JPH0861369A - Hydrostatic gas bearing - Google Patents

Abstract

PURPOSE: To reduce the consumed flow rate, maintaining the necessary load capacity, as for a hydrostatic gas bearing which has each opposed type thrust bearing on the load side and the reverse side, and has a necessary quantity of air feed holes on each thrust bearing surface. CONSTITUTION: An air feeding hole such as an autogenous throttle hole 14' of a load side thrust bearing surface 13' is formed on the bottom surface of an annular groove 18, and a thrust bearing slit 12' is reduced as small as possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrostatic gas bearing used for a main shaft of a punching machine.

[0002]

2. Description of the Related Art Conventionally, as a hydrostatic bearing used for a main shaft of a punching machine, there are those shown in FIGS. 3 (a), 3 (b) and 3 (c). That is, the main shaft 1 has a thrust plate 2, and a lower bearing member 3 facing the outer diameter surface of the main shaft 1 below the thrust plate 2 and the lower surface of the thrust plate 2 is attached to the housing 4. Further, the upper bearing member 5 facing the outer diameter surface of the main shaft 1 above the thrust plate 2 and the upper surface of the thrust plate 2 has a housing 4
Mounted on.

The lower bearing member 3 is provided with a journal bearing portion 6 and a thrust bearing portion 7, and the journal bearing portion 6 has an outer diameter surface of the main shaft 1 and a journal bearing clearance 8.
Have journal bearing surfaces 9 facing each other, and the journal bearing surface 9 is provided with self-made throttle holes 11.

The thrust bearing portion 7 is composed of the thrust plate 2
And a thrust bearing surface 13 facing each other through a thrust bearing clearance 12, and the self-made throttle hole 14 is provided in the thrust bearing surface 13.

A thrust bearing portion 7'is provided on the upper bearing member 5, and the thrust bearing portion 7'has a thrust bearing surface 13 'which faces the thrust plate 2 with a thrust bearing clearance 12'. The thrust bearing surface 13 'is provided with a self-made throttle hole 14'.

When compressed gas is supplied to the passage 15 provided in the housing 4, the journal bearing clearance 8 and the thrust are transmitted from the throttle holes 11, 14, 14 'provided in the journal bearing portion 6 and the thrust bearing portions 7, 7'. Bearing clearance 12,
The compressed gas flows into 12 'and supports the main shaft 1 in a non-contact manner.

The main shaft 1 has a collet chuck 16
Is attached, and the collet chuck 16 holds the tool 17. When the spindle 1 is rotated at a high speed by a motor or the like, the tool 17 is rotated, and by punching the tool 17 against the work, drilling or the like can be performed. Tool 1
The spindle 1 is displaced with respect to the housing 4 by the force of pressing the workpiece 7 and the work. As a result, the upper thrust bearing surface 13 'serves as a load receiving surface and the lower thrust bearing surface 13 serves as an anti-load side.

Conventionally, the thrust bearings used for the main shaft 1 of a drilling machine are generally the same in structure, without any distinction between the load side and the non-load side. However, from the perspective of preventing seizures and other failures, thrust bearings have been proposed in which the bearing on the load side, the number of holes, and the diameter of the holes are larger on the load side than on the anti-load side. (Japanese Patent Laid-Open No. 2-209622). This is one in which the bearing clearance on the load side is increased when there is no load so that the bearing clearance on the load side approaches the bearing clearance on the anti-load side in a loaded state.

[0009]

The load capacity of the thrust bearing used for the main shaft of a drilling machine is determined by the purpose and method of use. Here, as an example, consider a case where the load capacity W _{OA on} the load side and the load capacity W _OB on the anti-load side are required. However, W _OA > W _OB .

FIG. 4 shows a load capacity characteristic curve diagram when the above load capacity is satisfied and the same self-made throttle thrust bearing is used on the load side and the anti-load side. In this case, if the load capacity on the load side is W _1A and the load capacity on the anti-load side is W _1B , then W _1A
= W _1B and W _1A = W _OA , W _1B > W _OB .
That is, it can be said that the load capacity of the bearing on the anti-load side is larger than necessary.

Generally, in a thrust bearing, when the bearing area is constant, there is a relation that the flow rate increases as the load capacity increases. Therefore, the flow rate of the bearing shown in FIG. Will be.

As a method for solving this problem, as described in the above-mentioned Japanese Patent Laid-Open No. 2-209622, the number of air supply holes in the bearing on the load side is made larger than that on the bearing on the anti-load side, or the load is reduced. There is a method of making the air supply hole diameter of the side bearing larger than that of the bearing on the opposite side. In other words, reduce the number of air supply holes in the bearing on the anti-load side compared to that on the load side,
Alternatively, it is conceivable to reduce the flow rate of the bearing on the anti-load side by making the supply hole diameter of the bearing on the anti-load side smaller than that of the bearing on the load side.

[0013] indicates the load capacitance characteristic curve diagram when considering W _OB in this way were selected bearing in FIG. Load capacity W _2A on the load side of this case, when the load capacitance W _2B of the anti-load side and W _2B = W _OB. As a result, it is possible to reduce the consumption flow rate to some extent.

However, in recent years, the performance of punching machines and the like has been improved, and further reduction of the flow rate consumed has been demanded, and the above method alone may not be sufficient.

Therefore, according to the present invention, in a hydrostatic gas bearing having opposing thrust bearings on the load side and the anti-load side respectively, the flow rate consumed by the thrust bearing portion is further reduced while maintaining the required load capacity. The purpose is to do.

[0016]

In order to solve the above-mentioned problems, the present invention has opposing thrust bearings on the load side and the anti-load side, and each thrust bearing surface has a required number of air supply holes circumferentially. In the static pressure gas bearing provided above, only the air supply hole of the load side thrust bearing surface is provided on the bottom surface of the annular groove, and the thrust bearing clearance is made as small as possible.

[0017]

As an example, FIG. 6 shows a load capacity characteristic curve in the case where a grooved bearing having a bearing area and load capacity equivalent to those of the load side bearing shown in FIG. 5 is used. Due to the surface drawing effect of the groove, the grooved bearing has a load capacity equivalent to that of the self-made throttle bearing when the clearance is small, but the load capacity is larger than that of the self-made throttle bearing as the bearing clearance increases (see the wavy line). Also becomes smaller. Therefore, if the load capacity on the load side in this case is W _3A and the load capacity on the anti-load side is W _3B , then W _3A = W _2A
> W _0A , W _3B > W _2B = W _0B .

Here, since the load side bearing and the anti-load side bearing both have an unnecessarily large load capacity,
It is possible to reduce the bearing clearance and load capacity. Generally, the smaller the bearing clearance is, the smaller the consumption flow rate is. Therefore, reducing the clearance is an effective means for reducing the consumption flow rate.

FIG. 7 shows the result of reducing the bearing clearance in consideration of the load capacities W _OA and W _OB . In this case, if the load capacity W _{4A on} the load side and the load capacity W _4B on the opposite side are W _4A = W
_OA , W _4B = W _0B . In this way, by using a grooved thrust bearing as the load side bearing and a self-made throttle bearing as the counter load side bearing, it is possible to reduce the flow rate consumption of the thrust bearing portion used for the main shaft of a drilling machine, etc. Become.

[0020]

EXAMPLE The example shown in FIGS. 1 (a), (b) and (c) is
Since the basic structure is the same as that of the conventional example shown in FIG. 6, the same parts are denoted by the same reference numerals and the description thereof is omitted.

The difference lies in the thrust bearing surface 1 on the load side.
3'is a throttle hole 14 'provided on the bottom surface of a groove 18 concentric with the main shaft 1 and a thrust bearing clearance 12' is set to be as small as possible (for example, 20 μm).

With the above construction, the load capacity characteristic as shown in FIG. 7 is obtained, and the load capacity on the load side is W.
The load capacity W _4A on the side of _{4 A} and the anti-load side can be matched with the required load capacity W _0A and W _0B , respectively.

FIG. 2 shows a specific example of the groove 18 and the self-made throttle hole 14 'formed in the groove bottom. The groove 1 has a width a of 0.7 mm and a depth b of 0.01 mm (10 μm). ).

It should be noted that instead of the self-made throttle hole, an air supply hole having another suitable shape can be adopted.

[0025]

As described above, according to the present invention, the required load capacity is provided by providing the air supply hole of the load side thrust bearing surface on the bottom surface of the annular groove and making the thrust bearing clearance as small as possible. It is possible to reduce the consumption flow rate while ensuring the amount.

[Brief description of drawings]

FIG. 1A is a cross-sectional view of an embodiment. FIG. 1B is a plan view of a load side thrust bearing surface of the same. FIG. 1C is a plan view of an anti-load side thrust bearing surface of the same.

FIG. 2 is a partially enlarged sectional view of the above.

FIG. 3A is a cross-sectional view of a conventional example. FIG. 3B is a plan view of a load side thrust bearing surface of the same. FIG. 3C is a plan view of an anti-load side thrust bearing surface of the same.

[Figure 4] Load capacity characteristic diagram

[Figure 5] Load capacity characteristic diagram

[Figure 6] Load capacity characteristic diagram

[Figure 7] Load capacity characteristic diagram

[Explanation of symbols]

 1 main shaft 2 thrust plate 3 lower bearing member 4 housing 5 upper bearing member 6 journal bearing part 7, 7'thrust bearing part 8 journal bearing clearance 9 journal bearing surface 11 self-made throttle hole 12, 12 'thrust bearing clearance 13, 13' Thrust bearing surface 14, 14 Self-made throttle hole 15 Passage 16 Collet chuck 17 Tool 18 Groove

Claims (1)

[Claims] 1. A static pressure gas bearing having opposing thrust bearings on the load side and the anti-load side, respectively, and having a required number of air supply holes on each thrust bearing surface, wherein the air supply holes on the load side thrust bearing surface are provided. The static pressure gas bearing is characterized in that only the thrust bearing clearance is provided as small as possible on the bottom surface of the annular groove.