JPH05149710A - Photoelectric linear scale - Google Patents

Abstract

PURPOSE:To inexpensively output highly accurate positional information by generating detecting pulses having phase differences in time from a photoelectric element group mounted on a traveling object and outputting a pulse string composed of position signals, the number of which is twice as large as the number of the photoelectric elements per pitch of slits, from a pulse string conversion and output circuit when the traveling object passes through the slits. CONSTITUTION:Slits 16 are provided in a linear scale main body 11 at regular intervals with a (pitch) width of Ps/2. A detecting head 13 has a U-shaped structure and mounted on a traveling object 12. A group of light emitting section 15a and a group of light receiving sections 15b are respectively fitted to the left and right frames of the head 13 and a group of a plurality of photoelectric elements is provided at regular intervals in the running direction of the head 13 and incorporated in the head 13 so that part or all of the total irradiated surface can be housed in the slits. Then detecting pulses having a slit width of Ps/2 are generated with phase differences in time. In addition, by providing a pulse string conversion and output circuit 17, the detecting pulses are converted into pulses having a frequency which is twice as high as that of the detecting pulses and the position signal of the pulse string is outputted to a control section by superimposing the converted pulses upon the signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric linear scale which outputs position information for position control by a linear scale main body provided along a moving path of a moving body and a photoelectric element group mounted on the moving body.

[0002]

2. Description of the Related Art As shown in FIG. 10, a linear scale main body provided along a moving path of a moving body and a detecting element mounted on the moving body output position information to a traveling control unit. The scale is the linear scale body 1
The head 2 having a detection element indirectly connected thereto so that the vibration of the mobile body 3 is not directly transmitted to the mobile body 3 is moved as the mobile body 3 travels, and position information is output to a control unit 4 including a sequencer or a microcomputer for control. The unit 4 performs necessary arithmetic counter processing and controls the position of the moving body by accelerating and decelerating and stopping the traveling motor M through a built-in control system.

In the linear scale which outputs the position information as described above, since the detecting element is provided in a non-contact state with the main body of the linear scale, a proximity switch or a reed switch actuated by a magnetic force line is used as the detecting element. The linear scale main body at the stop position is detected, a position signal which is an absolute address corresponding to the stop position is output, and the traveling motor is controlled in comparison with a target address preset in the control unit. ..

[0004]

The conventional linear scale lacks positional information in the vicinity of the stop position, and it is difficult to obtain a high stop accuracy. SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and provide an inexpensive photoelectric linear scale that outputs highly accurate position information.

[0005]

In order to achieve the above object, a linear scale according to the present invention comprises a linear scale main body provided along a moving path of the moving body and a moving body in a position close to the linear scale main body. The linear scale main body has slits with a uniform pitch along the movement path and a 1/2 pitch width, and the detection head has a slit width of the linear scale main body and a required detection accuracy. It has a light projecting surface having a suitable number of transmissive photoelectric element groups set correspondingly, and a light receiving surface facing the light projecting surface across the slit, and moreover, the slit of the linear scale body is provided on the moving body. It is characterized in that it has a pulse train conversion output circuit for converting an ON / OFF phase difference signal generated by transmission into a pulse train for position information of double frequency.

In the rear scale, light reflecting surfaces and non-reflecting surfaces may be provided alternately at equal pitches, and the photoelectric element group may be of a reflection type. That is, the linear scale body alternately has equal-length light-reflecting surfaces and non-reflecting surfaces along the moving path of the moving body, and the detection head corresponds to the light-reflecting surface or the non-reflecting surface of the linear scale body. It is also possible to have an appropriate number of reflective photoelectric device groups set by the above.

[0007]

When a proper number of photoelectric element groups built in the head at a proper pitch are mounted on a moving body and run and pass through a slit of the linear scale body, they turn on and off with a phase difference.
The F signal is repeatedly output, and the pulse train conversion output circuit outputs a pulse train which is twice as many position signals as the number of photoelectric element groups per slit pitch, thereby detecting the position of the moving body.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the drawings. 1 and 2 are a front view and a side view showing an embodiment of the photoelectric linear scale of the present invention. In the figure,
10 is a moving path, 11 is a linear scale main body provided along the moving path, 12 is a moving body, 13 is a detection head mounted on the moving body, 15a is a light emitting portion of a photoelectric element, 15b is a light receiving portion of the photoelectric element, Reference numeral 16 is a slit provided in the linear scale main body 11, and 17 is a pulse train conversion output circuit.

As shown in FIGS. 1 and 2, the linear scale main body 11 is provided at equal intervals so that the slits 16 have a width of Ps / 2 (pitch). The detection head 13 has a U-shaped structure and is provided on the moving body 12 so that the linear scale main body 11 can travel along the moving path while sandwiching the linear scale main body 11 so as not to come into contact therewith. Further, the left and right frames 13a and 13b of the detection head 13 that sandwiches the linear scale main body 11 are respectively provided with a light projecting unit group 15a and a light receiving unit 15b group so that a plurality of photoelectric element groups 15 are arranged in the traveling direction. The detection pulses are provided at intervals so that a part or all of the entire irradiation light surface runs within the slit so that the detection pulse having the slit width can be generated with a temporal phase difference. Further, a pulse train conversion output circuit 17 is provided in the detection head 13 or in the vicinity thereof, and the pulse train conversion output circuit 17
The pulse signal is converted into a pulse having a doubled frequency, and the pulse signal is superimposed and output as a position signal of the pulse train to the control unit.

FIGS. 3 and 4 show the pitch Ps of the slits 16.
5 is a chart showing the positional relationship between the slits and the elements and the detection pitch of the detection pulse and the superimposed pulse train by each element when the number of photoelectric elements for = 20 mm is 2 elements 5 mm pitch and 10 elements 1 mm pitch. Figure 3
When Ps = 20 mm and two photoelectric elements 5 mm pitch A and B are set, FIG. 4 shows that Ps = 20 mm and light receiving element 1 mm pitch 10 elements A, B, C, D, E, F, G, H, I , J shows the detection pulse and the superposed pulse train by each photoelectric element when set, respectively, the pulse train in the case of FIG.
That is, the detection pitch (detection accuracy) Px is 5 mm, and the pulse train in the case of FIG. 4, that is, the detection pitch Px is 1 mm.
mm. In both cases of FIGS. 3 and 4, when the slit pitch Ps is given, the number N of required photoelectric elements is N ≧ Ps / 2 · P with respect to the required detection pitch Px (detection accuracy).
It is set by x.

Next, FIGS. 5 and 6 show changes in the detected pitch when the pitch Ps of the slits is changed to 18 mm and 9 mm in the case where the photoelectric element is a 9-mm pitch element.
The pulse train, that is, the detection pitch is 1 mm in the case of FIG. 5 and 0.5 mm in the case of FIG. 6, and the detection accuracy is further improved. Similar to FIGS. 5 and 6, the photoelectric element shown in FIG. 7 has a detection pitch of 0.1 mm when the slit pitch 4Ps is 1.8 mm in the case of 9 elements having a 1 mm pitch, which greatly improves the detection accuracy. It shows that you do.

FIGS. 8 and 9 show that the rear scale body is provided with light reflecting surfaces and non-reflecting surfaces alternately at equal pitches.
Another embodiment in which the photoelectric element group is a reflection type is shown. That is, the linear scale main body 21 includes the moving body 12
Along the movement path of the light reflection surface 26a and the non-reflection surface 2 of equal length
6b are alternately provided, and the detection head 23 has an appropriate number of reflective photoelectric element groups 15 set corresponding to the light reflecting surface or the non-reflecting surface of the linear scale main body. The light projecting portion 15a and the light receiving portion 15b of the photoelectric element group 15 are arranged on the linear scale body 21 at equal intervals in the traveling direction of the detection head 23.
It is built in at the bottom of. Also in this case, the position of the moving body can be detected with high accuracy by converting it into a pulse having a frequency twice that of the detection pulse group, superimposing the pulse on it, and outputting the position signal of the pulse train to the control unit.

[0013]

As described above, according to the photoelectric linear scale of the present invention, a high-precision linear scale can be obtained at a low cost, and particularly in the case shown in FIG. 7, the detection accuracy can be increased up to 0.1 mm. Since the position information can be sent to the control unit of the traveling body at the detection pitch just before the stop, high-precision position control can be performed.

[Brief description of drawings]

FIG. 1 is a front view of an embodiment of a photoelectric linear scale according to the present invention.

FIG. 2 is a side view showing a partial cross section of FIG.

FIG. 3 shows a constant slit pitch (20 m in FIG. 1).
It is a chart which shows the detection pitch when changing the number of photoelectric elements when it is set to (m).

FIG. 4 is a chart showing the detection pitch when the slit pitch Ps is changed when the photoelectric element has a pitch of 1 mm and 9 elements in FIG.

FIG. 5 is a chart showing a detection pitch in the case where the photoelectric element is a 9-mm pitch element and the slit pitch Ps is 18 mm.

FIG. 6 is a chart showing a detection pitch when the slit pitch Ps in FIG. 5 is set to 9 mm.

FIG. 7 shows a slit pitch Ps of 1.8 mm in FIG.
It is a chart which shows the detection pitch in the case of.

FIG. 8 is a front view of an embodiment in which a linear scale main body is provided with light reflecting surfaces and non-reflecting surfaces alternately at equal pitches.

9 is a side view of FIG.

FIG. 10 is a diagram showing an outline of a conventional position control device for a moving body using a linear scale.

[Explanation of symbols]

 10 Moving Path Horizontal 11,21 Linear Scale Main Body 12,22 Moving Body 13,23 Detection Head 15 Photoelectric Element 15a Light Emitting Section 15b Light Receiving Section 16 Slit 17 Pulse Conversion Output Circuit 26a Light Reflecting Section 26b Non-Reflecting Section

Claims (2)

[Claims] 1. A linear scale main body provided along a moving path of a moving body, and a detection head mounted on the moving body at a position close to the linear scale main body, wherein the linear scale main body moves along the moving path. At equal pitch and 1 /
The detection head has a slit having a width of 2 pitches, and the detection head has a projection surface having an appropriate number of transmissive photoelectric device groups set corresponding to the slit width of the linear scale body and the required detection accuracy, and the slit. Has a light-transmitting surface and a light-receiving surface facing the light-transmitting surface, and further, the ON / OFF phase difference signal generated by passing through the slit of the linear scale main body in the moving body is converted into a pulse train for position information of double frequency. A photoelectric linear scale having a pulse train conversion output circuit. 2. The linear scale main body alternately has equal-length light reflecting surfaces and non-reflecting surfaces along a moving path of a moving body, and the detection head is a light reflecting surface of the linear scale main body. The photoelectric linear scale according to claim 1, further comprising an appropriate number of reflective photoelectric device groups set corresponding to the non-reflective surface.