JP2004195587A - Main spindle device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a main spindle device having superior damping performance, sliding performance, and a bearing sleeve having high rigidity. <P>SOLUTION: This main spindle device 10 has: the bearing sleeve 14 movably arranged in the axial direction in the rear side of a housing 11; a sleeve housing 15 out-fitted to the bearing sleeve 14; rear stage bearings 12 and 13 fitted in the bearing sleeve 14 and arranged in the rear side of the housing 11; a rotatably supported shaft 19 fitted in the rear stage bearings 12 and 13; and a preload means 16 for applying a preload to the rear stage bearings 12 and 13. Axial dampers 17 and 18 are arranged between the bearing sleeve 14 and the sleeve housing 15 for generating damping force in at least the shaft direction. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a high-speed spindle used for a machine tool spindle or the like, and relates to an improvement in a constant-pressure preload mechanism of a spindle device having a rolling bearing that has been pre-pressed at a constant pressure.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a constant-pressure preload spindle device used for a machining center or the like as shown in FIG. 6 for supporting a spindle rotating at a high speed is widely known.
The spindle device 100 shown in FIG. 6 includes a housing 61 as a fixing member including a front cover 62, an outer cylinder 63, a rear cover 64, an inner housing (fixed) 67, and a sleeve housing 71 described later, and a front side of the housing 61. The bearings 65 and 66 are a set of combined angular contact ball bearings (parallel combination) arranged in the front stage, and the bearings are a set of combined angular contact ball bearings (parallel combination) supported on the rear side of the housing 61. 68 and 69 are provided.
[0003]
Further, a bearing sleeve 70 externally fitted to the subsequent bearings 68, 69, a sleeve housing 71 supported on the outer periphery of the bearing sleeve 70, a preload spring 72 mounted on the bearing sleeve 70, and bearings 65, 66, 68. , 69, a motor 74 in which a rotor 75 is fixed to the shaft 73 and a stator 76 is fixed to the outer cylinder 63, and a drawbar 77 supported in the shaft 73.
Further, the bearing sleeve 70 is slidably supported on the inner diameter surface 71 a of the sleeve housing 71.
[0004]
The outer rings of the bearings 65 and 66 are fixed to the inner housing 67 by an outer ring retainer 79. The outer rings of the bearings 68 and 69 are fixed to the bearing sleeve 70 by an outer ring retainer 78. The inner rings of the bearings 65, 66, 68, 69 are fixed to the shaft 73 at predetermined intervals.
The preload spring 72 pulls the bearing sleeve 70 rearward through the outer ring retainer 78 to apply a preload to the bearings 68 and 69 at the subsequent stage. The preload acts on the bearings 65 and 66 because the preload acts in the direction of pulling the shaft 73 backward.
Further, the draw bar 77 and the clamp unit 77 'inserted into the shaft 73 are mechanisms for holding a tool (not shown) at the tip of the clamp unit 77', but their description is omitted because they are known.
[0005]
In such a spindle device 100, when the shaft 73 is rotated by the motor 74, the rotor 75 and the bearings 65, 66, 68, and 69 of the motor 74 generate heat and thermally expand. Even in the case where a relative displacement occurs in the wheel, the preload acting on the bearings 65, 66, 68, 69 is reduced by the bearing sleeve 70 sliding in the axial direction with respect to the inner diameter surface 71 a of the sleeve housing 71 by the preload spring 72. I try to keep it constant.
A spindle device having such a constant-pressure preload mechanism is used for high-speed rotation because it has a feature that the preload does not increase even at high-speed rotation as compared with a spindle device of fixed-position preload.
[0006]
As the sliding method of the bearing sleeve, in addition to the sliding surface method, a sliding method using a ball (Patent Document 1 below) and a hydrostatic sleeve method (Patent Document 2 below) are exemplified.
[0007]
By the way, the functions required of the bearing sleeve for the main shaft rotating at high speed include, besides the above-mentioned slidability, radial rigidity and vibration damping property (particularly, axial damping).
In the sliding surface method, since the sliding is performed on the sliding surface, the damping property is good. However, since the housing (sleeve housing) and the outer diameter of the bearing sleeve are supported with a certain gap, the bearing sleeve is not supported. Sliding failure may occur due to inclination or the like. When a slide failure occurs, the preload of the rolling bearing fluctuates, and as a result, seizure may be caused.
[0008]
Further, in the sliding method using a ball, since the ball is supported, the sliding property is good, but the radial rigidity is low and the damping property is low.
On the other hand, in the static pressure type sleeve system, it was found that there was no problem in the sliding property and the radial rigidity, but the damping property in the axial direction was low.
The damping properties of the bearing sleeve are disclosed in Patent Documents 3 and 4 below.
[0009]
[Patent Document 1]
JP-A-62-278311
[Patent Document 2]
JP-A-58-46223
[Patent Document 3]
JP-A-10-238538
[Patent Document 4]
JP-A-8-166018
[0010]
[Problems to be solved by the invention]
However, in the main shaft device 100 that rotates at a high speed, the axial resonance frequency of the bearing sleeve 70 is often lower than the maximum rotation speed of the shaft 73 and the draw bar 77. If the axial damping is weak, the bearing sleeve 70 moves in the axial direction. There is a possibility that large self-excited vibrations will occur and the vehicle will fall into an operation impossible state.
Further, when the spindle device 100 is used for a machine tool, if the bearing sleeve 70 has poor damping properties and cannot absorb vibration, there is a concern that the quality of the machined surface of the machine tool may be degraded.
[0011]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a spindle device having a high-rigidity bearing sleeve having good damping performance and sliding performance.
[0012]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a spindle device, wherein a rotatable shaft, a front stage bearing in which an outer ring having an inner ring inner surface fitted to a front portion of the shaft is fixed to a housing, and an inner ring inner surface being fitted to the rear portion of the shaft. A main shaft device comprising: a rear-stage bearing, and a preload means for applying a constant-pressure preload to a bearing sleeve externally fitted to an outer-diameter outer surface of the rear-stage bearing.
The bearing sleeve is statically supported by the inner diameter of the housing, and an axial damper for generating an axial damping force in the bearing sleeve is disposed between the bearing sleeve and the housing.
[0013]
According to the spindle device having the above-described configuration, since the bearing sleeve is supported by the hydrostatic bearing structure, the bearing sleeve floats at the center of the housing axis, so that good slidability is obtained.
In addition, necessary radial rigidity can be secured by appropriately designing various conditions such as the oil viscosity, pressure, the size of the throttle, the pocket, and the like, and the bearing clearance in the hydrostatic bearing. Further, the axial damper causes the bearing sleeve to have an axial damping property, so that self-excited vibration in the axial direction does not occur. As a result, it is possible to obtain a spindle device having a high-rigidity bearing sleeve having good damping performance and sliding performance.
[0014]
According to a second aspect of the present invention, in the spindle device, the axial damper is an O-ring mounted on the bearing sleeve and slidably disposed with respect to the housing with a predetermined amount of collapse. The spindle device according to claim 1, wherein:
[0015]
According to the spindle device having the above-described configuration, when the O-ring is used as the axial damper, the O-ring is rich in workability and versatility, so that the spindle device can be manufactured without requiring a complicated production process.
In addition, if the O-ring is slidably disposed on the housing with a predetermined amount of crushing, greater axial damping performance and slidability can be obtained. A spindle device having a bearing sleeve having the same can be obtained.
[0016]
The spindle device according to claim 3 of the present invention, wherein the preload means and the axial damper are a hydraulic piston, a hydraulic pump for supplying pressure to the hydraulic piston, a throttle between the hydraulic pump and the hydraulic piston, The spindle device according to claim 1, wherein the main shaft device is a hydraulic piston mechanism provided with:
[0017]
According to the spindle device having the above configuration, the preload means and the axial damper are hydraulic piston mechanisms each including a hydraulic piston, a hydraulic pump, and a throttle between the hydraulic pump and the hydraulic piston. In addition, a spindle device having a bearing sleeve having high rigidity can be obtained.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a spindle device of the present invention will be described in detail with reference to FIGS. 1A is a sectional view of a main part of a spindle device according to a first embodiment of the present invention, FIG. 1B is a sectional view around a bearing sleeve in the spindle device shown in FIG. 1, and FIG. 3A is a graph showing the relationship between the amount of crushing of the ring and the damping rate, FIG. 3A is a graph showing the frequency response when the O-ring in FIG. 1 is not used, and FIG. 3B is a graph showing the O-ring in FIG. FIG. 4A is a half-sectional view of a main part of a spindle device according to a second embodiment of the present invention, and FIG. 4B is an enlarged view of a main part of the spindle device in FIG. FIG. FIG. 5 is a sectional view of a spindle device according to a third embodiment of the present invention. 1 (a) and 4 (a), the front part of the spindle device is the same as that shown in FIG. 6, so that illustration of the front part is omitted. Further, in the second embodiment, members and the like having the same configurations and operations as the members and the like already described are denoted by the same reference numerals in the drawings, and the description thereof will be simplified or omitted.
[0019]
As shown in FIG. 1A, a spindle device 10 according to a first embodiment of the present invention includes a pair of rear-stage rolling bearings 12 and 13 disposed on the rear side of a housing 11 and a pair of rear-stage rolling bearings 12 and 13. A bearing sleeve 14 externally fitted to the sleeve 13 and movably arranged in the axial direction, a sleeve housing 15 extrapolated to the bearing sleeve 14, a preload spring 16 for applying a preload to the bearing sleeve 14, and mounted on the bearing sleeve 14. O-rings 17 and 18 as first and second axial dampers, and a rotatably supported shaft 19 fitted inside the rolling bearings 12 and 13.
[0020]
One end of the rear housing 21 and the sleeve housing 15 of the housing 11 communicates with the inner diameter of the sleeve housing 15, and the other end communicates with an oil supply port 22 formed on a side of the rear housing 21. A refueling flow path 23 is formed. An oil supply pipe 24 is connected to the oil supply port 22. The oil supply pipe 24 is connected to a hydraulic pump 27 through a throttle 25 and a distributor 26.
[0021]
One end of the rear housing 21 and the sleeve housing 15 is communicated with the inner diameter of the sleeve housing 15 and the other end is formed on a side of the rear housing 21 in a path different from the oil supply passage 23. An oil discharge passage 29 communicating with the oil discharge port 28 is formed. An oil drain pipe 30 is connected to the oil drain port 28. The oil drain pipe 30 is connected to an oil tank 31 opened to the atmospheric pressure.
[0022]
The preload spring 16 is locked at the rear end of the sleeve housing 15. The preload spring 16 is in contact with the outer ring pressing member 32. Since the outer ring holding member 32 is in contact with the rear end of the bearing sleeve 14 and the outer ring of the rolling bearing 13, it has a function of applying a preload to the rolling bearings 12 and 13.
[0023]
The bearing sleeve 14 is configured as a hydrostatic bearing. The outer diameter of the bearing sleeve 14 is fitted to the inner diameter of the sleeve housing 15 with a predetermined gap. Specifically, the outer diameter of the bearing sleeve 14 is φ150 mm, and the diameter gap is 30 to 40 μm.
[0024]
On the outer diameter surface of the bearing sleeve 14, first, second, third, and fourth static pressure pockets 33, 34, 35, and 36 are provided at four locations on the circumference at a substantially central portion in the axial direction and are evenly provided. In addition, two oil drain grooves 37 and 38 are formed at both ends of the bearing sleeve in a circumferential groove shape.
The four static pressure pockets 33, 34, 35, 36 are arranged corresponding to the oil supply passage 23 of the sleeve housing 15. In addition, hydraulic oil from a hydraulic pump 27 is supplied to each oil supply path through a throttle 25. The supplied hydraulic oil flows through the gap between the bearing sleeve 14 and the sleeve housing 15, flows from the oil drain grooves 37 and 38 to the oil drain 28 through the oil drain channel 29, and returns to the oil tank 31.
[0025]
On the outer diameter surface of the bearing sleeve 14, two damper attachment grooves 39, 40 are formed axially outside the oil drain grooves 37, 38, and the first and second axials are formed in the damper attachment grooves 39, 40. Dampers 17 and 18 are mounted. The first and second axial dampers 17 and 18 are O-rings (O-rings) formed in an annular shape, and are formed using, for example, synthetic rubber such as nitrile rubber.
The first and second axial dampers 17 and 18 not only serve to block the working oil for the hydrostatic bearing from entering the inside of the shaft 19 but also serve as dampers for obtaining axial damping. It is. The axial dampers 17 and 18 are mounted with a shim allowance of 4 to 15% of the wire diameter of the O-ring.
[0026]
The axial damping force in the bearing sleeve 14 cannot be sufficiently obtained only by the hydrostatic bearing. The shear stress of the fluid when the bearing sleeve 14 moves in the axial direction is approximated by the following equation. Value.
Axial damping force F ≒ μ ・ A ・ v / Δd (N)
Here, μ: viscosity coefficient of fluid (Pa · s)
A: Area of outer diameter of bearing sleeve 14 (m ^Two )
v: axial velocity of bearing sleeve 14 (m / s)
Δd: Radial gap of bearing sleeve 14 (mm)
As a result of the calculation using the above equation, it was found that the value of the axial damping force was very small, and in an actual high-speed spindle, there was a possibility that self-excited vibration in the axial direction would occur in the bearing sleeve 14. 17 and 18 are used.
[0027]
The bearing sleeve 14 is formed with nozzle mounting holes 41 and 42 penetrating in the radial direction, and the nozzle pieces 43 and 44 are fixed to the nozzle mounting holes 41 and 42. The nozzle pieces 43 and 44 inject lubricant into the bearing spaces of the rolling bearings 12 and 13. Nozzle pieces 43, 44 are fixed to the nozzle mounting holes 41, 42, respectively.
, 44 are formed with spaces 45, 46 outside.
[0028]
Two dummy holes 47 and 48 are formed on the outer diameter surface of the bearing sleeve 14 inside the oil drain grooves 37 and 38 and at the opposite phase positions of the spaces 45 and 46. The reason why the dummy holes 47 and 48 are provided is that the space portions 45 and 46 are formed in the outer diameter of the bearing sleeve 14 by the nozzle pieces 43 and 44 being inserted into the bearing sleeve 14. Since the pressure balance of the hydrostatic bearing may be lost due to 46 and the bearing sleeve 14 may not float at the center of the sleeve housing 15, a dummy having the same diameter as the space portions 45 and 46 may be provided at the opposite phase positions of the nozzle pieces 43 and 44. This is because holes 47 and 48 are provided to maintain pressure balance.
[0029]
As shown in FIG. 1B, the oil supply passages 23 are arranged at substantially equal intervals at four circumferential positions on the side of the rear housing 21, and the four static pressure pockets 33, 34, 35, Reference numerals 36 are arranged at equal intervals at four locations on the circumference corresponding to the oil supply passage 23 on the outer diameter surface of the bearing sleeve 14. The oil drain passage 29 is disposed between the second static pressure pocket 34 and the third static pressure pocket 35, and the dummy holes 47 and 48 are disposed at positions in opposite phases of the spaces 45 and 46. The oil drain passage 29 may be provided at any phase.
[0030]
In such a spindle device 10, it is assumed that the bearing sleeve 14 is moved toward the first static pressure pocket 33 due to the influence of an external force or the like. At this time, the gap between the first static pressure pocket 33 and the sleeve housing 15 is reduced, so that the flow rate of the oil flowing through the first static pressure pocket 33 is reduced. As a result of the decrease in the flow rate, the pressure drop in the throttle 25 is reduced, so that the pressure in the first static pressure pocket 33 is increased.
[0031]
On the other hand, since the flow rate of the oil flowing to the third static pressure pocket 35 at the opposed position increases, the pressure drop at the throttle increases, the pressure in the third static pressure pocket 35 decreases, and the bearing sleeve 14 is moved. It receives a force in the direction of the fourth static pressure pocket 36 opposite to the first static pressure pocket 33. By the action of this force, the bearing sleeve 14 always keeps floating in the center of the sleeve housing 15. As a result, strong radial rigidity and excellent slidability can be maintained.
[0032]
The restrictor 25 is arranged so that the pressure in each of the static pressure pockets 33, 34, 35, 36 becomes approximately 50% of the supply pressure of the hydraulic pump 27 when the bearing sleeve 14 is in a neutral state (in a state where there is no external force). Is set. Furthermore, since the temperature and the gap between the sleeves change during high-speed rotation, it is desirable to adjust the aperture so as to achieve a 50% aperture state during high-speed rotation.
Specifically, the supply pressure of the hydraulic pump 27 is set to 1.5 to 5 MPa, the oil used is set to a grade of VG15 to 68, and the throttle 25 is a stainless steel pipe having an inner diameter of 0.3 to 1.0 mm (to a predetermined length). Cut). At this time, it is generally inexpensive to use a stainless steel pipe as the throttle 25, but the rigidity of the hydrostatic bearing is greatly affected by the performance of the throttle 25. May be used.
[0033]
FIG. 2 is a graph showing the relationship between the amount of crushing of the axial dampers 17 and 18 in terms of the shrinkage (%) with respect to the wire diameter (diameter), and examining the attenuation rate (%) corresponding to the amount of shrinkage. It is a graph of the axial damping performance test according to a substitute.
In the test shown in FIG. 2, an external force vibration in the axial direction was applied to the bearing sleeve 14 by a vibrator, the transfer function of the vibrating force and the vibration displacement was experimentally obtained, and the damping rate in the axial primary mode was calculated. The higher the damping rate, the greater the vibration damping effect.
[0034]
As is clear from the test of FIG. 2, when there is no axial damper (O-ring) corresponding to the shrinkage allowance (0), the attenuation rate is as low as about 3%, and there is almost no attenuation effect.
It can be seen that the damping effect increases as the shrinkage increases. However, when the shrinkage is extremely increased, the damping effect is increased, but the sliding resistance during the sliding movement is increased, and the sliding property is reduced. Therefore, it was found that it is desirable to set the shrinkage margin to 4 to 10% of the O-ring diameter.
[0035]
FIGS. 3A and 3B are graphs of tests for examining a transfer function (frequency response) in order to confirm the damping effect of the axial damper.
FIG. 3A shows a case without an axial damper, and FIG. 3B shows a case using an axial damper with a staking allowance of 5%.
As a result of the test, the vibration at the resonance point is lower by about 12 dB (about 1/4) when the axial damper having the shim allowance of 5% (0.15 mm) is used than the case without the axial damper. There was found.
[0036]
According to the spindle device 10 of the first embodiment, the axial dampers 17, 18 that generate a damping force at least in the axial direction are arranged between the bearing sleeve 14 and the sleeve housing 15 that are arranged to be movable in the axial direction. ing.
Further, the bearing sleeve 14 is supported by a hydrostatic bearing structure. As a result, the bearing sleeve 14 floats at the center of the axis of the sleeve housing 15, so that good slidability is obtained. In addition, necessary radial rigidity can be secured by appropriately designing various conditions such as the oil viscosity, pressure, the size of the throttle, the pocket, and the like, and the bearing clearance in the hydrostatic bearing. Further, the axial dampers 17 and 18 cause the bearing sleeve 14 to have a damping property, so that self-excited vibration in the axial direction does not occur. As a result, it is possible to obtain a spindle device having a bearing sleeve having high rigidity, which has good damping performance and sliding performance.
[0037]
In addition, since the O-rings are used as the axial dampers 17 and 18, the workability and versatility are enhanced, so that the spindle device can be manufactured without requiring a complicated production process. If the O-rings serving as the axial dampers 17 and 18 are slidably disposed on the sleeve housing 15 with a predetermined crush amount, greater axial damping performance and slidability can be obtained, so that higher damping is achieved. A spindle device having a bearing sleeve having high rigidity, having high performance and sliding performance can be obtained.
[0038]
Next, a spindle device according to a second embodiment of the present invention will be described.
The spindle device 50 shown in FIG. 4A is obtained by adding a sliding friction type axial damper 51 to the axial dampers 17 and 18 of the spindle device 10 of the first embodiment.
As shown in FIG. 4B, four sliding friction axial dampers 51 are provided at equal intervals on a plate member 52 disposed on the outer diameter surface of the outer ring pressing member 32 and on the circumference of the rear housing 21. And a plunger 53 arranged in the radial direction of the rear housing 21.
[0039]
The plate members 52 are arranged at a plurality of locations on the circumference and are fixed to the inner diameter surface of the rear housing 21 by screws 54. The outer ring holding member 32 is fixed to the bearing sleeve 14.
The plunger 53 is housed in a case 56 via an urging spring 55, and presses the plate member 52 in the radial direction of the outer ring pressing member 32 by a predetermined elastic repulsive force accumulated in the urging spring 55. As a result, when the bearing sleeve 14 vibrates in the axial direction, the plate member 52 and the outer ring pressing member 32 are relatively displaced, and the damping force is applied to the sleeve 14 by the solid frictional force between the plate member 52 and the outer ring pressing member 32 due to the pressing of the plunger. Occurs.
[0040]
The axial friction damper 51 of the sliding friction type is simply composed of a plate member 52 and a plunger 53 with a small number of parts, so that it is relatively inexpensive and has excellent damping characteristics without hindering the slidability of the bearing sleeve 14. Can be obtained.
Here, since slippage occurs between the plate member 52 and the outer diameter surface of the outer ring pressing member 32, as a countermeasure against the wear, the plate member 52 is made of a quenched product of tool steel and is resistant to the outer ring pressing member 32. It is desirable to apply plating or coating for abrasion. In the present embodiment, a 0.3 mm thick SK material (Hrc50) thin plate is used as the plate member 52, and the biasing force of the biasing spring 55 is set to 10 to 200N.
[0041]
According to the spindle device 50 of the second embodiment, the axial dampers 17, 18 that generate a damping force at least in the axial direction are arranged between the bearing sleeve 14 and the sleeve housing 15 that are arranged to be movable in the axial direction. Further, an axial damper 51 of a sliding friction type is provided.
Therefore, the added axial damper 51 further improves the axial damping characteristics, so that it is possible to obtain a spindle device having a high-rigidity bearing sleeve having good damping performance and sliding performance.
The axial damper also has a feature that the pressing force of the spring can be easily changed from the outside, so that the damping force can be easily adjusted to an optimum value.
[0042]
Next, a spindle device according to a third embodiment of the present invention will be described.
The main shaft device 70 shown in FIG. 5 has a bearing in which the inner housing 7 is fitted inside the inner diameter surface of the outer cylinder 9 forming the front part of the housing 11, and is movably arranged in the axial direction on the inner diameter surface of the inner housing 7. Sleeve 14 is inserted.
The combined angular contact ball bearings 12 and 12 in the first and second rows and the combined angular contact ball bearings 13 and 13 in the third and fourth rows from the left side in the drawing are preloaded with a constant pressure on the inner surface of the bearing sleeve 14.
[0043]
According to the spindle device 70 of the third embodiment, the axial dampers 17a, 17b, 18 which are O-rings for generating a damping force at least in the axial direction are arranged between the bearing sleeve 14 and the inner housing 7.
The bearing sleeve 14 is supported by a hydrostatic bearing structure. As a result, the bearing sleeve 14 floats at the center of the axis of the inner housing 7, so that good slidability is obtained. In addition, necessary radial rigidity can be secured by appropriately designing various conditions such as the oil viscosity, pressure, the size of the throttle, the pocket, and the like, and the bearing clearance in the hydrostatic bearing. And, the axial dampers 17a, 17b, 18 make the bearing sleeve 14 have a damping property, so that self-excited vibration in the axial direction does not occur. As a result, it is possible to obtain a spindle device having a bearing sleeve having high rigidity, which has good damping performance and sliding performance.
[0044]
On the other hand, the cylindrical roller bearing 57 supports the rear end of the shaft 19, stably rotates the shaft 19, and absorbs the elongation of the shaft 19 due to heat generated by a motor roller.
The bearing sleeve 14 does not show a static pressure pocket or the like, but forms a static pressure bearing on the inner surface of the inner housing 7 as in the first embodiment.
The bearing sleeve 14 also serves as a hydraulic piston. The pressure of the hydraulic pump 27 is applied to the sleeve pressure receiving surface 58 via the throttle 25, and the oil pressure applied to the sleeve pressure receiving surface 58 pushes the bearing sleeve 14 backward, so that the bearings 12, 12, 13, and 13 are pressed. This is a configuration for applying a preload.
Even if the hydraulic pump 27 does not operate at all, a necessary preload is applied by the auxiliary preload spring 16 in order to maintain a certain rotational performance by applying a preload.
[0045]
The hydraulic pressure from the hydraulic pump 27 is transmitted to the sleeve hydraulic chamber 59 through the throttle 25 through the oil supply pipe 24 provided outside and inside the spindle. When the bearing sleeve 14 does not move at a high speed, the oil (hydraulic oil) does not flow and is merely pressed. Therefore, there is no pressure change at the throttle 25, and the pressure of the hydraulic pump 27 and the pressure of the sleeve hydraulic chamber 59 are equal. Become. This makes it easy to calculate the pressure required to obtain the desired preload.
Suppose that the bearing sleeve 14 is suddenly moved to the left in the drawing due to the vibration. At this time, since the volume of the sleeve hydraulic chamber 59 is reduced, the hydraulic oil in the hydraulic chamber is pushed out and tends to return toward the hydraulic pump 27. At that time, since the hydraulic oil must pass through the throttle 25, the pressure in the sleeve hydraulic chamber 59 increases. That is, the bearing sleeve 14 receives a resistance force from the left side so as not to be moved to the left side.
Similarly, when the bearing sleeve 14 moves to the right, it receives resistance from the right. That is, an axial damping force acts on the bearing sleeve 14, and the bearing sleeve 14 is a preload applying mechanism that also serves as an axial damper.
With this configuration, a bearing sleeve structure having simple and strong damping, high radial rigidity, and good slidability can be obtained, and a spindle device capable of low-vibration and high-speed rotation can be obtained.
[0046]
In the case of the O-rings and the friction dampers of the first and second embodiments, since a damping force larger than the frictional force cannot be obtained, the damping may be insufficient when a large vibration occurs. In the embodiment, a large damping force substantially proportional to the magnitude of the vibration can be obtained. On the other hand, almost no damping force is generated for a small vibration.
Therefore, when combined with the second embodiment in which the damping force of the solid frictional force can be generated even with a small vibration, a more suitable spindle device can be obtained.
[0047]
Note that the pressure of the hydraulic pump 27 can be normally as low as 0.05 to 0.5 MPa due to the relationship between the area of the pressure receiving surface and the required preload, so a piston that converts compressed air into hydraulic pressure as a hydraulic pump can be used. Inexpensive pumps of the type can be used.
The throttle 25 can be a low-cost, small-diameter stainless steel pipe similar to that used for the hydrostatic bearing of the first embodiment. In designing the throttle 25, the attenuation obtained is higher as the throttle is stronger, but it is preferable that the damper 25 does not hinder the movement of the bearing sleeve 14 in normal operation. That is, the time (usually several seconds) required for the shaft 19 to perform the maximum acceleration (or the reverse rapid deceleration) from the stop to the maximum rotation, and the movement amount in which the bearing sleeve 14 moves by the action of the centrifugal force (this embodiment) In this case, it is preferable to design the throttle 25 so that a large force is not generated as compared with the preload at the moving speed of the bearing sleeve 14 calculated from an angular ball bearing having a diameter of 70 mm in the case of 30,000 rpm (about 0.15 mm).
Further, in the present embodiment, the bearing sleeve 14 and the hydraulic piston are integrated, but a configuration in which a hydraulic piston is separately provided to push the bearing sleeve 14 may be adopted.
[0048]
Note that the present invention is not limited to the above-described embodiment, and appropriate modifications and improvements can be made. For example, the numbers of the oil supply passages, the oil discharge passages, and the static pressure pockets are not limited, and may be six or eight other than four.
Further, the number of the axial dampers shown in the first embodiment is not limited. For example, two axial dampers may be arranged at both ends of the bearing sleeve.
Further, as the material of the axial damper shown in the first embodiment, synthetic rubber such as acrylic rubber, silicon rubber, fluorine rubber or the like, or natural rubber may be used instead of nitrile rubber. Further, an O-ring provided with a coating for preventing adhesion of the O-ring when not used for a long period of time may be used.
Further, as the axial damper shown in the second embodiment, a fluid damper in which oil, air, or the like is sealed in a sealed case may be used instead of the biasing spring.
[0049]
【The invention's effect】
As described above, according to the spindle device of the present invention, the axial damper that generates the damping force in the axial direction is disposed between the housing and the bearing sleeve movably disposed in the axial direction. Is a structure of a hydrostatic bearing. Therefore, since the bearing sleeve floats at the center of the axis of the housing, good slidability can be obtained.
In addition, necessary radial rigidity can be secured by appropriately designing various conditions such as the oil viscosity, pressure, the size of the throttle, the pocket, and the like, and the bearing clearance in the hydrostatic bearing. The axial damper allows the bearing sleeve to have the axial damper function, so that self-excited vibration in the axial direction does not occur, and the bearing sleeve has good damping performance and sliding performance, and has a high rigidity. A spindle device can be obtained.
[Brief description of the drawings]
1A is a sectional view of a main part of a spindle device according to a first embodiment of the present invention, and FIG. 1B is a sectional view around a bearing sleeve in FIG.
FIG. 2 is a graph showing the relationship between the amount of collapse of the O-ring and the attenuation rate in FIG.
3A is a graph illustrating a frequency response when an O-ring is not used in a spindle device, and FIG. 3B is a graph illustrating a frequency response when an O-ring is used in FIG. 1;
FIG. 4A is a sectional view of a main part of a spindle device according to a second embodiment of the present invention, and FIG. 4B is an enlarged view of a main part of the main spindle device in FIG.
FIG. 5 is a sectional view of a spindle device according to a third embodiment of the present invention.
FIG. 6 is a sectional view of a conventional spindle device.
[Explanation of symbols]
9 outer cylinder (first housing)
10,50 spindle device
11 Housing
12,13 Rolling bearing (later stage bearing)
14 Bearing sleeve
15 Sleeve housing (second housing)
16 Preload spring (preload means)
17, 17a, 17b, 18, 51 Axial damper
19 axes
25 Aperture
27 Hydraulic pump

Claims (3)

A rotatable shaft, a front-stage bearing in which an outer ring with an inner ring inner surface fitted to the front portion of the shaft is fixed to the housing, a rear-stage bearing with an inner ring inner surface fitted in the rear portion of the shaft, and an outer ring outer diameter of the rear-stage bearing A preload means for applying a constant preload to the bearing sleeve externally fitted on the surface,
A spindle device wherein the bearing sleeve is supported by the inner diameter of the housing under a static pressure, and an axial damper for generating an axial damping force in the bearing sleeve is provided between the bearing sleeve and the housing. . 2. The spindle device according to claim 1, wherein the axial damper is an O-ring mounted on the bearing sleeve and slidably disposed with respect to the housing with a predetermined amount of collapse. 3. . The preload means and the axial damper are a hydraulic piston mechanism including a hydraulic piston, a hydraulic pump that supplies pressure to the hydraulic piston, and a throttle between the hydraulic pump and the hydraulic piston. The spindle device according to claim 1.

Images