JPS62139948A - Ignition timing control device for internal combustion engine of direct fuel injection type - Google Patents

Abstract

PURPOSE:To remove carbon deposits from ignition plugs as effective counter- measures against smoke by carrying out multi-ignition discharge once in an early compression stroke or a suction stroke prior to the start of fuel injection with delayed fuel injection timing at the time of supercharging. CONSTITUTION:A gasoline engine 1 is fitted with fuel injection nozzles 2a-2d and ignition plugs 3a-3d corresponding thereto. Each ignition plug is connected to an ignition coil 5a or 5b via high tension cords 4a-4d. At the time of supercharging, multi-ignition discharge is carried out once in an early compression stroke or a suction stroke prior to injection stat with delayed fuel injection timing. In this way, carbon deposits on ignition plugs can be removed and effective counter-measures against smoke become thereby available.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to direct injection internal combustion engines, and in particular to ignition timing control for direct injection gasoline engines that takes measures against smoldering spark plugs during supercharging. Regarding equipment.

[Problems to be solved by conventional technology and invention]

Direct cylinder injection spark ignition engines are known in the art.

This attempts to achieve lean burn through stratified intake, but in practice it has many problems, such as the difficulty of achieving good stratification under all operating conditions, which reduces nitrogen oxides. (NOx) and hydrocarbons (IIC
) There is a problem that emissions increase. For these reasons, this type of engine is currently not very popular.

On the other hand, in such a direct injection gasoline engine with a supercharger, if the output air-fuel ratio is set to around 13 compared to the stoichiometric air-fuel ratio of 14.7 without stratifying the air-fuel mixture, the compression During a stroke, multiple fuels must be injected into the cylinder within a short period of time, which creates a problem in that the fuel is unevenly distributed within the cylinder and causes the spark plug to smolder. However, if the compression ratio is increased to improve engine efficiency, the injection timing must be delayed to prevent knocking, which injects fuel into a narrower space for a shorter period of time, which further exacerbates this problem.

Means and operation for solving problem C] The object of the present invention is to provide an ignition timing control device for a direct injection internal combustion engine that solves the above-mentioned problems. multiple ignition discharge is performed once at the beginning of the compression stroke or intake stroke before the start of injection, and then discharge (ignition) is performed again at a predetermined ignition timing after the start of injection. In this case, carbon adhering to the electrodes is removed by multiple discharges before the start of injection. In addition, when there is no supercharging, the injection timing is set at the beginning of the intake stroke and the compression stroke, and then the discharge for ignition is performed, and the cylinder is controlled so that multiple discharges for carbon removal are not performed. An object of the present invention is to provide an ignition timing control device for an internal direct injection type internal combustion engine.

〔Example〕

FIG. 1 is a schematic block diagram of a direct injection internal combustion engine and its peripheral devices to which the present invention is applied. In Figure 1,
For example, a four-cylinder gasoline engine l is provided with injection nozzles 28 to 2d and corresponding spark plugs 3a to 3d. Each spark plug is connected to an ignition coil 58 or 5b via high tension cords 48-4d. Ignition coil 5a! The ignition coil 5b carries the 2 and 1 h3 cylinders, respectively. That is, this system does not require a distributor. This is because the device of the present invention has a long ignition discharge period, making it difficult to distribute power using a distributor. Further, the electronic control circuit 7 receives a signal a from the crank angle sensor 14, a TDC signal from the top dead center angle sensor 15, and a signal C from the cylinder discrimination sensor 16. Further, when a supercharger (not shown) is driving, that is, when an electromagnetic clutch of the supercharger is directly connected, a signal d indicating a supercharging state is input. Furthermore, a signal e from an engine coolant temperature sensor (not shown) is also input.

As shown in the flowchart described later, the electronic control circuit 7
Based on these input signals, a discharge instruction signal f, cylinder instruction signals g and h are sent to the igniter 6, and a fuel injection instruction signal i is sent to the drive section 13. A signal line 17 is provided from the drive unit 13 to each of the injection nozzles 2a to 2d for each injection nozzle. Fuel is supplied from the fuel tank 8 to the fuel pump 9
The pressure is further maintained at a constant pressure by the delivery pipe 10. When any of the injection nozzles 28 to 2d receives a signal from the signal line 17 indicating an injection instruction, the injection nozzle opens and fuel is injected at approximately the same pressure as in the pipe 10. The signal line 17 carries not only control signals for injection instructions but also supply signals for nozzle drive energy. Since a high voltage is required here, energy is supplied from the battery 11 to the drive section 13 after the voltage is boosted by the DC/DC converter 12.

FIG. 2 is a sectional view of an injection nozzle, a spark plug, and a cylinder combustion chamber of the engine shown in FIG. In Figure 2,
Injection nozzle 2 (28~2d) and spark plug 3 (38~
3d) is screwed to the cylinder/door 25.

The combustion chamber consists of this cylinder head 25 and cylinder block 2.
4 and the piston 23. The rear sides (not shown) of the intake valves 21 and 22 have a helical shape to generate a strong swirl. Carbon adheres to the shaded area around one electrode at the tip of the spark plug 3, causing ``smolder 1''.

FIG. 3(a) is a detailed circuit diagram of the ignition coil and spark plug shown in FIG. 1. As mentioned above, this type does not require a distributor, and spark plugs 3a and 3
They are simultaneously discharged at d and one is used for ignition. Figure 3 (
b) is the negative side coil L1.

Current waveform ALI 7 AL2 of L2 and current waveform Vt3 of secondary coil L3 are shown. Two spark plugs, for example 3a and 3d, are shown in the secondary coil L3 of the transformer 31. - On the next side, there is a loop consisting of battery B, coil L1, diode 34, and power transistor 32, and a loop consisting of battery B, coil L2, diode 35, and power transistor 33. Reference numeral 36 denotes a pulse generation circuit which, when input with the discharge instruction signal k or l generated by the igniter 6, generates a pulse signal only during the period when this signal is input. This pulse signal is ANDed with a command from the computer 71 to turn the power transistors 32 and 33 on and off alternately, forming current waveforms AL+ and A as shown in FIG. 3(b).
Obtain l1. This current causes V to the spark plug.
An AC voltage such as L3 is generated, for example, as shown in FIG. 4 (described later).
Multiple discharge is performed during the period t1 to t2 of al.

Figure 4 (al, (bl) is a time chart of injection and ignition (discharge) of the device according to the present invention. Figure 4 (a) is during supercharging, and Figure 4 (b) is without supercharging. In FIG. 4 (al), a discharge is performed to remove smoldering during a period t1 to t2. This discharge is performed by a discharge instruction signal k or l. The stroke at this time is approximately from bottom dead center to the intake valve. The period is from the end of intake until the valve closes to the beginning of compression. At this time, the fuel injection is delayed so that no fuel is injected yet, so that no flame is generated because there is only air (the carbon in the spark plug can be sufficiently removed). Immediately thereafter, fuel injection is started by the injection instruction signal i and continues for a period T1.

At the end of this injection, regular discharge for ignition occurs during period t3 ~
This is done at t5. Considering ignitability, discharge is started at time t3, which is slightly earlier than the injection end time [4]. The stroke at this time is in the latter stage of compression. In Fig. 4(b), no measures against smoldering should be taken.

do not have. During period T2, fuel is injected according to injection instruction signal i. The process at this time is the initial stage of compression.

Then, during the period t6 to t7, regular discharge for ignition is performed by the discharge instruction signal k or l. The stroke at this time is in the latter stage of compression.

FIG. 5 is a detailed block diagram of the electronic control circuit 7 shown in FIG. 1. In Fig. 5, signals from a crank angle sensor 14, top dead center angle (TDC) sensor 15, cylinder discrimination sensor 16, water temperature sensor, supercharging state sensor, etc. are input control consisting of an A/D converter, a multiplexer, and an input boat. It is input to a circuit 71, and a central processing unit (CPU) 72 controls discharge, injection, etc. based on a flowchart described later. 73 is a read-only memory (ROM) that stores a predetermined control program; 74 is a random access memory (RAM) that temporarily stores data; 75
is the output boat. Further, 76 and 77 are drive circuits for each of the injectors 2a to 2d and ignition coils 38 to 3d.

FIGS. 6(a) and 6(b) are detailed block diagrams of the fifth drive circuit. FIG. 6(a) shows a drive circuit for discharge, and FIG. 6(b) shows a drive circuit for injection. That is, there is a circuit (ta) that controls discharge for removing smoldering and discharge for ignition for the spark plug, and a circuit (b) for controlling the opening of the injection nozzle (injector). The drive circuit consists of registers, counters, comparators, and switching circuits. The operation of the injection drive circuit shown in FIG.
72 selects one of the drive circuits provided for each injector based on the counter value indicating the injector in the RAM, and writes a value Ti corresponding to the valve opening time of the injector to the registers 52a and 63a of the selected drive circuit. After that, the drive circuit operates as follows. That is, first, the counter 64a is reset, and the counter 64a is reset when the crankshaft is 1.
Start counting the pulse signal (10CA signal) from the crank angle sensor that is output every time it rotates. When this count value and the written value of the register 63a become equal, the injector opens based on the output signal of the comparator 66a and starts fuel injection. At the same time counter 61
a is reset and this counter 61a starts counting clock pulses. Next, when this count value and the value of the register 62a become equal, the comparator 65
Based on the output signal of a, the injector is closed and fuel injection is stopped.

The operation of the discharge drive circuit shown in FIG. After writing this into the registers 62 and 63, the counter 64 is reset and starts counting the pulse signal (16CA) from the crank angle sensor.This counter value and the written register 63 are reset.
When the values become equal, current is applied based on the output signal of the comparator 66 to discharge an ignition pulse. At the same time, the counter 61 is reset and starts counting clock pulses. Next, when this count value and the value of the register 62 become equal, the current supply is stopped based on the output signal of the comparator 65.

FIG. 7 shows a control routine (a) for starting a cleaning discharge for removing smoldering and a control routine (bl) for starting an ignition discharge.
It shows. In Figure 7 (al), first, it is determined whether supercharging or non-supercharging is being performed, that is, whether the electromagnetic clutch for supercharging is on or off (step 1).If it is off, no smoldering measures are taken. First, discharge and injection are performed as shown in Figure 4 (bl) (step 2).In the case of supercharging, the bottom dead center (B) of the intake stroke is
An interrupt is made (step 3) at D C), and at this time counters 61 and 64 of FIG. 6 (al, (bl)
, 61a, 64a (step 4
). Next, the time for starting the cleaning discharge is calculated by the CPU 72 (step 5), and is output to the register 62 (
Step 6). Furthermore, the timing of the end of the cleaning discharge is determined by the CPU.
72 (step 7) and output to the register 63 (step 8). Since this time is also the fuel injection start time, the output of register 63a is the same as register 62a.
(Step 9). Then, the CPU 72 calculates the timing of the end of fuel injection (step 10) and outputs it to the register 63a.

FIG. 7 (bl is a control routine for ignition discharge.

In Fig. 7 (bl), it is determined whether supercharging or non-supercharging is performed (step ■) in the same way as in (a), and when there is no supercharging, the same as above (without taking any measures (step 2)). During supercharging, an interrupt is performed at a predetermined crank angle of the compression stroke (step 3).Next, the counters 61 and 64 are reset (step 4), and the calculation of the ignition discharge start timing is performed at CPt.
172 (step 5) and output to the register 62 (step 6). Further, the CPU 72 calculates the end timing of the ignition discharge (step 7).
It is output to register 63.

〔Effect of the invention〕

According to the present invention, in a direct injection engine, during supercharging, the fuel injection timing is delayed and multiple ignition discharge is performed once at the beginning of the compression stroke or during the intake stroke before the start of injection, so that the spark plug can withstand It is possible to remove attached carbon and prevent smoldering.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a direct injection engine to which the present invention is applied and its peripheral equipment; Fig. 2 is a sectional view of the injection nozzle, spark plug, and cylinder combustion chamber shown in Fig. 1; Fig. 3 ( al is a detailed circuit diagram of the ignition coil and spark plug in Figure 1, Figure 3 (top) is a current and voltage waveform diagram of the coil in Figure 3 (a), Figure 4 (a) is during supercharging. Fig. 4 (BL is a discharge and injection timing chart during non-supercharging), Fig. 5 is a detailed diagram of the electronic control circuit shown in Fig. 1, Fig. 6 (a), ( b) is a detailed diagram of the drive circuit in FIG. 5, FIG. 7 (aJ is a control routine for cleaning discharge according to the present invention, and FIG. 7 (bl is a control routine for ignition discharge). (Explanation of symbols) ■・・・・・・4 cylinder direct injection gasoline engine, 28~2d...Injection nozzle 38~3d...Spark plug, 48~4d...High tension code, 5a, 5
b...Ignition coil, 6...Igniter, 7...Electronic control circuit, 8...Fuel tank, 9... ...Fuel pump, 10...Delivery pipe, 11...
...Battery, 12...DC/DC converter, 13
...... Drive section, 14... Crank angle sensor, 15...
...Top dead center angle sensor, 16...
Cylinder discrimination sensor, 21, 22...Intake valve, 23...Piston, 24...Cylinder block, 25...
······cylinder head. Injection nozzle and spark plug and (G) Timing chart during supercharging (a) Timing chart when not supercharging (b) Figure 4 Detailed diagram of electronic control circuit Figure 5 Control routine for cleaning discharge (a) $7 figure

Claims (1)

[Claims] 1. In an ignition timing control system for a direct injection internal combustion engine that injects fuel directly into the cylinder combustion chamber, during supercharging, multiple ignitions for spark plug cleaning are performed before the start of fuel injection and at the early stage of the compression stroke. After the multiple ignition discharge is completed, fuel is injected and an ignition discharge is performed at a predetermined ignition timing, and during non-supercharging, fuel is injected at the early stage of the compression stroke and the fuel is injected at a predetermined ignition timing. An ignition timing control device for an in-cylinder direct injection internal combustion engine, characterized in that it is configured to perform ignition discharge.