Combination liquid-cooled exhaust manifold assembly and catalytic converter assembly for a marine engine

An exhaust system for a marine engine comprising liquid-cooled manifold and catalytic converter assemblies. Each assembly uses a separate cooling system to cool either the exhaust manifold or a shell inside which resides the catalytic converter. The housing or shell containing the catalytic converter uses water to cool an exterior surface of a water jacket to an acceptable temperature conforming to federal regulations. The liquid-cooled manifold assembly may use either water or glycol to cool outer cooling tubes surrounding exhaust tubes extending from the engine block to the catalytic converter assembly.

FIELD OF THE INVENTION

The present invention relates to exhaust systems for combustion engines and, more particularly, to the exhaust manifold and catalytic converter of such exhaust systems.

BACKGROUND OF THE INVENTION

Exhaust systems for a combustion engine generally include a manifold connected to the combustion engine at one end and bolted to an exhaust pipe at the other end. The exhaust pipe extends a distance from the manifold and generally has a catalytic converter system bolted thereto. These catalytic converter systems generally include a ceramic substrate having a catalyst coated thereon and a metal housing surrounding the substrate. In general, the catalysts require a minimum temperature to react with the emissions and reduce them. Higher reaction temperatures enhance the removal of harmful emissions from the exhaust gases. The core temperature of conventional catalytic converters is typically 1,000 to 1,400° F. In automobile applications, the exterior surfaces of the catalytic converters are air cooled, rather than water-cooled, to a temperature of about 600 to 1,000° F. Such high temperature far exceeds the 200° F. set by the United States Coast Guard for the exterior temperature of the exhaust system of inboard or stern drive engines.

Although catalytic converters have been required in cars for many years, they have not been required in marine vessels with inboard or stern drive engines. However, in 2009, catalytic converters began being required by federal law in new marine vessels with inboard or stern drive engines. This requirement is challenging because it has been difficult to maintain a sufficiently cooled exterior temperature for marine applications while also maintaining a sufficiently high enough temperature in the element or core of the catalytic converter. The United States Coast Guard has a limit of 200° F. for the exterior temperature of the exhaust system of inboard or stern drive engines. The United States Environmental Protection Agency (“USEPA”) has emissions standards which require use of a catalytic converter in inboard or stern drive engines.

One known method of reducing the exterior temperature of the housing in which resides a catalytic converter for a marine vessel is to water cool the housing. This concept is disclosed in U.S. Patent Publication No. US 2009/0175772, published Jul. 9, 2009.

However, there is a need to maintain all exposed surfaces below the 200° F. limit by surrounding the exhaust manifold with liquid to cool the tubes containing the exhaust prior to these exhaust gases entering a liquid cooled catalytic converter.

SUMMARY OF THE INVENTION

According to embodiments of the present invention, an exhaust system for a marine engine comprises the combination of a liquid-cooled exhaust manifold assembly and a liquid-cooled catalytic converter assembly. The exhaust manifold assembly comprises a plurality of tube assemblies, each of the tube assemblies comprising an exhaust tube extending from a mounting plate secured to a marine engine to the catalytic converter assembly and an outer tube surrounding the exhaust tube. These concentric tubes are different lengths, the outer tube being shorter than the exhaust tube. The tubes are twisted, optimized in size and shape, to give optimal engine performance. The outer tube of each tube assembly is spaced from the exhaust tube and defines a cooling cavity therebetween. The outer and inner or exhaust tubes of each tube assembly are welded to the mounting plate, thereby increasing the efficiency of the manufacturing process. More specifically, the exhaust tube of each tube assembly is flared at one end, the flared portion being welded to the outer tube and being welded to the mounting plate. The outer tube of each tube assembly has flattened sides adapted to fit inside a similarly shaped opening in the mounting plate. The catalytic converter assembly, located downstream of the liquid-cooled exhaust manifold assembly, functions to control engine exhaust emissions exiting the liquid-cooled exhaust manifold assembly.

The exhaust manifold assembly further comprises a feed tube and a collector. Liquid in the form of water or glycol is circulated from a fluid source via a first pump through a feed tube. The feed tube may be made of stainless steel and have liners inside extension of the feed tube. The liners may be made of soft steel and are intended to rust before the feed tube does. The feed tube is in fluid communication with the cooling cavity of each tube assembly. The cooling fluid used in the exhaust manifold assembly is collected in a collector after having passed through the cooling cavities of the tube assemblies and exits the collector through a collector outlet so as to always maintain the outside temperature of the outer tubes of the exhaust manifold assembly at less than 200° F. whenever the engine to which the manifold is connected is operated.

An inlet port is provided for supplying cooling water to fluid passage surrounding a catalytic converter housing to cool and maintain the outside surface of the catalytic converter assembly below a predetermined temperature. This water passage surrounding the catalytic converter discharges the water into the exhaust gases at the discharge end of the catalytic converter assembly.

Water from a second pump is also circulated through a fluid passage surrounding the catalytic converter housing so that the catalytic converter is always water-cooled and the outside temperature of the converter assembly maintained at a temperature of less than 200° F. when the engine is operated. From the exhaust or downstream side of the catalytic converter assembly, the water from the fluid passage flows around the catalytic converter assembly inner shell and is mixed with exhaust gases to be discharged with the exhaust gases after the gases have passed through the catalytic converter.

According to another aspect of the present invention, the exhaust system for a marine engine comprises: a liquid-cooled catalytic converter assembly including a catalytic converter fixed inside an inner shell and an outer shell surrounding the inner shell, the inner and outer shells defining a fluid passage therebetween. The outer shell is joined to the inner shell proximate an inlet end of the catalytic converter assembly. The outer shell has a fluid inlet in fluid communication with the fluid passage to introduce fluid into the fluid passage to cool and maintain the outside surface of the catalytic converter assembly below a predetermined temperature when liquid passes through the fluid passage.

The liquid-cooled exhaust manifold assembly comprises a plurality of tube assemblies welded to a mounting plate, each of the tube assemblies comprising an exhaust tube and an outer tube surrounding the exhaust tube. The outer tube is spaced from the exhaust tube and defines a cooling cavity therebetween. Liquid is supplied to the cooling cavity via a feed tube and is collected in a collector. The cooling liquid passes through the collector and exits via a collector port or outlet to cool the outside surface of the outer tube to maintain the outside temperature of the outer tube below a predetermined temperature. The outer tube of each tube assembly is welded to a baffle, which is welded to the collector to keep fluid used in the exhaust manifold assembly separate from fluid used in the catalytic converter assembly.

According to another aspect of the present invention, the exhaust system for a marine engine comprises a liquid-cooled exhaust manifold assembly and a liquid-cooled catalytic converter assembly downstream of the manifold assembly. The catalytic converter assembly includes a catalytic converter, an inner shell and an outer shell surrounding the inner shell. The inner and outer shells define a fluid passageway therebetween. The outer shell has a fluid inlet in fluid communication with the fluid passage to introduce fluid into the fluid passage to cool and maintain the outside surface of the catalytic converter assembly below a predetermined temperature when liquid passes through the fluid passage.

The liquid-cooled exhaust manifold assembly comprises a feed tube, a collector having an outlet and a mounting plate for securing the exhaust system to the marine engine. A plurality of tube assemblies are welded to the mounting plate. Each of the tube assemblies comprises an exhaust tube and an outer tube surrounding the exhaust tube. The outer tube of the tube assembly is shorter than the exhaust tube. The outer tube is welded to the mounting plate at one end and welded to a baffle at the other end, the baffle being welded to the collector. Each of the exhaust tubes is welded to the mounting plate at one end and to the catalytic converter assembly at the other end. Fluid may be introduced through the feed tube, passed between the exhaust and outer tubes of each of the tube assemblies and out the outlet of the collector to cool the outside surface of the tube assemblies to maintain the outside temperature of the tube assemblies below a predetermined temperature.

Thus, the exhaust system of the present invention has two separate cooling systems, each one functioning to cool the exterior temperature of a part of the exhaust system. These and other objects and advantages will be more readily apparent from the following drawings and detailed description.

It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of embodiments of the invention. The specific design features of embodiments of the invention as disclosed herein, including, for example, specific dimensions, orientations, locations and shapes of various illustrated components, as well as specific sequences of operations (e.g., including concurrent and/or sequential operations), will be determined in part by the particular intended application and use environment. Certain features of the illustrated embodiments may have been enlarged or distorted relative to others to facilitate visualization and clear understanding.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to the drawings, and particularly toFIG. 1, there is illustrated a diagrammatic illustration of an exhaust system10for a marine engine12(shown in phantom inFIG. 1). Arrows14are shown inFIG. 1illustrating exhaust gases exiting the cylinders of the marine engine12and entering the exhaust system10. Although the drawings illustrate the engine12having four cylinders, those skilled in the art will appreciate that the present invention may be used with two cylinder marine engines or any other like engine.

The exhaust system10comprises a combination of two basic components: a liquid-cooled exhaust manifold assembly16and a liquid-cooled catalytic converter assembly18located downstream of the exhaust manifold assembly16. In order to assemble the exhaust system10, the two components, the liquid-cooled exhaust manifold assembly16and a liquid-cooled catalytic converter assembly18, are welded together.

Referring toFIGS. 1 and 2, the components of the liquid-cooled exhaust manifold assembly16will be described. The liquid-cooled exhaust manifold assembly16comprises a mounting plate20made of steel having mounting holes22therethrough for mounting the liquid-cooled exhaust manifold assembly16to the engine block12with fasteners23(only one being shown inFIG. 1). As best shown inFIG. 2, mounting plate20also has a plurality of spaced exhaust holes24therethrough which allow the exhaust gases to pass through the mounting plate20and into the catalytic converter assembly18via tubular tube assemblies26. As best illustrated inFIGS. 1 and 2, each of the tube assemblies26comprises an exhaust tube or inner tube32and an outer tube34surrounding the exhaust tube32. Each of the exhaust tubes32and each of the outer tubes34has a hollow interior, the exhaust tube32and outer tube34of each tube assembly26being concentric.

As best illustrated inFIG. 2, each of the exhaust holes24of mounting plate20has a non-circular shape. Each of the exhaust holes24has what is known in the industry as a “double D” shape having two flat sides28and two arcuate or curved sides30.

As shown inFIGS. 2 and 7, the exhaust tube32and outer tube34of each tube assembly26are secured to each other and to the mounting plate20via a continuous circular weld36. As best shown inFIG. 7, the exhaust tube32of each tube assembly26is flared outwardly at one end along a flared portion38, thereby giving an end portion40of the exhaust tube32a larger diameter than the diameter of the remainder of the exhaust tube32. This flaring of the exhaust tube32enables the exhaust tube32to be welded to the outer tube34of the tube assembly26with continuous weld36, as shown inFIG. 7.

As shown inFIG. 1, the end of each outer tube34of each tube assembly26has opposed flattened sides41which are sized to fit inside the uniquely shaped exhaust holes24of the mounting plate20. In other words, each tube assembly26is sized to fit inside one of the exhaust holes24of the mounting plate20and be welded to the mounting plate20from the upper side ofFIG. 2with a continuous weld36. SeeFIG. 7also.

As shown inFIGS. 2,5and7, the exhaust tube32of each tube assembly26is welded at one end to the outer tube34of the tube assembly and mounting plate20at weld36. As shown inFIG. 5, the other end of the hollow tubular exhaust tube32of each tube assembly26is welded to a collector42and, more specifically, to a bottom portion44of the collector42at locations46, as shown inFIG. 5. As best shown inFIG. 5A, the collector42has a cup-shaped portion48and a baffle50. The cup-shaped portion48includes bottom portion44and a continuous side portion52extending towards the catalytic converter assembly18from the bottom portion44. The baffle50has four circular holes54through which pass the exhaust tube assemblies26, as shown inFIGS. 5 and 5A. As shown inFIG. 5, the outer tubes34of the tube assemblies26are welded to the baffle50at locations58and extend partially beyond the baffle50into the interior of the cup-shaped portion48of collector42. Like the baffle50, the bottom portion44of cup-shaped portion48of collector42has four circular holes56through which pass the exhaust tubes32of the tube assemblies26, as shown inFIGS. 3 and 5. The inner or exhaust tubes32of the tube assemblies26are welded at locations46to the bottom portion44of cup-shaped portion48of collector42and extend partially beyond the bottom portion44of cup-shaped portion48of collector42.

Each of the tubular exhaust tubes32is the same length to optimize engine performance. Similarly, each of the outer tubes34is the same length to optimize engine performance. The hollow exhaust tubes32are longer than the outer tubes34of each tube assembly26. During operation of the marine engine12, exhaust gases pass through the interior of the tubular exhaust tubes32into the catalytic converter assembly18, as shown by arrows15. SeeFIG. 5.

As best shown inFIGS. 1,2and7, exhaust manifold assembly16further comprises a feed tube60having a main linear portion62and a plurality of extensions64. Each of the extensions64extends perpendicular to the main linear portion62. The feed tube60may be made of stainless steel. The outer tube34of each tube assembly26has a nipple66, shown in cross-section inFIG. 7and shown in perspective inFIGS. 1 and 2. As shown inFIG. 7, a connector68extends between the nipple66of the outer tube34of the tube assembly26and the extension64of the feed tube60. The connector68covers the outer surfaces of the nipple66of the outer tube34of the tube assembly26and the extension64of the feed tube60. In one embodiment, the connector is a rubber hose; however, it may be made of any desirable material. Both the nipple66of the outer tube34of the tube assembly26and the extension64of the feed tube60have an annular bump70which aids in maintaining the connector68in place. A pair of hose clamps72, a first clamp over the portion of connector68surrounding the nipple66of the outer tube34of the tube assembly26and a second clamp surrounding the connector68over the extension64of the feed tube60, help secure them together. When tightened, the hose clamps72constrict or tighten the connector68over the nipple66of the outer tube34of the tube assembly26and the extension64of the feed tube60, as shown inFIG. 7.

As shown inFIGS. 2 and 7, each tube assembly26has a cooling cavity74defined by the inner and outer tubes32,34spaced from each other. As shown inFIG. 2, exhaust from the marine engine12passes through the tubular exhaust tubes32into the catalytic converter assembly18. This exhaust is cooled by either glycol or water passing through the cooling cavities74of the tube assemblies26. As shown by arrows76, the cooling fluid enters the cooling cavities74from the feed tube60through the extensions64of the feed tube60and then through the nipples66of the outer tubes34of tube assemblies26. The cooling fluid, as shown by arrows78ofFIG. 5, passes through the cooling cavities74of the tube assemblies26and enters the interior of collector42. Once inside the collector42, the cooling fluid exits the collector42via fluid or collector outlet80, as shown by arrow49inFIGS. 2 and 5. The cooling fluid exiting the collector outlet80of collector42, shown by arrow49ofFIGS. 2 and 5, may be recycled as shown inFIG. 6or returned to its source, as shown inFIG. 6A.

According to one aspect of the invention shown inFIG. 6, glycol from a fluid source82is pumped via a first pump84via conduit or pipe86to the feed tube60, through the cooling cavities74of the tube assemblies26of the exhaust manifold assembly16, out the cooling cavities74of the tube assemblies26into collector42, out collector42via collector outlet80and passes via conduit or pipe88back to the fluid source82. This is considered a closed-loop system and used primarily for use in salt water to prevent corrosion of the exhaust tube assemblies26.

According to another aspect of the invention shown inFIG. 6A, water from a fluid source90is pumped via a first pump92via conduit or pipe94to the feed tube60, through the cooling cavities74of the exhaust tube assemblies26, out the collector42via collector outlet80and passes via conduit or pipe96back to the fluid source, which is commonly the water of a water body on which the boat is used. This is considered an open system and used primarily for use in fresh water without affecting the tubular exhaust assemblies26which are exposed to the fluid of the cooling cavities74in both embodiments.

FIGS. 3 and 4illustrate the liquid-cooled catalytic converter assembly18which comprises a catalytic converter96held in place via a compressible mat98inside an inner shell or housing100. An outer shell102surrounds the inner shell100and is welded to the inner shell100at location104proximate an inlet106to the liquid-cooled catalytic converter assembly18and at locations108proximate bosses110. Bosses110are adapted to receive oxygen sensors112which help determine whether catalytic converter96is functioning properly. A fluid passage114is defined between the inner and outer shells100,102. As shown inFIGS. 3 and 4, the inner shell100is not concentric with the outer shell102proximate an outlet116of the liquid-cooled catalytic converter assembly18. Therefore, as shown inFIG. 4, the fluid passage114is crescent-shaped in cross-section proximate the outlet116of the catalytic converter assembly18.

A boss118having a passage120therethrough is welded to the outer shell102around an opening122(seeFIG. 3) through the outer shell102to create a fluid inlet124. Water or some other fluid is pumped from fluid pump126through the fluid inlet124(see arrow51ofFIGS. 1,2,3and5) into the fluid passage114. The fluid is illustrated inside fluid passage114by the arrows128inFIG. 3, while the exhaust is illustrated by arrows130ofFIG. 3. After the fluid exits the fluid passage114, it is mixed with the exhaust gases and both together exit the outlet of the liquid-cooled catalytic converter assembly18. As illustrated inFIGS. 6 and 6A, fluid, such as water from a fluid source132, is pumped via a pump126via conduit or line134into the fluid inlet124of the liquid-cooled catalytic converter assembly18. The fluid is then passed through the fluid passage114and exits the liquid-cooled catalytic converter assembly18, as indicated by the arrows136, as shown inFIGS. 6 and 6A.

FIG. 3illustrates two wire mesh dams138,140welded to the inner sleeve100and located inside the fluid passage114of the liquid-cooled catalytic converter assembly18. The second wire mesh dam140is located downstream of the first wire mesh dam138. The purpose of these wire mesh dams138,140is to channel the water flow inside the fluid passage114to optimize the outer surface cooling of the outer sleeve102. These wire mesh dams138,140force the water to cascade from section to section, allowing the water to fill around the entire fluid passage114, resulting in consistent outer surface cooling and reducing the possibility of hot spots. Without these dams, the water flow would partially fill the bottom half of the fluid passage114, especially at low engine revolution and low pump flow pressure, resulting in the top surface of the sleeve to exceed the maximum allowable temperature.

As shown inFIG. 7, each nipple66of each outer tube34of each tube assembly26has a liner142therein. The liner142is made of mild steel that will rust before the stainless steel of the feed tube60. The presence of the liners142makes it less likely that the feed tube60will rust.

Although we have described various embodiments of the invention, we do not intend to be limited except by the scope of the following claims.