Special-shaped workpiece inner hole coaxiality detector

Abstract

A special-shaped workpiece inner hole coaxiality detector belongs to the field of mechanical part detection instruments and is composed of a rotating device, a detection device and a supporting device, the rotating device and the detection device are placed on a detection platform, and the rotating device comprises a motor, a pinion, a rotary table base, a rotating platform and a clamp body. The detection device comprises a laser displacement sensor, a data processing and displaying device and a sensor supporting frame. The laser displacement sensor is placed on a reference axis of an inner hole of the special-shaped workpiece, the laser displacement sensor emits a laser beam and receives reflected light while the workpiece rotates, displacement data of a measured surface are obtained, the circle center and the radius of the workpiece are fitted through a least square method optimization algorithm, and the maximum distance is found out to serve as a coaxiality error. The instrument can detect the coaxiality of a plurality of holes at one time, so that the detection efficiency is improved, and personal errors are reduced.

Description

Technical Field

[0001] The invention relates to a coaxiality detector for inner holes of special-shaped workpieces, in particular to an instrument that uses a laser displacement sensor to measure the coaxiality of inner holes of special-shaped workpieces, and belongs to the field of mechanical parts detection instruments. Background Art

[0002] Coaxiality is an important parameter indicator of positioning tolerance. It describes the degree of deviation between the actual axis and the reference axis. If the deviation exceeds the given range, it will have a serious impact on subsequent use. Coaxiality measurement is usually applied to rotating parts, such as shaft parts, bearing seat holes, etc. These parts need to maintain a high coaxiality during rotation to ensure the smooth operation and accuracy of the machine or equipment. The coaxiality testers on the market are generally suitable for regular rotating parts. During the measurement process, they can ensure that the reference axis of the parts is at the same horizontal height during the rotation process. However, for special-shaped workpieces, due to the irregular shape, the reference axis will deviate from the center due to gravity during the rotation along the reference axis, and the measured error is too large.

[0003] With the development of intelligent manufacturing technology and the continuous advancement of precision measurement technology, coaxiality measurement technology has also been significantly developed. Traditional internal hole coaxiality detectors include lever dial indicator type, micrometer type, gauge measurement type, V-shaped bracket and steel ball combination type, etc. However, the detection methods of these instruments are not only too cumbersome to operate, but also easily restricted by the shape and size of parts, and the measurement accuracy is low.

[0004] Laser displacement sensor is a high-precision sensor that uses laser technology for measurement. It can accurately measure the position, displacement and other changes of the measured object without contact. Laser displacement sensor is mainly composed of laser, laser detector, measurement circuit, optical process, signal processing system and data output interface. These parts work together to complete the whole process from laser emission, reception, signal processing to data output.

[0005] The balance shaft housing is an important part of heavy-duty vehicles. The coaxiality between several holes of this part is required to be high. The current detection is done manually, with low detection efficiency and low detection accuracy. Therefore, a high-precision coaxiality detector is urgently needed, but this instrument is currently not available. Summary of the invention

[0006] In view of the lack of a coaxiality detector for a balancing shaft housing, the present invention provides a coaxiality detector for the inner hole of a special-shaped workpiece.

[0007] The present invention is realized through the following technical scheme: a coaxiality detector for the inner hole of a special-shaped workpiece, which is composed of a rotating device, a detection device and a detection platform. The rotating device and the detection device are placed on the detection platform. The rotating device includes a clamp body, a motor, a pinion, a balancing shaft shell, a turntable base and a rotating platform. A hollow cylindrical slot is provided on the upper surface of the rotating platform to position the balancing shaft shell and the clamp body to ensure that the balancing shaft shell and the clamp body do not deviate during the rotation process. The clamp body is set to be circular, which is conducive to driving the balancing shaft shell to rotate, and the internal shape of the clamp body is embedded with the balancing shaft shell, so as to achieve the purpose of fixing and clamping the balancing shaft shell. The clamp body clamps the balancing shaft shell coaxially. It is placed on a rotating platform so that the axis center of the inner hole of the balance shaft housing does not deviate from the reference axis during the rotation process. Gear teeth are arranged on the circumferential surface of the rotating platform, and the gear teeth are meshed with the pinion. The motor is placed on the motor support frame and is coaxially connected to the pinion. The detection device includes three laser displacement sensors, a data processing and display device and a sensor support frame. The sensor support frame is fixed on the connecting rod of the central axis of the upper surface of the turntable base. The laser displacement sensor is placed on the sensor support frame and is at the same horizontal height as the surface to be measured. The data processing and display device is placed on the detection platform to display the detection accuracy. In addition, a single-chip microcomputer is installed inside to convert the algorithm into program code for operation.

[0008] The working process of the laser displacement sensor includes: the laser displacement sensor collects displacement data of the workpiece surface in real time; converts the collected displacement data into three-dimensional coordinate values ​​to form cloud data, and performs filtering and smoothing; uses the collected point cloud data to fit the center and radius of the workpiece through the least squares optimization algorithm; calculates the distance from the fitting center to the reference axis, and finds the maximum distance as the coaxiality error; outputs the coaxiality error to the user interaction interface; determines and calibrates the error range.

[0009] The benefit of the invention is that, due to the uneven mass distribution of the special-shaped workpiece, the reference axis will deviate from the center due to the gravity during the rotation along the reference axis, resulting in a large measurement error. Therefore, when designing the fixture, the dynamic balance of the workpiece and the uniformity of the mass distribution of the clamp body are fully considered, a circular clamp body is designed, and the reference axis of the workpiece and the clamp body is placed perpendicular to the measuring platform, so that the axis of the workpiece does not deviate from the reference axis during the rotation process. The use of laser displacement sensors to measure coaxiality improves the accuracy of coaxiality measurement of the inner hole of special-shaped workpieces. Compared with traditional measurement methods, non-contact measurement can be achieved, which reduces the burden on operators and improves the efficiency of workpiece precision detection. Through the precise measurement of the laser sensor, the diameter data of different positions of the balance shaft housing can be quickly and accurately obtained, so as to accurately calculate its coaxiality. In addition, the laser displacement sensor has the characteristics of high automation, can monitor and record measurement data in real time, and can be easily integrated with a computer or data processing system to further improve the efficiency of data analysis and processing. As a part of modern industrial measurement technology, laser displacement sensors provide an efficient, accurate and reliable solution for the coaxiality measurement of balanced shaft housings, greatly promoting the quality control of the manufacturing process and improving production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Attached Figure 1 It is a structural schematic diagram of the present invention, Figure 2 This is a schematic diagram of the structure of the present invention without the clamping body and the balance shaft housing. Figure 3 The schematic diagram of the structure of the turntable base and the laser displacement sensor assembly is shown in the figure. Figure 4 is a schematic diagram of the rotating platform structure. Figure 5 This is a specific structural diagram of the special-shaped workpiece clamp. Figure 6 The schematic diagram of the balance shaft housing structure is shown in Figure 2. Figure 7 This is the working flow chart of the laser displacement sensor. Figure 8 The measured surface profile of the balance shaft housing

[0011] In the figure, 1. detection platform, 2. clamping body, 3. balance shaft housing, 4. laser displacement sensor, 5. sensor support frame, 6. rotating platform, 7. pinion, 8. motor, 9. motor support frame, 10. data processing and display device, 11. turntable base, 12. connecting rod. DETAILED DESCRIPTION

[0012] A sensor-based coaxiality detector for the inner hole of a special-shaped workpiece is composed of a rotating device, a detection device and a detection platform 1. The rotating device and the detection device are placed on the detection platform 1. The rotating device includes a clamp body 2, a motor 8, a pinion 7, a balancing shaft housing 3, a turntable base 11 and a rotating platform. A hollow cylindrical groove is provided on the upper surface of the rotating platform 6 to position the balancing shaft housing 3 and the clamp body 2 to ensure that the balancing shaft housing 3 and the clamp body 2 do not deviate during the rotation process. The clamp body 2 is set to a circular shape, which is conducive to driving the balancing shaft housing 3 to rotate, and the internal shape of the clamp body 2 is embedded with the balancing shaft housing 3, so as to achieve the purpose of fixing and clamping the workpiece. The clamp body 2 The balance shaft housing 3 is clamped and coaxially placed on the rotating platform 6, so that the inner hole axis of the balance shaft housing 3 does not deviate from the reference axis during the rotation process. The rotating platform 6 is provided with gear teeth on the circumferential surface, and the gear teeth are meshed with the pinion 7. The motor 8 is placed on the motor support frame 9 and is coaxially connected with the pinion 7. The detection device also includes three laser displacement sensors 4, a measurement result display screen 10 and a sensor support frame 5. The sensor support frame 5 is fixed on the connecting rod 12 of the central axis of the upper surface of the turntable base 11. The laser displacement sensor 4 is placed on the sensor support frame 5 and is at the same horizontal height as the measured surface. The data processing and display device 10 is placed on the detection platform 1. A single-chip microcomputer is installed inside the data processing and display device 10, which converts the algorithm into program code for operation and displays the detection accuracy.

[0013] When the instrument is used, the workpiece is placed in the hollow cylindrical slot, and the workpiece is positioned and clamped using the clamp body 2. The motor 8 drives the pinion 7 to rotate, and the rotation of the pinion 7 drives the rotating platform 6 to rotate. The rotating platform 6 drives the balancing shaft housing 3 clamped by the clamp body 2 to rotate around the reference axis. At the same time, three laser displacement sensors 4 collect displacement data on the hole surface. After the data is collected, calculation and processing are performed to obtain the coaxiality data of the measured hole.

[0014] Figure 8 The working process of the laser displacement sensor of the present invention includes:

[0015] S1: The laser displacement sensor 4 collects displacement data of the inner hole surface of the balance shaft housing 3 in real time;

[0016] Among them, the laser displacement sensor collects displacement data in the following way: the laser displacement sensor emits a laser beam which is reflected back to the sensor through the inner hole surface of the workpiece, and the receiver inside the sensor detects the angle of the reflected light, and calculates the distance from the object surface to the sensor through the triangle formed by the light beam in the sensor.

[0017] The calculation formula is as follows:

[0018] x ω =mcosθ i

[0019] y ω =msinθ i

[0020] In the above formula, θ i is the angle of reflected light, m ​​is the distance of receiving reflected light, and the collected displacement data is x ω ,y ω .

[0021] S2: Convert the collected displacement data into three-dimensional coordinate values ​​to form cloud data, and perform filtering and smoothing processing; use the collected point cloud data to fit the center and radius of the workpiece through the least squares optimization algorithm;

[0022] The basic idea of ​​the least squares method is to fit a circle using the collected data and find the center of the fitted circle (x c ,y c ) and radius R.

[0023] Assume that the rectangular coordinates of the point on the contour of the measured hole are (x i ,y i ), i = 1, 2, 3, 4...n, n is the number of measurement points.

[0024] The shape of the balance shaft housing surface is circular, and the collected data can be expressed as:

[0025] R 2 =(x a) 2 +(yb) 2 (1.1)

[0026] The center of the circle (x c ,y c ) coordinates are (a, b), and the radius of the circle is R.

[0027] If c = R 2 -a 2 -b 2 , substituting into 1.1, we can write:

[0028] x 2 +y 2 -ax-bx-c=0 (1.2)

[0029]

[0030] Substituting the measured values ​​into equation 1.2, we can obtain a system of equations consisting of n linear equations:

[0031]

[0032] Among them, coefficients a, b, c are unknowns. Using the matrix to solve the above linear equations, we get:

[0033]

[0034] The coordinates of the center of the fitted circle and the radius R are:

[0035]

[0036] S3: Calculate the center of the fitting circle (x i ,y i ) to the reference axis, and find the maximum distance as the coaxiality error;

[0037] The displacement coordinates of the reference axis are expressed as (x, y). c ,y c ) to the reference axis can be calculated using the following formula:

[0038]

[0039] As a positioning tolerance, the coaxiality error theoretically refers to the change in the position of the measured axis relative to the reference axis, and actually reflects the non-concentricity of the center of each cross-section. Therefore, the center and radius of each cross-section on the workpiece surface are fitted to solve the distance d between each fitted center and the reference axis. i , the maximum distance deviation T d As coaxiality error.

[0040] T d =maxd i

[0041] S4: The coaxiality error T d Output to the user interface; determine and calibrate the error range.

[0042] For those skilled in the art, according to the teachings of the present invention, without departing from the principles and spirit of the present invention, changes, modifications, substitutions and variations made to the implementation methods are still within the protection scope of the present invention.

Claims

1. An algorithm for detecting the coaxiality of inner holes of special-shaped workpieces, characterized in that: The laser displacement sensor workflow includes: S1: The laser displacement sensor collects displacement data of the workpiece surface in real time; S2: Convert the collected displacement data into three-dimensional coordinate values ​​to form cloud data, and perform filtering and smoothing processing; use the collected point cloud data to fit the center and radius of the workpiece through the least squares optimization algorithm; S3: Calculate the distance from the center of the fitting circle to the reference axis, and find the maximum distance as the coaxiality error; S4: Output the coaxiality error to the user interface; determine and calibrate the error range.

2. The coaxiality detection algorithm for inner hole of a special-shaped workpiece according to claim 1, characterized in that: The calculation formula for real-time acquisition of workpiece surface displacement data by the laser displacement sensor is: x ω =m cosθ i and w =m sinθ i In the above formula, θ i is the angle of reflected light, m ​​is the distance of receiving reflected light, and the collected displacement data is x ω ,y ω .

3. The coaxiality detection algorithm for inner hole of a special-shaped workpiece according to claim 1, characterized in that: The least squares optimization algorithm for fitting the center and radius is: The collected displacement coordinates (x i ,y i ) into the equation R 2 =(x a) 2 +(yb) 2 , we get a linear system of n equations: Using the matrix to solve the above equations, we get: The coordinates of the center of the fitted circle and the radius R are:

4. The coaxiality detection algorithm for inner hole of a special-shaped workpiece according to claim 1, characterized in that: The distance d from the center of the fitting circle to the reference axis i The calculation formula is: Among them, (x, y) is the displacement coordinate of the reference axis, (x c ,y c ) are the coordinates of the center of the fitting circle.

5. A coaxiality detector for inner holes of special-shaped workpieces, which is composed of a rotating device, a detection device and a detection platform, wherein the rotating device and the detection device are placed on the detection platform, and is characterized in that: The rotating device includes a clamping body, a motor, a turntable base, a gear, a rotating platform and a balancing shaft shell. The clamping body clamps the balancing shaft shell coaxially and places it on the rotating platform. Gear teeth are arranged on the circumferential surface of the rotating platform, and the gear teeth are meshed with the pinion. The motor is placed on the motor support frame and connected coaxially with the pinion. The detection device includes a laser displacement sensor, a sensor digital display screen and a sensor support frame. The sensor bracket is fixed on the connecting rod of the central axis of the upper surface of the turntable base. The laser displacement sensor is placed on the sensor support frame and is at the same horizontal height as the surface to be measured. The data processing and display device is placed on the detection platform to display the detection accuracy. A single-chip microcomputer is installed inside to convert the algorithm into program code for operation.

6. The coaxiality detector for inner hole of a special-shaped workpiece according to claim 5, characterized in that: The motor drives the pinion to rotate, the rotation of the pinion drives the rotating platform to rotate, and the rotating platform drives the special-shaped workpiece to rotate around the reference axis. At the same time, the laser displacement sensor collects the displacement data of the workpiece surface in real time.

7. The coaxiality detector for inner hole of a special-shaped workpiece according to claim 5, characterized in that: A hollow cylindrical slot is provided on the upper surface of the rotating platform to position the workpiece and the clamp body to ensure that the workpiece and the clamp body do not deviate during the rotation process.

8. The coaxiality detector for inner holes of special-shaped workpieces according to claim 5, characterized in that: The clamp body is set to be circular, which is conducive to the rotation of the workpiece, and the internal shape of the clamp body can be embedded with the special-shaped workpiece, so as to achieve the purpose of fixing and clamping the workpiece, and the axis center of the inner hole of the workpiece coincides with the axis center of the clamp body, so that the axis center of the workpiece does not deviate from the reference axis during rotation.

Images