Method and apparatus for cooling fan control algorithm

[0002] This invention relates to the control of a cooling fan on a work machine, and, more particularly, to a control algorithm which controls the speed of a cooling fan as needed by controlling the amount of power provided to the fan.

[0003] A work machine, such as a wheel loader, hydraulic excavator, forwarder, or track-type tractor typically generates a great deal of engine heat during operation. This engine heat is often exacerbated by a high ambient temperature at the work location. Additionally, in an effort to make the machine operate more quietly, the engine compartment of the machine is often heavily muffled and insulated, which also raises the engine compartment temperature. It is therefore desirable to run a cooling fan or other airflow provider to draw, push, or otherwise direct heat away from the engine compartment.

[0004] Conversely, often regulations require that the noise produced by the work machine be less than a predetermined level or rate. As much of the noise produced by the machine is caused by the cooling fan of the machine, it is thus advantageous to regulate the operation of the cooling fan to provide the least amount of noise while still maintaining the desired cooling characteristics. This is often done by running the cooling fan at a reduced speed or by selectively turning the fan off.

[0005] An example of a cooling fan control algorithm is disclosed in U.S. Pat. No. 6,045,482, issued Apr. 4, 2000 to Dipchand V. Nishar et al. (hereafter referenced as '482). '482 discloses a system for controlling air flow to an engine cooling system which includes a control computer responsive to a number of engine and/or engine accessory operating conditions, and to various engine operational states to control operation of an engine cooling device. Examples of the engine and/or engine accessory operating conditions include engine coolant temperature, rate of change of engine coolant temperature, intake manifold air temperature, air conditioner refrigerant pressure, and fan speed factor.

[0006] Accordingly, the art has sought an apparatus and method of a cooling fan control system for a work machine which: measures one or more temperature inputs from the work machine; controls the cooling fan without requiring that the cooling fan be monitored; controls the cooling fan to provide a reduction in noise produced by the work machine; proportionally modulates a pump which directly drives a motor; limits the rate of change of the proportional modulation to prevent driver diagnostics and hydraulic system instabilities; provides lower fuel consumption; provides reduced overcooling of the engine inlet air and hydraulic fluid in cold ambient conditions; provides greater operator comfort; may be used in a timely and efficient manner; and is more economical to manufacture and use.

[0007] The present invention is directed to overcoming one or more of the problems as set forth above.

[0008] In an embodiment of the present invention, a method for controlling a fan on a work machine is provided. The method includes the steps of producing an inlet manifold air temperature signal responsive to a sensed temperature of air at an inlet manifold, producing an engine coolant temperature signal responsive to a sensed temperature of an engine coolant fluid, producing a hydraulic sump temperature signal responsive to a sensed temperature of a hydraulic fluid, and producing a transmission lube oil temperature signal responsive to a sensed temperature of a transmission fluid. The method also includes the steps of reading the inlet manifold air temperature signal, engine coolant temperature signal, hydraulic sump temperature signal, and transmission lube oil temperature signal and responsively calculating a fan current value; and reading the fan current value and responsively controlling the fan.

[0009] In an embodiment of the present invention, an apparatus for controlling an engine cooling fan is provided. The apparatus includes one or more temperature sensors, an electronic control module, and a fan control device. The temperature sensors are adapted to measure one or more temperatures and responsively produce one or more temperature signals. The electronic control module is adapted to receive the temperature signals and responsively produce a fan current signal. The fan control device is adapted to receive the fan current signal and responsively control a driving force provided to the engine cooling fan.

[0010] In an embodiment of the present invention, a method for use in an engine cooling system for a work machine is provided. The method includes the steps of generating a current signal based on at least one temperature input, and reading the current signal and responsively providing power to a cooling member.

[0011] FIG. 1 is a block diagram of a preferred embodiment of the present invention;

[0012] FIG. 2 is a flowchart of an algorithm based on a preferred embodiment of the present invention; and

[0013] FIG. 3 is a graph of the inverse relationship between the fan current value (I) and the cooling fan 114 speed (F) in a preferred embodiment of the present invention.

[0014] A preferred embodiment of the present invention provides a method and apparatus of controlling a fan on a work machine. The following description uses a wheel loader as an example only. This invention may be applied to other types of work machines, for example, hydraulic excavators or track-type tractors.

[0015] As shown in FIG. 1, a cooling fan control system 100 for a work machine includes an inlet manifold air temperature sensor 102, an engine coolant temperature sensor 104, a hydraulic sump temperature sensor 106, and a transmission lube oil temperature sensor 108. Any other temperature properties of the work machine may be sensed and monitored, additionally or substitutionally to these four, without departing from the spirit and scope of the present invention. The inlet manifold air temperature sensor 102 produces an inlet manifold air temperature signal (t_i) responsive to a sensed temperature of air at an inlet manifold of a work machine. The engine coolant temperature sensor 104 produces an engine coolant temperature signal (t_e) responsive to a sensed temperature of the engine coolant of the work machine. The hydraulic sump temperature sensor 106 produces a hydraulic sump air temperature signal (t_h) responsive to a sensed temperature of hydraulic fluid in the hydraulic sump of the work machine. The transmission lube oil temperature sensor 108 produces an transmission lube oil temperature signal (t_t) responsive to a sensed temperature of the lubrication oil of a transmission of the work machine.

[0016] An electronic control module (hereafter referenced as ECM) 110 reads the t_l, t_e, t_h, and t_tsignals and responsively produces a fan current value (I) which controls the hydraulic fluid flow through a fan electrohydraulic (E/H) valve 112 which powers a cooling fan 114 to provides airflow to the engine compartment of the work machine.

[0017] It is to be understood that the element referenced herein as a cooling fan 114 can include one or more single, dual, or variable speed fans, or any other electrically, electronically, or electrohydraulically actuable device which operates to provide cooling airflow to the engine compartment.

[0018] In a preferred embodiment, the ECM 110 is a computer including a microprocessor chip manufactured by Motorola Inc. located in Schaumburg, Ill. However, other suitable ECMs are known in the art, any one of which could be readily and easily used in connection with an embodiment of the present invention. A specific program code can be readily and easily written from the flowchart, shown in FIG. 2, in the specific assembly language or microcode for the selected microprocessor chip.

[0019] The computer is adapted to receive the t_i, t_e, t_h, and t_tsignals and provide a fan current value (I) in response to the t_i, t_e, t_h, and t_tsignals. Preferably the computer is one of many readily available computers capable of processing numerous instructions. It should be appreciated that the computer may include multiple processing units configured in a distributed structure environment and forming a system.

[0020] FIG. 2 is a flowchart detailing an algorithm based on a preferred embodiment of the present invention. The execution of the program starts at first control block 200. The t_i, t_e, t_h, and t_tsignals are read by the ECM 110 at second control block 202. If there is an error associated with the reading of any one of the t_i, t_e, t_h, and t_tsignals (that is, if any of these signals is unavailable or improper), a default value is chosen for the erroneous signal at third control block 204. Whether or not there is a read error, the ECM 110 then calculates a corresponding error signal t_i′, t_e′, t_h′, and t_t′ for each of the t_l, t_e, t_h, and t_tsignals at fourth control block 206. These error signals t_l′, t_e′, t_h′, and t_t′ are calculated responsive to the original t_i, t_e, t_h, and t_tsignals and to predetermined multiplier values and target values for each of the original t_i, t_e, t_h, and t_tsignals.

[0021] At fifth control block 208, a controlling temperature signal (T) is chosen from the error signals t_i′, t_e′, t_h′, and t_t′. The choice of T is made by a predetermined method and can be adjusted through adjustment of the chosen predetermined multiplier values and target values. One option for choosing which error signal t_l′, t_e′, t_h′, and t_t′ to use as T is to choose the highest of the error signals t_i′, t_e′, t_h′, and t_t′.

[0022] Regardless of the error signal t_i′, t_e′, t_h′, and t_t′ chosen, a PI controller or other hardware or software device produces the fan current value (I) responsive to T at sixth control block 210. With T as the input, I may be produced through the use of an algorithm, lookup table, chart, any combination thereof, or any other method which permits a predictable output from an input. If there is in error in the production of I, I is set to a predetermined minimum fan current value (I_mm) at seventh control block 212.

[0023] Whether or not there is an error associated with I, I is compared to I_minat first decision block 214. If I is less than I_min, I is set to I_minat seventh control block 212. If I is greater than I_min, no change is made. Control then passes to second decision block 216.

[0024] At second decision block 216, I is compared to I_max. If I is greater than I_max, I is set to I_maxat eighth control block 218. If I is less than I_max, no change is made. Control then passes to third decision block 216.

[0025] At third decision block 220, the rate of change of I (dI/dt) is compared to a maximum rate of change value (dI/dt)_max. If dI/dt is greater than (dI/dt)_max, dI/dt is set to (dI/dt)_maxat ninth control block 222. If dI/dt is less than (dI/dt)_max, no change is made. Control then passes to tenth control block 224.

[0026] At tenth control block 224, a signal corresponding to I is provided to the fan electrohydraulic (E/H) valve 112. At eleventh control block 226, the fan E/H valve controls the hydraulic fluid supplied to the cooling fan 114 responsive to the value of I. At twelfth control block 228, the hydraulic fluid controls the cooling fan 114 speed (F). Advantageously, if there is an error providing the signal corresponding to I to the fan electrohydraulic (E/H) valve 112, I is assumed to be I_minat thirteenth control block 230 and control then returns to eleventh control block 226. Regardless of the presence of an error, the program logic returns to first control block 200 from twelfth control block 228.

[0027] The logic of FIG. 2 is performed every control loop to help regulate F to be the minimum speed necessary for providing a desired airflow to the work machine. However, those skilled in the art know that aspects of the control of F could be determined at other frequencies depending on factors like the read frequencies of the temperature sensors without deviating from the invention as defined by the appended claims.

[0028] While aspects of the present invention have been particularly shown and described with reference to the preferred embodiment above, it will be understood by those skilled in the art that various additional embodiments may be contemplated without departing from the spirit and scope of the present invention. For example, the temperature sensors may read different temperatures than the examples given above, the cooling fan may be an air-providing device other than a traditional fan, the cooling fan may be operated electrically or electronically rather than electrohydraulically, or the operator may be prompted for input if a signal error occurs. However, a device or method incorporating such an embodiment should be understood to fall within the scope of the present invention as determined based upon the claims below and any equivalents thereof.

[0029] As discussed herein and shown in the accompanying drawings, the present invention provides a method and apparatus of a cooling fan control system 100. In operation, it is desirable to control the cooling fan 114 of a work machine such that the cooling fan 114 operates as little as possible while still maintaining proper airflow to the engine compartment (not shown) of a work machine (not shown).

[0030] In operation, the ECM 110 receives at least one temperature signal from at least one temperature sensor. Examples of these signals are an inlet manifold air temperature signal (t_i), an engine coolant temperature signal (t_e), a hydraulic sump air temperature signal (t_h), and an transmission lube oil temperature signal (t_t). These temperatures are modified to provide error signals t_i′, t_e′, t_h′, and t_t′, which are calculated responsive to the original t_l, t_e, t_h, and t_tsignals and to predetermined multiplier values and target values for each of the original t_i, t_e, t_h, and t_tsignals. One of the error signals t_i′, t_e′, t_h′, and t_t′ is then chosen, according to predetermined criteria, to be the controlling temperature signal (T).

[0031] Once T is chosen, a proportional controller or other well-known hardware or software device produces the fan current value (I) responsive to T. I is then limited between predetermined maximum and minimum values. Advantageously, the maximum and minimum values stem from the flow compensator on a variable hydraulic pump and from the pressure compensator on a variable displacement piston pump, respectively. After I is limited between maximum and minimum values, the rate of change of I with respect to time is limited to a predetermined maximum rate value. Preferably, this maximum rate value prevents driver diagnostics and hydraulic system instabilities.

[0032] FIG. 3 illustrates the inverse relationship between the fan current value (I) and the cooling fan 114 speed (F) in a preferred embodiment of the present invention. FIG. 3 is meant to be illustrative and does not necessarily represent actual values of this inverse relationship. As can be readily seen, the relationship is constructed so that an absence of the I input results in a maximum fan speed. This function prevents overheating of the work machine due to a lost signal.

[0033] Controlling I controls current to the proportional E/H valve, which responsively governs the hydraulic fluid powering the cooling fan 114. Optionally, I can be used to control any regulator supplying power to any cooling device.

[0034] The method and apparatus of certain embodiments of the present invention, when compared with other apparatus and methods, may have the advantages of: measuring one or more temperature inputs from the work machine; controlling the cooling fan without requiring that the cooling fan be monitored; controlling the cooling fan to provide a reduction in noise produced by the work machine; proportionally modulating a pump which directly drives a motor; limiting the rate of change of the proportional modulation to prevent driver diagnostics and hydraulic system instabilities; providing lower fuel consumption; providing reduced overcooling of the engine inlet air and hydraulic fluid in cold ambient conditions; providing greater operator comfort; use in a timely and efficient manner; and being more economical to manufacture and use. Such advantages are particularly worthy of incorporating into the design, manufacture, and operation of wheel loaders and other work machines. In addition, the present invention may provide other advantages that have not been discovered yet.

[0035] It should be understood that while a preferred embodiment is described in connection with a wheel loader, the present invention is readily adaptable to provide similar functions for other work machines. Other aspects, objects, and advantages of the present invention can be obtained from a study of the drawings, the disclosure, and the appended claims.