Internal-combustion engines – Cooling – Automatic coolant flow control
Reexamination Certificate
2000-04-20
2002-11-19
Kamen, Noah P. (Department: 3747)
Internal-combustion engines
Cooling
Automatic coolant flow control
C123S041100
Reexamination Certificate
active
06481388
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device that drives a cooling fan.
2. Description of the Related Art
In hydraulically driven machinery such as construction machinery, an engine drives a hydraulic pump, and pressure oil discharged from the hydraulic pump is supplied to hydraulic actuators such as hydraulic cylinders via control valves. In this way, the machinery is able to operate.
The engine and the pressure oil have to be cooled.
Cooling devices that use water-cooling techniques are principally used for the cooling of engines. Specifically, cooling is performed by circulating a coolant cooling water through a water jacket provided in the engine main body. Coolant that has been heated up inside the water jacket is guided to a radiator where it is cooled down, and the cooled coolant is then returned to the water jacket.
The pressure oil is cooled by guiding the oil through an oil cooler. Energy losses inside the hydraulic circuit are conducted to the pressure oil in the form of heat. Like the coolant, the pressure oil is guided to an oil cooler where it is cooled down, and the cooled pressure oil is then returned to the hydraulic circuit.
The radiator and oil cooler are both cooled by a flow of air generated by a cooling fan. In most cases the oil cooler and radiator are installed sequentially along the passage of the airflow generated by the cooling fan. This specific arrangement is normally considered to be efficient for cooling purposes.
This cooling fan is attached to the drive shaft of the engine. The rotation speed of the cooling fan thus depends on the rotation speed of the engine.
There is a demand for freedom of layout of the engine and cooling fan as a means of addressing problems associated with the space available for their installation. Consequently, a measure has been adopted whereby the cooling fan is made independent of the engine. This approach is disclosed in Japanese Patent Application Laid-open No. 6-58145.
This publication describes an invention wherein a variable capacity hydraulic pump for driving the fan and a fixed capacity hydraulic motor for driving the fan are installed separately from the engine, and the cooling fan is driven by supplying the pressure oil discharged from the variable capacity hydraulic pump for driving the fan to the fixed capacity hydraulic motor for driving the fan.
In this case, a solenoid control valve for exclusive fan drive use is provided which controls the swash plate of the variable capacity hydraulic pump. Then, according to which temperature range the coolant temperature falls into from among three stages of temperatures, a control signal is applied to the solenoid of the abovementioned solenoid control valve, and the rotation speed of the cooling fan is thereby switched between three stages.
A technique disclosed in Japanese Unexamined Patent Application JP-A No. S63-124820 has also been employed.
This publication describes an invention wherein a fixed capacity hydraulic pump for driving the fan and a fixed capacity hydraulic motor for driving the fan are provided separately from the engine, and the cooling fan is driven by supplying the pressure oil discharged from the fixed capacity hydraulic pump for driving the fan to the fixed capacity hydraulic motor for driving the fan via a flow rate control valve.
In this case, the fixed capacity hydraulic pump discharges pressure oil at a flow rate corresponding to the magnitude of the engine rotation speed. Then, by controlling the aperture of the flow rate control valve, the flow rate of the pressure oil supplied from the fixed capacity hydraulic pump to the fixed capacity hydraulic motor is controlled, and the rotation speed of the cooling fan is controlled.
To reduce the noise produced by construction machinery, there has also been a demand in recent years for reducing the fan rotation speed and reducing energy losses.
In all the inventions described in the abovementioned publications, the cooling fan is driven with a hydraulic pump as a drive source that is separate from the engine. This has the effect of increasing the freedom in the arrangement of the cooling fan radiator, oil cooler and other equipment, and makes it possible to shield the engine while cooling it with the cooling fan at the same time. However, these inventions have suffered from the following problems.
Specifically, the invention of the abovementioned Japanese Patent Application Laid-open No. 6-58145 only controls the rotation speed of the cooling fan in three stages according to which of the three stages of temperature regions the coolant temperature belongs to. As a result, the coolant is not necessarily cooled with optimal energy efficiency. The noise generated by the cooling fan itself may also become greater then necessary. Specifically, since the rotation speed of the cooling fan is varied in three stages, there will be cases when the cooling fan is rotated at a greater speed than is necessary and sufficient for cooling. The noise produced by the cooling fan also increases by an amount corresponding to this increase in rotation speed.
Also, the invention of the abovementioned Japanese Patent Application Laid-open No. 63-124820 only controls the pressure oil supplied to the fixed capacity hydraulic motor from the fixed capacity hydraulic pump by controlling the aperture of the flow rate control valve. Consequently, energy losses occur due to the recirculation of pressure oil from the flow rate control valve to the tank.
Specifically, since the flow rate of pressure oil discharged from the fixed capacity hydraulic pump increases correspondingly with increases in the engine rotation speed, a large amount of pressure oil is restricted by the flow control valve and recirculated to the tank when the engine rotation speed is large. Thus, when the engine rotation speed is large, the amount recirculated to the tank increases and energy losses occur.
Therefore, the present invention is directed at solving the problem of making it possible to drive a cooling fan with a hydraulic source in the most energy efficient way, and at enabling the noise to be controlled to a minimum.
SUMMARY OF THE INVENTION
Therefore, the first invention of the present invention is a cooling fan drive control device equipped with a hydraulic pump
2
driven by a drive source
1
, a cooling fan
8
which cools cooling water of the drive source
1
, and a hydraulic motor
7
which is operated by pressure oil discharged from the hydraulic pump
2
and causes the cooling fan
8
to rotate,
wherein it also comprises:
a cooling water temperature sensing means
23
which senses a temperature of the cooling water,
a target fan rotation speed setting means
50
which sets a target fan rotation speed corresponding to the temperature sensed by the cooling water temperature sensing means
23
, and
a capacity control means
47
,
40
which controls a capacity
2
a
of the hydraulic pump
2
or the hydraulic motor
7
according to a difference between a fan rotation speed of the cooling fan
8
and the target fan rotation speed set by the target fan rotation speed setting means
50
.
The first invention is described with reference to FIGS.
1
(
a
) and
1
(
b
) and FIG.
2
.
With the first invention, a target fan rotation speed FAN
RPM
is set according to the temperature T
c
sensed by the cooling water temperature sensing means
23
. The capacity
2
a
of the hydraulic pump
2
or hydraulic motor
7
is then controlled by the capacity control means controller
47
, EPC valve
40
so that the fan rotation speed N of the cooling fan
8
becomes the abovementioned target fan rotation speed FAN
RPM
.
With the first invention, a target fan rotation speed FAN
RPM
that is necessary and sufficient for cooling is determined from the current temperature T
c
of the cooling water, and the cooling fan
8
is rotated at this target fan rotation speed FAN
RPM
.
Consequently, the cooling water is cooled with optimal energy efficiency. Also, the noise generated by the cooling fan itself does not become g
Benton Jason
Kamen Noah P.
Komatsu Ltd.
Varndell & Varndell PLLC
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