JPH02298636A - Fuel injection type engine - Google Patents

Abstract

PURPOSE:To prevent fuel from spitting and blowing-by by previously setting an area in which a predetermined engine speed area and a throttle valve opening area are overlapped each other as an area in which injected fuel is not taken in smoothly and changing injection start timing in this area. CONSTITUTION:An air intake pipe 26 is connected via a reed valve 28 to an air intake port 30 opened at the side wall of the cylinder 12 of a 2 cycle internal combustion engine 10, and an electromagnetic type fuel injection valve 44 and a shutter type throttle valve 52 are provided at the air intake pipe 26. A pressure detector 50 as an intake air quantity detecting means, a potentiometer 54 for detecting the opening theta of a throttle valve, the rotational speed N of a crankshaft 20 and a rotational speed detecting means 56 for detecting a crank angle alpha are provided and output signals therefrom are input to a control unit 58. In an area in which a predetermined engine speed area and a predetermined throttle valve opening area are overlapped each other, i.e., an area wherein injected fuel is not intaken in smoothly, injection opening timing is changed to prevent the fuel from spitting.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention injects fuel (gasoline, etc.) into the intake airflow upstream of the combustion chamber, such as in the intake passage or scavenging passage, and The invention relates to a fuel-injected engine that ignites.

(Background of the Invention) A fuel injection engine is known that injects fuel (such as gasoline) into intake air, draws a mixture into a combustion chamber, and ignites it with an ignition plug. Conventionally, in this type of engine, the intake air amount is detected using an air flow meter or the like, and the fuel injection time width is changed depending on the intake air amount, but the injection start timing is set at a constant crank angle. That is, it is a scheduled injection method in which injection starts at a constant crank angle, and the injection end point is controlled to vary depending on the amount of intake air.

However, in this case, depending on the operating conditions of the engine, the fuel may not be sucked in smoothly, and the fuel may be blown out to the upstream side of the intake pipe. For example, during high-speed operation, the intake timing and the intake pulsation are not necessarily synchronized, and this timing difference also changes depending on the slot valve opening. This problem becomes particularly important when fuel is injected separately for each cylinder, and is particularly noticeable in racer engines in which the throttle valve is directly exposed to the atmosphere without using an air cleaner.

On the other hand, some two-stroke engines inject fuel into the scavenging passage, but the injection start timing is usually determined to prevent fuel from blowing through. However, because the crank angle at which intake air blow-through occurs varies depending on operating conditions such as rotational speed and throttle valve opening, it has been difficult to completely prevent fuel blow-through under all operating conditions.

As described above, when fuel blows back or blows through, there arises a problem of poor fuel efficiency. In addition, in a two-stroke engine, especially in the case of a mixed lubrication system, such blowback or blow-through can make the supply of lubricating oil unstable.

(Purpose of the Invention) The present invention was made in view of the above circumstances, and it is possible to improve fuel efficiency by preventing fuel from blowing back or blowing through, and when applied to a mixed lubrication type two-stroke engine, it is possible to improve lubrication. The purpose of the present invention is to provide a fuel injection type engine that can improve reliability.

(Structure of the Invention) According to the present invention, it is an object of the present invention to provide a fuel injection engine that is equipped with an intake air amount detection means, a crank angle detection means, and a control device that determines an injection amount according to the intake air amount. A fuel injection device comprising speed detection means and throttle opening detection means, wherein the control device changes the fuel injection start timing within a range surrounded by a predetermined engine speed range and a predetermined throttle opening range. 6 Achieved by injection type engine (Example) Fig. 1 is an overall system diagram of an embodiment of the present invention, Fig. 2 is a control characteristic diagram based on injection time, and Fig. 3 is a diagram showing injection timing. .

In FIG. 1, reference numeral 10 is a two-stroke internal combustion engine with preloaded crank chamber, 12 is a cylinder, 14 is a piston, 16 is a spark plug, 18 is a crankcase, 20 is a crankshaft, 22
is a connecting rod. A crank chamber 24 is formed within the crankcase 18 .

26 is an intake pipe, and this intake pipe 26 is connected to the intake boat 30 via a reed valve 28. 32 is an exhaust boat, and 34 is an exhaust pipe.

36 is a scavenging boat, and this scavenging boat 36 communicates with the crank chamber 24 through a scavenging passage 38.

40 is a fuel tank, and 42 is an electric fuel pump. 4
Reference numeral 4 denotes an electromagnetic fuel injection valve, and fuel pumped from a fuel pump 42 is supplied to this injection valve 44 . Reference numeral 46 denotes a pressure regulator, which keeps the pressure of the fuel fed from the fuel pump 42 to the injection valve 44 constant. That is, the fuel pump 42
When the fuel pressure supplied to the injection valve 44 exceeds a predetermined pressure, the pressure regulator 46 opens and a portion of the fuel is circulated to the fuel tank 40 via the vibrator 48 .

50 is a pressure detection device attached to the crankcase 18, which detects the internal pressure P of the crank chamber 24, and detects the internal pressure P.
outputs an electric signal of a voltage corresponding to , that is, a voltage signal p. In this embodiment, the intake air amount is detected based on the internal pressure P of the crank chamber 24, and therefore, in this embodiment, the pressure detection device 50 forms the intake air amount detection means.

Reference numeral 52 denotes a shutter type throttle valve that moves up and down from above within the intake pipe 26 to change the area of the intake passage. The throttle valve 52 opens and closes in conjunction with, for example, a driver's operation of a throttle lever. 54 is a potentiometer for determining the throttle valve opening degree θ. Reference numeral 56 denotes a rotational speed detection means for detecting the rotational speed N and crank angle α of the crankshaft 20, which detects a magnet fixed to the crankshaft 20 using a coil, for example.

Reference numeral 58 denotes a control device comprised of a microcomputer, into which various signals such as crank chamber pressure p, rotational speed N, crank angle α, throttle opening θ, or engine temperature T are input. The control device 58 determines the optimal fuel injection amount corresponding to the operating condition based on these various input signals,
The fuel injection valve 44 calculates the injection time for this injection amount.
Open the valve. For example, under operating conditions in which the amount of fluctuation in the crank chamber pressure P corresponds well to the amount of intake air, the injection time is determined based on this internal pressure P and the rotational speed N. (at the time of opening), control is performed to correct it by the throttle valve opening θ, etc. Here, the control device 58 has a built-in memory 58A, and this memory 5
8A, the characteristics at the optimum injection time are stored in advance in accordance with the operating conditions.

In addition, the memory 58A of the control device stores a range of certain operating conditions indicated by diagonal lines in FIG. Under operating conditions that do not occur, normal scheduled injection is performed. For example, as shown in Figure 3A, top dead center (
Injection is started at a crank angle of α1 before TDC), and the injection valve is opened for an injection time determined according to the operating condition (TDC).
The diagonally shaded range in the figure is the range where the fuel injected from the injection valve 44 cannot be smoothly sucked into the intake pipe 26 during low-load, high-speed operation and is sprayed back, and the engine operating conditions fall within this range. and the control device 58 changes the injection start timing. For example, as shown in FIG. 3B, the injection start timing is advanced to 02 to prevent fuel from spraying back. The injection time τ2 at this time is determined depending on the operating state.

In this embodiment, the amount of intake air is determined based on the crank chamber pressure P, but it goes without saying that in the present invention, an air flow meter may be provided in the intake pipe to detect the amount of intake air.

In addition, in this embodiment, the engine rotation speed and crank angle α
are detected by a common rotational speed detection means 56, but it goes without saying that they may be detected by separate detectors.

In addition, in this embodiment, a fuel injection valve is installed near the throttle valve, and the injection start timing is changed to prevent fuel from being sprayed back from the intake pipe, but it can also be applied to an engine that injects fuel into the scavenging passage of a two-stroke engine. can. In this case, the injection start timing is determined to prevent the fuel from blowing through the combustion chamber together with the fresh air.

Furthermore, the present invention is applicable not only to 2-stroke engines but also to 4-stroke engines, and includes these.

(Effects of the Invention) As described above, the present invention presets the range where the predetermined engine speed range and the predetermined throttle valve opening range overlap as the range in which the injected fuel is not sucked smoothly. While normal scheduled injection is performed, starting at a predetermined crank angle, the injection start timing is changed within this range to prevent fuel from blowing back or blowing through, which reduces wasteful fuel consumption. This makes it possible to improve fuel efficiency. Furthermore, when applied to a mixed lubrication type two-stroke engine, lubricating oil can be supplied smoothly and lubrication reliability can be improved.

[Brief explanation of the drawing]

FIG. 1 is an overall system diagram of an embodiment of the present invention, FIG. 2 is a control characteristic diagram with respect to injection time, and FIG. 3 is a diagram showing injection timing. 44... Fuel injection valve, 50... Pressure detection device as intake air amount detection means, 52... Throttle valve, 54... Potentiometer as throttle opening detection means, 56... Engine rotation speed Detection means, 58...control device.

Claims (1)

[Scope of Claims] A fuel injection engine comprising an intake air amount detection means, a crank angle detection means, and a control device that determines an injection amount according to the intake air amount, the engine rotation speed detection means and a throttle opening degree. Detecting means, wherein the control device changes the fuel injection start timing within a range defined by a predetermined engine speed range and a predetermined throttle opening range.