JPH048847A - Fuel injection control device for two-cycle engine - Google Patents

Abstract

PURPOSE:To prevent an ignition plug from becoming a hot point to restrain pre-ignition, and to reduce generation amount of end gas to restrain knocking by delaying angle of at least an injection end time of fuel at generation of pre-ignition or knocking. CONSTITUTION:In a combustion chamber 17, an electrode part 18a of an ignition plug 18 is inserted. Also, at the upper part of the combustion chamber 17, an air fuel injection device 19 is mounted. And the air fuel injection device 19 is mainly constituted of a valve mechanism 21 and a fuel injection valve 22. In the meantime, an ECU 25 takes in a pressure signal (a) from a pressure sensor 23 and other signals (b) indicating engine driving state and puts out an air injection control signal A to the valve mechanism 21, a fuel injection control signal B to the fuel injection valve 22 and an ignition timing control signal C to an ignition device 25, respectively. At this time, when pre-ignition is generated, each of the control signals A and B is corrected and put out so that angle of injection end time of air and fuel is delayed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a two-stroke engine equipped with a fuel injection device, and particularly to a two-stroke engine equipped with a fuel injection device. The present invention relates to a fuel injection control device that can prevent this by correcting the injection timing.

[Conventional technology]

Two-stroke engines equipped with air-fuel injection devices that inject fuel directly into cylinders together with compressed air have recently attracted attention. In this type of engine, for example, in a low speed and low load operating range, fuel is supplied to a part of the combustion chamber in the form of a snowball,
The fuel snow mass is ignited to perform so-called stratified combustion. Therefore, the spark plug is generally arranged so that its electrode portion protrudes into the cylinder to ensure ignition of the snowpack.

[Problem that the invention seeks to solve]

However, when the spark plug protrudes into the cylinder as described above, the electrode of the spark plug tends to become hot during operation, which causes the problem that the electrode becomes a hot point and preignition is likely to occur.

In addition, in the operating region where the injected fuel is widely diffused in the combustion chamber, that is, in the operating range where so-called premix combustion occurs, the flame caused by spark ignition compresses the end gas located at the end of the combustion chamber adiabatically. Become. When the temperature of these end gases rises above a predetermined value, they ignite and burn all at once.
This rapid combustion causes a significant pressure imbalance state, so-called knocking.

An object of the present invention is to provide a fuel injection control device for a two-stroke engine that can prevent the pre-ignition and knocking described above.

Means for Solving Problem c] The present invention provides a two-stroke engine equipped with a fuel injection device that directly injects fuel into a cylinder, and a spark plug that ignites the fuel injected from the injection device. A fuel injection control device that controls fuel injection timing and injection period, and includes a detection means for detecting the occurrence of preignition or knocking, and a control device for controlling fuel injection from the fuel injection device based on a detection signal from the detection means. The present invention is characterized in that it includes at least injection timing correction means for retarding the injection end timing.

Here, in the present invention, retarding at least the injection end timing of fuel means that both the injection start timing and the end timing are delayed.
In other words, this includes both cases in which the entire timing is retarded and cases in which only the end timing is retarded while the start timing remains the same.

[Effect]

According to the fuel injection control device according to the present invention, at least the end timing of fuel injection is retarded when preignition or knocking occurs, so even in the latter half of the compression stroke when the cylinder internal pressure increases and preignition is likely to occur, the fuel injection control device As a result, the spark plug is cooled by the injected fuel, suppressing a temperature rise near the electrode, and making it difficult for pre-ignition to occur.

Furthermore, since the fuel injection end timing is delayed, the fuel is injected when the cylinder pressure increases. Therefore, the difference between the cylinder internal pressure and the fuel injection pressure becomes smaller, and the penetration force of the spray becomes weaker, making it difficult for the fuel to diffuse inside the cylinder, and as a result, the amount of end gas generated decreases.
As a result, knocking is suppressed.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

1 to 5 are diagrams for explaining an air-fuel injection control device for an air-fuel injection type two-cycle engine according to an embodiment of the present invention, FIG. 1 is a configuration diagram thereof, and FIG. 2 is an injection An injection timing diagram showing the conditions, Fig. 3 is a cross-sectional side view of an air-fuel injection type two-stroke engine, and Fig. 4 is a pre-ignition diagram.

A crank angle-cylinder pressure characteristic diagram for explaining the knocking state, and FIG. 5 is a flowchart diagram for explaining the operation.

In the figure, reference numeral 1 is a water-cooled two-stroke parallel three-cylinder engine configured to directly inject air and fuel into the cylinders.
Two cylinders 3a are mounted with cylinder bodies 3 formed in parallel in the crankshaft direction and fixed with bolts, and a cylinder head 4 is fixed onto the cylinder bodies 3 with fastening bolts 4b. Here, the fastening bolt 4b has a load one-shaft type pressure sensor 23.
is installed, which detects pressure fluctuations within the combustion chamber 17, which will be described later.

A combustion recess 4a that forms a combustion chamber 17 with a recess 5a formed on the upper surface of the piston 5 inserted into the cylinder 3a is provided in a portion of the lower surface of the cylinder 4 corresponding to each cylinder 3a. An electrode portion 18a of a spark plug 18 is inserted into the combustion chamber 17. An air-fuel injection device 19 is installed in the upper portion of each combustion chamber 17 on the upper surface of the cylinder head 4, respectively. Each air-fuel injection device 19 mainly includes an injection body 20 inserted and fixed into the cylinder head 4, and a valve mechanism 21 that opens and closes injection ports of an air chamber and a fuel chamber formed in the injection body 20 with a valve body. and the above injection body 2
The fuel injection valve 22 is mounted on the rear side of the outer wall of the fuel injection valve 22 and supplies fuel to the fuel chamber. Also,
14a is a fuel rail for supplying fuel, and 14b is an air rail for supplying compressed air. While the valve mechanism 21 opens the injection port with the valve body, compressed air in the air chamber is injected into the cylinder, and fuel from the fuel injection valve 22 is injected into the cylinder.

Each piston 5 is connected to a crank arm 6a of a crankshaft 6.
The crank arm 6a is located within the crank chamber 2a. Further, an intake port 2b for introducing outside air is formed on the back side of each crank chamber 2a. Each intake port 2b is provided with a closed valve 7 for opening and closing the intake port 2b, and is further connected to an intake manifold 8.

Further, each branch part of an exhaust pipe 16 is connected to the exhaust port 3b formed above each of the intake ports 2b of the cylinder body 3, and after the exhaust pipe 16 merges into one pipe, it is bent downward. and extends to the rear of the vehicle.

24 is the valve mechanism 21. This is an ECU that controls the injection timing, injection period, etc. of air and fuel by the fuel injection valve 22, and the ignition timing by the ignition device 25.

The ECU 25 is inputted with a pressure signal a from a pressure sensor 23 attached to the above-mentioned fastening pole 4b and signals indicating engine operating conditions such as accelerator opening, engine rotation speed, crank angle, etc. An air injection control signal A that controls the injection period is output to the valve mechanism 21, a fuel injection control signal B that controls the fuel injection timing and injection period is output to the fuel injection valve 22, and an ignition timing control signal C is output to the ibnirasilane device. Output to 25.

Here, the ECU 24 determines the occurrence of pre-ignition or knocking based on the pressure waveform from the pressure sensor 23.
), the pressure p2 reaches the maximum value after the predetermined angle θ, and the pressure fluctuates at a frequency of KHz. If the pressure p3 reaches the maximum pressure near the top dead center and is significantly higher than the normal maximum pressure (for example, 30 kg/cm" at low load, knocking is determined). At load 7 Q kg/c
s'' in FIG. 4 (see C1), it is determined that pre-ignition has occurred.

The ECU 24 also functions as a correction means for injection timing and ignition timing, and if it is determined that pre-ignition has occurred, it sends a control signal to retard the end timing of air and fuel injection. Correct and output A and B. In this case, for example, as shown in FIG.
If pre-ignition occurs in step 1, either a method of retarding only the injection end time while leaving the injection start time unchanged (R2), or a method of retarding both the injection start time and end time (R3). will be adopted.

Furthermore, if the frequency of occurrence of the above-mentioned pregeninsilane is high, the retardation amount is set to be large.

In addition, if it is determined that knocking has occurred, if the knocking occurrence intensity 1 order amount is relatively small, only the timing control signal C is corrected so that the ignition timing is retarded; if it is large, the ignition timing is The control signal AB is corrected so as to retard the air-fuel injection end timing. Note that in this case as well, any of the above-mentioned methods R2 and R3 may be employed.

Next, the effects of this embodiment will be explained with reference to FIG. 5.

After the pressure signal a from the pressure sensor 23 is amplified by an amplifier circuit, noise components are removed by a bypass filter, and it is determined whether or not knocking has occurred (step 5l-34). If not,
The control signals A-C are output as they are, and the engine is operated with the normal ignition timing and air-fuel injection timing (
On the other hand, if it is determined that knocking has occurred, only the control signal C is corrected and output so that the ignition timing is retarded, or the control signal The control signal AB is corrected and output so that the fuel injection end timing is retarded (
Step S5. S6).

Further, after noise components are removed from the amplified signal by a low-pass filter, it is determined whether or not pre-ignition has occurred (steps S7 and S8). If no pre-ignition has occurred, the injection is operated at the normal injection timing. On the other hand, if pre-ignition has occurred, the control signal AB is corrected and output so that the air-fuel injection end timing is retarded, and the engine is operated in the retarded state (step 39). , 310).

In this way, in this example, when pre-ignition occurs, the end timing of air-fuel injection is delayed.
Fuel is injected even in the latter half of the compression stroke when the temperature of the electrode 18a portion of the spark plug 18 tends to rise, and this fuel can cool the electrode 18a and suppress the temperature rise, thereby suppressing the occurrence of pre-ignition. Here, when the method (R2) of retarding only the injection end timing is adopted, the injection time is extended and the injection amount is increased, so that the cooling effect is further improved.

Also, if knocking occurs, its intensity.

Since the injection timing of the air fuel is retarded depending on the situation, the fuel is injected when the cylinder pressure increases. Therefore, the difference between the cylinder internal pressure and the fuel injection pressure becomes smaller, and the penetration force of the spray becomes weaker, making it difficult for the fuel to diffuse inside the cylinder.As a result, the amount of end gas ordered decreases, and as a result, knocking is suppressed. be done. Furthermore, if only the injection timing is retarded while the ignition timing remains the same, the time from when the air-fuel is injected to the ignition, that is, the time during which the fuel can diffuse, will be shortened, and from this point of view as well, the diffusion of the fuel will be suppressed. The amount of end gas generated is reduced, and as a result, knocking is suppressed. Furthermore, since the fuel injection timing is retarded, the scavenging airflow within the cylinder is attenuated, and from this point of view as well, fuel diffusion is suppressed.

In the above embodiment, the fuel injection end timing is retarded when either pre-ignition or knocking occurs, but in the present invention, it is not necessarily necessary to retard the timing in both cases. In this case, it is possible to respond only by adjusting the ignition timing, and in the case of pre-ignition, it can also be responded to by retarding the fuel injection end timing.

Further, in the above embodiment, a case has been described in which fuel is injected together with compressed air, but the present invention is of course applicable to a type of engine in which only fuel is injected.

〔Effect of the invention〕

As described above, according to the fuel injection control device for a two-stroke engine according to the present invention, at least the end timing of fuel injection is retarded when pre-ignition or knocking occurs, so that the spark plug is connected to the hot point. This has the effect of preventing pre-ignition from occurring and suppressing noaking by reducing the amount of end gas generated.

[Brief explanation of the drawing]

1 to 5 are diagrams for explaining a fuel injection control device according to an embodiment of the present invention, in which FIG. 1 is a configuration diagram thereof, FIG. 2 is a characteristic diagram showing its fuel injection timing, and FIG. Figure 3 is a cross-sectional side view of a two-stroke engine, Figure 4 (al
, (bl, tel are crank angle-cylinder pressure characteristic diagrams, respectively, and FIG. 5 is a flowchart diagram. In the figure, 1 is a two-stroke engine, 3a is a cylinder, 18 is a spark plug, and 22 is a fuel injection Valve (fuel injection device), 23 is a pressure sensor (pressure detection means), 24 is ECU
(injection timing correction means), a is a detected pressure signal. Patent Applicant Yamaha Motor Co., Ltd. Agent Patent Attorney Tsutomu Shimofu Figure 1 Figure 2 Figure 4 Figure Full 7 - Figure 3 Figure 5

Claims (1)

[Claims] (1) In a two-stroke engine equipped with a fuel injection device that directly injects fuel into a cylinder and a spark plug that ignites the fuel injected from the injection device, the fuel that controls the injection timing and period of the fuel The injection control device includes a detection means for detecting the occurrence of pre-ignition or knocking, and an injection timing correction means for retarding at least the end timing of injection of fuel from the fuel injection device based on a detection signal from the detection means. A fuel injection control device for a two-stroke engine, comprising: