Upper centering fixture for single-tooth broaching of internal splines, broaching system and its design method

Abstract

The present invention discloses an upper centering fixture for internal spline single-tooth broaching, a broaching system and a design method thereof. The upper centering fixture for internal spline single-tooth broaching of the present invention includes an upper centering body and a flat key. The upper centering body is a two-stage stepped shaft with a larger upper diameter and a smaller lower diameter, and a guide rod through hole is axially provided thereon; the outer circle of its small-diameter section is a stop cylindrical surface and is matched with the inner hole of the upper part of the workpiece, and the lower plane of its large-diameter section is a stop step plane and presses on the upper plane of the workpiece; the diameter of the stop cylindrical surface is D1 and the center is point O, the diameter of the guide rod through hole is d1 and the center is point O′. A flat key installation groove is machined at one end of the guide rod through hole along OO′, and a guide rail groove is machined at the other end. The guide rod through hole, the flat key installation groove and the guide rail groove are all axisymmetric figures, and the axis of symmetry is the straight line OO′. The flat key is arranged in the flat key installation groove. The horizontal distance between point O and point O′ is the upper centering eccentricity e, and its value range is 0.5D - (c + n + m - p) ≤ e ≤ 0.5d - (c + n + q + k). The present invention realizes broaching processing throughout the whole process of roughing and finishing, and improves work efficiency.

Description

Technical Field

[0001] The present invention belongs to the field of mechanical manufacturing, and particularly relates to an upper centering fixture used in single-tooth broaching of internal splines, the entire broaching system, and its design method. Background Art

[0002] In the field of mechanical manufacturing, internal splines in heavy machinery have large specifications, many varieties, small batches, and large longitudinal dimensions of teeth (tooth length sometimes reaches 1000 mm). Such large-specification internal splines cannot be processed by general-specification gear shapers and broaching machines, and a broaching machine with a single-row single-tooth broach needs to be selected. For each tooth groove processed, the workpiece rotates intermittently and evenly by 1 / Z turns until Z tooth grooves are broached one by one. Selecting this process for single-piece and small-batch processing of large-specification internal splines is appropriate technically and economically.

[0003] However, there is currently no design method for the eccentricity in the upper centering fixture for heavy-duty internal spline broaching in the industry. In the past, the eccentricity was determined based on empirical values, and the problems that are likely to occur are as follows: First, interference will occur between the tool and the inner hole of the workpiece after the tool is installed, that is, the tool will touch the workpiece before broaching; second, the radial feed of the tool is small and cannot reach the bottom of the keyway, that is, the processing of the keyway cannot be guaranteed. When such problems occur, it is necessary to re-select the machine tool guide rod, feed rod, tool rod, tool, or replace the upper centering, which greatly wastes time, has low production efficiency, and may even cause the scrapping of the entire part. At the same time, due to the lack of control over the installation of the machine tool guide rod, the processing quality of the bottom and side surfaces of the spline groove cannot meet the requirements of the drawing. In addition, due to the lack of space for tool feeding, chips, cutting fluid, and observation in the upper centering, the smooth progress of broaching cannot be guaranteed. Summary of the Invention

[0004] The problem to be solved by the present invention is to provide an upper centering fixture for single-tooth broaching of internal splines, a broaching system, and its design method. The upper centering fixture of the present invention ensures the radial processing of the keyway by determining a reasonable eccentricity. The broaching system of the present invention ensures the processing quality of the keyway itself by the installation requirements for the machine tool guide rod in the broaching system. At the same time, the upper centering fixture of the present invention ensures the smooth progress of broaching by configuring a chip removal groove, etc. In short, the present invention realizes broaching processing throughout the rough and finish machining, greatly saves time, and improves work efficiency.

[0005] The upper centering fixture for broaching a single tooth of internal splines in the present invention includes an upper centering body and a flat key. The upper centering body is a two-stage stepped shaft with a larger upper diameter and a smaller lower diameter, and a guide rod through-hole is axially provided thereon. The outer circle of its small-diameter section is a stop cylinder surface, which is matched with the inner hole of the upper part of the workpiece. The lower plane of its large-diameter section is a stop step plane, which presses on the upper plane of the workpiece. The diameter of the stop cylinder surface is D1, and the center is point O. The diameter of the guide rod through-hole is d1, and the center is point O'. A flat key installation groove is machined at one end of the guide rod through-hole along OO', and a guide rail groove is machined at the other end. The guide rod through-hole, the flat key installation groove, and the guide rail groove are all axisymmetric figures, and the axis of symmetry is the straight line OO'. The flat key is arranged in the flat key installation groove. The horizontal distance between point O and point O' is the upper centering eccentricity e, and its value range is 0.5D - (c + n + m - p) ≤ e ≤ 0.5d - (c + n + q + k). The value of the upper centering eccentricity e is a range, and when taking a specific value within this range, it is e'. In the formula: c is the minimum value of the horizontal installation distance from the cutting tool to the center of the guide rod, and its value is related to the machine tool; n is the projection of the cutting tool in the horizontal direction, and its value is related to the cutting tool; q is the radial cutting space, and its value is related to the processing technology, generally taking more than 5 mm; k is the horizontal distance between the two ends of the bottom surface of the spline and its center, and its value is related to the workpiece; m is the projection of the maximum value of the radial feed of the cutting edge of the cutting tool in the horizontal direction, and its value is related to the machine tool; p is the radial feed allowance, and its value is related to the processing technology, generally taking more than 3 mm; the minor diameter of the spline on the workpiece is d, the major diameter is D, and the groove width is B.

[0006] Further, n = N * cosV, where N is the length of the cutting tool, V is the angle between the tool installation surface and the horizontal plane. The angle V is related to the tool installation surface and the position of point P during use. u is the angle between the tool rod and the front plane of the feed rod, and point P is the contact point between the tool rod and the inclined plane of the feed rod. When the position of point P changes, the angle u changes accordingly. The angle V is preferably between 10° and 13°, that is, n ≈ 0.98N ≈ N.

[0007] Further, a chip removal groove is provided on the upper centering body. The chip removal groove is arranged outside the guide rail groove. The chip removal groove is an axisymmetric figure, and the axis of symmetry is the straight line OO'. The width B1 of the chip removal groove is at least 60 mm wider than the width B of the cutting tool.

[0008] Further, an observation hole is provided on the upper centering body. The width B2 of the observation hole is greater than 80 mm. The observation hole can be without a notch or can have a notch.

[0009] Further, two weight-reducing holes are provided on the upper centering body, and the two weight-reducing holes are symmetric about the straight line OO'.

[0010] Furthermore, two lifting screw holes are provided on the upper centering body. The two lifting screw holes are symmetrical about the straight line OO′, and the deviation value s of the center connection line of the two lifting screw holes from the center O of the upper centering body is the same as the deviation value of the center of gravity of the lower centering fixture.

[0011] The broaching system for internal spline single-tooth broaching of the present invention includes a machine tool workbench, a lead screw, a moving workbench, a rotary workbench, a lower centering fixture, a machine tool guide rod, a feed rod, a tool rod, a tool, and an upper centering fixture. The upper centering fixture includes an upper centering body and a flat key. The moving workbench is connected to the machine tool workbench through the lead screw, the rotary workbench is connected to the moving workbench, the lower centering fixture is fixed on the rotary workbench and positioned by the positioning spigot of the rotary workbench, and the workpiece is placed in the lower centering fixture. The machine tool guide rod passes through the holes of the upper centering fixture, the workpiece, and the lower centering fixture. Its lower end is fixed on the upper plane of the machine tool workbench, and its upper section is matched with the guide rod through hole of the upper centering body and connected to the upper centering body through a flat key. The feed rod and the tool rod are both embedded in the guide groove of the machine tool guide rod. The tool rod is in contact with the feed rod through the feed rod inclined surface, and the tool is arranged on the tool rod.

[0012] The design method of the upper centering fixture and the broaching system of the present invention basically considers the following five aspects to ensure the broaching work of the single-row single-tooth broaching machine: First, there is a radial cutting space; second, there is a radial feed allowance; third, the upper centering controls the machine tool guide rod to be vertical along the vertical direction of the radial feed; fourth, the upper centering controls the machine tool guide rod to be vertical along the radial feed direction; fifth, there is a space for tool movement, chips, cutting fluid, and observation.

[0013] Furthermore, in order to ensure that the tool will not interfere with the inner hole of the workpiece (collide with the tool) after installation and can reach the bottom of the keyway, it is necessary to design the size of the upper centering eccentricity e, which must meet the following two conditions: To ensure the first condition, that is, the tool has a radial cutting space q, the following formula ① should hold: e + c + n + q + k ≤ d / 2, where: the value of the radial cutting space q is related to the processing technology and is generally taken as more than 5 mm; c is the minimum value of the horizontal installation distance from the tool to the center of the guide rod, and its value is related to the machine tool; n is the projection of the tool in the horizontal direction, and its value is related to the tool; k is the horizontal distance between the two ends of the spline bottom surface and its center, and its value is related to the workpiece; d is the minor diameter of the spline on the workpiece 16; To ensure the second condition, that is, the tool has a radial feed allowance p, the following formula ② should hold: e + c + n + m ≥ p + D / 2, where: m is the projection of the maximum value of the radial feed of the cutting edge of the tool in the horizontal direction, and its value is related to the machine tool; the value of the radial feed allowance p is related to the processing technology and is generally taken as more than 3 mm; D is the major diameter of the spline on the workpiece 16; Solving inequalities ① and ②, the value range of the upper centering eccentricity e is as follows: 0.5D - (c + n + m - p) ≤ e ≤ 0.5d - (c + n + q + k) ③. When formula ③ has a solution, the value of the upper centering eccentricity e is a range. When taking a specific value within this range, it is e', which ensures the radial cutting of the spline; when 0.5D - (c + n + m - p) > 0.5d - (c + n + q + k), formula ③ has no solution, and it is necessary to reselect the machine tool and the tool.

[0014] Furthermore, in order to ensure the machining dimension and machining accuracy of the spline groove along the axial direction, the following two conditions are met: The third condition is to ensure that the upper centering controls the guide rod of the machine tool to be vertical along the vertical direction of the radial feed, that is, Y = 0: Among them, the lower part of the machine tool guide rod and the center of the upper plane of the machine tool workbench are the origin O1', and its Y = 0; The machine tool rotary worktable and the machine tool workbench are connected by a long flat key, and its center is point O1, and its Y = 0; The lower centering component fixes the workpiece, the axis OO1 of the workpiece is vertical, and the Y of point O = 0; The machine tool guide rod is connected to the symmetric flat key groove of the upper centering body through a flat key, the axis O'O1' of the machine tool guide rod is vertical, and the Y of point O' = 0; The Y of the four points O1', O1, O, O' is 0, which ensures the keyway symmetry; The fourth condition is to ensure that the upper centering controls the guide rod of the machine tool to be vertical along the radial feed direction, that is, e1 = e': Among them, e1 is the horizontal distance between the center O1 of the machine tool rotary worktable during use and the center O1' of the machine tool guide rod on the upper plane of the machine tool workbench, and e' is the specific value of the upper centering eccentricity; The lower centering fixture fixes the workpiece, the axis OO1 of the workpiece is vertical, the machine tool guide rod is connected to the symmetric flat key groove of the upper centering body through a flat key, the axis O'O1' of the machine tool guide rod is vertical, and the straight line O'O1' ∥ straight line OO1. Coupled with the Y = 0 of the four points in condition three, then at this time e1 = e', which ensures that the bottom surface of the spline groove is consistent in depth along the axis of the entire spline sleeve.

[0015] Furthermore, in order to ensure the fifth condition, i.e., there is space for tool movement, chips, cutting fluid, and observation on the upper centering fixture: a chip removal groove is designed on the upper centering, with a width B1, where B1 is more than 60 mm wider than the tool; an observation hole is designed on the upper centering, with a width B2 of the observation hole being more than 80 mm; two weight reduction holes are designed on the upper centering, and the two weight reduction holes are symmetric about the straight line OO'; two lifting screw holes are designed on the upper centering, and the two lifting screw holes are symmetric about the straight line OO'. The deviation value s of the center connection line of the two lifting screw holes from the upper centering center is the same as the deviation value of the center of gravity of the lower centering fixture, i.e., the center of gravity of the fixture is on the center connection line of these two screw holes.

[0016] The advantages of the present invention are as follows: First, by designing the eccentricity of the upper centering fixture, it not only ensures that the tool has a radial cutting-in space q so that the tool will not collide before broaching, but also ensures a radial feed allowance p so that the bottom surface of the keyway can be broached, thereby ensuring the radial machining of the keyway. Second, by designing the installation requirements of the machine tool guide rod and the workpiece in the broaching system, the perpendicularity of the machine tool guide rod is ensured, thus ensuring the machining quality of the keyway itself, such as the symmetry of the side surface and the straightness of the bottom surface. Third, by designing relevant chip removal grooves, etc. on the upper centering fixture, it ensures that there is space for tool movement, chips, cutting fluid, and observation on the upper centering, ensuring the smooth progress of broaching.

[0017] In short, the present invention can perfectly select or design the eccentricity and other related dimensions at one time, realizing the broaching process of roughing and finishing, greatly saving time and improving work efficiency. The present invention makes the design and selection of fixtures no longer blind, which is a significant progress in the single-tooth broaching process method and is applicable to heavy machinery. Description of the Drawings

[0018] Figure 1 is the front view of the upper centering fixture of the present invention;

[0019] Figure 2 is Figure 1 the top view of

[0020] Figure 3 is the front view of the broaching system of the present invention.

[0021] Figure 4 is Figure 3 the top view (removing the workbench and the lower centering fixture) of

[0022] Figure 5 is the schematic diagram for calculating the eccentricity of the upper centering fixture of the present invention.

[0023] Figure 6 is Figure 5 the top view of Detailed Embodiment

[0024] The present invention will be further described in detail below in conjunction with the accompanying drawings, so that those skilled in the art can understand it more clearly.

[0025] Embodiment 1

[0026] As Figure 1 、 Figure 2 shown, the upper centering fixture for internal spline single-tooth broaching of the present invention includes an upper centering body 9 and a flat key 10. The upper centering body 9 is a two-stage stepped shaft with a larger upper diameter and a smaller lower diameter, and a guide rod through-hole is arranged along the axial direction. The outer circle of its small-diameter section is a spigot cylindrical surface 7, which is matched with the inner hole of the upper part of the workpiece 16. The lower plane of its large-diameter section is a spigot step plane 8, which presses on the upper plane of the workpiece 16. The diameter of the spigot cylindrical surface is D1, and the center is point O. The diameter of the guide rod through-hole is d1, and the center is point O'. A flat key installation groove is machined at one end of the guide rod through-hole along OO', and a guide rail groove is machined at the other end. The guide rod through-hole, the flat key installation groove, and the guide rail groove are all axisymmetric figures, and the axis of symmetry is the straight line OO'. The flat key 10 is arranged in the flat key installation groove. The horizontal distance between point O and point O' is the upper centering eccentricity e, and e satisfies 0.5D - (c + n + m - p) ≤ e ≤ 0.5d - (c + n + q + k). The value of the upper centering eccentricity e is a range, and when a specific value is taken within this range, it is e'.

[0027] Embodiment 2

[0028] As Figure 3 、 Figure 4 shown, taking a vertical broaching machine as an example for illustration: The broaching system for internal spline single-tooth broaching of the present invention includes a machine tool workbench 1, a lead screw 2, a moving workbench 3, a rotary workbench 4, a lower centering fixture 6, a machine tool guide rod 11, a feed rod 12, a tool rod 14, a tool 15, and an upper centering fixture including an upper centering body 9 and a flat key 10.

[0029] Among them, the moving workbench 3 is connected to the machine tool workbench 1 through the lead screw 2. The rotary workbench 4 is connected to the moving workbench 3. The lower centering fixture 6 is fixed on the rotary workbench 4 and is positioned by the positioning spigot 5 of the rotary workbench 4. The workpiece 16 is placed in the lower centering fixture 6. The machine tool guide rod 11 passes through the holes of the upper centering fixture, the workpiece 16, and the lower centering fixture 6. Its lower end is fixed on the upper plane of the machine tool workbench 1, and its upper section is matched with the guide rod through-hole of the upper centering body 9 and is connected to the upper centering body 9 through the flat key 10. The feed rod 12 and the tool rod 14 are both embedded in the guide groove of the machine tool guide rod 11. The tool rod 14 contacts the feed rod 12 through the feed rod inclined surface 13. The tool 15 is arranged on the tool rod 14.

[0030] Embodiment 3

[0031] The design method of the upper centering fixture and broaching system of the present invention basically considers the following five aspects to ensure the broaching operation of the single-row single-tooth broaching machine: First, there is a radial cutting-in space; second, there is a radial feed allowance; third, the upper centering controls the machine tool guide rod to be vertical along the vertical direction of the radial feed; fourth, the upper centering controls the machine tool guide rod to be vertical along the radial feed direction; fifth, there is a space for tool movement, chips, cutting fluid, and observation.

[0032] The following combines Figure 3 , Figure 4 , Figure 5 , Figure 6 to elaborate in detail on the design method of the upper centering fixture and broaching of the present invention:

[0033] The lower part of the machine tool guide rod 11 is installed on the upper plane of the machine tool table 1, and its center is O1'. Taking O1' as the origin, the direction radially outward along the workpiece 16 is the X direction, the direction axially downward along the workpiece 16 is the Z direction, and the Y direction is perpendicular to the X direction and the Z direction; the center of the rotary table 4 is O1, the center of the positioning stop diameter D1 of the upper centering body 9 is O, and the center of the guide rod through-hole diameter d1 is O'; the projection of the cutting edge AA on the tool 15 in the front view is the point a; the horizontal distance between the point O and the point O' is the upper centering eccentricity e.

[0034] During the broaching process, the tool 15 together with the tool rod 14 and the feed rod 12 makes a cutting movement vertically downward along the axis Z of the workpiece 16. After each cutting reciprocating stroke, the contact point P between the tool rod 14 and the inclined surface 13 of the feed rod 12 slides a certain amount along the inclined surface 13, so that the cutting edge a increases a radial feed amount, thereby realizing the radial feed; when the contact point P slides along the inclined surface 13, the change range of the cutting edge a from the bottom to the top is from the point a1 to the point a2, and the line segment a1a2 is parallel to the inclined surface 13, and the maximum value of the radial feed amount is the projected length m of the line segment a1a2; the minimum value of the horizontal installation distance from the tool 15 to the center of the machine tool guide rod 11 is c; the length of the tool 15 is N, the projection of the tool length in the horizontal direction is n, the angle between the tool installation surface and the horizontal plane is V, and the angle between the tool rod 14 and the front plane of the feed rod 12 is u, n = N * cosV. Among them, the angle V of the horizontal plane is related to the tool installation surface on the tool rod and the position of the P point during use. When the position of the P point changes, the angle u changes accordingly. Generally, the angle V is between 10° and 13°, so n ≈ 0.98N ≈ N.

[0035] Assume that the spline 17 in the workpiece 16 is a rectangular spline, the minor diameter of the spline is d, the major diameter of the spline is D, and the groove width is B; Figure 1 , Figure 2 The wire mesh area in is the metal entity to be machined in one of the spline grooves in the workpiece. To machine and remove it, the wire mesh area must be within the range of the projection m of a1a2.

[0036] In order to ensure that the tool does not interfere with the inner hole of the workpiece (collide with the tool) after installation and can reach the bottom of the keyway, it is necessary to design the size of the upper centering eccentricity e, and the following two conditions must be met:

[0037] The first condition is to ensure that the tool has a radial cutting-in space q, that is, the following formula holds:

[0038] e + c + n + q + k ≤ d / 2 ①

[0039] In the formula: The value of the radial cutting-in space q is related to the machining process, and generally takes more than 5 mm; c is the minimum value of the horizontal installation distance from the tool to the center of the guide rod, and its value is related to the machine tool; n is the projection of the tool in the horizontal direction, and its value is related to the tool; k is the horizontal distance between the two ends of the bottom surface of the spline and its center, and its value is related to the workpiece; q is the minimum distance between the cutting edge of the tool and the inner wall of the spline sleeve in the X-axis direction after the tool is installed.

[0040] The second condition is to ensure that the tool has a radial feed allowance p, that is, the following formula ② holds:

[0041] e + c + n + m ≥ p + D / 2 ②

[0042] In the formula: m is the projection of the maximum value of the radial feed of the cutting edge of the tool in the horizontal direction, and its value is related to the machine tool; p is the radial feed allowance, and its value is related to the machining process, and generally takes more than 3 mm; p is the horizontal distance between the bottom plane of the keyway of the spline sleeve and the maximum value of the radial feed of the cutting edge.

[0043] By solving the inequalities ① and ②, the value range of the upper centering eccentricity e is as follows:

[0044] 0.5D - (c + n + m - p) ≤ e ≤ 0.5d - (c + n + q + k) ③

[0045] When the formula ③ has a solution, the value of the upper centering eccentricity e is a range. When taking a specific value within this range, it is e'. At this time, e ensures the realization of the above two conditions, thus ensuring the radial cutting:

[0046] When 0.5D - (c + n + m - p) > 0.5d - (c + n + q + k), ③ has no solution, and it is necessary to reselect the machine tool and the tool.

[0047] In the machining of the spline keyway, the true radial net machining feed is f + k: where f = (D - d) / 2: When the bottom of the rectangular spline is a plane (a type of heavy rectangular spline, the bottom plane of each groove is tangent to the large-diameter cylindrical surface), k = [d - (d 2 -B 2 ) 0.5 / 2; When the large diameter of the rectangular spline is a cylindrical surface or the spline is an involute spline, k = 0.

[0048] On the premise that the radial cutting of the spline groove is ensured by the dimension of the upper centering eccentricity e, the axial cutting of the spline groove must meet the following two conditions:

[0049] The third condition is to ensure that the upper centering controls the machine tool guide rod to be vertical along the vertical direction of the radial feed, that is, Y = 0: Among them, the lower part of the machine tool guide rod 11 and the center of the upper plane of the machine tool table 1 are the origin O1', and its Y = 0; the machine tool rotary table 4 and the machine tool table 1 are connected by a long flat key, and its center is point O1, and its Y = 0; the lower centering fixture 6 fixes the workpiece 16, the axis OO1 of the workpiece 16 is vertical, and the Y of point O = 0; the machine tool guide rod 11 is connected to the symmetric keyway of the upper centering body 9 through a flat key 10, the axis O'O1' of the machine tool guide rod 11 is vertical, and the Y of point O' = 0; the Y of the four points O1', O1, O, and O' = 0, which ensures the symmetry of the keyway.

[0050] When each rough drawing or finish drawing of a keyway is completed, the workpiece 16 rotates 1 / Z circle with the rotary table 4, and the upper centering fixture ensures that it does not rotate through the flat key 10, thereby ensuring uniform indexing.

[0051] The fourth condition is to ensure that the upper centering controls the machine tool guide rod to be vertical along the radial feed direction, that is, e1 = e': Among them, e1 is the horizontal distance between the center O1 of the machine tool rotary table 4 and the center O1' of the machine tool guide rod 11 on the upper plane of the machine tool table 1 during use, and e' is the specific value of the upper centering eccentricity e; the lower centering fixture 6 fixes the workpiece 16, the axis OO1 of the workpiece 16 is vertical, the machine tool guide rod 11 is connected to the symmetric keyway of the upper centering body 9 through a flat key 10, the axis O'O1' of the machine tool guide rod 11 is vertical, and the straight line O'O1' ∥ straight line OO1. Coupled with the Y = 0 of the four points in condition three, then at this time e1 = e', which ensures that the bottom surface of the spline groove is consistent in depth along the axis of the entire spline sleeve.

[0052] The realization of the above two conditions ensures the processing dimensions, processing accuracy, form and position tolerances, etc. of the spline groove on the premise of ensuring radial cutting in conditions one and two, thus meeting the requirements of the processing drawing.

[0053] Precisely measure the actual value of the specific value e' of the centering eccentricity (accurate to 0.01 mm) before use and print it on the obvious part of the fixture. During processing, e1 is executed according to the actual value of e'.

[0054] The fifth condition is to ensure that there is space for tool movement, chips, cutting fluid, and observation for the upper centering:

[0055] A chip removal groove is designed on the upper centering device, with its width B1. Generally, B1 is more than 60 mm wider than the tool. An observation hole B2 is designed on the upper centering device. The width of the observation hole B2 is generally more than 80 mm. According to specific circumstances, the observation hole can be without a notch or with a notch. According to the specific situation of the upper centering device, two weight reduction holes 18 are arranged on the upper centering device. The two weight reduction holes 18 are symmetric about the straight line OO′, which is also beneficial to the hoisting balance. In order to facilitate the hoisting of the upper centering device, two hoisting screw holes 19 are arranged on the upper centering device. The two hoisting screw holes 19 are symmetric about the straight line OO′. The deviation value s of the center connection line of the two hoisting screw holes from the center of the upper centering body 9 is the same as the deviation value of the center of gravity of the lower centering fixture 6, that is, the center of gravity of the fixture is on the center connection line of these two screw holes.

[0056] Please note that when describing the upper centering fixture, broaching system and its design method of the present invention, the shape of the upper centering fixture shown in the attached drawings of the present invention is taken as the reference. However, the shape structure of the upper centering fixture is not limited to the shape shown in the attached drawings of the present invention. As long as it involves the single-tooth broaching of the internal spline of the spline sleeve by a single-tooth broaching machine using a heavy-duty machine internal spline, and the upper centering fixture, broaching system and its design method are the same as or similar to the content disclosed in the present invention, they are all within the protection scope of the present invention.

[0057] The advantages of the present invention are as follows: First, by designing the eccentricity of the upper centering fixture, it not only ensures that the tool has a radial cutting space q so that the tool will not touch the workpiece before broaching, but also ensures the radial feed allowance p so that the bottom surface of the keyway can be broached, thus ensuring the machining of the keyway in the radial direction. Second, by designing the installation requirements of the machine tool guide rod and the workpiece in the broaching system, the perpendicularity of the machine tool guide rod is ensured, thereby ensuring the machining quality of the keyway itself, such as the symmetry of the side surface and the straightness of the bottom surface. Third, by designing relevant chip removal grooves, etc. on the upper centering fixture, it ensures that there is space for tool movement, chips, cutting fluid, and observation on the upper centering device, ensuring the smooth progress of broaching.

[0058] In short, the upper centering fixture and broaching system of the present invention select or design corresponding positioning dimensions and eccentric amounts according to the broaching equipment and workpiece elements to realize the full-process broaching action of roughing and finishing. The design method of the present invention comprehensively considers the internal relationships and variation laws of several fixture elements, machine tools, tools, and workpiece parameters, making the design and selection of fixtures no longer blind. It perfectly selects or designs the eccentric amount and other relevant dimensions at one time, realizes the full-process broaching of roughing and finishing, greatly saves time, and improves work efficiency. The present invention is a significant progress in the single-tooth broaching process method and is applicable to single-tooth broaching machines for heavy-duty machine internal splines.

Claims

1. The upper centering fixture for broaching a single tooth of an internal spline, characterized in that: It includes an upper centering body (9) and a flat key (10). The upper centering body (9) is a two-stage stepped shaft with a larger upper diameter and a smaller lower diameter, and a guide rod through-hole is axially provided thereon. The outer circle of its small-diameter section is a spigot cylindrical surface (7) that mates with the inner hole at the upper part of the workpiece (16), and the lower plane of its large-diameter section is a spigot step plane (8) that presses on the upper plane of the workpiece (16). The diameter of the spigot cylindrical surface is D1, and the center is point O. The diameter of the guide rod through-hole is d1, and the center is point O'. A flat key installation groove is machined at one end of the guide rod through-hole along OO', and a guide rail groove is machined at the other end. The guide rod through-hole, the flat key installation groove, and the guide rail groove are all axisymmetric figures, and the axis of symmetry is the straight line OO'. The flat key (10) is arranged in the flat key installation groove. The horizontal distance between point O and point O' is the upper centering eccentricity e, and its value range is 0.5D - (c + n + m - p) ≤ e ≤ 0.5d - (c + n + q + k). The value of the upper centering eccentricity e is a range, and when taking a specific value within this range, it is e'. In the formula: c is the minimum value of the horizontal installation distance from the tool to the center of the guide rod, and its value is related to the machine tool; n is the projection of the tool in the horizontal direction, and its value is related to the tool; q is the radial cutting space, and its value is related to the processing technology, taking more than 5 mm; k is the horizontal distance between the two ends of the bottom surface of the spline and its center, and its value is related to the workpiece; m is the projection of the maximum value of the radial feed of the cutting edge of the tool in the horizontal direction, and its value is related to the machine tool; p is the radial feed allowance, and its value is related to the processing technology, taking more than 3 mm; the minor diameter of the spline (17) on the workpiece (16) is d, the major diameter is D, and the groove width is B; the machine tool guide rod (11) passes through the holes of the upper centering fixture, the workpiece (16), and the lower centering fixture (6). The feed rod (12) and the tool rod (14) are both embedded in the guide groove of the machine tool guide rod (11). The tool rod (14) contacts the feed rod (12) through the feed rod inclined surface (13). The tool (15) is arranged on the tool rod (14).

2. The upper centering fixture according to claim 1, characterized in that: n = N * cosV, where N is the length of the tool (15), V is the angle between the tool installation surface and the horizontal plane. The angle V is related to the tool installation surface and the position of point P during use. u is the angle between the tool rod (14) and the front plane of the feed rod. Point P is the contact point between the tool rod (14) and the inclined surface (13) of the feed rod (12). When the position of point P changes, the angle u changes accordingly; the angle V is between 10° and 13°, that is, n ≈ 0.98N ≈ N.

3. The upper centering fixture according to claim 1, characterized in that: A chip removal groove is provided on the upper centering body (9). The chip removal groove is arranged outside the guide rail groove. The chip removal groove is an axisymmetric figure, and the axis of symmetry is the straight line OO'. The width B1 of the chip removal groove is at least 60 mm wider than the width B of the tool.

4. The upper centering fixture according to claim 1, characterized in that: An observation hole is provided on the upper centering body (9). The width B2 of the observation hole is greater than 80 mm. The observation hole can be without a notch or with a notch.

5. The upper centering fixture according to claim 1, characterized in that: Two weight-reducing holes (18) are provided on the upper centering body (9). The two weight-reducing holes (18) are symmetric about the straight line OO'.

6. The upper centering fixture according to claim 1, characterized in that: There are two lifting screw holes (19) provided on the upper centering body (9). The two lifting screw holes (19) are symmetric about the straight line OO'. The deviation value s of the center connection line of the two lifting screw holes from the center O of the upper centering body (9) is the same as the deviation value of the center of gravity of the lower centering fixture (6).

7. A broaching system for single-tooth broaching of internal splines, characterized in that: It includes a machine tool workbench (1), a lead screw (2), a moving workbench (3), a rotary workbench (4), a lower centering fixture (6), a machine tool guide rod (11), a feed rod (12), a tool rod (14), a tool (15), and the upper centering fixture described in any one of claims 1-6. The upper centering fixture includes an upper centering body (9) and a flat key (10); the moving workbench (3) is connected to the machine tool workbench (1) through the lead screw (2), the rotary workbench (4) is connected to the moving workbench (3), the lower centering fixture (6) is fixed on the rotary workbench (4) and is positioned by the positioning spigot (5) of the rotary workbench (4), and the workpiece (16) is placed in the lower centering fixture (6); the machine tool guide rod (11) passes through the holes of the upper centering fixture, the workpiece (16), and the lower centering fixture (6), its lower end is fixed on the upper plane of the machine tool workbench (1), and its upper section is fitted with the guide rod through hole of the upper centering body (9) and is connected to the upper centering body (9) through the flat key (10); the feed rod (12) and the tool rod (14) are both embedded in the guide groove of the machine tool guide rod (11), the tool rod (14) contacts the feed rod (12) through the feed rod inclined surface (13), and the tool (15) is arranged on the tool rod (14).

8. The design method of the broaching system for internal spline single-tooth broaching according to claim 7, characterized in that: Consider from the following five aspects to ensure the broaching work of the single-row single-tooth broaching machine: First, there is a radial cutting-in space. Second, there is a radial feed allowance. Third, the upper centering controls the machine tool guide rod to be vertical in the vertical direction of the radial feed. Fourth, the upper centering controls the machine tool guide rod to be vertical in the radial feed direction. Fifth, there is a space for tool movement, chips, cutting fluid, and observation; in order to ensure that the tool will not interfere with the inner hole of the workpiece after installation and can reach the bottom of the broached keyway, therefore, the size of the upper centering eccentricity e must be designed, and it must meet the following two conditions: To ensure the first condition, that is, the tool has a radial cutting-in space q, the following formula ① should hold: e + c + n + q + k ≤ d / 2 ① In the formula: The value of the radial cutting-in space q is related to the processing technology and is taken as more than 5 mm; c is the minimum value of the horizontal installation distance from the tool to the center of the guide rod, and its value is related to the machine tool; n is the projection of the tool in the horizontal direction, and its value is related to the tool; k is the horizontal distance between the two ends of the bottom surface of the spline and its center, and its value is related to the workpiece; d is the minor diameter of the spline (17) on the workpiece (16). To ensure the second condition, that is, the tool has a radial feed allowance p, the following formula ② should hold: e + c + n + m ≥ p + D / 2 ② In the formula: m is the projection of the maximum value of the radial feed of the cutting edge of the tool in the horizontal direction, and its value is related to the machine tool; the value of the radial feed allowance p is related to the processing technology and is taken as more than 3 mm; D is the major diameter of the spline (17) on the workpiece (16). Solving the inequalities ① and ②, the value range of the upper centering eccentricity e is as follows: 0.5D - (c + n + m - p) ≤ e ≤ 0.5d - (c + n + q + k) ③ When the equation ③ has a solution, the value of the upper centering eccentricity e is within a range. When taking a specific value within this range as e', the radial cutting of the spline is ensured. When 0.5D - (c + n + m - p) > 0.5d - (c + n + q + k), the equation ③ has no solution, and the machine tool and cutting tool need to be reselected.

9. The design method according to claim 8, characterized in that: To ensure the machining dimensions and machining accuracy of the spline groove along the axial direction, the following two conditions need to be met: The third condition is to ensure that the upper centering controls the machine tool guide rod to be vertical along the vertical direction of the radial feed, that is, Y = 0: Among them, the lower part of the machine tool guide rod (11) and the center of the upper plane of the machine tool workbench (1) is the origin O1', and its Y = 0; the machine tool rotary workbench (4) and the machine tool workbench (1) are connected by a long flat key, and its center is point O1, and its Y = 0; the lower centering fixture (6) fixes the workpiece (16), the axis OO1 of the workpiece (16) is vertical, and the Y of point O = 0; the machine tool guide rod (11) is connected to the symmetric flat key groove of the upper centering body (9) through a flat key (10), the axis O'O1' of the machine tool guide rod (11) is vertical, and the Y of point O' = 0; the Y values of the four points O1', O1, O, and O' are all 0, ensuring the symmetry of the key groove. The fourth condition is to ensure that the upper centering controls the machine tool guide rod to be vertical along the radial feed direction, that is, e1 = e': Among them, e1 is the horizontal distance between the center O1 of the machine tool rotary workbench (4) during use and the center O1' of the machine tool guide rod (11) on the upper plane of the machine tool workbench (1), and e' is the specific value of the upper centering eccentricity e; the lower centering fixture (6) fixes the workpiece (16), the axis OO1 of the workpiece (16) is vertical, the machine tool guide rod (11) is connected to the symmetric flat key groove of the upper centering body (9) through a flat key (10), the axis O'O1' of the machine tool guide rod (11) is vertical, and the straight line O'O1' ∥ straight line OO1. Coupled with the Y values of the four points in condition three being 0, then at this time e1 = e', ensuring that the bottom surface of the spline groove has a consistent depth along the axis of the entire spline sleeve.

10. The design method according to claim 8, characterized in that: To ensure the fifth condition, that is, the upper centering fixture has space for tool movement, chips, cutting fluid, and observation: A chip removal groove is designed on the upper centering, and its width B1 is more than 60 mm wider than the cutting tool. An observation hole is designed on the upper centering, and the width B2 of the observation hole is more than 80 mm. Two weight reduction holes (18) are designed on the upper centering, and the two weight reduction holes (18) are symmetric about the straight line OO'. Two lifting screw holes (19) are designed on the upper centering, and the two lifting screw holes (19) are symmetric about the straight line OO'. The deviation value s of the center connection line of the two lifting screw holes from the upper centering center is the same as the deviation value of the center of gravity of the lower centering fixture (6), that is, the center of gravity of the fixture is on the center connection line of these two screw holes.

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