JPS6131409B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a device that detects the position of an object by generating signals as the object moves and counting the number of waveforms. An incremental rotary encoder has been known as a position detection device that detects the position of an object by generating a signal as the object moves and counting the number of waveforms. . The principle is the first
As shown in the figure, a pattern is carved into the rotary slit plate 1 in which light transmitting portions 1a and light blocking portions 1b are arranged continuously at a predetermined pitch and concentrically with the rotating shaft 5 on the same circumference. A light emitting diode 3 and a photodiode 4 are arranged across a plate 1 and a fixed slit 2 in which a pattern is engraved at the same pitch. By rotating the light emitting diode 3 as it moves, the light incident on the photodiode 4 from the light emitting diode 3 is blocked a number of times corresponding to the amount of movement, thereby changing the waveform of the signal obtained from the photodiode 4. The position of the object is detected by counting the number of pulses. In such a position detection device, the resolution of position detection is determined by the number of pulses obtained per rotation of the rotary slit plate 1. Conventionally, resolution has been improved by increasing the number of light and dark patterns on the rotating slit plate (increasing the density) to increase the number of pulses per rotation. However, with this method, as the number of bright and dark patterns increases, the width of each bright and dark pattern must be narrowed, but since there is a limit to the precision of marking the bright and dark patterns, it is possible to increase the diameter of the rotating slit plate. It was necessary to ensure a wide range of brightness and darkness. This has resulted in the disadvantage that the detection device becomes larger and heavier. It is an object of the present invention to provide a position detection device that can eliminate the above-mentioned drawbacks of the conventional device and improve resolution without increasing the size of the device. According to this invention, a plurality of signals each corresponding to the amount of movement of the object to be detected and whose phases are shifted by a predetermined angle from each other are created by a combination of a light and dark pattern and a plurality of photocouplers, The position (linear position or angular position) of the object is detected by comparing these multiple signals with adjacent phases, detecting their cross points, and accumulating the number of cross points. ing. That is, by using a plurality of signals whose phases are shifted by a predetermined angle, information obtained by dividing the signal into each phase angle can be obtained, so that high resolution can be obtained even when the density of bright and dark patterns remains low. ing. Moreover, in the present invention, it is possible to obtain not only a resolution equal to the number of signals but also a resolution higher than the number of signals. In this way, when dividing originally obtained information to improve resolution, it is necessary that each division width be equal. For this purpose, it is necessary to generate a number of signals corresponding to the number of divisions by shifting the phase by an angle corresponding to the number of divisions. By the way, the phase shift 2
When comparing signals, as shown in Figure 2, the signals S1 and S2 cross every 180 degrees, so the cross points X1, X2, X3,
By counting X4, X5, X6, . . . , twice the resolution can be obtained compared to counting the number of waveforms of each signal S1 or S2. This invention utilizes this to achieve high resolution with a small number of detection signals. When comparing items with adjacent phases, a detection signal (a signal obtained from a detection means such as a photocoupler)
If the number of is n, then n-1 combinations are obtained, so if the resolution is increased by a factor of 2 in each combination, the overall resolution will be increased by a factor of 2 (n-1). However, in this case, the division widths are made equal (each division width is 1/2 (n-1) of one wavelength).
), it is necessary to appropriately set the phase of the detection signal to a value corresponding to the number of detection signals. Specifically, if the phases of the detection signals are set in the relationship shown in Table 1 depending on the number of detection signals, equal division widths can be obtained. Note that in the case of n=2, the number of signals and the resolution are exceptionally equal, and this does not meet the purpose of the present invention of obtaining a resolution greater than the number of signals, and is therefore excluded from the present invention.

[Table] Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 3 schematically shows an example of the internal configuration of an incremental rotary encoder to which the present invention is applied. The embodiment shown in FIG. 3 is an example in which the number of detection signals is three, that is, the resolution is four times as large. In Fig. 3, the rotating slit plate 1
0 has a portion 10a that transmits light and a portion 1 that blocks light.
A pattern consisting of 0b is formed continuously at a predetermined pitch, concentrically with the rotating shaft 11, and on the same circumference. The rotating shaft 11 of the rotating slit plate 10 is rotated in accordance with the movement of a position detection target (not shown).
For the rotating slit plate 10, photocouplers P1, P2, P3 (light emitting diodes D
1, D2, D3 and photodiodes d1, d
2, d3) are arranged, and light emitting diodes D1, D
2, the light from D3 passes through the transparent portion 10a of the rotating slit plate 10 to the photodiodes d1, d2,
d3, respectively. From the photodiodes d1, d2, and d3, signals are taken out of phase by 90° according to Table 1. For this purpose, photocouplers P1, P2, P3
90°/360 of the light and dark pattern of the rotating slit plate 10
They may be arranged by shifting them by 1/4 pitch in the continuous direction (circumferential direction of the rotating slit plate 10). Of course, one pitch is an extremely short distance, and the photo couplers P1, P2, P3 are shifted by 1/4 pitch during that distance.
Since it is difficult to line up the pitches, the pitches are placed so that they are relatively shifted by 1/4 pitch at every few positions, and as a result, signals with the phase shifted by 1/4 are obtained. Just do it. Rotating slit plate 10 and photodiode d1,
There are slit groups 12-1 and 12 between d2 and d3.
A light-receiving fixed slit plate 12 having numbers -2 and 12-3 formed therein is arranged. This fixed slit plate 12
blocks the photodiodes d1, d2, d3 from being irradiated with light from an oblique direction, and connects the optical axis of each photocoupler P1, P2, P3 with the rotating slit plate 10.
This is to allow the light from the light emitting diodes D1, D2, D3 to be incident on the photodiodes d1, d2, d3 only at positions where the transparent portions 10a of the light emitting diodes D1, D2, and D3 completely coincide with each other. Therefore, the slit groups 12-1, 12-2, and 12-3 are formed on the optical axes of the photocouplers P1, P2, and P3, respectively. In addition, each slit group 12-1, 12-2, 1
2-3 consists of a plurality of slits formed at the same pitch as the pattern of the rotating slit plate 10, and a large amount of light is transmitted to the photodiodes d1, d2,
The S/N ratio is improved by making the light incident on d3. FIG. 4 shows the transparent portion (slit) 10a of the rotating slit plate 10 and the slits 12-1, 12-2, 12 of the fixed slit plate 12 in the embodiment shown in FIG.
This figure schematically shows the positional relationship with -3.
That is, the slit 12- of the fixed slit plate 12
1, 12-2, and 12-3 are out of phase by 1/4 pitch with respect to 1 pitch T of the pattern of the rotating slit plate 10, and the slit 12-1 is in the transparent part 10.
The slit 12-2 coincides with the transparent part 10a at a position rotated by 1/4T after aligning with point a, and further rotated by 1/4T.
In the rotated position, the slit 12-3 is the transparent part 10
It is designed to match a. Therefore, as shown in FIG. 5, from the photocouplers P1, P2, and P3, one period corresponds to a predetermined amount of rotation T of the rotating slit plate 10 (i.e., a predetermined amount of movement of the object to be detected), and each period is 1/1. Signal SA whose phase is shifted by 4 periods
1, SA2, and SA3 are extracted. FIG. 6 shows an example of a circuit for determining the position of the object to be detected based on the signals SA1, SA2, and SA3. Figure 7 is an operating waveform diagram of Figure 6, (a) is the signal SA1, SA2, SA3, (b) is the signal SB12, (c)
is the signal SB23, (d) is the output of the edge trigger pulse oscillator 21-1, (e) is the output of the edge trigger pulse oscillator 21-2, and (f) is the output of the OR circuit 22. In Fig. 6, photodiodes d1, d
Signals SA1, SA2, SA output from 2, d3
3 are signals whose phases are adjacent to each other, that is, signals SA
1 and signal SA2, and signal SA2 and signal SA3 are compared by comparison amplifiers 20-1 and 20-2, respectively.
As a result, the comparator amplifiers 20-1 and 20-2 output pulse signals SB1 as shown in FIG. 7b and c, respectively.
2, SB23 is output. This pulse signal SB1
2, SB23 has a cycle of detection signals SA1, SA2, SA
Same as period T in 3, duty cycle is 50%
These are signals whose phases are shifted by 1/4 period from each other. Output signal SB of comparison amplifiers 20-1 and 20-2
12, SB23 is the edge trigger pulse oscillator 21
-1 and 21-2, respective rising and falling edges are extracted. Figures 7d and 7e show the pulses extracted in each case. The outputs of the edge trigger pulse generators 21-1 and 21-2 are logically summed by an OR circuit 22 and accumulated by an up/down counter 23. Output of OR circuit 22 SB12+SB23
As shown in Fig. 7f, the detection signals SA1, SA2,
Since the period is 1/4 of the period of SA3, signal SA1
Position detection can be performed with four times the resolution compared to the case where the number of waveforms of (or signal SA2 or signal SA3) is directly accumulated. Incidentally, the accumulation by the counter 23 is switched to addition or subtraction depending on the rotational direction of the rotating slit plate 10 (that is, depending on the moving direction of the object to be detected). The rotation direction of the rotating slit plate 10 is determined by the output pulses SB12 and SB2 of the comparison amplifiers 20-1 and 20-2.
This can be determined by detecting which of them rises first using 3. That is, as shown in the direction identification circuit 24 in FIG.
12 and signal 12, gated mono multivibrator 26 is driven by signal 12 and SB23, and their outputs drive flip-flop circuit 27.
By setting and resetting the flip-flop circuit 27, a signal corresponding to the direction of rotation is obtained from the flip-flop circuit 27 as shown in FIG. If the up/down counter 23 is switched to up counting or down counting by this signal, the count value will accurately correspond to the position of the object to be detected. The above uses 3 photocouplers to increase the resolution to 4.
Although the case of doubling is shown, it can be carried out similarly in other cases as well. For example, when using six photocouplers, the phase is set to 36 as shown in Table 1.
It is only necessary to arrange them by shifting them by ゜. The operating waveform diagram at that time is shown in FIG. In Figure 9, (a) shows the six detection signals SC1 to SC6, (b) compares SC1 to SC2, (c) compares SC2 and SC3, and (d) shows SC3 and SC4.
(e) is a comparison of SC4 and SC5, (f) is a comparison of SC5,
Comparison of SC6, (g) is the pulse signal obtained by the above comparison. In other words, the photocoupler outputs a signal whose phase is shifted by 36 degrees as shown in Figure 9a.
SC1 to SC6 are obtained. If we compare these signals with adjacent phases, we can see that the period is the same as that of the detection signals SC1 to SC6, the duty cycle is 50%, and the phase is 36° each (i.e., Five pulse signals shifted by 1/10 period) are obtained. By extracting the edges of these pulse signals and taking their logical sum, the period T of the original signals SC1 to SC6 can be reduced to 1/10 as shown in Figure 9g.
A divided pulse signal is obtained. Therefore, by counting these pulse signals, position detection can be performed with ten times the resolution. Further, the present invention may have various variations other than those shown in the above embodiments, such as the following. Application to non-optical methods The transparent part of the rotating slit plate is formed as a groove,
Multiple limit switches are placed there with their phases shifted by a predetermined angle to mechanically generate signals. Application to Linear Scale In the embodiments described above, the linear movement of the object to be detected was converted into the rotational movement of the rotary slit plate 1 for detection, but linear movement can also be directly detected. In other words, a linear slit plate is arranged in the direction of movement of the object to be detected, and the photocoupler is sandwiched between it and opposed to each other, so that the positional relationship between them changes linearly as the object to be detected moves. Position detection can be performed in the same way. In this case as well, resolution can be improved by arranging a plurality of photocouplers with their phases shifted by a predetermined angle (electrical angle when one cycle is 360°). Use as an angular position detector In the above-described embodiment, the case of detecting a position in a linear direction was shown, but it can also be used as an angular position detecting means for a machine whose angle changes. In the above-mentioned embodiment, a plurality of photocouplers were arranged with the phase shifted by a predetermined angle for one row of bright and dark patterns, but conversely, a plurality of light and dark patterns were formed in parallel with the phase shifted by a predetermined angle. , similar detection can be carried out by arranging photocouplers at the same position in the continuous direction corresponding to each pattern. For example, to quadruple the resolution, three bright and dark patterns 31, 32,
33 are formed with their phases shifted by 1/4 of the pitch T, and photocouplers P31, P32, P33 corresponding to each pattern 31, 32, 33 are arranged at the same position in the continuous direction thereof. In the embodiment of FIG. 3, photocouplers P1, P
2 and P3 were placed independently, but the 11th
As shown in the figure, one light emitting element D40 has multiple light receiving elements d40-1, d40-2, d40-3.
If it is irradiated all at once, the light emitting element D4
Even if 0 deteriorates over time, the levels of all detection signals change at the same rate, and the interval between the cross points between each detection signal is constant, so detection accuracy does not decrease, and since the number of elements is small, it is economical. It is also a target. As explained above, according to the present invention, a plurality of detection signals whose phases are shifted by a predetermined angle are created, and a signal obtained by dividing the period of the original signal is obtained by these signals, so that the detection signal Position detection can be performed with high resolution without increasing the frequency (that is, without increasing the density of the bright and dark pattern in the optical encoder). In addition, the cross points detected based on the comparison of two signals are detected at two points in one period of the original signal, so high resolution can be obtained with a small number of detection signals, resulting in miniaturization, high reliability, and a highly economical detector can be realized. (As shown in Table 1, the resolution can be increased by 2(n-1) times with n counting signals).

[Brief explanation of the drawing]

Fig. 1 is a perspective view schematically showing the internal structure of an incremental rotary encoder, Fig. 2 is a waveform diagram showing a state in which two signals with different phases cross each other, and Fig. 3 is an application of the present invention to an incremental rotary encoder. FIG. 4 is a perspective view showing an embodiment of the mechanical components in the case where the positional relationship between the slit 10a of the rotating slit plate 10 and the fixed slits 12-1, 12-2, and 12-3 in FIG. 3 is schematically shown. FIG. 5 is a diagram showing the signal waveforms obtained from the photocouplers P1, P2, and P3 of FIG. 3, and FIG.
A block diagram showing an embodiment of a circuit that performs position detection based on signals obtained from P2 and P3, FIG. 7 is an operating waveform diagram of the circuit in FIG. 6, and FIG.
Figure 9 is an operation waveform diagram when position detection is performed based on six detection signals, Figure 10 is a diagram showing the operation of the direction identification circuit shown in Figure 9, and Figure 10 is a diagram showing multiple bright and dark patterns in which the photocoupler is shifted in phase by a predetermined angle. FIG. 11 is a perspective view showing a modified example of the photocoupler. 10... Rotating slit plate, 11... Rotating shaft, 1
2... fixed slit plate, P1, P2, P3... photo coupler (D1, D2, D3... light emitting diode, d1, d2, d3... photo diode),
20-1, 20-2...comparison amplifier, 21-1,
21-2...edge trigger pulse oscillator, 24...
... Direction identification circuit, 31, 32, 33 ... Bright and dark pattern row, P31, P32, P33 ... Photocoupler, 40 ... Light emitting element, d40-1, d40-
2, d40-3... Light receiving element.

Claims (1)

[Scope of Claims] 1. A pattern in which parts that transmit light and parts that block light are continuously formed at a predetermined pitch, and the light is received with the phase shifted by 1/2 (n-1) of the pitch. n (n≧3) pairs of photocouplers, each arranged with the pattern in between in the continuous direction of the pattern, and arranged so that the relative position with the pattern changes in accordance with the movement of the position detection target. , circuit means for comparing n signals obtained from the photocoupler with adjacent phases (excluding the n-th and 1-th signals) and detecting their cross points; A position detecting device comprising circuit means for accumulating the number of cross points detected and determining the accumulated value as the position of the position detection object. 2. A pattern in which parts that transmit light and parts that block light are continuously formed at a predetermined pitch is shifted by 1/2 (n-1) of the pitch to form a pattern of n (n≧3).
) The pattern rows are arranged in parallel, and the pattern rows are arranged in such a way that each pattern is received at the same position in the continuous direction of the pattern rows, and the relative position with respect to the pattern rows corresponds to the movement of the position detection target. n sets of photocouplers arranged so as to change according to A position detection device comprising circuit means for detecting cross points, and circuit means for accumulating the number of cross points detected by the circuit means and obtaining the accumulated value as the position of the position object.