Machine tool, gear measuring device, error measuring method, gear manufacturing method, and computer program

Abstract

To provide a technique capable of measuring a gear shape error.SOLUTION: The machine tool includes a controller configured to execute an error measurement process. In the error measurement processing, an approach start point and an approach direction of a touch trigger probe held by a tool holding device are determined based on a posture of a gear-shaped workpiece held by a workpiece holding device, an actuator is controlled to move the touch trigger probe from the approach start point in the approach direction, and a center position of a tip ball of the touch trigger probe when the touch trigger probe is brought into contact with a surface of the workpiece by the movement is obtained, the method includes determining a candidate value of an error between a gear shape and a target shape of a gear product, generating a cross-sectional model representing a cross-sectional shape of a tooth surface based on the candidate value, the target shape, and a posture, obtaining a minimum distance between the cross-sectional model and a center position, changing the candidate value, and determining, as the error, a candidate value at which an absolute value of a difference between the minimum distance and a radius of a tip ball is equal to or less than an allowable value.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a machine tool, a gear measuring device, an error measurement method, a gear manufacturing method, and a computer program. [Background technology]

[0002] In many gear manufacturing processes, a workpiece is roughly machined into a gear shape using a machine tool, the workpiece is then removed from the machine tool, and errors are measured using a dedicated gear measuring device such as that described in Patent Document 1.Based on the measurement results, the workpiece is then reattached to the machine tool and finish-machined.

[0003] One technique that can solve these problems is the machine tool described in Patent Document 2. The machine tool described in Patent Document 2 processes a workpiece into a gear shape, then measures errors using a touch probe attached to the machine tool, automating a series of operations from rough processing to finish processing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-234775 [Patent Document 2] Japanese Unexamined Patent Publication No. 61-070401 Summary of the Invention [Problem to be solved by the invention]

[0005] In the machine tool of Patent Document 2, the hard ball at the tip of the touch probe needs to be moved until it contacts both teeth of the gear, so a touch probe with a hard ball that matches the gear shape must be selected.

[0006] An object of the technology disclosed in the present application is to provide a technology that can measure gear form errors using a touch probe selected regardless of the gear form, for example. [Means for solving the problem]

[0007] A machine tool according to a first aspect of the present disclosure includes a workpiece holding device, a tool holding device, an actuator, and a control device. The workpiece holding device is configured to hold a workpiece. The tool holding device is configured to hold one of a touch probe and at least one tool. The actuator is configured to move the tool holding device relative to the workpiece holding device. The control device is configured to control the tool holding device and the actuator and to perform an error measurement process. The error measurement process includes determining the approach start point and approach direction of the touch probe held by the tool holding device based on the attitude of the workpiece machined into a gear shape held by the workpiece holding device, controlling the actuator to move the touch probe from the approach start point in the approach direction, determining the center position of the tip ball of the touch probe when the touch probe comes into contact with the surface of the workpiece as a result of the movement, determining a candidate value for the error between the gear shape and the target shape of the gear product, generating a cross-sectional model representing the cross-sectional shape of the tooth flank based on the candidate value, the target shape and the attitude, determining the minimum distance between the cross-sectional model and the center position, changing the candidate value, and determining, as the error, the candidate value for which the absolute value of the difference between the minimum distance and the radius of the tip ball is equal to or less than a tolerance.

[0008] According to a second aspect of the present disclosure, the machine tool according to the first aspect further includes a tool changer configured to change any one of the touch probe and the at least one tool held by the tool holding device for another tool.

[0009] According to a third aspect of the present disclosure, the machine tool according to the first aspect is configured such that a control device controls the tool changer so that the tool holding device selectively holds a first tool, a second tool, and a touch probe among at least one tool, and receives first to third commands. The control device is configured, upon receiving the first command, to control the actuator so that the first tool machines the workpiece into a gear shape. The control device is configured, upon receiving the second command, to execute an error measurement process. The control device is configured, upon receiving the third command, to control the actuator so that the second tool adjusts the movement path based on the error to manufacture a gear product.

[0010] An error measurement method according to a fourth aspect of the present disclosure includes having a computer determine an approach start point and approach direction of a touch probe based on the attitude of a workpiece machined into a gear shape, controlling an actuator to move the touch probe in the approach direction from the approach start point, having the computer determine the center position of the tip ball of the touch probe when the touch probe comes into contact with the surface of the workpiece as a result of the movement, and having the computer calculate an error between the gear profile and a target shape of a gear product based on the center position. Having the computer calculate the error includes determining candidate values ​​for the error, generating a cross-sectional model representing the cross-sectional shape of the tooth flanks based on the candidate values, the target shape, and the attitude, determining the minimum distance between the cross-sectional model and the center position, changing the candidate value, and determining, as the error, the candidate value for which the absolute value of the difference between the minimum distance and the radius of the tip ball is equal to or less than a tolerance.

[0011] According to a fifth aspect of the present disclosure, in the machine tool according to the first aspect or the error measurement method according to the fourth aspect, determining the approach start point and the approach direction includes determining a contact target point of the target shape. The approach direction is determined as the direction of a normal vector of a tangent plane of the target shape at the contact target point when the gear product is placed in the attitude, or the reverse. The approach start point is determined at a position facing in the opposite direction to the approach direction from the contact target point.

[0012] According to a sixth aspect of the present disclosure, in the machine tool or error measurement method according to the fifth aspect, the contact target point is a point on the pitch circle of the gear product. When the gear product is an involute gear, the value of the parameter of the involute curve representing the pitch point is equal to the pressure angle. When the gear product is a cycloidal gear and the curve model is made up of an epicycloidal curve and a hypocycloidal curve, the pitch circle is the same as the base circle used to generate the cycloidal curve. When the gear product is a trochoidal gear and the curve model is an epitrochoidal parallel curve, the contact target point is not limited to the intersection of the trochoidal parallel curve and the pitch circle, but may also be the intersection of the trochoidal parallel curve and the root circle, or the intersection of the trochoidal parallel curve and the tip circle.

[0013] According to a seventh aspect of the present disclosure, in the machine tool or error measurement method according to the fifth or sixth aspect, a first plane that is perpendicular to the tangential plane and includes the contact target point, and the gear rotation axis when the gear product is placed in that attitude are defined. Of multiple curves represented by cutting the target shape with the first plane, a target curve that passes through the contact target point is moved in a direction away from the gear rotation axis when the gear product is placed in that attitude on the first plane, and the cross-sectional model is represented by a model curve.

[0014] According to an eighth aspect of the present disclosure, in the machine tool or error measurement method according to the seventh aspect, the first plane is a plane obtained by rotating a second plane perpendicular to the gear rotation axis around a straight line passing through the gear rotation axis or the contact target point on the second plane by a helix angle defined by the tooth profile of the target shape.

[0015] According to a ninth aspect of the present disclosure, in the machine tool or error measurement method according to the seventh or eighth aspect, the minimum distance is the distance between the central position and a nearby point among multiple points on the model curve that has the smallest distance from the central position.

[0016] According to a tenth aspect of the present disclosure, in the machine tool or error measurement method according to any one of the seventh to ninth aspects, the model curve is a curve segment obtained by shifting a curve segment that is a target curve between a first intersection of the target curve and a root circle or base circle of the target shape centered on the gear rotation axis and a second intersection of the target curve and a tip circle of the target shape centered on the gear rotation axis by a candidate value in the separation direction. When the model curve is an involute curve, the first intersection may be an intersection of the target curve and one of the base circle and the root circle, whichever has a smaller radius. When the model curve is a cycloid curve, or when the model curve is a cycloid curve, the first intersection may be an intersection of the root circle and the target curve. When the curve model is an epitrochoid parallel curve and the contact target point is an intersection of the trochoid parallel curve and the root circle, two adjacent intersections of the tip circle and the target curve may be the first and second intersections. When the curve model is an epitrochoid parallel curve and the contact target point is an intersection point between the trochoid parallel curve and the tip circle, two adjacent intersection points between the root circle and the target curve may be defined as the first intersection point and the second intersection point.

[0017] According to an eleventh aspect of the present disclosure, in a machine tool or error measurement method according to any one of the seventh to tenth aspects, the model curve can be expressed by using parameters for each coordinate of a two-dimensional coordinate system that defines a position on a first plane, and the positions of multiple points on the first plane can be found by changing the parameters by the same amount.

[0018] According to a twelfth aspect of the present disclosure, the error measurement method according to any one of the fourth to eleventh aspects includes positioning the workpiece so that its orientation is a predetermined orientation before contacting the touch probe with the surface of the workpiece, or setting a coordinate system for moving the touch probe in accordance with the orientation of the workpiece. Furthermore, according to the twelfth aspect of the present disclosure, in the machine tool according to any one of the first, fifth, or eleventh aspects, the control device controls the workpiece holding device so that the orientation of the workpiece is a predetermined orientation before contacting the touch probe with the surface of the workpiece, or sets a coordinate system for moving the touch probe in accordance with the orientation of the workpiece. The predetermined orientation is preferably a gear-shaped orientation in which the contact target point can be analytically determined in the predetermined coordinate system. Furthermore, the coordinate system set in accordance with the orientation of the workpiece is preferably a coordinate system in which the contact target point can be analytically determined.

[0019] A gear manufacturing method according to a thirteenth aspect of the present disclosure includes, when a first command is received by the computer of any of the fourth to eleventh aspects, causing the computer to control the actuator to machine a workpiece into a gear shape with a first tool held by a tool holding device of a machine tool. The gear manufacturing method includes, when a second command is received by the computer, causing the computer to control the actuator to move the touch probe in accordance with the error measurement method of any of the fourth to eleventh aspects, thereby calculating an error. The gear manufacturing method includes, when a third command is received by the computer, causing the computer to control the actuator to adjust a movement path of a second tool held by the tool holding device based on the error, thereby causing the second tool to manufacture a gear product.

[0020] A gear manufacturing method according to a fourteenth aspect of the present disclosure further includes, when the computer of any of the first to thirteenth aspects receives a first command, causing the computer to control a tool changer of the machine tool so that the tool holding device of the machine tool holds a first tool. The gear manufacturing method further includes, when the computer receives a second command, causing the computer to control the tool changer to replace the implement held by the tool holding device with a touch probe. The gear manufacturing method further includes, when the computer receives a third command, causing the computer to control the tool changer to replace the touch probe held by the tool holding device with a second tool.

[0021] According to a 15th aspect of the present disclosure, the gear manufacturing method according to the 13th or 14th aspect includes causing the computer to execute a process of controlling the workpiece holding device to rotate the workpiece so that its orientation is a predetermined orientation or to set a coordinate system for moving the touch probe in accordance with the orientation of the workpiece before contacting the touch probe with the surface of the workpiece. According to the 15th aspect of the present disclosure, in the machine tool according to the 3rd aspect, the control device is configured to rotate the workpiece so that its orientation is a predetermined orientation or to control the workpiece holding device to set a coordinate system for moving the touch probe in accordance with the orientation of the workpiece before contacting the touch probe with the surface of the workpiece. Note that the predetermined orientation is preferably a gear shape orientation that allows analytical determination of the contact target point in the predetermined coordinate system.

[0022] A gear measuring device according to a sixteenth aspect of the present disclosure includes a computer configured to execute the error measurement method according to any one of the fourth to twelfth aspects.

[0023] A computer program according to a seventeenth aspect of the present disclosure comprises instructions that, when executed by a computer, cause the computer to execute the error measurement method according to any one of the fourth to twelfth aspects.

[0024] A computer program according to an eighteenth aspect of the present disclosure comprises instructions that, when executed by a computer of a machine tool, cause the computer to carry out the gear manufacturing method according to either the thirteenth or fourteenth aspect.

[0025] According to a 19th aspect of the present disclosure, the computer program according to the 18th aspect includes instructions for causing the computer to execute a process of controlling the workpiece holding device to rotate the workpiece so that the orientation of the workpiece assumes a predetermined orientation before the touch probe is brought into contact with the surface of the workpiece, or to set a coordinate system for moving the touch probe in accordance with the orientation of the workpiece, where the predetermined orientation is preferably a gear-shaped orientation that allows analytical determination of the contact target point in the predetermined coordinate system.

[0026] A computer-readable medium according to a twentieth aspect of the present disclosure comprises instructions that, when executed by a computer, cause the computer to carry out an error measurement method according to any one of the fourth to twelfth aspects.

[0027] A computer readable medium according to a twenty-first aspect of the present disclosure comprises instructions which, when executed by a computer of a machine tool, cause the computer to carry out a gear manufacturing method according to either the thirteenth or fourteenth aspect.

[0028] According to a 22nd aspect of the present disclosure, the computer-readable medium according to the 21st aspect includes instructions for causing a computer to execute a process of controlling the workpiece holding device to rotate the workpiece so that the orientation of the workpiece assumes a predetermined orientation before the touch probe contacts the surface of the workpiece, or setting a coordinate system for moving the touch probe in accordance with the orientation of the workpiece, wherein the predetermined orientation is preferably a gear-shaped orientation in the predetermined coordinate system that allows analytical determination of the contact target point.

[0029] The machine tool according to the first aspect, the error measurement method according to the fourth aspect, the gear measuring device according to the sixteenth aspect having a computer configured to execute the error measurement method according to the fourth aspect, the computer program according to the seventeenth aspect having instructions for causing a computer to execute the error measurement method according to the fourth aspect, and the computer-readable medium according to the twentieth aspect having instructions for causing a computer to execute the error measurement method according to the fourth aspect all use a cross-sectional model to estimate the error between the gear profile and the target profile of a gear product from the position of the center of the tip ball of the touch probe when the touch probe contacts the surface of the workpiece. Therefore, since it is not necessary to move the touch probe until it contacts both teeth of the gear, it is possible to measure gear errors using a touch probe selected regardless of the gear profile.

[0030] In the machine tool according to the fifth aspect, the error measurement method according to the fifth aspect, the gear measuring device according to the sixteenth aspect comprising a computer configured to execute the error measurement method according to the fifth aspect, the computer program according to the seventeenth aspect comprising instructions for causing a computer to execute the error measurement method according to the fifth aspect, and the computer readable medium according to the twentieth aspect comprising instructions for causing a computer to execute the error measurement method according to the fifth aspect, the touch probe is brought into contact with the surface of the workpiece approximately perpendicularly, making it less likely for slippage to occur after contact and enabling gear errors to be measured with high accuracy.

[0031] In the machine tool according to the sixth aspect, the error measurement method according to the sixth aspect, the gear measuring device according to the sixteenth aspect comprising a computer configured to execute the error measurement method according to the sixth aspect, the computer program according to the seventeenth aspect comprising instructions for causing a computer to execute the error measurement method according to the sixth aspect, and the computer-readable medium according to the twentieth aspect comprising instructions for causing a computer to execute the error measurement method according to the sixth aspect, when the gear product is an involute gear, the approach direction can be easily derived using the number of teeth and pressure angle of the gear specifications.When the gear product is a cycloidal gear, the approach direction is tangent to the pitch circle, making it easy to derive.

[0032] In the machine tool according to the seventh aspect, the error measurement method according to the seventh aspect, the gear measuring device according to the sixteenth aspect having a computer configured to execute the error measurement method according to the seventh aspect, the computer program according to the seventeenth aspect having instructions for causing a computer to execute the error measurement method according to the seventh aspect, and the computer readable medium according to the twentieth aspect having instructions for causing a computer to execute the error measurement method according to the seventh aspect, when a workpiece is produced by a tool that produces a gear such as a hob, the tooth profile surface is formed so as to shift relative to the approach direction of the hob, so that a highly accurate cross-sectional model can be produced.

[0033] The machine tool according to the eighth aspect, the error measurement method according to the eighth aspect, the gear measuring device according to the sixteenth aspect having a computer configured to execute the error measurement method according to the eighth aspect, the computer program according to the seventeenth aspect having instructions for causing a computer to execute the error measurement method according to the eighth aspect, and the computer readable medium according to the twentieth aspect having instructions for causing a computer to execute the error measurement method according to the eighth aspect make it possible to generate with high accuracy a cross-sectional model of a workpiece having a helical gear shape.

[0034] The machine tool according to the ninth aspect, the error measurement method according to the ninth aspect, the gear measuring device according to the sixteenth aspect comprising a computer configured to execute the error measurement method according to the ninth aspect, the computer program according to the seventeenth aspect comprising instructions for causing a computer to execute the error measurement method according to the ninth aspect, and the computer readable medium according to the twentieth aspect comprising instructions for causing a computer to execute the error measurement method according to the ninth aspect, are capable of determining the coordinates of an approximate solution of the contact point.

[0035] In the machine tool according to the tenth aspect, the error measurement method according to the tenth aspect, the gear measuring device according to the sixteenth aspect comprising a computer configured to execute the error measurement method according to the tenth aspect, the computer program according to the seventeenth aspect comprising instructions for causing a computer to execute the error measurement method according to the tenth aspect, and the computer readable medium according to the twentieth aspect comprising instructions for causing a computer to execute the error measurement method according to the tenth aspect, the model curve can be expressed by an involute curve in the case of an involute gear, by an epitrochoid parallel curve in the case of a trochoid gear, and by an epicycloid curve and a hypocycloid curve in the case of a cycloid gear, which facilitates mathematical modeling.

[0036] The machine tool according to the 11th aspect, the error measurement method according to the 11th aspect, the gear measuring device according to the 16th aspect having a computer configured to execute the error measurement method according to the 11th aspect, the computer program according to the 17th aspect having instructions for causing a computer to execute the error measurement method according to the 11th aspect, and the computer-readable medium according to the 20th aspect having instructions for causing a computer to execute the error measurement method according to the 11th aspect make it possible to accurately determine an approximate solution for the contact point.

[0037] In the machine tool according to the 12th aspect, the error measurement method according to the 12th aspect, the gear measuring device according to the 16th aspect having a computer configured to execute the error measurement method according to the 12th aspect, the computer program according to the 17th aspect having instructions for causing a computer to execute the error measurement method according to the 12th aspect, and the computer readable medium according to the 20th aspect having instructions for causing a computer to execute the error measurement method according to the 12th aspect, the coordinate system of the model curve and the center position can be determined depending on the attitude of the workpiece.

[0038] In the machine tool according to the second aspect, the touch probe and the tool can be replaced by the machine tool, so that the burden on the user when performing an operation that combines machining and error measurement can be reduced.

[0039] In the machine tool according to the third aspect, the gear manufacturing method according to the thirteenth aspect, the computer program according to the eighteenth aspect, and the computer-readable medium according to the twenty-first aspect, which includes instructions for causing a computer to execute the gear manufacturing method according to the thirteenth aspect, by loading a machining program including the first command to the third command into the machine tool, it is possible to cause the machine tool to automatically execute a series of operations including rough machining, error measurement, and finish machining without removing the workpiece from the machine tool.

[0040] In the machine tool according to the third aspect, the gear manufacturing method according to the fourteenth aspect, the computer program according to the eighteenth aspect having instructions for causing a computer to execute the gear manufacturing method according to the fourteenth aspect, and the computer-readable medium according to the twenty-first aspect having instructions for causing a computer to execute the gear manufacturing method according to the fourteenth aspect, by loading the machining program including the first command to the third command into the machine tool, tool replacement can also be automated, and the machine tool can automatically execute all of the series of operations from rough machining, error measurement, and finish machining.

[0041] In the machine tool according to the 15th aspect, the gear manufacturing method according to the 15th aspect, the computer program according to the 19th aspect, and the computer-readable medium according to the 22nd aspect, the coordinate system of the model curve and the center position can be determined according to the attitude of the workpiece. [Effects of the Invention]

[0042] According to the technology disclosed in the present application, for example, it is not necessary to move the touch probe until it contacts both teeth of the gear, and therefore it is possible to measure gear errors using a touch probe selected regardless of the gear shape. [Brief explanation of the drawings]

[0043] [Figure 1] FIG. 1 shows a schematic configuration of a machine tool according to a first embodiment. [Figure 2] FIG. 2 is a hardware block diagram of the control device. [Figure 3] FIG. 3 shows the state of the workpiece related to the error measurement by the control device. [Figure 4] FIG. 4 is a flowchart showing each operation of the error measurement process of the control device. [Figure 5] FIG. 5 is a diagram for explaining a shape model that represents the cross-sectional shape of the tooth flank when the gear product is a spur gear. [Figure 6] FIG. 6 is a schematic diagram showing the approach start point and approach direction when the gear product is a spur gear. [Figure 7] FIG. 7 shows an example of a machining program. [Figure 8] FIG. 8 is a flowchart showing each operation of the gear manufacturing process performed by the control device. [Figure 9] FIG. 9 is a flowchart showing each operation of the gear manufacturing process performed by the control device. [Figure 10A] FIG. 10A is a schematic diagram showing the approach start point and approach direction when the gear product is a helical gear. [Figure 10B] FIG. 10B is a schematic diagram showing another method for determining the approach start point and approach direction when the gear product is a helical gear. [Figure 11A] FIG. 11A is a schematic diagram showing the approach start point and approach direction when the gear product is a standard bevel gear. [Figure 11B] FIG. 11B is a schematic diagram showing another method for determining the approach start point and approach direction when the gear product is a standard bevel gear. [Figure 12A] FIG. 12A is a cross-sectional view of an example reducer including a trochoid gear. [Figure 12B] FIG. 12B is a cross-sectional view of another example of a reducer including a trochoid gear. [Figure 13A] FIG. 13A is a schematic diagram showing the approach start point and approach direction when the external gear product as shown in FIG. 12A is a trochoid gear. [Figure 13B]FIG. 13B is a schematic diagram showing another method for determining the approach start point and the approach direction when the external gear product as shown in FIG. 12A is a trochoid gear. [Figure 14] FIG. 14 is a schematic diagram showing the approach start point and approach direction when the gear product is a cycloidal gear. DETAILED DESCRIPTION OF THE INVENTION

[0044] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings showing embodiments thereof, in which the same reference numerals designate corresponding or substantially identical components.

[0045] First Embodiment <Overall structure> Fig. 1 shows a schematic configuration of a machine tool 100 according to a first embodiment. The X axis shown in Fig. 1 runs along the height direction of the machine tool 100, the Y axis runs along the depth direction of the machine tool 100, and the Z axis runs along the width direction of the machine tool 100. The B direction is the circumferential direction of the Y axis, and the C direction is the circumferential direction of the Z axis.

[0046] As a rough machining operation, the machine tool 100 performs gear cutting operations such as hobbing and gear skiving on a workpiece W1 held by a workpiece spindle 122 to machine the workpiece W1 into a gear shape. However, the machine tool 100 may also machine a workpiece W1 that has been rough machined by a machine tool other than the machine tool 100 into a gear product by performing deburring and finishing operations. As shown in FIG. 1 , the machine tool 100 includes a column 110, a tool headstock 112, a workpiece headstock 120, and a tool changer 130. The column 110, the workpiece headstock 120, and the tool changer 130 are arranged on a base 140.

[0047] The column 110 is movable in the Y-axis direction and the Z-axis direction on the base 140. A tool headstock 112 is attached to the column 110. The tool headstock 112 is movable in the X-axis direction relative to the column 110. The tool headstock 112 is rotatable in the B-direction, which is the circumferential direction of a rotation axis A1 along the Y-axis direction, relative to the column 110. The machine tool 100 includes a first actuator ACT1 configured to move the tool headstock 112 in the X-axis direction and the B-direction. The first actuator ACT1 includes, for example, at least one motor and a power conversion mechanism such as a ball screw. The first actuator ACT1 may have separate motors for moving the tool headstock 112 in the X-axis direction and the B-direction. Alternatively, the first actuator ACT1 may have separate power conversion mechanisms, one for moving the tool headstock 112 in the X-axis direction from one motor and the other for moving the tool headstock 112 in the B direction. The machine tool 100 includes a tool spindle 114. The tool spindle 114 is also referred to as a tool gripper. The tool spindle 114 is attached to the tool headstock 112. The tool spindle 114 is rotatable relative to the tool headstock 112 about a rotation axis A2 along the X-axis direction. The machine tool 100 includes a second actuator ACT2 configured to rotate the tool spindle 114 about the rotation axis A2. The second actuator ACT2 is, for example, a motor. The tool spindle 114 is configured to hold one implement of a touch probe 150 or at least one machine tool 160. The touch probe 150 will be described in detail below.

[0048] The machine tool 100 includes a workpiece spindle 122. The workpiece spindle 122 is also referred to as a workpiece gripper. The workpiece spindle 122 is attached to a workpiece headstock 120. The workpiece spindle 122 is rotatable in a C direction, which is the circumferential direction of a rotation axis A3. The rotation axis A3 is along the Z direction. The workpiece spindle 122 is configured to hold a workpiece W1. The workpiece spindle 122 may grip the workpiece W1 via a chuck or the like. The machine tool 100 includes a fourth actuator ACT4 configured to rotate the workpiece spindle 122 in the circumferential direction of the rotation axis A3. The fourth actuator ACT4 is, for example, a motor.

[0049] The machine tool 100 includes a third actuator ACT3 configured to move the workpiece headstock 120 in the Z-axis direction. The third actuator ACT3 includes, for example, a motor and a power conversion mechanism such as a ball screw. The first to fourth actuators ACT1 to ACT4 are collectively referred to as actuator ACT. The functions of the first to fourth actuators ACT1 to ACT4 are not limited to those described above. For example, the first actuator ACT1 may move the tool headstock 112 in the X-axis direction and the Z-axis direction. In other words, the machine tool 100 includes an actuator ACT configured to move the tool holding device (tool spindle 114) relative to the workpiece holding device (workpiece spindle 122). The first to fourth actuators ACT4 preferably include a rotation sensor such as an encoder to detect the amount of movement and rotation angle of the controlled object.

[0050] The tool changer 130 is configured to change one of the touch probe 150 and the at least one tool 160 held by the tool spindle 114 for another. Specifically, the tool changer 130 includes a magazine arm 132 and a stocker 134. The magazine arm 132 is rotatable about an axis along the Z-axis direction. The magazine arm 132 is movable in the Z-axis direction relative to the stocker 134. The stocker 134 stores the touch probe 150 and the at least one tool 160 so that the touch probe 150 and the at least one tool 160 are movable in the X-axis direction. The at least one tool 160 includes at least one of a hob, a skiving cutter, a side cutter having a cross section in the shape of a tooth groove, a pinion cutter, and a mill tool.

[0051] The tool change by the tool changer 130 is performed as follows: The tool headstock 112 moves in the X-axis direction and pivots in the B-axis direction so that the tool attached to the tool spindle 114 faces the tool changer 130. The column 110 approaches the tool changer 130 in the Y-axis direction and the Z-axis direction to move the tool to the tool change position. The magazine arm 132 has a first gripper at one end in the extension direction of the magazine arm 132 and a second gripper at the other end in the extension direction. The first gripper holds the tool attached to the tool spindle 114 in order to remove the tool attached to the tool spindle 114. When the magazine arm 132 moves away from the tool spindle 114 in the Z-axis direction, the tool is removed from the tool spindle 114. In order to mount another tool on the tool spindle 114, the magazine arm 132 rotates about an axis along the Z-axis direction and moves the other tool gripped by the second gripper to a tool mounting position. When the column 110 approaches the tool changer 130 in the Z-axis direction, another tool is mounted on the tool spindle 114.

[0052] Machine tool 100 is equipped with a control device 1 for controlling rotation about each rotation axis and movement in each axial direction. Control device 1 is configured to control tool spindle 114 (tool holding device), work spindle 122 (workpiece holding device), and actuator ACT. Control device 1 is connected to a base 140. Here, control device 1 may be connected to another location on machine tool 100, and may be installed separately from base 140 as long as it is capable of transmitting control signals and receiving detection results. Control device 1 is provided with a display 40 and an input interface 50. Input interface 50 may include a touch panel built into display 40. The display 40 and input interface 50 together form a graphical user interface. However, display 40 and input interface 50 may be provided separately from control device 1.

[0053] FIG. 2 is a hardware block diagram of the control device 1. As shown in FIG. 2, the control device 1 includes a processor 10, a memory 20, a sensor control circuit 30, a display circuit 42, and an input circuit 52. The processor 10, the memory 20, the sensor control circuit 30, the display circuit 42, and the input circuit 52 are connected to each other via a bus 1A. The memory 20 stores programs and data necessary for machining. The processor 10 is a hardware processor consisting of electrical circuits. It reads and executes programs stored in the memory 20, thereby realizing the various functions of the control device 1. The various functions realized by the control device 1 include processes such as rough machining of gears, gear phase detection, gear deburring, finishing, and tooth surface profile measurement. Because the processor 10 and the memory 20 have the same functions as a general computer, the control device 1 may also be referred to as a computer 1C.

[0054] Specifically, the memory 20 is configured to store a machining program 22, gear data 24, an interpreter 26, an actuator control library 27, and a sensor processing library 28. The machining program 22 is written in program code, such as EIA / ISO program code, and includes commands for machining the workpiece W1 into a gear shape, detecting the posture of the workpiece W1, and measuring the error between the gear shape of the machined workpiece W1 and the target shape of a gear product. The gear data 24 includes dimensions of the target shape (e.g., module, pressure angle, and number of teeth). The gear data 24 may be three-dimensional CAD data.

[0055] The interpreter 26 is a program for analyzing commands written in the machining program 22 and executing at least one of an actuator control library 27 and a sensor processing library 28. That is, the control device 1 is configured to accept various commands written in the machining program 22 (e.g., first to fifth commands shown in FIGS. 8 and 9 , described later) by executing the interpreter 26. The actuator control library 27 is a program for executing commands written in the machining program 22 for controlling the tool changer 130, commands written in the machining program 22 for driving or moving the workpiece spindle 122 or the tool spindle 114, and commands for measuring the error between the gear profile of the machined workpiece W1 and the target shape of a gear product. The sensor processing library 28 is a program for executing commands for detecting the attitude of the workpiece W1 and commands for measuring the error between the gear profile of the machined workpiece W1 and the target shape of a gear product. The detected attitude of the workpiece W1 is, for example, the gear phase in the C direction of the workpiece spindle 122. When the interpreter 26 receives a command for controlling the tool changer 130 described in the machining program 22, the interpreter 26 calls the actuator control library 27 and executes processing to control the tool changer 130 so that the tool spindle 114 (tool holding device) selectively holds a first tool and a second tool out of at least one tool (machine tool) and the touch probe 150. In other words, the control device 1 is configured to control the tool changer 130 so that the tool spindle 114 (tool holding device) selectively holds the first tool and the second tool out of at least one tool and the touch probe 150. When the interpreter 26 receives a command to measure the error between the gear shape of the workpiece W1 and the target shape of the gear product, the interpreter 26 calls the actuator control library 27 and executes processing to move the touch probe 150 held by the tool spindle 114, and then calls the sensor processing library 28 and executes processing to detect a contact state using a contact sensor attached to the touch probe 150.

[0056] When the sensor processing library 28 is executed, the sensor control circuit 30 receives a detection signal output from a contact sensor attached to the touch probe 150, thereby detecting whether the tip ball 152 of the touch probe 150 has come into contact with an object. The actuator control circuit 32 includes an electric circuit that generates control signals to the drivers of the first to fourth actuators ACT1 to ACT4 when the first to fourth actuators ACT1 to ACT4 are motors. For example, when the actuator control library 27 outputs a target rotation speed or target torque of the motor based on a command written in the machining program 22, the actuator control circuit 32 outputs a control signal (e.g., a pulse signal) to the driver corresponding to the target rotation speed or target torque. The control signal from the control device 1 and the detection signal from the touch probe 150 are transmitted and received via a cable 140C between the control device 1 and the base 140.

[0057] The display circuit 42 is, for example, a video card, and is connected to the display 40. The display circuit 42 controls drawing on the display 40 under the control of the processor 10. The input circuit 52 is connected to the input interface 50. The input circuit 52 outputs an operation received by the input interface 50 to the processor 10 as an operation input signal.

[0058] <Error measurement processing of workpiece> FIG. 3 shows the state of the workpiece W1 involved in error measurement by the control device 1. Area SP2 in FIG. 3 is an enlarged view of area SP1. The control device 1 moves at least one machine tool 160, such as a hob or skiving cutter, in a radial direction (machining approach direction) relative to the rotation axis A3 of the workpiece spindle 122 to machine, for example, a cylindrical workpiece W1 into a gear shape. Therefore, the gear rotation axis A4 of the workpiece W1 coincides with the rotation axis A3 of the workpiece spindle 122. In FIG. 3, the target shape of the gear product is indicated by the dotted line TS, and the outer shape of the workpiece W1 is indicated by the outer peripheral surface PS. Considering the nature of machining using a hob or skiving cutter, if a geometric model consisting of only two adjacent teeth T1 and T2 is considered, the outer peripheral surface PS exists at a position separated from the target shape TS by an error e in the machining approach direction. While FIG. 3 illustrates a case in which the Y-axis direction is the same as the machining approach direction, the machining approach direction may be in another direction.

[0059] When workpiece W1 is machined into a gear shape by a hob or skiving cutter, it is unknown to machine tool 100 at what angle the tooth grooves or teeth of workpiece W1 held by workpiece spindle 122 are located in direction C, which is the circumferential direction of rotation axis A3 of workpiece spindle 122. In other words, the phase of the gear represented by the outer peripheral surface PS formed on workpiece W1 relative to workpiece spindle 122 in direction C is unknown to machine tool 100. Therefore, in order to measure error e, machine tool 100 detects the phase of the gear in direction C relative to workpiece spindle 122.

[0060] Here, in this embodiment, the gear phase P represented by the outer peripheral surface PS is defined as follows. The phase P is the angle formed by a position on the C-axis of the outer peripheral surface PS relative to a reference position RL on the C-axis, which is the circumferential direction of the gear rotation axis A4 of the workpiece W1. The reference position RL corresponds, for example, to the machining approach direction. In the following description, the reference position RL corresponds to the positive direction of the Y-axis. As shown in FIG. 3, when the intersections CP1 and CP2 of the pitch circle PC of a gear product and the outer peripheral surfaces PS of two adjacent teeth T1 and T2 are defined as points CP1 and CP2, respectively, and the midpoint of the curved segments CP1 and CP2 on the outer peripheral surface PS is defined as CP0, the phases of points CP1, CP2, and CP0 are defined as P1, P2, and P0, respectively. Note that points CP1, CP2, and CP0 are not limited to points on the pitch circle PC, but may be on any circumference between the addendum circle AC and the root circle RC, centered on the rotation axis of the gear product.

[0061] In this embodiment, the phases P1 and P2 are determined by moving the touch probe 150 relative to the workpiece W1 in the circumferential direction of the pitch circle PC, and the phase P0 can be determined by defining the center phase of the phases P1 and P2 as P0. Specifically, for example, when the X and Y coordinates of the tip sphere 152 of the touch probe 150 are positioned between two adjacent teeth T1 and T2, the distance the touch probe 150 can move in the Z axis direction is longer than the distance it can move when it contacts the gear side surface SS. Taking advantage of this, the control device 1 determines the X and Y coordinates of the center position of the tip sphere 152 of the touch probe 150 so that the X and Y coordinates of the tip sphere 152 of the touch probe 150 are positioned between the two adjacent teeth T1 and T2. Note that these X and Y coordinates are preferably set on the pitch circle PC. The control device 1 then moves the tip sphere 152 of the touch probe 150 in the Z axis direction so that it is positioned between the two adjacent teeth T1 and T2. The positions of points CP1, CP2, and CP0 in the Z-axis direction are shown in the lower diagram of FIG.

[0062] Next, the fourth actuator ACT4 is driven to rotate the workpiece W1 around the rotation axis A3 (gear rotation axis A4), and points CP1 and CP2 are brought into contact with the touch probe 150. When points CP1 and CP2 are brought into contact with the touch probe 150, they are spaced apart from the center position of the tip ball 152 of the touch probe 150 by the radius of the tip ball 152, but they are spaced apart in opposite directions by the radius of the tip ball 152. Therefore, the phase P0 when the rotation angle of the fourth actuator ACT4 is set to an arbitrary angle θ can be obtained from the rotation angle θ0 that is exactly midway between the rotation angle θ1 of the fourth actuator ACT4 when point CP1 is brought into contact with the touch probe 150 and the rotation angle θ2 of the fourth actuator ACT4 when point CP2 is brought into contact with the touch probe 150.

[0063] Once the phase P0 is known, the control device 1 rotates the workpiece W1 around the rotation axis A3 (gear rotation axis A4) by driving the fourth actuator ACT4 so that point CP0 is located on the Y-axis. Alternatively, the control device converts the X-axis and Y-axis into X'-axis and Y'-axis by rotating them around the Z-axis so that point CP0 is located on the Y'-axis, and executes the following movement of the touch probe 150 and the coordinate system of the error e in the X'Y' coordinate system. The following description will be given assuming that the workpiece W1 is rotated so that point CP0 is located on the Y-axis, but if coordinate conversion to the X'Y' coordinate system is performed, the XY coordinate system in the following description can be read as the X'Y' coordinate system.

[0064] After performing the above preprocessing, the control device 1 is configured to execute the error measurement process described below. FIG. 4 is a flowchart showing the error measurement method according to this embodiment, that is, each operation of the error measurement process performed by the control device 1 (computer 1C). When the processor 10 receives a predetermined command written in the machining program 22, it executes the actuator control library 27 and the sensor processing library 28 to execute steps S18 and S19. In step S18, the processor 10 determines the orientation of the workpiece W1. The orientation of the workpiece W1 is, for example, the phase P0 of the point CP0 described above. In other words, the error measurement method includes having the computer 1C determine the orientation of the workpiece W1.

[0065] In step S19, the processor 10 positions the workpiece W1 so that its posture is a predetermined posture, or sets a coordinate system for moving the touch probe 150 to correspond to the posture of the workpiece. That is, the error measurement method includes having the computer 1C position the workpiece W1 so that its posture is a predetermined posture, or set a coordinate system for moving the touch probe 150 to correspond to the posture of the workpiece, before bringing the touch probe 150 into contact with the surface of the workpiece W1 for error measurement. For example, "the posture of the workpiece W1 is a predetermined posture" means that the workpiece W1 is rotated so that the point CP0 is on an axis (the Y-axis in the example of FIG. 3) extending from the rotation axis A3 (the gear rotation axis A4) in the opposite direction to the machining approach direction. That is, "positioning the workpiece W1 so that its posture is a predetermined posture" means that the workpiece W1 is rotated to a posture that facilitates calculations for the error measurement process, which will be described later. Setting a coordinate system for moving the touch probe 150 in accordance with the attitude of the workpiece means setting a coordinate system (X'Y' coordinate system) based on an axis (X' axis) directed from the rotation axis A3 (gear rotation axis A4) toward the center point CP0 between adjacent teeth T1 and T2 and an axis (Y' axis) perpendicular to that as the coordinate system for moving the touch probe 150 for error measurement. In other words, setting a coordinate system for moving the touch probe 150 in accordance with the attitude of the workpiece means setting a coordinate system for moving the touch probe 150 in a coordinate system that facilitates calculations for the error measurement process described below.

[0066] In step S21, the processor 10 determines the approach start point APSP and approach direction APD of the touch probe 150 held by the tool spindle 114 (tool holding device) based on the posture of the workpiece W1 machined into a gear shape and held by the workpiece spindle 122 (workpiece holding device). In other words, the error measurement method involves having the computer 1C determine the approach start point APSP and approach direction APD of the touch probe 150 based on the posture of the workpiece W1 machined into a gear shape. Hereinafter, the contents of the flowchart will be explained using an example in which the gear product is an involute gear and a spur gear. Similar calculations can be made when the gear product is other gears, and the calculation method in that case will be described in a modified example. Figure 5 is a diagram illustrating a shape model representing the cross-sectional shape of the tooth flank when the gear product is a spur gear (the target shape TS of the gear product, the outer peripheral surface PS of the workpiece W1).

[0067] At this time, the coordinates (x, y) of the XY coordinate system of the point P on the target shape TS are expressed as the following (Equation 1) and (Equation 2) using a parameter α (rad). x=Rb / cosα*sin(π / (2*N)-invA+invα) (Equation 1) y=Rb / cosα*cos(π / (2*N)-invA+invα) (Equation 2) The parameter α is an angle as shown in Figure 5. In (Equation 1) and (Equation 2), Rb is the radius of the base circle BC. The angle A (rad) is the pressure angle. N is the number of teeth of the gear product. The radius Rp of the pitch circle PC is 1 / cosA times the radius Rb of the base circle BC. The involute angle invA is tan A-A, and the involute angle invα is tan α-α. Note that (Equation 1) and (Equation 2) utilize the fact that when the intersection of the involute curve and the base circle BC is on the Y-axis, the parameter α (rad) is equal to the pressure angle A (rad) at the contact target point PP(s), which is the intersection of the involute curve and the pitch circle PC.

[0068] TIFF2026013779000002.tif58170

[0069] TIFF2026013779000003.tif74170

[0070] TIFF2026013779000004.tif55170

[0071] TIFF2026013779000005.tif37170

[0072] In step S23, the processor 10 determines whether or not the touch probe 150 has come into contact with the workpiece W1 as a result of the movement. In other words, the error measurement method includes determining whether or not the touch probe 150 has come into contact with the surface of the workpiece W1 as a result of the movement. Specifically, the processor 10 can determine whether or not the touch probe 150 has come into contact with the workpiece W1 depending on whether or not the processor 10 has received a detection signal output from a contact sensor attached to the touch probe 150. If the touch probe 150 has not come into contact with the workpiece W1 (No in step S23), step S23 is repeated.

[0073] When the touch probe 150 comes into contact with the surface of the workpiece W1 due to this movement (Yes in step S23), in step S24, the processor 10 determines the center position of the tip sphere 152 of the touch probe 150 at that time. In other words, the error measurement method includes having the computer 1C determine the center position of the tip sphere 152 of the touch probe 150 when the touch probe 150 comes into contact with the surface of the workpiece W1 due to this movement. Specifically, the processor 10 calculates the center position SeP(s) of the tip sphere 152 from the output of the rotation sensor of the first actuator ACT1 or the third actuator ACT3 at the time when the detection signal is received. In the following description, the coordinates of the center position SeP(s) are assumed to be (x(s), y(s), z(s)).

[0074] Next, in step S25, processor 10 determines a candidate value e(i) for the error between the gear profile (outer peripheral surface PS) and the target profile TS of the gear product. That is, the error measurement method includes having computer 1C determine the candidate value e(i). Specifically, processor 10 determines candidate value e(i) by increasing it by a predetermined increment from a predetermined negative value. In step S26, processor 10 generates a cross-sectional model (i) representing the cross-sectional shape of the tooth flank based on candidate value e(i), target profile TS, and the predetermined orientation. That is, the error measurement method includes having computer 1C generate a cross-sectional model M(i) representing the cross-sectional shape of the tooth flank based on candidate value e(i), target profile TS, and the predetermined orientation.

[0075] In generating the cross-sectional model M(i), a first plane CS1 (see the lower diagram in Figure 6) that is perpendicular to the tangential plane TP(s) and includes the contact target point PP(s), and the gear rotation axis A4 when the gear product is placed in the specified attitude are defined. The cross-sectional model M(i) is represented by a model curve MCL(s,i) obtained by shifting a target curve TCL(s) that passes through the contact target point PP(s) on the first plane CS1 in the direction away from the gear rotation axis A4 (Y direction) from the first plane CS1. This model curve MCL(s,i) is a curve segment obtained by shifting the target curve TCL(s) between a first intersection SP(s) of the target curve TCL(s) with the root circle RC or base circle BC of the target shape TS, which is centered on the gear rotation axis A4, and the target curve TCL(s), and a second intersection EP(s) of the target curve TCL(s) with the tip circle AC of the target shape TS, which is centered on the gear rotation axis A4, in the separation direction (Y direction) by a candidate value e(i). A first end point SP'(s,i) of MCL(s,i) is located at a position shifted by the candidate value e(i) in the Y direction from the position of the first intersection SP(s). A second end point EP'(s,i) of MCL(s,i) is located at a position shifted by the candidate value e(i) in the Y direction from the position of the second intersection EP(s).

[0076] In the example of Figure 6, the radius Rb of the base circle BC is larger than the radius Rr of the root circle RC. However, depending on the gear design, the radius Rr of the root circle RC may be larger than the radius Rb of the base circle BC. The first intersection point SP(s) is the intersection point between the root circle RC or the base circle BC, whichever has the larger radius, and the target curve TCL(s). In the example of Figure 6, the X and Y coordinates of the first intersection point SP(s) are expressed as (Rb * sin(π / (2*N) - invA), Rb * cos(π / (2*N) - invA)). The X and Y coordinates of the second intersection point EP(s) are expressed as (Ra * sin(π / (2*N) - invA + invα1), Ra * cos(π / (2*N) - invA + invα1)). Here, Ra is the radius of the tip circle AC, α1 is a parameter for defining the coordinates of the second intersection point EP(s), and α1 = arccos(Rb / Ra).

[0077] At this time, according to (Equation 1) and (Equation 2), the XY coordinates (x(i,α), y(i,α)) of any point on the cross-sectional model M(i) (model curve MCL(s,i)) are given by x(i,α)=Rb / cosα*sin(π / (2*N)-invA+invα) (Formula 6) y(i,α)=Rb / cosα*cos(π / (2*N)-invA+invα)+e(i) (Equation 7) (However, 0≦α≦arccos(Rb / Ra)) This will be expressed as follows.

[0078] When the radius Rr of the root circle RC is greater than the radius Rb of the base circle BC, the X and Y coordinates of the first intersection point SP(s) are expressed as (Rr * sin(π / (2*N) - invA + invα2), Rr * cos(π / (2*N) - invA + invα2)). Here, Rr is the radius of the root circle RC, and α2 is a parameter for defining the coordinate of the first intersection point SP(s), where α2 = arccos(Rb / Rr). In this case, the range of α in (Equation 6) and (Equation 7) is arccos(Rb / Rr) ≦ α ≦ arccos(Rb / Rr). In this way, the above-described model curve (curve segment) can be expressed by parameters for each coordinate in the two-dimensional coordinate system (X and Y coordinates) that defines the position on the first plane CS1.

[0079] In step S27, the processor 10 calculates the minimum distance L(i) between the cross-sectional model M(i) (model curve MCL(s,i)) and the center position SeP(s). In other words, the error measurement method includes having the computer 1C calculate the minimum distance L(i) between the cross-sectional model M(i) (model curve MCL(s,i)) and the center position SeP(s). The minimum distance L(i) is the distance between the center position SeP(s) and the nearest point among multiple points on the model curve MCL(s,i) that is the shortest distance from the center position SeP(s). In calculating the minimum distance, α(j) (j is from 0 to the division number - 1) is prepared by equally dividing α in 0≦α≦arccos(Rb / Rr) or arccos(Rb / Rr)≦α≦arccos(Rb / Rr). The division number is preferably 100 or more. In other words, the positions of the above-mentioned multiple points on the first plane CS1 can be calculated by changing the parameters by the same amount. Then, the processor 10 determines α(j) that minimizes D(i,j) expressed by (Equation 8) as αmin, and determines the square root of D(i,j) corresponding to αmin as the minimum distance L(i). D(i,j)={x(i,α(j))-x(s)} 2 +{x(i,α(j))-y(s)} 2 (Formula 8) In step S28, processor 10 determines whether the absolute value of the difference between minimum distance L(i) determined in step S27 and the radius of tip ball 152 of touch probe 150 is equal to or less than a tolerance. In other words, the error measurement method includes having computer 1C determine whether the absolute value of the difference between minimum distance L(i) determined in step S27 and the radius of tip ball 152 of touch probe 150 is equal to or less than a tolerance. This tolerance is determined according to the required accuracy of the gear product. If the absolute value of this difference is greater than the tolerance (No in step S28), the process returns to step S25, and candidate value e(i+1) = e(i) + Δe (Δe is the increment described above) is determined, and steps S26 to S28 are repeated.

[0080] If the absolute value of this difference is equal to or less than the tolerance (Yes in step S28), in step S29, processor 10 determines candidate value e(i) as the error e. That is, processor 10 changes candidate value e(i) and determines, as the error e, the candidate value e(i) where the absolute value of the difference between minimum distance L(i) and the radius of tip sphere 152 is equal to or less than the tolerance. That is, the error measurement method changes candidate value e(i) and causes computer 1C to determine, as the error e, the candidate value e(i) where the absolute value of the difference between minimum distance L(i) and the radius of tip sphere 152 is equal to or less than the tolerance. In this way, the error measurement method causes computer 1C to calculate the error e between the gear profile of workpiece W1 and the target shape TS of the gear product based on center position SeP(s).

[0081] <Linkage between error measurement processing and gear machining processing> The machine tool 100 is capable of executing both gear machining and error measurement processing by processing a machining program 22 in which commands for performing such error measurement processing have been added to program code for machining the workpiece W into a gear shape or gear product. FIG. 7 shows an example of such a machining program 22. For ease of reference, "line number:" has been added to the left of the machining program 22 in FIG. 7. The control device 1 executes an interpreter 26, an actuator control library 27, and a sensor processing library 28 to analyze the machining program 22 and perform gear manufacturing processing corresponding to the commands in the machining program 22. FIGS. 8 and 9 are flowcharts showing the gear manufacturing method according to this embodiment, i.e., the operations of the gear manufacturing processing performed by the control device 1 (computer 1C).

[0082] In Figure 7, line number 1 indicates the start of the program, line number 2 indicates the program number, line number 3 describes the sequence number used for recursive calls, and line number 4 is a command to set the work coordinate system to the offset specified by the G54 command.

[0083] The control device 1 according to this embodiment determines whether a first command has been received in step S1 of FIG. 8. The first command is, for example, a combination of the G310 command to the G312 command shown in FIG. 7. This can be determined, for example, by determining whether the interpreter 26 executed by the control device 1 has read the G310 command to the G312 command. The G310 command on line number 5 and the G311 command on line number 6 are commands for inputting hob specifications and operating conditions, and the G312 command on line number 7 is a command for inputting machining conditions. The G311 command on line number 6 is an example of a first tool specifying command Y28 for specifying a first tool (e.g., a hob, a skiving cutter, or a milling tool) capable of performing gear machining and held by the tool spindle 114 of the machine tool 100. The first tool specified in the example of line number 6 is a hob. Note that the T number associated with the first tool specifying command is not limited to a T number specifying a hob, but may also be a T number specifying another tool for gear machining.

[0084] The commands written in lines 5 to 7 are an example of a first command that controls the actuator ACT so that the first tool machines the workpiece W1 into a gear shape. In the command in line 7, the number after J represents the cutting depth in the Y-axis direction. The second command may be a command for inputting the specifications, operating conditions, and machining conditions of the skiving cutter. Furthermore, the second command may be a command for inputting the tool path and cutting conditions (rotation speed, feed rate, etc.) for machining with a mill tool. The first tool defining command may also be a separate command (e.g., M60) separated from the first command.

[0085] If the first command has not been accepted (No in step S1), the control device 1 waits until the first command is accepted. Upon accepting the first command (Yes in step S1), the control device 1 controls the tool changer 130 in step S2 so that the tool spindle 114 (tool holding device) holds a first tool of the at least one tool 160. In other words, the gear manufacturing method according to this embodiment includes, upon acceptance of the first command by the computer 1C, having the computer 1C control the tool changer 130 of the machine tool 100 so that the tool spindle 114 (tool holding device) of the machine tool 100 holds the first tool.

[0086] Next, when the control device 1 receives the first command (Yes in step S1), in step S3 it controls the actuator ACT so that the first tool machines the workpiece W1 into a gear shape. In other words, the gear manufacturing method according to this embodiment includes causing the computer 1C to control the actuator ACT so that the first tool machines the workpiece W1 into a gear shape when the computer 1C receives the first command.

[0087] Specifically, the processor 10 controls the movement of the column 110 in the Z-axis direction and the rotation of the tool headstock 112 about the rotation axis A1. For example, the processor 10 moves the column 110 by outputting a PWM signal to a stepping motor. Then, while rotating the work spindle 122 about the rotation axis A3 and the tool spindle 114 about the rotation axis A2, the processor 10 controls the movement of the tool headstock 112 in the Y-axis direction and the movement of the column 110 in the Y-axis and Z-axis directions so as to bring the hob into contact with the outer peripheral surface of the cylindrical workpiece W1. In this way, a gear is formed on the workpiece W1.

[0088] Line number 8 in FIG. 7 is an example of a fourth command for determining the orientation of the workpiece W1. This example shows a G340 command as the fourth command for measuring the phase (position on the C-axis) of the midpoint CP0 between two adjacent teeth. The G340 command includes a fourth tool defining command H38.61 for defining the touch probe 150 held by the tool spindle 114 of the machine tool 100. However, the fourth tool defining command may be a separate command (e.g., M60) separated from the fourth command. The control device 1 according to this embodiment determines whether the fourth command has been received in step S4 of FIG. 8. If the fourth command has not been received (No in step S4), the control device 1 waits until the fourth command is received. When the control device 1 receives the fourth command (fourth tool defining command) (Yes in step S4), in step S5 the control device 1 controls the tool changer 130 to replace the tool (first tool) held by the tool spindle 114 (tool holding device) with the touch probe 150. In other words, the gear manufacturing method according to this embodiment includes, when the computer 1C receives the fourth command, having the touch probe 150 control the tool changer 130 to replace the tool (first tool) held by the tool spindle 114 (tool holding device) of the machine tool 100 with the touch probe 150. Thereafter, the control device 1 executes the processing of step S18 in FIG. 4. The processing result of this command is output to macro variable #802 of the control device 1.

[0089] Lines 9 and 10 in FIG. 7 are examples of a fifth command for positioning the workpiece W1 so that the workpiece W1 assumes a predetermined orientation, or for setting a coordinate system for moving the touch probe 150 in accordance with the orientation of the workpiece. Line 9 in FIG. 7 is a command for substituting the value of macro variable #802 output in step S18 into macro variable #5245 of the control device 1. This macro variable #5245 is a variable that specifies the offset of the C-axis. Line 10 in FIG. 7 is a command for setting a coordinate system for moving the touch probe 150 (the above-mentioned X'Y' coordinate system in which the midpoint CP0 between two adjacent teeth passes through the Y' axis) by setting the value set in macro variable #5245 as the offset of the C-axis. The fifth command may also be a command for rotating the workpiece spindle 122 based on macro variable #802 so that the midpoint CP0 passes through the Y' axis.

[0090] The control device 1 according to this embodiment determines whether or not a fifth command has been received in step S6 of Fig. 8. If the fifth command has not been received (No in step S6), the control device 1 waits until the fifth command is received. If the control device 1 receives the fifth command (Yes in step S6), it executes the process of step S19 of Fig. 4. That is, the gear manufacturing method according to this embodiment includes causing the computer 1C to execute a process of controlling the workpiece spindle 122 (workpiece holding device) so that the workpiece W1 assumes a predetermined posture before the touch probe 150 is brought into contact with the surface of the workpiece W1 for error measurement, or to set a coordinate system for moving the touch probe 150 in accordance with the posture of the workpiece, and causing the computer 1C to control the tool changer 130 of the machine tool 100 so that the tool spindle 114 (tool holding device) of the machine tool 100 holds a first tool.

[0091] Line number 11 in FIG. 7 is an example of a second command for executing the error measurement process related to steps S21 to S29 in FIG. 4. This example shows a G344 command as the second command for executing a process in which gear specifications are input as arguments and the above-mentioned error e is output as a margin. The G344 command further includes a second tool defining command H38.61 for defining the touch probe 150 held by the tool spindle 114 of the machine tool 100. The G344 command may also include an argument related to the approach distance L. However, the second tool defining command may be a separate command (e.g., M60) separated from the second command. In the example of FIG. 4, the second tool defining command and the fourth tool defining command specify the same touch probe 150, but they may specify different touch probes 150.

[0092] The control device 1 according to this embodiment determines whether a second command has been received in step S7 of FIG. 9. This can be determined, for example, by determining whether the interpreter 26 executed by the control device 1 has read the second command. If the second command has not been received (No in step S7), the control device 1 waits until the second command is received. When the control device 1 receives the second command (second tool defining command) (Yes in step S7), the control device 1 controls the tool changer 130 in step S8 to replace the tool held by the tool spindle 114 (tool holding device) with the touch probe 150. In other words, the gear manufacturing method according to this embodiment includes, when the computer 1C receives the second command (second tool defining command), having the touch probe 150 control the tool changer 130 to replace the first tool held by the tool spindle 114 (tool holding device) of the machine tool 100 with the touch probe 150. In the example of FIG. 4, the second tool defining command and the fourth tool defining command are the same, so tool change is not performed. In this case, the operation of step S5 may be considered to be the same as the operation of step S8.

[0093] Furthermore, when the control device 1 receives the second command (Yes in step S7), it executes the error measurement process relating to steps S21 to S29 in Fig. 4. The control device 1 outputs the output value of this process to macro variable #784 of the control device 1. Thus, the gear manufacturing method according to this embodiment includes, when the computer 1C receives the second command, controlling the actuator ACT to move the touch probe 150 in accordance with the error measurement process relating to steps S21 to S29 in Fig. 4, and causing the computer 1C to calculate the error e between the gear profile of the workpiece W1 and the target shape TS of the gear product.

[0094] Line number 12 in Figure 7 is a command that sets the workpiece coordinate system to the offset specified by the G54 command. Line number 13 sets up a process that jumps to the sequence number written in line number 20 and ends the machining program 22 if the macro variable #784 output by the G344 command is 0 or less.

[0095] In FIG. 7, lines 14 and 15 contain the same commands as lines 5 and 6. Line 16 is almost the same command as line 7, except that the value of macro variable #784 is added to the value after J. This command specifies that the error e described above is to be added to the cutting depth in the Y-axis direction. The combination of commands written in lines 14 to 16 is an example of a third command that controls actuator ACT to manufacture a gear product using a second tool based on the error e. The G311 command in line 15 is an example of a third tool definition command for specifying a second tool (e.g., a hob, skiving cutter, or milling tool) that can perform gear machining and is held by the tool spindle 114 of the machine tool 100 in Y28. In the example of FIG. 4, the third tool definition command and the first tool definition command may specify the same hob, and the first and second tools are the same, but they may specify other tools for gear machining, not just the same hob.

[0096] The control device 1 according to this embodiment determines whether a third command has been received in step S9 of FIG. 9. This determination can be made, for example, by determining whether the interpreter 26 executed by the control device 1 has read a combination of the G310 command to the G312 command. If the third command has not been received (No in step S9), the control device 1 waits until the third command is received. If the control device 1 receives the third command (Yes in step S9), the control device 1 controls the tool changer 130 in step S10 to replace the touch probe 150 held by the tool spindle 114 (tool holding device) with a second tool among at least one tool. That is, the gear manufacturing method according to this embodiment includes having the computer 1C control the tool changer 130 to replace the touch probe 150 held by the tool spindle 114 (tool holding device) with the second tool when the computer 1C receives the third command. While the example in FIG. 4 shows an example in which the first tool and the second tool are the same, the first tool and the second tool may be the same tool or different tools.

[0097] Next, when the control device 1 receives the third command (Yes in step S9), in step S11, it controls the actuator ACT to adjust the movement path of the second tool based on the error and cause the second tool to manufacture a gear product. In other words, the gear manufacturing method according to this embodiment includes, when the computer 1C receives the third command, having the computer 1C control the actuator ACT to adjust the movement path of the second tool based on the error and cause the second tool to manufacture a gear product. <Application to helical gears> In the above example, the gear product is an involute gear and a spur gear, but the present invention can also be applied to helical gears, bevel gears, or cycloidal gears. In all of these cases, the cross-sectional model M(i) is expressed as a curve represented by parameters obtained by shifting the target curve TCL(s) in a predetermined direction, and the approach direction is determined to be the direction of the normal vector of the tangent plane TP(s) of the target shape TS at the contact target point PP(s), or vice versa. In all of these cases, once the cross-sectional model M(i), approach direction, and approach start point are determined, the error e can be detected using the same algorithm as in the above embodiment, so this algorithm will be explained below.

[0098] TIFF2026013779000006.tif47170

[0099] For comparison, Figure 10A also shows the model curve MCL(s,i) for a spur gear. The target curve on the X"Y plane is denoted as TCL(h), the contact target point as PP(h), the tangent plane as TP(h), the first intersection as SP(h), and the second intersection as EP(h). The first end point of MCL(h,i) is denoted as SP'(h,i), and the second end point of MCL(h,i) is denoted as EP'(h,i). In this case, the X"Y plane is defined as a first plane CS1 that is perpendicular to the tangent plane TP(h) and includes the contact target point PP(h). The first plane CS1 is a plane obtained by rotating a second plane CS2 (XY plane) perpendicular to the gear rotation axis A4 on the second plane CS2 around a straight line (Y axis) that passes through the gear rotation axis A4 by a helix angle β defined by the tooth profile of the target shape TS. The first endpoint SP'(h,i) of MCL(h,i) is located at a position shifted by the candidate value e(i) in the Y direction from the position of the first intersection SP(h). The second endpoint EP'(h,i) of MCL(h,i) is located at a position shifted by the candidate value e(i) in the Y direction from the position of the second intersection EP(h).

[0100] In this case, the X" coordinate of each point on the target curve TCL(h) can be obtained by multiplying the X coordinate of each point on the target curve TCL(s) by cos β. The X" coordinate of each point on the model curve MCL(h,i) can be obtained by multiplying the X coordinate of each point on the model curve MCL(s,i) by cos β. Therefore, according to (Equation 6) and (Equation 7), the X" and Y coordinates (x(i,α), y(i,α)) of any point on the model curve MCL(h,i) are x(i,α)=Rb / cosα*sin(π / (2*N)-invA+invα)*cosβ (Equation 9) y(i,α)=Rb / cosα*cos(π / (2*N)-invA+invα)+e(i) (Equation 10) (However, 0≦α≦arccos(Rb / Ra) (when Rb≧Rr), arccos(Rb / Rr)≦α≦arccos(Rb / Ra)(Rb <Rrのとき)) This will be expressed as follows.

[0101] In this case, if the angle between the line where the tangential plane TP(h) and the X"Y plane intersect and the Y axis is θp(h), then tanθp(h)=tanθp(s)*cosβ (Equation 11) The above holds. The X and Y coordinates of the contact target point PP(s) are expressed as (Rp*sin(π / (2*N)), Rp*cos(π / (2*N)), and therefore the X and Y coordinates of the contact target point PP(h) are expressed as (Rp*sin(π / (2*N))*cosβ, Rp*cos(π / (2*N)). The difference D between the Y coordinate of the approach start point APSP(s) and the Y coordinate of the contact target point PP(s) is expressed as shown in the following (Equation 12). D=Rb / cos(A+π / (2*N))-Rp*cos(π / (2*N)) =Rp*{cosA / cos(A+π / (2*N))-cos(π / (2*N))} =Rp*sin(π / (2*N))*tanθp(s) (Equation 12) The difference D' between the Y coordinate of the approach start point APSP(h) and the Y coordinate of the contact target point PP(h) is expressed as in the following (Equation 13). D'=Rp*sin(π / (2*N))*cosβ*tanθp(h) (Equation 13) TIFF2026013779000007.tif40170

[0102] TIFF2026013779000008.tif65170

[0103]

number

[0104] TIFF2026013779000010.tif31170

[0105]

number

[0106] <Application to bevel gears> TIFF2026013779000012.tif55170

[0107] For ease of explanation, the model curve MCL(b,i) is not shown in Figure 11A. Instead, the relationship between the target curve TCL(s) for a spur gear and the target curve TCL(b) for a standard bevel gear is shown. The target point of contact of the standard bevel gear is represented as PP(b), the tangent plane as TP(b), the first intersection as SP(b), and the second intersection as EP(b). In this case, the XY" plane is defined as the first plane CS1 that is perpendicular to the tangent plane TP(b) and includes the contact target point PP(b). The first plane CS1 is a plane obtained by rotating the second plane CS2 (XY plane), which is perpendicular to the gear rotation axis A4, on the second plane CS2 around a straight line (X axis) that passes through the gear rotation axis A4 by a reference cone angle δ defined from the tooth profile of the target shape TS. The model curve MCL(b,i) is a position moved by the candidate value e(i) in the Y" direction with respect to the target curve TCL(b). In other words, it is a position away from the candidate value e(i) / cosδ in the Y direction.

[0108] In this case, the Y" coordinate of each point on the target curve TCL(b) can be obtained by multiplying the Y coordinate of each point on the target curve TCL(s) by cosδ. The Y" coordinate of each point on the model curve MCL(b,i) can be obtained by multiplying the Y coordinate of each point on the model curve MCL(s,i) by cosδ. Therefore, according to (Equation 4) and (Equation 5), the XY" coordinates (x(i,α), y(i,α)) of any point on the model curve MCL(b,i) are given by x(i,α)=Rb / cosα*sin(π / (2*N)-invA+invα) (Formula 17) y(i,α)=Rb / cosα*cos(π / (2*N)-invA+invα)*cosδ+e(i) (Equation 18) (However, 0≦α≦arccos(Rb / Ra) (when Rb≧Rr), arccos(Rb / Rr)≦α≦arccos(Rb / Ra)(Rb <Rrのとき)) This will be expressed as follows.

[0109] In this case, if the angle between the Y axis and the line where the tangent plane TP(b) and the XY" plane intersect is θp(b), then tanθp(b)=tanθp(s) / cosδ (Equation 19) The XY coordinates of the contact target point PP(s) are expressed as (Rp*sin(π / (2*N)), Rp*cos(π / (2*N)), so the XY coordinates of the contact target point PP(b) are expressed as (Rp*sin(π / (2*N)), Rp*cos(π / (2*N)*cosδ).

[0110] The difference D' between the Y" coordinate of the approach start point APSP(b) and the Y" coordinate of the contact target point PP(b) is expressed as the following (Equation 20). D'=Rp*sin(π / (2*N))*tanθp(b) (Equation 20) TIFF2026013779000013.tif55170

[0111] TIFF2026013779000014.tif67170

[0112]

number

[0113] TIFF2026013779000016.tif34170

[0114]

number

[0115] TIFF2026013779000018.tif34170

[0116] FIG. 12A is a cross-sectional view of an example reducer 200 including a trochoid gear. FIG. 12B is a cross-sectional view of another example reducer 201 including a trochoid gear. The reducer 200 includes an internal gear 210 composed of multiple internal pins 214 rotatably attached inside an outer cylinder 212, and an external gear 220 that meshes with the internal gear 210. Speed ​​reduction is achieved by the difference between the number of internal pins 214 and the number of teeth of the external gear 220. In many cases, the number of teeth of the external gear 220 is one less than the number of internal pins 214. The external gear 220 has an outer shape defined by an epitrochoid parallel curve. The reducer 201 includes an external gear 221 composed of multiple external pins 224 rotatably attached inside an inner cylinder 222, and an internal gear 211 that meshes with the external gear 221. Speed ​​reduction is achieved by the difference between the number of external pins 224 and the number of teeth of the internal gear 211. In many cases, the number of external pins 224 is one less than the number of teeth of the internal gear 211. The external shape of the internal gear 211 is defined by a hypotrochoid parallel curve. The case of FIG. 12A will be explained below. For the internal gear 211 shown in FIG. 12B, the epitrochoid parallel curve of the external gear 220 shown in FIG. 12A can be applied to the hypotrochoid parallel curve, so explanation will be omitted.

[0117] TIFF2026013779000019.tif39170

[0118] The radius of the internal pin 214 is R OP Then, the XY coordinates (x, y) of point P on the epitrochoid parallel curve are generally expressed by (Equation 24) and (Equation 25). x=x0+R OP cosθ (Equation 24) y=y0+R OP sinθ (Equation 25) (x0, y0), cos θ, and sin θ are expressed by the following equations. x0=-a*sinφ+Rp*sin(φ / Zb) (Equation 26) y0=-a*cosφ+Rp*cos(φ / Zb) (Equation 27)

[0119]

number

[0120]

number

[0121] where φ is a parameter for drawing the epitrochoid curve. Rp is the radius of the pitch circle PC (base circle BC) of the internal pin 214. Zb is the number of internal pins 214. One period of Φ is 2πZb. Za is the number of teeth of the external gear 8. x is a correction coefficient that determines the curvature of the epitrochoid curve. The radius of the rolling circle in the model that draws the epitrochoid curve is R. T Then, t and a are expressed by the following equations. t=(Rp-R T ) / Rp (Equation 30) a=Rp(1-t) / Zb=R T / Zb (Formula 31) The larger t is, the smaller the curvature of the epitrochoidal curve becomes, and the smaller t is, the larger the curvature of the epitrochoidal curve becomes. Here, for example, when expressed as φ=2nπ+φ0 (n: integer, 0≦φ0<2π), the relationship between φ0 and t from 0 to 2π is stored in memory 20. In other words, the same value of t is applied every 2π. Once φ is determined, t is determined from the relationship, a is determined from (Equation 31), and the XY coordinates (x, y) of P are determined based on (Equations 24) to (Equations 29).

[0122] Here, point P0 in FIG. 13A is obtained by setting the parameter φ to 0. Point P0, which coincides with the first intersection point SP(s) of the target curve TCL(s), can be found from the values ​​of (x, y) when the parameter φ is set to 0. Point P1, which coincides with the second intersection point EP(h) of the target curve TCL(s), can be found from the values ​​of (x, y) when the parameter φ is set to π. The contact target point PP(s) is x 2 +y 2 The value of Rp 2 The (x, y) that is closest to can be found as an approximate solution.

[0123] TIFF2026013779000022.tif86170

[0124] The XY coordinates (x(i), y(i)) of a point on the model curve MCL(s,i) are expressed as follows based on (x, y) expressed by (Equation 24) and (Equation 25) and the above candidate value e(i): x(i)=x (Equation 34) y(i)=y+e(i) (Equation 35) TIFF2026013779000023.tif61170

[0125] TIFF2026013779000024.tif29170

[0126] In a cycloidal gear, the pitch circle PC and the base circle BC coincide, and the target curve TCL(s) is expressed as an epicycloid outside the base circle BC, and as a hypocycloid inside the base circle BC. The epicycloid is expressed as the locus of a point on a circle when an outer rolling circle of radius Re rolls without slip on the base circle BC. The hypocycloid is expressed as the locus of a point on a circle when an inner rolling circle of radius Rh rolls without slip on the base circle BC.

[0127] Therefore, the XY coordinates (x(i,θe), y(i,θe)) of any point on the epicycloid of the model curve MCL(s,i) are expressed by the following matrix.

[0128]

number

[0129] The XY coordinates (x(i,θh), y(i,θh)) of any point on the hypocycloid of the model curve MCL(s,i) are expressed by the following matrix.

[0130]

number

[0131] TIFF2026013779000027.tif58170

[0132] The machine tool 100, error measurement method, interpreter 26 having instructions for causing a computer 1C to execute the error measurement method, actuator control library 27, and sensor processing library 28 according to this embodiment use the cross-sectional model M(i) (model curve MCL(h,i)) to estimate the error e between the gear profile (outer peripheral surface PS) of the workpiece W1 and the target profile TS of the gear product from the center position SeP(s) of the tip ball 152 of the touch probe 150 when the touch probe 150 comes into contact with the surface of the workpiece W1. Therefore, since there is no need to move the touch probe 150 until it comes into contact with both teeth of the gear, it is possible to measure the gear error using a touch probe 150 selected regardless of the gear profile.

[0133] Furthermore, the machine tool 100, gear manufacturing method, interpreter 26 having instructions for causing computer 1C to execute the gear manufacturing method, actuator control library 27, and sensor processing library 28 according to this embodiment are capable of processing the first command to the fifth command, and therefore, by loading a machining program 22 including the first command to the fifth command into machine tool 100, it is possible to cause machine tool 100 to automatically execute a series of operations including rough machining, error measurement, and finish machining. <Modification> In the above embodiment, the contact target point PP(s) is located on the pitch circle PC of the gear product. However, it may be located at another point on the target curve TCL(s). In this case, the contact target point PP(s) can be determined using (Equation 1), (Equation 2), etc. In addition, while the model of the error e has been described as being obtained by shifting the target curve in the Y-axis direction, the model curve MCL(s,i) may be generated by adding an offset of the error e to the base circle radius Rb to generate an involute curve, a trochoid parallel curve, an epicycloid curve, or a hypocycloid curve. In this case, the separation direction is not limited to a specific axial direction, but may be any radial direction relative to the gear rotation axis A4.

[0134] 7 are commands for involute spur gears and helical gears, but dedicated commands applicable to involute bevel gears, trochoidal gears, and cycloidal gears are also provided, and the dedicated commands may be processed by the interpreter 26, actuator control library 27, and sensor processing library 28 of the control device 1 in the same way as the G310, G311, G312, G340, and G344 commands. Alternatively, parameters specific to involute bevel gears, trochoidal gears, and cycloidal gears may be added to the arguments of the G310, G311, G312, G340, and G344 commands so that these gears can be processed in the same way as involute spur gears and helical gears. Furthermore, the first through fifth commands described above may be combined into one, or at least two of the commands may be partially combined into one command. Specifically, the fourth command, the fifth command, and the second command may be integrated into one command.

[0135] Some or all of the functions of the logic of the interpreter 26, actuator control library 27, and sensor processing library 28 of the above-mentioned control device 1 may be realized by a dedicated processor or integrated circuit. The above-mentioned interpreter 26, actuator control library 27, and sensor processing library 28 may be stored not only in the memory 20 built into the control device 1 but also in a storage medium that is removable from the control device 1 and readable by the control device 1, such as a disk such as a floppy disk, optical disk, CD-ROM or magnetic disk, an SD card, a USB memory, or an external hard disk.

[0136] The workpiece gripper may be a gripper such as a vise that can grip a workpiece, instead of the work spindle 122. In that case, the machine tool 100 may be a machine tool that processes the workpiece W into a gear shape or a gear product using a milling tool.

[0137] In the above embodiment, an example was shown in which the error detection method according to Fig. 4 is implemented when a predetermined command is received by the machining program 22 in the machine tool 100. However, the error detection method according to Fig. 4 may also be implemented by a dedicated measuring device such as that disclosed in Japanese Patent Application Laid-Open No. 2006-234775. In this case, the dedicated measuring device is provided with the configuration of the computer 1C described above. Furthermore, the error detection method according to Fig. 4 may be implemented by any input from the user, not just a command by the machining program 22.

[0138] In this application, the term "comprises" and its derivatives are open-ended terms that describe the presence of elements and do not exclude the presence of other elements not listed. This also applies to the terms "have," "include," and their derivatives.

[0139] The terms "member," "part," "element," "body," and "structure" may have multiple meanings, such as a single part or multiple parts.

[0140] Ordinal numbers such as "first" and "second" are merely terms used to identify components and do not have any other meaning (e.g., a particular order). For example, the presence of a "first element" does not imply the presence of a "second element," and the presence of a "second element" does not imply the presence of a "first element."

[0141] Words expressing degrees such as "substantially," "about," and "approximately" can refer to reasonable deviations that do not significantly change the end result. All numerical values ​​described in this application can be interpreted to include words such as "substantially," "about," and "approximately."

[0142] In this application, the phrase "at least one of A and B" should be interpreted to include A only, B only, and both A and B.

[0143] It is apparent that various changes and modifications of the present invention are possible in light of the above disclosure, and therefore, the present invention may be practiced otherwise than as specifically disclosed herein without departing from the spirit of the present invention.

Claims

1. a workpiece holding device configured to hold a workpiece; a tool holding device configured to hold one of a touch probe and at least one tool; an actuator configured to move the tool holding device relative to the workpiece holding device; a control device configured to control the tool holding device and the actuator and to perform an error measurement process; Equipped with The error measurement process includes: determining an approach start point and an approach direction of the touch probe held by the tool holding device based on the attitude of the workpiece machined into a gear shape and held by the workpiece holding device; controlling the actuator to move the touch probe in the approach direction from the approach start point; determining a center position of the tip ball of the touch probe when the touch probe comes into contact with the surface of the workpiece by the movement; determining a candidate value of the error between the gear profile and a target profile of a gear product; generating a cross-sectional model representing a cross-sectional shape of the tooth surface based on the candidate value, the target shape, and the posture; determining a minimum distance between the cross-sectional model and the center position; The candidate value is varied, and the candidate value for which the absolute value of the difference between the minimum distance and the radius of the tip sphere is equal to or smaller than a tolerance is determined as the error. Including, Machine tools.

2. and a tool changer configured to change one of the touch probe and the at least one tool held by the tool holding device for another tool. The machine tool according to claim 1.

3. The control device a control unit configured to control the tool changer so that the tool holding device selectively holds a first tool and a second tool of the at least one tool and the touch probe, and to receive first to third commands; When the first command is received, the actuator is controlled so that the first tool is used to machine the workpiece into the gear shape; When the second command is received, the error measurement process is executed; and when the third command is received, the actuator is controlled to adjust the movement path of the second tool based on the error to manufacture the gear product. The machine tool according to claim 2.

4. The computer determines the approach start point and approach direction of the touch probe based on the orientation of the workpiece machined into a gear shape, controlling an actuator to move the touch probe in the approach direction from the approach start point; causing the computer to determine the center position of the tip ball of the touch probe when the touch probe comes into contact with the surface of the workpiece by the movement; and causing the computer to calculate an error between the gear profile and a target profile of a gear product based on the center position. This includes: The calculation of the error by the computer includes: determining candidate values ​​for the error; generating a cross-sectional model representing a cross-sectional shape of the tooth surface based on the candidate value, the target shape, and the posture; determining a minimum distance between the cross-sectional model and the center position; The candidate value is varied, and the candidate value for which the absolute value of the difference between the minimum distance and the radius of the tip sphere is equal to or smaller than a tolerance is determined as the error. Including, Error measurement method.

5. determining the approach start point and the approach direction includes determining a contact target point of the target shape; the approach direction is determined as a direction of a normal vector of a tangent plane of the target shape at the contact target point when the gear product is placed in the attitude, or the reverse of that direction; The approach start point is determined to be a position facing in a direction opposite to the approach direction from the contact target point. The error measurement method according to claim 4.

6. a first plane that is perpendicular to the tangential plane and includes the contact target point, and a gear rotation axis when the gear product is placed in the attitude are defined; the cross-sectional model is represented by a model curve obtained by shifting, on the first plane, a target curve passing through the contact target point among a plurality of curves represented by cutting the target shape with the first plane, in an away direction away from the gear rotation axis. The error measurement method according to claim 5 .

7. the first plane is a plane obtained by rotating a second plane perpendicular to the gear rotation axis on the second plane around the gear rotation axis or a straight line passing through the contact target point by a helix angle defined by a tooth profile of the target shape. The error measurement method according to claim 6.

8. the minimum distance is the distance between the central position and a nearby point among a plurality of points on the model curve that has the smallest distance from the central position; The error measurement method according to claim 6.

9. the model curve is a curve segment obtained by moving a curve segment that is the target curve between a first intersection point of the target curve and a root circle or a base circle of the target shape centered on the gear rotation axis, and a second intersection point of the target curve and a tip circle of the target shape centered on the gear rotation axis by the candidate value in the separation direction. The error measurement method according to claim 8.

10. the model curve can be expressed by parameters of each coordinate in a two-dimensional coordinate system that defines a position on the first plane; The positions of the plurality of points on the first plane are determined by changing the parameters by the same magnitude. The error measurement method according to claim 9.

11. Before bringing the touch probe into contact with the surface of the workpiece, the workpiece is positioned so that the orientation of the workpiece is a predetermined orientation, or a coordinate system for moving the touch probe is set in accordance with the orientation of the workpiece. further comprising: The error measurement method according to claim 4.

12. When the computer according to any one of claims 4 to 10 receives a first command, the computer controls the actuator so as to machine the workpiece into the gear shape with a first tool held by a tool holding device of a machine tool; When the computer receives the second command, the actuator is controlled to move the touch probe in accordance with the error measurement method of any one of claims 4 to 11, causing the computer to calculate the error; and when the computer receives the third command, the computer controls the actuator to adjust a movement path of a second tool held by the tool holding device based on the error, and to cause the second tool to manufacture the gear product. A gear manufacturing method comprising:

13. A gear measuring device comprising a computer configured to execute the error measurement method of any one of claims 4 to 11.

14. A computer program comprising instructions which, when executed by a computer, cause the computer to carry out the error measurement method of any one of claims 4 to 11.

15. A computer program comprising instructions that, when executed by a computer, cause the computer to carry out the gear manufacturing method of claim 12.

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