JPH0885006A - Main spindle supporting device for machine tool - Google Patents

Abstract

PURPOSE: To provide a main spindle supporting device for a machine tool, which can surely and always apply a necessary preload to a bearing part, which supports the main spindle. CONSTITUTION: In the main spindle supporting device for the machine tool, which supports a main spindle 3 in a freely rotatable manner with respect to a spindle head 1, a first bearing part 10, which is installed in the forward, inner peripheral surface 15 of the spindle head 1 in order to support the main spindle 3, a sleeve 11, which is arranged in the inward part of the rear, inner peripheral surface 20 of the main spindle 21 in such a manner that the sleeve 11 can make reciprocal motion in the axial direction, and a second bearing part 12, which is installed in the inner, peripheral surface 21 in order to support the main spindle 3, are prepared. In addition, a magnetic bearing device 13, which holds the sleeve 11 by means of magnetic force with respect to the rear, inner peripheral surface 20, and a spring 50, which is interposed between the spindle head 1 and the sleeve 11 and which energizes the sleeve 11 in the axial direction so as to apply a necessary preload to the first and second bearing parts 10, 12, are prepared, so that the sleeve 11 can be supported in a non- contact condition with respect to the spindle head 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle support device for machine tools, and more particularly to a spindle support device having a structure in which a constant preload is constantly applied to a bearing portion of the spindle.

[0002]

2. Description of the Related Art In a machine tool, a spindle mounted with a tool or provided with a mounting member (for example, a chuck) for mounting a workpiece (workpiece) is rotated in a spindle head through a bearing portion to rotate the workpiece. The workpiece is machined by relatively moving the tool, but a preload is applied to the bearing in order to eliminate the rattling between the outer ring and the inner ring of the bearing and to obtain the rotational accuracy and rigidity of the main shaft. ing.

However, as the spindle rotational speed increases, the thermal displacement of the spindle increases, making it impossible to maintain a constant preload. Therefore, a technique of a spindle structure that constantly maintains a constant preload is disclosed. For example, JP-A-2-2792
In JP-A-03-2003, in order to apply a preload to a bearing that supports a main shaft, a preload variable type spindle unit having a structure in which a bearing box that presses the bearing in the axial direction is fitted inside an outer cylinder and moved in the axial direction is disclosed. Proposed.

[0004]

In this case, the bearing box is in sliding contact with the outer cylinder, but the moving distance of the bearing box in the axial direction is extremely small. The problem was that it was not always smooth and that the preload could not be kept constant. This also applies to the case where the rolling linear bearing such as a ball slide is used to move the point contact. In addition, since there is a minute gap between the bearing box and the outer cylinder, there is a possibility that vibration may occur in the gap and fine sliding wear may occur on the sliding surface.

The present invention has been made to solve the above problems, and provides a spindle support device for a machine tool that can always reliably apply a required preload to a bearing portion that supports the spindle. To aim.

[0006]

In order to achieve the above object, the present invention provides a spindle support device for a machine tool, which rotatably supports a spindle with respect to a spindle head, in which a front inner peripheral surface of the spindle head is provided. A first bearing portion mounted to pivotally support the main shaft, a sleeve disposed inside the rear inner peripheral surface of the main spindle head so as to be reciprocally movable in the axial direction, and attached to the inner peripheral surface of the sleeve. And a magnetic bearing device for holding the sleeve by a magnetic force with respect to the inner peripheral surface of the main spindle head rear portion, and a second bearing portion axially supporting the main spindle, and interposed between the main spindle head and the sleeve. In addition, an elastic member for biasing the sleeve in the axial direction to apply a required preload to the first and second bearing portions is provided, and the sleeve can be supported in a non-contact manner with respect to the spindle head.

[0007]

In the present invention, since the sleeve having the second bearing portion attached thereto is held against the rear inner peripheral surface of the spindle head by the magnetic force of the magnetic bearing device, the sleeve is attached to the rear inner peripheral surface of the spindle head. On the other hand, it moves smoothly in a small distance in the axial direction in a non-contact state.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention, FIG. 2 is a partially enlarged view of FIG. 1, FIG. 3 is a view taken in the direction of arrow B of FIG. In this embodiment, a machining center is used as the machine tool, but other types of machine tools such as an NC lathe may be used.

As shown in the figure, the machining center is provided with a spindle head 1, and the spindle support device 2 is provided with a spindle head 1.
On the other hand, the main shaft 3 is rotatably supported. The spindle 3 is
The rotor 4 and the stator 5 are rotatably driven by a built-in motor 6 in which the rotor 4 and the stator 5 are arranged between the spindle 3 and the spindle head 1,
Rotate against. The spindle head 1 is provided with a lid member 7 fastened and fixed to the tip end thereof, and the spindle 3 is fitted with a lid member 7
Is rotatably fitted to the inner peripheral surface 8 of the.

The spindle support device 2 supports a first bearing portion 10 for supporting the front portion of the spindle 3, a sleeve 11 arranged at the rear end of the spindle head 1, and a rear portion or a central portion of the spindle 3. The second bearing portion 12, the magnetic bearing device 13 that holds the sleeve 11 movably in the axial direction with respect to the spindle head 1, and the magnetic bearing device 13 that is interposed between the spindle head 1 and the sleeve 11 and that has an elastic force. And a spring 50 which is an elastic member for urging the sleeve 11 in the axial direction via the shaft 11 to give a required preload to the first and second bearing portions 10 and 12.
Can be supported without contact. Further, the gap d between the rear inner peripheral surface 20 of the spindle head 1 and the sleeve 11 is extremely small.

The first bearing portion 10 is attached to the front inner peripheral surface 15 of the spindle head 1 and rotatably supports the spindle 3. The first bearing portion 10 includes a pair of rolling bearings 16 and 17 arranged side by side in the axial direction, and a spacer 18 mounted between the bearings 16 and 17.

The sleeve 11 is arranged in a non-contact state inside the rear inner peripheral surface 20 of the spindle head 1 so as to be capable of reciprocating in the axial direction with a minute gap d. The second bearing portion 12 having substantially the same configuration as the first bearing portion 10 has a structure symmetrical to the first bearing portion 10 in the axial direction, and includes a pair of rolling bearings 16 and 17, and a bearing 16 , 17 and a spacer 18a mounted between the two. The magnetic bearing device 13 holds the sleeve 11 against the inner peripheral surface 20 of the spindle head rear portion by magnetic force.

A plurality of springs 50, which are biasing members, are evenly arranged in the circumferential direction. The springs 50 move the sleeve 11 in the axial direction, and the first and second bearing portions 10,
It is designed to give 12 a preload. The spring 50 is attached by engaging both ends with a recess in the rear end surface 51 of the spindle head 1 and a recess in the flange side surface 53 of the sleeve 11 facing the rear end surface 51. The sleeve 11 is biased in the direction of arrow C. Further, for example, one detent member 55 is provided between the sleeve 11 and the spindle head 1, so that the sleeve 11 does not move in the rotational direction with respect to the spindle head 1.

Bearing 1 of first and second bearing portions 10 and 12
The inner rings 6 and 17 are press-fitted and fixed to the outer peripheral surface 3 a of the main shaft 3. The outer races of the bearings 16 and 17 in the first bearing portion 10 are press-fitted and fixed to the front inner peripheral surface 15 of the spindle head 1. The outer races of the main shafts 16 and 17 of the second bearing portion 12 are press-fitted and fixed to the inner peripheral surface 21 of the sleeve 11.

The magnetic bearing device 13 includes an inner peripheral surface 2 of the spindle head 1.
0 and the outer peripheral surface 33 of the sleeve 11 and a magnetic bearing portion 22 disposed in the opposing portion, and a plurality (for example, four) of the eddy current type disposed in the circumferential direction in order to detect the gap d in the radial direction. The radial direction displacement sensor 23, a position detection circuit 24 that calculates and detects the position of the sleeve 11 by a detection signal from the displacement sensor 23, and controls the magnetic bearing portion 22 based on the calculation result of the detection circuit 24. Control circuit 25 for calculating the current supplied to each electromagnetic body (magnet stator) 37
And a power amplifier circuit 26 that amplifies a control signal output from the control circuit 25 and outputs a current to the magnetic bearing portion 22.

The control circuit 25 compares the reference signal circuit 30 for generating a reference signal with the deviation between the reference signal output from the reference signal circuit 30 and the position of the sleeve 11 calculated by the position detection circuit 24. A circuit 31 and a signal processing circuit 32 that processes the signal output from the deviation comparison circuit 31 by PID control or the like and outputs a control signal to the power amplification circuit 26 are provided.

The magnetic bearing portion 22 includes a circular magnetic body (radial rotor) 35 on the floating side mounted in an annular groove 34 formed on the outer peripheral surface 33 of the sleeve 11, and a rear inner peripheral surface 20 of the spindle head. A plurality of sets (for example, four sets) of electromagnetic bodies 37 on the fixed side mounted in the formed groove portion 36 are provided.

The magnetic body 35 is made of a ferromagnetic body such as an annular laminated silicon steel plate. The electromagnetic body 37 is composed of a convex portion 38 of a laminated silicon steel plate and an exciting coil wound around the convex portion 38. The two convex portions 38 form one set of the electromagnetic body 37, and the magnetic body 35 is interposed therebetween. One closed magnetic loop R is formed. One displacement sensor 23 is arranged for each closed magnetic loop R.

In the magnetic bearing device 13, the gap d corresponding to the displacement δ of the center O ₂ of the sleeve 11 with respect to the rotation center O ₁ of the main shaft 3 is detected by the displacement sensor 23, and each electromagnetic body 3 is detected.
By controlling the electromagnetic force of 7, the centers O ₁ and O ₂ are made to coincide with each other so that the displacement δ is brought close to zero, whereby the sleeve 11 is always held at a predetermined position.

Annular projections 11a and 11a are provided on both sides of the magnetic body 35 mounting portion of the sleeve 11. The gap between the convex portion 11a and the spindle head 1 is a gap between the magnetic body 35 and the convex portion 38 of the electromagnetic body 37 (for example, 0.2 to 0.3 m).
m) A minute amount (for example, 0.01 to 0.02 m)
m). This is to prevent the accident from spreading when the magnetic bearing device 13 is abnormal or when an abnormal external force is applied to the main shaft 3 due to a collision or the like.

Next, the operation of this embodiment will be described.
First, the magnetic bearing device 13 is turned on, and the control circuit 2
The electromagnetic body 37 is excited by the control signal from the motor 5 via the power amplification circuit 26 to hold the magnetic body 35 by the magnetic force. As a result, the sleeve 11 is held in the center position in a non-contact state with the rear inner peripheral surface 20 of the spindle head 1.

Next, the motor 6 for driving the spindle is turned on to rotate the spindle 3, and the work is processed by the tool 41. While the main shaft 3 is rotating, the first and second bearing portions 10 and 12 generate heat,
Even if thermal displacement occurs in the spindle 3 and the like, the sleeve 11 keeps the spindle head 1
Since it is held in a non-contact state with respect to, it can smoothly move in a small distance in the axial direction (for example, several μm to several tens of μm),
The preload is automatically adjusted so that it always becomes a proper constant value.

Therefore, the spindle 3 can be rotated at a high speed. Further, since the magnetic bearing portion 22 does not need lubrication, maintenance is unnecessary and the life is semipermanent. Moreover, since the vibration of the main shaft 3 can be suppressed by the magnetic bearing portion 22, fine movement wear does not occur. Furthermore, the spindle 3
Even if the sleeve 11 is slightly thermally deformed due to heat generation, the gap d exists, so that the moving operation of the sleeve 11 is not adversely affected.

[0023]

Since the present invention is configured as described above, the required preload can always be reliably applied to the bearing portion that supports the main shaft.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram according to an embodiment of the present invention.

FIG. 2 is a partially enlarged view of FIG.

FIG. 3 is a view taken in the direction of arrow B in FIG. 1 and a part thereof is shown in a cross section taken along line III-III.

[Explanation of symbols]

 1 Spindle Head 2 Spindle Support Device 3 Spindle 10 First Bearing Part 11 Sleeve 12 Second Bearing Part 13 Magnetic Bearing Device 15 Front Inner Surface 20 Rear Inner Surface 21 Sleeve Inner Surface 50 Spring (Elastic Member)

Claims (1)

[Claims] 1. A spindle support device for a machine tool, which rotatably supports a spindle with respect to a spindle head, comprising: a first bearing portion mounted on a front inner peripheral surface of the spindle head to pivotally support the spindle. A sleeve disposed inside the rear inner peripheral surface of the spindle head so as to be capable of reciprocating in the axial direction, and a second sleeve mounted on the inner peripheral surface of the sleeve to pivotally support the main spindle.
Bearing part, a magnetic bearing device for holding the sleeve by magnetic force against the inner peripheral surface of the spindle head rear part, and the magnetic bearing device is interposed between the spindle head and the sleeve and urges the sleeve in the axial direction. And a resilient member for applying a required preload to the first and second bearing portions, and the sleeve can be supported in a non-contact manner with respect to the spindle head. .