JP7494549B2 - Gear Processing Equipment - Google Patents

Description

The present invention relates to a gear processing device.

Patent Document 1 describes the use of a hob cutter to create a tooth profile on a workpiece. As machining of the workpiece progresses, the machining resistance changes, causing the load on the rotation of the hob cutter to fluctuate. In particular, the load gradually increases at the start of cutting, remains high and stable in the middle, and gradually decreases at the end of cutting. Patent Document 1 describes the electrical detection of load fluctuations, the calculation of a correlation value between the detection signal and the tooth trace error of the workpiece, and the application of a corrective rotation to the workpiece support table in accordance with the correlation value. This is said to make it possible to correct the tooth trace direction error of the workpiece.

Patent Document 2 also describes using a tool-exchangeable machining center, rather than a dedicated hob machine, to machine a workpiece by attaching a hob cutter to the tool spindle of the machining center. In this case, the hob cutter is supported on one side, so the rigidity supporting the hob cutter is low. This can cause errors in the tooth profile machined into the workpiece compared to the ideal involute tooth profile. Therefore, Patent Document 2 describes creating and machining a tooth profile using a correction hob cutter with a concave or convex portion formed on the inclined surface of the approximately trapezoidal cutting blade.

Japanese Patent Application Laid-Open No. 59-81017 JP 2015-208806 A

However, it was found that when the hob cutter is supported by a cantilever, the correction described in Patent Document 1 alone is not sufficient to correct the load. In other words, it was found that when the hob cutter is supported by a cantilever, there exists behavior that cannot be expressed simply by the load gradually increasing at the start of cutting, remaining stable at a high level in the middle period, and gradually decreasing at the end of cutting.

In addition, the correction hob cutter described in Patent Document 2 is a special tool and therefore expensive. Therefore, there is a need to reduce the tooth lead error without using special tools.

The present invention aims to provide a gear cutting device that can correct tooth trace error without using special tools when the hob cutter is cantilevered.

One aspect of the present invention is
A hob cutter for machining a tooth profile on a workpiece;
a tool spindle device that rotatably supports the hob cutter in a cantilever manner;
a workpiece spindle device that rotatably supports the workpiece;
a drive device that moves the tool spindle device and the workpiece spindle device relative to each other;
a measuring device for measuring a deflection amount of the hob cutter or a value corresponding to a rotational synchronization deviation of the work spindle device relative to the tool spindle device;
a correction processing unit that corrects a cutting amount by the hob cutter or a rotational synchronization deviation of the workpiece spindle device with respect to the tool spindle device based on the value measured by the measuring device;
Equipped with
The hob cutter has a number of cutting edges in the axial direction that is greater than the number of cutting edges used in one machining operation,
The correction processing unit is in a gear machining apparatus and performs correction based on the value measured by the measuring device and the axial position of the hob cutter used for machining.
Another aspect of the present invention is a hob cutter for machining a tooth profile on a workpiece,
a tool spindle device that rotatably supports the hob cutter in a cantilever manner;
a workpiece spindle device that rotatably supports the workpiece;
a drive device that moves the tool spindle device and the workpiece spindle device relative to each other;
a measuring device for measuring a deflection amount of the hob cutter or a value corresponding to a rotational synchronization deviation of the work spindle device relative to the tool spindle device;
a correction processing unit that corrects a cutting amount by the hob cutter or a rotational synchronization deviation of the workpiece spindle device with respect to the tool spindle device based on the value measured by the measuring device;
Equipped with
The correction processing unit is in a gear machining device that determines a correction amount based on the value measured by the measuring device when machining the machining start end portion in the tooth width direction of the actual workpiece, and performs correction when machining the central portion of the actual workpiece in the tooth width direction based on the determined correction amount.

The inventors have discovered that a unique cantilever-induced motion occurs when the hob is supported in a cantilever manner. The unique cantilever-induced motion is a motion in which, when a tooth profile is generated on a workpiece, the hob is supported in a cantilever manner, so that the amount of deflection or vibration of the hob becomes large at the machining start end in the tooth width direction of the tooth profile, and the amount of deflection or vibration of the hob becomes small at the center in the tooth width direction. When the unique cantilever-induced motion occurs, the correction processing unit corrects the cutting amount or rotational synchronization deviation based on a value equivalent to the amount of deflection or rotational synchronization deviation of the hob measured by the measuring device. Therefore, the tooth trace error caused by the unique cantilever-induced motion in the case of cantilever support can be reduced.

FIG. 1 is a diagram illustrating an example of a gear machining device. FIG. 13 is a diagram showing processing by the tip side of a hob cutter. FIG. 13 is a diagram showing processing by the center part of a hob cutter. FIG. 13 is a diagram showing processing by the base end side of a hob cutter. FIG. FIG. 2 is a diagram showing a trajectory of a blade of a hob cutter relative to a workpiece in an ideal state. FIG. 4 is a diagram showing a trajectory of a blade of a hob cutter relative to a workpiece when machining a machining start end portion. FIG. 13 is a diagram showing a tooth lead error when machining using the tip side of a hob cutter. FIG. 13 is a diagram showing a tooth lead error when machining by the center part of a hob cutter. FIG. 13 is a diagram showing a tooth lead error when machining using the base end side of a hob cutter. FIG. 13 is a diagram showing a change in Y-axis effective current when machining is performed by the tip side of a hob cutter. FIG. 13 is a diagram showing a change in Y-axis effective current when machining is performed by the central portion of a hob cutter. FIG. 13 is a diagram showing a change in Y-axis effective current when machining is performed by the base end side of the hob cutter. FIG. 13 is a diagram showing a change in A-axis effective current when machining is performed by the tip side of a hob cutter. FIG. 13 is a diagram showing a change in A-axis effective current when machining is performed by the central portion of a hob cutter. FIG. 13 is a diagram showing a change in A-axis effective current when machining is performed by the base end side of a hob cutter. FIG. 2 is a functional block diagram showing the gear machining device. 1 is a flowchart showing a first example of a gear machining method. FIG. 13 is a diagram showing a trajectory of a blade of a hob cutter relative to a workpiece when a cutting-in correction is performed. FIG. 13 is a diagram showing a trajectory of a blade of a hob cutter relative to a workpiece when rotation synchronous correction is performed. 1 is a flowchart showing a first example of a gear machining method.

(1. Configuration of gear machining device 1)
The gear cutting device 1 will be described with reference to Fig. 1. The gear cutting device 1 is a device that generates a tooth profile on the workpiece W by using the hob cutter T by moving the hob cutter T and the workpiece W relatively to each other.

In this example, the gear machining device 1 is a general-purpose machine tool, for example, a machining center. In other words, the machining center is configured to be tool replaceable, and is capable of machining according to the attached tool. For example, in addition to the hob cutter T, replaceable tools include gear skiving cutters, end mills, milling tools, drills, turning tools, threading tools, grinding tools, etc. Note that in FIG. 1, the tool exchange device and the tool magazine for storing the tools are not shown.

In this example, the machining center serving as the gear machining device 1 is basically a horizontal machining center. However, the gear machining device 1 can be configured in other ways, such as a vertical machining center.

As shown in FIG. 1, the gear cutting device 1 has, for example, three mutually orthogonal linear axes (X-axis, Y-axis, Z-axis) as drive axes. Here, the direction of the rotation axis of the hob cutter T (equal to the rotation axis of the tool spindle) is defined as the Z-axis direction, and two axes perpendicular to the Z-axis direction are defined as the X-axis direction and the Y-axis direction. In FIG. 1, the horizontal direction is the X-axis direction, and the vertical direction is the Y-axis direction. Furthermore, the gear cutting device 1 further has two rotation axes (A-axis and B-axis) as drive axes for changing the relative position of the hob cutter T and the workpiece W. The gear cutting device 1 also has a Ct axis as a rotation axis for rotating the hob cutter T.

In other words, the gear machining device 1 is a 5-axis machining device (a 6-axis machining device when the tool spindle (Ct axis) is taken into account) capable of machining free-form surfaces. Here, instead of a configuration having an A-axis (a rotation axis about the X-axis in the reference state) and a B-axis (a rotation axis about the Y-axis in the reference state), the gear machining device 1 may be configured to have a Cw-axis (a rotation axis about the Z-axis in the reference state) and a B-axis, or may be configured to have an A-axis and a Cw-axis.

In the gear cutting device 1, the configuration for moving the hob cutter T and the workpiece W relative to one another can be selected as appropriate. In this example, the gear cutting device 1 allows the hob cutter T to move linearly in the Y-axis and Z-axis directions, allows the workpiece W to move linearly in the X-axis direction, and further allows the workpiece W to rotate about the A-axis and B-axis. In addition, the hob cutter T can rotate about the Ct axis.

The gear machining device 1 comprises a bed 10, a workpiece holding device 20, and a tool holding device 30. The bed 10 is formed in any shape, such as a substantially rectangular shape, and is installed on the floor surface. The workpiece holding device 20 allows the workpiece W to move linearly in the X-axis direction relative to the bed 10, and to rotate about the A-axis and B-axis. The workpiece holding device 20 mainly comprises an X-axis moving table 21, a B-axis rotating table 22, and a workpiece spindle device 23.

The X-axis moving table 21 is provided so as to be movable in the X-axis direction relative to the bed 10. Specifically, the bed 10 is provided with a pair of X-axis guide rails extending in the X-axis direction (front-to-back direction in FIG. 1), and the X-axis moving table 21 is driven by a driving device such as a linear motor or a ball screw mechanism (not shown) to move back and forth in the X-axis direction while being guided by the pair of X-axis guide rails.

The B-axis rotating table 22 is placed on the top surface of the X-axis moving table 21, and moves back and forth in the X-axis direction together with the X-axis moving table 21. The B-axis rotating table 22 is also arranged to be rotatable about the B-axis relative to the X-axis moving table 21. A rotating motor (not shown) is housed in the B-axis rotating table 22, and the B-axis rotating table 22 is driven by the rotating motor to be able to rotate about the B-axis.

The workpiece spindle device 23 is mounted on the B-axis rotating table 22 and rotates about the B-axis integrally with the B-axis rotating table 22. The workpiece spindle device 23 supports the workpiece W so that it can rotate about the A-axis. In this example, the workpiece spindle device 23 supports the workpiece W in a cantilever manner. The workpiece spindle device 23 is equipped with a rotary motor (not shown) that rotates the workpiece W. In this way, the workpiece holding device 20 allows the workpiece W to move in the X-axis direction relative to the bed 10 and to rotate about the A-axis and B-axis.

The tool holding device 30 mainly comprises a column 31, a saddle 32, and a tool spindle device 33. The column 31 is provided so as to be movable in the Z-axis direction relative to the bed 10. Specifically, the bed 10 is provided with a pair of Z-axis guide rails extending in the Z-axis direction (left-right direction in FIG. 1), and the column 31 is driven by a driving device such as a linear motor or a ball screw mechanism (not shown) to move back and forth in the Z-axis direction while being guided by the pair of Z-axis guide rails.

The saddle 32 is disposed on the side of the column 31 facing the workpiece W (the left side in FIG. 1), parallel to a plane perpendicular to the Z-axis direction. A pair of Y-axis guide rails extending in the Y-axis direction (the up-down direction in FIG. 1) are provided on the side of the column 31, and the saddle 32 reciprocates in the Y-axis direction by being driven by a driving device such as a linear motor or a ball screw mechanism (not shown).

The tool spindle device 33 is mounted on the saddle 32 and moves in the Y-axis direction together with the saddle 32. The tool spindle device 33 supports the hob cutter T so that it can rotate about the Ct axis. In this example, the tool spindle device 33 supports the hob cutter T in a cantilever manner. The tool spindle device 33 is equipped with a rotary motor (not shown) that rotates the hob cutter T. In this way, the tool holding device 30 holds the hob cutter T so that it can move in the Y-axis and Z-axis directions relative to the bed 10 and can rotate about the Ct axis.

(2. Description of machining state by hob cutter T)
The state in which a tooth profile is generated on a workpiece W by the hob cutter T will be described with reference to FIGS. 2A to 2C and 3. FIG.

As shown in Figures 2A and 3, the base end side (right side of Figure 2A) of the hob cutter T is the part that is attached to the tool spindle unit 33 and is supported in a cantilevered manner. The hob cutter T also has multiple blade portions on the outer circumferential surface of the tip side (free end side). The multiple blade portions are arranged in a spiral shape. The multiple blade portions of the hob cutter T are arranged in multiple revolutions. In other words, the hob cutter T has multiple cutting edge rows in the axial direction. In this example, the hob cutter T has 5 to 6 cutting edge rows.

In the tooth profile creation process, the central axis of the hob cutter T and the central axis of the workpiece W have an intersection angle. In this example, the intersection angle is 90°, but it can be an angle other than 90°. The hob cutter T is rotated around its central axis, and the workpiece W is rotated synchronously around its central axis while the hob cutter T is moved relatively in the direction of the central axis of the workpiece W.

In this example, the hob cutter T has the upper end of the workpiece W as its machining position. In other words, the above operation is achieved by moving the hob cutter T and the workpiece W relatively in the X-axis and Z-axis directions while the hob cutter T is positioned in the Y-axis direction. However, the machining position is not limited to the upper end of the workpiece W, and can be other positions in the circumferential direction of the workpiece W.

As shown in FIG. 2A, the number of cutting edges used in one machining operation in the axial direction of the hob cutter T is 2 to 3. In other words, the hob cutter T has a greater number of cutting edges (5 to 6 rows) than the number of cutting edges used in one machining operation in the axial direction (2 to 3 rows). Therefore, the hob cutter T can machine the workpiece W using cutting edges at different axial positions.

Specifically, FIG. 2A shows the state where the workpiece W is machined by the blade row at the tip side of the hob cutter T. FIG. 2B shows the state where the workpiece W is machined by the blade row at the axial center of the hob cutter T. FIG. 2C shows the state where the workpiece W is machined by the blade row at the base end side of the hob cutter T. In this way, the hob cutter T can improve its lifespan by being able to machine the workpiece W by blade rows at different axial positions.

Here, since the hob cutter T is supported by a cantilever, the tip side of the hob cutter T is prone to bending. The amount of bending of the hob cutter T varies depending on the axial position used for machining in the hob cutter T. The amount of bending of the hob cutter T is greatest when machining at the tip side of the hob cutter T shown in FIG. 2A, next greatest when machining at the center of the hob cutter T shown in FIG. 2B, and least when machining at the base end side of the hob cutter T shown in FIG. 2C.

Furthermore, in the tooth profile generation process, the processing load changes successively. Therefore, as the hob cutter T bends during processing, the tip side of the hob cutter T vibrates in the bending direction. The magnitude of the vibration of the hob cutter T differs depending on the axial position of the hob cutter T used for processing. The magnitude of the vibration of the hob cutter T is greatest when processing at the tip side of the hob cutter T shown in FIG. 2A, next greatest when processing at the central part of the hob cutter T shown in FIG. 2B, and smallest when processing at the base end side of the hob cutter T shown in FIG. 2C. In other words, the greater the amount of bending of the hob cutter T, the greater the magnitude of the vibration.

In this way, the hob cutter T is supported in a cantilever manner, which causes deflection and vibration. The operation related to the deflection and vibration according to the axial position of the hob cutter T used in the above-mentioned machining is called the cantilever-induced operation.

(3. Definition of machining position of workpiece W)
The machining position of the workpiece W will be defined with reference to Fig. 3. As shown in Fig. 3, when machining the workpiece W with a hob cutter T, the hob cutter T is rotated and the workpiece W is synchronously rotated while the hob cutter T is moved relatively in the central axis direction of the workpiece W to generate a tooth profile on the workpiece W.

In this example, when the cross angle is 90°, the hob cutter T moves in the X-axis direction. However, when the cross angle is tilted from 90°, the hob cutter T moves in a direction tilted from the X-axis direction.

Figure 3 shows the state in which the hob cutter T is moved from right to left relative to the workpiece W. Here, in the workpiece W, the machining start end in the tooth width direction of the tooth profile is L1, the center in the tooth width direction is L2, and the machining end end in the tooth width direction is L3. The machining start end L1, the center L2 in the tooth width direction, and the machining end end L3 each perform different cantilever-induced operations as described above. Details will be described later.

(4. Trajectory of the blade of the hob cutter T)
The trajectory of the blade of the hob cutter T will be described with reference to Figures 4A and 4B. Figure 4A shows an ideal state. By moving the hob cutter T and the workpiece W relative to each other, the blade of the hob cutter T moves relative to the workpiece W as shown by the outline arrow in Figure 4A. The blade cuts in from the upper right of Figure 4A and exits from the upper left. At this time, the tooth surface A0 formed on the workpiece W is the tooth surface on the cutting start side, and the tooth surface B1 is the tooth surface on the cutting end side.

However, as described above, the hob cutter T generates a cantilever-induced motion during machining. In other words, the hob cutter T generates deflection and vibration. As shown by the black arrow in Figure 4B, the blade of the hob cutter T generates deflection and vibration when machining the tooth surface on the cutting start side.

As a result, when machining the tooth flank on the cutting start side (the right tooth flank in FIG. 4B), the blade of the hob cutter T is positioned at a position shifted in the opposite direction from the ideal tooth flank A0 (the left side in FIG. 4B). Therefore, the tooth flank on the cutting start side has an uncut portion with respect to the ideal tooth flank A0, and has a positive tooth lead error.

On the other hand, when machining the tooth flank on the cutting end side (the left tooth flank in FIG. 4B), the blade of the hob cutter T is positioned at a position shifted in the cutting direction (left side in FIG. 4B) from the ideal tooth flank B0. This state occurs because the hob cutter T maintains the shift that occurred when machining the tooth flank on the cutting start side. In other words, the tooth flank on the cutting end side is overcut with respect to the ideal tooth flank B0, resulting in a negative tooth lead error.

(5. Machining Accuracy of Workpiece W and State of Gear Machining Device 1 During Machining)
The machining accuracy of the workpiece W, i.e., the tooth lead error, when the machining position of the hob T is as shown in Figures 2A, 2B, and 2C will be described with reference to Figures 5A, 5B, and 5C. Figures 5A to 5C correspond to Figures 2A to 2C.

In the figures, the up-down direction is the tooth trace direction of the teeth machined into the workpiece W. Also, in Figures 5A-5C, the right-hand diagram shows tooth surface A on the right-hand side of Figures 4A and 4B, where cutting begins, and the ideal tooth surface is indicated as A0. Here, the ideal tooth surface A0 is the position on tooth surface A that is most cut.

In addition, in Figures 5A-5C, the left diagram shows tooth surface B on the left side of Figures 4A and 4B where the cutting ends, with the ideal tooth surface indicated as B0. The ideal tooth surface B0 is a position based on the ideal tooth surface A0 on the tooth surface A on the cutting start side. Also, the machining start position on the workpiece W is indicated as Ms, and the machining end position is indicated as Me. In other words, machining progresses from bottom to top in the diagrams.

As shown in FIG. 5A, when the axial position of the hob cutter T used for machining is at the tip side, the right tooth surface A has a positive tooth lead error when machining the machining start end L1 (shown in FIG. 3) and the machining end end L3 of the workpiece W. In other words, uncut portions are generated. The right tooth surface A has a slight positive tooth lead error when machining the center portion L2 in the tooth width direction of the workpiece W, but is close to the ideal tooth surface A0.

On the other hand, the left tooth surface B has a negative tooth trace error at the machining start end L1 of the workpiece W and at the machining end end L3 of the workpiece W. The left tooth surface B has a slight negative tooth trace error when machining the center portion L2 of the workpiece W in the tooth width direction, but is close to the ideal tooth surface B0.

As shown in Figures 5B and 5C, when the axial position of the hob cutter T used for machining is at the center or base end, the same tendency is observed as when it is at the tip end. However, the magnitude of the tooth trace error is largest when the axial position of the hob cutter T used for machining is at the tip end, followed by the center, and smallest at the base end. Also, when comparing machining of the machining start end L1 of the workpiece W with machining of the machining end end L3 of the workpiece W, the tooth trace error tends to be larger when machining the machining start end L1 of the workpiece W.

Next, the behavior of the effective current in the Y-axis drive unit, i.e., the drive unit that moves the saddle 32 in the Y-axis direction relative to the column 31, will be described with reference to Figures 6A to 6C. Figures 6A to 6C correspond to Figures 2A to 2C.

In the figure, the machining start time is Ts and the machining end time is Te. Also, the time to machine the machining start end L1 of the workpiece W shown in FIG. 3 is T1, the time to machine the center L2 in the tooth width direction of the workpiece W is T2, and the time to machine the machining end end L3 of the workpiece W is T3.

Here, the fluctuation in the Y-axis effective current correlates with the magnitude of the vibration in the Y-axis direction caused by the hob cutter T. In other words, the greater the fluctuation in the Y-axis effective current, the greater the vibration of the hob cutter T in the Y-axis direction. In terms that are independent of the mechanical configuration, the Y-axis effective current here is the drive current of the drive unit in a direction perpendicular to the rotation centerline of the hob cutter T, and corresponds to the vibration of the tool spindle unit 33 in a direction perpendicular to the rotation centerline of the hob cutter T.

As shown in FIG. 6A, when the axial position of the hob cutter T used for machining is on the tip side, the Y-axis effective current fluctuates significantly when machining the machining start end L1 of the workpiece W (time T1). When machining the center L2 in the tooth width direction of the workpiece W (time T2), the magnitude of the fluctuation in the Y-axis effective current is smaller than when machining the machining start end L1 of the workpiece W. When machining the machining end end L3 of the workpiece W (time T3), the magnitude of the fluctuation in the Y-axis effective current is smaller than when machining the machining start end L1 of the workpiece W, but larger than when machining the center L2 in the tooth width direction of the workpiece W.

As shown in Figures 6B and 6C, when the axial position of the hob cutter T used for machining is at the center or base end, the same tendency is observed as when it is at the tip end. However, the magnitude of fluctuation in the Y-axis effective current is greatest when the axial position of the hob cutter T used for machining is at the tip end, followed by the center, and least at the base end. Also, when comparing machining the machining start end L1 of the workpiece W with machining the machining end end L3 of the workpiece W, the magnitude of fluctuation in the Y-axis effective current tends to be greater when machining the machining start end L1 of the workpiece W.

Furthermore, from Figures 6A to 6C, the magnitude of the fluctuation in the effective current of the Y-axis is greatest when the axial position of the hob cutter T shown in Figure 6A is at the tip end, next greatest when the axial position shown in Figure 6B is at the center, and smallest when the axial position shown in Figure 6C is at the base end. In other words, the magnitude of the fluctuation in the effective current of the Y-axis tends to be greater as the axial position moves from the base end toward the tip.

Next, the behavior of the effective current of the A-axis drive unit, i.e., the motor that drives and rotates the workpiece W in the workpiece spindle unit 23, will be described with reference to Figures 7A-7C. Figures 7A-7C correspond to Figures 2A-2C.

In the figure, the machining start time is Ts and the machining end time is Te. Also, the time to machine the machining start end L1 of the workpiece W shown in FIG. 3 is T1, the time to machine the center L2 in the tooth width direction of the workpiece W is T2, and the time to machine the machining end end L3 of the workpiece W is T3.

Here, the fluctuation in the A-axis effective current correlates with the deviation in the rotational direction of the workpiece W (rotational synchronization deviation) when the workpiece W is machined by the hob cutter T. In other words, the greater the fluctuation in the A-axis effective current, the greater the deviation in synchronization between the rotation of the hob cutter T and the rotation of the workpiece W.

As shown in FIG. 7A, when the axial position of the hob cutter T used for machining is on the tip side, the A-axis effective current fluctuates significantly when machining the machining start end L1 of the workpiece W (time T1). When machining the center L2 in the tooth width direction of the workpiece W (time T2), the magnitude of the fluctuation in the A-axis effective current is smaller than when machining the machining start end L1 of the workpiece W. When machining the machining end end L3 of the workpiece W (time T3), the magnitude of the fluctuation in the A-axis effective current is smaller than when machining the machining start end L1 of the workpiece W, but larger than when machining the center L2 in the tooth width direction of the workpiece W.

As shown in Figures 7B and 7C, when the axial position of the hob cutter T used for machining is at the center or base end, the same tendency is observed as when it is at the tip end. However, the magnitude of the fluctuation in the A-axis effective current is greatest when the axial position of the hob cutter T used for machining is at the tip end, followed by the center, and least at the base end. Also, when comparing machining the machining start end L1 of the workpiece W with machining the machining end end L3 of the workpiece W, the magnitude of the fluctuation in the A-axis effective current tends to be greater when machining the machining start end L1 of the workpiece W.

From the above, when machining the machining start end L1 of the workpiece W, the tooth trace error, the magnitude of fluctuation in the Y-axis effective current, and the magnitude of fluctuation in the A-axis effective current are all larger than when machining the central portion L2. Also, when machining the machining end end L3 of the workpiece W, the tooth trace error, the magnitude of fluctuation in the Y-axis effective current, and the magnitude of fluctuation in the A-axis effective current are all larger than when machining the central portion L2.

Furthermore, when machining at the tip of the hob cutter T, the tooth trace error, the magnitude of fluctuation in the Y-axis effective current, and the magnitude of fluctuation in the A-axis effective current are all larger than when machining at the center or base end of the hob cutter T.

In other words, it can be said that the magnitude of the fluctuation in the Y-axis effective current and the magnitude of the fluctuation in the A-axis effective current represent values equivalent to the tooth trace error. The magnitude of the fluctuation in the Y-axis effective current is a value equivalent to the amount of deflection of the hob cutter T, and the magnitude of the fluctuation in the A-axis effective current is a value equivalent to the deviation in rotational synchronization of the workpiece spindle unit 23 with respect to the tool spindle unit 33.

(6. Functional Block Configuration of Gear Machining Device 1)
The functional block configuration of the gear machining device 1 will be described with reference to Fig. 8. An example of the mechanical configuration of the gear machining device 1 is as shown in Fig. 1. Here, the functional configuration of the gear machining device 1 will be described.

The gear machining device 1 includes at least a measuring device 41, an axial position acquisition unit 42, a correction processing unit 43, a control device 44, and a driving device 45. The measuring device 41 is a measuring device that measures a value corresponding to the amount of deflection of the hob cutter T when a cantilever-induced operation occurs, or a measuring device that measures a value corresponding to the rotational synchronization deviation of the workpiece spindle device 23 relative to the tool spindle device 33.

For example, the measuring device 41 can be a sensor that measures the effective current of the Y-axis drive motor as a value corresponding to the amount of deflection of the hob cutter T. The measuring device 41 can also be a sensor that measures the effective current of the A-axis drive motor as a value corresponding to the rotational synchronization deviation of the workpiece spindle device 23 relative to the tool spindle device 33. If the measuring device 41 can obtain synchronization deviation information of the A-axis drive motor and the Ct-axis drive motor, the measuring device 41 can also be an instrument that obtains the synchronization deviation information as a value corresponding to the rotational synchronization deviation. The measuring device 41 can also calculate the rotational synchronization deviation using the angle difference between the motors by obtaining the value of the rotation angle sensor of the A-axis drive motor and the value of the rotation angle sensor of the Ct-axis drive motor. The measuring device 41 can also be a displacement sensor that can directly measure the amount of deflection of the hob cutter T.

In this example, the workpiece W has a smaller amount of deflection and vibration than the hob cutter T. Therefore, it is possible not to consider the deflection of the workpiece W. However, it is also possible to consider the case where the workpiece W deflects in the same way as the hob cutter T. In other words, the workpiece W is supported by a cantilever, and a cantilever-induced motion occurs in the same way as the hob cutter T. In this case, the measuring device 41 may include, in addition to the above, a measuring device that measures a value equivalent to the amount of deflection of the workpiece W, or a measuring device that measures a value equivalent to the rotational synchronization deviation of the workpiece W.

As shown in Figures 2A-2C, the axial position acquisition unit 42 acquires the axial position of the hob cutter T used for machining. The axial position can be acquired from a command value (NC program). In detail, the axial position acquisition unit 42 acquires whether the axial position of the hob cutter T used for machining is the tip side, the center, or the base end side. Although the axial position acquisition unit 42 has three stages in the above, it may have two stages or four or more stages. In addition, the axial position acquisition unit 42 can also apply a position sensor of the Z-axis movement motor or a linear gauge (linear scale) that can measure the linear position of the Z axis to acquire the position. The axial position acquisition unit 42 also measures the X-axis and Y-axis to acquire the positions.

The correction processing unit 43 performs correction based on the value measured by the measuring device 41 and the axial position of the hob cutter T used for machining acquired by the axial position acquisition unit 42. The correction processing unit 43 may, for example, correct the amount of cutting by the hob cutter T, or may correct the rotational synchronization deviation of the workpiece spindle device 23 relative to the tool spindle device 33.

The correction processing unit 43 must determine the amount of cut or the rotational synchronization deviation as the amount of correction. The amount of correction can be determined by creating a map that shows the relationship between the measurement results of the measuring device 41 and the amount of correction based on past performance.

The correction amount can also be determined using machine learning. In this case, in the learning phase, a trained model that represents the relationship between the measurement results and the correction amount is generated using machine learning, and in the inference phase, the correction amount is determined using the trained model and the value measured by the measuring device 41.

The amount of correction is determined so as to reduce the tooth trace error in the workpiece W. For example, the amount of correction may be set so as to change the positions of the hob cutter T at the machining start end L1 and the machining end end L3 in the tooth width direction. The amount of correction may also be set so as to change the position of the hob cutter T at the center L2 in the tooth width direction. The amount of correction is a different value depending on the axial position of the hob cutter T used for machining.

The control device 44 controls the drive device 45 based on the command value (NC program) and the result of correction by the correction processing unit 43. In other words, the control device 44 controls the drive device 45 so as to reduce the tooth trace error in the workpiece W through correction.

The correction processing unit 43 and the control device 44 can be embedded systems such as a PLC (Programmable Logic Controller) or a CNC (Computerized Numerical Control) device, or can be a personal computer or a server, or can simply be equipped with a microcomputer (processor) or a storage device and perform control and processing.

The drive unit 45 is a device that moves the tool spindle unit 33 and the workpiece spindle unit 23 relative to one another. In this example, the drive unit 45 includes a drive unit that drives the X-axis moving table 21 linearly, a drive unit that drives the B-axis rotating table 22 rotationally, a drive unit that drives the workpiece W rotationally in the workpiece spindle unit 23, a drive unit that drives the column 31 linearly, a drive unit that drives the saddle 32 linearly, and a drive unit that drives the hob cutter T rotationally in the tool spindle unit 33.

(7. First Example of Gear Machining Method)
9, 10A and 10B, a first example of a gear cutting method using the gear cutting apparatus 1 will be described. In this example, trial cutting is performed, and a correction amount is determined using measurements from the trial cutting, and cutting is performed while making the correction during actual cutting.

As shown in FIG. 9, first, the control device 44 starts trial machining (step S1). Trial machining is machining of a trial workpiece W. Next, during the trial machining, measurements are made by the measuring device 41 (step S2). Then, measurements are continued until the trial machining is completed (step S3: No). When the trial machining is completed (S3: Yes), the correction processing unit 43 determines a correction amount based on the measurement value measured by the measuring device 41 during the trial machining (step S4). The correction amount may be determined using a map generated in advance, as described above, or machine learning.

Then, the control device 44 starts the actual machining (step S5). The actual machining is the machining of the actual workpiece W, which is different from the trial workpiece W. The control device 44 performs correction control based on the correction amount during the actual machining (step S6). Then, the control device 44 continues the correction control until the actual machining is completed (step S7: No). When the actual machining is completed (S7: Yes), the processing is terminated.

Here, two types of correction methods are given as examples. The first correction method is a method of correcting the cutting depth, as shown in FIG. 10A. That is, in the tooth width direction of the workpiece W, the cutting depth at the machining start end L1 and machining end end L3 (in this example, the cutting depth in the Y-axis direction) is made larger than the command value. In the center part L2 in the tooth width direction of the workpiece W, the cutting depth is set to the same value as the command value.

In FIG. 10A, A1 and B1 are the tooth surfaces that are machined using the corrected command value when there is no deflection or vibration of the hob cutter T. By correcting the cutting depth, ideal tooth surfaces A0 and B0 can be formed even if the hob cutter T deflects and vibrates due to the machining load generated at the machining start end L1 in the tooth width direction of the workpiece W.

The second correction method, as shown in FIG. 10B, corrects the rotational synchronization of the workpiece spindle 23 with respect to the tool spindle 33. That is, the rotational synchronization deviation at the machining start end L1 and machining end end L3 in the tooth width direction of the workpiece W is corrected. In FIG. 10B, A1 and B1 are tooth flanks machined by the corrected command value when there is no deflection or vibration of the hob cutter T. By correcting the rotational synchronization deviation, ideal tooth flanks A0 and B0 can be formed even if the hob cutter T deflects and vibrates due to the machining load generated at the machining start end L1 in the tooth width direction of the workpiece W.

As described above, when the cantilever-induced motion specific to the hob cutter T occurs, the correction processing unit 43 corrects the cutting depth or rotational synchronization deviation based on the value corresponding to the amount of deflection or rotational synchronization deviation of the hob cutter T measured by the measuring device 41. Therefore, it is possible to reduce the tooth trace error caused by the cantilever-induced motion specific to the case where the hob cutter T is supported by a cantilever.

(8. Second Example of Gear Machining Method)
A second gear cutting method using the gear cutting apparatus 1 will be described with reference to Fig. 11. In this example, a correction amount is determined in an early stage of actual cutting without performing trial cutting, and cutting is performed while making corrections in the subsequent cutting.

As shown in FIG. 11, the control device 44 starts machining the machining start end L1 (shown in FIG. 3) of the workpiece W (production workpiece) (step S11). Next, during machining of the machining start end L1 of the workpiece W, measurements are made by the measuring device 41 (step S12). Measurements are continued until machining of the machining start end L1 is completed (step S13: No).

When the processing of the processing start end L1 is completed (S13: Yes), the correction processing unit 43 determines the correction amount based on the measurement value measured by the measuring device 41 during processing of the processing start end L1 (step S14). The two types of correction amount described in the first correction method can be applied to determine the correction amount.

Next, machining of the center portion L2 in the tooth width direction of the workpiece W is started (step S15). The control device 44 performs correction control based on the correction amount in machining the center portion L2 (step S16). Then, correction control is continued until machining is completed, that is, until machining is completed up to the machining end portion L3 of the workpiece W (step S17: No). When machining is completed (S17: Yes), the process is terminated.

Here, if correction control is suddenly performed based on the correction amount at the timing of the transition from the machining start end L1 to the center L2 in the tooth width direction of the workpiece W, a step may be formed on the tooth surface of the workpiece W. Therefore, immediately after the transition from non-correction control to correction control, it is advisable to gradually increase the influence ratio of the correction amount. As a result, the adverse effects of starting correction control can be suppressed.

As a result, it is possible to reduce the tooth trace error caused by the unique cantilever-induced motion when the hob cutter T is supported by a cantilever. In addition, since trial machining is no longer necessary, it is possible to prevent the production of unnecessary workpieces W.

1: Gear machining device, 10: Bed, 20: Workpiece holding device, 21: X-axis moving table, 22: B-axis rotating table, 23: Workpiece spindle device, 30: Tool holding device, 31: Column, 32: Saddle, 33: Tool spindle device, 41: Measuring device, 42: Axial position acquisition unit, 43: Correction processing unit, 44: Control device, 45: Driving device, A, A0, A1, B, B0, B1: Tooth surface, L1: Workpiece machining start end, L2: Center of workpiece in tooth width direction, L3: Workpiece machining end end, T: Hob cutter, W: Workpiece

Claims (8)

a hob cutter for machining teeth on a workpiece;
a tool spindle device that rotatably supports the hob cutter in a cantilever manner;
a workpiece spindle device that rotatably supports the workpiece;
a drive device that moves the tool spindle device and the workpiece spindle device relative to each other;
a measuring device for measuring a deflection amount of the hob cutter or a value corresponding to a rotational synchronization deviation of the work spindle device relative to the tool spindle device;
a correction processing unit that corrects a cutting amount by the hob cutter or a rotational synchronization deviation of the workpiece spindle device with respect to the tool spindle device based on the value measured by the measuring device;
Equipped with
The hob cutter has a number of cutting edges in the axial direction that is greater than the number of cutting edges used in one machining operation,
The correction processing unit performs correction based on the value measured by the measuring device and an axial position of the hob cutter used for machining . A hob cutter for machining a tooth profile on a workpiece;
a tool spindle device that rotatably supports the hob cutter in a cantilever manner;
a workpiece spindle device that rotatably supports the workpiece;
a drive device that moves the tool spindle device and the workpiece spindle device relative to each other;
a measuring device for measuring a deflection amount of the hob cutter or a value corresponding to a rotational synchronization deviation of the work spindle device relative to the tool spindle device;
a correction processing unit that corrects a cutting amount by the hob cutter or a rotational synchronization deviation of the workpiece spindle device with respect to the tool spindle device based on the value measured by the measuring device;
Equipped with
The correction processing unit determines a correction amount based on the value measured by the measuring device when machining the machining start end portion in the tooth width direction of the actual workpiece, and performs correction when machining the central portion of the actual workpiece in the tooth width direction based on the determined correction amount . The workpiece spindle device supports the workpiece by a cantilever.
3. The gear machining device according to claim 1, wherein the hob cutter is supported in a cantilever manner and the workpiece is supported in a cantilever manner to generate the tooth profile on the workpiece. The gear machining device according to any one of claims 1 to 3, wherein the measuring device measures the vibration of the tool spindle unit or the workpiece spindle unit in a direction perpendicular to the rotation centerline of the hob cutter, or the drive current of the drive unit for driving the hob cutter in a direction perpendicular to the rotation centerline of the hob cutter, as the value corresponding to the amount of deflection of the hob cutter or the rotational synchronization deviation of the workpiece spindle unit relative to the tool spindle unit. A gear machining device according to any one of claims 1 to 3, wherein the measuring device measures the drive current of the rotary motor in the tool spindle device, the drive current of the rotary motor in the workpiece spindle device, and the rotational synchronization deviation between the rotary motor in the tool spindle device and the rotary motor in the workpiece spindle device as the value corresponding to the deflection of the hob cutter or the rotational synchronization deviation of the workpiece spindle device relative to the tool spindle device. The gear machining device according to any one of claims 1 to 5, wherein the correction processing unit determines a correction amount based on the value measured by the measuring device when machining a test workpiece, and performs correction based on the determined correction amount when machining a production workpiece different from the test workpiece. 2. The gear machining device according to claim 1, wherein the correction processing unit determines a correction amount based on the value measured by the measuring device when machining a machining start end portion in the face width direction of the production workpiece, and performs correction based on the determined correction amount when machining a central portion in the face width direction of the production workpiece. 8. The gear machining device according to claim 2 , wherein the correction processing unit performs correction based on the determined correction amount when machining the center portion and the machining end portion in the face width direction of the workpiece.

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