Gear machining apparatus and gear machining method

Abstract

To provide a gear machining device and a gear machining method with improved machining accuracy.SOLUTION: A first center axis position calculation unit 101 configured to calculate a first position of the center axis CA of the workpiece W at each index angle in the preparation stage, a rotation axis position calculation unit 102 configured to calculate a position of the rotation axis Cw of the workpiece spindle device 50, and a second center axis position calculation unit 103 configured to calculate a second position of the center axis CA of the workpiece W corresponding to the index angle in the grinding stage. And a grinding control section 104 configured to correct the grinding position of the grinding tool 43 corresponding to the index angle in the grinding stage, and index and grind the workpiece W by the grinding tool 43 based on the corrected grinding position of the grinding tool 43.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a gear machining device and a gear machining method. [Background technology]

[0002] Conventionally, there is known a gear processing device that uses a gear grinding wheel to grind the tooth flanks formed on the outer surface of a workpiece by rough processing such as shaving or hobbing (see Patent Document 1). When grinding, the grinding blade of the gear grinding wheel is aligned with the tooth flanks of the workpiece. In Patent Document 1, the alignment between the workpiece and the gear grinding wheel is performed using a sensor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-60027 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when a workpiece is attached to the work spindle of a gear cutting machine, it is not easy to perfectly align the central axis of the workpiece with the rotational axis of the work spindle, and if the central axis of the workpiece is misaligned with the rotational axis of the work spindle, it is difficult to achieve sufficient machining accuracy.

[0005] The present invention has been made in view of the above-mentioned problems, and aims to provide a gear cutting device and a gear cutting method with improved cutting accuracy. [Means for solving the problem]

[0006] One aspect of the present invention is a grinding tool for index grinding tooth spaces in a gear workpiece; a workpiece spindle device configured to hold the workpiece and be able to index the workpiece at a predetermined angle around a rotation axis; a sensor that detects coordinates of a predetermined position of the workpiece in a state where the workpiece is attached to the workpiece spindle device and the workpiece spindle device is indexed to each of a plurality of index angles as a preparation stage; a first central axis position calculation unit configured to calculate a first position of a central axis of the workpiece at each index angle in the preparation stage based on the detection value of the sensor; a rotation axis position calculation unit configured to calculate a position of a rotation axis of the workpiece spindle device based on the first positions at a plurality of index angles in the preparation stage; a second central axis position calculation unit configured to calculate a second position of the central axis of the workpiece corresponding to the index angle of the grinding stage based on the rotation axis of the workpiece spindle device and the index angle of the workpiece spindle device in the grinding stage; and a grinding control unit configured to correct the grinding position of the grinding tool corresponding to the index angle of the grinding stage based on the second position, and to index-grind the workpiece with the grinding tool based on the corrected grinding position of the grinding tool.

[0007] Another aspect of the present invention is A gear machining method for index grinding tooth grooves in a gear workpiece using a grinding tool, comprising: a workpiece mounting step of mounting the workpiece on a workpiece spindle device configured to be indexable at a predetermined angle around a rotation axis; a position detecting step of detecting coordinates of a predetermined position of the workpiece by a sensor in a state where the workpiece is attached to the workpiece spindle device and the workpiece spindle device is indexed to each of a plurality of index angles as a preparation step; a first central axis position calculation step of calculating a first position of the central axis of the workpiece at each index angle in the preparation step based on the detection value of the sensor; a rotation axis position calculation step of calculating a position of a rotation axis of the workpiece spindle device based on the first positions at the plurality of index angles in the preparation step; a second central axis position calculation step of calculating a second position of the central axis of the workpiece corresponding to the index angle in the grinding stage based on the rotation axis of the workpiece spindle device and the index angle in the grinding stage of the workpiece spindle device; and an index grinding step of correcting the grinding position of the grinding tool corresponding to the index angle of the grinding stage based on the second position, and index-grinding the workpiece with the grinding tool based on the corrected grinding position of the grinding tool. [Effects of the Invention]

[0008] According to one and other aspects of the present invention, even if the central axis of the workpiece is misaligned with the rotational axis of the workpiece spindle device when the workpiece is attached to the workpiece spindle device, the grinding position of the grinding tool corresponding to the index angle in the grinding stage is corrected based on a second position of the central axis of the workpiece corresponding to the index angle in the grinding stage, and the workpiece is index-ground using the grinding tool based on the corrected grinding position of the grinding tool. This makes it possible to suppress misalignment between the grinding tool and the workpiece in the grinding stage. As a result, the machining accuracy of gears can be improved.

[0009] As described above, according to the above aspects, it is possible to provide a gear machining device and a gear machining method with improved machining accuracy. [Brief explanation of the drawings]

[0010] [Figure 1] 1A and 1B are diagrams showing a gear machining device according to a first embodiment, in which FIG. 1A shows the gear machining device with a grinding device attached thereto, and FIG. 1B shows the gear machining device with a cutting device attached thereto. [Figure 2] FIG. 1 is a block diagram of a gear machining device according to a first embodiment. [Figure 3] FIG. 2 is a schematic diagram illustrating a step of cutting a workpiece with a cutting tool in the first embodiment. [Figure 4] 1 is a side view showing a grinding tool according to a first embodiment. [Figure 5]3 is a main flow diagram showing the operation of the gear machining device according to the first embodiment. [Figure 6] 1 is a flowchart of a preparation process in the first embodiment. [Figure 7] 1 is a flowchart of a grinding process in the first embodiment. [Figure 8] FIG. 2 is a front view showing a state in which a workpiece is attached to a jig in the first embodiment. [Figure 9] FIG. 2 is a schematic diagram illustrating a preparation step according to the first embodiment. [Figure 10] 1A and 1B are diagrams for explaining the grinding process of embodiment 1, where (a) is a diagram for explaining the initial index grinding process, and (b) is a diagram for explaining a method for correcting the grinding position of the grinding tool when the workpiece is rotated at an index angle. DETAILED DESCRIPTION OF THE INVENTION

[0011] (Embodiment 1) 1. Gear processing equipment 1 The gear machining device 1 shown in Fig. 1(a) performs index grinding of tooth grooves 61 in a gear workpiece W using a grinding tool 43 (see Figs. 10(a) and 10(b)). In this embodiment, a configuration is shown in which a disc-shaped gear grinding wheel is used as the grinding tool 43. Note that the gear machining device 1 may also be configured to use a threaded grinding wheel as the grinding tool 43, and the threaded grinding wheel may have any shape, such as an hourglass-shaped grinding wheel, a barrel-shaped grinding wheel, or a cup-shaped grinding wheel with one end having a smaller diameter than the other end.

[0012] As shown in FIG. 1(b), the gear machining apparatus 1 of this embodiment cuts tooth grooves 61 into the workpiece W by moving (feeding) the cutting tool 41 relative to the workpiece W while rotating the cutting tool 41 and the workpiece W synchronously (see FIG. 3). The grinding tool 43 and the cutting tool 41 are configured to be interchangeable. The gear machining apparatus 1 includes a skiving cutter as the cutting tool 41. The gear machining apparatus 1 may also include a hob cutter as the cutting tool 41 and hob a gear into the workpiece W. However, the cutting tool 41 may be omitted. The gear machining apparatus 1 of this embodiment grinds tooth grooves 61 of a gear formed by cutting.

[0013] The workpiece W will be described with reference to Fig. 8. The workpiece W to be machined is a gear (external gear or internal gear) with convex teeth formed on the outer or inner peripheral surface. The internal gear workpiece W in this embodiment is exemplified by a spur gear whose tooth trace direction is parallel to the rotation axis of the workpiece W. Note that each tooth may have a helix angle, and the tooth trace direction may be inclined with respect to the rotation axis.

[0014] 1(a) and 1(b), in this embodiment, the gear machining apparatus 1 has the configuration of a five-axis machining center having three linear axes and two rotational axes as drive axes for changing the relative position and attitude of the workpiece W, and the cutting tool 41 and grinding tool 43. Here, in this embodiment, the gear machining apparatus 1 has three orthogonal axes (X-axis, Y-axis, and Z-axis) as linear axes, and B-axis and Cw-axis as rotational axes. Note that the B-axis is, for example, a rotational axis about the Y-axis, and the Cw-axis is a rotational axis about the central axis of the workpiece W.

[0015] 2. Configuration of gear processing device 1 As shown in Figures 1(a) and 1(b), the gear machining apparatus 1 mainly comprises a bed 10, a column 20, a saddle 30, a tool spindle device 40, a workpiece spindle device 50, and a control device 100. The bed 10 is formed in a substantially rectangular shape and is arranged horizontally. A Z-axis guide 11 is arranged on the upper surface of the bed 10 to drive the column 20 in a direction parallel to the Z-axis. A Z-axis motor (not shown) is also arranged on the bed 10 to rotate the Z-axis guide 11.

[0016] A Y-axis guide 21 for driving the saddle 30 in a direction parallel to the Y-axis is disposed on a side surface (sliding surface) 20a of the column 20 that is parallel to the Y-axis. A Y-axis motor (not shown) for driving and rotating the Y-axis guide 21 is disposed on the column 20.

[0017] The tool spindle unit 40 is arranged parallel to the Z-axis. The tool spindle unit 40 is rotatably supported on the saddle 30, and is rotated by a spindle motor (not shown) housed in the column 20 (or the saddle 30). The tool spindle unit 40 exchangeably supports a cutting tool 41 and a grinding tool 43. The cutting tool 41 or the grinding tool 43 is held in a tool holder 42 and attached to the tip of the tool spindle unit 40.

[0018] 4, the grinding tool 43 is attached to the tip of the tool holder 42. The grinding tool 43 is formed in a disk shape and is configured to be rotatable around an axis parallel to the X-axis. The grinding tool 43 converts the rotational motion of the tool spindle unit 40 around the Ct axis into rotational motion around an axis parallel to the X-axis direction using a known method, and rotates the grinding tool 43 around the axis parallel to the X-axis direction.

[0019] As shown in FIG. 1(b), the cutting tool 41 rotates around the Ct axis, which is a rotation axis parallel to the Z axis and rotates around the central axis of the tool spindle unit 40, in conjunction with the rotation of the tool spindle unit 40. As shown in FIG. 3, the cutting tool 41 cuts tooth grooves 61 into the inner surface of the workpiece W, which has an internal gear shape, while rotating synchronously with the workpiece W. The cutting tool 41 in this embodiment is a skiving cutter, and is designed based on the shape of the tooth grooves 61 to be formed in the workpiece W. The cutting tool 41 is rotated around the tool spindle Ct axis while attached to the tool spindle unit 40.

[0020] The workpiece W may be roughly machined to form the tooth grooves 61, then hardened, and then cut using a skiving cutter, or the rough machining and hardening may be omitted and the tooth grooves 61 may be formed in the workpiece W using a skiving cutter.

[0021] The grinding tool 43 and the tool holder 42, or the cutting tool 41 and the tool holder 42, move in a direction parallel to the Z-axis relative to the bed 10 as the column 20 and the saddle 30 move. Also, the grinding tool 43 and the tool holder 42, or the cutting tool 41 and the tool holder 42, move in a direction parallel to the Y-axis as the saddle 30 moves.

[0022] As shown in FIG. 1(a), an X-axis guide 12 for moving the workpiece spindle unit 50 in a direction parallel to the X-axis is disposed on the upper surface of the bed 10. An X-axis motor (not shown) for driving and rotating the X-axis guide 12 is disposed on the bed 10. The workpiece spindle unit 50 is rotatable about the B-axis by a B-axis motor (not shown). The workpiece spindle unit 50 holds a workpiece W via a jig 51. The jig 51 and the workpiece W are rotated about the Cw-axis by the workpiece spindle motor (not shown), and are also rotated about the Cw-axis by the workpiece spindle motor at a predetermined index angle. The Cw-axis is the central axis of rotation of the workpiece W when attached to the jig 51.

[0023] The gear machining device 1 also includes a tool changer 44 (see FIG. 2). The tool changer 44 automatically changes a tool attached to the tool spindle device 40 with a tool held in a tool magazine (not shown). For example, the tool changer 44 automatically changes a cutting tool 41 attached to the tool spindle device 40 with a grinding tool 43 held in the tool magazine. The configuration and operation of the tool changer 44 are well known and can be found in, for example, Japanese Patent Application Laid-Open No. 2018-103330, and therefore a description thereof will be omitted.

[0024] The gear machining device 1 is equipped with a sensor 70. The sensor 70 detects the coordinates of a predetermined position on the workpiece W when the workpiece W is attached to the workpiece spindle device 50 and the workpiece spindle device 50 is indexed to each of a plurality of index angles as a preparation stage. The predetermined position is not particularly limited and may be, for example, the outer peripheral surface 62 of the internal gear-shaped workpiece W. The sensor 70 may be disposed on any member, such as the workpiece spindle device 50 or the tool changer 44. The sensor 70 may be configured to come into contact with at least three points on the workpiece W to detect the coordinates of the predetermined position on the workpiece W. However, the sensor 70 may also be configured to come into contact with the workpiece W at four or more points. The sensor 70 may also be a non-contact type such as a laser sensor.

[0025] 2, the control device 100 is a computer device whose main components are a CPU, ROM, RAM, and various interfaces, and constitutes a CNC (Computer Numerical Control) device and a PLC (Programmable Logic Controller) device that performs machining by comprehensively controlling the operation of the gear machining device 1. In other words, the control device 100 is configured to perform position control and rotation drive control of the cutting tool 41, grinding tool 43, and workpiece W based on a machining program (NC program).

[0026] As shown in FIG. 2, the control device 100 mainly includes a first center axis position calculation unit 101, a rotation axis position calculation unit 102, a second center axis position calculation unit 103, a grinding control unit 104, a cutting control unit 105, a workpiece rotation control unit 106, and a memory unit 107.

[0027] The first central axis position calculation unit 101 calculates a first position of the central axis CA of the workpiece W at each index angle in the preparation stage based on the detection value relating to the coordinates of the predetermined position detected by the sensor 70.

[0028] The rotation axis position calculation unit 102 calculates the position of the rotation axis Cw of the workpiece spindle device 50 based on the first positions at the plurality of index angles in the preparation stage.

[0029] The second center axis position calculation unit 103 calculates a second position of the center axis CA of the workpiece W corresponding to the index angle in the grinding stage based on the rotation axis Cw of the workpiece spindle device 50 and the index angle in the grinding stage of the workpiece spindle device 50.

[0030] The grinding control unit 104 corrects the command grinding position of the grinding tool 43 corresponding to the index angle of the grinding stage based on the second position, and index-grinds the workpiece W using the grinding tool 43 based on the corrected grinding position of the grinding tool 43.

[0031] The cutting control unit 105 cuts the tooth grooves 61 of the workpiece W by rotating the cutting tool 41 and the workpiece W synchronously and feeding them relatively based on the position of the rotation axis Cw of the workpiece spindle device 50.

[0032] The workpiece rotation control unit 106 controls the drive of the workpiece spindle motor (not shown) using the rotation angle detected by an encoder (not shown) provided on the workpiece spindle motor, and rotates the workpiece W held by the workpiece spindle device 50 around the Ct axis.

[0033] The memory unit 107 mainly stores an index angle, a command grinding position, and a machining program. The index angle is an angle for rotating the workpiece W at a predetermined index angle. The command grinding position is a grinding position of the grinding tool 43 in the grinding stage based on the machining program when the workpiece W is attached to the workpiece spindle device 50 without any error.

[0034] 3. Gear processing method Next, a gear cutting method according to this embodiment will be described with reference to the flowcharts shown in Figures 5 to 7 and Figures 8 to 10. However, the gear cutting method is not limited to the following description.

[0035] 5 shows a main flow of the gear machining method of this embodiment. First, a workpiece mounting step (S10) is executed in which a workpiece W is mounted on the gear machining apparatus 1. As a result, the workpiece W is mounted on the workpiece spindle device 50 via a jig 51.

[0036] 8, when the workpiece W is attached to the jig 51, the center of rotation Cw of the workpiece spindle device 50 may not coincide with the central axis CA of the gear workpiece W. If the gear is ground without performing position correction in a state in which the center of rotation Cw of the workpiece spindle device 50 does not coincide with the central axis CA of the gear workpiece W, the shape of the gear tooth profile may deviate from the designed shape.

[0037] In Figure 8, the position of the grinding tool 43 is shown by a dashed line when the center of rotation Cw of the workpiece spindle device 50 is used as a reference. When the center of rotation Cw of the workpiece spindle device 50 and the central axis CA of the gear workpiece W coincide, the tooth grooves 61 to be ground are located at the position of the grinding tool 43 shown by the dashed line. However, when the center of rotation Cw of the workpiece spindle device 50 and the central axis CA of the gear workpiece W do not coincide, as shown in Figure 8, the position of the grinding tool 43 and the actual positions of the tooth grooves 61 of the workpiece W are misaligned in the circumferential direction of the workpiece W. As a result, the pitch of the gear tooth grooves 61 may be misaligned in the circumferential direction.

[0038] Next, a preparation step (S20) (an example of a preparation stage) is executed. A flowchart of the preparation step (S20) is shown in Fig. 6. When the preparation step (S20) is executed, the sensor 70 detects the position coordinates of the outer peripheral surface 62 of the workpiece W in a state where the workpiece W is attached to the workpiece spindle device 50 and the workpiece spindle device 50 is indexed at a predetermined index angle (S21).

[0039] S21 will be described with reference to Fig. 9. In Fig. 9, dimensions are exaggerated to illustrate a state in which the rotation center Cw of the workpiece spindle device 50 and the central axis CA of the gear workpiece W do not coincide. The same is true for Fig. 10.

[0040] First, with the workpiece W attached to the workpiece spindle device 50 via the jig 51, the position coordinates of at least three locations on the outer peripheral surface 62 of the workpiece W are detected by contacting the sensor 70 (S21). In this embodiment, first, the position coordinates of multiple locations (four locations in this embodiment) on the outer peripheral surface 62 of the workpiece W shown in the lower part of FIG. 9 are detected. This position of the workpiece W is set as the reference position in the process of detecting the position coordinates of the outer peripheral surface 62 of the workpiece W, and the angle is set to 0°. The four measurement locations on the outer peripheral surface 62 of the workpiece W may be positioned at equal intervals or at unequal intervals in the circumferential direction of the workpiece W. The number of measurement locations may also be two, three, or five or more. Based on the detected position coordinates of the four locations, the first center axis position calculation unit 101 calculates the position coordinates (a, b) of the first position P1 of the center axis CA of the workpiece W (S22). For example, the coordinates of the center position of a circle that passes through the four detected points can be calculated, and the coordinates of the center position of this circle can be set as the position coordinates (a, b) of the first position P1. However, the method of calculating the position coordinates (a, b) of the first position P1 is not limited to the above.

[0041] Next, the workpiece spindle device 50 rotates the workpiece W at a predetermined index angle as shown by the arrow A1 (S23). That is, as shown by the arrow A1 in Fig. 9, the workpiece spindle device 50 rotates the workpiece W by 90° clockwise with the first position P1 as a reference.

[0042] The first center axis position calculation unit 101 determines whether or not the position detection has been completed by detecting the position of the workpiece W at all the index angles (S24). If the position detection of the workpiece W has not been completed at all the index angles (S24: N), S21 to S24 are repeated.

[0043] The process of repeating S21 to S24 will be described with reference to Fig. 9. When the workpiece W is rotated around the center of rotation Cw of the workpiece spindle device 50, the workpiece W revolves around the center of rotation Cw of the workpiece spindle device 50 and rotates around the central axis CA of the workpiece W. To illustrate the state in which the workpiece W rotates, fixed points on the workpiece W are marked with black circles in Fig. 9. At a first position P1, the black circle is located on the bottom side of Fig. 9, and at a first position P2 rotated 90° clockwise, the black circle is located on the left side of Fig. 9.

[0044] The first central axis position calculation unit 101 calculates the position coordinates (c, d) of the central axis CA of the workpiece W at the first position P2 in the same manner as in the case of the first position P1.

[0045] Next, the workpiece spindle device 50 rotates the workpiece W 90° clockwise with respect to the first position P2 as indicated by the arrow A2. That is, the workpiece W is rotated 180° clockwise with respect to the first position P1 as the reference. In this state, the first center axis position calculation unit 101 calculates the position coordinates (e, f) of the first position P3 of the center axis CA of the workpiece W in the same manner as described above. At the first position P3, the black circle is located at the top of FIG.

[0046] Next, the workpiece spindle device 50 rotates the workpiece W 90° clockwise with respect to the first position P3 as indicated by the arrow A3. That is, the workpiece W is rotated 270° clockwise with respect to the first position P1 as the reference. In this state, the first center axis position calculation unit 101 calculates the position coordinates (g, h) of the first position P4 of the center axis CA of the workpiece W in the same manner as described above. At the first position P4, the black circle is located on the right side of FIG.

[0047] However, the workpiece spindle device 50 may also rotate the workpiece W counterclockwise. Furthermore, the angle by which the workpiece W is rotated is not limited to 90°, and the workpiece W can be rotated by any angle.

[0048] When position detection of the workpiece W has been completed for all index angles (S24: Y), the rotational axis position calculation unit 102 acquires the calculated first positions P1 to P4 and calculates the position of the rotational axis Cw of the workpiece spindle unit 50 based on the first positions P1 to P4 at the multiple index angles (S25). As shown in FIG. 9, the rotational axis position calculation unit 102 calculates the position coordinates (x, y) of the position O of the rotational axis Cw of the workpiece spindle unit 50 based on the position coordinates (a, b) to (g, h) of the first positions P1 to P4. For example, the coordinates of the center position of a circle that passes through the first positions P1 to P4 can be calculated, and the coordinates of the center position of this circle can be set as the position coordinates (x, y) of the position O of the rotational axis Cw of the workpiece spindle unit 50. Furthermore, the coordinates of the intersection of a line connecting the first position P1 and the third position P3 with a line connecting the second position P2 and the fourth position P4 can be calculated, and the coordinates of this intersection can be set as the position coordinates (x, y) of the position O of the rotation axis Cw of the workpiece spindle device 50. However, the method of calculating the position coordinates (x, y) of the position O of the rotation axis Cw of the workpiece spindle device 50 is not limited to the above.

[0049] This completes the preparation step (S20).

[0050] Next, returning to FIG. 5, the cutting step (S30) (an example of a cutting stage) is executed. In this embodiment, tooth spaces 61 in the workpiece W are cut by the cutting tool 41. When the cutting step (S30) is executed, the workpiece spindle unit 50 rotates the workpiece W around the rotation axis Cw of the workpiece spindle unit 50, calculated in S25 of FIG. 6, as the central axis. Meanwhile, the tool spindle unit 40 rotates the cutting tool 41 synchronously with the workpiece W. The tool spindle unit 40 cuts tooth spaces 61 in the workpiece W by moving the cutting tool 41 along the rotation axis Cw of the workpiece spindle unit 50 (see FIG. 3).

[0051] Next, when the cutting step (S30) of the workpiece W is completed, a tool changing step (S40) is executed. The tool changer 44 replaces the cutting tool 41 attached to the tool spindle unit 40 with the grinding tool 43 stored in the tool magazine, and attaches the grinding tool 43 to the tool spindle unit 40.

[0052] Next, a grinding step (S50) (an example of a grinding stage) is performed. Fig. 7 shows a flowchart of the grinding step (S50).

[0053] When the grinding step (S50) is performed, the first index grinding is performed (S51). The workpiece spindle device 50 places the workpiece W at an initial position. In detail, as shown in FIG. 10(a), the workpiece spindle device 50 rotates the workpiece W about the rotation axis Cw and moves it to a first position P1. The first position P1 is the same as the first position P1 calculated in S22 of FIG. 6. This first position P1 corresponds to the initial position.

[0054] Next, the grinding control unit 104 corrects the commanded grinding position of the grinding tool 43 based on the position coordinates (a, b) of the first position P1. The commanded grinding position is the designed grinding position of the grinding tool 43 commanded by the machining program. That is, it is the position of the grinding tool 43C shown by the dashed line in FIG. 10(a). The position of the grinding tool 43C at this commanded grinding position is corrected to the position of the grinding tool 43 shown by the solid line in FIG. 10(a). Note that the workpiece WC shown by the dashed line in FIG. 10(a) indicates the position of the workpiece W based on the machining program.

[0055] The grinding control unit 104 performs index grinding on the workpiece W using the grinding tool 43 whose grinding position has been corrected. As shown in Fig. 10(a), the grinding tool 43 of this embodiment is formed in a disk shape and is disposed with its rotation axis parallel to the X-axis. As a result, the grinding tool 43 of this embodiment is configured to grind the tooth groove 61a of the workpiece W that is located below the first position P1.

[0056] Returning to FIG. 7 , when the first index grinding (S51) is completed, the workpiece W is rotated around the rotation axis Cw by a predetermined index angle θ (S52). In this embodiment, the workpiece W is rotated clockwise. However, the workpiece W may also be configured to be rotated counterclockwise. In detail, as shown in FIG. 10( b), the workpiece W is rotated around the rotation axis Cw of the workpiece spindle unit 50 by a predetermined index angle θ, as indicated by the arrow B. As a result, the workpiece W rotates from the position of the workpiece W indicated by the dashed line in FIG. 10( b) to the position of the workpiece W indicated by the solid line. As a result, the position of the central axis of the workpiece W moves from the first position P1 to the second position P′2.

[0057] Next, the position coordinates of the second position P'2 are calculated (S53). First, the position coordinates of the first position P1 are changed from the position coordinates (a, b) in the Cartesian coordinate system to position coordinates (r, 0) based on a rotating coordinate system whose coordinate origin is the position O of the rotation axis Cw of the workpiece spindle device 50. r is the distance between the position O of the rotation axis Cw of the workpiece spindle device 50 and the first position P1. The angle formed between the position O of the rotation axis Cw of the workpiece spindle device 50 and the first position P1 is set to 0°.

[0058] Next, the second center axis position calculation unit 103 calculates the position coordinates of the second position P'2 based on the position O(x, y) of the rotational axis Cw of the workpiece spindle unit 50 and the index angle θ of the workpiece spindle unit 50 during the grinding stage. In this embodiment, the position coordinates of the second position P'2 are calculated as (r, θ). That is, the calculation is performed by a coordinate transformation that rotates the first position P1 by the index angle θ in a rotating coordinate system whose origin is the position O of the rotational axis Cw of the workpiece spindle unit 50.

[0059] However, the position coordinates of the first position P1 do not need to be converted into a rotational coordinate system. In this case, the position coordinates of the command grinding position are also in a Cartesian coordinate system, and the position coordinates of the corrected grinding tool 43 are also in a Cartesian coordinate system.

[0060] Returning to FIG. 7, next, the grinding control unit 104 corrects the position coordinates of the commanded grinding position based on the position coordinates (r, θ) of the second position P'2 (S54). Specifically, the position of the grinding tool 43 indicated by the dashed line in FIG. 10(b) is rotated clockwise by an angle θ in a rotational coordinate system whose origin is the position O of the rotation axis Cw of the workpiece spindle device 50. This calculates the position of the grinding tool 43 indicated by the solid line in FIG. 10(b). As a result, the grinding control unit 104 corrects the position of the grinding tool 43C arranged at the commanded grinding position shown in FIG. 10(a) to the position of the grinding tool 43 indicated by the solid line in FIG. 10(b) via the position of the grinding tool 43 indicated by the dashed line in FIG. 10(b).

[0061] Returning to Fig. 7, next, the grinding control unit 104 performs index grinding on the workpiece W using the grinding tool 43 based on the corrected grinding position of the grinding tool 43 (S55). That is, the grinding control unit 104 grinds the tooth groove 61b using the grinding tool 43 whose position has been corrected. The tooth groove 61b is located adjacent in the counterclockwise direction to the tooth groove 61a ground in the first index grinding (S51) (see Fig. 10(b)).

[0062] Next, the grinding control unit 104 determines whether grinding of the tooth grooves 61 of the workpiece W has been completed at all index angles (S56). If grinding of the tooth grooves 61 of the workpiece W has not been completed at all index angles (S56: N), S52 to S56 are repeated.

[0063] When grinding of the tooth grooves 61 of the workpiece W has been completed at all index angles (S56: Y), the grinding step (S50) ends. Returning to Fig. 5, the operation of the gear cutting device 1 is now complete.

[0064] 4. Effects of this form Next, the effects of this embodiment will be described. The gear machining apparatus 1 according to this embodiment includes a grinding tool 43, a workpiece spindle device 50, a sensor 70, a first center axis position calculation unit 101, a rotation axis position calculation unit 102, a second center axis position calculation unit 103, and a grinding control unit 104. The grinding tool 43 indexes and grinds tooth grooves 61 in a gear workpiece W. The workpiece spindle device 50 holds the workpiece W and is configured to be able to index the workpiece W at a predetermined angle about the rotation axis. The sensor 70 detects the coordinates of a predetermined position of the workpiece W when the workpiece W is attached to the workpiece spindle device 50 and the workpiece spindle device 50 is indexed to each of a plurality of index angles in a preparation stage. The first center axis position calculation unit 101 calculates a first position of the center axis CA of the workpiece W at each index angle in the preparation stage based on the detection value of the sensor 70. The rotational axis position calculation unit 102 calculates the position of the rotational axis Cw of the workpiece spindle unit 50 based on a first position at a plurality of index angles in the preparation stage. The second center axis position calculation unit 103 calculates a second position of the center axis CA of the workpiece W corresponding to the index angle in the grinding stage based on the rotational axis Cw of the workpiece spindle unit 50 and the index angle of the workpiece spindle unit 50 in the grinding stage. The grinding control unit 104 corrects the grinding position of the grinding tool 43 corresponding to the index angle in the grinding stage based on the second position, and index-grinds the workpiece W with the grinding tool 43 based on the corrected grinding position of the grinding tool 43.

[0065] According to this embodiment, even if the central axis CA of the workpiece W is misaligned with the rotation axis Cw of the workpiece spindle device 50 when the workpiece W is attached to the workpiece spindle device 50, the grinding position of the grinding tool 43 corresponding to the index angle in the grinding stage is corrected based on the second position of the central axis CA of the workpiece W corresponding to the index angle in the grinding stage, and the workpiece W is index-ground by the grinding tool 43 based on the corrected grinding position of the grinding tool 43. This makes it possible to suppress misalignment between the grinding tool 43 and the workpiece W in the grinding stage. As a result, the machining accuracy of the gear can be improved.

[0066] Furthermore, according to this embodiment, the workpiece W can be index-ground by the grinding tool 43 with the central axis CA of the workpiece W aligned with the rotation axis Cw of the workpiece spindle device 50. In other words, the workpiece W can be index-ground by the grinding tool 43 with the center of rotation of the workpiece W aligned with the center of rotation of the workpiece spindle device 50 without any misalignment. This makes it possible to suppress misalignment of the tooth grooves 61a of the workpiece W when the workpiece W is rotated in a plane perpendicular to the central axis CA of the workpiece W. This improves the machining accuracy of the gears.

[0067] The second center axis position calculation unit 103 according to this embodiment calculates the second position of the center axis CA of the workpiece W corresponding to the index angle in the grinding stage, using a rotational coordinate system whose origin is the position of the rotational axis Cw of the workpiece spindle device 50. According to this embodiment, the calculation process can be simplified compared to when the second position is calculated using an orthogonal coordinate system.

[0068] The grinding control unit 104 according to this embodiment corrects the grinding position of the grinding tool 43 corresponding to the index angle in the grinding stage using a rotational coordinate system whose origin is the position of the rotational axis Cw of the workpiece spindle device 50. According to this embodiment, the calculation process can be simplified compared to when the grinding position of the grinding tool 43 is corrected using an orthogonal coordinate system.

[0069] The grinding tool 43 of this embodiment includes a disk-shaped gear grinding wheel. This allows the tooth grooves 61 of the workpiece W to be formed one by one, thereby improving machining accuracy. Furthermore, with the grinding tool 43 of this embodiment, in the finishing step of gear machining of the workpiece W, the abrasive grains of the grinding tool 43 can be set according to the finishing accuracy while suppressing positional deviation of each tooth groove 61a of the workpiece W, thereby enabling high-precision machining.

[0070] The sensor 70 of this embodiment is a contact type that detects the coordinates of a predetermined position on the workpiece W by coming into contact with at least three points on the workpiece W. This improves the detection accuracy of the first position of the workpiece W.

[0071] The gear machining apparatus 1 of this embodiment further includes a cutting tool 41 and a cutting control unit 105. The cutting tool 41 cuts the tooth grooves 61 of the gear. The cutting control unit 105 cuts the tooth grooves 61 of the workpiece W by rotating the cutting tool 41 and the workpiece W synchronously while feeding them relatively based on the position of the rotation axis Cw of the workpiece spindle device 50. The grinding control unit 104 grinds the tooth grooves 61 of the gear cut by the cutting tool 41. According to this embodiment, the cutting process and the grinding process can be integrated compared to when the cutting process and the grinding process are performed by separate machining apparatuses, thereby reducing the setup time for tool replacement and the like. This improves the efficiency of the machining process of the workpiece W. Furthermore, by performing efficient cutting and accurate grinding, it is possible to achieve both improved machining efficiency and improved machining accuracy.

[0072] The gear machining device 1 of this embodiment further includes a tool changer 44 for changing the cutting tool 41 and the grinding tool 43. This further reduces the time required for changing tools, thereby further improving the machining efficiency of the workpiece W.

[0073] The cutting tool 41 of this embodiment is a skiving cutter, which can improve the efficiency of the process of forming the tooth grooves 61 of the workpiece W.

[0074] This embodiment is a gear machining method for index-grinding tooth grooves 61 in a gear workpiece W using a grinding tool 43, and includes a workpiece mounting step (S10), a position detection step (S21), a first center axis position calculation step (S22), a rotation axis position calculation step (S25), a second center axis position calculation step (S53), and an index grinding step (S55). In the workpiece mounting step (S10), the workpiece W is mounted on a workpiece spindle device 50 that is configured to be indexable at a predetermined angle about the rotation axis. In the position detection step (S21), with the workpiece W mounted on the workpiece spindle device 50 and with the workpiece spindle device 50 indexed to each of a plurality of index angles as a preparation stage, the coordinates of a predetermined position of the workpiece W are detected by a sensor 70. A first center axis position calculation step (S22) calculates a first position of the center axis CA of the workpiece W at each index angle in the preparation stage based on the detection value of the sensor 70. A rotation axis position calculation step (S25) calculates the position of the rotation axis Cw of the workpiece spindle device 50 based on the first position at a plurality of index angles in the preparation stage. A second center axis position calculation step (S53) calculates a second position of the center axis CA of the workpiece W corresponding to the index angle in the grinding stage based on the rotation axis Cw of the workpiece spindle device 50 and the index angle of the workpiece spindle device 50 in the grinding stage. An index grinding step (S55) corrects the grinding position of the grinding tool 43 corresponding to the index angle in the grinding stage based on the second position, and index-grinds the workpiece W by the grinding tool 43 based on the corrected grinding position of the grinding tool 43.

[0075] The gear cutting method of this embodiment further includes a cutting step (S30) of cutting tooth grooves 61 in the workpiece W by feeding the cutting tool 41 and the workpiece W relatively while rotating them synchronously, based on the position of the rotation axis Cw of the workpiece spindle device 50 calculated in the rotation axis position calculation step (S25). An index grinding step (S55) grinds the tooth grooves 61 formed by executing the cutting step (S30).

[0076] The present invention is not limited to the above-described embodiments, and can be applied to various embodiments within the scope of the present invention.

[0077] When the workpiece W is a helical gear, in the grinding stage, the grinding position of the grinding tool 43 is corrected at a predetermined index angle, and then the tooth grooves 61 can be ground by the grinding tool 43 while rotating the workpiece W a predetermined amount in a clockwise or counterclockwise direction.

[0078] The grinding tool 43 of this embodiment may be configured such that the rotation of the tool holder 42 is transmitted by a pulley and a belt to rotate the grinding wheel of the grinding tool 43. Also, the grinding process may be performed by advancing the tool holder 42 along the axial direction of rotation toward the workpiece W, and after grinding is completed, moving the tool holder 42 upward and then retracting along the axial direction of rotation of the tool holder 42. Also, the position of the tooth groove to be machined on the workpiece W is not particularly limited, and may be, for example, upward or in any other direction. [Explanation of symbols]

[0079] 1: gear cutting device, 40: tool spindle device, 41: cutting tool, 43: grinding tool, 44: tool changer, 50: workpiece spindle device, 61, 61a, 61b: tooth groove, 62: outer peripheral surface, 70: sensor, 100: control device, 101: first center axis position calculation unit, 102: rotation axis position calculation unit, 103: second center axis position calculation unit, 104: grinding control unit, 105: cutting control unit, CA: center axis of workpiece, Ct: tool spindle, Cw: rotation axis, S10: workpiece mounting process, S21: position detection process, S22: first center axis position calculation process, S25: rotation axis position calculation process, S30: cutting process, S40: tool changer process, S53: second center axis position calculation process, S55: index grinding process, W: workpiece

Claims

1. a grinding tool for index grinding tooth spaces in a gear workpiece; a workpiece spindle device configured to hold the workpiece and to be able to index the workpiece at a predetermined angle around a rotation axis; a sensor that detects coordinates of a predetermined position of the workpiece in a state where the workpiece is attached to the workpiece spindle device and the workpiece spindle device is indexed to each of a plurality of index angles as a preparation stage; a first central axis position calculation unit configured to calculate a first position of a central axis of the workpiece at each index angle in the preparation stage based on the detection value of the sensor; a rotation axis position calculation unit configured to calculate a position of a rotation axis of the workpiece spindle device based on the first positions at a plurality of index angles in the preparation stage; a second central axis position calculation unit configured to calculate a second position of the central axis of the workpiece corresponding to the index angle of the grinding stage based on the rotation axis of the workpiece spindle device and the index angle of the workpiece spindle device in the grinding stage; a grinding control unit configured to correct a grinding position of the grinding tool corresponding to an index angle of the grinding stage based on the second position, and to index-grind the workpiece with the grinding tool based on the corrected grinding position of the grinding tool.

2. The second center axis position calculation unit 2. The gear machining device according to claim 1, wherein the device is configured to calculate a second position of the central axis of the workpiece corresponding to the index angle in the grinding stage using a rotating coordinate system whose origin is the position of the rotation axis of the workpiece spindle device.

3. The grinding control unit 3. The gear machining device according to claim 1, wherein the grinding position of the grinding tool corresponding to the index angle in the grinding stage is corrected using a rotational coordinate system whose origin is the position of a rotation axis of the workpiece spindle device.

4. The gear machining device according to claim 1 , wherein the grinding tool comprises a disc-shaped gear grinding wheel.

5. 2. The gear machining device according to claim 1, wherein the sensor is a contact type that detects coordinates of a predetermined position on the workpiece by contacting at least three points on the workpiece.

6. moreover, a cutting tool for cutting the tooth grooves of the gear; and a cutting control unit configured to cut the tooth grooves of the workpiece by feeding the cutting tool and the workpiece relatively while rotating them synchronously based on the position of the rotation axis of the workpiece spindle device, The gear machining device according to claim 1 , wherein the grinding control unit is configured to grind the tooth grooves of the gear cut by the cutting tool.

7. moreover, 7. The gear machining apparatus according to claim 6, further comprising a tool changing device for changing the cutting tool and the grinding tool.

8. 7. The gear machining device according to claim 6, wherein the cutting tool is a skiving cutter.

9. A gear machining method for index grinding tooth grooves in a gear workpiece using a grinding tool, comprising: a workpiece mounting step of mounting the workpiece on a workpiece spindle device configured to be indexable at a predetermined angle around a rotation axis; a position detecting step of detecting coordinates of a predetermined position of the workpiece by a sensor in a state where the workpiece is attached to the workpiece spindle device and the workpiece spindle device is indexed to each of a plurality of index angles as a preparation step; a first central axis position calculation step of calculating a first position of a central axis of the workpiece at each index angle in the preparation step based on the detection value of the sensor; a rotation axis position calculation step of calculating a position of a rotation axis of the workpiece spindle device based on the first positions at a plurality of index angles in the preparation step; a second central axis position calculation step of calculating a second position of the central axis of the workpiece corresponding to the index angle in the grinding stage based on the rotation axis of the workpiece spindle device and the index angle in the grinding stage of the workpiece spindle device; and an index grinding step of correcting a grinding position of the grinding tool corresponding to an index angle of the grinding stage based on the second position, and index-grinding the workpiece with the grinding tool based on the corrected grinding position of the grinding tool.

10. moreover, a cutting step of cutting the tooth grooves of the workpiece by rotating a cutting tool and the workpiece synchronously and feeding them relatively based on the position of the rotation axis of the workpiece spindle device calculated in the rotation axis position calculation step, 10. The gear machining method according to claim 9, wherein the index grinding step grinds the tooth grooves formed by performing the cutting step.

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