A machining method of a gearbox oil pump gear and an oil pump gear clamping device

Abstract

The present application relates to a kind of gearbox oil pump gear machining method and oil pump gear clamping device, including grinding wheel dressing process parameter, complete grinding wheel dressing;Control oil pump gear full-tooth surface design precision, at least control three tooth surface distortion precision and drum shape modification in the direction of tooth height and tooth width, carry out tooth area partition modification;Carry out grinding wheel grinding, and tooth profile modification tooth area is partitioned when grinding, realize tooth profile modification, then carry out tooth direction modification and distortion correction;Workpiece is clamped using oil pump gear clamping device, grinding wheel moves, removes surface material.The clamping device has the pressure transmission medium of fluidity, causes the elastic deformation of thin-walled sleeve to the positioning clamping of workpiece, and the device structure is simple, centering is accurate, clamping force is uniform, easy to use and the advantages such as auxiliary time is saved because of clamping and centering simultaneously;Gearbox oil pump gear machining method solves the problem of insufficient gear precision, can effectively guarantee the machining precision requirement and strength requirement of oil pump gear.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of gear machining, and particularly relates to a machining method and clamping device for a gearbox oil pump gear. BACKGROUND

[0002] The double clutch transmission has a complex structure, wherein the gearbox is composed of a plurality of gears and an input shaft, and the oil pump gear is a component part. Since assembly precision and gear precision are required to be high, the positioning reference precision of the inner hole is required to be within 0.01 mm. However, due to the characteristics of the oil pump gear, such as small modulus, small tooth width and large number of teeth, the oil pump gear is easily deformed in the machining process, so that the gear precision is difficult to guarantee. The existing technology generally adopts the expansion sleeve clamping mode, but since the inner hole of the oil pump gear is small, the positioning precision cannot meet the design requirements. SUMMARY

[0003] The application aims to provide a machining method for a gearbox oil pump gear and a clamping device to solve the problem of insufficient gear precision.

[0004] The application is achieved by the following technical scheme.

[0005] A machining method for a gearbox oil pump gear comprises the following steps.

[0006] A. Formulate the grinding wheel dressing process parameters, and complete the grinding wheel dressing by adopting three modes of rough grinding, semi-precision grinding and precision grinding;

[0007] B. Control the design precision of the oil pump gear full tooth surface, control at least three tooth surface distortion precision and drum-shaped modification in the tooth height and tooth width directions, and perform tooth area modification;

[0008] C. Perform grinding wheel grinding, divide the tooth profile modification tooth area during grinding, realize tooth profile modification, and then perform tooth direction modification and distortion correction;

[0009] D. Use the oil pump gear clamping device to clamp the workpiece, so that the coaxiality of the oil pump gear reaches 0.002 mm, the grinding wheel moves, and the surface material is removed.

[0010] Further, the grinding wheel dressing process parameters in step A include the dressing times and the radial dressing feed amount, wherein the radial dressing feed amount is the radial feed amount of the dressing roller relative to the grinding wheel.

[0011] Further, a large radial dressing feed amount is selected for rough grinding to perform one-time dressing, and a small radial dressing feed amount is selected for semi-precision grinding and precision grinding to perform multiple times of dressing. The dressing times are selected to be 1-3 times, the radial dressing feed amount is 0.01-0.05 mm, and suitable speed ratios and minimum overlap ratios are selected.

[0012] Further, the minimum overlap ratio is set to 1.1-10, the overlap ratio is 1.1-2 during rough grinding; the overlap ratio is 4-8 during semi-fine grinding and fine grinding.

[0013] Further, the speed ratio refers to the ratio of the circumferential speed of the dressing roller to the circumferential speed of the grinding wheel, which is selected to be 0.4-0.8 during rough grinding; the speed ratio can be selected to be -0.4--0.8 during fine grinding.

[0014] Further, in step B, the variable pressure angle grinding wheel mode is adopted, the positions of the grinding wheel axial points and the positions of the gear width are corresponded during processing, the reverse compensation of the distortion error is realized, and thus the full tooth surface precision is controlled.

[0015] Further, in step C, the tooth profile modification step is that: according to the modification requirements, the grinding wheel profile corresponding interval is modified (X / Y axis linkage) and the mapping profile is obtained, and the single tooth surface gear grinding reaches the design of the gear tooth profile modification.

[0016] Further, in step C, the tooth modification step is that: according to the tooth end modification, the drum shape and other modification requirements, the grinding wheel is moved through the X / Y / A axis linkage to form the grinding wheel movement track to meet the modification and helix angle correction requirements.

[0017] Further, in step C, the distortion correction step is that: the tooth profile lines at both ends of the tooth direction are set to four positions, the correction values of the four points are set according to the measured tooth profile inclination errors of 1a and 1c, and the grinding wheel is moved through the X / Y / A axis linkage to complete the distortion correction.

[0018] A kind of oil pump gear clamping device for the machining method of gearbox oil pump gear, the oil pump gear clamping device, including clamping body 1, hydraulic expansion sleeve 2, piston rod 3, positioning end face 4 and oil cavity 5, hydraulic expansion sleeve 2 is assembled on clamping body 1 according to hot mounting process, and pre-tightening force is generated, oil cavity 5 is filled with hydraulic oil, piston rod 3 is pushed, and the thin wall part of hydraulic expansion sleeve 2 is uniformly deformed in radial under the pressure action of hydraulic oil, so that the fitting gap between workpiece and hydraulic expansion sleeve 2 is eliminated, so that workpiece is clamped.

[0019] Compared with the prior art, the beneficial effects of the present application are:

[0020] The clamping device has a flowable pressure transmission medium, which causes the thin-walled sleeve to elastically deform to position and clamp the workpiece. The device has the advantages of simple structure, accurate centering, uniform clamping force, easy use, and saving of auxiliary time due to simultaneous clamping and centering. The machining method of gearbox oil pump gear solves the problem of insufficient gear precision, effectively guarantees the machining precision and strength requirements of the oil pump gear. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced as follows. It should be understood that the following drawings only show some of the embodiments of the present application, and therefore should not be considered as a limitation to the scope, and for those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0022] Figure 1 Principle of gear machining generating distortion error;

[0023] Figure 2 Schematic diagram of tooth profile partition modification;

[0024] Figure 3 Schematic diagram of grinding wheel grinding;

[0025] Figure 4 Diagram of grinding wheel motion trajectory;

[0026] Figure 5 Thin wall thickness t / mm of hydraulic expansion sleeve;

[0027] Figure 6 Thin wall thickness t / mm of hydraulic expansion sleeve. DETAILED DESCRIPTION

[0028] The present application will be further described below in conjunction with the embodiments:

[0029] The present application will be further described below in conjunction with the embodiments:

[0030] It should be noted that: similar labels and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. Meanwhile, in the description of the present application, the terms "first", "second" and the like are only used for distinguishing description, and cannot be understood as indicating or implying relative importance.

[0031] The oil pump gear has many machining procedures in the machining process, the gear precision is high, can reach 6 levels, and the roughness Ra is 0.6, but in the machining process, the tooth width is small (7.3mm), the tooth number is large (71), so the full tooth precision is difficult to guarantee. The minimum value of EAP point required by the part drawing is 100.639, the hob is directly designed according to the minimum value in the design, so the position is sensitive after heat treatment. Generally, the allowance of TIF point is required to be more than 0.03mm, but the oil pump gear is thin with small tooth width, and the deformation after heat treatment is larger than other parts, so the TIF point cannot be ground. The present application solves the problems of insufficient precision and the like by changing the gear grinding form, allowance distribution and the dressing strategy of the grinding wheel. Meanwhile, a new clamping device is adopted, the device has a flowable pressure transmission medium, so that the thin-walled sleeve is elastically deformed to position and clamp the workpiece. The device has the advantages of simple structure, accurate centering, uniform clamping force, easy use, saving auxiliary time due to simultaneous clamping and centering and the like.

[0032] The machining method of the gearbox oil pump gear comprises the following steps:

[0033] A, the grinding wheel dressing process parameters are formulated, and three modes of rough grinding, semi-fine grinding and fine grinding are adopted to complete the grinding wheel dressing.

[0034] The grinding wheel dressing process parameters include the dressing frequency and the radial dressing feed amount, wherein the radial dressing feed amount is the radial feed amount of the dressing roller relative to the grinding wheel. A large radial dressing feed amount is selected for rough grinding, and one dressing is performed; small radial dressing feed amounts are selected for semi-fine grinding and fine grinding, and multiple dressings are performed, the dressing frequency is selected to be 1-3 times, the radial dressing feed amount is 0.01-0.05mm, and suitable speed ratio and minimum overlap ratio are selected. The minimum overlap ratio is set to be 1.1-10, the overlap ratio is 1.1-2 for rough grinding, and the overlap ratio is 4-8 for semi-fine grinding and fine grinding. The speed ratio refers to the peripheral speed ratio of the dressing roller relative to the grinding wheel, which is selected to be 0.4-0.8 for rough grinding, and the speed ratio can be selected to be-0.4--0.8 for fine grinding.

[0035] B, the full tooth surface design precision of the oil pump gear is controlled, at least three tooth surface distortion precisions and drum-shaped modifications in the tooth height and tooth width directions are controlled. The variable pressure angle grinding wheel mode is adopted, the positions of the axial points of the grinding wheel and the positions of the gear width are corresponded in the machining process, the reverse compensation of the distortion error is realized, and thus the full tooth surface precision is controlled. The tooth area partition modification is performed.

[0036] C, grinding wheel grinding, tooth profile modification tooth area is divided into zones, tooth profile modification, tooth modification and distortion correction.The steps of the tooth profile modification are: according to the modification requirements, the grinding wheel profile corresponding interval is modified (X / Y axis linkage) and the mapping profile is obtained, and the single tooth surface grinding reaches the design of gear tooth profile modification.The steps of the tooth modification are: according to the tooth end modification, the drum shape and other modification requirements, the grinding wheel is moved through the X / Y / A axis joint movement to form the grinding wheel movement trajectory to achieve the modification and helix angle correction requirements.The steps of the distortion correction are: the tooth profile lines at both ends of the tooth direction are set with four positions, the correction values of the four points are set according to the measured tooth profile inclination errors of 1a and 1c, and the grinding wheel is completed through the X / Y / A axis linkage.

[0037] D, the workpiece is clamped by using the oil pump gear clamping device, so that the coaxiality of the oil pump gear reaches 0.002mm, and the grinding wheel moves to remove the surface material.

[0038] The oil pump gear clamping device used in the processing method of the oil pump gear of the gearbox, the oil pump gear clamping device comprises a clamping body 1, a hydraulic expansion sleeve 2, a piston rod 3, a positioning end face 4 and an oil cavity 5, the hydraulic expansion sleeve 2 is assembled on the clamping body 1 in accordance with the hot assembly process, and a pre-tightening force is generated, the oil cavity 5 is filled with hydraulic oil, the piston rod 3 is pushed, and the thin wall part of the hydraulic expansion sleeve 2 is uniformly deformed in the radial direction under the pressure of the hydraulic oil, so that the fitting gap between the workpiece and the hydraulic expansion sleeve 2 is eliminated, thereby clamping the workpiece.

[0039] The processing method of the oil pump gear of the gearbox, in the grinding, the tooth profile modification tooth area is divided into zones, the tooth profile modification: according to the modification requirements, the grinding wheel profile corresponding interval is modified (X / Y axis linkage) and the mapping profile is obtained, and the single tooth surface grinding reaches the design of gear tooth profile modification.The tooth modification: according to the tooth end modification, the drum shape and other modification requirements, the grinding wheel is moved through the X / Y / A axis joint movement to form the grinding wheel movement trajectory to achieve the modification and helix angle correction requirements.The distortion correction method: the tooth profile lines at both ends of the tooth direction are set with four positions, the correction values of the four points are set according to the measured tooth profile inclination errors of 1a and 1c, and the grinding wheel is completed through the X / Y / A axis linkage.Using the variable pressure angle grinding wheel mode, the positions of the grinding wheel axial points and the positions of the gear width are corresponding in the processing, so that the reverse compensation of the distortion error is realized, and finally the goal of controlling the full tooth surface precision is achieved.

[0040] The machining method of the gearbox oil pump gear wheel comprises the following steps:

[0041] Compared with the traditional expansion sleeve, the clamping device can be smaller, the cooperation gap between the workpiece and the hydraulic expansion sleeve is eliminated, the expansion is more uniform, the elastic deformation amount of the thin-walled sleeve is reduced from 0.012mm to 0.004mm, the deformation of the oil pump gear center hole is reduced, the centering is accurate, the clamping force is uniform, and the auxiliary time is saved due to the simultaneous clamping and centering.

[0042] Embodiment 1

[0043] A machining method of a gearbox oil pump gear wheel comprises the following steps:

[0044] First, reasonable grinding wheel dressing process parameters are given.

[0045] The dressing quality of the grinding wheel will directly determine the error precision of the tooth profile line, and through appropriate dressing process parameter combination, the grinding characteristics of the dressable grinding wheel can be effectively improved to improve the grinding efficiency and the surface quality of the ground tooth surface.

[0046] In this embodiment, the dressing parameters mainly include the following key elements:

[0047] 1. Dressing frequency and radial dressing feed amount.

[0048] The radial dressing feed amount is the radial feed amount of the dressing roller relative to the grinding wheel. With the increase of the radial dressing feed amount, the grinding wheel will be dressed more roughly, and the larger the roughness of the grinding wheel will directly affect the cutting force of the grinding wheel and the shape error value of the dressed tooth profile. In order to ensure the cutting force, a larger radial dressing feed amount is generally selected for rough grinding, and one dressing is performed; in order to ensure the tooth profile shape error and improve the tooth surface precision, a smaller radial dressing feed amount is generally selected for semi-fine grinding and fine grinding, and multiple dressings are performed. The dressing frequency is selected to be 1-3 times, and the radial dressing feed amount is 0.01-0.05mm.

[0049] At the same time, unreasonable speed ratio (close to 0 or 1) and minimum overlap ratio (too close to or equal to 1) should be avoided.

[0050] Because, excessive radial dressing feed will aggravate the wear of dressing roller, even possible to make dressing roller and grinding wheel damage, directly lead to the tooth profile shape error value after grinding wheel dressing, the overlap ratio will seriously affect the surface roughness of grinding wheel and then affect the tooth profile shape error after grinding wheel dressing. The smaller the overlap ratio, the more rough the surface of the grinding wheel after dressing; the larger the overlap ratio, the more delicate the surface of the grinding wheel after dressing. Theoretically the minimum overlap ratio can be 1, but in order to protect the dressing roller, usually set in the range of 1.1~10, avoid to select the limit value. In order to obtain higher grinding efficiency and avoid the risk of grinding burn and crack in rough grinding, the overlap ratio should be small, generally 1.1~2; in order to reduce the grinding surface roughness and tooth profile shape error value, and obtain better grinding surface quality, the overlap ratio should be large in semi-fine grinding and fine grinding, generally 4~8.

[0051] Speed ratio refers to the ratio of the circumferential speed of the dressing roller to the circumferential speed of the grinding wheel. The speed ratio is signed, with the rotating direction of the dressing roller and the grinding wheel at the tangent point being distinguished: positive for same direction, negative for opposite direction. The speed ratio will also seriously affect the roughness of the grinding wheel. Generally, in order to ensure the cutting efficiency of the grinding wheel in rough grinding, the dressing should be carried out in the same direction to make the surface of the grinding wheel rough, the larger the speed, the more rough the grinding wheel tends to be, which can be selected between 0.4~0.8 in rough grinding; in order to reduce the tooth profile shape error of the grinding wheel and improve the precision of the tooth surface, the dressing should be carried out in the same direction to make the surface of the grinding wheel fine, which can be selected between-0.4~-0.8 in fine grinding.

[0052] In the grinding wheel dressing stage, it is usually divided into fine grinding and rough grinding, both of which adopt the strategy of continuous dressing of grinding wheel, while the embodiment adopts three modes of rough grinding, semi-fine grinding and fine grinding, among which semi-fine grinding and fine grinding adopt discontinuous dressing strategy, that is, the first tooth groove, the second tooth groove, the last tooth groove, the third tooth groove, the second last tooth groove and so on are ground first, which can make the tooth groove division more uniform, the grain removal of the grinding wheel moderate, and the cumulative pitch Fp more uniform.

[0053] 2. Secondly, the oil pump gear usually requires full tooth surface design precision control, that is, at least three cross-section precision (tooth surface distortion precision) and drum-shaped modification in tooth height and tooth width direction are required. Due to the processing principle of helical gear, the modification curve at any position of tooth height is different, and the combination of part of the modification curve and its extension to both ends will bring about more or less grinding of the tooth top and tooth root, and the opposite grinding trend of the upper and lower end faces caused by the helix angle will lead to tooth surface distortion, and the helix angle and drum-shaped amount design directly contribute to the distortion. By adopting variable pressure angle grinding wheel mode, the positions of the grinding wheel in the axial direction and the positions of the gear width are corresponded in the processing, so as to realize reverse compensation of distortion error and finally achieve the goal of controlling full tooth surface precision.

[0054] By micro-modifying the gear and tooth direction of the oil pump gear, the micro-modification includes tooth profile modification, tooth direction modification and tooth surface distortion.

[0055] (1) Tooth profile modification: the meshing area (TIF-EAP) is divided into 1-3 intervals, each interval can be provided with straight line or curve modification, and pressure angle correction can be provided, and there are theoretically 32 modification schemes;

[0056] (2) Tooth direction modification: the tooth width B is divided into 1 or 3 intervals, each interval can be provided with straight line or curve modification, and tooth width helix angle correction, and there are theoretically 11 tooth direction modification schemes;

[0057] (3) Tooth surface distortion: three-section (1a / 1b / 1c) tooth profile inclination deviation modification variable V; V=0 without distortion, V≠0 distortion design, usually without distortion design, the tooth profile lines (1a, 1c) at both ends of the tooth direction are provided with four position points, the correction values of the four position points are set according to the measured tooth profile inclination errors of 1a and 1c, and the grinding wheel completes the distortion correction through the joint movement of X / Y / A axes.

[0058] The tooth profile and tooth direction are divided into multiple intervals, each interval can be designed with straight line / curve modification, drum shape, angle correction, and there are more than 30 commonly used combination schemes of tooth profile+tooth direction+distortion, and the modification tolerance is 0.006-0.01mm, and the distortion tolerance is 0.004mm. Through accurate calculation and control of the position of each point, the tooth surface modification and distortion correction accuracy can reach ±0.003mm, 0.004mm.

[0059] 3. The tooth profile modification region is divided into zones, and the tooth profile modification is:

[0060] According to the modification requirements, the grinding wheel profile is modified in the corresponding interval (X / Y axis linkage) and the mapping profile is obtained, and the single tooth surface grinding achieves the design of gear tooth profile modification.

[0061] Tooth direction modification: according to the tooth end modification, drum shape and other modification requirements, the grinding wheel moves through the joint movement of X / Y / A axes to form the grinding wheel movement trajectory to achieve the modification and helix angle correction requirements.

[0062] Distortion correction method: the tooth profile lines at both ends of the tooth direction, (1a, 1c) lines are provided with four positions, and the correction values of the four points are set according to the measured tooth profile inclination errors of 1a and 1c, and the grinding wheel completes the distortion correction through the joint movement of X / Y / A axes. As shown in the figure, the light blue is 1a and the dark purple is 1c. Figure 1

[0063] ​4、Through the above grinding wheel movement mode, surface material can be accurately removed, and machining precision can be effectively improved. Through the above method, the precision of the oil pump gear can be effectively improved, and at the same time, the oil pump gear is used together with a clamping device of the oil pump gear. The device has high centering precision, is in cylindrical surface contact with the inner hole of the oil pump gear, has large contact area, high machining precision and small positioning error, and can make the coaxiality of the oil pump gear reach 0.002 mm. The fixture is composed of a clamp body 1, a hydraulic expansion sleeve 2, a piston rod 3, a positioning end face 4, an oil cavity 5 and the like. The hydraulic expansion sleeve 2 is assembled on the clamp body 1 in interference fit according to the hot mounting process, and generates a certain pre-tightening force. The oil cavity 5 is filled with hydraulic oil, the piston rod 3 is pushed, the thin wall part of the hydraulic expansion sleeve 4 is uniformly deformed in the radial direction under the pressure of the hydraulic oil, and the fitting gap between the workpiece and the hydraulic expansion sleeve is eliminated, so that the workpiece is clamped. Through optimization design, the safe clamping torque of work is 150 N.m, the rated locking stiffness of the hydraulic expansion sleeve is 8000 N.m / °, the working oil pressure range is 30-80 MPa, the outer circle clamping deformation of the workpiece is about 3 mu m, and the maximum stress of the workpiece is about 90 MPa.

[0064] It should be noted that the above are only the preferred embodiments of the present application and the technical principles applied. Those skilled in the art will understand that the present application is not limited to the specific embodiments described herein, and those skilled in the art can make various obvious changes, readjustments and substitutions without departing from the scope of the present application. Therefore, although the present application has been described in more detail through the above embodiments, the present application is not limited to the above embodiments, and can include more other equivalent embodiments without departing from the concept of the present application, and the scope of the present application is determined by the scope of the appended claims.

Claims

1. A method for machining a gearbox oil pump gear, characterized in that, Includes the following steps: A. Establish grinding wheel dressing process parameters, employing three modes: rough grinding, semi-finish grinding, and finish grinding. These parameters include the number of dressing cycles and the radial dressing feed rate, where the radial dressing feed rate is the feed amount of the dressing roller relative to the radial direction of the grinding wheel. For rough grinding, a large radial dressing feed rate is used for a single dressing cycle. For semi-finish and finish grinding, a small radial dressing feed rate is used for multiple dressing cycles, with 1 to 3 cycles and a radial dressing feed rate of 0.01 to 0.05 mm. Suitable speed ratios and minimum overlap ratios are selected. The minimum overlap ratio is set between 1.1 and 10, with 1.1 to 2 for rough grinding and 4 to 8 for semi-finish and finish grinding. The speed ratio refers to the ratio of the dressing roller's circumferential speed to the grinding wheel's circumferential speed; for rough grinding, it is selected between 0.4 and 0.8; for finish grinding, the speed ratio can be selected between -0.4 and -0.

8. B. Control the design accuracy of the entire tooth surface of the oil pump gear, and control the torsion accuracy and drum-shaped modification of at least three tooth surfaces in the tooth height and tooth width directions, and perform tooth section modification. By using a variable pressure angle grinding wheel, the position of each point on the grinding wheel axis corresponds to the position of the gear width during machining, thereby achieving reverse compensation for torsion error and controlling the accuracy of the entire tooth surface. C. Grinding with a grinding wheel: During gear grinding, the tooth profile modification area is divided into sections for tooth profile modification, tooth direction modification, and torsion correction. The tooth profile modification steps are as follows: according to the grinding requirements, the corresponding section of the grinding wheel profile is modified (X / Y axis linkage) to obtain the mapped profile, and single-tooth surface grinding achieves the design of gear tooth profile modification. The tooth direction modification steps are as follows: according to the tooth end edge modification, drum shape, and other edge modification requirements, the grinding wheel moves through the X / Y / A axis in conjunction to form the grinding wheel motion trajectory to achieve the modification and helix angle correction requirements. The torsion correction steps are as follows: four positions are set for the tooth profile lines (1a, 1c) at both ends of the tooth direction. Based on the measured tooth profile tilt error of 1a and 1c, correction values ​​are set for the four points respectively. The grinding wheel completes the torsion correction through the X / Y / A axis linkage. D. Use the oil pump gear clamping device to clamp the workpiece, so that the coaxiality of the oil pump gear reaches 0.002mm, and the grinding wheel moves to remove the surface material.

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