JPH0346183Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) This invention is designed to reduce combustibility by branching the intake passage into a main intake passage and a sub-intake passage, and providing a control valve that opens and closes the main intake passage according to the load. The present invention also relates to an intake system for an engine that aims to improve output.

(Prior Art) An example of such an intake system for an engine is the one shown in Japanese Utility Model Application Laid-Open No. 59-7538. In other words, the intake passage connected to the intake port provided in the cylinder head is composed of a main intake passage and a sub-intake passage, and there is a control system in the main intake passage that closes the main intake passage when the load is low and opens it when the load is high. It is equipped with a valve to provide a swirl to the air-fuel mixture supplied to the combustion chamber through the auxiliary intake passage to improve combustibility at low loads, and to improve output at high loads. A large amount of air-fuel mixture with little passage resistance is supplied to the combustion chamber through the main intake passage.

By the way, in order to sufficiently obtain such an effect, it is preferable that the axes of the communication between the low-load auxiliary intake passage and the intake port be as perpendicular to each other as possible and close to the tangential direction of the intake port;
It is preferable that the main intake passage for high loads and the intake port communicate with each other in a direction in which their respective axes coincide as much as possible. In order to satisfy both of these requirements while also meeting the constraints of the engine mounting space, the intake passage in the cylinder head is generally formed in the vicinity of the intake port in a curved manner.

On the other hand, for the purpose of improving intake air filling efficiency, the opening timings of the intake valve and exhaust valve are generally made to overlap. , the inside of the main intake passage, which has a relatively large volume downstream of the control valve, becomes negative pressure, and dilution gas tends to enter this part due to blowback. Therefore, in order to reduce this amount of intrusion as much as possible, it is desirable that the control valve provided in the main intake passage be located as close to the intake port of the cylinder head as possible. However, in order to satisfy this requirement, as mentioned above, the intake passage in the cylinder head is often bent in the vicinity of the intake port, so the control valve must be located at or immediately near this bend. It will be necessary to set it up.

On the other hand, when the control valve opens the main intake passage, it is rotated about the control valve shaft until the valve body becomes parallel to the flow of the air-fuel mixture, and then the main intake passage is divided into two at the position of the valve body. However,
When the control valve is disposed in a straight section of the intake passage, the cross-sectional areas of the two passages formed by the bisection are almost the same on the upstream and downstream sides of the valve body, and therefore the main intake passage The flow of the air-fuel mixture flowing through the air is not disturbed, and intake resistance can be reduced to ensure smooth intake. However, when the control valve is disposed at the bend as described above, since the control valve is generally butterfly-shaped, when the control valve opens, the rear end of the valve body may come off the center of the cross section of the passage. It will be close to the upper wall of the passage,
Therefore, the flow above the valve body is constricted downstream of the valve body, and the flow below the valve body is diffused downstream. Therefore, there is a risk that the flow of the air-fuel mixture in the main intake passage may be disturbed by the valve body, and in that case, when a high-speed and large amount of air-fuel mixture flows through the main intake passage under high load, a large intake resistance may occur. This results in a decrease in output.

(Purpose of the invention) This invention was made in view of the above problems.
The control valve is placed as close as possible to the intake port side to reduce the blowback of dilution gas into the intake passage, as well as to reduce the intake resistance due to the bending of the intake port when the control valve is fully open. The purpose is to provide an air intake device.

(Structure of the invention) In the present invention, the intake passage is composed of a main intake passage and a sub-intake passage for swirl generation, and the downstream end of the main intake passage leading to the intake port of the cylinder head is approximately centered on the axis of the combustion chamber. The main intake passage is formed in the direction of the main intake passage and bent approximately to the side immediately upstream of the intake port.
A butterfly-shaped control valve is provided to control the amount of intake air flowing down the main intake passage during low load, and the sub intake passage is
In an engine intake system in which the upstream end branches from the main intake passage upstream of the control valve and the downstream end opens near the intake port of the main intake passage, the upstream side of the bend in the main intake passage is a straight line. The control valve is arranged such that its valve shaft is located immediately upstream of the bending point of the main intake passage, and the downstream piece is located at the bending point when fully opened, The piece is provided with a bent portion that follows the curve of the bent portion when the piece is fully opened.

With this configuration, even if the control valve is provided as close as possible to the bending point immediately upstream of the intake port, it is possible to reduce the possibility that the downstream piece of the control valve becomes intake resistance when the control valve is fully opened, and to disturb the flow of intake air. Without any
Further, by providing the control valve as described above, the amount of dilution gas entering the intake passage is reduced.

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

1 and 2, a cylinder head 1 of an engine is provided with a combustion chamber 2, an intake passage 3, and an exhaust passage 4, and an intake port 6 having an intake valve 5 is provided at the downstream end of the intake passage 3 for combustion. An exhaust port 8 opens into the combustion chamber 2 and has an exhaust valve 7 at the upstream end of the exhaust passage 4 . An intake manifold 9 having an intake passage 3 connected to the intake passage 3 is fixed to the cylinder head 1, and further, on the upstream side of the intake manifold 9, the flow rate of the air-fuel mixture from a carburetor (not shown) is connected to the engine. A throttle valve 10 is provided which is controlled according to the load.

The intake passage 3 in the cylinder head 1 and the intake manifold 9 is branched midway into a main intake passage 3a that takes air mainly during high loads and a sub intake passage 3b that takes air during low loads. 3 has a bent shape immediately upstream of the intake port 6, and the main intake passage 3
The axis A of a is configured to substantially coincide with the axis of the combustion chamber 2 at the intake port 6 portion, that is, the downstream end of the main intake passage leading to the intake port 6 is formed approximately in the direction of the combustion chamber axis. ing. On the upstream side of the above-mentioned bending point, the main intake passage 3a extends substantially laterally in a straight line. On the other hand, the auxiliary intake passage 3b for generating swirl branches into the main intake passage 3a at a point downstream of the throttle valve 10 in the middle of the intake manifold 9 and upstream of the control valve 11 described later. 3a so as to merge immediately upstream of the intake port 6, and the direction thereof is substantially perpendicular to the intake port 6, that is, substantially tangential to the combustion chamber 2. That is, from the main intake passage 3a, a large amount of the air-fuel mixture can be supplied to the combustion chamber 2 without much swirl, and from the auxiliary intake passage 3b, the air-fuel mixture can be supplied to the combustion chamber 2 with swirl. It is configured.

Main intake passage 3 in the intake manifold 9
A butterfly-shaped control valve 11 is rotatably provided in the inside a, and is rotatable on a control valve shaft 12, and this control valve 11 fully opens the main intake passage 3a at high loads and closes the main intake passage 3a at low loads. Diaphragm device 13
It is designed to be able to open and close at . That is, the diaphragm device 13 is the throttle valve 10
The negative pressure in the intake passage 3 downstream of the negative pressure introduction passage 1
4, and when the load is high, that is, when the negative pressure is small, the control valve 11 is driven via the link mechanism 15 so that the main intake passage 3a is fully opened, and when the load is low,
That is, when the negative pressure is large, the control valve 11 is driven so that the main intake passage 3a is closed. The opening/closing control of the control valve 11 may be performed by the control unit 16 by detecting the load condition of the engine by some means, rather than by detecting the negative pressure as described above.

Furthermore, the control valve 11 has its valve shaft 12 located immediately upstream of the bending point of the main intake passage 3a,
Further, the downstream piece is arranged so as to be located at the bending point when fully opened, and this downstream piece is provided with a bent portion 11a that follows the curve of the bending point when fully opened.

Next, the effect will be explained. When the load is low, the main intake passage 3a is closed by the control valve 11, so the air-fuel mixture passes through the auxiliary intake passage 3b, enters the intake passage 3 immediately upstream of the intake port 6, and is supplied to the combustion chamber 2.
Also, during high load, the main intake passage 3a is connected to the control valve 1.
1 is opened, and the air-fuel mixture is mainly supplied to the combustion chamber 2 through the main intake passage 3a. Therefore, when the load is low, the air-fuel mixture is supplied to the combustion chamber 2 at high speed and swirled, and when the load is high, a large amount of the air-fuel mixture is supplied to the combustion chamber 2 with little intake resistance. When the control valve 11 is fully open under high load, its downstream piece faces into the bent intake passage 3 of the cylinder head 1, but since this member is provided with a bent part 11a that follows the bend, intake resistance is reduced. Since the cross-sectional area of the flow path does not change between the upper side and the lower side of the control valve 11, turbulence of the flow does not occur. Furthermore, if the entire control valve is located at a bend in the main intake passage 3a, even if the entire control valve is bent to provide a rectifying effect, the bend wall will increase, leading to an increase in intake resistance, and Although it becomes difficult to ensure sealing performance when the valve is opened, in the present invention, the control valve is arranged so that only the downstream piece is located at the bending point when the control valve 11 is fully opened, so it is effectively possible to maintain the control valve's fully open state. Intake resistance at the valve is reduced, and sealing performance is ensured when the valve is closed.

(Effects of the invention) As described above, according to the invention, a butterfly-shaped structure is installed in the main intake passage, which is immediately upstream of the bending point in the intake passage immediately upstream of the intake port of the cylinder head and becomes the main passage under high loads. By interposing a control valve and providing a bent portion on the downstream side of the control valve so as to follow the bending of the intake passage when the control valve is fully opened,
Even if the control valve is installed as close as possible to the intake port, the opening/closing action of this control valve will reduce the increase in intake resistance in the main intake passage and the disturbance of the flow, especially when fully opened, and will reduce the risk of large amounts of air flowing under high loads. The air-fuel mixture can be smoothly supplied to the combustion chamber, improving engine output. In particular, the control valve is arranged such that its valve shaft is located immediately upstream of the bending point of the main intake passage, and the downstream piece is located at the bending point when fully opened, and the downstream piece is provided with a bending part. Therefore, it is possible to effectively reduce intake resistance and ensure sealing performance when the valve is closed.

In addition, by providing the control valve close to the intake port, it is possible to reduce the amount of dilution gas that tends to enter the main intake passage, especially at low loads, thereby improving combustibility at low loads. It can be done.

[Brief explanation of drawings]

FIG. 1 is a sectional view of essential parts of an engine intake system according to an embodiment of the present invention, and FIG. 2 is a sectional view of the overall configuration of the engine intake system. 1...Cylinder head, 3...Intake passage, 3a
...Main intake passage, 3b...Sub-intake passage, 6...Intake port, 11...Control valve, 11a...Bending portion.

Claims (1)

[Scope of utility model registration request] The intake passage is composed of a main intake passage and a sub-intake passage for swirl generation, and the main intake passage has a downstream end that reaches the intake port of the cylinder head, which is formed approximately in the axial direction of the combustion chamber, and is directly connected to the intake port. A butterfly-shaped control valve is provided in the main intake passage, which bends approximately to the side at the upstream side, and controls the amount of intake air flowing down the main intake passage during low load. In an engine intake system that branches from a main intake passage upstream of a control valve and has a downstream end open at a position near an intake port of the main intake passage, the upstream side of the bent portion of the main intake passage is formed in a straight line, The control valve is arranged so that its valve stem is located immediately upstream of the bending point of the main intake passage, and its downstream piece is located at the bending point when it is fully opened. An intake device for an engine, comprising a bent portion that follows the curve of the bent portion.