JPS6263126A - Suction device for engine - Google Patents

Abstract

PURPOSE:To make propergation of a pressure wave performable almost uniformly, by forming a curved part of a suction pipe into a sectional flat form, in case of a device which installs the suction pipe connecting a suction port of each cylinder to a surge tank and having the upward curved part. CONSTITUTION:In case of a suction device which connects a suction port 4 of each cylinder 2 to a suction expansion chamber 10 extending in a cylinder train direction interconnectly via each independent suction passage 8, each interconnecting part 16, interconnecting each of these suction passages 8 mutually via branch holes 15 extending in parallel with the suction expansion chamber 10 and being branched off from each independent suction passage 8, is connected to the point midway in each independent suction passage 8. Each of these independent suction passages 8 is constituted of suction pipes 9 consisting of an upstream side part 9a and a downstream side part 9b to be curved along a circumferential surface of a surge tank 11 constituting the suction expansion chamber 10. And, the curved part of the suction pipe 9 is formed so as to become a flat form causing the passage section to make the length in the cylinder train direction a long diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an intake system for an engine that is designed to improve output through the dynamic effect of intake air.

(Prior art) Conventionally, in an engine intake system, a negative pressure wave generated with the start of intake is reflected at the open end of the intake passage to the atmosphere or the intake expansion chamber on the upstream side of the intake passage, and becomes a positive pressure wave. Taking advantage of the fact that the air is returned toward the intake port, the positive pressure wave reaches the intake port just before the intake valve closes and forces the intake air into the combustion chamber. Some devices are designed to increase the filling efficiency of intake air using the so-called inertia effect of intake air.

For example, as described in Japanese Unexamined Patent Publication No. 56-115819, the length of the intake passage is changed depending on the engine speed, for example, the intake passage for each cylinder is branched into two at the upstream part. The upstream ends of these passages are opened to the intake expansion chamber, etc., and an on-off valve is provided in the short passage, and this on-off valve is opened in the high rotation range to open the intake passage. An intake device is known in which the effective length of the engine is shortened (see FIG. 6 of the above-mentioned publication) and the inertia effect of intake air is enhanced in both the low rotation range and the high rotation range.

By the way, in order to obtain the inertial effect of intake air in the low rotation range, it is necessary to increase the length of the intake passage, but in the conventional intake system described above, due to space constraints in the engine room, it is necessary to increase the length of the intake passage. The intake pipe extends from the intake port to the outside of the engine body, curves upward from the engine body, and communicates with the surge tank. However, the intake passage of the above-mentioned intake pipe has a substantially circular cross section, and the radius of curvature differs between the inner and outer circumferential sides of the intake passage in the curved portion of the intake pipe. There is a problem in that the propagation of the pressure waves is different in each part of the cross section of the intake passage and is not uniform. Also.

Although it is conceivable to simply reduce the inner diameter (passage diameter) of the intake pipe, this is not desirable because the intake air filling efficiency decreases.

(Objective of the Invention) Therefore, the present invention provides an engine intake device that can make the propagation of pressure waves substantially uniform in the intake passage of the curved portion of the intake pipe, regardless of whether it is on the inner circumferential side or the outer circumferential side. The purpose is to

(Structure of the Invention) In order to achieve the above object, the present invention provides that the curved portion of the intake pipe is formed so that the cross section of the intake passage has a flat shape whose major axis is the length in the output axis direction. It is characterized by The flat shape reduces the difference in the radius of curvature between the inner and outer sides of the curved portion of the intake pipe, reduces the difference in the length of the intake passage in the intake pipe, and reduces the propagation of pressure waves. The cross section of the intake passage is substantially uniform at each location, and the dynamic effect of intake air can be efficiently obtained.

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

In FIG. 1 showing an embodiment in which the present invention is applied to a four-cylinder engine, reference numeral 1 denotes an engine body, and the longitudinal direction (
The first to fourth cylinders 2 are formed in series in a direction perpendicular to the plane of the paper, and an output shaft (not shown) is provided along the same direction. Each cylinder 2 has a combustion chamber 3 formed above a piston (not shown), an intake port 4 and an exhaust port 5 opening in this combustion chamber 3, and intake valves 6 in both ports 4 and 5, respectively. and an exhaust valve 7 are installed.

Each intake port 4 of each cylinder 2 is connected to the downstream end of an intake pipe 9 that constitutes an independent intake passage 8 for each cylinder 2. On the other hand, the upstream end of the intake pipe 9 extends outward from the engine body 1, and an intake expansion chamber 1 curves upwardly in the engine body 1 and extends parallel to the cylinder row direction (output shaft direction).
It is connected to a surge tank 11 that constitutes 0. Note that the passage lengths of each independent intake passage 8 are set to be approximately the same length.

Outside air is introduced into the surge tank 11 through an intake air introduction pipe 12, and this intake air introduction pipe 12 is provided with a throttle valve 13 for controlling the amount of intake air. Further, a fuel injection valve 14 is disposed near the downstream end of each independent intake passage 8 .

In the middle of each of the independent intake passages 8, there is a communication section that extends parallel to the intake enlarged chamber 10 in the cylinder row direction and communicates the independent intake passages 8 with each other via a branch hole 15 that branches from each independent intake passage 8. Note that the lengths of the passages from the branch points of the respective independent intake passages 12 from the communication portions 16 to the respective cylinders 2 are set to be approximately the same length.

Each branch hole 15 is provided with an on-off valve 17 that opens and closes the branch hole 15, and each on-off valve 17 is fixed to a valve shaft 18 extending in the direction of the cylinder row. Opening and closing are integrally controlled via an actuator by a control circuit receiving the output of the detection means, etc., thereby controlling the communication between the independent intake passages 8 through the communication portion 16 according to the engine operating state,
Closed in the low speed range when the engine speed is less than the set value,
It constitutes a control means that controls the valve to be opened in a high rotation range where the engine rotation speed is higher than a set value. Note that the opening/closing operation of the on-off valve 17 according to the engine speed may be performed at least at high loads when output is required, and the on-off valve 17 may be in the open or closed state at low loads. It may be maintained.

The upstream portion 9a of each of the intake pipes 9 is curved along the contour of the surge tank 11 and is integrally formed with the surge tank 11, so that the upstream portion 9a of the intake manifold 19
It constitutes a. The upstream portion 19a of the intake manifold 19 also forms an upper portion 16a of the communication portion 16 by sharing a part of the constituent walls of the upstream portion 9a of the intake pipe 9 and the surge tank 11. On the other hand, the downstream portion 9b of each intake pipe 9 is also integrally molded to constitute the downstream portion 19b of the intake manifold 19, and a portion of its constituent wall is shared to form the lower portion 16b of the communication portion 16. There is. Therefore, the upstream and downstream portions 1 of the intake manifold 19
By combining 9a and 19b, each curved independent intake passage 8 that communicates between the intake expansion chamber 10 and the intake port 4 of each cylinder 2, and each independent intake passage 8 that branches from each independent intake passage 8 and connects each independent intake passage 8 to each other. A communication portion 16 is formed to communicate with the air intake system, thereby making the intake system more compact.

Furthermore, since each independent intake passage 8 is formed in a flat cross section over the entirety with the major axis being the length in the output axis direction, the curved portion of each intake pipe 9 is shaped as shown in FIG. In addition, the cross section of the independent intake passage 8 has a flat shape whose major axis is the length Ll in the cylinder row direction.

There is almost no difference in passage length between the inner circumferential side and the outer circumferential side of the independent intake passage 8. therefore.

The difference between the passage length Ll on the inner circumferential side and the passage length L3 on the outer circumferential side of each independent intake passage 12 is smaller than that of the conventional one.

With the above configuration, when each on-off valve 17 is closed and the communication between the independent intake passages 8 through the communication portion 16 is cut off, the pressure wave of negative pressure generated during the intake stroke is transmitted to the intake expansion chamber 10. In other words, the pressure wave of the negative pressure and its reflected wave propagate through a relatively long passage, so that the oscillation period of the pressure wave becomes equal to the opening/closing period of the intake valve 6 in the low rotation range. As a result, the inertia effect of the intake air in the low rotation range is increased,
Intake air filling efficiency is increased.

On the other hand, when the on-off valves 17 are opened and the independent intake passages 8 are in communication with each other through the communication portions 16, the pressure waves of negative pressure generated during the intake stroke are reflected by the communication portions 16, and the negative pressure waves are reflected by the communication portions 16. By shortening the length of the passage used for the propagation of pressure waves and their reflected waves, the inertial effect of the intake air is enhanced in the high rotation range, and in this operating range, the pressure waves propagated from other cylinders are also reduced. This effectively acts through the communication portion 16, and the filling efficiency in the high rotation range is greatly increased.

In this way, by closing the on-off valve 17 in the low rotation range and opening the on-off valve 17 in the high rotation range, the intake air filling efficiency can be increased in the entire rotation range, and the output can be improved. In particular, since the curved portion of the independent intake passage 8 is flat, the difference in passage length between the inner circumference side and the outer circumference side of the curved portion does not become large as in the conventional case, and the inner circumference side of the independent intake passage 8 , pressure waves propagate almost uniformly regardless of the outer circumferential side, increasing the inertia effect of intake air and improving intake air filling efficiency.

Although the above embodiment is an example in which the length of the independent intake passage 8 is variable, the length of the independent intake passage 8 is not limited to this. As long as the engine intake system has an intake pipe that communicates with the surge tank and utilizes the dynamic effect of intake air, the passage length may be constant.

Moreover, although the above embodiment is an example used for a multi-cylinder engine, it goes without saying that the present invention can also be applied to a single-cylinder engine.

(Effects of the Invention) As described above, in the present invention, since the curved portion of the intake pipe is made flat, the difference in the length of the intake passage between the inner circumferential side and the outer circumferential side of the curved portion is reduced. Propagation of pressure waves can be made almost uniform.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is an overall configuration diagram of an intake system for a four-cylinder engine, FIG. 2 is a sectional view of the upstream portion of the intake manifold taken along the line ■-■ in FIG. 1, and FIG. is a schematic diagram along the ■-■ line in Figure 1, and Figure 4 is a schematic diagram along the line m in Figure 1.
It is a sectional view taken along the V-mV line. l...Engine body, 2...Cylinder, 4
...Intake port, 9...Intake pipe, 11
······Surge tank.

Claims (1)

[Claims] (1) In an engine intake system having an intake pipe that extends from the intake port to the outside of the engine body, curves upwards of the engine body, and communicates with the surge tank, the curved portion of the intake pipe has a cross section of the intake passage that is the output axis. An intake device for an engine, characterized in that it is formed into a flat shape whose major axis is the length in the direction.