JP2001280147A - Series two-stage turbo supercharging system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a series two-stage turbo supercharging system capable of carrying out an operation while holding safety of a supercharger of a high pressure stage by providing a waste gate valve which is opened/closed according to a pressure ratio of a compressor in the supercharger of the high pressure stage. SOLUTION: In the turbo supercharging system 1 of a series two-stage supercharging wherein a first turbine 31 of a first supercharger 30 and a second turbine 41 of a second supercharger 40 are disposed from an upstream side of an exhaust passage 22 of an internal combustion engine 10 in order, and a second compressor 42 of the second supercharger 40 and a first compressor 32 of the first supercharger 30 are disposed from the upstream side of an intake passage 12 in order; a waste gate valve 34 disposed in the first turbine 31 is opened/closed according to a ratio between first intake pressure Pid of a downstream side of the first compressor 32 and second intake pressure Piu of the upstream side of the first compressor 32.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-line two-stage turbocharging system in an internal combustion engine such as a diesel engine, in which compressors are arranged in two stages in series.

[0002]

2. Description of the Related Art In a turbocharged engine,
In addition to the single-stage turbocharging system in which only one stage of supercharging is performed by the compressor, in order to sufficiently supply and charge the intake air to the cylinder, a large-capacity turbine is driven when the load or rotation speed is large, There is a switching-type two-stage turbocharging system that switches to a small-capacity turbine when the rotation speed is low, and drives and supercharges the turbine.

[0003] Further, since the exhaust gas discharged from the one-stage exhaust gas turbine still has a sufficient amount of available exhaust energy, a second-stage exhaust gas turbine is provided, and the pressure of the first-stage compressor is increased. In-line two-stage turbocharging system that improves the charging efficiency of the intake air to the cylinders and increases the engine output by supplying the supplied air to the engine with a second stage compressor that further compresses and boosts the pressure and supplies it to the engine with high supercharging Proposed.

[0004] This in-line two-stage turbocharger system combines large and small turbochargers with different turbine diameters, and in a low engine speed region, mainly uses the smaller turbocharger to improve the response and the turbo lag. At the same time, the larger turbocharger is pre-rotated. Then, in the high rotation range, the larger supercharger is operated to perform supercharging with a sufficient supercharging pressure.

When the compressors are arranged in two stages in series, as shown in FIG. 1, when the supply pressure ratio of the turbine 31 at the high pressure stage on the upstream side of the exhaust reaches the allowable rotation speed of the turbine 31, as shown in FIG. When the supply pressure ratio is reached, it is necessary to prevent over-rotation of the turbine 31 and protect the supercharger. Therefore, a waste gate 33 having a waste gate valve 34 is provided so that the turbine 31 is allowed to operate. It is necessary to open the waste gate valve 34 before the rotation speed is reached to bypass the exhaust gas G.

The wastegate valve itself is also provided in the prior art one-stage turbocharging system, and as shown in FIG. 5, uses a diaphragm type valve actuator 70 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 of the compressor, exceeds a certain value, the diaphragm 71 moves
The drive shaft 73 is driven in the direction of the arrow X by overcoming the urging force of No. 2 to open a waste gate valve (not shown) at the end of the drive shaft 73.

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 excessively increasing. This prevents the intake pressure (boost pressure) that is supercharged from becoming too high, causing knocking and cylinder damage.

[0008]

However, when the conventional wastegate valve is used, the valve is opened and closed by the boost pressure value.
There is a problem that it cannot be used in the in-line two-stage turbocharging system as shown in FIG.

In other words, in the case of a single-stage turbocharging system, the boost pressure and the pressure ratio correspond substantially to one to one.
Opening the valve at a predetermined boost pressure means opening the valve at a corresponding predetermined pressure ratio. On the other hand, in the case of the in-line two-stage turbocharging system 1 as shown in FIG. Even when the pressure ratio of the compressor 32 of the supercharger 30 of the low pressure stage is low, the boost which is the intake pressure immediately before entering the intake manifold 11 or the intercooler 15 due to the level of the pressure ratio of the compressor 42 of the supercharger 40 of the low pressure stage. Since the pressure Pid increases or decreases, the pressure ratio of the compressor 32 of the supercharger 30 in the high-pressure stage and the boost pressure Pid become 1
No one-to-one correspondence.

[0010] Therefore, the in-line two-stage turbocharging system 1
In this case, the pressure ratio of the supercharger 30 in the high-pressure stage may be high regardless of whether the boost pressure Pid is high or low. It cannot be determined whether the rotation speed is close to or has a margin.

Therefore, the waste gate 34 for emergency opening of the turbine 31 at the high pressure stage is set in accordance with the boost pressure Pid.
When the pressure ratio of the supercharger 40 on the low pressure stage side is small, the pressure ratio of the supercharger 30 on the high pressure stage side is high, and the rotation speed of the turbine 31 reaches the allowable rotation speed. However, since the boost pressure Pid does not become high enough to enter the danger range, the wastegate valve 34 continues to supply the exhaust gas with the valve closed, and the turbocharger 30 is damaged.

When the pressure ratio of the supercharger 40 at the low pressure stage is large, the pressure ratio of the supercharger 30 at the high pressure stage is low, and the rotation speed of the turbine 31 does not reach the allowable rotation speed. Even when there is no danger in the supercharger 30 of the stage, the wastegate valve 34 is opened, so that appropriate control of the in-line two-stage turbocharger system 1 may not be performed.

[0013] The present invention has been made to solve the above-mentioned problem, and the object of the present invention is not to increase the boost pressure but to increase the pressure.
The high-pressure supercharger is provided with a wastegate valve that opens and closes in accordance with the pressure ratio of the compressor, to provide a two-stage in-line turbocharger system that can operate while maintaining the safety of the high-pressure supercharger. is there.

[0014]

The in-line two-stage turbocharging system for achieving the above object is constituted as follows.

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 an exhaust passage of an internal combustion engine from an upstream side. In a turbocharger system in which a second compressor driven by two turbines and a first compressor driven by the first turbine are arranged in two stages in series from the upstream side of an intake passage, exhaust gas flowing into the first turbine is A wastegate valve to be bypassed is provided, and the wastegate valve opens and closes 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. It is formed.

2) In the above-mentioned in-line two-stage turbocharging system, the valve actuator of the waste gate valve is connected to an internal piston disposed between the first air chamber and the second air chamber, and to the internal piston. And a drive shaft for opening and closing the waste gate valve.
An air chamber is formed on the upstream side of the first compressor, and the second air chamber is formed on the downstream side of the first compressor. The first piston receives a first pressure of the internal piston on the first air chamber side. The area ratio between the surface and the second pressure receiving surface on the side of the second air chamber is set to be the pressure ratio between the first intake pressure and the second intake pressure when the waste gate valve is opened. Form.

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 involved, the area ratio and the pressure ratio need not be exactly the same. However, it suffices that the values be substantially the same, including the correction values during these operations.

In the above-described series two-stage turbocharger system, the waste gate valve provided in the first supercharger of the high pressure stage is connected to the first intake pressure (boost) on the outlet side of the first compressor of the high pressure stage. Pressure), not the high pressure stage
The on-off valve is opened and closed according to the pressure ratio between the first intake pressure on the outlet side of the compressor and the second intake pressure on the inlet side, so that the boost pressure changes according to the pressure ratio of the compressor in the low pressure stage. The high-pressure stage turbocharger can be safely operated.

The waste gate valve is connected to the first intake pressure on the outlet side of the first compressor of the high pressure stage and the second intake pressure on the inlet side.
Considering the case of operating with a pressure difference from the intake pressure, in a two-stage in-line turbocharger system, for example,
Even at the same pressure difference of 100 kPa, the inlet pressure (second
(Intake pressure) depends on the pressure ratio of the compressor in the low pressure stage, so that the inlet pressure is 100 kPa and the outlet pressure (first
In some cases, the inlet pressure is 200 kPa and the pressure ratio is 2, and sometimes the inlet pressure is 200 kPa and the outlet pressure is 300 kPa and the pressure ratio is 1.5, so it is not directly related to the pressure ratio of the supercharger in the high-pressure stage. You can see that.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A series two-stage turbocharging system according to the present invention will be described below with reference to the drawings.

First, the overall configuration of the in-line two-stage turbocharging system will be described.

As shown in FIG. 1, the in-line two-stage turbocharging system 1 includes an exhaust manifold 21 of an engine 10.
The first turbine 31 of the first supercharger 30 at the high pressure stage and the second turbine at the low pressure stage
The second turbine 41 and the muffler (silencer) 23 of the supercharger 40 are provided.

In the intake passage 12 connected to the intake manifold 11, air cleaners 1 are arranged in order from the upstream side.
3, the first compressor 42 of the second supercharger (turbocharger) 40 of the low pressure stage, the intermediate charge cooler 50, the first compressor 32 of the first supercharger 30 of the high pressure stage, the charge cooler ( An intercooler (charge cooler) 15 is provided.

An electric fan 51 is provided immediately adjacent to the intermediate air supply cooler 50 to cool the supply air A which has been heated by being compressed by the second compressor 42 of the second supercharger 40 at the low pressure stage. A control device 60 for controlling the electric fan 51
Is provided. This control device 60 usually also serves as an engine control unit.

The control device 60 determines the operating state of the engine from the load sensor 61, the rotational speed sensor 62, and the like.
When it is necessary to enhance the cooling of the intake air that has been compressed and heated by the second compressor 42 in the low pressure stage, such as in a high-load high-speed operation region of the engine 10, control is performed to turn on the electric fan 51 to cool the intermediate supply air. It is configured to increase the cooling capacity of the vessel 50.

The cooling of the air supply cooler 15 downstream of the first compressor 32 of the first supercharger 30 is disposed in front of or behind the engine 10 and is directly operated by the engine, similarly to the known technique. It is configured to be cooled by a cooling fan (not shown) or running wind.

Further, the first supercharger 30 of the high pressure stage
An exhaust bypass passage 24 bypassing the first turbine 31 and an adjusting valve 25 provided at the inlet of the exhaust bypass passage 24, and the opening and closing of the adjusting valve 25 is controlled based on the engine speed and the like. Thereby, the first turbine 31 of the first supercharger 30 and the second supercharger 40
Of the second turbine 41 is adjusted. 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.

According to the in-line two-stage turbocharger system 1, the exhaust gas G discharged from the exhaust manifold 21 of the engine 10 is sent to the first supercharger 30 at the high pressure stage to drive the first turbine 31. And the first compressor 3 on the same axis
2 is rotated to supercharge the intake air, and the gas that has passed through the first turbine 31 is further sent to a second supercharger 40 of a low pressure stage to drive a second turbine 41, and the muffler 23
It is released to the atmosphere through.

On the other hand, after the supply air A has passed through the air cleaner 13, the second compressor 42 of the second supercharger 40 at the low pressure stage.
And then cooled by an intermediate fan cooler 50 cooled by an electric fan 51 and then cooled by a first compressor 32 of a first supercharger 30 in a high pressure stage.
Then, the pressure is further increased and the temperature is increased. After being cooled by the air supply cooler 15, the air is supplied to the intake manifold 11.

[Wastegate Valve] Next, the first supercharger 3 of the in-line two-stage turbocharger system which is a feature of the present invention.
The waste gate valve 34 provided at 0 will be described.

The wastegate valve 34 is for allowing the first turbine 31 to bypass the exhaust gas flowing for emergency opening, and as shown in FIG.
The first turbine 31 is provided.

Even if the regulating valve 25 of the exhaust bypass passage 24 fails, the first high-pressure stage of the high-pressure stage into which the exhaust gas discharged from the exhaust manifold 21 directly flows.
The turbine 31 can be protected.

The waste gate valve 34 is shown in FIGS.
The valve actuator 35 is opened and closed by a valve actuator 35 as shown in FIG. 3. The valve actuator 35 is formed to have a first air chamber 38a, a second air chamber 38b, and an internal piston 37 partitioning the first air chamber 38a and the second air chamber 38b. 37
Is a drive shaft 3 for opening and closing the waste gate valve 34.
6.

The first air chamber 38a is provided with a first intake pressure Piu upstream of the first compressor 32 so as to have a second intake pressure Piu.
The second air chamber 38 b communicates with the intake passage 12 on the upstream side of the compressor 32, and the second air chamber 38 b has a first intake pressure Pid on the downstream side of the first compressor 32, so that the intake passage on the downstream side of the first compressor 32 is formed. 12, and is configured to communicate therewith.

As shown in FIG. 4, the area S of the first pressure receiving surface 37a of the internal piston 37 on the first air chamber 38a side is determined.
a and the area S of the second pressure receiving surface 37b on the side of the second air chamber 38b.
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 are determined so that the ratio (Sa / Sb) with respect to b becomes a predetermined value Cp. Form. In this case, the area ratio (Sa / Sb) is (D ×
D) / (D × D−d × d) = Cp.

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 for pressing the internal piston 37 is provided in the first air chamber 38a. Set up. The spring force of the coil spring 37a is set so that the waste gate valve 34 can exert the minimum urging force required to return to the valve closing position when the engine is stopped.

According to the configuration of the valve actuator 35, the second (upstream) side of the first compressor 32
When the relationship between the intake pressure Piu and the first intake pressure Pid on the downstream side (outlet side) is Piu × Sa <Pid × Sb, the internal piston 37 and the drive shaft 36 move in the direction of the arrow X, and the waste gate valve 34 is opened. In addition, Pi x Sa>
When Pid × Sb, the internal piston 37 and the drive shaft 36 move in the direction of arrow Y, and the wastegate valve 3
4 is closed.

The state in which the waste gate valve 34 is opened is Piu × Sa <Pid × Sb.
(Sa / Sb) <(Pid / Piu), where the pressure ratio (Pid / Piu) of the first compressor 32 is a predetermined value Cp
This is the case.

In practical use, the friction between the internal piston 37 and the spring force of the coil spring 37a for returning the internal piston 37 to the valve closing position when the engine is stopped are related. Sb) and the pressure ratio (Pid / Piu) do not need to be exactly the same value, but are substantially the same value including the correction value at the time of operation.

An example of this dimension is as follows.
The upstream pressure Piu of the compressor 32 is about 1 in absolute pressure.
50 kPa (about 1.5 atm), downstream pressure Pid is about 30
0 kPa (3.0 atm), the upstream pressure P
iu is 100 kPa to 200 kPa and the downstream pressure Pid is often opened at 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 / Sb) is set to 2, and D = 3.
cm, Sa = 7 cm2, Sb = 3.5c
m2, and d = 2.1 cm.

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 at which the wastegate valve 34 is opened.

Therefore, according to the in-line two-stage turbocharger system having the above-described 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. The valve is opened when the pressure ratio (Pid / Piu) of the first compressor 32 exceeds a predetermined value Cp. Therefore, even if the adjustment valve 25 of the exhaust bypass passage 24 fails for some reason, the high pressure The first supercharger 30 of the stage can be protected and can be operated safely.

[0043]

As described above, according to the in-line two-stage turbocharger system according to the present invention, the wastegate valve provided in the first supercharger of the high pressure stage is provided with the waste gate valve of the first compressor of the high pressure stage. Since the on-off valve is opened and closed based on the pressure ratio between the intake pressure on the outlet side and the intake pressure on the inlet side, 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 in-line 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 diagrams 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 side sectional view.

FIG. 5 is a side sectional view showing a configuration of a valve actuator of a conventional wastegate valve.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Turbocharger system 10 Internal combustion engine 12 Intake passage 22 Exhaust passage 30 First turbocharger 31 First turbine 32 Second compressor 33 Westgate 34 Westgate 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 (2)

[Claims] A first turbine of a first supercharger and a second turbine of a second supercharger driven by exhaust gas are provided in series in an exhaust passage of an internal combustion engine from an upstream side. In a turbocharger system in which a second compressor driven by two turbines and a first compressor driven by the first turbine are arranged in two stages in series from the upstream side of an intake passage, exhaust gas flowing into the first turbine is A wastegate valve for bypassing is provided, and the wastegate valve opens and closes 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. Series 2 characterized by being formed
Stage turbocharging system. 2. The valve actuator of the waste gate valve includes 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 waste gate valve to open and close. The first air chamber is formed on the upstream side of the first compressor, the second air chamber is formed on the downstream side of the first compressor, and the first air chamber is formed on the downstream side of the first compressor. A first pressure receiving surface on the 1 air chamber side,
The area ratio with the second pressure receiving surface on the second air chamber side is formed to be the pressure ratio between the first intake pressure and the second intake pressure when the waste gate valve is opened. The in-line two-stage turbocharging system according to claim 1, wherein: