JPH0363652B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to a supercharger equipped with a supercharger that can reduce the noise generated in the intake passage when operating the exhaust brake and also ensure sufficient braking performance. It concerns diesel engines.

[Conventional technology]

Since a diesel engine does not have a throttle valve in its intake passage, the amount of intake air becomes excessive during idling, etc., which increases compression resistance of the engine and tends to cause torque fluctuations. This torque fluctuation causes the engine to vibrate and generate vibration noise. Therefore, an intake shutter is installed in the intake passage to open and close the intake passage, and when idling, the intake shutter is throttled to reduce the amount of intake air. Therefore, structures are known that aim to reduce the amount of engine vibration and vibration noise.

In addition, diesel engines such as those mentioned above have
Furthermore, an exhaust brake is often provided, which increases exhaust pressure and suppresses engine rotation by interposing an exhaust shutter in the exhaust passage and closing the exhaust shutter. In a diesel engine that has such an exhaust brake, when the exhaust brake is operated, the intake shutter is also throttled in the same way as when idling, but when the intake shutter is fully closed, the air is sucked into the combustion chamber of the engine. Due to the lack of fresh air, the pressure within the combustion chamber cannot rise sufficiently, leading to problems such as deterioration of the braking performance of the exhaust brake. Therefore, conventionally, in order to prevent deterioration of brake performance, the intake shutter was not fully closed when operating the exhaust brake, but was kept slightly open so that fresh air could be sufficiently sucked into the combustion chamber. It is customary to

On the other hand, for example, in Japanese Patent Application Laid-open No. 56-101032, a bypass passage that bypasses the intake shutter as described above is connected to the intake passage, and when the exhaust brake is operated, the intake shutter is fully closed and the bypass passage is connected to the intake shutter. A bypass passage is opened by operating an intervening opening/closing control means such as a solenoid valve, and fresh air is introduced through the bypass passage, thereby suppressing deterioration of exhaust brake performance.

However, when the intake shutter is not fully closed when the exhaust brake is operated as described above, but is kept slightly open to supply fresh air to the combustion chamber, there is a problem in that noise is generated. In other words,
When the exhaust brake is operated as described above, noise (hereinafter referred to as blowback sound) is generated when the airflow flowing backward from the combustion chamber to the intake passage (hereinafter referred to as blowback airflow) passes through the narrow air passage within the intake passage. . In the above case, since the passage at the intake shutter is narrowed,
Blowback noise is generated at this location, and this results in leakage to the outside from the entrance of the intake passage.

On the other hand, in the configuration disclosed in Japanese Patent Application Laid-Open No. 56-101032, since the intake shutter is fully closed when the exhaust brake is operated, no noise is generated at this location. Further, at this time, the blowback airflow is guided to a bypass passage opened to introduce fresh air.
Therefore, by providing the bypass passage with a defined shape so as not to generate noise depending on the airflow at this time, a structure that can maintain braking performance when operating the exhaust brake and at the same time suppress blowback noise. It is possible to do so.

[Problem to be solved by the invention]

However, unlike the above-mentioned conventional example, in a turbocharged diesel engine in which a supercharger is interposed in the intake passage, blowback noise cannot be sufficiently suppressed with a configuration in which a bypass passage that simply bypasses the intake shutter is provided. However, there is a problem in that it tends to generate a lot of noise. In other words, if a bypass passage that bypasses the intake shutter is provided downstream of the supercharger based on the configuration of JP-A-56-101032, fresh air can be filled using the supercharger. It is expected to be more effective in terms of maintaining braking force, and if we assume that the blowback sound propagates within the intake passage and leaks out from the entrance of the intake passage, it will be possible to increase the effectiveness of the It is therefore thought that the propagation of sound waves is suppressed and noise is further reduced. However, in reality, rather than the supercharger suppressing sound wave propagation, the supercharger itself becomes a source of noise. In other words, when the blowback airflow after passing through the bypass passage passes through a supercharger or an intercooler connected with the supercharger, there is a gap between the casing of the supercharger and the blower, and the honeycomb-shaped airflow of the intercooler. The air passes through narrow passages such as between cores, and as it passes through these narrow passages, new noise is generated.As a result, a large amount of noise leaks out from the entrance of the intake passage.

The present invention has been made in view of the above-mentioned conventional problems, and its object is to suppress noise generation in the intake passage of a diesel engine with a supercharger without impairing brake performance when operating the exhaust brake. Our goal is to provide the following.

[Means to solve the problem]

In order to achieve the above object, the turbocharged diesel engine of the present invention has an air cleaner, a supercharger, and an intake shutter for opening and closing this intake passage sequentially interposed in the intake passage from the upstream side, and also has the above-mentioned features. A bypass passage that bypasses the intake shutter and is equipped with opening/closing control means is connected to the intake passage, while an exhaust passage is provided with an exhaust shutter for opening and closing the exhaust passage, and the intake shutter is opened in synchronization with the valve opening of the exhaust shutter. The turbocharged diesel engine is configured to close the valve and open the bypass passage by operating the opening/closing control means, wherein the bypass passage bypasses the intake shutter and the supercharger. , the upstream end is connected to a portion of the intake passage between the air cleaner and the supercharger.

[Effect]

With the above configuration, fresh air can be sufficiently sucked into the combustion chamber through the bypass passage when the exhaust brake is operated, so the internal pressure of the combustion chamber can be raised sufficiently to ensure the required braking performance of the exhaust brake. can. In addition, the blowback airflow from the combustion chamber is guided to a bypass passage where blowback noise is less likely to occur, and the upstream end of this bypass passage is connected to a portion of the intake passage between the air cleaner and the supercharger. Therefore, the above airflow does not pass through the supercharger, and therefore,
There is no new blowback sound generated by the supercharger. As a result, exhaust braking performance can be ensured, and the generation of noise can be suppressed.

〔Example〕

An embodiment of the present invention will be described below based on FIG.

Intake passage 2 of diesel engine 1 with supercharger
is provided with an air cleaner 3, a supercharger 4, an intercooler 5, and an intake shutter 6 for opening and closing the intake passage 2, while an exhaust shutter 8 for opening and closing the exhaust passage 7 is provided.

These intake shutters 6 and exhaust shutters 8 are driven to open and close by respective power chambers 9 and 10 connected to a vacuum source (not shown). The pressure receiving chambers 9a, 10a of each power chamber 9, 10 have an intake shutter 6 facing the vacuum pressure of the pressure receiving chambers 9a, 10a.
Alternatively, springs 9b and 10b are inserted to bias the exhaust shutter 8 to the open position, and each pressure receiving chamber 9a,
10a are electromagnetically operated three-way valves 11 and 1, respectively;
2, the vacuum source is switched and connected to the atmosphere. These three-way valves 11 and 12 are configured to simultaneously connect the respective pressure receiving chambers 9a and 10a to a vacuum source based on the driver's operation of the exhaust brake via a control circuit (not shown).

The intake passage 2 is provided with a bypass passage 13 that bypasses the supercharger 4, intercooler 5, and intake shutter 6 from downstream of the air cleaner 3, and an opening/closing control means for controlling opening/closing of the bypass passage 13 is provided in the middle of the bypass passage 13. Fourteen electromagnetic on-off valves 15 are provided. The opening/closing control means 14 is composed of the electromagnetic opening/closing valve 15 and a control circuit (not shown) that controls the operation of the electromagnetic opening/closing valve 15. This control circuit closes the intake shutter 6 and the exhaust shutter 8 based on the driver's exhaust brake operation. The electromagnetic on-off valve 15 is configured to open in synchronization with the valve.

The bypass passage 13 is formed with an orifice 16 for adjusting the blowback sound volume to set the volume and frequency of the blowback sound generated inside the bypass passage to a frequency that is not harsh on the ears.

In the above configuration, when the driver operates the exhaust brake, the exhaust shutter 8 is closed, and the internal pressure of the exhaust passage 7 on the combustion chamber side increases, thereby suppressing the rotation of the engine. This blowback into the intake passage 2 due to the closing of the exhaust shutter 8 is prevented by the intake shutter 6, which is fully closed in synchronization with the exhaust shutter 8. Thereby, generation of blowback noise due to the intake shutter 6 can be completely prevented. On the other hand, since the electromagnetic on-off valve 15 is opened in synchronization with the closing of the intake shutter 6 and the exhaust shutter 8, the blowback from the combustion chamber is directed to the bypass passage 13. The frequency of the blowback sound from the bypass passage 13 is set by the orifice 16 to a frequency that is not harsh on the ears, and its volume is limited.
Almost no problem. Furthermore, since the upstream end of this bypass passage 13 is connected to a portion of the intake passage 2 between the air cleaner 3 and the supercharger 4, the blowback airflow from the combustion chamber is directed to the intercooler 5 and the supercharger 4. The flow also bypasses the air and flows towards the air cleaner 3. Therefore, the airflow does not pass through the intercooler 5 and the supercharger 4, so the intercooler 5 and the supercharger 4
does not become a new source of noise, and as a result, in a diesel engine with a supercharger, the noise when operating the exhaust brake can be made sufficiently small. In addition, since a sufficient amount of fresh air can be sucked into the combustion chamber via the bypass passage 13,
The internal pressure of the combustion chamber can be made sufficiently high, and the desired braking performance of the exhaust brake can be ensured.

〔Effect of the invention〕

As described above, in the supercharged diesel engine of the present invention, the bypass passage connected to the intake passage bypasses the intake shutter and the supercharger, so that the upstream end is connected to the air cleaner and the supercharger in the intake passage. The structure is connected to the part between the two.

As a result, when operating the exhaust brake, fresh air can be sufficiently sucked into the combustion chamber through the bypass passage, so that the internal pressure of the combustion chamber can be raised sufficiently to ensure the required braking performance of the exhaust brake. , the airflow blown back from the combustion chamber is guided into the bypass passage, and since this airflow does not pass through the turbocharger, the turbocharger does not become a source of noise, thereby reducing noise from the intake passage. This has the effect of reducing the

[Brief explanation of drawings]

FIG. 1 is a block diagram schematically showing essential parts of an intake and exhaust system of a supercharged diesel engine, showing one embodiment of the present invention. 1 is a diesel engine with a supercharger, 2 is an intake passage, 3 is an air cleaner, 4 is a supercharger, 5 is an intercooler, 6 is an intake shutter, 7 is an exhaust passage, 8
13 is an exhaust shutter, 13 is a bypass passage, and 14 is an opening/closing control means.

Claims (1)

[Scope of Claims] 1. An air cleaner, a supercharger, and an intake shutter for opening and closing the intake passage are sequentially interposed in the intake passage from the upstream side, and also includes an opening/closing control means that bypasses the intake shutter. A bypass passage is connected to the intake passage, and an exhaust shutter for opening and closing the exhaust passage is provided, and the intake shutter is closed in synchronization with the closing of the exhaust shutter, and the opening/closing control means In a diesel engine with a supercharger that opens the above-mentioned bypass passage upon operation, the above-mentioned bypass passage has an upstream end that connects the air cleaner and the supercharger in the intake passage in order to bypass the above-mentioned intake shutter and the supercharger. A diesel engine with a supercharger characterized by being connected to a part between.