JPH0599080A - Intake system for internal combustion engine - Google Patents

Abstract

(57) [Summary] [Purpose] To prevent knocking of internal combustion engines. An intake manifold 12 that branches from a surge tank 3 common to each cylinder and is connected to an intake port 2 of each cylinder includes a large-diameter main intake passage 13 and a small-diameter auxiliary intake passage 13 that are connected in parallel for each cylinder. The main intake passage 13 having a large diameter is formed of a material having low thermal conductivity such as a synthetic resin, and the sub intake passage 14 having a small diameter is formed of an aluminum alloy. Made of highly resistant material, surge tank 3 and main intake passage 1
3 is provided with an intake control valve 17 that opens in a high load operation range, and an EGR passage 6 is opened in a common intake passage 4 on the upstream side of the surge tank 3 for an internal combustion engine. When transitioning to the high load operation range in the acceleration mode, the pipe wall temperature of the main intake passage 13 is low, so there is no risk that the low temperature intake air due to EGR cut or decrease will be heated to cause a transient knock.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake system provided with an exhaust gas recirculation (EGR) system in an internal combustion engine.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication No. 59-213922 discloses that
An intake passage connecting a surge tank of an internal combustion engine and an intake port of each cylinder of a cylinder head is a main intake passage formed of a cast pipe integrally formed with the surge tank or fixedly connected to the main intake passage, and is arranged so as to be curved outside thereof. And a sub intake passage made of a thin pipe having a long passage cross section and a small passage cross-sectional area.The main intake passage and the sub intake passage intersect at an acute angle in the intake port, and the main intake passage has a control valve. Is provided to control the intake system of the internal combustion engine to be "closed" in the low and medium speed range and to be "open" in the high speed and high load range of the engine.

The above prior art aims to reduce the size and weight of an internal combustion engine having a main intake passage and an auxiliary intake passage, and to prevent an increase in ventilation resistance at the confluence of the two intake passages. However, although not directly related to the gist of the invention, in the illustrated embodiment, part of the exhaust gas is introduced into the intake air in the surge tank by the EGR system.

[0004]

According to the prior art disclosed in the above-mentioned publication, the main intake passage, which is generally a thick casting pipe, receives heat from the cylinder head to store a large amount of heat. Although the temperature of the pipe wall also rises, in the operating state of the acceleration mode, control is performed when shifting from the low / medium speed range where EGR is performed to the high speed / high load range where EGR is reduced or cut. Most of the intake air flows into the intake port through the main intake passage when the valve is opened, so a large amount of heat stored in the tube wall of the thick main intake passage is released into the intake air. As a result, the intake air temperature, which should be originally low, rises and becomes higher than the steady state when the lead angle is set.As a result, transient knock occurs in the engine, acceleration is not performed smoothly, and harmful vibration and noise are generated. There is. The present invention aims to solve this problem of the prior art by the invention.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides that intake manifolds branched from a surge tank common to each cylinder and connected to an intake port of each cylinder are mutually connected for each cylinder. It is composed of a large-diameter main intake passage and a small-diameter auxiliary intake passage that are connected in parallel, and the large-diameter main intake passage is formed of a material having low thermal conductivity such as synthetic resin, The small-diameter auxiliary intake passage is made of a material having high thermal conductivity such as aluminum alloy, and an intake control valve that opens in a high-load operating range is provided between the surge tank and the large-diameter main intake passage. EG is installed in the common intake passage upstream of the surge tank.
An intake system for an internal combustion engine, characterized in that an R passage is open.

[0006]

In the medium-low-load operation state of the engine in which EGR is executed, the intake control valve is closed in the large-diameter main intake passage, so that the intake air at a relatively high temperature, including exhaust gas, does not appear It flows only through the small-diameter auxiliary intake passage formed of a material having high heat conductivity. Therefore, the intake air radiates heat in the auxiliary intake passage to lower the temperature, and normal knocking is less likely to occur. Further, at this time, the exhaust gas is opened to the common intake passage on the upstream side of the surge tank.
Since it is mixed into the intake air from the passage, the exhaust gas is sufficiently diffused in the intake air, and the EGR rate does not vary from cylinder to cylinder.
Knock does not occur in a cylinder having a low R ratio.

In the acceleration mode, when the operating state of the engine shifts from the medium / low load region to the high load region, the EGR is stopped or the EGR rate is reduced to lower the intake air temperature. At this time, in the device, the intake control valve opens, and most of the intake air flows through the large-diameter main intake passage. Since the large-diameter main intake passage is made of a material with low thermal conductivity, such as synthetic resin, it does not transfer heat from the cylinder head, etc. to which it is connected, and it operates in the medium and low load range. Since the intake control valve is closed in this state, relatively high temperature intake air does not flow, so that the wall temperature of the main intake passage remains low. Therefore, since the intake air does not receive heat from the pipe wall of the main intake passage and its temperature does not rise at the time of shifting to the high load operation range, there is no possibility of causing a transient knock.

[0008]

1 and 2 showing an embodiment of the present invention, reference numeral 1 denotes a cylinder head of a four-cylinder internal combustion engine, which is installed in any one of four combustion chambers formed therein. The open intake port is shown as 2. Reference numeral 3 is a surge tank common to the four cylinders, the intake passage 4 on the upstream side thereof communicates with an air cleaner (not shown), and a throttle valve 5 is provided in the middle thereof. An EGR passage 6 is opened in an intake passage 4 between the surge tank 3 and the throttle valve 5. The EGR passage 6 communicates with an exhaust passage (not shown), and an EGR control valve 7 is provided in the middle thereof. There is. The EGR control valve 7 is opened / closed by a diaphragm type actuator 9 to which negative pressure or atmospheric pressure for control is selectively (in some cases, duty ratio controlled) supplied from a vacuum switching valve 8. Further, the vacuum switching valve 8 switches between a negative pressure for control and an atmospheric pressure according to a control signal output from the electronic control unit 10.

An intake manifold 1 branched from a common surge tank 3 and connected to an intake port 2 of each cylinder.
2 includes two intake passages 13 and 14 for each cylinder. The large-diameter main intake passage 13 is made of a heat-resistant synthetic resin or the like, and has a relatively high heat insulating property because the characteristic of the synthetic resin is low thermal conductivity. On the other hand, the small-diameter auxiliary intake passage 14 formed in parallel with the main intake passage 13 is made of a material having high thermal conductivity, such as an aluminum alloy. Each pair of intake passages 13, 1
Nos. 4 and 5 merge at a mounting portion 15 to the cylinder head 1 and are smoothly connected to the intake port 2, and a fuel injection valve 16 is attached to the mounting portion 15.

An intake control valve 17 is provided at a position where the upstream side inlet of the main intake passage 13 of each cylinder opens to the surge tank 3. In this example, the intake control valve 1 is provided.
The diaphragm 7 is opened and closed by a diaphragm type actuator 18. As in the case of the actuator 9 of the EGR control valve 7, a negative pressure for control introduced via a check valve 11 from a vacuum switching valve 19 that is switched by a control signal of the electronic control device 10 described above is applied to the actuator 18. And either atmospheric pressure are supplied alternatively.

FIG. 3 and FIG. 4 show two types of setting examples regarding the opening / closing relationship between the EGR control valve 7 and the intake control valve 17. In each case, the horizontal axis represents the engine speed Ne, and the vertical axis represents the intake air amount Q / revolution speed N indicating the magnitude of the load. FIG. 3 shows an embodiment in which the EGR control valve 7 is simply opened and closed, and the hatched area surrounded by the broken line is E
This is a region where the GR control valve 7 is opened and EGR is executed.
The outside thereof indicates a region where the EGR control valve 7 is closed and EGR is stopped. As can be seen from this figure, in this embodiment, the EGR is executed in a relatively low load operation range and is stopped in a high load and high rotation speed range.

The hatched area above the chain line is the intake control valve 17
Indicates a high load operation range in which most of the intake air passes through the main intake passage 13, and the intake control valve 17 closes and the intake air flows only through the sub intake passage 14 in a region below the alternate long and short dash line. This shows an operating range with a relatively low load. In the example of FIG. 3, the intake control valve 17 is opened only in the high-load operation range of the regions where the EGR is stopped. In a relatively low load operation range, the intake control valve 17 is closed, and all intake air flows through the auxiliary intake passage 14 and is supplied to the intake port 2 of the cylinder head 1. Therefore, a relatively large amount of EGR is generated in this state. Even if it is executed, the intake air whose temperature has risen due to the mixture of the exhaust gas introduced from the EGR passage 6 radiates heat while flowing through the auxiliary intake passage 14 having high thermal conductivity, and the temperature lowers. Is less likely to occur.

When the low-to-medium load operating range is shifted to the high-load operating range, the EGR control valve 7 is closed to stop the EGR and the intake control valve 17 is opened. Although it flows through the intake passage 13, in the illustrated embodiment, since the main intake passage 13 is closed in the EGR execution region, the main intake passage 13 does not come in contact with the intake air of a relatively high temperature including exhaust gas. Since the intake passage 13 is made of a synthetic resin having low heat conductivity, the temperature of the pipe wall of the main intake passage 13 does not rise due to the heat of the cylinder head 1. The temperature is kept lower than in the case of the prior art, and the low temperature intake air at the time of high load does not absorb heat from the pipe wall of the main intake passage 13 and does not rise in temperature. Therefore, transient knock does not occur even when shifting to the high load operation range in the acceleration mode.

In the embodiment shown in FIG. 4, the EGR control valve 7 is not simply opened / closed but duty ratio is controlled, or
A valve that can take an intermediate opening is used as the R control valve 7,
It shows an example in which the amount of GR can be adjusted. x is a predetermined value of the EGR rate, which is a value such as 5%. A region of relatively low load and low rotation surrounded by a broken line in FIG. 4 is an operating region where the EGR rate is higher than 5%, and the EGR rate is lower than 5% in other operating regions. In the high load operation range above the alternate long and short dash line where the intake control valve 17 is opened, the EGR rate is reduced within the range of 5% to 0%.

In the case of FIG. 4 as well, the same can be said as described with reference to FIG. That is, in the operating range surrounded by the broken line where the EGR rate is higher than 5%, the intake control valve 17 is closed, so that the intake air having a high temperature does not flow in the main intake passage 13, and the intake valve is made of synthetic resin. Since the main intake passage 13 made of a highly heat insulating material does not transfer heat from the cylinder head 1, the temperature of the pipe wall remains low. Therefore, even when the intake control valve 17 is opened by shifting to the high load operation range, the EGR rate becomes lower than 5%, and the intake air temperature decreases,
Most of the intake air flows through the main intake passage 13, so that the intake air does not absorb heat from the pipe wall and its temperature rises, which causes no transient knock.

As in the embodiment shown in FIGS. 1 and 2, E
By providing the opening of the GR passage 6 in the intake passage 4 on the upstream side of the surge tank 3 and on the downstream side of the throttle valve 5, the recirculated exhaust gas introduced from the EGR passage 6 is uniformly diffused in the intake air, and the multi-cylinder In the case of an internal combustion engine, variations in EGR, such as a difference in EGR rate for each cylinder, are prevented.
It also solves the problem that knock occurs in some cylinders with a low GR rate. As a result, it is generally possible to increase the compression ratio and improve fuel efficiency and output.

[0017]

By implementing the present invention, not only the usual knock in the medium / low load operating state is prevented, but also in the acceleration mode, when the medium / low load operating state transitions to the high load operating state. Since the transient knock that occurs can be prevented, the operation of the engine becomes smooth over the entire area, and no harmful vibration or noise is generated.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view showing an embodiment of an intake device of the present invention.

2 is a cross-sectional plan view of a portion of the embodiment of FIG.

FIG. 3 is a diagram showing a setting example of an opening / closing relationship between an EGR control valve and an intake control valve.

FIG. 4 is a diagram showing another setting example of the opening / closing relationship between the EGR control valve and the intake control valve.

[Explanation of symbols]

 1 ... Cylinder head 2 ... Intake port 3 ... Surge tank 4 ... Common intake passage 5 ... Throttle valve 6 ... EGR passage 7 ... EGR control valve 8 ... Vacuum switching valve 9 ... Actuator 10 ... Electronic control device 11 ... Check valve 12 ... intake manifold 13 ... main intake passage 14 ... auxiliary intake passage 15 ... mounting portion 16 ... fuel injection valve 17 ... intake control valve 18 ... actuator 19 ... vacuum switching valve

Claims (1)

[Claims] 1. A large-diameter main intake passage and a small-diameter sub-intake passage in which an intake manifold branched from a surge tank common to each cylinder and connected to an intake port of each cylinder is connected in parallel for each cylinder. And the large-diameter main intake passage is formed of a material having low thermal conductivity such as synthetic resin, and the small-diameter sub-intake passage has high thermal conductivity such as aluminum alloy. An intake control valve, which is made of a material, is provided between the surge tank and the large-diameter main intake passage and opens in a high load operation range, and an EGR is provided in a common intake passage upstream of the surge tank.
An intake device for an internal combustion engine, characterized in that the passage is open