Cooling system having pulsed fan control

A cooling system is provided for an engine. The cooling system may have an air cooler configured to cool intake air being supplied to the engine. The cooling system may also have a sensor configured to generate a temperature signal indicative of a temperature of the intake air and a fan in proximity to the air cooler. The cooling system may further have a controller in communication with the sensor and the fan. The controller may be configured to cause the fan to operate at a speed that is a function of the temperature signal when the temperature of the intake air is above a threshold temperature. The controller may further be configured to selectively cause the fan to pulse when the temperature of the intake air drops below the threshold temperature.

TECHNICAL FIELD

The present disclosure relates generally to a cooling system, and more particularly, to a cooling system having pulsed fan control.

BACKGROUND

Engine-driven machines, such as dozers, loaders, excavators, motor graders, and other types of heavy equipment typically include a cooling system that cools the associated engine below a threshold temperature. The cooling system consists of one or more air-to-air or liquid-to-air heat exchangers that chill, among other things, coolant circulated throughout the engine and/or intake air directed into the engine. Heat from the coolant or intake air is transferred to air by a fan that is speed controlled based on temperatures of one or more of the various systems being cooled (e.g., engine).

Many cooling system fans are hydraulically powered. Specifically, a fan circuit may include a pump driven by the engine of the machine to draw in low-pressure fluid and discharge the fluid at elevated pressures to a motor that is connected to the fan. When temperatures are higher than desired, the fan circuit increases the speed of the fan. When temperatures are low, the fan circuit decreases the speed of the fan. However, due to a minimum inlet pressure requirement of the motor, the fan often has a limit on the minimum speed. Therefore, in some situations, for example, in cold ambient conditions, even when operating at the minimum speed, the fan may provide more cooling than is required or desired. This excessive cooling can cause icing of the engine inlet manifold.

One control strategy of preventing over cooling of the engine is described in U.S. Pat. No. 6,453,853 (the '853 patent) issued to Hawkins et al. on Sep. 24, 2002. Specifically, the '853 patent describes a strategy for controlling a hydraulic cooling fan. The control strategy reduces the possibility of engine overcooling during cold weather operation by turning the fan completely off whenever engine compartment temperatures are within acceptable limits and there is no request for fan speed.

Although the system of the '853 patent may reduce the likelihood of engine over cooling, it may still be less than optimal. Specifically, because the system of the '853 patent turns the fan completely off for an extended period of time, there is a risk that thermal shock of system components may occur when the fan is turned back on. Another control strategy to allow operation at lower temperatures is to raise engine speed and add loads to the system, but doing so greatly reduces fuel economy of the engine.

The cooling system of the present disclosure is directed to overcoming one or more of the problems set forth above and/or other problems with existing technologies.

SUMMARY

In one aspect, the present disclosure is directed to a cooling system for an engine. The cooling system may include an air cooler configured to cool intake air being supplied to the engine and a sensor configured to generate a temperature signal indicative of a temperature of the intake air. The cooling system may also include a fan in proximity to the air cooler and a controller in communication with the sensor and the fan. The controller may be configured to cause the fan to operate at a speed that is a function of the temperature signal when the temperature of the intake air is above a threshold temperature. The controller may further be configured to selectively cause the fan to pulse on and off when the temperature of the intake air is below the threshold temperature.

In another aspect, the present disclosure is directed to a method of cooling an engine. The method may include directing combustion intake air through an air cooler to cool the combustion intake air and directing combustion intake air from the air cooler into the engine. The method may also include generating a temperature signal indicative of a temperature of the combustion intake air and driving a fan in proximity to the air cooler that is a function of the temperature signal when the temperature of the combustion intake air is above a threshold temperature. The method may further include selectively pulsing the fan on and off when the temperature of the combustion intake air is below the threshold temperature.

In another aspect, the present disclosure is a machine. The machine may include a chassis, an engine mounted to the chassis, and traction devices configured to support the chassis. The machine may also include an air cooler configured to cool intake air being supplied to the engine and a sensor configured to generate a temperature signal indicative of a temperature of the intake air. The machine may also include a fan in proximity to the air cooler and a controller in communication with the sensor, and the fan. The controller may be configured to cause the fan to operate at a speed that is a function of the temperature signal when the temperature of the intake air is above a threshold temperature. The controller may further be configured to selectively cause the fan to pulse on and off when the temperature of the intake air is below the threshold temperature.

DETAILED DESCRIPTION

FIG. 1illustrates an exemplary machine10. In the depicted embodiment, machine10is a wheel loader. It is contemplated, however, that machine10may embody another type of machine such as an articulated haul truck, a motor grader, or any other machine or vehicle. It is also contemplated that machine10may find potential application in stationary systems, if desired, such as in power generation and/or fluid pumping systems. Machine10may include, among other things, a chassis12supported by traction devices14(e.g., wheels), an engine enclosure16mounted to chassis12, and an engine18disposed within enclosure16and operable to traction device14.

Engine18may be any type of combustion engine such as, for example, a two- or four-stroke diesel engine, a gasoline engine, or a gaseous fuel-power engine. As shown inFIG. 2, engine18may include an engine block20that at least partially defines a plurality of cylinders22. A piston (not shown) may be slidably disposed within each cylinder22to reciprocate between a top-dead-center position and a bottom-dead-center position, and a cylinder head (now shown) may be associated with each cylinder22. Each cylinder22, piston, and cylinder head may together at least partially define a combustion chamber. In the illustrated embodiment, engine18includes six cylinders arranged in an inline configuration. However, it is contemplated that engine18may include a greater or lesser number of cylinders22and that cylinders22may be arranged in a V-configuration, in an opposing-piston configuration, or in another configuration, if desired

As shown inFIG. 2, a plurality of different systems may cooperate to enhance operation of engine18, including an air induction system24, an exhaust system26, and a cooling system28. Air induction system24may be configured to direct intake air or a mixture of intake air and fuel into engine18for combustion. Intake air as used herein may also be referred to as combustion air or charge air. Exhaust system26may be configured to direct exhaust resulting from the combustion process to the atmosphere. Cooling system28may be configured to reduce temperatures of engine18(e.g., of coolant circulating through engine18and/or of the combustion intake air directed into engine18) to help improve an efficiency of engine18and/or longevity of engine18.

Air induction system24may include multiple components configured to condition and introduce compressed air into cylinders22. For example, air induction system24may include an air cooler30(e.g., an air-to-air heat exchanger) located downstream of one or more compressors32. Compressor(s)32may be connected to cooler30(e.g., via a passage34), and configured to pressurize inlet air directed to cooler30. After transferring heat to cooler30(e.g., to air passing through adjacent channels in cooler30), the pressurized air from compressor(s)32may flow into cylinders22of engine18via an inlet manifold36. It is contemplated that air induction system24may include different or additional components than described above such as, for example, a throttle valve, variable valve actuators associated with each cylinder22, filtering components, compressor bypass components, and other known components that may be selectively controlled to affect an air-to-fuel ratio of engine18, if desired.

In some embodiments, a sensor may be associated with air induction system24. For example, a temperature sensor38may be disposed at a location upstream and/or downstream of the cooler30(e.g., within passage34and/or inlet manifold36), and configured to generate a signal indicative of an intake air temperature. As will be explained in more detail below, the temperature signal from sensor38may be used to help control cooling system28. For example, the signal may be used to control a flow rate of cooling air passing through the channels of cooler30described above. It is also contemplated that additional temperature sensors may be associated with air induction system24, such that controlling a flow rate of cooling air passing through the channels of cooler30may be a function of one or more temperature sensors indicative of the temperature of different system components.

Exhaust system26may include multiple components that condition and direct exhaust from cylinders22to the atmosphere. For example, exhaust system26may include an exhaust passage40(e.g., an exhaust manifold), one or more turbines42driven by exhaust flowing through exhaust passage40, and an exhaust stack44connected to an outlet of turbine(s)42. It is contemplated that exhaust system26may include different or additional components than described above such as, for example, aftertreatment components, an exhaust compression or restriction brake, bypass components, an attenuation device, and other known components, if desired.

Cooling system28may include, among other things, a fan46situated proximate cooler30and engine18. In the disclosed embodiment, fan46is hydraulically actuated to pull or push air through the channels of cooler30and across engine18, thereby cooling the compressed intake air entering engine18and absorbing heat from external surfaces of engine18. Specifically, a motor48may be connected to drive fan46, and a pump50may be fluidly connected to motor48by way of a supply passage52and a return passage54. Pump50may be, for example, a variable displacement pump powered by engine18. Pump50may pressurize fluid (e.g., a dedicated hydraulic oil) and direct the pressurized fluid to motor48by way of supply passage52. After passing through motor48and imparting mechanical rotation thereto, the fluid (now at a lower pressure) may be returned to pump50by way of return passage54. It should be noted that, while the disclosed cooling system is shown as a closed-loop system, according to an exemplary embodiment, pump50could alternatively be connected to motor48via an open-loop that may incorporate a reservoir tank. Such an open-loop configuration can help regulate the temperature of the pressurized fluid and prevent overheating.

In the disclosed configuration, a displacement and rotational speed of pump50, in conjunction with a displacement of motor48or position of a bypass valve (not shown), may determine a speed of fan46. And the speed of fan46may directly relate to the flow rate of cooling air directed through cooler30and the corresponding temperature of the intake air directed into engine18. Accordingly, the speed of fan46and the temperature of the intake air may be adjusted by selectively adjusting the displacement of pump50and/or the displacement of motor48or position of the bypass valve. In the disclosed embodiment, only pump50has variable displacement capability (i.e., only pump50has an adjustable displacement mechanism56). However, it is contemplated that only motor48could alternatively have variable displacement capability or that both pump50and motor48could have variable displacement capability, if desired.

In one embodiment, motor48may have a minimum speed. The minimum speed may correspond with a minimum inlet pressure of motor48. When the speed of motor48falls below this speed, the pressure at the inlet of motor48may be too low for efficient operation. That is, it may be possible for motor48to stop rotating, due to the inlet pressure being too low at below minimum motor48speed. In the disclosed embodiment, the minimum speed of motor48may be about 500 rpm.

A controller58may be associated with cooling system28and configured to regulate a speed of fan46based on the signal from sensor38. For example, controller58may be in communication with the displacement mechanism56of pump50(and/or of motor48, if so equipped). And based on a value of the signal, controller58may be configured to selectively adjust a displacement of pump50, thereby adjusting the speed of fan46. It is also contemplated that in other embodiments, controller58may be configured to selectively adjust a displacement of pump50based on the signal from sensor38and one or more additional temperature signals from sensors monitoring other components or fluids of machine10.

Controller58may be a single microprocessor or multiple microprocessors that includes a mechanism for controlling an operation of cooling system28. Numerous commercially available microprocessors can be configured to perform the functions of controller58. It should be appreciated that controller58could readily be embodied in a general machine microprocessor capable of controlling numerous engine and/or machine functions. Controller58may include a memory, a secondary storage device, a processor, and any other components for running an application. Various other circuits may be associated with controller58such as power supply circuitry, signal conditioning circuitry, solenoid driver circuitry, and other types of circuitry.

FIG. 3illustrates an exemplary cooling system process implemented by controller58.FIG. 3will be discussed in more detail below to better illustrate the disclosed concepts.

INDUSTRIAL APPLICABILITY

The disclosed control system may be applicable to any machine that benefits from regulated cooling. The disclosed control system may help to keep system components at desired temperatures that promote efficient operation. The operation of cooling system28will now be explained with regard toFIG. 3.

During operation of machine10, intake air may be drawn in by compressor32, pressurized, and directed through passage34to cooler30. As the intake air passes through channels in cooler30, a flow of cooling air may be forced through adjacent channels by fan46. As both flows of air pass through cooler30, heat may be transferred from the intake air to the cooling air. The cool, compressed air may then be directed into engine18, mixed with fuel, and combusted. Exhaust resulting from the combustion process may then be directed out of engine18via exhaust passage40and through turbine42where energy in the exhaust is recaptured and used to drive compressor32.

During engine operation, controller58may continuously monitor a temperature of the intake air entering engine18to ensure that the air is at a desired temperature that promotes efficient operation (Step202). In particular, the air should be sufficiently cool to increase its density and thereby allow a desired amount of intake air to be forced into cylinders22during each engine cycle, without being so cold that moisture in the air freezes within inlet manifold36. A portion of the moisture in the air may be present in an exhaust gas recirculation (EGR) air stream that mixes with the intake air. If the moisture freezes inside inlet manifold36, the flow of air into inlet manifold36may become restricted, resulting in unstable engine18operation. Accordingly, controller58may monitor the temperature of the intake air, and selectively drive fan46at a speed that is a function of the temperature signal (e.g., intake air temperature) when the temperature is above a threshold temperature (Step204). Controller58may cause fan46to speed up or slow down based on a value of the signal. For example, as the temperature of the air increases, controller58may proportionally increase a displacement of pump50, thereby increasing motor48speed and the speed of fan46. Likewise, as the temperature of the air decreases, controller58may proportionally decrease the displacement of pump50or it may open a bypass valve to bypass pressurized fluid around motor48.

The speed of motor48may only be decreased until the minimum motor speed is reached. As described above, the minimum motor speed in the disclosed example may be about 500 rpm. Accordingly, when the speed of motor48reaches the minimum motor speed, controller58may stop reducing the displacement of pump50.

In some embodiments, fan46may still generate too much airflow when motor48has ramped to its minimum speed. Unless accounted for, overcooling of engine18could result, causing icing of inlet manifold36and unstable engine operation. For this reason, controller58may determine whether the temperature of the intake air is too low (e.g., below the threshold temperature) and fan46is operating at the minimum speed (e.g., pump50has been ramped down and is operating at its minimum displacement) (Step206). As long as pump50remains above its minimum speed displacement or above the threshold temperature (Step206: No), control may loop through steps202-206.

However, when it is determined that the temperature of the intake air is below the threshold temperature and fan46is operating at the minimum speed (Step206: Yes), controller58may be configured to selectively cause fan46to pulse on-and-off (Step208). Controller58may cause fan46to pulse on-and-off by eliminating the torque input to fan46for a desired period of time, reapplying the torque input for a desired period of time, and again eliminating the torque input. In one embodiment, the off-period of time (i.e., the period of time during which motor48is not applying torque to fan46) may be about equal to the on-period of time (i.e., the period of time during which motor48is applying torque). For example the on- and off-periods of time may be about equal to 5-60 seconds each. In another embodiment, the off-period of time is different than the on-period of time. The on- and/or off-periods of time may stay the same throughout engine operation regardless of temperature, or change based on the temperature, as desired. For example, as the temperature of the intake air reduces even further, the off-period of time may increase. And as the temperature of the intake air increases, the on-period of time may increase. In general, fan46may be caused to pulse at a rate that maintains the temperature of the intake air at a substantially constant value. In the disclosed example, the temperature may be maintained within about 5° C. of the threshold temperature.

There may be many different ways in which controller58could cause the pulsing of fan46(i.e., inhibit motor48from applying torque and cause motor48to apply torque). In one embodiment, controller58may inhibit motor48from applying torque by step-wise reducing the displacement of pump50to a neutral (i.e., zero angle) position. In another embodiment, pump50may be disconnected from engine18and/or from motor48. In yet another embodiment, supply passage52may be connected directly to return passage54(e.g., utilizing a valve), such that pressurized fluid from pump50bypasses motor48. Other methods may also be utilized, as desired.

After initiating pulsing of fan46, controller58may continue to monitor the temperature of the intake air and compare the temperature to the threshold value (Step210). As long as the intake air temperature remains below the threshold temperature (Step210: Yes) after initiation of fan pulsing (Step208), control may loop through steps208-210. If the intake air temperature is not below the threshold temperature (Step210: No), then controller58may return to step202.

By causing fan46to pulse during extreme cold weather conditions, engine18may be inhibited from overcooling and components of cooling system28may not be exposed to damaging thermal shock. That is, the components (e.g., pump50, motor48, passages52and54, fluid, etc.) of cooling system28, by still being periodically operational, may remain at a substantially constant temperature that promotes longevity of the components. In particular, the components may not be allowed to cool off due to inactivity to a level that would cause thermal shock loading when operation is resumed. In addition to extending the life of these components, the operating range of machine10may also be improved. Specifically, machine10may be able to operate at even lower temperatures without increasing a risk of component failure due to thermal shock loading.

By preventing thermal shock and over cooling (e.g., icing of inlet manifold36), the cold operating temperature performance (COTP) of machine10can be improved. For example, without pulsing the cold temperature idling capability of machine10may be about between about 0 and −10° C., because below that temperature, overcooling may become problematic. In contrast, by pulsing fan46as described herein the cold temperature idling capability of machine10may drop from to less than −40° C. Therefore, pulsing provides a larger temperature range in which machine10may operate while still preventing overcooling and thermal shock and it allows increased idling time without the need for refueling (i.e., increased fuel economy).

It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed cooling system. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed cooling system. For example, although the present disclosure is illustrated in the context of a cooling fan for intake air associated with an engine and other machine systems, the present disclosure may also be used in a similar manner to control coolant temperatures inside the engine. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.