JPS58203220A - Pneumatic thrust bearing unit - Google Patents

Abstract

PURPOSE:To properly determine or vary the clearance in a pneumatic bearing by mounting one of bearing members which make up the pneumatic bearing so that it can be slided in the axial direction of a rotary shaft. CONSTITUTION:A bearing member 8 of a pneumatic thrust bearing 9a is provided with a movable bearing member 11 which forms another pneumatic thrust bearing 9b in the opposed relation to the left end face of a flange 7 of a rotary shaft 1. When a pressure sensor 28 which is provided for the pneumatic thrust bearing 9a senses a pressure P and outputs it in the form of a signal P to a computing unit 29, it compares the signal with a pressure P1 corresponding to the optimum bearing clearance, in order to vary the preset pressure P2 of a pressure governor 24. As the result, the movable bearing member 11 moves to the right or left to maintain the clearance between the bearing members at the optimum value.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thrust air bearing device in which a bearing clearance can be set according to usage conditions.

Because air bearings have very low friction, they are beginning to be used practically in high-speed and high-precision rotating parts where stick-slip is a concern. The advantages and disadvantages of air bearings are that the viscosity of air, which is a lubricant, is very low compared to liquid lubricants such as oil. It is necessary to improve the surface accuracy of the bearing and reduce the bearing clearance. In addition, although specific numerical values differ depending on conditions such as the shape, size, and air supply pressure of each air bearing, the bearing rigidity of an air bearing is determined by the bearing gap between the bearings, as shown in Figure 1. It changes sensitively depending on the size, and shows a peak value when the bearing clearance is at a predetermined value. Therefore, when using air bearings, setting the bearing clearance becomes an important issue. Furthermore, the relationship between the bearing gap and the air discharge flow rate tends to be as shown in FIG. 2, and when the bearing gap is small, the discharge flow rate, that is, the flow rate of air flowing through the bearing gap, decreases. The air flowing through this bearing gap has the effect of suppressing heat generation in the bearing, so at low speeds there is no problem with heat generation even if the bearing gap is small, but at high speeds the bearing gap should be increased to some extent. If the discharge flow rate is not increased, heat will be generated. Thus, in air bearings, the size of the bearing gap is an important point.

As mentioned above, the purpose of the present invention is to focus on the bearing clearance that greatly affects the characteristics of air bearings, and to control this bearing clearance, the thrust air bearing device can be used in a state more suitable for the usage conditions. is to provide.

Another object of the present invention is to provide a thrust air bearing device that allows a specific rotating shaft to be used under different operating conditions such as low speed and high speed by controlling the bearing clearance.

To achieve this object, the present invention provides a thrust air bearing device in which air bearings are formed on opposite end faces of a rotating shaft, in which air bearings are formed opposite to each other on both end faces of the rotating shaft. A thrust air bearing device in which at least one of the bearing members is movable in the axial direction of a rotating shaft, and a bearing clearance can be appropriately set or changed by changing the axial position of the bearing member. be.

Note that air or i
- Various means can be employed, such as fluid pressure such as oil, screws, magnetic force, or a combination of these and springs.

Further, in the thrust air bearing device of the present invention, if a means for detecting the size of the gap between the air bearings is added and the bearing members are automatically moved in relation to the output signal, it is possible to avoid heat generation during operation. Adaptive control such as compensating for changes in bearing clearance due to displacement or automatically changing bearing clearance according to command values becomes possible.

Note that various means can be used to detect the bearing clearance, such as detecting the pressure inside the air bearing using a pressure sensor, detecting the discharge flow rate of the air bearing described above, and detecting the displacement of the rotating shaft.

3 and 4 showing one embodiment of the present invention will be explained below. 1 is a rotating shaft driven by the main motor 2, 3.4 is a bearing member forming a radial air bearing 5.6, 7 is a collar provided on the rotating shaft 1, and 8 is a collar 7 shown in FIGS. 3 and 4. A thrust air bearing C/ae is formed between the right end face of the bearing member C/ae, and each of the aforementioned bearing members 3 and 4°8 is attached to the base 10.

The bearing member of the thrust air bearing 9a is provided with a movable bearing member II forming a thrust air bearing 9bk facing the left end face of the boxwood 7 in FIGS. 3 and 4. This movable bearing member 11 is incorporated so as to be movable only in the axial direction of the rotary shaft 1 by means of a guide pin 12.

The movable bearing member 11 is provided with a plurality of channels 13, one end of which opens on its outer peripheral surface and the other end of which opens toward the left end surface of the collar 7. Pressurized air maintained at a predetermined pressure po is supplied. Note that 15 is a sealing member provided for each flow path 13. Further, the bearing member 8 has a collar 7.
A plurality of passages 16 are provided which open toward the right end surface of the cylinder, and pressurized air maintained at a predetermined pressure Po is supplied thereto. A space 17 is formed on the outer peripheral side of the collar 7, and this space 17 is opened to the atmosphere through a plurality of exhaust ports 18 provided in the bearing member 8. On the other hand, the base side of the brim 7 is
It is open to the atmosphere through gaps 19 and 20 between the bearing member 8 and the movable bearing member 11 and the rotating shaft 1, as well as a gap 27, which will be described later.

The inner surface of the lid 21 fixed to the bearing member 8 faces the left end face of the movable bearing member 11 with a small gap 522 in FIGS. 3 and 4, as shown in FIGS.
v-Ch O7p' 2p:1:, to 1. , a flow path 23 communicating with the gap 22 is provided, and a pressure regulator 24 is provided.
Pressurized air is supplied from a pressurized air supply source (not shown) through the gap 22. The outer circumferential side of the gap 22 is opened to the atmosphere via a space 25 through an exhaust port 26, and the inner circumferential side is connected to a lid. A gap 27 between the rotary shaft 1 and the rotary shaft 1 is opened to the atmosphere.

A pressure sensor 28 is embedded in the bearing surface of the bearing member 8 to detect the pressure P within the thrust air bearing 9a. The output signal p from the pressure sensor 28 is transmitted to the calculation section 29. The calculation unit 29 converts the pressure Pi into the value of the bearing clearance C or uses it as a control signal as it is, and changes the pressure regulator 24 so that the output signal p becomes a predetermined value. Change the pressure of pressurized air supplied to the gap 22 at the left end of the bearing member 11 to P2',
By moving the movable bearing member 11 to the right or left, the value of the bearing clearance C is changed. Note that the calculation unit 29 adjusts the pressure regulator 24 so as to keep the output signal p always constant, or further adjusts the output signal p according to a predetermined relationship according to the rotation speed of the rotating shaft 1. The pressure regulator 24 is configured to adjust the pressure regulator 24 to change pt.

Next, the operation of this device will be explained. As shown in Figures 1 and 2, the characteristics of air bearings are determined by the shape and dimensions of each air bearing, so the optimum bearing clearance C1 of thrust air bearings qa and 9b is determined in advance, and then The pressure Pl inside the thrust air bearing qa is determined in advance. The optimum bearing clearance C1 or the pressure P1 is input into the calculation section 29 as a set value. Then the channel 14.1
When pressurized air is supplied from 3.degree. The pressure P tends to be high when the bearing clearance C is small and low when it is large, so when the output signal p is small, the calculation unit 2
9, the set pressure of the pressure regulator 24 is increased to increase the left gap 22 of the movable bearing member 11, and the movable bearing member 11 is moved to the right in FIGS. 3 and 4.

This movement reduces the bearing clearance C and increases the pressure P. When the output signal p is large, the movable bearing member 11 is moved to the left, contrary to the above, to increase the bearing clearance C.
If P is increased, the pressure P will decrease. In this way, when the pressure P, that is, the bearing clearance C is not the optimum bearing clearance C1 inputted to the calculation unit 29, and the pressure P becomes Pl, the calculation unit 29 stabilizes the set pressure of the pressure regulator 24, and the movable bearing member 11 't - Hold in that position 0 At this time, in FIGS. 3 and 4, the left thrust air bearing 9b is formed symmetrically with the right thrust air bearing 9a, so the load is not biased. If this is ignored, the bearing clearance C of this left thrust air bearing 9b will also be set to the optimum bearing clearance C1. Note that when the load acting on the rotating shaft 1 is, for example, rightward, the left and right thrust air bearings 9a.

Although the bearing clearances C of 9b are different, these bearing clearances C change at a predetermined rate depending on the load.

Therefore, the thrust air bearings 9a and 9b compensate for machining and assembly errors in the collar 7 and the bearing member 8 of the rotating shaft 1 to ensure that the air bearings have the desired characteristics and support the rotating shaft 1. do.

Note that when only one thrust air bearing qb side is made movable as in this embodiment, the rotary shaft 1 moves in the axial direction by 1/2 of the amount of movement, but the amount of movement of the movable bearing member II is small, so the movement of the rotating shaft 1 is negligible.

However, if it is desired to suppress the movement of the rotation axis j, the left and right thrust air bearings qa and qb may be configured to move symmetrically.

The bearing clearance C of the thrust air bearing qa, 9b is:
It may change due to the temperature rise of the bearing part due to rotation of the rotating shaft 1 or other factors. Due to this change in the bearing clearance C, the pressure P changes, and the output signal p changes. This output signal p
When this changes, the pressure regulator 24 is activated by the calculating section 29, and the movable bearing member +1' is moved to maintain the bearing clearance C at the optimum bearing clearance C1. Therefore, the thrust air bearings qa and qb continue to support the rotating shaft 1 in the desired state by compensating for changes due to thermal displacement during operation.

In addition, the optimal bearing clearance C is set in the calculation unit 29 as a value corresponding to changes in the rotational speed of the rotating shaft 10. For example, when the rotational speed is high, the bearing clearance C is increased to increase the air discharge flow rate and perform cooling function. If the engine is configured to be corrected to a value that increases the number of revolutions, it is possible to operate the engine in a state that corresponds to changes in the rotational speed.

FIG. 5 shows another embodiment of the present invention, in which the movable bearing member 11 is moved by a feed motor 30 and a screw 31 which is rotated forward and backward by the feed motor.

As a means for moving the movable bearing member 11, in addition to the above-mentioned embodiments, other means such as hydraulic pressure using a cylinder system, magnetic force, spring, etc. can be adopted, and in some cases, manual setting may be used. Good too. Furthermore, the detection of the bearing clearance C is not limited to the pressure sensor 28, and the bearing clearance C and the discharge flow rate of pressurized air have a certain relationship in each air bearing as shown in FIG. Therefore, it goes without saying that various means such as detecting the bearing clearance c4- from the discharge flow rate or detecting from the amount of axial movement of the rotating shaft 1 can be employed.

As described above, according to the present invention, the advantages of air bearings can be more fully demonstrated, and they can be used in conditions suitable for the usage conditions, and one rotating shaft can be used at different speeds such as high speed and low speed. It can also be used under various conditions, and if configured to automatically control the bearing clearance, it can compensate for changes in the bearing clearance due to thermal expansion during operation and maintain the optimum condition at all times, and even changes in rotational speed. It also automatically responds to various conditions, providing the optimum conditions over a wide range of rotational speeds.

[Brief explanation of drawings]

Figure 1 is a curve diagram showing an example of the relationship between the bearing clearance of an air bearing and bearing static rigidity, Figure 2 is a curve diagram showing an example of the relationship between the bearing clearance of an air bearing and the discharge flow rate of pressurized air; 3 is a sectional view showing one embodiment of the present invention, FIG. 4 is an enlarged view of the main part of FIG. 3, and FIG. 5 is a sectional view of the main part showing another embodiment of the invention. DESCRIPTION OF SYMBOLS 1...Rotating shaft, 7...Brim, 8...Bearing member, qa, 9b...Thrust air bearing, 11...Movable bearing member, +2...Guide bin, +3.14.
16.23... Channel, 18.26... Outlet,
22... Gap, 24... Pressure regulator, 28...
・Pressure sensor, 29...Calculation unit, 30...Feed motor, 31...Screw. Applicant: Toshiba Machine Co., Ltd.

Claims (1)

[Claims] 1. In a thrust air bearing device in which air bearings are formed on opposing end surfaces of a rotating shaft, a bearing member that forms air bearings on opposite end surfaces of the rotating shaft. An air bearing device characterized in that at least one of the two is movable in the axial direction of a rotating shaft. 2. The thrust air bearing device according to claim 1, wherein the moving side bearing member is movable by a change in fluid force opposing the pressure of the air bearing. 3. The thrust air bearing device according to claim 1, wherein the moving side bearing member is made movable by a screw. 4. The bearing member on the moving side is provided so as to be movable between two predetermined positions, and configured to be movable automatically from one position to the other position according to the rotation speed of the rotating shaft. A thrust air bearing device according to claim 1.2 or 3. 5. In a thrust air bearing device in which air bearings are formed on opposite end faces of the rotating shaft, at least one of the bearing members that form air bearings on opposite end faces of the rotating shaft. movable in the axial direction of the rotating shaft, and means for detecting the size of the gap between the air bearings, and the bearing member can be moved in response to an output signal from the means.
Thrust air bearing device with % characteristics. 6. The thrust air bearing device according to claim 7, wherein the means for detecting the size of the gap in the air bearing is a pressure sensor that detects the pressure within the air bearing. 7. The thrust air bearing device according to claim 7, wherein the means for detecting the size of the gap between the air bearings is configured to detect from the flow rate of air discharged to the air bearings. 8. The thrust air bearing device according to claim 7, wherein the means for detecting the size of the gap in the air bearing is detected from the displacement of the rotating shaft.