Gear machining method and gear machining device

Abstract

This invention provides a gear machining method and a gear machining apparatus. The gear machining method and apparatus, which machine one side of a tooth surface within a tooth groove by synchronous rotation of a gear-shaped workpiece and a cutting tool, include: determining the interaxial distance between the rotation axis of the workpiece and the rotation axis of the cutting tool during machining of the tooth surface based on the difference between a predetermined reference diameter and an actual diameter, i.e., the tool tip diameter difference; determining the initial phase of the rotation phase of the workpiece and the rotation phase of the cutting tool at the start of the synchronous rotation based on the tool tip diameter difference; and machining the tooth surface at the determined interaxial distance starting from the start of the synchronous rotation.

Description

Technical Field

[0001] This disclosure relates to gear machining methods and gear machining apparatus. Background Technology

[0002] German Patent Application Publication No. 10329413 describes a method for machining the involute curve tooth surface by rotating the workpiece and the cutting tool synchronously with the workpiece and the cutting tool arranged in parallel, so that the cutting tool tip trajectory is a cycloidal curve.

[0003] Japanese Patent Application Publication No. 2020-19096 describes gear machining using a rotary scraper.

[0004] The cutting method described in German Patent Application Publication No. 10329413 achieves a higher cutting speed compared to the scraping process described in Japanese Patent Application Publication No. 2020-19096. However, as mentioned above, this cutting method uses a cycloidal trajectory for the cutting tool to cut the involute tooth surface. Therefore, the portion of the cycloidal curve that approximates the involute curve is used for tooth surface cutting. The portion of the cycloidal curve used for tooth surface cutting is determined by the position of the cutting tool tip.

[0005] However, due to repeated cutting processes, the cutting tool tip wears. In other words, the position of the cutting tool tip changes from its initial state. Furthermore, this change in the cutting tool tip position due to wear results in machining errors on the tooth surface. Additionally, for example, when using a cutting insert as the cutting tool tip, the cutting tool tip position changes due to errors in insert assembly, etc. In this case, similar to wear, machining errors on the tooth surface also occur. Summary of the Invention

[0006] This disclosure provides a gear machining method and gear machining apparatus that can reduce the machining error of the tooth surface when the position of the cutting tool tip changes in high-speed cutting machining.

[0007] 1. Gear machining methods

[0008] According to one aspect of this disclosure, a gear machining method involves synchronously rotating a gear-shaped workpiece with pre-formed tooth profiles and a cutting tool to machine one side of the tooth surface within the tooth groove of the workpiece.

[0009] The gear machining method described above includes: arranging the rotation axis of the workpiece and the rotation axis of the cutting tool in parallel; determining the interaxial distance between the rotation axis of the workpiece and the rotation axis of the cutting tool when machining the tooth surface based on the tool tip diameter difference, wherein the tool tip diameter difference is the difference between a predetermined reference diameter and an actual diameter, and the predetermined reference diameter is the distance from the rotation axis of the cutting tool to the tool tip; determining the initial phase of the rotation phase of the workpiece and the rotation phase of the cutting tool at the start of the synchronous rotation based on the tool tip diameter difference; starting the synchronous rotation of the workpiece and the cutting tool in the determined initial phase state, and moving the tool tip of the cutting tool relative to the workpiece along a predetermined trajectory; and machining the tooth surface at the determined interaxial distance starting from the synchronous rotation.

[0010] According to this gear machining method, synchronous rotation begins at an initial phase determined by the tool tip diameter difference, and tooth surface machining is performed at the inter-axis distance determined by the tool tip diameter difference. Therefore, even if a tool tip diameter difference occurs due to wear, tool component installation errors, etc., the machining error of the tooth surface can be reduced.

[0011] 2. Gear machining equipment

[0012] According to other embodiments of this disclosure, a gear machining apparatus, by synchronously rotating a gear-shaped workpiece with pre-formed tooth profile and a cutting tool, processes the tooth surface within the tooth groove of the workpiece. The apparatus includes the cutting tool and a control device for controlling the workpiece and the cutting tool, with the rotation axis of the workpiece and the rotation axis of the cutting tool arranged parallel to each other.

[0013] The aforementioned control device is configured to determine the interaxial distance between the rotation axis of the workpiece and the rotation axis of the cutting tool during the machining of the tooth surface based on the tool tip diameter difference, and to determine the initial phase of the rotation phase of the workpiece and the rotation phase of the cutting tool at the start of the synchronous rotation based on the tool tip diameter difference. The synchronous rotation of the workpiece and the cutting tool begins when the workpiece and the cutting tool are positioned at the determined initial phase, and the tool tip moves relative to the workpiece along a predetermined trajectory. Machining of the tooth surface is performed at the determined interaxial distance starting from the synchronous rotation. The tool tip diameter difference is the difference between a predetermined reference diameter and the actual diameter, where the predetermined reference diameter is the distance from the rotation axis of the cutting tool to the tool tip. This gear machining apparatus achieves the same effect as the aforementioned gear machining method. Attached Figure Description

[0014] Figure 1 It is a diagram representing a machine tool.

[0015] Figure 2 It is a diagram showing the workpiece and the cutting tool.

[0016] Figure 3 This is a three-dimensional view of the cutting tool in the first example.

[0017] Figure 4 This is a perspective view of the cutting tool in the second example.

[0018] Figure 5 It is a diagram showing the relative movement trajectory of the cutting tool's tool blade relative to the workpiece.

[0019] Figure 6 It is a diagram showing the relative movement trajectory of the cutting tool tip of a cutting tool with respect to the workpiece.

[0020] Figure 7 It is a diagram showing the wear state of the cutting tool tip.

[0021] Figure 8 It is an enlarged view of the tooth surface, showing the tooth surface Wb1 before machining and the target tooth surface Wb2 after machining.

[0022] Figure 9 This is an enlarged view of the tooth surface. In addition to the tooth surfaces Wb1 and Wb2, it also shows the actual tooth surface Wb3 after machining without the tool tip diameter difference ΔH.

[0023] Figure 10 This is a diagram representing multiple machining conditions A-D when there is a tool tip diameter difference ΔH.

[0024] Figure 11 It is an enlarged view of the tooth surface, showing not only tooth surfaces Wb1 and Wb2, but also the actual tooth surface Wb3 after machining under machining condition A.

[0025] Figure 12 It is an enlarged view of the tooth surface, showing not only tooth surfaces Wb1 and Wb2, but also the actual tooth surface Wb3 after machining under machining condition B.

[0026] Figure 13 It is an enlarged view of the tooth surface, showing not only tooth surfaces Wb1 and Wb2, but also the actual tooth surface Wb3 after machining under machining condition C.

[0027] Figure 14 It is an enlarged view of the tooth surface, showing not only tooth surfaces Wb1 and Wb2, but also the actual tooth surface Wb3 after machining under machining condition D.

[0028] Figure 15 It is a diagram showing the tooth thickness error on the pitch circle and at the tooth tip for machining conditions A-D.

[0029] Figure 16 This is a graph showing the relationship between the tool tip diameter difference ΔH and the correction value of the initial phase.

[0030] Figure 17 This is a functional block diagram representing the control device.

[0031] Figure 18 This is a flowchart representing the process of the basic processing condition determination section.

[0032] Figure 19 This is a flowchart illustrating the processing of the tooth surface machining section. Detailed Implementation

[0033] 1. Workpiece W

[0034] Before machining, the workpiece W is a gear shape with teeth formed on its outer or inner circumferential surface. In other words, the workpiece W has a pre-formed tooth shape. Furthermore, the tooth surface within the tooth grooves is the machining area. After machining, the tooth surface is formed as an involute curve. In other words, by machining the pre-formed tooth surface, the tooth thickness is reduced, resulting in a finished shape with an involute curve. Moreover, the tooth surface before machining can be either an involute curve or a non-involute curve shape.

[0035] Furthermore, regarding the tooth profile of workpiece W, the tooth line direction can be parallel to the rotation axis of workpiece W, or the tooth line direction can be at an angle relative to the rotation axis of workpiece W. In the former case, the tooth surface of workpiece W is the tooth surface of a spur gear, while in the latter case, the tooth surface of workpiece W is the tooth surface of a helical gear.

[0036] 2. Example of machine tool 1

[0037] A gear machining apparatus, or machine tool 1, that performs cutting machining on the tooth surface of a gear, which is a workpiece W, is an apparatus that performs cutting machining on the tooth surface by moving a cutting tool T relative to the workpiece W. Furthermore, the machine tool 1 includes multiple structures for moving the cutting tool T relative to the workpiece W. A machining center is an example of the machine tool 1 described above.

[0038] Reference Figure 1 The example of machine tool 1 will be explained. In this example, machine tool 1 is a machining center capable of tool changing. In particular, in addition to the tooth surface cutting machining in this example, the machining center of machine tool 1 can also pre-cut the tooth profile on the workpiece W through gear scraping, hobbing, etc. The machining center of machine tool 1 is basically configured as a horizontal machining center. In addition, although the above configuration is given for machine tool 1, other configurations such as vertical machining centers can be used.

[0039] like Figure 1As shown, machine tool 1, for example, has three mutually orthogonal linear axes (X-axis, Y-axis, and Z-axis) as drive axes. Here, the direction of the rotation axis of the cutting tool T (equal to the rotation axis of the tool spindle) is defined as the Z-axis direction, and the two axes orthogonal to the Z-axis direction are defined as the X-axis direction and the Y-axis direction. Figure 1 In this design, the horizontal direction is defined as the X-axis, and the vertical direction as the Y-axis. Furthermore, the machine tool 1 has two rotary axes (B-axis and Cw-axis) as drive axes for changing the relative posture of the cutting tool T and the workpiece W. Additionally, the machine tool 1 has a Ct-axis as a rotary axis for rotating the cutting tool T.

[0040] In other words, machine tool 1 is a five-axis machining center capable of machining freeform surfaces (or a six-axis machining center if the tool spindle (Ct axis) is considered). Here, machine tool 1 can also be configured to have a B-axis (rotational axis about the Y-axis in the reference state) and a Cw-axis (rotational axis about the Z-axis in the reference state), or it can be configured to have an A-axis (rotational axis about the X-axis in the reference state) and a B-axis, or it can be configured to have an A-axis and a Cw-axis.

[0041] In machine tool 1, a configuration can be appropriately selected to allow the cutting tool T to move relative to the workpiece W. In this example, machine tool 1 can allow the cutting tool T to move linearly in the Y-axis and Z-axis directions, can allow the workpiece W to move linearly in the X-axis direction, and can rotate the workpiece W about the B-axis and about the Cw-axis. Additionally, the cutting tool T can rotate about the Ct-axis.

[0042] Machine tool 1 includes a bed 10, a workpiece holding device 20, and a tool holding device 30. The bed 10 is formed into an arbitrary shape, such as a generally rectangular shape, and is disposed on a mounting surface. The workpiece holding device 20 enables the workpiece W to move linearly relative to the bed 10 along the X-axis, and enables it to rotate about the B-axis and about the Cw-axis. The workpiece holding device 20 mainly includes an X-axis moving worktable 21, a B-axis rotary worktable 22, and a workpiece spindle assembly 23.

[0043] The X-axis moving table 21 is configured to move relative to the bed 10 along the X-axis direction. Specifically, the bed 10 is provided with a moving table in the X-axis direction ( Figure 1 A pair of X-axis guide rails extending in the front-back direction; the X-axis moving worktable 21 is driven by a linear motor or ball screw mechanism (not shown) and guided by the pair of X-axis guide rails to reciprocate in the X-axis direction.

[0044] The B-axis rotary table 22 is mounted on top of the X-axis movable table 21 and reciprocates along the X-axis direction integrally with the X-axis movable table 21. Furthermore, the B-axis rotary table 22 is configured to rotate about the B-axis relative to the X-axis movable table 21. A rotary motor (not shown) is housed in the B-axis rotary table 22, allowing it to rotate about the B-axis by being driven by the rotary motor.

[0045] The workpiece spindle assembly 23 is mounted on the B-axis rotary table 22 and rotates integrally with the B-axis rotary table 22 around the B-axis. The workpiece spindle assembly 23 includes a workpiece spindle base 23a, a workpiece spindle housing 23b, and a workpiece spindle 23c. The workpiece spindle base 23a is fixed to the top of the B-axis rotary table 22.

[0046] The workpiece spindle housing 23b is fixed to the workpiece spindle base 23a and has a cylindrical inner circumferential surface centered on the Cw axis centerline, which is orthogonal to the B axis centerline. The workpiece spindle 23c is rotatably supported on the workpiece spindle housing 23b. The workpiece W is held in the workpiece spindle 23c in a detachable manner. In other words, the workpiece spindle 23c holds the workpiece W in the workpiece spindle housing 23b in a manner that allows it to rotate about the Cw axis, and rotates integrally with the workpiece W.

[0047] Inside the workpiece spindle housing 23b are installed a rotary motor (not shown) for rotating the workpiece spindle 23c and an encoder (not shown) for detecting the rotation angle of the workpiece spindle 23c. In this way, the workpiece holding device 20 can move the workpiece W relative to the bed 10 in the X-axis direction, and can also rotate it about the B-axis and about the Cw-axis.

[0048] The tool holding device 30 mainly includes a column 31, a saddle 32, and a tool spindle assembly 33. The column 31 is configured to move relative to the bed 10 in the Z-axis direction. Specifically, the bed 10 is provided with a Z-axis moving part (…). Figure 1 A pair of Z-axis guide rails extending in the left-right direction; column 31 is driven by a linear motor or ball screw mechanism (not shown) and guided by the pair of Z-axis guide rails to reciprocate in the Z-axis direction.

[0049] The saddle 32 is disposed on the side of the workpiece W side of the column 31. Figure 1 The left side of the column 31 is parallel to a plane orthogonal to the Z-axis. A side surface extending towards the Y-axis is provided on the side of the column 31. Figure 1 A pair of Y-axis guides extending in the vertical direction, the saddle 32 is driven by a linear motor or ball screw mechanism (not shown) to reciprocate in the Y-axis direction.

[0050] A tool spindle assembly 33 is disposed on a saddle 32 and moves integrally with the saddle 32 in the Y-axis direction. The tool spindle assembly 33 includes a tool spindle housing 33a and a tool spindle 33b. The tool spindle housing 33a is fixed to the saddle 32 and has a cylindrical inner circumferential surface centered on a Ct-axis centerline parallel to the Z-axis. The tool spindle 33b is rotatably supported on the tool spindle housing 33a. The cutting tool T is detachably held on the tool spindle 33b. In other words, the tool spindle 33b holds the cutting tool T in the tool spindle housing 33a so that it can rotate about the Ct-axis and rotates integrally with the cutting tool T.

[0051] Inside the tool spindle housing 33a are a tool rotation motor (not shown) that rotates the tool spindle 33b, and an encoder (not shown) that detects the rotation angle of the tool spindle 33b. In this way, the tool holding device 30 holds the cutting tool T so that it can move relative to the bed 10 in the Y-axis and Z-axis directions and can rotate about the Ct axis.

[0052] 3. Detailed composition of cutting tool T

[0053] 3-1. Detailed composition of the cutting tool T in the first example

[0054] Reference Figure 2 as well as Figure 3 The configuration of the cutting tool T will be explained. In the first example, the cutting tool T is a rotary tool used to cut the tooth surface Wb within the tooth groove Wa of the workpiece W, where the tooth line direction is parallel to the rotation axis of the workpiece W. The rotation axis Cw of the workpiece W is arranged parallel to the rotation axis Ct of the cutting tool T. By rotating the cutting tool T synchronously relative to the workpiece W in this state, the tooth surface Wb of the gear that is the workpiece W is cut.

[0055] The cutting tool T comprises a tool body Ta and a cutting tool Tb. The tool body Ta is, for example, formed into a cylindrical shape, and is held at the tool spindle 33b with its central axis aligned with the Ct axis centerline of the tool spindle 33b. The tool body Ta is, for example, formed of steel.

[0056] A cutting tool Tb is disposed at the front end of the tool body Ta and is configured to protrude radially outward from the tool body Ta. The cutting tool Tb is formed, for example, from a superhard material. The cutting tool Tb is formed in a plate shape. In other words, the cutting tool Tb is formed as a plate extending radially into the cutting tool T in a right-angled section of the cutting tool T. Specifically, in this example, the cutting tool Tb is formed as a trapezoid when viewed from the normal direction of the plate-shaped surface. However, this shape of the cutting tool Tb is not limited to a trapezoid and can also be formed as a rectangle.

[0057] In the first example, since the cutting tool T is used to cut the tooth surface Wb, which is parallel to the rotation axis Cw of the workpiece W, the tool tool Tb of the cutting tool T is set so that the extension direction of the plate is parallel to the central axis Ct of the tool body Ta.

[0058] Therefore, the tool cutter Tb has a front end face Tb1 on the radially outer side of the cutting tool T, and a side face Tb2 facing the circumferential direction of the cutting tool T. Moreover, in the tool cutter Tb, the part that performs the cutting of the tooth surface Wb of the workpiece W is the edge portion Tb3 (tool tip) of the front end face Tb1 and the side face Tb2.

[0059] Here, in Figure 2 In the example, workpiece W is an external gear, but it can also be an internal gear. In this case, the cutting tool T is located inside the workpiece W, which is an internal gear, and the rotation axis Ct of the cutting tool T is eccentric relative to the rotation axis Cw of the workpiece W.

[0060] 3-2. Detailed Composition of Cutting Tool T in Example 2

[0061] Reference Figure 4 The construction of the cutting tool T in the second example will be explained. The cutting tool T in the second example is a rotary tool that performs cutting on the tooth surface Wb, where the tooth line direction has an angle with the axis of rotation Cw of the workpiece W. In other words, the cutting tool T in the second example is a tool for cutting the tooth surface of a helical gear.

[0062] The tool cutter Tb of the cutting tool T is arranged along the line of the torsion angle of the cutting tool T, which corresponds to the torsion angle of the tooth surface Wb of the workpiece W. The tool cutter Tb has a side surface Tb2 that is a three-dimensional curved surface along the line of the cutting tool T corresponding to the torsion angle of the tooth surface Wb of the workpiece W.

[0063] 4. Basic processing methods

[0064] Reference Figure 5 as well as Figure 6 The basic machining method for the tooth surface Wb of workpiece W using cutting tool T is explained. Figure 5 The double-dotted line indicates that in such a case Figure 2 As shown, with the workpiece W rotating clockwise and the cutting tool T rotating counterclockwise, the motion trajectory of the tool Tb of the cutting tool T is assumed to be that the workpiece W is fixed.

[0065] In other words, the cutting tool Tb moves in the order A1→A2→A3→A4→A5. This is because the cutting tool T rotates counterclockwise (refer to...). Figure 2 Therefore, the posture of the tool knife Tb is as it moves from A1 to A5, the tip Tb3 of the tool knife Tb relative to the base of the tool knife Tb ( Figure 5The upper end moves counterclockwise. Furthermore, since the cutting tool T rotates synchronously with the workpiece W, the rotation axis Ct of the cutting tool T approximately revolves relative to the workpiece W. Therefore, as... Figure 5 As shown, the position and orientation of the tool Tb change relative to the workpiece W.

[0066] exist Figure 6 In the diagram, the thick solid line represents the relative movement trajectory of the tool tip Tb3 of the cutting tool Tb relative to the workpiece W. In other words, as shown... Figure 6 As shown, by aligning the rotation axis Cw of the workpiece W and the rotation axis Ct of the cutting tool T in parallel, and rotating the workpiece W and the cutting tool T synchronously, the tip Tb3 of the tool Tb moves relative to the workpiece W along a predetermined trajectory. This predetermined trajectory is a cycloidal curve.

[0067] First, as shown in A1→A2→A3, in this action, the cutting tip Tb3 of the tool Tb processes the tooth surface Wb from the tooth tip to the tooth root within the tooth groove Wa. At A3, the processing endpoint of the tooth surface Wb is reached.

[0068] Next, as shown in A3→A4→A5, after reaching the machining endpoint of the tooth surface Wb, the tool tip Tb3 of the tool Tb continues to move along the prescribed trajectory, and the tool tip Tb3 is not in contact with the tooth surface Wb, so that the tool tip Tb3 is withdrawn from the internal space of the tooth groove Wa to the outside of the tooth groove Wa.

[0069] Here, the tooth surface Wb of the workpiece W is an involute curve, and the trajectory of the tool tip Tb3 of the cutting tool Tb is a cycloid curve. Therefore, the tooth surface Wb is machined using the portion of the cycloid curve that approximates the involute curve of the tooth surface Wb, which is the trajectory of the tool tip Tb3 of the cutting tool Tb. This can be achieved by setting the rotational speed ratio of the workpiece W to the cutting tool T, the tool tip diameter of the cutting tool Tb, and the rotational phase adjustment amount of the cutting tool T relative to the workpiece W.

[0070] In addition, Figure 5 as well as Figure 6 This illustrates the machining of one tooth surface Wb within a tooth groove Wa. By performing this action across all tooth grooves Wa, it is possible to machine one tooth surface Wb within all tooth grooves Wa. Furthermore, for the other tooth surface Wb, machining can be performed in the same manner by reversing the rotation direction of the workpiece W and the cutting tool T.

[0071] 5. Explanation of the tip diameter difference of the utility knife Tb

[0072] Reference Figure 7 The tip diameter difference of the tool cutter Tb is explained. Figure 7This illustrates the wear state of the tool tip Tb3 due to repeated machining by the tool tool Tb. In other words, due to the wear of the tool tool Tb, the actual diameter of the tool tool Tb (the actual tip diameter (radius) of the tool tool Tb after wear) is different from the reference diameter of the tool tool Tb (the tip diameter (radius) of the tool tool Tb before wear).

[0073] Here, in Figure 7 In this context, the tip diameter difference ΔH corresponds to the wear amount, and is the difference between the tip diameter of the tool tool Tb before wear (a specified reference diameter) and the tip diameter of the tool tool Tb after wear (the actual diameter). Furthermore, the tip diameter of the tool tool Tb refers to the diameter from the rotation axis Ct of the cutting tool T. Figure 2 The distance from the tip Tb3 (as shown in the figure) to the blade tip Tb3.

[0074] In addition to wear of the tool cutter Tb, when using a cutting insert assembly as the tip of the cutting tool T, the tip diameter of the cutting tool T varies due to installation errors in the cutting insert assembly. In this case, since a predefined reference diameter for the tip diameter of the cutting tool T is established, a difference between the defined reference diameter and the actual diameter may occur depending on the installation state of the cutting insert assembly. The tip diameter difference ΔH represents the difference between the defined reference diameter and the actual diameter in the cutting insert assembly.

[0075] 6. The shape of the tooth surface Wb when there is a difference in tool tip diameter ΔH.

[0076] The shape of the tooth surface Wb is studied when the tip Tb3 of the tool tool Tb has a tip diameter difference ΔH relative to the reference diameter due to wear, etc. First, in Figure 8 In the enlarged view of the tooth surface Wb shown, Wb1 represents the tooth surface before machining, and Wb2 represents the target tooth surface (ideal tooth surface) after machining. Both the tooth surface Wb1 before machining and the target tooth surface Wb2 after machining are involute curves. Furthermore, in... Figure 8 In the middle, the dotted line represents the nodal circle.

[0077] If the tooth surface Wb is machined under the condition that the tool tip Tb3 is unworn, i.e., the tip diameter difference ΔH is zero, then the actual machined tooth surface Wb3 is: Figure 9 The thick solid line represents the target tooth surface Wb2. In other words, if the tool tip diameter difference ΔH is zero, then the actual machined tooth surface Wb3 matches the target tooth surface Wb2. Specifically, the actual machined tooth surface Wb3 matches the target tooth surface Wb2 across the entire area from the tooth tip to the tooth root. In other words, the actual machined tooth surface Wb3 matches the target tooth surface Wb2 whether at the tooth tip, the pitch circle, or the center of the tooth height.

[0078] Furthermore, the basic machining conditions are determined to be that the tool tip Tb3 of the cutting tool Tb is unworn, i.e., the tip diameter difference ΔH is zero. Therefore, the actual tooth surface Wb3 after machining is consistent with the target tooth surface Wb2 after machining, and the situation described above is self-evident. The basic machining conditions include the interaxial distance between the rotation axis Cw of the workpiece W and the rotation axis Ct of the cutting tool T, the distance between the rotation axis Ct of the cutting tool T and the tip Tb3 of the tool tool Tb (i.e., the tip diameter), and the relationship between the rotation phase of the workpiece W and the rotation phase of the cutting tool T.

[0079] Here, as an example of the wear state of the tool tip Tb3 of the tool tool Tb, under the condition that the tip diameter difference ΔH is a fixed value that is not zero, for Figure 10 The machining conditions A-D shown are examined individually. Machining conditions A-D differ depending on whether the inter-axis distance and initial phase are corrected relative to the basic machining conditions, or whether no corrections are made.

[0080] The correction of the inter-axis distance refers to adjusting the inter-axis distance between the workpiece W's rotation axis Cw and the cutting tool T's rotation axis Ct relative to the basic machining conditions, based on the tool tip diameter difference ΔH. In this example, the correction value of the inter-axis distance is made consistent with the tool tip diameter difference ΔH. The correction of the initial phase refers to adjusting the initial phase of the rotation phase of the workpiece W and the cutting tool T at the start of synchronous rotation, relative to the basic machining conditions.

[0081] Machining condition A involves no correction of the inter-axis distance or the initial phase; that is, machining is performed according to the basic machining conditions themselves. Machining condition B involves only correction of the inter-axis distance, without correction of the initial phase. Machining conditions C and D involve correction of both the inter-axis distance and the initial phase. However, machining conditions C and D have different correction values ​​for the initial phase.

[0082] Figure 11 The actual tooth surface Wb3 under machining condition A is shown as a thick solid line. If compared with... Figure 9 Comparing this to the case where there is no difference in tool tip diameter ΔH, it can be seen that... Figure 11 The actual tooth surface Wb3 in the tool tip diameter difference ΔH is moved parallel to the positive Y-axis direction. At this time, as... Figure 15 As shown, under machining condition A, the tooth thickness error on the pitch circle is 140 μm, and the tooth thickness error at the tooth tip is 130 μm, both of which have large errors.

[0083] Figure 12 The actual tooth surface Wb3 under machining condition B is shown as a thick solid line. Because the tool tip diameter difference ΔH is corrected for the inter-axis distance, it is... Figure 11Compared to the uncorrected case, the actual tooth surface Wb3 is closer to the target tooth surface Wb2. For example... Figure 15 As shown, under machining condition B, the tooth thickness error at the pitch circle is 40 μm, and the tooth thickness error at the tooth tip is 115 μm. The trajectory of the tool tip Tb3, i.e., the cycloidal curve, depends on the tool tip diameter of the cutting tool T (the distance between the rotation axis Ct of the cutting tool T and the tool tip Tb3). Therefore, it can be seen that the tooth thickness error is caused by the change in the tool tip diameter, which results in a tool tip diameter difference ΔH.

[0084] Figure 13 The actual tooth surface Wb3 under machining condition C is shown as a thick solid line. Machining condition C includes corrections for both the inter-axis distance and the initial phase. For example... Figure 13 As shown, machining condition C determines the initial phase correction value so that, on the pitch circle, the actual tooth surface Wb3 matches the target tooth surface Wb2. Therefore, as... Figure 15 As shown, under machining condition C, the tooth thickness error at the pitch circle is 0 μm, and the tooth thickness error at the tooth tip is 75 μm. Under machining condition C, the tooth thickness error at the tooth tip is the largest. It can be seen that machining condition C not only makes the tooth thickness error at the pitch circle zero, but also makes the maximum error smaller than the maximum error (115 μm) under machining condition B.

[0085] Figure 14 The actual tooth surface Wb3 under machining condition D is shown as a thick solid line. Machining condition D includes correction for the inter-axis distance and initial phase. For example... Figure 14 As shown, machining condition D determines the initial phase correction value to be at the tooth tip, where the actual tooth surface Wb3 matches the target tooth surface Wb2. Therefore, as... Figure 15 As shown, under machining condition D, the tooth thickness error at the tooth tip is 0 μm, and the tooth thickness error at the pitch circle is 95 μm. Under machining condition D, the tooth thickness error is largest at the position near the tooth root on the tooth surface Wb, such as near the pitch circle. It can be seen that machining condition D not only makes the tooth thickness error at the tooth tip zero, but also makes the maximum error smaller than the maximum error (115 μm) under machining condition B.

[0086] The above research results demonstrate that by correcting not only the inter-axis distance but also the initial phase, the tooth thickness error at a specific location on the tooth surface Wb can be reduced to zero, and the maximum error can be minimized. The location where the tooth thickness error is reduced to zero can be appropriately selected based on the initial phase correction value. Furthermore, by correcting the initial phase, the overall average error of the tooth surface Wb can also be minimized.

[0087] 7. Relationship between the tip diameter difference ΔH and the correction value of the initial phase

[0088] Next, refer to Figure 16 The relationship between the tool tip diameter difference ΔH and the correction value of the initial phase is explained. For example, as... Figure 13 As shown, the correction value for the initial phase is the correction value that makes the tooth thickness error on the pitch circle zero.

[0089] like Figure 13 As shown, when the tool tip diameter difference ΔH is zero, the initial phase correction is zero. This initial phase is determined based on the basic machining conditions. As the tool tip diameter difference ΔH increases, the initial phase correction increases. In this example, the initial phase correction is proportional to the tool tip diameter difference ΔH.

[0090] Thus, by determining the correction value of the initial phase based on the tool tip diameter difference ΔH, and machining at the determined initial phase (the initial phase of the basic machining conditions plus the correction value), the tooth thickness error on the pitch circle can be made zero. Furthermore, when the tooth thickness error at the tooth tip is zero, the relationship between the tool tip diameter difference ΔH and the correction value of the initial phase is different. However, in this case, they are still approximately proportional.

[0091] Here, the relationship between the tool tip diameter difference ΔH and the correction value of the initial phase can be determined either based on the actual machining results or through simulation. This relationship is not limited to a ratio and can also be approximated by a curve.

[0092] 8. Composition of the control device 50

[0093] Reference Figure 17 The functional module configuration of the control device 50 of the machine tool 1 described above will be explained. The control device 50 includes a basic machining condition determination unit 51, an inter-axis distance determination unit 52, an initial phase determination unit 53, a machining condition storage unit 54, and a tooth surface machining unit 55.

[0094] The basic machining condition determination unit 51 determines the basic machining conditions (basic machining condition determines the process) that allow machining of the target tooth surface when the tool tip Tb3 of the tool Tb is a specified reference diameter. The basic machining conditions are the tool tip Tb3 and... Figure 6 The trajectory of the thick solid line (cycloidal curve) is part of the machining condition where the tooth surface Wb of the involute curve is consistent. The basic machining conditions include the reference diameter of the tool tip Tb3 of the tool Tb, the interaxial distance between the axis of rotation Cw of the workpiece W and the axis of rotation Ct of the cutting tool T during machining, and the initial phase of the workpiece W and the cutting tool T at the start of synchronous rotation. The basic machining conditions, described later, determine the processing.

[0095] When a tool tip diameter difference ΔH exists, the inter-axis distance determination unit 52 determines the inter-axis distance during machining based on the tool tip diameter difference ΔH (inter-axis distance determination process). When the position of the tool tip Tb3 of the cutting tool T changes due to wear, the inter-axis distance determination unit 52 determines the inter-axis distance based on the tool tip diameter difference ΔH that changes due to wear. When an installation error occurs in the insert component, the inter-axis distance determination unit 52 determines the inter-axis distance based on the tool tip diameter difference ΔH caused by the installation error.

[0096] In this example, the inter-axis distance determination unit 52 determines the inter-axis distance by subtracting the obtained tool tip diameter difference ΔH from the inter-axis distance under the basic machining conditions determined by the basic machining conditions determination unit 51.

[0097] When a tool tip diameter difference ΔH exists, the initial phase determination unit 53 determines the initial phase of the workpiece W and the cutting tool T at the start of synchronous rotation based on the tool tip diameter difference ΔH (initial phase determination process). When the position of the cutting tool Tb3 changes due to wear, the initial phase determination unit 53 determines the initial phase based on the tool tip diameter difference ΔH that changes due to wear. When an installation error occurs in the insert assembly, the inter-axis distance determination unit 52 determines the initial phase based on the tool tip diameter difference ΔH caused by the installation error.

[0098] In this example, the initial phase determination unit 53 is based on Figure 16 The relationship between the tool tip diameter difference ΔH and the correction value of the initial phase shown determines the correction value of the initial phase corresponding to the acquired tool tip diameter difference ΔH. Next, the initial phase determination unit 53 determines the initial phase by adding the determined correction value of the initial phase to the initial phase under the basic machining conditions determined by the basic machining condition determination unit 51.

[0099] Here, as Figure 13 As shown, the initial phase determination unit 53 can also determine the initial phase to minimize the error relative to the target value on the pitch circle of the tooth surface Wb. Additionally, as... Figure 14 As shown, the initial phase determination unit 53 can also determine the initial phase to minimize the error of the tooth tip of the tooth surface Wb relative to the target value. Alternatively, the initial phase determination unit 53 can also determine the initial phase to minimize the overall average error of the tooth surface Wb.

[0100] The machining condition storage unit 54 stores the basic machining conditions determined by the basic machining condition determination unit 51. Furthermore, when a tool tip diameter difference ΔH exists, the machining condition storage unit 54 stores the corrected inter-axis distance determined by the inter-axis distance determination unit 52 and the corrected initial phase determined by the initial phase determination unit 53.

[0101] The tooth surface machining unit 55 controls the drive device 60, such as the motor, based on the machining conditions (basic machining conditions, corrected inter-axis distance, and corrected initial phase) stored in the machining condition storage unit 54. As described above, the tooth surface machining unit 55 controls the tool cutter Tb to enter the tooth groove Wa along a predetermined trajectory and machine the tooth surface Wb from the tooth tip to the tooth root. After machining the tooth surface Wb, the tooth surface machining unit 55 controls the tool cutter to retract out of the tooth groove Wa by moving it along a predetermined trajectory.

[0102] 9. Basic processing conditions determine the treatment.

[0103] Reference Figure 18 The basic machining condition determination process (basic machining condition determination step) of the basic machining condition determination unit 51 will be explained. As described above, it is necessary to find the portion of the cycloidal curve of the tool tip Tb3 that approximates the involute curve of the tooth surface Wb. Furthermore, in the cycloidal curve, it is necessary to establish a positional relationship between the workpiece W and the cutting tool T such that the tool tip Tb3 of the tool Tb performs cutting from the tooth tip to the tooth root of the tooth surface Wb. Additionally, it is necessary to perform cutting on all tooth surfaces Wb in the workpiece W, including multiple tooth grooves Wa. To achieve these requirements, the basic machining conditions are determined through the basic machining condition determination process described below.

[0104] like Figure 18 As shown, the number of cutting edges of the cutting tool T is determined (step S1). For example, Figure 2 The cutting tool T shown has one cutting edge. The number of cutting edges is preferably one, two, or three. Next, the rotational speed ratio between the workpiece W and the cutting tool T is determined (step S2). In other words, the conditions under which the tool Tb can cut all the tooth surfaces Wb are determined. The rotational speed ratio used to cut all the tooth surfaces Wb each time by the tool Tb is determined.

[0105] Next, input any initial value for the tip diameter of the tool tool Tb (step S3). Next, with the workpiece W fixed, use the rotational speed ratio and the tip diameter of the tool tool Tb to calculate the tip Tb3 of the tool tool Tb as the cycloidal motion trajectory (step S4).

[0106] Next, determine whether the trajectory of the tool tip Tb3, i.e., the cycloidal curve, is consistent with the tooth surface Wb, which is an involute curve (step S5). If they are inconsistent (S5: no), then change the tip diameter of the tool tip Tb (step S6). Then, repeat steps S4 and S5.

[0107] If the condition is consistent with step S5 (S5: Yes), the tip diameter (reference diameter) of the tool tool Tb is determined at this time (step S7). If the determined tip diameter (reference diameter) of the tool tool Tb and the rotational speed ratio are used, then in the radial range of the workpiece W where the tooth surface Wb exists, a portion of the cycloidal curve of the tip Tb3 of the tool tool Tb approximates the involute curve of the tooth surface Wb.

[0108] Next, the rotation phase adjustment is determined so that the trajectory of the tool tip Tb3 of the cutting tool Tb cuts from the tooth tip of the tooth surface Wb toward the tooth root (step S8). Based on the relationship between the rotation phase of the workpiece W and the rotation phase of the cutting tool T, there are cases where the tool tool Tb enters the internal space of the tooth groove Wa while machining the tooth surface Wb, and then retracts from the internal space of the tooth groove Wa without contact with the tooth surface Wb. Additionally, based on the rotation phase, there are cases where the tool tool Tb does not contact the tooth surface Wb when entering the internal space of the tooth groove Wa, but contacts the tooth surface Wb when retracting from the internal space of the tooth groove Wa. Furthermore, based on the rotation phase, there are cases where the tool tool Tb cannot enter the tooth groove Wa and collides with the tooth. Therefore, it is decided to achieve... Figure 5 as well as Figure 6 The amount of rotational phase adjustment for the action shown. In this way, the processing conditions are determined.

[0109] According to the gear machining method described above, although only one side of the tooth surface Wb is machined, the cutting speed is much higher than that of rotary scraping or hobbing. Therefore, even using a small-diameter cutting tool T, the tooth surface Wb can be machined with high precision. In particular, this method is effective in machining internal gears where the outer diameter of the cutting tool T is limited.

[0110] 10. Tooth surface machining

[0111] Reference Figure 19 The tooth surface machining process (tooth surface machining step) of the tooth surface machining unit 55 will be explained. First, the rotation phase of the workpiece W and the rotation phase of the cutting tool T are positioned at the initial phase determined by the initial phase determination unit 53 (initial phase determination step) (step S11). Next, the synchronous rotation of the workpiece W and the cutting tool T begins (step S12).

[0112] Next, at least one of the workpiece W and the cutting tool T is moved parallel to each other so that the distance between the axis of rotation Cw of the workpiece W and the axis of rotation Ct of the cutting tool T is consistent with the distance determined by the distance determination unit 52 (distance determination process). Then, at the distance determined by the distance determination unit 52, the tooth surface Wb is machined by the tool tool Tb (step S13). Next, the cutting tool T is retracted from the workpiece W by returning the distance to its initial state (step S14). Then, the rotation of the workpiece W and the cutting tool T is stopped, and the tooth surface machining process ends (step S15).

[0113] According to the gear machining method described above, synchronous rotation begins at an initial phase determined by the tool tip diameter difference ΔH, and the tooth surface Wb is machined at the inter-axis distance determined by the tool tip diameter difference ΔH. Therefore, even if a tool tip diameter difference ΔH occurs due to wear, tool component installation errors, etc., the machining error of the tooth surface Wb can be reduced.

Claims

1. A gear machining method, comprising machining one side of the tooth surface within the tooth groove of a gear-shaped workpiece with pre-formed tooth profile on the workpiece by synchronous rotation of the workpiece and a cutting tool, the method comprising: The rotation axis of the workpiece and the rotation axis of the cutting tool are arranged in parallel. Based on the tool tip diameter difference, the interaxial distance between the rotation axis of the workpiece and the rotation axis of the cutting tool when machining the tooth surface is determined. The tool tip diameter difference is the difference between a specified reference diameter and the actual diameter. The specified reference diameter is the distance from the rotation axis of the cutting tool to the tool tip of the cutting tool. Based on the aforementioned tool tip diameter difference, the rotation phase of the workpiece and the initial phase of the rotation phase of the cutting tool at the start of the aforementioned synchronous rotation are determined. The synchronous rotation of the workpiece and the cutting tool begins in the state of being positioned at the determined initial phase, and the tip of the cutting tool moves relative to the workpiece along a predetermined trajectory; and Starting with the aforementioned synchronous rotation, the aforementioned tooth surface is machined at the determined inter-axis distance.

2. The gear machining method according to claim 1, wherein, The determination of the aforementioned inter-axis distance includes determining the inter-axis distance based on the difference in the cutting tool tip diameter, which varies due to the wear of the cutting tool tip. The determination of the initial phase is based on the difference in the cutting tip diameter, which varies due to the wear of the cutting tool tip.

3. The gear machining method according to claim 2, wherein, The determination of the initial phase includes determining the initial phase to minimize the error relative to the target value on the pitch circle of the tooth surface of the workpiece.

4. The gear machining method according to claim 2, wherein, The determination of the initial phase includes determining the initial phase to minimize the error of the tooth tip of the tooth surface of the workpiece relative to the target value.

5. The gear machining method according to any one of claims 1 to 4, wherein, The aforementioned trajectory is a cycloid curve. The tooth surface described above is an involute curve. The machining of the tooth surface includes machining the tooth surface using the portion of the cycloidal curve that approximates the involute curve.

6. A gear machining apparatus, comprising machining the tooth surface within the tooth groove of a gear-shaped workpiece with pre-formed tooth profile on the workpiece by synchronous rotation of the workpiece and a cutting tool, wherein the apparatus includes: The aforementioned cutting tools; and The control device controls the interaction between the workpiece and the cutting tool. The gear machining apparatus described above is configured with the rotation axis of the workpiece and the rotation axis of the cutting tool parallel to each other. The above-mentioned control device is configured as follows: Based on the tool tip diameter difference, the interaxial distance between the rotation axis of the workpiece and the rotation axis of the cutting tool when machining the tooth surface is determined. The tool tip diameter difference is the difference between a specified reference diameter and the actual diameter. The specified reference diameter is the distance from the rotation axis of the cutting tool to the tool tip of the cutting tool. Based on the aforementioned tool tip diameter difference, the rotation phase of the workpiece and the initial phase of the rotation phase of the cutting tool at the start of the aforementioned synchronous rotation are determined. The synchronous rotation of the workpiece and the cutting tool begins in the state of being positioned at the determined initial phase, and the tip of the cutting tool moves relative to the workpiece along a predetermined trajectory; and Starting with the aforementioned synchronous rotation, the aforementioned tooth surface is machined at the determined inter-axis distance.

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