KR100656649B1 - spindle bearing support structure for high speed - Google Patents

Abstract

The present invention relates to a bearing support structure of a spindle for high-speed rotation to reduce the friction of the sliding surface between the rear heat housing and the main housing having a sliding structure to absorb the thermal displacement of the spindle configured to support the ball bearing at both ends, the ball bearing Both ends of the main shaft 40 are supported by the phosphorus heat transfer bearings 62a and 62b and the after heat bearings 72a and 72b, and the after-heat housing 70 supporting the after-row bearings 72a and 72b is the main housing ( In the main shaft configured to be able to move in the axial direction at 50, there is a lubrication member between the rear heat housing (70) and the main housing (50).

Description

Spindle bearing support structure for high speed

1 is a cross-sectional view showing a bearing support structure of a spindle for a conventional machining center

Figure 2 is a cross-sectional view showing an embodiment of the bearing support structure of the main shaft for high speed rotation according to the present invention

Figure 3 is a cross-sectional view showing another embodiment of the bearing support structure of the main shaft for high speed rotation according to the present invention

* Explanation of Signs of Major Parts of Drawings *

62a, 62b: Heat transfer bearing 72a, 72b: Heat transfer bearing

40: spindle 70: post heat housing

50: main housing 70a: outer peripheral surface

70b: Grease Pocket 80: Oilless Bearing

50b, 80a: Inner peripheral surface 80d: Solid lubricant

The present invention relates to a bearing support structure of the main shaft for high speed rotation, and more particularly, friction of the sliding surface between the rear heat housing and the main housing having a sliding structure to absorb the thermal displacement of the main shaft configured to support the ball bearings at both ends. The present invention relates to a bearing support structure of a main shaft for high-speed rotation in which grease pockets are machined on the outer circumferential surface of a after-heat housing or an oilless bearing is installed in the main housing to lower the coefficient.

In general, since the precision of rotation of the main shaft of the machining center directly affects the degree of machining, it is necessary to prevent micro-movement in the axial direction and the perpendicular direction of the axis during rotation to enable precision machining.

Such a structure of a main shaft for a conventional machining center is shown in FIG. 1, and as shown in FIG. 1, the electrothermal bearings 22a, 22b, 22c, and 22d supporting the front side of the main shaft 20 are a kind of ball bearings. The after-row bearing 24 which consists of an angular contact bearing and supports the rear part of the main shaft 20 was comprised by the roller bearing.

The outer ring of the above heat transfer bearings 22a, 22b, 22c, and 22d is fixed to the housing 26 by the bearing cover 27, and the inner ring is formed on the main shaft 20 by the bearing sleeve 28. The heat transfer bearings 22a, 22b, 22c, and 22d are paired in pairs to be preloaded in opposite axial directions, respectively. It was designed to simultaneously support loads acting in the direction perpendicular to the shaft.

In addition, the inner ring of the after-row bearing 24 installed at the rear portion was fixed to the jaw portion of the main shaft 20 by a bearing sleeve 30 installed on the main shaft 20, and the outer ring was attached to the bearing cover 32. It is fixed to the housing 26 to improve the bending rigidity of the main shaft 20 and to minimize the shaking during rotation to improve the rotational stability of the main shaft 20.

In addition, unlike the heat transfer bearings 22a, 22b, 22c, and 22d, the after-heat bearing 24 provided at the rear end of the main shaft 20 does not restrain in the axial direction, but only a load acting in the direction perpendicular to the axis. It was a supporting structure, and was configured to absorb heat deformation while moving in the axial direction with respect to the heat displacement of the main shaft (20).

That is, when the main shaft 20 rotates at high speed, thermal deformation occurs due to frictional heat generated from the rolling contact portion or the sliding contact portion, and in particular, since the main shaft 20 is made longer in the axial direction than other components, the thermal displacement occurs. Is accumulated and shows large movement in the axial direction. If both ends of the main shaft 20 are restrained in the axial direction by the front and rear bearings, thermal deformation of the main shaft 20 occurs in the front and rear axial directions so that the machining precision decreases. In addition, the bearing life is shortened, and if the thermal deformation is severe, the bearing may be damaged.

Therefore, the heat transfer bearings 22a, 22b, 22c, and 22d, which are the parts of the tool, are moved in the axial direction without applying an axial preload to the heat transfer bearing 24 in order to induce heat deformation in the opposite direction to the position where the tool is bitten. It is made of structure that can be.

However, such a conventional main shaft, while the angular contact bearing used in the electrothermal bearings 22a, 22b, 22c, and 22d is a kind of ball bearing, and thus the allowable rotational speed is high, the roller bearing used in the after-row bearing 24 is Since the ball bearing has a significantly lower allowable rotational speed than the ball bearing, it acts as a detrimental factor in the speeding up of the main shaft, thus reaching a limit in increasing the rotational speed of the spindle.

On the other hand, the main shaft is proposed to speed up by supporting both ends of the main shaft with a ball bearing, the motor is built in the center of the main shaft, and both the heat transfer bearing and the after-row bearing supporting both ends of the main shaft are composed of angular contact bearings It was designed to be rotatable, and the rear heat housing supporting the rear heat bearing was configured to absorb the heat displacement while moving along the slide surface in the main housing.

In addition, the ball bushing is interposed to reduce the friction between the main housing and the after-heating housing to guide the post-heating housing, which creates a new design constraint to increase the diameter of the main housing to install the ball bushing. In particular, since the machining accuracy can be ensured only when the relative deviations of the diameters of the balls forming the ball bushes satisfy the allowable values, the precision of the main shaft may be reduced depending on the precision of the ball bushings. In the process of assembling, a little preload should be applied, but there was a possibility of acting as a gap due to the measurement error.By the characteristics of the ball bush, the cloud of the ball appears in the form of point contact. The problem of deterioration may occur, and in order to prevent this, the contact of the ball of the ball bush When the heat treatment process is added to increase the surface hardness of the slide surface of the after-heat housing has a problem that the manufacturing process becomes difficult.

In addition, several balls are installed in the ball bush. In order to prevent the balls from coming into contact with each other during the rolling motion, a retainer is provided to keep the gap of the balls constant. There was a problem that the ball generates noise in the retainer by the vibration generated when the high speed rotation.

The present invention has been made to solve the above problems, the object of which is to speed up the main shaft and at the same time have a simple structure, can reduce the diameter of the main housing by the guide mechanism for guiding the rear heat housing, the rear heat housing The friction coefficient of the sliding surface between the main housing and the lower can be lowered below an allowable value, and the bearing support structure of the main shaft for the high speed rotation to prevent the noise that may occur in the sliding portion for guiding the rear heat housing.

In order to achieve the object of the present invention, both ends of the main shaft are supported by a heat transfer bearing and a post heat bearing, which are ball bearings, and the rear heat housing supporting the after heat bearing is configured to move in the axial direction from the main housing, It has the characteristic that grease pocket was formed in the outer peripheral surface.

According to another embodiment of the present invention, both ends of the main shaft are supported by a heat transfer bearing and a post heat bearing, which are ball bearings, and the rear heat housing supporting the after heat bearing can move in the axial direction in the main housing. In the bearing support structure, there is a lubrication member between the rear heat housing and the main housing.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 and 3, the heat transfer housing 60 is fixed to the front of the main shaft 40 and the main housing 50, and the rear heat housing 70 is installed to move in the axial direction. Heat transfer bearings 62a and 62b in the form of ball bearings (angular contact bearings) and preheating bearings 72a and 72b which can be preloaded in the axially opposite types to the heat transfer housing 60 and the after heat housing 70. ) Is installed.

That is, the outer ring of the heat transfer bearings 62a and 62b is fixed to the heat transfer housing 60 by the bearing support cap 64, and the inner ring thereof is fixed to the main shaft 40 by the sleeve 66.

In addition, the outer ring of the rear row bearings 72a and 72b is fixed to the rear row housing 70 by a bearing support cap 74, and the inner ring of the rear row bearings 72a and 72b is fixed to the main shaft 40 by a sleeve 76, and the rear row housing ( 70 is coupled to enable the sliding movement in the axial direction on the sliding surface 52 of the main housing 50.

Then, between the bearing support cap 74 supporting the outer ring of the after-row bearings 72a and 72b and the main housing 50, the bearing support cap 74 in the direction in which the main shaft 40 causes thermal displacement in the axial direction. Preload spring (90) for pushing) is installed to rebound to both sides, bearing support cap (74) is coupled with the rear heat housing (70).

On the other hand, Figure 2 shows an embodiment of the present invention for lowering the coefficient of friction between the rear heat housing 70 and the main housing 50, the outer peripheral surface 70a of the rear heat housing 70 as shown here By forming a grease pocket 70b into which grease 100 can be injected during assembly, the sliding coefficient of the grease pocket 70b is lowered to lower the coefficient of friction between the main housing 50 and the rear heat housing 70.

That is, the grease pocket 70b may be formed, for example, in an annular shape in which the cross-sectional shape is an arc shape, the cross-sectional shape is constant in the circumferential direction, and may be formed in a plurality at regular intervals in the axial direction. .

In addition, Figure 3 shows another embodiment of the present invention for lowering the coefficient of friction between the after-heat housing 70 and the main housing 50, as shown therein solid lubricant (80d) made of carbon (graphite) The inner circumferential surface 80a of the oilless bearing 80 after pressing and fixing the lubricating member that is radially bonded to the circumference, that is, the oilless bearing 80 by compression shrinkage to the inner circumferential surface 50b of the main housing 50. Then, by assembling the after-heating housing 70, the friction coefficient between the after-heating housing 70 and the O-ringless bearing 80 was configured to be lowered.

In the drawings, reference numeral 120 denotes a built-in motor.

Hereinafter, the operation according to the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIGS. 2 and 3, when the main shaft 40 rotates at a high speed and heat is generated from the rolling contact surface of the bearing, the built-in motor 120, and the like, the main shaft 40 is thermally expanded in the axial direction.

At this time, the heat transfer bearings 62a and 62b supporting the front portion of the main shaft 40 which the tool bites are provided by the bearing support cap 64 and the sleeve 66 to the heat transfer housing 60 fixed to the main housing 50. The main shaft 40 is expanded while being deformed to the rear side where the after-row bearings 72a and 72b are located because the rear-row housing 70 is configured to slide in the axial direction.

In this process, the inner ring and sleeve 76 of the after-row bearings 72a and 72b move axially together with the main shaft 40, and at the same time, the bearing support cap 74 is moved by the elastic force of the preload spring 90 40) is pushed in the direction of thermal expansion.

At this time, since the bearing support cap 74 and the after-heating housing 70 are coupled, the after-heating housing 70 is also pushed along the bearing support cap 74 in the axial direction to push the outer ring of the after-row bearings 72a and 72b. It acts to maintain the preload of the bearing.

Meanwhile, when the grease pocket 70b formed on the outer circumferential surface 70a of the rear heat housing 70 is formed as shown in FIG. 2, grease injected into the grease pocket 70 b during the sliding of the rear heat housing 70 is performed. As the oil film is formed between the main housing 50 and the after heat housing 70, the friction coefficient of the sliding surface is lowered, and the movement is smoothed.

In addition, as shown in FIG. 3, when the oilless bearing 80 is squeezed to the inner circumferential surface 50b of the main housing 50, the heatless housing 70 is formed on the circumference of the oilless bearing 80 in a sliding process. By the lubrication action by the solid lubricant 80d, the sliding surface friction coefficient between the oilless bearing 80 and the post heat housing 70 is lowered, and the movement is smoothed.

As described above, in the present invention, since both ends of the main shaft are supported by ball bearings, the main shaft can be speeded up, and a grease pocket is formed or formed in the rear heat housing configured to slide in the axial direction when the main shaft is thermally expanded. Since the oilless bearing is installed in the structure, the coefficient of friction between the rear heat housing and the main housing can be significantly reduced without using the ball bush as in the past, and thus the diameter of the main housing can be made smaller. It is effective to make the spindle design more freely, and because the moving body is not interposed between the rear housing and the main housing, the precision of the spindle can be guaranteed, and the structure is simplified, making it easy to manufacture, and the sliding part It is effective to prevent noise that can occur.

Claims (5)

Both ends of the main shaft 40 are supported by the heat transfer bearings 62a and 62b and the after heat bearings 72a and 72b, and the after-heat housing 70 supporting the after-row bearings 72a and 72b is the main housing 50. In the bearing support structure of the main shaft for the high-speed rotation configured to move in the axial direction, Bearing support structure of the main shaft for high-speed rotation, characterized in that having a lubrication member between the rear heat housing (70) and the main housing (50). The method of claim 1, wherein the lubricating member is configured by pressing the oilless bearing 80 for guiding the rear heat housing 70 between the rear heat housing 70 and the main housing 50 by shrink fit. Bearing support structure of the main shaft for high speed rotation characterized in that. 3. The bearing support structure of claim 2, wherein the oilless bearing (80) has a solid lubricant (80d) applied radially to the circumference thereof. 4. The bearing support structure of claim 3, wherein the solid lubricant (80d) is made of carbon. 2. The bearing support structure of claim 1, wherein the lubrication structure is provided with a grease pocket (70b) on an outer circumferential surface (70a) of the rear heat housing (70) or the main housing (50).

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