Abstract:
An idle stop-start control method includes initiating a monitoring system, determining if the engine is running, and monitoring the engine to detect a shut-down condition or a sustain condition. The method includes initiating the restarting of an engine based on the condition of input parameters.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a control method and more particularly to an idle stop-start control method for an internal combustion engine. 
     BACKGROUND OF THE INVENTION 
     Control methods are used in various applications to analyze data and perform actions; as such, control methods have vast applicability in the automotive arts. To that end, many controls within the engine and transmission utilize methods which are either user implemented or automatic. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a method for providing idle start-stop control for an internal combustion engine. The invention allows for appropriate engine shut down only when there is insufficient demand for the benefits obtained from a running engine. 
     In one aspect of the invention, a method of starting and shutting down an engine of a vehicle during use thereof to conserve energy includes the following steps. A plurality of vehicle operating conditions are monitored and an engine shut-down indicator is set whenever each of the plurality of vehicle operating conditions are acceptable. An engine sustain indicator is set whenever any one of the plurality of vehicle operating conditions is unacceptable. The engine is shut down whenever the engine is running and the shut-down indicator is set. The engine is started whenever the engine is not running and the engine sustain indicator is set. 
     In another aspect of the invention, a system for starting and shutting down an engine of a vehicle during use thereof to conserve energy includes a vehicle engine controller and a plurality of sensors for monitoring a plurality of vehicle operating conditions, the sensors being coupled to the vehicle engine controller. The engine controller is operative to shut down the engine whenever the engine is running and each of the plurality of sensors indicates an acceptable operating condition. The engine controller is further operative to start the engine whenever the engine is not running and any one of the plurality of sensors indicates an unacceptable condition. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description and the accompanying drawing, wherein: 
     FIGS. 1A and 1B present a flow chart showing a general logical progression of the idle stop-start control method in accordance with the teachings of the present invention; and 
     FIG. 2 sets forth a functional block diagram of a system arranged in accordance with the principles of the invention. 
    
    
     DETAILED DESCRIPTION 
     With reference to FIGS. 1A and 1B, idle stop-start control method  10  begins at power-up step  101 . At step  103 , the control method will not activate until the vehicle&#39;s engine is determined to be running. When the engine is deemed running, the method then proceeds to the wait period step  105  to allow for an engine warm-up interval. 
     After the warm-up period, the method proceeds to step  117  of FIG. 1B to begin a series of tests to determine whether an engine sustain or an engine shut-down condition state should be set. 
     The series of decision steps in FIG. 1B comprises multiple determinations of various engine and vehicle conditions. While the preferred embodiment requires that all of the conditions tested in steps  117 - 129  be satisfied to trigger a change in engine status, differing vehicle configurations may demand that certain conditions be relaxed or even eliminated to ensure compatibility across many vehicle configurations. Hence, the requirement that all conditions be satisfied for a status change serves as an example but does not serve to limit the invention as disclosed. 
     With further reference to the flow chart of FIG. 1B, step  117  determines if the engine is at a normal running temperature, for example, a range of 170° F. (≈76° C.) to 240° F. (≈116° C.). If the temperature is deemed abnormal, the method proceeds to step  133  to set a sustain condition flag. The method then returns to point B of FIG.  1 A. 
     If the temperature is deemed normal, the method proceeds to decision block  119  where it is determined whether or not the vehicle is at rest. If the vehicle is not at rest, the method proceeds to step  133  and the sustain condition flag is set. 
     If the vehicle is determined to be at rest, then the method proceeds to decision block  121  where the state of the transmission is tested to determine whether the vehicle is in forward gear. If not in a forward gear, then step  133  is entered where the sustain condition flag is set. If the vehicle is in forward gear, the method proceeds to decision block  123  which determines whether the service brake is depressed. If the brake is not depressed, the method proceeds to step  133  to set the sustain condition flag. If the service brake is depressed, the method proceeds to decision block  125  where it is determined whether or not the vehicle accessories, such as the air conditioning units, are under a high load condition. 
     If the accessories are in a high load condition then the method proceeds to step  133  where the sustain condition flag is set. If not under high load at the accessories, the method proceeds to decision block  127  where the status of the electrical system of the vehicle is checked. If the electrical system is found to be in an abnormal operational state, the method proceeds to block  133  to set the sustain condition flag. If the status of the electrical system of the vehicle is normal, then the method proceeds to decision block  129 . 
     Decision block  129  examines the number of engine shut downs over a predetermined past time interval. If the number of shut downs of the engine exceeds a predetermined maximum value, then block  133  sets the sustain condition flag. If the number of shut downs is less than or equal to the predetermined maximum, then the routine proceeds to block  131  where a shut-down condition flag is set. The method then returns to step B of FIG.  1 A. 
     Returning now to point B of FIG. 1A, at decision block  107 , the method determines whether the vehicle&#39;s engine is currently running. If the engine is running, the method proceeds to decision block  109  which monitors the condition of the shut down flag. If the shut-down condition has been set (as in FIG.  1 B), the engine is shut down at step  111  and the routine returns to point A of FIG.  1 B. If at step  109  the shut-down condition has not been set, then no action is taken, and the routine returns to point A of FIG.  1 B. 
     If at step  107  the engine is determined not to be running, then the method proceeds to decision  113  to examine the state of the sustain condition flag. If the sustain condition has been set, then the engine is started at step  115  and the routine returns to point A of FIG.  1 B. If the sustain condition flag is not set at step  113 , then no action is taken with regard to changing the engine status and the routine proceeds to point A of FIG.  1 B. 
     With further reference to decision step  119  of FIG. 1B, it may be appropriate in a hybrid vehicle utilizing both electric and internal combustion engines to also include a coast condition to indicate that engine status change may be required. In the hybrid vehicle situation, to satisfy the condition of being completely at rest, such a vehicle may come to a complete stop or be in a coast condition. The coast condition would generally be defined as a condition wherein the driver has depressed the service brake or has not pressed any pedal but the vehicle is still in motion. If a hybrid vehicle has not come to a complete stop or is not in a coast condition at step  119 , the method would proceed to step  133  for setting a sustain condition flag. If, on the other hand, the vehicle has come to a complete stop or is in a coast condition, the routine will then proceed to the next test at decision block  121 . 
     With reference to FIG. 2, a block diagram of a system arranged for implementing the method of FIGS. 1A and 1B is set forth. A software program for conducting the steps set forth above in conjunction with FIGS. 1A and 1B could, for example, reside in a microprocessor-based engine controller  202  of the vehicle. Controller  202  would, via a bidirectional data bus  220  be coupled for receipt of sensor signals from a variety of sources. 
     Such sensors would include engine temperature sensor  204 , speed sensor or speedometer  206 , gear state sensor  208 , brake pedal position sensor  210 , accessory load sensors  212  and electrical system scan points  214 . 
     In the particular embodiment, the idle stop-start control method  10  is integral to a vehicle with automatic transmission and an internal combustion engine. Those skilled in the art, however, will readily appreciate that the method  10  can be used in multiple types of vehicles and with many different types of power plants. Further, automatic transmissions may take the form of various automatically controlled transmissions, clutchless manual transmissions, or automatically-controlled manual transmissions. As such, use in a vehicle with an automatic transmission and with an internal combustion engine is intended only as an example and otherwise does not serve to limit the disclosed invention. 
     One skilled in the art will readily appreciate that varying maximum and minimum temperatures can accommodate other engine and vehicle-wide demands. For example, physical limitations of the engine design may warrant restricting the upper limit of the engine temperature to avoid damage to engine components. In another example, environmental concerns may change the lower limit of engine temperatures to avoid running the engine too cold and possibly increasing environmental pollutants. As such, normal engine temperatures, and the permissible deviations from the normal engine temperatures, are examples and do not serve to limit the invention as disclosed. 
     As described earlier, temperatures outside the aforementioned normal ranges will cause the method  10  to proceed to step  133  without shutting down the engine. For example a hot engine (where engine coolant temperature is higher than normal; such as congested traffic in the middle of summer), will generally always indicate that conditions are not set for engine shut down. 
     An example of an accessory high-load condition at step  125  of FIG. 1B, is where the air conditioning of the vehicle is on, requiring the air conditioning compressor to be running. Demand for air conditioning in the vehicle could cause the idle stop-start method  10  to enter a sustain condition at step  133 . Other load conditions could also produce the same result; for example, in a scenario where defogging performance is required from the heating, ventilation and air conditioning (HVAC) system in tandem with an electric heating element, the load on the HVAC system and other accessories would also cause the idle stop-start method  10  proceed to step  133 . 
     Vehicle electrical status is normal at step  127  of FIG. 1B when the common electrical systems monitored in a vehicle are normal. For example, it is common to monitor system voltage and faults from the engine controller  202  (FIG.  2 ). As such, abnormal readings from the common engine monitoring sensors or fault warnings produced by the engine controller will cause the method  10  to enter a sustain condition at step  133 . 
     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.