JP2011021504A - Multi-stage supercharging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multi-stage supercharging apparatus in which a space occupied by a supercharger is narrowed with a simple structure and structural components are simplified capable of accurately controlling a bypass flow rate in a transition zone for switching from a high pressure stage turbo to a low pressure stage turbo. <P>SOLUTION: In this multi-stage supercharging apparatus having a high pressure stage waste gate valve 7 provided in a high pressure stage turbine 20, the high pressure stage waste gate valve is disposed at the downstream side of an opening part 20b provided in a high pressure stage turbine case 20a and bypassing the upstream side and the downstream side of a turbine rotor 20c. The high pressure stage waste gate valve includes a valve element 70 capable of abutting on and separating from the opening part, a coil spring 74 for biasing the valve element toward the opening, and a fixing bolt 75 for holding one end of the coil spring. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a multistage supercharging device used for an internal combustion engine such as a diesel engine.

  In an internal combustion engine such as a diesel engine, a two-stage turbocharging system including a low-pressure stage turbocharger and a high-pressure stage turbocharger is known for high output and low fuel consumption (Patent Documents 1 and 2).

  In recent years, research on premixed compression ignition combustion that enables simultaneous reduction of low NOx and low smoke in a diesel engine has been actively conducted. This premixed compression ignition combustion generates and burns a uniform and lean mixture at an early stage, and as a technical problem, increasing the engine load (fuel injection amount) causes premature ignition and makes it difficult to control the ignition timing. Therefore, there is a problem that the operation region is limited to a low load region (a region where the fuel injection amount is small).

  As a method of expanding the operation range by premixed compression ignition combustion, it is known that it is effective to suppress combustion by combining with high EGR (exhaust gas recirculation) and to ensure A / F (air-fuel ratio). It has been. Specifically, it is conceivable to obtain a high EGR rate and a high A / F by using a two-stage turbocharger and obtaining a high boost from a low-speed and low-load region with a high-pressure small turbo.

  The two-stage turbocharger is also effective as a means to achieve both a reduction in fuel consumption in urban (low / medium / low / medium load) driving with a high-pressure turbocharger with a small capacity and a high output with a low-pressure turbocharger with a large capacity. is there.

  The conventional multistage supercharging device shown in FIG. 4 will be briefly described.

  As shown in FIG. 4A, the intake pipe 4 is connected to the intake manifold 10 of the engine 1, and the exhaust pipe 5 is connected to the exhaust manifold 11. The intake pipe 4 is provided with an intercooler 40, a high-pressure stage compressor 21 of the high-pressure turbocharger 2, and a low-pressure stage compressor 31 of the low-pressure stage turbocharger 3 in order from the downstream, and upstream and downstream of the high-pressure stage compressor 21. A bypass valve 25 is provided in the intake bypass pipe 24 to be connected.

  The exhaust pipe 5 is provided with a high-pressure stage turbine 20 of the high-pressure stage turbocharger 2 and a low-pressure stage turbine 30 of the low-pressure stage turbocharger 3 in order from the upstream. A bypass valve 5 c that switches between the high-pressure stage turbocharger 2 and the low-pressure stage turbocharger 3 is provided in a bypass flow path 5 b provided between the exhaust manifold 11 and the exhaust pipe 5.

  The bypass valve 5c is generally a butterfly type as shown in FIGS. 5A and 5B, and is disposed on the downstream side of the exhaust so as to cover the opening 20b of the high-pressure stage turbine case 20a. The opening 20b is provided in a partition wall 20d that partitions the upstream side and the downstream side of the turbine rotor 20c of the high-pressure turbine 20. The bypass valve 5 c includes a valve body 82 that is supported at one end by a rotating shaft 80 and is rotatably supported around a shaft center of the rotating shaft 80 via a support arm 81. The opening 20b is closed by the contact, and the valve body 82 is rotated together with the support arm 81 as shown by an arrow W by an actuator device (not shown) to open the opening 20b.

JP 2007-138798 A JP 2009-92045 A

  By the way, the butterfly-type bypass valve 5c has a high sensitivity of the gas flow rate with respect to the valve opening (the rotation angle of the support arm 81), and the rotation angle of the support arm 81 when the slight flow rate is desired to be controlled. Control becomes difficult. As a means for solving this, as shown in FIG. 4B, one butterfly-type small valve 5e is added to the bypass flow path 5d, and first the small valve 5e is opened to bypass the exhaust gas to the low-pressure turbine 30; Although it is conceivable to control by opening the bypass valve 5c after a predetermined time has elapsed, it is not preferable in terms of the number of parts and space.

  The present invention has been made in view of the above points, and an object of the present invention is to simplify the components with a compact and simple structure and to bypass in a transition region where a high-pressure turbo is switched to a low-pressure turbo. An object of the present invention is to provide a multistage supercharging device capable of precisely controlling the flow rate.

  In order to solve the above problems, the present invention provides a high-pressure stage turbocharger and a low-pressure stage turbocharger connected in series to an engine, and a high-pressure stage wastegate valve provided in a high-pressure stage turbine of the high-pressure stage turbocharger. In the multi-stage supercharging device, the high-pressure stage waste gate valve includes an opening provided in a high-pressure stage turbine case and communicating with the upstream side and the downstream side of the turbine rotor, bypassing the turbine rotor, and downstream of the opening part. Fixed to the high pressure stage turbine case, a valve body disposed on the side and capable of abutting and separating from the opening, a coil spring for biasing the valve body toward the opening and closing the valve body A fixing bolt for holding one end of the coil spring, and the valve body presses the coil spring in response to a predetermined engine exhaust pressure. Contracted and is characterized in that so as to open by spaced apart from the opening.

  The coil spring preferably has one end in contact with the valve body and the other end in contact with the fixing bolt.

  The valve body, the coil spring, and the fixing bolt are preferably arranged coaxially.

  Moreover, it is preferable that the said valve body is formed so that the shape of the pressure receiving surface facing the said opening part may be dented in spherical shape.

  A bypass passage for bypassing the high-pressure turbine is provided between the engine and the low-pressure turbine of the low-pressure turbocharger; a bypass valve for opening and closing the passage is provided in the bypass passage; Is preferably controlled by the boost pressure of a boost pressure sensor provided downstream of the high-pressure compressor of the high-pressure turbocharger.

  According to the present invention, there is provided a multi-stage supercharging device capable of simplifying component parts with a compact and simple structure and precisely controlling a bypass flow rate in a transition region for switching from a high-pressure turbo to a low-pressure turbo. be able to.

FIG. 1 is a schematic diagram showing a configuration of a multistage supercharging device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a high-pressure stage wastegate valve of the multistage supercharging device shown in FIG. FIG. 3 is a diagram showing an example of a control region map for opening and closing the high-pressure stage wastegate valve based on the engine speed and load. 4A and 4B are schematic views showing the configuration of a conventional multistage supercharging device, in which FIG. 4A shows the case where there is one bypass valve, and FIG. 4B shows the case where there are two bypass valves. 5A and 5B are views showing a turbocharger to which a conventional waste gate valve is attached. FIG. 5A is a cross-sectional view of a turbine portion, and FIG. 5B is an enlarged cross-sectional view of a portion A of FIG.

  A preferred embodiment of the present invention will be described with reference to the accompanying drawings.

  In the present embodiment shown in FIGS. 1 and 2, members having the same functions as those shown in the conventional examples of FIGS. 4 and 5 will be described with the same reference numerals.

  As shown in FIG. 1, an intake pipe 4 through which intake air flows is connected to an intake manifold 10 of the engine 1. An exhaust pipe 5 through which exhaust gas flows is connected to the exhaust manifold 11 of the engine 1. A high-pressure stage turbocharger 2 and a low-pressure stage turbocharger 3 are connected to the intake pipe 4 and the exhaust pipe 5 in series from the side closer to the engine.

  The high-pressure stage turbocharger 2 is driven by receiving exhaust gas discharged from the engine 1, and a high-pressure stage compressor 21 that is driven by the high-pressure stage turbine 20 and boosts intake air supplied to the engine 1. have. The intake pipe 4 is provided with an intercooler 40 that cools the intake air boosted by the high-pressure compressor 21.

  The high-pressure stage turbine 20 connected to the exhaust pipe 5a is provided with a high-pressure stage waste gate valve 7 in a bypass passage 22 that connects the upstream and downstream of the high-pressure turbine 20 by bypassing the turbine rotor 20c. The high pressure stage waste gate valve 7 controls the amount of exhaust gas that bypasses the turbine rotor 20 c of the high pressure stage turbine 20.

  A bypass passage 5b is provided between the exhaust manifold 11 and the low-pressure stage turbocharger 3. A bypass valve 5c for bypassing the high-pressure stage turbine 20 is provided in the bypass passage 5b so as to be openable and closable. Yes. The bypass valve 5 c controls the opening degree to bypass the high-pressure turbine 20 of the high-pressure turbocharger 2 and send exhaust gas to the low-pressure turbine 30 of the low-pressure turbocharger 3.

  The high-pressure compressor 21 is connected to the intake pipe 4, and the bypass valve 25 that bypasses the high-pressure compressor 21 is provided with a bypass valve 25 that opens when the outlet pressure of the high-pressure compressor 21 exceeds a predetermined pressure. . The bypass valve 25 controls the amount of air that bypasses the high-pressure compressor 21. A boost pressure sensor 26 for detecting a boost pressure (supercharging pressure) is provided in the intake pipe 4 on the downstream side of the high-pressure compressor 21. The boost pressure sensor 26 opens the bypass valve 25 by detecting the predetermined pressure, and controls the opening of the bypass valve 5c by driving an actuator (not shown) by detecting the predetermined boost pressure. It is.

  The low-pressure stage turbocharger 3 is driven by receiving an exhaust gas discharged from the engine 1, and a low-pressure stage compressor 31 that is driven by the low-pressure stage turbine 30 and boosts intake air supplied to the engine 1. have. The low-pressure stage turbine 30 has a waste gate, and a waste-gate pipe 32 serving as a waste-gate flow path that bypasses the low-pressure stage turbine 30 is provided with a low-pressure stage waste gate valve 33 that opens when a predetermined supercharging pressure is exceeded. It has been. The low pressure stage waste gate valve 33 controls the amount of exhaust gas that bypasses the low pressure stage turbine 30.

  Further, the engine 1 is provided with an EGR flow path 6 that extracts a part of the exhaust gas from the exhaust system and returns it to the intake system of the engine 1 again. The EGR flow path 6 is provided with an EGR cooler 60 and an EGR valve 61. One end of the EGR flow path 6 is connected to the exhaust manifold 11, and the other end is connected to the intake pipe 4 downstream from the intercooler 40. . EGR gas is introduced from the exhaust manifold 11 through the EGR flow path 6 through the EGR cooler 60 and the EGR valve 61 to the intake manifold 10 from the intake pipe 4. The EGR valve 61 is controlled to open and close according to the operating conditions of the engine 1.

  The high-pressure stage waste gate valve 7 will be described with reference to FIGS. 1 and 2.

  The high-pressure stage waste gate valve 7 is provided in the bypass flow path 22 as described above. That is, the opening 20b is provided in the partition wall 20d that partitions the upstream side and the downstream side of the turbine rotor 20c rotatably provided in the high-pressure turbine case 20a, and the high-pressure stage waste is provided downstream of the opening 20b. A gate valve 7 is disposed so that the high-pressure stage waste gate valve 7 can be opened and closed in response to engine exhaust pressure (turbine inlet pressure). The high-pressure stage wastegate valve 7 is fixed by being screwed into a valve body 70 that contacts or separates from the opening 20b, a coil spring 74 that urges the valve body 70 toward the opening 20b, and a lid member 20e. The fixing bolt 75 is configured to hold the coil spring 74. The lid member 20e is integrally coupled to the high-pressure turbine case 20a via a gasket 77 that seals the exhaust gas.

  The valve body 70 is formed in the center portion with a pressure receiving surface 71 formed in a spherical shape on the side facing the opening 20b, a recess 72 formed on the opposite side to hold the coil spring 74, and the central portion. And a protrusion 73. A protrusion 76 is formed at the tip of the fixing bolt 75, and a full lift adjustment margin L is formed by the protrusion 76 and the protrusion 73 of the valve body 70.

  The valve body 70 is formed so that the pressure receiving surface 71 is recessed in a spherical shape as described above, and a sufficient area for receiving the engine exhaust pressure is ensured in a narrow space of the high-pressure turbine case 20a. .

  In this way, the high-pressure stage waste gate valve 7 is configured not as a butterfly type but as a direct acting type with a coil spring so that the relationship between the gas flow rate and the valve lift L has linearity (linearity) to improve controllability. Yes. That is, the lift amount L changes proportionally according to the exhaust pressure, and the curtain area obtained by multiplying the circumferential length of the opening 20b and the lift amount L changes proportionally according to the lift amount L. Since the gas flow rate changes in proportion to the proportional change in the curtain area, the relationship between the gas flow rate and the valve lift L has linearity. Therefore, it is easy to control the gas flow rate (bypass flow rate) in the bypass flow path 22, and precise control can be performed by adjusting the set load of the coil spring 74. In addition, the pressure-receiving surface is recessed into a spherical shape to increase the pressure-receiving area, and the sensitivity to the valve-opening pressure is improved while narrowing.

  Next, the operation of this embodiment will be described with reference to FIG.

  When the engine 1 is running at low speed, the exhaust gas from the engine 1 is sent from the exhaust manifold 11 to the high-pressure turbine 20 of the high-pressure turbocharger 2 through the exhaust pipe 5a. At this time, the bypass valve 5c is closed, and no exhaust gas flows from the bypass flow path 5b. Even if the flow rate of the exhaust gas flowing toward the high-pressure turbine 20 at a low speed is low, the high-pressure turbine 20 is appropriately driven because it has a small capacity, and a predetermined supercharging pressure is secured by the high-pressure compressor 21. be able to. The exhaust gas sent from the high-pressure turbine 20 flows to the low-pressure turbine 30, but the low-pressure turbine 30 has a large capacity and the flow rate of the exhaust gas flowing to the low-pressure turbine 30 side is small. Virtually no supercharging. In this way, the low-speed to medium-speed range of the engine 1 is supercharged by the high-pressure stage turbocharger 2.

  As the engine speed increases, the low pressure stage turbocharger is controlled by fully opening the bypass valve 5c and the bypass valve 25 when the engine 1 is in the medium to high speed range (higher speed range than the boundary C of the control area map shown in FIG. 3). Supercharge at 3. Since the low-pressure stage turbine 30 has a large capacity, the bypass valve 5c is fully opened to bypass the entire amount of exhaust gas, the high-pressure stage turbocharger 2 does not substantially operate, and the exhaust gas in the exhaust manifold 11 is low-pressure stage turbocharger. 3 is introduced.

  In the low-pressure stage turbocharger 3, the low-pressure stage compressor 31 is coaxially driven by the low-pressure stage turbine 30 to pressurize the air from the intake pipe 4 and suck it into the high-pressure stage compressor 21 of the high-pressure stage turbocharger 2 through the intake pipe 4. Then, the air is supplied from the intake manifold 10 to the engine 1 through the intake pipe 4 and the intercooler 40.

  By the way, in the high speed region of the engine 1, the bypass valve 5c and the bypass valve 25 may be fully opened in this way to completely switch from the high pressure turbine 20 to the low pressure turbine 30, but the boundary A shown in the control region map of FIG. In order to expand the operating range of premixed compression ignition combustion in the transition region (boundary transition from low engine speed, low engine speed, low engine speed, low load region to high load region, high fuel injection amount) In addition, it is necessary to precisely control the opening degree of the bypass valve of the two-stage supercharging device to optimize the EGR rate and the A / F.

  Here, paying attention to the relationship between the opening of the bypass valve and the flow rate, as described above, if the opening shape is a butterfly type, precise opening control is difficult, and the input is based on the supercharging pressure via a diaphragm actuator or the like. The poppet valve type that opens and closes has linearity in the characteristics of the opening and flow rate and is easy to control, but it can be said that there are large errors such as actuator operation errors and operation delays for precise control. In addition, as described above, a combination of a precise control small-diameter valve and a large-diameter valve for bypassing the entire flow rate is also conceivable, but the number of valves increases and the piping becomes complicated, which causes a problem in mountability in a vehicle.

  Therefore, a major feature of the present invention is that the high-pressure stage wastegate valve of the high-pressure stage turbocharger 2 can be controlled in the transition region of switching from the high-pressure stage turbocharger 2 to the low-pressure stage turbocharger 3 as described above. The opening of the high-pressure stage wastegate valve 7 is adjusted by a coil spring 74 that is directly assembled to the high-pressure stage wastegate valve 7 so that the valve 7 is opened to a predetermined lift by a predetermined engine exhaust pressure. That is, the high-pressure stage waste gate valve 7 eliminates the diaphragm actuator that is adjusted with the normal boost pressure, and is adjusted with the set load of the coil spring 74 that is directly assembled to the high-pressure stage waste gate valve 7. (Lift amount L) and flow rate characteristics are linear and easy to control precisely, and can be immediately controlled according to engine exhaust pressure without operation delay.

  In the transition region of switching between the high-pressure stage turbocharger 2 and the low-pressure stage turbocharger 3, first, the valve body 70 opens to a predetermined lift while gradually pressing and contracting the spring 74 according to the exhaust pressure, and the rotation of the high-pressure stage turbine 20. While suppressing the rise, the exhaust gas flows to the low-pressure stage turbine 30 via the bypass passage 22, and the minute flow rate in the transition region can be easily and appropriately controlled.

  When a further air flow rate is required, the bypass valve 5c is controlled to open by an actuator (not shown) as indicated by an arrow B in the control region map shown in FIG. That is, the bypass valve 5c is controlled by a boost pressure (detected by a boost pressure sensor 26 provided on the downstream side of the high-pressure compressor 21) correlated with the engine exhaust pressure at which the high-pressure stage waste gate valve 7 operates.

  As described above, according to the present invention, in the high-pressure stage waste gate valve 7 of the high-pressure stage turbocharger 2 used in the two-stage supercharging device, the opening degree adjustment of the high-pressure stage waste gate valve 7 is directly assembled to this. By using a direct-acting valve body 70 with a coil spring 74, the relationship between the gas flow rate and the valve lift L is linearized, and the controllability is improved, so that the EGR rate and A / F can be precisely controlled, and an expansion of the operation range of premixed compression ignition combustion can be expected.

  Further, since the coil spring 74 is directly assembled to the high pressure stage waste gate valve 7, the valve element 70 is immediately opened and closed by the engine exhaust pressure, and can be controlled without delay in operation.

  Furthermore, since only the coil spring 74 needs to be assembled between the valve body 70 and the fixing bolt 75, the space occupied by the two-stage supercharging device and the simplification of the components can be promoted with a simple configuration.

DESCRIPTION OF SYMBOLS 1 Engine 2 High pressure stage turbocharger 3 Low pressure stage turbocharger 4 Intake pipe 5 Exhaust pipe 5b Bypass flow path 5c Bypass valve 6 EGR flow path 7 High pressure stage waste gate valve 20 High pressure stage turbine case 20a High pressure stage turbine case 20b Opening 20c Turbine rotor 20d Partition wall 20e Lid 21 High-pressure stage compressor 22 Bypass passage 25 Bypass valve 26 Boost pressure sensor 30 Low-pressure stage turbine 33 Low-pressure stage waste gate valve 70 Valve body 71 Pressure receiving surface 74 Coil spring 75 Fixing bolt

Claims (5)

In a multi-stage supercharging device having a high-pressure stage turbocharger and a low-pressure stage turbocharger connected in series to an engine, and a high-pressure stage wastegate valve provided in a high-pressure stage turbine of the high-pressure stage turbocharger,
The high-pressure stage wastegate valve is provided in a high-pressure stage turbine case and is disposed on the downstream side of the opening, the opening connecting the upstream and downstream sides of the turbine rotor by bypassing the turbine rotor, and the opening A valve body that can be brought into contact with and separated from the part, a coil spring for urging the valve body toward the opening and closing it, and holding one end of the coil spring fixed to the high-pressure turbine case And fixing bolts to
The multistage supercharging device according to claim 1, wherein the valve body presses and contracts the coil spring in accordance with a predetermined engine exhaust pressure to separate the coil spring from the opening.   The multistage supercharging device according to claim 1, wherein one end of the coil spring is in contact with the valve body and the other end thereof is in contact with the fixing bolt.   The multistage supercharging device according to claim 1 or 2, wherein the valve body, the coil spring, and the fixing bolt are arranged coaxially.   The multistage supercharging device according to any one of claims 1 to 3, wherein the valve body is formed such that a pressure receiving surface facing the opening is recessed in a spherical shape.   A bypass passage for bypassing the high-pressure stage turbine is provided between the engine and the low-pressure stage turbine of the low-pressure stage turbocharger, and a bypass valve for opening and closing the passage is provided in the bypass passage. The multistage supercharging device according to any one of claims 1 to 4, wherein the multistage supercharging device is controlled by a boost pressure of a boost pressure sensor provided on a downstream side of a high-pressure compressor of the high-pressure turbocharger.

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