JP3738653B2 - Series two-stage turbocharging system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an in-line two-stage turbocharging system in which compressors are arranged in two-stage series in an internal combustion engine such as a diesel engine.
[0002]
[Prior art]
In an engine with a turbocharger, in addition to a single-stage turbocharger system that performs supercharging by a compressor only in one stage, in order to sufficiently supply intake air to a cylinder and fill it, it is large when the load and rotation speed are large. There is a switching type two-stage turbocharging system that drives a turbine with a capacity, switches to a turbine with a small capacity when the load or rotation speed is small, and drives this to supercharge.
[0003]
In addition, since the exhaust gas discharged from the first stage exhaust gas turbine still has sufficient exhaust energy that can be used, a second stage exhaust gas turbine is provided and compressed and pressurized by the first stage compressor. Has been proposed, a second-stage turbocharging system that improves the charging efficiency of the intake air to the cylinders and increases the engine output by further compressing and boosting the pressure with a second stage compressor and supplying it to the engine with high supercharging. Yes.
[0004]
This series two-stage turbocharger system combines large and small turbochargers with different turbine diameters, and supercharges mainly with the smaller turbocharger in the low engine speed range, improving response and turbo lag, and large The supercharger is pre-rotated. In the high speed range, the larger supercharger is operated to supercharge with a sufficient supercharging pressure.
[0005]
In this way, when the compressors are arranged in two stages in series, as shown in FIG. 1, the supply air pressure when the supply air pressure ratio of the turbine 31 in the high pressure stage upstream of the exhaust gas reaches the allowable rotation speed of the turbine 31. In this case, it is necessary to protect the turbocharger by preventing the turbine 31 from over-rotation. Therefore, a waste gate 33 provided with a waste gate valve 34 is provided so that the turbine 31 can reach an allowable rotational speed. It is necessary to open the waste gate valve 34 before reaching the exhaust gas G.
[0006]
The wastegate valve itself is also provided in the prior art one-stage turbocharging system. As shown in FIG. 5, a diaphragm type valve actuator 70 is used to introduce intake air downstream of the compressor, When the value of the boost pressure Pi, which is the intake pressure on the outlet side, exceeds a certain value, the diaphragm 71 overcomes the urging force of the spring 72 and drives the drive shaft 73 in the direction of the arrow X. The waste gate valve is not opened.
[0007]
By opening the waste gate valve, the exhaust gas is bypassed, the rotation of the turbine is suppressed, and the pressure of the intake air supplied to the engine is prevented from rising excessively. At the same time, the engine is supercharged. This prevents the intake pressure (boost pressure) from becoming too high and causing knocking or cylinder damage.
[0008]
[Problems to be solved by the invention]
However, when this waste gate valve according to the prior art is used, since it is configured to open and close depending on the value of the boost pressure, there is a problem that it cannot be used in the series two-stage turbocharging system as shown in FIG.
[0009]
In other words, in the case of a one-stage turbocharged system, the boost pressure and the pressure ratio correspond approximately to one-to-one, so that opening the valve with a predetermined boost pressure opens the valve with the corresponding predetermined pressure ratio. On the other hand, in the case of the series two-stage turbocharging system 1 as shown in FIG. 1, even if the pressure ratio of the compressor 32 of the high-pressure supercharger 30 is low, the low-pressure stage supercharging system 1 is operated. The boost pressure Pid, which is the intake pressure immediately before entering the intake manifold 11 or the intercooler 15, increases or decreases depending on the pressure ratio of the compressor 42 of the feeder 40. The pressure ratio of the compressor 32 and the boost pressure Pid do not correspond one-to-one.
[0010]
Therefore, in the case of the series two-stage turbocharging system 1, the pressure ratio of the high-pressure supercharger 30 may be high regardless of whether the boost pressure Pid is high or low. It cannot be determined whether the stage turbocharger 30 has a speed close to the allowable speed or a speed with a margin.
[0011]
Accordingly, when the wastegate 34 for emergency opening of the high-pressure turbine 31 corresponding to the boost pressure Pid is opened and closed, when the pressure ratio of the low-pressure stage supercharger 40 is small, the high-pressure stage supercharger Even if the pressure ratio of 30 is high and the rotational speed of the turbine 31 reaches the allowable rotational speed, the boost pressure Pid does not become so high as to enter the danger range. It will continue to supply and will result in the turbocharger 30 being damaged.
[0012]
Further, when the pressure ratio of the supercharger 40 on the low pressure stage side is large, the pressure ratio of the supercharger 30 on the high pressure stage side is low so that the rotational speed of the turbine 31 does not reach the permissible rotational speed. Even when there is no danger in the feeder 30, the wastegate valve 34 opens, and thus the appropriate control of the two-stage turbocharging system 1 in series may not be possible.
[0013]
The present invention has been made to solve the above-described problems, and its purpose is to provide a high-pressure supercharger with a wastegate valve that opens and closes according to the pressure ratio of the compressor, not the boost pressure, An object of the present invention is to provide a series two-stage turbocharger system that can be operated while maintaining the safety of the high-pressure stage turbocharger.
[0014]
[Means for Solving the Problems]
The series two-stage turbocharging system for achieving the above object is configured as follows.
[0016]
A first turbine of a first supercharger and a second turbine of a second supercharger driven by exhaust gas are provided in series in the exhaust passage of the internal combustion engine from the upstream side and driven by the second turbine. A turbocharger system in which a second compressor and a first compressor driven by the first turbine are arranged in two stages in series from the upstream side of an intake passage, and a wastegate that bypasses exhaust gas flowing into the first turbine The waste gate valve is provided in series, and the waste gate valve is formed to open and close in accordance with a ratio between a first intake pressure downstream of the first compressor and a second intake pressure upstream of the first compressor. In the stage turbocharger system,
The valve actuator of the wastegate valve has an internal piston disposed between the first air chamber and the second air chamber, and a drive shaft connected to the internal piston and driving the wastegate valve to open and close,
The first air chamber is formed in communication with the upstream side of the first compressor and the second air chamber is formed in communication with the downstream side of the first compressor.
The area ratio between the first pressure receiving surface on the first air chamber side of the internal piston and the second pressure receiving surface on the second air chamber side is defined as the first intake pressure when the waste gate valve is opened. It is formed so as to have a pressure ratio with the second intake pressure.
[0017]
In addition, since the friction of the internal piston and the spring force for returning the internal piston to the valve closing position when the engine is stopped are related, the area ratio and the pressure ratio do not necessarily have to be exactly the same value. The values may be substantially the same including the correction values at the time of operation.
[0018]
In the series two-stage turbocharging system having the above-described configuration, the wastegate valve provided in the first supercharger in the high pressure stage has a first intake pressure (boost pressure) on the outlet side of the first compressor in the high pressure stage. Without opening / closing valve depending on the pressure ratio between the first intake pressure on the outlet side of the first compressor in the high pressure stage and the second intake pressure on the inlet side, the boost pressure changes depending on the pressure ratio of the compressor in the low pressure stage. The turbocharger in the high pressure stage of the series two-stage turbocharger system can be operated safely.
[0019]
Considering the case where the wastegate valve is operated with a pressure difference between the first intake pressure on the outlet side of the first compressor in the high pressure stage and the second intake pressure on the inlet side, in the two-stage serial turbocharging system, For example, even if the pressure difference is the same 100 kPa, the inlet pressure (second intake pressure) varies depending on the pressure ratio of the low-pressure stage compressor, so the inlet pressure is 100 kPa and the outlet pressure (first intake pressure) is 200 kPa. In some cases, the pressure ratio is 2, and in some cases, the inlet pressure is 200 kPa, the outlet pressure is 300 kPa, and the pressure ratio is 1.5. Therefore, the pressure ratio is not directly related to the pressure ratio of the high-pressure supercharger.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a series two-stage turbocharging system according to the present invention will be described with reference to the drawings.
[0021]
First, the overall configuration of the series two-stage turbocharging system will be described.
[0022]
As shown in FIG. 1, this series two-stage turbocharger system 1 is connected to the exhaust passage 22 connected to the exhaust manifold 21 of the engine 10 in order from the upstream side of the first supercharger 30 of the high pressure stage. 1 turbine 31, the 2nd turbine 41 of the 2nd supercharger 40 of a low voltage | pressure stage, and the muffler (silencer) 23 are provided.
[0023]
Further, in the intake passage 12 connected to the intake manifold 11, in order from the upstream side, the air cleaner 13, the first compressor 42 of the second supercharger (turbocharger) 40 in the low pressure stage, the intermediate charge air cooler 50, A first compressor 32 and a charge air cooler (intercooler: charge cooler) 15 of the first supercharger 30 in the high pressure stage are provided.
[0024]
Then, an electric fan 51 is provided in the immediate vicinity of the intermediate air supply cooler 50 to cool the air supply A that has been compressed by the second compressor 42 of the second supercharger 40 in the low-pressure stage and raised in temperature. A control device 60 for controlling the fan 51 is provided. The control device 60 usually serves as an engine control unit.
[0025]
The control device 60 determines the operating state of the engine from the load sensor 61, the rotational speed sensor 62, and the like, and is compressed by the second compressor 42 in the low pressure stage such as the high load high rotation operating region of the engine 10 to increase the temperature. When it is necessary to increase the cooling of the intake air, the electric fan 51 is controlled to be turned on, and the cooling capacity of the intermediate air supply cooler 50 is increased.
[0026]
Further, the cooling of the intake air cooler 15 on the downstream side of the first compressor 32 of the first supercharger 30 is arranged in front of or behind the engine 10 to directly cool the cooling fan ( It is configured to be cooled by running wind or the like (not shown).
[0027]
Further, an exhaust bypass passage 24 that bypasses the first turbine 31 of the first supercharger 30 in the high-pressure stage is provided, and an adjustment valve 25 is provided at the inlet of the exhaust bypass passage 24. The driving amount of the first turbine 31 of the first supercharger 30 and the second turbine 41 of the second supercharger 40 is adjusted by controlling the opening and closing of 25 based on the engine speed and the like. By this adjustment, the ratio of the compression ratio of the supply air by the first compressor 32 in the high pressure stage and the second compressor 42 in the low pressure stage is adjusted.
[0028]
According to this series two-stage turbocharging system 1, the exhaust gas G discharged from the exhaust manifold 21 of the engine 10 is sent to the first supercharger 30 in the high-pressure stage to drive the first turbine 31 and coaxially. The upper first compressor 32 is rotated to supercharge the intake air, and the gas that has passed through the first turbine 31 is further sent to the second supercharger 40 in the low pressure stage to drive the second turbine 41. Then, it is released to the atmosphere through the muffler 23.
[0029]
On the other hand, the supply air A is compressed by the second compressor 42 of the second supercharger 40 in the low pressure stage after passing through the air cleaner 13, and then the intermediate supply air cooler 50 is cooled by the electric fan 51. Then, the air is further compressed and heated by the first compressor 32 of the first supercharger 30 in the high pressure stage, and is cooled by the air supply cooler 15 and then supplied to the intake manifold 11. The
[0030]
(Westgate valve)
Next, the wastegate valve 34 provided in the first supercharger 30 of the series two-stage turbocharging system that is a feature of the present invention will be described.
[0031]
This waste gate valve 34 is for bypassing the exhaust gas which flows in for emergency opening with respect to the 1st turbine 31, and is provided in the 1st turbine 31, as shown in FIG.
[0032]
In the unlikely event that the adjustment valve 25 of the exhaust bypass passage 24 breaks down, the high-pressure first turbine 31 into which the exhaust gas discharged from the exhaust manifold 21 directly flows can be protected. .
[0033]
The waste gate valve 34 is opened and closed by a valve actuator 35 as shown in FIGS. 2 to 3, and the valve actuator 35 is an internal piston that partitions the first air chamber 38a and the second air chamber 38b. The internal piston 37 is connected to a drive shaft 36 that opens and closes the wastegate valve 34.
[0034]
The first air chamber 38a communicates with the intake passage 12 on the upstream side of the first compressor 32 so as to be the second intake pressure Piu on the upstream side of the first compressor 32, and the second air chamber 38b is The first intake pressure Pid on the downstream side of the first compressor 32 is configured to communicate with the intake passage 12 on the downstream side of the first compressor 32.
[0035]
As shown in FIG. 4, the ratio (Sa) of the area Sa of the first pressure receiving surface 37a on the first air chamber 38a side of the internal piston 37 and the area Sb of the second pressure receiving surface 37b on the second air chamber 38b side. / Sb) is determined by determining the diameter D of the internal piston 37 and the diameter d of the area adjusting portion 36b of the drive shaft 36 connected to the second pressure receiving surface 37b so that the predetermined value Cp is obtained. In this case, the area ratio (Sa / Sb) is (D × D) / (D × D−d × d) = Cp.
[0036]
In order to restrict the movement of the internal piston 37, a stopper 37b is provided in the second air chamber 38b, and a coil spring 37a that presses the internal piston 37 against the stopper 37b is provided in the first air chamber 38a. The spring force of the coil spring 37a is set to such a strength that the wastegate valve 34 can exhibit a minimum urging force that can return to the valve closing position when the engine is stopped.
[0037]
According to the configuration of the valve actuator 35, the relationship between the second intake pressure Piu on the upstream side (inlet side) and the first intake pressure Pid on the downstream side (outlet side) of the first compressor 32 is Piu × Sa <Pid ×. When Sb is reached, the internal piston 37 and the drive shaft 36 move in the arrow X direction, and the wastegate valve 34 is opened. When Piu × Sa> Pid × Sb, the internal piston 37 and the drive shaft 36 move in the arrow Y direction, and the wastegate valve 34 is closed.
[0038]
The state in which the waste gate valve 34 is opened is Piu × Sa <Pid × Sb. This is the case of (Sa / Sb) <(Pid / Piu), and the pressure ratio of the first compressor 32 ( This is a case where (Pid / Piu) is equal to or greater than a predetermined value Cp.
[0039]
In practice, the friction of the internal piston 37 and the spring force of the coil spring 37a for returning the internal piston 37 to the closed position when the engine is stopped are related. Therefore, the area ratio (Sa / Sb) is not necessarily limited. The pressure ratio (Pid / Piu) does not have to be exactly the same value, and is substantially the same value including a correction value at the time of operation.
[0040]
As an example of this dimension, the upstream pressure Piu of the first compressor 32 in the high pressure stage is about 150 kPa (about 1.5 atm) in terms of absolute pressure, and the downstream pressure Pid is about 300 kPa (3.0 atm). Therefore, the valve is often opened when the upstream pressure Piu is 100 kPa to 200 kPa and the downstream pressure Pid is 200 kPa to 400 kPa. For example, when the valve is opened when the pressure ratio Cp is 2 or more, the area ratio (Sa / If Sb) is set to 2, and D = 3 cm, Sa = 7 cm @ 2, Sb = 3.5 cm @ 2, and d = 2.1 cm.
[0041]
According to the wastegate valve 34 having this configuration, the wastegate valve 34 can be opened at a predetermined pressure ratio Cp by setting Cp to a pressure ratio that opens the wastegate valve 34.
[0042]
Therefore, according to the series two-stage turbocharging system having the above configuration, the wastegate valve 34 provided in the first turbine 31 of the first supercharger 30 in the high-pressure stage is driven by the first turbine 31. Since the valve opens when the pressure ratio (Pid / Piu) of the compressor 32 exceeds a predetermined value Cp, even if the adjustment valve 25 of the exhaust bypass passage 24 fails for some reason, 1 The supercharger 30 can be protected and can be operated safely.
[0043]
【The invention's effect】
As described above, according to the in-series two-stage turbocharging system according to the present invention, the wastegate valve provided in the first supercharger of the high pressure stage has the intake pressure on the outlet side of the first compressor of the high pressure stage. Therefore, the first supercharger in the high-pressure stage can be reliably protected and can be operated safely.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a series two-stage turbocharging system according to the present invention.
FIG. 2 is a perspective view showing a configuration of a valve actuator of a wastegate valve used in the series two-stage turbocharging system according to the present invention.
FIG. 3 is a side sectional view of the valve actuator of FIG. 2;
4A and 4B are views showing a pressure receiving surface of the valve actuator of FIG. 2, wherein FIG. 4A shows a first pressure receiving surface, and FIG. 4B shows a second pressure receiving surface. It is a sectional side view.
FIG. 5 is a side sectional view showing a configuration of a valve actuator of a waste gate valve according to the prior art.
[Explanation of symbols]
1 Turbocharger system 10 Internal combustion engine 12 Intake passage 22 Exhaust passage 30 First supercharger 31 First turbine 32 Second compressor 33 Wastegate 34 Wastegate valve 35 Valve actuator 36 Drive shaft 37 Internal piston 37a First pressure receiving surface 37b Second pressure receiving surface 38a First air chamber 38b Second air chamber 40 Second supercharger 41 Second turbine 42 Second compressor Pid First intake pressure Piu Second intake pressure

Claims (1)

A first turbine of a first supercharger and a second turbine of a second supercharger driven by exhaust gas are provided in series in the exhaust passage of the internal combustion engine from the upstream side and driven by the second turbine. A turbocharger system in which a second compressor and a first compressor driven by the first turbine are arranged in two stages in series from the upstream side of an intake passage, and a waist that bypasses exhaust gas flowing into the first turbine the gate valve is provided, the wastegate valve is formed in so that the closing opening in accordance with the ratio between the second intake pressure upstream of the first downstream-side first intake pressure and said first compressor of the compressor in series two-stage turbocharging system,
The valve actuator of the wastegate valve has an internal piston disposed between the first air chamber and the second air chamber, and a drive shaft connected to the internal piston and driving the wastegate valve to open and close,
The first air chamber is formed in communication with the upstream side of the first compressor and the second air chamber is formed in communication with the downstream side of the first compressor.
The area ratio between the first pressure receiving surface on the first air chamber side of the internal piston and the second pressure receiving surface on the second air chamber side is defined as the first intake pressure when the waste gate valve is opened. A series two-stage turbocharging system, wherein the two-stage turbocharging system is formed to have a pressure ratio with the second intake pressure.

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