KR20170082801A

KR20170082801A - Pre-load change device for spindle bearing

Info

Publication number: KR20170082801A
Application number: KR1020160002010A
Authority: KR
Inventors: 정성일
Original assignee: (주)성림엔지니어링
Priority date: 2016-01-07
Filing date: 2016-01-07
Publication date: 2017-07-17

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable preload apparatus for a spindle bearing, and more particularly, to a variable preload apparatus for a spindle, which comprises a bearing housing coupled between a front half bearing and a rear half bearing for preloading a bearing coupled to the outside of a spindle, The present invention relates to a variable preload device for a spindle bearing capable of pressing a rear bearing by the operation of a piston and by controlling a preload applied to the rear bearing by pressing the piston with fluid or compressed air.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a pre-load change device for a spindle,

Generally, a bearing formed around the shaft (spindle) to assist in the rotation of the shaft is given a preload so that the shaft can accurately position the shaft in the axial direction (the axial direction) and the radial direction (radial direction) A case in which vibration is restrained, a case in which vibration is suppressed, a case in which vibration is suppressed, a case in which vibration is suppressed, a case in which vibration is suppressed, a vibration is suppressed, Or to hold the rolling member in the correct position with respect to the raceway wheel, and the like.

In other words, the preload of the bearing greatly affects the shaft rigidity, vibration, noise, heat, product processing precision depending on the preload method and preloading conditions. The static preload is mainly applied when the shaft rotates at high speed, Applies when the axis rotates at low speed or medium speed.

In case of using variable preload, static preload is used for high-speed rotation of shaft, and preload can be controlled by changing the position of pressing member which can pressurize bearing by applying positive preload at low speed and medium speed.

As a variable preload device of such a bearing, there is a device for controlling a preload using a piezoelectric element such as disclosed in the publication of Utility Model No. 96-29232, and disclosed in Published Utility Model No. 94-27675 or Published Utility Model No. 91-14403 There is a device for automatically adjusting the preload using the same spring as disclosed, and a device for changing the preload of the main shaft bearing of a machining center such as Patent Registration No. 246309.

First, the device that adjusts the preload using a piezoelectric element has a slow reaction speed, and it is difficult to precisely control the preload. The device that automatically adjusts the preload by using the spring always applies the same static preload only to the bearing, There is a problem that can not give a variable preload.

The preload changing device of the above-mentioned machining center main shaft bearing related to the variable preload device is advantageous in that the reaction speed is fast by controlling the preload of the variable variable by using the hydraulic pressure. However, since the preload of the piston, cylinder, The construction of the spring and the like is complicated, resulting in an increase in manufacturing cost, and it is difficult to precisely control the preload.

As another prior art, there is a variable preload apparatus and method proposed by Japanese Patent No. 10-0925919 for use of compressed air.

The variable preload device includes: an inlet for introducing compressed air; an air chamber for accommodating the compressed air entering the inlet; and a compression chamber for compressing the compressed air in the air chamber A bearing sleeve which is moved in association with the piston, and a bearing whose preload is controlled by the bearing sleeve, and between the bearing sleeve and the housing, a ball A variable preload device for a bearing using compressed air has been proposed in which a preload spring is compressed and compressed when compressed air is pushed, The adjustment of the preload applied to the inner ring by fixing the inner ring There is a problem that it is difficult to see the effect due to the variable preload because the preload is adjusted at the end portion of the spindle and is far from the cutting point of the workpiece close to the chuck.

Therefore, the present invention is characterized in that a bearing housing is coupled between a first half bearing and a second half bearing so that a preload can be given to a bearing coupled to the outside of a spindle capable of rotating at a high speed, and the bearing housing is pressed And the preload applied to the rear half bearing by pressing the piston as operating oil can be selected as a static preload according to the rotational speed of the spindle shaft or a variable preload as a result of the pressurization of the operating oil. And to provide a variable preload device for a bearing.

Another object of the present invention is to provide a variable preload device for a spindle bearing which has a ball bush coupled to the outside of a bearing housing so as to absorb axial deformation and radial deformation of the spindle.

Another object of the present invention is to provide a variable preload device for a spindle bearing, which is provided with a displacement sensor capable of grasping the amount of axial displacement of the spindle at one side of the spindle to determine the amount of movement of the spindle in consideration of the amount of displacement of the spindle.

The present invention relates to a variable preload device for controlling a preload of a bearing coupled to a spindle capable of high-speed rotation, the variable preload device comprising an inlet and an outlet for receiving and operating oil, and a hydraulic pressure applied to the inlet and outlet, And a bearing housing contacting the end face of the piston and guiding the movement of the piston and a bearing housing contacting the end face of the bearing slide and applying pressure to the rear bearing.

The variable preload device for a spindle bearing according to the present invention is characterized in that the bearing housing is coupled to the outside of the rear half bearing so that the bearing coupled to the outside of the spindle capable of rotating at high speed can be preloaded, Since the preload applied to the bearing by pressing the piston as operating oil can be selected as a static preload according to the rotational speed of the shaft or as a variable preload according to the pressure of the operating oil, It has the effect of selectively applying the pressure and moving the piston by using the hydraulic oil to improve the response speed and it is possible to absorb the axial deformation and the radial deformation of the spindle by coupling the ball bush to the outside of the bearing housing There is an effect that the axial direction of the spindle on one side of the spindle By installing a displacement sensor that can determine the wiryang in view of the amount of displacement of the spindle by determining a movement amount of the main shaft it is possible to improve the machining accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
2 is a partial schematic view of the present invention
3 is a partial schematic view of the present invention

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

The present invention relates to a variable preload apparatus for controlling a preload of a bearing coupled to a spindle capable of high-speed rotation, the apparatus comprising: The variable preload device includes an inlet and an outlet for introducing and discharging working oil and compressed air and a piston 12 moved in a direction away from the tool holder 21 by a hydraulic pressure applied to the inlet and outlet 10, A bearing housing 13 for contacting the end face of the piston 12 and guiding the movement of the piston 12 and a bearing housing 17 for contacting the end face of the bearing slide 13 and applying pressure to the rear half bearings 30c, .

A total of five bearings 30a, 30b, 30c, 30d and 31 are coupled to the spindle shaft 1. One of the four bearings 30a, 30b, 30c and 30d except the roller bearing 31, 21 are referred to as a first half bearing for convenience and the remaining two bearings are referred to as a second half bearing.

A spindle shaft 1 supported by a plurality of bearings 30a, 30b, 30c, 30d, and 31 is formed in a cylindrical body 20, A rotor 41 fixedly coupled to the spindle shaft 1 for rotating the spindle shaft 1 and a stator 40 formed on the outer peripheral surface of the rotor 41 for rotating the rotor 41, The rotor 41 and the stator 40 are commonly referred to as built-in spindle motors.

A draw bar 23 is inserted in the spindle shaft 1. A piston 24 is reciprocated in the direction of the rotation axis of the spindle shaft 1 by application of working oil or compressed air to one side of the draw bar 23, A cylinder 26 is formed around the piston 24 to prevent hydraulic pressure or air pressure applied to the operation of the piston 24 from leaking to the outside. And a gripper 32 for gripping the tool holder 21 is provided on the other side.

Therefore, when the draw bar 23 is advanced toward the tool holder 21 due to the hydraulic pressure applied to the piston 24, the shank of the tool holder 21 can be pulled out of the gripper 32, The drawbar 23 is also moved backward in the direction away from the tool holder 21 so that the gripper 32 is rotated in the direction of the rotation center axis of the spindle shaft 1 and the gripper 32 hold the shank of the tool holder 21.

A helical coil spring 34 is formed in the spindle shaft 1 so that the drawbar 23 can be moved by the piston 24 by applying a force to always hold the drawbar 23 toward the piston 24, When the pushing force toward the holder 21 is released, the drawbar 23 returns to the piston 24 and the elastic force of the helical coil spring 34, that is, the pulling force of the drawbar 23, (Chucking force) of the tool holder 21 is increased.

On the other hand, the inlet / outlet port 10 is a passage through which the working oil or compressed air enters and exits, and is installed in the radial direction of the spindle body 20 so that the working oil or compressed air flows in the radial direction perpendicular to the rotation axis of the spindle shaft 1 And may be formed in the cross-sectional direction of the body 20 as the case may be.

One end of the inlet / outlet 10 communicates with a groove on a circumferential surface formed at one side edge of the piston 12. The groove on the circumferential surface of the piston 12 is engaged with the body 20, The chamber 10a is formed and the working oil or the compressed air that has entered through the inlet and outlet 10 remains in the chamber 10a and presses the piston 12. [ At this time, the piston 12 is moved in contact with the bearing slide 13, and the piston 12 is moved to prevent the working oil or compressed air applied to the chamber 10a from leaking to the outside beyond the piston 12. [ Grooves are formed on the inner circumferential surface and the outer circumferential surface of the base plate and O-rings are respectively coupled to the grooves.

The bearing slide 13 is moved along with the movement of the piston 12 in the axial direction of the spindle shaft 1. The bearings 30c and 30d are accommodated in one side of the bearing slide 13 And the bearing housing 17 is coupled to the rear bearing 30. The preload applied to the rear bearings 30c and 30d varies depending on the amount of movement of the bearing slide 13. [

That is, the inner rings of the front half bearings 30a and 30b and the rear half bearings 30c and 30d are engaged with the lock nut 29, the space 15 and the inner collars 7 and 9 in a state of being coupled with the spindle shaft 1. [ And the preload applied to the bearings 30a, 30b, 30c, and 30d becomes higher as the lock nut 29 is coupled to the spindle shaft 1. [

In addition, the outer rings of the bearings 30a, 30b, 30c, and 30d are finely changed in position, and the pressure applied to the balls in the bearings is varied. The bearing housings 30c and 30d, The outer ring 17 is engaged with the end face of the outer ring of the bearings 30c and 30d so that the pressure applied to the outer ring 8 is changed as the pressure applied to the bearing housing 17 is changed, 30c, and 30d.

The pressure of the operating oil or compressed air applied to the chamber 10a pushes the piston 12 toward the lock nut 29 and the repulsive force acts on the front half bearings 30a and 30b, 10, the preliminary pressure is increased not only in the rear bearings 30c, 30d but also in the front bearing 30a, 30b so that the rigidity of the main shaft is increased.

In the illustrated embodiment, the front half bearings 30a and 30b closest to the tool holder 21 are held in the correct position when no pressure is applied through the inlet / outlet 10, and the rear half bearings 30c and 30d A variable preload can be given by the oil pressure applied through the inlet and outlet 10 and a static preload is applied by the spring 28 when the oil pressure is zero.

The pressure applied to the bearings 30a, 30b, 30c and 30d varies in accordance with the rotation speed of the spindle shaft 1. When the spindle shaft 1 rotates at a relatively high speed, , And when the spindle shaft 1 rotates at a relatively low speed, the piston 12 is pressed by the operating oil to raise the preliminary pressure to secure the rigidity of the main shaft.

That is, the static preload is generated by forming the spring 28 between the piston 12 and the bearing slide 13 so that when the position of the piston 12 is kept in contact with the seal plate 11, Thereby pushing the bearing slide 13 toward the bearing housing 17 and thus applying the positive pressure preload to the bearing by pressing the outer race of the rear half bearings 30c and 30d housed in the bearing housing 17. [

When a variable preload, that is, a pressure higher than the pressure applied to the spring 28, is applied to the rear half bearings 30c and 30d, the oil pressure or air pressure is applied to the inlet / 13 and the bearing slide 13 presses the bearing housing 17 and thereby presses the outer ring of the rear half bearings 30c and 30d to finally apply a preload to the balls of the rear half bearings 30c and 30d When the piston 12 is pushed by the applied oil pressure or air pressure, the first half bearings 30a and 30b are also pressed by the repulsive force.

A ball bush 16 is coupled to the outside of the bearing housing 17 in order to reduce the friction of the bearing housing 17 and to absorb thermal deformation of the spindle shaft 1 due to overheating.

That is, when the spindle shaft 1 rotates at a high speed, a lot of heat is generated due to the friction with the bearings 30a, 30b, 30c, and 30d, whereby axial deformation and radial deformation simultaneously occur.

At this time, the deformation in the axial direction is absorbed by the inner rings of the bearings 30a, 30b, 30c, and 30d, and the deformation in the radial direction is limited by the body 20. Therefore, And the bearings 30a, 30b, 30c, and 30d, which are coupled between the main body 20 and the body 20, are subjected to a considerable load.

Accordingly, the ball bushing 16 is coupled to the outside of the bearing housing 17 so that the ball formed on the ball bushing 16 is compressed or finely moved, thereby absorbing a certain amount of radial deformation of the spindle shaft 1, When the bearing housing 17 moves in the axial direction of the spindle shaft 1, it is easy to adjust the preliminary pressure applied to the bearing 30 by reducing the friction.

An oil air discharge pipe 22, which is an oil lubrication device, is installed at one side of the bearing to increase the lubricity of the bearing 30 and cool the oil. The oil air is supplied to the bearing through the pipe formed in the out- 30b, 30c, and 30d and discharged through the oil air discharge pipe 22 to cool the bearings 30a, 30b, 30c, and 30d. Although the illustrated embodiment shows that only one oil air discharge pipe 22 is installed, a plurality of actual oil air discharge pipes 22 are provided, and a part thereof is omitted.

A cylindrical body 20 is coupled to the outside of the spindle shaft 1. A front cover 1 is coupled to the body 20 and external impurities are attached to one side of the spindle shaft 1. [ A bearing fixing spacer 5 and a labyrinth collar 4 having gaps of a canopy structure are combined to prevent penetration into the bearing 30. The displacement sensor 33 is coupled to the front cover 1, By sensing the amount of displacement of the fixed spacer 5, the axial displacement of the spindle shaft 1 due to thermal expansion or heat shrinkage is sensed.

That is, in the case of the spindle shaft 1, the temperature is rapidly increased in accordance with the high-speed rotation, so that a plurality of cooling water passages are formed in the body 1 for cooling the spindle shaft. However, The heat of the shaft 1 itself is maintained in a relatively high state. As a result, the spindle shaft 1 undergoes thermal deformation in the axial direction, which results in machining error of the workpiece due to axial displacement of the spindle shaft.

A displacement sensor 33 is attached to one side of the front cover 2 to grasp the amount of axial displacement of the spindle shaft 1. The present invention grasps the amount of movement of the bearing fixing spacer 5, The machining error of the workpiece can be reduced by reducing or increasing the amount of movement of the workpiece.

When the labyrinth collar 4 and the bearing fixing spacer 5 are coupled to each other, gaps are formed in the valley structure. Since the gaps are twisted in a complicated shape, external impurities, that is, chips or cutting oil It is possible to prevent penetration into the body 20.

The outer collar 6 and the inner collar 7 are provided with nozzles for supplying lubricating oil through the oil air and are arranged to adjust the distance between the front bearing 30a and the front bearing 30b. Is a seal cover to which air is supplied to prevent impurities from penetrating. The front bearing housing 18 is configured to receive the bearing housing 17, the cooling cover 19 is configured to install the cooling water passage, The cover 25 is a cover for finishing the spindle, and the roller bearing 31 is a structure for supporting the spindle shaft 1.

As a result, the variable preloading apparatus for a spindle bearing according to the present invention is configured such that the bearing housing is coupled to the outside of the rear half bearing so as to pre-press the bearing coupled to the outside of the spindle capable of rotating at high speed, And the preload applied to the bearing by pressing the piston as operating oil can be selected as a static preload according to the rotational speed of the shaft or a variable preload as a result of the pressure of the operating oil. Therefore, the rotational speed of the spindle And the response speed is improved by moving the piston using the operating oil. The ball bushing is coupled to the outside of the bearing housing, and the axial deformation and the radial deformation of the spindle There is an effect that the spindle can be absorbed, By determining the amount of movement of the main shaft installed in view of the amount of displacement of the spindle displacement sensors that can determine the amount of displacement effort it is possible to improve the machining accuracy.

1. Spindle shaft 2. Front cover 3. Air seal cover
4. Labyrinth collar 5. Bearing fixing spacer 6. Out color
7. Inner Color 8. Out Color 9. Inner Color
10. Entrance and Exit 10a. Chamber 11. Seal plate
12. Piston 13. Bearing slide 14. Out collar
15. Bearing fixing spacer 16. Ball bushing 17. Bearing housing
18. Front bearing housing 19. Cooling cover 20. Body
21. Tool holder 22. Oil air outlet tube 23. Drawbar
24. Piston 25. End cover 26. Cylinder
27. Spring Spacer 28. Spring 29. Lock Nut
30; bearing
30a, 30b. First half bearings 30c, 30d. Rear bearing
31. Roller Bearings 32. Grippers 33. Displacement Sensors
34. helical coil spring 40. stator 41. rotor

Claims

A variable preload device for controlling a preload of a bearing coupled to a spindle capable of high speed rotation,
The variable preload apparatus includes an inlet and an outlet 10 through which operating oil and compressed air are introduced and discharged and a piston 12 moved in a direction away from the tool holder 21 by hydraulic pressure applied to the inlet and outlet 10, And a bearing housing (17) which abuts against the end face of the bearing slide (13) and exerts a pressure on the rear bearing (30c, 30d) And a variable preload device for the spindle.

The method according to claim 1,
And a ball bushing (16) is coupled to the outside of the bearing housing (17) to reduce movement friction of the bearing housing (17) and to absorb thermal deformation due to overheating of the spindle shaft (1) Variable preloading device.

The method according to claim 1,
The front half bearings 30a and 30b closest to the tool holder 21 maintain a correct position when no pressure is applied through the inlet and outlet 10 and the rear half bearings 30c and 30d are positioned at the inlet 10, And a variable preload can be given by the hydraulic pressure applied through the second clutch.

The method according to claim 1,
A spring 28 is formed between the bearing slide 13 and the piston 12 to apply a static preload to the bearing 30 due to the elasticity of the spring 28 when there is no hydraulic pressure applied to the inlet 10 Variable preloading device for bearing for spindle.

The method according to claim 1,
An oil air discharge pipe 22 as an oil lubrication device is installed at one side of the bearing to increase the lubricity of the bearing 30 and cool the oil. The oil air is supplied to the bearings 30a 30b, 30c, 30d and discharged through the oil air discharge pipe 22 to cool the bearings 30a, 30b, 30c, 30d.

The method according to claim 1,
A cylindrical body 20 is coupled to the outside of the spindle shaft 1 and a front cover 1 is coupled to the body 20. An impurity of an external impurity is supplied to one side of the spindle shaft 1 A bearing fixing spacer 5 and a labyrinth collar 4 which are formed with gaps of a canopy structure are coupled to the front cover 1. A displacement sensor 33 is coupled to the front cover 1, (5), thereby detecting the axial displacement of the spindle shaft (1) due to thermal expansion or thermal shrinkage of the spindle shaft (1).

The method according to claim 1,
The inner rings of the rear half bearings 30c and 30d and the front half bearings 30a and 30b are engaged with the lock nut 29 and the space 15 and the inner collars 7 and 9 in a state of being coupled with the spindle shaft 1. [ And the preload applied to the bearings 30a, 30b, 30c, and 30d is higher as the lock nut 29 is coupled to the spindle shaft 1. In this case, .

The method according to claim 1,
The pressure applied to the rear half bearings 30c and 30d and the front half bearings 30a and 30b varies in accordance with the rotational speed of the spindle shaft 1. When the spindle shaft 1 rotates at a relatively high speed, , And when the spindle shaft (1) rotates at a relatively low speed, the piston (12) is pressurized by the operating oil to increase the preliminary pressure to secure the rigidity of the spindle.