Internal-combustion engines – Cooling – Devices for cooling liquid by air flow
Reexamination Certificate
1999-05-17
2001-02-27
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Cooling
Devices for cooling liquid by air flow
C165S041000, C165S051000
Reexamination Certificate
active
06192839
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a cooling apparatus for a construction machine, and more particularly to a cooling apparatus for a construction machine which is adapted to cool heat exchangers, such as a radiator and an oil cooler, with a fan driven by an engine, and a construction machine provided with the cooling apparatus.
BACKGROUND ART
Heretofore, there has been known a cooling apparatus for cooling a heat exchanger with a fan driven by an engine. JP, U, 63-4400, for example, discloses a cooling apparatus comprising a heat exchanger, a propeller fan whose rotary shaft is rotated by the driving force of an engine to produce a stream of cooling air for cooling the heat exchanger, and a shroud provided downstream of the heat exchanger for introducing the cooling air to the suction side of the propeller fan, wherein a substantially disk-shaped back plate is provided just behind rotor blades of the propeller fan on the blowoff side, the back plate having almost the same diameter as an outline of the propeller fan. Such a construction is effective to avoid the occurrence of turbulence caused by interference between a main stream of the cooling air produced in the centrifugal direction on the blowoff side of the propeller fan and a reverse stream tending to return toward the heat exchanger side after being separated from the main stream, and hence to reduce noise generated by the fan.
DISCLOSURE OF THE INVENTION
In the field of construction machines, a movement to make regulations on noise and vibration of construction machines more strict has recently appeared for protecting the living environment of inhabitants, and it is nearly certain that the more strict regulations will be enforced in near future. One example of modified regulations is described below. At present, noise evaluation is performed by evaluating the no-load maximum revolution speed of an engine when the body of a construction machine is in a static condition (i.e., stationary noise evaluation). Evaluation under a dynamic condition of the body of a construction machine, more specifically, under simulated working loads during such operations as excavation, traveling and turning, (i.e., working noise evaluation) will be adopted instead in the future. Also, according to the current regulations, noise is measured in a planar manner at plural points spaced a predetermined distance from the body in four directions laterally of the body. The noise measurement will be made instead three-dimensionally at plural points locating on a hemisphere around the body. Further, the current noise measurement only requires the body to be positioned on the surface of the hard ground. It will be required instead for hydraulic excavators, for example, to basically position the machine on concrete or asphalt in noise measurement. Then, for hard ground, it will be obliged to add a modification value to the basically measured noise value.
Under the background set forth above, future construction machines will be required to suppress noise down to a lower level than that allowed currently.
To cope with the requirement, it is conceivable to reduce noise by applying the above-mentioned prior art to a cooling apparatus for a construction machine. In this case, a substantially disk-shaped back plate, which has almost the same diameter as a propeller fan rotatably driven by an engine of the construction machine, is provided between the propeller fan and the engine.
In that case, noise can be reduced, but a flow rate of air necessary for cooling heat exchangers, such as a radiator and an oil cooler, cannot be ensured at a sufficient level because a resistance of a main stream of cooling air in the centrifugal direction is increased and the flow rate of is reduced. Insufficient cooling of a radiator would mar cooling of an engine and deteriorate combustion efficiency of the engine, thus resulting in a reduction of engine power. Also, insufficient cooling of an oil cooler would expedite thermal deterioration of hydraulic working oil used for operating hydraulic equipment, thus resulting in a reduction of performance of the hydraulic equipment (e.g. hydraulic pump, control valves, hydraulic cylinders). Further, in recent construction machines including intercoolers, the intercooler is also cooled with the cooling air. Insufficient cooling of the intercooler would raise the temperature of intake air of the engine, thus resulting in the problem of further deteriorating combustion efficiency of the engine and lowering engine power correspondingly.
On the other hand, cooling apparatus adapted for application to construction machines are proposed aiming at an increase of the flow rate of air and a reduction of noise. JP, A, 8-254119, for example, discloses a cooling apparatus comprising, as with the above-mentioned cooling apparatus for general machines, a heat exchanger, an propeller fan, a shroud, and a substantially disk-shaped back plate, wherein a diameter size of the substantially disk-shaped back plate is limited to be not larger than an outline of rotor blades, and a flow guide in the form of fixed baffle blades is provided on the outer peripheral side of the substantially disk-shaped back plate. With this structure, swirling components of cooling air blown off from the propeller fan are rectified into axial components to recover dynamic pressure loss, thereby increasing the air flow rate and reducing noise.
However, another problem below arises when such a cooling apparatus is applied to construction machines.
In some of hydraulic excavators, for example, the engine revolution speed can be set to a value optimum for a working form by selecting a mode corresponding to the working form. One of four modes is selected, by way of example; i.e., an idling mode where the engine is idling at a low revolution speed, a fine operating mode which is suitable when actuators are desired to operate at a slow speed in, e.g., leveling or lifting work, an economy mode which is suitable when it is desired to save energy during excavation, and a power mode which is suitable when actuators are desired to operate with strong power to obtain a great excavating force. In this case, the engine revolution speed is set to, by way of example, about 600-900 rpm (on no-load condition; this is equally applied to the following rpm value) when the idling mode is selected, about 1500 rpm when the fine operating mode is selected, about 1800 rpm when the economy mode is selected, and about 2200 rpm when the power mode is selected. Thus, the mode selection causes a difference in engine revolution speed on the order of about maximum 1600 rpm.
Also, while work is being performed in one selected mode, the engine revolution speed may vary depending on change of a load during the work. It is known, for example, that when a relief valve in a hydraulic circuit is operated, the engine revolution speed usually lowers about 100 rpm. It is also known that at the moment when the load is maximized during the so-called deep digging, the engine revolution speed lowers about 300 rpm.
Further, in construction machines with an auto-idling function, even when any of other modes than the idling mode is selected, the engine revolution speed lowers down to the idling revolution speed temporarily upon shift to the auto-idling operation.
As mentioned above, the engine revolution speed may vary over a considerably wide range in construction machines. A variation of the engine revolution speed also changes the revolution speed of a fan driven by the engine to a large extent. Each time the fan revolution speed changes, the swirling components of cooling air blown off from the fan are changed in direction and speed.
In the cooling apparatus disclosed in JP, A, 8-254119, the flow guide serving as baffling means is in the form of fixed blades. Therefore, the flow guide can efficiently rectify only those swirling components of cooling air which have the direction and the speed in a certain narrow range substantially uniquely corresponding to the configuration of the fixed blades. For the other
Takeshita Seiichirou
Watanabe Osamu
Harris Katrina B.
Hitachi Construction Machinery Co. Ltd.
Mattingly, Stanger & Malur
Yuen Henry C.
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