Machine tool provided with clamping jig for rotationally-symmetrical body

Provided is a machine tool which performs a cutting work on a workpiece, in which holes are provided at three or more points in a circumferential direction of a jig in the vicinity of a point at which the jig comes into contact with the workpiece when the workpiece is placed on the jig, and the workpiece is moved toward a rotation center of the jig by blowing air from an air supply unit toward the workpiece through the holes.

RELATED APPLICATIONS

The present application claims priority to Japanese Application Number 2014-127076, filed Jun. 20, 2014, the disclosure of which is hereby incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a machine tool provided with a clamping jig for a rotationally-symmetrical body, and particularly to a machine tool provided with a jig which clamps a workpiece when the workpiece of a rotationally-symmetrical body such as an impeller used in a compressor or the like is subjected to a cutting work.

2. Description of the Related Art

Recently, an impeller used in a vehicle, an air conditioner, or the like is increasingly formed by a cutting work. In the cutting work of the impeller, particularly in a rough machining stage before a finishing machining, a cutter having a large diameter is used or the cutting speed is increased in order to efficiently perform the cutting work and reduce the machining time, in many cases. In addition, in order to use the cutter having a large diameter or increase the cutting speed, as a method of bearing a high cutting load, an impeller workpiece needs to be fixed to a cutting jig. In addition, for good rotational balance of a product after being subjected to the cutting work, the cutting work needs to be performed without eccentricity of a workpiece.

JP 2011-513077 W discloses a machine tool for cutting a workpiece having a center hole, which includes a workpiece support table on which the workpiece is placed, a workpiece holding portion having a gripping arm which presses the workpiece from above, and a driving unit which rotates the workpiece around the center axis line thereof, wherein the workpiece support table has a protrusion which is fitted into the center hole of the workpiece from below, a tip end of the gripping arm has a protrusion which is fitted into the center hole of the workpiece from above, and the protrusion presses the workpiece downward.

However, in the apparatus disclosed in JP 2011-513077 W, a mechanism for bringing the protrusions into contact with the hole is provided, and the angle of the end surface of the hole and the inclined surface of the protrusion have line contact therebetween. Therefore, there is concern that non-contact may occur depending on the precision of the shapes of the hole and the protrusions.

JP 2005-538854 W discloses an apparatus including a tie rod and a support element to clamp a rotationally-symmetrical body for machining, in which a spring force in a direction opposite to a tensile force is applied to the support element, the support element is configured to be bent in an axial direction when the rotationally-symmetrical body abuts the support element because the spring force is weaker than the tensile force, and the support element is elastically supported by a stop of the apparatus and is allowed to move in an axial direction of the clamped rotationally-symmetrical body.

However, in the apparatus disclosed in JP 2005-538854 W, a mechanism for bringing the support element having a centering action into contact with the workpiece is used, and the support element is movable in the axial direction.

In the technique disclosed in any of JP 2011-513077 W and JP 2005-538854 W described above, when a workpiece is fixed to a jig, a mechanism for centering the workpiece on the jig is not present, and thus the workpiece is not centered and is clamped with eccentricity. Therefore, when a cutting work is performed thereon, there is concern that the rotational balance of a product after the cutting work may be degraded.

SUMMARY OF THE INVENTION

The invention provides a machine tool in which a workpiece can be mounted on a jig without eccentricity and the rotational balance of a product after a cutting work is improved.

According to a first aspect of the invention, a machine tool includes: a jig capable of fixing a workpiece to perform a cutting work on the workpiece; a rotating table capable of rotating the workpiece; and an air supply unit capable of supplying air, in which the jig includes at least three holes on a circumference in the vicinity of a point at which the jig comes into contact with the workpiece when the workpiece is fixed, and the air supply unit is capable of supplying the air through the holes.

The jig may include an inclined surface which is depressed toward a rotation center from an outer edge portion of the jig, and the holes may be provided in the inclined surface.

The jig may include a protrusion capable of being fitted into a center hole of the workpiece, and the holes may be provided in the protrusion of the jig.

The jig may include a drawing bar which penetrates through a center hole of the workpiece and allows the workpiece to be drawn in a direction of the jig, and the holes may be provided in the drawing bar.

The jig may include a jig center hole portion and a drawing bar which is substantially concentrically connected to the center hole of the workpiece, and the holes may be provided in the drawing bar.

The jig may include a jig center hole portion into which a protrusion of the workpiece having the protrusion is capable of being inserted, and the holes may be provided in the jig center hole portion.

The machine tool may further include a pressure adjusting unit capable of controlling a pressure of the air which is discharged from each of the holes and is blown toward the workpiece placed on the jig.

According to a second aspect of the invention, a machine tool includes: a jig capable of fixing a workpiece to perform a cutting work on the workpiece; an arm which presses the workpiece against the jig; a rotating table capable of rotating the workpiece; and an air supply unit capable of supplying air, in which the arm includes holes at three or more points on a circumference in the vicinity of a point at which the arm comes into contact with the workpiece when the workpiece is fixed to the jig, and the air supply unit is capable of supplying the air through the holes.

The arm may include an arm protrusion capable of being inserted into a center hole of the workpiece, and the holes may be provided in the arm protrusion.

The arm may include an arm center hole portion into which a protrusion of the workpiece having the protrusion is capable of being inserted, and the holes may be provided in the arm center hole portion.

The machine tool may further include a pressure adjusting unit capable of controlling a pressure of the air which is discharged from each of the holes and is blown toward the workpiece placed on the jig.

According to the invention, it is possible to provide a machine tool in which a workpiece can be mounted on a jig without eccentricity and the rotational balance of a product after a cutting work is improved.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A machine tool according to the invention includes a rotating table10as illustrated inFIG. 1. A jig12is provided on the rotating table10, and a workpiece14having the shape of a rotationally-symmetrical body is fixed onto the jig12. The workpiece14is fixed to the jig12by being pressed against the jig12by an arm16provided above the workpiece14(as described later, there may be cases where the workpiece14is fixed to the jig12without the use of the arm16depending on circumstances). The workpiece14fixed to the jig12is rotated by the rotating table10and is machined by a tool18.

First, a first embodiment of the machine tool according to the invention will be described with reference toFIGS. 2 and 3.

Air supply holes52(52a,52b, and52c) are provided in the upper surface of the jig12is provided with in the vicinity of a location where the jig12comes into contact with the workpiece14when the workpiece14is placed on the jig12. As illustrated inFIG. 3, the air supply holes52a,52b, and52care provided at three points in the upper surface of the jig12at equal distances from the rotation center C and at equal angles (120 degrees therebetween). In addition, the three air supply holes52a,52b, and52care connected to an air supply unit100and are configured such that air supplied from the air supply unit100is blown from each of the air supply holes52a,52b, and52ctoward the workpiece14.

It is preferable to align the rotation center of the workpiece with the rotation center C of the jig. However, in an initial stage in which the workpiece14is mounted on the jig12, the rotation center C of the jig12and the rotation center of the workpiece14are not aligned with each other during the mounting. In this case, in this embodiment, air is blown toward the air supply holes52a,52b, and52cat the three points from the air supply unit100at the same degree of pressure.

As an example, inFIG. 2, it is assumed that the workpiece14is mounted in a state of being slightly biased toward the left with respect to the rotation center C of the jig12. In this case, the gap between the workpiece14and the jig12is narrow on the left side and is wide on the right side. When air is blown from the air supply holes52in this state, the pressure in the gap between the jig12and the workpiece14on the left side with a narrower gap is higher than that on the right side. Therefore, a force to move the workpiece14from the left toward the right is exerted. As a result, the workpiece14is moved from the left side toward the right side in such a direction in which the rotation center thereof is aligned with the rotation center C of the jig12. In this manner, the rotation center of the workpiece14is centered to be aligned with the rotation center of the jig12by blowing air from the air supply holes52. After the rotation center of the workpiece14is aligned with the rotation center of the jig12, the workpiece14is clamped by the jig12and may be machined.

In addition, in this embodiment, an example in which the air supply holes52are provided at the three points (52a,52b, and52c) is used for the description. However, even in a case where the air supply holes52are provided at four or more points, the same effect is obtained. In addition, in this embodiment, the air supply holes52positioned at the three points are provided with equal intervals therebetween. However, the air supply holes52may also be disposed with intervals therebetween which are not equal to each other and the pressure of the air blown from each of the air supply holes52is adjusted by a pressure adjusting unit (not illustrated) such that the pressure of the air from the air supply holes52which are close to each other is set to be low and the pressure of the air from the air supply holes52which are far from each other is set to be high. Accordingly, the rotation center of the workpiece14can be centered to be aligned with the rotation center of the jig12by blowing the air from the air supply holes52. The same is applied to the other embodiments as follows.

Next, a second embodiment of the machine tool according to the invention will be described with reference toFIGS. 4and5.

In this embodiment, the jig12has a protrusion24in the vicinity of the rotation center C thereof, and the protrusion24is configured to be fitted into the center hole22provided in the workpiece14.

In this embodiment, air supply holes54are provided in the upper surface of the protrusion24of the jig12in the vicinity of a location where the protrusion24comes into contact with the workpiece14when the workpiece14is placed on the jig12. As illustrated inFIG. 5, the air supply holes54are provided at three points (air supply holes54a,54b, and54c), and as illustrated inFIG. 5, the air supply holes54a,54b, and54care provided at the three points in the upper surface of the jig12at equal distances from the rotation center C and at equal angles (120 degrees therebetween). In addition, the three air supply holes54a,54b, and54care connected to an air supply unit (not illustrated) and are configured such that air supplied from the air supply unit is blown from each of the air supply holes54a,54b, and54ctoward the workpiece14. The supply of the air from the air supply unit toward the air supply holes54and a mechanism for moving the workpiece14toward the direction of the rotation center C of the jig12by supplying the air are the same as those of the first embodiment described above.

Next, a third embodiment of the machine tool according to the invention will be described with reference toFIGS. 6 and 7.

In this embodiment, the arm16has a protrusion26in the vicinity of a site through which the rotation center C of the jig12passes, and the protrusion26is configured to be fitted into a center hole28provided in the workpiece14.

In this embodiment, air supply holes56are provided in the lower surface of the protrusion26of the arm16in the vicinity of a location where the protrusion26comes into contact with the workpiece14when the workpiece14is placed on the jig12. As illustrated inFIG. 7, the air supply holes56are provided at three points (air supply holes56a,56b, and56c), and as illustrated inFIG. 7, the air supply holes56a,56b, and56care provided at the three points in the lower surface of the protrusion26of the arm16at equal distances from the rotation center C and at equal angles (120 degrees therebetween). In addition, the three air supply holes56a,56b, and56care connected to an air supply unit (not illustrated) and are configured such that air supplied from the air supply unit is blown from each of the air supply holes56a,56b, and56ctoward the workpiece14. The supply of the air from the air supply unit toward the air supply holes56and a mechanism for moving the workpiece14toward the direction of the rotation center C of the jig12by supplying the air are the same as those of the first embodiment described above.

Next, a fourth embodiment of the machine tool according to the invention will be described with reference toFIG. 8.

In this embodiment, the workpiece14is provided with a protrusion30, and the protrusion30of the workpiece14is configured to be inserted into a center hole provided in the arm16.

In this embodiment, air supply holes58are provided in the lower surface of the arm16in the vicinity of a location where the arm16comes into contact with the workpiece14when the workpiece14is placed on the jig12. The air supply holes58are provided at three points, and the air supply holes58are provided at the three points in the lower surface of the arm16at equal distances from the site through which the rotation center C passes and at equal angles (120 degrees therebetween). In addition, the air supply holes58provided at the three points are connected to an air supply unit (not illustrated) such that air supplied from the air supply unit is blown. In addition, the three air supply holes58are connected to an air supply unit (not illustrated) and are configured such that the air supplied from the air supply unit is blown from each of the air supply holes58toward the workpiece14. The supply of the air from the air supply unit toward the air supply holes58and a mechanism for moving the workpiece14toward the direction of the rotation center C of the jig12by supplying the air are the same as those of the first embodiment described above.

Next, a fifth embodiment of the machine tool according to the invention will be described with reference toFIG. 9.

In this embodiment, a drawing bar34is mounted on the jig12and is configured such that the drawing bar34is fitted into a center hole32provided in the workpiece14and the workpiece14is drawn in the jig12via the drawing bar34fitted into the workpiece14.

In this embodiment, three points of the outer periphery of the drawing bar34are provided with air supply holes60at equal intervals therebetween (120 degrees therebetween). The air supply holes60are connected to a conduit having the same axis as the center axis of the drawing bar34and to an air supply unit (not illustrated) which is connected to the conduit such that the air supplied from the air supply unit is blown from the air supply holes60of the drawing bar34. The supply of the air from the air supply unit toward the air supply holes60and a mechanism for moving the workpiece14toward the direction of the rotation center C of the jig12by supplying the air are the same as those of the first embodiment described above.

Next, a sixth embodiment of the machine tool according to the invention will be described with reference toFIG. 10.

Even in this embodiment, as in the fifth embodiment described above, the drawing bar34is mounted on the jig12, and the drawing bar34is fitted into a center hole36provided in the workpiece14. A difference from the fifth embodiment is that the center hole36of the workpiece14does not penetrate through the workpiece14to the top and is provided to reach an intermediate position of the workpiece14.

In this embodiment, three points of the outer periphery of the drawing bar34are provided with air supply holes62at equal intervals therebetween (120 degrees therebetween). The air supply holes62are connected to a conduit having the same axis as the center axis of the drawing bar34and to an air supply unit (not illustrated) which is connected to the conduit such that the air supplied from the air supply unit is blown from the air supply holes62of the drawing bar34. The supply of the air from the air supply unit toward the air supply holes62and a mechanism for moving the workpiece14toward the direction of the rotation center C of the jig12by supplying the air are the same as those of the first embodiment described above.

Next, a seventh embodiment of the machine tool according to the invention will be described with reference toFIG. 11.

In this embodiment, the workpiece14is provided with a protrusions38, and the protrusions38is configured to be inserted into a jig center hole40provided in the jig12.

In this embodiment, air supply holes64are provided in the jig12such that the supply holes64may be blocked by the protrusion38of the workpiece14when the protrusion38of the workpiece14is inserted into the center hole40of the jig12. Three air supply holes64are provided on the circumference in the jig center hole40about the rotation center C of the jig12with equal intervals therebetween (at an angle of 120 degrees therebetween). The three air supply holes64are connected to an air supply unit (not illustrated) and are configured such that air supplied from the air supply unit is blown from each of the air supply holes64toward the workpiece14. The supply of the air from the air supply unit toward the air supply holes64and a mechanism for moving the workpiece14toward the direction of the rotation center C of the jig12by supplying the air are the same as those of the first embodiment described above.

In addition, the invention can be appropriately modified to, in addition to the above-described embodiments, a configuration in which air supply holes are provided in the jig12and the peripheral members thereof or in the arm16and the peripheral members thereof and air is blown from the air supply holes. The number of air supply holes may be four or more, and a plurality of air supply holes may not necessarily be disposed with equal intervals therebetween.