Patent Publication Number: US-7592782-B2

Title: Supercapacitor engine starting system with charge hysteresis

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of application Ser. No. 10/876,389, filed Jun. 25, 2004, now U.S. Pat. No. 7,319,306, issued Jan. 15, 2008. 
    
    
     BACKGROUND OF THE INVENTION 
     The development of the supercapacitor (ie., a capacitor of greater than 200 Farads) has resulted in the use of capacitors as stores of electric energy for starting automotive engines. A fairly early example is U.S. Pat. No. 5,146,095, issued to Tsuchiya et al. Here a supercapacitor is charged up as the automobile driver turns his key to start his vehicle. Then the charge on the supercapacitor is used to start the automobile engine. This procedure avoids the strong current draw from the battery that is otherwise necessary every time an automobile is started. 
     One disadvantage of this mechanism, however, is that the vehicle user must wait for the supercapacitor to be charged up every time he starts his automobile. Also, there is a possibility that the engine will not start, given the amount of energy stored in the capacitor. Furthermore, it appears that if the capacitor were broken and unable to accept a full charge, that the vehicle operator would be left with a nonfunctional vehicle. 
     Although a number of other references exist detailing the use of a supercapacitor in starting an internal combustion engine, none of these references detail a system that both avoids an intense current draw from the battery at first starting up an engine and that almost never requires the automobile user to wait when first starting his automobile. 
     SUMMARY OF THE INVENTION 
     In a first separate aspect the present invention is an internal combustion motor assembly, including an internal combustion motor, a starter and a battery. In addition, the motor assembly includes a capacitor assembly, a capacitor charging assembly and a conductive network, logic and controlled switching assembly, adapted to place the motor assembly into one of a set of states. This set includes a first state in which the capacitor assembly is electrically connected to and receiving charge from the capacitor charging assembly, but is not electrically connected to the starter; a second state in which the capacitor assembly is electrically connected to and powers the starter; and a third state in which both the battery and the capacitor assembly are electrically connected to and power the starter. The conductive network, logic and controlled switching assembly places the internal combustion motor assembly into the third state after it has been in the second state and any one of a predetermined set of criteria sets is met. 
     In a second separate aspect, the present invention is an internal combustion motor assembly including an internal combustion motor, a starter, a capacitor adapted to, at least in part, power the starter, and a capacitor charging assembly adapted to charge the capacitor. In addition, a capacitor charging control element is adapted to control the capacitor charging assembly so that the capacitor is charged to a first voltage and is later recharged to the first voltage whenever its voltage drops below a second voltage that is at least 0.5 volts lower than the first voltage. 
     In a third separate aspect, the present invention is an internal combustion motor assembly including an internal combustion motor, a battery, a starter, a capacitor adapted to, at least in part, power the starter, and a capacitor charging assembly adapted to charge the capacitor. In addition, a capacitor charging sensing and control circuit is adapted to detect a condition in which the capacitor has at least some impairment in its ability to accept charge and is adapted to respond to this condition by switching the motor assembly to a state in which the capacitor is not used to power the starter. 
     In a fourth separate aspect, the present invention is an internal combustion motor assembly including an internal combustion motor, a starter, and a capacitor charging assembly adapted to charge the capacitor to a first voltage level. In addition, a manual engine start actuator is adapted to permit an operator to activate the starter and a capacitor low voltage starter lockout system disables the actuator when the capacitor is not charged to a predetermined voltage. 
     The foregoing and other objectives, features and advantages of the invention will be more readily understood upon consideration of the following detailed description of the preferred embodiment(s), taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of an internal combustion motor assembly according to the present invention. 
         FIG. 2  is a flow chart of a scheme of operation of the motor assembly of  FIG. 1 , according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
     Referring to  FIG. 1 , a preferred embodiment of the present invention includes an internal combustion motor assembly  10 . Conventional items included in assembly  10  include a motor  12 , a starter  14 , an alternator  20  and a motor start actuator  22  for permitting a vehicle operator to start the motor  12 . In addition, a battery assembly  16  and a capacitor assembly  18  include one or more batteries and capacitors, respectively. In addition, a DC-to-DC converter/controller  26  is controlled by an internal logic unit  40 , which is also a part of a conductive network, logic and controlled switching assembly  28 . The starter  14  is provided with electrical power in accordance with a predetermined scheme, discussed below, implemented by assembly  28 . 
     Also included in assembly  28  and controlled by unit  40  are a battery-to-starter relay  42  and a capacitor-to-starter relay  44 . An electrical system actuator  46  is used by a vehicle operator to activate the vehicle electrical system, prior to starting the motor. A “wait-to-start” light  50  advises a vehicle operator to not press the start actuator  22 , in accordance with criteria described below. 
       FIG. 2  illustrates the operation  100  of assembly  10  by logic unit  40 . When the electric system is first activated (block  102 ), unit  40  checks to see if the capacitor voltage, V c , is above the minimum voltage for starting the motor, V min , required for the present temperature (box  103 ). At below 0° c., V min  is equal to 29 Volts and at greater than 0° c., V min  is equal to 24 Volts. The temperature may be measured either at the logic unit  40 , at capacitor assembly  18  or at motor  12 . In one preferred embodiment logic unit  40  receives temperature measurements both from motor  12  and from capacitor assembly  18  and sets V min  on the basis of the temperature reading from motor  12 , as this is the best indication of how much energy will be required to start motor  12 . 
     If V c  is below V min , the start actuator  22  is disabled and the “wait to start” light  50  is activated (block  104 ); then the converter/controller  26  charges the capacitor assembly  18  (block  106 ) until a voltage, V max , is reached (box  108 ). V max , similar to V min , is a function of the temperature measured at that time. In one preferred embodiment V max  is 28 Volts at greater than 0° C., and 30 Volts at below 0° C. In one preferred embodiment all logic measurements are taken at logic unit  40 . In another preferred embodiment a temperature measurement taken at the capacitor assembly  18  determines V max  because the maximum voltage to which a capacitor can be charged is inversely related to temperature. After V max  is reached, the converter/controller  26  stops delivering current to capacitor assembly  18 , the engine start actuator  22  is enabled and the “wait to start” light  50  is deactivated (box  110 ). At this point, motor  12  is ready to be started and the assembly  10  waits for a start engine signal from actuator  22 . 
     When a “start engine” signal is received (box  116 ), logic unit  40  closes the capacitor relay  44  (along with the starter solenoid), causing the capacitor assembly  18  to power the starter  14  (block  118 ). After the starter  14  has been driven by the capacitor assembly for a time period, T BT , (box  120 ) of typically less than a second, the logic unit  40  commands the battery relay  42  to close, causing the battery assembly  16  to assist the capacitor in the further process of engine starting (block  122 ). For below freezing temperatures T BT  equals 0.35 seconds, while at above freezing temperatures T BT  is effectively set to infinity, with the battery not being utilized to help start the engine. 
     In this manner, at below freezing temperatures the battery assembly  16  assists the motor  12  starting process but is not subjected to the destructive large current draw that is necessary in the first few tenths of a second of the starting process. Logic unit  40  then waits for the motor to start (box  124 ) before opening relays  42  (at below freezing temperatures) and  44  (block  126 ). 
     At this point V c  is again compared with V min  and if V c  is smaller then is charged again (block  104  through block  110 ). In this sequence, V c  will typically reach V max  while the engine is running and typically will continue above V min  until the next engine start command is received. When this is the case, the engine may be started immediately, without waiting for the capacitor to be charged up. Only if at the time the electrical system is actuated (block  102 ) so much charge has bled from the capacitor assembly  18  that V c  is below V min , must the vehicle operator wait through a capacitor recharge sequence. 
     A capacitor recharge at electrical system actuation is more likely at below freezing temperatures, as the hysteresis is only 1 Volt in this temperature range. This is acceptable, however, because an electric heating element engine warm up sequence, typically taking far longer to accomplish than the capacitor charge sequence, must typically occur at these temperatures. Consequently, the capacitor charge operation does not cause an actual delay to the vehicle operator. The fact that in most instances the motor  12  can be started without a delay, when desired, is a major advantage of this preferred embodiment. 
     The converter/controller  26  is able to detect if electric current is flowing to capacitor assembly  18 . If capacitor assembly  18  is not accepting electric current at voltages below V max , then this condition is noted (a “fault” is set) by logic unit  40  and capacitor assembly  18  is effectively taken out of the circuit, with no further capacitor charging being effected and without the use of the capacitor assembly  18  in engine starting. Subsequently, when the ignition is enabled again, the fault is cleared and a further attempt is made to charge the capacitor assembly  18 . If it again does not accept charge, the fault is reset. 
     The terms and expressions that have been employed in the foregoing specification are used as terms of description and not of limitation. There is no intention, in the use of such terms and expressions, of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims which follow.