Internal-combustion engines – Cooling – With liquid coolant circulating means
Reexamination Certificate
1999-12-20
2001-06-19
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Cooling
With liquid coolant circulating means
C123S041100
Reexamination Certificate
active
06247429
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a cooling water circulating apparatus adapted to send out cooling water flowing there into an engine or a radiator by a water pump.
2. Description of the Related Art
The known cooling apparatuses for internal combustion engines include an apparatus disclosed in Japanese Patent Laid-Open No. 88582/1997. The techniques included in this apparatus are to reduce the limitation placed on the arrangement of various auxiliary machines driven via a crankshaft, a belt and a chain, by driving a cooling water supply pump by a cam shaft, fixing the water pump to a cylinder head so as to join a discharge port of the water pump to an inlet port of a cooling water passage on a suction side of the cylinder head, thereby forming the suction side cooling water passage as a water passage on a discharge side of the water pump, whereby, even when the resistance of the suction side cooling water passage is large, negative pressure on a suction side of the water pump increases to prevent the occurrence of cavitation therein.
However, in such a related art apparatus, the cooling water is circulated by a water pump alone which is driven by a cam shaft rotated with a rotational frequency ½ times as high as that of the crankshaft, so that, when the temperature of the cooling water increases higher than a predetermined level, a required flow rate of the cooling water cannot be secured unless the capacity of the water pump is increased. In order to secure a required flow rate of the cooling water, the cooling water discharge performance (head) of the pump has to be improved, and, in order to increase the pump head, the dimensions of the water pump have to be increased. This causes a driving force of the water pump to increase, so that the fuel consumption also increases.
SUMMARY OF THE INVENTION
Therefore, the technical problem to be solved by the present invention is how to provide a cooling water circulating apparatus capable of securing a required flow rate of cooling water without increasing the heads of water pumps.
To solve the problem, a first aspect of the invention provides a cooling water circulating apparatus adapted to circulate cooling water through an engine or a radiator, including a first water pump which has a first supply port for supplying thereinto cooling water which is to flow through the interior of an engine, and a first discharge port for discharging therefrom the supplied cooling water to the engine again, and which is connected to and rotated with a cam shaft of the engine, a control mechanism adapted to cut off a flow of the cooling water, which is directed from a radiator to the first supply port, when the temperature of the cooling water is not higher than a predetermined level, and communicate the radiator and first supply port with each other when the temperature of the cooling water is higher than the predetermined level, and a second water pump which has a second supply post for supplying thereinto cooling water which is to flow through the interior of the engine, and a second discharge port for discharging therefrom the supplied cooling water to the supply port of the first water pump, and which is electrically rotated in accordance with the temperature of the cooling water.
According to the first aspect of the invention, when the temperature of the cooling water is not higher than a predetermined level, the first water pump is rotated with the cam shaft of the engine, receives the supply of cooling water from the first supply port and discharges the same toward the first discharge port. The discharged cooling water cools the engine on the inner side thereof. When the temperature of the cooling water becomes higher than a predetermined level, the radiator and first supply port are communicated with each other by the control mechanism, and the cooling water discharged from the first water pump is supplied to the engine and radiator. Since the cam shaft is rotated with a rotational frequency ½ times as high as that of the crankshaft, it is considered that, when the cooling water is discharged to the engine and radiator, a discharge rate of the first water pump decreases in some cases. According to the invention, the second water pump is rotated electrically in accordance with the temperature of the cooling water. Therefore, when the driving of the first water pump alone causes a discharge rate of the cabling water to decrease, the second water pump is rotated to enable the shortage of the discharge rate to be filled up. Owing to this operation, a suitable quantity of cooling water can always be circulated. Since the second water pump is electrically operated, the rotational frequency thereof can be controlled, and the flow rate of the cooling water can also be arbitrarily regulated.
A case where the second water pump is set so that it is not rotated when the temperature of the cooling water is not higher than a predetermined level, and rotated electrically when the temperature of the cooling water is higher than a predetermined level as described in the statement of a second aspect of the invention will be discussed. When the temperature of the cooling water becomes higher than a predetermined level, the second water pump is driven, and the control mechanism communicates the radiator and first supply port with each other. Consequently, the cooling water is supplied from the second supply port, and discharged from the second discharge port.
Since the cooling water is thus circulated at a required flow rate through both the engine and radiator by rotating the electrically driven second water pump, it becomes possible to secure a required flow rate of the cooling water without increasing the dimensions of the first water pump even when the first water pump is driven with the cam shaft.
REFERENCES:
patent: 3999598 (1976-12-01), Fehr et al.
patent: 4369738 (1983-01-01), Hirayama
patent: 4768484 (1988-09-01), scarselletta
patent: 6199518 (2001-03-01), Hotta et al.
patent: 9-88582 (1997-03-01), None
Hara Naohiro
Ozawa Yasuo
Aisin Seiki Kabushiki Kaisha
Harris Katrina B.
Reed Smith Hazel & Thomas LLP
Yuen Henry C.
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