JP2006242008A - Turbocharger - Google Patents

Abstract

【Task】
A turbocharger that improves responsiveness and suppresses the generation of white smoke.
[Solution]
A turbo equipped with a turbine impeller 8 driven by exhaust gas from the engine 13, a compressor impeller 7 that compresses air by the rotation of the turbine impeller, and a rotating shaft 1 that connects the turbine impeller and the compressor impeller. In the charger 35, a water-lubricated bearing is applied to the bearing of the rotary shaft 1. And a part of engine cooling water is used as lubricating water of a water-lubricated bearing.
[Selection] Figure 1

Description

  The present invention relates to a turbocharger provided with a water-lubricated bearing.

  In a conventional turbocharger, a turbine impeller is attached to one end face of a rotating shaft accommodated in a bearing housing, and the rotating shaft rotates when engine exhaust gas is blown onto the turbine impeller. A compressor impeller is attached to the other end of the rotating shaft, and air is compressed by the rotation of the compressor impeller and supplied to the engine.

  The rotating shaft is rotatably supported by a radial bearing, and the radial displacement is suppressed. Note that the externally pressurized lubricating oil is supplied from the radial bearing oil supply hole to the radial bearing through the oil supply port. In addition, a thrust bearing is installed on the rotating shaft, and the thrust force acting on the rotating shaft is received to restrict the axial movement of the rotating shaft. For example, a turbocharger having such a configuration is described in Japanese Patent Application Laid-Open No. 2003-166537.

JP 2003-166537 A

  In a conventional turbocharger, oil is used as a lubricant for the bearing. Since oil has a high viscosity coefficient, bearing loss increases when applied to a bearing that rotates at a high speed of 100,000 revolutions per minute or more like a turbocharger. Depress the accelerator pedal to increase the amount of fuel supplied to the engine to increase the engine speed, increase the engine displacement and increase the turbine speed, and consequently increase the compressor discharge pressure from the increased compressor speed. This increases the engine intake pressure and increases the engine power to increase the acceleration. In this series of operations, the turbocharger's rotational performance has a great influence on the responsiveness from the increase of exhaust gas to the increase of intake pressure and the acceleration of the engine, and bearing loss is the main factor.

  Furthermore, generation of white smoke is a problem when using oil as a lubricant. In the gap between the back surface of the compressor impeller and the housing surface, a swirl flow accompanying the rotation of the compressor is generated, and a static pressure gradient is formed which increases from the rotating shaft surface toward the compressor outlet by the friction disk effect. . For this reason, the pressure of the rotating shaft surface on the back surface of the compressor is lower than the static pressure at the compressor outlet. This pressure drop is determined by the radius of the impeller, the rotational speed, the outlet pressure, and the like. A similar pressure distribution also occurs on the rear surface of the turbine impeller. However, since the compressor outlet static pressure> the turbine inlet static pressure, a pressure distribution that decreases from the compressor side to the turbine side is formed on the rotating shaft. The lubricant is pushed by this pressure gradient and leaks from the bearing portion to the rear surface of the turbine impeller. The lubricant that leaks once and adheres to the rear surface of the impeller is blown to the outer diameter side of the impeller by centrifugal force and mixed into the exhaust gas, and white smoke is generated by exhaust heat of the engine.

  An object of the present invention is to provide a turbocharger that improves responsiveness and suppresses the generation of white smoke.

  Both the responsiveness of the above turbocharger and the generation of white smoke were problems caused by using oil as a lubricant. Accordingly, in the present invention, a water-lubricated bearing using a lubricant composed of an aqueous solution containing water as a main component is applied as a lubricant having a low viscosity and having a small viscosity change due to a temperature difference.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the turbocharger which improved responsiveness and suppressed generation | occurrence | production of white smoke.

FIG. 1 is a view showing a bearing lubricating water system of a turbocharger which is an embodiment of the present invention. The cooling system equipment for the engine 13 includes a cooling water pump 15 that supplies cooling water to the cooling line 33 of the engine 13, a radiator 14 that releases heat of the cooling water that has passed through the engine 13 to the atmosphere, and cooling that is supplied to the engine 13. A thermostat 17 that detects the temperature of the water and a flow rate switching valve 16 that switches the flow rate of the cooling water based on the detected temperature of the cooling water at the thermostat 17 are provided. Cooling water is supplied to the cooling line 33 for cooling the engine 13 by the cooling water pump 15. The cooling water that has passed through the engine cooling section is guided to the radiator 14 by the cooling water pipe 34. The cooling water guided to the radiator 14 is returned again to the cooling water pump 15 by the pipe 20. A flow rate switching valve 16 that is opened and closed by a thermostat 17 is installed between the radiator 14 and the cooling water pump 15. One of the flow rate switching valves 16 is connected to the piping 20 on the cooling water outlet side of the radiator 14, and the other (outlet side) is connected to the outlet piping 19 of the engine cooling unit. When the temperature of the cooling water passing through the thermostat 17 is low, the piping 19 side is opened and the cooling water is directly returned to the engine. When the cooling water temperature rises, the piping 20 side is opened and the radiator 14 is opened. Return the passed cooling water to the engine. Cooling water is periodically injected into the replenishing tank 18 to maintain the amount of cooling water in the cooling water line.

  The turbocharger 35 is connected to the intake duct 10 at the compressor suction side, sucks outside air through the filter 9, and supplies the pressurized air from the compressor discharge pipe 28 to the engine intake pipe 30 through the intercooler 29. Further, the exhaust gas of the engine is supplied from the exhaust pipe 31 to the turbine impeller 8 of the turbocharger 35 to operate the turbine. The exhaust gas of the turbine impeller 8 is discharged from the exhaust duct 11 through the muffler 12.

In this embodiment, a water-lubricated bearing is applied to the turbocharger bearing, and a part of engine cooling water is supplied as the lubricant. The thrust bearing 2 and the radial bearings 5a and 5b of the turbocharger are provided with radial bearing lubricating water supply pipes 24a and 24b and thrust bearing lubricating water supply pipe 25 from a cooling water branch pipe 21 branched from the discharge side of the cooling water pump 15. Supplied through. Since the rotating shaft of the turbocharger rotates at a high speed, a filter 22 is installed in the cooling water branch pipe 21 to remove foreign matters contained in the cooling water. Further, a flow rate regulator 23 such as an orifice is installed in the cooling water branch pipe 21 to set the flow rate of lubricating water supplied to the bearing. The bearing drainage discharged from each bearing is merged in the bearing drainage pipe 27 via the pipes 26 and 32, and further merged with the cooling water after cooling the engine in the pipe 34 and supplied to the radiator 14. The cooling water whose heat has been exchanged by the radiator 14 and whose exhaust heat has been removed is supplied again to the engine 13 and the turbocharger 35 by the cooling water pump 15.

  FIG. 5 shows the relationship between the accelerator pedal depression amount and the engine acceleration when oil is used as the bearing lubricant of the turbocharger and when water is used. Compared to oil-lubricated bearings, it can be seen that there is a large difference in acceleration performance especially in the low speed range where the amount of depression of the accelerator pedal is small, due to the difference in bearing loss due to the viscosity of the lubricant.

  In the turbocharger according to the above-described embodiment, water or an aqueous solution is used as a bearing lubricant. Therefore, the viscosity of water is an order of magnitude less than 1/15 to 1/30 that of oil, and the bearing loss is greatly reduced. As a result, the response of the turbocharger is remarkably improved. In addition, since the viscosity itself is small, even when a change in viscosity due to a change in water temperature occurs, there is almost no influence on the rotation shaft vibration due to the change in viscosity. Furthermore, even when leakage from the bearing portion occurs, there is an effect that white smoke is not generated because it becomes water vapor in the exhaust gas.

  In addition, when oil-lubricated bearings are applied to the bearings, it is necessary to provide a lubricating oil system separately from the engine cooling water system. Since a lubricating water system that is shared as the lubricating water for the bearing is formed, the lubricating water system can be simplified.

  In this embodiment, the bearing lubricating water cooled by the radiator 14 is supplied. That is, when the lubricating water is boiled, that is, when it is supplied to the bearing portion in a state where gas and liquid are mixed, there is a possibility that the lubricating water does not sufficiently reach the bearing portion, and the function as a lubricant may not be performed. There is. On the other hand, in the present embodiment, since the lubricating water after being cooled by the radiator 14 is supplied to the bearing, it is possible to prevent boiling of the lubricating water. Thereby, since the lubricating water is supplied to the bearing portion in a liquid state, the advantage of the lubricating performance of the water-lubricated bearing can be maintained. Also, in conventional oil lubricated bearings, there was a possibility that the oil would harden at a high temperature at the bearing portion. However, in this embodiment, since water is used as the lubricant, the water in the bearing portion evaporates, and the bearing It can also suppress that the reliability of a part is impaired.

  FIG. 6 is a diagram showing another embodiment of the present invention. In this embodiment, the basic configuration is the same as that shown in FIG. 1, but a lubricating water tank 37 is installed in the bearing drain pipe 27 of the turbocharger 35, and a lubricating water return pump 60 is installed downstream thereof. Is different. Here, in the configuration of FIG. 1, in order to merge the bearing drainage into the pipe 34 and send it to the radiator side, a head difference is required between the bearing part of the turbocharger 35 and the joining part of the pipe 34. There may be some restrictions on the charger mounting position. Therefore, in this embodiment shown in FIG. 6, in order to eliminate the restriction of the mounting position of the turbocharger, a lubricating water tank 37 is installed at the lowest point position of the bearing drain pipe 27 as viewed in the direction of gravity, and the bearing drainage is once performed. The water is stored here, and from here to the confluence of the pipe 34 is pumped by the lubricating water return pump 60.

  In the embodiment shown in FIG. 1 and FIG. 6 above, the engine coolant is used as a bearing lubricant for the turbocharger. Therefore, the coolant is an aqueous solution of an antifreeze such as ethylene glycol. The bearing loss of the turbocharger can be greatly reduced because it is an order of magnitude lower than oil. This has the effect of improving the responsiveness of the turbocharger at the time of rapid acceleration and at low temperatures. Further, even when this lubricant leaks from the bearing portion to the turbine side, white smoke is not generated in the exhaust gas because it evaporates due to exhaust heat.

  FIG. 2 is a sectional view showing the structure of a turbocharger to which the present invention is applied. As shown in FIG. 2, a turbine impeller 8 is attached to the right end of the rotary shaft 1 accommodated in the bearing housing, and an engine exhaust gas (not shown) is blown onto the turbine impeller 8 to rotate. The shaft 1 rotates. A compressor impeller 7 is attached to the left end of the rotating shaft 1. Air is compressed by the rotation of the compressor impeller 7 and supplied to an engine (not shown). The rotating shaft 1 is rotatably supported by radial bearings 5a and 5b, and the displacement in the radial direction is suppressed. Note that a lubricant made of an aqueous solution pressurized outside is supplied to the radial bearings 5a and 5b from the radial bearing water supply hole 6. A thrust collar 3 is fitted to the rotary shaft 1, and this thrust collar 3 constitutes a bearing device together with the radial bearing housing 4 and the thrust bearing 2.

  As the radial bearing used in FIG. 2, a multi-arc bearing that is effective in reducing shaft vibration caused by unbalance of the high-speed rotating body is used. When unstable vibration such as oil whip becomes a problem, a tilting pad bearing is used. As the thrust bearing, a taper round bearing having a high load resistance is used.

  FIG. 3 is a view showing another embodiment of the present invention. In the embodiment of FIG. 1, the turbocharger bearing lubricant uses engine cooling water. The cooling water pump 15 shown in FIG. 1 normally obtains power directly from the engine crankshaft. For this reason, the pumping flow rate of the cooling water also changes depending on the engine speed. On the other hand, the water-lubricated bearing installed in the turbocharger 35 forms a water film between the bearing and the rotary shaft to support the load. It is unnecessary. Since the water film is as thin as several tens of microns, if foreign matter enters the lubricant, the bearing surface will be damaged and the bearing will be damaged. Therefore, the embodiment of FIG. 3 is an example in which the deterioration of the lubricating water purity due to the combined use with the engine cooling water is prevented, and only the necessary lubricating water flow rate is always supplied constantly.

  As shown in FIG. 3, the bearing lubrication water supply system of the turbocharger is newly provided with a lubrication water pump 39, a lubrication water radiator 38, and a lubrication water tank 37. The lubricant composed of the aqueous solution stored in the lubricating water tank 37 is guided to the lubricating water radiator 38 from the pipe 36 by the operation of the lubricating water pump 39, and the cooling water branch installed on the discharge side of the lubricating water pump 39. Through the pipe 21, the turbocharger radial bearing lubricating water supply pipes 24 a and 24 b and the thrust bearing lubricating water supply pipe 25 are supplied. The cooling water branch pipe 21 is provided with a filter 22 and a flow rate regulator 23 as in the embodiment of FIG. The bearing drainage flows from the pipes 26 and 32 to the bearing drainage pipe 27 and returns to the lubricating water tank 37 again.

  In the present embodiment, the bearing lubricating water of the turbocharger forms a dedicated supply line separate from the engine cooling water system, so that only the flow rate necessary for forming the water film of the water bearing can always be stably supplied. Furthermore, since the supply line is completely independent from other cooling water lines, there is an effect that the lubricating water component and the water quality can be managed independently. The responsiveness at the time of sudden acceleration, the prevention of the generation of white smoke, and the like can obtain the same effects as the embodiment shown in FIG.

  In the embodiment shown in FIG. 3, it is possible to carry out the case where no antifreeze or the like is mixed to reduce the viscosity of the bearing lubricating water. In this case, in order to prevent freezing of the lubricating water and to prevent damage to the piping due to freezing, when the engine is stopped, the highest position in the piping system is provided so that water remaining in the lubricating water supply line can be dropped into the lubricating water tank 37. A valve that can be opened to the atmosphere is provided at the part, and the valve is closed when the engine is operating and opened when the engine is stopped. Further, the installation height of the lubricating water pump 39 is set to be equal to or lower than the surface of the lubricating water tank 37 so that water remains in the lubricating water pump 39 even when the water returns to the lubricating water tank 37. Avoid malfunctions of the pump due to air contamination when starting the pump. Further, a heater (not shown) is installed in the lubricating water tank 37 to prevent the lubricating water from freezing by operating the heater before the ambient temperature falls below the freezing point so that the lubricating water does not freeze while the engine is stopped. By using only water as the lubricating water, it is possible to prevent the solvent from being deposited on the lubricating water system and the bearing portion. Furthermore, it is desirable to use water from which hard components such as potassium and calcium are removed.

  FIG. 4 shows another embodiment of the present invention. FIG. 4 shows an example in which a water-lubricated bearing is applied to a turbocharger equipped with an electric generator. A turbocharger has been developed in which a motor-generator is attached to a rotating shaft of a turbocharger and the motor-generator is operated as a motor or a generator according to the operating state of the engine. It is operated as an electric motor to assist supercharging of the turbocharger at low speed, or is operated as a generator to extract electric power from exhaust gas energy supplied to the turbocharger.

  A permanent magnet 42 and its holding member 43 are wound around the central portion of the rotating shaft 1, and radial bearings 5a and 5b, thrust collar 3, thrust bearing 2, and seals 45a and 45b are installed. Further, the stator 40 is installed in the entire circumferential direction so as to surround the rotating shaft 1 at a position facing the permanent magnet 42 attached to the central portion of the shaft. The turbocharger housing includes a compressor housing 55 and a turbine housing 56. The thrust bearing 2 and radial bearings 5 a and 5 b include bearing housings 4 a and 4 b, and the stator 40 includes a stator housing 44. The stator housing 44 is sandwiched and installed between the bearing housings 4a and 4b.

  A stator cooling jacket 41 is attached to the outer periphery of the stator 40. Cooling water is supplied to the cooling jacket 41 from a cooling water supply hole 46 provided in the stator housing 44. The cooling water that has passed through the stator cooling jacket 41 is discharged from the cooling water discharge hole 47 to the outside. Further, the aqueous bearing lubricant is supplied to the radial bearings 5a and 5b from the bearing lubricating water supply holes 48a and 48b, and to the thrust bearing 2 from the thrust bearing lubricating water supply hole 49. The lubricant that passes through the bearings is discharged to the outside through the lubricating water discharge holes 50a and 50b.

  Further, in this embodiment, in order to prevent the dielectric breakdown of the stator due to the lubricant, which is an aqueous solution, leaking from the bearing portion to the stator 40 side, seal portions 45a and 45b are provided between the radial bearings 5a and 5b and the stator installation portion. Provided. Specifically, from the seal air introduction hole 52 vacated in the wall surface of the compressor discharge scroll 54, a part of the discharge air of the compressor is used as the seal air, and the seal portion 45a is passed through the seal air introduction holes 53, 53a, 53b It is configured to supply to 45b. Thereby, it is possible to prevent the bearing lubricant from entering the stator portion. The lubricating water can be supplied to the bearing portion by providing the supply system shown in FIGS. The same applies to the supply of cooling water to the stator cooling jacket 41 attached to the outer periphery of the stator.

  According to this embodiment, even in a turbocharger equipped with a motor-generator, an aqueous solution can be used as a bearing lubricant, which is effective in response of the turbocharger and prevention of white smoke generation.

The figure which shows the bearing lubricating water system | strain of the turbocharger which is one Example of this invention. Sectional drawing which shows the structure of the turbocharger to which this invention is applied. The figure which shows the other Example of this invention. The figure which shows the structure of the turbocharger provided with the motor-generator. The figure which shows the effect of this invention. The figure which shows the other Example of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Rotary shaft, 2 ... Thrust bearing, 3 ... Thrust collar, 4 ... Radial bearing housing, 5a, 5b ... Radial bearing, 6 ... Radial bearing water supply hole, 7 ... Compressor impeller, 8 ... Turbine impeller, 10 ... Intake Duct, 11 ... Exhaust duct, 13 ... Engine, 14 ... Radiator, 15 ... Cooling water pump, 16 ... Flow rate switching valve, 17 ... Thermostat, 21 ... Cooling water branch pipe, 24a, 24b ... Radial bearing lubricating water supply pipe, 25 ... thrust bearing lubricating water supply pipe, 27 ... bearing drain pipe, 29 ... intercooler, 30 ... engine intake pipe, 31 ... engine exhaust pipe, 35 ... turbocharger, 37 ... lubricating water tank, 38 ... radiator for lubricating water, 39 ... Circulating water pump, 40 ... stator, 41 ... stator cooling jacket, 42 ... permanent magnet, 45a, 45b ... seal part, 46 ... cooling Supply hole 47 ... Cooling water discharge hole, 48a, 48b ... Bearing lubricating water supply hole, 49 ... Thrust bearing lubricating water supply hole, 50a, 50b ... Lubricating water discharge hole, 51 ... Thrust bearing lubricating water discharge hole, 53, 53a 53b ... Seal air introduction holes.

Claims (8)

In a turbocharger comprising a turbine impeller driven by exhaust gas of an engine, a compressor impeller that compresses air by rotation of the turbine impeller, and a rotary shaft that connects the turbine impeller and the compressor impeller.
A turbocharger using a water-lubricated bearing as the bearing of the rotating shaft.   The turbocharger according to claim 1, wherein the water-lubricated bearing is configured to use engine cooling water as lubricating water.   The water-lubricated bearing is configured such that a part of cooling water supplied to the engine from an engine cooling water pump is supplied via a radiator, and bearing drainage is returned to the radiator inlet of the engine cooling water. The turbocharger according to claim 2, wherein the turbocharger is provided.   4. The turbocharger according to claim 3, wherein the turbocharger includes a lubricating water tank that stores the bearing drainage, and a lubricating water return pump that circulates the bearing drainage of the lubricating water tank back to the radiator inlet. 5. Charger.   The turbocharger includes a radiator for lubricating water that cools the lubricating water of the water-lubricated bearing, a lubricating water pump that supplies the lubricating water cooled by the radiator for lubricating water to the water-lubricated bearing, and a lubricant that accumulates bearing drainage. The turbocharger according to claim 1, further comprising a water tank, wherein a circulation path for circulating the bearing wastewater as lubricating water is formed.   The turbocharger according to claim 5, wherein an installation height of the lubricating water pump is set below the lubricating water tank.   The turbocharger includes a motor-generator configured by attaching a permanent magnet to a rotating shaft between the turbine impeller and a compressor impeller and installing a stator on the outer periphery of the permanent magnet, and the bearing of the rotating shaft. A radial bearing that suppresses the radial displacement of the rotating shaft and a thrust bearing that suppresses the axial displacement, and a seal portion is provided between the radial bearing and the permanent magnet installation portion, and the seal portion The turbocharger according to claim 1, wherein a seal air introduction hole for supplying a part of the discharge air of the compressor impeller is provided in the turbocharger.   The turbocharger according to claim 1, wherein the turbocharger is configured such that lubricating water that has passed through a filter is supplied to a water-lubricated bearing.

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