Machine tools, machining methods, and programs

Abstract

We provide technology to improve the accuracy of gear cutting processes. [Solution] The machine tool comprises a workpiece spindle and a tool holder. The tool has multiple teeth of different lengths arranged in an arc in order of tooth length. The machine tool comprises a rotation drive unit that rotates the workpiece spindle, a feed drive unit that moves the tool holder, and a control unit. The control unit repeatedly performs a gear cutting process that forms grooves on the workpiece surface by reciprocating the tool holder in the direction of the rotation axis at each position from a predetermined start position to a predetermined end position in the radial direction of the rotation axis, and an angle adjustment process that rotates the workpiece spindle by a predetermined angle. The starting position when performing the gear cutting process for the second time is closer to the workpiece surface than the first time, or the distance at which the gear cutting tool is initially moved from the starting position to the workpiece side when performing the gear cutting process for the second time is greater than the distance at which the tool is initially moved from the starting position to the workpiece side when performing the gear cutting process for the first time.

Description

Technical Field

[0001] The present disclosure relates to a machine tool, a machining method, and a program.

Background Art

[0002] Japanese Unexamined Patent Application Publication No. 2023-180411 (Patent Document 1) discloses a broaching machine that uses a broach to cut the surface of a workpiece. The broach is a long, rod-shaped tool with a structure in which a large number of cutting edges are arranged on the outer circumference. Also, the broach has dimensions that gradually increase from the cutting edges on the tip side (roughing edges) to the cutting edges on the end side (finishing edges).

[0003] The broaching machine disclosed in Patent Document 1 cuts the surface of the workpiece by linearly driving the broach in the longitudinal direction of the broach, so that each cutting edge cuts the surface of the workpiece. As a result, the broaching machine can complete rough cutting to finish cutting of the workpiece by simply driving the broach in a linear direction once.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The broaching machine disclosed in Patent Document 1 is a dedicated machine that only performs broaching. On the other hand, depending on the machine tool, various machining operations such as turning are possible. A machine tool capable of turning has a workpiece spindle for rotatably holding a workpiece. In such a machine tool, it is desired to realize tooth cutting similar to broaching without using a dedicated tool such as that used in a broaching machine.

[0006] This disclosure was made to solve the problems described above, and in one aspect, its objective is to provide a technology for achieving gear cutting in a machine tool equipped with a workpiece spindle. [Means for solving the problem]

[0007] In one example of this disclosure, a machine tool is provided. The machine tool comprises a work spindle configured to hold a workpiece and a tool holder configured to hold a tool for gear cutting. The tool has a plurality of teeth of different lengths arranged in an arc in order of tooth length. The machine tool comprises a rotation drive unit for rotating the work spindle about a rotation axis along the axial direction of the work spindle, a feed drive unit for moving the tool holder, and a control unit for controlling the rotation drive unit and the feed drive unit. The control unit performs a gear cutting process by reciprocating the tool holder in the direction of the rotation axis at each position from a predetermined starting position to a predetermined ending position in the radial direction of the rotation axis, so that the plurality of teeth form grooves on the machined surface of the workpiece, and an angle adjustment process for rotating the work spindle by a predetermined angle based on the completion of the gear cutting process. The gear cutting process and the angle adjustment process are performed repeatedly. The starting position during the second execution of the gear cutting process is closer to the machined surface of the workpiece than the starting position during the first execution of the gear cutting process, or the distance the gear cutting tool is initially moved from the starting position towards the workpiece during the second execution of the gear cutting process is greater than the distance the gear cutting tool is initially moved from the starting position towards the workpiece during the first execution of the gear cutting process.

[0008] In one example of this disclosure, the multiple tooth heights include adjacent first and second teeth. The tooth height of the first tooth is higher than the tooth height of the second tooth. The control unit rotates the workpiece spindle in the rotational process such that the first tooth then cuts the groove formed by the second tooth.

[0009] In one example of this disclosure, the angle adjustment process described above involves rotating the workpiece spindle by a predetermined angle toward the first tooth of the first and second teeth.

[0010] In one example of this disclosure, the machined surface is the inner circumferential surface of the workpiece. The plurality of teeth are arranged along the circumferential direction of the outer circumferential surface of the tool.

[0011] In one example of this disclosure, the machined surface is the outer circumferential surface of the workpiece. The plurality of teeth are arranged in an arc shape opposite to the arc along the circumferential direction of the outer circumferential surface of the tool.

[0012] Another example of this disclosure provides a machining method using a machine tool. The machine tool comprises a workpiece spindle configured to hold a workpiece and a tool holder configured to hold a tool for gear cutting. The tool has a plurality of teeth of different lengths arranged in an arc in order of tooth length. The machine tool comprises a rotation drive unit for rotating the workpiece spindle about a rotation axis along the axial direction of the workpiece spindle, a feed drive unit for moving the tool holder, and a control unit for controlling the rotation drive unit and the feed drive unit. The machining method performs a gear cutting process in which the plurality of teeth form grooves on the machined surface of the workpiece by reciprocating the tool holder in the direction of the rotation axis at each position from a predetermined starting position to a predetermined ending position in the radial direction of the rotation axis, and an angle adjustment process in which the workpiece spindle is rotated by a predetermined angle based on the completion of the gear cutting process. The gear cutting process and the angle adjustment process are performed repeatedly. The starting position during the second execution of the gear cutting process is closer to the machined surface of the workpiece than the starting position during the first execution of the gear cutting process, or the distance the gear cutting tool is initially moved from the starting position towards the workpiece during the second execution of the gear cutting process is greater than the distance the gear cutting tool is initially moved from the starting position towards the workpiece during the first execution of the gear cutting process.

[0013] Another example of this disclosure provides a program for use in a machine tool. The machine tool comprises a workpiece spindle configured to hold a workpiece and a tool holder configured to hold a tool for gear cutting. The tool has a plurality of teeth of different lengths arranged in an arc in order of tooth length. The machine tool comprises a rotation drive unit for rotating the workpiece spindle about a rotation axis along the axial direction of the workpiece spindle, a feed drive unit for moving the tool holder, and a control unit for controlling the rotation drive unit and the feed drive unit. The program causes the machine tool to perform a gear cutting process in which the plurality of teeth form grooves on the machined surface of the workpiece by reciprocating the tool holder in the direction of the rotation axis at each position from a predetermined starting position to a predetermined ending position in the radial direction of the rotation axis, and an angle adjustment process in which the workpiece spindle is rotated by a predetermined angle based on the completion of the gear cutting process. The gear cutting process and the angle adjustment process are performed repeatedly. The starting position during the second execution of the gear cutting process is closer to the machined surface of the workpiece than the starting position during the first execution of the gear cutting process, or the distance the gear cutting tool is initially moved from the starting position towards the workpiece during the second execution of the gear cutting process is greater than the distance the gear cutting tool is initially moved from the starting position towards the workpiece during the first execution of the gear cutting process.

[0014] The above and other objects, features, aspects and advantages of the present invention will become apparent from the following detailed description relating to the invention, which will be understood in conjunction with the accompanying drawings. [Brief explanation of the drawing]

[0015] [Figure 1] This is a diagram showing the external appearance of a machine tool. [Figure 2] This is a diagram showing an example of the configuration of a machine tool. [Figure 3] This figure shows an example of a drive mechanism for a machine tool. [Figure 4] This figure shows an example of the hardware configuration of the control unit. [Figure 5] It is a diagram showing an example of a toothing tool. [Figure 6] It is a diagram showing a state where the toothing tool is performing toothing on the workpiece. [Figure 7] It is a diagram showing the process of gear machining on the inner peripheral surface of the workpiece W from the Y-axis direction. [Figure 8] It is a diagram showing the process of gear machining following FIG. 7 from the Z-axis direction. [Figure 9] It is a diagram showing the process of gear machining following FIG. 8 from the Y-axis direction. [Figure 10] It is a diagram showing a toothing tool having two teeth. [Figure 11] It is a diagram showing the positional relationship between the toothing tool and the workpiece W when the rotation axis of the tool spindle is at the starting position. [Figure 12] It is a diagram showing the positional relationship between the toothing tool and the workpiece W when the rotation axis of the tool spindle is at the end position. [Figure 13] It is a diagram showing the positional relationship between the toothing tool and the workpiece W when the rotation axis of the tool spindle is at the starting position. [Figure 14] It is a flowchart showing the flow of the toothing process. [Figure 15] It is a diagram showing a state where the toothing tool according to the modification example is performing toothing on the outer peripheral surface of the workpiece from the direction of the rotation axis CE.

Embodiments for Carrying Out the Invention

[0016] Hereinafter, each embodiment according to the present invention will be described with reference to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated. In addition, each embodiment and each modification example described below may be selectively combined as appropriate.

[0017] <A. Machine Tool 100> First, with reference to Figure 1, a machine tool 100 according to the first embodiment will be described. Figure 1 is a diagram showing the external appearance of the machine tool 100.

[0018] As used herein, "machine tool" is a concept that encompasses various devices equipped with the function of processing a workpiece. Machine tool 100 may be a horizontal machining center or a vertical machining center. Alternatively, machine tool 100 may be a cutting machine, grinding machine, multi-tasking machine, 5-axis machining center, etc. Furthermore, machine tool 100 is not limited to performing only removal processing. Machine tool 100 may perform addition processing in addition to removal processing.

[0019] The machine tool 100 has a tool storage area AR1 and a machining area AR2. The tool storage area AR1 and the machining area AR2 are separated by a cover 130.

[0020] The tool storage area AR1 is equipped with a magazine 5 and an ATC (Automatic Tool Changer) 6. The machining area AR2 is equipped with a tool spindle 30. The tool spindle 30 is an example of a tool holder 20 configured to hold a tool.

[0021] The tool spindle 30 processes the workpiece using at least one of the multiple tools held in the magazine 5. More specifically, the machine tool 100 drives the magazine 5 to move the tool corresponding to the machining process (hereinafter also referred to as the "next tool to be used") to the first tool change position. The machine tool 100 also drives the tool spindle 30 to move the tool mounted on the tool spindle 30 (hereinafter also referred to as the "used tool") to the second tool change position. Subsequently, the ATC 6 exchanges the next tool to be used, which is waiting at the first tool change position, with the used tool, which is waiting at the second tool change position. The tool exchange is performed through a door D provided in the partition between the machining area AR2 and the tool storage area AR1. The door D is a sliding door and is opened and closed by a drive source such as a motor. Subsequently, the tool spindle 30 processes the workpiece using the mounted next tool to be used.

[0022] Further, the machine tool 100 is provided with an operation panel 400. The operation panel 400 includes a display 405 for displaying various information related to machining and operation keys 406 for receiving various operations on the machine tool 100.

[0023] <B. Device Configuration of Machine Tool 100> Next, referring to FIG. 2, the device configuration of the machine tool 100 will be described. FIG. 2 is a diagram showing an example of the device configuration of the machine tool 100.

[0024] The machine tool 100 includes a bed 11, a workpiece spindle 22, an opposing workpiece spindle 27, and a tool spindle 30.

[0025] For the sake of convenience of explanation, hereinafter, the direction parallel to the rotation axis direction of the workpiece spindle 22 is also referred to as the "Z-axis direction". Also, one side in the Z-axis direction is also referred to as the "positive Z-axis side", and the other side in the Z-axis direction is also referred to as the "negative Z-axis side". In the example of FIG. 2, the left side when viewing the machining area AR2 from the front of the machine tool 100 corresponds to the "positive Z-axis side". Also, in the example of FIG. 2, the right side when viewing the machining area AR2 from the front of the machine tool 100 corresponds to the "negative Z-axis side".

[0026] Furthermore, one direction on the horizontal plane orthogonal to the Z-axis direction is also referred to as the "Y-axis direction". Also, one side in the Y-axis direction is also referred to as the "positive Y-axis side", and the other side in the Y-axis direction is also referred to as the "negative Y-axis side". In the example of FIG. 2, the back side when viewing the machining area AR2 from the front of the machine tool 100 corresponds to the "positive Y-axis side". Also, in the example of FIG. 2, the front side when viewing the machining area AR2 from the front of the machine tool 100 corresponds to the "negative Y-axis side".

[0027] Furthermore, the direction perpendicular to both the Y-axis and Z-axis directions is referred to as the "X-axis direction." Additionally, one side of the X-axis direction is called the "positive X-axis direction," and the other side is called the "negative X-axis direction." In the example in Figure 2, the direction of gravity corresponds to the positive X-axis direction. Also, in the example in Figure 2, the upward direction corresponds to the "negative X-axis direction."

[0028] Furthermore, the rotation axis of the workpiece spindle 22 is referred to as "rotation axis C". Rotation axis C is parallel to the Z-axis direction and is also the rotation axis of the opposing workpiece spindle 27.

[0029] Furthermore, the axis of rotation of the tool spindle 30 is referred to as the "axis of rotation CE". The axis of rotation CE of the tool spindle 30 is also the axis of rotation of the tool T mounted on the tool spindle 30. The direction of the axis of rotation CE changes with the rotational drive of the tool spindle 30.

[0030] The bed 11 is a base member for supporting various devices installed within the machine tool 100. In the example shown in Figure 2, the bed 11 supports the workpiece spindle 22, the opposing workpiece spindle 27, and the tool spindle 30. The bed 11 is installed on the floor of a factory or similar facility. The bed 11 is made of a metal such as cast iron.

[0031] The workpiece spindle 22 is configured to rotate while holding the workpiece W. More specifically, the workpiece spindle 22 is provided with a first chuck mechanism 23. The first chuck mechanism 23 is a mechanism for fixing the workpiece W to the workpiece spindle 22. The workpiece spindle 22 is also configured to rotate around a rotation axis C.

[0032] The opposing workpiece spindle 27 rotates the workpiece W while supporting it from the side opposite to the workpiece spindle 22. More specifically, the opposing workpiece spindle 27 is configured to be movable in the Z-axis direction by various drive mechanisms such as a motor, and can support the workpiece W from the side opposite to the workpiece spindle 22. Further, a second chuck mechanism 28 is provided on the opposing workpiece spindle 27. The second chuck mechanism 28 is a mechanism for fixing the workpiece W to the opposing workpiece spindle 27. Furthermore, the opposing workpiece spindle 27 is configured to be rotatable about the rotation axis C.

[0033] The tool spindle 30 is provided at a position higher than the workpiece spindle 22 and the opposing workpiece spindle 27. Further, the tool spindle 30 is configured to be able to hold the tool T, and holds the tool spindle 30 rotatably about the rotation axis CE. Also, the tool spindle 30 is configured to be movable in each of the X-axis direction, Y-axis direction, and Z-axis direction by various drive mechanisms such as a motor. Further, the tool spindle 30 is configured to be able to swing by various drive mechanisms such as a motor. As an example, the tool spindle 30 is configured to be rotatable about the B-axis centered on the Y-axis direction.

[0034] Various types of tools T can be mounted on the tool spindle 30 according to the machining mode. The tool T is mounted on the tool spindle 30 by the above-described ATC 6. The tool spindle 30 performs cutting by bringing the tool T into contact with the workpiece W fixed to the workpiece spindle 22. As an example, the tool T is a tooth cutting tool described later. The tool T as a tooth cutting tool performs tooth cutting on the outer peripheral surface or inner peripheral surface of the workpiece W to form a gear. The tooth cutting tool is, for example, housed in the magazine 5. When the machine tool 100 performs tooth cutting on the workpiece W, the machine tool 100 calls the tooth cutting tool housed in the magazine 5 and mounts the tooth cutting tool TC on the tool spindle 30 via the ATC 6.

[0035] <C. Drive mechanism of the machine tool 100> Next, referring to FIG. 3, the drive mechanism in the machine tool 100 will be described. FIG. 3 is a diagram showing an example of the drive mechanism of the machine tool 100.

[0036] As shown in Figure 3, the machine tool 100 includes the work spindle 22 described above, the opposing work spindle 27 described above, the tool spindle 30 described above, the control unit 50, the rotary drive unit 210, the feed drive unit 220, the feed drive unit 230A, the rotary drive unit 230B, and the rotary drive unit 230C.

[0037] The control unit 50 controls various devices that make up the machine tool 100. For example, the control unit 50 controls the rotary drive unit 210, the feed drive unit 220, the feed drive unit 230A, the rotary drive unit 230B, and the rotary drive unit 230C.

[0038] The configuration of the control unit 50 is arbitrary. The control unit 50 may consist of a single control unit or multiple control units. As an example, the control unit 50 includes at least one of a CNC (Computer Numerical Control) and a PLC (Programmable Logic Controller).

[0039] The rotary drive unit 210 is a drive mechanism for rotating the workpiece spindle 22 around the rotation axis C (see Figure 2). In the example shown in Figure 3, the rotary drive unit 210 consists of a motor driver 211C and a motor 212C.

[0040] The motor driver 211C sequentially receives input from the control unit 50 for the target rotation angle or target rotation speed of the workpiece spindle 22, and outputs a current to the motor 212C corresponding to the target rotation angle or target rotation speed. As a result, the workpiece held by the workpiece spindle 22 rotates around the rotation axis C. The motor 212C may be an AC motor, a stepping motor, a servo motor, or any other type of motor.

[0041] The feed drive unit 220 is a drive mechanism for driving the opposing workpiece spindle 27. The feed drive unit 220 may consist of a single drive unit or multiple drive units. In the example shown in Figure 3, the feed drive unit 220 consists of a motor driver 221Z and a motor 222Z.

[0042] The motor driver 221Z sequentially receives input of a target position for the opposing workpiece spindle 27 from the control unit 50 and outputs a current corresponding to the target position to the motor 222Z. As a result, the motor 222Z moves the opposing workpiece spindle 27 to any position in the Z-axis direction. The motor 222Z may be an AC motor, a stepping motor, a servo motor, or any other type of motor.

[0043] The feed drive unit 230A is a drive mechanism for moving the tool spindle 30. The feed drive unit 230A may consist of a single drive unit or multiple drive units. In the example shown in Figure 3, the feed drive unit 230A consists of motor drivers 231X to 231Z and motors 232X to 232Z.

[0044] The motor driver 231X sequentially receives input from the control unit 50 regarding the target position of the tool spindle 30 in the X-axis direction, and outputs a current corresponding to the target position to the motor 232X. This allows the motor 232X to drive the tool spindle 30 to any position in the X-axis direction. The motor 232X may be an AC motor, a stepping motor, a servo motor, or any other type of motor.

[0045] The motor driver 231Y sequentially receives input from the control unit 50 regarding the target position of the tool spindle 30 in the Y-axis direction, and outputs a current corresponding to that target position to the motor 232Y. This allows the motor 232Y to drive the tool spindle 30 to any position in the Y-axis direction. The motor 232Y may be an AC motor, a stepping motor, a servo motor, or any other type of motor.

[0046] The motor driver 231Z sequentially receives input from the control unit 50 regarding the target position of the tool spindle 30 in the Z-axis direction, and outputs a current corresponding to the target position to the motor 232Z. As a result, the motor 232Z moves the tool spindle 30 to any position in the Z-axis direction. The motor 232Z may be an AC motor, a stepping motor, a servo motor, or any other type of motor.

[0047] The rotary drive unit 230B is a drive mechanism for rotating the tool spindle 30 around an axis perpendicular to the rotation axis CE. The rotary drive unit 230B may consist of a single drive unit or multiple drive units. In the example shown in Figure 3, the rotary drive unit 230B consists of a motor driver 231B and a motor 232B.

[0048] The motor driver 231B sequentially receives input from the control unit 50 for a target rotation angle or target rotation speed of the tool spindle 30 centered on the Y-axis direction, and outputs a current to the motor 232B corresponding to the target rotation angle or target rotation speed. The motor 232B rotates the tool spindle 30 around the B-axis centered on the Y-axis direction. The motor 232B may be an AC motor, a stepping motor, a servo motor, or any other type of motor.

[0049] The rotary drive unit 230C is a drive mechanism for rotating the tool spindle 30 around the rotation axis CE (see Figure 2). In the example shown in Figure 3, the rotary drive unit 230C consists of a motor driver 231C and a motor 232C.

[0050] The motor driver 231C sequentially receives from the control unit 50 an input of the target rotation angle or the target rotation speed of the tool spindle 30, and outputs a current corresponding to the target rotation angle or the target rotation speed to the motor 232C. The motor 232C rotationally drives the tool spindle 30 with the rotation axis CE as the rotation center. The motor 232C may be an AC motor, a stepping motor, a servo motor, or other types of motors.

[0051] <D. Hardware Configuration of Control Unit 50> Next, referring to FIG. 4, the hardware configuration of the control unit 50 shown in FIG. 3 described above will be explained. FIG. 4 is a diagram showing an example of the hardware configuration of the control unit 50.

[0052] The control unit 50 includes a control circuit 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, a communication interface 104, and an auxiliary storage device 120. These components are connected to an internal bus 109.

[0053] The control circuit 101 is constituted by, for example, at least one integrated circuit. The integrated circuit can be constituted by, for example, at least one CPU, at least one GPU (Graphics Processing Unit), at least one ASIC (Application Specific Integrated Circuit), at least one FPGA (Field Programmable Gate Array), or a combination thereof.

[0054] The control circuit 101 controls the operation of the control unit 50 by executing various programs such as a control program 122. Based on receiving an execution instruction of the control program 122, the control circuit 101 reads the control program 122 from the auxiliary storage device 120 or the ROM 102 into the RAM 103. The RAM 103 functions as a working memory and temporarily stores various data necessary for the execution of the control program 122.

[0055] The communication interface 104 is an interface for performing periodic communication with an external device using a field network. As the field network, for example, EtherCAT (registered trademark), EtherNet / IP (registered trademark), CC-Link (registered trademark), or CompoNet (registered trademark) is adopted.

[0056] The auxiliary storage device 120 is a storage medium such as a hard disk or a flash memory. The auxiliary storage device 120 stores a control program 122, setting parameters 124, and the like. The setting parameter 124 is a parameter referred to by the control program 122. Details of the setting parameter 124 will be described later.

[0057] Note that the storage locations of the control program 122 and the setting parameters 124 are not limited to the auxiliary storage device 120, and may be stored in a storage area of the control circuit 101 (for example, a cache memory), the ROM 102, the RAM 103, an external device (for example, a server), or the like.

[0058] Further, the control program 122 may be provided not as a single program but incorporated into a part of an arbitrary program. In this case, various processes according to the present embodiment are realized in cooperation with an arbitrary program. Even a program that does not include such a part of the module does not deviate from the gist of the control program 122 according to the present embodiment. Furthermore, a part or all of the functions provided by the control program 122 may be realized by dedicated hardware. Furthermore, the control unit 50 may be configured in a form such as a so-called cloud service in which at least one server executes a part of the processing of the control program 122.

[0059] <E. Tooth cutting tool TC> Next, we will describe a gear cutting tool TC, which is a type of tool T, with reference to Figures 5 and 6. Figure 5 shows an example of a gear cutting tool TC. Figure 6 shows the gear cutting tool TC performing gear cutting on a workpiece W.

[0060] The machine tool 100 has the function of milling, which involves bringing a rotating tool T into contact with a workpiece W fixed to the workpiece spindle 22, and turning, which involves bringing a tool T into contact with a workpiece W that is being rotated by the workpiece spindle 22, as well as gear cutting on the workpiece W. A gear cutting tool, which is a type of tool T, is used for gear cutting.

[0061] In the example shown in Figure 6, a cross-section of a cylindrical workpiece W in the YZ plane is displayed, and the gear cutting tool TC is cutting gears on the inner circumferential surface of the workpiece W.

[0062] As described above, when the machine tool 100 performs gear cutting on the workpiece W, it retrieves the gear cutting tool TC stored in the magazine 5 and mounts the gear cutting tool TC on the tool spindle 30 via the ATC 6. The machine tool 100 then performs gear cutting on the machined surface of the workpiece W by reciprocating the tool spindle 30 in the direction of the rotation axis CE, with the rotation axis CE of the tool spindle 30 parallel to the rotation axis CE of the workpiece spindle 22. Gear cutting may be performed only on the forward stroke when the tool spindle 30 is reciprocated, or it may be performed on both the forward and return strokes when the tool spindle 30 is reciprocated. Details of this gear cutting process will be described later.

[0063] The gear cutting tool TC consists of a main body TC1 and a tooth section TC2. The main body TC1 has a roughly cylindrical shape centered on the axis ACT. The axis ACT is the central axis of the main body TC1. The tooth section TC2, also called a tip (or insert), is configured to be detachable from the main body TC1.

[0064] The axis ACT of the gear cutting tool TC is parallel to the rotation axis CE when mounted on the tool spindle 30. Typically, the axis ACT of the gear cutting tool TC and the rotation axis CE of the tool spindle 30 are coaxial. Therefore, in the following explanation, the axis ACT of the gear cutting tool TC and the rotation axis CE of the tool spindle 30 will be described as synonymous axes.

[0065] In the TC2 tooth region, multiple teeth with varying heights are formed in an arc shape. This height refers to the distance from the root to the tip. The root corresponds to the groove formed by two adjacent teeth. The tip corresponds to the top of the tooth.

[0066] In the example in Figure 5, three teeth TE1 to TE3 with different tooth heights are shown. More specifically, the tooth height of tooth TE1 is higher than that of tooth TE2. The tooth height of tooth TE2 is higher than that of tooth TE3. Tooth TE1, which has the highest tooth height, is a finishing tooth used to finish the machined surface of the workpiece. Tooth TE3, which has the lowest tooth height, is a roughing tooth used for rough machining.

[0067] The difference in tooth height between adjacent teeth is, for example, constant. More specifically, if the tooth height of the tallest tooth TE1 is "H" and the number of teeth of the gear cutting tool TC is "Tn", then the difference in tooth height between adjacent teeth is "H / Tn".

[0068] In the following, unless otherwise specified, teeth TE1 to TE3 will also be referred to as tooth TE, with the exception of at least one of them. Note that the number of teeth TE formed on the gear cutting tool TC does not need to be three; two or more are sufficient.

[0069] The gear cutting tool TC shown in Figure 5 is a tool for cutting gears on the inner circumferential surface of a workpiece W. In such a gear cutting tool TC, each tooth TE is arranged along the circumferential direction of the outer surface of the gear cutting tool TC. More specifically, the tips of each tooth TE are arranged at approximately equal intervals in the circumferential direction of the outer surface of the gear cutting tool TC. In addition, the tip surfaces of each tooth TE extend in a direction parallel to the axis ACT.

[0070] More specifically, each tooth TE has a tooth tip TT, a rake face RF, and a flank face FF.

[0071] The tooth tip TT is the portion that is pressed against the workpiece W. In other words, the tooth tip TT corresponds to the ridge line portion where the rake face RF and the flank face FF intersect.

[0072] In the example of FIG. 6, an acute tooth tip TT is shown, but the angle of the tooth tip TT does not necessarily have to be acute. Also, the tooth tip TT does not necessarily have to be sharp and may be rounded.

[0073] The rake face RF is one of the two faces extending from the tooth tip TT and is the face that contacts the workpiece W in the feed drive direction of the tool spindle 30. In other words, the rake face RF is the face along which the chips of the workpiece W flow when the workpiece W is cut with teeth.

[0074] The flank face FF is the other of the two faces extending from the tooth tip TT. That is, the flank face FF is a face that extends from the tooth tip TT in a direction different from that of the rake face RF. The flank face FF is a face provided to reduce unnecessary wear with the workpiece surface.

[0075] <F. Gear machining> As machining that can be performed by the machine tool 100 according to the embodiment, gear machining is mentioned. Gear machining is realized by repeatedly executing a "tooth cutting machining process" for forming a groove in the workpiece W and an "angle adjustment process" for rotating the workpiece spindle 22.

[0076] In the "gear cutting process," the machine tool 100 reciprocates the tool spindle 30 in the direction of the rotation axis C,CE at each position from the starting position to the ending position in the radial direction of the rotation axis C of the tool spindle 30. As this reciprocating drive is repeated, gear grooves are formed on the machined surface of the workpiece W. In the subsequent "angle adjustment process," the machine tool 100 rotates the workpiece spindle 22 by a predetermined angle. The machine tool 100 achieves gear machining of the workpiece W by repeatedly performing these "gear cutting process" and "angle adjustment process" in sequence.

[0077] The gear machining process using machine tool 100 will be explained in more detail below with reference to Figures 7 to 9. Figure 7 shows the gear machining process on the inner circumferential surface of the workpiece W, viewed from the negative side in the Y-axis direction.

[0078] Steps S1 to S3 represent the first "gear cutting process". The machine tool 100 performs multiple reciprocating drive processes in a single "gear cutting process".

[0079] More specifically, in step S1, the machine tool 100 performs the first reciprocating drive process of the tool spindle 30.

[0080] First, the machine tool 100 controls the rotation drive unit 230B described above so that the rotation axis CE of the tool spindle 30 and the rotation axis C of the workpiece spindle 22 are parallel. Next, the machine tool 100 moves the tool spindle 30 to a predetermined starting position SP1. The starting position SP1 is defined, for example, by setting parameter 124 (see Figure 4). As a result, the tooth tip of the gear cutting tool TC is positioned at coordinate P1.

[0081] Since the tool spindle 30 and the gear cutting tool TC move as a single unit, the position controlled by the command value may be a position relative to the tool spindle 30, or a position relative to the tooth tip of the gear cutting tool TC.

[0082] Next, the machine tool 100 drives the tool spindle 30 by a distance ΔDA1 in the radial direction RD of the rotation axis C of the tool spindle 30. In the example in Figure 7, the radial direction RD is shown as a direction parallel to the X axis, but it can be any direction perpendicular to the tool spindle 30 (i.e., a direction on the XY plane).

[0083] Next, the machine tool 100 drives the tool spindle 30 in the positive Z-axis direction, feeding it by a distance ΔD. This causes the teeth of the gear cutting tool TC to pass inside the inner surface of the workpiece W. The machine tool 100 may cut the workpiece surface from the first reciprocating drive, or it may start cutting the workpiece surface from a predetermined number of reciprocating drive cycles or later. In the example in Figure 7, the machine tool 100 does not cut the workpiece surface during the first reciprocating drive.

[0084] Next, the machine tool 100 retracts the gear cutting tool TC from the inner surface of the workpiece W based on the fact that the gear cutting tool TC has left the inner surface of the workpiece W. For example, the machine tool 100 drives the tool spindle 30 by a distance ΔDA1 in the opposite direction to the radial direction RD (i.e., the positive side of the X-axis direction). This retracts the tool spindle 30 to the starting position SP1.

[0085] Next, the machine tool 100 drives the tool spindle 30 in the negative Z-axis direction by a distance ΔD. This causes the tooth tip of the gear cutting tool TC to be positioned at coordinate P1 again.

[0086] Next, in step S2, the machine tool 100 performs a second reciprocating drive process of the tool spindle 30.

[0087] More specifically, the machine tool 100 drives the tool spindle 30 radially RD by a distance ΔDA2. The distance ΔDA2 during the second reciprocating drive is longer than the distance ΔDA1 during the first reciprocating drive. The difference between distance ΔDA1 and distance ΔDA2 corresponds to the cutting width of the workpiece W. This cutting width is, for example, 0.05 mm. The cutting width per pass may always be constant or may be gradually reduced.

[0088] Next, the machine tool 100 drives the tool spindle 30 in the positive Z-axis direction by a distance ΔD. Then, based on the fact that the gear cutting tool TC has left the inner surface of the workpiece W, the machine tool 100 retracts the gear cutting tool TC from the inner surface of the workpiece W. For example, the machine tool 100 drives the tool spindle 30 in the opposite direction to the radial direction RD (i.e., the positive X-axis direction) by a distance ΔDA2. This retracts the tool spindle 30 to the starting position SP1.

[0089] Next, the machine tool 100 drives the tool spindle 30 in the negative Z-axis direction by a distance ΔD. This causes the tooth tip of the gear cutting tool TC to be positioned at coordinate P1 again.

[0090] The machine tool 100 repeatedly performs the above reciprocating drive process until the gear cutting tool TC reaches a predetermined end position EP. Step S3 shows the Nth reciprocating drive process at the end position EP.

[0091] More specifically, the machine tool 100 drives the gear cutting tool TC, located at coordinate P1, radially RD by a distance ΔDA3. Next, the machine tool 100 drives the tool spindle 30 in the positive Z-axis direction by a distance ΔD. Subsequently, the machine tool 100 drives the tool spindle 30 in the opposite direction to the radial RD (i.e., positive X-axis direction) by a distance ΔDA3. Then, the machine tool 100 drives the tool spindle 30 in the negative Z-axis direction by a distance ΔD.

[0092] Through the above steps S1 to S3, the machine tool 100 reciprocates the tool spindle 30 in the direction of the rotation axis CE at each position from the starting position SP1 to the ending position EP in the radial direction RD.

[0093] Figure 8 shows the gear machining process following Figure 7, viewed from the negative side of the Z-axis direction. As shown in step S4, after the execution of steps S1 to S3, grooves G1 to G3 are formed on the inner circumferential surface of the workpiece W. Groove G1 is formed by tooth TE1. Groove G2 is formed by tooth TE2. Groove G3 is formed by tooth TE3.

[0094] In step S5, after the first gear cutting process is completed, the machine tool 100 rotates the workpiece spindle 22 by a predetermined angle Δθ. The angle Δθ is defined, for example, by setting parameter 124 (see Figure 4).

[0095] At this time, the machine tool 100 rotates the workpiece spindle 22 in the rotational direction corresponding to the tooth side with the higher tooth height. In the example of teeth TE1 to TE3 in Figure 8, the tooth height increases in a counterclockwise direction, so the machine tool 100 rotates the workpiece spindle 22 counterclockwise. More specifically, the machine tool 100 rotates the workpiece spindle 22 so that tooth TE1 faces the direction of the groove G2 formed by tooth TE2.

[0096] Figure 9 shows the gear machining process following Figure 8, viewed from the negative side of the Y-axis. While the first gear cutting process was shown in Figure 7, Figure 9 shows the second gear cutting process.

[0097] In subsequent gear cutting operations, grooves have already been formed on the workpiece surface to some extent. Therefore, the machine tool 100 sets the starting position SP2 for the second gear cutting operation closer to the workpiece surface than the starting position SP1 for the first gear cutting operation. In this embodiment, since the machined surface is the inner circumferential surface of the workpiece W, the starting position SP2 is closer to the inner circumferential surface of the workpiece W than the starting position SP1. As a result, the machine tool 100 can reduce the number of reciprocating drives of the tool spindle 30, even if the depth of cut change is set to the same amount as in the first gear cutting operation. Consequently, the machining time can be shortened. In addition, since the starting position SP2 can be brought closer to the groove formed in the first gear cutting operation, the distance over which the gear cutting tool TC travels idle can be reduced.

[0098] More specifically, in step S6, the machine tool 100 moves the tool spindle 30 to a predetermined starting position SP2 while maintaining the rotation axis CE of the tool spindle 30 and the rotation axis C of the workpiece spindle 22 in parallel. The starting position SP2 is defined, for example, by setting parameter 124 (see Figure 4). As a result, the machine tool 100 positions the tooth tip of the gear cutting tool TC at position P2.

[0099] Next, the machine tool 100 drives the tool spindle 30 in the radial direction RD by a distance ΔDB1. The distance ΔDB1 is shorter than the distance ΔDA1 described above.

[0100] Next, the machine tool 100 drives the tool spindle 30 in the positive Z-axis direction, feeding it by a distance ΔD. This causes the teeth of the gear cutting tool TC to pass inside the inner surface of the workpiece W. The machine tool 100 may cut the workpiece surface from the first reciprocating drive process shown in Figure 9, or it may start cutting the workpiece surface from a predetermined number of reciprocating drive processes or later. In the example in Figure 9, the machine tool 100 does not cut the workpiece surface during the first reciprocating drive.

[0101] Next, the machine tool 100 retracts the gear cutting tool TC from the inner surface of the workpiece W based on the fact that the gear cutting tool TC has left the inner surface of the workpiece W. For example, the machine tool 100 drives the tool spindle 30 by a distance ΔDB1 in the opposite direction to the radial direction RD (i.e., the positive side of the X-axis direction). This retracts the tool spindle 30 to the starting position SP2.

[0102] Next, the machine tool 100 drives the tool spindle 30 in the negative Z-axis direction by a distance ΔD. This causes the tooth tip of the gear cutting tool TC to be positioned again at coordinate P2.

[0103] Next, in step S7, the machine tool 100 performs a second reciprocating drive process of the tool spindle 30.

[0104] More specifically, the machine tool 100 drives the tool spindle 30 radially RD by a distance ΔDB2. The difference between distance ΔDB1 and distance ΔDB2 corresponds to the cutting width of the workpiece W. This cutting width is, for example, 0.05 mm. The cutting width per pass may always be constant or may be gradually reduced.

[0105] Next, the machine tool 100 drives the tool spindle 30 in the positive Z-axis direction by a distance ΔD. Then, based on the fact that the gear cutting tool TC has left the inner surface of the workpiece W, the machine tool 100 retracts the gear cutting tool TC from the inner surface of the workpiece W. For example, the machine tool 100 drives the tool spindle 30 in the opposite direction of the radial direction RD (i.e., the positive X-axis direction) by a distance ΔDB2. This retracts the tool spindle 30 to the starting position SP2.

[0106] Next, the machine tool 100 drives the tool spindle 30 in the negative Z-axis direction by a distance ΔD. This causes the tooth tip of the gear cutting tool TC to be positioned again at coordinate P2.

[0107] The machine tool 100 repeatedly performs a reciprocating drive process of the tool spindle 30 until the gear cutting tool TC reaches a predetermined end position EP. Step S8 shows the Mth reciprocating drive process at the end position EP. The integer "M" shown in Figure 9 is smaller than the integer "N" shown in Figure 7.

[0108] More specifically, the machine tool 100 drives the gear cutting tool TC, which is at position P2, radially RD by a distance ΔDB3. Next, the machine tool 100 drives the tool spindle 30 in the positive Z-axis direction by a distance ΔD. Then, the machine tool 100 drives the tool spindle 30 in the opposite direction of radial RD (i.e., positive X-axis direction) by a distance ΔDB3. Then, the machine tool 100 drives the tool spindle 30 in the negative Z-axis direction by a distance ΔD. This causes the tooth tip of the gear cutting tool TC to be back at coordinate P2.

[0109] Through the above steps S6 to S8, the machine tool 100 reciprocally drives the tool spindle 30 in the directions of the rotation axes C and CE at each position from the start position SP2 to the end position EP in the radial direction RD.

[0110] Thereafter, the machine tool 100 executes the rotation process of the work spindle 22 described in FIG. 8 and starts the third tooth cutting process. As described above, the machine tool 100 realizes the gear machining of the work W by repeatedly executing the tooth cutting process for forming a groove in the work W and the angle adjustment process for rotating the work spindle 22.

[0111] <G. Setting parameter 124> Next, referring to FIGS. 10 to 13, a method for calculating the above-described start position SP1 (see FIG. 7), the above-described end position EP (see FIGS. 7 and 9), and the above-described start position SP2 (see FIG. 9) will be described. FIG. 10 is a view showing a tooth cutting tool TC having two teeth TE1 and TE2 from the negative side in the Z-axis direction.

[0112] First, parameters used in the calculation of the start positions SP1 and SP2 and the end position EP will be described.

[0113] The radial axis ACX shown in FIG. 10 is an axis passing through the axis ACT and the centers of the teeth TE1 and TE2. In the example of FIG. 10, the axis ACX is directed toward the negative side in the X-axis direction.

[0114] The angle ΔR shown in FIG. 10 corresponds to the angle formed by the direction from the axis ACT toward the tooth TE1 of the finish tooth and the radial axis ACX. The angle ΔR is defined, for example, in the tool information provided by the tool manufacturer.

[0115] The "X" shown in FIG. 10 is the distance between the axis ACT and the tooth TE1 in the X-axis direction. The angle "X" is defined, for example, in the tool information provided by the tool manufacturer.

[0116] The method for calculating the starting position SP1 will be explained with reference to Figure 11. Figure 11 shows the positional relationship between the gear cutting tool TC and the workpiece W when the rotation axis CE of the tool spindle 30 is located at the starting position SP1.

[0117] The starting position SP1 in the X-axis direction is calculated using the following equation (1) in a coordinate system whose origin is the rotation axis C of the workpiece spindle 22.

[0118] (Formula (1)) TIFF0007887003000002.tif39170 The "D / 2" shown in equation (1) is a parameter for specifying the starting position SP1. "D / 2" may be pre-set or arbitrarily set by the user. "D / 2" is set to less than the radius of the inner circumference of the workpiece W.

[0119] The method for calculating the end position EP will be explained with reference to Figure 12. Figure 12 shows the positional relationship between the gear cutting tool TC and the workpiece W when the rotation axis CE of the tool spindle 30 is located at the end position EP.

[0120] The end position EP in the X-axis direction is calculated using the following equation (2) in a coordinate system with the rotation axis C of the workpiece spindle 22 as the origin.

[0121] (Formula (2)) TIFF0007887003000003.tif41170 The "E / 2" shown in equation (2) is a parameter for specifying the end position EP. "E / 2" indicates the distance between the rotation axis C of the workpiece spindle 22 and the tooth root surface of the workpiece W that is formed as a gear. "E / 2" may be pre-set or may be set arbitrarily by the user.

[0122] The method for calculating the starting position SP2 will be explained with reference to Figure 13. Figure 13 shows the positional relationship between the gear cutting tool TC and the workpiece W when the rotation axis CE of the tool spindle 30 is located at the starting position SP2.

[0123] The starting position SP2 in the X-axis direction is calculated using the following equation (3) in a coordinate system whose origin is the rotation axis C of the workpiece spindle 22.

[0124] (Formula (3)) TIFF0007887003000004.tif38170 In equation (3), "H" represents the tooth height of tooth TE1 as a finishing tooth. "Tn" represents the number of teeth of the gear cutting tool TC. "H" and "Tn" are read, for example, from the gear cutting tool TC information specified in the tool database.

[0125] If the height difference between adjacent teeth is constant, then "H / Tn" is equal to that height difference. In this case, the starting position SP2 will be a value corresponding to that height difference. That is, the starting position SP2 will be a value corresponding to the height difference between teeth TE1 and TE2, or between teeth TE2 and TE3.

[0126] <H.フローチャート> Next, with reference to Figure 14, the control flow related to the gear cutting process will be explained. Figure 14 is a flowchart showing the flow of the gear cutting process.

[0127] The process shown in Figure 14 is realized, for example, by the control unit 50 of the machine tool 100 executing the control program 122 described above. In other aspects, some or all of the process may be performed by circuit elements or other hardware.

[0128] In step S110, the control unit 50 initializes a variable "i" for managing the number of times the gear cutting process is executed. As an example, the variable "i" is initialized to "0".

[0129] In step S112, the control unit 50 controls the rotation drive unit 230B described above so that the rotation axis C of the workpiece spindle 22 and the rotation axis CE of the tool spindle 30 are parallel.

[0130] In step S114, the control unit 50 controls the feed drive unit 230A to drive the tool spindle 30 to a predetermined machining start position on the XY plane. For the first gear cutting operation, the machining start position is the start position SP1 (see Figure 7) described above. For subsequent gear cutting operations, the machining start position is the start position SP2 (see Figure 9) described above.

[0131] In step S116, the control unit 50 reciprocates the tool spindle 30 in the direction of the rotation axis CE at each position from the starting position SP1 or starting position SP2 to the ending position EP (see Figures 7 and 9). This forms grooves on the machined surface of the workpiece. The reciprocating drive process has been described above, so it will not be repeated.

[0132] In step S117, the control unit 50 increments the variable "i". That is, the control unit 50 increases the variable "i" by 1.

[0133] In step S118, the control unit 50 performs an angle adjustment process to rotate the workpiece spindle 22. This causes the control unit 50 to rotate the workpiece spindle 22 by a predetermined angle. The angle adjustment process is as described above, so its explanation will not be repeated.

[0134] In step S120, the control unit 50 determines whether the gear cutting operation is being performed for the first time. For example, the control unit 50 determines that the gear cutting operation is being performed for the first time if the variable "i" is "1". If the control unit 50 determines that the gear cutting operation is being performed for the first time (YES in step S120), it switches the control to step S122. Otherwise (NO in step S120), the control unit 50 switches the control to step S130.

[0135] In step S122, the control unit 50 updates the starting position SP1 for the gear cutting process to the starting position SP2.

[0136] In step S130, the control unit 50 determines whether to end the gear cutting process. As an example, based on the fact that the work spindle 22 has made one revolution, the control unit 50 determines to end the gear cutting process. Alternatively, based on the fact that the variable "i" has reached a predetermined number of times, the control unit 50 determines to end the gear cutting process. If the control unit 50 determines to end the gear cutting process (YES in step S130), it ends the process shown in FIG. 14. Otherwise (NO in step S130), the control unit 50 returns the control to step S114.

[0137] <I. Modified Example> Next, referring to FIG. 15, the gear cutting tool TC' according to the modified example will be described. FIG. 15 is a view showing the state in which the gear cutting tool TC' according to the modified example is performing gear cutting on the outer peripheral surface of the work W in the direction of the rotation axis CE.

[0138] In the above-described gear cutting tool TC, the teeth TE were arranged side by side in the circumferential direction of the outer peripheral surface of the gear cutting tool TC. In contrast, in the gear cutting tool TC' according to this modified example, the teeth TE are arranged in an arc shape opposite to the arc along the circumferential direction of the outer peripheral surface of the gear cutting tool TC'.

[0139] FIG. 15 shows a gear cutting tool TC' having four teeth TE1 to TE4. The teeth TE1 to TE are arranged to match the shape of the outer peripheral surface of the work W.

[0140] The machine tool 100 uses the gear cutting tool TC' according to this modified example to realize the above-described gear cutting process.

[0141] More specifically, the control unit 50 executes a gear cutting process that reciprocally drives the tool spindle 30 in the direction of the rotation axis C at each position from a predetermined start position SP1 in the radial direction RD of the rotation axis C to a predetermined end position EP in the radial direction RD. As a result, the teeth TE1 to TE4 form grooves on the outer peripheral surface of the workpiece W. Next, based on the completion of the gear cutting process, the control unit 50 executes an angle adjustment process that rotates the workpiece spindle 22 by a predetermined angle. By repeatedly executing the gear cutting process and the angle adjustment process in this order, grooves are formed on the outer peripheral surface of the workpiece W.

[0142] The start position SP2 during the execution of the second gear cutting process is closer to the outer peripheral surface of the workpiece W than the start position SP1 during the execution of the first gear cutting process. As a result, the machine tool 100 can reduce the number of reciprocating drive processes of the tool spindle 30. Consequently, the processing time can be shortened.

[0143] <J. Others> In the above description, the tool spindle 30 is given as an example of the tool holding unit 20, but the tool holding unit 20 is not limited to the tool spindle 30. As another example, the tool holding unit 20 may be a turret. The turret is configured to be rotatable about a rotation axis (hereinafter also referred to as "rotation axis CE'") parallel to the rotation axis C. The turret holds a plurality of tools at intervals in the circumferential direction about the rotation axis CE'. Typically, the turret performs turning by bringing a fixed tool held by the turret into contact with the workpiece W that is rotationally driven by the workpiece spindle 22.

[0144] In addition, the tools held by the turret include the above-described gear cutting tool TC. The turret can perform not only turning but also gear cutting using the gear cutting tool TC.

[0145] More specifically, the turret is configured to be able to feed in each of the X to Z axis directions by various drive mechanisms such as motors. The turret is driven to feed in the direction of the rotation axis CE' with the gear cutting tool TC facing the rotation axis CE', thereby achieving the gear cutting process described above. Even a machine tool equipped with such a turret can achieve the gear cutting process described herein.

[0146] In the embodiment described above, the starting position SP2 of the second gear cutting process was set to move radially closer to the workpiece side than the starting position SP1 of the first gear cutting process, but the present invention is not limited to this. That is, the starting positions SP1 of the first gear cutting process and SP2 of the second gear cutting process may not be changed, and the travel distance of the tool TC for the first gear cutting process may be changed. In other words, the initial radial travel distance ΔDA1 of the tool TC in the first gear cutting process is changed to the initial travel distance ΔD in the second gear cutting process. B1 It may be increased by a predetermined value. For example, ΔD B1 -ΔDA1 can be set based on the depth of the second deepest groove among the grooves formed in the first gear cutting operation. With this approach, the initial position setting of the tool spindle 30 does not need to be changed between the first and second gear cutting operations, making it easier to prevent interference between the workpiece and the tool spindle 30. In addition, the amount of time the tool TC misses the workpiece can be reduced in subsequent gear cutting operations, thus shortening the overall machining time.

[0147] Furthermore, the machining method according to the present invention may be used not only for machining gears, but also, for example, for machining splines.

[0148] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of Symbols]

[0149] 5 Magazine, 11 Bed, 20 Tool Holder, 22 Work Spindle, 23 First Chuck Mechanism, 27 Opposing Work Spindle, 28 Second Chuck Mechanism, 30 Tool Spindle, 50 Control Unit, 100 Machine Tool, 101 Control Circuit, 102 ROM, 103 RAM, 104 Communication Interface, 109 Internal Bus, 120 Auxiliary Storage Device, 122 Control Program, 124 Setting Parameters, 130 Cover, 210 Rotary Drive Unit, 211C Motor Driver, 212C Motor, 220 Feed Drive Unit, 221Z Motor Driver, 222Z Motor, 230A Feed Drive Unit, 230B Rotary Drive Unit, 230C Rotary Drive Unit, 231B Motor Driver, 231C Motor Driver, 231X Motor Driver, 231Y Motor Driver, 231Z Motor Driver, 232B Motor, 232C motor, 232X motor, 232Y motor, 232Z motor, 400 control panel, 405 display, 406 operation key, ACT axis, ACX axis, AR1 tool storage area, AR2 machining area, C rotary axis, CE rotary axis, CE' rotary axis, D door, EP end position, FF relief face, G1 groove, G2 groove, G3 groove, P1 coordinate, P2 coordinate, RD radial direction, RF rake face, SP1 start position, SP2 start position, T tool, TC gear cutting tool, TC1 main body, TC2 teeth, TC' gear cutting tool, TE tooth, TE1 tooth, TE2 tooth, TE3 tooth, TE4 tooth, TT tooth tip, W workpiece.

Claims

1. A workpiece spindle configured to hold a workpiece, It comprises a tool holder configured to hold a tool for gear cutting, and the tool has a plurality of teeth of different tooth lengths arranged in an arc shape in order of tooth length, A rotational drive unit for rotating the workpiece spindle, with a rotation axis along the axial direction of the workpiece spindle as the center axis, A feed drive unit for moving the tool holding unit, The system comprises a control unit for controlling the rotational drive unit and the feed drive unit, The control unit, At each position from a predetermined starting position to a predetermined ending position in the radial direction of the rotation axis, the tool holder is reciprocated in the direction of the rotation axis, thereby performing a gear cutting process in which the plurality of teeth form grooves on the machined surface of the workpiece. Based on the completion of the gear cutting process, an angle adjustment process is performed to rotate the workpiece spindle by a predetermined angle. The gear cutting process and the angle adjustment process are performed repeatedly. A machine tool in which the starting position during the second gear cutting process is closer to the machined surface of the workpiece than the starting position during the first gear cutting process.

2. The aforementioned plurality of teeth include the first and second teeth which are adjacent to each other. The height of the first tooth is greater than the height of the second tooth. The machine tool according to claim 1, wherein the control unit rotates the workpiece spindle in the angle adjustment process such that the first tooth then cuts the groove formed by the second tooth.

3. In the angle adjustment process, the workpiece spindle is rotated by a predetermined angle toward the first tooth of the first and second teeth, according to claim 2.

4. The machined surface is the inner circumferential surface of the workpiece. The machine tool according to any one of claims 1 to 3, wherein the plurality of teeth are arranged along the circumferential direction of the outer surface of the tool.

5. The machined surface is the outer circumferential surface of the workpiece. The machine tool according to any one of claims 1 to 3, wherein the plurality of teeth are arranged in an arc shape opposite to the arc along the circumferential direction of the outer surface of the tool.

6. A machining method using a machine tool comprising a work spindle configured to hold a workpiece, a tool holder configured to hold a tool for gear cutting, wherein the tool has a plurality of teeth of different tooth lengths arranged in an arc in order of tooth length, a rotation drive unit for rotating the work spindle around a rotation axis along the axial direction of the work spindle, a feed drive unit for moving the tool holder, and a control unit for controlling the rotation drive unit and the feed drive unit, At each position from a predetermined starting position to a predetermined ending position in the radial direction of the rotation axis, the tool holder is reciprocated in the direction of the rotation axis, thereby performing a gear cutting process in which the plurality of teeth form grooves on the machined surface of the workpiece. Based on the completion of the gear cutting process, an angle adjustment process is performed to rotate the workpiece spindle by a predetermined angle. The gear cutting process and the angle adjustment process are performed repeatedly. A machining method wherein the starting position during the second execution of the gear cutting process is closer to the machined surface of the workpiece than the starting position during the first execution of the gear cutting process.

7. A program for use in a machine tool comprising a work spindle configured to hold a workpiece, a tool holder configured to hold a tool for gear cutting, the tool having a plurality of teeth of different tooth lengths arranged in an arc in order of tooth length, a rotation drive unit for rotating the work spindle around a rotation axis along the axial direction of the work spindle, a feed drive unit for moving the tool holder, and a control unit for controlling the rotation drive unit and the feed drive unit, The aforementioned program is for the machine tool, At each position from a predetermined starting position to a predetermined ending position in the radial direction of the rotation axis, the tool holder is reciprocated in the direction of the rotation axis, thereby performing a gear cutting process in which the plurality of teeth form grooves on the machined surface of the workpiece. Based on the completion of the gear cutting process, an angle adjustment process is performed to rotate the workpiece spindle by a predetermined angle. The gear cutting process and the angle adjustment process are performed repeatedly. A program in which the starting position during the second execution of the gear cutting process is closer to the machined surface of the workpiece than the starting position during the first execution of the gear cutting process.

Images