Optical probe measurement method for micro-gears

Abstract

The application discloses a light probe measurement method for a micro gear. The method is based on a light probe measuring head of a point self-focusing principle. Firstly, a standard ball is used to determine the maximum allowable measurement inclination angle of the light probe measuring head, then the offset distance required for measuring different modulus gears is determined, the measurement path is planned, and then the acquisition of the full tooth surface data of the micro gear is realized. The application adopts a 632.8nm wavelength laser, is equipped with a 100 times microscopic objective lens, and can adjust a laser spot with a spot diameter less than 1um. The application can be used for measuring the gear slot of a micro gear with a modulus less than 0.1mm. The measurement path adopted by the application can effectively reduce the measurement error introduced by the too large tooth surface inclination angle, and improves the measurement precision of the gear measurement. The method has wide application, and is especially suitable for the full tooth surface measurement of the micro gear.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of precision measurement, in particular to a light probe measurement method for micro gear. BACKGROUND

[0002] Micro gear generally refers to micro gear with module less than 0.1mm and addendum circle diameter less than 1mm. The geometric precision measurement of micro gear as a representative of micro parts with complex geometric shape is a worldwide problem. Mainly because the tooth groove width is too small, the traditional contact measurement means cannot detect the micro tooth groove root due to the limitation of the size of the measuring ball, that is, the complete tooth profile cannot be measured. The optical measurement means cannot effectively obtain the tooth root data due to the limitation of the tooth surface inclination. Therefore, the research on the light probe measurement method for micro gear has become an effective means to solve the above problems. SUMMARY

[0003] The purpose of the present application is to realize the measurement of full tooth surface data of micro gear with module less than 0.1mm, and a light probe measurement method for micro gear is proposed. The method is based on the light probe probe head based on the point self-focusing principle. First, the maximum allowable measurement inclination angle of the light probe probe head is determined by using the standard ball, and then the offset distance required for measuring different module gears is determined, the measurement path is planned, and then the full tooth surface data of the micro gear is obtained.

[0004] The above object is achieved by the following technical scheme:

[0005] The measurement system based on the light probe measurement method for micro gear includes a light probe probe head, an axis controller, a three-axis controller, a one-dimensional micro motion platform, a three-dimensional moving table, an x-axis linear grating, a y-axis linear grating, a probe linear grating, a rotary shaft circular grating, an upper computer display system, a measured gear and a standard ball. The light probe probe head is a laser probe head based on the point self-focusing principle. When the light spot of the light probe probe head objective is focused on the surface of the measured gear, the light probe probe head is in a balanced state. When the surface of the measured gear is in an off-focus state, the internal self-focusing sensor will send a command to the one-axis controller, and through the movement of the one-dimensional micro motion platform, the surface of the measured gear is again located on the focal plane of the light probe probe head. The displacement of the one-dimensional micro motion platform is recorded by the probe linear grating. The three-dimensional moving table can realize three-dimensional motion in x direction, y direction and rotary direction. The three-axis controller is used to control the motion of the three-dimensional moving table, the x-axis linear grating, the y-axis linear grating and the rotary shaft circular grating are used to measure the two-dimensional linear displacement and one-dimensional angular displacement of the measured gear. Combined with the motion of the one-dimensional micro motion platform, the measurement of the surface data of the measured gear can be completed.

[0006] The maximum allowed measurement inclination angle of the light probe stylus is tested using a standard ball. First, the standard ball is installed on a three-dimensional moving stage, and the optical axis of the light probe stylus objective is adjusted to pass through the center of the standard ball. Then, the standard ball is moved to the first limit position and the second limit position along the negative direction of the x-axis and the positive direction of the x-axis respectively, and the measurement data is collected using the light probe stylus. The measurement error is obtained by comparing the measurement data with the theoretical data, and the error curve is drawn. According to the maximum allowed error set in advance, the first allowed inclination angle position in the negative direction of the x-axis and the second allowed inclination angle position in the positive direction of the x-axis are determined. Then the first allowed inclination angle α and the second allowed inclination angle β are obtained. The smaller angle of the first allowed inclination angle α and the second allowed inclination angle β is defined as the maximum allowed measurement inclination angle γ.

[0007] Before the measurement starts, first define the center of the measured gear as the origin O of the coordinate system. Then make the addendum center of a tooth located on the x-axis. Next, take the x-axis as the starting point and rotate counterclockwise around the origin of the coordinate system to find the first tooth with a right tooth surface inclination angle ε1 less than the maximum allowed measurement inclination angle γ, and define this tooth as the first measured tooth in the positive direction of the y-axis. Then take the x-axis as the starting point and rotate clockwise around the origin of the coordinate system to find the first tooth with a left tooth surface inclination angle ε2 less than the maximum allowed measurement inclination angle γ, and define this tooth as the first measured tooth in the negative direction of the y-axis.

[0008] When measuring the gear, follow the steps below:

[0009] Step one: First, measure the right tooth surface of the first measured tooth in the positive direction of the y-axis. The light probe stylus moves along the first path of the light probe stylus, and the three-dimensional moving stage rotates synchronously clockwise.

[0010] Step two: After completing the measurement of the right tooth surface of the first measured tooth in the positive direction of the y-axis, the light probe stylus moves along the second path of the light probe stylus to measure the left tooth surface of the first measured tooth in the negative direction of the y-axis.

[0011] Step three: The light probe stylus moves along the third path of the light probe stylus for measurement, and the three-dimensional moving stage rotates synchronously counterclockwise.

[0012] Step four: After completing the measurement of the left tooth surface of the first measured tooth in the negative direction of the y-axis, the light probe stylus moves along the fourth path of the light probe stylus to return to the initial position of the light probe stylus.

[0013] Step five: The three-dimensional moving stage rotates clockwise by an angle of one tooth.

[0014] Step six: The light probe stylus moves along the first path of the light probe stylus for measurement, and the three-dimensional moving stage rotates synchronously clockwise.

[0015] Step seven: The light probe stylus moves along the second path of the light probe stylus.

[0016] Step eight: the optical probe head moves along the third path of the optical probe head, and the three-dimensional moving table rotates counterclockwise synchronously.

[0017] Step nine: the optical probe head moves along the fourth path of the optical probe head and returns to the initial position of the optical probe head.

[0018] Step ten: the three-dimensional moving table rotates clockwise by an angle of one tooth.

[0019] Next, steps six to ten are repeated until the left tooth surface and the right tooth surface of all the teeth of the measured gear are measured, and finally all the measurement data are spliced to obtain the measurement data of all the teeth of the measured gear.

[0020] The present application has the following characteristics and beneficial effects:

[0021] 1. The present application adopts a 632.8nm wavelength laser, equipped with a 100 times microscopic objective lens, and can adjust the laser spot diameter to be less than 1μm. It can be used to measure the tooth groove of a small gear with a module less than 0.1mm.

[0022] 2. The measurement path adopted by the present application can effectively reduce the measurement error introduced by the too large tooth surface inclination angle, and improve the measurement accuracy of gear measurement.

[0023] The method of the present application has wide application, and is especially suitable for full tooth surface measurement of small gears. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 Schematic diagram for measuring a small gear by an optical probe head.

[0025] Figure 2 Schematic diagram for determining the maximum allowable measurement inclination angle of an optical probe head.

[0026] Figure 3 Schematic diagram for determining the allowable inclination angle range.

[0027] Figure 4 Schematic diagram for the measurement path of a small gear.

[0028] The markings in the diagram are: 1-Optical probe head; 2-One-axis controller; 3-One-dimensional micro-motion platform; 4-Three-axis controller; 5-Y-axis linear grating; 6-X-axis linear grating; 7-Three-dimensional moving stage; 8-Host computer display system; 9-Gear under test; 10-Rotation axis circular grating; 11-Linear grating for probe; 12-Standard sphere; 13-First limit position; 14-Second limit position; 15-First allowable tilt angle position; 16-Second allowable tilt angle position; 17-First gear tooth under test in the positive Y-axis direction; 18-First gear tooth under test in the negative Y-axis direction; 19-First path of optical probe head; 20-Second path of optical probe head; 21-Third path of optical probe head; 22-Fourth path of optical probe head. Detailed Implementation

[0029] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. However, this should not be construed as limiting the scope of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0030] like Figure 1 As shown, the measurement system based on the optical probe measurement method for micro-gears includes an optical probe head 1, a one-axis controller 2, a three-axis controller 4, a one-dimensional micro-motion platform 3, a three-dimensional moving stage 7, an x-axis linear grating 6, a y-axis linear grating 5, a probe linear grating 11, a rotary axis circular grating 10, a host computer display system 8, the gear under test 9, and a standard sphere 12. The optical probe head 1 is a laser probe based on the point self-focusing principle. When the objective lens of the optical probe head 1 focuses the light spot precisely on the surface of the gear under test 9, the optical probe head 1 is in a balanced state. When the surface of the gear under test 9 is out of focus, the internal self-focusing sensor sends a command to the one-axis controller 2, which controls the movement of the one-dimensional micro-motion platform 3 to bring the surface of the gear under test 9 back onto the focal plane of the objective lens of the optical probe head 1. The displacement of the one-dimensional micro-motion platform 3 is recorded by the probe linear grating 11. The three-dimensional moving stage 7 can realize three-dimensional movement in the x, y, and rotation directions. The three-axis controller 4 controls the movement of the three-dimensional moving stage 7. The x-axis linear grating 6, the y-axis linear grating 5, and the rotary axis circular grating 10 are used to measure the two-dimensional linear displacement and one-dimensional angular displacement of the gear 9 under test, respectively. Combined with the movement of the one-dimensional micro-motion platform 3, the surface data of the gear 9 under test can be measured.

[0031] like Figure 2The maximum allowable measurement inclination γ of the optical probe probe head 1 is tested using a standard ball 12. First, the standard ball 12 is installed on the three-dimensional moving table 7, and the optical axis of the objective lens of the optical probe probe head 1 is adjusted to pass through the center of the standard ball 12. Then, the standard ball 12 is moved to the first limit position 13 and the second limit position 14 along the negative direction of the x-axis and the positive direction of the x-axis respectively, and the measurement data is collected using the optical probe probe head 1. The measurement data is compared with the theoretical data to obtain the measurement error, and the error curve is drawn. According to the maximum allowable error Δ e , the first allowable inclination position 15 in the negative direction of the x-axis and the second allowable inclination position 16 in the positive direction of the x-axis are determined. Then the first allowable inclination α and the second allowable inclination β are obtained. The smaller angle of the first allowable inclination α and the second allowable inclination β is defined as the maximum allowable measurement inclination γ.

[0032] Before the measurement starts, first define the center of the measured gear 9 as the origin O of the coordinate system. Then make the addendum center of a tooth located on the x-axis. Next, take the x-axis as the starting point and rotate counterclockwise around the origin of the coordinate system to find the first tooth with a right tooth surface inclination angle ε1 less than the maximum allowable measurement inclination γ, and define this tooth as the first measured tooth 17 in the positive direction of the y-axis. Then take the x-axis as the starting point and rotate clockwise around the origin of the coordinate system to find the first tooth with a left tooth surface inclination angle ε2 less than the maximum allowable measurement inclination γ, and define this tooth as the first measured tooth 18 in the negative direction of the y-axis.

[0033] When measuring the gear, the following steps are taken:

[0034] Step one: first measure the right tooth surface of the first measured tooth 17 in the positive direction of the y-axis. The optical probe probe head 1 moves along the first path 19 of the optical probe probe head, and the three-dimensional moving table 7 rotates synchronously clockwise.

[0035] Step two: after completing the measurement of the right tooth surface of the first measured tooth 17 in the positive direction of the y-axis, the optical probe probe head 1 moves along the second path 20 of the optical probe probe head to measure the left tooth surface of the first measured tooth 18 in the negative direction of the y-axis.

[0036] Step three: the optical probe probe head 1 moves along the third path 21 of the optical probe probe head for measurement, and the three-dimensional moving table 7 rotates synchronously counterclockwise.

[0037] Step four: after completing the measurement of the left tooth surface of the first measured tooth 18 in the negative direction of the y-axis, the optical probe probe head 1 moves along the fourth path 22 of the optical probe probe head to return to the initial position of the optical probe probe head.

[0038] Step five: the three-dimensional moving table 7 rotates clockwise by an angle of one tooth.

[0039] Step six: the light probe head 1 moves along the light probe head first path 19 for measurement, and the three-dimensional moving table 7 rotates synchronously clockwise.

[0040] Step seven: the light probe head 1 moves along the light probe head second path 20.

[0041] Step eight: the light probe head 1 moves along the light probe head third path 21 for measurement, and the three-dimensional moving table 7 rotates synchronously counterclockwise.

[0042] Step nine: the light probe head 1 moves along the light probe head fourth path 22 and returns to the initial position of the light probe head.

[0043] Step ten: the three-dimensional moving table 7 rotates clockwise by an angle of one tooth.

[0044] Next, steps six to ten are repeated until the left and right tooth surfaces of all the teeth of the measured gear 9 are measured, and finally all the measurement data are spliced to obtain the measurement data of all the teeth of the measured gear 9.

[0045] The above description of disclosed embodiments enables those skilled in the art to carry out or use the present application, and various modifications of the embodiments are obvious to those skilled in the art. The general principles defined herein can be embodied in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown in the present application, but will be required to conform to the widest scope of principles and novel features disclosed herein.

Claims

1. A photoelectric probe measurement method for micro gears, comprising a measurement system including a photoelectric probe head, a one-axis controller, a three-axis controller, a one-dimensional micro-motion platform, a three-dimensional moving stage, an x-axis linear grating, a y-axis linear grating, a linear grating for the probe head, a rotary axis circular grating, a host computer display system, the gear under test, and a standard sphere; the photoelectric probe head is a laser probe based on the point self-focusing principle; the photoelectric probe head is in a balanced state when the objective lens of the photoelectric probe head focuses the light spot onto the surface of the gear under test; When the surface of the gear under test is out of focus, the internal self-focusing sensor sends a command to the one-axis controller, which controls the movement of the one-dimensional micro-motion platform to bring the surface of the gear under test back onto the focal plane of the objective lens of the optical probe head. The displacement of the one-dimensional micro-motion platform is recorded by the probe head using a linear grating. The three-dimensional moving stage realizes three-dimensional movement in the x, y, and rotation directions. The three-axis controller controls the movement of the three-dimensional moving stage, and the x-axis linear grating, y-axis linear grating, and rotation axis circular grating are used to measure the two-dimensional linear displacement and one-dimensional angular displacement of the gear under test, respectively. Combined with the movement of the one-dimensional micro-motion platform, the complete... The measurement of the surface data of the gear under test is as follows: Before the measurement begins, the center of the gear under test is first defined as the origin O of the coordinate system; then, the center of the tooth tip of a certain tooth is located on the x-axis; starting from the x-axis, rotate counterclockwise around the origin of the coordinate system to find the first tooth with a tooth surface inclination angle ε1 on the right tooth surface that is less than the maximum allowable inclination angle γ, and define this tooth as the first tooth under test in the positive direction of the y-axis; then, starting from the x-axis, rotate clockwise around the origin of the coordinate system to find the first tooth with a tooth surface inclination angle ε2 on the left tooth surface that is less than the maximum allowable inclination angle γ, and define this tooth as the first tooth under test in the negative direction of the y-axis; Its characteristic is that the following steps are followed when measuring gears: Step 1: First, measure the right tooth surface of the first tooth of the gear being measured in the positive y-axis direction; the optical probe moves along the first path of the optical probe to measure, and the three-dimensional moving stage rotates clockwise synchronously. Step 2: After completing the measurement of the right tooth surface of the first tooth under test in the positive y-axis direction, the optical probe moves along the second path of the optical probe to measure the left tooth surface of the first tooth under test in the negative y-axis direction. Step 3: The optical probe head moves and measures along the third path of the optical probe head, while the three-dimensional moving stage rotates counterclockwise synchronously. Step 4: After completing the measurement of the left tooth surface of the first measured tooth in the negative y-axis direction, the optical probe moves along the fourth path of the optical probe and returns to the initial position of the optical probe. Step 5: Rotate the 3D moving stage clockwise by the angle of one gear tooth; Step Six: The optical probe head moves and measures along the first path of the optical probe head, while the three-dimensional moving stage rotates clockwise synchronously. Step 7: The optical probe head moves along the second path of the optical probe head; Step 8: The optical probe head moves and measures along the third path of the optical probe head, while the three-dimensional moving stage rotates counterclockwise synchronously. Step 9: The optical probe head moves along the fourth path of the optical probe head and returns to the initial position of the optical probe head; Step 10: The 3D moving stage rotates clockwise by the angle of one gear tooth; Next, repeat steps six through ten until the left and right tooth surfaces of all gear teeth have been measured. Finally, combine all the measurement data to obtain the measurement data of all the gear teeth being measured.

2. The optical probe measurement method for micro gears according to claim 1, characterized in that: The maximum permissible tilt angle of the optical probe head is determined using a standard sphere. First, the standard sphere is mounted on a three-dimensional moving stage, and the optical axis of the optical probe objective lens is adjusted so that it passes through the center of the standard sphere. Then, the standard sphere is moved to the first and second limit positions along the negative and positive x-axis directions, respectively, and measurement data is collected using the optical probe head. The measurement data is compared with theoretical data to obtain the measurement error, and an error curve is plotted. Based on the pre-set maximum permissible error, the first permissible tilt angle position in the negative x-axis direction and the second permissible tilt angle position in the positive x-axis direction are determined. This yields the first permissible tilt angle α and the second permissible tilt angle β. The smaller angle between the first permissible tilt angle α and the second permissible tilt angle β is defined as the maximum permissible measurement tilt angle γ.

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