JPS61279401A - Main spindle device - Google Patents

Abstract

PURPOSE:To enable a single main spindle to perform cutting over a wide range from heavy cutting to light cutting and high speed cutting, by organically combining a rolling bearing and a static pressure pneumatic bearing and using both of the bearings to selectively display their function in accordance with a use. CONSTITUTION:A main spindle 2, holding a tool 56 in the front end part is rotatably supported by a ball bearing 4, roller bearing 5, sleeves 6, 7 and radial metals 8, 9. The main spindle, being supported by static pressure, is rotated at a high speed by supplying pressurized air 55 from charge air holes 29, 38. A main spindle device, stopping a charge of air from the holes 29, 38, presses forward the radial metal 9 by supplying air from a charge air hole 45, and the spindle 2, being set in a condition that it is supported by a rolling bearing, is enabled to perform heavy cutting.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to, for example, a main spindle device for a machine tool, and more particularly to a composite type main spindle bearing that is a combination of a rolling bearing and a hydrostatic bearing.

As is well known in the prior art, although rolling bearings have high rigidity and high load capacity, there is a limit to their rotational speed. on the other hand,
Hydrostatic air bearings can relatively easily achieve ultra-high rotational speeds with high rotational accuracy, but on the other hand, their rigidity and additional capacity are smaller than those of rolling bearings. Therefore, by combining these rolling bearings and hydrostatic bearings in a composite manner, their advantages can be obtained at the same time.

For example, the invention of Japanese Patent Publication No. 58-37081 discloses a means for combining a rolling bearing and a hydrostatic fluid bearing as means for supporting the main shaft of a machine tool.

In the above invention, although the above advantages are utilized, switching between the rolling bearing and the hydrostatic air bearing is performed passively depending on the magnitude of the radial load. Therefore, pressurized air must always be supplied to the hydrostatic air bearing, and a non-contact seal is required at the air supply portion, so air supply efficiency becomes an issue.

Further, in the above invention, depending on the magnitude of the radial metal load, there is a region that acts as a sliding bearing, and as a countermeasure for this, special members such as ceramics are required for the inner diameter portion of the shaft and the bearing. However, even if such a special member is used, the countermeasure against sliding wear cannot be completely achieved.For this reason, a state without slipping is desired.

Purpose of the Invention Therefore, the purpose of the present invention is to organically combine a rolling bearing and a hydrostatic air bearing as a means for the main spindle bearing of this type of machine tool, so that the functions of both of these bearings can be freely adjusted depending on the application. By making it possible to select between the two types, the scope of use of the spindle can be expanded, and a wide range of cutting can be performed with a single spindle, from general heavy cutting to light cutting and high-speed cutting with small diameter tools.

SUMMARY OF THE INVENTION Therefore, the present invention concentrically combines a rolling bearing, a radial metal, and a main shaft inside a housing, and displaces the radial metal in the axial direction of the main shaft, that is, in the thrust direction. Either integral rotation with the thrust metal or relative rotation between the main shaft and the radial metal can be selected.

When the radial metal rotates integrally with the main shaft, the rolling bearing is selected so that it can function as a bearing. In addition, the radial metal forms a space with respect to the main shaft, and when it functions as a static pressure bearing, the radial metal and rolling bearing are fixed inside the housing, and the main shaft receives the load from the radial metal. It receives static pressure from the pressurized fluid and becomes rotatable in a static pressure bearing state.

Such selective switching between both bearings is performed by displacing the radial metal in the thrust direction. When the radial metal rotates integrally with the main shaft,
By fitting into each other with tapered surfaces, they connect the main shaft in a precisely centered manner inside the housing. According to a preferred embodiment, the radial metal displacement means is configured such that the radial metal acts as a piston inside the housing and is driven by pressure fluid from the outside. Therefore, selection of a rolling bearing or a hydrostatic bearing can be made positively, independently of the load on the main shaft, simply by switching the pressure fluid from the outside. In this way, this spindle device can be used in a wide range of applications, from heavy cutting to high-speed light cutting.

Embodiment FIGS. 1 to 3 show a main spindle device 1 of a machine tool according to the present invention.
It shows. The main spindle device 1 of this embodiment, for example, holds the main spindle 2 in a two-point supported state at its front end and rear end.

In other words, this main shaft 2 has two angular ball bearings 4 on the front end side, two cylindrical roller bearings 5 on the rear end side, inside the front and rear housings 3 which are cylindrical and double as cylinders.
Sleeves 6.7 concentrically assembled inside them
It is rotatably supported by a first radial metal 8 and a second radial metal 9.

The sleeve 6 and the first radial metal 8 on the front end side are
They are assembled in a state where they fit into each other, and each is fitted inside a corresponding ball bearing 4. The second radial metal 9 on the rear end side also serves as a piston inside the housing 3 which also serves as a cylinder, and fits inside the front and rear roller bearings 5 and into the sleeve 7 on the outer periphery thereof. Note that the front and rear roller bearings 5 are maintained at a constant distance by a collar 10 fitted inside the housing 3.

The opening surface of the housing 3 is blocked by covers 11, 12, 13, and 14, which also serve as bearing holders, with the front end side and the rear end side as one unit. 15.16
are formed respectively. The sleeve 6 and the radial metal 8 on the front end side are in contact with the inner circumferential surface of the cover 11.12 by a sealing material 17.18 such as a gasket fixed to their end surfaces, so that the portion can be closed.

Similarly, in order to close the pressure chamber 16, the cover 13.14 on the rear end side is attached to the peripheral surface of the flange 21 integral with this radial metal 9 by means of a sealing member 19.20 such as an O-ring, or to the radial metal 9. It is in a state where it can be directly contacted with the rear end surface in a sealed state. The bearing of this flange 21 is fixed to the front end surface of the radial metal 9 via a retainer 22.

In addition, the entire inner circumferential surface of the radial metal 8.9 is
or a part thereof, forming a first tapered surface 23 and a second tapered surface 24 in mutually different directions, and connecting them to a first tapered surface 25 formed on the outer circumferential surface of the main shaft 2.
, and are opposed to the second tapered surface 26. There are gaps between these tapered surfaces 23, 24, 25, 26, the inner peripheral surface of the radial metal 9 at the rear end, and the corresponding outer peripheral surface of the main shaft 2, that is, spaces 27, 28 for the hydrostatic bearing.
is formed.

Furthermore, the housing 3 on the front side forms an air supply hole 29 for the static pressure bearing that communicates with the inside;
The tapered surface 2 passes through the communication hole 30 of the sleeve 6, the annular groove 31 of the radial metal 8, and the plurality of communication passages 32.
A large number of nozzles 33 are uniformly formed along the inner circumference of the nozzle 3.

These nozzles 33 are formed along the radial direction of the radial metal 8 toward the center. The air supply hole 29 is connected to the thrust metal 35 from the internal space of the housing 3, that is, the pressure chamber 15, through the communication hole 34 of the sleeve 6.
has reached the nozzle 36. This thrust metal 35 is fixed inside the sleeve 6, and its nozzle 36
is opposed to a thrust surface 37 of a flange-like portion formed at the bottom of the tapered surface 25. Similarly, the air supply hole 38 of the housing 3 on the rear end side is connected to the collar 10, the sleeve 7, the communication hole 39, 40 of the radial metal 9, and the annular groove 41.
It reaches a large number of nozzles 43 formed on the inner circumferential surface of the radial metal 9 via communication passages 42 . Note that both of the communication passages 32 and 42 communicate with the outside air through exhaust holes 46 and 47.

Furthermore, the radial metal 9 forms a pressure chamber 44 with the cover 14, and this pressure chamber 44 is formed in the cover 14 as a drive device for moving the radial metal 9 toward the front end side. Air supply holes 45 allow connection to a source of pressurized fluid.

Incidentally, in the above embodiment, the main shaft 2 is driven by a turbine system. That is, a casing 48 is provided between the front and rear housings 3 so as to surround the main shaft 2, and a nozzle body 49 is attached inside the casing 48. The high-pressure driving fluid 50 passes from the supply hole 51 of the casing 48 through the supply groove 53 to the nozzle 5 of the nozzle body 49.
3 to 2 rows of blades 54 formed on the outer peripheral surface of the main shaft 2
is injected tangentially to the This allows the main shaft 2 to rotate at high speed in a predetermined direction.

Function of the Embodiment FIG. 1 shows a state in which the main shaft 2 is supported by a hydrostatic air bearing. Of course, the main shaft 2 holds the tool 56 at its tip.

The front end portion of the main shaft 2 is supported by static pressure generated by pressurized air 55 in a space 27 between the tapered surface 23 of the radial metal 8 and the opposite tapered surface 25 of the main shaft 2 in a static pressure bearing. This pressurized air 55 is supplied from the air supply hole 29 , passes through the communication hole 30 , the annular groove 31 and the communication path 32 , and is injected into the hydrostatic bearing space 27 from each nozzle 33 .

As shown in FIG. 3, this nozzle 33 simultaneously generates a component force in the thrust direction as well as a component force in the radial direction. Moreover, since the pressurized air 55 is injected from the nozzle 36 toward the thrust surface 37 through the communication hole 34, the pressurized air 55 here is only balanced with the component force in the thrust direction on the tapered surface 25. This generates static pressure. As a result, the main shaft 2 receives static pressure in the radial direction and the thrust direction, and is statically supported inside the sleeve 6.7 and the radial metal 8.9 in a non-contact state. Note that, as shown in FIG. 3, a portion of the pressurized air 55 flowing in from the nozzles 33 and 36 passes through the groove 57 formed in the radial direction in the thrust metal 35, passes through the gap in the main shaft 2, and exits to the outside. released. In this state, spindle 2
receives the driving fluid 50 from the nozzle 53 and rotates at high speed, and is in a state where the tool 56 at its tip can perform light cutting, which is mainly necessary for a workpiece or the like.

On the other hand, the rear part of the main shaft 2 is similarly supported by a hydrostatic bearing in the space 28 using pressurized air 55 from the nozzle 43.

At this time, the internal pressure of the pressure chambers 15 and 16 increases with the pressurized air 55.
The pressure is increased until it becomes approximately equal to the pressure of

Due to this pressure, the front and rear sealing members 17.18 are brought into contact with the inner peripheral surface of the cover 11.12, and the pressurized air 5.
5 is confined inside the pressure chamber 15 while being hermetically sealed. Note that a portion of this pressurized air 55 is exhausted to the atmosphere from the exhaust hole 46.

Similarly, the pressurized air 55 inside the pressure chamber 16 moves the sleeve 7 and the radial metal 9 rearward as pistons, presses the rear end surface of the radial metal 9 against a sealing member 20 such as an O-ring, and Cover flange 21 1
By pressing against the sealing material 19 of No. 3, the pressure chamber 16 is closed.
The interior is sealed. Of course, even in this state, a portion of the pressurized air 55 is exhausted to the outside through the exhaust hole 47.

This support state of the static pressure air bearing is due to the air supply hole 29.
It can be positively set by supplying pressurized air 55 from the section 38. In this state, light cutting is possible at high speed and with high rotation accuracy.

Next, the supporting state of the rolling bearing is changed by stopping the supply of pressurized air 55 from the air supply hole 29.38 and
is arbitrarily selected by supplying pressurized air 55 from . That is, first, when the air supply from the air supply holes 29, 38 stops, the state of the static air bearing is released. After that, pressurized air 55 is supplied from the air supply hole 45 . This pressurized air 55 enters the inside of the pressurizing chamber 44 and pushes the radial metal 9 in the forward direction, and the radial metal 9, sleeve 7, flange 21 and bearing move the presser 22 in the forward direction together with the inner ring of the roller bearing 5. move it. During this movement process, the tapered surface 24 of the radial metal 9 comes into contact with the tapered surface 26 of the main shaft 2, holding the main shaft 2 in an aligned state inside the radial metal 9, and further moves the main shaft 2 toward the front end side. However, due to the mutual engagement of the tapered surfaces 23, 25, a centering condition is achieved, and the rolling bearing is set in a supported condition inside the housing 3 by the ball bearing 4, the degree sleeve 6 and the radial metal 8. Note that the rear radial metal 9 has a tapered surface 2.
The main shaft 2 is contacted only at the portion 4, and the other portions other than the tapered surface 26 do not contact the outer circumferential surface of the main shaft 2, ensuring contact between the tapered surfaces 23 and 25 on the front side.

In addition, in this state, since the internal pressure of the pressure chamber 15.16 is the same value as the atmosphere, all the sealing materials 17.1
8.19.20 is remote from the opening surface of the cover 11.12 or the radial metal 9 and the flange 21. Furthermore, when the main shaft 2 rotates, the sealing material 17, 18 receives the centrifugal force and deforms into a flat shape on the same plane as the attachment part, thereby releasing the part. In this way, the main shaft 2 is connected to the sleeve 6.7 and the radial metal 8.
By being concentrically combined with 9 and frictionally fitted and integrated, they are supported by the ball bearings 4 and roller shafts 5 in a rolling pair within the front and rear housings 3.

Note that when this rolling bearing is in a supported state, the rearward thrust applied to the main shaft 2 is supported by the pressure of the pressure chamber 44, that is, the pressure of the pressurized air 55. Main shaft 2
When a thrust force greater than this pressure acts on the main shaft 2, the thrust surface 37 of the main shaft 2 comes into contact with the opposing surface of the thrust metal 35, and is supported by the rear ball bearing 4 via the sleeve 6.6 Modification of the invention Although the above embodiments are directed to machine tools, the present invention can also be applied to other spindle devices.

The radial metal 9 that also serves as a piston and the pressure chamber 44 as a cylinder chamber are not limited to the rear side of the main shaft 2, but can also be formed on the front side or only on the front side.

Therefore, the inclination directions of the tapers 23, 24, 25, and 26 may be set in a relationship opposite to that of the embodiment.

Of course, the turbine-type drive means is just one example, and the drive source may be an electric motor, or may be of a type in which external rotational force is guided by other drive means such as a belt or gears.

Effect of the invention The present invention provides the following unique effects.

First, when a rolling bearing is supported, the radial metal of the hydrostatic air bearing fitted into the inner ring of the rolling bearing rotates while being integrated with the main shaft due to the fit of the chill bar and surface, so it acts as a sliding bearing. There is no area and therefore no frictional resistance or wear parts as in the past.

Next, the rolling bearing condition and the hydrostatic air bearing condition are actively adjusted depending on the purpose of use, and each function works completely independently, so the hydrostatic air bearing is in the supported condition. There is no need for non-contact seals when supplying pressurized air, and the necessary parts can be set to a completely sealed state. Therefore, wasteful release of pressurized air in a static air bearing state is eliminated.

Furthermore, since the hydrostatic air bearing can be completely sealed in the supported state, it will not be affected by exhaust gas even if grease is used to lubricate the rolling bearing.

Further, in the case of a hydrostatic air bearing, pressurized air can be easily supplied to the bearing regardless of the presence of grease or the like.

[Brief explanation of drawings]

FIG. 1 is a sectional view of the spindle device of a machine tool according to the present invention, FIG. 2 is a sectional view of a nozzle portion, and FIG. 3 is a partial sectional view showing the relationship of component forces on a tapered surface. l... Main spindle device of machine tool, 2... Main spindle, 3... Housing, 4... Ball bearing, 5... Roller bearing, 6.7...
Sleeve, 8..First radial metal, 9..Second radial metal, 11.12.13.14..Cover, 15.16.44..Pressure chamber, 17.18.19.2
0...Sealing material, 23.25...First tapered surface, 24
．． 26...Second tapered surface, 27.28...Static pressure bearing is space, 29.38.45...Air supply hole, 33.43...
Nozzle, 35... Thrust metal, 36... Nozzle, 3
7. Thrust surface, 46.47. Exhaust hole, 55. Pressurized air.

Claims (1)

[Claims] a cylindrical first radial metal rotatably supported via a rolling bearing within the housing; a cylindrical second radial metal rotatably and slidably supported via a rolling bearing within the housing; A drive device that slides this second radial metal, a main shaft inserted into the first and second radial metals, and a main shaft facing the inner peripheral surfaces of the first and second radial metals, respectively. In a spindle device in which first and second tapered surfaces are respectively formed, the second radial metal is slid by the drive device to abut the main spindle and both tapered surfaces, and the two radial metals are brought into contact with each other. The main shaft is supported by the rolling bearing through the second radial metal, while a gap is formed between the main shaft and both tapered surfaces by the retreat of the second radial metal, and the main shaft is statically supported by pressurized air. A spindle device characterized by: