Patent Publication Number: US-6339741-B1

Title: Engine speed control with resume from idle or near idle

Description:
TECHNICAL FIELD 
     The present invention relates to systems and methods for controlling engine speed of an internal combustion engine. 
     BACKGROUND ART 
     Electronically controlled internal combustion engines have a wide variety of applications which may include driving various machinery including pumps, for example. Diesel engines are often used to provide motive power to vehicles or vessels, in addition to powering auxiliary equipment using a power take-off (PTO) mode of operation and appropriate couplings which may include a geared transmission. Engines may also be used in stationary applications for powering generators, driving irrigation pumps, driving compressors, or in petroleum drilling applications, for example. 
     In one particular application, diesel engines have been used to power petroleum mud pumps which are used to supply fluid to a drilling bit when a well is being drilled. The drilling rig operator will carefully adjust the engine speed to achieve a desired pumping rate, typically using a hand throttle potentiometer. The optimum speed typically varies from job to job and may vary depending upon the characteristics of the area being drilled. Once the operator has dialed-in the appropriate speed, the engine continues driving the pump at that speed until a new section of drilling pipe must be added. At that point, the operator brings the engine back to idle and disengages the transmission or clutch to allow a new section of pipe to be threaded in place. After adding the new section of pipe, the operator must then gradually increase the engine speed and pumping rate to again dial-in the optimum speed for the current conditions. While stationary engines may be equipped with a constant speed/cruise control function, they do not allow resuming to a preselected engine speed from idle operation. 
     DISCLOSURE OF INVENTION 
     An object of the present invention is to provide a system and method for controlling an engine which provides the ability to automatically return to a selected engine speed from idle or near idle. 
     Another object of the present invention is to provide a system and method for controlling a diesel engine utilized in a pumping application to return to an operator selected set speed after running at an alternate or high idle speed. 
     A further object of the present invention is to provide a system and method for controlling an engine used in a petroleum drilling application to allow operators to return to a previously dialed-in engine speed after adding or changing pipe. 
     Yet another object of the present invention is to provide an engine with a cruise control function capable of resuming to a previously selected set speed from idle or near idle. 
     A still further object of the present invention is to provide a system and method for controlling an engine in a pumping application with throttle controls positioned at multiple locations such that the engine returns to a previously selected set speed from idle or near idle operation. 
     In carrying out the above objects and other objects, features, and advantages of the present invention, a method for controlling an engine used for a pumping application includes adjusting a throttle to select a desired engine speed, storing the desired engine speed in memory, reducing the engine speed to a speed at or near idle, and automatically returning the engine speed to the stored desired engine speed from idle or near idle. 
     A system for controlling an engine used in a pumping application includes at least one throttle to select a desired engine speed, at least one switch to indicate that the selected engine speed should be stored, at least one switch to indicate that the engine speed should be controlled to a previously stored engine speed, and an engine controller in communication with the switches and the at least one throttle, the engine controller operative to control the engine speed based on inputs received from the at least one throttle and the switches to control the engine speed to a previously stored engine speed from idle or near idle. 
     In one embodiment, at least two throttle controls are provided to remotely control the engine speed from corresponding control stations. The throttle controls may be any of a number of types including hand-operated, foot pedals, etc. 
     The present invention provides a number of advantages. For example, the present invention allows an operator to carefully select an operating speed for the engine for a particular application or operating condition, return the engine to idle, and subsequently automatically return to the previously selected engine speed from idle or near idle without further readjustment. In petroleum drilling applications, the present invention allows the operator to dial-in an appropriate speed for current conditions, return the engine to idle or near idle while adding or changing pipe, and return to the previously dialed-in engine speed without further adjustments using the throttle. 
     The above advantages, and other advantages, objects, and features of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a schematic/block diagram illustrating operation of a system or method for engine speed control for a petroleum mud pump application according to one embodiment of the present invention; 
     FIG. 2 is a schematic illustrating typical control switch connections for a system or method of controlling engine speed in pumping applications according to one embodiment of the present invention; 
     FIG. 3 is a schematic illustrating connections for a multiple throttle control according to one embodiment of the present invention; 
     FIG. 4 is a flow chart illustrating operation of a system or method for controlling engine speed according to one embodiment of the present invention; and 
     FIG. 5 is a flow chart illustrating operation of a system or method for controlling engine speed with dual throttle control according to one embodiment of the present invention. 
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     FIG. 1 is a schematic/block diagram illustrating operation of a system or method for engine speed control for a petroleum mud pump application according to one embodiment of the present invention. System  10  includes an internal combustion engine  12 , preferably a diesel engine, connected via a coupling  14  to a pump  18 . Coupling  14  may include a clutch  16  and/or transmission (not shown). Drilling apparatus  20  is used to drive sections of drilling pipe  22  into the ground. 
     In operation, engine  12  is started and warmed up prior to connection to pump  18  via coupling  14 . After engine  12  has warmed up, the operator carefully adjusts the engine speed until a desired pumping rate is obtained for the particular drilling conditions. Pump  18  is used to supply fluid to a drilling bit on the end of pipe sections  22  as the well is being drilled. The desired pumping rate, and therefore the desired engine speed, will vary from job to job. Once the operator dials-in the desired speed, preferably using a hand-operated throttle, he will maintain the speed until a new section of drilling pipe  22  must be added. At that point, engine  12  is brought back to idle and coupling  14  is disengaged while new pipe is added to sections  22 . Because automatic speed control/cruise control will not resume from idle, prior to the present invention the operator was required to manually readjust the engine speed to obtain the desired pumping rate using the hand-operated throttle. As described in greater detail below, the present invention provides for automatically returning the engine speed of engine  12  to a previously stored desired engine speed from idle or near idle operation. 
     FIG. 2 is a schematic illustrating typical control switch connections for a system or method of controlling engine speed in pumping applications according to one embodiment of the present invention. Engine  12  is preferably controlled by an electronic engine control module (ECM)  30  which receives signals generated by various engine sensors and processes the signals to control various actuators such as fuel injectors (not shown) on engine  12 . ECM  30  preferably includes one or more types of computer readable storage media, indicated generally by reference numeral  36 , for storing data representing instructions executable by a computer to control engine  12 . Computer readable storage media  36  may also include calibration information in addition to working variables, parameters, and the like. In one embodiment of the present invention, computer readable storage media  36  include a random access memory (RAM)  38  in addition to various non-volatile memory such as read-only memory (ROM)  40 , and non-volatile RAM (NVRAM)  42 . Computer readable storage media  36  communicate with microprocessor  34  and input/output (I/O) circuitry  44  via a standard control/address bus. As will be appreciated by one of ordinary skill in the art, computer readable storage media  36  may include various types of physical devices for temporary and/or persistent storage of data which may include solid state, magnetic, optical, and combination devices. For example, computer readable storage media  36  may be implemented using one or more physical devices such as DRAM, PROMS, EPROMS, EEPROMS, Flash Memory, and the like. Depending upon the particular application, computer readable storage media  36  may also include floppy disks, CD ROMs, and the like. 
     In a typical application, ECM  30  processes inputs, which may include various digital inputs represented generally by reference numeral  46  in addition to inputs from various types of sensors, by executing instructions stored in computer readable media  36  to generate appropriate output signals for control of engine  12 . Various types of sensors and switches may be used to monitor and control engine  12  based on current operating conditions. For example, variable reluctance sensors may be used to monitor crankshaft position and/or engine speed. Variable capacitance sensors may be used to monitor various pressures such as barometric air, manifold, oil, and pump pressures. Variable resistance sensors may be used to monitor positions such as a throttle position which is preferably a hand-operated throttle for pumping applications. In one embodiment, a hand-operated throttle comprises a potentiometer which provides a variable resistance signal to ECM  30  indicative of a commanded engine speed. 
     In the embodiment illustrated in FIG. 2, digital inputs/outputs  46  may include various switches and/or lights mounted on dash panel  48  used to control engine  12  and provide information to the operator. In this embodiment, dash panel  48  includes a light  50  connected via a digital output to ECM  30  which indicates the automatic speed control mode is engaged. A cruise enable switch  52 , resume/accelerate switch  54 , set/coast switch  56 , brake or clutch switch  58 , and ALT_MIN_VSG or alternate idle switch  60  are provided to control the automatic speed control mode of engine  12 . Preferably, enable switch  52  is a SPST switch while resume switch  54  and set switch  56  are momentary contact switches. Brake switch  58  is preferably a momentary contact, normally closed switch connected to ground. Switch  60  provides a digital input which causes engine  12  to operate at an alternate idle speed. The alternate idle speed is preferably above the normally programmed idle speed. In one embodiment, the alternate idle speed is about 50 rpm higher than the normal idle speed. Preferably, the alternate idle speed ranges between about 0 and 200 rpm higher than the regular idle speed. However, this value may vary depending upon the particular application. 
     In operation, after the engine has warmed up, the operator utilizes a throttle, such as a hand-operated throttle (FIG.  3 ), to dial-in the desired engine speed. The cruise enable switch  52  is engaged along with the ALT_MIN_VSG switch  60 . Once the desired engine speed is dialed-in, set switch  56  is engaged and ECM  30  captures or stores the current engine speed as a desired set speed. The throttle is then returned to the idle position while the automatic speed control mode is active in controlling the engine speed to the desired set speed. When additional pipe needs to be added, brake switch  58  is momentarily engaged to disengage the automatic speed control mode and return the engine to the alternate idle speed. When the pipe has been added and the operator is ready to continue drilling, resume switch  54  is engaged to automatically return the engine speed to the previously determined set speed without additional manipulation of the throttle. 
     FIG. 3 is a schematic illustrating connections for an optional multiple throttle control according to one embodiment of the present invention. The configuration of FIG. 3 allows the engine speed to be controlled by more than one throttle so that the throttles can be positioned at multiple control stations for various applications which may include petroleum drilling applications, fire truck applications, cranes, and the like. Throttle controls may include a hand throttle, a foot pedal assembly, a voltage divider circuit, or frequency input, among others. The multiple throttle implementation illustrated in FIG. 3 allows hand throttles  74 A,  74 B to be installed at multiple locations indicated by reference numerals  70  and  72 , for example. Hand throttles  74 A,  74 B are preferably implemented using a variable resistance device such as a potentiometer. The implementation illustrated in FIG. 3 allows only one hand-operated throttle  74 A,  74 B to be active at any one time to provide a commanded engine speed to ECM  76  to control engine  68 . Interlocked switches  76 ,  78 , and  80  are controlled via a control relay  82  which is energized by power supply  84  based on the position of switches  86  and  88 . ECM  76  monitors the switch inputs to determine the currently active hand-operated throttle control based on the position of switch  78 . When the operator switches control from one hand-operated throttle to another, ECM  76  maintains the current engine speed until the newly selected throttle control is qualified by reducing the commanded engine speed for that throttle to idle and then increasing it to the current engine speed position. Once qualified, the engine speed is controlled by the newly selected hand-operated throttle. If qualification does not succeed within a predetermined time period, such as 30 seconds, engine speed will be ramped down from its current value to idle or the alternate idle speed if activated. If the newly selected throttle becomes qualified, the ramp down process will be stopped and the newly selected throttle will have control of the engine speed. 
     FIGS. 4 and 5 are flowcharts illustrating operation of a system or method for controlling engine speed according to one embodiment of the present invention. As will be appreciated by one of ordinary skill in the art, the block diagrams of FIGS. 4 and 5 represent control logic which may be implemented or effected in hardware, software, or a combination of hardware and software. The various functions are preferably effected by a programmed microprocessor such as included in the DDEC controller manufactured by Detroit Diesel Corporation, Detroit, Mich. Of course, control of the engine may include one or more functions implemented by dedicated electric, electronic, or integrated circuits. As will also be appreciated by those of skill in the art, the control logic may be implemented using any of a number of known programming and processing techniques or strategies and is not limited to the order or sequence illustrated in the figures. For example, interrupt or event-driven processing is typically employed in real-time control applications, such as control of an engine rather than a purely sequential strategy as illustrated. Likewise, parallel processing, multi-tasking, or multi-threaded systems and methods may be used to accomplish the objectives, features, and advantages of the present invention. The invention is independent of the particular programming language, operating system, processor, or circuitry used to develop and/or implement the control logic illustrated. Likewise, depending upon the particular programming language and processing strategy, various functions may be performed in the sequence illustrated, at substantially the same time, or in a different sequence for accomplishing the features and advantages of the present invention. The illustrated functions may be modified, or in some cases omitted, without departing from the spirit or scope of the present invention. 
     In the various embodiments of the present invention, the control logic illustrated in FIGS. 4 and 5 is implemented primarily in software and is stored in computer readable storage media within the ECM. As one of ordinary skill in the art will appreciate, various control parameters, instructions, and calibration information stored in the ECM may be selectively modified by the engine owner/operator while other information is restricted to authorized service or factory personnel. The computer readable storage media may also be used to store engine operating information and diagnostic information for maintenance/service personnel. 
     Block  100  of FIG. 4 represents starting of the engine. The engine operates at the programmed idle speed until warmed-up as represented by block  102 . The alternate idle or ALT_MIN_VSG switch is engaged as represented by block  104 . In one embodiment, this modifies the engine idle speed by increasing it to about 650 rpm from about 600 rpm. The cruise enable switch is then engaged as represented by block  106 . A hand-operated throttle is preferably used to dial-in the desired engine operating speed as represented by block  108 . A set speed switch is then engaged as represented by block  110  to capture or store the desired set speed based on the current operating speed of the engine. The hand-operated throttle is then adjusted back to the idle position as shown at block  112 . The engine speed will then be controlled by the automatic speed control mode to maintain the desired set speed. A brake switch or disengage switch is operated as represented by block  114  to return the engine to the alternate idle speed corresponding to the ALT_MIN_VSG speed which is preferably user selectable or calibratible. After completing the necessary operations, the resume switch is engaged to automatically return the engine to the previously selected set speed from idle or near idle. As used throughout the description of the invention and as will be appreciated by those of ordinary skill in the art, idle speeds will vary from application to application. At or near idle is intended to encompass settings within about 30% of idle speed. In one preferred embodiment, idle speed is set to 600 rpm while the alternate idle or ALT_MIN_VSG speed is set to 650 rpm. 
     FIG. 5 illustrates selection of a hand-operated throttle for multiple throttle controlled applications. As described above, the present invention contemplates the use of more than one throttle with only one throttle active at any particular time to control the engine speed. A throttle select or station select switch is used to indicate which throttle is desired to control the engine as represented by block  130 . Before transferring control to the selected throttle, block  132  determines whether the newly selected throttle is qualified. In a preferred embodiment, the newly selected throttle is qualified by reducing its position to idle and returning the position to a position corresponding to the current engine speed. Once the throttle is qualified as determined by block  132 , the engine speed is controlled based on the newly selected throttle position  134 . 
     If the newly selected throttle control has not been qualified as indicated by block  132 , block  136  determines whether a calibratible time period has expired. In one embodiment, the period is set to 30 seconds. If the time period has expired without throttle qualification, the engine speed is ramped down to idle or near idle as represented by block  138 . Otherwise, block  140  maintains the current engine speed until a qualified throttle provides a new command. 
     As such, the present invention provides a system and method for automatically and/or remotely controlling engine speed of an internal combustion engine to return to a previously stored speed from at or near idle speed. The present invention allows operators to dial-in an engine speed using a hand-operated throttle control, return engine speed to idle or near idle, and then resume engine speed to the stored value without further manipulation of the hand-operated throttle. The present invention preferably uses a variable speed governor mode rather than a traditional cruise control mode which would require a vehicle speed sensor (VSS) for proper operation. 
     While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.