JPS62237111A - Journal bearing - Google Patents

Abstract

PURPOSE:To control vibration of a pad due to minute self-excited vibration of a rotor by scraping off a metal portion of the pad extending over the whole width of the pad to increase oil film pressure. CONSTITUTION:Each inside diameter side of end surface portion on inlet side for lubricating oil 7 of pads 2a-2c among pads 2a-2e, which are positioned on the upper half side, is scraped off. Lubricating oil 7 is let flow in at the right end surface of the pad 26 and drawn by rotation of a rotor 1 to enter a gap between the inner surface of the pad 2b and the rotor 1. When the lubricating oil flows through the gap between the pad 2b and the rotor 1, it forms a wedge-shaped oil film in the gap, with a supporting point 6 of the pad 2b as a vertex and with the end surface portion of the pad 2b as a base. Accordingly, oil film pressure is increased, so that the pads are not excited by minute vibration of the rotor to improve stability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention is mainly used in high-speed rotating equipment such as gas turbines, steam turbines, and compressor/generators.

[Conventional technology]

The inner diameter surface of the pad is made of a single arc, as shown in the mold list by Daido Metal Kogyo K., and the oil film pressure generated on the pad located on the upper half side is transferred to the pad located on the lower half side. When the self-excited micro-vibration of the rotor occurs, which is extremely lower than the oil film pressure that occurs, the effect of suppressing this is small.

[Background of the invention]

It is well known that tailing pad type journal bearings are excellent in stability and vibration damping at high speeds, and are particularly effective in preventing oil whip.

Widely used under high speed and low load conditions. However, the self-excited micro-vibrations generated by the instability of the equilibrium position of the journal, which is found in low-load rotors, have a considerable effect on the stability of the pad. In particular, in the case of tailing pad type journal bearings, the oil film pressure generated on the pads located on the upper half side is extremely small compared to the oil film pressure generated on the pads located on the lower half side, and this is due to the influence of minute vibrations of the journal. The pad located in the upper half has an unstable inclination angle and repeats minute vibrations, causing a see-saw movement of the pad around the pad's fulcrum.

Eventually, the pad end surface will come into contact with the journal,
This could lead to a situation that could cause significant damage to the entire machine.

[Purpose of the invention]

The purpose of the present invention is to prevent the pad from being excited by self-excited minute vibrations caused by the instability of the equilibrium position of the journal, which is seen in low-load rotors, and to prevent the pad from coming into contact with the journal even if the pad is excited and begins a see-saw movement. Our goal is to provide journal bearings that do not.

[Embodiments of the invention]

Only the pad portion of the tailing pad type journal bearing according to the present invention is shown in FIG. 1, FIG. 2 shows the assembled state of the pad, and FIG. 3 shows the detailed portion of the present invention.

In FIG. 1, pads 2a to 2e are assembled into a structure as shown in FIG. 2 and incorporated into a bearing housing as a tailing pad type journal bearing. That is, in FIG. 2, the pad 2b is held in the pad retainer 3 by the support pins 5 at both axial end faces thereof. Furthermore, the pad 2b is pivotally supported by the pivot 4 at its tip 6, and is structured to be able to see-saw in the radial direction by supporting the pivot pin tip 6. FIG. 1 is a view of the pads 2a to 2e taken out when viewed from the left in FIG. 2. That is, the pads 2a to 2e are arranged around the rotor 1 in segments,
The oil film 7 that has passed through the pad retainer 3 is transferred to the pads 2a to 2e.
As shown in the figure, the oil passes through the gap 8 and enters the gap between the pads 2a to 2e and the rotor 1, forming a wedge-shaped oil film and holding the rotor 1. At this time, the rotation direction of the rotor 1 is counterclockwise. These pads 28-2e
The inner diameter side of the end face on the inlet side of the lubricating oil 7 of the pads 2a to 2C located on the upper half side is scraped off.

Tapered diagonal area 9 surrounded by a dashed-dotted line shown in Figure ff13
is a detailed view of the scraped part.

In FIG. 3, lubricating oil 7 flows in from the right end surface of pad 2b, is drawn by the rotation of rotor 1, and enters the gap between the inner surface of pad 2b and rotor 1, and as it flows through the gap between pad 2b and rotor 1, this A wedge-shaped oil film is formed in the gap, with the fulcrum 6 of the pad 2b as the apex and the end face of the pad 2b as the base.

The pressure of the oil film is generated to be maximum near the fulcrum 6 and minimum at the end surface of the pad 2b. The situation of this oil film pressure is shown in Fig. 4. Fig. 4 shows the pad 2 supported by the fulcrum 6.
The oil film pressure generated on the inner surfaces of a to 2b is shown by a single point lri line P. The oil film pressure P generated on the lower half pads 2a to 2e is equal to the oil film pressure P generated on the upper half pads 2a to 2c.
It is a much larger value. This phenomenon has been introduced in various literature. Further monitoring of the oil film pressure on the upper half pad, which is smaller than the oil film pressure on the lower half pad, reveals that the oil film pressure on the inlet side is smaller than the oil film pressure on the outlet end in the direction of rotor rotation. It is characteristic that By scraping the inner surface of the pad, which corresponds to the area where the oil film pressure is low, over the entire width of the pad, the oil film pressure increases as shown by the oil film pressure distribution P' shown by the broken line in Figure 4, and the pad is excited by the minute vibrations of the rotor. stability is improved. Furthermore, as shown in FIG. 5, in the case of the conventional pad, the oil film pressure distribution is a curve with an apex on the left side of the fulcrum 6 as shown by curve P, and the moment M around the fulcrum 6 due to the oil film pressure is □2M2 does not become zero, it is very sensitive to the excitation of the see-saw motion centered on the fulcrum 6, and it is in an unstable state because it immediately reacts by 1 due to minute vibrations of the rotor. However, when looking at the pressure distribution P' according to the present invention, the moment M1. due to the oil film pressure around the fulcrum 6. M is almost zero, which is a very stable state, and the see-saw movement of the pad can be suppressed.

On the other hand, during the operation of a machine, it is difficult to maintain an equilibrium state in which the moment around the fulcrum of the pad is always zero from start to stop. If the moment around the fulcrum of the pad does not become zero and the pad begins to see-saw, with the conventional pad shape, the inner diameter of the end surface of the pad will come into contact with the journal, leading to damage to the journal and pad. As shown in the figure, by scraping off in a tapered shape like the scraped part 9.

Contact between the pad and the journal can be prevented against a certain degree of see-saw movement of the pad.

〔Effect of the invention〕

According to the present invention, by suppressing the vibration of the pad due to minute self-excited vibrations of the rotor, it is possible to prevent the entire machine from stopping due to large vibrations.
Alternatively, mechanical damage to parts such as rotors and bearings can be prevented.

Even if vibrations are excited in the pad and the see-saw movement becomes large to some extent, the pad and rotor will not come into contact with each other, and damage to the pad and rotor can be prevented.

[Brief explanation of drawings]

Fig. 1 is an axial view of the pad portion of a tailing pad type journal bearing according to an embodiment of the present invention arranged around the rotor, and Fig. 2 is an axial view of Fig. 1.
3 is a sectional view of part ■ in FIG. 1, FIG. 4 is an oil film pressure distribution diagram generated in the conventional bearing and the bearing according to the present invention, and FIG. 5 is the oil film pressure shown in FIG. 4. It is a detailed diagram of one pad of distribution. 1st iris 2 hard 薯 30 back LF entrance

Claims (1)

[Claims] 1. In a journal bearing consisting of a pad divided into several segments on the inner circumference, the metal part of the pad located on the upper half side is extended from the end surface of the pad by an appropriate length. A journal bearing characterized by having its entire width cut out. 2. The journal bearing according to claim 1, wherein the shaved portion has a tapered shape.