230 is cleared by the rise of the rectangular wave signal shown in FIG. 4 (7). At the same time, the pulse counting section 170 receives a signal from the square wave conversion@220 and is cleared. Thereafter, the set value calculation section 230 operates the pulse counting section 17.
After receiving the output from 0, the number of stitches is counted until the rising edge of the signal shown in FIG. The calculation process is explained in the fifth
To explain using the flowchart in the figure, first, in the first step, it is checked whether the signal shown in FIG. 4 (7) has risen, and if it has not risen, the same check is repeated.

When the signal shown in Figure 4 (7) rises, the set value is cleared in the next step, and then it is checked whether the signal shown in Figure 4 (8) has risen. The check is repeated.

When the signal shown in FIG. 4 (8) rises, the output M of the pulse counting section 170 at that time is taken in. The pulse counter 170 is cleared at the same time as the signal rises in FIG. 4(7), so its output M corresponds to the number of pulses during the duration of the reference signal. Next, when the output M of the pulse counting section 170 is an even number, it is left as is, and when it is an odd number, 1 is added to it, and the value is divided by 2 to obtain a set value. This set value is output to the pulse counting section 170, and either the counted value of the pulse counting section 170 is replaced with this set value and counting is continued, or this set value is subtracted from the counted value of the pulse counting section 170, and counting is continued. Continue. In this way, the reference value can be set.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view of a digital transshift using the incremental encoder of the present invention, and FIG.
2 is a diagram showing the main slit plate of the encoder, FIG. 2 is a diagram showing the sub slit plate, FIG. 3 is a block diagram showing the signal processing circuit, and FIG. 4 is a diagram showing the signal waveform in the signal processing circuit. Fig. 5 is a flowchart showing the operation of the position value calculation section. Fig. 1 Fig. 2': 3bb Fig. 4 F8) ”-

Claims (1)

[Claims] a main slit plate having a regular main slit lattice with a constant pitch; and a main slit plate movable relative to the main slit plate in the arrangement direction of the main slit lattice, having the same pitch as the main slit lattice and only two pinches thereof. A sub-slit plate having two sub-slit lattices formed by being displaced from each other; and a sub-slit plate having two sub-slit lattices formed by being displaced from each other; a displacement signal generating means for generating two displacement signals representing the relative displacement according to a change in overlap; a direction discriminator for discriminating a displacement direction from the two displacement signals; and a discriminator for discriminating between the two displacement signals and the direction. In the incremental encoder, the incremental encoder has a pulse forming section that forms a pulse according to the relative displacement from the output of the section, and the amount of relative displacement is known by counting the displacement pulses. includes reference slit gratings that overlap each other at a reference position, a reference signal generating means for generating a reference signal according to the overlapping state of the reference slit gratings, and measuring the width of the reference signal and discriminating the measurement result from the direction. 1. An incremental encoder comprising a reference value setting means for setting a reference value from the output of the section.