JP7559686B2 - Gear Processing Equipment - Google Patents

Description

The present invention relates to a gear processing device.

Patent Document 1 describes a gear processing device that calculates the phase of the teeth pre-formed on the workpiece and the phase of the blade of the gear cutting tool before machining gear teeth on the workpiece with the gear cutting tool. Patent Document 2 describes a gear processing device that uses a sensor to detect the phase of a recess provided on the shaft of the gear cutting tool, and determines the phase of the tool based on the phase of the recess.

JP 2019-115948 A JP 2020-59088 A

However, if thermal displacement occurs in the structure of the gear processing device, the positions of the gear cutting tool and the workpiece will shift from the reference position, making it impossible to machine gear teeth on the workpiece with high precision. Therefore, it is important to understand the relative positions of the gear cutting tool and the workpiece after thermal displacement.

The present invention was made in consideration of these problems, and aims to provide a gear cutting device that can perform gear cutting with high precision even when thermal displacement occurs in the structure of the gear cutting device.

One aspect of the present invention is
a gear cutting tool including a blade portion having a plurality of tool blades in a circumferential direction, and a shaft portion that is integral with the blade portion and has a cylindrical outer circumferential surface;
a tool spindle device that rotatably holds the gear cutting tool;
a workpiece spindle device that rotatably holds a workpiece to be machined by the gear cutting tool;
a moving device that moves the tool spindle device and the workpiece spindle device relatively;
A sensor provided on the workpiece spindle device and capable of detecting a distance from the gear cutting tool;
a control device that controls the moving device while synchronously controlling the rotation of the tool spindle device and the workpiece spindle device in order to machine gear teeth on the workpiece;
Equipped with
The gear cutting tool is applied to a plurality of types of gear cutting tools, each of which has a different diameter of the cylindrical outer circumferential surface of the shaft portion,
The control device includes:
a tool coordinate calculation unit that calculates position coordinates of a central axis of the gear cutting tool relative to the workpiece spindle device after thermal displacement based on a detection result of the sensor;
a machining control unit that controls the moving device to machine the workpiece while controlling the rotation of the tool spindle device and the workpiece spindle device in synchronization with each other based on the position coordinates calculated by the tool coordinate calculation unit; and
Equipped with
The tool coordinate calculation unit includes:
a moving process is executed to relatively move the sensor and the gear cutting tool in a direction perpendicular to a central axis of the gear cutting tool and perpendicular to a distance detection direction of the sensor, while the sensor is opposed to the cylindrical outer peripheral surface of the shaft portion of the gear cutting tool;
a calculation process is executed to calculate the position coordinates after thermal displacement of the central axis of the gear cutting tool based on a distance between the gear cutting tool and the cylindrical outer peripheral surface detected by the sensor when the sensor and the gear cutting tool are moved relative to each other;
The movement process includes:
the larger the diameter of the cylindrical outer peripheral surface of the gear cutting tool attached to the tool spindle device, the slower the speed at which the sensor and the gear cutting tool are moved relative to each other;
In the gear cutting device, the smaller the diameter of the cylindrical outer peripheral surface of the gear cutting tool attached to the tool spindle device, the faster the relative movement of the sensor and the gear cutting tool is.

Another aspect of the present invention is
a gear cutting tool including a blade portion having a plurality of tool blades in a circumferential direction, and a shaft portion that is integral with the blade portion and has a cylindrical outer circumferential surface;
a tool spindle device that rotatably holds the gear cutting tool;
a workpiece spindle device that rotatably holds a workpiece to be machined by the gear cutting tool;
a moving device that moves the tool spindle device and the workpiece spindle device relatively;
A sensor provided on the workpiece spindle device and capable of detecting a distance from the gear cutting tool;
a control device that controls the moving device while synchronously controlling the rotation of the tool spindle device and the workpiece spindle device in order to machine gear teeth on the workpiece;
Equipped with
The gear cutting tool is applied to a plurality of types of gear cutting tools, each of which has a different diameter of the cylindrical outer circumferential surface of the shaft portion,
The control device includes:
a tool coordinate calculation unit that calculates position coordinates of a central axis of the gear cutting tool relative to the workpiece spindle device after thermal displacement based on a detection result of the sensor;
a machining control unit that controls the moving device while synchronously controlling the rotation of the tool spindle device and the workpiece spindle device based on the position coordinates calculated by the tool coordinate calculation unit in order to machine the workpiece; and
Equipped with
The tool coordinate calculation unit includes:
a moving process is executed to relatively move the sensor and the gear cutting tool in a direction perpendicular to a central axis of the gear cutting tool and perpendicular to a distance detection direction of the sensor, while the sensor is opposed to the cylindrical outer peripheral surface of the shaft portion of the gear cutting tool;
a calculation process is executed to calculate the position coordinates after thermal displacement of the central axis of the gear cutting tool based on a distance between the gear cutting tool and the cylindrical outer peripheral surface detected by the sensor when the sensor and the gear cutting tool are moved relative to each other;
The tool coordinate calculation unit includes:
When the sensor and the gear cutting tool are moved relative to each other, the sensitivity of an amplifier circuit of the sensor is increased as the diameter of the cylindrical outer peripheral surface of the gear cutting tool attached to the tool spindle device increases,
This gear machining device is configured such that, when the sensor and the gear cutting tool are moved relative to one another, the smaller the diameter of the cylindrical outer peripheral surface of the gear cutting tool attached to the tool spindle device, the lower the sensitivity of the amplifier circuit of the sensor.

According to a gear cutting device according to one aspect of the present invention, the sensor detects the distance to the shaft of the gear cutting tool. The sensor is provided on the workpiece spindle device. Therefore, the sensor detects the relative position of the shaft of the gear cutting tool with respect to the workpiece spindle device.

Here, in order to machine gear teeth on a workpiece with high precision when thermal displacement occurs in the structure of the gear processing device, it is important to grasp the relative positions of the workpiece and the gear cutting tool after thermal displacement. As described above, the sensor directly detects the gear cutting tool and is provided on the workpiece spindle device. Therefore, the sensor is equivalent to directly detecting the relative positions of the workpiece and the gear cutting tool after thermal displacement. In other words, by using the detection results of the sensor, even if thermal displacement occurs, it is possible to machine gear teeth on the workpiece with high precision by grasping the relative positions of the workpiece and the gear cutting tool after thermal displacement.

Furthermore, the sensor detects the distance between the cylindrical outer circumferential surface of the shaft of the gear cutting tool, and the tool coordinate calculation unit of the control device calculates the position coordinates of the central axis of the gear cutting tool relative to the workpiece spindle device after thermal displacement based on the detection result of the sensor. Here, the sensor detects the distance between the cylindrical outer circumferential surface of the shaft of the gear cutting tool while moving the sensor and the gear cutting tool relative to each other. The relative movement direction is a direction perpendicular to the central axis of the gear cutting tool and perpendicular to the distance detection direction of the sensor when the sensor is facing the cylindrical outer circumferential surface of the shaft of the gear cutting tool.

The value detected by the sensor therefore forms an arc shape in radial cross section on the cylindrical outer circumferential surface of the shaft portion of the gear cutting tool. When the value detected by the sensor is at its smallest, the sensor is detecting a position on the cylindrical outer circumferential surface that passes through the sensor's detection portion and the central axis of the gear cutting tool. By using the detection results of the sensor thus detected, the position coordinates of the central axis of the gear cutting tool after thermal displacement can be obtained.

As described above, the detection value of the sensor changes in an arc shape on the radial cross section of the cylindrical outer circumferential surface of the shaft of the gear cutting tool. In other words, the rate of change of the detection value of the sensor (the differential value of the detection value at the position in the relative movement direction) differs depending on the diameter of the cylindrical outer circumferential surface of the shaft of the gear cutting tool. The larger the diameter of the cylindrical outer circumferential surface, the smaller the rate of change of the detection value, and the smaller the diameter of the cylindrical outer circumferential surface, the greater the rate of change of the detection value.

Then, the movement process of the tool coordinate calculation unit of the control device moves the sensor and the gear cutting tool relatively slower the larger the diameter of the cylindrical outer peripheral surface of the gear cutting tool attached to the tool spindle device. On the other hand, the movement process moves the sensor and the gear cutting tool relatively faster the smaller the diameter of the cylindrical outer peripheral surface of the gear cutting tool attached to the tool spindle device.

In other words, the movement process sets the relative speed between the sensor and the gear cutting tool to a first speed when a gear cutting tool having a cylindrical outer circumferential surface with a first diameter is attached to the tool spindle device. On the other hand, when a gear cutting tool having a cylindrical outer circumferential surface with a second diameter smaller than the first diameter is attached to the tool spindle device, the movement process sets the relative speed between the sensor and the gear cutting tool to a second speed that is faster than the first speed.

In other words, when the diameter of the cylinder's outer peripheral surface is large, even if the change in distance between the sensor's detection unit and the cylinder's outer peripheral surface is small, the sensor is moved at a low speed, so it is possible to obtain with high accuracy the time when the sensor's detection value is smallest. On the other hand, when the diameter of the cylinder's outer peripheral surface is small, the change in distance between the sensor's detection unit and the cylinder's outer peripheral surface is large, so it is possible to obtain with high accuracy the time when the sensor's detection value is smallest, even if the sensor is moved at high speed.

In this way, by changing the moving speed according to the diameter of the cylindrical outer surface, the position coordinates of the central axis of the gear cutting tool after thermal displacement can be obtained with high precision. As a result, gear teeth can be machined on the workpiece with high precision.

If the moving speed is slow regardless of the diameter of the cylindrical outer surface, it is possible to obtain the position coordinates after thermal displacement of the central axis of the gear cutting tool with high accuracy. However, if the moving speed is always slow, the processing time will be long. Therefore, instead of always slowing it down, as described above, when the diameter of the cylindrical outer surface is small, the moving speed is made fast. This makes it possible to shorten the time required to obtain the position coordinates.

According to a gear cutting device in another aspect of the present invention, when the tool coordinate calculation unit of the control device moves the sensor and the gear cutting tool relatively, the larger the diameter of the cylindrical outer circumferential surface of the gear cutting tool attached to the tool spindle device, the higher the sensitivity of the amplifier circuit of the sensor. On the other hand, the smaller the diameter of the cylindrical outer circumferential surface of the gear cutting tool attached to the tool spindle device, the lower the sensitivity of the amplifier circuit of the sensor.

In other words, it is as follows. When a gear cutting tool having a cylindrical outer circumferential surface with a first diameter is attached to the tool spindle device, the tool coordinate calculation unit sets the sensitivity of the sensor's amplifier circuit to a first sensitivity. On the other hand, when a gear cutting tool having a cylindrical outer circumferential surface with a second diameter smaller than the first diameter is attached to the tool spindle device, the tool coordinate calculation unit sets the sensitivity of the sensor's amplifier circuit to a second sensitivity lower than the first sensitivity.

As described above, the detection value of the sensor changes in an arc shape on the radial cross section of the cylindrical outer circumferential surface of the shaft of the gear cutting tool. In other words, the rate of change of the detection value of the sensor (the differential value of the detection value at the position in the relative movement direction) differs depending on the diameter of the cylindrical outer circumferential surface of the shaft of the gear cutting tool. The larger the diameter of the cylindrical outer circumferential surface, the smaller the rate of change of the detection value, and the smaller the diameter of the cylindrical outer circumferential surface, the greater the rate of change of the detection value.

When the diameter of the cylinder's outer peripheral surface is large, even if the change in distance between the sensor's detection unit and the cylinder's outer peripheral surface is small, the sensitivity of the amplifier circuit is high, so it is possible to obtain with high accuracy the time when the sensor's detection value is smallest. On the other hand, when the diameter of the cylinder's outer peripheral surface is small, the change in distance between the sensor's detection unit and the cylinder's outer peripheral surface is large, so even if the sensitivity of the amplifier circuit is low, it is possible to obtain with high accuracy the time when the sensor's detection value is smallest.

In this way, by changing the sensitivity of the amplifier circuit according to the diameter of the cylindrical outer surface, it is possible to obtain the position coordinates of the central axis of the gear cutting tool after thermal displacement with high precision. As a result, gear teeth can be machined on the workpiece with high precision.

If the sensitivity were to be increased regardless of the diameter of the cylindrical outer surface, when the diameter of the cylindrical outer surface is small, the movement range would be short when the sensor and the gear cutting tool are moved relatively in a direction perpendicular to the sensor's distance detection direction, making it difficult to grasp the position of the short distance. In other words, if the sensitivity is increased when the diameter of the cylindrical outer surface is small, there is a risk that the position coordinates after thermal displacement of the central axis of the gear cutting tool cannot be obtained with high accuracy. Therefore, rather than always increasing the sensitivity, as described above, the sensitivity is decreased when the diameter of the cylindrical outer surface is small.

FIG. 1 is a diagram illustrating an example of a gear machining device. 1 is a view of the workpiece and tool viewed from a direction perpendicular to the rotation axis of the workpiece in the XZ plane, with the dashed line showing the tool indicating the position after gear machining has been performed on the workpiece. 1 is a view of the workpiece and the tool as viewed from the Y direction, and the dashed line showing the tool indicates the position after gear machining has been performed on the workpiece. FIG. 2 is a functional block diagram showing a partial configuration of the gear machining device. 4 is a flowchart showing a process performed by a control device. 5 is a flowchart showing a process performed by a tool coordinate calculation unit of the control device. Fig. 1 is a diagram for explaining the movement process in the tool coordinate calculation process, where (a) is for a gear skiving cutter with a small shaft diameter, and (b) is for a gear skiving cutter with a large shaft diameter. The right column in each of (a) and (b) shows the relative positions of the sensor and the gear skiving cutter when the thermal displacement is zero. This is a graph showing the detection value detected by the movement process in the X-axis direction, and the detection value of the sensor versus the X-axis position, where (a) is for a gear skiving cutter with a small shaft diameter, and (b) is for a gear skiving cutter with a large shaft diameter. This is a graph showing the detection value detected by the movement process in the X-axis direction, and the detection value of the sensor versus detection time, where (a) is for a gear skiving cutter with a small shaft diameter, and (b) is for a gear skiving cutter with a large shaft diameter. 11 is a graph showing upper and lower limit values in an abnormality determination process in a tool coordinate calculation process. 5 is a flowchart showing a process performed by a tool phase calculation unit of the control device. FIG. 11 is a diagram illustrating a tool phase calculation process.

(1. Configuration of gear machining device 1)
The gear machining device 1 will be described with reference to Fig. 1. The gear machining device 1 is a device that generates a tooth profile (gear teeth) on the workpiece W by using the gear skiving cutter T by moving the workpiece W and a gear skiving cutter T relatively while rotating the workpiece W as a gear cutting tool.

In this embodiment, the gear processing device 1 is a general-purpose machine tool, for example, a machining center. The machining center is configured to be tool-replaceable, and can perform processing according to the attached tool. For example, replaceable gear cutting tools include a gear skiving cutter T, a hob cutter, a shaper cutter, etc. By replacing with a hob cutter or a shaper cutter, the gear processing device 1 becomes a device that processes a tooth profile (gear teeth) on the workpiece W by hobbing or shaping.

In addition, examples of interchangeable tools other than gear cutting tools include end mills, milling tools, drills, turning tools, threading tools, grinding tools, etc. Note that the tool exchange device and the tool magazine for storing tools are not shown in FIG. 1.

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

As shown in FIG. 1, the gear machining 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 gear skiving cutter T (equal to the rotation axis of the tool spindle) is defined as the Z-axis direction, and the two axes perpendicular to the Z-axis direction are defined as the X-axis and Y-axis. In FIG. 1, the horizontal direction is the X-axis direction, and the vertical direction is the Y-axis direction.

The gear processing device 1 further has one rotation axis (B axis) as a drive axis for changing the relative position between the workpiece W and the gear skiving cutter T. In this embodiment, the B axis is a rotation axis whose center of rotation is the Y axis direction. The gear processing device 1 also has a Ct axis as a rotation axis for rotating the gear skiving cutter T, and a Cw axis as a rotation axis for rotating the workpiece W.

In the gear processing device 1, the configuration for moving the workpiece W and the gear skiving cutter T relative to each other can be selected as appropriate. For example, the gear processing device 1 may be configured to have an A-axis with the X-axis direction as the center of rotation instead of the B-axis. In the following, an example is given of the gear processing device 1 in which the gear skiving cutter T can move linearly in the Y-axis and Z-axis directions, the workpiece W can move linearly in the X-axis direction, and the workpiece W can rotate about the B-axis.

The gear machining device 1 includes a bed 10, a workpiece holding device 20, a tool holding device 30, a sensor 40, and a control device 50. The bed 10 is installed on an installation surface and formed into a shape corresponding to the shape of the workpiece holding device 20 and the shape of the tool holding device 30. In this embodiment, the bed 10 is, for example, rectangular. On the upper surface of the bed 10, a pair of X-axis guide rails 11 extending in the X-axis direction and a pair of Z-axis guide rails 12 extending in the Z-axis direction are formed.

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 B-axis and Cw-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 driven by a driving device such as a linear motor or a ball screw mechanism (not shown) and moves in the X-axis direction while being guided by the X-axis guide rail 11 of the bed 10. The B-axis rotating table 22 is placed on the upper surface of the X-axis moving table 21 and moves in the X-axis direction together with the X-axis moving table 21. The B-axis rotating table 22 is also provided so as to be rotatable on 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 can be rotated on the B-axis by driving the rotating motor.

The workpiece spindle device 23 is provided on the B-axis rotating table 22 and rotates about the B-axis together with the B-axis rotating table 22. The workpiece spindle device 23 holds the workpiece W rotatably. A rotary motor (not shown) is housed in the workpiece spindle device 23, and the workpiece spindle device 23 can rotate the workpiece W about the Cw axis by driving the rotary motor. 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 rotate about the B axis and the Cw axis.

In detail, the workpiece spindle device 23 includes a housing 23a and a spindle 23b. The housing 23a of the workpiece spindle device 23 is fixed to the B-axis rotating table 22, and the spindle 23b of the workpiece spindle device 23 is rotatably supported by the housing 23a. A workpiece W is attached to the tip of the spindle 23b. In other words, the workpiece W is cantilevered by the spindle 23b of the workpiece spindle device 23.

The tool holding device 30 mainly comprises a column 31, a saddle 32, and a tool spindle device 33. The column 31 is driven by a driving device such as a linear motor or a ball screw mechanism (not shown) and moves in the Z-axis direction while being guided by the Z-axis guide rail 12 of the bed 10. A Y-axis guide rail 31a is formed on the surface (left surface in FIG. 1) that extends in the vertical direction of the column 31. The saddle 32 is driven by a driving device such as a linear motor or a ball screw mechanism (not shown) and moves in the Y-axis direction while being guided by the Y-axis guide rail 31a of the column 31.

The tool spindle device 33 is mounted on the saddle 32 and moves integrally with the saddle 32 in the Y-axis direction. The tool spindle device 33 holds the gear skiving cutter T. A rotary motor (not shown) is housed in the tool spindle device 33, and the tool spindle device 33 is capable of rotating the gear skiving cutter T on the Ct axis by driving the rotary motor. In this way, the tool holding device 30 holds the gear skiving cutter T so that it can move in the Y-axis and Z-axis directions relative to the bed 10 and can rotate on the Ct axis.

In detail, the tool spindle device 33 includes a housing and a spindle. The housing of the tool spindle device 33 is fixed to the saddle 32, and the spindle of the tool spindle device 33 is rotatably supported by the housing. A gear skiving cutter T is attached to the tip of this spindle. In other words, the gear skiving cutter T is cantilevered by the spindle of the tool spindle device 33.

The sensor 40 is provided in the housing 23a of the workpiece spindle device 23. The sensor 40 is a sensor capable of detecting the distance to the gear skiving cutter T. For example, a non-contact distance sensor using eddy current or laser is preferably used as the sensor 40. Since the sensor 40 is provided in the housing 23a of the workpiece spindle device 23, it moves integrally with the housing 23a of the workpiece spindle device 23. The housing 23a of the workpiece spindle device 23 includes the main components constituting the housing 23a, components attached to the main components, and the like. The sensor 40 may also be provided so that the detection unit can be moved forward and backward.

The control device 50 is equipped with an arithmetic processing device (processor) and a storage device, and controls each drive device by executing a machining program. In other words, the control device 50 controls the rotation of the gear skiving cutter T, the rotation of the workpiece W, and the relative movement between the workpiece W and the gear skiving cutter T. The control device 50 then controls each drive device while synchronously controlling the rotation of the workpiece spindle device 23 and the tool spindle device 33 in order to machine gear teeth on the workpiece W.

(2. Configuration of gear skiving cutter T)
The configuration of the gear skiving cutter T will be described with reference to Figures 2 and 3. The gear skiving cutter T includes a blade portion Ta and a shaft portion Tb.

The blade portion Ta has multiple tool blades in the circumferential direction. The axial end faces of the multiple tool blades in the blade portion Ta form the rake faces, and the radial outer surfaces of the tool blades form the relief faces. In this embodiment, the circumscribing surface of the blade portion Ta, i.e., the surface connecting the radial outer surfaces of the tool blades, which are the relief faces, forms a conical surface. However, the circumscribing surface of the blade portion Ta can also be configured to form a cylindrical surface.

The shank Tb is integrally formed on the back side of the rake face of the blade Ta and is coaxial with the blade Ta. The shank Tb has a cylindrical outer peripheral surface Tb1. The central axis of the cylindrical outer peripheral surface Tb1 is coaxial with the central axis of the blade Ta. The shank Tb further has a phase reference element Tb2 formed in a concave shape with respect to the cylindrical outer peripheral surface Tb1 at a portion of the circumferential direction. Note that the phase reference element Tb2 may be formed in a convex shape instead of a concave shape.

In this embodiment, the gear machining device 1 can be applied to multiple types of gear skiving cutters T. In detail, the gear machining device 1 can be applied to multiple types of gear skiving cutters T with different diameters of the cylindrical outer circumferential surface Tb1 of the shaft portion Tb. In other words, gear skiving cutters T with different diameters of the cylindrical outer circumferential surface Tb1 are interchangeably mounted on the tool spindle device 33.

(3. Explanation of gear skiving)
The state in which a tooth profile (gear teeth) is generated on a workpiece W by the gear skiving cutter T will be described with reference to Figs. 2 and 3.

As shown in Figure 3, in gear skiving processing, the rotation axis At of the gear skiving cutter T is set at an intersection angle θ with an axis parallel to the rotation axis Aw of the workpiece W. Also, as shown in Figure 2, the rotation axis At of the gear skiving cutter T and the rotation axis Aw of the workpiece W are parallel to the X-Z plane. As shown in Figure 2, the center-to-center distance between the rotation axis At of the gear skiving cutter T and the rotation axis Aw of the workpiece W, i.e., the distance in the Y-axis direction, is Da.

The workpiece W is rotated around the rotation axis Aw (Cw axis), and the gear skiving cutter T is rotated around the rotation axis At (Ct axis). The gear skiving cutter T is moved relative to the workpiece W in the direction of the rotation axis Aw of the workpiece W while synchronizing the rotation of the workpiece W and the rotation of the gear skiving cutter T, thereby generating a tooth profile on the workpiece W. In gear skiving, each tooth groove portion of the workpiece W is machined only once by the gear skiving cutter T while the workpiece W rotates once.

(4. Functional Block Configuration of Gear Machining Device 1)
Next, functions of a portion of the configuration of the gear machining device 1 will be described with reference to Fig. 4. As shown in Fig. 4, the gear machining device 1 includes an X-axis moving device 61 for relatively moving the workpiece W and the gear skiving cutter T in the X-axis direction, a Y-axis moving device 62 for relatively moving them in the Y-axis direction, and a Z-axis moving device 63 for relatively moving them in the Z-axis direction.

In this embodiment, the X-axis moving device 61 is a driving device such as a linear motor or a ball screw mechanism for moving the X-axis moving table 21 in the X-axis direction relative to the bed 10. The Y-axis moving device 62 is a driving device such as a linear motor or a ball screw mechanism for moving the saddle 32 in the Y-axis direction relative to the column 31. The Z-axis moving device 63 is a driving device such as a linear motor or a ball screw mechanism for moving the column 31 in the Z-axis direction relative to the bed 10.

As shown in FIG. 4, the gear machining device 1 further includes a workpiece spindle device 23, a tool spindle device 33, and a rotation device 64. As described above, the workpiece spindle device 23 constitutes the workpiece holding device 20 and holds the workpiece W rotatably around the Cw axis. As described above, the tool spindle device 33 constitutes the tool holding device 30 and holds the gear skiving cutter T rotatably around the Ct axis. The rotation device 64 is a moving device for changing the attitude of the workpiece W and the gear skiving cutter T. In this embodiment, the rotation device 64 includes a rotary motor for rotating the B-axis rotating table 22 about the B axis relative to the X-axis moving table 21.

The sensor 40 detects the distance to the gear skiving cutter T. In detail, the sensor 40 detects the distance to the cylindrical outer peripheral surface Tb1 or the phase reference element Tb2 of the shaft portion Tb of the gear skiving cutter T shown in Figures 2 and 3. As shown in Figure 4, the sensor 40 includes a detection unit 41 and an amplifier circuit 42. The detection unit 41 outputs a physical quantity such as a current or voltage corresponding to the detected distance, and the amplifier circuit 42 amplifies the physical quantity output by the detection unit 41 and outputs it to the control device 50. The amplifier circuit 42 performs processing with a resolution according to the set sensitivity.

The control device 50 includes a tool coordinate calculation unit 51, a tool phase calculation unit 52, and a machining control unit 53. The tool coordinate calculation unit 51 inputs the physical quantity amplified by the amplifier circuit 42 of the sensor 40 as the detection result of the sensor 40. In detail, the tool coordinate calculation unit 51 inputs the distance between the cylindrical outer peripheral surface of the shaft portion Tb of the gear skiving cutter T detected by the sensor 40 as the detection result of the sensor 40. The tool coordinate calculation unit 51 calculates the position coordinates of the central axis of the gear skiving cutter T relative to the workpiece spindle device 23 based on the detection result of the sensor 40. In particular, the tool coordinate calculation unit 51 calculates the position coordinates after thermal displacement of the central axis of the gear skiving cutter T.

When a tool change is performed, the tool phase calculation unit 52 calculates the phase of the gear skiving cutter T attached to the tool spindle device 33. In particular, the tool phase calculation unit 52 inputs the physical quantity amplified by the amplifier circuit 42 of the sensor 40 as the detection result of the sensor 40. In particular, the tool phase calculation unit 52 inputs the distance between the shaft portion Tb of the gear skiving cutter T detected by the sensor 40 and the phase reference element Tb2 as the detection result of the sensor 40. Furthermore, the tool phase calculation unit 52 inputs the rotation angle of the tool spindle (corresponding to the rotation angle of the gear skiving cutter T) detected by the rotation angle detector constituting the tool spindle device 33.

The tool phase calculation unit 52 calculates the phase of the phase reference element Tb2 of the shaft portion Tb as the reference phase for the blade portion Ta of the gear skiving cutter T based on the detection result of the sensor 40 and the rotation angle of the tool spindle. In other words, the tool phase calculation unit 52 obtains the circumferential position of the tool blade that serves as the reference for the blade portion Ta of the gear skiving cutter T.

The machining control unit 53 generates control command values based on the machining program and the detection results of the sensor 40. The control device 50 controls the X-axis moving device 61, the Y-axis moving device 62, and the Z-axis moving device 63 as moving devices, and further controls the workpiece spindle device 23, the tool spindle device 33, and the rotation device 64.

In particular, the machining control unit 53 controls the X-axis moving device 61, Y-axis moving device 62, and Z-axis moving device 63 as moving devices to machine the workpiece W while synchronously controlling the rotation of the workpiece spindle device 23 and the tool spindle device 33 based on the position coordinates calculated by the tool coordinate calculation unit 51 and the reference phase of the gear skiving cutter T calculated by the tool phase calculation unit 52, and further controls the workpiece spindle device 23, the tool spindle device 33, and the rotation device 64.

The gear machining device 1 further includes an operation panel 70. The operation panel 70 is provided with a display screen and various mechanical buttons. For example, touch-type operation buttons are displayed on the display screen, and the machining program, information on the workpiece W, and the status of each device of the gear machining device 1 are displayed. The operation panel 70 includes at least an operation preparation button 71 and a machining program start button 72. The operation preparation button 71 and the machining program start button 72 may be mechanical buttons or may be touch-type operation buttons displayed on the display screen.

When the operation preparation button 71 is pressed or touched, the control device 50 makes each device of the gear processing device 1 ready to execute a processing program. For example, the coolant pump and lubricating oil pump start operating, and the valves for supplying air are driven. When the operation preparation button 71 is pressed or touched, some of the devices of the gear processing device 1 start operating, and the gear processing device 1 gradually warms up.

When the machining program start button 72 is pressed or touched, the control device 50 executes the machining program. In other words, when the machining program start button 72 is pressed or touched, machining is started.

(5. Processing of the control device 50)
The processing (control method) of the control device 50 will be described with reference to Fig. 5. The processing of the control device 50 described below will be centered on the calculation processing of the correction value when thermal displacement occurs, and the tool phase calculation processing when a tool change is performed.

The gear machining device 1 is composed of structures that generate thermal displacement, such as the bed 10, column 31, saddle 32, and housing of the workpiece spindle device 23. Therefore, thermal displacement occurs in the structures due to the influence of the environmental temperature, heat generated by driving devices such as pumps and motors, and the temperature of fluids such as coolants and lubricating oils.

When the operation preparation button 71 is pressed or touched, some of the driving devices, such as the pump, start operating, causing the temperature of the gear processing device 1's structures to rise. Furthermore, when the processing program start button 72 is pressed or touched, the gear processing device 1 processes the workpiece W, generating heat from each driving device and heat associated with the movement of the structures. As a result, the temperature of the gear processing device 1's structures rises.

When the operation preparation button 71 is pressed or touched, the gear processing device 1 starts the operation preparation operation. Then, the thermal displacement of the workpiece W and the gear skiving cutter T caused by the thermal displacement of the structure of the gear processing device 1 gradually increases after the start of the operation preparation operation. In other words, the gear processing device 1 enters a thermally unsteady state after the start of the operation preparation operation.

Then, after a certain time has elapsed since the start of the operation preparation operation, the thermal displacement of the structure of the gear machining device 1 becomes constant, and the thermal displacement of the workpiece W and the gear skiving cutter T also becomes constant. In other words, the gear machining device 1 becomes in a thermally steady state after a certain time has elapsed since the start of the operation preparation operation.

Then, by correcting the thermal displacement between the workpiece W and the gear skiving cutter T and machining the workpiece W, it is possible to machine the desired gear teeth on the workpiece W. Therefore, understanding the thermal displacement correction value is important for performing high-precision machining.

In addition, when a tool change is performed, the exact phase of the gear skiving cutter T attached to the tool spindle device 33 is not clear. In order to perform gear skiving processing, it is necessary to know the exact phase of the gear skiving cutter T when it is attached to the tool spindle device 33.

The processing of the control device 50 will be described below. The control device 50 performs tool coordinate calculation processing (tool coordinate calculation step ST1). The tool coordinate calculation processing is performed by the tool coordinate calculation unit 51. That is, the tool coordinate calculation processing calculates the position coordinates of the central axis of the gear skiving cutter T relative to the workpiece spindle device 23 based on the detection result of the sensor 40. When thermal displacement occurs, the tool coordinate calculation processing calculates the position coordinates of the central axis of the gear skiving cutter T relative to the workpiece spindle device 23 after the thermal displacement.

The control device 50 then determines whether or not it is necessary to obtain a thermal displacement correction value (necessity determination step ST2). The thermal displacement correction value is obtained, for example, before the start of continuous machining of the workpiece W, and at any timing during continuous machining. When obtained at any timing, the acquisition interval can be shortened in a thermally unsteady state, enabling high-precision machining of the workpiece W.

Next, when the control device 50 determines that the thermal displacement correction value is to be acquired (ST3: Yes), it sets a correction value for machining the workpiece W using the position coordinates after the thermal displacement of the central axis of the gear skiving cutter T acquired by the tool coordinate calculation process (correction value setting process ST4). On the other hand, when the control device 50 determines that the thermal displacement correction value is not to be acquired (ST3: No), it does not set the thermal displacement correction value (ST4).

The control device 50 then determines whether or not a tool change has been performed (tool change determination process ST5), and if a tool change has been performed (ST5: Yes), performs a tool phase calculation process (tool phase calculation process ST6). The tool phase calculation process is performed by the tool phase calculation unit 52. The tool phase calculation process calculates a reference phase for the blade portion Ta of the gear skiving cutter T mounted on the tool spindle device 33 based on the detection result of the sensor 40 and the rotation angle of the rotating spindle detected by the rotation angle detector provided in the tool spindle device 33. On the other hand, if a tool change has not been performed (ST5: No), the control device 50 does not perform the tool phase calculation process (ST6).

Then, the control device 50 causes the machining control unit 53 to machine the workpiece W using the gear skiving cutter T (machining step ST7). If a thermal displacement correction value has been set, the machining control unit 53 processes the workpiece W taking into account the thermal displacement correction value. In addition, the machining control unit 53 machines the workpiece W based on the reference phase of the blade portion Ta of the gear skiving cutter T acquired after the tool change.

Although a detailed explanation is omitted, if the gears are already formed on the workpiece W, it is necessary to obtain the phase of the workpiece W when it is attached to the workpiece spindle device 23.

(6. Tool Coordinate Calculation Processing)
Next, the tool coordinate calculation process in the processing of the control device 50, that is, the process by the tool coordinate calculation unit 51 (tool coordinate calculation method) will be described in detail with reference to FIGS.

The tool coordinate calculation unit 51 executes a movement process that moves the sensor 40 and the gear skiving cutter T relative to each other (movement step ST11). In the movement process, the movement speed is changed according to the diameter of the cylindrical outer circumferential surface Tb1 of the shaft portion Tb of the gear skiving cutter T. Here, the diameter of the cylindrical outer circumferential surface Tb1 is stored in the control device 50 for each type of gear skiving cutter T. The control device 50 acquires the diameter of the cylindrical outer circumferential surface Tb1 stored in association with the gear skiving cutter T attached to the tool spindle device 33, and determines a movement speed according to the acquired diameter of the cylindrical outer circumferential surface Tb1.

Refer to FIG. 7 for details of the movement process. FIG. 7(a) shows a case where a gear skiving cutter T with a small diameter of the cylindrical outer circumferential surface Tb1 is attached to the tool spindle device 33. The sensor 40 is opposed to the cylindrical outer circumferential surface Tb1 of the shaft portion Tb of the gear skiving cutter T. In this embodiment, the detection portion 41 of the sensor 40 is opposed to the cylindrical outer circumferential surface Tb1 in the Y-axis direction. In addition to the cylindrical outer circumferential surface Tb1, the shaft portion Tb of the gear skiving cutter T is provided with a phase reference element Tb2. In other words, the tool spindle device 33 is rotationally positioned so that the phase reference element Tb2 is not opposed to the detection portion 41 of the sensor 40.

Then, the sensor 40 and the gear skiving cutter T are moved relative to each other. In this embodiment, they are moved relatively in the X-axis direction. In other words, the movement direction is perpendicular to the central axis of the gear skiving cutter T and perpendicular to the distance detection direction of the sensor 40. In FIG. 7(a), the sensor 40 is moved in the left-right direction. The movement speed in this case is Va.

Figure 7 (b) shows a case where a gear skiving cutter T with a large diameter of the cylindrical outer circumferential surface Tb1 is mounted on the tool spindle device 33. In this case as well, the sensor 40 is opposed to the cylindrical outer circumferential surface Tb1 of the shaft portion Tb of the gear skiving cutter T. In this embodiment, the detection portion 41 of the sensor 40 is opposed to the cylindrical outer circumferential surface Tb1 in the Y-axis direction. Then, the sensor 40 and the gear skiving cutter T are moved relatively. In this embodiment, they are moved relatively in the X-axis direction. The moving speed in this case is Vb.

Here, the moving speed Va when the diameter of the cylindrical outer peripheral surface Tb1 shown in the left column of FIG. 7(a) is small is greater than the moving speed Vb when the diameter of the cylindrical outer peripheral surface Tb1 shown in the left column of FIG. 7(b) is large. In other words, in the movement process, the tool coordinate calculation unit 51 moves the sensor 40 and the gear skiving cutter T at a relatively slower speed as the diameter of the cylindrical outer peripheral surface Tb1 of the gear skiving cutter T attached to the tool spindle device 33 becomes larger. On the other hand, the tool coordinate calculation unit 51 moves the sensor 40 and the gear skiving cutter T at a relatively faster speed as the diameter of the cylindrical outer peripheral surface Tb1 of the gear skiving cutter T attached to the tool spindle device 33 becomes smaller.

In other words, the movement process sets the relative speed between the sensor 40 and the gear skiving cutter T to a first speed when a gear skiving cutter T with a cylindrical outer peripheral surface Tb1 having a first diameter is attached to the tool spindle device 33. On the other hand, when a gear skiving cutter T with a cylindrical outer peripheral surface Tb1 having a second diameter smaller than the first diameter is attached to the tool spindle device 33, the movement process sets the relative speed between the sensor 40 and the gear skiving cutter T to a second speed that is faster than the first speed. In other words, the movement speeds Va and Vb may have a monotonically decreasing relationship with respect to the diameter of the cylindrical outer peripheral surface Tb1, and may have, for example, a negative linear relationship or a nonlinear relationship.

Then, the tool coordinate calculation unit 51 executes a calculation process to calculate the position coordinates after the thermal displacement of the central axis of the gear skiving cutter T (calculation step ST12). Here, as shown in the left column of (a) and (b) of FIG. 7, when the gear skiving cutter T is moved in the X-axis direction, the sensor 40 detects the distance in the Y-axis direction from the detection unit 41 of the sensor 40 to the cylindrical outer peripheral surface Tb1.

Therefore, as a calculation process, the tool coordinate calculation unit 51 first obtains the distance in the Y-axis direction to the cylindrical outer peripheral surface Tb1 detected by the sensor 40 when the gear skiving cutter T is moved in the X-axis direction. The distance detected by the sensor 40 in the left column of FIG. 7(a) is as shown in FIG. 8(a). In FIG. 8(a), each detection point (sampling point) is indicated by a black circle. In FIG. 8(a), the horizontal axis is the X-axis position, so the two-dot chain line connecting the black circles corresponds to the shape of the small-diameter cylindrical outer peripheral surface Tb1.

The separation distance detected by the sensor 40 in the left column of FIG. 7(b) is as shown in FIG. 8(b). In FIG. 8(b), each detection point (sampling point) is indicated by a black circle. In FIG. 8(b), the horizontal axis is the X-axis position, so the two-dot chain line connecting the black circles corresponds to the shape of the large-diameter cylindrical outer circumferential surface Tb1.

As described above, the moving speed Va on the small-diameter cylindrical outer peripheral surface Tb1 shown in FIG. 7(a) is greater than the moving speed Vb on the large-diameter cylindrical outer peripheral surface Tb1 shown in FIG. 7(b). Therefore, when comparing FIG. 8(a) and (b), the distance interval (sampling distance interval) of the detection points on the small-diameter cylindrical outer peripheral surface Tb1 shown in FIG. 8(a) is wider than the distance interval of the detection points on the large-diameter cylindrical outer peripheral surface Tb1 shown in FIG. 8(b).

In FIG. 9(a), when the diameter of the cylindrical outer peripheral surface Tb1 is small, the horizontal axis is time and the vertical axis is the detection value of the sensor 40, with each detection point (sampling point) shown as a black circle. In FIG. 9(b), when the diameter of the cylindrical outer peripheral surface Tb1 is large, the horizontal axis is time and the vertical axis is the detection value of the sensor 40, with each detection point (sampling point) shown as a black circle. In FIG. 9(a) and (b), the line connecting the black circles is shown as a two-dot chain line. The black circles in FIG. 9(a) and (b) indicate the detection values of the sensor 40 at sampling times t1 to t13.

In other words, when comparing the case where the cylindrical outer peripheral surface Tb1 has a small diameter with the case where it has a large diameter, as shown in (a) and (b) of FIG. 9, the sampling time interval is the same, but as shown in (a) and (b) of FIG. 8, the moving speeds Va and Vb are different, so the sampling distance interval in the X-axis direction is different.

8(a) and 8(b), the tool coordinate calculation unit 51 calculates, as a calculation process, the X-axis position coordinates Xa, Xb at which the separation distance is minimum based on the separation distance detected by the sensor 40. In other words, the tool coordinate calculation unit 51 calculates the position coordinates Xa, Xb after thermal displacement of the central axis of the gear skiving cutter T in the relative movement direction (X-axis direction) between the sensor 40 and the gear skiving cutter T based on the separation distance detected by the sensor 40.

Furthermore, as shown in the left columns of (a) and (b) of FIG. 7, the tool coordinate calculation unit 51 calculates the minimum values Ya and Yb of the separation distance based on the separation distance detected by the sensor 40 as a calculation process. Here, the diameter of the cylindrical outer peripheral surface Tb1 is known. Therefore, the tool coordinate calculation unit 51 calculates the position coordinates Ya1 and Yb1 after thermal displacement of the central axis of the gear skiving cutter T in a direction perpendicular to the central axis of the gear skiving cutter T and perpendicular to the relative movement direction between the sensor 40 and the gear skiving cutter T (Y-axis direction) based on the separation distance detected by the sensor 40.

Here, when the thermal displacement in the right column of FIG. 7(a) is zero, the minimum value of the separation distance detected by the sensor 40 is the reference value Ya0. In other words, the difference ΔYa between the separation distance Ya detected by the sensor 40 in the left column of FIG. 7(a) and the reference value Ya0 is the amount of thermal displacement in the Y-axis direction.

When the thermal displacement in the right column of FIG. 7(b) is zero, the minimum value of the separation distance detected by the sensor 40 is the reference value Yb0. In other words, the difference ΔYb between the separation distance Yb detected by the sensor 40 in the left column of FIG. 7(b) and the reference value Yb0 is the amount of thermal displacement in the Y-axis direction. This amount of thermal displacement in the Y-axis direction is the thermal displacement correction value in the Y-axis direction.

The difference ΔXa, ΔXb (not shown) between the X-axis position coordinates Xa, Xb of the central axis of the gear skiving cutter T at which the separation distance detected by the sensor 40 shown in Figures 8(a) and 8(b) is the smallest and the reference X0 in the X-axis direction when there is no thermal displacement is the amount of thermal displacement in the X-axis direction. This amount of thermal displacement in the X-axis direction is the thermal displacement correction value in the X-axis direction.

Then, the tool coordinate calculation unit 51 executes an abnormality determination process based on the magnitude of the thermal displacement, the upper limit value Thu, and the lower limit value Thd (abnormality determination process ST13). As shown in FIG. 10, the abnormality determination process determines an abnormality when the difference ΔYa, ΔYb between the Y-axis position of the center axis of the gear skiving cutter T when the separation distance detected by the sensor 40 is at a minimum and the reference in the Y-axis direction when there is no thermal displacement exceeds the upper limit value Thu or falls below the lower limit value Thd.

As described above, the gear machining device 1 is in a thermally unsteady state after the start of the operation preparation operation, and is in a thermally steady state after a certain time has passed since the start of the operation preparation operation. As shown in FIG. 10, the thermal change amounts ΔYa and ΔYb gradually increase when in a thermally unsteady state, and are approximately constant when in a thermally steady state.

Therefore, the upper limit value Thu and the lower limit value Thd for determining an abnormality are also set to increase with the passage of time in a thermally unsteady state. On the other hand, the upper limit value Thu and the lower limit value Thd are set to constant values regardless of the passage of time in a thermally steady state.

Next, if the result of the abnormality determination process is not abnormal (ST14: No), the tool coordinate calculation unit 51 ends the tool coordinate calculation process. On the other hand, if the result of the abnormality determination process is abnormal (ST14: Yes), the tool coordinate calculation unit 51 executes abnormality processing (abnormality processing step ST15). The abnormality processing is, for example, processing to stop the operation of the machining program, processing to notify the operator or manager, processing to communicate abnormality information to a management device, etc. When abnormality processing is executed, the tool coordinate calculation process itself is not terminated, the next processing of the control process shown in FIG. 5 is not executed, and the control process itself is stopped.

(7. Tool Phase Calculation Processing)
Next, the tool phase calculation process in the processing of the control device 50, that is, the processing by the tool phase calculation unit 52 (tool phase calculation method) will be described in detail with reference to FIGS. 11 and 12. FIG.

The tool phase calculation unit 52 positions the sensor 40 and the gear skiving cutter T for phase calculation (positioning step ST21). This positioning is performed at a position where the distance between the cylindrical outer peripheral surface Tb1 of the shaft portion Tb of the gear skiving cutter T and the detection portion 41 of the sensor 40 is minimized in the above-mentioned tool coordinate calculation process.

Then, the tool phase calculation unit 52 rotates the gear skiving cutter T in the positioned state (rotation process ST22). Then, as shown in FIG. 12, the phase reference element Tb2 of the shaft portion Tb of the gear skiving cutter T passes a position facing the detection portion 41 of the sensor 40. At this time, the sensor 40 detects the distance to the cylindrical outer peripheral surface Tb1 of the shaft portion Tb of the gear skiving cutter T and the distance to the phase reference element Tb2. Then, the tool phase calculation unit 52 acquires the distance detected by the sensor 40. Furthermore, the tool phase calculation unit 52 acquires the rotation angle of the tool spindle detected by a rotation angle detector provided in the tool spindle device 33.

Then, the tool phase calculation unit 52 executes a calculation process to calculate the phase of the phase reference element Tb2 based on the separation distance detected by the sensor 40 and the rotation angle of the tool spindle (calculation step ST23). Here, the phase reference element Tb2 is located at a position corresponding to the phase of a specified tool blade of the blade portion Ta. Therefore, in the calculation process of the tool phase calculation unit 52, the reference phase of the blade portion Ta of the gear skiving cutter T is calculated. Then, the process by the tool phase calculation unit 52 is terminated.

(8. Effects)
According to the above-described gear machining device 1, the sensor 40 detects the distance to the shaft portion Tb of the gear skiving cutter T. The sensor 40 is provided on the workpiece spindle device 23. Therefore, the sensor 40 detects the relative position of the shaft portion Tb of the gear skiving cutter T with respect to the workpiece spindle device 23.

Here, in order to machine gear teeth on the workpiece W with high precision when thermal displacement occurs in the structure of the gear machining device 1, it is important to grasp the relative positions of the workpiece W and the gear skiving cutter T after thermal displacement. The sensor 40 directly detects the gear skiving cutter T and is provided on the workpiece spindle device 23. Therefore, the sensor 40 is equivalent to directly detecting the positions of the workpiece W and the gear skiving cutter T after relative thermal displacement. In other words, by using the detection result of the sensor 40, even if thermal displacement occurs, it is possible to machine gear teeth on the workpiece W with high precision by grasping the relative positions of the workpiece W and the gear skiving cutter T after thermal displacement.

Furthermore, the sensor 40 detects the distance between the shaft portion Tb of the gear skiving cutter T and the cylindrical outer peripheral surface Tb1, and the tool coordinate calculation unit 51 of the control device 50 calculates the position coordinates after thermal displacement of the central axis of the gear skiving cutter T relative to the workpiece spindle device 23 based on the detection result of the sensor 40. Here, the sensor 40 detects the distance between the shaft portion Tb of the gear skiving cutter T and the cylindrical outer peripheral surface Tb1 while moving the sensor 40 and the gear skiving cutter T relative to each other. The relative movement direction is a direction perpendicular to the central axis of the gear skiving cutter T and a direction perpendicular to the distance detection direction of the sensor 40 when the sensor 40 is facing the cylindrical outer peripheral surface Tb1 of the shaft portion Tb of the gear skiving cutter T.

The detection value by the sensor 40 is therefore an arc-shaped radial cross section of the cylindrical outer circumferential surface Tb1 of the shaft portion Tb of the gear skiving cutter T. When the detection value by the sensor 40 is at its smallest, the sensor 40 is detecting a position on the cylindrical outer circumferential surface Tb1 that passes through the detection portion 41 of the sensor 40 and the central axis of the gear skiving cutter T. By using the detection result of the sensor 40 thus detected, the position coordinates of the central axis of the gear skiving cutter T after thermal displacement can be obtained.

As described above, the detection value of the sensor 40 changes in an arc shape in a radial cross section of the cylindrical outer circumferential surface Tb1 of the shaft portion Tb of the gear skiving cutter T. In other words, the rate of change of the detection value of the sensor 40 (the differential value of the detection value at the position in the relative movement direction) differs depending on the diameter of the cylindrical outer circumferential surface Tb1 of the shaft portion Tb of the gear skiving cutter T. The larger the diameter of the cylindrical outer circumferential surface Tb1, the smaller the rate of change of the detection value, and the smaller the diameter of the cylindrical outer circumferential surface Tb1, the greater the rate of change of the detection value.

Therefore, the movement process of the tool coordinate calculation unit 51 of the control device 50 moves the sensor 40 and the gear skiving cutter T at a relatively slower speed the larger the diameter of the cylindrical outer peripheral surface Tb1 of the gear skiving cutter T attached to the tool spindle device 33. On the other hand, the movement process moves the sensor 40 and the gear skiving cutter T at a relatively faster speed the smaller the diameter of the cylindrical outer peripheral surface Tb1 of the gear skiving cutter T attached to the tool spindle device 33.

In other words, the movement process sets the relative speed between the sensor 40 and the gear skiving cutter T to a first speed when a gear skiving cutter T with a cylindrical outer peripheral surface Tb1 having a first diameter is attached to the tool spindle device 33. On the other hand, when a gear skiving cutter T with a cylindrical outer peripheral surface Tb1 having a second diameter smaller than the first diameter is attached to the tool spindle device 33, the movement process sets the relative speed between the sensor 40 and the gear skiving cutter T to a second speed that is faster than the first speed.

In other words, when the diameter of the cylindrical outer peripheral surface Tb1 is large, even if the change in the distance between the detection unit 41 of the sensor 40 and the cylindrical outer peripheral surface Tb1 is small, the sensor 40 is moved at a low speed, so the time when the detection value by the sensor 40 is small can be obtained with high accuracy. On the other hand, when the diameter of the cylindrical outer peripheral surface Tb1 is small, the change in the distance between the detection unit 41 of the sensor 40 and the cylindrical outer peripheral surface Tb1 is large, so the time when the detection value by the sensor 40 is small can be obtained with high accuracy, even if the sensor is moved at high speed.

In this way, by changing the moving speed according to the diameter of the cylindrical outer peripheral surface Tb1, the position coordinates of the central axis of the gear skiving cutter T after thermal displacement can be obtained with high precision. As a result, gear teeth can be machined on the workpiece W with high precision.

If the moving speed is slowed regardless of the diameter of the cylindrical outer peripheral surface Tb1, the position coordinates after thermal displacement of the central axis of the gear skiving cutter T can be obtained with high accuracy. However, if the moving speed is always slow, the processing time will be long. Therefore, instead of always slowing it down, as described above, the moving speed is made fast when the diameter of the cylindrical outer peripheral surface Tb1 is small. This makes it possible to shorten the time required to obtain the position coordinates.

(9. Modifications)
In the above, the relative moving speed between the sensor 40 and the gear skiving cutter T is changed according to the diameter of the cylindrical outer circumferential surface Tb1. In addition, in the calculation process (ST12), when the tool coordinate calculation unit 51 moves the sensor 40 and the gear skiving cutter T relatively, the larger the diameter of the cylindrical outer circumferential surface Tb1 of the gear skiving cutter T attached to the tool spindle device 33, the higher the sensitivity of the amplifier circuit 42 of the sensor 40. On the other hand, the smaller the diameter of the cylindrical outer circumferential surface Tb1 of the gear skiving cutter T attached to the tool spindle device 33, the lower the sensitivity of the amplifier circuit 42 of the sensor 40.

In other words, the sensitivity of the amplifier circuit 42 of the sensor 40 is set to a first sensitivity when a gear skiving cutter T having a first diameter on the cylindrical outer peripheral surface Tb1 is attached to the tool spindle device 33. On the other hand, when a gear skiving cutter T having a second diameter on the cylindrical outer peripheral surface Tb1 smaller than the first diameter is attached to the tool spindle device 33, the tool coordinate calculation unit 51 sets the sensitivity of the amplifier circuit 42 of the sensor 40 to a second sensitivity lower than the first sensitivity. In other words, the sensitivity of the amplifier circuit 42 may have a monotonically increasing relationship with respect to the diameter of the cylindrical outer peripheral surface Tb1, and may have, for example, a positive linear relationship or a nonlinear relationship.

In this case, when the tool coordinate calculation unit 51 moves the sensor 40 and the gear skiving cutter T relative to each other, the tool coordinate calculation unit 51 keeps the relative movement speed between the sensor 40 and the gear skiving cutter T constant regardless of the diameter of the cylindrical outer peripheral surface Tb1 of the shaft portion Tb of the gear skiving cutter T.

Here, when the diameter of the cylindrical outer peripheral surface Tb1 is large, even if the change in the distance between the detection unit 41 of the sensor 40 and the cylindrical outer peripheral surface Tb1 is small, the sensitivity of the amplifier circuit 42 is increased, so it is possible to obtain with high accuracy the time when the detection value by the sensor 40 is smallest. On the other hand, when the diameter of the cylindrical outer peripheral surface Tb1 is small, the change in the distance between the detection unit 41 of the sensor 40 and the cylindrical outer peripheral surface Tb1 is large, so it is possible to obtain with high accuracy the time when the detection value by the sensor 40 is smallest, even if the sensitivity of the amplifier circuit 42 is reduced.

In this way, by changing the sensitivity of the amplifier circuit 42 according to the diameter of the cylindrical outer circumferential surface Tb1, the position coordinates after thermal displacement of the central axis of the gear skiving cutter T can be obtained with high precision. As a result, gear teeth can be machined on the workpiece W with high precision.

If the sensitivity were to be increased regardless of the diameter of the cylindrical outer peripheral surface Tb1, when the diameter of the cylindrical outer peripheral surface Tb1 is small, the movement range when the sensor 40 and the gear skiving cutter T are moved relatively in a direction perpendicular to the distance detection direction of the sensor 40 would be short when the distance is short, making it difficult to grasp the position of the short distance. In other words, if the sensitivity is increased when the diameter of the cylindrical outer peripheral surface Tb1 is small, there is a risk that the position coordinates after thermal displacement of the central axis of the gear skiving cutter T cannot be obtained with high accuracy. Therefore, instead of always increasing the sensitivity, as described above, when the diameter of the cylindrical outer peripheral surface Tb1 is small, the sensitivity is decreased.

Reference Signs List 1 Gear machining device 23 Workpiece spindle device 33 Tool spindle device 40 Sensor 41 Detection unit 42 Amplifier circuit 50 Control device 51 Tool coordinate calculation unit 52 Tool phase calculation unit 53 Machining control unit 61 to 64 Movement device T Gear cutting tool Ta Blade portion Tb Shaft portion Tb1 Cylinder outer peripheral surface Tb2 Phase reference element W Workpiece

Claims (9)

a gear cutting tool including a blade portion having a plurality of tool blades in a circumferential direction, and a shaft portion that is integral with the blade portion and has a cylindrical outer circumferential surface;
a tool spindle device that rotatably holds the gear cutting tool;
a workpiece spindle device that rotatably holds a workpiece to be machined by the gear cutting tool;
a moving device that moves the tool spindle device and the workpiece spindle device relatively;
A sensor provided on the workpiece spindle device and capable of detecting a distance from the gear cutting tool;
a control device that controls the moving device while synchronously controlling the rotation of the tool spindle device and the workpiece spindle device in order to machine gear teeth on the workpiece;
Equipped with
The gear cutting tool is applied to a plurality of types of gear cutting tools, each of which has a different diameter of the cylindrical outer circumferential surface of the shaft portion,
The control device includes:
a tool coordinate calculation unit that calculates position coordinates of a central axis of the gear cutting tool relative to the workpiece spindle device after thermal displacement based on a detection result of the sensor;
a machining control unit that controls the moving device to machine the workpiece while controlling the rotation of the tool spindle device and the workpiece spindle device in synchronization with each other based on the position coordinates calculated by the tool coordinate calculation unit; and
Equipped with
The tool coordinate calculation unit includes:
a moving process is executed to relatively move the sensor and the gear cutting tool in a direction perpendicular to a central axis of the gear cutting tool and perpendicular to a distance detection direction of the sensor, while the sensor is opposed to the cylindrical outer peripheral surface of the shaft portion of the gear cutting tool;
a calculation process is executed to calculate the position coordinates after thermal displacement of the central axis of the gear cutting tool based on a distance between the gear cutting tool and the cylindrical outer peripheral surface detected by the sensor when the sensor and the gear cutting tool are moved relative to each other;
The movement process includes:
the larger the diameter of the cylindrical outer peripheral surface of the gear cutting tool attached to the tool spindle device, the slower the speed at which the sensor and the gear cutting tool are moved relative to each other;
A gear machining device in which the smaller the diameter of the cylindrical outer peripheral surface of the gear cutting tool attached to the tool spindle device, the faster the relative movement of the sensor and the gear cutting tool. The gear cutting device according to claim 1, wherein the calculation process calculates the position coordinates after thermal displacement of the central axis of the gear cutting tool in the relative movement direction between the sensor and the gear cutting tool based on the distance to the cylindrical outer circumferential surface of the gear cutting tool detected by the sensor when the sensor and the gear cutting tool are moved relative to each other. The gear cutting device according to claim 1 or 2, wherein the calculation process calculates the position coordinates after thermal displacement of the central axis of the gear cutting tool in a direction perpendicular to the central axis of the gear cutting tool and perpendicular to the direction of relative movement between the sensor and the gear cutting tool, based on the distance to the cylindrical outer circumferential surface of the gear cutting tool detected by the sensor when the sensor and the gear cutting tool are moved relative to each other. The control device further executes an abnormality determination process for determining that an abnormality has occurred when a difference between the position coordinate after the thermal displacement detected by the sensor and a reference when there is no thermal displacement exceeds an upper limit value or falls below a lower limit value;
The upper limit or the lower limit is
the value is set to increase with time in a thermally unsteady state after a preparation operation for operation of the gear machining apparatus is started,
4. The gear machining device according to claim 1, wherein the differential pressure is set to a constant value regardless of the passage of time in a thermal steady state following the thermal unsteady state. The control device further includes a tool phase calculation unit that calculates a reference phase of the cutting edge of the gear cutting tool based on a detection result of the sensor,
5. The gear machining device according to claim 1, wherein the machining control unit controls the moving device, the tool spindle device and the workpiece spindle device to machine the workpiece, based on the position coordinates calculated by the tool coordinate calculation unit and the reference phase calculated by the tool phase calculation unit. the shaft portion includes the cylindrical outer circumferential surface, and a phase reference element formed in a circumferential portion thereof in a concave or convex shape with respect to the cylindrical outer circumferential surface,
The calculation process by the tool coordinate calculation unit calculates the position coordinates after thermal displacement of the central axis of the gear cutting tool based on a distance from the shaft portion to the cylindrical outer peripheral surface detected by the sensor, and
The gear cutting device according to claim 5 , wherein the tool phase calculation unit calculates the reference phase of the gear cutting tool based on a distance from the shaft portion to the phase reference element detected by the sensor. a gear cutting tool including a blade portion having a plurality of tool blades in a circumferential direction, and a shaft portion that is integral with the blade portion and has a cylindrical outer circumferential surface;
a tool spindle device that rotatably holds the gear cutting tool;
a workpiece spindle device that rotatably holds a workpiece to be machined by the gear cutting tool;
a moving device that moves the tool spindle device and the workpiece spindle device relatively;
A sensor provided on the workpiece spindle device and capable of detecting a distance from the gear cutting tool;
a control device that controls the moving device while synchronously controlling the rotation of the tool spindle device and the workpiece spindle device in order to machine gear teeth on the workpiece;
Equipped with
The gear cutting tool is applied to a plurality of types of gear cutting tools, each of which has a different diameter of the cylindrical outer circumferential surface of the shaft portion,
The control device includes:
a tool coordinate calculation unit that calculates position coordinates of a central axis of the gear cutting tool relative to the workpiece spindle device after thermal displacement based on a detection result of the sensor;
a machining control unit that controls the moving device while synchronously controlling the rotation of the tool spindle device and the workpiece spindle device based on the position coordinates calculated by the tool coordinate calculation unit in order to machine the workpiece; and
Equipped with
The tool coordinate calculation unit includes:
a moving process is executed to relatively move the sensor and the gear cutting tool in a direction perpendicular to a central axis of the gear cutting tool and perpendicular to a distance detection direction of the sensor, while the sensor is opposed to the cylindrical outer peripheral surface of the shaft portion of the gear cutting tool;
a calculation process is executed to calculate the position coordinates after thermal displacement of the central axis of the gear cutting tool based on a distance between the gear cutting tool and the cylindrical outer peripheral surface detected by the sensor when the sensor and the gear cutting tool are moved relative to each other;
The tool coordinate calculation unit includes:
When the sensor and the gear cutting tool are moved relative to each other, the sensitivity of an amplifier circuit of the sensor is increased as the diameter of the cylindrical outer peripheral surface of the gear cutting tool attached to the tool spindle device increases,
A gear machining device in which, when the sensor and the gear cutting tool are moved relative to each other, the smaller the diameter of the cylindrical outer peripheral surface of the gear cutting tool attached to the tool spindle device, the lower the sensitivity of the amplifier circuit of the sensor. The gear cutting device according to claim 7, wherein the tool coordinate calculation unit keeps the relative movement speed between the sensor and the gear cutting tool constant regardless of the diameter of the cylindrical outer peripheral surface of the gear cutting tool when moving the sensor and the gear cutting tool relative to each other. The gear cutting tool is a gear skiving cutter having a plurality of tool blades with rake faces on the axial end faces and relief faces on the radial outer faces. The gear cutting device according to any one of claims 1 to 8.

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