JPS64579B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an engine intake system, and more particularly to an engine intake system that supplies intake air to the engine using a turbocharger driven by the pressure of exhaust gas from the engine.

By equipping an internal combustion engine with a turbocharger, it is possible to improve its output. However, since the turbocharger turbine is driven by the pressure of the engine's exhaust gas, when the engine speed is low, the pressure of the exhaust gas is naturally low. The disadvantage is that the efficiency of the turbocharger is low, and therefore the turbocharger does not have sufficient effect when the engine speed is low. In other words, turbocharged engines generally have low low-speed torque. Therefore, the displacement is small,
Moreover, highly supercharged turbo engines cannot be used in vehicles that require a large starting force, such as dump trucks.

To compensate for the low-speed torque of an engine equipped with a turbocharger, measures have been taken to improve the efficiency of the turbocharger's compressor, to blow compressed air into the turbine when the engine speed is low, and to perform inertial supercharging. Ta. Alternatively, countermeasures have been taken, such as configuring the turbocharger to be a low-speed type by providing a wastegate. However, even with all of the above measures, sufficient low-speed torque cannot be obtained, and for vehicles such as dump trucks that require strong starting power, it is difficult to obtain sufficient low-speed torque. The engine could not be adopted.

The present invention has been made in view of these problems, and an object of the present invention is to provide an intake system for an engine that allows sufficient low-speed torque to be obtained.

In order to achieve this object, the present invention comprises a main pipe as a part of the intake pipe from the compressor of the turbocharger driven by the pressure of the engine's exhaust gas to the intake manifold of the engine. A supercharger driven by part of the output of the engine is interposed in the branch pipes connected in parallel, and a bypass pipe is provided upstream and downstream of the supercharger to communicate the branch pipes. . A switching valve is provided at the connection between the branch pipe and the main pipe and the bypass pipe, respectively, and a microcomputer that outputs a control signal to the actuator of each switching valve is provided, so that the microcomputer mounts the engine. When the vehicle starts, suddenly accelerates, or the exhaust brake is activated, the branch pipe is opened and the main pipe and the bypass pipe are closed. The switching valves are controlled to close the branch pipe and open the main pipe and the bypass pipe when it is detected that the vehicle is running.

In this way, when the microcomputer detects that the vehicle is being started or rapidly accelerated, the air discharged from the turbocharger is compressed by the supercharger and then supplied to the engine. The pressure on the outlet side of the compressor of the turbocharger becomes lower than the pressure on the inlet side due to the suction action of the compressor, thereby promoting an increase in the rotation of the compressor, thereby improving the rotation start-up characteristics of the turbocharger. Therefore, the lack of low-speed torque and the lack of rapid acceleration performance, which are characteristics of engines equipped with turbocharging, are improved, and the starting characteristics and rapid acceleration performance of the vehicle are improved. In addition, when the exhaust brake is activated, the air discharged from the turbocharger is compressed by the supercharger and then supplied to the engine, which increases engine pumping loss and causes engine damage by driving the supercharger. The load increases, which increases the braking capacity of the engine brake.

On the other hand, when the vehicle is being driven at medium to high speeds, that is, when the turbocharger is operating in a highly efficient range, the air discharged from the turbocharger bypasses the supercharger and is supplied to the engine. . At the same time, since the upstream and downstream sides of the supercharger are maintained in communication via the bypass pipe, the air compressed by the supercharger circulates through the passage formed by the branch pipe and the bypass pipe, and the supercharger is connected to the engine. to prevent it from becoming a burden. For this reason, deterioration in fuel efficiency during medium and high speed driving, which is frequently driven, is suppressed to the necessary minimum.

In this way, the turbocharger, which is driven by the energy of the engine's exhaust gas (exhaust gas pressure), is constantly driven to perform supercharging while increasing the region where the efficiency of the turbocharger is low and the pumping loss of the engine. The supercharger is substantially interposed in the intake passage from the turbocharger to the engine only in regions where the turbocharger is desirable, and the supercharger is substantially disconnected in regions where the efficiency of the turbocharger is high to avoid causing a load on the engine. As a result, starting performance and sudden acceleration performance are improved without deterioration of fuel efficiency, and the effectiveness of engine braking is improved.

Embodiments of the present invention will be described in detail below based on the drawings. The drawing shows a six-cylinder diesel engine 1 according to this embodiment, and intake air is sequentially supplied to each cylinder of the engine 1 through an intake pipe 2 and an intake manifold 3. Exhaust gas generated by the combustion explosion within the cylinder is discharged into the atmosphere through an exhaust manifold 4 and an exhaust pipe 5. Furthermore, this engine 1 is equipped with a turbocharger 6, the turbine 7 of which is connected to the exhaust pipe 5.
It is connected to the. Further, a compressor 8 of the turbocharger 6 is connected to the intake pipe 2. Furthermore, an air cleaner 9 is connected to the intake pipe 2.

A portion of the intake pipe 2 is constituted by a main pipe 10, and a roots pipe 11 constituting a branch pipe is connected in parallel to the main pipe 10. Furthermore, a bypass pipe 12 is provided in parallel to the main pipe 10 and the roots pipe 11. A super charger (hereinafter referred to as the Roots super charger) 13 using a Roots blower is installed in the Roots pipe 11, and the Roots pipe 11 upstream from the Roots super charger 13 and the Roots super charger 13 downstream from the Roots super charger 13 are interposed in the Roots pipe 11. It communicates with the bypass pipe 11. The Roots supercharger 13 has a gear 14 which meshes with a gear 16 fixed to the crankshaft 15 of the engine 1. That is, the Roots supercharger 13 is configured to be driven by a portion of the output of the engine 1. Switching valves 17 and 18 are provided at the branch between the main pipe 10 and the roots pipe 11, and these switching valves 17 and 18 are switched by air actuators 19 and 20, respectively. It's summery.

The supply of compressed air to the air actuators 19 and 20 is controlled by solenoid valves 21 and 22. Also, bypass pipe 12
A switching valve 23 is provided to close the outlet side of the switching valve 23, and the opening and closing of this switching valve 23 is also controlled by an air actuator 24. The supply of compressed air to the air actuator 24 is also controlled by the solenoid valve 25. Furthermore, the three solenoid valves 21, 2
2 and 25 are each controlled by a control signal from a microcomputer 26. The engine 1 is connected to the microcomputer 26.
The detection outputs of a rotation detection sensor 27 that detects the rotation of the exhaust brake and a brake sensor 28 that detects the operation of the exhaust brake are respectively input.

Next, turbocharged engine 1 according to the above configuration
The operation will be explained. First, when a vehicle equipped with this engine 1 starts, accelerates suddenly, or climbs a steep slope, the Roots supercharger 13 compresses the intake air to increase its volumetric efficiency. ing. That is, when the rotation detection sensor 27 detects that the rotation speed of the engine 1 is not high, the microcomputer 26 supplies a control signal to the solenoid valves 21 and 22, and supplies compressed air to the actuators 19 and 20. These valves 21 and 22 will be opened to do so. Therefore, in this case, the pair of switching valves 17 and 18 are rotated to the position shown by the chain line in the figure, thereby closing the main pipe 10 of the intake pipe 2. Furthermore, according to instructions from the microcomputer 26, the solenoid valve 2
5, and supply compressed air to the air actuator 24 from an air tank (not shown) to connect the bypass pipe 1.
2 is closed by a switching valve 23.

Therefore, in this case, the intake air that has passed through the air cleaner 9 and the compressor 8 of the turbocharger 6 passes through the roots pipe 11 of the intake pipe 2. Moreover, a Roots super charger 13 is connected to this pipe 11, and the engine 1
Since the supercharger 13 is driven by the supercharger 13 through the gears 16 and 14, the intake air is compressed by the supercharger 13. This compressed air then passes through the intake manifold 3 to the engine 1.
will be supplied to each cylinder. Moreover, at this time, more fuel is supplied from the fuel injection pump (not shown) to each cylinder of the engine 1, and mixed with the above intake air, causing a combustion explosion.
Higher output will be obtained. Also, when starting or suddenly accelerating like this, engine 1
Since the amount of air discharged from the compressor 8 of the turbocharger 6 is smaller than the required air amount, the pressure on the outlet side of the compressor 8 is lower than the pressure on the inlet side. This pressure reversal phenomenon is further doubled by the suction action of the Roots supercharger 13, causing a larger amount of air to pass through the compressor 8. The engine is driven to promote an increase in its rotational speed. Therefore, due to the synergistic effect of increasing the amount of intake air due to the suction action of the Roots supercharger 13 and promoting an increase in the rotational speed of the turbocharger 6, the energy of the exhaust gas rapidly increases, and the driving force of the turbine 7 of the turbocharger 6 rapidly increases. Become.
Therefore, the rotation start-up characteristics of the turbocharger 6 are improved, and the starting characteristics and rapid acceleration performance of the vehicle equipped with the engine 1 are improved.

In this way, in the engine 1 of this embodiment,
When the rotational speed is low and a large torque is required, the roots supercharger 13 increases the intake air filling efficiency, thereby improving the output. Therefore, even if the rotational speed of the engine 1 is low and the effect of the turbocharger 6 is not fully exerted, the low-speed torque can be supplemented by the Roots supercharger 13, and moreover, the suction effect of the Roots supercharger 13 Turbocharger 6
Since the startup of the rotation of the turbocharger 6 is promoted, the rotation of the turbocharger 6 increases in a very short time and a highly efficient supercharging operation is started. This allows for strong starting power, rapid acceleration, and the ability to climb steep slopes. Therefore, such an engine is suitable for compensating for the lack of low-speed torque of a small-displacement, highly supercharged engine.

Next, when the vehicle equipped with this engine 1 runs at medium or high speed, this is detected by the rotation detection sensor 27, and the microcomputer 26 closes the solenoid valves 21 and 22, respectively. Therefore, the supply of compressed air to the actuators 19, 20 is cut off, and the switching valves 17, 18
is rotated to the position shown by the solid line in the figure.
Therefore, in this case, intake air no longer flows into the roots pipe 11 and the bypass pipe 12.
That is, all the intake air passes through the main pipe 10. Therefore, when the rotational speed of the engine 1 is sufficiently high, the intake air is compressed by the compressor 8 of the turbocharger 6 and supplied to each cylinder of the engine 1, thereby improving the output. .

In this case, the microcomputer 26
In response to the instruction, the solenoid valve 25 is closed, and the actuator 24 switches the switching valve 23 to the position shown by the solid line in the figure. Therefore, the roots pipe 11 and the bypass pipe 12 form an endless air passage. Therefore, the air compressed by the Roots supercharger 13 circulates endlessly through the passage made up of the pipes 11 and 12, thereby recovering the work of the Roots supercharger 13. Therefore, the Roots supercharger 13, which is connected to the engine 1 through the gears 16 and 14, is prevented from being a load on the engine 1, and deterioration of fuel efficiency is kept to a minimum.

Next, when the vehicle equipped with this engine 1 applies engine brake, the engine brake sensor 28 detects this. As a result, the microcomputer 26 supplies control signals to the three solenoid valves 21, 22, and 25, respectively.
Compressed air is supplied to three actuators 19, 20, and 24. Therefore, in this case, the three switching valves 17, 18, 23 are rotated to the positions shown by chain lines in the figure, as in the case of starting. Therefore, in this case, the intake air compressed by the turbocharger 6 is further compressed by the Roots supercharger 13. In other words, the Roots supercharger 13 uses a part of the output of the engine 1 to further compress the intake air, and as a result, the Roots supercharger 13 acts as a load on the engine. Since a large amount of compressed air is supplied to the engine 1, the pumping loss of the engine 1 increases. Therefore, from this, the braking force of the engine 1 is further increased, and it becomes possible to further increase the braking force of the engine brake.

Although the present invention has been described above with reference to an illustrated embodiment,
The present invention is not limited to the above embodiments, and various modifications can be made based on the technical idea of the present invention. For example, in the above embodiment, when the Roots supercharger 13 is not used, the work of the Supercharger 13 is recovered by the Roots pipe 11 and the bypass pipe 12. A clutch may be interposed between the gear 13 and the gear 13.
Further, in the above embodiment, the roots supercharger 13 is used to mainly improve low speed torque, but it is possible to use various other superchargers instead of the roots supercharger.

As is clear from the above description, according to the present invention, in a region where the efficiency of the turbocharger is high and does not adversely affect the fuel efficiency of the engine, the supercharger is substantially removed from the passage leading from the compressor of the turbocharger to the intake manifold of the engine. While disconnecting to perform highly efficient supercharging, the supercharger path is set as an endless circulation path to sufficiently suppress the energy consumption of this supercharger, and in areas where the efficiency of the turbocharger is low, such as starting and sudden acceleration. The air discharged from the turbocharger is compressed by the supercharger and then supplied to the engine to compensate for the lack of low-speed torque and improve acceleration performance.Moreover, the suction action of the supercharger also improves the rotation start-up characteristics of the turbocharger. As a result, starting performance and rapid acceleration performance are greatly improved. Furthermore, even when the engine brake is activated, the air discharged from the turbocharger is compressed and supplied to the engine in the same way as when starting or suddenly accelerating. By feeding the compressed air into the engine, the pumping loss of the engine can also be increased, so the braking force of the engine brake can be increased.

[Brief explanation of drawings]

The drawing is a plan view showing an intake system for an engine according to an embodiment of the present invention. In addition, in the symbols used in the drawings, 1... Diesel engine, 2... Intake pipe, 6... Turbo charger, 10... Main pipe, 11... Roots pipe, 13... Roots super charger, 1
7, 18... switching valve, 19, 20... air actuator.

Claims (1)

[Claims] 1. A main pipe constituting a part of the intake pipe from the compressor of the turbocharger driven by the pressure of the engine's exhaust gas to the intake manifold of the engine, a branch pipe connected in parallel to the main pipe, and the branch pipe. a supercharger installed in the engine and driven by a part of the output of the engine; a bypass pipe that connects the branch pipe upstream and downstream of the supercharger; and a connection between the branch pipe and the main pipe. and a switching valve provided in the bypass pipe, and a microcomputer that outputs a control signal to the actuator of each of the switching valves, and detects the start, sudden acceleration, and operation of the exhaust brake of a vehicle equipped with the engine. When the branch pipe is opened and the main pipe and the bypass pipe are closed, when it is detected that the vehicle equipped with the engine is traveling at medium or high speed, the branch pipe is closed and the main pipe is closed. and an intake system for an engine, characterized in that each of the switching valves is controlled to switch so as to open the bypass pipe.