Cooling System for a Liquid-Cooled Engine

1. Field of the Invention

The present invention relates to a cooling system for a liquid-cooled engine mounted on a vehicle as a vertical engine.

2. Description of the Related Art

As disclosed in U.S. Pat. No. 4,891,840, for example, a cooling system for a liquid-cooled engine as described above includes a duet extending from a cooling fan disposed rearwardly of a radiator to a muffler, whereby air taken in to cool the radiator is used also to cool the muffler. Specifically, the air delivered by the cooling fan flows through a curved air passage formed in a relatively narrow space between the engine and a hood, and out of the vehicle after directly colliding with the muffler. With this construction, the air delivered by the cooling fan is subjected to a relatively strong resistance. In order to cause a large quantity of air to flow past the radiator, the cooling fan must have an increased air impelling performance.

In order to lessen the resistance applied to the air delivered by the cooling fan, it is possible to cause the air to flow out of the vehicle through a duct extending straight forward from the cooling fan, as disclosed in U.S. Pat. No. 4,766,983, for example. In this case, however, the muffler cannot be exposed to the air currents produced by the cooling fan. In order to cool the muffler efficiently, it is necessary to devise a construction to suspend the muffler in a lower forward position of the vehicle, for example, so that air currents act directly on the muffler during a run.

In the case of a vehicle having a liquid-cooled engine with a radiator, the larger quantity of air the cooling fan causes to flow through the radiator, the more effectively the radiator is cooled. Therefore, in order to extend the use of air to cooling of the muffler, it is important to form such an air passage from the cooling fan to the muffler as to impose little or no burden on the cooling fan.

The object of the present invention is to provide a cooling system in which cooling air currents delivered by a cooling fan through a radiator are used also in forcibly cooling a muffler without significantly affecting the air currents.

The above object is fulfilled, according to the present invention, by a cooling system for a vehicle having a radiator disposed above an engine, and a muffler disposed in a region below the engine, comprising:

an air intake guide for guiding cooling air to the radiator from outside;

an exhaust guide for guiding a large part of the cooling air having flowed past the radiator, forwardly of the vehicle;

a cooling fan for producing air currents flowing from the air intake guide past the radiator to the exhaust guide; and

guide means provided for at least one side of the exhaust guide for guiding part of the cooling air having flowed passed the radiator to the muffler.

A quantity of air discharged forwardly and a quantity of air directed to the muffler may be appropriately selected by the exhaust guide for guiding a large part of the cooling air having flowed past the radiator, forwardly of the vehicle and the guide means for guiding part of the cooling air having flowed passed the radiator to the muffler.

In a preferred embodiment of the invention, the guide means includes a muffler cover substantially covering the muffler, and ducts extending between the muffler cover and the exhaust guide. The ducts forming the guide means are capable of transmitting the cooling air to desired positions of the muffler reliably and without substantial loss. Thus, a small quantity of air may be allocated to the ducts. As a result, a large part of air currents produced by the cooling fan flows to the exhaust guide, thereby entailing only a negligible resistance to exhaust flows.

The cooling air should desirably be directed to connections between exhaust pipes and the muffler. It is therefore preferable that the ducts open adjacent the connections between the exhaust pipes of the engine and the muffler.

Where the exhaust gas is not sufficiently cooled by cooling of the muffler, it is proposed as a preferred embodiment of the invention that the muffler includes an exhaust opening and an exhaust pipe connected to each other with a gap therebetween, whereby air in the muffler cover is drawn into the exhaust pipe by ejector action. With this construction, the exhaust gas mixes with the cooling air delivered by the cooling fan, to be exhausted from the vehicle through the exhaust pipe at a sufficiently low temperature.

As a construction suited for allocating a large quantity of air delivered by the cooling fan to the exhaust guide, and the remaining small quantity of air to the guide means, the present invention proposed to place the exhaust guide directly forwardly of the cooling fan, and the guide means in opposite regions transversely of the exhaust guide. That is, a large, central part of air currents from the cooling fan is discharged forwardly of the vehicle, while small parts of the air currents in the opposite side regions are given to the muffler through the guide means or ducts. This construction includes two ducts. In the case of a two-cylinder engine having two exhaust pipes, each duct may have an opening opposed to a connection between each exhaust pipe and the muffler.

Where a carburetor is disposed forwardly of the engine, the exhaust guide may include a cooling air release directed toward the carburetor. This construction reliably protects the carburetor which is vulnerable to heat.

Other features and advantages of the present invention will be apparent from the description of the preferred embodiment taken with reference to the drawings.

FIG. 1 is a side elevation of a riding lawn tractor employing a cooling system according to the present invention;

FIG. 2 is a side view in vertical section of a forward portion of the riding lawn tractor;

FIG. 3 is a front view in vertical section of the forward portion of the riding lawn tractor;

FIG. 4 is a perspective view of a dust netting;

FIG. 5 is a front view in vertical section of a muffler and adjacent components; and

FIG. 6 is a perspective view of the muffler and adjacent components.

FIG. 1 shows a mid-mount type riding lawn tractor having a mower 7 suspended from a tractor body 1 between front and rear wheels 2 and 3. This riding lawn tractor includes an engine hood 4 disposed on a forward portion thereof and housing a vertical engine 5 with an output shaft extending downward. The engine 5 has an output pulley for transmitting drive through a belt transmission 6 to the mower 7. The mower 7 is vertically movably attached to body frames 1A through a link mechanism 8 raised and lowered by operating a hand lever 9.

As shown in FIG. 2, the engine hood 4 houses the engine 5 which is water-cooled and has a horizontal radiator 11 and a radiator cooling fan 12 arranged in an upper position. A battery 13 is mounted rearwardly of the engine 5, while an air cleaner 14, a carburetor 15 and a muffler 16 are arranged forwardly of the engine 5. A box-shaped dust netting 19 is disposed above the radiator 11. A fan cover 20 extends forward from a space between the radiator 11 and engine 5. The fan cover 20 substantially covers the cooling fan 12 in combination with a lower surface of the radiator 11 and an upper surface of the engine 5, and acts as an exhaust guide for forwardly exhausting cooling air delivered from the cooling fan 12.

As shown in FIGS. 2 through 4, a shield 21 is connected to a bottom of the dust netting 19 to cover side surfaces of the radiator 11 and fan cover 20. Further, a heat shielding plate 22 straddles, and is fixedly connected to, an upper forward surface of the dust netting 19. A shield 26 is provided between the engine 5 and battery 13 for guiding radiator cooling air drawn in through intake openings 17a and 17b formed in a rear grille and side grilles constituting a control panel 17, to a rear bulge of the dust netting 19. This shield 26, hood 4 and control panel 17 define an intake air guide for guiding the cooling air from outside to the radiator 11. Trims 21a and 22a acting as seals are secured to a lower end of the shield 21 and an outer periphery of the heat shielding plate 22, respectively. Further, cushion elements 25 are arranged between the bottom of the dust netting 19 and the upper surface of the radiator 11 for preventing entry of hot air and suppressing noise. The box-shaped dust netting 19 is connected to the radiator i 1 through elastic engaging pieces 23 formed of plate springs and arranged in front and rear and fight and left positions of the radiator 11, and bent pieces 24 formed by bending edges of an opening in the bottom of the dust netting 19.

The fan cover 20 is a box-shaped cover defining an intake opening 20a in the upper surface, and an exhaust opening 20b in the front surface. The fan cover 20 also defines an exhaust opening 20c in the lower surface thereof. The lower surface includes a scoop 20d for allowing cooling air to flow at an appropriate rate out of the exhaust opening 20c.

As seen from FIG. 3, the engine 5 is a V-type 2-cylinder engine, and exhaust gases from combustion chambers in the respective cylinders are guided to the muffler 16 through exhaust pipes 27 arranged at opposite sides of the engine 5. Ducts 28 are provided at opposite sides of a forward portion of the fan cover 20, whereby the cooling air discharged from regions at opposite sides of the exhaust opening 20b in the front surface of the fan cover 20 is guided toward the muffler 16 and directed to connections between the muffler 16 and exhaust pipes 27.

As will be understood from FIGS. 3, 5 and 6, the muffler 16 extends transversely of the tractor body inside a bumper frame 1B, U-shaped in plan view, interconnecting forward ends of right and left body frames 1A. The muffler 16 directs the exhaust gas laterally outwardly of the tractor body, and is covered by a muffler cover 29 formed of an upper cover 29A and a lower cover 29B fixed to the bumper frame 1B. The upper cover 29A has an upper surface and right and left side surfaces. The right and left side surfaces extend further rearward than the upper surface. The lower cover 29B has a lower surface and right and left side surfaces. The lower surface defines four exhaust openings 29a. The muffler 16 includes a muffler body 16A and an exhaust pipe 16B. The exhaust pipe 16B is attached to an exhaust opening 29b formed in a side surface of the lower cover 29B. The muffler body 16A has an outlet pipe 16a extending into the exhaust pipe 16B with a space 50 therebetween. The heat in the muffler cover 29 is released outside the tractor body by ejector action of exhaust gas flows. The exhaust pipe 16B is bent upward to direct the exhaust gas flows clear of dead leaves and the like collected on the ground. A rear muffler cover 29C is disposed rearwardly of the muffler body 16A and bolted to the bumper frame 1B to prevent the heat of the muffler 16 from being applied to an ignition coil 30 of the engine 5. The radiator cooling air having cooled the area adjacent the exhaust pipes 27 is thereby guided downward to flow out through the exhaust opening 29b. Perforated metal sheets 31 are provided for the exhaust openings 29a of the lower cover 29B to avoid a direct contact between dead leaves and the muffler body 16A.

According to the above construction, the cooling fan 12 draws cooling air through the intake openings 17a and 17b formed in the control panel 17 and gaps between an upper hood 4A and a lower hood 4B. The air stripped of dust by the dust netting 19 cools the radiator 11. Then, a large part of the cooling air flows downward and forward through the fan cover 20, and flows forward and out through exhaust openings 4a in the front surface of the hood 4. A small part of the cooling air is guided by the ducts 28 to flow to the muffler 16, and out through the exhaust openings 29a formed in the lower surface of the muffler cover 29B. The cooling air guided into the right and left ducts 28 is directed to the connections between the muffler 16 and exhaust pipes 27, thereby to cool efficiently the hottest regions including the connections between the muffler 16 and exhaust pipes 27. The cooling air passing through the openings 20c in the lower surface of the fan cover 20 flows past the carburetor 15, and reaches exposed portions of the exhaust pipes 27 and the upper cover 29A of the muffler cover 29. The cooling air entering the muffler cover 29 cools the muffler 16, and then flows out through the exhaust opening 29b of the lower cover 29B of the muffler cover 29.

The above embodiment has been described in relation to the muffler structure for the two-cylinder engine having two exhaust pipes. The invention is applicable also to a two-cylinder engine in which exhaust gases from respective cylinder chambers are transmitted through an exhaust manifold and a single exhaust pipe to a muffler. In this case, only one duct 28 may be adequate.