JPH0431649A - Injection controller of cylinder injection engine - Google Patents

Abstract

PURPOSE:To realize lean fuel by providing a fuel injection control unit to inject fuel intermittently in a cylinder by way of dividing fuel into a front step and a rear step, and providing an air injection control unit to inject air in a cylinder by way of dividing air into a front step and a rear step. CONSTITUTION:An air fuel injection device 19 installed on the upper part of each combustion chamber 1 of a cylinder head is constituted of a valve structure 19 to open and close an injection port of an air chamber 20a formed in an injection body 20 and a main fuel injection valve 22 to inject fuel in a fuel chamber 20b formed in the periphery of the air chamber 20a in a water cooling type two-cycle engine 1, and it is controlled by ECU 24 as an injection control device. At the time of this control, air and fuel are too spark-advanced by (t) more than usual at the time to start injection and injection completion time is made to be the same as usual, and subsequently, air is successively injected from the start of injection to the completion, and fuel is controlled to inject by way of dividing it in a front step and a rear step.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an injection control device for a direct injection engine that directly injects fuel into a cylinder together with compressed air, and particularly relates to an injection control device for a direct injection engine that injects fuel directly into a cylinder together with compressed air. Concerning improvements in air and fuel injection methods.

[Conventional technology]

In general, in a gasoline engine, as shown in Figure 7, the amount of nitrogen oxides (NOx) in the exhaust gas reaches its maximum near the stoichiometric air-fuel ratio (A/F-14, 8), and when the air-fuel ratio is increased beyond this, (for example, A/F-18 to 20), it decreases significantly.

This lean combustion also improves thermal efficiency, reduces the amount of fuel required, and improves fuel efficiency. Therefore, the exhaust gas is purified,
In addition, in order to improve the fuel efficiency rate, it is necessary to achieve the above-mentioned lean combustion.

By the way, there is a direct injection engine that directly injects fuel into a cylinder together with compressed air. FIG. 5 shows a combustion chamber portion of a bay injection type two-stroke engine. In this engine, an air-fuel injection device 32 is mounted on a cylinder head 31 that covers the upper surface of a cylinder body 30 so as to face a combustion chamber 33. In this engine, as shown in FIG. 6, the air-fuel injection device 32 injects fuel continuously from the injection start time to the end time with the same injection timing and injection period as air. An ignition plug (not shown) ignites a mixture 34 of the fuel and outside air supplied into the cylinder 30a via a scavenging boat.

[Problem that the invention seeks to solve]

In order to reduce the amount of NOx produced and improve the fuel efficiency in the direct injection engine, it is effective to increase the A/F and perform the lean combustion described above. Above mixture 3
It is possible to increase the A/F in step 4 by advancing the injection timing and increasing the mixing time with the outside air supplied to the surrounding area, but if the A/F is extremely increased, the spark plug Sparks alone cannot ignite; some kind of powerful ignition source is required.

The present invention has been made in view of the above circumstances, and provides an injection control device for a direct injection engine that can reduce the amount of NOx produced and improve the fuel efficiency by ensuring an ignition source and enabling lean combustion. is intended to provide.

[Means for Solving the Problems] The present invention provides an injection control device for a direct injection engine that directly injects fuel together with compressed air into a cylinder.
A fuel injection control means that divides fuel into a front stage and a rear stage and injects the fuel into the cylinder intermittently; and an air injection valve that divides the air into the front stage and the rear stage and injects the air intermittently or continuously from the front stage to the rear stage. It is characterized by comprising an air injection control means for injecting air into the cylinder.

Here, various aspects can be adopted for the injection timing of the front stage and the rear stage in the present invention. For example, compared to the conventional injection timing, ■ advance the injection start time of the front stage, and ■ advance the injection start time of the front stage. At the same time, the injection end timing of the subsequent stage can be delayed.

[Effect]

According to the injection control device according to the present invention, since the fuel is divided into the front stage and the rear stage and injected, for example, the injection timing of the front stage is set to a relatively early stage, and the injection timing of the rear stage is set immediately before ignition. This enables the lean combustion described above. In other words, the fuel injected in the first stage mixes with a large amount of surrounding outside air because it takes a long time to ignite and the distance it travels is long because the cylinder pressure is low. The mixture becomes a lean mixture and is widely distributed within the combustion chamber, and then the fuel injected at the later stage is distributed inside the lean mixture Q at a relatively high concentration that can be ignited. If ignition is performed in this condition,
The high-concentration mixture ignites and becomes a fully developed flame, which causes the lean mixture to also burn. Therefore, the more the injection timing in the first stage is advanced, the leaner the combustion becomes, and the closer the injection timing in the latter stage is to the ignition timing, the more reliable the flame source becomes.

In this way, in the present invention, the highly concentrated mixture is located within the lean YiI mixture, making it possible to achieve lean combustion as a whole, lowering the combustion temperature, reducing the amount of NOx formed, and improving thermal efficiency. This reduces the amount of fuel required and improves fuel efficiency.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 to 3 are diagrams for explaining an injection control device for a direct injection two-stroke engine according to an embodiment of the present invention, and FIG. Figure (bl is the injection waveform diagram, Figure 2 is air.

A fuel injection timing diagram, FIG. 3 is a cross-sectional side view of an engine in which this embodiment is adopted.

In the figure, reference numeral 1 denotes a water-cooled two-stroke parallel three-cylinder engine configured to directly inject air and fuel into the cylinders. It has a structure in which cylinder bodies 3 formed in parallel in the axial direction are mounted and fixed with bolts, and a cylinder head 4 is fixed on the cylinder body 3 with bolts.

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. The electrode portion 18a of the spark plug is inserted into the combustion chamber 17. The piston 5 is connected to the crankshaft 6 via the stove 7 door 6b, and the crank arm 6a portion of the crankshaft 6 is housed in the crank chamber 2a, and the rear side of the crank chamber 2a is An intake port 2b for introducing outside air is formed. 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. Note that 3b is an exhaust boat, and 16 is an exhaust manifold.

An air-fuel injection device 19 is installed in the upper portion of each combustion chamber 17 of the cylinder head 4, respectively. Each air-fuel injection device 19 mainly includes an injection body 20 inserted and fixed into the cylinder Rad 4, and a valve mechanism 21 that opens and closes an injection port of an air chamber 20a formed in the injection body 20 using a pulp 21a. , the above injection body 2
The main fuel injection valve 22 is attached to the rear side of the outer wall of the engine 0 and injects fuel into the fuel chamber 20b formed around the air chamber 20a. Note that the injection port of the fuel chamber 20b is located at the valve seat of the valve 21a. Also 14
14a is a fuel rail for supplying fuel, and 14b is an air rail for supplying compressed air.

24 is an ECU as an injection control device that controls the operation of the air-fuel injection device 19, and functions as an air injection control means for injecting air according to the injection waveform b1 of the first output of air by the valve mechanism 21. , fuel injection valve 2
2 functions as a fuel injection control means for injecting fuel along the injection waveform C1 or dl. Note that the injection waveform CI is an example in which the front stage is short and the i stage is long, and the injection waveform di is an example in which the front stage is short and the rear stage is short.

Next, the effects of this embodiment will be explained.

In the conventional device, air and fuel are continuously injected at the same timing and period, as shown by the injection waveform a in FIG.
The CU 24 controls the valve mechanism 21 so that the air is injected along the injection waveform bl (the first time), and controls the fuel injection valve 22 so that the fuel is injected along the injection waveform c1 or di.
control so that it is injected along the That is, the injection start timing for both air and fuel is advanced by t compared to the conventional one, and the injection end timing is the same as the conventional one. Air is injected continuously from the start to the end of the injection, and fuel is injected into the front stage cB and the rear stage cA, or the front stage dB, the rear stage d71. It is divided and sprayed. In addition, Fig. 2 shows the above-mentioned injection timing in terms of crank angle.
bl indicates the timing in the medium speed operation region.

Since the preceding stage cB, dB or dB' is advanced,
Fuel injected in this first stage takes a long time to ignite, so sufficient mixing time can be obtained, and since it is injected when the cylinder pressure is low, the fuel can reach farther and interact with the surrounding outside air. They are mixed to form a lean mixture B, which enters the combustion chamber 17.
It is widely distributed within the country. On the other hand, the fuel injected at the later stage cA, dA, or dA' takes a short time to ignite and does not reach a sufficient distance, and is not sufficiently mixed with the outside air around the NE, resulting in a relatively high concentration air-fuel mixture. A, and is located at the center of the lean mixture B, that is, near the electrode portion 18a of the spark plug 18. When ignition is performed by the spark plug 18 in this state, the high concentration mixture A is ignited, and the surrounding lean Fl mixture B is also reliably combusted by the flame.

In this embodiment, the fuel injection is divided into the first stage and the second stage, and the highly concentrated mixture A is distributed near the electrode part 18a of the spark plug, and the lean mixture B is distributed around it.
Since the NOx is widely distributed, lean combustion is performed as a whole, and the amount of NOx produced is reduced. Furthermore, the amount of fuel required is reduced due to the lean combustion, which improves fuel efficiency.

In the above embodiment, the air-fuel injection end timing is made to match that of the conventional one, but this is different from the injection waveform b2. in FIG. 4. c.
2. As shown in d2, the injection start timings of the first stages 02B and d2B may be advanced by t1, and the injection end times of the second stages c2A and d2A may be delayed by t2.

Further, in the above embodiment, the compressed air is continuously injected, but the compressed air may be configured so that it is injected over the entire fuel injection period, and does not necessarily need to be injected continuously. Therefore, for example, it may be divided into an earlier stage and a later stage according to the fuel injection, and in this case, the compressed air injection period may be longer than the fuel injection period.

Furthermore, in the above embodiment, a simultaneous injection type engine was described in which air and fuel are injected separately and simultaneously into the cylinder, but in the case of the front-stage injection in the present invention, fuel is injected in advance into a chamber and mixed with air. It can also be applied to a so-called precharge type in which the fuel is injected into the cylinder.

Further, in the above embodiment, a case of a two-stroke engine was explained, but the present invention can also be applied to a four-stroke engine.

〔Effect of the invention〕

As described above, according to the engine injection control device according to the present invention, the fuel is divided into the front stage and the rear stage and injected, so that a part of the combustion chamber is provided with a mixture having a concentration that can be ignited by the spark plug. At the same time, the lean air-fuel mixture can be widely distributed around the high-concentration air-fuel mixture, thereby realizing lean combustion, reducing the amount of NOx produced, and improving the fuel efficiency.

[Brief explanation of drawings]

Figures 1 to 3 show an injection control system for a direct injection two-stroke engine according to an embodiment of the present invention! FIG. 1 (tal) is a schematic diagram of the combustion chamber, FIG. 2 (a)7 is a diagram showing the injection waveform, and FIG. 3 is a cross-sectional side view of the engine according to the embodiment, FIG. 4 is a diagram showing a modified example of the injection waveform, FIGS. 5 to 7 are diagrams for explaining conventional problems, and FIG. FIG. 5 is a configuration diagram of the combustion chamber portion, FIG. 6 is an injection waveform diagram, and FIG. 7 is an A/F-Nox characteristic diagram. In the figure, 1 is a cylinder injection engine, and 3a is a cylinder (
21 is a pulp mechanism (air injection valve), 22 is a fuel injection valve, 24 is an ECU (fuel injection control means, air injection control means), cA, dA. c2A and d2A are rear stages, and cB, dB, c2B, and d2B are front stages. Patent Applicant Yamaha Motor Co., Ltd. Agent Patent Attorney Tsutomu Shimofu ■ Figure 4

Claims (1)

[Claims] (1) In an injection control device for a direct injection engine that directly injects fuel together with compressed air into a cylinder, there is provided a fuel injection control means that divides fuel into a front stage and a rear stage and intermittently injects the fuel into the cylinder. An injection control device for a direct injection engine, comprising: air injection control means for dividing air into the front stage and the rear stage and injecting the air into the cylinder intermittently or continuously from the front stage to the rear stage. .