Automatic temperature and humidity regulation – Cooling radiator
Reexamination Certificate
2000-04-20
2002-02-26
Paik, Sang (Department: 3742)
Automatic temperature and humidity regulation
Cooling radiator
Reexamination Certificate
active
06349882
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a controlling device for a hydraulically operated cooling fan of construction equipment such as a bulldozer, hydraulic excavator, a wheel loader, and the like.
BACKGROUND ART
Generally, the use of cooling air blown from a cooling fan belt-driven by an engine is the widely used way of cooling the engine and a hydraulic equipment system of construction equipment. In this way, however, the rotational frequency of the cooling fan is proportional to the engine speed. Thus, cooling air is sent to a radiator and an oil cooler even when temperatures of engine cooling water, hydraulic oil, and the like do not reach a warming-up temperature appropriate for machine operation, for example, immediately after the starting of the engine. As a result, the cooling water and the hydraulic oil are supercooled, and more time is required for warming up.
As a prior art to settle the above disadvantage, a way of driving the cooling fan by means of an electric motor or a hydraulic motor the rotational frequency of which is controlled independently of engine rotation is known. As a prior art of a cooling system of construction equipment to which this way of cooling fan drive is applied, for example, a prior art disclosed in Japanese Patent Laid-open Bullctin No.10-68142 is given, and
FIG. 13
shows a circuit diagram of a cooling system described in the above Bulletin.
In
FIG. 13
, a radiator
42
a
and an oil cooler
42
b
are disposed separately from an engine
41
, and cooled by a cooling fan
45
. The oil cooler
42
b
is disposed downstream of the radiator
42
a
with respect to air flow which arises during reverse rotation of the cooling fan
45
. The cooling fan
45
is driven to stop, rotate normally, or rotate reversely by a hydraulic motor
48
controlled by a solenoid-controlled change-over valve
47
in a fan drive circuit
46
. The solenoid-controlled change-over valve
47
is automatically switched by a controlling device
50
having an outside air temperature sensor
51
, a cooling water temperature sensor
52
, and a hydraulic oil temperature sensor
53
. When all of an outside air temperature, a cooling water temperature, and a hydraulic oil temperature are lower than a set temperature at the starting of the engine, the controlling device
50
allows the rotation of the cooling fan
45
to remain stopped even if the engine
41
starts. Further, when the hydraulic oil temperature is lower than the set temperature although the cooling water temperature rises to the set temperature or more, the cooling fan
45
is reversed, whereby hydraulic oil in the oil cooler
42
b
is warmed up by warm air which has passed through the radiator
42
a
and dust which chokes the radiator
42
a
and the like is removed by against wind. Furthermore, when the cooling water temperature and the hydraulic oil temperature are not less than the set temperature, the cooling fan
45
is allowed to rotate normally to thereby cool cooling water and hydraulic oil.
It is described that as the result of the above, it becomes possible to shorten warming-up time of the hydraulic equipment and to improve cooling efficiency by removal of dust which chokes the radiator
42
a
and the oil cooler
42
b.
In the art disclosed in the aforesaid Japanese Patent Laid-open No.10-68142, however, there arise the following disadvantages.
Normal rotation, stop, and reverse rotation of the cooling fan
45
are controlled according to the cooling water temperature, the hydraulic oil temperature, and the outside air temperature. But, the aforesaid control is ON-OFF control, so that fine control can not be provided, and thereby optimum cooling efficiency is not obtained. Further, the cooling fan
45
is not controlled depending on the load of the engine
41
. Hence, when the load of the engine
41
changes, the rotational frequency of the cooling fan
45
also changes, whereby cooling at optimum efficiency according to the cooling water temperature, the hydraulic oil temperature, and the outside air temperature can not be provided.
SUMMARY OF THE INVENTION
In view of the aforesaid disadvantages, an object of the present invention is to provide a controlling device for a hydraulically operated cooling fan capable of obtaining optimum cooling efficiency by continuously controlling a rotational frequency of the cooling fan according to a cooling water temperature, a hydraulic oil temperature, and an engine speed.
A first configuration of a controlling device for a hydraulically operated cooling fan according to the present invention is characterized in that
a controlling device for a hydraulically operated cooling fan in which a cooling system composed by forcedly cooling a radiator for cooling cooling water for an engine and an oil cooler for cooling, hydraulic oil for a hydraulic system by means of the cooling fan is provided independently of the engine, includes
a hydraulic motor for driving the cooling fan,
a variable displacement hydraulic pump capable of controlling a rotational frequency of the hydraulic motor,
a cooling water temperature sensor for detecting, a cooling water temperature,
a hydraulic oil temperature sensor for detecting a hydraulic oil temperature,
an engine speed sensor for detecting an engine speed, and
a controller which inputs detected signals from the cooling water temperature sensor, the hydraulic oil temperature sensor, and the engine speed sensor, computes and outputs a discharge capacity command value of the variable displacement hydraulic pump according to the inputted cooling water temperature, hydraulic oil temperature, and engine speed, and continuously controls a rotational frequency of the cooling fan by means of the variable displacement hydraulic pump.
According to the above configuration, the cooling fan rotational frequency is continuously controlled by the variable displacement hydraulic pump according to the cooling water temperature, the hydraulic oil temperature, and the engine speed, whereby the cooling fan rotational frequency is controlled smoothly without involving sharp change without being affected by rotational change of the engine. As a result, the cooling water temperature and the hydraulic oil temperature can be controlled finely, thus providing, optimum cooling efficiency.
The controlling device for the hydraulically operated cooling fan may have a configuration in which
the controller controls an upper limit of the cooling fan rotational frequency at a predetermined rotational frequency irrespective of changes in the engine speed when the engine speed is not less than a predetermined engine speed.
According to the above configuration, the upper limit of the cooling fan rotational frequency is controlled at the predetermined rotational frequency irrespective of changes in the engine speed when the engine speed is not less than the predetermined engine speed. Accordingly, since the rotational frequency of the cooling fan is almost constant even if engine load increases and thereby the engine speed decreases, cooling capacity does not lower. Moreover, the rotational frequency of the cooling fan is almost constant even if the engine load decreases and thereby the engine speed increases, thereby not causing supercooling and unnecessary consumption of energy, which enables efficient cooling. Generally, as for the cooling fan, when the rotational frequency thereof exceeds some rotational frequency level, a produced sound abruptly increases, but an increase in cooling capacity corresponding to an increase in fan drive energy is not given. Meanwhile, according to the configuration of the present invention, the rotation of the fan at excessively high speed such as described above can be avoided, thus enabling efficient cooling from the viewpoint of noise reduction of the cooling fan and fan drive energy, and further serving the prevention of breakage of the cooling fan.
Further, the controlling device for the hydraulically operated cooling fan may have a configuration in which
the upper limit of the cooling fan rotational frequency is set acc
Kita Ikuo
Nakagawa Tomohiro
Okada Toshikazu
Uemura Atsushi
Yamamoto Shigeru
Armstrong, Westerman, Hattori, McLeland & Naughton, LLP.
Komatsu Ltd.
Paik Sang
Robinson Daniel
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