Abstract:
The present invention provides a control apparatus for controlling an internal combustion engine that enables preferable acceleration in response to the running status of the internal combustion engine. When a computer which computes the fuel supply of the internal combustion engine at each engine cycle according to engine parameters detects a change in the throttle opening level of the internal combustion engine from a low opening level which is lower than a predetermined opening level to a non-low opening level which is higher than the predetermined level and when the computer detects that a variation Δθ TH  in the opening level of a throttle is equal to or greater than a predetermined value, the computer generates different increment correction values and corrects fuel supply according to the increment correction values.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a control apparatus for controlling an internal combustion engine that controls a fuel injector of the internal combustion engine. 
     2. Background Art 
     An apparatus disclosed in Japanese Patent Kokai No. 8-135491 is known as a controller which controls the amount of fuel injection to an automobile internal combustion engine based on the opening level of a throttle valve mounted to an intake system. The controller detects the opening level θ TH  of a throttle valve at each engine cycle and retrieves a fuel increment correction coefficient from a map in accordance with Δθ TH = TH (current value)−θ TH  (previous value) which is the difference between θ TH  (previous value) detected previously and θ TH  (current value) detected currently. Then, the amount of fuel injection is determined by multiplying this fuel increment correction coefficient to a reference amount of fuel injection that is determined from the number of revolutions of an internal combustion engine and the intake manifold pressure. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     A control apparatus mentioned above corrects and determines the reference amount of fuel injection only in accordance with the variation in the opening level of the throttle valve Δθ TH  irrespective of the current value of the opening level of the throttle valve. On the other hand, different amounts of fuel injection are required when an accelerating operation is started at a small throttle valve opening level, for example, when an automobile is accelerated from a standstill status or decelerating status, or when the accelerating operation is started at a large throttle valve opening level, for example, when an automobile is accelerated from an ordinary running status. However, in these cases, there was a problem in that the conventional control apparatus provided the same fuel increment correction coefficient by calculation if Δθ TH  was the same value. 
     In view of the foregoing, the object of the present invention is to provide a control apparatus for controlling an internal combustion engine that enables preferable acceleration in response to the running status of the internal combustion engine. 
     The control apparatus for controlling an internal combustion engine by the present invention comprises computing means for computing the fuel supply of the internal combustion engine at each engine cycle based on engine parameters of the internal combustion engine and control means for controlling a fuel injector to supply fuel to the engine according to the amount of fuel supply computed, which is characterized in that the computing means includes first means for generating a first signal when the first means detects a change in the throttle opening level of the internal combustion engine from a low opening level which is lower than a predetermined opening level to a non-low opening level which is higher than said predetermined level, second means for generating a second signal when the second means detects that a variation Δθ TH  in the throttle opening level is equal to or greater than the predetermined value, third means for generating an increment correction value differently when said first detection signal is generated and when said second detection signal is generated respectively, and fourth means f or correcting the amount of fuel supply according to said increment correction values. 
     According to an aspect of the present invention, the control apparatus for controlling an internal combustion engine allows the e engine e to be desirably accelerated in response to the running conditions of the engine because the increment correction values are generated differently when first and second detection signals are generated. 
     Additionally, according to another aspect of the present invention, the low opening level being in the totally closed status provides preferable acceleration even when the throttle valve is opened from the totally closed status. 
     Furthermore, according to another aspect of the present invention, an increment correction value is generated in response to the number of fuel injections counted from the time of generation of the first detection signal. Therefore, preferable acceleration is provided in the case of opening the throttle valve from the low opening level to a non-low level opening. 
     Still furthermore, according to still another aspect of the present invention, an increment t correction value is generated in response to variation Δθ TH  when the second detection signal is generated. Therefore, preferable acceleration is provided even when the throttle valve is opened from an opening level except for the low opening level. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic diagram showing the configuration of an internal combustion engine, intake system, exhaust system, and a control system of the internal combustion engine; 
     FIG. 2 is a flowchart showing a subroutine for detecting the opening level of a throttle valve; 
     FIG. 3 is a flowchart showing a subroutine for retrieving increment correction values; and 
     FIG. 4 is a graph illustrating the relationship between the number of fuel injections and increment correction values. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Hereinafter, the embodiments of the present invention will be described with reference to the drawings. 
     FIG. 1 shows the configuration of an internal combustion engine, intake system, exhaust system, and a control system of the internal combustion engine. 
     An intake system  2  of an internal combustion engine  1  is provided with a throttle valve  3  for controlling an air intake from the outside of a vehicle. The throttle valve  3  is provided with a throttle valve opening-level sensor  11  for detecting the opening of the throttle valve  3 . Moreover, the intake system  2  is also provided with an intake pipe pressure sensor  12  for detecting the pressure of intake air and with an intake air temperature sensor  13  for detecting the temperature of intake air. Additionally, the intake system  2  is also provided with a fuel injector  4 , whereby the internal combustion engine  1  sucks a mixture of intake air and fuel injected by the fuel injector  4  and then burns the intake air-fuel mixture to rotationally drive a crank shaft (not shown). The internal combustion engine  1  is provided with a cooling-water temperature sensor  14  for detecting temperature of the cooling water used for cooling the internal combustion engine. Near the crankshaft, there is a crank angle sensor provided for detecting the angle of the crankshaft, and a crankshaft reference angle sensor for detecting the reference angle of the crankshaft. The air-fuel mixture burnt in the internal combustion engine  1  is exhausted as exhaust gas to an exhaust system  5 . The exhaust system  5  is provided with an oxygen concentration sensor  17  for detecting the oxygen concentration of the exhaust gas. In addition, near the internal combustion engine  1 , there is provided an atmospheric pressure sensor  18  for detecting the atmospheric pressure. 
     Various types of sensors  11  through  14 ,  17 , and  18  mentioned above send output signals to an electronic control unit  30  (hereinafter called the “ECU”). Output signals, sent from the throttle valve opening-level sensor  11 , the intake pipe pressure sensor  12 , the intake air temperature sensor  13 , the cooling-water temperature sensor  14 , the oxygen concentration sensor  17 , and the atmospheric pressure sensor  18 , are supplied to level conversion circuitry  21  in order to be converted into predetermined voltage signals, and then supplied to a multiplexer  31  (hereinafter called the “MPX”) within the ECU  30 . In accordance with commands sent from a CPU  34  at a predetermined timing, the MPX  31  selectively supplies, to an A/D converter  32 , either one of the output signals sent from the throttle valve opening-level sensor  11 , the intake pipe pressure sensor  12 , the intake air temperature sensor  13 , the cooling-water temperature sensor  14 , the oxygen concentration sensor  17 , or the atmospheric pressure sensor  18 . The A/D converter  32  converts supplied signals into digital signals to supply the digital signals to an I/O bus  33 . The I/O bus  33  allows the CPU  34  to input and output signals of data and address. 
     On the other hand, signals sent from the crank angle sensor  15  such as pulse signals generated at every  30  degrees of crank angle are supplied to a waveform shaping circuit  22  for waveform shaping, then to an interruption input of the CPU  34  and to an rpm counter  37 . The rpm counter  37  outputs digital values according to the number of revolutions of the internal combustion engine. Output signals sent from the rpm counter  37  are supplied to the I/O bus  33 . And, signals sent from the crankshaft reference angle sensor  16 , such as pulse signals sent when the piston reaches the top dead center (hereinafter called the “TDC”), are supplied to a waveform shaping circuit  23  for waveform shaping, and then supplied to the interruption input of the CPU  34 . The construction mentioned above allows the CPU  34  to detect the reference position of the crankshaft, the number of revolutions of the internal combustion engine, and the angle of the crankshaft. 
     A drive circuit  24  for driving a ROM  35 , a RAM  36 , and the fuel injector  4  is connected to the I/O bus  33 . The CPU  34  sends fuel injection control commands to the fuel injector  4  for controlling a fuel injection valve (not shown) of the fuel injector  4 , thereby controlling the fuel supply. In addition, the ROM  35  stores a program for detecting the opening level of the throttle valve  3  according to the flowchart shown in FIG.  2  and stores another program for retrieving increment correction values T ACC  according to the flowchart shown in FIG.  3 . Furthermore, ROM  35  stores a map that defines the relationship between the number of fuel injections and increment correction values T ACC , which will be explained in FIG.  4 . 
     The ECU  30  includes operating means, first means, second means, third means, and fourth means. In the explanation below, it is to be understood that variables and flags to be used in the CPU  34  have been completely initialized, for example, F 1  has been initialized into 1, F 2  into 0, F_TACC into 0, and n into 0, which will be described later. It is also to be understood that the internal combustion engine has completed necessary operations for start-up and has been in operation. 
     FIG. 2 is a flowchart showing a subroutine for detecting the opening level of a throttle valve. This operation is carried out at predetermined intervals, for example, at every 30 degrees of crank angle. 
     First, a throttle opening level θ TH  of the throttle valve  3  is detected (step S 11 ). Then, it is determined whether or not the throttle opening level θ TH  is at a predetermined opening level, for example, at an opening level smaller than 0.5 to 0.6 degrees such as that at a fully closed level (step S 12 ). When the throttle opening level θ TH  is found to be smaller than a predetermined opening level, flag F 1  is set to 1 (step S 13 ) and then the present subroutine is ended. The flag F 1  shows whether or not the throttle opening level θ TH  is at a low opening level which is lower than a predetermined opening level. 
     On the other hand, when throttle opening level θ TH  is found to be greater than a predetermined opening level, that is, at a non-low opening level in step S 12 , it is judged whether the value of the flag F 1  is 1 or not (step S 14 ). When the value of the flag F 1  is found to be 1, the F_TACC is set to 1 (step S 15 ), the flag F 1  is set to 0 (step S 16 ), and the present subroutine is ended. The flag F_TACC shows whether or not the throttle valve  3  has been opened from a low opening level which is lower than a predetermined opening level to a non-low opening level, and if the value of F_TACC is set to 1, a first detection signal is sent. On the other hand, when the value of flag F 1  has been found to be not equal to 1 in Step S 14 , the flag F 1  is set to 0 (step S 16 ), and the present subroutine is immediately ended. 
     FIG. 3 is a flowchart showing a subroutine for retrieving fuel increment correction values TACC. This operation is executed at predetermined intervals of time, for example, at every TDC. 
     First, it is judged whether the flag F 2  is equal to 1 or not (step S 21 ). The flag F 2  shows whether the retrieving processing of the T ACC  is being executed or not which is carried out when the throttle valve has been opened from a low opening level. When it is found that the value of the flag F 2  is not equal to 1, it is judged whether the flag F_TACC is equal to 1 or not (step S 22 ). When the throttle valve  3  has been opened from a low opening level which is lower than a predetermined opening level, the flag F_TACC is determined to be equal to 1 and then the flag F_TACC is set to 0 (step S 23 ). Subsequently, it is determined whether or not the number of fuel injections n, for example, 8 times is greater than a predetermined number of injections (step S 24 ). The number of fuel injections n is counted after the throttle valve has been judged to be opened from a low opening level. When the number of fuel injections n is judged to be equal to or less than the predetermined number of injections, the number of fuel injections n is increased by 1 (step S 25 ). Then, an increment correction value T ACC  corresponding to the number of fuel injections is retrieved with reference to the relationship shown in FIG. 4 between the number of fuel injections n and increment correction value T ACC  (step S 26 ). Whereby, the flag F 2  is set to 1 (step S 27 ) and finally the present subroutine is ended. 
     Then, in the case of again executing the T ACC  retrieving routine as shown in FIG. 3, the value of flag F 2  is determined to be equal to 1 in step S 21  because the value of flag F 2  was changed to 1 at Step S 27  when the present subroutine was previously executed. And, when the number of fuel injections n has been judged to be equal to or less than the predetermined number of fuel injections (step S 24 ), the steps S 25 , S 26 , and S 27  are executed and the present subroutine is ended. As mentioned above, when the throttle valve  3  has been opened from a low opening level which is lower than the predetermined opening level, the processing mentioned above will be executed repeatedly until the number of fuel injections n is determined to be greater than the predetermined number of fuel injections in step S 24 . 
     On the other hand, when the number of fuel injections n has been judged to be greater than the predetermined number of fuel injections in Step S 24 , the number of fuel injections n is initialized to 0 (step S 28 ), and the difference Δθ TH  between the previously detected opening level θ TH  (previous value) of the throttle valve and the currently detected opening level θ TH  (current value) of the throttle valve is calculated (step S 29 ). Then, it is judged whether or not Δθ TH  is equal to or greater than a predetermined value, for example, 0.3 degrees (step S 30 ). When Δθ TH  has been determined to be equal to or greater than the predetermined value, a second detection signal is generated and an increment correction value T ACC  corresponding to the A TH is retrieved from the related map between the Δθ TH  stored in the ROM  35  and increment correction value T ACC  (step S 31 ). Then the flag F 2  is set to 0 (step S 32 ) and the present subroutine is ended. On the other hand, when Δθ TH  has been determined to be smaller than the predetermined value in Step S 30 , the flag F 2  is set to 0 (step S 32 ) and the present subroutine is ended. 
     Further, the value of the flag F 2  is equal to 0 and the value of the flag F_TACC is equal to 0, when the value of the flag F_TACC has not been set to 1 in Step S 15  as mentioned above in FIG. 2, that is, when it has been judged that the present status is not the case where the throttle valve  3  has been opened from a low opening level which is lower than the predetermined opening level. Therefore, after the value of the flag F 2  is judged to be not equal to 1 (step S 21 ) and the value of the flag F_TACC is not equal to 1 (step S 22 ) in FIG. 3, the processing of the steps S 29 , S 30 , and S 31  is executed and the present subroutine is ended. 
     After the present subroutine has been carried out, the amount of fuel injection is calculated from an equation such as T OUT =T 0  (NE, PB)×K TA ×K TW ×K PA ×K 022 +T ACC  in order to control the amount of fuel injection supplied by the fuel injector  4 , where T 0  (NE, PB) is the reference amount of fuel injection calculated from the number of revolutions NE of the internal combustion engine and the intake manifold pressure PB, K TA  is a correction coefficient for intake air temperature, K TW  is a correction coefficient for the cooling water of the internal engine, K PA  is a correction coefficient for the atmospheric pressure, and K 02 is a correction coefficient for the concentration of oxygen contained in the exhaust gas. 
     In the embodiment mentioned above, the case of calculating the increment correction value T ACC  as an addition correction term is shown, however, the increment correction coefficient K ACC  may be calculated. In this case, K ACC  is calculated not as an addition term but as a multiplication term, such as in T OUT=T   0  (NE, PB)×K TA ×K TW ×K PA ×K 02 ×K ACC . 
     FIG. 4 is a graph illustrating the relationship between the number of fuel injections n and increment correction values T ACC . 
     The increment correction value T ACC  has the greatest value when the value of fuel injections n is equal to 1, and takes smaller values with an increasing number of fuel injections. Such a relationship between the number of fuel injections n and the increment correction value T ACC  allows the internal combustion engine to be accelerated with desirable acceleration when the throttle valve is opened from a low opening level which is lower than the predetermined opening level. The relationship between the number of fuel injections n and the increment correction value T ACC  is stored in the ROM  35  as a numerical map and is referenced in Step S 26  in FIG. 3 mentioned above. This relationship has been determined, for example, by a pretest such as an actual engine test. 
     The internal combustion engine in the present specification includes an internal combustion engine which combusts fluid fuel such as a hybrid engine. 
     As described above, the control apparatus for controlling an internal combustion engine of the present invention allows the engine to be desirably accelerated in response to the running conditions of the engine because the increment correction values are generated differently when first and second detection signals are generated. 
     Additionally, according to another aspect of the present invention, the low opening level being in the totally closed status provides preferable acceleration even when the throttle valve is opened from the totally closed status. 
     Furthermore, according to another aspect of the present invention, an increment correction value is generated in response to the number of fuel injections counted from the time of generation of the first detection signal. Therefore, preferable acceleration is provided in the case of opening the throttle valve from the low opening level to a non-low level opening. 
     Furthermore, according to another aspect of the present invention, an increment correction value is generated in response to variation Δθ TH  when the second detection signal is generated. Therefore, preferable acceleration is provided even when the throttle valve is opened from an opening level other than the low opening level.