JPS6244095B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ignition timing control method for a spark-ignition internal combustion engine.

In electronic ignition control for internal combustion engines, the energization time of the ignition coil is controlled by the energization control signal from the microcomputer, and excess or insufficient energization can cause problems such as overheating of the coil or a drop in secondary generated voltage. Therefore, the output accuracy of the energization control signal is required to be high. However, conventionally, when using a microcomputer to convert the ignition advance angle into time based on information from various sensors representing the operating state and output the above-mentioned energization control signal, for example, the required Because time is used, it does not take into account that the crankshaft rotational speed differs in the crank angle position during the ascending process as it approaches top dead center and the descending process as it moves away from top dead center, so highly accurate ignition timing control is not possible. If required, the influence of such changes in crankshaft rotational speed during one rotation of the crankshaft cannot be ignored.

The present invention aims to improve the accuracy of the ignition timing control method by resolving these drawbacks.

In the present invention, a microcomputer is used to convert the optimal ignition advance angle into time based on information from various sensors that detect the operating state of the internal combustion engine, and when the signal is output to the igniter, it is installed in the distributor. A pulse signal is generated for each crank angle divided into a predetermined number of equal parts by a signal generator, the time required for rotation between the pulses is measured, and the output signal is output at the required time. The accuracy of ignition timing control is improved by performing calculations to convert the current time to the energization time.

Figure 1 shows the overall connection configuration in one embodiment when the present invention is applied to a four-cylinder internal combustion engine, in which an angular position signal is generated for each angular position that divides one revolution of the crankshaft into 12 equal parts. The angular position rotor 11 configured as above and the reference position rotor 12 that generates one pulse of reference position signal per combustion cycle are attached to the distributor rotation shaft as one unit, and a signal generator that generates pulses when the rotor approaches. 21,2
On the other hand, various sensors 391 to 398 provide information such as the cooling water temperature of the internal combustion engine, intake air amount, no-load signal switch status, etc., and a distributor 50
The optimum ignition timing is calculated based on a predetermined calculation formula from the rotational speed calculated from the crank angle required time obtained from the signal generator 21 of An electronic control circuit 30 having a built-in microcomputer 34 that calculates the time required for up to is supplied to the igniter 40 as an energization signal. The igniter 40 determines an optimum energization time based on the rectangular wave pulse of the energization signal, and conducts the power transistor 42 at the determined time interval so as to supply battery current to the primary coil of the ignition coil 41. The igniter 4 uses the falling edge of the square wave pulse as the ignition timing.
0 cuts off the power transistor 42 to cut off the power to the primary coil of the ignition coil 41, and transmits the high voltage generated in the secondary coil to the desired cylinder via the distribution rotor 51 of the distributor 50. The configuration is such that the fuel is supplied to the spark plug 60.

In this embodiment, one rotation of the crankshaft of the internal combustion engine is divided into 12 equal parts, and a signal generator is provided that inputs every 30 degrees of crank angle. Store in access memory (RAM). Taking a four-cylinder internal combustion engine as an example, the ignition interval is 180 degrees, so six RAMs are prepared. Fig. 2-2 shows the correspondence between the crank angle and the RAM, and Fig. 4 shows the correspondence between the RAM and the period of time required for 30 degrees of the internal combustion engine, which the inventor found through experiments. Based on this required time T30, the required time TH until the optimum ignition timing is calculated, and the time when the crank angle signal is input is added and set in the compare register. After the required time TH has elapsed, a match occurs between the compare register and the timer, and the ignition output port process is executed. For example, if the optimal ignition timing is 50°BTDC, count down the required time using RAME's 30° required time T30E.
Calculate TH = (60-50)/30 x T30E. If it is 5° BTDC, use RAMF's 30 degree time required T30F to count down the required time TH = (30-5)/30 x T30F
Calculate by switching the calculation to find .

Next, an embodiment of the calculation procedure in the microcomputer 34 will be described with reference to FIGS. 2-2 and 3. In the flowchart shown in Figure 3, L310
00 is the internal combustion engine's main routine, which can be calculated from various input information such as cooling water temperature, intake air amount, no-load detection signal, etc. from various sensors 391 to 398 connected to the electronic control circuit 30, and the time required for 30° crank angle. The optimal ignition timing is calculated based on a preset calculation formula from the rotation speed information, and from that value the count number of interrupt occurrences (RMA display name) when turning on the energization signal to the igniter
NCNT) and crank angle from interrupt timing to ON processing crank angle (RAM display name θON)
and the crank angle (RAM display name θOFF) up to the OFF processing crank angle are respectively stored in the RAM.

As shown in FIG. 1, the angular position rotor 11 and the angular position signal line generated by the signal generator 21 are connected to the interrupt port 31 of the microcomputer 34 in the electronic control circuit 30, and the reference position rotor 12 and A reference position signal line generated by signal generator 22 is also connected to interrupt port 32. If an interruption of the reference position signal occurs, the program jumps to the routine L13000 from the middle of the main routine and sets the flag F1. Also, if an angle position signal interrupt occurs, L220
Jump to routine 00, read the time when the interrupt occurred from the free timer counter (FTC), store it in RO, find the difference between that stored value and the previous interrupt occurrence time stored value (RAM display name SDO), and send it to R2. Calculate the time required for 30° crank angle, and calculate the time required for the 30° crank angle to the RAM (RAM display name T30i...i) indicated by the angular position interrupt counter (RAM display name CNT).
CNT value) and updates and stores the current interrupt occurrence time in SDO. Then, the content stored in R2 is stored at the RAM address R1 of the numerical value shown in R1.
The address is updated for each CNT.
Next, after adding 1 to CNT, flag F1 is checked, and if flag F1 is set, CNT is changed to the initial value A. If the flag F1 is not set, it is checked whether the value of CNT is greater than F, and if it is, CNT is changed to the initial value A. If the value of CNT is smaller than or equal to F, check whether it is the timing to process the ignition signal ON or OFF determined in advance in the main routine of L31000, and if not, RTI (Return
Interrupt) returns to the main routine that was being executed before the interrupt. CNT value is ON or ON of energization signal
If it is time to perform OFF processing, use T30i
Read out (i...CNT value) and turn the energization signal ON or OFF based on the crank angle calculated from the CNT value.
Convert the angle θ until the At this time, the time TH can be determined using the expression TH=θ/30×T30i. The result of this operation is set in the compare register, and flag F2 is set when processing ON, otherwise flag F2 is reset and the process returns to the main routine that was being executed before the interrupt. L4 is a subroutine that handles a compare match interrupt when the contents of the compare register and the value of the free-run timer counter match. It stores the port status in R3, checks whether the value of flag F2 is 1, and if it is YES. For example, the logical sum of the contents of R3 and the contents of F2 is taken and stored in R3.
If the value of flag F2 is not 1, the contents of R3 and F2 are ANDed and stored in R3.
Then, the contents of R3 are output to the port.

The signal waveforms of each part in the above processing are shown in 2-1.
As shown in the figure. Here, the reference position signal indicates a necessary edge portion of the signal output when 12 and 22 in FIG. 1 are close to each other, and is a signal of 1 pulse/1 rotation. The angle plate signal shows the edge part of the signal that is output when 11 and 21 in Figure 1 are close to each other.
It is a signal of 24 pulses/1 rotation. The free-run timer is the value of the free-run timer counter in the CPU, which takes on a large value as the time clock counts up, and becomes zero when it overflows.
Continue counting again. The compare register is
Indicates the value set in the compare register in the CPU, and is updated every time the angular position signal interrupts, which sets the output of the energization signal. The energization signal output is a signal output from the microcomputer 34. The countdown time indicates the difference between the compare register setting value and the free run timer counter, and is not a signal waveform. The timing chart at the bottom shows which process is being executed at that timing.

When the internal combustion engine is operated according to the above procedure, the main routine is normally executed, but CNT and T30i are updated every time an angular position signal is input.
゜The time required between crank angles is continuously memorized. Figure 2-2 shows the correspondence between the RAM address and the crank angle position when the interrupt position of the angular position signal following the interruption of the reference position signal is set to the top dead center of the internal combustion engine. This shows the state in which the contents of RAM are updated for each angle.

As shown in Figure 4, at the top dead center of each cylinder, the rotational speed decreases due to compression, so approximately
The rotation speed changes with a 180° crank angle cycle.
Therefore, since the time required for each crank angle differs, when converting angle into time, if you use the time required for a specific crank angle or the average time between 180° crank angles, there will be a calculation error on the ON side of the energization signal and a calculation error on the OFF side. It can be seen that the output accuracy of the energization signal deteriorates because the calculation error is caused and the energization signal is not uniform. In the embodiment according to the present invention, at the interrupt timing of the angular position signal at which the countdown time is actually set, the time required for the 30° crank angle of the same crank angle phase exactly one ignition before is read out, and the angle θ is calculated as the time TH.
, it is possible to eliminate calculation errors due to speed fluctuations that occur during one combustion cycle of the internal combustion engine, and improve the output accuracy of the energization signal that controls the ignition timing.

Although this embodiment has been explained using a 4-cylinder engine as an example, the same calculation can be applied to internal combustion engines with other cylinder numbers by allocating the number of RAMs equally divided within the ignition cycle. The period of signal generation is 30
Not only for each crank angle, but also for each crank angle of 15°, 20°, and 60°, the same effect can be obtained based on the balance between calculation accuracy and calculation speed. In addition, the calculation timing for converting from angle to time is determined after the ignition timing is determined in the main routine, and the CNT for which the energization signal is to be turned ON or OFF is determined.
Read T30i, calculate it, store the countdown time in RAM, and turn on the energization signal or
It is also possible to set the time in the compare register when an interrupt occurs for the angular position signal that is to be turned off.

[Brief explanation of the drawing]

Fig. 1 is an overall connection configuration diagram of an embodiment in which the present invention is applied to a four-cylinder internal combustion engine, Fig. 2-1 is a signal waveform diagram at angles within the electronic control circuit, and Fig. 2-1 is a diagram of signal waveforms at angles within the electronic control circuit.
-Figure 2 shows the corresponding RAM at each crank angle
FIG. 3 is a flowchart showing the calculation procedure of the microcomputer in the embodiment of the present invention, and FIG. 4 is a diagram showing the correspondence between the period of time required for a 30° crank angle of an internal combustion engine and RAM. 11... Rotor, 12... Reference position rotor, 2
1, 22...signal generator, 30...electronic control circuit, 31, 32...interrupt port, 34...microcomputer, 341...accumulator and controller, 342...read-only memory, 343... ...Random access memory, 344...Free running timer counter, 345...Input port, 346...Free running timer counter, 347...Compare register, 348...Output port, 392...
…Accelerator opening switch fully closed side signal sensor,
393...Transmission neutral switch signal sensor, 394...Air conditioning switch signal sensor, 395...
...Vehicle speed signal sensor, 396...Cooling water temperature signal voltage sensor, 397...Intake air amount signal voltage sensor,
398... battery voltage sensor, 40... igniter, 41... ignition coil, 42...
Power transistor, 50...Distributor, 60...Spark plug, 70...Battery.

Claims (1)

[Scope of Claims] 1. Divide the crank angle corresponding to one ignition cycle into a plurality of equal angle sections, and generate an angular position signal at each start time of each section in synchronization with the rotation of the crankshaft, The required crankshaft rotation time for each section is calculated and stored from the generation time of the angular position signal for each section, and based on the parameters indicating the engine operating status,
Calculate the ignition timing angle for each predetermined cycle, determine which section the ignition timing angle belongs to, and determine which section the ignition timing angle belongs to based on the previous crankshaft rotation time required for the section to which it belongs and the calculated ignition timing angle. An ignition timing control method for a spark ignition internal combustion engine that calculates the time from the start time to the ignition timing angle and generates an ignition signal when this time elapses.