A method for quickly trimming an ellipsoidal worm grinding wheel for grinding face gears

Abstract

The application belongs to the technical field of face gear grinding processing, and particularly relates to a method for quickly cleaning a root of an ellipsoidal worm grinding wheel for grinding a face gear. The initial position of a roller cutter and the ellipsoidal worm grinding wheel is defined; the minimum side gap between the helical surface of the ellipsoidal worm grinding wheel and the roller grinding edge during the cleaning process is calculated; and the minimum side gap obtained in step 2 is ensured to be not more than the critical side gap, and the cleaning root process of the ellipsoidal worm grinding wheel is completed. By adjusting the rotation angle of the A-axis of the machine tool, and combining the linkage of the B, Y and Z axes of the machine tool, the roller can sequentially clean the residual amount at the root of the grinding wheel along the helical groove track of the grinding wheel without interference with the helical surface of the grinding wheel. Compared with the previous cleaning root method, the total length of the cleaning root is 22 seconds. If the previous cleaning root numerical control program is used to clean the residual amount at the root of the grinding wheel completely, the total length of the cleaning root shown in the generated report is 606 seconds, and the time cost saving rate can reach 96%.

Description

Technical Field

[0001] This invention belongs to the field of face gear grinding technology, specifically relating to a method for rapid root cleaning and dressing of an ellipsoidal worm grinding wheel for grinding face gears. Background Technology

[0002] Face gear transmission has advantages such as compact structure, convenient installation and debugging, and large overlap, and has been successfully applied in many occasions such as helicopter main reducers and automobile differentials.

[0003] In the aerospace industry, the precision requirements for the tooth surfaces of face gears are very high. Therefore, research on high-precision grinding technology for hardened face gears is particularly important. To adapt to the special tooth structure of face gears, grinding tools need to be designed specifically for them. With technological innovation, the face gear grinding tool currently used is an ellipsoidal worm wheel with complex curved surface features. Currently, high-precision machining of face gears is mainly carried out through grinding with ellipsoidal worm wheels. Compared with disc grinding wheels, ellipsoidal worm wheels have the advantages of high grinding accuracy, fast grinding efficiency, and relatively lower requirements for machine tool precision. Its disadvantage is that its complex curved surface dressing is relatively difficult.

[0004] The design and dressing of ellipsoidal worm grinding wheels are crucial for improving the tooth surface accuracy and grinding efficiency of face gears. Currently, the design and dressing methods of ellipsoidal single-start worm grinding wheels for grinding face gears have been gradually developed. However, as the research deepens, new challenges have emerged in grinding face gears with ellipsoidal single-start worm grinding wheels.

[0005] After dressing, standard double-cone diamond grinding wheels leave noticeable root residue at the tooth root. This residue interferes with the tooth tip of face gears during grinding, requiring cleaning with a grinding wheel – a process known as root cleaning. Root cleaning with ellipsoidal worm grinding wheels has always been a crucial step in grinding wheel dressing technology. However, current root cleaning processes suffer from incomplete toolpath planning for the grinding wheel tool, resulting in over 80% of the toolpath being idle travel during the process, which is extremely time-consuming. While offsetting the grinding wheel dressing trajectory can achieve root cleaning, this method also involves significant idle travel, leading to very low root cleaning efficiency.

[0006] Therefore, there is an urgent need to propose a rapid root clearing and trimming method in order to solve the above-mentioned technical problems. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing root cleaning processes, such as excessive idle travel and low efficiency, by proposing a novel method for rapid root cleaning of gear grinding surfaces using an ellipsoidal worm wheel. This method involves determining a point E on the top of the roller and placing this point at the root of the tooth groove of the ellipsoidal worm wheel, ensuring that point E can only move along the helical trajectory at the root of the grinding wheel. By adjusting the rotation angle of the machine tool's A-axis and coordinating the B, Y, and Z axes, the roller can sequentially clean the residual material at the root of the grinding wheel along the helical groove trajectory without interfering with the helical surface of the grinding wheel, significantly improving the root cleaning efficiency of the grinding wheel.

[0008] To achieve the above objectives, the present invention provides a technical solution:

[0009] A method for rapid root cleaning and dressing of ellipsoidal worm grinding wheels for grinding gear surfaces includes the following steps:

[0010] Step 1: Define the initial positions of the roller cutter and the ellipsoidal worm wheel for root cleaning;

[0011] Step 2: Calculate the minimum backlash between the helical surface of the ellipsoidal worm wheel and the grinding edge of the roller during the root cleaning process;

[0012] Step 3: Ensure that the minimum backlash obtained in Step 2 does not exceed the critical backlash, and complete the root cleaning process of the ellipsoidal worm wheel.

[0013] A further technical solution of the present invention is as follows: In step 1, the initial position definition process is as follows: a point E is determined on the top of the roller, the conical roller is placed in the central tooth groove on the top of the grinding wheel, and point E is placed on the root circle of the tooth groove in the middle part of the virtual production gear, wherein point E is the intersection of the horizontal line where the roller dressing point G is located and the vertical symmetry line of the roller.

[0014] A further technical solution of the present invention is: in step 2, the minimum side clearance calculation process is as follows:

[0015] Establish a coordinate system at the vertex of the grinding edge on the roller. The X-axis of this coordinate system coincides with the grinding edge on the roller, and the Y-axis is perpendicular to the grinding edge and points outward. When the roller rotates around point E, the grinding edge on the roller will approach a tooth profile of the virtual feed gear. Represent the discrete points of this virtual feed gear tooth profile on the coordinate system at the vertex of the grinding edge on the roller. Find the minimum value y among the discrete points. min y min This refers to the minimum backlash between the roller grinding blade and the helical surface of the ellipsoidal worm wheel during the rapid root cleaning process.

[0016] A further technical solution of the present invention is: in step 3, the process of cleaning the root of the ellipsoidal worm wheel is as follows:

[0017] Position the grinding wheel and roller at the initial cleaning position defined in step 1. The conical roller is now in the middle of the grinding wheel cutting edge width. The cleaning of the root residue on each side of the grinding wheel cutting edge width is divided into n rounds. Each adjustment of the machine tool A-axis angle represents one round. The process for each round is as follows: After the machine tool A-axis is given a rotation angle and fixed, when the machine tool B-axis starts to rotate, the machine tool Y and Z axes compensate for the offset of the ellipsoidal worm grinding wheel helical tooth groove caused by the rotation through linkage, so that the roller E point is fixed in the relative position of the grinding wheel groove.

[0018] A further technical solution of the present invention is as follows: In step 3, the cutting width of the grinding wheel is divided into two parts, left and right: first, the right half of the cutting width of the grinding wheel is quickly cleaned, and then the left half of the cutting width of the grinding wheel is quickly cleaned; when cleaning the left half of the grinding wheel, the B axis of the machine tool rotates forward, the virtual feed gear rotates counterclockwise, and the A axis of the machine tool is adjusted clockwise; when cleaning the right half of the grinding wheel, the B axis of the machine tool rotates forward, the virtual feed gear rotates clockwise, and the A axis of the machine tool is adjusted counterclockwise.

[0019] A further technical solution of the present invention is as follows: In step 3, before each round of root clearing, the rotation angle of the machine tool A axis is adjusted so that the rolling profile is close to the safe spiral surface of the grinding wheel. The safe spiral surface of the grinding wheel is defined as the grinding wheel surface that the rolling profile gradually moves away from during each round of processing, and maintains a critical clearance with it, while staying away from the dangerous spiral surface of the grinding wheel. The dangerous spiral surface of the grinding wheel is defined as the grinding wheel surface that the rolling profile gradually approaches during each round of processing.

[0020] A further technical solution of the present invention is: in step 3, the rotation angle of the virtual generating gear is... When the virtual gear rotates clockwise by a certain angle in one cycle... Afterwards, to return the backlash of the grinding wheel and roller to their initial position, the machine tool's A-axis needs to rotate counterclockwise by an angle of [missing value]. satisfy and equal.

[0021] A further technical solution of the present invention is: the geometric motion relationship in step 3 of the root clearing process:

[0022] From the initial position of the root cleaning to the starting position of the first round of root cleaning on the right side of the grinding wheel, the machine tool's A-axis rotates counterclockwise by one angle. With the machine tool rollers fixed, to ensure that point E′ returns to point E, where point E′ is the extreme position of a single roller, the machine tool Y-axis needs to move in the reverse direction by a length a_1, and the machine tool Z-axis needs to move in the forward direction by a length b_1.

[0023] Starting from the first round of cleaning, the machine tool's B, Y, and Z axes work together to clean the root of the grinding wheel. Adjust the angle of the machine tool's A axis. Before starting the second round of cleaning, ensure that the backlash is returned to the initial state. To return from point E′ to point E, the machine tool's Y axis needs to move in the reverse direction by a length a_2, and the machine tool's Z axis needs to move in the forward direction by a length b_2.

[0024] After the starting position of the second round is accurately determined, the machine tool's B, Y, and Z axes are linked to perform root clearing, and the root clearing process is consistent with the first round. Repeat the same round process, including adjusting the machine tool's A axis and performing root clearing with the machine tool's B, Y, and Z axes linked.

[0025] A further technical solution of the present invention is: in step 3, boundary conditions for cleaning the roots on both sides of the grinding wheel are set, and the cycle is stopped by limiting the cumulative amount of the virtual gear rotation angle.

[0026] Beneficial effects:

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] (1) This invention proposes a rapid root cleaning and dressing method for grinding surface gears using ellipsoidal worm grinding wheels, which overcomes the shortcomings of low efficiency in domestic ellipsoidal worm grinding wheel root cleaning technology. The method involves rapidly cleaning and dressing the ellipsoidal worm grinding wheel on a five-axis CNC machine tool. By adjusting the rotation angle of the machine tool's A-axis and combining the linkage of the machine tool's B, Y, and Z axes, the roller can sequentially clean the residual amount at the root of the grinding wheel along the trajectory of the grinding wheel's helical groove without interfering with the helical surface of the grinding wheel. Compared with the previous root cleaning method, the total root cleaning time is 22 seconds. If the previous root cleaning CNC program is used to clean all the residual amount at the root of the grinding wheel, the total root cleaning time shown in the report is 606 seconds, and the time cost saving rate can reach 96%.

[0029] (2) This invention proposes a method for rapid root cleaning and dressing of ellipsoidal worm grinding wheels for grinding gears. During root cleaning, the larger the module and helix angle of the virtual generating gear, the larger the minimum backlash of the roller grinding edge and the helical surface of the grinding wheel; the larger the rotation angle and pressure angle of the virtual generating gear per rotation or the higher the height of the roller dressing point, the smaller the minimum backlash of the roller grinding edge and the helical surface of the grinding wheel; the number of teeth of the virtual generating gear has little effect on the minimum backlash. Attached Figure Description

[0030] Figure 1 Schematic diagram of an ellipsoidal worm gear grinding wheel;

[0031] Figure 2 Image showing the root residue after dressing with a grinding wheel;

[0032] Figure 3 This is a schematic diagram of the initial position of the root clearing.

[0033] Figure 4This is a schematic diagram showing the interference between the grinding wheel blade and the helical surface of the grinding wheel during root cleaning.

[0034] Figure 5 The initial positional geometric relationship of the virtual gear and roller;

[0035] Figure 6 The rotational positional geometry of the virtual gear and roller;

[0036] Figure 7 This is a schematic diagram of the left and right halves of the grinding wheel;

[0037] Figure 8 For cleaning the root, a line graph showing the minimum backlash of the roller grinding edge and the grinding wheel helical surface corresponding to different rotation angles in each round of the virtual gear;

[0038] Figure 9 To clean the starting position of the first cycle on the right side of the single-head worm grinding wheel;

[0039] Figure 10 This marks the starting position for root cleaning on the right side of the grinding wheel;

[0040] Figure 11 This is the limit position for the first round of root cleaning on the right side of the grinding wheel;

[0041] Figure 12 This marks the starting position for the second round of root cleaning on the right side of the grinding wheel.

[0042] Figure 13 This is a schematic diagram of the root boundary.

[0043] Figure 14 Comparison of cleaning effects at the root of an ellipsoidal worm gear grinding wheel;

[0044] Figure 15 This is a schematic diagram of the root cleaning process apparatus.

[0045] The reference numerals in the figure are:

[0046] 11-Ellipsoidal worm grinding wheel; 12-Virtual generating gear normal section; 1-Roller; 2-Grinding wheel tooth profile; 3-Worm grinding wheel; 4-Root residual area; 32-Tooth root circle; 33-Virtual generating gear; 34-Grinding wheel; 41-Roller grinding edge; 44-Roller grinding edge and grinding wheel helical surface interference; 53-Profile one; 54-Profile two; 5-Minimum backlash; 71-Left half of grinding wheel; 73-Right half of grinding wheel; 91-Diamond roller; 93-Machine tool spindle; 101-Starting pose; 104-Virtual generating gear tooth root circle; 115-First round limit pose; 121-Second round starting pose. Detailed Implementation

[0047] The present invention will be further described in detail below with reference to specific embodiments, but this does not constitute any limitation on the present invention.

[0048] Example 1

[0049] See Figures 1-15 The technical solution of the present invention is as follows:

[0050] The technical solution adopted in this invention is: a design method for a double-headed worm grinding wheel for face gear grinding, the method flow of which is as follows:

[0051] The ellipsoidal worm grinding wheel 11 used for grinding gears has a normal tooth profile that simulates the normal tooth profile of a virtual gear, hence it is also called a variable pressure angle worm grinding wheel. Figure 1 The diagram shows an ellipsoidal worm grinding wheel 11. When dressing a worm grinding wheel with a standard double-cone roller, the dressing point of the roller envelops the helical surface of the worm grinding wheel through several helical trajectories. The helical surface has a certain helix angle, so the axial section tooth profile and the normal section tooth profile of the worm grinding wheel are different. Since the helix angle is relatively small, the axial section tooth profile of the worm grinding wheel can be regarded as approximately the same as the normal section.

[0052] The ellipsoidal worm grinding wheel 11 was dressed using a roller, leaving a noticeable root residue at the center of the grinding wheel tooth grooves. Figure 2 The figure shows the root residue after the grinding wheel is dressed. The dotted lines in the figure represent the extreme positions when the roller conical profile dresses the left and right helical surfaces of the worm grinding wheel. Points P and P′ correspond to the extreme positions of the roller dressing point at the root of the grinding wheel, respectively. The shaded area is the root residue area of ​​the grinding wheel that cannot be dressed by the roller.

[0053] Due to the influence of the virtual feed gear parameters and roller parameters, the residual amount at the root of the grinding wheel will vary. If this residual amount is not removed, it may interfere and scrape against the tooth tip of the face gear during subsequent grinding, causing damage to the tooth tip of the face gear. When the worm grinding wheel grinds the face gear, the tooth tip line of the face gear is tangent to the root circle 104 of the virtual feed gear. Therefore, interference and scraping between the grinding wheel root and the tooth tip of the face gear can only be avoided when the residual amount at the root of the ellipsoidal worm grinding wheel 11 does not exceed the root circle of the virtual feed gear.

[0054] This method ensures that the relative position of a point on the top of the conical roller within the helical tooth groove of the worm grinding wheel remains constant during the grinding wheel root cleaning process. The B, Y, and Z axes of the machine tool are linked, allowing the point on the top of the roller to gradually move on the root circle of the virtual generating gear of the generating worm grinding wheel. When the B axis rotates to a certain angle, the A axis angle needs to be adjusted to avoid interference and collision between the grinding wheel surface and the roller surface. Then, the B, Y, and Z axes are linked again to gradually clean the root residue of the grinding wheel.

[0055] Before rapid root clearing, the initial positions of the roller cutter and the ellipsoidal worm wheel 11 for root clearing were determined. To prevent interference between the roller and the wheel during the root clearing process, a calculation model for the minimum side clearance 5 of the roller and the wheel was established, and the influence of relevant parameters on the minimum side clearance 5 was analyzed.

[0056] Step 1: Define the initial positions of the roller cutter and the ellipsoidal worm wheel 11 for root cleaning.

[0057] Since the helical surface of the ellipsoidal worm grinding wheel 11 is generated by a pair of symmetrical involute tooth profiles on both sides of the virtual gear tooth groove, when the B-axis rotation angle of the machine tool is 0°, the normal section tooth profile at the top of the grinding wheel is symmetrical along the middle line of its tooth groove. To simplify the model, the axial section tooth profile at the top of the grinding wheel is set as the normal section tooth profile.

[0058] Place the conical roller into the center tooth groove at the top of the grinding wheel. Figure 3 The diagram shows the initial position for root cleaning. A point E is determined on the top of the roller and placed on the root circle of the virtual gear tooth groove. Point E is the intersection of the horizontal line where the roller dressing point G is located and the vertical symmetry line of the roller. By adjusting the height of the roller dressing point, the amount of insertion of the top of the roller into the root circle 104 of the virtual gear tooth can be adjusted, thereby enabling the removal of residual material from the root of grinding wheels of different sizes.

[0059] Step 2: Calculation of the minimum backlash 5 between the ellipsoidal worm grinding wheel 11 and the roller during the root cleaning process.

[0060] During the root cleaning process, the roller grinding edge 41 may interfere with the helical surface of the ellipsoidal worm grinding wheel 11. Figure 4 The diagram shows the interference between the grinding wheel cutting edge 41 and the helical surface of the grinding wheel during root cleaning. Figure 4 (b) is Figure 4 (a) is a magnified view of a portion of the image.

[0061] To prevent root cleaning interference, it is necessary to solve for the minimum backlash 5 between the roller grinding edge 41 and the helical surface of the ellipsoidal worm grinding wheel 11. To find the minimum backlash 5 between the roller grinding edge 41 and the helical surface of the grinding wheel, it is first necessary to obtain the tooth surface equations of the grinding wheel cross-sectional profile and the roller cross-sectional profile at the initial root cleaning position.

[0062] The tooth surface equation of the virtual gear is given as follows:

[0063]

[0064] In the formula, r s M is the radial vector of the gear; sc The coordinate transformation matrix for the rack cutter and the gear; r c n is the radial vector of the rack cutter; s n is the normal vector of the gear;c is the normal vector of the rack cutter.

[0065]

[0066] In the formula, f cs The meshing equation between the rack cutter and the feed gear; n s The normal vector of the gear; v cs (s) The relative speed between the rack cutter and the feed gear.

[0067] The cross-sectional profile equation of the roller is given as follows:

[0068] Establish a coordinate system X at point E on the roller section. g O g Y g , Figure 5 (a) shows the initial positional geometry of the virtual gear and roller. Figure 5 (b) shows a magnified view of the minimum side clearance 5 at the initial position, where the roller semi-cone angle is known to be α. g The thickness of the roller top is S g The height of the roller dressing point is H. g ,but

[0069] The equation of the straight line for the roller cross-section profile 53 is:

[0070]

[0071] The equation of the straight line for the roller cross-section profile 2.54 is:

[0072]

[0073] The coordinate points of the roller cross-section profile are changed from the coordinate system X. g O g Y g Transform to the coordinate system X of the virtual gear s O s Y s The transformation matrix is ​​as follows:

[0074]

[0075] In the formula, r fs The radius of the root circle of the virtual gear.

[0076] The solution for the minimum backlash 5 of the grinding wheel shaft section tooth profile and the roller section tooth profile can be simplified to the solution for the minimum backlash 5 of the virtual gear normal section 12 tooth profile and the roller section profile. Let the vertex of the roller profile 53 be in the coordinate system X. s O s Y sThe coordinates on the curve are (x_g, y_g). To easily obtain the minimum side clearance 5, a coordinate system X is established at the vertex of the rolling profile 53. b O b Y b ,like Figure 5 As shown, X b The shaft coincides with the roller cross-sectional profile 53. Then, the coordinate point set of the virtual gear tooth profile above the roller cross-sectional profile 53 is moved from its own coordinate system X. s O s Y s Transform to X b O b Y b In the coordinate system, the transformation matrix is:

[0077]

[0078] in,

[0079]

[0080]

[0081] In the formula, α g θ is the semi-cone angle of the roller; b For line segment O b O s With the horizontal axis X g The included angle; O b O s Point O b Point O s The length.

[0082] In coordinate system X b O b Y b The above diagram shows the set of coordinate points on the tooth profile of the virtual gear. The y-value of each coordinate point is the distance from the tooth profile point to the roller section profile -53. Therefore, the minimum value y can be obtained. min This value is the minimum side clearance 5 between the initial positions of the roller surface and the grinding wheel surface.

[0083] The minimum backlash 5 between the grinding wheel and the roller at different rotation angles during the root cleaning process is calculated below. The grinding wheel is determined to be right-handed. When the machine tool's B-axis rotates by a certain angle... At that time, the virtual gear rotates by an angle. Simultaneously, the Y and Z axes of the machine tool are linked, ensuring that the relative position of point E of the roller remains unchanged at the virtual gear tooth groove. Figure 6(a) shows a schematic diagram of the rotational positional geometry of the virtual gear and the roller. The roller grinding edge 41 moves from position ① to position ②. The distance between the roller grinding edge 41 at position ② and the two sides of the tooth groove of the virtual gear changes. When the roller grinding edge 41 rotates from position ① along point E by an angle... When the roller grinding edge 41 at position ③ changes in the distance between the two sides of the virtual gear tooth groove, it is the same as the change in the distance between the roller grinding edge 41 at position ②. Therefore, position ②, which corresponds to the actual working condition of the roller, can be assumed to be position ③, which is easier to analyze geometrically. Figure 6 (b) shows a partial enlarged view of the minimum side clearance 5 at position ③ of the roller grinding edge 41.

[0084] Let the coordinate system be X g O g Y g Rotate counterclockwise by one angle around point E To coordinate system X g′ O g′ Y g′ The coordinate points of the rolling profile are moved from the X coordinate system. g′ O g′ Y g′ Transform to coordinate X s O s Y s The transformation matrix is ​​as follows:

[0085]

[0086] In the formula, r fs The radius of the root circle of the virtual gear; The rotation angle of the virtual gear.

[0087] Let the vertices of the rotated roll profile (53) lie in the coordinate system X. s O s Y s Let the coordinates on the vertex be (x_g′, y_g′). Establish a coordinate system X at this vertex. b′ O b′ Y b′ ,like Figure 6 As shown in (a), where X b′ The shaft and roller cross-sectional profile coincide at 53. Then, the coordinate point set of the tooth profile on the virtual gear is moved from its own coordinate system X. s O s Y s Transform to X b′ O b′ Y b′ In the coordinate system, the transformation matrix is:

[0088]

[0089] in,

[0090]

[0091]

[0092] In the formula, α g θ is the semi-cone angle of the roller; b′ For line segment O b′ O s The angle with the horizontal axis; For virtual gear rotation angle; O b′ O s Point O b′ Point O s The length.

[0093] In coordinate system X b′ O b′ Y b′ The above diagram shows the set of coordinate points on the tooth profile of the virtual gear. The y-value of each coordinate point is the distance from the tooth profile point to the roller section profile -53. Therefore, the minimum value y can be obtained. min This value is the minimum side clearance 5 between the roller surface and the grinding wheel surface at different rotation angles during the root cleaning process.

[0094] Step 3: Rapid root cleaning process using an ellipsoidal worm gear grinding wheel

[0095] Position the grinding wheel and roller at the initial cleaning positions defined in step 1. The conical roller is now at the midpoint of the grinding wheel's width. Divide the grinding wheel into two parts, as follows: Figure 7 As shown.

[0096] During the root cleaning process, the right half 73 of the grinding wheel is cleaned first, followed by the left half 71. The root residue cleaning on each side is divided into n rounds. Each adjustment of the A-axis angle represents one round. The process for each round is as follows: After fixing the A-axis of the machine tool at a given rotation angle, when the B-axis of the machine tool begins to rotate, the Y and Z axes of the machine tool compensate for the offset of the helical tooth groove of the ellipsoidal worm grinding wheel 11 due to rotation, so that the roller E point is fixed in the relative position of the grinding wheel groove. As the grinding wheel rotates, the rotation angle of the virtual feed gear gradually increases, and the side clearance between the roller grinding edge 41 and the grinding wheel helical surface continuously decreases. When the virtual feed gear rotates to a certain angle, the side clearance between the roller grinding edge 41 and the grinding wheel helical surface reaches its minimum value.

[0097] Before cleaning the root, the critical backlash between the grinding wheel edge 41 and the helical surface of the grinding wheel must be determined (the critical backlash is the minimum backlash 5 between the grinding wheel and the grinding wheel so that their tooth surfaces do not interfere with each other during root cleaning). If the backlash between the grinding wheel edge 41 and the helical surface of the grinding wheel is less than the critical value, tooth surface interference may occur during the machining process, which may damage the grinding wheel tooth surface. Therefore, before the start of the next cycle of operation, the A-axis rotation angle of the machine tool must be adjusted so that the backlash between the grinding wheel edge 41 and the helical surface of the grinding wheel returns to the safe range.

[0098] The minimum backlash 5 of the roller grinding edge 41 and the grinding wheel helical surface during root cleaning will be affected by the rotation angle, module, pressure angle, helix angle, number of teeth, and roller dressing point height of each round of the virtual production gear. The following example will illustrate this in detail. The initial basic parameters used in the example are shown in Table 1.

[0099] Table 1. Basic parameters required for solving the minimum backlash of roller grinding and grinding wheel helical surfaces.

[0100]

[0101]

[0102] Given a series of virtual gear rotation angles per rotation, according to step 2, the minimum backlash 5 of the grinding wheel's helical surface and the grinding roller's grinding edge 41 during root cleaning are calculated. Figure 8 The figure shows the minimum backlash 5 of the roller grinding edge 41 and the grinding wheel helical surface corresponding to different rotation angles of the virtual gear in each rotation. As can be seen from the figure, the larger the rotation angle of the virtual gear in each rotation during root cleaning, the smaller the minimum backlash 5 of the roller grinding edge 41 and the grinding wheel helical surface.

[0103] For the parameters of virtual gear module, pressure angle, helix angle, number of teeth and roller dressing point height, calculation examples are performed one after another.

[0104] Conclusion: During root clearing, the larger the module and helix angle of the virtual gear, the larger the minimum backlash 5 of the roller grinding edge 41 and the grinding wheel helical surface; the larger the rotation angle and pressure angle of the virtual gear per rotation or the higher the height of the roller dressing point, the smaller the minimum backlash 5 of the roller grinding edge 41 and the grinding wheel helical surface; the number of teeth of the virtual gear has little effect on the minimum backlash 5.

[0105] By determining the five parameters—rotation angle, module, pressure angle, helix angle, and roller dressing point height—of the virtual feed gear per rotation, the minimum backlash 5 of the roller grinding edge 41 and the helical surface of the grinding wheel during root cleaning can be obtained. It must be ensured that this minimum backlash 5 does not exceed the critical backlash. Once the basic parameters of the roller and the virtual feed gear are determined, the minimum backlash 5 can be adjusted in real time using the roller dressing point height and the rotation angle of the virtual feed gear per rotation. The roller dressing point height needs to be adjusted appropriately based on the amount of residue at the root of the grinding wheel, while the rotation angle of the virtual feed gear per rotation can effectively adjust the minimum backlash 5.

[0106] The rotation angle range of the virtual generator gear in each round is limited, restricting the rotation angle range of the machine tool's B-axis in each round. The rotation angle range of the B-axis, in turn, determines the length of the root clearing path in each round. The total root clearing path is constant. When the root clearing path in each round is short, the number of rounds of root clearing increases, leading to a greater accumulation of motion errors on each axis of the machine tool. Therefore, it is necessary to find ways to increase the rotation angle of the virtual generator gear in each round of root clearing.

[0107] To increase the virtual gear rotation angle during each round of root clearing, the A-axis rotation angle must be adjusted before each round of root clearing to bring the rolling profile closer to the grinding wheel's safety spiral surface (grinding wheel safety spiral surface: the grinding wheel surface from which the rolling profile gradually moves away during each round of machining), maintaining a critical clearance with it, and keeping it away from the grinding wheel's danger spiral surface (grinding wheel danger spiral surface: the grinding wheel surface from which the rolling profile gradually moves towards during each round of machining). Figure 9 The image shows the initial position of the first cycle for cleaning the right side of the single-head worm grinding wheel. This method of adjusting the starting position 101 of the grinding wheel for each cycle by adjusting the A-axis rotation angle can double the range of side clearance variation between the roller grinding edge 41 and the grinding wheel helical surface in each cycle, and extend the grinding wheel cleaning path length in each cycle to nearly twice the original length.

[0108] After the first round of B, Y, and Z axis linkage is completed, the rotation angle of the virtual production gear is... At this point, the rotation angle of axis A needs to be adjusted to prepare for the next round of grinding wheel cleaning. It has been verified that when the virtual feed gear rotates clockwise by one angle in one round... Afterwards, to return the backlash between the grinding wheel and the roller to its initial position, the A-axis needs to rotate counterclockwise by an angle of... and and equal.

[0109] Since the center of the grinding wheel on the machine tool does not coincide with axis A, the distance O from axis A to the center of the virtual production gear can be obtained when the offset distance of axis A from the center of the grinding wheel is known. s O A :

[0110]

[0111] In the formula, O s The center of the virtual production gear; O w Center of the grinding wheel; O A Center of the machine tool's A-axis; O s O A E is the distance from axis A to the center of the virtual production gear. ws O is the distance between the roller axis and the grinding wheel axis; w O A α3 is the distance from the center of the grinding wheel to the center of axis A; α3 is the distance from the center of the w O A With O w O s The included angle.

[0112] The geometric relationships in the root clearing process will now be explained:

[0113] From the initial position of the root cleaning to the starting position of the first round of root cleaning on the right side of the grinding wheel, the machine tool's A-axis rotation angle rotated counterclockwise by one angle. Figure 10 As shown, with the machine tool rollers fixed, to ensure that point E′ returns to point E, the machine tool's Y-axis needs to move counterclockwise by a length a_1, and the machine tool's Z-axis needs to move clockwise by a length b_1.

[0114]

[0115]

[0116] In the formula, r fs The root circle radius of the virtual gear; O s O A The distance from axis A to the center of the virtual production gear; The rotation angle of the virtual gear.

[0117] Starting from the initial position of the first round, the machine tool uses simultaneous B, Y, and Z axes to clean the root of the grinding wheel. Figure 11 The image shows the limit position of the first round of root cleaning on the right side of the grinding wheel. From the starting position of the first round to the limit position of the first round, the incremental relationship of the machine tool's B, Y, and Z axes is as follows:

[0118]

[0119] In the formula, This represents the angle increment along the B-axis. For virtual gear rotation angle; Z w Z represents the number of worm gear grinding wheel heads. s This refers to the number of teeth on the gear.

[0120] When the virtual gear rotation angle is less than or equal to At that time, roller point E moves clockwise on the root circle of the tooth in the fourth quadrant of the virtual gear coordinate system:

[0121] The positive feed rate ΔY along the Y-axis can be expressed as:

[0122]

[0123] In the formula, r fs The radius of the root circle of the virtual gear is 104. This represents the angle that the virtual gear has already rotated. For the virtual gear rotation angle increment; This is the increment of the grinding wheel rotation angle.

[0124] The negative feed rate ΔZ along the Z-axis can be expressed as:

[0125]

[0126] When the virtual production gear rotation angle is greater than Less than At that time, roller E moves clockwise on the root circle of the first quadrant of the virtual gear:

[0127] The positive feed rate ΔY along the Y-axis can be expressed as:

[0128]

[0129] The positive feed rate ΔZ along the Z-axis can be expressed as:

[0130]

[0131] Adjust the machine tool's A-axis angle to prepare for the second round of root clearing. The virtual feed gear rotated clockwise during the first round of root clearing. To achieve the initial relative position between the roller surface and the grinding wheel surface, the A-axis needs to rotate counterclockwise. angle, Figure 12 The image shows the starting position of the second round of root cleaning on the right side of the grinding wheel.

[0132] The distance the machine tool moves along the Y and Z axes from point E′ back to point E can be expressed as:

[0133] a_2=L_2*sin(α_5) (21)

[0134] b_2=L_2*cos(α_5) (22)

[0135] In the formula, a_2 is the distance the machine tool moves along the Y-axis; b_2 is the distance the machine tool moves along the Z-axis; L_2 is the length from point E to point E′; α_5 is the angle between line segment E′E and the vertical direction.

[0136] After the starting position of the second round is accurately determined, the machine tool begins joint cleaning along the B, Y, and Z axes, following the same cleaning process as the first round. The third and subsequent rounds follow the same process as the second round, including adjusting the A axis and performing joint cleaning along the B, Y, and Z axes. To limit the number of rounds, boundary conditions for cleaning on both sides of the grinding wheel need to be set. Since the virtual feed gear will accumulate rotation angle as the number of rounds increases, the round cycle can be stopped by limiting this accumulation.

[0137] Figure 13 The diagram shown is a schematic of the root cleaning boundary. The thickness of the grinding wheel is known to be T. w When roller E rotates from the top to point M, the intersection of the root circle and the grinding wheel boundary, on the virtual gear tooth root circle 104, the angle corresponding to this arc length is... Solve it

[0138]

[0139] In the formula, T w r is the thickness of the grinding wheel. fs The radius of the root circle of the virtual gear is 104. To limit the boundary conditions for the cumulative rotation angle of the virtual gear, when Greater than When n reaches n, the root clearing loop stops, where n is the number of rounds.

[0140] After cleaning the right side of the grinding wheel, clean the left half of the area. The specific approach is the same as cleaning the right side, with the slight difference that the machine tool's B axis rotates forward, the virtual production gear rotates counterclockwise, and the A axis is adjusted clockwise.

[0141] Example 2

[0142] The following provides a simulation test to verify the above-mentioned rapid root cleaning method of the ellipsoidal worm wheel 11. The relevant parameters of the embodiment are shown in Table 1.

[0143] According to the parameters in the embodiment, the backlash of the worm wheel and roller at the initial root cleaning position is calculated by the program, and the result is 0.5871mm. Then, a critical backlash value is determined to be 0.25mm. The maximum rotation angle per round of the virtual form with a backlash less than the critical backlash value is calculated by the program to be 6°. The limit backlash value under this rotation angle is 0.2761mm. This value is less than the critical backlash value and meets the requirements.

[0144] The VERICUT machining simulation software was used to simulate a YK7363 machine tool performing rapid root cleaning on an ellipsoidal worm grinding wheel 11. For comparison purposes, only the root residue on the right half 73 of the grinding wheel was cleaned. Figure 14The image shows a comparison of the cleaning effect at the root of the ellipsoidal worm grinding wheel 11. As can be seen from the image, the root residue on the right side of the grinding wheel was completely cleaned away, and there was no interference with the helical surface of the grinding wheel.

[0145] The VERICUT software completely cleans the residue at the root of the grinding wheel. A root cleaning report is generated using the software's report creation function. The report shows that the total root cleaning time was 22 seconds. If the traditional root cleaning CNC program were used to completely clean the residue at the root of the grinding wheel, the generated report would show a total root cleaning time of 606 seconds. The time and cost savings rate of the fast root cleaning method can reach 96%.

[0146] In summary, the novel rapid root cleaning method for ellipsoidal worm grinding wheels 11 proposed in this invention overcomes the shortcomings of low efficiency in domestic ellipsoidal worm grinding wheel root cleaning technology. This method enables rapid root cleaning and dressing of the ellipsoidal worm grinding wheel 11 on a five-axis CNC machine tool. By adjusting the A-axis rotation angle of the machine tool and combining the linkage of the B, Y, and Z axes, the roller sequentially cleans the residual material at the root of the grinding wheel along the spiral groove trajectory without interfering with the helical surface of the grinding wheel. Compared with previous root cleaning methods, this method achieves a time cost saving rate of up to 96%, significantly improving the root cleaning efficiency of the grinding wheel.

[0147] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A method for quickly trimming the grinding face of an ellipsoidal worm grinding wheel for grinding face gears, characterized in that: The method comprises the following steps: Step 1: defining the initial position of the roller cutter and the ellipsoidal worm grinding wheel; The initial position definition process is as follows: a point E is determined at the top of the roller, the conical roller is placed into the center tooth groove at the top of the grinding wheel, and the point E is placed on the dedendum circle at the middle part of the virtual profile gear tooth groove, wherein the point E is the intersection of the horizontal line of the roller dressing point G and the vertical symmetry line of the roller; Step 2: calculating the minimum side gap between the ellipsoidal worm grinding wheel helical surface and the roller grinding edge during the grinding process; The minimum side gap calculation process is: a coordinate system is established at the vertex of the grinding blade on the roller, the X axis of the coordinate system is coincided with the grinding blade on the roller, and the Y axis is perpendicular to the grinding blade on the roller and outward, when the roller rotates along the E point by an angle, the grinding blade on the roller will be close to a tooth profile of a virtual generating gear, the discrete points of the virtual generating gear tooth profile are represented on the coordinate system at the vertex of the grinding blade on the roller, and the minimum value y min , y min is found in the y value of the discrete points, that is, the minimum side gap amount of the grinding blade on the roller and the spiral surface of the ellipsoidal worm grinding wheel in the rapid root cleaning process; Step 3: ensuring that the minimum side gap obtained in step 2 does not exceed the critical side gap, and completing the ellipsoidal worm grinding wheel grinding process; The ellipsoidal worm grinding wheel grinding process is as follows: the grinding wheel and the roller are in the initial position defined in step 1, the conical roller is at the middle position of the grinding wheel edge width at this time, the root residual cleaning of each side of the grinding wheel edge width is divided into n times, and each adjustment of the machine tool A-axis angle represents one round. Each round process is as follows: after a rotation angle of the machine tool A-axis is given, the machine tool B-axis is fixed, and when the machine tool B-axis starts to rotate, the machine tool Y and Z axes correct the offset of the ellipsoidal worm grinding wheel helical tooth groove due to rotation through linkage, so that the relative position of the roller E point in the grinding wheel groove is fixed. The grinding wheel edge width is divided into left and right two parts: the right half of the grinding wheel edge width is first quickly cleaned, and then the left half of the grinding wheel edge width is quickly cleaned. When the left half of the grinding wheel is cleaned, the machine tool B-axis rotates forward, the virtual profile gear rotates counterclockwise, and the machine tool A-axis adjusts clockwise. When the right half of the grinding wheel is cleaned, the machine tool B-axis rotates forward, the virtual profile gear rotates clockwise, and the machine tool A-axis adjusts counterclockwise.

2. The method of claim 1, wherein the method is characterized by: In step 3, before each round of cleaning, the rotation angle of the machine tool A-axis is adjusted to make the roller profile close to the safe helical surface of the grinding wheel, the safe helical surface of the grinding wheel is defined as the grinding wheel surface gradually away from the roller profile during each round of machining and maintains a critical side gap, and the dangerous helical surface of the grinding wheel is defined as the grinding wheel surface gradually close to the roller profile during each round of machining.

3. The method of claim 1, wherein the method is characterized by: In step 3, the rotation angle of the virtual gear is φ. s When the virtual gear rotates clockwise by an angle φ in one cycle... s Afterwards, to return the backlash between the grinding wheel and the roller to its initial position, the machine tool's A-axis needs to rotate counterclockwise by an angle of φ. A , satisfying φ A With φ s equal.

4. The method of claim 1, wherein the method is characterized by: In step 3, the geometric motion relationship during the cleaning process is as follows: From the initial position of the root cleaning to the starting position of the first round of root cleaning on the right side of the grinding wheel, the A-axis of the machine tool rotates counterclockwise by an angle φ s In the case of fixed machine tool rollers, to ensure that the E' point returns to the E point, the E' point being the limit position of a single round, the Y-axis of the machine tool needs to move in the reverse direction by a length a_1, and the Z-axis of the machine tool needs to move in the forward direction by a length b_1; From the first round starting position, the machine tool B, Y and Z axes are linked to clean the root of the grinding wheel, the angle of the machine tool A-axis is adjusted, and before the second round of cleaning starts, the side gap amount needs to return to the starting state, so that the E' point returns to the E point, the machine tool Y-axis needs to move reversely by a length a_2, and the machine tool Z-axis needs to move forward by a length b_2; After the starting position of the second round is found, the machine tool B, Y and Z axes are linked to clean, and the cleaning process is consistent with the first round. The consistent round process is repeated, including adjusting the machine tool A-axis and cleaning the machine tool B, Y and Z axes.

5. The method of claim 1, wherein the method is characterized in that: In step 3, the boundary conditions of the grinding wheel on both sides are set, and the cumulative amount of the virtual profile gear rotation angle is limited to stop the round cycle.

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