CN103913479A - Device for detecting thermal expansion coefficient of grating ruler - Google Patents

Abstract

The invention relates to a device for detecting a thermal expansion coefficient of a grating ruler and solves the problem of thermal expansion in an existing grating measurement technology. The device comprises a constant-temperature device, a length measurement device, a grating ruler fixing frame and a signal processing circuit, wherein the constant-temperature device comprises a temperature measurement element and a temperature control element. The length measurement device is used for measuring a position value subjected to temperature correction of a reading head of the grating ruler; the grating ruler fixing frame is used for fixing a grating ruler to be detected; the grating ruler to be detected is a grating ruler of a position reading which is not subjected to temperature compensation; the signal processing circuit is used for processing length signals from the grating ruler and the length measurement device and a temperature signal from a temperature sensor, so as to obtain the thermal expansion coefficient of the grating ruler to be detected.

Description

A device for detecting thermal expansion coefficient of grating ruler

technical field

The invention relates to a device for detecting the thermal expansion coefficient of the grating ruler, which is used for accurately measuring the thermal expansion coefficient of the grating ruler.

Background technique

Grating ruler (also known as grating line displacement sensor) is a position readout device commonly used in modern displacement measurement systems. It is divided into open type and closed type in terms of structure. It includes steel tape grating ruler and glass grating ruler in terms of material. The upper part includes incremental grating rulers and absolute grating rulers. These types of grating rulers are widely used in the machine tool industry and other processing, manipulation and testing systems. Due to the complex and diverse processing environments and large temperature differences, local temperature fluctuations are generated during processing. Inhomogeneity, etc., all have thermal expansion effects. If the thermal expansion is not compensated, the machining accuracy will be greatly affected.

To compensate for thermal expansion, the thermal expansion coefficient of the grating scale must first be known, and the reading of the grating scale can be corrected through the thermal expansion coefficient.

The typical measurement of the coefficient of thermal expansion includes measuring the coefficient of linear expansion of the metal with optical levers, and now it is widely used to measure the coefficient of thermal expansion by interferometry in the thermostat. However, these measurement methods are mainly aimed at specific materials, and often for one substance, while the grating scale is often a composite of multiple substances. For example, the closed glass grating scale is a composite of glass pasted on the metal scale shell. body, its thermal expansion coefficient is no longer the thermal expansion coefficient of a single chemical composition, but the result of the interaction of multiple materials. Secondly, the overall shape of the grating scale is irregular, and the glass main scale is inside the scale shell. To detect the glass in the grating scale It is difficult or even not applicable to use the usual method to determine the coefficient of thermal expansion. If the characteristics and readings of the grating scale itself can be used to detect the thermal expansion coefficient combined with the laser interferometer, then not only the structure is simple, the operation is convenient, and the result is reliable.

Contents of the invention

In order to solve the problem of thermal expansion in the existing grating measurement technology and provide a reliable thermal expansion compensation coefficient, the invention provides a device for detecting the thermal expansion coefficient of the grating scale based on the grating scale product.

A device for detecting the thermal expansion coefficient of a grating ruler, including a closed box, the box is used for a constant temperature device for constant air temperature in the box, and a standard length measuring device for measuring the position of the reading head of the grating ruler to be measured, used for A second temperature measuring element and a signal processing device for measuring the temperature of the main scale material of the grating scale to be measured; its feature is that the point with the same reading of the grating scale to be measured is positioned at the same point to be measured at a different temperature on the main scale; the standard length measuring device Measure the distance between different points to be measured on the grating ruler to be measured, and the signal processing device calculates according to the distance between the measurement points measured by the standard length measuring device at different temperature points and the variation of the distance at different temperatures Thermal expansion coefficient of the scale segment between the two measuring points.

Beneficial effects of the present invention: the structure and measurement method of the device according to the present invention are specially aimed at the characteristics of grating scale composite materials, and utilize the positioning function of the grating scale reading itself to effectively solve the key problem of positioning both ends in the thermal expansion measurement technology. Cooperate with the standard length measuring device and use multi-point measurement to not only measure the thermal expansion coefficient of the grating ruler, but also obtain the change of the thermal expansion coefficient on the grating ruler.

Description of drawings

Fig. 1 is a structural representation of a device for detecting the thermal expansion coefficient of a grating ruler according to the present invention;

Fig. 2 is a schematic diagram of signal connections in a device for detecting the coefficient of thermal expansion of a grating ruler according to the present invention;

Fig. 3 is a block diagram of the operation flow of a device for detecting the thermal expansion coefficient of a grating ruler according to the present invention.

Detailed ways

Specific Embodiments 1. This embodiment is described in conjunction with FIGS. 1 to 3. A device for detecting the coefficient of thermal expansion of a grating ruler includes a detection device box 1 as a closed box for the entire device; a constant temperature device 2, Used for constant detection device box 1 internal air temperature, the constant temperature device further includes a first temperature measuring element 2-2, used to measure the air temperature inside the measuring box, a temperature control element 2-1, according to the first The reading of the temperature measuring element is used to heat or cool the detection device box; a standard length measuring device 3 is used to measure the position of the reading head of the grating ruler 5 to be tested; a grating ruler fixing device 6 is used to fix the grating ruler 5 to be detected ; fixed on the workbench 7; a second temperature measuring element, used to measure the material temperature of the main ruler of the grating ruler to be measured; a signal processing device, used to process the grating ruler to be detected Measure the signal of the element and obtain the value of the thermal expansion coefficient; locate the point with the same reading on the main scale 5-1 of the grating scale to be tested at the same point to be measured at different temperatures, and the standard length measuring device 3 measures the grating scale to be tested 5, the distance between different points to be measured, the second temperature measuring element 4 measures the material temperature of the main ruler 5-1 of the grating ruler to be measured, and the signal processing device 9 is based on the measurement measured by the standard length measuring device 3 at different temperature points The distance between the points and the change in this distance at different temperatures calculates the coefficient of thermal expansion of the grating segment between the two measurement points.

The grating scale to be tested in this embodiment is an absolute grating scale, or an incremental grating scale with reference marks. The standard length measuring device 3 may be a laser interferometer or a grating ruler with a temperature compensation function. The grating scale to be tested can be reflective or transmissive.

In this embodiment, in the vicinity of the same temperature point, for two points to be measured of a grating ruler section to be detected, two different temperatures, respectively measure the distance between the two temperature values and the two points to be measured , as a set of measurement data, and calculate the corresponding thermal expansion coefficient, repeat this process n times (n is greater than or equal to 2), and take the arithmetic mean value of the thermal expansion coefficient obtained n times as the thermal expansion coefficient between the two points to be measured. Near the same temperature, set m points to be measured (m is greater than or equal to 3) on the grating scale to be tested, and measure the thermal expansion coefficient of the adjacent points to be measured, the thermal expansion coefficient of different sections at this temperature.

The present embodiment is described in conjunction with Fig. 2, and described signal processing device 9 is used for processing the signal from grating ruler to be measured, standard side length device 3, the second temperature measuring element 4 and obtains thermal expansion coefficient value; Read grating ruler to be measured The same point locates the same point to be measured at different temperatures on the main scale 5 of the grating ruler to be measured. In the actual operation of this embodiment, two different readings whose reading difference is far smaller than the expansion can be approximated as the same point, such as , for aluminum, the coefficient of expansion is about 2.3×10 ^-5 ℃ ^-1 , and for a grating measuring 1m, the expansion at 1 ℃ ^-1 is 23 microns, and the judgment standard can be set to be less than or equal to 0.1 microns, namely The points whose absolute value difference is less than or equal to 0.1 micron are approximated as the same point. The standard length measuring device 3 measures the distance between two different points to be measured on the grating scale to be measured 5, the second temperature measuring element 4 measures the material temperature of the glass main ruler in the grating scale to be measured 5, and the signal processing device 9 is based on the two At different temperature points, the distance between the measurement points measured by the standard length measuring device 3 and the variation of the distance between the two different temperature points are used to calculate the thermal expansion coefficient of the grating segment between the two measurement points. The operation process is combined with Figure 3,

In this embodiment, it is assumed that in the first measurement, the temperature of the entire measurement system is kept constant to 20 degrees Celsius, and the temperature measured by the second temperature measuring element 4 is T1 (the measured temperature value is very close to 20 degrees Celsius), in the grating scale segment to be measured , the readings at both ends of the section measured by the standard measuring device 3 are S1_1 and S1_2 respectively, and the readings at both ends of the section measured by the grating ruler 5 to be tested are D1_1 and D1_2 respectively. Change the temperature. In this embodiment, the relative value of the temperature change should be greater than or equal to 2 degrees Celsius. For example, the temperature rises by about 5 degrees Celsius. At this time, the temperature measured by the second temperature measuring element 4 is T2. In the section of the grating scale to be measured, the standard The readings at both ends of the section measured by the measuring device 3 are S2_1 and S2_2 respectively, and the readings at the two ends of the section measured by the grating ruler 5 to be tested are D2_1 (with a difference of less than 0.1 microns from D1_1), D2_2 (with a difference of less than 0.1 microns from D2_1 microns). Then for this measurement, the following calculation will be realized in the signal processing device 9, and the coefficient of thermal expansion lt of the grating ruler segment is obtained as:

$\mathrm{<span\; class="notranslate">\; lt</span>}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; [</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In this embodiment, the grating ruler 5 to be tested has an absolute measurement function, that is, the reading of each point on the grating ruler to be tested is unique, and it can be an absolute grating ruler, and the current absolute position reading can be obtained at any time. Or an incremental grating ruler with a reference position, the absolute position information of the current position can be obtained during the reading process. The thermal expansion coefficient measured in this way can correspond to a certain section of the grating scale.

The present invention is not limited to the above embodiments. If the above basic principles are used, the standard length measuring device can be a high-precision grating ruler with temperature compensation function, which can greatly reduce the cost of the device and make it easier to install. The grating scale to be tested can be not only a transmissive grating scale, but also a reflective grating scale, which greatly improves the application range of the device. Near the same temperature point, for the points to be measured at both ends of a grating scale section to be detected, two different temperatures, respectively measure the two temperature values and the distance between the two points to be measured, as a set of measurement data , and calculate the corresponding coefficient of thermal expansion, repeat this process for a total of n times (n is greater than or equal to 2), and take the arithmetic mean value of the coefficient of thermal expansion obtained n times as the coefficient of thermal expansion between the two points to be measured, so that the measured thermal expansion coefficient Has higher stability. Near the same temperature, set m points to be measured (m is greater than or equal to 3) on the grating scale to be tested, and measure the thermal expansion coefficient of the adjacent points to be measured. The thermal expansion coefficients of different sections at this temperature can not only get the The different expansion coefficients of the grating scale segments compare the uniformity of the expansion coefficient of the grating scale, and at the same time enable the grating scale to obtain more accurate temperature compensation.

Claims (8)

1. the device for detection of grating scale thermal expansivity, comprise enclosed housing (1), described case is for the thermostat (2) of the interior air themperature of constant casing (1), for measuring the standard measuring motion (3) of grating ruler reading head to be measured position, for measuring the second temperature-measuring element (4) and the signal processing apparatus of main scale (5-1) material temperature of grating scale to be measured; It is characterized in that, by the same tested point of the upper different temperatures of point location main scale (5-1) identical grating scale reading to be measured; Standard measuring motion is measured the distance between different tested points on grating scale to be measured, described signal processing apparatus (9) is according on different temperature spots, and the distance between the measurement point that standard measuring motion (3) is measured and the variable quantity of this distance under different temperatures calculate the thermal expansivity of grating scale section between these two measurement points.

2. a kind of device for detection of grating scale thermal expansivity according to claim 1, it is characterized in that, described thermostat (2) comprises the first temperature-measuring element (2-2), for measuring the air themperature of this measurement box house, temperature control component (2-1), according to the reading of the first temperature-measuring element (2-2), casing (1) is heated or freezed.

3. a kind of device for detection of grating scale thermal expansivity according to claim 1, is characterized in that, also comprises grating scale stationary installation (6), for fixing grating scale to be detected.

4. a kind of device for detection of grating scale thermal expansivity according to claim 1, is characterized in that, grating scale to be measured is absolute grating scale, or is the increment type grating scale with reference marker.

5. a kind of device for detection of grating scale thermal expansivity according to claim 1, is characterized in that, described standard measuring motion (3) is for having laser interferometer or the grating scale of temperature compensation function.

6. a kind of device for detection of grating scale thermal expansivity according to claim 1, is characterized in that, described grating scale to be detected (5) is reflective or transmission-type.

7. a kind of device for detection of grating scale thermal expansivity according to claim 1, it is characterized in that, near same temperature point, for the tested point of two of grating scale to be detected (5), with two different temperatures, measure respectively the distance between two temperature values and the tested point at two ends, as one group of measurement data, and calculate corresponding thermal expansivity, duplicate measurements n time, n is more than or equal to 2, the thermal expansivity using the arithmetic mean of the thermal expansivity obtaining for n time as between these two tested points.

8. a kind of device for detection of grating scale thermal expansivity according to claim 1, is characterized in that, near same temperature, m tested point is set on grating scale to be detected (5), and m is more than or equal to 3; Adjacent tested point is measured to thermal expansivity, obtain the thermal expansivity of different sections at this temperature.