Outboard motor cooling system with inserts to affect operating temperatures

Abstract

Inserts are disposed in water passages of the engine of an outboard motor in order to inhibit the flow of water, drawn from a body of water, in thermal communication with certain portions of cylinder walls of the engine. Extensions are formed as an integral part of the inserts in order to maintain the proper location of the inserts within the cooling passages.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is generally related to cooling systems for engines and outboard motors and, more particularly, to inserts that are intended to affect the rate of flow of cooling water through the water jackets formed within the structures of those engines.

2. Description of the Related Art

Those skilled in the art of marine propulsion systems are aware of many different cooling systems used to control the operating temperature of engines used in those marine propulsion devices. Marine propulsion devices present a specific and unique difficulty in the control of engine operating temperatures. Open systems, in which water is drawn from a body of water and pumped through cooling passages of the engine, are forced to use the water drawn from those bodies of water as the cooling medium. That water can vary significantly in temperature from nearly freezing to temperatures in excess of 80 degrees Fahrenheit. Although thermostats can be used to affect the rate of flow of cooling water through engine water passages, the initial intake of cooling water from a body of water can significantly reduce the temperature of certain portions of the engine to magnitudes that can lead to significant fuel dilution problems. As an example, overcooled cylinder walls can condense fuel vapors to liquid form and cause the condensed fuel to mix with oil used for lubrication. That mixing of condensed fuel with lubricating oil, which is referred to herein as dilution, can adversely affect the operation of the engine if it is not appropriately addressed. The problem of very cold water being drawn directly from a body of water and pumped to the cooling passages of an engine are not experienced in land vehicles which incorporate closed cooling systems that can more easily be regulated to control the internal operating temperature of both the coolant and the engine through which the coolant flows.

British patent 1,012,082, which was published on Dec. 8, 1965, describes a cooling system for an internal combustion engine. An internal combustion engine has a cylinder wall comprising a cast portion in which a liner is located, a cooling passage adjacent to the outer surface of the cylinder wall, a piston which is reciprocable within the cylinder adjacent the inner surface of the cylinder wall, a cylinder head closing one end of the cylinder, and a liner that has projections on its outer surface which contact the inner surface of the cast portion of the wall of the cylinder and the projections are dimensioned, shaped and positioned to give a greater degree of heat transfer to the cast portion of the cylinder wall at the combustion end of the cylinder than at the other end for a given temperature difference between the inner and outer surfaces of the wall.

U.S. Pat. No. 4,569,313, which issued to Nobu on Feb. 11, 1986, describes a cooling water path for an internal combustion engine. The path is characterized in that within a water jacket in the cylinder head there are installed a plurality of head partition walls located between adjacent cylinders extending the full width of the head with a ventilation hole provided at the top.

U.S. Pat. No. 6,295,954, which issued to Suzuki on Oct. 2, 2001, describes a cylinder block for water cooled engines. The engine has a top deck, a cylinder wall structure defining a row of cylinder bores, and a water jacket wall structure defining a water jacket around the cylinder bores. The jacket wall structure has a plurality of cylinder head bolt bosses each formed with a bolt hole for a cylinder head bolt for fastening a cylinder head at the top deck of the cylinder block.

U.S. Pat. No. 6,834,625, which issued to Matsutani et al. on Dec. 28, 2004, describes a cooling apparatus of an internal combustion engine. A cooling apparatus of an internal combustion engine includes a closed deck type cylinder block and an insert. The cylinder block includes a water jacket and an upward deck including a water hole formed therein. The insert is disposed in the water jacket and inserted into the water jacket through the water hole. The insert is fixed relative to the cylinder block at a water hole portion such that the insert is fixed in position in a flow direction of the cooling water.

U.S. Pat. No. 6,874,451, which issued to Matsutani et al. Apr. 5, 2005, describes a cooling apparatus of an internal combustion engine. It includes an insert that is deformable, and a surface of the insert opposing a cylinder bore wall is close to the cylinder bore wall after the insert is inserted into a water jacket. A cooling apparatus of an internal combustion engine includes a cylinder block having a water jacket in which an insert is disposed. The cylinder block is machined so that a water hole or an aperture having a size corresponding to a size of the insert is formed in the cylinder block and the insert can be inserted into the water jacket through the water hole the aperture.

U.S. Pat. No. 7,032,547, which issued to Xin on Apr. 25, 2006, describes a cylinder block cooling arrangement for a multi-cylinder internal combustion engine. An insert of a Siamese-type internal combustion engine that separates a water jacket surrounding the cylinders into an upper portion and a lower portion is described. Below a predetermined engine speed coolant flows primarily in the upper water jacket portion so as to provide enhanced cooling at the upper portions of the cylinders. Above a predetermined engine speed coolant is introduced into the lower water jacket portion from the upper water jacket portion so as to provide improved cooling of the lower cylinder portions, without compromising cooling of the upper cylinder portions or the conjoined cylinder wall portions.

The patents described above are hereby expressly incorporated by reference in the description of the present invention.

An article, titled “Fuel Savings for Toyota” describes the use of inserts within cooling jackets of internal combustion engines for automobiles. The inserts are described as resulting in a significant fuel economy saving of approximately 1%. The function of the water jacket spacer is the equalization of the cylinder wall temperatures and average engine temperatures. The water jacket spacer addresses this challenge by reducing the friction between pistons and cylinders. The upper part of the spacer adjusts and cools down the flow rate of the coolant. The lower part limits the flow rate of the coolant and keeps it relatively warm.

Inserts, disposed within cooling jackets of engines, are generally known to those skilled in the art for use in internal combustion engines that are used in land vehicles with closed cooling systems. These vehicles use closed cooling systems in which the coolant is recirculated continually under the operational control of one or more thermostats. As such, the temperature of the coolant can be controlled with relatively high accuracy to prevent overcooling or overheating of portions of the engine relative to other portions. Internal combustion engines used in marine propulsion devices often incorporate open cooling systems in which water is drawn from a body of water in which the marine propulsion device is operated. No control is available over the incoming temperature of the water drawn from the lake or ocean and pumped directly to the cooling passages of the engine. This presents a unique difficultly since very cold cooling water can overcool certain portions of the engine. Meanwhile, other portions of the engine, which are heat producing, require the temperature to be maintained below certain upper threshold magnitudes.

It would therefore be significantly beneficial if a cooling system could be provided in which cooling water is allowed to flow easily to certain heat producing regions of the engine while being inhibited from flowing directly into other non-heat producing portions.

SUMMARY OF THE INVENTION

An outboard motor cooling system, in accordance with a preferred embodiment of the present invention, comprises an engine which comprises a block portion and a head portion. The block portion has a cylinder disposed to support a piston therein for reciprocation along a generally horizontal path. A water passage is formed within the engine and disposed in thermal communication with the cylinder. The water passage has a first portion extending in a direction generally toward a crankcase of the engine and a second portion extending in a direction generally toward the head of the engine. A water pump is disposed in fluid communication with the water passage and with a body of water in which the outboard motor is operating. The water pump is configured to draw water from the body of water and induce the water to flow through the water passage. An insert is disposed within the water passage at a location which inhibits the water from flowing in thermal communication with a portion of the cylinder extending away from the head.

In a preferred embodiment of the present invention, the location in which the insert is disposed within the water passage is within the first portion of the water passage. In certain embodiments, the present invention can further comprise an extension formed as an integral portion of the insert and extending in a direction into the second portion of the water passage. The insert is made of a water impermeable material in a preferred embodiment of the present invention and is shaped to provide an interference fit with the water passage. The insert is configured to have a plurality of ribs formed on at least one of its surfaces in a preferred embodiment. The engine can comprise two cylinders. The water passage can be disposed in thermal communication with both of the two cylinders. The insert can be disposed within the water passage at the location which inhibits the water from flowing in thermal communication with the portions of the two cylinders extending away from the head. The water is returned to the body of water after passing through the water passage in thermal communication with the cylinder.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more fully and completely understood from a reading of the description of the preferred embodiment in conjunction with the drawings, in which:

FIG. 1 shows the engine block of an engine of a 4-stroke outboard motor;

FIG. 2 is a side section view of the engine in FIG. 1;

FIG. 3 is a highly schematic representation showing the flow of water from a body of water into the engine cooling passages of an outboard motor;

FIGS. 4 and 5 show isometric views of two inserts used in a preferred embodiment of the present invention;

FIG. 6 is a graphical representation of surface temperatures taken during empirical studies of a preferred embodiment of the present invention;

FIG. 7 shows a series of oil temperatures taken at various engine speeds; and

FIG. 8 shows the beneficial effects on percent oil dilution resulting from the use of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Throughout the description of the preferred embodiment of the present invention, like components will be identified by like reference numerals.

FIG. 1 shows an engine 10 having two cylinders, 21 and 22. In FIG. 1, two inserts, 31 and 32, are shown disposed within a water jacket surrounding the cylinders, 21 and 22.

FIG. 2 is a side section view of the illustration shown in FIG. 1. For purposes of reference, point 40 is an axis of rotation of a crankshaft (not shown in FIGS. 1 and 2) that is connected by connecting rods to pistons disposed in the first and second cylinders, 21 and 22. The pistons are not shown in FIGS. 1 and 2. The inserts, 31 and 32, are disposed within a cooling jacket 44 that surrounds the cylinders. The upper surface 50 of the engine block is shaped to receive a gasket on its planar surface and a head portion of the engine, with the gasket being disposed between the engine block 60 and the engine head (not shown in FIGS. 1 and 2). Those skilled in the art of engine construction are well aware of the various types of engine heads that can be used to form an engine with the engine block shown in FIGS. 1 and 2.

FIG. 3 is a highly schematic representation of an outboard motor showing the engine block 60 and an engine head 61 attached to the block. It should be understood that, although FIG. 3 shows the head 61 above the block 60, this is not the case in the normal arrangement of the engine of an outboard motor. Instead, the head portion 61 is disposed at a forward position in front of the block portion 60. In other words, the pistons within the cylinders move in a reciprocating pattern along horizontal axes. The crankshaft is supported for rotation about a generally vertical axis and it drives a driveshaft that extends vertically downward through a driveshaft housing. The driveshaft is connected in torque transmitting relation with the propeller shaft which causes a rotation of a propeller. Water is drawn by a pump 70 and caused to flow in the direction of the arrows in FIG. 3 to the engine block 60. The water flows through various cooling passages and cooling jackets within the engine block 60 and the head 61. The arrows in FIG. 3 show the water passage as extending upward only through the engine block 60 from which it returns to the body of water 68 from which it was drawn. This is an open loop cooling system, in which water from the body of water 68 is used to remove heat from heat generating portions of the engine and then return to the body of water. The water flows through the engine at approximately the temperature of the water within the body of water 68. Although some slight warming occurs as it passes through the engine, the water is initially at the temperature of the body of water when it is drawn upwardly by the pump 70.

With continued reference to FIGS. 1-3, points 81 and 82 in FIG. 1 represent axes along which pistons are supported within the cylinders 21 and 22 for reciprocal motion. It should be understood that the primary heat producing region in FIG. 2 is the upper portion of the cylinders closest to the combustion chambers within the head. It can be seen that the inserts, 31 and 32, fill a majority of the cooling jacket 44 in the portion which is farther from the engine head and closest to the crankcase 88. The walls of the cylinders closest to the crankcase 88 receive the least amount of heat generated during the combustion process.

FIGS. 4 and 5 are isometric views of the inserts, 31 and 32, described above in conjunction with FIGS. 1 and 2. When the cooling jackets 44 are formed during a casting procedure, the depth is not necessarily uniform for all portions of the cooling jacket. This is due to various limitations required to provide a satisfactory casting. In addition, the depth of the water jacket, measured as a distance from surface 50, is sometimes greater than is necessary for cooling purposes. Therefore, the cylinders, 21 and 22, can be overcooled if the entire cooling jacket 44 is used. With the inserts, 31 and 32, disposed within the cooling jacket 44, water drawn from the body of water 68, as described above in conjunction with FIG. 3, is prevented from circulating in the portion of the cylinder wall most proximate the crankcase 88 and farthest away from the heat generating region of the combustion chamber.

With continued reference to FIGS. 4 and 5, it can be seen that the height of insert 31 is significantly less than the height of insert 32 because of the configuration of the water jacket 44 illustrated in FIG. 2. It can also be seen that both inserts, 31 and 32, have ribs 90 extending along the surface 92 that faces inwardly toward the cylinders, 21 and 22, as described above in conjunction with FIGS. 1 and 2.

With continued reference to FIGS. 1-5, it can be seen that the primary purpose of the inserts, 31 and 32, is to fill a portion of the water jacket 44 and prevent the circulation of cold water proximate the walls of the cylinders that are in a region farthest from the heat producing portions near the combustion chambers. In other words, they take up space that would otherwise be filled with cold water that could be drawn from the body of water 68 in the manner described above.

One of the primary problems in engine cooling systems associated with marine propulsion devices is that very cold water can be drawn from a body of water 68 and caused to flow in thermal communication with various portions of the cooling passages of the engine. If portions of the cylinders walls are overcooled, this can lead to the condensation of fuel from the fuel vapor circulating within the cylinders. If this condensation occurs, the pistons can wipe the condensed fuel droplets in a direction toward the crankcase and cause the condensed fuel to mix with the oil within the crankcase. This creates a dilution of the oil and can have a deleterious effect on its lubricating capabilities. Eventually, it can collect in the oil sump to the degree that actually causes the oil sump to overflow because of the additional quantity of liquid provided by the condensed fuel. Both situations can be seriously disadvantageous to the proper operation of a marine engine. One of the primary functions of the present invention is to prevent or inhibit the overcooling of the portion of the cylinders walls farthest from the combustion chambers in the head of the engine and closest to the crankcase.

FIG. 6 is a graphical representation of some test results performed during the development of the present invention. It shows a line 100 that represents the average engine cylinder wall temperatures taken at various selected locations in an engine incorporating the inserts, 31 and 32, of the present invention. Line 110 represents the same engine without the inserts in place. As can be seen, the temperatures are significantly higher at the selected engine wall locations in the engine 100 that includes the inserts. By raising the engine wall temperatures, condensation of fuel vapor is decreased and, as a result, the amount of dilution of the engine oil is significantly decreased. FIG. 7 is a graphical representation which shows a line 200 that represents oil temperature at various engine speeds of the oil sump temperatures in an engine incorporating the inserts, 31 and 32, of the present invention. Line 210 shows the oil sump temperatures in an engine which does not contain the inserts. The consistent increase at all engine operating temperatures can be seen.

With continued reference to FIGS. 6 and 7, it should be understood that the surface temperatures represented in FIG. 6 and the oil temperatures represented in FIG. 7, by themselves, do not represent a functional improvement that is the primary goal of the present invention. Instead, the temperatures of the surfaces illustrated in FIG. 6 and the oil illustrated in FIG. 7 show an intermediate result that leads to the intended beneficial result which will be described below.

FIG. 8 shows actual measurements of percent oil dilution, by volume, taken during the operation of two engines. Line 300 shows the actual measured oil dilution percentage for a 20 horsepower 4-stroke engine that does not include the inserts of the present invention. Line 310 shows the actual measured oil dilution percentages, by volume, resulting in a 20 horsepower 4-stroke engine that includes the inserts of the present invention. During the testing that resulted in the data shown in FIG. 8, the engines were run at a constant 4300 RPM for two hours. After a preliminary warm-up period, the percentage of oil dilution was measured at zero minutes after the warm-up, 30 minutes, 60 minutes, 90 minutes, and 120 minutes after the warm-up. As is dramatically evident in FIG. 8, the percentage of oil dilution represented by line 300 is significantly higher than that represented by line 310. Line 310 shows the results and the improvement obtained through the use of the inserts of the present invention. By reducing the amount of cooling water flowing through the regions of the water jacket 44 closest to the crankcase and furthest from the combustion chambers, the percentage of oil dilution is significantly reduced.

With continued reference to FIGS. 1-8, it can be seen that an outboard motor cooling system made in accordance with a preferred embodiment of the present invention comprises an engine having a block portion 60 and a head portion 61. The block portion 60 has a cylinder, 21 or 22, disposed to support a piston therein for reciprocation along a generally horizontal path, 81 or 82. A water jacket 44 formed within the engine and disposed in thermal communication with the cylinder, 21 or 22, is disposed within the engine block. The water jacket 44 has a first portion extending in a direction toward a crankcase 88 of the engine and a second portion extending in a direction toward the head. A water pump 70 is disposed in fluid communication with the water jacket 44 and with a body of water 68 in which the outboard motor is operating. The water pump 70 is configured to draw water from the body of water 68 and induce the water to flow through the water jacket 44. An insert, 31 or 32, is disposed within the water jacket 44 at a location which inhibits the water from flowing in thermal communication with a portion of the cylinder extending away from the head 61.

With continued reference to FIGS. 1-8, the location in which the insert is disposed is within the first portion of the water jacket 44. This is shown in FIG. 2. An extension 35 is formed as an integral portion of the insert, 31 or 32, and extends in a direction into the second portion of the water passage. In other words, the extensions extend from the main body of the inserts, 31 and 32, and toward the head 61 and away from the crankcase 88. The primary purpose of the extensions 35 is to maintain the location of the main body of the inserts at their locations which are closest to the crankcase 88 and away from the head 61. In a preferred embodiment of the present invention, the inserts, 31 and 32, are made of a water impermeable material. Such a material is thermoplastic copolyester elastomer which is available in commercial quantities from the DuPont Corporation under the name Hytrel 5526. The inserts, 31 and 32, are shaped to provide an interference fit with the water jacket 44. The insert is configured to have a plurality of ribs 90 formed on at least one of its surfaces. The engine, in one embodiment of the present invention, comprises two cylinders, 21 and 22. The water jacket 44 is disposed in thermal communication with the two cylinders, 21 and 22, and the insert is disposed within the water passage at the location which inhibits the water from flowing in thermal communication with the portions of the two cylinders extending away from the head 61. The water is returned to the body of water 68 after passing through the water jacket 44 in thermal communication with the cylinder.

Although the present invention has been described with particular specificity and illustrated to show a preferred embodiment, it should be understood that alternative embodiments are also within its scope.

Claims

1. An outboard motor cooling system, comprising: an engine comprising a block portion and a head portion, said block portion having a cylinder disposed to support a piston therein for reciprocation along a generally horizontal path;a water passage formed within said engine and disposed in thermal communication with said cylinder, said water passage having a first portion extending in a direction toward a crankcase of said engine and a second portion extending in a direction toward said head, said first and second portions being spaced apart horizontally;a water pump disposed in fluid communication with said water passage and with a body of water in which said outboard motor is operating, said water pump being configured to draw water from said body of water and induce said water to flow through said water passage; andan insert disposed within said water passage at a location which inhibits said water from flowing in thermal communication with a portion of said cylinder extending away from said head in a horizontal direction.

2. The cooling system of claim 1, wherein: said location is within said first portion of said water passage.

3. The cooling system of claim 1, further comprising: an extension, formed as an integral portion of said insert and extending in a direction into said second portion of said water passage.

4. The cooling system of claim 1, wherein: said insert is made of a water impermeable material.

5. The cooling system of claim 1, wherein: said insert is shaped to provide an interference fit with said water passage.

6. The cooling system of claim 1, wherein: said insert is configured to have a plurality of ribs formed on at least one of its surfaces.

7. The cooling system of claim 1, wherein: said engine comprises two of said cylinders, said water passage is disposed in thermal communication with said two cylinders, said insert being disposed within said water passage at said location which inhibits said water from flowing in thermal communication with said portions of said two cylinders extending away from said head.

8. The cooling system of claim 1, wherein: said water is returned to said body of water after passing through said water passage in thermal communication with said cylinder.

9. An outboard motor cooling system, comprising: a four stroke engine comprising a block portion and a head portion, said block portion having a cylinder disposed to support a piston therein for reciprocation along a generally horizontal path;a water passage formed within said engine and disposed in thermal communication with said cylinder, said water passage having a first portion extending in a direction toward a crankcase of said engine and a second portion extending in a direction toward said head, said first and second portions being spaced apart horizontally;a water pump disposed in fluid communication with said water passage and with a body of water in which said outboard motor is operating, said water pump being configured to draw water from said body of water and induce said water to flow through said water passage; andan insert disposed within said water passage at a location which inhibits said water from flowing in thermal communication with a portion of said cylinder extending away from said head, said location being within said first portion of said water passage and spaced apart from said head in a horizontal direction.

10. The cooling system of claim 9, wherein: said insert is shaped to provide an interference fit with said water passage.

11. The cooling system of claim 10, further comprising: an extension, formed as an integral portion of said insert and extending in a direction into said second portion of said water passage.

12. The cooling system of claim 9, wherein: said engine comprises two of said cylinders, said water passage is disposed in thermal communication with said two cylinders, said insert being disposed within said water passage at said location which inhibits said water from flowing in thermal communication with said portions of said two cylinders extending away from said head.

13. The cooling system of claim 9, wherein: said insert is made of a water impermeable material.

14. The cooling system of claim 9, wherein: said insert is configured to have a plurality of ribs formed on at least one of its surfaces.

15. The cooling system of claim 9, wherein: said water is returned to said body of water after passing through said water passage in thermal communication with said cylinder.

16. An outboard motor cooling system, comprising: an engine comprising a block portion and a head portion, said block portion having a cylinder disposed to support a piston therein for reciprocation along a generally horizontal path;a water passage formed within said engine and disposed in thermal communication with said cylinder, said water passage having a first portion extending in a direction toward a crankcase of said engine and a second portion extending in a direction toward said head, said first and second portions being spaced apart horizontally;a water pump disposed in fluid communication with said water passage and with a body of water in which said outboard motor is operating, said water pump being configured to draw water from said body of water and induce said water to flow through said water passage, said water being returned to said body of water after passing through said water passage in thermal communication with said cylinder; andan insert disposed within said water passage at a location which inhibits said water from flowing in thermal communication with a portion of said cylinder extending away from said head in a horizontal direction.

17. The cooling system of claim 16, wherein: said engine comprises two of said cylinders, said water passage is disposed in thermal communication with said two cylinders, said insert being disposed within said water passage at said location which inhibits said water from flowing in thermal communication with said portions of said two cylinders extending away from said head.

18. The cooling system of claim 17, wherein: said location is within said first portion of said water passage, said insert being shaped to provide an interference fit with said water passage.

19. The cooling system of claim 18, wherein: said insert is made of a water impermeable material and is configured to have a plurality of ribs formed on at least one of its surfaces.

20. The cooling system of claim 19, further comprising: an extension, formed as an integral portion of said insert and extending in a direction into said second portion of said water passage.