Abstract:
A passive control device is interposable between an oxygen sensor and an electric control unit of a motor vehicle to modify a reference voltage used by the electric control unit so that a richer fuel mixture is provided to an internal combustion engine of the motor vehicle than would otherwise be provided in absence of the passive control device. The passive control device directly passes the voltage signal from the oxygen sensor to the electronic control unit without modification. The passive control device works with the electronic control unit to provide a richer fuel mixture without reprogramming the electronic control unit.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/024,697, filed Jan. 30, 2008, the entire of which is incorporated herein by reference. 
     
    
     FILED OF THE INVENTION 
       [0002]    The present invention relates generally to the closed-loop air/fuel control of an internal combustion engine. More particularly, to the modification of the closed-loop air/fuel control without modifying the programming of an electronic control unit (ECU) used to control the internal combustion engine. 
       BACKGROUND OF THE INVENTION 
       [0003]    Most modern internal combustion engines utilize a form of electronic fuel-injection (EFI) system to control the air/fuel ratio (AFR) of the combustion mixture. The EFI system works to control the air/fuel ratio under all operating conditions to achieve the desired engine performance, emissions, driveability, and fuel economy. EFI systems use a programmed electronic control unit (ECU) or module (ECM) to monitor engine operating conditions and control fuel injection to increase or decrease the air/fuel ratio depending on the engine operating conditions. The ECU operates either in an open-loop controlled fuel injection with predetermined fuel maps, or in a closed-loop feedback-controlled fuel injection. Closed-loop feedback-controlled fuel injection varies the fuel injector output according to real-time sensor data rather than operating with the predetermined (open-loop) fuel map. Real-time sensor data from an oxygen sensor (or “O 2  sensor”) is used to measure the proportion of oxygen (O 2 ) in the exhaust gas. The oxygen sensor generates an electrical voltage indicating the amount of oxygen measured in the exhaust gas. The oxygen sensor generates a voltage in the range of about 0 to 1 volts. Higher voltages (greater than 0.5 volts) means there is less oxygen in the exhaust and indicates a rich mixture. Lower voltages (less than 0.5 volts) means there is more oxygen in the exhaust and indicates a lean mixture. The ECU reads the oxygen sensor voltage signal and produces fuel injector control signals to operate the fuel injectors to either richen the fuel mixture or to lean the fuel mixture. 
         [0004]    For gasoline fuel burning engines, manufactures typically preprogram the ECU to control the fuel injectors to maintain a stoichiometric AFR of 14.7:1 for the majority of engine operating conditions. Any mixture less than 14.7:1 is considered to be a rich mixture, any more than 14.7:1 is a lean mixture. Most oxygen sensors are manufactured to generate a voltage of 0.5 volts when the AFR is 14.7:1. 
         [0005]    It is known to modify an existing ECU to adjust the performance of the internal combustion engine. Heretofore, modifying an existing ECU has required reprogramming the programmable eprom or computer chip, replacing the eprom with another eprom having a different program, or piggy backing the ECU with another controller that operates to intercept signals, modify the intercepted signals and then pass the modified signal to various engine operating components to achieve the desired engine performance. 
         [0006]    Various problems can arise when an existing ECU is modified as indicated above. The physically changed or new eprom must be to manufacture&#39;s application, and during use may cause knocking, drivability issues both at idle and wide open throttle, lean misfires, detonation, signaling of trouble codes in vehicles equipped with on-board diagnostic (OBD), void manufacture&#39;s warranties, and require physical modification of the engine&#39;s electrical wiring harness. 
         [0007]    Accordingly, there is a need for an apparatus and method that can be employed to modify the performance of internal combustion, and specifically, the air/fuel ratio of an internal combustion engine that overcomes the drawbacks of the prior art. 
       SUMMARY OF THE INVENTION 
       [0008]    The preferred embodiments of the present invention addresses this need by providing a passive control device that is interposable between an exhaust gas sensor, such as an oxygen sensor, and the electronic control unit (ECU) to modify the air/fuel ratio without reprogramming the ECU. The device operates to pass through the oxygen sensor voltage signal to the ECU without modification to the voltage signal, and to modify a reference voltage used by the ECU in determining the value of the voltage signal. 
         [0009]    To achieve these and other advantages, in general, in one aspect, an apparatus for modifying the performance of an internal combustion engine of a motor vehicle including fuel injectors, an oxygen sensor for sensing the amount of oxygen in the exhaust gas produced by the internal combustion engine, and a preprogrammed electronic control unit for receiving a voltage signal from the oxygen sensor, and in response thereto producing fuel injector control signals controlling the operation of the fuel injectors, is provided. The apparatus includes a voltage modifying means for proportionally modifying a reference voltage as a function of the voltage signal of the oxygen sensor to modify the fuel injector control signals produced by the electronic control unit without modifying the programming of the electronic control unit, and the voltage modifying means being interposable between the oxygen sensor and the electronic control unit. 
         [0010]    In general, in another aspect, the voltage modifying means modifies the reference voltage to cause the electronic control unit to produce fuel injector control signals that provide a richer fuel mixture to the internal combustion engine than what would be provided in the absence of the voltage modifying means. 
         [0011]    In general, in another aspect, the voltage modifying means passes through the voltage signal of the oxygen sensor to the electronic control unit without modification of the voltage signal. 
         [0012]    In general, in another aspect, the voltage modifying means includes a resistor circuit which passes through the voltage signal of the oxygen sensor to the electronic control unit without modification to the voltage signal, and divides the voltage signal of the oxygen sensor based upon the resistance values of a resistor pair and adds the divided voltage to the reference voltage. 
         [0013]    In general, in another aspect, a method for adjusting the performance of an internal combustion engine of a motor vehicle including fuel injectors, an oxygen sensor for sensing the amount of oxygen in the exhaust gas produced by the internal combustion engine, and a preprogrammed electronic control unit for receiving a voltage signal from the oxygen sensor, and in response thereto producing fuel injector control signals controlling the operation of the fuel injectors is provided. The method includes the steps of:
       (a) interposing a voltage modifying means between the oxygen sensor and the preprogrammed electronic control unit;   (b) passing voltage signals from the oxygen sensor to the preprogrammed electronic control unit without modification to the voltage signals;   (c) proportionally modifying a reference voltage with the voltage modifying means as a function of the passed voltage signals from the oxygen sensor to produce a modified reference voltage;   (d) generating modified fuel injector control signals as a function of the modified reference voltage without changing the programming of the preprogrammed electronic control unit; and   (e) employing the modified fuel injector control signals to cause the fuel injectors to provide a richer fuel mixture to the internal combustion engine than would be provided in the absence of the step of modifying the reference voltage.       
 
         [0019]    There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood and in order that the present contribution to the art may be better appreciated. 
         [0020]    Numerous objects, features and advantages of the present invention will be readily apparent to those of ordinary skill in the art upon a reading of the following detailed description of presently preferred, but nonetheless illustrative, embodiments of the present invention when taken in conjunction with the accompanying drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of descriptions and should not be regarded as limiting. 
         [0021]    As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
         [0022]    For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated preferred embodiments of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    The accompanying drawings, which are included to provide further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate preferred embodiments of the invention and together with the description serve to explain the principles of the invention, in which: 
           [0024]      FIG. 1  is a diagrammatic view of an internal combustion engine and exhaust system having an exhaust sensor, ECU and a passive control device of the present invention operatively associated therewith; 
           [0025]      FIG. 2  is a representative oscilloscope display illustrating both a non-modified wave form of a voltage signal of an oxygen sensor as seen by a ECU (shown in solid line), and a modified wave form of the same voltage signal as seen by the ECU (shown in dashed line); 
           [0026]      FIG. 3   a  is a diagrammatic view of an ECU connected to an oxygen sensor without the control device of the present invention; 
           [0027]      FIG. 3   b  is the view of  FIG. 3   a  with the control device of the present invention interposed the oxygen sensor and ECU; 
           [0028]      FIG. 4  is a diagrammatic view of an alternate configuration of the control device of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0029]    Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. 
         [0030]    In  FIG. 1  there is shown conventional motor vehicle internal combustion engine  10  having one or more fuel injectors  12  arranged in an air intake passage  14 , an exhaust gas sensor  16 , such as an oxygen sensor, arranged in an exhaust passage or pipe  18 . The oxygen sensor  16  of a conventional construction is employed for sensing the amount of oxygen in the exhaust passing through the exhaust pipe  18 . An electronic control unit (ECU)  20  is operatively coupled to the fuel injectors  12 , and is operatively coupled to the oxygen sensor  16  to receive voltage signals  17  therefrom. The ECU  20 , in response to voltage signals from the oxygen sensor  16 , produces fuel injector control signals  13  controlling the operation of the fuel injectors  12 , in accordance with the preprogramming of the ECU. A control device  22  in accordance with the present invention is shown interposed between the oxygen sensor  16  and the ECU  20 . 
         [0031]    With reference to  FIG. 2 , there is depicted an oscilloscope display with a typical oxygen sensor voltage wave form being shown in solid lines. With reference to this, it should be noted that fuel injectors operate in a pulsed manner to inject fuel for combustion. The air/fuel pulses resulting from the associated electronic control unit would have the same wave form. The upper and lower portions of the normal wave form are substantially of the same magnitude and are respectively in a rich zone and a lean zone on opposed sides of a pre-determined stoichiometric line representing a set stoichiometric air/fuel ratio (AFR). That is, in a conventional arrangement the pulse portions fall generally evenly in the rich and lean zones so that the desired overall average stoichiometric value, in this instance 14.7:1, is attained or closely approximated. 
         [0032]    The control device  22  operates to artificially shift the oxygen sensor voltage wave form as shown in dotted line by modifying a reference voltage that the ECU  20  measures in taking readings of the voltage signal  17  of the oxygen sensor  16 . The reference voltage is modify in proportion to the voltage signal  17 . In effect, with the control device  22 , the ECU  20  interprets the voltage signal  17  as indicating a more lean condition than what really exists, and in turn compensates for this by producing fuel injector control signals  13  that provide a richer fuel mixture to the internal combustion engine. 
         [0033]    With reference to  FIG. 3   a,  there is illustrated a schematic diagram of the oxygen sensor  16 , and the ECU  20  without the control device  22 . The oxygen sensor  16  is a typical two-lead type having a voltage signal lead  24 , and a signal ground lead  26 . The ECU  20  has a voltage signal input  28  and a signal ground input  30 . The voltage signal lead  24 , and the signal ground lead  26  are connected to the voltage signal input  28  and signal ground input  30 , respectively through a pair cooperating connectors  32 ,  34 . The ECU  20  measures the voltage potential between the voltage signal lead  24  and the signal ground lead  26  to determine the amplitude of the voltage output by the oxygen sensor  16 . In essence, the voltage on the signal ground lead  26  is used as a reference voltage in determining the voltage output by the oxygen sensor  16 . Conventionally, this reference voltage would be 0 volts. 
         [0034]    Now with reference to  FIG. 3   b,  there is illustrated the same schematic diagram as  FIG. 3   a  with the control device  22  removable interposed between the oxygen sensor  16  and the ECU  20 . The control device  22  is detachably connected to the oxygen sensor  16  by connectors  32 ,  36 , and is detachably connected to the ECU  20  by connectors  34 ,  38 . The control device  22  includes a voltage signal lead  24 ′ and a signal ground lead  26 ′. The voltage signal lead  24 ′ interconnects the voltage signal lead  24  of the oxygen sensor  16  to the voltage signal input  28  of the ECU  20 . The signal ground lead  26 ′ interconnects the signal ground lead  26  of the oxygen sensor  16  to the signal ground input  30  of the ECU  20 . The voltage signal  17  is passed through from the oxygen sensor  16  to the ECU without modification to the voltage signal. The control device  22  further includes a voltage modifying means  40  that interconnects the voltage signal lead  24 ′ and the signal ground lead  26 ′. The voltage modifying means  40  proportionally modifies the reference voltage as a function of the voltage signal  17  of the oxygen sensor  16  to modify the fuel injector control signals  13  produced by the ECU  20  without modifying the programming of the ECU. The voltage modifying means  40  receives the voltage signal  17  as it is passed through, and operates to modify the reference voltage by adding a portion of the voltage signal  17  to the reference voltage. 
         [0035]    The voltage modifying means  40  includes a resistor circuit having a pair resistors  42  and  44  connected together in series with resistor  42  connected to the voltage signal lead  24 ′ and resistor  44  connected to a first portion  46  of the ground signal lead  24 ′. A second portion  48  of the signal ground lead  24 ′ is connected at one end intermediate resistors  42  and  44 , and is connectable at the other end to the ground signal input  30  of the ECU  20  through connectors  34 ,  38 . In this manner, the voltage signal  17  is divided across resistors  42  and  44  proportional to the resistance value of each resistor and is added to the reference voltage as the signal ground input  30 . While resistors  42  and  44  are illustrated as fixed resistance resistors, both resistor or either resistor could be replaced with a variable resistance resistor. 
         [0036]    The resistance values of resistors  42  and  44  may be selected such that approximately a ratio of 0.4:1 of the voltage signal  17  is added to the reference voltage. The resistance values of resistors  42  and  44  may be selected such that approximately a ratio of 0.37:1 of the voltage signal  17  is added to the reference voltage. The resistance values of resistors  42  and  44  may be selected such that approximately a ratio of 0.34:1 of the voltage signal  17  is added to the reference voltage. The resistance values of resistors  42  and  44  may be selected such that approximately a ratio of 0.29:1 of the voltage signal  17  is added to the reference voltage. The resistance values of resistors  42  and  44  may be selected such that no less than a ratio of 0.34:1 of the voltage signal  17  is added to the reference voltage. The resistance values of resistors  42  and  44  may be selected such that no more than a ratio of 0.29:1 of the voltage signal  17  is added to the reference voltage. 
         [0037]    The resistance values of resistors  42  and  44  may be selected such that resistor  42  has a resistance of 20,000 ohms, and resistor  44  has a resistance of 8,000 ohms. The resistance values of resistors  42  and  44  may be selected such that resistor  42  has a resistance of 20,000 ohms, and resistor  44  has a resistance of 10,000 ohms. The resistance values of resistors  42  and  44  may be selected such that resistor  42  has a resistance of 20,000 ohms, and resistor  44  has a resistance of 11,500 ohms. The resistance values of resistors  42  and  44  may be selected such that resistor  42  has a resistance of 20,000 ohms, and resistor  44  has a resistance of 13,000 ohms. 
         [0038]    In  FIG. 4 , there is shown an alternate configuration of the control device  22  where the oxygen sensor  16  is of the single wire type. In this configuration, the control device  22 ′ and the oxygen sensor  16  have independent grounds with the remaining elements the same as discussed above. 
         [0039]    A number of embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.