Internal-combustion engines – Frame construction – Horizontal cylinder
Reexamination Certificate
2002-06-13
2003-11-11
Kamen, Noah P. (Department: 3747)
Internal-combustion engines
Frame construction
Horizontal cylinder
C123S041100, C123S041440, C180S068400
Reexamination Certificate
active
06644261
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a structure of a water-cooled engine, in particular relates to a snowmobile engine cooling arrangement having cooling water passages for cooling a snowmobile engine.
(2) Description of the Prior Art
Conventionally, most small snow vehicle such as snowmobiles and the like use two-cycle engines because they are relatively simple in structure, light and compact and yet powerful. Recently, however, because of regulation of exhaust gas due to environmental issues and aiming at improvement in reduction of fuel consumption rate, there is a trend toward employing four-cycle engines.
As the engine structure for snowmobiles, water-cooled engines have been generally employed because they can stably cool the engine by cooling water, preventing the occurrence of overheating or overcooling and improving the output power and yet are effective in reducing noise.
As an example of conventional engine cooling arrangements, Japanese Patent Application Laid-Open No. 2001-12243 discloses a cooling system for a snowmobile engine. This cooling system is comprised of a cooling water jacket formed inside the engine, a heat exchanger for cooling the cooling water and a cooling water pump for transferring the cooling water so as to circulate the cooling water inside the engine, and further includes: a cooling water bypass through which the cooling water can pass, avoiding its flow into the heat exchanger; and a switching valve for permitting the cooling water to flow into the cooling water bypass, wherein the switching valve is adapted to switch the cooling water circuit in such a manner that the cooling water is allowed to pass through the heat exchanger when the cooling water is equal to or higher in temperature than a predetermined level, and the cooling water is restricted from passing through the heat exchanger and is conducted to the cooling water bypass when the temperature of the cooling water is lower than the predetermined temperature level.
Meanwhile, in contrast to two-cycle engines, which are high in power, light and compact, four-cycle engines need a camshaft and oil lubrication, inevitably tending towards large size.
In particular, when a four-cycle engine is included in a snowmobile, it is necessary to provide a contrived layout of the oil pan configuration, intake and exhaust systems and associated auxiliaries, in order to make the body and engine hood have similar size to those of a two-cycle engine.
Further, in general, when the mounted engine is of a water cooled type, a reservoir tank should be interposed within the piping of the cooling water. That is, it is necessary to take into account the installation space for this reservoir tank. Further, the reservoir tank needs to be arranged at a site where it is easy for cooling water to be re-supplied.
Since the snowmobile is used in cold areas, in order to stabilize the idling engine speed at the start of operation or in order to regulate the surging of the thermostat, it is necessary to consider the layout of the cooling water piping and the position of the thermostat.
Further, the cooling water pump for transferring cooling water is driven by a belt which is driven by the rotation of the crankshaft. This means the enlargement of the longitudinal size of the engine. Therefore it is necessary to arrange the cooling water pump at an appropriate position. Moreover, it is necessary to choose the position of the cooling water pump optimally, considering the positional relationship with an alternator, which is belt driven, so that the front-to-rear size of the engine will be minimized.
SUMMARY OF THE INVENTION
The present invention has been devised in view of the above conventional problems, it is therefore an object of the present invention to provide a cooling arrangement for a snowmobile engine, which is able to stabilize the engine idling speed at the start of operation and is improved in the work performance in supplying cooling water and realizes a space-saving engine layout.
In order to achieve the above object, the present invention is configured as follows:
In accordance with the first aspect of the present invention, a cooling arrangement for a snowmobile engine, includes: a cooling water jacket formed inside an engine; a heat exchanger for cooling water; a water pump for ejecting cooling water; and a thermostat for controlling supply of the cooling water ejected from the water pump into the engine, so as to cool the engine by circulating the cooling water inside the engine, and is characterized in that:
the engine is mounted with its cylinder head at top, and an exhaust manifold is disposed on the front side, with respect to the vehicle's direction of travel, of the cylinder head while an intake manifold is disposed on the rear side, with respect to the vehicle's direction of travel, of the cylinder head;
the water pump is disposed on the front side, with respect to the vehicle's direction of travel, of cylinder block of the engine, under the exhaust manifold and is coupled to a crankshaft projected from one side wall, with respect to the widthwise direction of the body, of the cylinder block, so that it is driven by the rotational force which is transmitted through a drive belt from a rotational member fitted on one end of the crankshaft;
a cooling water inlet port for leading cooling water into the cooling water jacket inside the engine is provided on the front side, with respect to the vehicle's direction of travel, of the cylinder block and under the exhaust manifold at a position close to the drive belt;
a cooling water outlet port through which cooling water is taken out from the interior of the engine is arranged on the engine's side face at a position over and opposite to the drive belt; and
the thermostat is arranged at the cooling water outlet port, at a point downstream with respect to the flow of cooling water.
In accordance with the second aspect of the present invention, the cooling arrangement for a snowmobile engine having the above first feature is characterized in that the cooling water outlet port is comprised of a thermo housing for incorporating the thermostat and a thermo cap for covering the thermostat, the thermo cap being connected to the heat exchanger by way of a cooling water passage.
In accordance with the third aspect of the present invention, the cooling arrangement for a snowmobile engine having the above second feature is characterized in that the thermo housing is formed with a first cooling water bypass passage which branches off at a point upstream, with respect to the flow of cooling water, of the thermostat and is connected by way of a throttle body to the cooling water passage at a point upstream of the water pump.
In accordance with the fourth aspect of the present invention, the cooling arrangement for a snowmobile engine having the above second feature is characterized in that the thermo housing is formed with a second cooling water bypass passage which branches off at a point upstream of the thermostat and is connected directly to the cooling water passage at a point upstream of the water pump without passing through the throttle body.
In accordance with the fifth aspect of the present invention, the cooling arrangement for a snowmobile engine having the above third feature is characterized in that the thermostat is used to control the outlet of cooling water after passage of the cooling water jacket inside the engine while the thermo housing side and cooling water passage side are kept so as to be in constant communication to each other through the first cooling water bypass passage and the second cooling water bypass passage.
In accordance with the sixth aspect of the present invention, the cooling arrangement for a snowmobile engine having the above fourth feature is characterized in that the thermostat is used to control the outlet of cooling water after passage of the cooling water jacket inside the engine while the thermo housing side and cooling water passage side are ke
Matsumura Hitoshi
Morii Hideshi
Sasaki Yutaka
Shibano Ken
Yatagai Yasuaki
Kamen Noah P.
Nixon & Vanderhye P.C.
Suzuki Motor Corporation
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