JPH04203B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The photoelectric displacement detection device of the present invention, in particular, the light intensity of the light emitter that supplies detection light between relatively moving slits, regardless of the power supply voltage or the voltage drop in the circuit.
This invention relates to the improvement of a stable photoelectric displacement detection device that can be controlled to a constant value.

[Prior art] Dial gauge micrometers with digital display, length measuring devices such as three-dimensional measuring machines, laser microphones that use laser beams to measure distances, table feeding devices for NC machine tools, etc. A mold displacement detection device is used, and a detection device with excellent measurement accuracy and durability has been put into practical use.

FIG. 1 shows the main parts of this type of displacement detection device, in which a main scale 10 made of glass or a thin stainless steel plate has a plurality of length measurement slits 10a and absolute value slits 10b aligned and arranged on its surface. A desired length measurement or position detection operation is performed along this main scale 10.

An index scale 12 and an absolute value scale 13 are provided near the main scale 10, and the index scale 12 and absolute value scale 13 have the length measuring slits 10a,
Index slits 12a, 12b, 13a corresponding to the absolute value slit 10b are provided, and the amount of slit movement is electrically detected by the relative movement of each scale 10, 12, 13, and this relative movement signal is Based on this, a length measurement or position detection function is achieved.

In order to photoelectrically convert the relative movement of each scale 10, 12, 13, both scales 10, 12, 13
In the figure, since it is a transmission type measuring device, the light emitters 14a, 14b, and 14c are provided on the main scale 10 side, and the light receiver 1 is provided on the index scale 12 side.
6a, 16b, and a light receiver 16c is provided on the absolute value scale 13 side, and these light emitting/receiving devices 14, 16
are the index slits 12a, 12b, 1
It is placed at a position corresponding to 3a. As is well known, both index slits 12a and 12b are arranged half a pitch apart from each other, so that the light transmitted through both scales 10 and 12 is a sine wave signal on one side and a cosine wave signal on the other. The signal is detected as a wave signal, and it is possible to perform a desired division operation using both signals having different phases.

Further, the above-mentioned absolute value scale 13 can output the moving position of the main scale 10 as an absolute value signal in cooperation with absolute value slits 10b which are provided intermittently on the surface of the main scale 10 and indicate the absolute value. , it is possible to know where the absolute value scale 13 is located on the main scale 10.

As described above, according to the conventional device, photoelectric conversion of the amount of displacement is performed, and then the relative displacement signal detected in this manner is subjected to necessary processing by the circuit shown in FIG. Ru.

FIG. 2 shows an example in which the displacement detection device is used as a length measuring device, and the relative movement displacement signals of each light receiver 16 are amplified by preamplifiers 18a, 18b, and 18c and then supplied to the detection circuit 20. be done. The detection circuit 20 includes a waveform shaping circuit 22 and a dividing circuit 24, and the dividing circuit 24 is configured to divide both of the aforementioned components as is well known.
Scale 1 by combining sine wave signal and cos wave signal
A division into measuring pitches smaller than the slit width of 0.12 is carried out.

The output of the detection circuit 20 is supplied via a counter 26 to a digital display 28, where the measured length is digitally displayed, and if necessary, the measured length is recorded by a printer 30.

In addition, the three light emitters 14a, 14b,
14c are connected to a power source via resistors 32a, 32b, and 32c, respectively, and a desired light emission effect is performed.

In the above-mentioned displacement detection device, the amount of light from the light emitter 14 has a large effect on the characteristics of the photoelectric conversion section, and therefore, a light emission function with a stable amount of light is always required. Therefore, in the conventional device, for example, in the case of the device shown in FIG. 2, the resistor 32 connected to each light emitting device 14 is finely adjusted to equalize the amount of light emitted by each light emitting device 14 and to adjust the amount of light emitted as necessary. By adjusting the preamplifier 18 accordingly, the output of each detection signal supplied to each detection circuit 20 was initially adjusted.

However, even with the initial adjustment performed before the measurement, the conventional device has the disadvantage that if the power supply voltage itself fluctuates, the amount of light emitted changes, and errors often occur in the detected value. It was hot.

In addition, as a conventional detection device for table feed control of NC machines, a detection section is provided for each NC movement axis, and this is centrally controlled by a power supply, operation switch, display, etc. installed on the fixed side. is becoming common.

Figure 3 shows an example of this type of NC control device, in which the photoelectric displacement detection devices shown in Figures 1 and 2 are installed for each of X, Y, and Z of the NC machine. , a light emitter 1 is placed at the moving part in each axis direction.
4. The light receiver 16 and the preamplifier 18 are integrated into the movable housing 32.

The fixed housing 34 includes a power supply 36, a detection circuit 20, and indicators 38, 40, 4 for each axis.
2 is provided.

The movable housings 32 are provided individually for each of X, Y, and Z, and are attached to the respective NC feed axes. Therefore, according to such a split-type detection device, which is electrically connected,
The power supply, operation switch group, and display section can be commonly installed on the fixed side, which greatly contributes to miniaturization of the device.

However, in such split-type detection devices, the length of the cable 44 that connects the fixed housing 34 and the movable side housing 32 varies depending on the device, and furthermore, the length of the cable 44 that connects the fixed housing 34 and the movable side housing 32 differs depending on the device, and furthermore, as shown in FIG. X, Y,
When multiple types of movable side devices are used, such as Z, the cable length may change for each axis, and as a result, the voltage on the fixed side may not be constant due to voltage drop within the cable 44. Even if there is a problem, there is a problem in that the amount of light from the light emitters provided on each movable side actually varies, and as a result, a non-negligible error is introduced into the measurement accuracy. As explained above, in the past, it was not always possible to obtain a stable supply current due to fluctuations in the power supply voltage or voltage drop to the light emitter, especially in a detection device that is divided into multiple detection sections. However, there was a problem in that the variation became large, which had a non-negligible negative effect on detection accuracy.

As an improved conventional device, it has been proposed to provide a voltage detector on the slider unit on the movable side and a device to control the power supply voltage, or to provide a separate constant power supply device within the slide unit. However, it is necessary to newly install cables, voltage detectors, and other complicated structures to guide the detection voltage, and there is also the problem that noise is mixed into the voltage detection and control lines. Further, the separate power supply device also had various problems such as having a negative effect on the sliding characteristics of the slider unit and increasing the size of the device.

In addition, in the installation structure of multiple detection units on the movable side described above, the actual voltage inside the movable side slider unit decreases by 4 to 6% due to cable loss compared to the power supply voltage on the fixed side, for example, 5 volts. , the amount of light from the light emitter also decreases by 10 to 15%, and if we take into account that the fixed side power supply voltage fluctuation is 5% up and down, the amount of emitted light may decrease by nearly 20%. It is clear that this significantly degrades the S/N ratio of the length measurement signal and has a large adverse effect on measurement accuracy.

[Object of the Invention] The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to be able to control the amount of light from a light emitter to always be constant regardless of fluctuations in power supply voltage or cable loss. Therefore, it is an object of the present invention to provide an improved photoelectric displacement detection device that can improve detection accuracy.

[Structure of the Invention] In order to achieve the above object, the present invention connects a constant current circuit to the light emitter itself, and this constant current circuit connects a light emitting circuit including a transistor and a resistor connected in series to the light emitter, and the light emitting circuit. Consisting of a constant voltage circuit having a shunt regulator connected in parallel to a light emitting circuit, the constant voltage action of the shunt regulator makes it possible to supply a constant current from the transistor to the light emitter. It is.

Further, according to the present invention, in addition to the index scale light emitting circuit and the light emitter, the constant voltage circuit is housed in the first casing of the moving side slide unit, and this first casing is used for detection. It is movably connected to the second housing on the fixed side, which has a circuit and a power supply device for driving the light emitting device, by a cable. As a result, even if the slide unit is separated from the fixed part, the light emitting unit will not emit light. This has the advantage that a stable constant voltage can be supplied to the device and good measurement accuracy can be obtained.

[Embodiments] Preferred embodiments of the present invention will be described below based on the drawings.

FIG. 4 shows a three-axis split type device for an NC machine to which the displacement detection device according to the present invention is applied, and the same members as those in FIG.

A characteristic feature of the present invention is that the light emitting devices 14 are supplied with their light emitting current by a constant current circuit, and this constant current circuit is connected to each light emitting device 14.
Transistors 46a, 46b, connected in series to
46c and resistors 48a, 48b, and 48c, and an unstable power supply including fluctuations and voltage drops supplied from the fixed side is supplied to this light emitting circuit.

In order to stabilize the constant current light emitting circuit including the transistor 46, in the present invention, a constant voltage circuit is connected to the light emitting circuit, and this constant voltage circuit includes a shunt regulator 50.
The embodiment shows the shunt regulator 5 used.
0 uses TI's TL431C, which outputs a constant voltage to its constant voltage terminal R. The shunt regulator 50 has its cathode input terminal K connected to the positive pole of the power supply via a resistor 52, and its anode terminal A connected to the negative pole.

Further, in the present invention, the cathode input terminal K of the shunt regulator 50 is connected to the base of each transistor 46, and the constant voltage terminal R mentioned above is connected to the emitter of the transistor 46.

The structure of the present invention is clear from the above description,
Due to the constant voltage action of the shunt regulator 50 described above, the supply current i flowing to the light emitter, that is, the light emitting diode 14c, is given by the resistance value of the resistor 48c as r,
The voltage at the constant voltage end R of the shunt regulator 50 is
If V _R is used, it can be obtained as i=V _R /r.

Therefore, as in the present invention, by connecting a constant voltage circuit using the shunt regulator 50 to a constant current light emitting circuit, the shunt regulator can be used even when the cable length fluctuates or the power supply voltage itself fluctuates. 50 outputs a constant voltage V _R to its constant voltage terminal R, so that the supply current i for light emission is always maintained at a constant value.

Furthermore, even if the characteristic characteristics of each transistor 46 slightly fluctuate due to temperature changes or the like, the cathode input terminal K of the shunt regulator 50 changes in accordance with the fluctuation, so that the voltage at the constant voltage terminal R It is clear that V _R remains constant;
In this embodiment, the shunt regulator 50
Since the cathode input terminal K of is connected to the base of each transistor 46, even if the reference voltage of the constant voltage terminal R is connected only to a single light emitting circuit, that is, the light emitting circuit of the light emitter 14c, it will not be connected to other light emitting circuits. Also, desired constant current control is applied from the base inputs of the transistors 46a and 46b, and all the light emitters 1
It becomes possible to obtain a constant current common to all four.

Of course, in the present invention, the shunt regulator 50 is connected to each light emitter 14a, 14b, 14c.
It is also possible to provide one for each light emitting circuit.

In actual circuit configuration, the transistor 4
It is preferable to select resistors 6a, 46b, 46c with substantially the same characteristics, and resistors 48a, 48
The resistance values of b and 48c are each initially adjusted and set to the same value.

As described above, according to the present invention, the supply current of the light emitter is controlled using a constant voltage circuit including a shunt regulator, and it is possible to control the current supplied to the light emitting device by using a constant voltage circuit including a shunt regulator. Therefore, it is possible to always obtain a stable amount of light emitted even in the case of light emission, and good detection accuracy can be achieved.

Furthermore, as shown in FIG. 4, by incorporating a constant voltage circuit including the shunt regulator into the housing 32 of the moving slider unit, a constant current can be supplied near each light emitting device. This is extremely suitable for a detection device in which the fixed side and movable side are separated.

[Effects of the Invention] As described above, the present invention has the advantage of being able to eliminate fluctuations in the supply current to the light emitter due to power supply voltage and other fluctuation factors, thereby achieving an extremely stable detection action. In particular, in a detection device that separates the movable side and the fixed side and connects them with a cable, the amount of light emitted can be kept constant regardless of the cable length, making it easy to replace the cable. Further, even in a device having a multi-axis slider unit, there are many advantages such as no variation in the amount of light emitted and detection accuracy among the axes, and no adjustment for each axis is required.

[Brief explanation of drawings]

Fig. 1 is a perspective view of the main parts of the slider part in a general photoelectric displacement detection device, Fig. 2 is a block diagram of a processing circuit suitable for Fig. 1, and Fig. 3 is an example of a conventional detection device for NC machines. Fig. 4 is an explanatory diagram showing an example of a detection device in which the fixed side and the operating side are separated.
FIG. 2 is an explanatory diagram showing a preferred embodiment of a displacement detection device according to the present invention used in an NC machine. 10... Main scale, 12... Index scale, 13... Absolute value scale, 14...
Light emitter, 16... Light receiver, 18... Preamplifier,
20...Detection circuit, 32...Moving side housing, 34...
...Movable side housing, 36...Power supply, 44...Cable, 46...Transistor, 48...Resistance, 50
...Shunt regulator, K...Cathode input terminal, R...Constant voltage terminal.

Claims (1)

[Scope of Claims] 1. A main scale having length measurement slits arranged in alignment, an index scale having index slits corresponding to the length measurement slits, and a light emitting device that irradiates detection light toward both scales. A photoelectric displacement detection device including a light receiver that receives transmitted light or reflected light of both scales, and a detection circuit that outputs a relative movement displacement signal of both scales based on outputs of the light receiver. is connected to a power source via a transistor and a resistor to form a light emitting circuit, and a constant voltage circuit consisting of a shunt regulator is connected to the light emitting circuit, and a cathode input of the shunt regulator is connected to the light emitting circuit. An end is connected to the base of the transistor and a constant voltage end is connected to the emitter of the transistor to control the supply voltage to the light emitter at a constant level, and the index scale, the light emitting circuit and the light emitter are connected to the first one of the movable slide unit. The detection circuit and the power supply device for driving the light emitter are housed in a second housing provided on the fixed side,
1. A photoelectric displacement detection device, wherein the two housings are movably connected to the first housing by a cable, and the constant voltage circuit is housed in the first housing. 2. In the device according to claim 1,
A plurality of light emitting circuits are provided within the movable housing, and the cathode input terminal of the shunt regulator of a single constant voltage circuit is connected to the base of the transistor provided in each of the light emitting circuits, and the shunt regulator is connected to the base of the transistor provided in each of the light emitting circuits. A photoelectric displacement detection device characterized in that a constant voltage end of the generator is connected to an emitter provided in any one of the light emitting circuits.