KR920009815B1 - Method of oscillation reduction of ship shaft and stem tube bearing therefor - Google Patents

Abstract

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Description

Vibration reduction method of ship shaft and stern tube bearing for it

1 is a schematic configuration diagram of an apparatus of an embodiment of the present invention.

2 is a II-II cross-sectional view of FIG.

3 to 5 are diagrams showing the maximum value tmax, minimum value tmin, and vibration reduction efficiency? Of each oil film thickness when Q _U / Q _D , rotation speed N, vibration force W _P are changed.

* Explanation of symbols for the main parts of the drawings

1: (stern tube) bearing 2, 2 ': oil pocket

The present invention relates to a vibration reduction method of a ship shaft and a stern tube bearing therefor.

In general, stern tube bearings are widely used so-called journal bearings in which an oil film is formed between the cylindrical inner diameter surface of the bearing and the shaft, and the shaft is supported by the oil film pressure generated by the rotation of the shaft. However, the propeller shaft supported by the stern tube bearing vibrates by vibrating force through the propeller by the backflow generated by the rotation of the propeller. Since such vibration is undesirable, countermeasures have been taken so that the pole force makes the vibration small. For example, it has been considered to design the stern shape so as to make the propeller return uniform, or to design the propeller shape so as to reduce the generation of the vibration force due to the return. However, even if it is possible to suppress the vibration force to some extent under certain operating conditions, if the operation and the environmental conditions change, the effect is already lost, and no measures have been taken to forcibly reduce the axial vibration based on the vibration force once generated. . In such a situation, the following problems have conventionally been encountered.

① In case of bad weather, if the propulsion force is more than expected, the stern tube bearing may be damaged. In other words, if the axial vibration becomes larger than expected, it is expected to cause metal contact between the shaft and the bearing, and there is a risk of wear or melting of the bearing metal.

(2) In shallow odd and spline streak ships, the structural propeller backflow unevenness is large and there is a limit to reduction of vibration force.

On the other hand, although the above-mentioned type has a hydrostatic oil pocket under the bearing, this is to alleviate one-sided contact between the shaft and the bearing due to the weight of the shaft including the propeller (static load). It does not work.

It is an object of the present invention to provide a method for vibration reduction that solves the above-mentioned conventional problems with respect to a shelf shaft, and a stern tube bearing therefor.

The present invention relates to a stern tube bearing in which a shaft is supported by a pressure of an oil film formed on an inner diameter surface of a bearing in order to achieve the above object. In the stern tube bearing which consists of supplying oil, and the oil film formed in the bearing inner diameter surface supports an axle by pressure, the stern tube bearing which implements this method WHEREIN: Multiple positions in the outer peripheral direction of the said bearing The oil pocket to which the positive pressure oil is supplied is formed.

According to the present invention as described above, even when the shaft is vibrated by the vibration force caused by the propeller return, the vibration can be reduced by the pressure of the oil pocket provided in the plural places. In other words, if the axis attempts to displace in the direction of one oil pocket, the pressure in the oil pocket rises, and thus acts in the direction of suppressing its amplitude. Since such an action is brought in from a plurality of oil pockets, vibration is reduced in any direction around the entire circumference.

EMBODIMENT OF THE INVENTION Below, the Example of this invention is described based on an accompanying drawing.

FIG. 1 is a schematic diagram showing the stern tube bearing and oil supply system of this embodiment, and FIG. 2 is a II-II cross-sectional view of FIG.

In the figure, S is supported by the stern tube bearing 1 on the propeller side. The stern tube bearing 1 has a static oil pocket (2, 2) in its rear region in addition to a so-called journal bearing in which an oil film of lubricating oil is formed between its cylindrical inner surface and the shaft, and the shaft is supported at the same pressure by rotation of the shaft. ′). These oil pockets 2, 2 'are formed in plural positions of the circumference, and in the upper and lower two positions in the drawing. In the upper and lower oil pockets 2 and 2 ', oil supply pipes 3 and 3' for supplying lubricating oil to the oil pockets are respectively provided with flow control valves 4 and 4 ', pumps 10 and 10', and It is connected to the oil tank 11 via the filters 7,7 '. The oil supply pipes 3 and 3 'are connected to the return pipes 3A and 3A' for returning oil to the oil tank 11 via a pressure regulating valve 5. In addition, the pumps 10 and 10 'are driven by motors 6 and 6', and in the oil supply pipes 3 and 3 ', the supply degree is a flow meter 8,8' which measures the flow rate and pressure of the lubricating oil. ) And pressure gauges 9 and 9 'are also attached.

In this embodiment, the lubricating oil is pumped from the oil tank 11 via the filters 7 and 7 'and by the pumps 10 and 10' driven by the motors 6 and 6 '. Thereafter, the lubricating oil is adjusted to a predetermined value by the pressure regulating valves 5, 5 'and the flow regulating valves 4, 4', respectively, and forcedly lubricated to the respective oil pockets 2, 2 '.

When the shaft vibrates due to the propulsion force of the propeller, when the shaft moves downward in the bearing 1, the pressure of the oil pocket 2 'installed on the lower surface of the bearing gradually rises, on the contrary, the oil pocket 2 installed on the bearing upper surface ) The pressure decreases. For this reason, the upward force is increased and the shaft is pushed up. On the other hand, when the shaft moves upward, the pressure of the oil pocket 2 'provided on the bearing upper surface gradually rises, while the pressure of the oil pocket 2' provided on the bearing lower surface decreases, and as a result, the downward force increases and the shaft I try to push it down.

In this way, the shaft generates a force in the opposite direction to the movement to reduce vibration (amplitude) of the shaft caused by the excitation force.

In the present embodiment, the vibration is reduced by the action of the upper and lower oil pockets as described above. At that time, the ratio Q _U / Q _V between the flow rate Q _U to the upper oil format and the flow rate Q _V to the lower oil pocket is determined. Is effective when 0 <Q _U <Q _V <1.

Test results for this example are shown in FIGS.

Fig. 3 shows how the angle from the horizontal axis changes the fluctuation range of the oil film thickness t at 315 °, that is, the maximum value tmax and minimum value tmin and the reduction effect η% of the axial vibration to Q _U / Q _V. Indicates whether or not The conventional one is almost equivalent to Q = 0, that is, Q _U / Q _V = 0. In this embodiment, with respect to film thickness t is insured stability narrows the range of the fluctuation range according to an increase of _U Q / Q _V. Therefore, the vibration reduction effect η also increases to support the stabilization. It is clear from the above that Q _U / Q _V is better, but the effect is almost obtained in the vicinity of Q _U / Q _V = 1, and since the flow rate increases, and thus the size of equipment is increased, 0 < The range of Q _U <Q _V <1 is considered practical.

Next, the result of changing the rotation speed N with respect to the same effect as FIG. 3 is shown in FIG. According to this, with respect to the film thickness t, compared with the conventional t'max and t'min represented by a broken line, in this Example, tmax and tmin are extremely stable, and the vibration reduction effect (η) also rotates. We are improving with number rise. In FIG. 4, the case of Q _U / Q _V = 0.5 is taken as an example. However, as apparent from FIG. 3, when 0 <Q _U <Q _{V, the} same effect is obtained. It is also confirmed. Next, FIG. 5 shows how the effect of FIG. 3 is caused by the change of the magnitude of the vibration force W _P. As a result, naturally, when the vibration force increases, the fluctuation of the oil film thickness t becomes somewhat large, but it is clear that it is significantly stable compared with the fluctuation range of the conventional oil film thickness t '. And the vibration reduction effect (eta) is also improving.

In the present embodiment as described above, two oil pockets are provided vertically and vertically. However, since the oil pockets need to be provided at a plurality of circumferential positions in the circumference, the pressure is not particularly limited to other numbers and positions. In that case, it is preferable to provide symmetrically with respect to arbitrary one diameter line. Also, if the oil pocket is provided at the rear of the stern tube bearing, it is effective because it comes close to the propeller.

Since the present invention is provided with a plurality of oil pockets around the stern tube bearing as described above, this oil pocket acts to reduce the vibration width with respect to the oscillating axis, thereby obtaining a very good vibration reduction effect. As a result, the life of the shaft and the bearing and the like are also extended, and the influence of vibration on other parts can be suppressed.

Claims (5)

A shaft bearing, in particular a stern tube bearing for a propeller shaft S of a ship, wherein the shaft S is formed by an oil film formed between the inner circumferential surface of the cylindrical stern tube bearing 1 and the shaft S. A stern tube bearing of a ship shaft supported by dynamic pressure based on the rotation of the gear shaft, further comprising a plurality of oil pockets 2, 2 'circumferentially distributed around the axis S, and the oil pockets 2, 2'. ) Are installed independently of each other, and a series of oil supply means 3 to 10; 2 'to 10' are respectively connected to supply different adjustable static pressures to each oil pocket 2 and 2 ', and the bearing 1 The ratio of the oil supply amount Q _U to the oil pocket 2 above the horizontal plane passing through) and the oil supply amount Q _V to the oil pocket 2 'below the horizontal plane is 0 <Q _U <Q _A stern tube bearing of a ship shaft, which is set to have a relationship of _V <1. The stern tube bearing according to claim 1, wherein the oil pocket (2 ') below the horizontal plane is supplied with a larger amount of oil than the oil pocket (2) above the horizontal plane. The stern tube bearing according to claim 1 or 2, wherein oil pockets (2, 2 ') are provided on the propeller side or the rear of the bearing in the axial direction. The stern tube bearing according to claim 1 or 2, wherein the oil pockets (2, 2 ') are provided symmetrically with respect to any diameter line passing through the bearing (1). 2. The vessel shaft according to claim 1, wherein each of the oil supply means (3 to 10; 3 'to 10') is provided with means (8,9: 8 ', 9') for measuring flow rate and pressure. Stern tube bearing.

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