KR100467363B1 - Sliding Bearing using Leaf Springs - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a leaf spring sliding bearing utilizing a leaf spring as a sliding bearing for supporting a load of a shaft by using a hydrodynamic force generated by rotation of the shaft. It is a bearing formed by attaching a leaf spring that can support the static load of the rotating shaft to the outer ring at regular intervals and forming a certain curvature at the tip of the leaf spring so as to generate fluid dynamic pressure through the rotating shaft and a certain area.

The present invention is simple in shape and inexpensive, but a plain bearing in which unstable vibration occurs at high speed and unstable vibration at high speed, but there is no unstable vibration at high speed, but it is very difficult to manufacture and expensive tilting pad bearing. It is a bearing that can overcome the disadvantages of each, such as low cost unstable vibration at high speed, excellent vibration damping force, and simple manufacturing. Radial bearings and axial bearings are separated, which requires more bearing space and can be operated simultaneously as axial bearings as well as radial bearings, and can use both oil and gas as working fluids. It is to provide a sliding bearing using an excited leaf spring.

Description

Leaf Spring Sliding Bearing {Sliding Bearing using Leaf Springs}

Rotating machines are easily found in home appliances and industrial machinery around us. In order to increase the operating efficiency per unit volume or unit weight, such a rotary machine is gradually increasing in speed, and the vibration problem is one of the most important problems due to the high speed. Bearings for rotating shafts in rotary machines play a very important role in the vibration control of rotating machinery as well as the load bearing function. Usually, a bearing can be classified into a rolling bearing using a rolling motion of a ball or a roller, and a sliding bearing using a fluid dynamic pressure generated in the fluid between the rotating shaft and the bearing. It can be divided into radial bearing and axial bearing according to the operating direction.

Rolling bearings are inexpensive because they can be mass-produced, while they have low vibration damping capacity and difficult support rigidity adjustment. The sliding bearings can be divided into oil bearings and gas bearings according to the type of fluid used. Oil bearings can easily make large fluid dynamic pressure even at low speeds by oil, and have the advantage of obtaining high vibration damping force. However, oil circulation and oil cooling system are required to cool high heat generated in narrow oil film and energy loss is high. There is this. Gas bearings have the disadvantages of making large fluid dynamic pressure at low speed, small load bearing capacity, and low vibration damping force, but do not require a separate circulation and cooling device and have very low energy loss.

To overcome these disadvantages of rolling bearings and sliding bearings, vibration dampers can be installed on the outside of the bearings for vibration isolation. Such vibration isolation dampers include a squeeze film damper for attenuating vibration by installing a narrow oil film outside the bearing, and a solid state damper for damping vibration by inserting rubber into the bearing. The present inventors have already obtained patents in six countries for vibration isolation devices (or dampers) using leaf springs that outperform conventional vibration isolation dampers such as squeeze film dampers and solid elastic dampers (Korea 115437, US 5,553,834, Germany DE). 4420 596 C2, Austria AT 401 808B, Japan 2665312, China 94108364). However, this vibration isolation damper does not improve the performance of the bearing itself but improves vibration characteristics by installing an additional device outside the existing bearing.

While oil sliding bearings (hereinafter referred to as 'oil bearings') have greater load bearing capacity and superior vibration damping capacity than rolling bearings, oil bearings of various designs have been developed to reduce unstable vibrations because unstable vibrations occur at high speeds. Oil bearings include plain bearings, pressure dam bearings, lobe bearings and floating ring bearings in Figure 1, but unstable vibrations occur at high speeds. In theory, the tilting pad bearings of Figures 2 and 3, which do not generate unstable vibrations even at high speeds, are used most often in high-speed rotating machines because they have the highest operating stability at high speeds. However, tilting pad bearings are very expensive.

Recently, various rotating machines are getting very high speed (more than 100,000 rpm) to increase the driving efficiency. The serious problems caused by the high speed are unstable vibration and energy loss. In particular, since energy loss is proportional to the square of rotation speed, it is a very important problem in terms of operating efficiency. Gas sliding bearings (hereinafter referred to as 'gas bearings') have a lot of new researches in recent years because they have excellent load bearing ability and high energy loss, especially at low speeds. Gas bearings include plain bearings, herring bone journal bearings with a herring bone in the plain journal to reduce instability, foil bearings with multiple thin sheets of bearings, and And tilting pad bearings. Gas bearings have the critical disadvantage that, unlike oil bearings, vibration damping capacity is very small.

The foil (or sheet) of the foil bearings (or sheet bearings) in Figure 4 is very thin and has very low support stiffness (sizes of 100 to 1,000 N / m supporting stiffness). Not capable of supporting In addition, since the foil cannot support the fluid dynamic pressure generated during rotation alone, it is also designed to mutually support the foils sequentially installed in the circumferential direction as shown in Fig. 4 (DE 23 61 226, Special 2001-0009528). ). In addition, the vibration damping force is small, there is a disadvantage that a very high vibration occurs when the rotor passes the resonance point.

The present invention has been made in consideration of the problem of unstable vibration at high speed and expensive price of sliding bearings and low vibration damping ability, especially in gas (sliding) bearings, and an object thereof is to provide sliding bearings using leaf springs. Leaf spring sliding bearings have excellent vibration stability and vibration damping force at high speeds, and are very inexpensive, so they can be used in high-demand products and use both oil and gas. Unlike general sliding bearings, radial bearings and axial bearings can act simultaneously, thus saving bearing installation space, inexpensive price, and synergistic effects in bearing operation.

Unlike rolling bearings, sliding bearings have excellent load carrying capacity, and oil bearings are especially used for large and high speed rotary machines due to their excellent vibration damping ability. The sliding bearing supports the load on the rotating shaft by forming a wedge-shaped space generated by the viscous fluid between the journal and the bearing as the shaft rotates, as shown in Figure 5. However, in the drainage formed on the opposite side, there is no load bearing ability or rather negative pressure occurs, which causes unstable vibration of the rotating shaft. In order to reduce the area where the negative pressure is generated, sliding bearings of various designs have been developed. The representative bearing is a tilting pad bearing, and theoretically, there is no area where the negative pressure is generated so that unstable vibration does not occur in all operating areas.

Tilting pad bearings are available in the tilting type of Figure 2 and the flexure pivot type of Figure 3. Compared to the tilting type bearing of Fig. 2, which is difficult to assemble and has a relatively high tolerance, the tilting pad bearing of the elastic pivot type of Fig. 3, which requires little assembly and has a low tolerance, has been very active recently as a patented bearing of KMC of USA. This tilting pad bearing has a disadvantage in that the design and manufacturing cost is very expensive. In addition, the tilting pad bearing has a relatively low vibration damping force compared to other sliding bearings, and thus, a very high vibration occurs when passing through a resonance point of a rotating machine.

The foil bearing in Figure 4 has a very thin thickness (less than 0.2 mm thick) and very low support stiffness (support stiffness less than 1,000 N / m), making it impossible to support the static load of the rotating shaft with foil alone, and also to damp vibrations. This is small. However, the leaf spring of the leaf spring sliding bearing of the present invention shown in Fig. 6 is a spring having a certain shape rather than the foil itself, which is very thick and has a very high supporting rigidity (support stiffness 1,000,000 to 100,000,000 N / m). The leaf springs alone can support the static load of the stationary shaft. Unlike foils, some form of bearing internal space is possible between the leaf spring and leaf spring. The constructed bearing internal space is utilized as a mechanism for improving vibration damping force. In addition, unlike spring bearings, leaf spring sliding bearings can define eccentricity, which is a deviation between the center of the bearing and the center of the journal, as shown in Fig. 7, and the radius of curvature and stir of the bearing like the tilting pad bearing as shown in Fig. 9. The difference in the curvature radius of the null can also define the preload of the bearing pads. Also, as shown in Fig. 8, depending on the tilting (or bending) angle of the leaf spring, it is possible to contact the bearing with a certain force in the journal or to maintain some clearance.

When the rotating journal vibrates, the volume of the fluid in the bearing inner space (3) formed between the leaf spring and the leaf spring changes, and the change of the fluid volume causes the leaf spring (2, 4) to have a constant shape and thickness. ) And the fluid moves between the narrow gap 8 between the bearing face plate 6. Due to the volume change of the fluid in the inner space 3 between the leaf spring and the leaf spring and the fluid flow between the narrow spring 8 between the leaf spring and the bearing face plate, a high vibration damping force is obtained unlike the foil bearing.

The biggest disadvantage of all gas bearings with foil bearings is their low vibration damping force. When the vibration damping force is small, the vibration damping force of the gas bearing is the biggest touchstone of the practical application of the gas bearing because the high vibration does not allow the rotor to pass through the resonance point. In this leaf spring sliding bearing, the gap between the side plates (6) and the leaf springs (2, 4) installed on both sides of the bearing is changed according to the fluid flow in the bearing inner space (3) caused by the rotational vibration. It is characterized by generating a high vibration damping force by adjusting through the size of (8).

In rotary machines, radial bearings are required to support radial loads on the rotating shaft, but axial bearings are also necessary because the axial loads act simultaneously. Until now, most bearings had separate radial and axial bearings, so each bearing had to be manufactured separately. This required not only a large bearing space on the rotating shaft, but also a lot of manufacturing cost. However, this leaf spring sliding bearing does not need to install a separate axial bearing because the side plate 6 installed on both sides of the radial bearing as well as the radial bearing serves as an axial bearing.

Figure 1 shows a plain bearing,

Figure 2 shows a tilting pad bearing (tilting type),

Figure 3 shows a tilting pad bearing (elastic pivot type)

Figure 4 shows a schematic of a foil (or sheet) bearing.

Figure 5 shows the bearing dynamic fluid distribution.

Figure 6 shows a schematic diagram of a leaf spring bearing,

Figure 7 shows the hydrodynamic actuation of a leaf spring bearing.

Figure 8 shows the bearing clearance with respect to the leaf spring tilting angle.

Figure 9 shows the preload of the leaf spring,

Figure 10 shows the leaf spring bearing-axial sectional view, and Figure 11 shows the flow chart for the leaf spring bearing.

The leaf spring, which can support the static load of the rotating shaft, is attached to the outer ring 1 at regular intervals, and the tip portion 4 of the leaf spring is formed with a constant curvature to widen the region of fluid dynamic pressure between the rotating shaft and the bearing. . Unlike the foil of the foil bearing, the leaf spring is very thick and the rigidity of the support is so large that the leaf spring alone can support the static load of the shaft and form a certain form of bearing inner space (3) between the leaf spring and the leaf spring. Can be. Static sag due to the weight of the shaft does not occur more than 0.2-0.4% of the shaft radius because of the large rigidity of the leaf spring.

When the shaft starts to rotate, a hydrodynamic force is generated between the leaf spring bearing 4 and the radial journal 5 to support the load. The hydrodynamic force of viscous fluid generated between the radial journal 5 and the leaf spring bearing 4 is formed between all leaf spring bearings surrounding the rotating journal. Since no negative pressure is generated that causes unstable vibration, very stable operation is possible.

When the rotating shaft passes the resonance point, a very large vibration occurs, and a large change occurs in the fluid volume in the bearing inner space 3 due to the vibration of the rotating shaft. At this time, the fluid in each bearing inner space (3) must flow out or flow in. This flow of fluid takes place between the side plates 6 on both outer sides of the bearing and the gap 8 on the leaf springs 2, 4. By adjusting the size of the gap 8 between the bearing side plates 6 and the leaf springs 2 and 4, the fluid flow can be adjusted and vibration damping force can be obtained according to the fluid flow. 4) High vibration damping force can be obtained by the squeeze (press) effect on the fluid inside.

As shown in Fig. 11, a spiral groove or the like is made in the axial journal (7) between the journal (5) and the rotating shaft, and the side plates (6) on both sides of the axial journal (7) and the bearings (6). ) Can be operated as an axial bearing. In particular, the gap 8 between the axial journal 7 in which pressure is generated in the axial bearing and the side plates 6 on both outer sides of the bearing changes in the bearing internal space 3 generated by the radial vibration of the rotating shaft. It is also the part where the fluid flow generated by By adjusting the direction of the grooves such as spirals engraved in the axial journal 7 of the rotating shaft to generate the axial pressure, the direction of fluid flow can be adjusted, so that the vibration damping force against radial vibration can be more effectively adjusted.

As described above, the present invention can provide a sliding bearing having high unstable vibration at high speed, high load bearing ability, and excellent vibration damping force. In the present invention, since the radial and axial bearings are operated simultaneously, the bearing occupies little space and the cost is very low.

In addition, the structure of the present invention has the advantage that mass production is possible at a very low cost. The plate spring bearings 2 and 4 can be manufactured in large quantities at low cost by using a press or the like. The plate spring bearings 2 and 4 can be bonded to the bearing outer ring 1. The whole manufacturing process can be automated, and it is inexpensive and the homogenization of products is possible.

Claims (7)

Attach the leaf springs (2,4) having rigidity to support the static load of the rotating shaft to the outer ring (1) at regular intervals to form a certain form of inner space (3) between the leaf spring and the leaf spring, It has a certain curvature at the front end of the leaf spring (4) to generate fluid dynamic pressure through the rotation axis and a certain area.When the rotation shaft is stopped, it is in contact with the rotation shaft by the self-weight of the shaft and the gap between the leaf spring, As the speed increases, the plate spring and the rotating shaft begin to come into non-contact due to the fluid dynamic pressure generated between the rotating shaft and the leaf spring, and when the vibration occurs, the fluid in the inner space (3) between the leaf spring and the leaf spring Bearings that generate vibration damping force while being compressed by deformation After the axial journals 7 are formed at both ends of the radial journal 5, the side plates 6 are attached to both ends, and the spiral plate or the like is formed in the side plates 6. As the rotating shaft 9 rotates, the axial pressure is formed by the fluid flow flowing from the outside of the bearing to the inside through the bearing clearance 8 by the friction force, so that the bearing in the axial direction can be supported. Bearings capable of operating directional bearings simultaneously The method of claim 2; As the axis of rotation rotates, the fluid in the bearing inner space (3) moves between the bearing clearance (8) between the outer side plates (6) and the leaf springs (2, 4) on both sides of the bearing. Bearing The method of claim 2; The vibration damping force can be generated by adjusting the amount of fluid flowing out of the bearing inner space 3 by adjusting the size of the gap 8 between the outer side plates 6 of the bearings and the leaf springs 2, 4. Bearing delete delete delete