GB2237066A

GB2237066A - I.c. engine mixture intake manifold

Info

Publication number: GB2237066A
Application number: GB9022475A
Authority: GB
Inventors: Ryuji Tayama; Masakatsu Kawada
Original assignee: Fuji Jukogyo KK; Fuji Heavy Industries Ltd
Current assignee: Subaru Corp
Priority date: 1989-10-18
Filing date: 1990-10-17
Publication date: 1991-04-24
Also published as: DE4033149A1; KR910008273A; GB9022475D0; JP2813734B2; JPH03134259A

Abstract

A series of grooves and recesses 12, 13a, 13b and 11-1 to 11-4 in the bottom of the common and branch intake passages 5 and 6-1 to 6-4 collect fuel from the mixture which is distributed evenly to the manifold branches. A baffle 8 evens the mixture flow to the branches. Coolant passages (14, Figs. 1,3 and 4) pass through the manifold beneath the collection grooves and recesses. <IMAGE>

Description

2 2::; 77 C) CS G, AN INTAKE MANIFOLD FOR AN ENGINE The present invention

relates to an intake manifold for an engine and more particularly to an intake manifold adapted to equally distribute air fuel mixture which is accumulated as liquid fuel to each cylinder in a four cylinder in-line engine.

There have been proposed various devices for preventing flow of the air fuel mixtures induced into the intake manifold of a multiple-cylinder engine from interfering with one another and for equalising the air fuel ratio in each cylinder in order to increase power of the engine. Japanese Utility Model Application Laid-Open 61-120072 discloses an intake manifold provided with a dam on the bottom thereof, at a position from which a plurality of intake passages branch. The liquid fuel is caught by the dam and intermittently spills from the dam and enters one of the cylinders. Consequentlyr the fuel is unevenly distributed to the cylinders, so that the engine cannot be properly started and the combustion becomes unstable.

Japanese Patent Application Laid-open 53-43122 discloses an intakemanifold provided with a recess and grooves in an inner wall of the manifold for accumulating fuel and with a passage along an outer periphery of the grooves for heating the fuel therein. The recess formed adjacent an inlet of the manifold is communicated with fuel supply passages through the grooves. The fuel supply passages are further 2 communicated with the cylinders. In order to equally distribute the fuel to the cylinders, each fuel supply passage has an orifice. Thus, the construction becomes complicated.

Moreover, each of the above-described intake manifolds is available only for an engine provided with a downdraught carburetor. The intake manifold can not be used in an engine provided with a sidedraught carburetor, because the distribution of the fuel tends to become unequal if the engine is slightly inclined.

The object of the present invention is to provide an intake manifold for a four-cycle engine where fuel is equally distributed to cylinders of the engine.

According to a first aspect of the present invention there is provided an intake manifold for an internal combustion comprising an intake passage communicating with a plurality of branch passages each of which is adapted for communication with one of the cylinders of an engine, an arrangement of channels extending along the bottoms of all the passages comprising, an inlet channel in the bottom of the inlet passage which communicates with branch channels extending one each into each branch passage and said arrangement of passages being convoluted so that the resistance of the flow of a liquid in each of the branch channels is equal.

3 According to a second aspect of the present invention, there is provided a manifold for a multi-cylinder engine comprising: an intake passage communicating with a plurality of branch passages, each branch passage being adapted for communication with one of the cylinders, a plurality of channels extending one each into the bottom of each passage, each of said channels joining with at least one other of the channels and a parent channelr at a junction where each daughter channel makes a junction angle with the parent channel, and the junctions being arranged so that the junction angles of the channels which present the most resistance to the flow of liquid through them are closer to 1800 than the junction angles of the other daughter channels in order that liquid flowing into the channels from a single, inlet parent channel is equally dispersed to each cylinder.

4 In an aspect of the invention, the groove provided in a longest branch intake passage has a larger sectional area than those of the other branch intake passages. The common intake passage is horizontal and each of the branch intake passages is downwardly curved.

A vertical baffle is provided in the common intake passage adjacent inlets of two middle branch intake passages. The baffle has a smaller width than a diameter of an inlet of the common intake passage.

The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.

Fig. 1 is a partially cutaway elevational view of a four-cylinder engine; Fig. 2 is a partially cutaway plan view of an intake system of the engine shown in Fig. 1; Fig. 3 is an elevation of the intake system as viewed from a direction shown by an arrow Z in the Fig. 2; and Fig. 4 shows a part of the intake system as viewed from the underside thereof.

Referring to Figs. 1 and 2, a four-cylinder in-line engine to which thei--present invention is applied has a cylinder block 1 inclined by 9 degrees, for example, 21.5 degrees, with respect to a horizontal line H of a vehicle body. A sidedraught carburetor 4 is mounted on the cylinder block 1 and connected to No.1 to No.4 cylinders provided in a cylinder head 2 through an intake manifold 3.

The intake manifold 3 has a linear common intake passage 5 communicated with the carburetor 4 and four branch intake passages 6-1, 6-2, 6-3 and 6-4 which are downwardly curved and communicated with the corresponding No.1 to No.4 cylinders. Respective centers 7-1, 7-2, 7-3 and 7-4 of the inlet openings of the intake passages 6-1 to 6-4 are substantially aligned along a line A as shown in Fig. 2.

Each branch intake passage has a length L. The length L of the intake passage 6-1 is larger than those of other intake passages. As shown in Fig. 1, the common intake passage 5 is linear and horizontal to the vehicle body.

As shown in Fig. 2, the intake passages 6-1 to 6-4 are so disposed that a distance between the centers 7-2 and 7-3 of the inner passages 6-2 and 6-3 connected to the No.2 and No.3 cylinders, respectively, is smaller than distances between the centers 7-1 and 7-2, 7-3 and 7-4.

Referring to Figs. 2 and 3, a vertical baffle 8 is provided in the common intake passage 5 at a position upstream of the centers 7-2 and 7-3 of the inlets of the branch intake passages 6-2 and 6- 3.. Spaces are provided on both sides of the baffle 8 so that intake air can flow through the main passage 5 without interference from the baffle 8. The baffle 8 has a front side 8a 6 perpendicular to a longitudinal direction of the common intake passage 5. A width d of the baffle 8 is smaller than the diameter D of the common inlet passage 5 at an inlet 3a connected to the carburetor 4. Inertia of the air fuel mixture which tries to flow from the carburetor 4 into the intake passages 6-2 and 6-3, is attenuated by the baffle 8. At the same time, the direction of the flow of the air fuel mixture is adjusted so that the air fuel mixture is equally distributed to each intake passage 6-1 to 6-4.

In-the common intake passage 5, a first recess 12 is formed in the bottom at a position upstream of the baffle 8. The recess 12 has a pair of-discharge passages 12a and 12b at both sides thereof. Both the passages 12a and 12b are communicated with a pair of second recesses 13a and 13b formed downstream of the recess 12. Each of the recesses 12, 13a and 13b has a predetermined capacity. From the second recess 13a, discharge grooves 11-1 and 11-2 extend along the bottoms of the intake passages 6-1 and 6-2, respectively. Similarly, discharge grooves 11-3 and 11-4 communicated with the recess 13b are formed in the bottom of the intake passages 6-3 and 6-4, respectively. The passages 12a and 12b are arranged such that extension lines of center lines thereof cross each other at a point 9 in an inlet side of the first recess 12. Similarly, centerlines of the grooves 11-1 and 11-2 cross each other at a point 10a in an 7 inlet portion of the second recess 13a, and centerlines of the grooves 11-3 and 11-4 cross at a point 10b. The fuel in the air-fuel mixture which adheres to the wall of the manifold 3 is accumulated in the recesses 12, 13a and 13b.

The fuel is equally led to each intake passage 6-1 to 6-4 through the grooves 11-1 to 11-4 which are formed in the horizontal part of the intake manifold 3.

Each of the outer grooves 11-1 and 11-4 is formed so as to align with the center line of the passage 12a and to pass the shortest route between the point l0a(10b) and the terminal end thereof. In addition, a sectional area of the groove 11-1 is larger than that of other grooves 11-2, 11-3 and 11-4 so that the fuel smoothly slows in the groove 11-1.

Hence, the time taken by the fuel to reach each terminal end of the groove is substantially the same despite the different lengths of the branch intake passages.

Referring to Figs. I and 4, a hot water passage 14 is provided under the first recess 12 and the second recesses 13a and 13b. An inlet 14a of the hot water passage 14 adjacent the second recess 13a is communicated with a waterjacket of the engine through a thermostatic valve (not shown). The passage 14 passes under the recesses 13a, 12, and makes a turn under the carburetor 4 and further passes under the second recess 13b and returns to the waterjacket through an outlet 14b. Thus, heated coolant is circulated in the hot water passage 14 to heat the manifold 3, thereby 8 enhancing vaporization of the fuel in the recesses and the fuel in the air-fuel mixture during cold engine state. After the engine is warmed up, the thermostatic valve is closed to stop suppling the coolant so that useless heating is prevented.

In operation, the air-fuel mixture is induced into the intake manifold 3 from the carburetor 4. The inertia of the fuel in the mixture is attenuated by the vertical buffle 8, thereby preventing the mixture from directly entering the inner intake passages 6-2 and 6-3. Since the width d of the baffle 8 is smaller than the diameter D of the inlet 3a of the intake manifold 3, the air-fuel mixture enters the intake passages 6-2 and 6-3 without being obstructed. Thus, the mixture is equally distributed to the intake passages 6-1, 6-2, 6-3 and 6-4.

On the other hand, the fuel adhered on the inner wall of the intake manifold 3 accumulates in the first recess 12 and the second recesses 13a, 13b. The accumulated fuel is heated by the heated coolant in the hot water passage 14 and varporized. The fuel accumulated in the first recess 12 flows into the second recesses 13a and 13b and further to intake passages 6-1 to 6-4 through the grooves 11-1 to 11-4. Thus, the fuel is equally distributed to respective cylinders. The outer grooves 11-1 and 11-4 have the shortest paths. Therefore, although each of the passages 6-1 and 6-4 is longer than the other passages 6-2 and 6-3, the fuel reaches each cylinder at substantially same time.

9 Furthermore, the sectional area of the groove lla is larger than those of the grooves 11-2 to 11-4, so that the fuel reaches the No.1 cylinder through the grooves 11-1 having the longest length at the same time as the fuel through other grooves. Thus, the air-fuel ratios in the cylinders become uniform, thereby improving starting characteristics of the engine.

From the foregoing it will be understood.that the present invention provides the intake manifold for the four-cylinder engine where the vertical baffle is provided in the manifold at the inlet thereof so that the air-fuel mixture is equally distributed to the cylinders of the engine. Hence, stable combustion is performed, thereby increasing engine power. The width of the baffle is sufficiently smaller than the diameter of the inlet of the manifold so that the flow of the air-fuel mixture is not interfered by the baffle. In addition, recesses are formed in the bottom of the manifold to accumulate the fuel adhered on the inner walls of the manifold, and grooves are provided to equally distribute the fuel to the cylinder so that the air-fuel ratios in the cylinders become substantially the same. Furthermore, the fuel in the recesses is heated by the heated coolant through the hot water passage formed beneath the recesses and sufficiently vaporized, thereby increasing combustion efficiency at the start of the engine.

While the presently preferred embodiment of the present invention has been shown and described, it is to be understood that this disclosure is for the purpose of illustration and that various changes and modifications may be made without departing from the scope of the invention as set forth in the appended claims.

is w 1 11

Claims

1. An intake manifold for an internal combustion comprising an intake passage communicating with a plurality of branch passages each of which is adapted for communication with one of the cylinders of an engine; an arrangement of channels extending along the bottoms of all the passages comprising, an inlet channel in the bottom of the inlet passage which communicates with branch channels extending one each into each branch passage and said arrangement of passages being convoluted so that the resistance of the flow of a liquid in each of the branch channels is equal.

2. A manifold for a multi-cylinder engine comprising: an intake passage communicating with a plurality of branch passages, each branch passage being adapted for communication with one of the cylinders, a plurality of channels extending one each along the bottom of each passage, each of said channels joining with at least one other of the channels and a parent channel at a junction where each daughter channel makes a junction angle with the parent channel, and the junctions being arranged so that the junction angles of the channels which present the most resistance to the flow of liquid through them are closer to 1800 than the junction angles of the other daughter channels in order that liquid flowing into the channels from 12 a single, inlet parent channel is equally dispersed to each cylinder.

3. An intake manifold for a four-cylinder in-line engine comprising an intake passage and four passages branching therefrom to communicate one each with each cylinder: a first recess provided in the bottom of said intake passage at an inlet portion thereof; four channels provided in the bottoms of said branch passages, each of which communicates with said first recess; and ' at least one of the channels provided in the outermost branch passages being arranged in a straight line.

4. A manifold according to claim 3, wherein the channel provided in the longest branch passage has a larger cross sectional area than the other channels.

5. A manifold according to claim 3 or claim 4, wherein said common intake passage is horizontal and each of said branch passages is downwardly curved.

6. A manifold according to any of the preceding claims 3 to comprising two second recesses provided in the bottom of said common intake passage at both sides thereof, each of which is communicated with said first recess and two of said branch 13 intake passages.

7. A manifold according to any of claims 3 to 6, further comprising a vertical baffle provided in said common intake passage adjacent inlets of two middle branch intake passages.

8. A manifold according to claim 7, wherein said baffle has a smaller width than a diameter of the inlet of said common intake passage.

9. A manifold as herein described with reference to figures 1 to 4.

Published 1991 at 7be Patent Office. State Houm 66/71 High Holborn. London WC I R 47?. Further copies may be obtained from Saks Branch. Unit 6. Nine Mile Point. Cwmrchnfach. Cross Keys. Newport NPI 7HZ. Printed by Multiplex techniques ltd. St Mary Cray. Kent.