Engine ignition timing control system and method

Abstract: An ignition timing control system and method for an internal combustion engine comprises engine revolution speed detecting means for detecting engine revolution speed of an engine, valve motion condition determining means for determining valve motion condition data of the engine, intake air pressure detecting means for detecting intake air pressure of air in an intake manifold, standard ignition timing calculating means for preparing a plurality of standard ignition timing calculating maps each of which shows the air pressure data of air in the intake manifold and the engine revolution speed data varied in response to the valve motion condition data and selecting one of the standard ignition timing maps in response to the valve motion condition data to calculate a standard ignition timing of each of the cylinders, target ignition timing calculating means for calculating for each of the cylinders a target ignition timing by compensating the standard ignition timing on the basis of the operating condition of the engine, and ignition driving means for driving the ignitor associated with each of the cylinders of the engine at the target ignition timing. The above ignition timing control system and method ensure the desirable level of the ignition timing.

Description: BACKGROUND OF THE INVENTION The present invention relates to engine ignition timing control system and method which are designed to utilize a speed density system for calculating the quantity of intake air in the combustion chamber of an internal combustion engine on the basis of pressure data in the intake manifold of the internal combustion engine and which have variable cylinder operation modes. The system for controlling ignition timing for an internal combustion engine, to which the present invention relates, comprises according to the preamble of claim 1. engine revolution speed detecting means for detecting an engine revolution speed of said engine and producing an output signal indicative of engine revolution speed data; intake air pressure detecting means for detecting a pressure at an intake manifold; a change-over mechanism for changing an operate state of an intake valve and/or an exhaust valve; valve operation state determining means for determining the operation state of said intake valve and/or said exhaust valve in accordance with an operating state of said change over mechanism; a plurality of standard ignition timing maps prepared in accordance with operation status of said intake valve and/or said exhaust valve, each of said maps defining a plurality of standard ignition timings on the basis of pressure data of said intake manifold and said engine revolution speed data; standard ignition timing setting means for determining a standard ignition timing for each of cylinders of the engine on the basis of said standard ignition timing maps; target ignition timing setting means for correcting the standard ignition timing determined by said standard ignition timing setting means in accordance with an operating state of the engine, and calculating a target ignition timing for each of said cylinders; and igniting means for igniting each of said cylinders at the target ignition timings. The method for controlling ignition timings for an internal combustion engine to which the invention relates comprises according to the preamble of claim 8 the steps of : (b1) determining an operating state of an intake valve and/or an exhaust valve of the engine on the basis of an operating state of a change-over mechanism for changing the operating state of said intake valve and/or said exhaust valve; (b4) detecting a revolution speed of the engine and a pressure inside an intake manifold, and producing engine revolution speed data and pressure data; (b5, b6) determining a standard ignition timing for each of cylinders of the engine on the basis of standard engine ignition timing maps, each of said standard ignition timing maps being prepared for each operating state of said intake valve and/or exhaust valve, and defining a plurality of standard ignition timings in accordance with a pressure data and the engine revolution speed data; (b9) correcting the determing standard ignition timing in accordance with the operating state of the engine, and calculating a target ignition timing for each of said cylinders; and igniting each of said cylinders at each target ignition timing. Such a system and method are known from US-A-4 398 520 which will be discussed later. The control system of the conventional internal combustion engine is so constructed that many operation data of the engine are gathered by many sensors for calculating predeterming control values in response to the operation data with suitable calculating means so that many actuators are driven by output signals responsiv to the calculated control values to enable many mechanism to be controlably driven in response to the predetermined control values. In the conventional internal combustion engine, the quantity of intake air (A/N) to be supplied to the combustion chamber is adjusted in response to the opening of a throttle valve, and the quantity of fuel corresponding to the quantity of intake air in response to the opening of the throttle valve and revolution of the engine is supplied to the combustion chamber of the engine so as to perform an ignition process that an adequate ignition timing in response to the quantity of intake air and the revolution of the engine. There has been well known in the art a typical engine which employs an ignition timing control system called "a speed density system" for calculating intake air quantity data for use in a fuel supply mechanism and advanced angle quantity data for use in ignition timing control on the basis of pressure levels of air in the intake manifold. The speed density system is advantageous in that a pressure sensor in provided in an air duct held in communication with the intake manifold to sense pressure levels of air in the intake manifold by way of the air duct instead of an airflow sensor provided in the intake manifold to directly sense the quantity of intake air in the intake manifold, resulting in reducing the intake air resistance of the intake manifold and thus in decreasing costs of the sensors. On the other hand, the internal combustion engine having such a speed density system is operated in such a manner that a map is prepared for a standard ignition timing b in response to an intake manifold pressure Pb in place of an intake air quantity A/N and an engine revolution Ne upon calculation of the ignition timing of the engine. In such an internal combustion engine, the standard ignition timing b is initially calculated in response to the engine revolution Ne and the intake manifold pressure Pb, and then compensated on the basis of coolant temperature Twt, intake air temperature Ta and the like for the purpose of calculating a target ignition timing adv. In the conventional speed density system, the intake manifold pressure including the intake air quantity data is sensed for calculation of the intake air quantity and the ignition timing of the engine so that the operation mode variation of each of the cylinders of the engine such as, for example, the variation of the valve opening and closing timing caused by high and low cams of the intake and exhaust mechanism, and the variation of the intake air quantity caused by switching all cylinders worked conditions and partial cylinders worked conditions in which the intake and exhaust mechanisms of the cylinders are partially held in their unworked condition. This results in the fact that the intake air presure, the intake air quantity and the ignition timing of the engine are not associated with each other, thereby reducing desirable levels of the calculated intake air quantity and ignition timing of the engine. In the GB-A-2 042 637 A there is disclosed a spark timing control system for internal combustion engine, which comprises first and second read only memories respectively storing optimum spark advance and dwell angle values determined independence on engine speed and load, and a microprocessor responsive to engine speed and load conditions for reading out optimum spark advance and dwell angle values. The disclosed system includes an air flow sensor responsive to the air flow to produce an analog signal proportional thereto, a crank engle sensor responsive to the degree of rotation of the engine crank shaft to produce crank standard angle indicative and crank pulse signals, a temperatur sensor fitted in the engine cylinder jacket to produce an engine temperatur indicative analog signal proportion to the engine cooling temperatur, an engine data switch responsive to the on-off-operation of the engine data to produce an on-off-signal, a transmission switch responsive to the transmission gear position to produce a gear position indicative signal, an engine speed sensor responsive to the speed of rotation of the engine to produce an engine speed indicative analog signal, and a manifold vacuum sensor responsive to the vacuum at the engine intake manifold to produce a manifold vaccum indicative analog signal. The system includes an input section, a microprocessor or central processing unit (CPU) using first and second read only memories and an output section. The first read only memory has a table consisting of spark advance values the microprocessor reads out in accordance with the engine speed and the pulse width. The table stored in the second read only memory consists of dwell angle values to be read in accordance with the engine speed and the pulse width. The red spark advance and dwell angle values are fed to the output section. In the DE-A-34 00 786 A1 there is disclosed an ignition measuring device, which measures the engine revolution speed from the ignition pulses. In the US-A-4,398,520 there is disclosed an ignition timing system, which produces adapted ignition timings in the full cylinder mode or in the part cylinder mode. The system comprises a computer with two read only memories, the first of which is an address for first fixed ignition timing values stored and the second is an address for second fixed ignition timing value stored. The two read only memories are connected to an arithmetic unit through a transfer switch. This transfer switch changes over when there is an switching-over from the for example full cylinder mode to the part cylinder mode. The arithmetic unit calculates optimum ignition timings from the read only memories contenz by taking into account crank shaft or flywheel rotation signals, intake manifold vacuum signals, intake air quantity, crank shaft speed signals and temperatur signals. The system disclosed in US-A-4,398,520 switches over from read only memory 1 to read only memory 2 which contain standard ignition timings without taking into account the valve motion status. Thus, the ignition timing is calculated ir-respective of the valves actuated by high speed cams or low speed cams. This has the result, that the ignition timings are not alwalys the optimum ignition timings. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide ignition timing control system and method of an engine which ensure that the calculation of the ignition timing takes into account the valve motion condition. For the system for controlling an ignition timing for an internal combustion engine the problem is solved by that said system is characterized in that said standard ignition setting means selects one of said standard ignition timing maps on the basis of results determined by valve operation state determining means, and reads a standard ignition timing from the selected map on the basis of the pressure data of said intake manyfold and the engine revolution speed data. Preferably said engine revolution speed detecting means includes an engine revolution sensor for detecting the engine revolution of the engine in the form of ignition pulses. Still preferably said intake air pressure detecting means includes a vacuum sensor provided in said intake manifold of the engine. Yet preferably said valve motion condition determining means determines whether one or most cylinders of the engine are held in the unworked conditions or all cylinders of the engine are held in their worked conditions. Preferibly said valve motion condition determining means determines whether the engine is held in a high speed operation condition derived from the valve motion conditions of cylinder valves in cylinders or held in a low speed operation condition derived from the valve motion conditions of said cylinder valve in the cylinders. Still preferably said valve motion condition determining means determines whether the engine is held in an operation condition derived from one ore more cylinders of the engine held in the unworked condition, the engine is held in a high speed operation condition derived from valve motion conditions of cylinder valves in cylinders, or held in a low speed operation condition derived from valve motion conditions of said cylinder valves in the cylinders. Still preferably said target ignition timing is calculated on the basis of data including at least one compensation value selected from temperatur of coolant in the engine, temperatur of air in the intake manifold, the opening of the throttle valve provided in the intake manifold of the engine, knocking and voltage level of battery. The problem is solved for method for controlling ignition timing for an internal combustion engine by that said method is characterized in that one of said standard ignition timing maps is selected in accordance with results determined by said operation state determining means, and a standard ignition timing is read from the selected map in accordance with the pressure data of said intake manifold and the engine revolution speed data. Preferably said engine revolution speed detection is performed by an engine revolution sensor in the form of ignition provilesis. Still preferably the intake air pressure detection is performed by a vacuum sensor provided in said intake manyfold of the engine. Yet preferably the valve motion condition determination includes determining whether one or more cylinders of the engine are held in the unworked conditions or all cylinders of the engine are held in the worked condition. Preferably the valve motion condition determination includes determining whether the engine is held in a high speed operation condition derived from the valve motion conditions of cylinder valves in cylinders or held in a low speed operation condition derived from the valve motion condition of said cylinder valves in cylinders. Still preferably the valve motion condition determination includes determining whether the engine is held in an operation condition derived from one or more cylinders of the engine held in the unworked conditions, the engine is held in a high speed operation condition derived from valve motion conditions of cylinders valve in cylinders, or held in a low speed operation condition derived from valve motion conditions of said cylinder valves in the cylinders. Yet preferably the target ignition timing is calculated on the basis of data including at least one compensation value selected from temperatur of coolant in the engine, temperatur of air in the intake manifold, the opening of the throttle valve provided in the intake manifold of the engine, knocking and voltage level of battery. BRIEF DESCRIPTION OF THE DRAWINGS The features and advantages of the engine ignition timing control system and method according to the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: Fig. 1 is a general constitutional view of an engine ignition timing control system exemplifying the present invention; Fig. 2 is a block diagram representing the functions of the ignition timing control system shown in Fig. 1; Fig. 3 is a block diagram of an ignition driving circuit provided in the ignition timing control system shown in Fig. 1; Fig. 4 is a block diagram representing the progressive motion of the ignition driving circuit in the ignition timing control system shown in Fig. 1; Fig. 5 is a progressive fluctuation diagram showing the standard ignition timings switched by the ignition timing control system shown in Fig. 1; Fig. 6 is a characteristic block diagram of a dwell angle calculating map utilized by the ignition timing control system shown in Fig. 1; Fig. 7 is a flowchart of a main routine through which the ignition timing control system shown in Fig. 1 is operated. Fig. 8 is a flowchart of an ignition timing calculation routine carried out by the ignition timing control system of Fig. 1; and Fig.. 9 is a flowchart of an ignition control routine carried by by the ignition timing control system of Fig. 1. DESCRIPTION OF THE PREFERRED EMBODIMENTS An ignition timing control system is shown iN Fig. 1 as assembled in a four cylinders, in-line engine (simply referred to as "engine E") having a mechanism for switching and varying valve motion conditions of intake and exhaust valves. The engine E comprises an intake manifold 1 which is constituted by an intake branched duct 6, a surge tank 9 securely connected to the intake branched duct 6, an intake duct 7 integrally formed with the surge tank 9, and an air cleaner not shown. The intake duct 7 is adapted to rotatably receive therein a throttle valve 2 having a rotational shaft 201 connected to a throttle lever 3 at the outer side of the intake manifold 1. The throttle lever 3 is connected to and rotated by an accelerator pedal (not shown) in such a manner that the throttle valve 2 is rotated in clockwise and anti-clockwise directions as shown in Fig. 1 by the throttle lever 3. The throttle valve 2 is forced to be closed by a suitable return spring (not shown) when the accelerator pedal is released to its home position. The throttle valve 2 is assembled with a throttle valve opening sensor 8 for producing an output signal of the opening data of the throttle valve 2. On the other hand, an intake bypass duct 101 is connected to the intake duct 7 in such a manner as to bypass the throttle valve 2 and is provided with an idle revolution control (ISC) valve 4 forced to be closed by a return spring 401 and driven by a stepping motor 5. The reference numeral 16 designates a first idle air valve which is designed to automatically perform a warming-up compensation in response to temperature of a coolant in the engine during the idling state of the engine. Further, the intake air temperature detecting means comprises an intake air temperature sensor 14 provided in the intake manifold 1 for producing an output signal of the data for intake air temperature (Ta). The engine is provided with a coolant sensor 11 for detecting the temperature of the coolant therein. The engine revolution speed detecting means comprises an engine revolution sensor 12 for detecting the engine revolution in the form of ignition pulses. The battery voltage detecting means comprises a battery sensor 27 for detecting a battery voltage VB. A knock sensor 21 is also provided for producing an output signal of knock data of the engine. The intake air pressure detecting means comprises a vacuum sensor 10 provided in the surge tank 9 for producing an intake manifold pressure (Pb) data. A cylinder head 13 forming in part the engine is provided with intake and exhaust passageways capable of being in communication with each of cylinders formed in the engine and opened and closed respectively by intake and exhaust valves (not shown) forming as a whole a valve motion system. The valve motion system is designed to be operatable under a low speed mode M-1 and a high speed mode M-2 by selectively driving low and high speed cams, respectively, while being operable under an unwork partial cylinders mode (modulated displacement mode) M-3 by holding the intake and exhaust valves of a first cylinder #1 and a fourth cylinder in their unworked conditions, respectively, with a second cylinder #2 and a third cylinder #3 being held in their worked conditions, respectively. The valve motion system comprises rocker arms assembled with low and high speed mode switching mechanism K1 and K2, the former of which is designed to hydraulically held the low speed cams of the intake and exhaust valves under their worked conditions at a predetermined low speed mode, and the latter of which is similarly designed to hydraulically hold the high speed cams of the intake and exhaust valves under their worked conditions at a predetermined high speed mode. The low and high speed mode switching mechanisms K1 and K2 are well known in the art and so constructed as to have the low and high speed cams and the rocker arms selectively engaged with and disengaged from each other by hydraulically switching the engagement and disengagement conditions between the rocker arms and their rocker arm shafts by way of respective slide pins not shown. The low speed mode switching mechanism K1 forming a valve motion condition switching mechanism is fed with pressure oil by a pressure oil circuit 22 through a first electromagnet valve 26, while the high speed mode switching mechanism K2 also forming the valve motion condition switching mechanism is fed with pressure oil by a pressure oil circuit 30 through a second electromagnet valve 31. It will be understood that both of the first electromagnet valve 26 and the second electromagnet valve 31 respectively having three-way constructions are not energized under the low speed mode M-1 of the valve motion system, while both of the first electromagnet valve 26 and the second electromagnet valve 31 are energized under the high speed mode M-2 of the valve motion system. The first electromagnet valve 26 is energized, while the second electromagnet valve 31 in not energized under the unworked partial cylinders mode M-3 of the valve motion system. The above electromagnet valves 26 and 31 are controlled by the output driving signal of an engine control unit (ECU) 15 which will be described hereinafter. The cylinder head 13 is shown in Fig. 1 as provided with injectors 17 for injecting fuel to the cylinders, respectively, in such a manner that the injectors 17 are supplied from an fuel supply source 19 with fuel adjusted under a predetermined pressure level by a fuel pressure adjusting means 18. The injection control is carried out by the engine control unit 15 mentioned above. The cylinder head 13 is assembled with ignition plugs 23 for the respective cylinders under the condition that the ignition plugs 23 of the cylinders #2 and #3 always held under their worked conditions are electrically connected to an ignitor 24 provided in a single ignition driving circuit and that the ignition plugs 23 of the cylinders #1 and #4 held under their worked and unworked conditions are connected to electrically connected to an ignitor 25 provided in another single ignition driving circuit. Both of the ignitors 24 and 25 are electrically connected to the engine control unit 15. The ignition driving circuit comprises a pair of timing control circuit 36 provided in the engine control unit 15 and a pair of driving circuits 241 and 251 for the respective ignitors 24 and 25. Only one of the control ciruit 36 is shown in Fig. 3. To the driving circuit 241 and 251 are electrically connected respectively power transistors 38 and 38 which are adapted to control opening and closing timing and energization time thereto and which are electrically connected to ignition coils 37 and 37. The timing control circuits 36 are respectively associated with the unworkable cylinders #1 and #4 capable of being held under their unworked conditions and the work cylinders #2 and #3 always held under their worked conditions in such a manner that the cylinders #1 to #4 are driven by standard signals ( o of a crank angle) of crank angle sensors 34 and crank angle signals (1° or 2° (Δ) of a unit pulse) of unit crank angle sensors 33. The unworkable cylinders #1 and #4 are shown in Fig. 3, but the work cylinders #2 and #3 are not shown. The standard signal  o is outputted to a one-shot circuit B so that the one-shot circuit B is triggered by the standard signal (on-off) of upper dead point  o (for example 75°) and the energization commencement signal is outputted and counts a predetermined delay time t1 after crank angle signals (a unit pulse 1° or 2°) are produced as best shown in Fig. 4. In this case, a target ignition timing b is calculated from the step b9 of a flowchart as will be described in Fig. 8. The one-shot circuit A is similarly triggered by the standard signal (on-off) and counts a delay time t1 and a predetermined number (delay time t2) of the crank signal corresponding to the dwell angle so as to produce ignition signals. A flip-flop F·F is set by the energization commencement signal of the one-shot circuit B and reset by the ignition signal of the one-shot circuit A. The opening and closing driving circuit 251 causes the power transistor 38 to be held "ON" during a period of time of the flip-flop F·F being set so as to maintain the ignition coil 37 energized. The ignition coil 37 causes its secondary side to have a high voltage current when the power transistor 38 is switched "OFF" so that the high voltage current is transmitted to and ignites the ignition plugs 23 of the unworkable cylinders #1 and #4 held in their unworked conditions. Similarly, the timing control circuit (not shown) for the work cylinders #2 and #3 is constructed in a similar manner as the timing control circuit for the unworkable cylinders #1 and #4. The secondary high voltage current of the ignition coil 37 is supplied to and ignites the work cylinders #2 and #3 at their target ignition timing b. The groups of the unworkable cylinders #1, #4 and the work cylinders #2 and #3 are alternately ignited at an interval, i.e., a crank angle of 180° degrees. The essential part of the engine control unit 15 is constituted by a micro-computer to perform the valve motion condition switching control and the ignition timing control in addition to the fuel injection control of the engine 1 and the throttle valve driving control which are well known in the art. The engine control unit 15 is shown in Fig. 2 as comprising an engine revolution sensor 12 for detecting the engine revolution speed Ne and a vacuum sensor 10 for detecting the intake air pressure Pb. The engine control unit 15 further comprises valve motion condition determining means for determining driving signals of first and second electromagnet valves 26 and 31 to produce output signals of the valve motion condition data for the respective cylinders held in their worked and unworked conditions. The engine control unit 15 further comprises standard ignition timing calculating means for calculating the standard ignition timing b in response to the intake air pressure Pb and the engine revolution speed Ne on the basis of the valve motion condition data of each of the cylinders. The engine control unit 15 further comprises a coolant sensor for detecting a coolant Tw, a throttle valve opening sensor 8 for detecting a throttle opening s, an intake air temperature sensor 14 for detecting intake air temperature Ta, a battery sensor 27 for detecting battery voltage VB, and a knock sensor 21 for detecting a knock signal Kn. The ignition timing calculating means thus constructed calculates a target ignition timing adv by compensating the standard ignition timing b on the basis of the operation data of the internal combustion engine. The ignition timing control system according to the present invention will be described along with its control program in Figs. 7 to 9. The main switch not shown is switched "ON" to commence the control of the engine control unit 15 along its main routine. Initially, functions of the means forming the embodiment of the invention are checked with the initial values thereof being set, and then many sensors read many operation data for advancement of the operation to a step a2. A fuel cut zone is determined from an operation map calculating the operation zone on the basis of the engine revolution N and A/N as load data of the engine to have the operation advance to a step a3, where the air fuel ratio feedback FLG is cleared and returned with the fuel cut FLG "1" at a step a4. On the other hand, when the operation condition of the engine is not maintained in the fuel cut zone at the step a2 to have the operation advance to the step a5, the fuel cut FLG is cleared, and whether or not the air fuel ratio feedback condition is met is then determined. At a step a7 upon the transition operation zone such as a power operation zone and before finish of the idling operation, the calculations are carried out on the air fuel ratio compensation coefficient KMAP responsive to the present operation data (A/N, N) and the idling operation increase quantity compensation coefficient Ka responsive to the coolant temperature Tw through a proper idling operation increase quantity compensation coefficient calculating map. The calculated values are stored in the address KAF and the operation is then progressed to a step a10. When the air fuel ratio feedback condition is met at the step a6, a target air fuel ratio responsive to the present operation data (A/N, N) is calculated for calculation of fuel quantity compensation coefficient K FB which can fulfil the above air fuel ratio. At a step a9, the fuel coefficient K FB is stored in the address KAF to have the operation advance to the step a10. At the step a10, the other fuel injection pulse width compensation coefficient KDT and the dead time compensation value TD of the fuel injection valve are set responsive to the operation condition of the engine to calculate each of compensation coefficients for use in the calculation of the target ignition timing adv. The compensation values thus calculated comprises a coolant compensation value wt varied in response to the temperature drop of the coolant, an acceleration retard acc corresponding to the differential value Δ s obtained by differentiating the throttle valve opening s, an intake air temperature compensating value at varied in response to the temperature drop of the intake air, and a knock retard value k increased in response to the knock signal Kn. The subsequent calculation is performed on the battery compensation value tb with its energization time period to be increased in response to the drop of the battery voltage VB. The operation advances to the step a11 where the other well known controls are performed and is then returned to the initial step. At the crank angle position of 180 degrees on the halfway of the main routine, the ignition timing calculating routine is executed. In the present operation mode, the valve operation condition determining means 20 serves as determining and selecting any one of low and high speed modes M-1, M-2 and the unworked partial cylinders mode M-3 in response to the "ON" and "OFF" data of the first and second electromagnets 26 and 31. After the determining and selecting the present operation mode, the operation mode variation determining means determines whether or not the present operation mode is identical to the previous operation mode. In the case of the operation mode being varied, the operation advances to a step b3, while in the case of the operation mode being not varied the operation advances to a step b2. At the step b3, the time T after the variation of the operation mode is "1", and the operation advances again to the step b1, subsequently advancing to the step b2 after the present operation mode is not varied from the previous operation mode, and then the time T after the variation of the operation mode is added by "1" to be renewed. It is to be noted that the operation mode variation determining means may include a function as the valve motion condition determining means. At the step b4, the engine revolution Ne is detected by the engine revolution sensor 12 and the intake air pressure Pb is detected by the vacuum sensor 10. At the step b5, the previous operation mode is determined as being in the low speed operation mode M-1, or the high speed operation mode M-2, or the unworked partial cylinders mode M-3, and the standard ignition timing b1 of the previous operation mode is calculated by the standard ignition timing maps m1, m2 and m3 as seen from Fig. 2. In this case, the low speed operation map m1 is employed for the low speed operation mode M-1 in the previous operation, the high speed operation map m2 is employed for the high speed operation mode in the previous operation, and the unworked partial cylinders operation map m3 is employed for the unwork cylinder operation mode M-3 in the previous operation. At the step b6, the present operation mode is determined as being in the low speed operation mode M-1, or the high speed operation mode M-2, or the unworked partial cylinders mode M-3, and the standard ignition timing b2 of the present operation mode is calculated by the standard ignition timing calculating maps m1, m2 and m3 in a similar fashion as shown in Fig. 2. At the steps b7 and b8, the standard ignition timing b is calculated in the following equation (3) by leveling the previous standard ignition timing b1 and the present standard ignition timing b2. A leveling coefficient αn is initially calculated in the following equations (1) and (2). Here, the leveling coefficients αn are calculated respectively by the equation (1) when the time T after the variation of the operation mode is lower than the predetermined value n and by the equation (2) when the time T after the variation of the operation mode is higher than the predetermined value n. Δa represents a leveling ratio which is for example set at about 0.1. α 1 = 0 α = α n-1 + Δa α n = 1 b = αnb2 + (1 - αn)b1 One example of the time progress variation characteristic of the standard ignition timing b thus calculated as above is shown in Fig. 5. It will be understood from Fig. 5 that the previous standard ignition timing b1 is corrected to progressively approach the present standard ignition timing b2 in response to the leveling ratio Δa. The above mentioned treatment results in the fact that the standard ignition timing b which is not precisely recognized upon the operation mode variation is corrected and compensated, thereby preventing the excessive deviation from the desirable ignition timing of each of the cylinders. At the step b9, the acceleration retard acc is calculated for calculating the target ignition timing adv by the following equation (4). adv = b + wt + at - acc At the step b10, a predetermined retard quantity is calculated in response to the knock signal Kn by a suitable map not shown to correct the target ignition timing adv toward the retard side. The knock retard map is previously established as shown in Fig. 2. At the step b11, the present ignition timing advn is stored in the previous ignition timing area adb (n-1) and the present leveling coefficient αn is stored in the previous leveling coefficient area α (n-1) , then returning the operation to the main routine. The ignition control treatment on the halfway of the main routine will now be described in Fig. 9. The ignition control routine is executed on the basis of the fact that the standard signal  o is varied from "OFF" to "ON" when each of the cylinders are at every upper dead point 75° (75°BTDC) (a crank angle of 180 degrees) on the halfway of the main routine. At this step C1, a predetermined data is detected and at the step C2 whether the commencement switch not shown "ON" or "OFF" is determined. The operation advances to the steps C3 and C4 upon its initial stage, while the operation advances to the steps C5 and C6 upon its non-initial stage. When the operation advances to the steps C3 and C4 upon its the initial stage, the fixed ignition timing (for example BTDC5°) and the dwell angle upon their initial stages are respectively set and returned to the main routine. When the operation, on the other hand, advances to the steps C5 and C6 upon its non-initial stage, the newest target ignition timing t and the dwell angle calculated from Fig. 6 are set to the timing control circuit 36 and returned to the main routine. In the full operation mode, the worked cylinders #2 and #3 are simultaneously ignited by the ignitor 24 while the unworkable cylinders #1 and #4 are simultaneously ignited by the ignitor 25. When those ignitors 24 and 25 are driven at every crank angle of 180 degrees, one and the other groups of the worked and unworkable cylinders #2, #3, #1 and #4 are alternately ignited at the vicinity of their compression upper dead point of the cylinder and at the vicinity of their exhaust dead point of the cylinder. The injector driving treatment is performed on the halfway of the main routine. The intake air quantity A/N calculated is detected in response to the intake air pressure Pb and the engine revolution Ne to calculate the standard fuel pulse width Tf. The target injector driving time is calculated by the air fuel ratio compensation coefficient KAF detected from the main routine, the compensation coefficient KDT of the atmospheric temperature and pressure, the injector action delay compensation value TD and the like. During the operations of all the cylinders the target fuel pulse widths Tinj are set to the drivers of all the injectors 17 of the cylinders #1-#4, while during the operations of the cylinders #1 and #4 held in their unworked conditions the target fuel pulse widths Tinj are set to the drivers 17 of the cylinders #2 and #3 so as to trigger the drivers and to return the operation to the main routine. As will be noted from the foregoing description, the present invention is advantageous in that the ignition timing can be performed for each of the cylinders of the internal combustion in response to the operation mode of the engine by detecting the engine revolution speed data and the intake manifold data by many sensors, determining the valve motion condition data, calculating the standard ignition timing in response to the valve motion condition data on the basis of the intake manifold pressure data and the engine revolution speed, and compensating the ignition timing of each of the cylinders to calculate the target ignition timing, resulting in the desirable ignition timing for each of the cylinders even in the speed density system.

Claims: A system for controlling ignition timing for an internal combustion engine, comprising: engine revolution speed detecting means (12) for detecting an engine revolution speed of said engine and producing an output signal indicative of engine revolution speed data (N); intake air pressure detecting means (10) for detecting a pressure (Pb) in an intake manifold; a change-over mechanism (K1, K2) for changing an operating state of an intake valve and/or an exhaust valve; valve operation state determining means (20) for determining the operation state of said intake valve and/or said exhaust valve in accordance with an operating state of said change-over mechanism (K1, K2); a plurality of standard ignition timing maps (m1,m2, m3) prepared in accordance with operation status of said intake valve and/or said exhaust valve, each of said maps (m1, m2, m3) defining a plurality of standard ignition timings (b) on the basis of pressure data (Pb) of said intake manifold and said engine revolution speed data (N); standard ignition timing setting means (15) for determining a standard ignition timing for each of cylinders of the engine on the basis of said standard ignition timing maps; target ignition timing setting means (15) for correcting the standard ignition timing determined by said standard ignition timing setting means (15) in accordance with an operating state of the engine, and calculating a target ignition timing ( adb) for each of said cylinders; and igniting means for igniting each of said cylinders at the target ignition timings ( adb), said system is characterized in that said standard ignition timing setting means (15) selects one of said standard ignition timing maps (m1, m2, m3) on the basis of results determined by said valve operation state determining means, and reads a standard ignition timing from the selected map on the basis of the pressure data (Pb) of said intake manifold and the engine revolution speed data (N). A system for controlling ignition timing for an internal combustion engine as set forth in claim 1, wherein said engine revolution speed detecting means (12) includes an engine revolution sensor (12) for detecting the engine revolution of the engine in the form of ignition pulses. A system for controlling ignition timing for an internal combustion engine as set forth in claim 1, wherein said intake air pressure detecting means (10) includes a vacuum sensor (10) provided in said intake manifold (1) of the engine. A system for controlling ignition timing for an internal combustion engine as set forth in claim 1, wherein said valve motion condition determining means (20) determines whether one or more cylinders of the engine are held in their unworked conditions or all cylinders of the engine are held in their worked conditions. A system for controlling ignition timing for an internal combustion engine as set forth in claim 1, wherein said valve motion condition determining means (20) determines whether the engine is held in a high speed operation condition derived form the valve motion conditions of cylinder valves in cylinders or held in a low speed operation condition derived from the valve motion conditions of said cylinder valves in the cylinders. A system for controlling ignition timing for an internal combustion engine as set forth in claim 1, wherein said valve motion condition determining means (20) determines whether the engine is held in an operation condition derived form one or more cylinders of the engine held in their unworked conditions, the engine is held in a high speed operation condition derived from valve motion conditions of cylinder valves in cylinders, or held in a low speed operation condition derived form valve motion conditions of said cylinder valves in the cylinders. A system for controlling ignition timing for an internal combustion engine as set forth in claim 1, wherein said target ignition timing is calculated on the basis of data including at least one compensation value selected from temperature of coolant in the engine, temperature of air in the intake manifold (1), the opening of the throttle valve (2) provided in the intake manifold (1) of the engine, knocking, and voltage level of battery. A method for controlling ignition timing for an internal combustion engine, comprising the steps of: (b1) determining an operating state of an intake valve and/or an exhaust valve of the engine on the basis of an operating state of a change-over mechanism for changing the operating state of said intake valve and/or said exhaust valve; (b4) detecting a revolution speed of the engine and a pressure inside an intake manifold, and producing engine revolution speed data (N) and pressure data (Pb); (b5, b6) determining a standard ignition timing (b) for each of cylinders of the engine on the basis of standard ignition timing maps (m1, m2, m3), each of said standard ignition timing maps (m1, m2, m3) being prepared for each operating state of said intake valve and/or exhaust valve, and defining a plurality of standard ignition timings in accordance with the pressure data (Pb) and the engine revolution speed data (N); (b9) correcting the determined standard ignition timing in accordance with the operating state of the engine, and calculating a target ignition timing ( adv) for each of said cylinders; and igniting each of said cylinders at each target ignition timing; said method is characterized in that one of said standard ignition timing maps (m1, m2, m3) is selected in accordance with results determined by said operating state determining means, and a standard ignition timing is read from the selected map in accordance with the pressure data (Pb) of said intake manifold and the engine revolution speed data (N). A method for controlling ignition timing for an internal combustion engine as set forth in claim 8, wherein said engine revolution speed detection is performed by an engine revolution sensor (12) in the form of ignition pulses. A method for controlling ignition timing for an internal combustion engine as set forth in claim 8, wherein the intake air pressure detection is performed by a vacuum sensor (10) provided in said intake manifold (1) of the engine. A method for controlling ignition timing for an internal combustion engine as set forth in claim 8, wherein the valve motion condition determination includes determining whether one or more cylinders of the engine are held in their unworked conditions or all cylinders of the engine are held in their worked conditions. A method for controlling ignition timing for an internal combustion engine as set forth in claim 8, wherein the valve motion condition determination includes determining whether the engine is held in a high speed operation condition derived form the valve motion conditions of cylinder valves in cylinders or held in a low speed operation condition derived from the valve motion conditions of said cylinder valves in the cylinders. A method for controlling ignition timing for an internal combustion engine as set forth in claim 8, wherein the valve motion condition determination includes determining whether the engine is held in an operation condition derived form one or more cylinders of the engine held in their unworked conditions, the engine is held in a high speed operation condition derived from valve motion conditions of cylinder valves in cylinders, or held in a low speed operation condition derived form valve motion conditions of said cylinder valves in the cylinders. A method for controlling ignition timing for an internal combustion engine as set forth in claim 8, wherein the target ignition timing is calculated on the basis of data including at least one compensation value selected from temperature of coolant in the engine, temperature of air in the intake manifold (1), the opening of the throttle valve (2) provided in the intake manifold (1) of the engine, knocking, and voltage level of battery.

Inventors: TOGAI KAZUHIDE, TOGAI, KAZUHIDE, Togai, Kazuhide, c/o Mitsubishi Jidosha Kogyo
Applicants: MITSUBISHI MOTORS CORP, MITSUBISHI JIDOSHA KOGYO KABUSHIKI KAISHA
Application year: 1993
Main classification: F02P5
IPC codes: F02P5, F02D17, F02P3, F02D41