A machine tool spindle with internal feedback and tilting pad constant pressure preload

Abstract

The present invention relates to an internal feedback tilting pad constant pressure preloaded machine tool spindle, comprising a front end cover, a front bearing, a spindle sleeve, a spindle, a rear bearing and a rear end cover, wherein a preload loading mechanism, a sliding sleeve and a unloading piston are also arranged in the spindle sleeve, wherein the sliding sleeve is sleeved outside the rear bearing and axially abuts against the rear bearing, and the unloading piston is pressed on the end face of the sliding sleeve, and the preload loading mechanism applies an axial elastic force to the sliding sleeve, thereby forming an internal tension between the front and rear bearings, and this internal tension is the constant pressure preload, so that the sliding surfaces of the front and rear bearings fit on the spindle journal surface, and ideal working performance is obtained. High pressure oil is injected instantaneously before the spindle is started, and the unloading piston and the sliding sleeve are pushed to overcome the elastic force and move, so that the sliding surfaces of the front and rear bearings are out of contact with the spindle, and the unloading effect is achieved, and the injection of high pressure oil is stopped after the spindle reaches the normal working speed, and the spindle resumes the constant pressure preloaded state to avoid contact friction at the moment of spindle startup, and the working life is extended.

Description

Technical Field

[0001] The invention relates to the technical field of machine tool spindles, and in particular to a machine tool spindle with internal feedback tilting pad constant pressure pre-tightening. Background Art

[0002] The working performance of the machine tool spindle depends to a large extent on the structure and performance of the spindle bearing. Due to its compact structure, excellent performance, especially relatively low manufacturing process requirements, simple lubrication system, and low maintenance costs, hydrodynamic sliding bearings are much more widely used in the application field of rotating spindles than static pressure dynamic and static pressure sliding bearings.

[0003] The hydrodynamic bearing, which is formed by the sliding of the main shaft diameter on the surface of the sliding bearing, relies on the relative movement between the two surfaces to form a pressure oil film to carry out the work. The hydrodynamic sliding bearing is divided into multi-wedge fixed pad bearings and tilting pad bearings according to the design principle of the oil wedge. The tilting pad hydrodynamic bearing is a commonly used structural form with better performance.

[0004] There is non-contact friction between the hydrodynamic bearing and the spindle in the working state. The working clearance of the bearing is one of its most important operating parameters. Usually, when the spindle structure is relatively simple, the bearing is more often configured with a fixed clearance, that is, once the spindle system is assembled and debugged, the working clearance of the bearing is fixed. However, its disadvantage is that the initial clearance size of the bearing cannot be adjusted at any time as the work needs change, and the best load-bearing performance is obtained according to the needs of the spindle operation. For example, the use status of the machine tool spindle is generally determined as a low-speed heavy-load type and a high-speed light-load type, and it is not necessary to take into account all working conditions. Therefore, the clearance preload control structure is designed for this demand, which is simple and practical, and can meet the performance requirements of the machine tool spindle with stable load and good damping characteristics, reducing bearing friction power consumption, reducing temperature rise, and suppressing vibration.

[0005] There is a practical disadvantage in all hydrodynamic bearing applications, that is, there is contact friction between the spindle and the bearing in the extremely short moment of starting and stopping the spindle. After the spindle is started and stopped repeatedly for a long time, the bearing is bound to be worn, reducing the service life of the hydrodynamic bearing. The actual conventional solution is to limit the frequency of starting and stopping the machine tool spindle to reduce the number of wear times, but this will affect work efficiency. Summary of the invention

[0006] In view of the above-mentioned technical problems existing in the prior art, the present invention provides a machine tool spindle with internal feedback tilting pad constant pressure pre-tightening, which can automatically adjust the bearing working clearance according to the working needs of the spindle to achieve the best working performance, and can also avoid contact friction of the bearing at the moment of starting, thereby extending the working life.

[0007] To achieve the above objectives, the present invention provides the following technical solutions.

[0008] Provided is a machine tool spindle with internal feedback tilting pad constant pressure preload, comprising a front end cover, a front bearing, a spindle sleeve, a spindle, a rear bearing and a rear end cover, wherein the front end cover and the rear end cover are fixed to the two ends of the spindle sleeve, the front bearing and the rear bearing are both internal feedback fluid-supported tilting pad dynamic pressure centripetal thrust tapered bearings, and the two together support the spindle, thereby forming a machine tool spindle with a front and rear double support structure for the spindle; the surfaces of the front bearing and the rear bearing in contact with the spindle shaft diameter are sliding surfaces, and the sliding surfaces are conical surfaces, which are installed corresponding to the conical shaft diameter surface of the spindle;

[0009] A preload mechanism, a sliding sleeve and a unloading piston are also provided in the main shaft sleeve. The sliding sleeve is sleeved outside the rear bearing and axially presses against the rear bearing. The unloading piston is pressed on the end face of the sliding sleeve. The preload mechanism applies axial elastic force to the sliding sleeve, thereby forming an internal tension as a constant-pressure preload between the front bearing and the rear bearing, so that the sliding surfaces of the front bearing and the rear bearing fit on the main shaft diameter surface to obtain ideal working performance; the main shaft sleeve is provided with a channel for inputting unloading high-pressure oil P2, and the unloading high-pressure oil P2 is instantly injected before the main shaft starts working. The unloading high-pressure oil P2 pushes the unloading piston and the sliding sleeve to overcome the elastic force and move, so that the sliding surfaces of the front bearing and the rear bearing are out of contact with the main shaft, thereby realizing unloading; after the main shaft reaches the normal working speed, the injection of the unloading high-pressure oil P2 is stopped to allow the main shaft to resume the constant-pressure preloading work.

[0010] Among them, the preload mechanism includes an inner nut, an outer nut, a spring and a loading ring. The inner nut is fixed in the main shaft sleeve, and the outer nut and the inner nut are threadedly connected. One end of the spring is against the outer nut, and the other end is against the loading ring, and the loading ring is against the sliding sleeve. The position of the outer nut relative to the inner nut is operated by external force to adjust the elastic force of the spring, and the elastic force forms an internal tension which is applied to the front bearing and the rear bearing through the loading ring and the sliding sleeve.

[0011] Among them, a groove is provided around the outer nut, and a window that can be opened is provided on the main shaft sleeve. After the window is opened by external force, the groove is clamped with a tool to turn the outer nut to adjust the degree of compression of the spring, thereby adjusting the size of the elastic force. After the adjustment is completed, the inner nut and the outer nut are locked.

[0012] Among them, the main shaft sleeve is equipped with a lubricating fluid P1 input and output hole system to ensure the smooth flow of lubricating fluid required by the front bearing and the rear bearing.

[0013] Preferably, the lubricating fluid P1 is lubricating oil, water lubricating liquid, gas or oil-gas two-phase lubricating liquid.

[0014] The front end cover and the rear end cover fixed to the two ends of the main shaft sleeve form a sealing structure with the main shaft to prevent the lubricating fluid P1 from overflowing and prevent the external contamination fluid from invading.

[0015] Among them, the front bearing and the rear bearing both include a bearing outer ring and a shoe installed on the inner surface of the bearing outer ring. The bearing uses the internal feedback fluid supporting force formed by the lubricating fluid P1 to achieve full-spherical contact between the shoe back supporting surface of the shoe and the inner surface of the bearing outer ring.

[0016] Among them, the present invention is suitable for precision machine tool spindles and other spindle systems with extremely wide range of speed and load changes.

[0017] Beneficial effects of the present invention:

[0018] The present invention provides a machine tool spindle with internal feedback tilting pad constant pressure preload, and a preload loading mechanism is provided. The preload loading mechanism applies elastic force to the sliding sleeve, so that the sliding surfaces of the front and rear bearings are kept in contact with the spindle, forming a predetermined clamping force to press the sliding surfaces of the front and rear bearings on the spindle neck surface, automatically adjusting the bearing working clearance to obtain ideal spindle working performance; unloading high-pressure oil is instantaneously injected before the spindle starts working, and the unloading high-pressure oil pushes the unloading piston and the sliding sleeve to overcome the preload elastic force, so that the sliding surfaces of the front and rear supports are out of contact with the spindle, thereby avoiding contact friction at the moment of spindle startup, achieving an unloading effect, and extending the working life. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of a machine tool spindle with internal feedback tilting pad constant pressure preload in an embodiment.

[0020] Figure 2 It is a three-dimensional structural diagram of the front bearing and the rear bearing used in the embodiment.

[0021] Reference numerals include:

[0022] Front end cover 1, front bearing 2, spindle sleeve 3, spindle 4;

[0023] Preload loading mechanism 5, inner nut 51, outer nut 52, spring 53, loading ring 54;

[0024] Rear bearing assembly 6, rear bearing 61, sliding sleeve 62, mounting seat 63;

[0025] Unloading piston 7;

[0026] Spindle rear end cover structure 8, rear end cover 81, and clamping inner nut 82;

[0027] Bearing outer ring 21, tile 22, oil collecting groove 23, deformation groove 24, mounting assembly 25, oil hole 26;

[0028] Lubricating fluid P1, unloading high-pressure oil P2. DETAILED DESCRIPTION

[0029] The present invention is described in detail below in conjunction with specific embodiments.

[0030] The machine tool spindle of this embodiment is as follows Figure 1 As shown, it includes a front cover 1, a front bearing 2, a main shaft sleeve 3, a main shaft 4, a rear bearing 61 and a rear cover 81. The front cover 1, the main shaft sleeve 3 and the rear cover 81 form a closed space in combination with the main shaft 4. The front cover 1 and the rear cover 81 play a role of sealing and oil separation. The front bearing 2 is limited in position by the front cover 1 and the main shaft sleeve 3 to bear the main load. The rear cover 81 is installed by a clamping inner nut 82. The rear cover 81 and the clamping inner nut 82 form a main shaft rear cover structure 8. The main shaft sleeve 3 is provided with an oil inlet hole for inputting the lubricating fluid P1 and an oil outlet hole for outputting the lubricating fluid P1 as shown by the solid arrow. The main shaft sleeve 3 is also provided with a channel connecting the oil inlet hole and the oil outlet hole, which is used to transport the low-pressure lubricating fluid P1 to the front bearing 2 and the rear bearing 61. The lubricating fluid P1 is lubricating oil, water lubricating liquid, gas or oil-gas two-phase lubricating liquid. The front bearing 2 and the rear bearing 61 jointly support the main shaft 4, forming a front and rear double-support simple support structure. The front bearing 2 and the rear bearing 61 are both internal feedback fluid-supported tilting pad dynamic pressure centripetal thrust bearings, and the surface in contact with the axial diameter of the main shaft 4 is a sliding surface, which is a conical surface and is installed corresponding to the conical axial diameter surface of the main shaft 4, respectively, to bear the radial load at both ends of the main shaft 4 and the relative axial direction load. The front bearing 2 and the rear bearing 61 are arranged in the main shaft sleeve 3 with the large end of the bearing facing outward.

[0031] The spindle sleeve 3 is also provided with a preload mechanism 5, a sliding sleeve 62 and a unloading piston 7. The sliding sleeve 62 is sleeved outside the rear bearing 61 and axially abuts against the rear bearing 61. The sliding sleeve 62 can creep in the support hole of the spindle sleeve 3, and the unloading piston 7 is pressed on the end surface of the sliding sleeve 62. The rear bearing 61 is matched with the spindle 4 through the mounting seat 63, and the rear bearing 61, the sliding sleeve 62 and the mounting seat 63 constitute a rear bearing assembly 6. The preload mechanism 5 includes an inner nut 51, an outer nut 52, a spring 53 and a loading ring 54. The inner nut 51 is fixed in the spindle sleeve 3. The outer nut 52 and the inner nut 51 are threadedly connected. One end of the spring 53 abuts against the head of the outer nut 52, and the other end abuts against the loading ring 54. The loading ring 54 abuts against the sliding sleeve 62. The elastic force of the spring 53 is applied to the rear bearing 61 through the loading ring 54 and the sliding sleeve 62. The elastic force forms an internal tension preload force between the front bearing 2 and the rear bearing 61. The preload force presses the sliding surfaces of the front bearing 2 and the rear bearing 61 against the journal surface of the spindle 4. In this embodiment, a groove is provided on the outer periphery of the outer nut 52, and a window that can be opened is provided on the spindle sleeve 3. Under normal circumstances, the window is sealed. When the elastic force of the spring 53 needs to be adjusted, the window is opened by external force and the groove is clamped with a tool to turn the outer nut 52 to adjust the degree of compression of the spring 53. In this way, the size of the elastic force can be adjusted. The principle of adjusting the size of the elastic force is that for the machine tool spindle with low-speed and heavy-load working requirements, the preload is relatively large, and for the machine tool spindle with high-speed and light-load working requirements, the preload is relatively small.

[0032] The spindle sleeve 3 is provided with a channel for inputting unloading high-pressure oil P2. The unloading high-pressure oil P2 is injected instantaneously before the spindle 4 starts working. The unloading high-pressure oil P2 pushes the unloading piston 7 and the sliding sleeve 62 to overcome the elastic force and move. The sliding sleeve 62 no longer axially presses against the rear bearing 61, so that the sliding surfaces of the front bearing 2 and the rear bearing 61 are out of contact with the spindle 4, achieving the unloading effect. After the spindle 4 reaches the normal working speed, the injection of the unloading high-pressure oil P2 is stopped. The present invention is suitable for precision machine tool spindles and other spindle systems with extremely wide range of variable speed and load.

[0033] Combination Figure 2As shown, the structure of the internal feedback fluid-supported tilting pad dynamic pressure radial thrust bearing takes the front bearing 2 as an example, and its structure includes a bearing outer ring 21, a plurality of pads 22 and a plurality of mounting components 25. The plurality of mounting components 25 are fixed to the bearing outer ring 21 and the plurality of pads 22 are limitedly mounted on the annular inner surface of the bearing outer ring 21. Two oil collecting grooves 23 are arranged on the sliding surface of each pad 22. The oil collecting grooves 23 can collect part of the pressure lubricating fluid P1 on the sliding surface and then feedback through the oil hole 26 into the oil cavity formed by the depression on the back of the pad 22, forming a radial supporting force on the pad 23. A deformation structure is arranged in the middle of the pad 22, dividing the pad 22 into two blocks. The mounting component 25 applies a radial elastic pressing force to the pad 22. When the bearing is working, under the action of the supporting force of the oil chamber on the back of the pad 22, the corresponding local block of the pad 22 overcomes the radial elastic pressing force and the load force of the main shaft 4, and tilts up with the deformation structure as a fulcrum, so that the bearing can be tilted, and a convergence gap is formed. The convergence gap enables the bearing to obtain a good lubrication and load-bearing effect. The generated internal feedback lubrication flow can additionally increase the working flow of the bearing, which is of great benefit to the heat dissipation and cooling of the bearing. The back of the pad 22 is provided with a deformation groove 24 that runs longitudinally along the axial direction. The longitudinal section of the deformation groove 24 is T-shaped, and the bottom width of the deformation groove 24 is relatively wide, so that a thin wall is formed between the bottom of the deformation groove 24 and the sliding surface of the pad 22, and the thin wall becomes the deformation structure of the pad. When not in use, the back of the pad 22 and the inner surface of the bearing outer ring 21 are tightly fitted spherical surfaces, so that the pad 22 can be limited in the axial direction, and the back of the pad 22 and the inner surface of the bearing outer ring 21 realize full surface contact support, which is conducive to stable support. The pad 22 is installed in the spherical surface of the bearing outer ring 21 to form a supporting spherical surface, and the center of the sphere coincides with the axis of the main shaft 4. Similarly, the pad of the rear bearing 61 is installed in the spherical surface of its bearing outer ring to form another supporting spherical surface. The main shaft 4 has a good self-aligning performance under the condition of front and rear spherical support.

[0034] In this embodiment, the bearing outer ring 21 has a full contact spherical surface for the bearing pad 22, and the working clearance is controlled by a fixed part structure to form a machine tool spindle 4. Compared with the conventional tilting pad dynamic pressure sliding bearing machine tool spindle, the bearing lubrication system is not changed, the operating cost is not increased, the bearing support structure is simple, the bearing has a self-aligning function, the initial clearance of the bearing is fixed, the load is stable and the damping characteristics are good, so as to achieve the purpose of reducing the friction power consumption of the bearing, reducing the temperature rise, and suppressing vibration. The machine tool spindle of the present invention is suitable for precision machine tool spindles and other spindle systems with extremely wide range of variable speed and load.

[0035] It should be noted that, since the pad backs of conventional tilting pad bearings are all small spherical point supports, the overall connectivity between the pads and the outer ring of the bearing is poor, and the effect of the preload mechanism is not easy to be stable. Therefore, the creative labor of the preload loading mechanism 5 set in the internal feedback fluid-supported tilting pad dynamic pressure radial thrust bearing of this embodiment can truly achieve the expected effect.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A machine tool spindle with internal feedback tilting pad constant pressure preload, comprising a front end cover, a front bearing, a spindle sleeve, a spindle, a rear bearing and a rear end cover, wherein the front end cover and the rear end cover are fixed to the two ends of the spindle sleeve, the front bearing and the rear bearing are both internal feedback fluid-supported tilting pad dynamic pressure centripetal thrust tapered bearings, and the two together support the spindle, thereby forming a machine tool spindle with a front and rear double support structure for the spindle; the surfaces of the front bearing and the rear bearing in contact with the spindle shaft diameter are sliding surfaces, and the sliding surfaces are conical surfaces, which are installed corresponding to the conical shaft diameter surface of the spindle, Other features include: A preload mechanism, a sliding sleeve and a unloading piston are also provided in the main shaft sleeve. The sliding sleeve is sleeved outside the rear bearing and axially presses against the rear bearing. The unloading piston is pressed on the end face of the sliding sleeve. The preload mechanism applies axial elastic force to the sliding sleeve, thereby forming an internal tension as a constant-pressure preload between the front bearing and the rear bearing, so that the sliding surfaces of the front bearing and the rear bearing fit on the main shaft diameter surface; the main shaft sleeve is provided with a channel for inputting unloading high-pressure oil P2, and the unloading high-pressure oil P2 is injected instantaneously before the main shaft starts working. The unloading high-pressure oil P2 pushes the unloading piston and the sliding sleeve to overcome the elastic force and move, so that the sliding surfaces of the front bearing and the rear bearing are separated from the main shaft, thereby realizing unloading; after the main shaft reaches the normal working speed, the injection of the unloading high-pressure oil P2 is stopped, so that the main shaft resumes the constant-pressure preloading work; The preload mechanism includes an inner nut, an outer nut, a spring and a loading ring. The inner nut is fixed in the main shaft sleeve. The outer nut and the inner nut are threadedly connected. One end of the spring abuts against the outer nut, and the other end abuts against the loading ring. The loading ring abuts against the sliding sleeve. The position of the outer nut relative to the inner nut is operated by external force to adjust the elastic force of the spring. The elastic force forms an internal tension which is applied to the front bearing and the rear bearing through the loading ring and the sliding sleeve. A groove is provided around the outer nut, and a window that can be opened is provided on the main shaft sleeve. After the window is opened by external force, a tool is used to clamp the groove to turn the outer nut to adjust the degree of compression of the spring, thereby adjusting the size of the elastic force. After the adjustment is completed, the inner nut and the outer nut are locked; The front bearing and the rear bearing both include a bearing outer ring, a plurality of pads and a plurality of mounting components, the plurality of mounting components are fixed to the bearing outer ring and the plurality of pads are limitedly mounted on the annular inner surface of the bearing outer ring, two oil collecting grooves are arranged on the sliding surface of each pad, the oil collecting grooves can collect part of the pressure lubricating fluid on the sliding surface and then feed it back through the oil holes into the oil cavity formed by the depression on the back of the pad, thereby forming a radial supporting force on the pad; a deformation structure is arranged in the middle of the pad, thereby dividing the pad into two blocks; the mounting components apply a radial elastic clamping force to the pad; when the bearing is working, under the action of the supporting force of the oil cavity on the back of the pad, the corresponding local block of the pad overcomes the radial elastic clamping force and the main shaft load force, and is tilted up with the deformation structure as a fulcrum, thereby realizing the tiltability of the pad and forming a convergent gap.

2. According to claim 1, the machine tool spindle with internal feedback tilting pad constant pressure preload is characterized by: The main shaft sleeve is equipped with a lubricating fluid P1 input and output hole system to ensure the smooth flow of lubricating fluid required by the front bearing and the rear bearing.

3. The machine tool spindle with internal feedback tilting pad constant pressure preload according to claim 2 is characterized by: The lubricating fluid P1 is lubricating oil, water lubricating liquid, gas or oil-gas two-phase lubricating liquid.

4. The machine tool spindle with internal feedback tilting pad constant pressure preload according to claim 3 is characterized by: The front cover and the rear cover fixed to the two ends of the main shaft sleeve form a sealing structure with the main shaft to prevent the lubricating fluid P1 from overflowing and prevent the external contamination fluid from intruding.

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