JP5256986B2 - Two-stage supercharging system for internal combustion engine, internal combustion engine and lubricating oil leakage prevention method thereof - Google Patents

Description

  The present invention relates to a structure and a method for preventing leakage of lubricating oil in a supercharging device in a two-stage supercharging system for an internal combustion engine.

  A two-stage turbocharging system (two-stage turbocharging) is used as a means for performing optimum supercharging in a wide operating range by using a supercharging device such as a turbocharger. This is because a turbocharger with a different capacity is arranged in the exhaust passage at the outlet of the exhaust manifold, a high capacity turbocharger is used with a small capacity turbo (high pressure stage turbo) in the low speed and low load area, and a large capacity in the high speed and high load area. High turbocharging is performed using a turbo (low pressure stage turbo). Further, in a region where each turbo region overlaps, a high-pressure turbo and a low-pressure turbo are used in series to perform two-stage supercharging.

  The switching of each turbo region is controlled by the exhaust switching valve attached to the exhaust manifold and the intake switching valve attached to the intake side to control the flow of exhaust gas and intake air, respectively, under optimal conditions of the turbo system It is controlled so that it can be driven.

  These turbocharger shaft lubrication and oil leakage prevention structures supply oil from the engine from the top of the center housing, lubricate the bearings, and return the oil to the engine side from the oil reservoir in the center housing. (For example, refer to Patent Document 1). With this oil leakage prevention mechanism, oil leakage to the compressor side of the turbocharger is prevented by a seal ring structure provided at the bearing portion of the shaft.

  In conventional turbocharged single turbo and twin turbocharged turbochargers, the compressor outlet side is basically positive pressure in the supercharged state, and positive pressure also acts on the back of the compressor. Oil leakage from the compressor to the back of the compressor could be prevented with a seal structure such as a seal ring.

However, in a two-stage turbocharging system in which a plurality of turbochargers may be used in series, for example, in the high-pressure stage turbo operation region, an intake passage between an upstream low-pressure stage turbo compressor outlet and a high-pressure stage compressor inlet is provided. Because of the negative pressure, the pressure between the low-pressure compressor blade and the center housing is also negative, and the oil that lubricates the bearings of the low-pressure turbocharger passes through the seal ring and leaks into the intake passage from the compressor outlet. When this oil leak occurs, there is a problem that the consumption of engine oil increases.
Japanese Utility Model Publication 2-85830

The present invention has been made to solve the above-described problems. The purpose of the present invention is to provide a lubricating oil in a bearing portion of a low-pressure compressor upstream of an intake passage even when a plurality of turbochargers are used in series. An object of the present invention is to provide a two-stage supercharging system for an internal combustion engine, an internal combustion engine, and a lubricating oil leakage prevention method thereof that can prevent leakage.

In order to achieve the above object, a two-stage turbocharging system for an internal combustion engine according to the present invention includes a two-stage turbocharging system in which a high-pressure stage turbocharger and a low-pressure stage turbocharger are connected in series. In a two-stage supercharging system of an internal combustion engine having a lubricating oil line for supplying lubricating oil to a bearing portion of a center housing portion of each of the high-pressure stage turbocharger and the low-pressure stage turbocharger, the low pressure of the low-pressure stage turbocharger A gas supply line for supplying a pressurized gas at the time of supercharging by a high-pressure stage turbocharger is provided between the rear face of the stage compressor and the seal ring of the bearing portion on the low-pressure stage compressor side.

  With this configuration, the gas supplied between the back surface of the low-pressure stage compressor and the seal ring of the bearing part on the low-pressure stage compressor side causes the low-pressure stage compressor to seal against the seal ring of the bearing part on the low-pressure stage compressor side. By increasing the pressure on the back side, it is possible to prevent the lubricating oil supplied to the bearing portion of the low-pressure stage turbocharger from leaking from the back side of the compressor to the intake passage side. In addition, as this gas, air (air) and other gas can be used.

  In the two-stage supercharging system for an internal combustion engine, a gas control valve provided in the gas supply line is opened during supercharging by the high pressure turbocharger, and the pressurized gas is supplied to the low pressure compressor side. It supplies to a bearing part, It is characterized by the above-mentioned.

  With this configuration, pressurized gas is supplied during supercharging of the high-pressure stage turbocharger in which the pressure balance in the bearing section on the low-pressure stage compressor side is greatly disrupted. Therefore, the pressure balance in the bearing section on the low-pressure stage compressor side at this time is By recovering, it becomes possible to efficiently use the pressurized gas and prevent leakage of the lubricating oil to the intake passage side.

  In order to achieve the above object, an internal combustion engine (engine) according to the present invention uses the above-described two-stage supply system. With this configuration, it is possible to provide an engine that has a two-stage supercharging system and prevents consumption of lubricating oil due to leakage.

In order to achieve the above object, a lubricating oil leakage prevention method for a two-stage turbocharging system of an internal combustion engine according to the present invention includes a two-stage turbocharging system in which a high-pressure turbocharger and a low-pressure turbocharger are connected in series. And a lubricating oil for a two-stage turbocharging system of an internal combustion engine, including a lubricating oil line for supplying engine lubricating oil to a bearing portion of a center housing portion of each of the high-pressure stage turbocharger and the low-pressure stage turbocharger In the leak prevention method,
Between the back surface of the low-pressure stage compressor of the low-pressure stage turbocharger and the seal ring of the bearing portion on the low-pressure stage compressor side, the pressurized gas is supplied to the low-pressure stage compressor during supercharging by the high-pressure stage turbocharger. The pressurized gas is supplied to the bearing on the side, and this pressurized gas increases the pressure on the back side of the low-pressure compressor with respect to the seal ring on the bearing on the low-pressure compressor. The lubricating oil supplied to the stage turbocharger bearing is prevented from leaking from the back side of the compressor to the intake passage side. With this configuration, it is possible to obtain the same effects as those of the two-stage supercharging system for the internal combustion engine described above.

In addition, by using the gas control valve as a pressure regulating valve (regulator), it is possible to control the pressure of the pressurized gas supplied to the bearing portion on the low-pressure stage compressor side. Therefore, excessive thrust direction ( It is possible to prevent a load in the axial direction) from being applied.

  Furthermore, the present invention can be applied to a conventional internal combustion engine by using pressurized air for an air brake as a supply source of the pressurized gas, without making a major modification such as newly installing a gas pressurizing device. It becomes possible to apply.

  According to the two-stage turbocharging system of an internal combustion engine and the lubricating oil leakage prevention method according to the present invention, the compressor outlet pressure of the low-pressure stage turbo is low in the operation region of the high-pressure stage turbo, and the bearing in the center housing of the low-pressure stage turbo Increase the pressure of the bearing part on the compressor side by supplying pressurized gas to the seal ring part and the back of the compressor when there is a possibility that the lubricating oil of the part will flow into the compressor side It is possible to prevent the lubricating oil from leaking to the compressor side.

  Hereinafter, a two-stage supercharging system for an internal combustion engine and a method for preventing leakage of lubricating oil according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a configuration of a two-stage supercharging system 1 for an internal combustion engine according to an embodiment of the present invention.

  This internal combustion engine two-stage turbocharging system 1 has a turbocharger with a small turbocharging capacity, that is, a high-pressure turbocharger 40, and a turbocharger with a large capacity, that is, a low-pressure turbocharger 20, according to the engine speed and engine load. An engine supercharging system using a plurality of different turbochargers.

In this two-stage turbocharging system 1 for an internal combustion engine, a high-pressure turbine of a high-pressure turbo turbo 40 and a low-pressure turbine 23 of a low-pressure turbo 20 are connected to an exhaust passage 4 connected to the exhaust manifold 3 of the internal combustion engine 2 from the upstream side. Is provided. Further, in the intake passage 5, a low-pressure stage compressor 21 of the low-pressure stage turbo 20 and a high-pressure stage compressor of the high-pressure stage turbo 40 are provided on the upstream side of the intercooler 6 from the upstream side . The low-pressure turbine 23 is provided with a waste gate 55.

  These high-pressure stage turbo 40 and low-pressure stage turbo 20 are respectively in a supercharged state only by the high-pressure stage turbo 40 by the opening / closing valve operation of the exhaust-side exhaust switching valve 54 and the intake-side intake switching valve 53, and the high-pressure stage turbo. 40 and the two-stage supercharging state by the low-pressure stage turbo 20 and the supercharging state by only the low-pressure stage turbo 20 are switched, and the supercharging optimum for the operating state of the internal combustion engine 2 is performed in each state. is there.

  In the intake passage 5, a first pressure sensor (pressure sensor at the low pressure stage compressor outlet) 51 is provided between the low pressure stage compressor outlet 61 and the intake air switching valve 53, and between the intake air switching valve 53 and the inlet of the intercooler 6, A second pressure sensor (intercooler inlet pressure sensor) 52 is installed. The output signals of these pressure sensors 51 and 52 are sent to an engine control device (not shown). Further, the valve position signals of the intake switching valve 53 and the exhaust switching valve 54 are also sent to the engine control device. Further, an exhaust main pressure sensor 50 is installed in the exhaust manifold 3 so that an output signal is sent to the engine control device.

  Next, the flow of the intake air A and the exhaust gas G when using the high-pressure stage turbo 40 and the low-pressure stage turbo 20 will be described.

The white arrows in FIG. 1 indicate the flow of the intake air A. The intake air A supplied from the intake passage 5 passes through the low-pressure stage compressor 21 of the low-pressure stage turbo 20 and passes through the compressor of the high-pressure stage turbo 40. It passes through and is supplied to the intercooler 6. The intake air A supplied to the intercooler 6 burns in a combustion chamber (not shown) of the engine to become exhaust gas G, is exhausted from the exhaust manifold 3, and the exhaust gas G indicated by a solid arrow is a high-pressure turbo. It passes through the turbine 40 and the low-pressure turbine 23 of the low-pressure turbine 20 and is discharged from the exhaust passage 4.

  When the high-pressure stage turbo 40 is not used, the intake air A flows by bypassing the high-pressure stage turbo 40 by operating the intake switching valve 53 and the exhaust switching valve 54.

  The two-stage turbocharging system 1 shown in FIG. 1 performs high supercharging using a small-capacity turbo (high-pressure turbo) in the low-speed and low-load range, and large-capacity turbo (low-pressure turbo) in the high-speed and high-load range. Use the to boost the supercharge. Further, in a region where each turbo region overlaps, a high-pressure turbo and a low-pressure turbo are used in series to perform two-stage supercharging. This makes it possible to perform optimum supercharging in a wide operating range.

  Next, lubrication of the bearing portions of the turbochargers 20 and 40 will be described. FIG. 2 shows an enlarged view of the bearing portion of the low-pressure turbocharger 20 in the two-stage turbocharging system 1. Each of the high-pressure stage turbo 40 and the low-pressure stage turbo 20 has an oil supply part 31 at the upper part of the center housing 36. The engine oil supplied from the engine from the oil supply part 31 is used as a lubricating oil L as a bearing part. 33, the bearing portion 37 and the like. The oil L supplied to the bearing portion 37 passes through the respective bearing portions 33, is collected by the oil reservoir 32 in the center housing 36, and returns to an oil pan (not shown) for engine oil.

  Further, in the shaft portion 27 outside the bearing portion 37, a structure in which the lubricating oil L does not leak into the blades such as the turbine blade 24 of the low-pressure turbine 23 and the low-pressure compressor 21 and the compressor blade 22, for example, A seal ring structure 35 and a labyrinth structure are provided. Furthermore, a thrust bearing 34 for suppressing the movement in the thrust direction is disposed on the compressor-side shaft portion 27.

  2 shows a partial cross-sectional view of the low-pressure stage turbo 20, the lubrication of the bearing part of the high-pressure stage turbo 40 is performed in substantially the same manner as the bearing part of the low-pressure stage turbo 20 shown in FIG.

  In the present invention, the air supply line (gas supply line) 10 is provided in the bearing portion 37 on the compressor side separately from the lubricating oil line 30 for the bearing portion 37 of the low-pressure stage turbo 20. One end side of the air supply line 10 is connected to a communication hole 12 provided between the seal ring 35 and the compressor blade 22. The communication hole 12 reaches the shaft portion 27 from the outside of the bearing portion 37.

  By this air supply line 10, pressurized air Ac controlled by the gas control valve 11 linked with engine control is supplied to the bearing portion 37 from the outside of the low-pressure stage turbo 20. Here, compressor air for an air brake mounted on the engine is used as the pressurized air Ac.

FIG. 3 shows a further enlarged view of the air supply line 10. Supply of pressurized air Ac from the air supply line 10 is performed by sensing the valve positions of the exhaust switching valve 54 and the intake switching valve 53 from the engine control device. In the operating region of the high-pressure stage turbo 40, the detected pressure P1 of the first pressure sensor 51 at the outlet of the low-pressure stage compressor 21 and the detected pressure P2 of the second pressure sensor 52 at the inlet of the intercooler 6 are determined by the engine control device. In a state where P1 <P2, that is, in a state where the high pressure turbocharger 40 is operating, the gas control valve 11 is opened, and the pressurized air is applied to the bearing portion 37 of the center housing 36 of the low pressure turbo 20. Ac is supplied. On the other hand, in the P1 ≧ P2 state, that is, in the state where the high-pressure stage turbocharger 40 is not operating, the gas control valve 11 is closed and the pressurized air Ac is not supplied to the bearing portion 37.

  As described above, by supplying the pressurized air Ac to the communication hole 12 as shown by the arrow in FIG. 3, control is performed to pressurize the space 29 between the seal ring 35 and the back surface 28 of the compressor blade 22.

  Thus, even when the air around the compressor blade 22 is sucked by the operation of the high-pressure stage turbo 40 and the negative pressure is generated, the negative pressure state is eliminated by the supply of the pressurized air Ac. It is possible to prevent the lubricating oil L supplied via 33 from getting over the seal ring 35 and leaking out.

  Therefore, according to the internal combustion engine and the internal combustion engine two-stage turbocharging system configured as described above, even when a plurality of turbochargers are used in series, in the bearing portion 37 of the low-pressure stage compressor 21 upstream of the intake passage 5. Leakage of the lubricating oil L can be prevented.

It is a figure which shows the structure of the internal combustion engine of embodiment which concerns on this invention, and its two-stage supercharging system. It is sectional drawing which shows the structure of the bearing part of the low pressure stage turbocharger of a two stage supercharging system. It is the elements on larger scale which show the structure of the periphery of the gas supply line of FIG.

Explanation of symbols

1 Two-stage turbocharging system 2 Engine 3 Exhaust manifold 6 Intercooler 10 Gas supply line 11 Gas control valve 12 Communication hole 20 Low-pressure stage turbocharger 21 Low-pressure stage compressor 28 Back face of low-pressure stage compressor 30 Space 30 Lubricating oil line 35 Seal ring 36 Center Housing 37 Bearing 40 High-pressure turbocharger P1 Low-pressure compressor outlet pressure P2 Intercooler inlet pressure A Intake air Ac Pressurized air G Exhaust gas L Lubricating oil

Claims (4)

A two-stage turbocharging system in which a high-pressure stage turbocharger and a low-pressure stage turbocharger are connected in series is provided, and the lubricating oil of the engine is used for bearings in the center housing portions of the high-pressure stage turbocharger and the low-pressure stage turbocharger. In a two-stage supercharging system for an internal combustion engine equipped with a lubricating oil line to supply
A gas supply line for supplying pressurized gas is provided between the back surface of the low-pressure stage compressor of the low-pressure stage turbocharger and the seal ring of the bearing portion on the low-pressure stage compressor side when supercharging is performed by the high-pressure stage turbocharger. A two-stage supercharging system for an internal combustion engine, characterized in that:   The gas control valve provided in the gas supply line is opened at the time of supercharging by the high pressure turbocharger, and the pressurized gas is supplied to the bearing portion on the low pressure stage compressor side. 2. A two-stage supercharging system for an internal combustion engine according to 1.   An internal combustion engine using the two-stage supercharging system according to claim 1 or 2. A two-stage turbocharging system in which a high-pressure stage turbocharger and a low-pressure stage turbocharger are connected in series is provided, and the lubricating oil of the engine is used for bearings in the center housing portions of the high-pressure stage turbocharger and the low-pressure stage turbocharger. In a method for preventing lubricating oil leakage of a two-stage supercharging system of an internal combustion engine having a lubricating oil line to be supplied to
Between the back of the low-pressure stage compressor of the low-pressure stage turbocharger and the seal ring of the bearing portion on the low-pressure stage compressor side , pressurized gas is supplied to the low-pressure stage compressor side during supercharging by the high-pressure stage turbocharger . Supplied to the bearing section, the pressurized gas increases the pressure on the back side of the low-pressure stage compressor against the seal ring on the bearing section on the low-pressure stage compressor side, and is supplied to the bearing of the low-pressure stage turbocharger. A method for preventing leakage of lubricating oil in a two-stage turbocharging system of an internal combustion engine, wherein the lubricating oil is prevented from leaking from the back side of the compressor to the intake passage side.

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