JP2853500B2 - Temperature compensation device for coordinate measuring machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature compensating device for a coordinate measuring machine, and more particularly to a temperature compensating device for a coordinate measuring machine for maintaining measurement accuracy in response to changes in ambient temperature.

[0002]

2. Description of the Related Art When the ambient temperature of a three-dimensional coordinate measuring machine changes so much that it cannot be ignored in maintaining the measurement accuracy, it is necessary to perform temperature correction in order to maintain the measurement accuracy. The temperature correction is performed in the following procedure. First, the temperature of a part, such as a scale member or a mechanism member of a three-dimensional coordinate measuring machine, which is considered to have an influence on the measurement accuracy, is periodically measured by a thermometer. Further, the temperature of the work to be measured is also measured. Next, from the measured temperature obtained by the measurement and the thermal expansion coefficient of the scale member of the three-dimensional coordinate measuring machine, the mechanism member, etc.,
The expansion / contraction ratios of these members are obtained by calculation, and the deformation ratio of each member is further obtained by calculation, and the temperature of the three-dimensional coordinate measuring machine is corrected. Next, the work shape and the like are measured by a three-dimensional coordinate measuring machine, and at the same time, the work temperature is corrected. Thereby, the measurement accuracy of the work shape and the like measured by the three-dimensional coordinate measuring machine is maintained.

[0003] Therefore, it is important to accurately measure the ambient temperature and the temperature of each member and to calculate a complicated temperature correction coefficient in performing temperature correction. Interface to send to computer,
Then, a thermometer system composed of software for calculating a complicated temperature correction coefficient is used.

[0004]

As described above, since the temperature compensation system includes the thermometer and the interface of the computer, there is a problem that the temperature compensation system has a complicated structure and is expensive. The present invention has been made in view of such circumstances, and has as its object to provide an inexpensive temperature measuring device for a coordinate measuring machine having a simple structure.

[0005]

In order to achieve the above object, the present invention provides a coordinate measuring machine for measuring the shape and the like of a workpiece with a probe movably provided in a coordinate axis direction, wherein a coefficient of thermal expansion is substantially reduced. A temperature correction unit provided on a reference surface of a base in parallel with a first correction member formed of a zero-value member and a second correction member formed of a thermally expandable member; The reference length of the correction member and the coefficient of thermal expansion of the second correction member are stored in advance, and the temperature at the time of measurement is determined from the previously stored data and the measurement length of the first and second correction members measured by the probe. A control unit for calculating a correction coefficient, wherein the temperature correction unit is disposed within a measurement range of the coordinate measuring machine, and the first and second correction members of the temperature correction unit are substantially aligned with the coordinate axes of the coordinate measuring machine. Parallel positioning And it features.

[0006]

According to the present invention, the temperature compensating unit includes first and second compensating members and a base. The first correction member is formed of a member having a substantially zero coefficient of thermal expansion, and the second correction member is formed of a member that can be thermally expanded. The first and second correction members are provided on a reference plane of the base in parallel with each other. The temperature correction unit is disposed within the measurement range of the coordinate measuring machine, and the first and second correction members of the temperature correction unit are positioned parallel to the coordinate axis of the coordinate measuring machine. Further, the reference lengths of the first and second correction members at the reference temperature and the coefficient of thermal expansion of the second correction member at the reference temperature are stored in advance. Further, the control unit calculates a temperature correction coefficient at the time of measurement from the data stored in advance and the measured length of the first and second correction members measured by the probe.

[0007]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a coordinate measuring machine according to the present invention; FIG. 1 is a perspective view of a three-dimensional coordinate measuring machine in which a temperature correcting device for a coordinate measuring machine according to the present invention is used. As shown in the figure, a pair of Y carriages 14 are provided on the main body 12 of the three-dimensional coordinate measuring machine 10 so as to be movable in the Y-axis direction. An X beam 16 is fixed to the upper ends of the pair of Y carriages 14, and an X carriage 18 is provided on the X beam 16 so as to be movable along the X beam 16 (in the X-axis direction). In addition, a Z carriage 20 is provided on the X carriage 18 so as to be movable in the Z axis direction. A probe 22 is provided at the lower end of the Z carriage 20. Therefore, since the probe 22 can move in three X, Y, and Z axes,
The shape and the like of the work can be measured by the probe 22.

FIG. 2 shows a temperature correcting device 24 of the coordinate measuring machine according to the present invention. As shown in FIG.
The end of a cylindrical body 28 is attached to the center of 6.
The cylindrical body 28 is a member having a thermal expansion coefficient of substantially zero, for example, “ZERODUR” (trade name) made of glass ceramic,
It is formed with. A cylindrical body 30 is disposed coaxially around the cylindrical body 28, and an end of the cylindrical body 30 is attached to the base 26. The cylindrical body 30 is formed of an aluminum material or the like whose thermal expansion coefficient is known. This cylinder 30
Accommodates the cylindrical body 28, so that the cylindrical body 28
0 protects against damage. The temperature compensating device 24 of the coordinate measuring machine is disposed within the measurement range of the coordinate measuring machine, and the cylinder 28 and the cylinder 30 are positioned substantially parallel to the axes of the coordinate measuring machine. Therefore, when the coordinate measuring machine is a three-dimensional coordinate measuring machine, three temperature correcting devices 24 of the coordinate measuring machine are required.

The operation when the temperature compensating device for a coordinate measuring machine according to the present invention configured as described above is used in a three-dimensional coordinate measuring machine will be described. The three temperature correction devices 24 are arranged within the measurement range of the three-dimensional coordinate measuring machine 10, and each of the cylindrical body 28 and the cylindrical body 30 are arranged in three axes of the X, Y, and Z axes of the three-dimensional coordinate measuring machine 10. Are positioned substantially parallel to the direction (see FIG. 1). In this case, the lengths of the cylindrical body 28 and the cylindrical body 30 of the three temperature correction devices 24 are measured in advance at a temperature of 20 ° (hereinafter, referred to as a reference temperature). That is, the length of each of the cylindrical body 28 and the cylindrical body 30 is
6 with the lengths up to the free ends 28A and 30A of the cylindrical body 28 and the cylindrical body 30, respectively. Then, the determined length L _{1 of} the cylindrical body 28 and the cylindrical body 30,
L ₂ and the reference length and setting, and stores the control unit 36 of the three-dimensional coordinate measuring machine 10 (see FIG. 1).

When the ambient temperature of the coordinate measuring machine 10 changes in step 100, the probe 22 of the coordinate measuring machine 10 causes the probe 28 of the cylindrical body 28 and the cylindrical body 30 arranged substantially parallel to the X axis. Each length L ₁ ′,
Measure L ₂ '. Next, in step 102, the measured lengths L ₁ ′ and L ₂ ′ are input to the control unit 36 of the three-dimensional coordinate measuring machine 10, and the control unit 36 calculates the length L ₁ ′ from the measured length L ₁ ′ of the cylinder 28. The cylindrical body 30 is calculated from the value D ₁ obtained by subtracting the reference length L ₁ of the cylindrical body 28 and the measured length L ₂ ′ of the cylindrical body 30.
Calculating a reference value D ₂ by subtracting the length L _2.

Further, in step 104, the temperature correction coefficients α _X , α _Y and α _Z of the X, Y and Z axes of the three-dimensional coordinate measuring machine 10 are calculated by the following equations (1), (2) and (3). Based on _{α X = D 1X / L 1X} ... (1) α Y = D 1Y / L 1Y ... (2) α Z = D 1Z / L 1Z ... (3) Next, the control unit 36 the following equation at step 106 (4 )
Calculating the temperature T _X by the following approximate expression based on.

[0012] Here, ρ is the coefficient of thermal expansion of the cylinder 30, and the coefficient of thermal expansion ρ of the cylinder 30 is stored in the control unit 36 of the three-dimensional coordinate measuring machine 10 in advance.

Similarly, the temperature T in the Y-axis direction and the Z-axis direction
Calculate _Y and T _Z. Then, in step 108, the temperature T of the cylinder 30 is calculated based on the following equation (5), and the calculated temperature T of the cylinder 30 is stored in the control unit 36. Then, the obtained temperature correction coefficients α _X , α _Y , and α _Z of the X, Y, and Z axes are determined by the control unit 36 of the coordinate measuring machine 10.
Is stored. The control unit 36 corrects the temperature of the measuring device during the measurement of the workpiece based on the stored temperature correction coefficients α _X , α _Y , and α _Z of the measuring device.

Further, since the thermal expansion coefficient of the work is stored in the control unit 36 of the three-dimensional coordinate measuring machine 10 in step 110, the control unit 36 sets the temperature T of the cylinder 30 as the temperature of the work. The temperature correction coefficient of the work can be obtained. Therefore, the temperature of the measured value is corrected based on the temperature correction coefficient of the measuring device and the work obtained by the measurement of the temperature correction device. The steps 100 to 110 are automatically performed based on a program in the control unit 36.

In the above-described embodiment, only the case where the lengths L ₁ and L ₂ of the cylindrical body 28 and the cylindrical body 30 set as the reference lengths are stored in the control unit 36 of the three-dimensional coordinate measuring machine 10 has been described. However, the present invention is not limited thereto, and the reference lengths L ₁ and L ₂ may be stored in the control unit 36 and stamped on the cylinder 28 and the like. Further, in the above-described embodiment, the case where the temperature is corrected when the ambient temperature of the coordinate measuring machine 10 changes has been described. However, the present invention is not limited to this, and the temperature correction is performed in a regular calibration cycle regardless of the change in the ambient temperature. You may.

In the above embodiment, the cylindrical body 28 is formed of a member having a coefficient of thermal expansion of substantially zero, and the cylindrical body 30 is formed of an aluminum material having a known coefficient of thermal expansion. The cylindrical body 28 is housed in the cylindrical body 30 to prevent the cylindrical body 28 from being damaged, but the invention is not limited to this. The cylindrical body 30 is formed in a cylindrical body or the like and is parallel to the cylindrical body 28. May be attached to the base 26.

[0017]

As described above, according to the temperature compensating device of the coordinate measuring machine according to the present invention, the temperature compensating unit includes the first and second compensating members and the base. The first correction member is formed of a member having a substantially zero coefficient of thermal expansion, and the second correction member is formed of a member that can be thermally expanded. 1st, 2nd
Each end of the correction member is provided on a reference plane of the base in parallel with each other. The temperature correction unit is disposed within the measurement range of the coordinate measuring machine, and the first and second correction members of the temperature correction unit are positioned substantially parallel to the coordinate axis of the coordinate measuring machine. Further, the reference lengths of the first and second correction members at the reference temperature and the coefficient of thermal expansion of the second correction member at the reference temperature are stored in advance. Further, the control unit obtains a three-dimensional coordinate measuring machine at the time of measurement and a temperature correction coefficient of the workpiece from the previously stored data and the measured length of the first and second correction members measured by the probe. And temperature correction of the work.

Therefore, since the temperature correction coefficient can be obtained only by providing the temperature correction unit in the coordinate measuring machine and measuring the length thereof, the structure can be simplified and the cost can be reduced. Further, it is possible to directly obtain a temperature correction coefficient which changes in a complicated manner under the influence of temperature and is difficult to obtain analytically.

[Brief description of the drawings]

FIG. 1 is a perspective view of a three-dimensional coordinate measuring machine using a temperature correcting device for a coordinate measuring machine according to the present invention according to the present invention.

FIG. 2 is an enlarged view of a main part of a temperature correction device of the coordinate measuring machine according to the present invention.

FIG. 3 is a flowchart for explaining the operation of the temperature correction device of the coordinate measuring machine according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... 3D coordinate measuring machine 22 ... Probe 24 ... Temperature correction unit 26 ... Base 28 ... Cylindrical body 30 ... Cylindrical body 36 ... Control part

Claims (3)

(57) [Claims] 1. A coordinate measuring machine for measuring a shape and the like of a workpiece by a probe movably provided in a coordinate axis direction, wherein a coefficient of thermal expansion provided at a position measurable by the probe is substantially zero. First correction member formed of a member
A second correction member formed of a thermally expandable member; storage means for storing a reference length of the first and second correction members at a reference temperature and a thermal expansion coefficient of the second correction member ; The reference length of the first correction member stored in the storage unit
And the measurement length of the first correction member measured by the probe
From the above, the temperature correction unit at the measurement temperature of the coordinate measuring machine
A first calculating means for calculating the number, and the first and second correction members stored in the storage means.
A reference length and a coefficient of thermal expansion of the second correction member;
Based on the measured lengths of the first and second correction members
Calculating means for calculating the ambient temperature of the coordinate measuring machine
And the measured actual values such as the shape of the work,
The temperature correction coefficient, the ambient temperature,
Based on the coefficient of thermal expansion of the work stored in the storage means,
And a correcting means for correcting the temperature. 2. The coordinate measuring machine according to claim 1, wherein the first correction member is a coordinate measuring machine.
Coordinate so that it is almost parallel to each coordinate axis.
The first computing means is disposed on a base of the target measuring machine,
The reference length of the first correction member stored in the storage unit
And each coordinate of the first correction member measured by the probe
From the measured length in the axial direction, the coordinate measuring machine is used for each coordinate axis.
Calculates the temperature correction coefficient at the measured temperature
The temperature compensating device for a coordinate measuring machine according to claim 1. Wherein said first and second correction member is formed into a cylindrical body and cylindrical body, respectively, the temperature of the circular column body coordinate measuring machine according to claim 1 or 2, characterized in that housed in the tubular body inside Correction device.