Non-contact measuring device and method for cylindricity of precision workpiece

Abstract

The present invention belongs to the field of cylindricity measurement, and in particular, relates to a non-contact cylindricity measurement device and method for precision workpieces, which solves the problems that the existing cylindricity measurement methods for precision workpieces cause damage to the workpiece itself, leave tiny scratches on the surface, and have large errors. The device includes a turntable and two groups of cylindrical autocollimators arranged on the side of the turntable; the turntable is used to fix the cylindrical workpiece to be measured, and the cylindrical workpiece to be measured is coaxial with the turntable; each group of cylindrical autocollimators includes a line light source, a spectroscopic element, a collimating cylindrical mirror and a standard cylindrical lens; the emitted light of the line light source passes through the spectroscopic element, the collimating cylindrical mirror, and the standard cylindrical lens in turn to become a converging line beam, and the focal line of the converging line beam is located at the rotation axis position of the turntable; the converging line beam is reflected by the surface of the cylindrical workpiece to be measured, returns along the original path, and is received by the light sensor through the spectroscopic element.

Description

Technical Field

[0001] The invention belongs to the field of cylindricity measurement, and in particular relates to a non-contact cylindricity measurement device and method for a precision workpiece. Background Art

[0002] In the field of mechanical processing, the cylindricity measurement of high-precision workpieces is one of the important contents of the design requirements. If the cylindricity of precision workpieces does not meet the requirements, it will lead to increased movement resistance, thereby increasing the wear of the workpiece and reducing its life. Therefore, it is necessary to measure the cylindricity of precision workpieces to ensure that they can meet the design requirements.

[0003] At present, the methods for measuring the cylindricity of precision workpieces mainly include the two-point method, the three-point method, the three-coordinate measurement method, etc. The principle is to use a stylus or a probe to measure multiple position points on the workpiece surface, and calculate the cylindricity information by data fitting. The above measurement methods have the following disadvantages:

[0004] 1. Use a stylus or probe to contact and measure the surface of a precision workpiece to measure the cylindricity. The stylus or probe may damage the workpiece itself, leaving tiny scratches on the surface.

[0005] 2. The precision workpiece is measured at several discrete points instead of continuously, which leads to large errors. Summary of the invention

[0006] In order to solve the problems that the existing method for measuring the cylindricity of precision workpieces causes damage to the workpiece itself, leaves tiny scratches on the surface, and has large errors, the present invention provides a non-contact measuring device and method for the cylindricity of precision workpieces.

[0007] To achieve the above purpose, the technical solution provided by the present invention is:

[0008] A non-contact measuring device for the cylindricity of a precision workpiece is special in that it comprises a turntable and two groups of cylindrical autocollimators arranged on the side of the turntable; the turntable is used to fix the cylindrical workpiece to be measured, and the cylindrical workpiece to be measured is coaxial with the turntable; each group of the cylindrical autocollimators comprises a line light source, a beam splitter, a collimating cylindrical mirror and a standard cylindrical lens; the emitted light of the line light source passes through the beam splitter, the collimating cylindrical mirror and the standard cylindrical lens in sequence to become a converging line light beam, and the focal line of the converging line light beam is located at the rotating axis position of the turntable; the converging line light beam is reflected by the surface of the cylindrical workpiece to be measured, returns along the original path, and is received by a light sensor through the beam splitter.

[0009] Furthermore, the generatrix of the cylindrical surface of the standard cylindrical mirror is parallel to the generatrix of the cylindrical surface of the collimating cylindrical mirror;

[0010] The line light source is located in the plane formed by the generatrix of the standard cylindrical lens and the collimating cylindrical lens;

[0011] The line light source is parallel to the pixel row or column of the photosensitive device and parallel to the generatrix of the cylindrical surface of the collimating cylindrical lens.

[0012] Furthermore, the sensitive surface of the photosensor is located on the focal plane of the collimating cylindrical mirror.

[0013] Furthermore, the two groups of cylindrical autocollimators are symmetrically arranged on both sides of the rotating axis of the turntable.

[0014] Furthermore, the F number of the standard cylindrical lens is 10-25, and the selection principle of the standard lens is that the size of the convergent light formed by the standard lens on the cylindrical workpiece perpendicular to the generatrix does not exceed 0.1 mm.

[0015] Furthermore, the photosensor is a CCD or CMOS array type photosensor.

[0016] Furthermore, the light splitting element is a light splitting prism with a light splitting ratio of 1:1 and an angle of 45° with the optical axis.

[0017] At the same time, the present invention provides a measurement method based on the non-contact measuring device for cylindricity of the precision workpiece, which is special in that it includes the following steps:

[0018] 1) Start the line light source, adjust the two sets of cylindrical autocollimators on the side of the turntable of the non-contact measuring device for the cylindricity of precision workpieces, so that the light beam emitted by the line light source converges after passing through the beam splitter, collimating cylindrical mirror and standard cylindrical lens, so that the focal line of the converged line light beam is located at the rotation axis position of the turntable;

[0019] 2) The cylindrical workpiece to be measured is coaxially mounted on the turntable of the non-contact measuring device for the cylindricity of the precision workpiece;

[0020] 3) The outgoing light of the line light source passes through the surface of the cylindrical workpiece to be measured, and the light beam returns along the original path through the beam splitter and is received by the light sensor;

[0021] 4) The turntable drives the cylindrical workpiece to be measured to rotate one circle, and the position of the focal line spot of the cylindrical workpiece to be measured is collected by the light sensor;

[0022] 5) The photosensor collects the position of the focal line spot on the surface of the cylindrical workpiece being measured, and the cylindricality information of the cylindrical workpiece being measured can be calculated through image processing.

[0023] Furthermore, in step 1), two sets of cylindrical autocollimators are arranged symmetrically about the rotation axis of the turntable.

[0024] Compared with the prior art, the advantages of the present invention are:

[0025] 1. The present invention is a non-contact measurement. The measurement of the cylindricity of the cylindrical workpiece to be measured is completely non-contact, avoiding damage to the surface of the cylindrical workpiece to be measured during the measurement. The turntable drives the cylindrical workpiece to be measured to rotate one circle, and the cylindricity information of the surface of the measured workpiece is completely received by the cylindrical autocollimator. The cylindricity information of the cylindrical workpiece to be measured can be obtained by analyzing the image received and collected by the photo sensor;

[0026] The cylindricity of the cylindrical workpiece is measured continuously, which avoids the problem of low measurement accuracy due to a small number of sampling points.

[0027] 2. Using two sets of cylindrical autocollimators symmetrical to the turntable axis can eliminate the measurement error caused by the misalignment between the workpiece generatrix and the turntable axis, thereby improving the measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a structural diagram of the non-contact measuring device for cylindricity of precision workpieces of the present invention;

[0029] Figure 2 This is a schematic diagram of the non-contact measurement principle of the cylindricity of a precision workpiece according to the present invention.

[0030] The reference numerals are as follows:

[0031] 1—cylindrical workpiece to be measured; 2—turntable; 3—standard cylindrical lens; 4—collimating cylindrical mirror; 5—beam splitter; 6—light sensor; 7—line light source. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0033] like Figure 1 As shown, a non-contact measuring device for the cylindricity of a precision workpiece comprises a turntable 2 and two groups of cylindrical autocollimators arranged on the side of the turntable 2; the turntable 2 is used to fix the cylindrical workpiece 1 to be measured, and the cylindrical workpiece 1 to be measured is coaxial with the turntable 2, and each group of cylindrical autocollimators comprises a line light source 7, and a standard cylindrical lens 3, a collimating cylindrical mirror 4, a spectroscopic element 5, and a light sensor 6 arranged in sequence from the inside of the turntable 2 to the outside; the light beam emitted by the line light source 7 passes through the spectroscopic element 5, and is reflected to the collimating cylindrical mirror 4, and becomes a parallel light beam through the collimating cylindrical mirror 4, and then becomes a convergent light through the standard cylindrical lens 3, and the focal line of the convergent line light beam is located at the rotation axis position of the turntable 2; the convergent line light beam is reflected by the detected part, passes through the standard cylindrical lens 3, the collimating cylindrical mirror 4, and the spectroscopic element 5 in sequence, and is received by the light sensor 6.

[0034] The busbars of the standard cylindrical lens 3 are parallel to the busbars of the cylinder of the collimating cylindrical mirror 4; the line light source 7 is located in the plane formed by the busbars of the standard cylindrical lens 3 and the collimating cylindrical mirror 4, the line light source 7 is parallel to the busbars of the cylinder of the collimating cylindrical mirror 4, and is parallel to the pixel rows or columns of the light sensor 6, and the sensitive surface of the light sensor 6 is located on the focal plane of the collimating cylindrical mirror 4.

[0035] The focal line of the converging line light beam is located at the center position of the turntable 2 (the rotation axis of the turntable 2), and is also roughly located on the generatrix of the cylindrical workpiece 1 to be measured. The converging line light beam returns to its original path through the cylindrical workpiece, and enters the light sensitive surface of the light sensor 6 through the standard cylindrical lens 3, the collimating cylindrical mirror 4 and the beam splitter.

[0036] During measurement, the turntable 2 rotates to drive the cylindrical workpiece to rotate one circle, so that the cylindricity information of the cylindrical workpiece is completely received by the cylindrical autocollimator on the side of the turntable 2, and the cylindricity information of the workpiece is reflected on the photo sensor 6. The cylindricity information of the cylindrical workpiece can be obtained by calculation and analysis based on the image collected by the cylindrical autocollimator.

[0037] The use of two cylindrical autocollimators symmetrical to the rotation axis is to eliminate the system error caused by the misalignment of the workpiece generatrix with the rotation axis of turntable 2, thereby improving the measurement precision.

[0038] The turntable 2 of the present invention is a high-stability air-floating turntable 2, the F number of the standard cylindrical lens 3 is 10 to 25, which is determined according to the cylindrical workpiece 1 to be measured, and the light sensor 6 is a CCD or CMOS array type light sensor. The light splitting element 5 is a light splitting plate or a light splitting prism or other light splitting device, preferably a light splitting prism, and the light splitting ratio is 1:1.

[0039] The positions of the line light source 7 and the light sensor 6 of the present invention can be interchanged.

[0040] The present invention provides a non-contact measurement method for the cylindricity of a precision workpiece, comprising the following steps:

[0041] 1) Start the line light source 7, adjust the cylindrical autocollimator on the side of the turntable 2 of the non-contact measuring device for the cylindricity of precision workpieces, so that the light beam emitted by the line light source 7 is converged after passing through the beam splitter 5, the collimating cylindrical mirror 4 and the standard cylindrical lens 3, so that the focal line of the converged line light beam is located at the rotation axis position of the turntable 2;

[0042] 2) The cylindrical workpiece 1 to be measured is coaxially mounted on the turntable 2 of the non-contact measuring device for the cylindricity of precision workpieces;

[0043] 3) The emitted light of the line light source 7 passes through the surface of the cylindrical workpiece 1 to be measured, and the light beam returns along the original path through the beam splitter 5 and is received by the light sensor 6;

[0044] 4) The turntable 2 drives the cylindrical workpiece 1 to be measured to rotate one circle, and the position of the focal line spot of the cylindrical workpiece 1 to be measured is collected by the light sensor 6;

[0045] 5) The light sensor 6 collects the position of the focus line spot on the surface of the cylindrical workpiece 1 to be measured, and the cylindricality information of the cylindrical workpiece 1 to be measured can be calculated through image processing.

[0046] Measuring principle see Figure 2 As shown, Figure 2 The solid circle is the ideal cylindrical section, and the dotted circle is the cylindrical section with a certain degree of cylindricity. If it is an ideal cylinder, the normal line of the cylinder surface is Figure 2 Middle straight line, Figure 2 The normal of the dashed circle ( Figure 2 The dotted straight line in the middle is inconsistent with the normal direction of the ideal cylinder. The normal direction of the cylinder can be obtained according to the change in the angle of the light beam reflected back from the cylindrical surface (the change in the focal spot position of the light-sensitive surface line). When the cylindrical workpiece rotates one circle, the change in the normal direction of the cylindrical workpiece can be obtained. The cylindricity of the workpiece can be calculated based on the change in the normal direction.

[0047] In step 1), two sets of cylindrical autocollimators are arranged symmetrically to the rotation axis of the turntable 2, which can eliminate the measurement error caused by the misalignment of the workpiece generatrix and the axis of the turntable 2, thereby improving the measurement accuracy.

[0048] The above is only a description of the preferred implementation mode of the present invention, and the technical solution of the present invention is not limited thereto. Any known deformation made by those skilled in the art on the basis of the main technical concept of the present invention belongs to the technical scope to be protected by the present invention.

Claims

1. A non-contact measurement method for the cylindricity of a precision workpiece, characterized in that: The adopted measuring device comprises a turntable (2) and two groups of cylindrical autocollimators arranged on the side of the turntable (2); The turntable (2) is used to fix the cylindrical workpiece (1) to be measured, and the cylindrical workpiece (1) to be measured is coaxial with the turntable (2); Each set of cylindrical autocollimators comprises a line light source (7), a beam splitter (5), a collimating cylindrical mirror (4) and a standard cylindrical lens (3); The outgoing light of the line light source (7) passes through the beam splitter (5), the collimating cylindrical mirror (4), and the standard cylindrical lens (3) in sequence to become a converging line light beam, and the focal line of the converging line light beam is located at the rotation axis position of the turntable (2); The convergent line light beam is reflected by the surface of the cylindrical workpiece (1) to be measured, returns along the original path, and is received by the light sensor (6) through the beam splitter element (5); The measurement method includes the following steps: 1) starting a line light source (7), adjusting two sets of cylindrical autocollimators on the side of a turntable (2) of a non-contact measuring device for the cylindricity of a precision workpiece, so that the light beam emitted by the line light source (7) is converged after passing through a beam splitter (5), a collimating cylindrical mirror (4) and a standard cylindrical lens (3), so that the focal line of the converged line light beam is located at the rotation axis position of the turntable (2); 2) The cylindrical workpiece (1) to be measured is coaxially mounted on a turntable (2) of a non-contact measuring device for the cylindricity of precision workpieces; 3) The emitted light from the line light source (7) passes through the surface of the cylindrical workpiece (1) to be measured, and the light beam returns along the original path through the beam splitter (5) and is received by the light sensor (6); 4) The turntable (2) drives the cylindrical workpiece (1) to be measured to rotate one circle, and the position of the focal line spot of the cylindrical workpiece (1) to be measured is collected by the light sensor (6); 5) The photo sensor (6) collects the position of the focus line spot on the surface of the cylindrical workpiece (1) to obtain the normal direction of the surface of the cylindrical workpiece (1). The cylindricality information of the cylindrical workpiece (1) to be measured can be calculated through image processing, which is specifically: If the cylindrical workpiece (1) is an ideal cylinder, the normal line of the cylindrical surface is a straight line. If it is not an ideal cylinder, the direction of the normal line of the cylindrical surface can be obtained based on the change in the angle of the light beam reflected back from the surface of the cylindrical workpiece (1). When the cylindrical workpiece (1) rotates one circle, the change in the direction of the normal line of the cylindrical workpiece (1) can be obtained. The cylindricity of the cylindrical workpiece (1) can be calculated based on the change in the direction of the normal line.

2. The non-contact measurement method for cylindricity of a precision workpiece according to claim 1, characterized in that: In step 1), the two groups of cylindrical autocollimators are arranged symmetrically with respect to the rotation axis of the turntable (2).

3. The non-contact measurement method for cylindricity of a precision workpiece according to claim 2, characterized in that: The generatrix of the cylinder of the standard cylindrical lens (3) is parallel to the generatrix of the cylinder of the collimating cylindrical lens (4); The line light source (7) is located in a plane formed by the generatrix of the standard cylindrical lens (3) and the collimating cylindrical lens (4); The line light source (7) is parallel to the pixel row or column of the light sensor (6), and is also parallel to the generatrix of the cylindrical surface of the collimating cylindrical mirror (4).

4. The non-contact measurement method for cylindricity of a precision workpiece according to any one of claims 1 to 3, characterized in that: The sensitive surface of the light sensor (6) is located on the focal plane of the collimating cylindrical mirror (4).

5. The non-contact measurement method for cylindricity of a precision workpiece according to claim 4, characterized in that: The two groups of cylindrical autocollimators are symmetrically arranged on both sides of the rotating axis of the turntable (2).

6. The non-contact measurement method for cylindricity of a precision workpiece according to claim 3, characterized in that: The F number of the standard cylindrical lens (3) is 10-25.

7. The non-contact measurement method for cylindricity of a precision workpiece according to claim 1, characterized in that: The light sensor (6) is a CCD or CMOS array light sensor.

8. The non-contact measurement method for cylindricity of a precision workpiece according to claim 1, characterized in that: The light splitting element (5) is a light splitting prism with a light splitting ratio of 1:1 and an angle of 45° with the optical axis.

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