JPS6052304B2 - Cylinder fuel injection internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a direct injection internal combustion engine in which fuel is directly injected into a combustion chamber and the injected fuel is ignited by a spark plug.

During the engine compression stroke, fuel is directly injected from the fuel injection valve into the combustion chamber to provide so-called stratified air supply, and the ignition plug is ignited near the richest mixture to enable stratified combustion. It is a direct injection internal combustion engine, and according to this,
Unlike premix engines, there is no need to provide an intake throttle valve, so thermal efficiency is increased and fuel efficiency is greatly improved.

(“SAETechnica1PaperSeries
780699” and the magazine “Automotive Eng.
ineering” August 1978 issue V01.86N0
．． 8P68-P75) Incidentally, severe knocking phenomena generally pose a problem for engines, such as impairing the durability of the engine, but it is known that fuel efficiency becomes extremely good in the slight knocking region. In the above-mentioned direct fuel injection engine, the fuel injection timing and ignition timing have important effects on combustion, and knocking tends to vary significantly when these factors are changed.

Based on these phenomena, the present invention provides a direct injection internal combustion engine that controls fuel injection timing and ignition timing while detecting the engine knocking state, thereby always achieving the best fuel efficiency characteristics. The purpose is to

Embodiments of the present invention will be described below based on the drawings.

In Fig. 1, 1 is the engine body, 2 is a fuel injection valve that injects fuel directly into the combustion chamber, 3 is an ignition plug that ignites a mixed layer of fuel and air, and these are the control devices described later. 5
The fuel injection timing and ignition timing are variably controlled by the signals from the respective engines.

Reference numeral 4 denotes an engine knocking sensor, which senses, for example, vibrations of the engine body 1 to detect a knocking state.

Reference numeral 6 denotes an engine rotation speed sensor which detects crank rotation angles (for example, at intervals of 1 degree).

Reference numeral 7 designates an engine load sensor, which outputs, for example, an accelerator pedal (not shown) that outputs a signal to increase or decrease the amount of fuel injection. function) to detect the load status.

Signals from each of these sensors 4, 6, and 7 are sent directly or indirectly to an arithmetic circuit 8 of the control device 5.

That is, the output of the knocking sensor 4 is determined by the determination circuit 9 by comparing the magnitude of engine vibration due to knocking with a reference value, and a determination signal representing the magnitude of knocking is input to the arithmetic circuit 8.

Further, the output from the rotational speed sensor 6 is waveform-shaped into a pulse signal synchronized with the crank rotation angle in the signal processing circuit 11, and is then inputted to the arithmetic circuit 8 in the same manner as described above.

The arithmetic circuit 8 calculates the optimal fuel injection timing, which is predetermined in accordance with the engine load and engine speed (however, the injection timing is determined by controlling the fuel supply pressure to the injection valve 2, as described later) and the ignition timing. The stored values in the memory circuit 12 are selected from time to time according to one operating condition (load and rotational speed), corrected based on the knocking condition, and then output to the drive circuit 13.

In other words, the arithmetic circuit 8 uses the signal from the knocking sensor 4 as a feedback signal during fuel injection! It adjusts the engine speed and ignition timing to maintain a slight knocking condition to always achieve the best fuel efficiency.

However, as shown in Figure 3, in the engine low and medium load range, the best fuel efficiency range (point A) is a slight knocking range that is 5 points outside the knocking limit C, so there is no problem;
In this load range, the fuel injection timing (especially the end of injection timing) and ignition timing are delayed, and the best results are in the range outside the knocking limit D, which is unfavorable for engine durability. Set so that the fuel efficiency of

Of course, if the actual knocking condition exceeds the permissible limit despite such control, correction is immediately made based on feedback control.

The fuel injection signal is supplied to a solenoid valve 15 that controls fuel pressure, and the solenoid valve 15 is inserted into a circuit that returns fuel discharged from a fuel pump 16 to a fuel tank 17, and reduces the fuel pressure when the valve is opened.

In other words, the fuel injection valve 2 is a pressure-type automatic valve that opens only while the supply fuel pressure is maintained above a predetermined valve opening pressure, and injects fuel into the combustion chamber. Once the solenoid valve 15 opens the return path to the fuel tank 17, the fuel pressure will drop and no fuel injection will occur. The electromagnetic valves 15 are provided corresponding to the fuel injection valves 2 of each cylinder, so that the drive circuit 13 sends injection signals out of phase to each cylinder.

The specific structure is shown in FIG. 2, and 18 is a fuel supply passage;
19 is a fuel return passage, 20 is a needle valve that opens and closes a valve port 21 that releases fuel to the return passage 19, and 22 is a needle valve 20.
The movable iron core moves integrally with the return spring 23.
(In this case, the solenoid valve 15 is constituted by an electromagnetic coil that closes the valve in opposition to the bias in the valve opening direction.)

When a pulse signal is supplied from the drive circuit 13, the electromagnetic valve 15 closes only while the pulse signal is on (high level), increasing the pressure in the fuel supply passage 18, and fuel is injected from the fuel injection valve 2. In the above configuration, based on the signals from the engine speed sensor 6 and the load sensor 7, the injection timing and ignition timing that provide the best fuel efficiency and output are selected from those stored in the memory circuit 12 in advance, Arithmetic circuit 8
The signal is output from the drive circuit 13 to the drive circuit 13.

Based on this, fuel is mainly injected during the compression stroke, and ignition is performed by the ignition plug 3 near the compression top dead center.

Even without providing a throttle valve in the intake system, the engine output can be increased or decreased by controlling the weight of fuel injected from the injection valve 2.

This is because the fuel injected during the compression stroke accumulates in layers with the air, and at compression top dead center, a rich mixture layer is formed around the ignition plug 3, resulting in good ignition and flame propagation. It is.

On the other hand, the engine knocking state is detected by the knocking sensor 4, and this is fed back to the calculation circuit 8, so the above-mentioned fuel injection timing and ignition timing are advanced until the best fuel efficiency point is obtained within a range that does not cause strong knocking. It will be done.

If knocking occurs, based on this, the fuel injection timing and ignition timing are delayed in accordance with the magnitude of knocking, and in this way, knocking is immediately avoided.

Immediately after this, the injection timing and ignition timing are advanced until just before knocking occurs again, and when knocking occurs again, they are delayed again, and such control operations are repeated.

As is clear from Figure 3, knocking can be avoided even if only the ignition timing or fuel injection timing is delayed.
Due to the relationship between the equal fuel consumption curves (Bl, Bl!, B3, etc. in the figure), retarding only one of them is disadvantageous in terms of fuel efficiency. By retarding both at the same time, the loss in fuel efficiency can be minimized. This allows you to avoid knocking while keeping the engine firmly in place.

As explained above, according to the present invention, the fuel injection timing and the ignition timing are feedback-controlled so as to always obtain the best fuel efficiency while detecting the knocking state, so the fuel efficiency is improved, which is an excellent feature of the direct fuel injection engine. Efficiency can be further improved. In particular, if this kind of feedback control is performed, even if there are variations in performance, fuel composition, and octane number between engines, it is possible to always control each engine to its optimum state.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention, FIG. 2 is a sectional view of a solenoid valve, and FIG. 3 is an equal fuel efficiency characteristic curve diagram using ignition timing and injection timing as parameters. 2...Fuel injection valve, 3...Ignition plug, 4
... Knocking sensor, 5 ... Control device, 6 ... Rotation speed sensor, 7 ... Load sensor, 8 ... Arithmetic circuit, 15... Solenoid valve.

Claims (1)

[Claims] 1. In a direct fuel injection internal combustion engine that has a fuel injection valve that directly injects fuel into a combustion chamber and a spark plug that ignites and burns a stratified mixture, a sensor that detects an engine knocking state and a sensor that detects the rotational speed and A sensor that detects the load,
The present invention includes a control device that corrects the optimum fuel injection timing and ignition timing selected according to the operating condition based on the knocking condition, and controls the operation of the fuel injection valve and the ignition plug based on the correction signal. Features a cylinder fuel injection type internal combustion engine.