EP4511189A1

EP4511189A1 - Machine tool

Info

Publication number: EP4511189A1
Application number: EP23801025.0A
Authority: EP
Inventors: Takahiro Nishiki
Original assignee: DMG Mori Co Ltd
Current assignee: DMG Mori Co Ltd
Priority date: 2022-11-16
Filing date: 2023-10-23
Publication date: 2025-02-26
Also published as: JP2024072432A; JP7443470B1; WO2024106141A1

Abstract

A machine tool includes a support frame (50) supporting a hob cutter (90) attached to a tool spindle at both ends in cooperation with a tool headstock (6). The support frame (50) is dismountably mounted onto the tool headstock (6) and fixed to the tool headstock (6) by a fixing mechanism. After the hob cutter (90) is held on the tool spindle, a controller drives the fixing mechanism to fix to the tool headstock (6) the support frame (50) supporting a non-held end of the hob cutter (90) and mounted on the tool headstock (6), and thereafter controls a tool spindle drive unit, a workpiece spindle drive unit, and a feed drive unit to machine a workpiece held on a workpiece spindle.

Description

MACHINE TOOL

The present invention relates to a machine tool including a tool support frame.

A machine tool has been known which generatively machines a tooth profile on a peripheral surface of a workpiece by synchronously rotating a hob cutter held on a tool spindle and a workpiece held on a workpiece spindle.

In some cases, this type of machine tool includes a tool changer so as to automatically change a tool held on the tool spindle (see, for example, Patent Literature 1 listed below). The tool changer performs the tool change between a tool magazine and the tool spindle. The tool magazine stores therein various types of tools, such as an end mill and a milling cutter, besides the hob cutter. In response to a command from a control unit, the tool changer selectively extracts a tool to be used in the next process from among the tools stored in the tool magazine and replaces the used tool held on the tool spindle with the extracted tool.

In the machine tool disclosed in Patent Literature 1, the hob cutter is attached to the tool spindle with only one end thereof supported. If the hob cutter is subjected to a high cutting load in machining, the free end side of the hob cutter can be elastically deformed in the direction of the cutting load because of its poor rigidity, which may result in the accuracy of machining of the tooth profile being lowered.

Accordingly, a machine tool has been proposed which prepares a tool assembly supporting both ends of the hob cutter using a support frame and integrally connecting the hob cutter and the support frame and holds the tool assembly on the tool spindle, so that the hob cutter is attached to the tool spindle with both ends thereof supported (see Patent Literature 2 listed below).

Japanese Unexamined Patent Application Publication No. 2022-017085 Japanese Unexamined Patent Application Publication No. 2001-79718

However, in the machine tool disclosed in Patent Literature 2, since the tool assembly is configured by integrally connecting the hob cutter and the support frame, the tool assembly is greater in size and weight than the hob cutter alone. Accordingly, the tool changer for automatically changing the tool assembly is necessarily increased in size.

That is to say, for example, where the machine tool includes a tool changer having a rotating-type change arm and performing tool change by holding the tools with the change arm, the change arm itself needs to have a high rigidity and the holding mechanism of the tool holding unit provided on the change arm needs to have a high strength. Further, the motor for rotating the change arm also needs to have an increased size. Accordingly, the overall structure of the tool changer is necessarily increased in size and the manufacturing cost for the tool changer is increased.

Further, where a plurality of hob cutters are to be used in the machine tool disclosed in Patent Literature 2, it is necessary to prepare each hob cutter in the form of the tool assembly configured by integrally connecting the support frame to the hob cutter. This results in a problem that the cost required for the hob cutters is significantly higher than that in the case where a single hob cutter is used.

The present invention has been achieved in view of the above-described circumstances, and an object of the invention is to provide a machine tool which enables a hob cutter to be attached to a tool spindle with both ends thereof supported and which achieves this both-end supporting of the hob cutter at lower cost.

To solve the above-described problem, the present invention provides a machine tool including:
a tool spindle that holds a hob cutter;
a tool headstock that rotatably holds the tool spindle;
a holding mechanism that causes the hob cutter to be held on the tool spindle;
a tool spindle drive unit that rotates the tool spindle;
a workpiece spindle that holds a workpiece;
a workpiece headstock that rotatably holds the workpiece spindle;
a workpiece spindle drive unit that rotates the workpiece spindle;
a feed drive unit that moves the tool headstock and the workpiece headstock relative to each other; and
a controller that controls the tool spindle drive unit, the workpiece spindle drive unit, and the feed drive unit, wherein:
the machine tool includes:
a support frame that is mountable onto and dismountable from the tool headstock and, when mounted on the tool headstock, rotatably supports a non-held end of the hob cutter held on the tool spindle by the holding mechanism; and
a fixing mechanism that fixes the support frame mounted on the tool headstock to the tool headstock without interposing the hob cutter;
the fixing mechanism is configured to be switchable between a fixing state for unremovably fixing the support frame to the tool headstock and an unfixing state for unfixing the support frame; and
the controller is configured to drive the holding mechanism to cause the hob cutter to be held on the tool spindle, then drive the fixing mechanism to fix to the tool headstock the support frame supporting the non-held end of the hob cutter and mounted on the tool headstock, and thereafter control the tool spindle drive unit, the workpiece spindle drive unit, and the feed drive unit to machine the workpiece held on the workpiece spindle.

In this machine tool, the hob cutter is held on the tool spindle by the holding mechanism being driven under control by the controller with the hob cutter attached to the tool spindle. Thereafter, the support frame in a state of supporting the non-held end of the hob cutter is mounted onto the tool headstock and then the fixing mechanism is driven under control by the controller, whereby the support frame is unremovably fixed to the tool headstock.

Thus, in this machine tool, the non-held end of the hob cutter held on the tool spindle is rotatably supported by the support frame fixed to the tool headstock. Consequently, the hob cutter is supported at both ends by the tool spindle and the support frame. That is to say, the hob cutter is held at the proximal end (held end) by the tool spindle and supported at the distal end (non-held end) by the support frame. The machine tool performs gear cutting using the thus both-end supported hob cutter. Therefore, as compared with the case where the hob cutter is supported at only one end by the tool spindle, elastic deformation of the hob cutter caused by a cutting load is suppressed and the machining accuracy is improved.

Further, in this machine tool, the support frame is configured as a separate element able to be separated from the hob cutter. Therefore, where there are a plurality of hob cutters to be used, it is possible to apply one common support frame to the plurality of hob cutters. In other words, it is not necessary to prepare a plurality of support frames in correspondence with the number of hob cutters. Accordingly, increase in the number of components is suppressed and the both-end supporting of the hob cutter is realized with an inexpensive configuration. Further, the both-end supporting of the hob cutter in this machine tool does not employ the conventional integrally-connected support frame and hob cutter. This enables the hob cutter and the support frame to be handled separately in handling the hob cutter. Therefore, the handling of the hob cutter is easy in terms of size and weight.

It is preferred that the controller is configured to move the tool headstock in a predetermined direction with the fixing mechanism in the unfixing state to mount and dismount the support frame onto and from the tool headstock using an operating force generated by the movement of the tool headstock.

This configuration enables mounting and dismounting of the support frame onto and from the tool headstock to be automatically carried out utilizing the movement of the tool headstock. Therefore, it is not necessary for an operator to manually mount the support frame onto the tool headstock, which reduces the physical burden on the operator and enables quick switching to the hob cutter.

It is preferred that the support frame has: an annular portion that has an annular shape and, with the support frame mounted on the tool headstock, engages with an engagement receiving portion formed on the tool headstock and surrounds a periphery of the hob cutter held on the tool spindle; a supporting portion that includes a bearing and rotatably supports with the bearing the non-held end of the hob cutter held on the tool spindle; and a connecting portion that connects the annular portion and the supporting portion.

In this configuration, the support frame is mounted onto the tool headstock by moving the support frame such that the hob cutter passes through the inside of the annular portion forming one end of the support frame. Thereafter, the annular portion of the support frame is engaged with the engagement receiving portion provided on the tool headstock and the distal end of the hob cutter is engaged with the supporting portion of the support frame, so that the support frame is completely mounted on the tool headstock. Thus, this configuration realizes the mounting of the support frame onto the tool headstock by a simple linear movement. Further, this configuration prevents the support frame from being largely offset radially outward with respect to the hob cutter, which improves the peripheral space efficiency.

It is preferred that: the engagement receiving portion provided on the tool headstock has an annular tapered surface formed coaxially with an axis of the tool spindle; the annular portion of the support frame has an annular tapered surface formed coaxially with an axis of the bearing, and the annular tapered surface of the annular portion is configured to fit with the annular tapered surface of the engagement receiving portion.

In this configuration, when the support frame is mounted onto the tool headstock, the annular tapered surface of the support frame is engaged with the annular tapered surface as the engagement receiving portion provided on the tool headstock. Thereby, the axis of support of the engagement receiving portion provided on the tool headstock and the axis of the supporting portion of the support frame are positioned coaxially with each other. Consequently, the axis of rotation of the hob cutter is maintained coaxially with the axis of the tool spindle, which improves the accuracy of tooth profile machining by the hob cutter.

It is preferred that the fixing mechanism is configured to, with the support frame mounted on the tool headstock, be switchable between the fixing state and the unfixing state by an action of a fluid pressure supplied through a fluid passage formed in the tool headstock.

Since the fixing mechanism is provided on the support frame, this configuration realizes the fixation of the support frame to the tool headstock without greatly changing the structure of an existing tool headstock. Therefore, even in the case where a tool headstock of an existing machine tool is modified in order to realize the both-end supporting of the hob cutter, it is possible to minimize the number of steps required for the modification and keep down the modification cost.

The support frame may be mounted onto a mounting receiving portion formed on an outer surface of the tool headstock. In this case, the tool headstock has the mounting receiving portion formed on an outer surface thereof and the mounting receiving portion has a mounting seat surface at a position offset radially from the tool spindle as viewed in the axial direction of the tool spindle and has an engagement receiving portion provided on the mounting seat surface. The support frame may have: a seat-surface contact portion that, with the support frame mounted on the mounting receiving portion of the tool headstock, engages with the engagement receiving portion formed on the mounting seat surface of the mounting receiving portion and contacts with the mounting seat surface; a supporting portion that includes a bearing and rotatably supports with the bearing the non-held end of the hob cutter held on the tool spindle; and a connecting portion that connects the seat-surface contact portion and the supporting portion.

In this configuration, the mounting seat surface is provided at a position offset radially from the tool spindle by the mounting receiving portion provided on the outer surface of the tool headstock. Thus, this configuration avoids the mounting seat surface being provided in the peripheral area of the tool spindle in the tool headstock where the structure is likely to be complicated. Therefore, it is possible to simplify the structure for mounting of the support frame and keep down the manufacturing cost for the structure.

The machine tool may be configured according to the following aspect:
the machine tool further includes:
a tool changer that has a tool change arm and a tool magazine storing a plurality of tools, including the hob cutter, attachable to the tool spindle and changes a tool held on the tool spindle with a tool stored in the tool magazine with the tool change arm; and
a storage that stores the support frame therein,
the feed drive unit is configured to move the tool headstock to a tool change position at which tool change is performed between the tool headstock and the tool changer and to a mounting/dismounting position at which mounting and dismounting of the support frame is performed between the tool headstock and the storage; and
the controller is configured to, when attaching the hob cutter stored in the tool magazine to the tool spindle, cause the feed drive unit to move the tool headstock to the tool change position, then cause the tool changer to attach the hob cutter stored in the tool magazine to the tool spindle, then cause the feed drive unit to move the tool headstock from the tool change position to the mounting/dismounting position so as to mount the support frame with the fixing mechanism in the unfixing state to the tool headstock using an operating force generated by the movement of the tool headstock, and then switch the fixing mechanism to the fixing state.

In this machine tool, when the hob cutter is used, under control by the controller, the hob cutter is attached to the tool spindle by the tool changer and then the tool headstock is moved to the mounting/dismounting position by the feed drive unit. Thereby, the support frame is mounted onto the tool headstock and the hob cutter is supported at both ends by the tool spindle and the support frame. After completion of the mounting of the support frame onto the tool headstock, the fixing mechanism is switched from the unfixing state to the fixing state. Thereby, the support frame is fixed to the tool headstock. The mounting of the support frame onto the tool headstock is carried out using an operating force generated by the movement of the tool headstock to the mounting/dismounting position. Therefore, it is not necessary to separately provide a dedicated device (for example, a robot or the like) for mounting the support frame onto the tool headstock.

It is preferred that the controller is configured to, when dismounting the support frame fixed to the tool headstock after completion of machining of the workpiece by the hob cutter, first cause the feed drive unit to move the tool headstock to the mounting/dismounting position so as to store the support frame into the storage, then unfix the support frame fixed by the fixing mechanism, and then cause the feed drive unit to move the tool headstock away from the mounting/dismounting position, thereby dismounting the support frame from the tool headstock.

In this configuration, after completion of machining of the workpiece by the hob cutter, the tool headstock is moved to the mounting/dismounting position by the feed drive unit under control by the controller. Thereby, the support frame mounted on the tool headstock is stored into the storage. After the support frame is stored into the storage, the fixing mechanism is switched to the unfixing state. Thereby, the fixation of the support frame to the tool headstock is released. After the fixation is released, the tool headstock is moved away from the mounting/dismounting position by the feed drive unit. Thereby, the support frame is dismounted from the tool headstock. This dismounting of the support frame is carried out using an operating force generated by the movement of the tool headstock away from the mounting/dismounting position. Therefore, it is not necessary to separately provide a dedicated device (for example, a robot or the like) for dismounting the support frame from the tool headstock.

It is preferred that the machine tool further includes a locking device that is switchable between a locking state for immovably locking the support frame stored in the storage and an unlocking state for unlocking the support frame.

This configuration enables the support frame to be immovably locked to the storage by the locking device, for example, while the tool headstock is being moved to the mounting/dismounting position by the feed drive unit and while the tool headstock is being moved away from the mounting/dismounting position by the feed drive unit, which enables smooth and reliable mounting and dismounting of the support frame onto and from the tool headstock.

It is preferred that the storage is arranged on a side opposite to the tool magazine with respect to the tool headstock.

This configuration utilizes a dead space located on the side opposite to the tool magazine with respect to the tool headstock to arrange the storage.

The machine tool may include a partition wall that separates a machining area as a space in which the tool spindle is located and a magazine housing space in which the tool magazine is housed and the storage may be arranged in the magazine housing space.

Since the storage is arranged in the magazine housing space, this configuration enables the tool change position to which the tool headstock is moved at the time of tool change and the mounting/dismounting position to which the tool headstock is moved at the times of mounting and dismounting of the support frame onto and from the tool headstock to be arranged as close as possible to each other. Therefore, the time until the tool headstock reaches the mounting/dismounting position after completion of the attachment of the hob cutter to the tool spindle is shortened. Consequently, the machining cycle time in the machine tool is shortened and the productivity thereof is improved.

As described above, in the machine tool according to the present invention, the support frame supporting the hob cutter is configured as a separate element able to be separated from the hob cutter. Therefore, where there are a plurality of hob cutters to be used, it is possible to apply one common support frame to the plurality of hob cutters. In other words, it is not necessary to prepare a plurality of support frames in correspondence with the number of hob cutters. Accordingly, increase in the number of components is suppressed and the both-end supporting of the hob cutter is realized with an inexpensive configuration.

Further, the both-end supporting of the hob cutter does not employ the conventional integrally-connected support frame and hob cutter. This enables the hob cutter and the support frame to be handled separately in handling the hob cutter. Therefore, the handling of the hob cutter is easy in terms of size and weight. Particularly, even in the case where the machine tool is configured to automatically change the tool attached to the spindle with the tool changer, the tool changer handles the tool alone. Therefore, increase in the size of the tool changer and increase in the manufacturing cost for the tool changer resulted from the both-end supporting of the hob cutter are prevented.

FIG. 1 is an overall perspective view illustrating a machine tool according to Embodiment 1. FIG. 2 is a front view of a tool headstock. FIG. 3 is a right side view of a support unit. FIG. 4 is a view (rear view) as viewed in the direction of arrow D in FIG. 3. FIG. 5 is a perspective view of the support unit. FIG. 6 is a sectional view taken along line V-V in FIG. 5. FIG. 7 is a schematic view illustrating a structure of a unit storage. FIG. 8 is a block diagram illustrating a configuration of a control system of the machine tool. FIG. 9A is an illustrative diagram for explaining the contents of tool change control. FIG. 9B is an illustrative diagram for explaining the contents of the tool change control. FIG. 9C is an illustrative diagram for explaining the contents of the tool change control. FIG. 9D is an illustrative diagram for explaining the contents of unit mounting control. FIG. 9E is an illustrative diagram for explaining the contents of the unit mounting control. FIG. 9F is an illustrative diagram for explaining the contents of the unit mounting control. FIG. 9G is an illustrative diagram for explaining the contents of the unit mounting control. FIG. 9H is an illustrative diagram for explaining the contents of the unit mounting control. FIG. 9I is an illustrative diagram for explaining the contents of the unit mounting control. FIG. 10 is a perspective view illustrating a support unit in Embodiment 2. FIG. 11 is a perspective view illustrating the support unit in FIG. 10 as dismounted. FIG. 12 is a plan view of a mounting seat surface of a mounting receiving portion provided on the tool headstock. FIG. 13 is a perspective view showing a state where the tool headstock is turned such that the distal end of the hob cutter is oriented toward the unit storage in the Embodiment 2. FIG. 14 is a view corresponding to FIG. 13 but illustrating a modification of the Embodiment 2. FIG. 15 is an illustrative diagram for explaining operations in Embodiment 3.Description of Embodiments

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a perspective view illustrating a machine tool according to Embodiment 1. Note that the terms “front”, “rear”, “left”, and “right” in the following description are defined with respect to the machine tool 1 as indicated by the directional axes in FIG. 1.

The machine tool 1 is a five-axis controlled combined lathe that includes a bed 2, a first workpiece headstock 3, a second workpiece headstock 4, a turret tool rest 5, a tool headstock 6 (an example of the tool rest), a tool spindle 7 (an example of the tool rotating member), and a controller 100 (see FIG. 8). The first workpiece headstock 3 and the second workpiece headstock 4 are arranged on the bed 2 to face each other in a Z-axis direction (left-right direction). The turret tool rest 5 is arranged between the first workpiece headstock 3 and the second workpiece headstock 4 to be movable in an X-axis direction (vertical direction) and the Z-axis direction. The tool headstock 6 is arranged on the bed 2 to be movable in the X-axis direction, a Y-axis direction (front-rear direction), and the Z-axis direction. The tool spindle 7 is held by the tool headstock 6 so as to rotationally drive a tool 9. The controller 100 controls operations of elements of the machine tool 1. The tool 9 that is attachable to the tool spindle 7 includes various types of tools, such as a hob cutter 90, an end mill, and a milling cutter. In the following description, these tools are referred to as “tool 9” when they do not need to be distinguished from each other.

On the bed 2, an automatic tool changer 8 is arranged on the left of a machining area S1 for machining of a workpiece W. The automatic tool changer 8 changes a tool 9 attached to the tool spindle 7 with a tool 9 to be used in the next process. The automatic tool changer 8 has two tool magazines 8a that are described later. The two tool magazines 8a are housed in a magazine housing space S2 that is adjacent to the left side of the machining area S1.

The machining area S1 and the magazine housing space S2 are separated by a partition wall 16 that is disposed vertically along the front-rear direction. The partition wall 16 has at the center thereof an opening 16a for tool change and a sliding-type ATC shutter 17 opening and closing the opening 16a. The ATC shutter 17 is configured to be slidable in the vertical direction by way of example. The ATC shutter 17 is not limited to this configuration and, for example, may be configured to be slidable in the left-right direction.

On the side opposite to of the automatic tool changer 8 with respect to the tool headstock 6, a unit storage 20 is provided. The unit storage 20 stores therein a support unit 40 that is to be mounted on the tool headstock 6 to perform hobbing, which is described later.

The first workpiece headstock 3 is fixed to a top surface of the bed 2. The first workpiece headstock 3 holds a first workpiece spindle 10 such that the first workpiece spindle 10 is rotatable about a C-axis parallel to the Z-axis. The second workpiece headstock 4 holds a second workpiece spindle 11 such that the second workpiece spindle 11 is coaxial with the first workpiece spindle 10 and is rotatable around the C-axis. The second workpiece headstock 4 is moved in the Z-axis direction by a feed motor 33a and a feed screw (not illustrated). The first workpiece spindle 10 is driven by a first spindle motor (not illustrated) and the second workpiece spindle 11 is driven by a second spindle motor (not illustrated). In hobbing, the first workpiece spindle 10 and the second workpiece spindle 11 rotate a workpiece W about the C-axis while respectively supporting both ends of the workpiece W.

The turret tool rest 5 has a turret 5a that is turnable about an axis parallel to the Z-axis, and the turret tool rest 5 is movable in the Z-axis direction and the X-axis direction by a feed motor and a feed screw (both not illustrated). The turret 5a has on the outer periphery thereof tools 5b arranged radially at intervals in the circumferential direction.

The tool headstock 6 is connected to a column 12, which is erected on the top surface of the bed 2, via a saddle 13, a slider 14, and a ram 15.

The column 12 has a portal shape extending across from the left end to right end of the top surface of the bed 2. The saddle 13 is slidably engaged with a pair of guide rails (not illustrated) arranged on a front side surface of the column 12; thus, the saddle 13 is movable in the Z-axis direction. The saddle 13 is driven in the Z-axis direction by a pair of upper and lower feed screws 31 (only one of which is illustrated in FIG. 1) and a pair of feed motors 30b.

The slider 14 is slidably engaged with a pair of right and left guide rails (not illustrated) arranged on a front side surface of the saddle 13; thus, the slider 14 is movable in the X-axis direction. The slider 14 is driven in the X-axis direction by a pair of feed screws 32 (only one of which is illustrated in FIG. 1) and a pair of feed motors 30c.

The ram 15 is inserted in a ram guide hole 14a formed in the slider 14 and is supported by a guide plate (not illustrated) to be movable in the Y-axis direction. The ram 15 is driven in the Y-axis direction by a single feed screw and a single feed motor (both not illustrated) arranged at the lower end of the slider 14.

The tool headstock 6 is fixed to a turning drive shaft (not illustrated) rotatably supported by the ram 15. The tool headstock 6 is turnable about a B-axis parallel to the Y-axis by a turning motor (not illustrated) coupled to the turning drive shaft.

<Automatic Tool Changer>
As illustrated in FIG. 1, the automatic tool changer 8 has two tool magazines 8a arranged side by side in the front-rear direction and a tool change arm (not illustrated). Each tool magazine 8a has a vertically elongated elliptical frame, a chain circulating along the frame, and a plurality of tool pots attached to the chain. The tool pots respectively detachably hold various tools 9 including a hob cutter 90, an end mill, and a milling cutter. A plurality of hob cutters 90 are stocked in the tool magazines 8a for the purpose of replacement in the event of wear and for the purpose of forming tooth profiles of different shapes.

The tool change arm is rotationally driven about an axis parallel to the Z-axis by a motor (not illustrated). In tool change, the ATC shutter 17 is opened and the tool headstock 6 is moved to a tool change position (see FIG. 9B described later). Thereby, a tool 9 held on the tool spindle 7 horizontally enters the magazine housing space S2. After the entry into the magazine housing space S2, the tool 9 is changed with a tool 9 to be used in the next process, which is indexed at a predetermined position by the tool magazines 8a, by the tool change arm.

<Tool Headstock>
As illustrated in FIG. 2, the tool headstock 6 has a turning housing 6a and a spindle housing 6b.

The turning housing 6a has a rectangular box shape in appearance. The turning housing 6a has an arcuate mount plate 6c integrally formed on a back face thereof. The mount plate 6c has in a peripheral edge portion thereof a plurality of through holes 6d formed at intervals in the circumferential direction. The mount plate 6c is fixed to the turning drive shaft by bolts (not illustrated) inserted through the through holes 6d; thus, the mount plate 6c is rotatable together with the turning drive shaft.

The spindle housing 6b is fixed to the turning housing 6a with the axis of rotation of the spindle housing 6b orthogonal to the axis of rotation (i.e., the B-axis) of the turning housing 6a. The spindle housing 6b is formed in an axially symmetrical tubular shape. The spindle housing 6b houses a bearing (not illustrated) rotatably supporting the tool spindle 7, a built-in motor (not illustrated) driving the tool spindle 7, and a drawbar mechanism (not illustrated) fixing a tool 9 to the tool spindle 7.

The spindle housing 6b is mounted on the turning housing 6a such that a part of the distal side of the spindle housing 6b is exposed to the outside. That is to say, the spindle housing 6b consists of a cylindrical unexposed portion 6e housed in the turning housing 6a and an exposed portion 6f exposed to the outside of the turning housing 6a.

The exposed portion 6f has a flange 6g, a large-diameter cylindrical portion 6h, and a small-diameter cylindrical portion 6i that arranged in sequence from the proximal side toward distal side of the spindle housing 6b. The flange 6g is fixed to a lower surface of the turning housing 6a by bolts (not illustrated).

A step surface 6j located at the boundary between the large-diameter cylindrical portion 6h and the small-diameter cylindrical portion 6i has therein an annular groove 6k formed along the entire circumference of the step surface 6j. The inner periphery of the annular groove 6k is formed to have an annular tapered outer surface 6l having a diameter reducing toward the distal side. This annular tapered outer surface 6l corresponds to the engagement receiving portion formed on the tool headstock 6 (the tool rest).

The small-diameter cylindrical portion 6i has an annular engagement protrusion 6m on a distal end portion of an outer peripheral surface hereof. The annular engagement protrusion 6m slightly protrudes radially outward from the outer peripheral surface of the small-diameter cylindrical portion 6i.

<Tool Spindle>
As illustrated in FIG. 2, the tool spindle 7 is supported via the not-illustrated bearing in the spindle housing 6b. The tool spindle 7 has a tool attachment hole 7a (illustrated only in FIG. 5 described later) formed at the distal end thereof, into which a tool 9 is to be attached. FIG. 2 shows an example in which a hob cutter 90 as an example of the tool 9 is attached in the tool attachment hole 7a.

<Hob Cutter>
The hob cutter 90 is a tool for hobbing that forms a tooth profile on a peripheral surface of a workpiece W supported by the first workpiece spindle 10 and the second workpiece spindle 11 (see FIG. 1).

As illustrated in FIG. 2, the hob cutter 90 has a tool body 91 and a holder 92. The tool body 91 has a shaft portion 91a and a cutting edge portion 91b. The cutting edge portion 91b has a larger diameter and is formed coaxially with the shaft portion 91a. A distal end portion of the shaft portion 91a is formed in a tapered shaft shape having a diameter reducing toward the distal side. The cutting edge portion 91b machines a workpiece W. The cutting edge portion 91b has a plurality of cutting edge rows corresponding to a tooth profile to be machined.

The holder 92 has a shape that is common to all tools 9 including the hob cutter 90. The holder 92 has a flange 92a, a shank 92b, and a pull bolt 92c.

The flange 92a is to be gripped by the tool change arm of the automatic tool changer 8 in tool change. The flange 92a is connected to the distal end of the shank 92b. The flange 92a protrudes radially outward from the shank 92b. The flange 92a has in an outer peripheral surface thereof a V-shaped gripping groove 92d formed along the entire circumference of the flange 92. In tool change, a gripper formed at either end of the tool change arm (not illustrated) engages with the V-shaped gripping groove 92d, whereby the hob cutter 90 is gripped by the tool change arm.

The shank 92b is formed in a tapered shaft shape able to fit into the tool attachment hole 7a. The pull bolt 92c is connected to the proximal end of the shank 92b to be coaxial with the shank 92b. The pull bolt 92c is pulled toward the proximal side in the axial direction by the drawbar mechanism housed in the spindle housing 6b. Thereby, the shank 92b of the hob cutter 90 is attached in the tool attachment hole 7a. Thus, the hob cutter 90 is held on the tool spindle 7 with only one end thereof supported (i.e., with only the proximal side thereof fixed to the tool spindle 7).

When hobbing is to be performed in the machine tool 1, a support unit 40 is mounted onto and fixed to the tool headstock 6 so as to change the hob cutter 90 from the one-end supported state to a both-end supported state.

<Support Unit>
FIG. 3 is a right side view showing a state where the support unit 40 is mounted on the tool headstock 6. FIG. 5 is an external perspective view of the support unit 40.

The support unit 40 has a support frame 50 and a fixing mechanism 60 (see FIG. 6 described later). The support frame 50 is to be dismountably mounted onto the tool headstock 6. The fixing mechanism 60 unremovably fixes the support frame 50 to the tool headstock 6.

In the state of being mounted on the tool headstock 6, the support frame 50 extends along the longitudinal direction of the hob cutter 90.

Specifically, the support frame 50 has an annular portion 51, a supporting portion 52, and a connecting portion 53.

The annular portion 51 is formed at one end in the extending direction of the support frame 50 so as to surround the periphery of the hob cutter 90. The annular portion 51 consists of an annular body 51a and an end-mounted ring 51b mounted on one end of the annular body 51b. The annular body 51a is formed integrally with the supporting portion 52 and the connecting portion 53.

As illustrated in FIG. 6, the end-mounted ring 51b is formed separately from the annular body 51a. The end-mounted ring 51b has a cylindrical portion 51c, a spigot portion 51d, and an annular protruding portion 51e. The spigot portion 51d and the annular protruding portion 51e are formed along the inner edges of the cylindrical portion 51c to be coaxial with the cylindrical portion 51c. The spigot portion 51d protrudes to the distal side in the axial direction. The annular protruding portion 51e protrudes to the proximal side in the axial direction. The spigot portion 51d is fitted on an inner peripheral surface of the annular body 51a. The annular protruding portion 51e has an annular tapered inner surface 51f. The annular tapered inner surface 51f forms an inner peripheral surface of the annular protruding portion 51e and has a dimeter reducing from the proximal side toward the distal side in the axial direction. The annular tapered inner surface 51f is to be engaged with the annular tapered outer surface 6l formed on the tool headstock 6.

The supporting portion 52 is spaced from the annular portion 51 in the axial direction. The supporting portion 52 includes a pair of bearings 70 and a rotatable member 80 as a hob-end engagement part. The supporting portion 52 is disposed perpendicularly to the axis of the annular portion 51. The supporting portion 52 has a bearing mount hole 52a formed therethrough. The bearing mount hole 52a is formed coaxially with the annular portion 51. The pair of bearings 70 are arranged at an interval in the axial direction are fitted in the bearing mount hole 52a.

The rotatable member 80 consists of a cylindrical portion 80a and a flange 80b. The cylindrical portion 80a is inserted inside the inner rings of the pair of bearings 70. The flange 80b is formed at the lower end of the cylindrical portion 80a. The flange 80b regulates the position in the axial direction of the rotatable member 80 with respect to the pair of bearings 70. The rotatable member 80 is fixed by a nut 81 at the side opposite to the flange 80b with respect to the pair of bearings 70 so as not to fall off. Thus, the rotatable member 80 is rotatably held by the supporting portion 52 via the pair of bearings 70. The rotatable member 80 has an end engagement hole 80c formed in an end surface thereof located on the annular portion 51 side. The end engagement hole 80c is to be engaged with the distal end of the hob cutter 90. The end engagement hole 80c is formed in a tapered hole shape corresponding to the shape of the distal end of the hob cutter 90.

As illustrated in FIGS. 3 and 4, the supporting portion 52 has a displacement sensor 76 embedded in an end surface thereof located on the side opposite to the connecting portion 53. The displacement sensor 76 constitutes a shape detector 75. The displacement sensor 76 has a light emitting element 77 emitting a laser beam and light receiving elements 78, 78 arranged on both sides of the light emitting element 77. The light emitting element 77 emits a laser beam toward an object. The laser beam is reflected by the object and received by the light receiving elements 78, 78. Based on the light receiving position on the light receiving elements 78, 78, the distance from the displacement sensor 76 to the object is detected. Note that the specific distance is calculated by a shape calculator 79 based on the output value from the displacement sensor 76. The displacement sensor 76 and the shape calculator 79 constitute the shape detector 75.

This shape detector 75 is able to, for example, measure the shape and phase of the tooth profile machined on the workpiece W by the hob cutter 90. For example, in FIG. 9I, the tool headstock 6 is moved upward to cause the displacement sensor 76 to face the tooth profile formed on the workpiece W. In this state, a laser beam is emitted toward the tooth profile by the light emitting element 77 of the displacement sensor 76. The laser beam is reflected by the tooth profile and received by the light receiving elements 78, 78. The output signals from the light receiving elements 78, 78 are processed by the shape calculator 79, whereby the distance between the displacement sensor 76 and the tooth profile is calculated. By rotating the workpiece W about the axis thereof in this state, the tooth profile is scanned by the displacement sensor 76. During this scanning, the shape and phase of the tooth profile are detected based on the distance between the displacement sensor 76 and the tooth profile calculated by the shape calculator 79. Note that the displacement sensor may be an eddy current sensor, an electromagnetic pick-up, or the like instead of the light emitting and receiving sensor.

The connecting portion 53 connects the annular portion 51 and the supporting portion 52. Specifically, the connecting portion 53 is composed of a rectangular column that extends parallel to the axis of the annular portion 51. The connecting portion 53 connects one point in the circumferential direction of the annular portion 51 and the end edge of the supporting portion 52. By way of example, but not limited to, the connecting portion 53 is composed of a single rectangular column. That is to say, the connecting portion 53 is not limited to being composed of a rectangular column and may have, for example, a trapezoidal plate shape or an arcuate shape. Further, the number of connecting portions 53 is not limited to one and may be two or more.

<Fixing Mechanism>
As illustrated in FIG. 6, the fixing mechanism 60 is arranged inside the annular portion 51 of the support frame 50.

The fixing mechanism 60 includes a sliding ring 61, an annular fixed ring 62, a flexible ring 63, and a holding ring 64. The sliding ring 61 is slidable in the axial direction along an inner guide surface 51g of the end-mounted ring 51b. The fixed ring 62 is fixed to a distal end surface of the end-mounted ring 51b. The flexible ring 63 is arranged inside the sliding ring 61. The holding ring 64 holds the flexible ring 63 so as to prevent the flexible ring 63 from falling off.

The end-mounted ring 51b, the fixed ring 62, and the sliding ring 61 together form an annular hydraulic chamber U0. The hydraulic chamber U0 consists of a first hydraulic chamber U1 and a second hydraulic chamber U2 that are respectively formed on both sides of a piston protrusion 61a, which is formed on an outer peripheral surface of the sliding ring 61, in the axial direction.

The flexible ring 63 has a ring body 63a, a plurality of flexible pieces 63b, and a plurality of engagement hooks 63c. The flexible pieces 63b are each connected at the proximal end to the ring body 63a. The engagement hooks 63c are respectively formed at the distal ends of the flexible pieces 63b. The ring body 63a is fitted and held in a holding groove 64a formed in the holding ring 64. The flexible pieces 63b are in contact with an inner peripheral surface of the sliding ring 61.

When a hydraulic pressure is supplied to the first hydraulic chamber U1, the piston protrusion 61a formed on the sliding ring 61 is pushed rightward in FIG. 6, whereby the sliding ring 61 as a whole is moved rightward. Thereby, the flexible pieces 63b are caused to fall radially inward with their proximal ends as a fulcrum. Consequently, the engagement hooks 63c formed at the distal ends of the flexible pieces 63b engage with the annular engagement protrusion 6m formed at the distal end of the spindle housing 6b. Thus, the spindle housing 6b and the support unit 40 are coupled (fixed) together so as not to be separated from each other in the axial direction.

When a hydraulic pressure is supplied to the second hydraulic chamber U2, the piston protrusion 61a formed on the sliding ring 61 is pushed leftward in FIG. 6, whereby the sliding ring 61 as a whole is moved leftward. Thereby, the flexible pieces 63b are spread radially outward with their proximal ends as a fulcrum by their restoring forces. Consequently, as indicated by the solid lines in FIG. 6, the engagement hooks 63c formed at the distal ends of the flexible pieces 63b disengage from the annular engagement protrusion 6m formed at the distal end of the spindle housing 6b. Thus, the coupling (fixation) between the spindle housing 6b and the support unit 40 in the axial direction is released.

As described above, the fixing mechanism 60 is switchable between the fixing state for fixing the support unit 40 to the tool headstock 6 (more particularly, the spindle housing 6b) and the unfixing state for unfixing the support unit 40.

When the support unit 40 is mounted on the spindle housing 6b, hydraulic supply lines L1 and L2 to the first hydraulic chamber U1 and the second hydraulic chamber U2 are established. That is to say, the spindle housing 6b has formed therein two hydraulic supply paths (not illustrated) for supplying a hydraulic oil to the hydraulic chambers U1, U2. When the support unit 40 is mounted on the spindle housing 6b, the two hydraulic supply paths communicate with two hydraulic supply passages (not illustrated) formed in the end-mounted ring 51b of the support unit 40. Thus, the hydraulic supply lines L1, L2 are established.

<Unit Storage>
The support unit 40 is stored in the unit storage 20 while hobbing is not being performed. The support unit 40 is mounted onto the tool headstock 6 by the tool headstock 6 being moved in the left-right direction, which is described later.

The unit storage 20 is formed in a rectangular box shape and arranged above the second workpiece headstock 4. The unit storage 20 is fixed to the bed 2 of the machine tool 1 via a connecting plate 21. The connecting plate 21 is connected to a lower surface of the unit storage 20 by a reinforcement rib 22.

As illustrated in FIG. 7, a first support 23 and a second support 24 for supporting the support unit 40 are erected on a bottom plate 20c of the unit storage 20.

The support unit 40 is placed on the tops of the first support 23 and second support 24 with the axis of the annular portion 51 parallel to the Z axis and with the connecting portion 53 positioned on the front side as viewed from the front of the machine tool 1.

Further, the unit storage 20 has therein a unit locking device 25 for locking the support unit 40 placed on the tops of the first support 23 and second support 24.

The unit locking device 25 has a pair of engagement pins 25a, a holding plate 25b, and a cylinder 25c. The pair of engagement pins 25a are held by the holding plate 25b. The cylinder 25c advances and retracts the holding plate 25b. The holding plate 25b is moved between a locking position and an unlocking position by the cylinder 25c. When the holding plate 25b is moved to the locking position, the pair of engagement pins 25a engage with a pair of engagement holes 25d formed in the support frame 50. Thereby, the support unit 40 as a whole, including the support frame 50, is locked to be immovable in the left-right direction (Z-axis direction). When the holding plate 25b is moved to the unlocking position, the pair of engagement pins 25a are moved in a direction away from the support frame 50. Thereby, the support unit 40 is allowed to move in the left-right direction (Z-axis direction).

The unit storage 20 has a rectangular opening 20b formed in a left side plate 20a thereof. The support unit 40 is loaded into and unloaded from the unit storage 20 through the opening 20b.

<Configuration of Control System>
As illustrated in FIG. 8, the machine tool 1 has the controller 100 that controls the overall operation of the machine tool 1. The controller 100 is composed of a computer including a CPU, a ROM, and a RAM.

The controller 100 is connected to a spindle rotation drive unit 101, a feed drive unit 102, a spindle turning drive unit 103, the automatic tool changer (ATC) 8, a shutter drive unit 104, a hydraulic supply device 105, and the unit locking device 25 so as to transmit and receive signals (control signals and other signals) to and from them.

The spindle rotation drive unit 101 includes the above-described built-in motor for driving the tool spindle 7.

The feed drive unit 102 includes feed motors (e.g., the above-described feed motors 30a to 30c) for moving the workpiece W and the tool 9 relative to each other in the X-axis direction, the Y-axis direction, and the Z-axis direction.

The spindle turning drive unit 103 includes the above-described turning motor for turning the tool headstock 6 about the B-axis.

The shutter drive unit 104 includes a motor for opening and closing the ATC shutter 17.

The hydraulic supply device 105 switches the fixing mechanism 60 between the fixing state and the unfixing state by controlling supply of the hydraulic oil to the hydraulic supply lines L1, L2 (see FIG. 6).

The controller 100 executes control of machining of the workpiece W in accordance with an NC program stored in a ROM or the like. Upon extracting a tool change command from the NC program during the execution, the controller 100 executes tool change control with respect to the automatic tool changer 8. In the tool change control, the automatic tool changer 8 performs the above-described tool change between the tool spindle 7 and the tool magazines 8a with the tool change arm.

Where the controller 100 extracts the tool change command from the NC program and determines that the tool change command designates a hob cutter 90 as the tool to be used in the next process, the controller 100 executes the tool change control and then executes unit mounting control for mounting the support unit 40 onto the tool headstock 6 and fixing the support unit 40 to the tool headstock 6. After completion of the machining using the hob cutter 90, the controller 100 executes unit dismounting control for dismounting the support unit 40 from the tool headstock 6.

<Tool Change Control and Unit Mounting Control>
FIGS. 9A to 9I are illustrative diagrams for explaining the contents of the tool change control (FIGS. 9A to 9C) and unit mounting control (FIGS. 9D to 9I) for the hob cutter 90. The bold arrows in the figures each indicate an operation to be performed next.

FIG. 9A shows a state where a tool 95 other than the hob cutter 90 is attached to the tool spindle 7 (see FIG. 2) supported by the tool headstock 6.

In the tool change control for the hob cutter 90, under control by the controller 100, the ATC shutter 17 is moved to the open position by the shutter drive unit 104 and the tool headstock 6 is moved to the tool change position by the feed drive unit 102 and the spindle turning drive unit 103 (see FIG. 9B).

After completion of the movement of the tool headstock 6, the tool change is performed by the automatic tool changer 8 to change the used tool 95 attached to the tool spindle 7 with the hob cutter 90 as the tool to be used in the next process stored in the tool magazines 8a. The hob cutter 90 attached to the tool spindle 7 through the tool change is fixed to the tool spindle 7 by the drawbar mechanism (see FIG. 9C).

After completion of the attachment of the hob cutter 90 to the tool spindle 7, the unit mounting control is executed as illustrated in FIGS. 9D to 9I. In the unit mounting control, under control by the controller 100, the tool headstock 6 is first retracted rightward by the feed drive unit 102 and the ATC shutter 17 is moved to the closed position by the shutter drive unit 104 (see FIG. 9D).

Subsequently, the tool headstock 6 is turned by 180° in the counterclockwise direction in FIG. 9D by the spindle turning drive unit 103 (it may be turned in the clockwise direction). Thereby, the distal end of the hob cutter 90 is bought into a state of facing the opening 20b of the unit storage 20 (FIG. 9E). In the state shown in FIG. 9E, the axial center of the hob cutter 90 has become coaxial with the annular portion 51 of the support unit 40 stored in the unit storage 20. Depending on the configuration, the hob cutter 90 cannot not be brought into such a coaxial state. In such a case, the position of the tool headstock 6 can be adjusted by the feed drive unit 102.

After the axial center of the hob cutter 90 becomes coaxial with the axial center of the annular portion 51 of the support unit 40, the tool headstock 6 is horizontally moved rightward by the feed drive unit 102 to a unit mounting/dismounting position (see FIG. 9F) with the fixing mechanism 60 maintained in the unfixing state (the state shown in FIG. 6) by the hydraulic supply device 105.

By this movement of the tool headstock 6 to the unit mounting/dismounting position, the annular tapered inner surface 51f formed on the annular portion 51 of the support frame 50 (see FIG. 6) is engaged with (fitted around) the annular tapered outer surface 6l formed on the tool headstock 6. Further, the distal end of the hob cutter 90 passes through the inside of the annular portion 51 and engages with the end engagement hole 80c of the rotatable member 80. After completion of this engagement (in other words, after completion of mounting of the support unit 40 to the tool headstock 6), the fixing mechanism 60 is switched to the fixing state by the hydraulic supply device 105. Thus, the support unit 40 is unremovably fixed to (mounted onto) the tool headstock 6.

After completion of the fixation of the support unit 40 to the tool headstock 6, the holding plate 25b is moved to the unlocking position by the unit locking device 25 (see FIG. 9G). In this state, the tool headstock 6 is retracted leftward by the feed drive unit 102, so that the support unit 40 is unloaded from the unit storage 20. Thereby, the support unit 40 is completely mounted onto the tool headstock 6.

After the support unit 40 is completed mounted, the tool headstock 6 is turned in the clockwise direction by the spindle turning drive unit 103 (see FIG. 9H). Thereafter, the tool spindle 7 is rotated in synchronization with the workpiece W to form a tooth profile on the peripheral surface of the workpiece W (see FIG. 9I).

The unit mounting control has been described above. The unit dismounting control (control for dismounting the support unit 40 from the tool headstock 6) is executed by the operations of the unit mounting control being performed in the reverse order (i.e., the order of FIGS. 9I, 9H, 9G ... and 9A); therefore, detailed description of the unit dismounting control is omitted here.

<Functions and Effects>
As described above, the machine tool 1 according to this embodiment includes the support unit 40. The support unit 40 has the annular tapered inner surface 51f to be engaged with the annular tapered outer surface 6l (an example of the engagement receiving portion) formed on the tool headstock 6 and includes the rotatable member 80 to be engaged with the distal end of the hob cutter 90 so as to allow rotation of the hob cutter 90.

This configuration enables the hob cutter 90 to be supported at both ends by the tool headstock 6 and the rotatable member 80 provided on the support frame 50. Therefore, as compared with the case where the hob cutter 90 is supported at only one end by the tool spindle 7, elastic deformation of the hob cutter 90 caused by a cutting load is suppressed and the accuracy of the tooth profile machining is improved. Further, the support unit 40 is configured separately from the hob cutter 90. Therefore, it is possible to apply one common support unit 40 to the plurality of hob cutters 90 stocked in the tool magazines 8a. That is to say, it is not necessary to prepare a plurality of support units 40 in correspondence with the number of hob cutters 90. Accordingly, increase in the number of components is suppressed and the both-end supporting of the hob cutter 90 is achieved with an inexpensive configuration.

The tool headstock 6 in this embodiment is configured to be movable in the left-right direction (an example of the predetermined direction). The support unit 40 is configured to be mounted onto and dismounted from the tool headstock 6 using the operating force generated by the tool headstock 6 being linearly moved rightward (predetermined moving operation) with the fixing mechanism 60 in the unfixing state (see FIGS. 9E to 9H).

This configuration enables mounting and dismounting of the support unit 40 onto and from the tool headstock 6 to be automatically carried out utilizing the rightward linear movement of the tool headstock 6. Therefore, it is not necessary for an operator to manually mount the support unit 40 onto the tool headstock 6. This reduces the physical burden on the operator and enables quick switching to the hob cutter 90. Further, it is also not necessary to separately provide a dedicated robot or the like for mounting the support unit 40 onto the tool headstock 6; thus, the mounting of the support unit 40 onto the tool headstock 6 is realized with an inexpensive configuration.

The support unit 40 in this embodiment has the support frame 50 extending along the longitudinal direction of the hob cutter 90 with the support unit 40 mounted on the tool headstock 6 and has the rotatable member 80 supported via the bearings 70 by the support frame 50. The support frame 50 has the annular portion 51 forming one end in the extending direction of the support frame 50, having the annular tapered inner surface 51f, and annularly surrounding the periphery of the hob cutter 90, has the supporting portion 52 forming the other end in the extending direction of the support frame 50 and holding the bearings 70, and has the connecting portion 53 connecting the annular portion 51 and the support portion 52.

This configuration enables the support unit 40 to be mounted onto the tool headstock 6 by moving the tool headstock 6 such that the hob cutter 90 passes through the inside of the annular portion 51 forming the one end of the support frame 50. Thus, the mounting of the support unit 40 onto the tool headstock 6 is realized by a simple linear movement. Further, this configuration prevents the support unit 40 from being largely offset radially outward with respect to the hob cutter 90, which improves the peripheral space efficiency.

The annular tapered outer surface 6l of the tool headstock 6 is formed coaxially with the axis of the tool spindle 7. The annular tapered inner surface 51f of the support frame 50 is formed coaxially with the axis of the rotatable member 80.

In this configuration, when the support unit 40 is mounted onto the tool headstock 6, the annular tapered inner surface 51f of the support frame 50 is engaged with the annular tapered outer surface 6l of the tool headstock 6. Thereby, the axis of the tool spindle 7 held by the tool headstock 6 and the axis of the rotatable member 80 provided on the support frame 50 are positioned coaxially with each other. Consequently, the axis of rotation of the hob cutter 90 is maintained coaxially with the axis of the tool spindle 7, which improves the accuracy of tooth profile machining by the hob cutter 90.

The fixing mechanism 60 is provided on the support frame 50. The fixing mechanism 60 is configured to be switchable between the fixing state and the unfixing state by the hydraulic pressure of the hydraulic oil supplied through the hydraulic supply passages (an example of the fluid passage) formed in the tool headstock 6 when the support frame 50 is mounted on the tool headstock 6.

Since the fixing mechanism 60 is provided on the support frame 50, this configuration realizes the fixation of the support frame 50 to the tool headstock 6 without greatly changing the structure of an existing tool headstock 6. Therefore, even in the case where a tool headstock 6 of an existing machine tool is modified in order to realize the both-end supporting of the hob cutter 90, it is possible to minimize the number of steps required for the modification and keep down the modification cost.

The unit storage 20 has therein the unit locking device 25. The unit locking device 25 is configured to be switchable between the locking state for immovably locking the support unit 40 and the unlocking state for unlocking the support unit 40.

This configuration enables the support unit 40 to be immovably locked to the unit storage 20 by the unit locking device 25 while the tool headstock 6 is being moved to the unit mounting/dismounting position by the feed drive unit 102 and while the tool headstock 6 is being moved away from the unit mounting/dismounting position by the feed drive unit 102, which enables smooth and reliable mounting and dismounting of the support unit 40 onto and from the tool headstock 6.

The unit storage 20 is arranged on the side opposite to the tool magazines 8a with respect to the tool headstock 6.

This configuration utilizes a dead space (in this embodiment, the space above the second workpiece headstock 4) located on the side opposite to the tool magazines 8a with respect to the tool headstock 6 to arrange the unit storage 20. This prevents the machine tool 1 from being increased in size by the addition of the unit storage 20.

(Embodiment 2)
FIG. 10 illustrates Embodiment 2. This Embodiment 2 differs from the above-described Embodiment 1 in that a support frame 250 is mounted onto a mounting receiving member 6p as the mounting receiving portion provided on an outer surface of the tool headstock 6. In the following description, elements identical to those in the Embodiment 1 are denoted by the same reference numerals as used in the Embodiment 1 and detailed description thereof is omitted.

Specifically, the tool headstock 6 in this embodiment has the mounting receiving member 6p that is optionally provided thereon. The support frame 250 is mounted onto and fixed to the mounting receiving member 6p via pull bolts 203.

<Mounting Receiving Member>
The mounting receiving member 6p is fixed to a front side surface of the turning housing 6a of the tool headstock 6 by bolts as illustrated in FIG. 11. The front side surface of the turning housing 6a has a circular plate-shaped mounting seat 6n for mounting the mounting receiving member 6p thereon. By way of example, the mounting receiving member 6p is mounted on the tool headstock 6. The mounting receiving member 6p may be formed integrally with the tool headstock 6.

The attachment receiving member 6p is composed of a substantially hexagonal column having a thickness in the front-rear direction. The mounting receiving member 6p is arranged such that a lower end surface thereof lies horizontally in a reference state where the axis of the tool spindle 7 is oriented vertically. The lower end surface of the mounting receiving member 6p functions as a unit mounting seat surface 6q for mounting the support frame 250 thereon. As viewed in the axial direction of the tool spindle 7, the unit mounting seat surface 6q is located at a position offset to the front side (in the radial direction).

As illustrated in FIG. 12, the unit mounting seat surface 6q has four clamping holes 6r therein.

The four clamping holes 6r are provided respectively corresponding to four clamping devices 65 incorporated in the mounting receiving member 6p. Each clamping device 65 is composed of a ball-lock type hydraulic clamping device that draws and clamps with a hydraulically driven ball lock mechanism the pull bolt 203 (see FIG. 13) inserted in the corresponding clamping hole 6r.

The mounting receiving member 6p has formed therein hydraulic supply paths (not illustrated) for supplying a hydraulic pressure to each clamping device 65. The supply of the hydraulic oil to each clamping device 65 is controlled by the hydraulic supply device 105 in response to a command from the controller 100. When the supply of the hydraulic pressure to each clamping device 65 is stopped, the ball lock is unlocked by a biasing member (not illustrated) in each clamping device 65, whereby the clamping devices 65 are brought into an unclamping state.

<Support Unit>
Similarly to the Embodiment 1, a support unit 240 is stored in the unit storage 20 when not used (i.e., while hobbing is not being performed) as shown in FIG. 13. For easy viewing, the unit locking device 25 provided in the unit storage 20 is omitted in FIG. 13.

As illustrated in FIGS. 10 and 13, the support unit 240 includes the support frame 250 and the clamping devices 65 as the fixing mechanism.

The support frame 250 has a seat-surface contact portion 251, a supporting portion 252, and a connecting portion 253. The seat-surface contact portion 251 has a rectangular block shape and is to be brought into contact with the unit mounting seat surface 6q of the mounting receiving member 6p. The supporting portion 252 has a rectangular plate shape and holds a rotatable member 260. The connecting portion 253 has an inclined beam shape and connects the seat-surface contact portion 251 and the support portion 252

The seat-surface contact portion 251 has a contact seat surface 251a (see FIG. 13) that is to be brought into contact with the unit mounting seat surface 6q. The pull bolts 203 protrude from the four corners of the contact seat surface 251a.

The supporting portion 252 including the rotatable member 260 has the same configuration as the supporting portion 52 including the rotatable member 80 described in the Embodiment 1; therefore, detailed description thereof is omitted here.

<Unit Mounting Control>
The operations of the unit mounting control in this embodiment are basically identical to those in the Embodiment 1; therefore, only the differences are described here. In this embodiment, when the tool headstock 6 is driven rightward to the unit mounting/dismounting position from the state shown in FIG. 13 (corresponding to the state shown in FIG. 9E in the Embodiment 1), the four pull bolts 203 protruding from the contact seat surface 251a of the support unit 240 engage with the clamping holes 6r formed in the mounting receiving member 6p of the tool headstock 6. After this engagement, the pull bolts 203 are clamped by the clamping devices 65, whereby the support unit 240 is unremovably fixed to the mounting receiving member 6p.

In this embodiment, the clamping holes 6r correspond to the engagement receiving portion that is formed on the mounting seat surface 6q of the mounting receiving member 6p of the tool headstock 6. Further, as described above, the clamping devices 65 correspond to the fixing mechanism.

Note that the unit dismounting control is executed by the operations of the unit mounting control being performed in the reverse order; therefore, detailed description of the unit dismounting control is omitted here.

<Functions and Effects>
As described above, the tool headstock 6 in this embodiment has the mounting receiving member 6p mounted on and fixed to an outer side surface thereof. The mounting receiving member 6p has the unit mounting seat surface 6q at a position offset to the front side (an example of the side of the tool spindle 7) as viewed in the axial direction of the tool spindle 7.

In this configuration, the unit mounting seat surface 6q is provided at a position offset from the tool spindle 7 by the mounting receiving member 6p provided on the tool headstock 6. Thus, this configuration avoids the unit mounting seat surface 6q being provided in the peripheral area of the tool spindle 7 in the tool headstock 6 where the structure is likely to be complicated. Consequently, it is possible to minimize modification of and addition to the tool headstock 6 and keep down the cost therefor.

(Modification of Embodiment 2)
FIG. 14 illustrates a modification of the Embodiment 2. This modification differs from the Embodiment 2 in that a protective plate 300 can be mounted onto the unit mounting seat surface 6q of the mounting receiving member 6p.

The protective plate 300 has a rectangular shape. The protective plate 300 has pull bolts 301 that protrude from the four corners of the protective plate 300.

The protective plate 300 is stored in a protective-plate storage 26 while hobbing is being performed. The protective-plate storage 26 is arranged below the unit storage 20. After hobbing is completed and the support unit 240 is stored into the unit storage 20, the tool headstock 6 is moved along the path indicated by the dashed and double-dotted arrows in FIG. 14. Thereby, the clamping holes 6r of the unit mounting seat surface 6q are engaged with the pull bolts 301 of the protective plate 300. The pull bolts 301 are thereafter clamped by the clamping devices 65, whereby the protective plate 300 is mounted onto and fixed to the unit mounting seat surface 6q. For the same reasons as described above for the support unit 40, a locking device (not illustrated) for locking the protective plate 300 is provided in the protective-plate storage 26.

In this modification, the protective plate 300 is mounted on and fixed to the unit mounting seat surface 6q of the mounting receiving member 6p while hobbing is not being performed. This prevents chips from adhering to the unit mounting seat surface 6q or entering the clamping holes 6r while machining other than hobbing is being performed.

(Embodiment 3)
FIG. 15 illustrates Embodiment 3. This embodiment differs from the Embodiments 1 and 2 in the location of the unit storage 20.

Specifically, the unit storage 20 in this embodiment is arranged in the magazine housing space S2. In FIG. 15, the solid lines indicate the state where the tool headstock 6 is positioned at the tool change position and the dashed and double-dotted lines indicate movement of the tool headstock 6 to the unit mounting/dismounting position.

In this embodiment, as can be seen from FIG. 15, the tool change position and the unit mounting/dismounting position are arranged as close as possible to each other. Therefore, the time until the support unit 240 is attached to the tool headstock 6 after completion of the attachment of the hob cutter 90 to the tool spindle 7 is shortened. Consequently, the machining cycle time is shortened and the productivity is improved.

(Other Embodiments)
In the above-described embodiments, the hob cutter 90 is held on the tool spindle 7 supported by the tool headstock 6. However, the present invention is not limited to this configuration. For example, a configuration is possible in which a hob cutter is held on a tool spindle supported by the turret tool rest 5. In this case, for example, the turret tool rest 5 can be configured to be movable in the front-rear direction (Y-axis direction) and the unit storage 20 can be arranged on the front side or the rear side of the turret tool rest 5. In this configuration, mounting and dismounting of the support unit 240 to and from the turret tool rest 5 is carried out by movement of the turret tool rest 5 in the front-rear direction. In this case, the turret tool rest 5 corresponds to the tool rest in the present invention.

In the above-described embodiments, the hob-end engagement part that engages with the distal end of the hob cutter 90 is constituted by the rotatable member 80 supported by the bearings 70. However, the hob-end engagement part is not limited thereto and may be constituted by, for example, a conical engaging and fixing member. In this case, for example, a configuration is possible in which the top of the engaging and fixing member engages with a small-diameter hole formed in a distal end surface of the hob cutter 90. This configuration enables the distal end of the hob cutter 90 to be rotatably supported by the engaging and fixing member with the contact area between the hob cutter 90 and the engagement fixing member as small as possible to suppress the frictional resistance between them.

In the above-described embodiments, the fixing mechanism 60 is provided on the support unit 240. However, the present invention is not limited thereto. For example, the fixing mechanism 60 may be provided on the tool headstock 6. Further, the fixing mechanism 60 is not limited to the hydraulically driven type as in the above-described embodiments. For example, the fixing mechanism 60 may have a configuration using an electric arm or a configuration using a magnetic attraction force.

In the above-described embodiments, the annular portion 51 of the support frame 50 is constituted by two members, namely, the annular body 51a and the end-mounted ring 51b. However, the present invention is not limited thereto. For example, the end-mounted ring 51b may be formed integrally with the annular body 51a.

The support unit 40 in the Embodiment 1 is configured such that the annular portion 51 of the support frame 50 surrounds the periphery of the hob cutter 90. However, the present invention is not limited to this configuration and a configuration is possible in which the support unit 40 is configured such that the annular portion 51 rotatably supports the side opposite to the distal side of the hob cutter 90, i.e., the proximal side of the hob cutter 90. In this configuration, the supporting portion 52 corresponds to the first support unit and the annular portion 51 corresponds to the second support unit. The support unit 40 and hob cutter 90 in this configuration are integrally attached to and detached from the tool spindle.

Further, the hob cutter 90 in this configuration may have a configuration in which the proximal side thereof is detachably supported by the annular portion 51 and the distal side thereof is detachably supported by the supporting portion 52. Alternatively, the hob cutter 90 and the support unit 40 may be configured to be undetachable from each other. In these cases, the hob cutter 90 and the support unit 40 are disturbed as an integral hob cutter unit.

It should be noted that the foregoing description of the embodiments is not limitative but illustrative in all aspects. One skilled in the art would be able to make variations and modifications as appropriate. The scope of the invention is not defined by the above-described embodiments, but is defined by the appended claims. Further, the scope of the invention encompasses all modifications made from the embodiments within a scope equivalent to the scope of the claims.

1 Machine tool
6 Tool headstock
7 Tool spindle
6l Annular tapered outer surface
6p Mounting receiving member
6q Unit mounting seat surface
6r Clamping hole
8 Automatic tool changer
8a Tool magazine
9 Tool
16 Partition wall
20 Unit storage
40 Support unit
50 Support frame
51 Annular portion
51f Annular tapered inner surface
52 Supporting portion
53 Connecting portion
60 Fixing mechanism
65 Clamping device
70 Bearing
80 Rotatable member
90 Hob cutter
100 Controller
102 Feed drive unit
203 Pull bolt
240 Support unit
250 Support frame
251 Seat-surface contact portion
252 Supporting portion
253 Connecting portion
260 Rotatable member
S1 Machining area
S2 Magazine housing space
W Workpiece

Claims

A machine tool comprising:
a tool spindle configured to hold a hob cutter;
a tool headstock configured to rotatably hold the tool spindle;
a holding mechanism configured to cause the hob cutter to be held on the tool spindle;
a tool spindle drive unit configured to rotate the tool spindle;
a workpiece spindle configured to hold a workpiece;
a workpiece headstock configured to rotatably hold the workpiece spindle;
a workpiece spindle drive unit configured to rotate the workpiece spindle;
a feed drive unit configured to move the tool headstock and the workpiece headstock relative to each other; and
a controller configured to control the tool spindle drive unit, the workpiece spindle drive unit, and the feed drive unit, wherein:
the machine tool includes:
a support frame mountable onto and dismountable from the tool headstock and configured to, when mounted on the tool headstock, rotatably support an non-held end of the hob cutter held on the tool spindle by the holding mechanism; and
a fixing mechanism configured to fix the support frame mounted on the tool headstock to the tool headstock without interposing the hob cutter;
the fixing mechanism is configured to be switchable between a fixing state for unremovably fixing the support frame to the tool headstock and an unfixing state for unfixing the support frame; and
the controller is configured to drive the holding mechanism to cause the hob cutter to be held on the tool spindle, then drive the fixing mechanism to fix to the tool headstock the support frame supporting the non-held end of the hob cutter and mounted on the tool headstock, and thereafter control the tool spindle drive unit, the workpiece spindle drive unit, and the feed drive unit to machine the workpiece held on the workpiece spindle.
The machine tool according to claim 1, wherein the controller is configured to move the tool headstock in a predetermined direction with the fixing mechanism in the unfixing state to mount and dismount the support frame onto and from the tool headstock using an operating force generated by the movement of the tool headstock.
The machine tool according to claim 1, wherein the support frame comprises:
an annular portion having an annular shape and configured to, with the support frame mounted on the tool headstock, engage with an engagement receiving portion formed on the tool headstock and surround a periphery of the hob cutter held on the tool spindle;
a supporting portion including a bearing and configured to rotatably support with the bearing the non-held end of the hob cutter held on the tool spindle; and
a connecting portion connecting the annular portion and the supporting portion.
The machine tool according to claim 3, wherein:
the engagement receiving portion provided on the tool headstock has an annular tapered surface formed coaxially with an axis of the tool spindle;
the annular portion of the support frame has an annular tapered surface formed coaxially with an axis of the bearing; and
the annular tapered surface of the annular portion is configured to fit with the annular tapered surface of the engagement receiving portion.
The machine tool according to claim 1, wherein the fixing mechanism is configured to, with the support frame mounted on the tool headstock, be switchable between the fixing state and the unfixing state by an action of a fluid pressure supplied through a fluid passage formed in the tool headstock.
The machine tool according to claim 1, wherein:
the tool headstock has a mounting receiving portion formed on an outer surface thereof and the mounting receiving portion has a mounting seat surface at a position offset radially from the tool spindle as viewed in an axial direction of the tool spindle and has an engagement receiving portion provided on the mounting seat surface; and
the support frame comprises:
a seat-surface contact portion configured to, with the support frame mounted on the mounting receiving portion of the tool headstock, engage with the engagement receiving portion formed on the mounting seat surface of the mounting receiving portion and contact with the mounting seat surface;
a supporting portion including a bearing and configured to rotatably support with the bearing the non-held end of the hob cutter held on the tool spindle; and
a connecting portion connecting the seat-surface contact portion and the supporting portion.
The machine tool according to claim 1, wherein:
the machine tool further includes:
a tool changer including a tool change arm and a tool magazine configured to store a plurality of tools, including the hob cutter, attachable to the tool spindle, the tool changer being configured to change a tool held on the tool spindle with a tool stored in the tool magazine with the tool change arm; and
a storage configured to store the support frame therein;
the feed drive unit is configured to move the tool headstock to a tool change position at which tool change is performed between the tool headstock and the tool changer and to a mounting/dismounting position at which mounting and dismounting of the support frame is performed between the tool headstock and the storage; and
the controller is configured to, when attaching the hob cutter stored in the tool magazine to the tool spindle, cause the feed drive unit to move the tool headstock to the tool change position, then cause the tool changer to attach the hob cutter stored in the tool magazine to the tool spindle, then cause the feed drive unit to move the tool headstock from the tool change position to the mounting/dismounting position so as to mount the support frame with the fixing mechanism in the unfixing state onto the tool headstock using an operating force generated by the movement of the tool headstock, and then switch the fixing mechanism to the fixing state.
The machine tool according to claim 7, wherein the controller is configured to, when demounting the support frame fixed to the tool headstock after completion of machining of the workpiece by the hob cutter, first cause the feed drive unit to move the tool headstock to the mounting/dismounting position so as to store the support frame into the storage, then unfix the support frame fixed by the fixing mechanism, and then cause the feed drive unit to move the tool headstock away from the mounting/dismounting position, thereby dismounting the support frame from the tool headstock.
The machine tool according to claim 8, wherein the machine tool further includes a locking device configured to be switchable between a locking state for immovably locking the support frame stored in the storage and an unlocking state for unlocking the support frame.
The machine tool according to claim 7, wherein the storage is arranged on a side opposite to the tool magazine with respect to the tool headstock.
The machine tool according to claim 7, wherein:
the machine tool includes a partition wall separating a machining area as a space in which the tool spindle is located and a magazine housing space in which the tool magazine is housed; and
the storage is arranged in the magazine housing space.
A hob cutter unit comprising:
a first support unit rotatably supporting a hob cutter and having a displacement sensor for detecting a shape displacement of a workpiece, the displacement sensor having a laser light emitter and a laser light receiver; and
a second support unit rotatably supporting a side opposite to a side supported by the first support unit of the hob cutter.