JPS6360245B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bearing mechanism for a turbocharger, and more specifically, a bearing mechanism for a turbocharger of a non-lubricated type that supports a rotating shaft using high pressure fluid in a high pressure air chamber of a compressor. Regarding.

Turbochargers are widely used because they are effective in increasing engine output. A turbocharger has a rotary shaft that has a turbine wheel located in the exhaust passage and a compressor wheel located in the intake passage, and is supported in the housing by an oil-lubricated bearing.In this way, the turbine wheel is rotated by the exhaust gas. If this is the case, the exhaust gas will reach a very high temperature, which will not have a positive effect on the bearings. High-temperature exhaust heat increases the temperature of the bearing, leading to early deterioration of the lubricating oil, and is a factor in increasing oil consumption or increasing the load on the oil pump. Furthermore, if the exhaust gas enters the bearing, impurities in the exhaust gas will adhere to the bearing, preventing normal rotation of the bearing, and eventually causing the turbocharger to malfunction.
Furthermore, the need to incorporate various mechanisms for lubricating oil complicates the structure of the turbocharger and increases the size of the turbocharger.

Therefore, Japanese Utility Model Application No. 55-85527 proposes having a turbine and a compressor wheel at both ends thereof, and having a rotary shaft disposed in a housing supported by the housing via a hydrodynamic bearing. . In this example, a pair of spaced apart bearings are fixed to a housing that supports a rotating shaft so as to create a gap with respect to the rotating shaft, and pressure gas from a compressor wheel is guided to a passage in the center of each bearing. Gas is distributed to the left and right in the gap between the bearing and the rotating shaft. In this known example or the example in which a spiral group is provided in the bearing part of this known example, the pressure in the part on the opposite side is lower than the pressure in the passage part that supplies pressure gas to the gap between the bearing and the rotating shaft. This will cause the rotation axis to become unbalanced. That is, the center of the bore of the housing and the center of rotation of the rotating shaft do not match.

Therefore, an object of the present invention is to supply high pressure air from the compressor wheel side to the bearing part of the rotating shaft of a turbocharger from the wheel side to the central part of the rotating shaft, thereby solving the above-mentioned drawbacks and cooling the bearing part. A turbocharger that is an effective bearing that removes wear particles, radiates frictional heat during low-speed rotation of the rotating shaft, and evens out pressure distribution in the gap between the bore and the bearing of the rotating shaft. The purpose is to provide a bearing mechanism for

Embodiments of the invention will be described with reference to the accompanying drawings.

The turbocharger 1 is located between a turbine casing 4 having an exhaust inlet 2 and an exhaust outlet 3 of an exhaust passage for engine combustion gas, and a compressor casing 6 having an air inlet 5 and a pressurized air outlet of the engine intake passage. , a turbine wheel 7 located at one end in the exhaust passage of the turbine casing 4, and a compressor wheel 8 located at the other end in the intake passage of the compressor casing 6.
and a body 10 that supports a rotating shaft 9 that supports.

A passage 12 communicating with a high pressure air chamber 11 on the compressor wheel 8 side is formed in the body 10, and this passage 12 communicates with chambers 13 and 14 provided on both sides of the body 10, respectively. Further, a pair of spiral group hydrodynamic bearing portions 16 and 17 are formed spaced apart from each other on the rotary shaft 9 passing through a bore 15 formed in the body 10. The rotating shaft between the bearing parts 16 and 17 has a small diameter, and an air passage 18 is formed between it and the inner wall surface of the bore 15, and the air passage 18 is opened to the atmosphere through a hole 19. A gap 20 is created between the bearing parts 16, 17 and the inner wall surface of the bore to allow the flow of high pressure air. 21 is a thrust bearing;
2 indicates color.

In the above configuration, when the turbocharger 1 operates, high pressure air is supplied to the high pressure air chamber 11 by the compressor wheel 8. The high pressure air flows into the chambers 13 and 14 through the passage 12, and the air in the chambers 13 and 14 flows through the bearing parts 16 and 1.
The air enters the gap 20 between the air hole 7 and the inner wall surface of the bore as a uniform pressure, then enters the air passage 18 and is discharged from the hole 19 to the atmosphere. Bearing parts 16, 17
The high-pressure air flowing between the bearing and the inner wall surface of the bore increases the bearing load, floats the rotating shaft 9, and enables the bearing to be operated without lubrication. Furthermore, the airflow released from the high-pressure air chamber 11 to the atmosphere via the bearings 16 and 17 not only causes the rotating shaft 9 to float, but also air-cools the bearings 16 and 17 and removes foreign matter present in the gap 20. can be removed. Therefore, the frictional heat caused by the contact between the bearings 16 and 17 and the inner wall surface of the bore that occurs when the turbocharger 1 rotates at low speeds is effectively radiated, and friction powder and foreign matter in the exhaust gas are effectively removed. Moreover, the pressure acting on the bearing portion of the rotary shaft becomes uniform on its outer peripheral surface, and the center of the bore coincides with the center of rotation of the rotary shaft, resulting in good balance of the rotary shaft.

Furthermore, in the present invention, even if high-pressure air leaks from the back of the compressor wheel to the dynamic pressure bearing, this leakage flow will flow in the same direction as the high-pressure air supplied from the body passage, preventing collision of the high-pressure air. No, the bearing effect is high, and there is no accumulation of foreign matter.

[Brief explanation of the drawing]

The figure is a sectional view showing an example of the present invention. In the diagram: 1...Turbo charger, 7...Turbine wheel, 8...Compressor wheel, 9...
... Rotating shaft, 10 ... Body, 11 ... High pressure air chamber, 12 ... Passage, 13, 14 ... Chamber, 15 ...
Bore, 16, 17...Bearing section, 20...Gap.

Claims (1)

[Claims] 1. A rotary shaft having a turbine wheel located in an exhaust passage at one end and a compressor wheel located in an intake passage at the other end is rotatably supported at both ends of a bore in the body via bearings. In the turbocharger bearing mechanism, the bearing part is a hydrodynamic bearing part with a spiral group, and the high pressure air in the high pressure air chamber on the compressor wheel side is directed to a passage provided in the body and to the outside of the hydrodynamic bearing part. The fluid flows from the outside of both bearing parts of the rotary shaft to the inside through a chamber located in the body and communicating with the bore, into a gap between the bore of the body and the bearing part of the rotary shaft. Bearing mechanism for turbocharger.