JPH0123658B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an oil drainage mechanism, and particularly to an oil drainage mechanism suitable for use in a turbocharger.

[Background of the invention]

A turbocharger, as seen in Japanese Utility Model Application Publication No. 51-3707, consists of a turbine that rotates at a high speed of 100,000 to 200,000 revolutions per minute or more, and compressor blades, which enable this high-speed rotation. This is due to the so-called full float metal that holds the shaft while rotating. However, for full float metal to work properly, it is generally 60~
A large amount of lubricating oil is required at 100 m/hr, and this oil typically supplies some of the engine's own lubricating oil. On the other hand, the amount of oil in the oil pan of an engine is small, about 2 to 6, so if the oil supplied to the turbocharger is not returned to the oil pan immediately, it will quickly become a problem in the oil pan. The oil will run out.

Due to these conditions, the oil that lubricates the turbocharger generally falls naturally into the engine oil pan through a drain pipe.

On the other hand, the turbine and compressor blades mentioned above are located in the exhaust gas and engine intake, respectively, and are equipped with a shaft sealing mechanism to prevent oil from leaking in the bearing chamber, but the rotation speed of the shaft changes every time. minutes 20
At over 10,000 revolutions, contact type shaft seals cannot be used due to seizure and increased mechanical loss, and a non-contact type shaft seal using a piston ring or labyrinth must be used. Therefore, oil accumulates inside the bearing chamber, causing damage to the shaft seal position (especially at the shaft center position).
If oil begins to accumulate above the level described above, the oil will overtake the non-contact type shaft sealing mechanism and leak out to each blade.The oil that leaks out to the turbine side may cause a fire due to its high temperature or leak to the compressor side. The oil may be sucked into the engine and deteriorate the engine, or
These oil leaks cause problems that significantly reduce the amount of oil in the engine oil pan.

Generally speaking, when releasing 60% of oil into the atmosphere per hour,
To prevent oil from accumulating in the bearing chamber, the inner diameter of the drain pipe must be 10 to 14 mm.

However, as mentioned above, the exhaust oil from the turbocharger communicates with the engine's oil pan, and the inside of this oil pan is affected by changes in volume due to the movement of the piston, and by gas blowing out in the combustion chamber. Unlike the atmosphere, the pressure fluctuates greatly. This fluctuating pressure tries to transmit to the bearing chamber of the turbocharger through the drain pipe mentioned above, but this pressure wave obstructs the oil flowing out from the bearing chamber, and according to experiments, it becomes air vesicles and drains into the drain. Reverse the oil that is
As a result, oil accumulates in the bearing chamber, causing the oil leakage accident described above.

Experiments have shown that in order to prevent these air spores from interfering with oil drainage, especially at low temperatures (-10°C to
-20℃), adjust the inner diameter of the drain pipe to φ18 to φ20.
It has to be made bigger.

In addition, 2, which has a large volume change due to piston movement,
For cylinders and three cylinders, the pressure fluctuations in the oil pan are even greater, and the internal diameter of the drain pipe may need to be φ25 or more. However, with the recent miniaturization of engines and accompanying miniaturization of turbos, the reality is that there is no space to install such a thick drain pipe.

[Purpose of the invention]

The object of the present invention is to eliminate the pressure difference between the upstream and downstream sides of the drain pipe, thereby preventing backflow due to air bubbles in the pipe, and thereby preventing oil leakage from the turbocharger. is to provide.

[Summary of the invention]

In order to achieve such an objective, the present invention investigated the condition inside the drain pipe of a turbo supercharger and found through experiments that the backflow of oil was due to air bubbles caused by pressure fluctuations occurring within the engine oil pan. The pressure is balanced so that this pressure fluctuation does not occur at least upstream and downstream of the drain pipe.

[Embodiments of the invention]

FIG. 1 is a configuration diagram showing an embodiment of an oil draining mechanism for a turbocharger according to the present invention. In the same figure,
1 is a turbo supercharger, and 2 is an engine. The turbocharger 1 consists of a compressor 3, a bearing chamber 4, and a turbine 25. A full float metal 5 is located inside the bearing chamber 4, and the full float metal 5 holds a shaft 6. At both ends of the shaft 6,
A compressor blade 7 and a turbine blade 8 are fixed, and shaft seals 9 and 10 formed by piston rings are provided at both ends of the bearing chamber 4 of the shaft 6, respectively. Engine 2 is
It consists of a combustion chamber 11, a piston 12, an oil pan 13, and a crankcase chamber 14. Also, the oil in the oil pan 13 is supplied to the oil supply port 16 provided in the bearing chamber 4 of the turbocharger 1 via the oil pump 15.
It is now possible to send oil to The oil supplied to the oil supply port 16 lubricates the full float metal 5 and the like, and then is collected at the oil drain port 17 at the lower end of the bearing chamber 4. Oil drain port 17 and engine 2
The crankcase chamber 14 has a drain pipe 18
It is communicated with. Further, a ventilation hole 19 is opened in the bearing chamber 4, and the ventilation hole 19 and the crankcase chamber 14 are communicated with each other through a ventilation pipe 20, so that the blow-by pressure of the engine 1 can be transferred to the bearing chamber 4.
The structure is designed to lead to. Bearing chamber 4 of ventilation hole 19
The opening is provided with an oil prevention plate 21 to prevent the oil flowing out from the full float metal 5 from scattering, and even if oil accumulates in the bearing chamber 4, the opening It opens above the center of the shaft 6 to prevent oil from getting on the shaft 19.

In such a configuration, the crankcase chamber 1
Let the pressure inside the bearing chamber 4 be P ₁ and the pressure inside the bearing chamber 4 be P ₂ .
An example of the operation of a two-cylinder engine will be explained with reference to FIGS. 2 and 3. In FIG. 2, the pistons of both cylinders are now moving in the downward direction, and in FIG. 3, they are similarly moving in the upward direction. In general, a two-cylinder engine consists of this repeated motion. Second
When the piston is descending as shown in the figure, combustion is occurring in one of the combustion chambers of the engine 2, not just the two-cylinder engine, and this high pressure is flowing from the outer circumference of the piston 12 to the crankcase chamber 14. The pressure inside the crankcase chamber 14 increases, but in a two-cylinder engine, _all the pistons 12 descend as shown in Figure 2, so the change in volume causes _P1 to rise further. Put it away.

On the other hand, as shown in FIG. 3, when all the pistons 12 begin to rise, this change in volume causes the pressure P ₁ in the crankcase chamber 14 to decrease. The state of this pressure change was experimentally determined as shown in line a in FIG. As shown in the figure, as the piston moves up and down, the pressure inside the crankcase increases.
It fluctuates between 100mmHg and -90mmHg.

When the state of the oil drained inside the drain pipe 18 under such operating conditions is visually observed, it is as shown in FIG. 4.
Here, in the conventional case, the pressure indicated by arrow a moves upward as a flow of air. That is, the air flow flows from the crankcase chamber 14 to the bearing chamber 4, and this air flow becomes the air bubble 22, which prevents the drained oil from falling as shown by arrow b, and finally, the drained oil flows back into the bearing chamber 4, causing the oil to leak out. If the oil level builds up and reaches the shaft seals 9 and 10, the oil will overcome the shaft seals and leak into the compressor and turbine blades 7 and 8. The differential pressure between the pressure P ₁ in the crankcase chamber 14 and the pressure P ₂ in the bearing chamber 4 at this time is shown by line b in FIG. air vesicle 2
Due to the occurrence of P 2, P ₁ becomes higher than P ₂ , and it can be seen experimentally that oil is flowing backwards.

However, if the embodiment is implemented, the pressure fluctuation P ₁ generated in the crankcase chamber 14 is transferred to the bearing chamber 4 upstream of the drain pipe 18 via the ventilation pipe 20 as shown by arrow a in FIG. Since the air bubbles 22 are not generated, the waste oil shown by the arrow b smoothly passes through the drain pipe 18 and falls from the bearing chamber 4 to the crankcase chamber 14. The differential pressure between P ₁ and P ₂ at this time is c in Figure 6.
As shown by the line, it becomes 0 and no pressure difference occurs, which indicates that the flow of drained oil in the drain pipe 18 is smooth, and there is no accumulation of oil in the bearing chamber 4 due to the backflow of drained oil. Oil leakage from the shaft seals 9 and 10 will not occur at all.

In the embodiment described above, the ventilation pipe 20 is connected to the oil pan 13 of the engine 2, but the invention is not limited to this, and the same effect can be obtained even if the ventilation pipe 20 is connected to the engine head cover.

〔Effect of the invention〕

As described above, according to the oil draining mechanism of the turbocharger according to the present invention, the pressure difference between the upstream and downstream sides of the drain pipe can be constantly eliminated, so there is no occurrence of air bubbles in the drain pipe, and oil can be drained smoothly. This makes it possible to prevent leakage from the shaft seal due to backflow of waste oil.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the oil drainage mechanism for a turbocharger according to the present invention, FIGS. 2 and 3 are sectional views explaining the operation of the oil drainage mechanism for the turbocharger, and FIG. 4 and 5 are partial cross-sectional views for explaining the effects of the present invention, and FIGS. 6 a to 6 c show operation diagrams of the conventional oil drain mechanism and the present invention. 1... Turbo supercharger, 2... Engine, 3...
Compressor, 4...Bearing chamber, 5...Full float metal, 6...Shaft, 7...Compressor blade, 8...Turbi blade, 9...Shaft seal,
10... shaft seal, 11... combustion chamber, 12... piston, 13... oil pan, 14... crankcase chamber, 15... oil pump, 16... oil filler port,
17...Drain hole, 18...Drain pipe, 19
...Vent hole, 20...Vent pipe, 21...Oil prevention plate, 22...Air cell, 25...Turbine.

Claims (1)

[Scope of Claims] 1. A so-called full-float metal that holds the shaft while rotating through forced lubrication is provided, and the waste oil after lubricating the metal is allowed to fall naturally in a drain pipe to the oil pan of the engine. In the oil drainage mechanism of a turbocharger that drains oil inward,
The bearing chamber in which the full float metal is held is communicated with the space above the oil level of the crankcase of the engine through a ventilation pipe, and an oil inflow prevention means is provided at the bearing chamber opening of the ventilation pipe. Oil drainage mechanism for turbo supercharger. 2. The oil drain mechanism for a turbocharger according to claim 1, wherein the oil inflow prevention means is constituted by a cover plate that covers the bearing chamber opening of the ventilation pipe and opens on the downstream side of the oil inflow. .