JPH0579339A - Exhaust device of engine with supercharger - Google Patents

Abstract

PURPOSE:To perform proper supercharging pressure control from a low intake air quantity range to a high intake air quantity range, by rationalizing fluid quantity characteristics of a waste gate valve and an exhaust bypass valve. CONSTITUTION:In an engine with supercharger in which supercharging pressure control is performed by opening control of an exhaust bypass valve 41 at the time of supercharging operation of only a main turbocharger 7, and the supercharging pressure control is performed by the opening control of a waste gate valve 31 at the time of supercharging operation of both the main turbocharger 7 and an auxiliary turbocharger 8, the diameter of an exhaust bypass port on which the exhaust bypass valve 41 sits is set smaller than the diameter of a waste gate port on which the waste gate valve 31 sits.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a main turbocharger and a sub-turbocharger, supercharges only the main turbocharger in a low intake air amount range, and operates both turbochargers in a high intake air amount range. The present invention relates to an exhaust system for a supercharged engine that supercharges with both turbochargers, a so-called 2-way twin turbo engine.

[0002]

2. Description of the Related Art An engine main body is provided with two main and sub turbochargers in parallel, and in the low intake air amount range, only the main turbocharger is operated to make one turbocharger. In the high intake air amount range, both turbochargers are operated. There is known a supercharged engine that employs a so-called 2-way turbo system that operates a charger.

The structure of an engine with a supercharger of this type is as shown in FIG. 9, for example. A main turbocharger (T / C-1) 92 and a sub turbocharger (T / C-2) 93 are provided in parallel with the engine body 91. The intake and exhaust systems connected to the sub turbocharger 93 are provided with an intake switching valve 94 and an exhaust switching valve 95, respectively, and an intake bypass valve 96 is provided in an intake bypass passage 97 that bypasses the compressor of the sub turbocharger 93. It is provided. In the low intake air amount range, the intake switching valve 94,
By fully closing both the exhaust switching valves 95, only the main turbocharger 92 is supercharged, and both switching valves 94 and 95 are fully opened in the high intake air amount range, and the intake bypass valve 96 is closed. Deputy turbocharger 93
Also, the turbocharger can be operated by performing supercharging operation. When shifting from the low intake air amount region to the high intake air amount region, the intake switching valve 95 and the exhaust switching valve 9
4 is closed, the exhaust bypass valve 98 is controlled to be small open, and the intake bypass valve 96 is closed to increase the running speed of the auxiliary turbocharger 93, thereby making the switching of the turbocharger smoother (at the time of switching). It is possible to perform small shocks.

As a prior art related to the 2-way twin turbo, the opening of the exhaust bypass valve is controlled when one turbocharger is used, and the opening of the wastegate valve is controlled when two turbochargers are used, so that the supercharging pressure becomes a target value. A control method is known (Japanese Patent Laid-Open No. 2-1981).
No. 7). In a two-way twin turbo engine, a wastegate valve is usually provided on the main turbocharger side and an exhaust bypass valve is provided on the sub-turbocharger side. The diameter of the waste gate port on which the waste gate valve is seated and the diameter of the exhaust bypass port on which the exhaust bypass valve is seated are set to be the same.

[0005]

However, the diameter of the waste gate port on which the waste gate valve is seated is set so that the boost pressure can be controlled even when the intake air amount is maximized. If the port diameter is directly applied to the exhaust bypass port, the following problems will occur.

The intake air amount during supercharging pressure control by controlling the opening degree of the exhaust bypass valve is about 1/2 of the intake air amount during supercharging pressure control by controlling the opening degree of the wastegate valve. Therefore, if the diameter of the exhaust bypass port is set to a large diameter so as to cover the low intake air amount region to the high intake air amount region, the control supercharging pressure hunts (disturbs). Further, if the diameter of the exhaust bypass port is too large, the flow rate of the exhaust gas changes greatly due to the opening and closing of the exhaust bypass valve, making it difficult to accurately control the boost pressure. Further, if the exhaust bypass port diameter is too large, it will be difficult to smoothly rotate the auxiliary turbocharger in the forward run, which is a problem.

The present invention pays attention to the above problems and optimizes the flow characteristics of the wastegate valve and the exhaust bypass valve,
An object of the present invention is to provide an exhaust system for an engine with a supercharger, which can perform excellent supercharging pressure control from a low intake air amount region to a high intake air amount region.

[0008]

According to the present invention, an exhaust system for a supercharged engine according to the present invention includes a main turbocharger and a sub-turbocharger, and only the main turbocharger has a supercharger during supercharging. While controlling the supply pressure,
When switching from supercharging operation of only the main turbocharger to supercharging operation by both turbochargers, an exhaust bypass valve that causes the auxiliary turbocharger to run in the running direction and control of supercharging pressure during supercharging by both turbochargers In a supercharged engine with a wastegate valve, the diameter of an exhaust bypass port on which the exhaust bypass valve is seated is set to be smaller than the diameter of the wastegate port on which the wastegate valve is seated. ..

[0009]

In the exhaust system for an engine with a supercharger configured as described above, the exhaust bypass port diameter is smaller than the waste gate port diameter, so the flow rate of exhaust gas accompanying opening and closing of the exhaust bypass valve is reduced. The change can be made small, and the supercharging pressure can be controlled with high accuracy, and the auxiliary turbocharger can smoothly perform the forward rotation. Also,
By making the diameter of the exhaust bypass port small, it becomes possible to sufficiently control the flow rate of the exhaust gas bypassed even in the low intake air amount range, and hunting of the control boost pressure is prevented.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an exhaust system for a supercharged engine according to the present invention will be described below with reference to the drawings.
1 to 8 show an embodiment of the present invention, and particularly show a case where the present invention is applied to a 6-cylinder engine mounted on a vehicle. In FIG. 6, 1 is an engine, 2 is a surge tank, and 3 is an exhaust manifold. The exhaust manifold 3 includes the cylinder groups # 1 to # 3 and the cylinder groups # 4 to #, which do not cause exhaust interference.
It is assembled into two of the 6-cylinder group, and the assembly portion is communicated by the communication passage 3a. Reference numerals 7 and 8 denote a main turbocharger and a sub turbocharger arranged in parallel with each other. Turbine 7a, 8a of turbocharger 7, 8 respectively
Is connected to the collecting portion of the exhaust manifold 3, and the compressors 7b and 8b are connected to the surge tank 2 via the intercooler 6 and the throttle valve 4.

The main turbocharger 7 is operated from the low intake air amount region to the high intake air amount region, and the sub turbocharger 8 is stopped in the low intake air amount region. An exhaust switching valve 17 is provided downstream of the turbine 8a of the auxiliary turbocharger 8 and an intake switching valve 18 is provided downstream of the compressor 8b in order to enable the sub turbocharger 8 to operate and stop.
When both the intake and exhaust switching valves 18 and 17 are open, both turbochargers 7 and 8 are operated. The exhaust bypass passage 40 is provided between the downstream side of the turbine 8a of the sub turbocharger 8 and the downstream side of the turbine 7a of the main turbocharger 7.
It is possible to communicate via. Exhaust bypass passage 40
An exhaust bypass valve 41 that opens and closes the exhaust bypass passage 40 is provided in the. The exhaust bypass valve 41 is adapted to be opened and closed by a diaphragm type actuator 42.

In the intake passage of the auxiliary turbocharger 8 which is stopped in the low intake air amount range, one turbocharger to two
In order to facilitate the switching to the individual turbocharger, an intake bypass passage 13 that connects the upstream side of the compressor 7b and the downstream side of the compressor 8b, and an intake bypass valve 33 disposed in the middle of the intake bypass passage 13 are provided. .. The intake bypass valve 33 is a diaphragm type actuator 1.
It is opened and closed by 0. A check valve 12 is provided in a bypass passage that connects upstream and downstream of the intake switching valve 18, and when the intake switching valve 18 is closed, the compressor outlet pressure on the side of the auxiliary turbocharger 8 is the main turbocharger 7.
When larger than the side, air is allowed to flow from the upstream side to the downstream side. In the figure, 14 indicates an intake passage on the compressor outlet side, and 15 indicates an intake passage on the compressor inlet side.

The intake passage 15 is connected to an air cleaner 23 via an air flow meter 24. The front pipe 20 forming the exhaust passage is connected to the exhaust muffler via the exhaust gas catalyst 21. The intake switching valve 18 is opened and closed by the actuator 11, and the exhaust switching valve 17 is opened and closed by the diaphragm actuator 16. The waste gate valve 31 is adapted to be opened and closed by the actuator 9.

Actuators 9, 10, 11, 16, 4
2 is activated by the introduction of supercharging pressure or negative pressure. Each actuator 9, 10, 11, 16,
In order to selectively switch the supercharging pressure or the negative pressure from the positive pressure tank 51 and the atmospheric pressure from the downstream of the air flow meter 24, the first, second, third, fourth, fifth, and 42 are shown. Sixth
Solenoid valves 25, 26, 27, 28, 32 and 44 are connected. Each solenoid valve 25, 26, 27, 28, 32, 4
Switching of No. 4 is performed according to a command from the engine control computer 29. The second solenoid valve 26
A check valve 45 which allows only one flow of the negative pressure is provided in the passage for introducing the negative pressure into the passage.

When the first solenoid valve 25 is turned on, the intake switching valve 1
Actuating the actuator 11 so that 8 is fully opened,
When OFF, the actuator 11 is operated so that the intake switching valve 18 is fully closed. When the fourth solenoid valve 28 is turned on, the actuator 16 is operated so as to fully open the exhaust gas switching valve 17, and when it is turned off, the actuator 16 is operated so as to fully close the exhaust gas switching valve 17. O of the third solenoid valve 27
N operates the actuator 10 so as to fully close the intake bypass valve 33, and OFF operates the actuator 10 so as to fully open the intake bypass valve 33.

A fifth step of bleeding the supercharging pressure applied to the actuator 42 for operating the exhaust bypass valve 41 to the atmosphere
The solenoid valve 32 is subjected to duty control instead of ON / OFF control. Similarly, the sixth solenoid valve 44 that bleeds the boost pressure applied to the actuator 9 that operates the wastegate valve 31 to the atmosphere is not ON / OFF controlled but is duty controlled. As is well known, the duty control is to control the energization time by the duty value, and the average current is variably controlled in an analog manner by digitally changing the ratio of energization and non-energization. The duty value is the ratio of the energization time to the time of one cycle, and when the energization time in one cycle is A and the non-energization time is B, the duty value = A / (A + B) × 100.
It is represented by (%).

The opening degree of the exhaust bypass valve 41 is controlled by changing the bleed amount (leak amount) of the supercharged air introduced into the diaphragm chamber 42a of the actuator 42 to the atmosphere by controlling the duty of the fifth solenoid valve 32. It is variable. The opening degree of the waste gate valve 31 is set so that the bleed amount (leak amount) of the supercharged air introduced into the diaphragm chamber 9a of the actuator 9 to the atmosphere is determined by the sixth solenoid valve 4.
It can be changed by changing the duty control of No. 4.

As shown in FIG. 7, the waste gate valve 31 is composed of a swing arm valve that opens downstream of the exhaust gas. A diaphragm chamber 9a is formed in the diaphragm actuator 9 connected to the waste gate valve 31. The diaphragm chamber 9a is a diaphragm 9
A diaphragm 9c is provided in the chamber 9b on the opposite side of the diaphragm chamber 9a.
A spring 9d that presses to the side is stored. The supercharging pressure is introduced into the diaphragm chamber 9a from the downstream side of the compressor 7b. The supercharged air introduced into the diaphragm chamber 9a is leaked to the atmosphere side via the sixth electromagnetic valve 44 as described above.

During engine operation, exhaust gas Pa of exhaust gas acts on the valve body 31a of the wastegate valve 31, and the force exerted on the valve body 31a by the exhaust pressure Pa and the wastegate valve 31 are connected. The wastegate valve 31 is opened when the sum of the force generated by the supercharging pressure acting in the diaphragm chamber 9a of the diaphragm actuator 9 exceeds a certain value. The closing operation of the waste gate valve 31 is performed by the urging force of the spring 9d.

As shown in FIG. 8, the exhaust bypass valve 41 is composed of a swing arm valve which opens to the exhaust downstream side. A diaphragm chamber 42a is formed in the diaphragm actuator 42 connected to the exhaust bypass valve 41. The diaphragm chamber 42a is a diaphragm 42c.
A chamber 42b on the opposite side of the diaphragm chamber 42a accommodates a spring 42d for pressing the diaphragm 42c toward the diaphragm chamber 42a. A supercharging pressure is introduced from the positive pressure tank 51 into the diaphragm chamber 42a. Diaphragm chamber 42
The supercharged air led to a is leaked to the atmosphere side via the fifth solenoid valve 32.

During engine operation, exhaust gas exhaust pressure acts on the valve body 41a of the exhaust bypass valve 41, and the force exerted on the valve body 41a by this exhaust pressure Pb is connected to the exhaust bypass valve 41. The exhaust bypass valve 41 is opened when the sum of the force generated by the supercharging pressure acting in the diaphragm chamber 42a of the diaphragm actuator 42 exceeds a certain value. The opening operation of the exhaust bypass valve 41 is performed by the urging force of the spring 42d.

Engine control computer 29
Is electrically connected to various operating condition detection sensors of the engine and receives signals from the various sensors. The engine operating condition detection sensor includes an intake pipe pressure sensor 30, a throttle opening sensor 5, an air flow meter 24 as an intake air amount measuring sensor, an engine speed sensor 50, and an oxygen sensor 19. The engine control computer 29 includes a central processor unit (CPU) for calculation, a read only memory (ROM) which is a read-only memory, a random access memory (RAM) for temporary storage, and an input / output interface (I).
/ O interface) and an A / D converter for converting analog signals from various sensors into digital quantities.

In this embodiment, the intake bypass valve 18 is provided to add the function of suppressing the rise of the intake air temperature by the compressor 8b during the approach rotation, but it is necessary for the climbing run that requires a long approach rotation time. When the vehicle hardly travels, the intake bypass valve 18 does not have to be provided and the device can be simplified.

FIG. 5 shows an assembled state of the main and sub turbochargers 7 and 8 in the engine 1 mounted on the vehicle. The main turbocharger 7 includes a compressor housing 61 that houses a compressor 7b, and a turbine 7a.
And a center housing 63 that connects the two housings 61, 62. The sub turbocharger 8 includes a compressor housing 71 that houses a compressor 8b, and a turbine 8a.
And a center housing 73 that connects the two housings 71, 72.

As shown in FIG. 1, the auxiliary turbocharger 8
An exhaust bypass port 72a on which the valve body 41a of the exhaust bypass valve 41 is seated is formed in a turbine housing 72 that houses the turbine 8a. As shown in FIG. 4, the wastegate valve 31 is provided in the turbine housing 62 that houses the turbine 7 a of the main turbocharger 7.
Is formed with a waste gate port 62a on which the valve body 31a is seated. Exhaust bypass port 72a diameter D
₂ is set to be smaller than the diameter D _{1 of the} wastegate port 62a.

Next, the operation of this embodiment will be described. In the high intake air amount region, both the intake switching valve 18 and the exhaust switching valve 17 are opened and the intake bypass valve 10 is closed. As a result, the two turbochargers 7 and 8 are driven, a sufficient amount of supercharged air is obtained, and the output is improved. Both the intake switching valve 18 and the exhaust switching valve 17 are closed and the intake bypass valve 33 is opened in the low speed range and at the time of high load. As a result, only one turbocharger 7 is driven. The reason why one turbocharger is used in the low intake air amount region is that the one turbocharger supercharging characteristic is superior to the two turbocharger supercharging characteristic in the low intake air amount region. By using one turbocharger, the boost pressure and torque rise faster, and the response becomes faster.

When shifting from the low intake air amount region to the high intake air amount region, that is, when switching from one turbocharger operation to two turbocharger operation, the intake switching valve 18
When the exhaust switching valve 17 is closed, the exhaust bypass valve 41 is controlled to be small open by duty control, and the intake bypass valve 33 is closed to increase the running speed of the auxiliary turbocharger 8 to switch the turbocharger. It becomes possible to carry out more smoothly (small shock when switching).

The diameter D ₁ of the waste gate port 62a on which the valve body 31a of the waste gate valve 31 is seated must be set so that the boost pressure can be controlled with the maximum intake air amount. Therefore, when the diameter D ₂ of the exhaust bypass port 72a is set to a large diameter D ₁ like the wastegate port 62a, the flow rate of the exhaust gas cannot be controlled sufficiently, resulting in hunting of the control boost pressure. If the diameter D ₂ of the exhaust bypass port 72a is too large, the flow rate of the exhaust gas changes greatly when the exhaust bypass valve 41 is opened and closed, which makes it difficult to control the boost pressure accurately.

In this embodiment, the exhaust bypass port 72a
Since the diameter D ₂ of the exhaust gas is set to be smaller than the diameter D _{1 of the} waste gate port 62a, the change in the flow rate of the exhaust gas due to the opening / closing of the exhaust bypass valve 41 can be reduced. Therefore, the flow rate of the exhaust gas to be bypassed can be accurately controlled, and highly accurate supercharging pressure control can be performed. In addition, since the change in the flow rate of exhaust gas can be made small, the auxiliary turbocharger 8 can smoothly perform the approach rotation at the time of switching from the one turbocharger to the two turbocharger.

Thus, the waste gate port 62a
By appropriately setting the diameters of the exhaust bypass port 72a and the exhaust bypass port 72a, an optimal flow passage cross-sectional area can be obtained, and excellent supercharging pressure control can be achieved both in one turbocharger and in two turbochargers with a large intake air amount. Can be performed.

[0031]

According to the present invention, since the diameter of the exhaust bypass port on which the exhaust bypass valve is seated is set smaller than the diameter of the wastegate port on which the wastegate valve is seated, only the main turbocharger is supercharged. In the low intake air volume range that operates, the flow rate of exhaust gas bypassed by the exhaust bypass valve can be accurately controlled,
Moreover, it is possible to reduce the change in the flow rate of exhaust gas due to the opening and closing of the exhaust bypass valve. Therefore, hunting of the control supercharging pressure can be prevented, and supercharging pressure control with high accuracy can be performed.

Further, since the flow rate of the exhaust gas bypassed by the exhaust bypass valve is accurately controlled, the auxiliary turbocharger can be smoothly rotated in the approach run when switching from one turbocharger to two turbochargers. You can

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a turbine housing of a main turbocharger in an exhaust system for a supercharged engine according to an embodiment of the present invention.

FIG. 2 is a front view of FIG.

FIG. 3 is a side view of FIG.

FIG. 4 is a cross-sectional view of a turbine housing of a sub turbocharger in an exhaust system for a supercharged engine according to an embodiment of the present invention.

FIG. 5 is a front view showing a state where the turbocharger of FIGS. 1 and 4 is assembled to an engine.

FIG. 6 is a system diagram of an engine with a supercharger according to an embodiment of the present invention.

7 is an enlarged cross-sectional view near the waste gate valve in the apparatus of FIG.

8 is an enlarged sectional view of the vicinity of the exhaust bypass valve in the device of FIG.

FIG. 9 is a schematic system diagram of a conventional engine with a supercharger.

[Explanation of symbols]

1 Engine 4 Throttle Valve 7 Main Turbocharger 8 Sub Turbocharger 17 Exhaust Changeover Valve 18 Intake Changeover Valve 29 Engine Control Computer 31 Westgate Valve 41 Exhaust Bypass Valve 62 Main Turbocharger Turbine Housing 62a Westgate Port 72 Subturbocharger Turbine Housing 72a Exhaust bypass port D ₁ Wastegate port diameter D ₂ Exhaust bypass port diameter

Claims (1)

[Claims] 1. A main turbocharger and a sub-turbocharger are provided to control the supercharging pressure at the time of supercharging of only the main turbocharger, and both turbochargers are operated by the supercharging operation of only the main turbocharger. In an engine with a supercharger equipped with an exhaust bypass valve that causes the sub-turbocharger to perform a boost rotation when switching to supercharging operation, and a wastegate valve that controls the supercharging pressure during supercharging by both turbochargers An exhaust device for a supercharged engine, wherein a diameter of an exhaust bypass port on which the exhaust bypass valve is seated is set to be smaller than a diameter of a wastegate port on which the waste gate valve is seated.