JPH08323505A - Machine tool - Google Patents

Abstract

PURPOSE: To improve an appearance of a finishing surface by supporting a main spindle with a magnetic bearing means in its slant posture so that the tool installing end part side becomes the feeding directional front side of a spindle device to a line orthogonal to the feeding direction of the spindle device to a work object. CONSTITUTION: In a lower side radial magnetic bearing part 11, these electromagnets 18a and 18b are controlled so that a gap between the first radial electromagnet 18a on the feeding directional side of a spindle device 4 and a main spindle 7 becomes smaller than that between the second radial electromagnet 18b on the anti-feeding directional side and the main spindle 7, and that the axis 7A in a lower part of the main spindle 7 becomes eccentric to the front side more than a neutral position. In an upper side radial magnetic bearing part 10, these electromagnets 17a and 17b are controlled so that a gap between the second radial electromagnet 17b on the anti- feeding directional side and the main spindle 7 becomes smaller than that between the first radial electromagnet 17a on the feeding directional side and the main spindle 7, and that the axis 7A in an upper part of the main spindle 7 becomes eccentric to the rear side more than the neutral position. Therefore, the main spindle 7 and a tool 3 incline to the neutral position so that the lower side becomes the front.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a machine tool, and more particularly, to a machine tool having a magnetic bearing spindle device in which a main shaft is supported by a magnetic bearing in a non-contact manner, and a flat tip surface orthogonal to an axis line such as an end mill. A tool for machining a workpiece by mounting a cylindrical machining tool with a cutting edge on its side and a spindle on the spindle and moving the spindle device and the workpiece relative to each other in a direction substantially orthogonal to the axis of the spindle device. Machine related.

[0002]

2. Description of the Related Art Conventionally, in this type of machine tool, the spindle and the axis of the machining tool are made to substantially coincide with the axis of the spindle device, and the spindle device is attached to the workpiece in a direction perpendicular to the axis of the machining tool. Was supposed to be sent.

[0003]

In the conventional machine tool as described above, since the feed direction of the spindle device with respect to the workpiece is exactly perpendicular to the axis of the machining tool, the machining tool such as the above end mill is used. When using, the tip surface of the processing tool matches the feed direction. For this reason, most of the side surface of the processing tool is processed only in the front part in the feed direction,
The tip surface of the working tool only scrapes the remaining surface after it has been machined in the front part of the side surface. Therefore, 1 processing tool
It is not possible to precisely process a work piece simply by sending it. Further, there is a problem that the finished surface does not have a uniform cutter mark and the finished surface does not look good.

The object of the present invention is to solve the above problems,
It is to provide a machine tool that is capable of precision machining and has a good finished surface.

[0005]

A machine tool according to the present invention includes a magnetic bearing spindle device to which a machining tool for machining a workpiece mounted at a predetermined position is mounted, a workpiece and the spindle device. A spindle unit having a tool mounting end for mounting a machining tool; a magnetic bearing unit for magnetically levitating and supporting the spindle in a non-contact manner; and a spindle unit. In the machine tool, the magnetic bearing means comprises a rotary drive means for rotationally driving, and the feed means has a function of relatively moving the workpiece and the spindle device in a direction substantially orthogonal to the axis of the spindle device. However, the main axis is
It is characterized in that the tool mounting end side is inclined and supported with respect to a line orthogonal to the feed direction of the spindle device with respect to the workpiece so that the tool mounting end side is on the front side in the feed direction of the spindle device.

For example, the magnetic bearing means is provided with an axial magnetic bearing portion for supporting the spindle in a non-contact manner in the axial direction, and a spindle mounted on the tool mounting end side and the counter tool mounting end side of the spindle. A first radial magnetic bearing portion and a second radial magnetic bearing portion that are supported in a non-contact direction, a spindle position detector that detects the axial and radial positions of the spindle, and a detection signal of the spindle position detector. And a magnetic bearing control unit that controls each of the magnetic bearing units so that the main shaft is supported at a predetermined target position, the first radial magnetic bearing unit and the second radial magnetic bearing unit, Each of the magnetic bearing control units includes four electromagnets arranged so as to sandwich the main shaft from both sides in a radial direction orthogonal to each other in a plane substantially perpendicular to the axis thereof. Based on the position signal from the main shaft position detection unit, the electromagnet whose gap between the electromagnet on the feed direction side of the spindle device and the main shaft is the opposite feed direction side among the four electromagnets of the first radial magnetic bearing unit And controlling the first radial magnetic bearing so as to be smaller than the gap between the main shaft and the electromagnet on the feed direction side of the spindle device among the four electromagnets of the second radial magnetic bearing. The second radial magnetic bearing unit is controlled so that the gap between the main shafts is larger than the gap between the electromagnet on the side opposite to the feed direction and the main shaft.

[0007]

When using a cylindrical machining tool such as an end mill having a flat tip surface orthogonal to the axis and a cutting edge on the side surface, the spindle is tilted so that the tool mounting end side is the front side in the feed direction. Therefore, the tip surface of the tool is inclined with respect to the feed direction, and the line on which the rear end of the tool tip surface in the feed direction moves is located inside the work piece rather than the line on which the front end moves. . For this reason, the remaining surface after being processed by the front side portion of the side surface of the tool is further processed by the tip surface, so that roughing and finishing are performed in succession by one feed. Therefore, precise machining can be performed with one feed, and a uniform cutter mark is provided on the finished surface due to the rear peripheral portion of the tip end surface of the tool, so that the finished surface looks good. During processing, cutting resistance acts on the tool in the opposite direction to the feed direction, but by pre-tilting the spindle so that the tool mounting end side is in front, the rigidity against cutting resistance increases and the load capacity increases. And heavy cutting becomes possible.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 schematically shows a main part of a machine tool used for milling or the like. In the following description, the right side of FIG. 1 is the front, the left side is the rear, and the left and right when viewing the front from the back is the left and right. Also, the longitudinal axis is the X axis,
The horizontal axis is the Y axis, the vertical axis is the Z axis, the front side is the positive direction of the X axis, the left side is the positive direction of the Y axis, and the upper side is the positive direction of the Z axis.

In FIG. 1, a moving table (2) on which a work piece (1) is fixed, and a magnetic bearing spindle device (on which a working tool (3) for working the work piece (1) is mounted are shown. 4) and the X-axis feed device (5) which constitutes a feed means for relatively moving the workpiece (1) and the spindle device (4) in the same direction by moving the table (2) in the X-axis direction. It is shown. Although not shown, the machine tool has
(1) and the spindle device (4), a Y-axis direction feed device that constitutes a feed means for relatively moving in the Y-axis direction, and a workpiece
There is also provided a Z-axis direction feed device which constitutes a feed means for relatively moving the (1) and the spindle device (4) in the Z-axis direction. These feeding devices need only be able to move the table (2) and the spindle device (4) relative to each other, and may drive either the table (2) or the spindle device (4).

FIG. 2 shows the overall schematic construction of the spindle device (4), and FIGS. 3 and 4 show the construction of each part thereof.

The spindle device (4) comprises a vertically arranged cylindrical casing (6) and a main shaft (7) rotatably supported in the casing (6) substantially vertically and in a non-contact state. . The main shaft (7) is non-contact supported by an axial magnetic bearing part (8) provided in the casing (6) and two upper and lower radial magnetic bearing parts (10) and (11), and constitutes a rotation driving means. It is rotated at high speed by the high frequency motor (12). The lower end of the spindle (7) is a tool mounting end (7a), and a machining tool (3) such as an end mill is mounted on this part. This tool (3) has a flat tip surface (3a) at the lower end that is orthogonal to its axis (3A), and this tip surface (3a) and side surface (3b)
It has a cylindrical shape with a cutting edge. Side of tool (3) (3
b) may be a cylindrical surface or a conical surface. The tool (3) is mounted on the spindle (7) such that its axis (3A) coincides with the axis (7A) of the spindle (7).

The axial magnetic bearing part (8) is for supporting the main shaft (7) in the axial direction (Z-axis direction), and the flange part (7b) at the middle part of the main shaft (7) is from above and below both sides. It is provided with a pair of annular electromagnets (axial electromagnets) (13a) (13b) arranged so as to be sandwiched. The axial electromagnets are collectively referred to by the reference numeral (13), and when it is necessary to distinguish them, the upper one is called the upper axial electromagnet (13a) and the lower one is called the lower electromagnet (13b). The upper and lower axial electromagnets (13) attract the flange portion (7b) of the spindle (7) by magnetic force to support the spindle (7) in the axial direction in a non-contact manner, and are connected to the magnetic bearing control circuit (14). Has been done. An axial position sensor (15) for detecting the axial position of the main shaft (7) is provided in the upper part of the casing (6). This sensor (15) is connected to the position detection circuit (16).

The radial magnetic bearings (10) and (11) are connected to the main shaft (7).
For supporting in the radial direction (X-axis and Y-axis directions). The upper radial magnetic bearing portion (second radial magnetic bearing portion) (10) is composed of four electromagnets (radial electromagnets) (17a) (17a) which are arranged so as to sandwich the main shaft (7) from both sides in the X-axis and Y-axis directions. 17b) (17c) (17d) are provided. These radial electromagnets are collectively referred to by the reference numeral (17), and when it is necessary to distinguish them, the one on the positive side in the X-axis direction (front side) is the upper first radial electromagnet (17a) and the negative side in the X-axis direction (rear side). The upper second radial electromagnet (17b), the Y axis direction positive side (left side) the upper third radial electromagnet (17c), and the Y axis direction negative side (right) the upper fourth radial electromagnet (17d). ). Similarly, the lower radial magnetic bearing portion (first radial magnetic bearing portion) (11) also has a lower first radial electromagnet (18).
a) A lower second radial electromagnet (18b), a lower third radial electromagnet (18c) and a lower fourth radial electromagnet (18d). These are collectively referred to by the reference numeral (18). The upper and lower radial electromagnets (17) (18) attract the main shaft (7) by magnetic force and support it in the radial direction in a non-contact manner, and are connected to the magnetic bearing control circuit (14) described above. A pair of front and rear radial position sensors (19a) (19b) for detecting the position of the upper part of the main shaft (7) in the X-axis direction and a position in the Y-axis direction are provided near the upper radial magnetic bearing (10). A pair of left and right radial position sensors (19c) (19d) for detection are provided. These upper radial position sensors are collectively referred to by the reference numeral (19). Also, near the lower radial magnetic bearing part (11),
A pair of front and rear radial position sensors (20a) (20b) for detecting the position of the lower part of the main shaft (7) in the X axis direction, and a pair of left and right radial position sensors for detecting the position of the Y axis direction.
(20c) and (20d) are provided. These lower radial position sensors are collectively referred to by the reference numeral (20). The upper and lower radial position sensors (19) (20) are connected to the position detection circuit (16) described above.

Axis line (4A) of the radial magnetic bearings (10) (11)
Coincides with the axis (6A) of the casing (6) and is parallel to the Z axis. This radial magnetic bearing (10) (11) axis (4
Let A be the axis of the spindle device (4).

The position detection circuit (16) detects the position of the spindle (7) in the Z-axis direction based on the output of the axial position sensor (15) and outputs the upper and lower radial position sensors (19) (20). It is for detecting the radial position of the main shaft (7) based on. The position sensors (15), (19) and (20) and the position detection circuit (16) constitute a spindle position detection unit for detecting the position of the spindle (7). The main shaft
The radial position of (7) includes the position of the center of gravity in the X-axis direction and the Y-axis direction, and the inclination of the axis (7A) in the XZ plane and the YZ plane.

The magnetic bearing control circuit (14) includes a position detection circuit (1
Based on the output of 6), it controls the axial electromagnet (13) and radial electromagnets (17) (18) so that the position of the main shaft (7) becomes a predetermined target position, and constitutes the magnetic bearing control unit. are doing. The position where the axis (7A) of the spindle (7) coincides with the axis (4A) of the spindle device (4) is called the neutral position of the spindle (7).

Motor (12) and magnetic bearing control circuit (14)
Is connected to an NC control device of a machine tool (not shown), and this NC control device controls the entire machine tool (for example, the feed direction of the feeding means and the cutting amount).

In the above machine tool, when the spindle device (4) is fixed at a fixed position and the spindle (7) and the tool (3) are rotating at high speed, the table (2) is attached to the spindle device (4).
It has a function of processing the workpiece (1) by sending it in the horizontal direction orthogonal to the axis line (4A), that is, the X-axis direction, the Y-axis direction, or both the X and Y axis directions. In this way, when the spindle device (4) is horizontally fed to the workpiece (1) for machining, the magnetic bearing control circuit (14) receives a signal indicating the feeding direction from the NC controller, Spindle device (4) axis (4
(A) That is, with respect to the neutral position, the main shaft (7) is inclined so that the tool mounting end (7a) side (lower side) is on the front side in the feeding direction of the spindle device (4) (13) ( 17) It is designed to control (18).

Next, referring to FIGS. 2 and 5, when the table (2) is fed in the negative direction of the X-axis by the X-axis direction feeding device (5), that is, the spindle device ( Four)
A description will be given of a case where the tool is fed in the positive direction (forward direction) of the X-axis for processing.

In this case, in the lower radial magnetic bearing portion (11), the gap between the first radial electromagnet (18a) on the feed direction side of the spindle device (4) and the main shaft (7) is the same as that on the counter feed direction side. 2 Radial electromagnets (18b) are smaller than those of the main shaft (7) so that the axis (7A) at the bottom of the main shaft (7) is eccentric to the front side from the neutral position.
(18b) control and at the same time, upper radial magnetic bearing part (10)
The gap between the second radial electromagnet (17b) on the opposite feed direction side and the spindle (7) is smaller than that between the first radial electromagnet (17a) on the feed direction side and the spindle (7).
These electromagnets (17a) and (17b) are controlled so that the axis (7A) at the upper part of (7) is eccentric to the rear side from the neutral position. The upper and lower third and fourth radial electromagnets (17c) (17d) (1
8c) (18d) and the axial electromagnet (13),
Perform the same control as when holding the spindle (7) in the neutral position. Upper and lower first and second radial electromagnets (17a) (17b) (1
By controlling 8a) and (18b) as described above, as shown in FIG. 5, the spindle (7) and the tool (3) are tilted so that the lower side is in front of the neutral position. Note that FIG.
Shows the inclination of the tool (3) exaggerated.
In such a state, the spindle device (4) is sent to the workpiece (1) in the positive direction of the X axis, and the horizontal surface (1a) of the workpiece (1) is processed. At this time, since the tool (3) is inclined so that the lower side is the front side in the X-axis direction, the front end surface (3a) of the tool (3) is the front side in the feeding direction (X-axis direction). The line (L1) on which the rear end (3c) of the tip surface (3a) of the tool (3) moves is the line (L1) on which the front end (3d) of the tip surface (3a) moves.
From 2), it is located inside (lower side) of the work piece (1).
For this reason, the remaining surface (1b) after processing at the front part of the side surface (3b) of the tool (3) will be further processed at the tip surface (3a), and roughing and finishing will be performed with one feed. It becomes a form that processing is done one after another. Therefore, it is possible to perform precise machining with one feed, and the rear edge of the tip surface (3a) of the tool (3) gives a uniform cutter mark on the finished surface (1c),
It also looks better. When the spindle device (4) is fed to the front side of the work piece (1) for machining, the tool (3) is subjected to a backward cutting resistance opposite to the feed direction, and this cutting resistance is 7) acts in a direction in which it is separated from the lower first radial electromagnet (18a) and the upper second radial electromagnet (17b). However, the main shaft (7) and the above two electromagnets (17b) (18
These electromagnets have a small gap with a).
(17b) and (18a) have a large force for attracting the spindle (7), so that the rigidity against cutting resistance is increased, the load capacity is increased, and heavy cutting is possible.

Spindle device (4) for the workpiece (1)
Is sent in the negative direction of the X-axis, the magnetic bearing control circuit (14)
The upper and lower first and second radial electromagnets (17a) (17b) (18a) (18b) are controlled so that the main shaft is inclined in the direction opposite to the above.

When the spindle device (4) is fed to the workpiece (1) by the Y-axis direction feed device in the Y-axis direction for machining, the magnetic bearing control circuit (14) is arranged so that the lower side of the spindle (7) is The upper and lower third and fourth radial electromagnets are arranged so that the main shaft (7) is inclined in the direction to the front of the feed direction of the spindle device (4).
(17c) (17d) (18c) (18d) is controlled.

The X-axis direction feed device (5) and the Y-axis direction feed device are simultaneously driven to drive the work piece (1) into a spindle device.
When (4) is sent simultaneously in both X and Y axis directions for machining,
The magnetic bearing control circuit (14) includes the first to fourth radial electromagnets (upper and lower) so that the main shaft (7) is inclined such that the lower side of the main shaft (7) becomes the front side of the feed direction of the spindle device (4). 17a) (17
b) Controls (17c) (17d) (18a) (18b) (18c) (18d).

[0025]

As described above, according to the machine tool of the present invention, it is possible to perform precision machining with one feed, and to make uniform cutter marks on the finished surface so that the finished surface looks good. Get better. Further, the rigidity with respect to the cutting resistance can be increased to increase the load capacity and heavy cutting can be performed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a main part of a machine tool showing an embodiment of the present invention.

FIG. 2 is an enlarged vertical sectional view showing a portion of a spindle device.

FIG. 3 is a horizontal sectional view of a radial magnetic bearing portion of the spindle device.

FIG. 4 is a horizontal sectional view of a radial position sensor portion of the spindle device.

FIG. 5 is a vertical cross-sectional view showing an enlarged part of a workpiece and a processing tool during processing.

[Explanation of symbols]

(1) Workpiece (2) Moving table (3) Machining tool (3A) Machining tool axis (4) Spindle device (4A) Spindle device axis (5) X-axis direction feeding device (feeding means) (6) Casing (7) Spindle (7A) Spindle axis (7a) Tool mounting end (8) Axial magnetic bearing (10) Upper radial magnetic bearing (2nd)
Radial magnetic bearing part) (11) Lower radial magnetic bearing part (No. 1)
(12) High-frequency motor (rotational drive means) (13a) (13b) Axial electromagnet (14) Magnetic bearing control circuit (magnetic bearing control unit) (15) Axial position sensor (spindle position detection unit) ( 16) Position detection circuit (spindle position detection part) (17a) (17b) (17c) (17d) Upper radial electromagnet (18a) (18b) (18c) (18d) Lower radial electromagnet (19a) (19b) (19c) ) (19d) Upper radial position sensor (spindle position detector) (20a) (20b) (20c) (20d) Lower radial position sensor (spindle position detector)

Claims (2)

[Claims] 1. A magnetic bearing spindle device on which a machining tool for machining a workpiece attached at a predetermined position is mounted, and a feeding means for relatively moving the workpiece and the spindle device. The spindle device includes a main shaft having a tool mounting end on which a machining tool is mounted, a magnetic bearing unit that magnetically levitates the main shaft to support the main shaft in a non-contact manner, and a rotation driving unit that rotationally drives the main shaft, In a machine tool having a function of relatively moving a work piece and the spindle device in a direction substantially orthogonal to an axis of the spindle device, the magnetic bearing means causes the main shaft to move the spindle with respect to the work piece. It is characteristic that the tool mounting end side is inclined and supported with respect to a line orthogonal to the feed direction of the spindle device so that the tool mounting end side is the front side in the feed direction of the spindle device. Machine tools to collect. 2. The magnetic bearing means includes an axial magnetic bearing portion for supporting the spindle in a non-contact manner in an axial direction, and a spindle mounted radially on the tool mounting end side and a counter tool mounting end side of the spindle. A first radial magnetic bearing portion and a second radial magnetic bearing portion that are supported in a non-contact direction, a spindle position detector that detects the axial and radial positions of the spindle, and a detection signal of the spindle position detector. And a magnetic bearing control unit that controls each of the magnetic bearing units so that the main shaft is supported at a predetermined target position, the first radial magnetic bearing unit and the second radial magnetic bearing unit, Each of the magnetic bearing control units includes four electromagnets arranged so as to sandwich the main shaft from both sides in a radial direction orthogonal to each other within a plane substantially perpendicular to the axis, and the magnetic bearing control unit includes the main shaft position. Based on the position signal from the detection unit,
Among the four electromagnets of the first radial magnetic bearing unit, the gap between the electromagnet on the feed direction side of the spindle device and the spindle is smaller than the gap between the electromagnet on the opposite feed direction side and the spindle. The first radial magnetic bearing portion is controlled, and the electromagnet on the feed direction side of the spindle device and the electromagnet on the opposite feed direction side of the four electromagnets of the second radial magnetic bearing portion are provided. The machine tool according to claim 1, wherein the second radial magnetic bearing portion is controlled so as to be larger than a gap between the spindles.