Novel pressure gas bearing

Abstract

The new pressure gas bearing belongs to the field of gas bearings. The bearing consists of a stepped shaft, a bearing, and left and right end caps. The working principle of the new pressure gas bearing is the same as that of a dynamic pressure gas bearing under environmental conditions. It uses the dynamic pressure effect of the pressurized gas in the large shaft clearance to carry radial load. This invention aims to solve two technical problems. First, it aims to substantially solve the world problem of "sealing the pressurized gas inside the bearing". By using a pressure-sealed container and assembling twice, the pressurized gas can be sealed inside the bearing. Second, it aims to completely solve the hidden danger of the gas bearing seizing the shaft. For this purpose, two measures are adopted: 1. The outer clearances (2) and (17) of the small shafts on both sides of the stepped shaft are absolutely unequal. 2. Improve the hardness of the bearing surface at high temperature, or spray a layer of hard material on the bearing surface. This invention returns the air compressor that was required for the operation of the pressure gas bearing from the West to the Western world. It does not require a throttle, and the bearing performance is better than that of the air compressor. The new pressure gas bearing is widely used in inertial navigation gyroscopes, precision machine tool spindles, high-speed power head bearings: boring heads, milling heads, high-speed magnetic heads of electronic computers, etc.

Description

[0001] This invention relates to a gas bearing, and more particularly to a pressure gas bearing. Background Technology

[0002] It has been universally believed that "sealing pressurized gas inside a bearing" is impossible. To date, there are no gas bearing products in the world that "seal pressurized gas inside a bearing." Furthermore, pressurized gas bearings require an air compressor to operate, and a throttle device must be designed inside the bearing. (See "Gas Lubrication Theory and Gas Bearing Design," edited by Wang Yunfei, Machinery Industry Press, 1999). Summary of the Invention

[0004] Manufacturing method of "new pressure gas bearing": Place the initially assembled gas bearing into a pressure-sealed container (20), and seal the container. Figure 2 A certain pressure of pure gas is introduced into the sealed container, and the ball bearing is pushed open to allow the pressurized gas to enter the gas bearing. At this time, the gas pressure inside and outside the gas bearing in the sealed container is equal. Sealing oil is then injected into the sealing oil ring grooves (3) and (16) on both sides. Figure 1 , 2 ), sealing the pressure gas inside the bearing. Open the exhaust valve (29)( Figure 3 Release the pressurized gas from the sealed container and remove the bearing.

[0005] The new pressure gas bearing operates on the same principle as the hydrodynamic gas bearing under environmental conditions, utilizing the hydrodynamic effect of pressurized gas sealed within the shaft clearance to bear radial loads. Let P be the pressure of the gas sealed within the bearing. a (1.033kgf / cm 2 If the pressure is controlled to operate at ambient atmospheric pressure, the bearing becomes a dynamic pressure gas bearing. Therefore, the new pressure gas bearing does not require an air compressor to input pressurized gas into the bearing from the outside, nor does it require a throttling device designed inside the bearing.

[0006] Let's review how, based on the Reynolds equation, the static stiffness of an infinitely long bearing is theoretically derived from hydrodynamic gas bearings:

[0007] Throughout the entire theoretical derivation process, environmental pressure P was considered. O Regardless of any restrictions, P O It can be any value. Because it has long been believed worldwide that "sealing pressurized gas within a bearing" is impossible, any hydrodynamic gas bearing can only be placed in ambient atmospheric pressure. Therefore, the ambient pressure of a hydrodynamic gas bearing can only uniquely be P. a =1.033 kgf / cm 2 Therefore, in the past theoretical derivation of the stiffness of hydrodynamic gas bearings, the environmental pressure p, which was originally theoretically unlimited, was taken into account. oChange to p in actual situation a This is why the environmental pressure in formula (1) is always p. a The reason is that this invention achieves "pressure gas sealing within the bearing," reducing the ambient pressure p of the main shaft. o Theoretically, it can be any design value (ambient pressure is defined as the gas pressure in all spaces within the bearing except for the main shaft clearance). Therefore, this paper will use the ambient pressure p in formula (1). a Then change it back to the original unrestricted p. o The theoretically derived bearing stiffness formula (1) is fully applicable to the "new pressure gas bearing".

[0008] Historically, people have only focused on the effect of compression coefficient Λ on bearing stiffness, and no one has studied the environmental pressure p. o The effect on bearing stiffness. The following analysis examines the environmental pressure p. o The effect of static stiffness k on steady flow in an infinitely long cylindrical pressure gas bearing. o The relationship (calculated using formula (1)) is as follows: Figure 5 The graph shows that the environmental pressure p o From the minimum value p a The bearing stiffness k initially increases with p. o The curve increases monotonically until it reaches a certain value p. c (9-10kgf / cm 2 After the bearing becomes approximately horizontal, its stiffness hardly increases further, therefore the gas pressure p sealed inside the bearing... c This can be considered as the maximum selectable value within the new pressure gas bearing, p c The new pressure gas bearing boasts a higher maximum gas supply pressure than previous pressure gas bearings. The increased stiffness is primarily achieved by increasing the gas pressure sealed within the bearing, something previously impossible worldwide.

[0009] The above describes the manufacturing method, working principle, and gas pressure p sealed inside the bearing of the new pressure gas bearing. o The range of values ​​for P a <p o ≤p c However, bearings still have the risk of seizure. To completely eliminate this risk, it is essential to first understand the seizure mechanism of gas bearings:

[0010] Shafts have a natural frequency when rotating at high speeds. When the rotational speed is near the natural frequency, resonance is inevitable; this is a law of natural science. During whirling, the primary condition for shaft seizure is contact between the shaft and the bearing; without contact, seizure will not occur. The previously held belief that the seizure mechanism was due to air-fuel compression is incorrect. There are two scenarios for shaft-bearing contact during whirling. One is contact between the shaft and bearing's two center lines at an angle (…). Figure 4(b) Line contact friction is small and will not cause the shaft to seize. Another type is when the shaft and bearing have parallel runout surfaces that come into contact. Under the action of a large resonant force (normal pressure), friction generates high temperatures (350°C or higher). The surface material of the metal softens at high temperatures, and the surface is easily scratched. Under the action of a continuous large resonant force, the scratched area increases and the scratches become more and more serious. After several starts and whirls, the coefficient of sliding friction on the surface of the bearing increases exponentially, and the frictional force increases greatly. When the resultant frictional torque about the shaft centerline is greater than the moment of inertia of the shaft, the shaft will seize immediately.

[0011] To completely solve the hidden danger of gas bearing seizure, there are two measures: 1. Improve the surface hardness of the metal at high temperature. There are various methods, such as carbon and nitrogen co-diffusion on the surface of 38crMoAL. Or spray a layer of hard alloy, such as WC or GT35, onto the surface. Improving the surface hardness at ambient temperature is useless. 2. Design the shaft as a stepped shaft. The outer gaps (2) and (17) of the two small shafts must be precisely (absolutely) unequal, with a difference of 0.01 to 0.02 mm (the inner holes of the left and right end caps are cut in one cut to ensure that the two hole diameters are absolutely equal and coaxial. The diameters of the two small shafts are absolutely unequal). This is the key to solving the problem of gas bearing seizure. During whirling, no matter how the stepped shaft jumps, the shaft and hole can only make inclined line contact because of the support, and cannot make surface contact. The frictional force and frictional torque of line contact are much smaller than those of surface contact. Line contact will not have the frictional marks that appear on the surface of surface contact, and line contact will not cause seizure. This structural design avoids seizure and reduces the starting torque of the motor, making the bearing easy to start. Stepped shafts not only help eliminate the risk of bearing seizure, but also help gas bearings improve axial load capacity.

[0012] The mechanism and solutions for bearing seizure have been introduced above. Now, the structure of the new pressure gas bearing will be introduced. Figure 1 The new pressure gas bearing consists of a stepped shaft (1), a bearing (9), and left and right end caps (6) and (14) (containing oil filling valves (5) and (13), oil holes (4) and (15), and oil ring grooves (3) and (16)). Figure 1 In a static state, the bearing shaft clearance (10), the two side thrust chambers (8), (11), and the inner clearances (7), (12) are filled with a certain pure pressurized gas (p). o The sealing between the pressurized gas and the outside world is achieved by the sealing oil in the oil ring grooves (3) and (16). Regardless of static or dynamic conditions, the oil adsorbed on the surface of the small shaft and the oil in the oil ring groove, as well as the oil in the oil ring groove and the oil adsorbed on the surface of the end cap inner hole, are still a continuous medium, so the sealing oil can effectively seal the pressurized gas. The inner gaps (7) and (12) on both sides of each oil ring groove are closer to the thrust chambers (8) and (11), and the outer gaps (2) and (17) are farther away from the thrust chambers. Figure 1The inner gaps on both sides are equal, 1-2mm. The outer gaps on both sides are absolutely unequal, with a difference (precise value) of 0.01-0.02mm. With this structural design, regardless of whether the shaft is stationary or running, the small shafts on both sides and the inner hole of the end cap cannot make surface contact due to the support; they can only make inclined line contact. Figure 4 (a) and (b)) indicate line contact friction; a small frictional torque will prevent the bearing from seizing. Regardless of static or dynamic conditions, the absolute value of the gas pressure sealed within the bearing is relatively small (p o ≤p c Because the gaps on both outer sides are extremely small (approximately 0.01mm and 0.02mm respectively), the resistance is extremely high, and the sealing oil will not be forced into the outer gaps. Several air grooves need to be axially opened on the surface of the stepped shaft (18). Figure 1 During the secondary assembly of the bearing, air is filled into the clearance (10) of the main shaft. Grooving the main shaft can also improve the radial stiffness of the bearing. In order to prevent the stepped shaft from tilting and scratching the inner hole at the end of the main shaft, the radial clearance required by the main shaft needs to be accurately calculated based on the unequal outer clearance (precise value) of the two small shafts on both sides, so as to ensure that the main shaft can never contact the bearing in any way, whether axially or radially. In order to add oil to the oil ring grooves (3) and (16), an oiling valve (5) and (13) are designed in each of the end caps (6) and (14). It is required that the sealing oil is not wetted and spread on the metal surface. It is also necessary to prevent the pressurized gas from leaking from the inside of the metal in contact with it to the outside. At this time, the seal is guaranteed by a metal material with good density. Of course, the metal material must be inspected for defects beforehand. In order to prevent the pressurized gas from leaking at the threaded connection between the end caps (6) and (14) and the bearing (9), it is necessary to weld the end caps and the bearing (9) together. Figure 1 One of the measures previously mentioned to address the risk of seizure in gas bearings is to increase the high-temperature hardness of the metal surface (increasing surface hardness under environmental conditions is ineffective). After increasing the hardness, precision machining is performed, requiring the shaft and bore surface roughness, cylindricity, and coaxiality to reach the highest precision. The precision-machined stepped shaft is placed into the precision-machined bearing, the axial position of the shaft within the bearing is calibrated, the end caps on both sides are screwed into the bearing, and then the end caps and bearing are welded together. At this point, the initial assembly of the new pressure gas bearing is complete. The secondary assembly is detailed in the following examples.

[0013] Gas bearings come in various forms worldwide. To increase their load-bearing capacity, people have had to use an air compressor to supply pressurized gas to the bearing from the outside. However, the maximum supply pressure is limited by the air hammer phenomenon, which consequently restricts the increase in load-bearing capacity. New pressure gas bearings, on the other hand, do not require an air compressor; they operate solely using the dynamic pressure effect of the pressurized gas sealed within the bearing. The maximum gas pressure p within the bearing... c Up to 9-10 kgf / cm 2 ( Figure 5The pressure is greater than the maximum supply pressure of the gas bearing, eliminating air hammer during operation. Each gas bearing does not require an air filter, and no throttle is needed inside the bearing. Furthermore, the unequal clearance on the outer sides of the two small shafts, combined with increased surface hardness at high temperatures, completely eliminates the risk of bearing seizure. Because no air compressor is needed during operation, the cost of gas bearings is significantly reduced, the bearing's space footprint is minimized, energy consumption from the air compressor is saved, and noise is reduced. The elimination of the throttle eliminates the need for its manufacturing process, reducing the workload for technicians. This new gas bearing effectively replaces the Western-era air compressor, offering superior bearing performance. This new gas bearing represents the future direction of gas bearing development. Attached Figure Description

[0014] Figure 1 New pressure gas bearing structure diagram

[0015] Stepped shaft (1). Small shaft outer clearance (2). (17), oil ring groove (3), (16), oil hole (4), (15), oil filling valve (5), (13), left and right end caps (6), (14), small shaft inner clearance (7), (12), thrust chamber (8), (11), bearing (9), large shaft clearance (10), large shaft air groove (18)

[0016] Figure 2 Secondary assembly structure diagram of the new pressure gas bearing

[0017] Threaded cap (19), pressure sealed container (20), filler pipe (21), (23), oil seal (22), (24), (25)

[0018] Figure 3 Diagram of the new pressure gas bearing being filled with gas.

[0019] Pressure gauge (26), precision pressure reducing valve (27), switch (28), exhaust valve (29)

[0020] Figure 4 Relative position diagram of shaft and bearing

[0021] (a) Shaft and bearing surface contact. (b) Shaft and bearing line contact.

[0022] Figure 5 Static stiffness k and environmental pressure p o Relationship diagram Detailed Implementation

[0023] The manufacturing of new pressure gas bearings is based on the following embodiments and appendices. Figure 1 , 2 As stated in section 3, the manufacture of new pressure gas bearings must be carried out using a pressure-sealed container (20). For example... Figure 2Unscrew the threaded cap (19) on the left side of the sealed container, place the initially assembled gas bearing into the sealed container, calibrate the axial and circumferential positions of the bearing, tighten the threaded cap (19), and seal the container. A clearance oil seal (25) is used between the small shaft on the right side and the sealed container, and a threaded seal (oil seal) is used on the threaded cap (19). These seals can be replaced with O-rings. Seal the oil filling pipes (21) and (23) with oil (film) (22) and (24). Figure 3 Turn on the switch (28) and let a certain pressure p o The pure gas enters the sealed container through the precision pressure reducing valve (27), filling the sealed container, and theoretically the pressure p o It can be any value. For example... Figure 2 To inflate the gas bearing, press down the two filler pipes (21) and (23) to push the balls apart, allowing pressurized gas to enter the thrust chambers (8) and (11) through the gap (approximately 1 mm) between the balls and the end cap, then into the main shaft gas groove (18) and fill it completely. Rotate the stepped shaft back and forth to fill the main shaft gap (10) with pressurized gas, filling the entire bearing and the external space. Whether or not there is air hammer during the entire inflation process is irrelevant. Figure 3 Keep the reading on the pressure gauge (26) at the design value p. o At this point, the gas pressure inside and outside the gas bearing in the sealed container is equal. Retract the refueling pipes (21) and (23), and close the switch (28). To facilitate refueling, several oil grooves are axially opened at the tip of the refueling pipe. Figure 2 (CC section view). Before entering the sealed container, an overflow valve should be designed in each of the two oil circuits. For example... Figure 2 On the left, press the filler pipe (21) downwards to push open the ball bearing, and press the pressure sealing oil through the filler valve (5) and oil hole (4) into the oil tank (3), filling the oil tank, filling the oil hole (4), and filling the entire internal space of the filler valve (5). Then retract the filler pipe (21). Add oil on the right side in the same way. Figure 3 Open the exhaust valve (29) to reduce the gas pressure inside the sealed container to ambient atmospheric pressure. Open the threaded cap (19) and remove the new pressure gas bearing. Primary and secondary assembly of the gas bearing must be performed under dust-free conditions.

Claims

1. A novel pressure gas bearing, characterized in that... A new gas bearing product that does not require an air compressor or throttle during operation; it simply seals the pressurized gas inside the bearing.

2. The new pressure gas bearing according to claim 1 is composed of a stepped shaft (1), a bearing (9), and end caps (6) and (14). The end caps are designed with a filling valve (5) and (13), an oil hole (4) and (15), and an oil ring groove (3) and (16).

3. According to claim 1, its characteristic is that Maximum value p of the gas pressure sealed in the bearing c (figure 5).

4. According to claim 1, its characteristic is that The outer gaps (2) and (17) of the two small shafts are absolutely unequal, differing by 0.01 to 0.02 mm, while the inner gaps (7) and (12) of the two small shafts are equal, ranging from 1 to 2 mm.

5. According to claim 1, the feature is that the surface of the main shaft has an air groove (18).

6. Method of manufacturing a new pressure gas bearing: The gas bearing is assembled and placed in a pressure tight container (20), which is closed (Fig. 2). A certain pressure of a pure gas p is introduced into the closed container o ≤ p c The gas bearing is pushed out of the way and the pressure gas enters the gas bearing, whereupon the gas pressure in the closed container is equalized inside and outside the gas bearing. Sealing oil is pressed into the oil sealing grooves (3), (16) on both sides (Fig. 1, 2), which seals the pressure gas inside the bearing. The exhaust valve (29) is opened (Fig. 3) and the pressure gas is released from the closed container and the bearing is removed.

7. The manufacturing method according to claim 6, characterized in that: Multiple openings (20) should be made on the wall of the pressure-sealed container to accommodate the installation of an air inlet pipe, an exhaust pipe, a pressure gauge, and two oil inlet pipes (Figures 2 and 3).

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