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

Abstract

Provided is a technique capable of measuring a gear shape error. 【Solution means】The machine tool includes a control device configured to execute error measurement processing. The error measurement processing determines the approach start point and approach direction of a touch probe held by a tool holding device based on the posture of a workpiece machined into a gear shape held by a workpiece holding device, controls an actuator to move the touch probe in the approach direction from the approach start point, obtains the center position of the tip sphere of the touch probe when the touch probe contacts the surface of the workpiece due to the movement, determines a candidate value for the error between the gear shape and the target shape of the gear product, generates a cross-sectional model representing the cross-sectional shape of the tooth surface based on the candidate value, the target shape, and the posture, obtains the minimum distance between the cross-sectional model and the center position, changes the candidate value, and determines, as the error, a 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 less than an allowable value.

Description

Technical Field

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

Background Art

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

[0003] As a technique for solving such problems, there is a machine tool as described in Patent Document 2. The machine tool according to Patent Document 2 measures errors using a touch probe attached to the machine tool after machining the workpiece into a gear shape, and automates a series of operations from rough machining to finish machining.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the machine tool of Patent Document 2, it is necessary to move the hard ball at the tip of the touch probe until it contacts both teeth of the gear. Therefore, a touch probe having a hard ball corresponding to the gear shape must be selected.

[0006] An object of the technology disclosed in the present application is to provide a technology capable of measuring gear shape errors using a touch probe selected regardless of the gear shape, for example.

Means for Solving the Problem

[0007] The machine tool according to the 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 any 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 execute an error measurement process. The error measurement process determines the approach start point and approach direction of the touch probe held by the tool holding device based on the posture of the workpiece machined into a gear shape held by the workpiece holding device, controls the actuator to move the touch probe in the approach direction from the approach start point, obtains the center position of the tip sphere of the touch probe when the touch probe contacts the surface of the workpiece by the movement, determines a candidate value for the error between the gear shape and the target shape of the gear product, generates a cross-sectional model representing the cross-sectional shape of the tooth surface based on the candidate value, the target shape, and the posture, obtains the minimum distance between the cross-sectional model and the center position, changes the candidate value, and determines 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 less than the allowable value as the error.

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

[0009] According to a third aspect of the present disclosure, in the machine tool according to the first aspect, the control device controls the tool changer so that the tool holding device selectively holds the first tool and the second tool among at least one tool and the touch probe, and is configured to receive commands from a first command to a third command. When receiving the first command, the control device is configured to control the actuator so as to machine a workpiece into a gear shape with the first tool. When receiving the second command, the control device is configured to execute error measurement processing. When receiving the third command, the control device is configured to control the actuator so as to adjust the movement path of the second tool based on the error and manufacture a gear product.

[0010] The error measurement method according to a fourth aspect of the present disclosure includes causing a computer to determine an approach start point and an approach direction of a touch probe based on the posture 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, causing the computer to obtain the center position of the tip sphere of the touch probe when the touch probe contacts the surface of the workpiece by the movement, and causing the computer to calculate an error between the gear shape and the target shape of the gear product based on the center position. Causing the computer to calculate the error includes determining a candidate value of the error, generating a cross-sectional model representing the cross-sectional shape of the tooth surface based on the candidate value, the target shape, and the posture, obtaining the minimum distance between the cross-sectional model and the center position, changing the candidate value, and determining, as the error, a 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 less than an allowable value.

[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 the normal vector of the tangent plane of the target shape at the contact target point when the gear product is arranged in the posture or the reverse thereof. The approach start point is determined at a position facing in the reverse direction of 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 intermediate variable of the involute curve representing the point on the pitch is equal to the pressure angle. When the gear product is a cycloid gear and the curve model consists of an epicycloid curve and a hypocycloid curve, the pitch circle is the same as the base circle for generating the cycloid curve. When the gear product is a trochoid gear and the curve model is an epitrochoid parallel curve, the contact target point is not limited to the intersection of the epitrochoid parallel curve and the pitch circle, but may be the intersection of the epitrochoid parallel curve and the root circle, or the intersection of the epitrochoid 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 tangent plane and includes the contact target point and the gear rotation axis when the gear product is arranged in the posture are defined. Among the plurality of curves represented by cutting the target shape by the first plane, a cross-sectional model is represented by a model curve that has been moved in the separation direction away from the gear rotation axis when the gear product is arranged in the posture on the first plane, passing through the target curve passing through the contact target point.

[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 twist angle defined from 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 closest point, among the plurality of points in the model curve, whose distance from the center position is the minimum, and the center 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 moving a curve segment between a first intersection point of a bottom circle or a base circle centered on the gear rotation axis in the target shape and the target curve and a second intersection point of a tip circle centered on the gear rotation axis in the target shape and the target curve in the separation direction by a candidate value. When the model curve is an involute curve, the first intersection point is an intersection point of the target curve and the circle with the smaller radius of the base circle and the bottom circle. When the model curve is a cycloid curve, or when the model curve is a cycloid curve, the first intersection point may be an intersection point of the bottom circle and the target curve. Further, when the curve model is an epitrochoid parallel curve and the contact target point is an intersection point of the trochoid parallel curve and the bottom circle, two adjacent intersection points of the tip circle and the target curve may be used as the first intersection point and the second intersection point. When the curve model is an epitrochoid parallel curve and the contact target point is an intersection point of the trochoid parallel curve and the tip circle, two adjacent intersection points of the bottom circle and the target curve may be used as the first intersection point and the second intersection point.

[0017] According to an eleventh aspect of the present disclosure, in the machine tool or error measurement method according to any one of the seventh to tenth aspects, the model curve can represent each coordinate of a two-dimensional coordinate system that defines a position on a first plane by a mediating variable, and the positions of a plurality of points on the first plane are obtained by changing the mediating variable by the same magnitude.

[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 arranging the workpiece so that the posture of the workpiece becomes a predetermined posture before bringing the touch probe into contact with the surface of the workpiece, or setting a coordinate system for moving the touch probe in correspondence with the posture of the workpiece. Further, according to a twelfth aspect of the present disclosure, in a machine tool according to the first aspect or any one of the fifth to eleventh aspects, the control device controls the workpiece holding device so that the posture of the workpiece becomes a predetermined posture before bringing the touch probe into contact with the surface of the workpiece, or sets a coordinate system for moving the touch probe in correspondence with the posture of the workpiece. Note that it is desirable that this predetermined posture is a posture of a gear shape such that a contact target point can be analytically obtained in a predetermined coordinate system. Also, it is desirable that the coordinate system set in correspondence with the posture of the workpiece is a coordinate system such that a contact target point can be analytically obtained.

[0019] According to a thirteenth aspect of the present disclosure, a gear manufacturing method includes causing an actuator to control a computer to machine a workpiece into a gear shape with a first tool held by a tool holding device of a machine tool when the computer receives a first command from any one of the fourth to eleventh aspects. The gear manufacturing method includes causing the actuator to control the computer to move the touch probe according to any one of the error measurement methods from the fourth to eleventh aspects when the computer receives a second command, and causing the computer to calculate an error. The gear manufacturing method includes causing the actuator to control the computer to adjust a movement path of a second tool held by the tool holding device based on the error and manufacture a gear product with the second tool when the computer receives a third command.

[0020] According to the 14th aspect of the present disclosure, when any computer up to the 13th aspect receives a first command, the gear manufacturing method further includes controlling, by the computer, a tool changer of a machine tool so that a tool holding device of the machine tool holds a first tool. When the computer receives a second command, the gear manufacturing method further includes controlling, by the computer, the tool changer so that an instrument held by the tool holding device is replaced with a touch probe. When the computer receives a third command, the gear manufacturing method further includes controlling, by the computer, the tool changer so that the touch probe held by the tool holding device is replaced with a second tool.

[0021] According to the 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 a workpiece holding device so as to rotate the workpiece so that the posture of the workpiece becomes a predetermined posture before bringing the touch probe into contact with the surface of the workpiece, or setting a coordinate system for moving the touch probe in correspondence with the posture of the workpiece. According to the 15th aspect of the present disclosure, in the machine tool according to the 3rd aspect, before bringing the touch probe into contact with the surface of the workpiece, the control device is configured to control the workpiece holding device so as to rotate the workpiece so that the posture of the workpiece becomes a predetermined posture, or set a coordinate system for moving the touch probe in correspondence with the posture of the workpiece. It is desirable that this predetermined posture is a posture of a gear shape such that a contact target point can be analytically obtained in a predetermined coordinate system.

[0022] A gear measuring device according to the 16th aspect of the present disclosure includes a computer configured to execute an error measurement method according to any one of the 4th to 12th aspects.

[0023] A computer program according to the 17th aspect of the present disclosure includes an instruction for causing a computer to execute an error measurement method according to any one of the 4th to 12th aspects when executed by the computer.

[0024] The computer program according to the 18th aspect of the present disclosure includes an instruction to cause a computer of a machine tool to execute the gear manufacturing method according to either the 13th aspect or the 14th aspect when executed by the computer.

[0025] According to the 19th aspect of the present disclosure, the computer program according to the 18th aspect includes an instruction to cause the computer to execute a process of controlling the workpiece holding device so as to rotate the workpiece so that the posture of the workpiece becomes a predetermined posture or set a coordinate system for moving the touch probe in accordance with the posture of the workpiece before the touch probe contacts the surface of the workpiece. Note that this predetermined posture is desirably a posture of a gear shape such that a contact target point can be analytically obtained in a predetermined coordinate system.

[0026] The computer-readable medium according to the 20th aspect of the present disclosure includes an instruction to cause a computer to execute the error measurement method according to any one of the 4th aspect to the 12th aspect when executed by the computer.

[0027] The computer-readable medium according to the 21st aspect of the present disclosure includes an instruction to cause a computer of a machine tool to execute the gear manufacturing method according to either the 13th aspect or the 14th aspect when executed by the computer.

[0028] According to the 22nd aspect of the present disclosure, the computer-readable medium according to the 21st aspect includes an instruction to cause the computer to execute a process of controlling the workpiece holding device to rotate the workpiece so that the posture of the workpiece becomes a predetermined posture or setting a coordinate system for moving the touch probe in accordance with the posture of the workpiece before the touch probe contacts the surface of the workpiece. Note that this predetermined posture is desirably a posture of a gear shape such that a contact target point can be analytically obtained in a predetermined coordinate system.

[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 including a computer configured to execute the error measurement method according to the fourth aspect, the computer program according to the seventeenth aspect including an instruction to cause a computer to execute the error measurement method according to the fourth aspect, and the computer-readable medium according to the twentieth aspect including an instruction to cause a computer to execute the error measurement method according to the fourth aspect estimate the error between the gear shape and the target shape of the gear product from the center position of the tip sphere of the touch probe when the touch probe contacts the surface of the workpiece using a cross-sectional model. Therefore, since it is not necessary to move the touch probe until it contacts both teeth of the gear, the gear error can be measured using a touch probe selected independently of the gear shape.

[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 including a computer configured to execute the error measurement method according to the fifth aspect, the computer program according to the seventeenth aspect including an instruction to cause a computer to execute the error measurement method according to the fifth aspect, and the computer-readable medium according to the twentieth aspect including an instruction to cause 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 substantially perpendicularly, so that slippage after contact is unlikely to occur and the gear error can be measured accurately.

[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 including a computer configured to execute the error measurement method according to the sixth aspect, the computer program according to the seventeenth aspect including an instruction to cause a computer to execute the error measurement method according to the sixth aspect, and the computer-readable medium according to the twentieth aspect including an instruction to cause 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 the pressure angle of the gear specification. When the gear product is a cycloid gear, the approach direction is the tangential direction of the pitch circle, making it easy to derive.

[0032] In a machine tool according to the seventh aspect, an error measurement method according to the seventh aspect, a gear measurement device according to the sixteenth aspect including a computer configured to execute the error measurement method according to the seventh aspect, a computer program according to the seventeenth aspect including an instruction to cause a computer to execute the error measurement method according to the seventh aspect, and a computer-readable medium according to the twentieth aspect including an instruction to cause a computer to execute the error measurement method according to the seventh aspect, when a workpiece is generated by a tool that generates a gear such as a hob, since a tooth profile surface is formed so as to shift with respect to the approach direction of the hob, an accurate cross-sectional model can be generated.

[0033] In a machine tool according to the eighth aspect, an error measurement method according to the eighth aspect, a gear measurement device according to the sixteenth aspect including a computer configured to execute the error measurement method according to the eighth aspect, a computer program according to the seventeenth aspect including an instruction to cause a computer to execute the error measurement method according to the eighth aspect, and a computer-readable medium according to the twentieth aspect including an instruction to cause a computer to execute the error measurement method according to the eighth aspect, an accurate cross-sectional model of a workpiece having a helical gear shape can be generated.

[0034] In a machine tool according to the ninth aspect, an error measurement method according to the ninth aspect, a gear measurement device according to the sixteenth aspect including a computer configured to execute the error measurement method according to the ninth aspect, a computer program according to the seventeenth aspect including an instruction to cause a computer to execute the error measurement method according to the ninth aspect, and a computer-readable medium according to the twentieth aspect including an instruction to cause a computer to execute the error measurement method according to the ninth aspect, the coordinates of an approximate solution of the contact point can be obtained.

[0035] In the machine tool according to the tenth aspect, the error measurement method according to the tenth aspect, the gear measurement device according to the sixteenth aspect including a computer configured to execute the error measurement method according to the tenth aspect, the computer program according to the seventeenth aspect including an instruction to cause the computer to execute the error measurement method according to the tenth aspect, and the computer-readable medium according to the twentieth aspect including an instruction to cause the computer to execute the error measurement method according to the tenth aspect, in the case of an involute gear, the model curve can be represented by an involute curve, in the case of a trochoid gear, the model curve can be represented by an epitrochoid parallel curve, and in the case of a cycloid gear, the model curve can be represented by an epicycloid curve and a hypocycloid curve, so that mathematical modeling can be facilitated.

[0036] In the machine tool according to the eleventh aspect, the error measurement method according to the eleventh aspect, the gear measurement device according to the sixteenth aspect including a computer configured to execute the error measurement method according to the eleventh aspect, the computer program according to the seventeenth aspect including an instruction to cause the computer to execute the error measurement method according to the eleventh aspect, and the computer-readable medium according to the twentieth aspect including an instruction to cause the computer to execute the error measurement method according to the eleventh aspect, an approximate solution of the contact point can be accurately obtained.

[0037] In the machine tool according to the twelfth aspect, the error measurement method according to the twelfth aspect, the gear measurement device according to the sixteenth aspect including a computer configured to execute the error measurement method according to the twelfth aspect, the computer program according to the seventeenth aspect including an instruction to cause the computer to execute the error measurement method according to the twelfth aspect, and the computer-readable medium according to the twentieth aspect including an instruction to cause the computer to execute the error measurement method according to the twelfth aspect, the model curve and the coordinate system of the center position can be determined according to the posture of the workpiece.

[0038] In the machine tool according to the second aspect, since the machine tool can exchange the touch probe and the tool, the user burden when performing an operation combining 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 including an instruction to cause a computer to execute the gear manufacturing method according to the thirteenth aspect, by causing the machine tool to read a machining program including the first to third commands, a series of operations of rough machining, error measurement, and finish machining can be automatically executed by the machine tool 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 fourteenth aspect, and the computer-readable medium according to the twenty-first aspect including an instruction to cause a computer to execute the gear manufacturing method according to the fourteenth aspect, by causing the machine tool to read a machining program including the first to third commands, tool change can also be automated, and all of a series of operations of rough machining, error measurement, and finish machining can be automatically executed by the machine tool.

[0041] In the machine tool according to the fifteenth aspect, the gear manufacturing method according to the fifteenth aspect, the computer program according to the nineteenth aspect, and the computer-readable medium according to the twenty-second aspect, a model curve and a coordinate system of a center position can be determined according to the posture of a workpiece.

Advantages of the Invention

[0042] According to the technology disclosed in the present application, for example, since it is not necessary to move the touch probe until it touches both of two teeth of a gear, gear error can be measured using a touch probe selected regardless of the gear shape.

Brief Description of the Drawings

[0043]

Figure 1

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Figure 13B

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Embodiments for Carrying Out the Invention

[0044] Hereinafter, the present invention will be specifically described based on the drawings showing its embodiments. In the drawings, the same reference numerals indicate corresponding or substantially identical configurations.

[0045] <First Embodiment> <Overall Configuration> FIG. 1 shows a schematic configuration of a machine tool 100 according to the first embodiment. Note that the X-axis shown in FIG. 1 is along the height direction of the machine tool 100, the Y-axis is along the depth direction of the machine tool 100, and the Z-axis is 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 rough machining, the machine tool 100 machines the workpiece W1 held by the workpiece spindle 122 into a gear shape by performing tooth cutting such as hobbing or gear skiving. However, the machine tool 100 may machine the workpiece W1 rough machined by a machine tool different from the machine tool 100 into a gear product by performing deburring and finish machining. As shown in FIG. 1, the machine tool 100 includes a column 110, a tool spindle head 112, a workpiece spindle head 120, and a tool changer 130. The column 110, the workpiece spindle head 120, and the tool changer 130 are arranged on the base 140.

[0047] The column 110 is movable in the Y-axis direction and the Z-axis direction on the base 140. A tool spindle head 112 is attached to the column 110. The tool spindle head 112 is movable in the X-axis direction with respect to the column 110. The tool spindle head 112 is pivotable in the B direction, which is the circumferential direction around the rotation axis A1 along the Y-axis direction, with respect to the column 110. The machine tool 100 includes a first actuator ACT1 configured to move the tool spindle head 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 separately have a motor for moving the tool spindle head 112 in the X-axis direction and a motor for moving the tool spindle head 112 in the B direction. Alternatively, the first actuator ACT1 may separately have a power conversion mechanism for moving the tool spindle head 112 in the X-axis direction and a power conversion mechanism for moving the tool spindle head 112 in the B direction from one motor. 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 spindle head 112. The tool spindle 114 is rotatable around the rotation axis A2 along the X-axis direction with respect to the tool spindle head 112. The machine tool 100 includes a second actuator ACT2 configured to rotate the tool spindle 114 around the rotation axis A2. The second actuator ACT2 is, for example, a motor. The tool spindle 114 is configured to hold either one of the touch probe 150 and at least one machine tool 160. Details of the touch probe 150 will be described later.

[0048] The machine tool 100 includes a lathe spindle 122. The lathe spindle 122 is also referred to as a workpiece gripper. The lathe spindle 122 is attached to the lathe spindle base 120. The lathe spindle 122 is rotatable in the C direction which is the circumferential direction around the rotation axis A3. The rotation axis A3 is along the Z-axis direction. The lathe spindle 122 is configured to hold the workpiece W1. The lathe 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 lathe spindle 122 in the circumferential direction around 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 lathe spindle base 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 the actuator ACT. Note that the functions of the first to fourth actuators ACT1 to ACT4 are not limited to the functions described above. For example, the first actuator ACT1 may move the tool spindle base 112 in the X-axis direction and the Z-axis direction. That is, the machine tool 100 includes an actuator ACT configured to relatively move the tool holding device (tool spindle 114) with respect to the workpiece holding device (lathe spindle 122). The first to fourth actuators ACT4 preferably include a rotation sensor such as an encoder in order to detect the moving amount and rotation angle of the controlled object.

[0050] The tool changer 130 is configured to exchange any one of the touch probe 150 and at least one tool 160 held by the tool spindle 114 for the other. 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 with respect to the stocker 134. The stocker 134 stores the touch probe 150 and at least one tool 160 so that they 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 tooth groove-shaped cross section, a pinion cutter, and a milling tool.

[0051] The exchange of the tool by the tool changer 130 is performed in the following procedure. The tool spindle base 112 moves in the X-axis direction and pivots in the B-axis direction so that the tool mounted on the tool spindle 114 faces the tool changer 130. The column 110 approaches the tool changer 130 in the Y-axis and Z-axis directions and moves the tool to the tool exchange position. The magazine arm 132 has a first gripper at one end in the direction in which the magazine arm 132 extends and a second gripper at the other end in the extending direction. The first gripper grips the tool mounted on the tool spindle 114 in order to remove the tool mounted on 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. The magazine arm 132 rotates about an axis along the Z-axis direction to mount another tool on the tool spindle 114 and moves the other tool gripped by the second gripper to the 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] The machine tool 100 is provided with a control device 1 in order to control the rotation around each rotation axis and the movement in each axis direction. The control device 1 is configured to control a tool spindle 114 (tool holding device), a workpiece spindle 122 (workpiece holding device), and an actuator ACT. The control device 1 is connected to a base 140. Here, the control device 1 may be connected to other parts of the machine tool 100, and may be installed separately from the base 140 as long as it can transmit control signals and receive detection results. The control device 1 is provided with a display 40 and an input interface 50. The input interface 50 may include a touch panel built in the display 40. A Graphical User Interface is realized by the display 40 and the input interface 50. However, the display 40 and the input interface 50 may be provided separately from the 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 composed of an electric circuitry, reads out the program stored in the memory 20, and executes the read program. Thereby, each function of the control device 1 is realized. Each function realized by the control device 1 includes processes such as rough machining of gears, phase detection of gears, deburring of gears, finish machining, and tooth surface profiling measurement. Since the processor 10 and the memory 20 also have the same functions as a general computer, the control device 1 may 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 described by a program code such as, for example, an EIA / ISO program code, and includes commands for, for example, machining the work piece W1 into a gear shape, detecting the posture of the work piece W1, and measuring the error between the gear shape of the machined work piece W1 and the target shape of the gear product. The gear data 24 includes specifications (dimensions) of the target shape (for example, 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 the commands described in the machining program 22 and executing at least one of the actuator control library 27 and the sensor processing library 28. That is, the control device 1 is configured to receive various commands (for example, the first to fifth commands shown in FIGS. 8 and 9 described later) described in the machining program 22 by executing the interpreter 26. The actuator control library 27 is a program for executing commands for controlling the tool changer 130 described in the machining program 22, commands for driving or moving the work spindle 122 or the tool spindle 114 described in the machining program 22, and commands for measuring the error between the gear shape of the machined workpiece W1 and the target shape of the gear product. The sensor processing library 28 is a program for executing commands for detecting the posture of the workpiece W1 and commands for measuring the error between the gear shape of the machined workpiece W1 and the target shape of the gear product. The detected posture of the workpiece W1 is, for example, the phase of the gear in the C direction of the work spindle 122. When the interpreter 26 receives a command for controlling the tool changer 130 described in the machining program 22, it calls the actuator control library 27 and executes a process of controlling the tool changer 130 so that the tool spindle 114 (tool holding device) selectively holds the first tool and the second tool among at least one tool and the touch probe 150. That is, 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 among at least one tool and the touch probe 150. When the interpreter 26 receives a command for measuring the error between the gear shape of the workpiece W1 and the target shape of the gear product, it calls the actuator control library 27, executes a process of moving the touch probe 150 held by the tool spindle 114, calls the sensor processing library 28, and executes a process of detecting the contact state by the 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, and detects whether the tip ball 152 of the touch probe 150 has contacted an object. The actuator control circuit 32 includes, for example, an electric circuit that generates control signals to their drivers when the first to fourth actuators ACT1 to ACT4 are motors. For example, when the actuator control library 27 outputs the target rotational speed and target torque of the motor based on the commands described in the machining program 22, the actuator control circuit 32 outputs control signals (for example, pulse signals) to the drivers corresponding to the target rotational speed and target torque. Note that the control signal from the control device 1 and the detection signal from the touch probe 150 are transmitted and received via the 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 the drawing of the display 40 according to the control of the processor 10. The input circuit 52 is connected to the input interface 50. The input circuit 52 outputs the operation received by the input interface 50 as an operation input signal to the processor 10.

[0058] <Error measurement process of workpiece> FIG. 3 shows the state of the workpiece W1 related to the error measurement of the control device 1. The area SP2 in FIG. 3 is an enlarged view of the area SP1. The control device 1 moves at least one machine tool 160, for example, a hob or a skiving cutter, in the radial direction (machining approach direction) with respect to the rotation axis A3 of the work spindle 122 to machine the workpiece W1 having a cylindrical shape, for example, into a gear shape. For this purpose, the gear rotation axis A4 of the workpiece W1 coincides with the rotation axis A3 of the work spindle 122. In FIG. 3, the target shape of the gear product is shown by a dotted line TS, and the outer shape of the workpiece W1 is shown by the outer peripheral surface PS. Due to the nature of machining by a hob or a skiving cutter, considering only the shape models of two adjacent teeth T1 and T2, the outer peripheral surface PS exists at a position separated from the target shape TS by an error e in the machining approach direction. In FIG. 3, the case where the Y-axis direction is equal to the machining approach direction is illustrated, but the machining approach direction may be other directions.

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

[0060] Here, the phase P of the gear represented by the outer peripheral surface PS in the present embodiment is defined as follows. The phase P is an angle formed by any position on the C-axis of the outer peripheral surface PS with respect to the reference position RL on the C-axis, which is the circumferential direction of the gear rotation axis A4 of the workpiece W1. Note that the reference position RL is, for example, a position corresponding to the machining approach direction. Hereinafter, the reference position RL will be described as corresponding to the positive Y-axis direction. As shown in FIG. 3, when the pitch circle PC of the gear product and the intersection points CP1 and CP2 of the outer peripheral surfaces PS of two adjacent teeth T1 and T2 are defined, and the midpoint of the curved portion CP1CP2 on the outer peripheral surface PS is CP0, the phases of the points CP1, CP2, and CP0 are set as P1, P2, and P0, respectively. Note that the points CP1, CP2, and CP0 are not limited to the points on the pitch circle PC, and may be on any circumference centered on the rotation axis of the gear product between the addendum circle AC and the root circle RC.

[0061] In the present embodiment, the phases P1 and P2 are obtained by relatively moving the touch probe 150 in the circumferential direction of the pitch circle PC with respect to the workpiece W1, and the phase P0 can be obtained by setting the phase at the center of the phases P1 and P2 as P0. Specifically, for example, when the X coordinate and Y coordinate of the tip sphere 152 of the touch probe 150 are positioned between two adjacent teeth T1 and T2, the control device 1 moves the touch probe 150 in the Z-axis direction and utilizes the fact that the moving distance in the Z-axis direction, which can be moved, becomes longer than the moving distance when contacting the gear side surface SS. Then, the control device 1 determines the X coordinate and Y coordinate of the center position of the tip sphere 152 of the touch probe 150 such that the X coordinate and Y coordinate of the tip sphere 152 of the touch probe 150 are positioned between two adjacent teeth T1 and T2. Note that it is desirable that these X coordinate and Y coordinate are provided at the coordinates on the pitch circle PC. Then, the control device 1 moves the touch probe 150 in the Z-axis direction so that the tip sphere 152 of the touch probe 150 is positioned between two adjacent teeth T1 and T2. Note that the positions of the points CP1, CP2, and CP0 in the Z-axis direction are shown in the lower diagram of FIG. 3.

[0062] Next, by driving the fourth actuator ACT4, the workpiece W1 is rotated around the rotation axis A3 (gear rotation axis A4), and the point CP1 and the point CP2 are brought into contact with the touch probe 150. The point CP1 and the point CP2 are separated from the center position of the tip sphere 152 of the touch probe 150 by the radius of the tip sphere 152 when being contacted by the touch probe 150, but are separated from each other in opposite directions by the radius of the tip sphere 152. Therefore, the phase P0 can be obtained when the rotation angle of the fourth actuator ACT4 is an arbitrary angle θ from the rotation angle θ0 that is exactly in the middle between the rotation angle θ1 of the fourth actuator ACT4 when the point CP1 is brought into contact with the touch probe 150 and the rotation angle θ2 of the fourth actuator ACT4 when the point CP2 is brought into contact with the touch probe 150.

[0063] When 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 the point CP0 is located on the Y-axis. Alternatively, the control device converts the X-axis and the Y-axis into the X'-axis and the Y'-axis rotated around the Z-axis so that the 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. Hereinafter, it will be described assuming that the workpiece W1 is rotated so that the point CP0 is located on the Y-axis. However, when the coordinate conversion to the X'Y' coordinate system is performed, the XY coordinate system in the following description may be read as the X'Y' coordinate system.

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

[0065] In step S19, the processor 10 arranges the workpiece W1 so that the posture of the workpiece W1 becomes a predetermined posture, or sets a coordinate system for moving the touch probe 150 in correspondence with the posture of the workpiece. That is, the error measurement method includes causing the computer 1C to arrange the workpiece W1 so that the posture of the workpiece W1 becomes a predetermined posture or to set a coordinate system for moving the touch probe 150 in correspondence with 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, for the posture of the workpiece W1 to become a predetermined posture means that the workpiece W1 is rotated so that the point CP0 becomes a point on an axis (Y-axis in the example of FIG. 3) extending in the direction opposite to the machining approach direction from the rotation axis A3 (gear rotation axis A4). That is, arranging the workpiece W1 so that the posture of the workpiece W1 becomes a predetermined posture means rotating the workpiece W1 to a posture that facilitates the calculation of the error measurement process described later. Setting a coordinate system for moving the touch probe 150 in correspondence with the posture of the workpiece means setting, as the coordinate system for moving the touch probe 150 for error measurement, 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 central point CP0 between the adjacent teeth T1 and T2 and an axis (Y' axis) perpendicular thereto. That is, setting a coordinate system for moving the touch probe 150 in correspondence with the posture of the workpiece means setting a coordinate system for moving the touch probe 150 to a coordinate system that facilitates the calculation of the error measurement process described later.

[0066] In step S21, the processor 10 determines the approach start point APSP and the 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 processed into a gear shape held by the work spindle 122 (workpiece holding device). That is, the error measurement method includes causing the computer 1C to determine the approach start point APSP and the approach direction APD of the touch probe 150 based on the posture of the workpiece W1 processed into a gear shape. Hereinafter, the content of the flowchart will be described by taking the case where the gear product is an involute gear and a spur gear as an example. When the gear product is another gear, it can be calculated in the same way, and the calculation method in that case will be shown in a modification example. FIG. 5 is a diagram for explaining a shape model representing the cross-sectional shape of the tooth surface (the target shape TS of the gear product, the outer peripheral surface PS of the workpiece W1) when the gear product is a spur gear.

[0067] At this time, the coordinates (x, y) of the point P on the target shape TS in the XY coordinate system are represented by the following (Equation 1) and (Equation 2) by the intermediate variable 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 intermediate variable α is an angle as shown in FIG. 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. Note that 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 tanA - A, and the involute angle invα is tanα - α. Note that (Equation 1) and (Equation 2) utilize the fact that when the intersection point of the involute curve and the base circle BC is on the Y-axis, the intermediate variable α (rad) is equal to the pressure angle A (rad) at the contact target point PP(s) which is the intersection point of the involute curve and the pitch circle PC.

[0068] TIFF0007706613000002.tif58170

[0069] TIFF0007706613000003.tif74170

[0070] TIFF0007706613000004.tif55170

[0071] TIFF0007706613000005.tif37170

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

[0073] When the touch probe 150 contacts the surface of the workpiece W1 by the movement (Yes in step S23), in step S24, the processor 10 obtains the center position of the tip sphere 152 of the touch probe 150 at that time. That is, the error measurement method includes causing the computer 1C to obtain the center position of the tip sphere 152 of the touch probe 150 when the touch probe 150 contacts the surface of the workpiece W1 by 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 set as (x(s), y(s), z(s)).

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

[0075] In the generation of the cross-sectional model M(i), a first plane CS1 (see the lower figure in FIG. 6) that is perpendicular to the tangent plane TP(s) and includes the contact target point PP(s) and the gear rotation axis A4 when the gear product is arranged in the predetermined posture 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) passing through the contact target point PP(s) among a plurality of curves represented by cutting the target shape TS by the first plane CS1 in the separation direction (Y direction) away from the gear rotation axis A4 on the first plane CS1. This model curve MCL(s,i) is a curve segment of the target curve TCL(s) between the root circle RC or the base circle BC centered on the gear rotation axis A4 of the target shape TS and the first intersection point SP(s) of the target curve TCL(s), and the tip circle AC centered on the gear rotation axis A4 of the target shape TS and the second intersection point EP(s) of the target curve TCL(s), which is shifted in the separation direction (Y direction) by the candidate value e(i). The first end point SP’(s,i) of MCL(s,i) is at a position shifted by the candidate value e(i) in the Y direction with respect to the position of the first intersection point SP(s). The second end point EP’(s,i) of MCL(s,i) is at a position shifted by the candidate value e(i) in the Y direction with respect to the position of the second intersection point EP(s).

[0076] In the example of Fig. 6, the case where the radius Rb of the base circle BC is larger than the radius Rr of the root circle RC is shown. However, depending on the gear design, there may be a case where the radius Rr of the root circle RC is larger than the radius Rb of the base circle BC. The first intersection point SP(s) is the intersection point of the circle with the larger radius among the root circle RC and the base circle BC and the target curve TCL(s). In the case of the example in Fig. 6, the XY coordinates of the first intersection point SP(s) are represented as (Rb*sin(π / (2*N)-invA), Rb*cos(π / (2*N)-invA)). The XY coordinates of the second intersection point EP(s) are represented as (Ra*sin(π / (2*N)-invA+invα1), Ra*cos(π / (2*N)-invA+invα1)). Here, Ra is the radius of the addendum circle AC, α1 is an intermediate variable 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 x(i,α) = Rb / cosα * sin(π / (2*N)-invA+invα) (Equation 6) y(i,α) = Rb / cosα * cos(π / (2*N)-invA+invα) + e(i) (Equation 7) (However, 0 ≤ α ≤ arccos(Rb / Ra)) It will be represented as such.

[0078] When the radius Rr of the root circle RC is larger than the radius Rb of the base circle BC, the XY 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, α2 is an intermediate variable for defining the coordinates of the first intersection point SP(s), and α2 = arccos(Rb / Rr). At this time, the range of α in (Equation 6) and (Equation 7) is arccos(Rb / Rr) ≤ α ≤ arccos(Rb / Ra). Thus, each coordinate of the two-dimensional coordinate system (XY coordinates) that defines the position on the first plane CS1 of the above-described model curve (curve segment) can be represented by an intermediate variable.

[0079] In step S27, the processor 10 obtains the minimum distance L(i) between the cross-sectional model M(i) (model curve MCL(s,i)) and the center position SeP(s). That is, the error measurement method includes causing the computer 1C to obtain 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 closest point having the minimum distance from the center position SeP(s) among a plurality of points on the model curve MCL(s,i). In calculating the minimum distance, α(j) (j ranges from 0 to the number of divisions - 1) obtained by equally dividing α in the range of 0 ≤ α ≤ arccos(Rb / Ra) or arccos(Rb / Rr) ≤ α ≤ arccos(Rb / Ra) is prepared. It is preferable that this number of divisions is 100 or more. That is, the positions of the above-described plurality of points on the first plane CS1 are obtained by changing the intermediate variable by the same magnitude. Then, the processor 10 obtains, as αmin, the α(j) that minimizes D(i,j) represented by (Equation 8), and sets 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 (Equation 8) In step S28, the processor 10 determines whether the absolute value of the difference between the minimum distance L(i) obtained in step S27 and the radius of the tip sphere 152 of the touch probe 150 is less than or equal to an allowable value. That is, the error measurement method includes causing the computer 1C to determine whether the absolute value of the difference between the minimum distance L(i) obtained in step S27 and the radius of the tip sphere 152 of the touch probe 150 is less than or equal to the allowable value. This allowable value is determined according to the required accuracy of the gear product. If the absolute value of this difference is greater than the allowable value (No in step S28), the process returns to step S25. After determining that the candidate value e(i + 1) = e(i) + Δe (Δe is the increment described above), steps S26 to S28 are repeated.

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

[0081] <Linkage between error measurement process and gear machining process> The machine tool 100 processes a machining program 22 in which a command for performing such error measurement processing is added to a program code for machining the workpiece W into a gear shape or a gear product, and can execute both gear machining and error measurement processing. FIG. 7 shows an example of such a machining program 22. In FIG. 7, "line number:" is added to the left side of the machining program 22 for convenience of reference. The control device 1 analyzes the machining program 22 by executing an interpreter 26, an actuator control library 27, and a sensor processing library 28, and executes a gear manufacturing process corresponding to the command of the machining program 22. FIGS. 8 and 9 are flowcharts showing each operation of the gear manufacturing method according to the present embodiment, that is, the gear manufacturing process performed by the control device 1 (computer 1C).

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

[0083] The control device 1 according to the present embodiment determines whether or not 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 whether or not the interpreter 26 executed by the control device 1 has read the G310 command to the G312 command. The G310 command in line number 5 and the G311 command in line number 6 are commands for inputting the specifications and operating conditions of the hob, and the G312 command in line number 7 is a command for inputting the machining conditions. The G311 command in line number 6 is an example of a first tool specification command for specifying a first tool (for example, a hob, a skiving cutter, a milling tool) that can perform gear machining held by the tool spindle 114 of the machine tool 100 at Y28. The first tool specified in the example of line number 6 is a hob. Note that the T number related to the first tool specification command is not limited to the T number specifying the hob, and may be a T number specifying another tool for performing gear machining.

[0084] Note that the commands described in line numbers 5 to 7 are an example of the first command for controlling the actuator ACT so as to machine the workpiece W1 into a gear shape using the first tool. Note that among the commands in line number 7, the numerical value after J represents the cutting amount in the Y-axis direction. Note that 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 (such as rotational speed and feed rate) for machining with a milling tool. Also, the first instrument specification command may be a separate command (for example, M60, etc.) separated from the first command.

[0085] When the first command has not been received (No in step S1), the control device 1 waits until the first command is received. When the control device 1 receives the first command (Yes in step S1), in step S2, it controls the tool changer 130 so that the tool spindle 114 (tool holding device) holds the first tool among at least one tool 160. That is, the gear manufacturing method according to the present embodiment includes 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 the first tool when the computer 1C receives the first command.

[0086] Next, when the control device 1 receives the first command (Yes in step S1), in step S3, it controls the actuator ACT so as to machine the workpiece W1 into a gear shape using the first tool. That is, the gear manufacturing method according to the present embodiment includes causing the computer 1C to control the actuator ACT so as to machine the workpiece W1 into a gear shape using the first tool 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 spindle head 112 around the rotation axis A1. For example, the processor 10 moves the column 110 by outputting a PWM signal to the stepping motor. Then, while rotating the workpiece spindle 122 around the rotation axis A3 and rotating the tool spindle 114 around the rotation axis A2, the processor 10 controls the movement of the tool spindle head 112 in the Y-axis direction and the movement of the column 110 in the Y-axis and Z-axis directions so that the hob cutter contacts the outer peripheral surface of the workpiece W1 on the cylindrical shape. Thereby, a gear is formed on the workpiece W1.

[0088] Line number 8 in FIG. 7 is an example of a fourth command for obtaining the posture 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 intermediate point CP0 between two adjacent teeth. The G340 command includes a fourth tool specification command for specifying the touch probe 150 held by the tool spindle 114 of the machine tool 100 at H38.61. However, the fourth tool specification command may be a separate command (for example, M60, etc.) separated from the fourth command. The control device 1 according to the present embodiment determines whether the fourth command is 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 specification command) (Yes in step S4), in step S5, it 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. That is, the gear manufacturing method according to the present embodiment includes causing the touch probe 150 to 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 when the computer 1C receives the fourth command. Thereafter, the control device 1 executes the process of step S18 in FIG. 4. The processing result of this command is output to the macro variable #802 of the control device 1.

[0089] Line numbers 9 and 10 in FIG. 7 are examples of the fifth command for arranging the workpiece W1 so that the posture of the workpiece W1 becomes a predetermined posture or for setting a coordinate system for moving the touch probe 150 in accordance with the posture of the workpiece. Line number 9 in FIG. 7 is a command for substituting the value of the macro variable #802 output in step S18 into the macro variable #5245 of the control device 1. This macro variable #5245 is a variable that defines the offset of the C axis. Line number 10 in FIG. 7 is a command for setting the coordinate system (the above-described X'Y' coordinate system arranged so that the intermediate point CP0 between two adjacent teeth passes through the Y' axis) for moving the touch probe 150 by setting the value set in the macro variable #5245 as the offset of the C axis. The fifth command may be a command for rotating the work spindle 122 so that the intermediate point CP0 passes through the Y' axis based on the macro variable #802.

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

[0091] Line number 11 in FIG. 7 is an example of a second command for executing the error measurement process according to steps S21 to S29 in FIG. 4. This example shows the G344 command as the second command, which executes a process of inputting the specifications of a gear as an argument and outputting the remaining substitute with the above-described error e. The G344 command further includes a second tool specification command for specifying the touch probe 150 held by the tool spindle 114 of the machine tool 100 at H38.61. Also, the G344 command may include an argument related to the approach distance L. However, the second tool specification command may be a separate command (for example, M60, etc.) separated from the second command. Also, in the example of FIG. 4, although the second tool specification command and the fourth tool specification command specify the same touch probe 150, a different touch probe 150 may be specified.

[0092] The control device 1 according to the present embodiment determines whether or not the second command has been received in step S7 of FIG. 9. This can be determined, for example, by whether or not the interpreter 26 executed by the control device 1 has read the second command. When 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 specification command) (Yes in step S7), in step S8, it controls the tool changer 130 to replace the tool held by the tool spindle 114 (tool holding device) with the touch probe 150. That is, the gear manufacturing method according to the present embodiment includes controlling the tool changer 130 to the touch probe 150 so that when the computer 1C receives the second command (second tool specification command), the first tool held by the tool spindle 114 (tool holding device) of the machine tool 100 is replaced with the touch probe 150. In the example of FIG. 4, since the second tool specification command and the fourth tool specification command are the same, tool change is not executed, but in that case, the operation in step S5 may be regarded as the same as the operation in step S8.

[0093] Furthermore, when the control device 1 receives the second command (Yes in step S7), it executes the error measurement process according to steps S21 to S29 in FIG. 4. The control device 1 outputs the output value of this process to the macro variable #784 of the control device 1. In this way, in the gear manufacturing method according to the present embodiment, when the computer 1C receives the second command, the actuator ACT is controlled to move the touch probe 150 according to the error measurement process according to steps S21 to S29 in FIG. 4, and the computer 1C calculates the error e between the gear shape of the workpiece W1 and the target shape TS of the gear product.

[0094] Line number 12 in FIG. 7 is a command for setting the work coordinate system to the offset specified by the G54 command. Line number 13 is set to jump to the sequence number described in line number 20 and end the machining program 22 when the macro variable #784 output by the G344 command is 0 or less.

[0095] In FIG. 7, line numbers 14 and 15 are the same commands as line numbers 5 and 6. Line number 16 is almost the same command as line number 7, but is different from the command in line number 7 in that the value of the macro variable #784 is added to the numerical value after J. This is a command indicating that the error e described above is added to the cutting amount in the Y-axis direction. The combination of the commands described in line numbers 14 to 16 is an example of a third command for controlling the actuator ACT to manufacture a gear product with the second tool based on the error e. The G311 command in line number 15 is an example of a third tool specification command for specifying the second tool (for example, hob, skiving cutter, milling tool) that can perform gear machining held by the tool spindle 114 of the machine tool 100 at Y28. In the example of FIG. 4, the third tool specification command and the first tool specification command may specify the same hob, and the first tool and the second tool may be the same, but not limited to the same hob, and other tools for performing gear machining may be specified.

[0096] The control device 1 according to this embodiment determines whether it has received a third command in step S9 of FIG. 9. This can be determined, for example, by whether the interpreter 26 executed by the control device 1 has read a combination of commands G310 to G312. When the third command has not been received (No in step S9), the control device 1 waits until the third command is received. When the control device 1 receives the third command (Yes in step S9), in step S10, it controls the tool changer 130 to replace the touch probe 150 held by the tool spindle 114 (tool holding device) with the second tool among at least one tool. That is, the gear manufacturing method according to this embodiment includes causing the computer 1C to control the tool changer 130 so that when the computer 1C receives the third command, the touch probe 150 held by the tool spindle 114 (tool holding device) is replaced with the second tool. In the example of FIG. 4, the first tool and the second tool show the same example, but 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 so as to manufacture a gear product. That is, the gear manufacturing method according to this embodiment includes causing the computer 1C to control the actuator ACT so that when the computer 1C receives the third command, the movement path of the second tool is adjusted based on the error to manufacture a gear product with the second tool. <Application in the case of helical gears> In the above example, an example where the gear product is an involute gear and a spur gear was given. However, the present invention is applicable even if the gear product is a helical gear or a bevel gear, or even if the gear product is a cycloid gear. In all of these cases, the cross-sectional model M(i) is represented as a curve represented by a mediation variable obtained by shifting the target curve TCL(s) in a predetermined direction, and the approach direction is determined by 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 the opposite thereof. In all of these cases, if the cross-sectional model M(i), the approach direction, and the approach start point are determined, the error e can be detected by the same algorithm as in the above embodiment. Therefore, the algorithm will be described.

[0098] TIFF0007706613000006.tif47170

[0099] In FIG. 10A, for comparison, the model curve MCL(s, i) in the case of a spur gear is also described. Also, the target curve on the X”Y plane is represented as TCL(h), the contact target point is represented as PP(h), the tangent plane is represented as TP(h), the first intersection point is represented as SP(h), and the second intersection point is represented as EP(h). The first end point of MCL(h, i) is represented as SP’(h, i), and the second end point of MCL(h, i) is represented 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) that is perpendicular to the gear rotation axis A4 by a twist angle β defined from the tooth profile of the target shape TS around a straight line (Y axis) passing through the gear rotation axis A4 on the second plane CS2. The first end point SP’(h, i) of MCL(h, i) is located at a position shifted by a candidate value e(i) in the Y direction with respect to the position of the first intersection point SP(h). The second end point EP’(h, i) of MCL(h, i) is located at a position shifted by a candidate value e(i) in the Y direction with respect to the position of the second intersection point EP(h).

[0100] At this time, 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 cosβ. 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 cosβ. Therefore, according to (Equation 6) and (Equation 7), the X"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) when Rb<Rr) It will be expressed as follows.

[0101] At this time, assuming that the angle formed by the straight line where the tangent plane TP(h) intersects the X"Y plane and the Y axis is θp(h), tanθp(h)=tanθp(s)*cosβ (Equation 11) holds. Since the XY coordinates of the contact target point PP(s) are represented as (Rp*sin(π / (2*N)), Rp*cos(π / (2*N))), the X"Y coordinates of the contact target point PP(h) are represented 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 follows 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 follows in the following (Equation 13). D’ = Rp * sin(π / (2 * N)) * cosβ * tanθp(h) (Equation 13) TIFF0007706613000007.tif40170

[0102] TIFF0007706613000008.tif65170

[0103]

Number

[0104] TIFF0007706613000010.tif31170

[0105]

Number

[0106] <Application in the case of bevel gears> TIFF0007706613000012.tif55170

[0107] In Fig. 11A, for the sake of convenience of explanation, the illustration of the model curve MCL(b,i) is omitted, and instead, the relationship between the curves of the target curve TCL(s) for the case of spur gears and the target curve TCL(b) for the case of standard stub bevel gears is shown. The contact target point of the standard stub bevel gear is represented as PP(b), the tangent plane is represented as TP(b), the first intersection point is represented as SP(b), and the second intersection point is represented 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) perpendicular to the gear rotation axis A4 around the straight line (X-axis) passing through the gear rotation axis A4 on the second plane CS2 by the reference cone angle δ defined from the tooth profile of the target shape TS. The model curve MCL(b,i) is set at a position shifted by the candidate value e(i) in the Y” direction with respect to the target curve TCL(b). That is, it is at a position separated by the candidate value e(i) / cosδ in the Y direction.

[0108] At this time, 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 x(i,α)=Rb / cosα*sin(π / (2*N)-invA+invα) (Equation 17) y(i,α)=Rb / cosα*cos(π / (2*N)-invA+invα)*cosδ+e(i) (Equation 18) (where 0≦α≦arccos(Rb / Ra) when Rb≧Rr, arccos(Rb / Rr)≦α≦arccos(Rb / Ra) when Rb<Rr) will be expressed as such.

[0109] At this time, if the angle formed by the straight line where the tangent plane TP(b) intersects the XY” plane and the Y axis is θp(b), then tanθp(b)=tanθp(s) / cosδ (Equation 19) holds. Since the XY coordinates of the contact target point PP(s) are expressed as (Rp*sin(π / (2*N)), Rp*cos(π / (2*N))), 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 follows in (Equation 20). D’=Rp*sin(π / (2*N))*tanθp(b) (Equation 20) TIFF0007706613000013.tif55170

[0111] TIFF0007706613000014.tif67170

[0112]

Number

[0113] TIFF0007706613000016.tif34170

[0114]

Number

[0115] TIFF0007706613000018.tif34170

[0116] FIG. 12A is a cross-sectional view of an example speed reducer 200 including a trochoid gear. FIG. 12B is a cross-sectional view of another example speed reducer 201 including a trochoid gear. The speed reducer 200 includes an internal gear 210 composed of a plurality of internal gear pins 214 rotatably attached inside an outer cylinder 212, and an external gear 220 meshing with the internal gear 210. Deceleration is achieved by the difference between the number of the plurality of internal gear 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 the plurality of internal gear pins 214. The outer shape of the external gear 220 is defined by an epitrocoid parallel curve. The speed reducer 201 includes an external gear 221 composed of a plurality of external gear pins 224 rotatably attached inside an inner cylinder 222, and an internal gear 211 meshing with the external gear 221. Deceleration is achieved by the difference between the number of the plurality of external gear pins 224 and the number of teeth of the internal gear 211. In many cases, the number of the plurality of external gear pins 224 is one less than the number of teeth of the internal gear 211. The outer shape of the internal gear 211 is defined by a hypotrocoid parallel curve. Hereinafter, the case of FIG. 12A will be described. For the internal gear 211 as shown in FIG. 12B, since the epitrocoid parallel curve of the external gear 220 as shown in FIG. 12A may be applied to the hypotrocoid parallel curve, the description thereof is omitted.

[0117] TIFF0007706613000019.tif39170

[0118] Let the radius of the internal gear pin 214 be R OP Then, the XY coordinates (x, y) of the 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), cosθ, and sinθ 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] However, φ is the intermediate variable for drawing the epitrochoid curve. Rp is the radius of the pitch circle PC (base circle BC) of the internal gear pin 214. Zb is the number of teeth of the internal gear pin 214. One period of Φ is 2πZb. Za is the number of teeth of the external gear 8. x is the correction coefficient for determining the curvature of the epitrochoid curve. Let the radius of the rolling circle in the model for drawing the epitrochoid curve be 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 (Equation 31) As t increases, the curvature of the epitrochoid curve decreases, and as t decreases, the curvature of the epitrochoid curve increases. Here, for example, when φ = 2nπ + φ0 (n: integer, 0 ≤ φ0 < 2π), the relationship between φ0 from 0 to 2π and t is stored in the memory 20. That is, the same value of t is applied with a period of 2π. When φ is determined, t is determined from the said 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, the point P0 in FIG. 13A is obtained by setting the intermediate variable φ to 0. The point P0 that coincides with the first intersection point SP(s) of the target curve TCL(s) can be obtained from the (x, y) values when the intermediate variable φ is 0. The point P1 that coincides with the second intersection point EP(h) of the target curve TCL(s) can be obtained from the (x, y) values when the intermediate variable φ is π. The contact target point PP(s) is the (x, y) whose value of x 2 +y 2 is closest to Rp 2 and can be obtained as an approximate solution.

[0123] TIFF0007706613000022.tif86170

[0124] The XY coordinates (x(i), y(i)) of the points on the model curve MCL(s, i)) are expressed as follows based on (x, y) represented by (Equations 24) and (Equations 25) and the candidate value e(i). x(i) = x (Equation 34) y(i) = y + e(i) (Equation 35) TIFF0007706613000023.tif61170

[0125] TIFF0007706613000024.tif29170

[0126] In a cycloid gear, the pitch circle PC coincides with the base circle BC. Outside the base circle BC, the target curve TCL(s) is represented by an epicycloid, and inside the base circle BC, the target curve TCL(s) is represented by a hypocycloid. An epicycloid is represented by the locus of a point on a circle when an outer rolling circle with a radius Re rolls without slipping on the base circle BC. A hypocycloid is represented by the locus of a point on a circle when an inner rolling circle with a radius Rh rolls without slipping on the base circle BC.

[0127] Therefore, among the model curves MCL(s,i), the XY coordinates (x(i,θe), y(i,θe)) of an arbitrary point on the epicycloid are represented by the following matrix.

[0128]

Number

[0129] Among the model curves MCL(s,i), the XY coordinates (x(i,θh), y(i,θh)) of an arbitrary point on the hypocycloid are represented by the following matrix.

[0130]

Number

[0131] TIFF0007706613000027.tif58170

[0132] The machine tool 100, error measurement method, interpreter 26 that provides an instruction to cause the computer 1C to execute the error measurement method, actuator control library 27, and sensor processing library 28 according to this embodiment estimate the error e between the gear shape (outer peripheral surface PS) of the workpiece W1 and the target shape 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 contacts the surface of the workpiece W1, using the cross-sectional model M(i) (model curve MCL(h,i)). Therefore, since it is not necessary to move the touch probe 150 until it contacts both of two teeth of the gear, the gear error can be measured using the touch probe 150 selected regardless of the gear shape.

[0133] Also, since the machine tool 100, gear manufacturing method, interpreter 26 that provides an instruction to cause the computer 1C to execute the gear manufacturing method, actuator control library 27, and sensor processing library 28 according to this embodiment can process the first command to the fifth command, by causing the machine tool 100 to read the machining program 22 including the first command to the fifth command, a series of operations of rough machining, error measurement, and finish machining can be automatically executed by the machine tool 100. <Modification Example> In the above-described embodiment, the case where the contact target point PP(s) is on the pitch circle PC of the gear product has been described, but it may be another point on the target curve TCL(s). In that case, the contact target point PP(s) can be determined using (Equation 1), (Equation 2), and the like. Also, although the model of the error e has been described for the model in which the target curve is shifted in the Y-axis direction, by adding an offset of the error e to the base circle radius Rb, an involute curve, a trochoid parallel curve, an epicycloid curve, and a hypocycloid curve are generated, and the model curve MCL(s,i) may be generated. In this case, the separation direction is not limited to a specific axial direction and is in all radial directions with respect to the gear rotation axis A4.

[0134] The G310, G311, G312, G340, and G344 commands in FIG. 7 are commands for spur gears and helical gears of involute gears. However, dedicated commands that can be separately applied to bevel gears, trochoid gears, and cycloid gears of involute gears are prepared. Similar to the G310, G311, G312, G340, and G344 commands, the interpreter 26, actuator control library 27, and sensor processing library 28 of the control device 1 may process the dedicated commands. By adding parameters specific to bevel gears, trochoid gears, and cycloid gears of involute gears as arguments to the G310, G311, G312, G340, and G344 commands, these gears can also be processed in the same way as spur gears and helical gears of involute gears. Also, the above-mentioned first command to fifth command may be integrated into one, or at least two of them may be partially integrated into one command. Specifically, the fourth command, fifth command, and second command may be integrated into one command.

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

[0136] The above-mentioned workpiece gripper may be a holding device such as a vise that can grip the workpiece instead of the above-mentioned workpiece 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-described embodiment, an example was shown in which when the machine tool 100 receives a predetermined command by the machining program 22, the error detection method according to FIG. 4 is implemented. However, the error detection method according to FIG. 4 may be implemented by a dedicated measuring device as disclosed in Japanese Patent Application Laid-Open No. 2006-234775. In this case, the configuration of the computer 1C described above is provided with the dedicated measuring device. Further, the error detection method according to FIG. 4 may be implemented not only by a command from the machining program 22 but also by any input by the user.

[0138] In the present application, "comprise" and its derivatives are non-limiting terms for explaining the existence of components and do not exclude the existence of other components not described. This also applies to "have", "include" and their derivatives.

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

[0140] Ordinal numbers such as "first" and "second" are merely terms for identifying configurations and do not have other meanings (for example, a specific order, etc.). For example, just because there is a "first element" does not implicitly mean that there is a "second element", nor does the existence of a "second element" implicitly mean the existence of a "first element".

[0141] Terms such as "substantially", "about", and "approximately" representing a degree may mean a reasonable amount of deviation so that the final result does not change significantly. All numerical values described in the present application may be interpreted as including terms such as "substantially", "about", and "approximately".

[0142] In the present application, the phrase "at least one of A and B" should be interpreted as including only A, only B, and both A and B.

[0143] In view of the above disclosure, it is obvious that various changes and modifications of the present invention are possible. Therefore, the present invention may be implemented in a manner different from the specific disclosure of this application without departing from the spirit of the present invention.

Claims

1. A workpiece holding device configured to hold a workpiece rotatably with respect to a rotation axis, A tool holding device configured to hold any one of a touch probe and at least one tool, An actuator configured to relatively move the tool holding device with respect to the workpiece holding device, A control device configured to control the tool holding device and the actuator and execute error measurement processing, Comprising, The error measurement processing is, Based on the posture of the workpiece machined into a gear shape held by the workpiece holding device with respect to the rotation axis, determine the approach start point and approach direction of the touch probe held by the tool holding device, Control the actuator to move the touch probe in the approach direction from the approach start point, Obtain the center position of the tip sphere of the touch probe when the touch probe contacts the surface of the workpiece due to the movement, Determine a candidate value for the error between the gear shape and the target shape of the gear product, Based on the candidate value, the target shape, and the posture, generate a cross-sectional model representing the cross-sectional shape of the tooth surface, which is defined to move away from the rotation axis in the radial direction with respect to the rotation axis, Obtain the minimum distance between the cross-sectional model and the center position, Change the candidate value, and determine 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 less than the allowable value as the error, Including, Machine tool.

2. Further comprising a tool changer configured to exchange any one of the touch probe and the at least one tool held by the tool holding device with another one of the tools, The machine tool according to claim 1.

3. The control device is, Configure the tool changer to selectively hold the first tool, the second tool, and the touch probe among the at least one tool by the tool holding device, and be configured to receive commands from the first command to the third command, When receiving the first command, configure to control the actuator to machine the workpiece into the gear shape with the first tool, When receiving the second command, configure to execute the error measurement processing, configured to control the actuator so as to adjust the movement path of the second tool based on the error and manufacture the gear product when receiving the third command The machine tool according to claim 2

4. held rotatably with respect to the rotation axis, and causing a computer to determine an approach start point and an approach direction of the touch probe based on the posture of the workpiece machined into a gear shape with respect to the rotation axis controlling an actuator to move the touch probe in the approach direction from the approach start point causing the computer to obtain the center position of the tip sphere of the touch probe when the touch probe contacts the surface of the workpiece by the movement causing the computer to calculate an error between the gear shape and the target shape of the gear product based on the center position including causing the computer to calculate the error determining a candidate value of the error generating a cross-sectional model representing a cross-sectional shape of a tooth surface, defined to be away from the rotation axis in a radial direction with respect to the rotation axis, based on the candidate value, the target shape, and the posture obtaining a 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 an absolute value of a difference between the minimum distance and the radius of the tip sphere is equal to or less than an allowable value 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 to be the direction of the normal vector of the tangent plane of the target shape at the contact target point when the gear product is arranged in the posture or the reverse thereof The approach start point is determined at a position facing in the reverse direction of the approach direction from the contact target point The error measurement method according to claim 4

6. A first plane perpendicular to the tangent plane and including the contact target point is defined The cross-sectional model is represented by a model curve obtained by shifting a target curve passing through the contact target point among a plurality of curves represented by cutting the target shape by the first plane in a separation direction away from the rotation axis on the first plane The error measurement method according to claim 5

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

8. The minimum distance is the distance between the center position and the closest point having the minimum distance from the center position among a plurality of points on the model curve. The error measurement method according to claim 6.

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

10. The model curve can represent each coordinate of a two-dimensional coordinate system defining a position on the first plane by a mediating variable. The positions of the plurality of points on the first plane are obtained by changing the mediating variable 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 arranged so that the posture of the workpiece becomes a predetermined posture, or a coordinate system for moving the touch probe corresponding to the posture of the workpiece is set. further comprising The error measurement method according to claim 4.

12. When the computer receives a first command according to any one of claims 4 to 10, the computer controls the actuator so that the workpiece is machined into the gear shape with a first tool held by a tool holding device of a machine tool. When the computer receives a second command, the computer controls the actuator to move the touch probe according to the error measurement method according to any one of claims 4 to 11 so that the computer calculates the error. When the computer receives a 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 so that the gear product is manufactured with the second tool. A gear manufacturing method including this.

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

14. A computer program comprising an instruction to cause the computer to execute any one of the error measurement methods according to claims 4 to 11 during execution by the computer.

15. A computer program comprising an instruction to cause the computer to execute the gear manufacturing method according to claim 12 during execution by the computer.

Images