JPH04194318A - Suction device for engine - Google Patents

Abstract

PURPOSE:To stabilize the state of operation by connecting lower ends of a bypass passage bypassing an inter-cooler to suction ports causing swirls in the combustion chamber. CONSTITUTION:During a low-revolution/low-load operation period in which a temperature rise in the combustion chamber is small in the compression stroke, suction is performed with the sucked air passing through a bypass passage 16 and being not cooled by an inter-cooler 14. Therefore, the fuel gasification and atomization are promoted utilizing a temperature rise in sucked air occurring as a result of its passing through a supercharger 13. Further, since downstream ends of the bypass passage 16 are connected to swirl ports 3, the fuel gasification and atomization are further promoted by swirls S caused at the swirl ports 3. Since, in particular, the suction valves opening and closing the swirl ports 3 are closed with a delay in response to the suction, the fuel gasification and atomization performance are secured through the actions of the swirls S against the small temperature rise in the combustion chamber during the compression stroke. The operational state during a low-revolution/ low-load operation period can be stabilized in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to improvement of an intake passage of an engine.

(Prior art) For engines equipped with a supercharger in the intake system, it is customary to place an intercooler downstream of the supercharger to lower the supercharging temperature and thereby improve charging efficiency. be done.

On the other hand, Japanese Patent Application Laid-Open No. 63-263220 discloses a supercharger,
An engine is disclosed in which a bypass passage that bypasses the intercooler is attached to a main intake passage in which an intercooler is disposed, and air is taken through the bypass passage during low rotation and low load operation. According to this, during the compression stroke, during low-speed, low-load operation where the temperature rise in the combustion chamber is small, intake air is carried out without being cooled by the intercooler, making it possible to ensure the vaporization and atomization of the fuel. This has the advantage of stable operating conditions.

(Problems to be Solved by the Invention) The purpose of the present invention is to further actively stabilize the operating condition during low rotation and low load operation on the premise of such an engine, that is, an engine equipped with the above-mentioned bypass passage. The purpose of the present invention is to provide an intake system for an engine with a

(Structure of the Invention) In order to achieve this technical problem, in the present invention, a vortex is created in the combustion chamber at the downstream end of the bypass passage, separate from the main intake port to which the main intake passage is connected. In addition to being connected to the vortex generation intake port, the main intake passage in which an intercooler etc. is disposed has a main intake passage located downstream of the part to which the upstream end of the bypass passage is connected and upstream of the intercooler. The structure is characterized by the provision of an on-off valve that is closed during low-speed, low-load operation and opened during other operating ranges.

(Example) Hereinafter, an example of the present invention will be described based on the attached drawings.

In Fig. 1, 1 is the engine body;
is an in-line four-cylinder reciprocating engine with four cylinders 2 arranged in series. Each cylinder 2 has two intake ports 3.4 facing its combustion chamber (not shown) and one exhaust port 6 connected to an exhaust passage 5.
Among the two intake ports 3.4, the first intake port 3 is a swirl port that generates a lateral vortex (swirl S) in the combustion chamber. And these intake ports 3.
4 are each provided with a known intake valve (not shown),
The exhaust port 6 is provided with an exhaust valve (not shown), and these intake valves and exhaust valves are opened and closed at predetermined timings synchronized with the rotation of the engine output shaft. This valve timing will be explained in detail later.

The intake system 10 of the engine main body 1 has a main intake passage 11 connected to the second intake port 4. In this main intake passage 11, a throttle valve 12, a supercharger 13 mechanically driven by the engine body 1, an intercooler 14, etc. are arranged in order from the upstream side to the downstream side.
In this main intake passage 11, a downstream part of the intercooler 14 is connected to the second intake port 4 (main intake port).
It is constituted by an independent intake passage 15 that is continuous with the intake passage.

The intake system 10 also includes a bypass passage 16 that bypasses the intercooler 14.

That is, the upstream end of the bypass passage 16 is connected to the main intake passage 11 between the supercharger 13 and the intercooler 14, and the downstream part of the bypass passage 16 is connected to a branch bypass branched for each cylinder 2. The downstream side of these branch bypass passages 17 is connected to the swirl port 3 of each corresponding cylinder 2.

A first on-off valve 18 and a second on-off valve 19 are provided in the main intake passage 11 and the bypass passage 16, respectively, and basically, the main intake passage 11 and the bypass passage are connected depending on the operating state. It is designed to be used as an alternative to 16. That is, the first
The on-off valve 18 is provided downstream of the region to which the upstream end of the bypass passage 16 is connected and upstream of the intercooler 14 . As shown in FIG. 2, when the first on-off valve 18 is opened, the second on-off valve 19 is basically closed, and the intake air is transferred to the intercooler 14.
On the other hand, when the first on-off valve 18 is closed, the second on-off valve 19 is opened, and the intake air passes through the bypass passage 16 without passing through the intercooler 14 and is combusted from the swirl port 3. supplied to the chamber. These first and second on-off valves 18.19 are operated by actuators 20.2.
1 performs opening and closing operations, and these actuators 2o and 21 are controlled based on signals from a control U.

In FIG. 1, reference numerals 22 and 23 indicate sensors, and the sensor 22 detects the opening degree (engine load) of the throttle valve 12. The sensor 23 detects the engine rotation speed.

Before explaining the specific control contents of the first and second on-off valves 18 and 19 by this control unit U,
The valve timing of the intake valve and exhaust valve will be explained.

FIG. 3 shows the valve timing of the intake valve and exhaust valve. A second intake valve (in FIG. 2,
(indicated by the dashed line ■). That is, the closing timing of the intake valve of the swirl port 3 is so-called late intake closing, thereby reducing the pumping loss during low-load operation. This reduction in pumping loss due to the late closing of the intake air is conventionally known, so its details will be omitted.

Based on the above, the first and second on-off valves 18.1
An example of the control in step 9 will be explained based on the flowchart shown in FIG. 4 with reference to FIG. 2.

First, in step Sl (hereinafter, rSJ is added to represent the step number), various information required for control is input, and then in S2, the current engine rotation speed Ne
It is determined whether the current engine load Pe is below a predetermined value Po (see Fig. 2) or not. A determination is made. When the determination in S3 is YES, that is, in low rotation and low load operation, the process proceeds to S4, where the first on-off valve 18 is closed and the second on-off valve 19 is opened (see Fig. 2). The intake air is supplied from the swirl port 3 to the combustion chamber through the bypass passage 16 without passing through the intercooler 14.

If the answer in S3 is No, that is, in low-speed, high-load operation, the process proceeds to S5, where the first on-off valve 18 is opened and the second on-off valve 19 is closed (see Figure 2).
After the intake air passes through the main intake passage 11 and is cooled by the intercooler 14, it is supplied to the combustion chamber from the second intake port 4.

Further, when the answer in S2 is No, that is, when high rotational speed operation is being performed, the process proceeds to S6, and the first and second on-off valves 18
．． 19 are both opened (see FIG. 2), and intake takes place using both the main intake passage 11 and the bypass passage 16.

In the above configuration, during low rotation and low load operation where the temperature rise in the combustion chamber is small during the compression stroke, the intercooler 1
Since the intake air is taken through the bypass passage 16 without being cooled by the supercharger 13, the temperature rise of the intake air as it passes through the supercharger 13 is directly utilized to promote vaporization and atomization of the fuel. Further, since the downstream end of the bypass passage 16 is connected to the swirl port 3, the swirl S generated in the swirl port 3 further promotes vaporization and atomization of the fuel. In particular, in this embodiment, since the intake valve that opens and closes the swirl port 3 closes late, the swirl S reduces the vaporization of the fuel even though the temperature rise in the combustion chamber during the compression stroke is small. It is possible to stabilize the operating condition during low rotation and low load operation.

The drawings after FIG. 5 show a second embodiment of the present invention. In explaining this second embodiment, the same reference numerals are given to the same elements as in the first embodiment, and the explanation thereof will be omitted, and only the characteristic parts of this second embodiment will be explained below. Add.

In this embodiment, as shown in FIG. 5, the downstream end of the main intake passage 11 is branched into two, and each branch passage 11a,
llb are connected to the intake ports 30 and 31, respectively. Among these intake ports 30, 31, a third intake port 32 having a small diameter is formed in the second intake port 31, and as shown in FIG. The third intake port 32 is directed toward the soil wall surface 33a on the exhaust port 6 side of the roof-shaped combustion chamber 33, and as shown in FIG. It is designed to generate a vortex (tumble) T. In addition, in FIG. 6, the reference numeral 34 is a piston.

The downstream end of the bypass passage 16 is connected to the third intake port 32, as shown in FIG. By closing valve 18, the third
Air is taken in through the intake port 32 of the vehicle. In addition, in FIG. 5, the reference numeral 33 is a fuel injection valve.

An example of the opening/closing control of the first opening/closing valve 18 will be explained based on the flowchart shown in FIG. A determination is made as to whether it exists or not. When the answer is YES in this Sll, the process advances to S12 and the on-off valve 18 is closed; on the other hand, when the answer is No, the on-off valve 18 is closed.
3, the on-off valve 18 is opened.

Although the present invention has been described in detail above, the present invention is not limited thereto, and, for example, the opening/closing timing of the swirl port 3 in the first embodiment is advanced, that is, the opening timing of the exhaust port 6 and the opening timing of the swirl port 3. It may be applied to a type of engine in which the overlap period with the combustion chamber is increased to ensure scavenging of the combustion chamber.

(Effects of the Invention) As is clear from the above description, according to the present invention, the downstream end of the bypass passage that bypasses the intercooler is connected to the intake port that generates a vortex in the combustion chamber. The vaporization and atomization of fuel during load operation can be further improved by the vortex flow within the combustion chamber, thereby making it possible to stabilize the operating state in this region.

[Brief explanation of the drawing]

Figures 1 to 4 show the first embodiment. Figure 1 is the overall system diagram of the first embodiment, Figure 2 is a diagram of the operating range of each on-off valve, and Figure 3 is the exhaust valve and intake valve. A diagram showing the valve timing of the valve. FIG. 4 is a flowchart showing an example of control. 5 to 7 show the second embodiment, FIG. 5 is an overall system diagram of the second embodiment, FIG. 6 is a vertical cross-sectional view of a cylinder, and FIG. 7 is a flowchart showing an example of control. . 1: Engine body 2: Cylinder 3 Nissir port 10: Intake system 11: Main intake passage 13: Supercharger 14: Intercooler 16: Bypass passage 18: First on-off valve 19: Second on-off valve 20.21 : Open/close valve actuator 22: Throttle opening sensor 23: Engine speed sensor 32: Third intake port (tumble generation port) U: Control unit S Niswar T: Tumble

Claims (1)

[Claims] (1) A supercharger and an intercooler are arranged in order from upstream to downstream in a main intake passage connected to a combustion chamber, and a bypass passage bypasses the intercooler in the main intake passage. In an engine in which intake air is taken through the bypass passage during low rotation and low load operation, the downstream side of the bypass passage is separate from the main intake port to which the main intake passage is connected. It is connected to an intake port for generating a vortex flow that generates a vortex flow in the combustion chamber, and the main intake passage includes a portion downstream of a portion to which the upstream end of the bypass passage is connected and upstream of the intercooler. An intake system for an engine, characterized in that it is provided with an on-off valve that is closed during low-speed, low-load operation and opened during other operating ranges.