JPS63302312A - Length measuring system - Google Patents

Abstract

PURPOSE:To enable highly accurate measurement, by correcting a value of a counter based on a temperature data from a temperature sensor to automatically compensate measuring errors for temperature changes. CONSTITUTION:A CPU35 inputs a data from an A/D converter 33, that is, that pertaining to temperatures of parts of a scale base material 11 detected with temperature sensors 131-133 through a system bus 34 to determine a mean of the data. Then, a correction factor corresponding to a detection temperature is read out from a correction table having correction factors stored corresponding to respective temperatures. Then, displacement in relative movement (displacement from an absolute value mark 14) obtained by a specified processing of a value of a counter 37, namely, a signal detected with a displacement detector 9 is multiplied by the correction factor to correct measured values and the results are displayed 36 through a system bus 34. Thus, measured values are always obtained with a high accuracy and a high reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a length measurement system. Specifically, one of two members that move relatively is provided with a reference scale having graduations for detecting displacement, and one of the other members is provided with a detector for reading the graduations of the reference scale. The present invention relates to an improvement of a length measuring system that detects the amount of relative displacement of two members by both.

[Conventional technology]

In fields such as machine tools and precision measuring instruments, displacement detection devices are used to accurately measure the amount of relative displacement between two relatively moving parts in order to achieve high-precision machining and high-precision measurement. There is.

Conventionally, as one such displacement detection device, for example, as shown in FIG. Among them, a reference scale 4 having eyes gt3 forming an optical grating at constant pitch intervals along the direction of relative movement is provided in the elongated box-shaped main body case 1 attached to the stationary body 100, while attached to the movable body 200. A displacement detection device is known in which a displacement detector 9 including an index scale 6 having a scale 5 facing the scale 3 and a light emitting/receiving device 7 and 8 is attached to a sliding body 2 via an arm 2A. .

This one is a standard scale 4 that accompanies the movement of the movable body 200.
The phase change between the scale 3 of the index scale 6 and the scale 5 of the index scale 6 is converted into an electrical signal by the displacement detector 9, and this electrical signal is processed in a predetermined manner to detect the amount of relative displacement between the stationary body 100 and the movable body 200. Therefore, the scale 3 of the reference scale 4 and the scale 5 of the index scale 6 must always be maintained with high precision regardless of temperature changes.

Therefore, in the conventional system, the reference scale 4 and the index scale 6 are made of a material such as glass having a small coefficient of linear expansion to cope with temperature changes in the installation environment.

(Problem to be Solved by the Invention) However, the above-mentioned response to temperature changes is to assume that the temperature changes in the installation environment are within the range and ignore errors associated with temperature changes within that range. Therefore, it is not necessarily satisfactory in the current situation where higher precision measurement is desired.

In particular, this type of displacement measuring device is used in a variety of environments, and its selection is at the discretion of the user.In particular, in environments where machine tools are installed, temperature changes are large, so it is not enough to just select materials for each scale. It is often unable to respond to temperature changes.

Further, the reference scale 4 and the index scale 6 are structured to be directly attached to the main body case 1 and the sliding body 2 which slide. Therefore, when sliding resistance heat is generated due to the sliding movement between the main body case 1 and the sliding body 2, or the sliding movement between the stationary body 100 and the movable body 200, it is transmitted to each scale, and as a result, the installation environment Since the above temperature changes are brought to each scale, measurement errors occur.

SUMMARY OF THE INVENTION An object of the present invention is to provide a length measuring system that automatically compensates for measurement errors due to temperature changes and enables highly accurate measurements. It is in.

[Means for solving problems]

Therefore, in the present invention, the temperature of the reference scale itself on which the scale for displacement detection is formed is directly detected, and the measured value is automatically corrected based on this temperature.

Specifically, there is a reference scale with graduations for displacement detection formed along the longitudinal direction of a linear scale base, a detector for reading the graduations of this reference scale, and a reference scale based on the signal of this detector. and a counter for determining the amount of relative movement displacement between the scale base material and the detector. The present invention is characterized in that a temperature sensor for detecting temperature is integrally provided, and a correction means is provided for correcting the value of the counter based on temperature data from the temperature sensor.

[Effect]

Therefore, the temperature of the scale base material itself is directly detected by the temperature sensor, and the measured value is corrected based on this temperature. For example, the measured value is corrected or detected based on the detected temperature and the linear expansion coefficient of the scale base material. Since the correction coefficient is checked in advance in accordance with the temperature and the measured value is corrected by multiplying the measured value by the correction coefficient corresponding to the detected temperature, it is possible to compensate for measurement errors due to temperature changes.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on FIGS. 1 to 4.

Fig. 1 shows the appearance of this embodiment. In the figure, an elongated box-shaped main body case 1 and a sliding body 2 are provided so as to be movable relative to each other.
A reference scale 10 is installed inside the main body case 1 along the relative movement direction, and a detector 9 is provided on the sliding body 2 to read the scale 12 of the reference scale 10 via an arm 2A. is installed.

The detector 9 is the same as that described in FIG. 5, and is composed of an index scale 6 having graduations 5 and a light emitting/receiving device 7.8.

As shown in FIG. 2, the reference scale 10 has slit-shaped displacement detection scales 12 arranged at a constant pitch along the longitudinal direction of a scale base material 11 made of a thin linear glass having a rectangular cross section. Temperature sensors 131 and 132 are formed at intervals of (for example, 10 μm pitch) and are located close to the scale 12 at predetermined intervals in the longitudinal direction of the same surface on which the scale I2 is formed to detect the temperature of the scale base material 11.
．． 13, are each provided integrally. In addition,
14 is an absolute value mark provided at a position corresponding to the temperature sensor 132 across the scale 12.

The slit-shaped scale 12 is formed by depositing a chromium film in a band shape along the longitudinal direction of the surface of the scale base material 11 and forming it into a slit shape by an etching method. In addition, each temperature sensor 131.13z, 133 is formed by vapor-depositing a rectangular platinum resistor whose resistance value changes with temperature changes at a predetermined position on the surface of the scale base material 11, and depositing this at the same time as the scale 12 is formed. The shape is marked with lines in the shape of Fig. 3.

Each temperature sensor 13. , 13t, 13,1, as shown in FIG.
a temperature-sensing section 21 meandering in a direction perpendicular to the longitudinal direction of the
The temperature sensing portion 21 is formed in a shape having rectangular terminal portions 22A and 22B at both ends thereof, respectively.

The temperature sensing portion 21 is formed in such a size that the resistance value becomes a preset value. Here, the thickness t is approximately 1 μm1
The width W is about 50 μm, the total length ff1 (length when stretched into one length) is about 4.7 cm, and the resistance value is about 100Ω.

Figure 4 shows the processing circuit of this length measurement system.
Each of the temperature sensors 131.13. , 13. Three bridge circuits 31+, 31g, and 3 detect the resistance values of
1s and these bridge circuits 31, . 31. ．． 31
3, an A/D converter 33 that converts the signal from the multiplexer 32 into a digital signal, and a system bus 34 connected to the A/D converter 33.
and a CPU 35 as a correction means connected via.

The CPU 35 takes in data from the A/D converter 33, that is, data regarding the temperature of each part of the scale base material 11 detected by each temperature sensor 13+, 13z, 133, through the system bus 34, and calculates the average value of this data. Then, a correction coefficient corresponding to the detected temperature is read out from a correction table (not shown) storing correction coefficients corresponding to each temperature, and this correction coefficient is calculated from the value of the counter 37, that is, the value detected by the displacement detector 9. The measured value is corrected by multiplying the relative movement displacement Wk (displacement amount from the absolute value mark 14) obtained by predetermined processing of the signal, and the result is displayed on the display 36 via the system bus 34.

Regarding the correction table, calculate the error between the measured value (value obtained from the counter 37) and the true displacement amount when the temperature of the scale base material 11 is changed, calculate the correction coefficient to cancel this error, and calculate the correction coefficient. A correction coefficient is determined and stored for each temperature.

Therefore, the value updated by the counter 37, that is, the amount of relative movement displacement that changes successively due to relative movement, is corrected based on the actual temperature of the scale base material 11 at each point in time, so the measurement Highly accurate and reliable measurement values can always be obtained without the need for

Therefore, according to this embodiment, since the temperature of the scale base material 11 itself is directly detected and the measured value is automatically corrected based on this temperature, the amount of relative movement displacement that changes sequentially due to relative movement is Since the temperature is automatically corrected based on the actual temperature of the scale base material 11 at each point in time, highly accurate and reliable measured values can be easily obtained without performing any calculations. Therefore, even if the installation environment has large temperature changes, or even if the scale base material 11 undergoes large temperature changes due to sliding resistance heat due to relative movement of two members, highly accurate measurements can always be achieved. can do.

Moreover, when correcting the measured value, each temperature sensor 13
+, scale base material 11 detected at 13t, 13s
All you have to do is find the average value of the data regarding the temperature of each part, read out the correction coefficient corresponding to the detected temperature from the correction table that stores correction coefficients corresponding to each temperature, and multiply the measured value by this correction coefficient. , a simple calculation is enough.

In addition, since temperature sensors 131, 13□, and 133 are provided at predetermined intervals in the longitudinal direction of the scale base material 11, the sliding guide surfaces between the main body case 1 and the sliding body 2 and the stationary body 10
Even if the sliding guide surface between 0 and the movable body 200 is not well finished and there are some areas where the sliding resistance is large,
Only the temperature sensor closest to it will have a higher temperature than the other temperature sensors, so these temperature sensors 131, 13□
It has the advantage of being able to determine the quality of the sliding guide surface from the temperature distribution of , 13 degrees.

In addition, in implementation, the method of correcting the measured value based on the detected temperature is not limited to the method described in the above embodiment.For example, each temperature sensor 13+, 131
．． The measured value may be corrected by calculation based on the detected temperature of the scale base material 11 and the linear expansion coefficient of the scale base material 11 obtained by 133.

In addition, for these corrections, three temperature sensors 13
+, 11.13. Rather than using the average value of the temperatures obtained in each case as the detected temperature, the detected temperature is determined by the temperature of the one closest to the sliding body 2 depending on the relative position of the two relatively moving members, that is, the position of the sliding body 2 with respect to the main body case 1. If the measured value is corrected using the temperature data from the sensors t3+, iaz, and i3 as the detected temperature, more accurate measurement is possible.
Even if the temperature in the longitudinal direction differs because the movable body 2 constantly slides back and forth only in a part of the slidable range, the temperature sensor 13. ．． 13
If you select □, 133, you can always perform highly accurate measurements.

Further, in the above embodiment, three temperature sensors 131.13t and 13s were provided in the longitudinal direction of the scale base material 11, but the number of temperature sensors may be at least one or more. Further, the structure of the temperature sensor is not limited to the platinum resistor described in the above embodiments, but may be any structure as long as it can detect temperature changes.

For example, a thermistor or the like may be used.

In addition, although the above embodiment is a case of a light transmission type displacement detection type, any displacement detection type may be used. For example, a reflective type using one main scale and two index scales may be used. Similarly, the scale 12 is
Although the slits constitute an optical grating, the present invention can also be applied to capacitive or electromagnetic slits.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide a length measurement system that automatically compensates for measurement errors due to temperature changes and enables highly accurate measurement.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an embodiment of the present invention, Fig. 2 is a perspective view showing a reference scale, Fig. 3 is an enlarged front view showing a temperature sensor provided on the reference scale, and Fig. 4 is a processing circuit. FIG. 5 is a cross-sectional view showing a conventional displacement detection device. 9...Detector, 10...Reference scale, 11...
Scale base material, 12...scale, 131.13z, 1
3s...Temperature sensor, 31+, 31g, 3 Is
... Bridge circuit, 32 ... Multiplexer, 33
...A/D converter, 35...CPU, 37...Counter.

Claims (4)

[Claims] (1) A reference scale with graduations for displacement detection formed along the longitudinal direction of a linear scale base, a detector for reading the graduations of this reference scale, and a reference scale detected from the signal of this detector. In a length measurement system that includes a counter that measures the amount of displacement relative to the scale base material, the surface of the scale base material on which the scale is formed is located close to the scale scale base material due to expansion and contraction of the scale base material. 1. A length measurement system, characterized in that a temperature sensor for detecting temperature is integrally provided, and a correction means for correcting the value of the counter based on temperature data from the temperature sensor. (2) The length measuring system according to claim 1, wherein a plurality of the temperature sensors are provided at predetermined intervals in the longitudinal direction of the scale base. (3) In claim 2, the correction means includes a plurality of bridge circuits including each of the temperature sensors, a multiplexer for transferring signals from each of the bridge circuits, and a plurality of bridge circuits configured to include each of the temperature sensors; A length measurement system comprising: an A/D converter that converts the signal into a digital signal; and a calculation means that corrects the value of the counter based on the data from the A/D converter. . (4) In claim 3, the calculation means includes a table storing correction coefficients corresponding to each temperature, and from this table a correction coefficient corresponding to the temperature obtained by the temperature sensor. A length measurement system characterized in that the length measurement system is configured to read out the value of the counter and multiply the value of the counter by the correction coefficient to correct the value of the counter.