Abstract:
A method and device for increasing the idling speed of an engine of a motor vehicle from a normal idle speed level to a higher preselected maximum idle speed level in response to a low output voltage from a power generating system of the engine and vehicle is disclosed for the purpose of preventing a severe discharge of a storage battery of the system to prevent disruption of engine ignition and reduced effectiveness of vehicle electrical components and to increase the service life of the battery and an electrical alternator of the system. The device can be operated in conjunction with or as a part of an conventional electronic control module (ECM) of the vehicle to take over control of the idle speed of the engine when a predetermined low output voltage of the system is sensed. Upon assuming control of the engine idle speed, the device raises the idle speed to a predetermined maximum safe level and maintains that level independent of engine loading for purposes of charging the battery to increase the system output voltage. After the system output voltage is restored to a predetermined maximum value, the device returns engine idle control to the ECM. Various features of the device are disclosed which block or terminate operation of the device when necessary for reasons of safety and engine protection.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to an electronic control device for automatically increasing an idle RPM level of an engine of a motor vehicle above a normal idle RPM to a higher preselected maximum idle RPM level to increase output voltage of an engine driven alternator to prevent or at least limit the rate of discharge of a storage battery of the vehicle. So long as the device is activated, the maximum RPM level is maintained regardless of variations in loading on the engine. 
     Broadly speaking, the idle RPM or idle speed of an internal combustion engine of a motor vehicle has long been controlled by electronic devices of the prior art. For example, modern automobile engines use a conventional electronic control module or ECM to control the normal idle speed of a vehicle engine, the normal idle speed usually being about 800 RPM in a standard internal combustion engine when running in a normal operating temperature range. Upon start-up of the engine, when cold, as when the vehicle has been inoperative for a long period of time in a wintry low temperature environment, the ECM will operate on start-up to increase the idle RPM to about 1000-1100 RPM, to aid in warming up the cold engine and to increase the operating temperature of various temperature sensitive components such as a catalytic converter and an oxygen sensor in the engine exhaust system. Once the engine has warmed up to a temperature at or near its normal operating temperature range, the ECM will operate to reduce the idle RPM back to the normal 800 RPM level and, thereafter, maintain that level subject to reductions that may occur due to variations in the loading on the engine. 
     In U.S. Pat. No. 5,998,881, granted to R. C. Wind et al. on Dec. 7, 1999, an apparatus and method is disclosed for reducing the idle speed of a vehicle engine from the normal 800 RPM idle level to a low level of about 500 RPM to improve vehicle fuel economy and reduce vehicle emissions. None of the aforementioned devices or methods of the prior art use an electronic device to increase engine idle RPM above normal idle RPM and maintain such an increased idle RPM at a preselected level regardless of engine load variations in response to a low vehicle electrical system output voltage in order to increase the output voltage so as to prevent a disruptive vehicle battery discharge and damage to an alternator of the electrical system. It would be advantageous to provide such a device for use in a motor vehicle, particularly a vehicle which is sometimes parked with the engine running at idle speed for long periods of time, during which periods there is a moderate to heavy demand for electrical energy being placed on an alternator of the vehicle by various electrical components and sub-systems used by the engine and vehicle. A police cruiser is an example of a vehicle which has numerous specialized electrical and electronic systems which can place a heavy energy demand upon the vehicle alternator while the vehicle is parked, as at an accident scene, running at idle speed for a long period of time. Because of such routine operating conditions, the storage batteries and alternators in police vehicles often require relatively frequent replacement, all at substantial cost. In addition, the inconvenience and danger that can also result in leaving a police officer stranded with an inoperative vehicle and dead battery as, for example, at a rural accident site or emergency scene (out of range of a hand held transceiver to the nearest police radio repeater), in the dark of night in severe winter weather with no high powered mobile radio communications link to his or her dispatcher and with no use of other electrical and electronic systems ordinarily available in an operative police vehicle, can be a serious problem. 
     Because the battery in a police cruiser is frequently discharged in the normal course of cruiser operation, the battery usually must be replaced frequently. Moreover, because the alternator of the cruiser is frequently required to deliver heavy current to such a severely discharged battery at or above its total rated maximum output, the alternator, likewise, must frequently be replaced. 
     Another prior art engine idle control apparatus is manufactured and sold in this country by Response Technologies, Inc. of Flanders, N.J. This apparatus, sold as a TCS-100 automatic engine idler, increases the idle speed of a motor vehicle engine from a normal idle RPM level to a higher RPM level in response to a low output voltage of the vehicle electrical power generating system, but does so by activating a vacuum servomechanism to open a fuel throttle of the engine by a calibrated or measured amount. Then, when the output voltage of the system increases to a preselected maximum value, the apparatus operates to, in turn, cause the servomechanism to close the throttle by the same calibrated or measured amount. 
     A difficulty encountered with this type of apparatus is that the higher RPM level is dependent upon loading and load variations on the engine. In other words, heavy loading or load variations on the engine will cause the higher RPM level to be reduced or subject to variations. Also, the chain or cable running from the servomechanism to the engine throttle will be subject to small length changes with age and variations in ambient temperature which can effect the amount of opening of the throttle and, thus, effect the higher RPM level sought to be obtained. Further, if the chain or cable were to fail, as for example, by reason of aging, rust or the like, the apparatus would be rendered inoperative. Finally, the subject apparatus does not control idle RPM level in the same manner as does an ECM of the vehicle. 
     By means of my invention, these and other shortcomings of the prior art are substantially eliminated. 
     SUMMARY OF THE INVENTION 
     It is an object of my invention to provide a device for controlling the idle speed of an engine of a motor vehicle to maintain a high output voltage level of an engine driven alternator of an electrical power generating system of the vehicle to prevent a disruptive discharge of a storage battery of the system. 
     It is a further object of my invention to provide an electronic device for increasing the idle speed of an engine of a motor vehicle to increase the output voltage of an engine driven alternator of an electrical power generating system of the vehicle to supply electrical load requirements of electrical components of the engine and vehicle without severely discharging a storage battery of the system. 
     It is also an object of my invention to provide a process or method for closely controlling an idle RPM of an engine of a motor vehicle, independent of engine loading, for preventing or at least limiting a disruptive discharge of a storage battery of an electrical power generating system of the vehicle. 
     It is another object of my invention to provide a device and method for closely controlling idle speed of an engine of a vehicle, regardless of engine loading, in response to low voltage output of an electrical power generating system of the vehicle to minimize vehicle storage battery discharge and damage to a vehicle alternator. 
     Briefly, in accordance with the objects of my invention, there is provided a device for assuming control of an idle speed control apparatus of an engine of a motor vehicle which is normally controlled by an ECM of the vehicle, the device comprising means for monitoring an output voltage of an electrical power generating system of the engine and vehicle. The device also includes means responsively connected to the monitoring means for generating a first signal indicative that the output voltage is less than a first preselected minimum value. The device further includes means responsively connected to the first signal generating means for generating a second signal which is capable of controlling the idle speed control apparatus of the engine to increase an idle speed of the engine from a normal idle speed level to a higher preselected maximum idle speed level. The device still further includes means responsively connected to the first signal generating means for switching control of the idle speed control apparatus from the ECM to the second signal generating means in response to the first signal. 
     These and other objects, features and advantages of my invention will become apparent to those skilled in the art from the following detailed description and attached drawings, upon which, by way of example, only the preferred embodiments of my invention is illustrated. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a block diagram of a motor vehicle, including an engine, an electrical power generating system with storage battery, a conventional electronic control module and a novel electronic device for controlling the idle RPM of the engine in accordance with my invention. 
     FIG. 2 shows a flow chart illustrating the operation of the idle RPM control device of FIG. 1 in accordance with the preferred method of my invention. 
     FIGS. 3A-3F show an electrical circuit diagram of the idle RPM control device of FIG. 1, thus illustrating a preferred embodiment of the device of my invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawing figures and, in particular, to FIG. 1, there is shown, in a preferred embodiment of my invention, a device, generally designated  10 , for controlling idle RPM or idle speed of an engine  12  of a motor vehicle  14 . The purpose of the device  10  (an electrical circuit diagram of which is shown in FIG. 3) is to prevent or at least limit and minimize a severe or disruptive discharge of a battery  16  of a conventional electrical power generating system  18  used by the engine  12  and vehicle  14 . The severe or disruptive discharge of which I speak is a substantial and/or prolonged discharge of the battery  16  sufficient to place a heavy load on an alternator of the system  18  and to reduce output voltage of the system  18  to such a low value that effective operation of vehicle electrical components is reduced. Such a discharge, if permitted to continue, will ultimately result in failure of the ignition system of the engine  12  to sustain firing of its cylinders, causing engine shut down, usually with no ability of the severely discharged battery  16  to restart the engine. The device  10  can be used with a wide variety of motor vehicle engine types, including both gasoline and diesel powered engines. The device  10  of the present example is especially useful with gasoline engines in police and other emergency vehicles. 
     Police vehicles typically contain numerous electrical components such as front flashers, overhead light bar, spot light, radio communications equipment, video monitoring equipment and radar in addition to the usual wipers, heater and air conditioner with blower, fuel pump, head lights, interior lights, radiator cooling fan, rear window defroster and the like. Often, a majority of these components will be in use at the same time as, for example, when a police vehicle is parked at the scene of a highway accident at night during extreme high or low temperature conditions or during heavy rain, while the engine is running for a prolonged period of time at idle speed. Under such conditions, the demand placed on the system  18  by such components can run as high as 160 amps, whereas a typical alternator of the system may only be capable of delivering about 130 amps. and, only at that level, when the engine  12  is running at a speed well in excess of the normal idle speed. As a result, the battery  16  often will discharge at a rapid rate. But, at idle speed, typically about 800 RPM, the same alternator is typically capable of delivering only about 90 amps. to its load, which, at a 160 amp. demand, means the battery  16  will discharge at an extremely rapid rate. As a result, the output voltage of the system  18  will drop rapidly. At a reduced output voltage of about 12.0 volts, most police mobile radio transmitters will begin to suffer reduction in r.f. power output, thus affecting the transmitters range of radio communication. As the output voltage of the system  18  continues to decrease, headlights begin to dim and the effectiveness of other electrical components decreases markedly. Finally, at an output voltage of less than about 10.5 volts, the engine ignition system will be unable to sustain adequate firing of the engine cylinders, thus causing the engine  12  to shut down, leaving the officer stranded with a dead battery and, possibly, out of communication with his or her dispatcher by virtue of being out of range with his or her relatively low power hand held transceiver to a police repeater. 
     The device  10 , when operative, is adapted to take over control of the idle speed of the engine  12  from a conventional electronic control module of ECM  20 , which normally controls the same, by controlling an engine idle speed control means such as a valve or other type of throttle  22 . This is accomplished, under prescribed conditions, through actuation of a relay  23  of the device  10  to shift operation of the throttle  22  from normal control by the ECM  20  to control by the device  10 . The device  10  actuates the relay  23  by energizing a coil  25  of the relay. By de-energizing the relay coil, the device  10  permits a switch  27  of the relay  23  to return to its normal state, as shown, to return control of the throttle  22  from the device  10  to the ECM  20 . The device  10 , when activated, thus controls the idle speed of the engine  12  in the same manner as does the ECM  20  during normal operating condition. 
     Referring now also to FIG. 2, a flow chart of operation of the device  10  is disclosed. When the engine  12  is started under cold conditions, the ECM  20  will typically operate to adjust the engine intake air valve  22  to raise the idle RPM to about 1000-1100 RPM and to approximately maintain that engine speed until the temperature of the liquid engine coolant increases to the value at or near normal coolant temperature for a warmed up engine  12 . This increased idle speed also aids in warming up a catalytic converter and an oxygen sensor in the exhaust system of the engine  12 . Both of these temperature sensitive components require relatively high temperatures for efficient and effective operation. Once the engine coolant and the temperature sensitive components reach their preselected set point temperatures, the ECM  20  automatically reduces the idle speed of the engine  12  back to the normal 800 RPM level by adjusting the intake air valve  22  in a reverse direction. A warm up cycle for the engine  12 , when parked and running solely at an RPM level dictated by the ECM  20 , from start up and running in the 1000-1100 RPM range to return of the warmed up engine to the normal 800 RPM idle level, takes about 4 minutes to complete. 
     Other than by adjusting the position of the intake air valve  22  to effect a high idle RPM during warm up and by otherwise adjusting the position of the intake air valve to return the engine  12  to a normal low level idle RPM following warm up, the ECM  20  exercises no other changes in the idle level of the engine  12 . I prefer to block operation of the device  10  for a pre-selected time period following start up of the engine  12 , for preferably about 5.0 minutes, to avoid interfering with the warm up function of the engine as regulated by the ECM  20 . This will ordinarily give the ECM  20  more than enough time to complete the warm up of the engine  12  and the temperature sensitive components. 
     In FIG. 2 it will be seen that the program by which the device  10  operates is initiated at block  24  by monitoring engine RPM. This is done in a conventional manner by measuring the speed of rotation of a flywheel on a crankshaft of the engine  12 . At block  26 , a determination is made as to whether the engine  12  is running by determining whether the engine RPM is at least at a preselected minimum RPM level, designated S min , which is sufficiently above the crank speed of the engine  12  during ignition start, preferably about 600 RPM. Since normal idle speed after warm up is about 800 RPM, but can be somewhat less under conditions of heavy and prolonged electrical loading on the alternator of the system  12 , this provides a reasonable minimum RPM level to ascertain than the engine is, indeed, running. If the answer at block  26  is NO, the program returns to block  24  along a return line  28  and repeats the inquiry until a YES answer is obtained. When a YES answer is obtained at block  26 , engine running time from the most recent start-up is monitored, as at block  30 , and a determination is made at block  32  whether the engine running time from the most recent start-up has been at least a preselected minimum time period, designated T min . As previously explained, I prefer to set T min  in the range of from about 4 to 5 minutes, preferably the latter. If the answer at block  32  is NO the program returns to block  24  to begin again but, if YES, the setting of a transmission of the vehicle  14  is monitored, as at block  34 , and inquiry is made at block  36  as to whether the transmission in a PARK condition. If NO, the program recycles to block  24  since I prefer not to use the device  10  to take over engine idle control and raise engine idle RPM with the vehicle transmission in gear for obvious safety reasons. But if the inquiry at block  36  results in a YES determination, the program proceeds to block  38  wherein a position of a foot brake switch is monitored. 
     Next, a determination is made as to whether the foot brake pedal switch is activated, as at block  40 . If an operator&#39;s foot is applied to the brake pedal, there is a possibility that he or she is about to place the transmission in gear. Accordingly, for safety reasons, I prefer not to permit the device  10  to take control of engine idle RPM under such conditions so that, if the answer at block  40  is YES, the program recycles to the block  24 . But, if the answer is NO, then, upon monitoring of the vehicle alternator or generator output voltage, designated V out , of the system  18 , as at block  42 , inquiry is made at block  44  as to whether the output voltage is less than a preselected minimum value, designated V min . I prefer to set V min  at 13.0 volts for reasons hereinafter more fully explained. In any event, the value of V min  should be set at about the output voltage of the system  18  which is just at or slightly above a low value wherein discharge of the battery  16  would ordinarily begin to occur, at least under conditions of light to moderate electrical loading on the alternator  18 . Under conditions of light electrical loading on the system  18 , the value V min  may even be sufficiently high that no discharging of the battery  16  is occurring at normal idle RPM. While there is some leeway here in setting V min , it should not be set so low that significant discharging will occur even at moderate electrical loads on the system  18  when the engine  12  is operating at normal idle RPM, and , of course, it should not be set so low that effectiveness of electrical devices operated by the system is decreased. 
     If the answer to the inquiry at block  44  is NO, then the programs returns to block  24  but, if YES, then the device  10  operates at block  46  to take control of the engine idle from the ECM  20  and to increase the idle level from the normal 800 RPM up to a safe maximum idle RPM level, designated S max . It is at this point in FIG. 2 that the relay  23  of FIG. 1 is energized to shift the idle control from the ECM  20  to the device  10 . In setting the voltage value for V min , it is important to start the step of increasing engine idle speed before there has been a substantial discharge of the battery  16 , at least for moderate electrical loading on the system  18 . For a modern eight-cylinder gasoline engine I prefer to set S max  at about 1300 RPM. However, S max  would probably be a somewhat lower value for a diesel engine, preferably about 1100 RPM, and somewhat higher for four and six cylinder engines. In any case, S max  should be selected at a high RPM level which is within a safe idle operating speed range for the particular engine  12  in use. Once S max  is reached, the engine  12  is closely maintained at this constant speed by the device  10 , even under varying electrical load conditions imposed on the system  18  by the vehicle electrical components and under varying engine loads. At the time when the idle RPM increase commences, as at block  46 , a timer monitors elapsed time in this mode, as at block  48 . Inquiry is then made at block  50  as to whether the elapse time has reached a preselected value, designated T 1 . If NO, the program recycles to the block  46 , as along the with line  56 , but, if YES, then a determination is made, as at block  52 , whether V out , as at block  42 , is at least equal to a preselected value falling within an acceptable operating voltage range for the system  18 , preferably well above the voltage value at which the battery  16  will be discharging. See the dashed line  54  representing a pilot or monitor line, rather than a program flow line, all of which program flow lines are unbroken lines. I call this pre-selected value V max  as shown in block  52  and prefer that it be established at about 13.8 volts. 
     If the inquiry at block  52  is NO, the device  10  resets or indexes the elapse time monitor, as at block  58 , and recycles to the block  48  to monitor an additional elapse time T 1  or, in the present example, an additional 5.0 minute increment while the increased idle RPM, S max , is maintained as at block  46 . But if the inquiry at block  52  is YES, then the device  10  returns idle RPM control to the ECM  20 , as at block  60 , by de-energizing the coil  25  of the relay  23  (FIG. 1) to permit the relay switch to return to its normal de-energized state as shown. Upon de-energizing the relay  23 , the program returns along the line  28  to its starting position at block  24 . There are, of course, circumstances which are conceivable wherein the current demands of the system  18  will continue to be greater than the alternator of the system of the vehicle  14  is capable of providing, even when being driven by the engine  12  at the high RPM level, S max , in which case, even though the engine  12  will continue to run at that level through successive 5.0 minute increments, the battery  16  will continue to supply the additional current required. While this will result in a discharge condition in a worse case scenario of heavy electrical loading on the system  18 , the rate of discharge will at least be limited and minimized. But, where such heavy loading on the alternator of the system  18  is intermittent, there will usually be at least one time period T 1  out of several successive similar time periods during which, at high idle RPM, S max , the battery  16  can be recharged while the system  18  is being brought back to the desired output voltage, V max . The voltage value V max  is selected such that, when achieved, and idle speed control is returned to the ECM  20 , the output voltage V out  will not decrease back to less than V min  for at least one minute to avoid rapid and unstable oscillation between a low RPM idle control by the ECM  20  and idle control at a higher RPM by the device  10 . 
     Referring now also to FIGS. 3A-3F, the latter mentioned figures show, in a preferred embodiment of my invention, a circuit diagram for the device  10  of FIG.  1 . The circuit thus shown can be conveniently mounted on a standard circuit board of generally rectangular shape, preferably having broad surface dimensions of about 3 inches by 4 inches. A circuit board of such dimensions will permit it, with all components mounted thereon, to be disposed and mounted within a housing of the ECM  20  of the type found under the dashboard on the driver&#39;s side of a Ford Motor Company manufactured Crown Victoria model automobile for at least the model years 1995 through 2001. By mounting the circuit board within the housing of the ECM  20 , the need for a lengthy wiring harness can be eliminated and, also, installation of the device  10  is greatly simplified. 
     The following table identifies the various components of the circuit of FIGS. 3A-3F. A CD-ROM appendix filed with the application of this patent contains the software programs for the microprocessors  66 ,  70  and  72  (identified in the program and in FIGS. 3A-3F as U4, U1 and U2, respectively) of the device  10 . 
     
       
         
               
               
             
           
               
                 TABLE 
               
               
                   
               
               
                 Components of FIG. 3 
                 Description 
               
               
                   
               
             
             
               
                 23 
                  1-DPDT 12 vdc relay, 1 amp. rating 
               
               
                 62 
                  1-#7805 12 vdc operated 5 vdc regulator 
               
               
                 64 
                  8-20 pfd capacitors, 35 volt rating 
               
               
                 65 
                  2-4.0 Mh crystals 
               
               
                 66 (also U4 in FIG. 3B) 
                  1-PIC 16C54 programmable microprocessor 
               
               
                 68 
                 10-1K ohm, ¼ watt resistors 
               
               
                 70 (also U1 in FIG. 3C) 
                  1-PIC 16C55 programmable microprocessor 
               
               
                 72 (also U2 in FIG. 3D) 
                  1-PIC 16C54 pulse width modulated signal 
               
               
                   
                 generator 
               
               
                 74 (also U3 in FIG. 3D) 
                  1-ADC 0820 analog-to-digital converter 
               
               
                 76 
                  4-2n2222 NPN transistors 
               
               
                 78 
                  2-47K ohm, ¼ watt resistors 
               
               
                 80 
                  1-10K ohm, ¼ watt resistors 
               
               
                 82 
                  1-TIP120 Darlington pair 
               
               
                 84 
                  1-10K ohm, 35 watt resistor 
               
               
                 86 
                  1-2k ohm, ¼ watt resistor 
               
               
                 88 
                  1-DPST 12 vdc relay, 1 amp. rating 
               
               
                   
               
             
          
         
       
     
     The charge timing processor  66  controls all timing activities of the device  10  whereas the main processor  70  coordinates all functions of the device  10 . The processor  72  functions as a pulse width modulated signal generator which directly controls the idle speed control  22  of the vehicle  14  along output lines  90 ,  92  when the relay  23  is energized (see FIGS. 1 and 3F ). While the relay  23  is shown in FIG. 1 as a double pole, single throw relay for simplicity in illustrating the general function of the device  10 , the relay  23  of the circuit of FIG. 3F is, preferably, a double pole, double throw relay  23  which, while performing the same function, also maintains a load, namely, the resistor  84 , on an idle speed control line  94  of the ECM  20  while the relay  23  is activated. The purpose of this additional function of the relay  23  is to prevent the ECM  20  from erroneously sensing a fault in its idle speed control circuit during the period when the device  10  is activated. 
     The relay  88  of FIG. 3F is used to alternate between sampling whether a gear selector switch of the transmission of the vehicle  14  is in a park condition, as at  96 , and sampling of the output voltage of the power generating system  18 , as at  98  (see also line  98  in FIG.  1 ). The relay  88  switches between these two states every 30 seconds while the device  10  is active. Speed of the engine  12  is monitored by sampling a tachometer operating input signal, as at  100 , in FIG.  3 E. The circuit of the device  10  of as shown in FIGS. 3A-3F is also adapted to block or cease operation in favor of operation of the engine idle control valve by the ECM  20  should a check engine light  102  of the vehicle  14  become activated (See FIG.  3 E). This is an additional feature of the device  10  instituted as a precaution as, for example, where the engine  12  might be dangerously low on oil. Brake input switch voltage is also monitored by the circuit of the device  10  at  104  in FIG.  3 E. If voltage is high, meaning above chassis ground, at either or both of the inputs  102  or  104 , the transistors  76  of FIG. 3E will operate to block activation of the relay  23  and, thus, block operation of the device  10  until the high voltage at those inputs is eliminated. Finally, the circuit of FIG. 3A is a 12.0vdc to 5.0vdc regulated power supply for powering the various active components of the circuit. See table for description of components thereof. 
     The circuitry of the device of my invention can also be combined with and made a part of the circuitry of an otherwise standard ECM of the vehicle in which it us used. 
     Although the present invention has been explained and illustrated with respect to specific details of certain preferred embodiments thereof, it is not intended that such details limit the scope of this patent other than as specifically set forth in the following claims, taking into consideration all reasonable equivalents thereof.