WO1994001664A1

WO1994001664A1 - An exhaust system for an internal combustion engine

Info

Publication number: WO1994001664A1
Application number: PCT/US1993/006568
Authority: WO
Inventors: Ronald W. Cruickshank
Original assignee: Cruickshank Ronald W
Priority date: 1992-07-13
Filing date: 1993-07-12
Publication date: 1994-01-20

Abstract

An exhaust system (30) includes expansion chambers (31 and 32) and common divider (40). The use of a common divider allows the exhaust system (30) to maintain a preferred individual expansion chamber design while remaining compact. This compact design allows the exhaust system (30) to be used in applications where high engine performance is desired but there is restricted area in which to accommodate an exhaust system. The expansion chambers (31 and 32) can have various cross-sectional profiles to match the application. The proportional length of common divider (40) relative to the total length of exhaust system (30) can vary by application.

Description

TITLE

AN EXHAUST SYSTEM FOR AN INTERNAL COMBUSTION ENGINE

FIELD OF THE INVENTION

The invention relates to exhaust systems for two-stroke internal combustion engines.

BACKGROUND OF THE INVENTION Description of prior art.

It is well known that the performance of a two-stroke internal combustion engine can be improved by providing each combustion chamber, or multiple combustion chambers firing together, with an individual exhaust pipe of an 'expansion chamber' design including a first divergent section and a following convergent section. In many applications where a two-stroke engine is used in a restricted engine area this preferred exhaust design has not been practical due to the space required by multiple expansion chambers of the current design. This has lead to the use of compromise systems such as two-into-one and three-into-one, header pipe into expansion chamber, designs with a considerable decrease in performance.

Previous inventions have disclosed a variety of means for providing compact exhausts for internal combustion engines.

U.S. patent 5,109,668 (Lindstedt 1992) discloses a marine exhaust system whereby the exhaust header passages are formed within a manifold assembly by passage dividers. This design, while compact and appropriate for four-stroke engines, addresses only the exhaust header pipe and collector sections and does not provide the desired divergent and convergent exhaust sections of an expansion chamber design.

U.S. patent 5,044,159 (Landfahrer 1991) discloses an exhaust system design which, in one arrangement, includes two co-axial diffusers of differing dimensions which are in communication with a common exhaust header. An object of this design is for the exhaust pulse from a given engine cylinder to travel into both diffusers and be effected by the differing dimensions of the two diffusers. This design does not provide the required separate expansion chamber for each combustion chamber and is subject to the previously discussed performance compromises of two-into-one and three-into-one designs.

U.S. patent 4,815,274 (Piatti 1989) discloses an exhaust system which includes an exhaust manifold and header passages which extend from the manifold into a partitioned tail pipe. This design provides header passages in the tail pipe which have substantially parallel center lines and are of substantially constant cross sectional area which provides a four-into-one and other like designs which are appropriate for four-stroke engines, but does not provide the divergent and convergent expansion chamber sections which are desired for two-stroke engine performance.

U.S. patent 2,423,602 (Magdeburger 1947) discloses a compact manifold which includes a cylindrical body divided by helicoid partitions. This design provides compact header passages within the manifold but does not provide the required expansion chamber exhaust.

OBJECTS AND ADVANTAGES

Accordingly, several objects and advantages of my invention are:

(a) To provide an exhaust system which maintains an optimal design of one 'expansion chamber' per combustion chamber, or group of simultaneously firing chambers, which is compact and can be accommodated in a restricted area.

(b) To provide an exhaust system consisting of multiple 'expansion chambers' and which is of a simplified design and can be readily manufactured.

(c) To provide an exhaust system consisting of multiple 'expansion chambers' which can be manufactured as a single unit. BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows an embodiment of the present invention incorporating two 'expansion chambers' .

Fig. 2 is a sectional view of Fig. 1 along line I-I.

Fig. 3 is a sectional view of an embodiment of the present invention.

Fig. 4 is a sectional view of an embodiment of the present invention.

Fig. 5 is a sectional view of an embodiment of the present invention.

Fig. 6 is a sectional view of an embodiment of the present invention.

Fig. 8 shows an embodiment of the present invention incorporating two expansion chambers in a staggered arrangement.

SUMMARY OF THE INVENTION

The present invention achieves the afore stated objectives and advantages by providing an exhaust system design which is both compact and maintains a preferred individual expansion chamber design. The compact design is achieved by enclosing the expansion chambers as a substantially single unit and using common or shared dividers between chambers so as to allow the shaping of the chambers into a compact cross sectional design. DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

Fig. 1 illustrates an exemplary embodiment of the present invention. Exhaust system 30 includes expansion chambers 31 and 32. Chamber 31 includes header passage 33, divergent section 35, and convergent section 37. Chamber 32 includes header passage 3 , divergent section 36, and convergent section 38. Common divider 40 is a divider between chambers 31 and 32 and allows for exhaust system 30 to be designed with a very compact cross sectional profile. Tail pipe 39 communicates with, and receives exhaust from, both chambers 31 and 32.

The design of exhaust system 30 can be varied so that the length of the common divider 40 can vary between spanning the entire length of exhaust system 30 and spanning only a very small section of exhaust system 30.

Exhaust system 30 can be constructed in multiple sections and then assembled, for example by bolting or clamping the sections together. Line II-II illustrates one possible division point which would divide exhaust system 30 into upstream and downstream sections. In operation the upstream section would be attached to the engine and the downstream section attached to the upstream section.

Fig. 2 illustrates a sectional view of exhaust system 30 of Fig. 1 along line I-I and illustrates one possible cross sectional design of chambers 31 and 32, and divider 40.

Fig. 3 illustrates a cross sectional view of exhaust system 45 which includes expansion chambers 46 and 47, and dividers 48 and 49 which are complementarily shaped and mounted closely together so that in combination they form an effective common divider between chambers 46 and 47.

Fig. 4 illustrates a sectional view of exhaust system 50 which includes chambers 51 and 52, and common divider 53. In this example the length of common divider 53 is less than the maximum diameter of the chambers 51 and 52.

Fig. 5 illustrates a sectional view of exhaust system 60 which includes chambers 61 and 62 which are both of substantially circular cross section. Chamber 62 is fully enclosed within chamber 61 by common divider 63.

Fig. 6 illustrates a sectional view of exhaust system 70 which includes chambers 71, 72, 73, and 74, and common dividers 75, 76,77, and 78. Exhaust system 70 would typically be used with a four combustion chamber engine and service each combustion chamber with an individual expansion chamber.

Fig. 7 illustrates a sectional view of exhaust system 80 which is substantially oval in shape and includes expansion chambers 81, 82, and 83. The profile of common dividers 84 and 85 illustrate that in any embodiment common dividers can be of various profiles such as corrugated, 84, and ribbed, 85.

Fig. 8 illustrates a sectional view of a staggered exhaust system 90 which includes expansion chambers 91 and 92, header passages 93 and 94, divergent sections 95 and 96, convergent sections 97 and 98, tail pipes 99 and 100, and common divider 101. This example illustrates that an exhaust system designed to utilize the present invention may include one or more expansion chambers in a staggered position. VARIATIONS IN ENGINE COMBUSTION CHAMBERS SERVICED BY HEADER PASSAGES

In order to achieve improved performance it is suggested that any one exhaust header passage and associated expansion chamber service only one engine combustion chamber or multiple combustion chambers which fire together. For example, exhaust system 30, Fig. 1, could be applied to a two combustion chamber engine, or to a four combustion chamber engine with chambers firing in pairs. When applied to a four chamber engine exhaust system 30 could be connected to a suitable four into 2 manifold or header passages 33 and 34 could be modified so that each branch into two passages.

VARIATIONS IN COMMON DIVIDER PROFILES

In some applications it can be beneficial to design common dividers with a non-linear profile so as to avoid flat areas in the dividers. Strong sonic pulses travel through the exhaust system which can cause 'ringing' or 'drumming' in flat surfaces. This effect can be particularly evident in systems constructed of thin materials such as sheet metal and can be greatly reduced by designing common dividers with surfaces such as curved, corrugated, or ribbed. Fig. 7 illustrates examples of such common divider designs.

Common dividers may be constructed of a single element or multiple elements of complimentary shape mounted closely together to form an effective common divider. Fig. 3 illustrates an example of such effective common divider. In any arrangements an exhaust system may include one or more common dividers and the common dividers may span varying percentages of the total length of the exhaust system. In some arrangements the common divider may span the entire length of the exhaust system including header passages. In other arrangements the common dividers may span only a small section of the exhaust system.

VARIATIONS IN TAIL PIPES.

In any application an exhaust system may include one or more tail pipes in communication with one or more expansion chambers. For example, in Fig. 1 tail pipe 39 receives exhaust from expansion chambers 31 and 32. In Fig. 8, expansion chambers 91 and 92 have individual tail pipes 99 and 100. Tail pipes can be positioned in any location within an exhaust system.

VARIATIONS IN CONSTRUCTION

In any arrangement an exhaust system can be constructed of any suitable material which can be formed into the required structure and can withstand the exhaust environment such as: metal which is cast, pressed, or welded sections, carbon fiber, composites, high temperature plastics, plastics with a temperature insulating lining or coating.

In any arrangement an exhaust system can be constructed as a single unit or constructed in multiple sections which are attached together (for example: bolted or clamped) . Joins in a multiple section construction can be longitudinal, latitudinal, or in any plane. In Fig. 1, line II-II is an example of a possible attachment point if exhaust system 30 was constructed in two sections.

COMBINATION WITH EXHAUST CONTROL AND EXHAUST VARYING DEVICES

In any arrangement the present invention may be combined with exhaust devices such as water injection, displaceable convergent sections, displaceable reflecting baffles, and exhaust control devices which varying any physical dimension of the exhaust system such as varying length header passages.

Although the descriptions above contain many specifications and specific modifications, these should not be construed as limiting the scope of the invention but as merely providing examples of some of the presently preferred embodiments of this invention. For example, in any arrangement where a single passage is referred to, specified, or implied, then the single passage may be replaced with a combination of multiple passages. The term 'passage' can include instances of both single and multiple passages.

Thus the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given.

Claims

CLAIMS: I claim:

1. An exhaust system for an internal combustion engine including at least two combustion chambers having an exhaust sub-system comprising: an exhaust passage means communicating with the exhaust port means of said combustion chamber; a divergent exhaust section positioned downstream of said exhaust passage means; a convergent exhaust section positioned downstream of said divergent exhaust section; and an effective dividing means which is at least partially common to said divergent exhaust section and at least one other said divergent exhaust section within said exhaust system.

2. An exhaust system according to claim 1 wherein the profile of said effective dividing means is selected from the group consisting of flat, curved, corrugated, and ribbed.

3. An exhaust system according to claim 1 wherein at least one said divergent exhaust section is staggered in relation to the position of at least one other said divergent exhaust section.

4. An exhaust system according to claim 1 wherein said effective dividing means consists of multiple dividing elements where at least two said dividing elements are of complimentary shape and positioned in close proximity to one another so as to substantially form a single effective dividing means.

5. An exhaust system according to claim 1 wherein at least one axial section one said divergent exhaust section is wholly contained within an adjacent said divergent exhaust section.

6. An exhaust system for an internal combustion engine with at least two combustion chambers comprising: multiple exhaust passages each communicating with at least one exhaust port means of said engine; a divergent exhaust section positioned downstream of each said exhaust passage; a convergent exhaust section positioned downstream of each said divergent exhaust section; effective dividing means which is common to at least two said divergent exhaust sections or to at least two said convergent exhaust sections.

7. An exhaust system according to claim 6 wherein the profile of said effective dividing means is selected from the group consisting of flat, curved, corrugated, and ribbed.

8. An exhaust system according to claim 6 wherein at least one said divergent exhaust section is staggered in relation to the position of at least one other said divergent exhaust section.

9. An exhaust system according to claim 6 wherein said effective dividing means consists of multiple dividing elements where at least two said dividing elements are of complimentary shape and positioned in close proximity to one another so as to form a single effective dividing means.

10. An exhaust system according to claim 6 wherein at least one axial section of one said divergent exhaust section is wholly contained within an adjacent part of one other said divergent exhaust section.