Abstract:
In accordance with an example embodiment, a system for managing a unique hydraulic system warmup method is described. A warmup system controller is central to the system and provides an interfacing point for communication to hardware components and a machine operator. The warmup system issues commands based on sensor inputs in light of defined rules and/or known physical properties of hydraulic fluids. Hydraulic system warmup is managed by the warmup system controller, which is configured to issue commands to affect hydraulic pumps and valves. By way of a controller managed process, the system functions to maximize hydraulic system pressure and limiting release of pressures in the lines, such that the pumps are able to maintain maximum pressure for a sufficient period of time.

Description:
TECHNICAL FIELD 
       [0001]    In general, a method and system is disclosed for warming hydraulic fluid in an electro-hydraulic pump and valve system. More specifically, the system facilitates warming of hydraulic fluid to an optimal operating temperature by at least partially retaining the fluid under pressure. 
       BACKGROUND 
       [0002]    Heavy machines including, for example, dozers, loaders, excavators, motor graders, etc. typically comprise a number of hydraulic actuators to perform various functions. Actuators are fluidly connected to a pump on the machine that provides pressurized hydraulic fluid to chambers within the actuators. As the pressurized hydraulic fluid moves into or through the chambers, the pressure of the fluid acts on hydraulic surfaces of the chambers to affect movement of the actuator and a connected implement (i.e., work tool). When the pressurized fluid is drained from the chambers it is returned to a low pressure tank on the machine. 
         [0003]    For machinery that includes a hydraulic system, it is typical practice to warm the fluid prior to valve and/or pump calibration. Also, when operating in particularly cold environments, it is often desirable or necessary to warm up the hydraulic fluid in order to improve hydraulic system performance. 
         [0004]    In a commonly implemented hydraulic system, a single load sensing pump (or fixed displacement pump in an open center valve configuration) is utilized to provide hydraulic flow to all implemented functions on the unit. In such a system, stalling one function raises the system pressure to its relief setting. Actuating a second function causes the pump to move fluid at that relief pressure setting, thus consuming hydraulic power and heating the fluid. 
         [0005]    In a dual pump system, pump flow may be split such that each pump independently controls an implement function. Stalling one function while actuating another does not necessarily lead to high pressure and high flow at each pump. Accordingly, for example, a first hydraulic pump may be stalled at high pressure with no flow while a second pump may move fluid at a low pressure. Neither the first pump nor the second pump consumes the power necessary for rapidly warming the hydraulic fluid. 
         [0006]    This issue causing a lack of warming in a dual pump configuration is also applicable to other hydraulic system configurations. A single function system, for example, being controlled by a single pump may experience this issue due to not having the capability of both stalling over relief and actuating simultaneously. 
       SUMMARY 
       [0007]    In general, the system and method warms hydraulic fluid within an implement that is dependent on hydraulic power (e.g., actuators, pistons, etc.). More specifically, a method is provided that enables an operator to interact with an application interface to engage, maintain and proceed with a warmup function. The warmup function is dependent on controlled pressurization and release of hydraulic pressures within a system. 
         [0008]    The system comprises a microcontroller (i.e., warmup controller) for receiving a first fluid temperature value from a temperature sensor and determining when the fluid temperature is less than a defined minimum temperature. In response to a request by an operator, the microcontroller transmits an instruction to cause a pump controller to increase fluid pressure. Such a request may be based on, for example, a fluid temperature value falling below a defined minimum temperature. Operator interaction with an implement controller causes a command to be sent for actuating an implement, which receives power from the hydraulic pump and valve system. A rate limiting valve command is likewise sent to a valve in response to the operator&#39;s actuating command. 
     
    
     
       BRIEF DESCRIPTION OF EXEMPLARY DRAWINGS 
         [0009]    A more complete understanding of the present invention may be derived by referring to the detailed description and claims when considered in connection with the Figures, wherein like reference numbers refer to similar elements throughout the FIGURES, and: 
           [0010]      FIG. 1  is a process flow chart showing operator and system implemented steps for executing the warmup method in accordance with one embodiment. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0011]    In a hydraulic pump system, a method to warm the hydraulic fluid includes electronically forcing a pressure compensated pump to function at full pressure by sending a high current command from a warmup system controller. The viscosity of hydraulic fluids varies with temperature changes, which creates noticeable differences in the response of hydraulically actuated implements. For example, an operator of a front-loader may observe performance differences when comparing the response of the loader&#39;s bucket having hydraulic fluid at ambient or room temperature to the performance of the loader when the hydraulic fluid has reached a normal operating temperature, typically 110° F. or higher. As such, it is common practice to operate the hydraulic main system pump for periods up to one hour prior to placing the system in operation. 
         [0012]    Hydraulic system warmup functions may vary slightly among different types of machinery and the amount of warming required; however similar core principles remain. One such warmup function includes positioning and maintaining a control valve, such that the valve pressure port is internally connected to the fluid tank or return port. Fluid from the pump is continuously circulated in a closed loop system or via the tank is an open loop system. The flow of hydraulic fluid through the hydraulic lines and the pump eventually raise the temperature of fluid to its normal operating temperature. 
         [0013]    Contrary to conventional warmup methods, the disclosed system and method accelerates hydraulic system warming by causing the hydraulic pumps to perform at full pressure for a period of time. More specifically, full pressure is managed by a pressure compensator, which limits pump outlet pressure to a predetermined level, while adjusting pump outlet flow to a level needed to maintain the set pressure. The pressure compensated pump will generally provide full pump flow at pressures below the compensator setting. Once the pump flow is restricted, pressure will build up to the setting of the compensator and then the pump will destroke to the level needed to maintain the compensator pressure setting. The full pressure state is maintained until the full flow capacity of the pump is satisfied. 
         [0014]    When pressures have been established by one or more pumps, an operator is prompted by a warmup system controller, to actuate one or more machine implements, thereby causing movement of hydraulic fluid from each pump. This combination of pressure and hydraulic fluid flow causes the hydraulic system to rapidly warm to sufficient operating temperature. 
         [0015]    The warming system controller may comprise a single microprocessor or multiple microprocessors configured to control the operation of the warmup system. The warming system controller may include proprietary hardware and software components or comprise a number of commercially available microprocessors configured to perform the functions of warming system controller. It should be appreciated that warming system controller may be readily embodied in a general machine microprocessor capable of controlling numerous machine functions. The warming system controller may include a memory, a secondary storage device, a processor, and any other components for running an application. Various other circuits may be associated with the controller such as power supply circuitry, signal conditioning circuitry, solenoid driver circuitry, and other types of circuitry. 
         [0016]    In one embodiment, additional warming is achieved by electronically limiting the hydraulic fluid flow. The flow commanded to each function may be electronically limited in order to impose restriction to the flow of fluid (to maintain pump pressure). It may also be electronically limited in order to prevent engine stalls due to drawing too much power from the hydraulic system. 
         [0017]    In a system with two valves for each implement (i.e., one driven by each pump), this warmup function may force both valves to open when the operator commands it. This allows pressurized fluid to move from both pumps through both valves to drive the function, more thoroughly warming the hydraulic circuit. 
         [0018]    Depending upon system response during the operation of this warmup method, a means of rate limiting the current command to the valves may be necessary. With the pumps driven to high pressure, opening the valves may lead to aggressive function behavior. Rate limiting the valve commands will help reduce the aggressive function behavior, thereby improving operator comfort while running the procedure. 
         [0019]    While presented herein as being specifically implemented within heavy equipment (e.g., loader, grader, backhoe, etc.), the system and method is not so limited. Those of ordinary skill in the art will appreciate that the warmup system may be applied to stationary hydraulic systems, for example, or any machine or apparatus that relies on hydraulic power to affect movement of an implement or component. Moreover, generating hydraulic pressure requires a power source (e.g., a diesel engine). However, the disclosed warmup system is not specific to any one configuration. 
         [0020]      FIG. 1  is a process flow chart showing operator and system implemented steps for executing the warmup method in accordance with one embodiment. An application interface may be provided to enable an operator to monitor and modify parameters relating to the warmup function. The application interface may be made accessible by way of an existing display screen or a display device that is specific to the warmup system. In another embodiment, the application interface is remotely accessible, allowing an operator, manager, technician, etc. to connect to the warmup system for viewing and optionally modifying warmup parameters. In one embodiment, the application interface includes a warmup menu. The warmup menu may conveniently display the most commonly used controls and monitors for managing the warmup system and specifically to receive user selections for invoking and/or aborting the warmup function, which comprises a number of steps. 
         [0021]    Accessing the warmup application interface by any means known in the art, an operator may be validated through a login and credential verification sequence. When secure and limited access is implemented, credential verification may be performed through any number of known or unique methods including, for example, user name and password combination, smartcard, PIN entry, biometric reading, etc. Further, a credential verification sequence may be implemented to assign user roles based on the identity of the validated user. For example, the warmup system may allow a manger to view and modify warmup parameters, while an operator may only monitor real-time parameter readings and/or view parameter settings. 
         [0022]    When a user is allowed access to manage functions and/or parameters of the warmup system, the warmup menu may be displayed within the application interface. At any point prior to committing parameter modifications and invoking the warmup function, the operator may choose to exit or leave the warmup menu at which time; the warmup routine may be aborted. Otherwise, the warmup menu selection invokes the warmup routine. 
         [0023]    In one embodiment, the warmup routine is engaged only after entering a warmup routine  100 , which includes a number of conditional validation steps. The validation steps may include determining, for example, whether the engine speed is at maximum, park brake is applied, hydraulics are enabled, operating mode is set to performance mode and no electro-hydraulic system faults are active  105 . If any of the validation steps returns false, the warmup system exits the warmup routine  135 . 
         [0024]    When a boom and boom position sensor are present, the warmup system may determine by means of position sensor feedback that the boom is resting at or near ground level. In another embodiment, the warmup system verifies that the applicable implement controller is set to a neutral position  110 . 
         [0025]    In one embodiment, a warmup routine may be invoked based on system implemented procedures, operator procedures, or any combination thereof. For example, as a procedure of the warmup routine, the warmup system may ensure that all pumps are provided a full current command  115 . In order for the warmup routine to proceed, the operator may be instructed, by way of the application interface, to invoke movement of the boom and bucket (i.e., implement), which causes the hydraulic fluid to warm. Based on the instruction, the operator interfaces with an implement controller to issue a command that includes a current value  120 . The command invokes implement movement. 
         [0026]    If an operator cancels the warmup routing or when the goal temperature is obtained, the warmup system exits the warmup routine  135 . Otherwise, rate limiting may be applied to the boom and bucket commands to optimize operation performance during a warmup routine. As used herein, rate limiting refers to as how quickly a valve current is raised to the operator commanded value or to a defined maximum value  125  or lowered to a defined minimum current value  130 . With the pumps driven to high pressure, opening the valves may lead to aggressive function behavior. Rate limiting the valve commands may help reduce the aggressive function behavior, improving operator comfort while running the procedure. When the valve current is at the minimum value, the routine returns to monitor for operator initiated commands  120 . 
         [0027]    In one embodiment, the warmup system exits the warmup routine on completion, which is marked by a maintained hydraulic fluid temperature over a defined period of time  130 . For example, the warmup routine may be considered complete and the function exited when a hydraulic temperature sensor returns values indicating that a reading of the hydraulic warmup achieved a threshold for a defined duration. Those of ordinary skill in the art will appreciate that any temperature and time parameters may be determined in accordance with a specific implementation and disclosure of such parameters herein are presented for explanation only. 
         [0028]    The hydraulic temperature sensor may comprise a sensor, probe, or thermistor configured to measure a temperature of the hydraulic system components. In one embodiment, a hydraulic temperature sensor is a fluid sensor associated with pressurized fluid residing within or flowing past various valves, hoses, lines, motors, and actuators as described herein. The hydraulic temperature sensor may generate a signal indicative of the temperature of the hydraulic fluid and direct this signal to the warmup system controller. When the hydraulic temperature signal indicates a temperature lower than a threshold value, for example approximately 30° C., the hydraulic system may be considered to be operating in a cold condition. 
         [0029]    The system may be described herein in terms of functional block components, optional selections and/or various processing steps. It should be appreciated that such functional blocks may be realized by any number of hardware and/or software components suitably configured to perform the specified functions. For example, the system may employ various integrated circuit components such as, memory elements, processing elements, logic elements, look-up tables, and/or the like. The integrated circuit components may carry out a variety of functions under the control of one or more microprocessors or other control devices. Similarly, software elements may be implemented with any programming or scripting language with the various algorithms being implemented with any combination of data structures, objects, processes, routines or other programming elements. 
         [0030]    As may be appreciated by one of ordinary skill in the art, the system may be embodied as a method, a data processing system, a device for data processing, a hardware controller, and/or a computer program product. Accordingly, the system may take the form of an entirely software embodiment, an entirely hardware embodiment, or an embodiment combining aspects of both software and hardware. 
         [0031]    Computer program code may also be stored in a computer-readable memory that may direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement functions of flowchart block or blocks. The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus include steps for implementing the functions specified in the description. 
         [0032]    In the foregoing specification, the system has been described with reference to specific embodiments. However, it may be appreciated that various modifications and changes may be made without departing from the scope of the invention. The specification and figures are to be regarded as illustrative in nature and are not intended to limit the invention to the specific steps and/or components shown and described. Accordingly, the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given above. For example, the steps recited in any of the method or process claims may be executed in any order and are not limited to the order presented. Moreover, all calculations, measurements, and values disclosed herein are presented for explanation only and are not intended to limit the scope of the invention to the specific disclosures. 
         [0033]    Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as critical, required, or essential features or elements of any or all the claims. As used herein, the terms “comprises”, “comprising”, or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Further, no element described herein is required for the practice of the invention unless expressly described as “essential” or “critical.”