Abstract:
An engine idle control method of an off highway vehicle. The method including the steps of: detecting a static load on the engine; detecting a dynamic load on the engine; determining if the static load is below a predetermined static level; determining if the dynamic load is less than a predetermined range; and engaging an auto-idle feature dependent upon both of the determining steps being true.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to the field of work machines. It relates more particularly to work machines with hydraulic systems. 
     2. Description of the Related Art 
     Off highway vehicles include construction equipment such as a backhoe loader, also called a loader backhoe, or shortened to “backhoe” within the common language of the industry, is a vehicle that includes a tractor like unit fitted with a bucket loader on the front and a backhoe on the back. Due to its size and versatility, backhoe loaders are very commonly used in agricultural pursuits as well as construction projects. The backhoe loader is also known as a TLB (Tractor-Loader-Backhoe), which is to say, a tractor fitted with a front loader and a rear backhoe attachment. 
     Backhoe loaders are very common and can be used for a wide variety of tasks such as: construction, small demolitions, the transportation of building materials, powering a variety of building equipment, digging holes/excavation, landscaping, breaking asphalt, and paving roads. Advantageously, the backhoe bucket can also be replaced with a variety of attachments including powered attachments such as a grapple, an auger, or a stump grinder. 
     The relatively small frame and precise control make backhoe-loaders very useful in areas that are too small for larger equipment. Their versatility and compact size makes them one of the most popular urban construction vehicles. For larger projects, a tracked excavator is generally used. 
     Vehicles, such as those used in the agricultural, forestry and construction industries are typically controlled by an operator sitting at an operator station. In the operation of the equipment there may be times in which the engine is set to run at a throttle speed that is unneeded when operations cease or are limited. For example, a backhoe may be used to dig a trench and while the operator is waiting for a depth check of the trench, the controls are not being directed to do any work so the operator manually reduces the engine speed to idle, to thereby reduce fuel consumption. 
     What is needed in the art is a control system that allows precise, reliable, detection of loads on the engine and controls an auto-idle feature without adding new sensors to the system. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a vehicle control system that detects engine load and executes an auto-idle control of the engine speed. 
     The present invention consists in one form thereof of an engine idle control method for an off highway vehicle. The method including the steps of: detecting a static load on the engine; detecting a dynamic load on the engine; determining if the static load is below a predetermined static level; determining if the dynamic load is less than a predetermined range; and engaging an auto-idle feature dependent upon both of the determining steps being true. 
     The present invention consists in another form thereof of an off highway vehicle including a chassis, an engine carried by the chassis and a controller in communication with the engine. The controller is configured to execute an engine idle control method that includes the steps of: detecting a static load on the engine; detecting a dynamic load on the engine; determining if the static load is below a predetermined static level; determining if the dynamic load is less than a predetermined range; and engaging an auto-idle feature dependent upon both of the determining steps being true. 
     An advantage of the present invention is that it provides additional features for the vehicle without the need for additional sensors. 
     Another advantage of the present invention is that it saves fuel. 
     Yet another advantage of the present invention is that it reduces engine wear. 
     Yet another advantage of the present invention is that it is responsive to the actions of the operator in an automated fashion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a side view of a vehicle in the form of a backhoe that utilizes an embodiment of a load detection method of the present invention for carrying out an auto-idle feature; 
         FIG. 2  is a state diagram that illustrates the logic of the auto-idle feature used with the vehicle of  FIG. 1 ; and 
         FIG. 3  is a flowchart that details steps of the load detection method used as an input to the auto-idle system shown in  FIG. 2  for the vehicle of  FIG. 1 . 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates an embodiment of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, and more particularly to  FIG. 1 , there is shown an earth-working machine  10 , referred to herein as a backhoe  10  that employs the present invention. Backhoe  10  includes a chassis  12  that carries an engine  14 . A loader is operatively positioned on the front of backhoe  10  and a hoe  18  is coupled to the back of vehicle  10 . Vehicle  10  additionally has a cab  20  with a seat  22 , a throttle  24  and hydraulic controls  26  therein. Additionally, there is a gear selector in the form of a FNR (Forward, Neutral, Reverse) transmission control and a BEI (Brake Enabled Idle) control, in cab  20 , although not separately illustrated. 
     Engine  14  includes an Engine Control Unit (ECU), which can be thought of as a controller that carries out control functions of engine  14  and receives input from sensors associated with the engine or from other sensors positioned about backhoe  10 . The controller executes programming instructions, such as those illustrated in  FIGS. 2 and 3 . 
     The present invention presents a method to control engine speed, such that engine  14  is automatically idled down during a period of disuse, and working speed is resumed thereafter, when vehicle  10  is being used in stationary operations. Software methods utilize existing vehicle and engine signals, and requires no additional sensors for operation. 
     Off Highway Industrial Vehicles, in particular Tractor Loader Backhoe  10 , are frequently utilized in stationary applications, where work cycles include intermittent intervals of material handling followed by idle periods. It is customary for the operator to statically set the engine throttle to a high power output position to accomplish this work. During the idle periods, in such stationary operations, it is desired to automatically reduce the engine speed, to reduce fuel consumption, emissions, noise, and wear on the machine. When the operator commands the machine back to working status (for example, by activating a hydraulic digging function), it is desired that the engine speed automatically return to the high output state. 
       FIG. 2  illustrates a state diagram illustrating a vehicle state  50  that provides a visual guide to the functions of the present invention. In state  52  (Hand Throttle Uncaptured) throttle  24  is disregarded and the visual display to the operator is normal with the engine running (or the key has just been activated). In state  54  the combination of the throttle  24  setting and the variable BEI_Activated are tested. If throttle  24  is not set to idle, then vehicle state  50  transitions to state  52 . Else if the variable BEI_Activated is TRUE (meaning Brake Enabled Idle set to Allowed by the operator and the service brakes have been activated), then vehicle state  50  transitions to state  52 . Else if the preceding conditions are met (throttle  24  is set to idle AND BEI_Activated is FALSE), then vehicle state  50  transitions to state  56 . 
     In state  56  (Hand Throttle Command Normal) throttle  24  is set to a command RPM, at which the ECU strives to maintain engine  14 , and the display is normal. If the One Touch Idle (OTI) button is toggled then vehicle state  50  transitions to state  62 . If the position of seat  22  is changed or BEI_Activated becomes TRUE then vehicle state  50  transitions to state  52 . If from state  56 , the variable AUTO_IDLE=TRUE and throttle  24  is not set to Idle then vehicle state  50  transitions to state  58 . 
     In state  58  a timer is initialized for a predetermined amount of time, such as 3 seconds, which allows a settling time in the system. This timer counts in state  60  and is used as a gating condition to exit state  60  and transition to state  56 . 
     In state  60  (Hand Throttle Command Auto Idle) the RPM command is Idle and the Display displays an Auto Idle icon. If timer  58  is expired, and one of the following occurs: the OTI button is toggled, or AUTO_IDLE_ENG_LOAD is TRUE, or throttle  24  is adjusted then vehicle state  50  transitions to state  56 . If, in state  60 , the position of seat  22  is changed, or BEI_Activated becomes TRUE, or FNR (Forward-Neutral-Reverse) is NOT Neutral, or the Auto Idle Switch is OFF, or there is an inducement, a derate (limited engine performance) or error condition then vehicle state  50  transitions to state  52 . 
     In state  62  (Hand Throttle Command OTI Idle), the RPM command is Idle and the Display displays an OTI icon. If the OTI button is toggled then vehicle state  50  transitions to state  56 . If the position of seat  22  is changed or BEI_Activated becomes TRUE then vehicle state  50  transitions to state  52 . 
       FIG. 3  is a flowchart providing another view of the present invention and that illustrates the steps taken to determine whether to engage the auto-idle feature discussed herein. Method  100  includes steps  102 ,  104 ,  106 ,  108  and  110 . At step  102  the ECU determines if engine  14  is experiencing a static load greater than X, which can be, for the sake of discussion, a 60% load value, which is an input variable available to the ECU. If the static load is greater than X, then method  100  proceeds to step  108  ensuring that the Auto-Idle is OFF. However, if the static load is not greater than X, then method  100  proceeds to step  104  where a further load determination is carried out by determining if there is a dynamic load above a predefined value. Here the load delta is determined to see if it is varying by more than a value Y over the preceding Z time units, Z being a moving time window of the most recent load data up until the present instant. For the purposes of illustration Y may be 15% and Z may be 0.25 second. If the dynamic load exceeds 15% within the last 0.25 second, then method  100  proceeds to step  108 , where the Auto-Idle feature is turned OFF. If the dynamic load does not exceed 15% then method  100  proceeds to step  106 . 
     At step  106  the ECU determines whether an operator timeout has expired. This is a predetermined time, that may be set by the operator, and if the time has elapsed, method  100  proceeds to set the Auto-Idle to ON. If the operator timeout has not expired then method  100  returns to step  102  and the static and dynamic loads are again checked. It is contemplated that the values for X, Y, Z, and the operator timeout can be other than those values discussed herein and may be selectable by an operator or an authorized person. It is further contemplated that the ECU may assume different values for one or more of X, Y, Z, depending on the present condition of Auto-Idle, for example, Auto-Idle OFF or Auto-Idle ON. 
     Advantageously the present invention uses the ECU to carry out the method of the invention and requires no additional sensors for operation. The present invention more reliably detects idle and working conditions at lightly loaded engine conditions versus a fixed threshold engine load detection system. It is contemplated that the present invention may be carried out using mechanical, hydro-mechanical, pneumatic, analog electrical/electronic and/or digital control elements. 
     Advantageously the present invention does not require dedicated motion, load, or pressure sensors to determine the working or non-working condition of the machine. The present invention addresses these shortcomings, as well as provides a method to more reliably detect idle or working conditions at lightly loaded engine conditions. 
     While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.