JP4146065B2 - Hydrostatic magnetic compound bearing spindle device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hydrostatic magnetic compound bearing spindle device equipped in a high-speed cutting device, a grinding device, or the like, and particularly to protect at the time of touchdown.
[0002]
[Prior art]
In order to perform high-efficiency and high-precision machining, a spindle device that can rotate at high speed, has high rotational accuracy, and has high static rigidity and dynamic rigidity is required. In response to this requirement, a hybrid non-contact bearing in which a static pressure gas bearing and a magnetic bearing are combined has been proposed (Japanese Patent Application No. 10-097505). According to this, it is possible to provide a compact bearing that takes advantage of the features of both bearings such as the excellent dynamic rigidity and rotational accuracy of the static pressure gas bearing and the excellent static rigidity of the magnetic bearing.
[0003]
[Problems to be solved by the invention]
Although the hydrostatic magnetic compound bearing is a non-contact bearing, the spindle may come into contact with the bearing surface when an excessive load is applied. Such contact of the main shaft is called touchdown. For this touchdown, the conventional magnetic bearing spindle uses a protective bearing made up of a rolling bearing. However, since the hydrostatic magnetic compound bearing is formed by forming a hydrostatic gas bearing in the magnetic bearing portion, the gap between the main shaft of the bearing portion and the magnetic bearing stator is narrow, for example, several tens of microns or less. Protective bearings consisting of normally used rolling bearings cannot be used.
This problem occurs not only in a hydrostatic magnetic composite bearing but also in a hydrostatic gas bearing.
In the case of a hydrostatic magnetic composite bearing, since the hydrostatic gas bearing surface forms an electromagnet of the magnetic bearing, the material of the hydrostatic gas bearing surface is limited to a magnetic metal having no lubricity. Therefore, when an excessive load is applied to the spindle, there is a greater possibility that the bearing portion will be adversely affected by the contact between the main shaft and the bearing surface.
[0004]
For the purpose of holding at such touchdown, the present applicant has proposed that a sliding member is provided in a hydrostatic magnetic compound bearing spindle device (Japanese Patent Application No. H11-071502).
However, if a sliding material with a low longitudinal elastic modulus such as carbon is used, the sliding material will be deformed when a very large load is applied due to damage to the tool during machining or collision with the workpiece due to misoperation. Then, the main shaft may be displaced more than the set clearance of the sliding material. In this case, there is a possibility that the protection function by the sliding material is not fulfilled.
[0005]
The object of the present invention is to provide a bearing or spindle having a static pressure gas bearing portion with a narrow bearing clearance even when an excessive load acts on the spindle and there is a touchdown between the spindle and the stationary member. It is an object of the present invention to provide a hydrostatic magnetic compound bearing spindle device that can prevent wear and damage.
Another object of the present invention is to eliminate problems caused by idle rotation of a rolling bearing for protection during touchdown.
Still another object of the present invention is to protect at the time of touchdown in a thrust type hydrostatic magnetic composite bearing.
Still another object of the present invention is to provide a static pressure capable of preventing the bearing and the spindle from being worn and damaged even when an excessive load acts on the spindle and there is a touchdown between the spindle and the stationary member. It is to provide a gas bearing spindle device.
[0006]
[Means for Solving the Problems]
A hydrostatic magnetic compound bearing spindle device according to the present invention is a spindle device in which a spindle is supported by a radial type hydrostatic magnetic compound bearing in which a hydrostatic gas bearing and a magnetic bearing are combined. The radial clearance between the inner diameter surface of the inner ring of the rolling bearing and the outer diameter surface of the main shaft is set to be equal to or less than the radial clearance of the hydrostatic magnetic composite bearing, and the main shaft is faced to the flange portion provided on the main shaft. A thrust type hydrostatic magnetic compound bearing is provided, and a thermal spray layer of molybdenum or carbon is formed on one of the bearing surface of the thrust type hydrostatic magnetic compound bearing and the flange surface of the main shaft facing the bearing surface. And a ceramic sprayed layer is applied to the other surface of the bearing surface and the main shaft collar surface .
According to this configuration, even when an excessive load is applied to the main shaft, the main shaft is supported by the rolling bearing before it contacts the hydrostatic magnetic composite bearing. This prevents damage to the hydrostatic magnetic composite bearing. Since a rolling bearing is used, unlike a sliding material having a small longitudinal elastic modulus, there is no problem of deformation even when the load is large, and reliable protection can be performed. In addition, since the rolling bearing gives a preload, even if the clearance between the bearing surface of the hydrostatic magnetic composite bearing and the main shaft is narrow, the rolling bearing can be designed not to contact the main shaft during normal rotation.
The rolling bearing preferably has zero bearing clearance by the preload. As a result, it is possible to cope with a case where the gap between the hydrostatic magnetic composite bearing and the main shaft is much narrower.
[0007]
In the present invention, the housing may be provided with a sliding material that is in pressure contact with the end face of the inner ring of the rolling bearing. Thus, by providing the sliding material, it is possible to prevent the inner ring from spinning due to the air shearing torque generated by the rotation of the main shaft during normal operation.
[0008]
In the present invention, the rolling bearing may be a double row angular ball bearing. The double row angular contact ball bearing may be a combination facing the front or a combination facing the back. When a double-row angular ball bearing is used, it is easy to apply a preload to make the bearing gap zero.
[0009]
Facing the flange portion provided in the upper Symbol spindle provided a thrust-type combined externally pressurized gas and magnetic bearing assembly of supporting the main shaft flange of the spindle facing the bearing surface and the bearing surface in the thrust-type combined externally pressurized gas and magnetic bearing assembly A sprayed layer of molybdenum or carbon is provided on one of the surfaces, and a ceramic sprayed layer is provided on the other surface of the bearing surface and the flange surface of the main shaft .
When a thrust type hydrostatic magnetic compound bearing is provided, the main shaft can be supported in a completely non-contact manner. In this case, as described above, by providing the bearing surface and the main shaft flange surface with the above-mentioned thermal sprayed layer, it is possible to improve the wear resistance and sliding characteristics at the time of touchdown in the thrust direction. Regarding the thrust bearing portion, it is difficult to place sliding members in parallel in the same manner as the radial bearing. In order to place the sliding member without reducing the original bearing area, the diameter of the flange portion of the main shaft is increased, but the natural frequency is significantly reduced. However, by providing the thermal spray layer on the bearing surface as described above, it is possible to protect at the time of touchdown without increasing the diameter.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIGS. In the hydrostatic magnetic compound bearing spindle device 1, the main shaft 4 is supported by a plurality of radial hydrostatic magnetic compound bearings 6 and 7 installed in a housing 5 and thrust hydrostatic magnetic compound bearings 8 and 9. A spindle drive source 10 is provided. Spindle drive source 10 is a motor built in the housing 5, a rotor 21 that is kicked set integrally with the main shaft 4, is composed of a stator 22 mounted on the housing 5, the spindle device 1 of the built-in motor type Constitute. A tool mounting portion 11 is provided at the tip of the main shaft 4. The draw bar 12 penetrating through the main shaft 4 is operated by an unclamping unit 13 behind the main shaft 4.
In this example, the bearings 6 to 9 and the spindle drive source 10 are arranged such that the front part (tool side part) and the rear part of the main shaft 4 are supported by radial hydrostatic magnetic composite bearings 6 and 7, and the middle is thrust. It is configured such that a spindle drive source 10 is arranged at the rear end, supported by static hydrostatic magnetic composite bearings 8 and 9.
[0012]
In the spindle device 1 having this configuration, as shown in an enlarged view in FIG. 2, a rolling bearing 41 for touchdown protection is installed in the housing 5 in the vicinity of the tip of the main shaft 4. The rolling bearing 41 is disposed closer to the distal end side of the main shaft 4 than the hydrostatic magnetic composite bearing 6 on the distal end side. The rolling bearing 41 applies a preload to make the bearing gap zero, and the radial gap d2 between the inner diameter surface of the inner ring 42 and the outer diameter surface of the main shaft 4 is set to be equal to or less than the radial gap d1 of the hydrostatic magnetic composite bearing 6. is there.
The rolling bearing 41 is formed of a deep groove ball bearing, and a rolling element 44 held by a cage (not shown) is interposed between an inner ring 42 and an outer ring 43. The preload of the rolling bearing 41 is given by fixing the outer ring 43 to the housing 5 with an interference fit. Specifically, in the rolling bearing 41, an outer ring 43 is tightly fitted to a bearing mounting surface 45 formed of a cylindrical surface provided in the housing 5, and a step 46 and a fixing ring 47 of the housing 5 following the bearing mounting surface 45. The outer ring 43 is fixed by being sandwiched in the axial direction. The fixing ring 47 is attached to the housing 5 with bolts 48.
[0013]
The configuration of each hydrostatic magnetic composite bearing 6-9 will be described. The front and rear radial type hydrostatic magnetic composite bearings 6 and 7 have the same configuration. The hydrostatic magnetic composite bearings 6 and 7 are obtained by combining hydrostatic gas bearings 6A and 7A and magnetic bearings 6B and 7B, respectively. The term “composite” as used in this specification means that both static pressure and magnetic bearings are combined so that a common part is generated. For example, a common part (radial bearing) is formed on a static pressure gas bearing surface and a magnetic bearing surface. Then, the axial overlapping portion) may be generated, or at least a part of components may be shared by both types of bearings.
[0014]
In this embodiment, as shown in FIG. 2, the diaphragm 23 of the static pressure gas bearing 6 </ b> A is provided in the core 23 of the electromagnet of the magnetic bearing 6 </ b> B, so that the core 23 constitutes a part of the static pressure gas bearing surface. Yes. The core 23 includes a pair of main core portions 23a and 23a that are separated in the axial direction, and a connecting core portion 23b that connects the main core portions 23a and 23a. The magnetic bearing 6 </ b> B is obtained by winding a coil 25 around a connecting core portion 23 b of the core 23. The coil 25 is embedded in a nonmagnetic material 26 such as a resin material. The magnetic bearing 7B and the static pressure gas bearing 7A have the same configuration as the magnetic bearing 6B and the static pressure gas bearing 6A, respectively.
[0015]
The hydrostatic gas bearing 6A includes a hydrostatic magnetic bearing surface 6Aa formed on the inner surface of the core 23 and the nonmagnetic body 26 to form a bearing gap d1 between the main shaft 4 and the main core portions 23a of the core 23. And a diaphragm 24a that is provided at 23a and opens to the hydrostatic bearing surface 6Aa. The restrictor 24a is provided at the tip of the air supply hole 24 opened on the outer diameter side surface of each main core portion 23a.
As shown in the stepped cross section in FIG. 3, the cores 23 are arranged at a plurality of circumferential locations around the main shaft 4 (four locations in the example in the figure) and are fixed to the housing 5. A gap between adjacent cores 23 in the circumferential direction is filled with a nonmagnetic material 27 such as a resin material. The nonmagnetic material 27 may be integrated with the nonmagnetic material 26 (FIG. 2) around the coil 25. The non-magnetic members 26 and 27 and the core 23 constitute the hydrostatic magnetic bearing surface 6Aa.
[0016]
FIG. 4 is an enlarged view of the thrust type hydrostatic magnetic composite bearings 8 and 9. The pair of bearings 8 and 9 are installed in the housing 5 so as to face both surfaces of the flange portion 4 a provided on the main shaft 4, and constitute a double-sided thrust type hydrostatic magnetic bearing 30. To do. The hydrostatic magnetic composite bearings 8 and 9 on both sides have the same configuration. These hydrostatic magnetic composite bearings 8 and 9 are obtained by combining hydrostatic gas bearings 8A and 9A and magnetic bearings 8B and 9B, respectively.
In this embodiment, by providing the diaphragm 33a of the static pressure gas bearings 8A and 9A on the core 33 of the electromagnet of the magnetic bearings 8B and 9B, the bearing components are shared and a part of the bearing surface overlaps in the axial direction. It is like that. The core 33 is formed in a C-shaped longitudinal section so that an opening 33d is formed on the surface facing the spindle flange 4a, and a coil 35 is accommodated therein. The opening 33d is filled with a nonmagnetic material. In the illustrated example, the core 33 has an assembly configuration of an inner peripheral core portion 33a and an outer peripheral core portion 33b having an L-shaped cross section, but may be a single piece. A spacer 29 is adjacent to the core 33 in the axial direction.
[0017]
The thrust type static pressure gas bearings 8A and 9A are provided on the core 33 and static pressure bearing surfaces 8Aa and 9Aa which are formed on the side surface of the core 33 and form a bearing gap d3 with the spindle flange 4a. The diaphragm 34a is open to the pressure bearing surfaces 8Aa and 9Aa. The restrictor 34 a is provided at the tip of the air supply hole 34 that opens to the outer diameter side surface of the core 33.
[0018]
The thrust-type hydrostatic magnetic composite bearings 8 and 9 have a thermal spray layer 51 of molybdenum or carbon on the bearing surfaces 8Aa and 9Aa, and a thermal spray layer 52 of ceramics on the flange surface of the main shaft 4. The material of the sprayed layers 51 and 52 may be made of ceramics for the sprayed layer 51 on the bearing surface and molybdenum or carbon for the sprayed layer 52 on the spindle surface opposite to the above.
[0019]
In the static pressure gas bearings 6A to 9A in the static pressure magnetic compound bearings 6 to 9 in FIG. 1, compressed air or other is supplied from the supply inlet 40a of the supply hole 40 provided in the housing 5. Of compressed gas is supplied.
[0020]
According to the spindle device 1 having this configuration, since the rolling bearing 41 for preventing touchdown is provided, even when an excessive load is applied to the main shaft 4, the main shaft 4 comes into contact with the hydrostatic magnetic composite bearings 6 and 7. It is supported by the rolling bearing 41. Therefore, wear and damage of the hydrostatic magnetic composite bearings 6 and 7 are prevented. Since the rolling bearing 41 is used, unlike the case of using a sliding material having a small longitudinal elastic modulus, there is no problem of deformation even when the load is large, and reliable protection can be performed. Further, since the rolling bearing 41 applies preload, even if the gap d1 between the bearing surface of the hydrostatic magnetic composite bearings 6 and 7 and the main shaft 4 is narrow, the rolling bearing can be designed not to contact the main shaft during normal rotation. When the bearing clearance of the rolling bearing 41 is reduced to zero by preloading, it is possible to cope with a case where the clearance d1 between the hydrostatic magnetic composite bearings 6 and 7 and the main shaft 4 is further narrowed.
[0021]
Further, the thrust type hydrostatic magnetic composite bearings 8 and 9 are provided with a thermal spray layer 51 of molybdenum or carbon on the bearing surface and a thermal spray layer 52 of ceramics on the surface of the main shaft. , 52 are in contact with each other and can be protected by sliding. Further, since the thermal spray layers 51 and 52 are provided, unlike the case where the sliding member for touchdown protection is provided side by side with the hydrostatic magnetic composite bearings 8 and 9, the touchdown is not performed without increasing the diameter. Can be protected.
[0022]
FIG. 5 shows an embodiment in which a rolling bearing 41A made up of a double row angular ball bearing is provided instead of the rolling bearing 41 made up of a deep groove ball bearing. Both rows of bearings 41Aa and 41Ab are combined with their fronts facing each other, and are fixed to the housing 5 by applying a preload in the axial direction. The axial preload is given by sandwiching the outer ring 43 of the bearings 41Aa and 41Ab in both rows in the axial direction by the stepped portion 46 and the fixing ring 47 that follow the bearing mounting surface 45 of the housing 5. The fixing ring 47 is attached to the housing 5 with a bolt 48. A ring member 49 for contacting the main shaft at the time of touchdown is fitted in an interference fit state on the inner diameter surface of the inner ring 42 across the bearings 41Aa and 41Ab in both rows. The ring member 49 and the inner ring 42 of each row of bearings 41Aa and 41Ab constitute an inner ring 50 of a rolling bearing 41A composed of a double row angular ball bearing. In this example, the gap d2 between the inner diameter surface of the ring member 49 and the main shaft 4 is set to be smaller than the bearing gap d1 of the hydrostatic magnetic composite bearings 6 and 7.
In the case of this configuration, a double row angular contact ball bearing is used as the rolling bearing 41A. Therefore, preload is easily applied, and the bearing clearance is easily made zero. Therefore, the present invention can also be applied when the bearing gap d1 of the hydrostatic magnetic composite bearings 6 and 7 is further narrowed. Other configurations and effects are the same as those of the first embodiment shown in FIGS.
In addition, the combination of the bearings 41Aa and 41Ab in both rows in the double row angular ball bearings may face the back. In terms of moment, it is preferable to arrange the backs to face each other.
[0023]
6 and 7 show examples in which the sliding member 60 is pressed against the end faces of the inner rings 42 and 50 of the rolling bearings 41 and 41A in the embodiments of FIGS. 2 and 5, respectively. The sliding member 60 is attached to a ring member 48 that fixes the outer ring 43 of the bearings 41, 41 </ b> A to the housing 5. That is, an annular recess is formed in the bearing-facing surface of the inner diameter portion of the ring member 47, and a ring-shaped sliding member 60 is attached to the annular recess in a fitted state. The sliding member 60 is a member having a low coefficient of friction such as carbon or fluorine resin.
When the sliding member 60 is provided in this manner, the inner rings 42 and 50 are prevented from rotating by the air shear torque generated by the rotation of the main shaft 4. For this reason, problems due to idle rotation of the useless inner rings 42 and 50 are prevented.
[0024]
The above embodiments have been described with respect to the case of the hydrostatic magnetic compound bearing spindle device including the radial hydrostatic magnetic compound bearings 6 and 7. However, the present invention is also applicable to a hydrostatic gas bearing spindle device. Can do. For example, in the first embodiment shown in FIGS. 1 to 4, instead of the static pressure magnetic composite bearings 6 and 7, a static pressure gas bearing 66 is provided as shown in FIG. good. In this case, a thrust type static pressure gas bearing (not shown) may be provided instead of the thrust type static pressure magnetic composite bearings 8 and 9 (FIG. 1).
[0025]
【The invention's effect】
The hydrostatic magnetic compound bearing spindle device of the present invention is provided with a rolling bearing provided with a preload in a housing, and a radial gap between the inner diameter surface of the inner ring of the rolling bearing and the outer diameter surface of the main shaft is set to a radial diameter of the hydrostatic magnetic compound bearing. A thrust type hydrostatic magnetic composite bearing is provided that is set to a clearance or less and faces the flange portion provided on the main shaft so as to support the main shaft, and the bearing surface of the thrust type hydrostatic magnetic composite bearing and the bearing surface thereof are provided. on one side one of the flange surfaces of the opposing main spindle is provided with a sprayed layer of molybdenum or carbon, because were subjected to thermal spray layer of ceramic on the other side of the bearing surface and the spindle flange face, the bearing clearance Even when a narrow static pressure gas bearing portion is provided, an excessive load acts on the main shaft, and even when there is a touchdown between the main shaft and the stationary side member, the influence on the bearing and the main shaft can be prevented .
[Brief description of the drawings]
FIG. 1 is a longitudinal side view of a spindle device according to an embodiment of the present invention.
FIG. 2 is an enlarged cross-sectional view in the vicinity of the tip end portion of the spindle device of the spindle device.
FIG. 3 is a transverse sectional view of a radial type hydrostatic magnetic compound bearing in the spindle device.
FIG. 4 is an enlarged sectional view of a thrust type hydrostatic magnetic compound bearing in the spindle device.
FIG. 5 is a partial sectional view of a spindle device according to another embodiment of the present invention.
FIG. 6 is a partial sectional view of a spindle device according to still another embodiment of the present invention.
FIG. 7 is a partial cross-sectional view of a spindle device according to still another embodiment of the present invention.
FIG. 8 is a partial cross-sectional view of an embodiment in which the present invention is applied to a static pressure gas bearing spindle device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Spindle apparatus 4 ... Main shaft 5 ... Housing 6-9 ... Static pressure magnetic compound bearing 6A-9A ... Static pressure gas bearing 6B-9B ... Magnetic bearing 6Aa, 7Aa ... Static pressure gas bearing surface 10 ... Spindle drive source 41 ... Rolling Bearings 51, 52 ... sprayed layer 60 ... sliding material d1, d2 ... radial gap

Claims (4)

In a spindle device that supports a main shaft by a radial type hydrostatic magnetic compound bearing in which a hydrostatic gas bearing and a magnetic bearing are combined, a rolling bearing with a preload is provided in a housing, and an inner diameter surface of an inner ring of the rolling bearing is the radial clearance between the outer diameter surface of the main shaft, and set the following radial clearance still magnetic composite bearing, the protection against touch down the main shaft contacts the members of the static pressure side by an excessive load to perform in the rolling bearing, the A thrust-type hydrostatic magnetic composite bearing that supports the main shaft is provided facing the flange portion provided on the main shaft, and the bearing surface of the thrust-type hydrostatic magnetic composite bearing and the shaft surface of the main shaft facing the bearing surface are provided. on one side, molybdenum or provided sprayed layer of carbon, combined externally pressurized gas and magnetic axial subjected to thermal spray layer of ceramic on the other side of the bearing surface and the spindle flange surface Spindle device.   2. The hydrostatic magnetic compound bearing spindle device according to claim 1, wherein a bearing clearance of the rolling bearing is made zero by the preload.   3. The hydrostatic magnetic compound bearing spindle according to claim 1, wherein a sliding member that presses against an end face of the inner ring of the rolling bearing is provided in the housing to prevent the inner ring from idling due to an air shearing torque generated when the spindle rotates. apparatus.   4. The hydrostatic magnetic compound bearing spindle device according to claim 1, wherein the rolling bearing is a double row angular ball bearing. 5.

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