Cooling apparatus for liquid-cooled internal combustion engine

Details Cooling apparatus for liquid-cooled internal combustion engine Cooling apparatus for liquid-cooled internal combustion engine

2000-01-24

2001-11-13

Arganbright, Tony M. (Department: 3747)

Internal-combustion engines

Cooling

Automatic coolant flow control

C123S041440, C123S041120

Reexamination Certificate

active

06314920

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATION
This application relates to Japanese Patent Application No. Hei. 10-214492 filed Jul. 29, 1998, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cooling apparatus for liquid-cooled internal combustion engine, and it is preferably applicable to an internal combustion engine of a vehicle.
2. Description of Related Art
As disclosed in JP-A-8-128559, it is known to maintain the cooling water temperature under light engine load higher than that under heavy engine load in order to improve the fuel consumption performance of a liquid-cooled internal combustion engine (hereinafter referred to as the “engine”).
Since a circulating pump for circulating the cooling water is generally driven by the engine, the circulation flow rate of the cooling water which circulates through the engine varies in proportion to the engine speed as shown in FIG.
9
. On the other hand, the cooling water temperature increases according to a decrease of the circulation flow rate. Accordingly, the circulation flow rate can be reduced by reducing the pump rotation speed when the engine load is light, because the cooling water temperature can be increased when the engine load is light.
According to the pump driven by the engine, the pump work is allowed to be small by reducing the circulation flow rate when the engine load is light. However, since the circulation flow rate is not variable according to the engine load, unnecessary pump work increases.
SUMMARY OF THE INVENTION
The present invention is made in light of the above-mentioned problem, and it is an object of the present invention to provide a cooling apparatus which decreases unnecessary pump work.
According to a cooling apparatus of the present invention, it includes a radiator for cooling a coolant circulating between a liquid-cooled internal combustion engine and the radiator. Furthermore, the cooling apparatus includes a pump driven independently from the liquid-cooled internal combustion engine for circulating the coolant between the liquid-cooled internal combustion engine and the radiator such that a temperature difference between a coolant temperature at a coolant outlet of the liquid-cooled internal combustion engine and a coolant temperature at a coolant inlet of the liquid-cooled internal combustion engine is maintained to be a predetermined value.
Accordingly, the circulation flow rate decreases as the load of the liquid-cooled internal combustion engine decreases. Thus, unnecessary pump work is reduced.
Further, since the coolant circulates such that a temperature difference between a coolant temperature at a coolant outlet of the liquid-cooled internal combustion engine and a coolant temperature at a coolant inlet of the liquid-cooled internal combustion engine is maintained to be a predetermined value, the temperature distribution of the liquid-cooled internal combustion engine is reduced. Accordingly, since the thermal distortion of the liquid-cooled internal combustion engine is prevented, the fuel economy is improved, and the engine durability is improved.


REFERENCES:
patent: 4726325 (1988-02-01), Itakura
patent: 5749330 (1998-05-01), Inoue et al.

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