Design method of stator inner curve of balanced vane pump

Abstract

This invention discloses a method for designing the inner curve of a balanced vane pump stator, comprising the following steps: S1, obtaining the inner curve profile of a sample stator; S2, preliminarily estimating the lift angle of the sample stator; S3, verifying the stator displacement; S4, obtaining polar coordinate data of a predetermined number of points on the inner curve profile of the stator; S5, converting the polar coordinate data of the predetermined number of points into rectangular coordinates; S6, copying the rectangular coordinate data values ​​to a first file; S7, opening the first file using 3D software; S8, after generating the curve in the 3D software, exporting and saving it as a second file in a predetermined format; S9, opening the second file and performing a simulation comparison with the inner curve profile of the sample stator; S10, repeating steps S5 to S9 until the generated curve matches the inner curve profile of the sample stator; S11, performing trial machining of the inner curve of the stator; S12, inspecting the trial-machined inner curve profile of the stator. This method for designing the inner curve of a balanced vane pump stator can improve the pass rate of stator inner curve machining.

Description

Technical Field

[0001] This invention belongs to the field of automotive hydraulic power steering pump technology. Specifically, this invention relates to a method for designing the internal curve of the stator of a balanced vane pump. Background Technology

[0002] Balanced vane pumps, as the power source for automotive hydraulic power steering systems, have been widely used due to their significant advantages such as compact structure, uniform flow, high volumetric efficiency, low noise, and smooth operation. The stator, as the core component of the vane pump, determines the motion state of the vanes through the shape and properties of its inner surface, significantly impacting the pump's performance, noise level, and lifespan.

[0003] like Figure 2 As shown, the inner surface of the stator of the balanced vane pump is approximately elliptical. This ellipse is composed of two small circular arcs, two large circular arcs, and four transition curves. When the rotor rotates, the vanes, under the action of centrifugal force and root pressure oil, move radially within the rotor slots and press against the inner surface of the stator. Multiple sealing spaces are formed by the vanes, the inner surface of the stator, the outer surface of the rotor, and the oil distribution plates on both sides. When the rotor rotates in the direction shown in the figure, the vanes extend outward during the process of moving from the small circular arc to the large circular arc via the transition curve, increasing the volume of the sealing space and drawing in oil. Then, during the process of moving from the large circular arc to the small circular arc via the transition curve, the vanes are gradually pressed into the slots by the interior of the stator, reducing the volume of the sealing space and forcing the oil out from the pressure port. Therefore, for each rotation of the rotor, each working space must complete two oil suction and oil pressure cycles.

[0004] The current method for manufacturing the stator inner curve involves a cam-grinding process. This method first uses the original sample stator profile to create the cam profile, and then grinds the stator inner curve using the cam profile's motion trajectory. This method has the following main drawbacks:

[0005] a. To manufacture the inner curve of the stator by grinding the cam, the inner curve of all the stators in one shift needs to be rough ground first, and then the inner curve needs to be finely ground after a second clamping.

[0006] b. Cams are ground to create the internal curves of the stator. When the cam is running, the cam and the machine tool spindle are in line contact, and the pressure at the contact point is high, making it prone to wear.

[0007] c. The cam is manufactured by grinding the internal curve of the stator, which results in poor product stability and makes it difficult to control the perpendicularity and roughness of the curve;

[0008] d. The cam is ground to the internal curve of the stator. The product model is single and not easy to modify. One internal curve of the stator needs to correspond to one cam.

[0009] e. After grinding the cam profile using a sample, surface nitriding treatment needs to be outsourced, which takes a long time (about 15 days). Summary of the Invention

[0010] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention provides a method for designing the internal curve of a balanced vane pump stator, with the purpose of improving the pass rate of stator internal curve machining.

[0011] To achieve the above objectives, the technical solution adopted by this invention is: a method for designing the internal curve of the stator of a balanced vane pump, comprising the following steps:

[0012] S1. Obtain the inner curve profile of the sample stator as a reference standard;

[0013] S2. Preliminary estimation of the lift angle of the sample stator;

[0014] S3. Measure the design parameters of the sample stator and verify whether the stator displacement meets the design requirements according to the displacement calculation formula.

[0015] S4. Based on the obtained design parameters of the sample stator, use a curve design tool to calculate and obtain the polar coordinate data of a set number of points on the inner curve contour of the sample stator.

[0016] S5. Convert the obtained polar coordinate data of a set number of points into rectangular coordinates;

[0017] S6. Create a new text document, copy the rectangular coordinate data values ​​obtained in step S5 into the text document, and then save the text document as the first file with the set format;

[0018] S7. Open the first file using 3D software;

[0019] After generating curves in S8 3D software, export and save them as a second file in the specified format.

[0020] S9. Open the second file and perform a simulation comparison with the inner curve profile of the sample stator obtained in step S1.

[0021] S10. Based on the comparison results, adjust the lift angle and curve design coefficient, recalculate, and then execute steps S5 to S9 again until the generated curve is consistent with the inner curve profile of the sample stator.

[0022] S11. Import the polar coordinate data obtained in step S4 into the CNC stator curve grinding machine and perform trial machining of the stator inner curve.

[0023] S12. Inspect whether the inner curve profile of the stator during trial machining is consistent with the inner curve profile of the sample stator.

[0024] In step S2, the lift angle is initially estimated based on the oil window angles of the front and rear oil distribution plates and the dimensions of the unloading groove of the sample stator.

[0025] In step S3, the design parameters of the sample stator include the major diameter and minor diameter data of the sample stator.

[0026] In step S3, the displacement calculation formula is as follows: Where R is the major radius of the arc portion of the inner surface of the vane pump stator, r is the minor radius of the arc portion of the inner surface of the vane pump stator, h is the vane height, s is the vane thickness, z is the number of vanes, and θ is the vane tilt angle.

[0027] In step S4, the lift angle, the major diameter and minor diameter data of the sample stator are substituted into the curve design tool for calculation to obtain 361 points of polar coordinate data.

[0028] In step S5, a new Excel spreadsheet is created to convert the polar coordinate data of 361 points into rectangular coordinates, with the Z value set to 0 for all points.

[0029] In step S7, the 3D software used is UG software.

[0030] In step S8, after the curve is generated, it is exported from the drawing module environment of UG software and saved in dxf or dwg format.

[0031] The method for designing the internal curve of the stator of the balanced vane pump also includes the following steps: S13, installing the stator with consistent measurement results into the pump assembly, and then conducting a test.

[0032] The method for designing the inner curve of the stator of a balanced vane pump according to the present invention has the following beneficial effects:

[0033] 1. CNC profile grinding machines are used to manufacture stator internal curves instead of cam grinding machines. Because the machining variables of CNC profile grinding machines are controllable and have automatic compensation functions, the stator internal curves have a high pass rate and good consistency.

[0034] 2. CNC profile grinding machines can manufacture stator internal curves without secondary clamping. After the rough grinding of the curve is completed, the worktable is moved to the fine grinding area for the final machining of the curve. This process is quick, efficient, and ensures the perpendicularity and roughness of the curve.

[0035] 3. The cam grinding of the stator inner curve is a product with a single model and the contour cannot be modified. Especially for products with the same positioning method, the same minor diameter, and different major diameters, trial processing can be achieved simply by modifying the curve design parameters using this method.

[0036] 4. The use of cams for grinding is eliminated, which saves on the cost of using cams and shortens the mass production time. Attached Figure Description

[0037] This manual includes the following figures, which illustrate the following:

[0038] Figure 1 It is a stator internal curve diagram;

[0039] Figure 2 This is a schematic diagram of the inner surface structure of the stator of a balanced vane pump in the prior art. Detailed Implementation

[0040] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, in order to help those skilled in the art to have a more complete, accurate and in-depth understanding of the concept and technical solutions of the present invention, and to facilitate its implementation.

[0041] This invention provides a method for designing the internal curve of the stator of a balanced vane pump, comprising the following steps:

[0042] S1. Obtain the inner curve profile of the sample stator as a reference standard;

[0043] S2. Preliminary estimation of the lift angle of the sample stator;

[0044] S3. Measure the design parameters of the sample stator and verify whether the stator displacement meets the design requirements according to the displacement calculation formula.

[0045] S4. Based on the obtained design parameters of the sample stator, use a curve design tool to calculate and obtain the polar coordinate data of a set number of points on the inner curve contour of the sample stator.

[0046] S5. Convert the obtained polar coordinate data of a set number of points into rectangular coordinates;

[0047] S6. Create a new text document, copy the rectangular coordinate data values ​​obtained in step S5 into the text document, and then save the text document as the first file with the set format;

[0048] S7. Open the first file using 3D software;

[0049] After generating curves in S8 3D software, export and save them as a second file in the specified format.

[0050] S9. Open the second file and perform a simulation comparison with the inner curve profile of the sample stator obtained in step S1.

[0051] S10. Based on the comparison results, adjust the lift angle and curve design coefficient, recalculate, and then execute steps S5 to S9 again until the generated curve is consistent with the inner curve profile of the sample stator.

[0052] S11. Import the polar coordinate data obtained in step S4 into the CNC stator curve grinding machine and perform trial machining of the stator inner curve.

[0053] S12. Inspect whether the inner curve profile of the stator during trial machining is consistent with the inner curve profile of the sample stator.

[0054] S13. Install the stator with consistent measurement results into the assembly pump, and then conduct the test;

[0055] S14. After meeting the above conditions, conduct small-batch trial assembly verification, and finally solidify and archive the stator curve data.

[0056] Specifically, the stator inner curve design method of the balanced vane pump of the present invention involves calculating and correcting the stator inner curve data using a self-developed curve design tool, and then importing the designed data into a CNC curve grinding machine to perform stator inner curve processing.

[0057] like Figure 1 As shown, the internal curve of the stator of the balanced vane pump mainly consists of eight parts: the small diameter region, the suction lift region, the large diameter region, the pressure drop region, the small diameter region, the suction lift region, the large diameter region, and the pressure drop region. Figure 1 The lb and fh curve segments are the small diameter region, the bc and hi curve segments are the oil suction lift region, the ce and ik curve segments are the large diameter region, and the ef and kl curve segments are the oil pressure drop region.

[0058] Balanced vane pumps, also known as double-acting vane pumps, have two oil suction and discharge processes in each sealed space during one revolution of the rotor. Therefore, the stator curves are arranged symmetrically, meaning that the 0° to 180° range of the stator curves is exactly the same as the 180° to 360° range.

[0059] The minor diameter region of the stator inner curve of a balanced vane pump is a concentric circular curve. This minor diameter is one of the important dimensions for calculating the stator displacement. It is usually measured directly by vernier calipers. In the figure, the bl curve segment and the fh curve segment are symmetrical along the vertical center line, while the ba curve segment, al curve segment, fg curve segment, and gh curve segment are symmetrical along the transverse center line.

[0060] The oil suction lift zone of the stator inner curve of a balanced vane pump is the oil suction zone, also known as the low-pressure zone. In this section of the curve, the hydraulic forces at the vane tip and the vane root are unbalanced. The vane tip acts on the low pressure of the suction chamber, while the root acts on the high pressure of the pressure chamber. The contact pressure between the vane tip and the inner surface curve of the stator is relatively large, making it impossible to form an oil film. This can easily cause wear in this section of the stator curve. Therefore, this section of the curve needs to be corrected using a self-developed curve design tool. After modifying the data parameters, the exported curve is compared with the original curve. The goal is to ensure that the vane can move smoothly along the curve, with no abrupt changes in radial velocity, acceleration, and rate of change of acceleration. At the same time, there should be a common tangent at the connection between the large and small diameters.

[0061] The stator inner curve of a balanced vane pump has a non-circular large-diameter section, also known as the pre-compression curve segment. Because this curve segment acts on the low pressure of the suction chamber at one end and the high pressure of the discharge chamber at the other, when the sealed working chamber changes from low pressure to high pressure, the high-pressure oil will rapidly reverse and flow back into the working chamber, causing a significant hydraulic shock. This greatly affects the pump's pressure pulsation, noise, and wear. Therefore, to prevent high-pressure backflow and hydraulic shock, this curve segment is designed as a non-circular, decreasing curve segment. Figure 1 As shown, the dimensions of points c and i, which are the boundary points between the oil suction lift zone and the large diameter zone, are the maximum dimensions of the inner surface of the stator. This dimension is also one of the important dimensions for calculating the stator displacement. It is usually measured directly by vernier calipers. When rotating from point c to point e and from point i to point k, the polar coordinates of the corresponding points gradually decrease.

[0062] The oil drop section of the stator inner curve of a balanced vane pump is the oil discharge zone, also known as the high-pressure zone. The contact pressure between the vane and the stator in this section is very small, and a good pressure oil film can be formed between them, basically in a fluid lubrication state. The contact pressure between the vane tip and the inner surface curve of the stator is mainly borne by the oil film. There is basically no direct contact friction between metals, and wear is usually not serious. However, the motion trajectory of this section of the curve has a significant impact on the performance and noise of the vane pump. Therefore, this section of the curve also needs to be corrected with the help of curve design tools. After modifying the data parameters, the curve is exported and compared with the original part curve for simulation. The purpose is to ensure that the vane can move smoothly when sliding along the curve, and that there are no sudden changes in radial velocity, acceleration, and rate of change of acceleration. At the same time, there should be a common tangent at the connection with the large and small diameters.

[0063] In step S2 above, the sample stator is projected or measured by coordinate measuring machine to obtain the inner curve profile of the stator, and saved in dxf or dwg format as a reference standard.

[0064] In step S2 above, the lift angle is initially estimated based on the oil window angles of the front and rear oil distribution plates and the dimensions of the unloading groove of the sample stator.

[0065] In step S3 above, the design parameters of the sample stator include the major diameter and minor diameter data of the sample stator. The major diameter and minor diameter data of the sample stator are accurately measured, and then the measurement results are substituted into the displacement calculation formula.

[0066] The formula for calculating displacement is: Where R is the major radius of the arc portion of the inner surface of the vane pump stator, r is the minor radius of the arc portion of the inner surface of the vane pump stator, h is the vane height, s is the vane thickness, z is the number of vanes, θ is the vane tilt angle, and R, r, h, s, z and θ are curve design coefficients.

[0067] In step S4 above, the lift angle, the major diameter and minor diameter data of the sample stator are substituted into the curve design tool for calculation to obtain 361 points of polar coordinate data.

[0068] Curve Design Tool Instructions: After inputting the lift angle, stator major diameter, and minor diameter, the tool calculates the polar coordinates of 361 points. These 361 points can then be input into the CNC machine tool for machining. The lift angle is obtained (estimated) by projecting the oil window angle of the distribution plate. Since the starting angle of the oil suction lift zone within the stator curve is uncertain (some products start at the oil suction window on the distribution plate, while others start one degree earlier), the accurate lift angle can only be determined by comparing the calculated 361 points with a sample part.

[0069] The principle of the curve design tool is as follows: set 0 to 361 angles, each angle corresponds to a point polar coordinate. In the small diameter area, the polar coordinate of the point is equal to half of the small diameter. In the oil suction lift area and the oil pressure drop area, set variable coefficients, calculate the sum and difference of the result with the small diameter through formula (1), modify the variable coefficient value, so that the corresponding polar coordinate value ρ changes. In the large diameter area, measure the change value of the stator large arc part size, calculate the difference between the result and the large diameter through formula (2), and obtain the corresponding polar coordinate value g. Then, use the angle to radian formula to obtain the X and Y values ​​of the 361 points obtained, select 0 for all Z values, and finally copy the X, Y and Z values ​​of the 361 points obtained and import them into UG software to generate curves.

[0070]

[0071] Where R is the major radius of the arc portion of the inner surface of the vane pump stator, r is the minor radius of the arc portion of the inner surface of the vane pump stator, θ is the transition curve angle, and α is the lift angle.

[0072]

[0073] Where d is the difference in the major diameter of the inner curve of the stator, a is the decreasing angle, and β is the decreasing curve angle.

[0074] In step S5 above, a new Excel spreadsheet is created to convert the polar coordinate data of 361 points into rectangular coordinates (X, Y, Z values), with the Z value set to 0.

[0075] In step S6 above, create a new text document, copy the 361 data values ​​of rectangular coordinates (X, Y, Z values) into the text document, save the text document as the first file, and change the file extension of the first file to .dat.

[0076] In step S7 above, the 3D software used is UG (Unigraphics NX). Open UG software, in the new model environment, click the Insert Spline command, and select the first file saved earlier by selecting points from the file.

[0077] In step S8 above, after the curve is generated, it is exported from the UG software's drawing module environment and saved in dxf or dwg format to form a second file.

[0078] In step S9 above, the second file is opened in the CAD software and compared with the sample stator profile obtained in step S1.

[0079] In step S10 above, based on the comparison results, adjust the lift angle, curve design coefficient and other data, recalculate and repeat steps S5 to S9 until the lift curve is consistent with the original sample curve height.

[0080] In step S11 above, the 361 polar coordinate data points generated in step S4 are imported into a CNC stator curve grinding machine for trial machining of the stator inner curve.

[0081] In step S12 above, the stator produced in the trial process is subjected to coordinate measuring machine (CMM) measurement to see if the inner curve profile of the stator is consistent with the inner curve profile of the standard sample.

[0082] In step S13 above, the stator with consistent measurement results is installed into the assembly pump, and its performance, noise, and wear on the inner curved surface are tested.

[0083] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution; or the direct application of the inventive concept and technical solution to other situations without modification, are all within the protection scope of the present invention.

Claims

1. A method for designing the internal curve of the stator of a balanced vane pump, characterized in that, Including the following steps: S1. Obtain the inner curve profile of the sample stator as a reference standard; S2. Preliminary estimation of the lift angle of the sample stator; S3. Measure the design parameters of the sample stator and verify whether the stator displacement meets the design requirements according to the displacement calculation formula. S4. Based on the obtained design parameters of the sample stator, use a curve design tool to calculate and obtain the polar coordinate data of a set number of points on the inner curve contour of the sample stator. S5. Convert the obtained polar coordinate data of a set number of points into rectangular coordinates; S6. Create a new text document, copy the rectangular coordinate data values ​​obtained in step S5 into the text document, and then save the text document as the first file with the set format; S7. Open the first file using 3D software; After generating curves in S8 3D software, export and save them as a second file in the specified format. S9. Open the second file and perform a simulation comparison with the inner curve profile of the sample stator obtained in step S1. S10. Based on the comparison results, adjust the lift angle and curve design coefficient, recalculate, and then execute steps S5 to S9 again until the generated curve is consistent with the inner curve profile of the sample stator. S11. Import the polar coordinate data obtained in step S4 into the CNC stator curve grinding machine and perform trial machining of the stator inner curve. S12. Inspect whether the inner curve profile of the stator during trial machining is consistent with the inner curve profile of the sample stator.

2. The method for designing the stator inner curve of a balanced vane pump according to claim 1, characterized in that, In step S2, the lift angle is initially estimated based on the oil window angles of the front and rear oil distribution plates and the dimensions of the unloading groove of the sample stator.

3. The method for designing the stator inner curve of a balanced vane pump according to claim 1, characterized in that, In step S3, the design parameters of the sample stator include the major diameter and minor diameter data of the sample stator.

4. The method for designing the stator inner curve of a balanced vane pump according to any one of claims 1 to 3, characterized in that, In step S3, the displacement calculation formula is as follows: Where R is the major radius of the arc portion of the inner surface of the vane pump stator, r is the minor radius of the arc portion of the inner surface of the vane pump stator, h is the vane height, s is the vane thickness, z is the number of vanes, and θ is the vane tilt angle.

5. The method for designing the stator inner curve of a balanced vane pump according to any one of claims 1 to 3, characterized in that, In step S4, the lift angle, the major diameter and minor diameter data of the sample stator are substituted into the curve design tool for calculation to obtain 361 points of polar coordinate data.

6. The method for designing the stator inner curve of a balanced vane pump according to claim 5, characterized in that, In step S5, a new Excel spreadsheet is created to convert the polar coordinate data of 361 points into rectangular coordinates, with the Z value set to 0 for all points.

7. The method for designing the stator inner curve of a balanced vane pump according to any one of claims 1 to 6, characterized in that, In step S7, the 3D software used is UG software.

8. The method for designing the stator inner curve of a balanced vane pump according to claim 7, characterized in that, In step S8, after the curve is generated, it is exported from the drawing module environment of UG software and saved in dxf or dwg format.

9. The method for designing the stator inner curve of a balanced vane pump according to any one of claims 1 to 6, characterized in that, It also includes the following steps: S13. Install the stator with consistent measurement results into the assembly pump, and then conduct the test.

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