Machine tool and hob phase alignment method

Abstract

To provide a machine tool and a method for phasing a hob that can align the phase of a hob with a gear with a simple configuration. [Solution] The machine tool includes a servo motor (171) having an encoder (176) for rotating a hob (61), and a control device (200). The hob (61) and the gear (71) are positioned relative to each other so that a cutting edge (62) of the hob (61) faces a first tooth (72A) and a second tooth (72B) of the gear (71) with a gap provided in the direction of the rotation axis of the hob (61), and when the hob (61) is rotated with the servo motor (171) in a servo-off state, the control device (200) is configured to be able to use a first rotational position (Pa) when the cutting edge (62) contacts the first tooth (72A) and a second rotational position (Pb) when the cutting edge (62) contacts the second tooth (72B), which are acquired based on the output from the encoder (176).

Description

[Technical Field]

[0001] The present invention relates to a machine tool and a method for phasing a hob. [Background technology]

[0002] For example, Japanese Patent Application Laid-Open No. 2003-165024 (Patent Document 1) discloses an initial phase alignment device and an initial phase alignment method for a gear grinding machine that aligns the phase of a grinding tool with a spiral groove at the time of initial meshing between the grinding tool and the workpiece in order to grind the workpiece.

[0003] The initial phase alignment device includes a servo gain setting unit that sets the servo gain of the work axis, a correction pulse adding unit that adds a correction pulse to the output of the work axis encoder that detects the rotation angle of the work axis, an accumulating pulse setting unit that sets a reference value for the accumulating pulse, and a contact position detection unit that obtains contact position data of the work axis when the accumulating pulse increases due to contact between the tooth surface of the work and the grinding surface of the grinding tool and reaches the reference value.

[0004] In addition, various gear machining devices are disclosed in Japanese Patent Laid-Open No. 2019-118977 (Patent Document 2), Japanese Patent Laid-Open No. 2019-115948 (Patent Document 3), and Japanese Patent Laid-Open No. 4-193414 (Patent Document 4). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-165024 [Patent Document 2] Japanese Patent Application Publication No. 2019-118977 [Patent Document 3] Japanese Patent Application Publication No. 2019-115948 [Patent Document 4] Japanese Patent Application Publication No. 4-193414 Summary of the Invention [Problem to be solved by the invention]

[0006] In the initial phase alignment method for a gear grinding machine disclosed in the aforementioned Patent Document 1, a correction pulse is added to the output of the work shaft encoder to rotate the work shaft, and when the accumulated pulse reaches a reference value, contact position data of the work shaft when the tooth surface of the workpiece comes into contact with the grinding surface of the grinding tool is obtained, thereby automating the initial phase alignment process.

[0007] However, implementing such a method requires the provision of a contact position detector, etc., which makes it difficult to configure the gear grinding machine simply. In particular, when gears are machined using a general-purpose machine tool rather than a dedicated gear grinding machine, there is a need to avoid providing the machine tool with a component that is used only for initial phase alignment.

[0008] An object of the present invention is to provide a machine tool and a method for phasing a hob that are capable of phasing a hob relative to a gear with a simple configuration. [Means for solving the problem]

[0009] A machine tool according to the present invention is a general-purpose machine tool capable of machining gears using a hob and also capable of machining workpieces other than gears. The machine tool includes an encoder, a servo motor for rotating the hob, and a control device for controlling the machine tool. The gear has first and second teeth adjacent to each other in the circumferential direction of the gear. The hob has a cutting edge. The hob and the gear are positioned relative to each other so that the cutting edge faces the first and second teeth with a gap in the direction of the rotation axis of the hob. When the hob is rotated with the servo motor in the servo-off state, the control device is configured to be able to use a first rotational position when the cutting edge contacts the first tooth and a second rotational position when the cutting edge contacts the second tooth, which are acquired based on the output from the encoder.

[0010] The hob phasing method according to the present invention is a method for phasing a hob with respect to a gear in a general-purpose machine tool that can machine gears using the hob and can also machine workpieces other than gears. The machine tool includes an encoder, a servo motor for rotating the hob, and a control device for controlling the machine tool. The gear has first and second teeth adjacent to each other in the circumferential direction of the gear. The hob has a cutting edge. The hob phase alignment method includes the steps of relatively positioning the hob and the gear so that the cutting edge faces the first tooth and the second tooth with a gap in the direction of the rotation axis of the hob; setting the servo motor to a servo-off state; rotating the hob with the servo motor in the servo-off state to bring the cutting edge into contact with the first tooth and the second tooth; identifying a first rotational position when the cutting edge contacts the first tooth and a second rotational position when the cutting edge contacts the second tooth, which are obtained by a control device based on the output from an encoder; and calculating a third rotational position located at the center of the first rotational position and the second rotational position. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a machine tool and a method for phasing a hob that are capable of phasing a hob with respect to a gear with a simple configuration. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a front view showing a machine tool according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing how a gear is finished by the machine tool in FIG. 1. [Figure 3] 3 is an enlarged view of the workpiece and hob in the area surrounded by the two-dot chain line III in FIG. 2. FIG. [Figure 4] FIG. 2 is a block diagram showing a configuration for gear machining in the machine tool in FIG. 1. [Figure 5] 5 is a diagram showing the input / output relationship (servo-on state) between the control device, the display unit, and the servo motor for the CT axis in FIG. 4. FIG. [Figure 6] 5 is a diagram showing the input / output relationship (servo-off state) between the control device, the display unit, and the servo motor for the CT axis in FIG. 4. FIG. [Figure 7] FIG. 10 is a diagram showing a first step of measuring the cutting edge position of the cutting edge. [Figure 8] FIG. 10 is a diagram showing a second step of measuring the cutting edge position of the cutting edge. [Figure 9] FIG. 10 is a diagram showing a third step of measuring the cutting edge position of the cutting edge. [Figure 10] 10 is a flowchart showing the flow of a hob phase alignment method. [Figure 11] FIG. 5 is a functional block diagram showing the control device in FIG. 4. [Figure 12] FIG. 10 is a functional block diagram showing a control device when a third rotation position is automatically calculated. DETAILED DESCRIPTION OF THE INVENTION

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the accompanying drawings, in which the same or corresponding elements are designated by the same reference numerals.

[0014] 1 is a front view showing a machine tool according to an embodiment of the present invention, in which the interior of machine tool 100 is shown by seeing through cover body 52 that forms the exterior of machine tool 100.

[0015] 1, machine tool 100 in this embodiment is a general-purpose machine tool that is capable of machining gears using a hob and is also capable of machining workpieces other than gears. Machine tool 100 is not a dedicated machine intended only for machining gears.

[0016] Machine tool 100 is a multi-tasking machine equipped with a turning function in which a tool is brought into contact with a rotating workpiece to machine the workpiece, and a milling function in which a tool is brought into contact with the workpiece to machine the workpiece. Machine tool 100 is an NC (Numerically Controlled) machine tool in which various operations for machining the workpiece are automated by computer numerical control.

[0017] In this specification, for the convenience of explaining the configuration of machine tool 100, the axis that is parallel to the rotation axis of the workpiece and extends horizontally will be referred to as the "Z-axis," the axis that is perpendicular to the Z-axis and extends horizontally will be referred to as the "Y-axis," and the axis that extends vertically will be referred to as the "X-axis."

[0018] First, a description will be given of the overall structure of the machine tool 100. The machine tool 100 has a bed 41, a first workpiece spindle 11, a second workpiece spindle 16, a tool spindle 21, and a tool rest 31.

[0019] The bed 41 is a base member for supporting the first work spindle 11, the second work spindle 16, the tool spindle 21, the tool rest 31, etc., and is installed on the floor of a factory, etc. The bed 41 is made of metal such as cast iron.

[0020] The first work spindle 11 and the second work spindle 16 are capable of holding a workpiece. The first work spindle 11 and the second work spindle 16 face each other in the Z-axis direction. The first work spindle 11 and the second work spindle 16 are provided mainly to rotate the workpiece during turning using a fixed tool. The first work spindle 11 is rotatable around a rotation center axis 101 parallel to the Z-axis. The second work spindle 16 is rotatable around a rotation center axis 102 parallel to the Z-axis. The first work spindle 11 and the second work spindle 16 are provided with a first chuck mechanism 13 and a second chuck mechanism 18, respectively, for detachably gripping the workpiece.

[0021] The machine tool 100 further has a servo motor 161 (see FIG. 4 described later). The servo motor 161 is provided on the first work spindle 11. The servo motor 161 corresponds to a motor for rotating the first work spindle 11 around the rotation central axis 101. The rotation central axis 101 corresponds to the "C axis" indicated next to the servo motor 161 in FIG. 4.

[0022] The first workpiece spindle 11 is fixed on a bed 41. The second workpiece spindle 16 is movable in the Z-axis direction by various feed mechanisms, guide mechanisms, motors, and the like.

[0023] The machine tool 100 may have a tailstock for supporting the center of rotation of the workpiece held by the first workpiece spindle 11, instead of the second workpiece spindle 16. In this case, the tailstock is disposed opposite the first workpiece spindle 11 in the Z-axis direction.

[0024] The tool spindle 21 is capable of holding a tool. The tool spindle 21 is rotatable around a rotation center axis 103 parallel to the X-axis in a reference posture described below. The tool spindle 21 has a built-in clamping mechanism (not shown) for detachably holding a tool.

[0025] The tool spindle 21 can also rotate around a rotation center axis 104 parallel to the Y axis (B-axis rotation). The rotation range of the tool spindle 21 is, for example, within a range of ±120° based on a reference position (the position shown in FIG. 1) in which the spindle end surface 23 of the tool spindle 21 faces downward.

[0026] The tool spindle 21 is supported on a bed 41 by a column or the like (not shown). The tool spindle 21 can be moved in the X-axis direction, the Y-axis direction, and the Z-axis direction by various feed mechanisms, guide mechanisms, motors, etc. provided on the column or the like.

[0027] The tool rest 31 is capable of holding tools. The tool rest 31 is provided below the tool spindle 21. The tool spindle 21 is arranged above the rotational axis 101 of the first work spindle 11 and the rotational axis 102 of the second work spindle 16, while the tool rest 31 is arranged below the rotational axis 101 of the first work spindle 11 and the rotational axis 102 of the second work spindle 16. The tool rest 31 is of a so-called turret type, and multiple tools are attached radially to perform rotational indexing.

[0028] The tool rest 31 has a swivel unit 32 and multiple tool holders (not shown). The swivel unit 32 is swivelable around a swivel center axis 105 parallel to the Z axis. The swivel unit 32 has an overall disk shape with its thickness oriented in the axial direction of the swivel center axis 105. The multiple tool holders (not shown) are made of block bodies capable of holding tools. The multiple tool holders are attached to the outer peripheral surface of the swivel unit 32. The multiple tool holders are lined up in the circumferential direction of the swivel center axis 105. As the swivel unit 32 swivels around the swivel center axis 105, the tools held in the tool holders move in the circumferential direction. The tool used for workpiece machining is indexed to a position at a predetermined angle in the circumferential direction of the swivel center axis 105.

[0029] The tool rest 31 has a milling function for rotating a tool held in a tool holder. The tool rest 31 further has a servo motor 171 (see FIG. 4 described later) and a power transmission mechanism (not shown). The servo motor 171 is built into the swivel unit 32. The power transmission mechanism is built into the tool holder. When a tool held in the tool rest 31 is used for milling, the rotational motion output from the servo motor 171 is transmitted to the tool via the power transmission mechanism (not shown).

[0030] The tool rest 31 can be moved in the X-axis direction and the Z-axis direction by various feed mechanisms, guide mechanisms, motors, and the like.

[0031] Machine tool 100 further includes servo motor 181 and servo motor 191 (see FIG. 4 below). Servo motor 181 corresponds to the motor for moving tool post 31 in the X-axis direction. Servo motor 191 corresponds to the motor for moving tool post 31 in the Z-axis direction.

[0032] The tool spindle 21 and tool rest 31 have the common function of holding a tool. The tool spindle 21 may be called a first tool rest, and the tool rest 31 may be called a second tool rest.

[0033] Machine tool 100 further has a cover body 52. ​​Cover body 52 forms the exterior of machine tool 100 and also defines machining area 51. Machining area 51 is a space where workpiece machining is performed, and is sealed by cover body 52 to prevent foreign matter such as chips or cutting oil resulting from workpiece machining from leaking out of machining area 51.

[0034] Although not shown in FIG. 1, machine tool 100 is further equipped with an automatic tool changer (ATC) for automatically changing the tool held by tool spindle 21, and a tool magazine for storing replacement tools.

[0035] Fig. 2 is a diagram showing how a gear is finished by the machine tool in Fig. 1. Fig. 3 is an enlarged view of the workpiece and hob in the area surrounded by the two-dot chain line III in Fig. 2. Referring to Figs. 1 to 3, machine tool 100 is capable of machining gear 71 using hob 61.

[0036] The first work spindle 11 holds a workpiece W on which a gear 71 is formed. The gear 71 has a plurality of teeth 72. The plurality of teeth 72 are provided on the outer peripheral surface of the workpiece W. The plurality of teeth 72 are aligned in the circumferential direction of the rotation center axis 101.

[0037] As an example, the workpiece W is a curvilinear coupling for a table of a machine tool, and the gear 71 meshes with a gear that inputs rotational motion from a motor to the curvilinear coupling. The gear 71 may be a spur gear. The gear 71 may have a diameter of 300 mm or more. The type of gear machined using the present invention is not particularly limited.

[0038] A hob machining unit 60 is attached to the tool rest 31. The hob machining unit 60 has a hob 61 and the aforementioned power transmission mechanism (not shown). The hob 61 is rotatable about a rotation center axis 106 that is inclined with respect to the Y axis by the lead angle of the hob 61. The hob 61 has a cutting edge 62 that is thread-shaped. The cutting edge 62 extends intermittently in a spiral shape around the rotation center axis 106. When a gear is machined by the hob machining unit 60 held on the tool rest 31, the rotational motion output from the servo motor 171 is transmitted to the hob 61 via a power transmission mechanism (not shown).

[0039] The rotation center axis 106 corresponds to the "CT axis" indicated on the servo motor 171 in FIG.

[0040] The flow of the method for machining the gear 71 will be described. First, rough machining is performed on the workpiece W to form the gear 71 on the outer peripheral surface of the workpiece W. Next, the workpiece W on which the gear 71 has been formed is removed from the machine tool 100. Next, a hardening process is performed on the workpiece W. Next, the hardened workpiece W is loaded back into the machine tool 100 and attached to the first workpiece spindle 11.

[0041] Next, the gear 71 is subjected to a finish machining to remove distortion caused by the hardening process. FIGS. 1 to 3 show the manner in which the gear 71 is finished. As shown in FIG. 3, the gear 71 has a first tooth 72A and a second tooth 72B that are adjacent in the circumferential direction of the rotation axis 101. The cutting edge 62 of the hob 61 is disposed in a valley portion between the first tooth 72A and the second tooth 72B. The cutting edge 62 meshes with the first tooth 72A and the second tooth 72B. The cutting edge 62 contacts the tooth flanks of the first tooth 72A and the second tooth 72B. The gear 71 is finish-machined by synchronously rotating the gear 71 and the hob 61 about the rotation axis 101 and the rotation axis 106, respectively.

[0042] As described above, in order to mesh the gear 71 with the cutting edge 62 of the hob 61, it is necessary to align the phase of the hob 61 with that of the gear 71 before finishing the gear 71.

[0043] More specifically, a touch probe is attached to the tool spindle 21, and the phase of the teeth 72 of the gear 71 is measured using the touch probe. The phase of the teeth 72 of the gear 71 is measured every time a hardened workpiece W is loaded into the machine tool 100. In addition, the cutting edge position of the cutting edge 62 is measured so that the cutting edge 62 of the hob 61 is positioned at the center position of the valley portion of the tooth 72 of the gear 71. The cutting edge position of the cutting edge 62 is measured every time a new hob 61 is attached to the tool post 31.

[0044] Next, a method for phasing the hob 61 with respect to the gear 71 will be described in detail. Fig. 4 is a block diagram showing the configuration for gear machining in the machine tool in Fig. 1. Fig. 5 is a diagram showing the input / output relationship (servo-on state) between the control device, display unit, and CT axis servo motor in Fig. 4.

[0045] 4 and 5, machine tool 100 further has an operation panel 120. Operation panel 120 has a display unit 140 and an operation unit 130. Display unit 140 is formed, for example, by a liquid crystal panel. Display unit 140 displays various information related to machining in machine tool 100. Operation unit 130 is formed, for example, by a touch panel type operation panel, switches, or other input interface. Operation unit 130 accepts input of various commands or information by an operator of machine tool 100.

[0046] The machine tool 100 further includes a control device 200. The control device 200 controls the operation of the machine tool 100.

[0047] The components of the control device 200 are realized by hardware including computing units such as a CPU (Central Processing Unit) and various computer processors, storage devices such as memory or storage, and wired or wireless communication lines connecting them, as well as software stored in the storage devices and supplying processing instructions to the computing units. The computer programs may be configured by device drivers, an operating system, various application programs located at higher layers than these, or libraries that provide common functions to these programs.

[0048] The control device 200 has a numerical control device 110. The numerical control device 110 executes a machining program that has been designed in advance. The machining program is written as an NC (Numerical Control) program. The numerical control device 110 controls servo drivers 151, 152, 153, and 154 (described later) in accordance with the machining program, and machines the workpiece W held by the first workpiece spindle 11.

[0049] The servo motor 171 has an encoder 176. The encoder 176 converts the rotation angle of the servo motor 171 into an electric signal and outputs it to the control device 200 as a feedback signal. The encoder 176 may be an optical type or a magnetic type. The encoder 176 may be an incremental type or an absolute type.

[0050] The control device 200 further includes a servo driver 151. The servo driver 151 controls the power supply to the servo motor 171 so that the servo motor 171 rotates in accordance with commands from the numerical control device 110, including a target rotation speed or a target position.

[0051] More specifically, the servo driver 151 sequentially calculates the actual rotational speed and actual rotational position of the servo motor 171 based on the output from the encoder 176, and controls the power supply to the servo motor 171 so that, for example, if the actual rotational speed is smaller than the target rotational speed, the rotational speed of the servo motor 171 increases, and if the actual rotational speed is larger than the target rotational speed, the rotational speed of the servo motor 171 decreases.

[0052] The control device 200 controls the display on the display unit 140. The control device 200 causes the display unit 140 to display the actual rotation speed and actual rotation position of the servo motor 171.

[0053] The control device 200 further includes a servo driver 152, a servo driver 153, and a servo driver 154. The servo driver 152, the servo driver 153, and the servo driver 154 are provided corresponding to the servo motor 181, the servo motor 191, and the servo motor 161, respectively. The servo motor 181, the servo motor 191, and the servo motor 161 include an encoder 186, an encoder 196, and an encoder 166, respectively.

[0054] The configurations of the servo driver 152, the servo driver 153, and the servo driver 154 are similar to the configuration of the servo driver 151. The configurations of the encoder 186, the encoder 196, and the encoder 166 are similar to the configuration of the encoder 176.

[0055] FIG. 6 is a diagram showing the input / output relationship (servo-off state) between the control device, the display unit, and the CT axis servo motor in FIG.

[0056] 5 is a state in which feedback control of servo motor 171 by servo driver 151 is operating based on the output from encoder 176. When power is supplied to machine tool 100, for example, a servo-on signal is input to servo driver 151, thereby obtaining the servo-on state of servo motor 171. In the servo-on state, when servo motor 171 stops, feedback control operates to maintain the rotational position, and the rotating shaft of servo motor 171 is locked.

[0057] 6 is a state in which feedback control of the servo motor 171 by the servo driver 151 based on the output from the servo driver 151 is stopped. When an operator operates a specific button provided on the operation unit 130, the input of a servo-on signal to the servo driver 151 is turned off, thereby obtaining the servo-off state of the servo motor 171. A command for putting the servo motor 171 into the servo-off state may be written in the NC program input to the numerical control device 110. In the servo-off state, since feedback control is stopped, the locked state of the rotating shaft of the servo motor 171 is released.

[0058] Furthermore, in this embodiment, even when the servo motor 171 is in a servo-off state, the encoder 176 is configured to be able to output an electric signal indicating the rotation angle of the servo motor 171 to the control device 200. The control device 200 calculates the actual rotation speed and actual rotation position of the servo motor 171 based on the output from the encoder 176, and causes the calculated actual rotation speed and actual rotation position of the servo motor 171 to be displayed on the display unit 140.

[0059] Figures 7 to 9 are diagrams showing steps for measuring the cutting edge position of the cutting edge. The ranges shown in Figures 7 to 9 correspond to the range shown in Figure 3. Figure 10 is a flowchart showing the flow of a hob phase alignment method.

[0060] Referring to Figures 1, 4, and 6 to 10, in the machine tool 100 of this embodiment, the hob 61 and the gear 71 are positioned relative to each other so that the cutting edge 62 faces the first tooth 72A and the second tooth 72B with a gap in the axial direction of the rotation center axis 106 (CT axis) of the hob 61, and when the hob 61 is rotated with the servo of the servo motor 171 in the servo-off state, the control device 200 is configured to be able to use the first rotational position Pa when the cutting edge 62 contacts the first tooth 72A and the second rotational position Pb when the cutting edge 62 contacts the second tooth 72B, which are obtained based on the output from the encoder 176.

[0061] 1 and 10, first, a hardened workpiece W is attached to the first workpiece spindle 11, and the hobbing unit 60 is attached to the tool rest 31 (S101).

[0062] Next, the phase of the gear 71 formed on the workpiece W is measured (S102). In this step, a touch probe is attached to the tool spindle 21. The tool spindle 21 is moved in the X-, Y-, and Z-axis directions to position the contact of the touch probe in the valley portion of the tooth 72 between the first tooth 72A and the second tooth 72B. The workpiece W is rotated in one direction and the other around the rotation center axis 101 (C-axis), and the contact of the touch probe is brought into contact with the first tooth 72A and the second tooth 72B, thereby obtaining position data for the first tooth 72A and the second tooth 72B.

[0063] The touch probe outputs the acquired position data of the first tooth 72A and the second tooth 72B to the control device 200. The control device 200 calculates the angle between the centers of the first tooth 72A and the second tooth 72B based on the position data from the touch probe.

[0064] Next, the position of the cutting edge of the cutting edge 62 of the hob 61 is measured. As shown in Figures 7 and 10, first, the cutting edge of the cutting edge 62 of the hob 61 is positioned relative to the gear 71 (S103).

[0065] In this step, the tool rest 31 is moved in the X-axis direction and the Z-axis direction to position the cutting edge 62 of the hob 61 between the first tooth 72A and the second tooth 72B of the gear 71. As shown in FIG. 7 , the cutting edge 62 faces the first tooth 72A and the second tooth 72B with a gap in the axial direction of the rotation center axis 106 (CT-axis) of the hob 61. The tip end 62t of the cutting edge 62 may be positioned radially outward of the reference circle 76 of the gear 71 in the rotation center axis 101 (C-axis). The tip end 72t of the first tooth 72A and the second tooth 72B may be positioned radially inward of the reference circle 66 of the cutting edge 62 in the rotation center axis 101 (C-axis).

[0066] 6 and 10, next, the servo motor 171 is set to the servo-off state (S104). In this step, for example, the operator sets the servo motor 171 to the servo-off state by operating the operation unit 130. As a result, the feedback control of the servo motor 171 is stopped, and the locked state of the rotating shaft of the servo motor 171 is released.

[0067] As shown in Figures 6, 8 and 10, next, the hob 61 is manually rotated to bring the cutting edge 62 into contact with the first tooth 72A, thereby identifying the first rotational position Pa when the cutting edge 62 comes into contact with the first tooth 72A (S105).

[0068] In this step, the worker holds the hob 61 and rotates it in one direction around the rotation central axis 106 (CT axis) to bring the cutting edge 62 into contact with the first tooth 72A. Because the servo motor 171 is in the servo-off state, the locked state of the rotating shaft of the servo motor 171 is released, so the worker can rotate the hob 61 manually.

[0069] While the hob 61 rotates, the encoder 176 outputs an electric signal indicating the rotation angle of the servo motor 171 to the control device 200. The control device 200 calculates the rotation position of the servo motor 171 based on the output from the encoder 176 and displays the calculated rotation position on the display unit 140. Through the display on the display unit 140, the operator identifies the first rotation position Pa when the cutting edge 62 contacts the first tooth 72A.

[0070] As shown in Figures 6, 9 and 10, the hob 61 is then manually rotated to bring the cutting edge 62 into contact with the second tooth 72B, thereby identifying the second rotational position Pb at which the cutting edge 62 comes into contact with the second tooth 72B (S106).

[0071] In this step, the worker rotates the hob 61 in the other direction around the rotation central axis 106 (CT axis) while gripping it, and brings the cutting edge 62 into contact with the second tooth 72B. Through the display on the display unit 140, the worker identifies the second rotation position Pb when the cutting edge 62 comes into contact with the second tooth 72B.

[0072] For example, when the servo motor 171 rotates the hob 61 and the cutting edge 62 comes into contact with the first tooth 72A or the second tooth 72B, which is the opposite of normal gear cutting, there is a problem in that the cutting edge 62 can easily be damaged. To address this problem, the servo motor 171 is set to the servo-off state in step S104, and the hob 61 is manually rotated in steps S105 and S106 to bring the cutting edge 62 into contact with the first tooth 72A and the second tooth 72B, thereby preventing excessive force from being applied from the gear 71 to the hob 61. This effectively prevents the cutting edge 62 from being damaged.

[0073] As shown in FIG. 10, next, a third rotational position Pc located at the center between the first rotational position Pa and the second rotational position Pb is calculated, and the third rotational position Pc is input to the control device 200 (S107).

[0074] In this step, the operator calculates the third rotational position Pc based on the first rotational position Pa identified in step S105 and the second rotational position Pb identified in step S106. As an example, if the first rotational position Pa is 75° and the second rotational position Pb is 77°, the third rotational position Pc is 76°. The operator displays an input screen for common variables on the display unit 140 and operates the operation unit 130 to input the third rotational position Pc as a parameter for identifying the cutting edge position of the hob 61.

[0075] By the above steps, the steps of matching the phase of the hob 61 with the gear 71 are completed.

[0076] Fig. 11 is a functional block diagram showing the control device in Fig. 4. Referring to Fig. 11, the control device 200 has a signal acquisition unit 211, a display control unit 212, and a parameter acquisition unit 213.

[0077] Signal acquisition unit 211 acquires a signal from encoder 176. Display control unit 212 controls image display on display unit 140. Parameter acquisition unit 213 acquires various parameters referenced in the NC program for operating machine tool 100.

[0078] 10, while the hob 61 is rotating, the encoder 176 sequentially outputs electric signals indicating the rotation angle of the servo motor 171 to the control device 200. The signal acquisition unit 211 acquires the signal from the encoder 176. The display control unit 212 causes the display unit 140 to display the rotation position of the servo motor 171, which changes from moment to moment, based on the signal from the encoder 176 acquired by the signal acquisition unit 211.

[0079] The operation unit 130 receives an input operation of the third rotational position Pc by the operator and outputs the operation signal to the control device 200. The parameter acquisition unit 213 acquires the third rotational position Pc as a parameter for specifying the cutting edge position of the hob 61 based on the operation signal from the operation unit 130.

[0080] In the present embodiment, display on display unit 140 has been described as an example of how control device 200 uses first rotational position Pa and second rotational position Pb, but the machine tool of the present invention is not limited to this. For example, control device 200 may be configured to automatically calculate third rotational position Pc that is located at the center of first rotational position Pa and second rotational position Pb.

[0081] 12 is a functional block diagram showing a control device for automatically calculating the third rotational position. Referring to FIG. 12, control device 200 has signal acquisition unit 211, first / second rotational position identification unit 216, third rotational position calculation unit 217, and parameter acquisition unit 213.

[0082] In a step corresponding to S105 in FIG. 10 , the operator holds the hob 61 and rotates it in one direction about the rotation central axis 106 (CT axis) to bring the cutting edge 62 into contact with the first tooth 72A. While the hob 61 rotates, the encoder 176 sequentially outputs electrical signals indicating the rotation angle of the servo motor 171 to the control device 200. The signal acquisition unit 211 acquires the signals from the encoder 176. When the cutting edge 62 contacts the first tooth 72A, the change in the rotation angle of the servo motor 171 stops. The first / second rotation position identification unit 216 identifies, as the first rotation position Pa, the rotation position corresponding to the rotation angle of the servo motor 171 when the change stops.

[0083] In a step corresponding to S106 in FIG. 10, the operator rotates the hob 61 in the other direction around the rotation central axis 106 (CT axis) while gripping it, bringing the cutting edge 62 into contact with the second teeth 72B. While the hob 61 rotates, the encoder 176 sequentially outputs electrical signals indicating the rotation angle of the servo motor 171 to the control device 200. The signal acquisition unit 211 acquires the signals from the encoder 176. When the cutting edge 62 contacts the second teeth 72B, the change in the rotation angle of the servo motor 171 stops. The first / second rotation position identification unit 216 identifies, as the second rotation position Pb, the rotation position corresponding to the rotation angle of the servo motor 171 at which the change stops.

[0084] 10 , the third rotational position calculation unit 217 calculates a third rotational position Pc located at the center between the first rotational position Pa and the second rotational position Pb, based on the first rotational position Pa and the second rotational position Pb identified by the first / second rotational position identification unit 216. The parameter acquisition unit 213 acquires the third rotational position Pc calculated by the third rotational position calculation unit 217 as a parameter for identifying the cutting edge position of the hob 61.

[0085] To summarize the configuration of machine tool 100 according to the embodiment of the present invention as described above, machine tool 100 according to the embodiment is a general-purpose machine tool that is capable of machining gear 71 using hob 61 and is also capable of machining workpieces other than gears. Machine tool 100 has encoder 176, servo motor 171 for rotating hob 61, and control device 200 for controlling machine tool 100. Gear 71 has first tooth 72A and second tooth 72B that are adjacent to each other in the circumferential direction of gear 71. Hob 61 has cutting edge 62. When the hob 61 and the gear 71 are positioned relative to each other so that the cutting edge 62 faces the first tooth 72A and the second tooth 72B with a gap in the axial direction of the rotation center axis 106 of the hob 61, and the hob 61 is rotated with the servo motor 171 in the servo-off state, the control device 200 is configured to be able to use the first rotational position Pa when the cutting edge 62 contacts the first tooth 72A and the second rotational position Pb when the cutting edge 62 contacts the second tooth 72B, which are obtained based on the output from the encoder 176.

[0086] With this configuration, the control device 200 can identify the cutting edge position of the cutting edge 62 of the hob 61 relative to the gear 71 by using the first rotational position Pa when the cutting edge 62 contacts the first tooth 72A and the second rotational position Pb when the cutting edge 62 contacts the second tooth 72B. In this case, when the hob 61 is rotated with the servo motor 171 in the servo-off state, the control device 200 acquires the first rotational position Pa and the second rotational position Pb based on the output from the encoder 176, so it is sufficient to use the original function of the encoder 176. Therefore, the phase of the hob 61 relative to the gear 71 can be aligned with a simple configuration.

[0087] Machine tool 100 further includes a display unit 140. Control device 200 causes display unit 140 to display the first rotational position Pa and the second rotational position Pb.

[0088] According to this configuration, the operator can identify the first rotation position Pa and the second rotation position Pb through the display on the display unit 140.

[0089] The control device 200 may also calculate a third rotational position Pc that is located at the center of the first rotational position Pa and the second rotational position Pb. With this configuration, the third rotational position Pc can be more easily acquired as a parameter for identifying the position of the cutting edge of the cutting edge 62 of the hob 61 relative to the gear 71.

[0090] Furthermore, the encoder 176 is configured to be able to output an electrical signal indicating the rotation angle of the servo motor 171 to the control device 200 when the servo motor 171 is in a servo-off state. With this configuration, by turning the servo motor 171 into a servo-off state, the hob 61 can be rotated manually, and while the hob 61 is rotating, the first rotation position Pa and the second rotation position Pb can be obtained by the control device 200 based on the output from the encoder 176.

[0091] The machine tool 100 further includes a first workpiece spindle 11 as a workpiece spindle, a turret-type tool rest 31, and a hob machining unit 60 attached to the tool rest 31 and holding a hob 61.

[0092] With this configuration, phase alignment between the gear held by the first work spindle 11 and the hob 61 held by the hob processing unit 60 attached to the tool rest 31 can be performed with a simple configuration.

[0093] The machining unit holding the hob 61 may be attached to the tool spindle 21. In view of the machining stroke, the embodiment in which the hob machining unit 60 is attached to the tool rest 31 is suitably applied to machining large diameter gears such as curvic couplings for the table of a machine tool.

[0094] In addition, the hob phase alignment method in this embodiment is a method of aligning the phase of the hob 61 with the gear 71 in a general-purpose machine tool 100 that is capable of machining the gear 71 using the hob 61 and is also capable of machining workpieces other than gears. The hob phase alignment method includes the steps of: relatively positioning the hob 61 and the gear 71 so that the cutting edge 62 faces the first tooth 72A and the second tooth 72B with a gap in the axial direction of the rotation center axis 106 of the hob 61 (S103); setting the servo motor 171 to a servo-off state (S104); rotating the hob 61 with the servo motor 171 in the servo-off state to bring the cutting edge 62 into contact with the first tooth 72A and the second tooth 72B (S105 / S106); identifying a first rotational position Pa when the cutting edge 62 contacts the first tooth 72A and a second rotational position Pb when the cutting edge 62 contacts the second tooth 72B, which are obtained by the control device 200 based on the output from the encoder 176 (S105 / S106); and calculating a third rotational position Pc located at the center of the first rotational position Pa and the second rotational position Pb (S107).

[0095] According to this configuration, the phase of the hob 61 relative to the gear 71 can be matched with a simple configuration.

[0096] In this embodiment, the machine tool of the present invention is described as a multi-task machine equipped with a first workpiece spindle 11, a second workpiece spindle 16, a tool spindle 21 (first tool rest), and a tool rest 31 (second tool rest), but is not limited to this. The machine tool of the present invention may also be a lathe equipped with a workpiece spindle and a second tool rest.

[0097] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0098] 11 First workpiece spindle, 13 First chuck mechanism, 16 Second workpiece spindle, 18 Second chuck mechanism, 21 Tool spindle, 23 Spindle end surface, 31 Turret, 32 Swivel unit, 41 Bed, 51 Machining area, 52 Cover body, 60 Hob machining unit, 61 Hob, 62 Cutting edge, 62t, 72t Tip, 66, 76 Reference circle, 71 Gear, 72 Teeth, 72A First tooth, 72B Second tooth, 100 Machine tool, 101, 102, 103, 106 Rotation center axis, 104, 105 Swivel center axis, 110 Numerical control device, 120 Operation panel, 130 Operation unit, 140 Display unit, 151, 152, 153, 154 Servo driver, 161, 171, 181, 191 Servo motor, 166, 176, 186, 196 encoder, 200 control device, 211 signal acquisition unit, 212 display control unit, 213 parameter acquisition unit, 216 second rotation position identification unit, 217 third rotation position calculation unit, Pa first rotation position, Pb second rotation position, Pc third rotation position, W workpiece.

Claims

1. A general-purpose machine tool capable of machining gears using a hob and also capable of machining workpieces other than gears, a servo motor for rotating the hob; an encoder capable of outputting an electrical signal indicating a rotation angle of the servo motor; a control device that has a servo driver that performs feedback control of the servo motor based on an output from the encoder and controls the machine tool, the gear has a first tooth and a second tooth adjacent to each other in a circumferential direction of the gear, The hob has a cutting edge, The hob and the gear are relatively positioned so that the cutting edge faces the first tooth and the second tooth with a gap in the rotation axis direction of the hob, and when the hob is rotated with the servo motor in a servo-off state, the control device is configured to be able to use a first rotational position when the cutting edge contacts the first tooth and a second rotational position when the cutting edge contacts the second tooth, which are acquired based on the output from the encoder, In the machine tool, the servo-off state of the servo motor is a state in which the feedback control operation of the servo motor by the servo driver based on the output from the encoder is stopped.

2. Further comprising a display unit, The machine tool according to claim 1 , wherein the control device displays the first rotational position and the second rotational position on the display unit.

3. The machine tool according to claim 1 , wherein the control device calculates a third rotational position located at the center of the first rotational position and the second rotational position.

4. 3. The machine tool according to claim 1, wherein the encoder is configured to be able to output an electric signal indicating a rotation angle of the servo motor to the control device when the servo motor is in a servo-off state.

5. a work spindle for rotating the work; A turret-type tool rest, The machine tool according to claim 1 or 2, further comprising a hob machining unit attached to the tool rest and holding the hob.

6. A method for phasing a hob with respect to a gear in a general-purpose machine tool that is capable of machining a gear using a hob and also capable of machining a workpiece other than a gear, comprising: The machine tool comprises: a servo motor for rotating the hob; an encoder capable of outputting an electrical signal indicating a rotation angle of the servo motor; a control device that has a servo driver that performs feedback control of the servo motor based on an output from the encoder and controls the machine tool, the gear has a first tooth and a second tooth adjacent to each other in a circumferential direction of the gear, The hob has a cutting edge, The hob phase alignment method includes: Relatively positioning the hob and the gear so that the cutting edge faces the first tooth and the second tooth with a gap in the rotation axis direction of the hob; setting the servo motor to a servo-off state; Rotating the hob in a servo-off state of the servo motor to bring the cutting edge into contact with the first tooth and the second tooth; Identifying a first rotational position when the cutting edge contacts the first tooth and a second rotational position when the cutting edge contacts the second tooth, the first rotational position being acquired by the control device based on an output from the encoder; calculating a third rotational position located at the center of the first rotational position and the second rotational position, The servo-off state of the servo motor is a state in which the operation of the feedback control of the servo motor by the servo driver based on the output from the encoder is stopped.

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