JPH03134244A - Fuel injection engine - Google Patents

Abstract

PURPOSE:To highly accurately control a small injection amount without using a high accurate injection valve by changing an opening time of the injection valve in accordance with the injection amount, at the time of high and intermediate load operations, and opening the injection valve by a number of times smaller than that in a plurality of cycles at the time of low load operation. CONSTITUTION:At the time of high and intermediate load operations, since an injection amount is increased with also a long injection time width, injection valves 40a, 40b are enabled to follow-up open-close timing with injection performed intermittently one time or a plurality of times in the predetermined timing in one cycle of an engine 10. Further at the time of high speed high load operation, the respective injection amount is reduced with improvement contrived of fuel consumption. At the time of low load operation with a throttle valve opening in not more than a fixed value, since an injection time, determined by a control unit 62, is decreased, the injection valves 40a, 40b are disabled from responding to this short injection time. Then at the time of low load operation where the throttle valve opening is decreased to not more than the predetermined value, injection is performed by thinning its number of times without corresponding to 1 cycle of the engine 10 in a range from the predetermined speed lower than an idling speed to a high speed side.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fuel injection engine that injects fuel (such as gasoline) into an intake air stream upstream of a combustion chamber and ignites it with a spark plug. .

(Background of the Invention) Two-cycle and four-cycle fuel injection engines are known that inject fuel (such as gasoline) into intake air, draw a mixture into a fuel chamber, and ignite the mixture with a spark plug. In conventional engines of this type, the intake air amount is detected using an air flow meter or the like, and the fuel injection amount is controlled based on this intake air amount. Here, the injection amount is controlled by changing the opening time width of the injection valve. In this case, the opening time width of the injection valve must be sufficiently short during low-load operation where the amount of intake air is small, especially during high-speed operation. However, the injection valve has a controllable minimum injection time width, and it has not been possible to limit the injection amount below the injection amount corresponding to this minimum injection time width. Furthermore, if an attempt is made to use the injection valve near this minimum injection time width, there is a problem in that highly accurate control of the injection amount becomes impossible.

On the other hand, it may be possible to use an injection valve with a sufficiently small minimum injection time width, but in this case, the control range of the injection amount would be very large, so the machining accuracy of the injection valve would have to be significantly improved, making it expensive. The problem arises that

(Object of the Invention) The present invention has been made in view of the above circumstances, and it is possible to control a small injection amount with high precision without using a high-precision injection valve with a significantly small minimum injection time width. The purpose is to provide a fuel-injected engine.

(Structure of the Invention) According to the present invention, it is an object of the present invention to provide a fuel injection engine equipped with a control device that determines an injection amount according to an amount of intake air. and a fuel pressure regulator that lowers the fuel pressure supplied to the fuel injection valve according to an increase in fuel pressure, and the control device opens the injection valve at a predetermined timing within one cycle of the engine during high/medium load operation, and adjusts the amount valve time width. While changing depending on the injection amount,
This is achieved by a fuel-injected engine characterized in that during low-load operation, the fuel injection valve is opened less than this number of cycles within a plurality of engine cycles.

(Embodiment) FIG. 1 is an overall configuration diagram of an embodiment of the present invention, FIG. 2 is a diagram showing the injection timing of the injection valve, and FIG. 3 is a control characteristic diagram of the injection amount M.

In Fig. 1, 10 is a crank chamber preload type 2-cycle 2
It is a cylinder engine and has two cylinders 12 and an upper cylinder 14. Each cylinder 12.1 in one common crankcase
Four crank chambers 16 and 18 are independently formed. 2
o is a crankshaft, and the pistons of each cylinder are connected to this crankshaft 2o by connecting rods.

Reference numeral 22 denotes an electric fuel pump, for example, a roller pump, which pumps fuel from the fuel tank 24 to a fuel injection valve 4o, which will be described later.

26 (26a, 26b) are shutter type no-throttle valves. Both throttle valves 26 are made almost symmetrically,
Each is connected to the crankcase by a rubber joint 28 (28a, 28b). Note that a reed valve is installed at the connection between the joint 28 and the crankcase. The throttle body 30 (30a, 30b) of each throttle valve 26 is attached to the valve plate 32 (30a, 30b) from above.
32a, 32b) are attached so that they can be raised and lowered. Rotation of a throttle grip (not shown) provided on the steering handle is controlled by levers 34 (34a, 34b),
Valve plate 32 by link 36 (36a, 36b)
is transmitted to move the valve plate 32 up and down. Throttle valve 26
The opening degree θ is detected by a potentiometer 38 attached to the right side of the right throttle valve 26b.

Electromagnetic fuel injection valves 40 (40a, 40b) are attached to each of these throttle bodies 30, and these inject fuel obliquely toward the intake flow direction from near the lower edge of the valve plate 32. These fuel injection valves 40 are of a so-called bottom-feed type, in which fuel is supplied from the side toward the injection port side rather than the electromagnetic coil. Fuel, which is pressure-fed from the fuel pump 22, is distributed and guided to the left and right sides by a delivery pipe to the fuel injection valves 40 of both cylinders.

42 (42a, 42b) is a fuel pressure regulator, which adjusts the fuel pressure fed from the fuel pump 22 to the injection valve 4o to a predetermined pressure determined by the intake negative pressure of each cylinder 12.14. That is, when the fuel pressure supplied from the fuel pump 22 to the injection valve 40 exceeds a predetermined pressure determined by the intake negative pressure, part of the fuel is circulated to the fuel pump 24.

This regulator 42 includes a diaphragm 44 (44a,
44b), an intake negative pressure chamber 46 (46a, 46b) and a fuel pressure chamber 48 defined by this diaphragm 44.
(48a, 48b). The intake negative pressure chamber 46 includes pipes 47 (47a, 47b) as intake negative pressure detection means.
Intake negative pressure is guided by. The fuel pressure chamber 48 is communicated with a pipe connecting the fuel pump 22 and the injection valve 40.
The fuel pressure of the injection valve 40 is guided. diaphragm 44
k: pressure m spring 50 (50a, 50b) &, ll;
t) A return force is applied to the fuel pressure chamber 48 side. Further, a fuel pressure adjustment nozzle 52 (52a, 52b) faces the diaphragm 44 from within the fuel pressure chamber 48, and the diaphragm 44
4 serves as a flapper that approaches and separates from this nozzle 52, forming a known flapper-nozzle type pressure adjustment mechanism.

Therefore, when the fuel pressure increases beyond a predetermined level, the pressure in the fuel pressure chamber 48 increases, and the diaphragm 44 compresses the spring 50 and is displaced, opening the nozzle 52. Since the intake negative pressure is guided to the negative pressure chamber 46, when the intake negative pressure increases, the fuel pressure at which the nozzle 52 starts to open becomes lower.

Generally, when the load is low, the fuel injection time becomes significantly short, and there are cases where the injection amount cannot be controlled solely by the injection time due to the limit of the responsiveness of the fuel injection valve 40. According to this embodiment, in this case, as will be described later, the number of injections of the fuel injection valve 40 is thinned out, and the injection amount is reduced by lowering the fuel pressure, so it is necessary to improve the responsiveness of the fuel injection valve 40. This eliminates the need for expensive fuel injection valves and enables highly accurate control. Furthermore, if the throttle valve 26 is suddenly closed during high-speed operation, the fuel injection amount will also sharply decrease and the fuel pressure will temporarily increase. However, according to this embodiment, the fuel pressure regulator 42 detects the intake negative pressure. Since the fuel pressure is quickly released, accurate control of the injection amount is possible at all times. When the diaphragm 44 leaves the nozzle 52 while compressing the spring 5o in this manner, the fuel in the fuel pressure chamber 48 is returned from the nozzle 52 to the fuel cylinder 22.

Note that the two fuel pressure regulators 42 are both attached to the outer surface of the throttle body 30 and are close to the fuel injection valve 40, so that highly accurate control of the injection pressure is possible.

54 (54a, 54b) is a pressure detector for detecting the internal pressure of the crank chamber 16.18, and is attached to the vehicle body frame via a rubber tamper.

These pressure detectors 54 are communicated with the left and right outer surfaces of the crankcase through vibrators 56 (56a, 56b), detect the internal pressure of the crank chamber 16, 18, and output electrical signals p8, pb corresponding to this internal pressure.

Note that each pipe 56 is provided with an air check valve 58 (5
8a, 58b) are attached (Fig. 1). This check valve 58 only allows outside air to flow into the pipe 56 and prevents the air-fuel mixture in the crank chamber 16, 18 from flowing into the pressure sensor 54.

A rotation speed detector 60 detects the rotation speed N of the crankshaft 2o and the ignition timing signal α.

62 is a control device composed of a microcomputer. This control device 62 has the throttle opening degree θ,
Signals such as crank chamber pressures pa and pb, rotational speed N, and ignition timing signal α are input. Further, various signals such as engine temperature T, engine acceleration/deceleration, engine brake, etc. may be input for control.

The control device 62 determines the optimum fuel injection amount M corresponding to the operating state based on these various input signals, determines the injection time for this injection amount M, and opens the solenoid valve of the fuel injection valve 40. Here, the control device 62 has a built-in memory 62A,
The characteristic of the optimum injection amount M shown in FIG. 3 is previously stored in the memory 62A in the form of an arithmetic expression or map, and the injection amount M is determined. During high/medium load operation, the injection amount M is large and the injection time width t is long, so the injection valve 40 can follow the opening and closing timing of the injection valve 40. Injection is performed intermittently once or multiple times at a fixed timing within the revolution. Figure 2 A shows one cycle β of the engine.
The figure shows that one injection is performed at a predetermined timing within the range of injection time width (t+, tz, . . . ) corresponding to the injection amount M.

Here, the characteristics of the optimum injection amount M shown in FIG. 3 will be explained. Figure 3 shows the optimum injection amount M for the rotational speed N and crank chamber pressure P. In this figure, the diagonally shaded portions ABCD and ABEF indicate the correction amounts due to temperature, atmospheric pressure, etc.
The part indicated by indicates the amount increased in the low speed rotation range. This increase in the low speed rotation range is suitable for increasing the engine output (low speed torque) at low speeds and obtaining engine output characteristics particularly suitable for trial competitions. Furthermore, the MNOPQR portion reduces the injection amount during high-speed, high-load operation, and the STU portion reduces the injection amount during high-speed, low-load operation to improve fuel efficiency.

When the load is low and the throttle valve opening θ is below a certain level, the injection time determined by the control device 62 becomes shorter. This makes the injection valve 40 unable to respond to this short injection time.

In this embodiment, the throttle valve opening θ is θ. At low load with the following opening degrees, the number of injections n is thinned out and injected in the range on the higher side of the speed N0 lower than the idling speed Nad, that is, the area surrounded by abcdUSTF, without making it correspond to one cycle of the engine. be.

Figures 2B and 2C show this situation. That is, the injection quantity is reduced by setting the number of injections n in the χ cycle of the engine to n<χ. Here, in the embodiment shown in FIG. 2B, the injection intervals are set at equal intervals, and in the embodiment shown in FIG. 2C, injection is stopped once every several cycles (for example, 3 cycles) to thin out the injection. In this figure, the thinned out injections are shown by phantom lines. Here, in FIGS. 2B and 2C, it is desirable that the time width t of one injection is a constant time width to that is reasonable for the injection valve 40; may be changed as appropriate depending on the load.

On the other hand, during low load operation, the fuel pressure regulator 42 lowers the fuel pressure and reduces the injection amount. That is, as the throttle valve opening θ decreases, the negative pressure in the intake pipe decreases, and accordingly, the diaphragm 44 compresses the spring 50, and the diaphragm 44 separates from the nozzle 52. Therefore, the fuel in the fuel pressure chamber 48 flows back to the fuel tank 24 from this nozzle 52, and the fuel pressure applied to the injection valve 40 decreases. As a result, the injection amount will decrease.

Note that the fuel pressure regulator of the present invention is not limited to this embodiment, and may be one that controls fuel pressure by opening and closing a solenoid valve without using a diaphragm. In this case, the optimum fuel pressure control characteristic may be stored in advance and, using this control characteristic, the optimum fuel pressure may be determined based on the intake negative pressure, the throttle valve opening, the engine rotation speed, etc. A sensor for detecting fuel pressure is provided here, and control can be performed so that the detected fuel pressure becomes the fuel pressure determined from the stored control characteristics.

Further, in this embodiment, the fuel pressure is controlled by detecting the negative pressure in the intake pipe (intake pipe negative pressure), but it is also possible to use a negative pressure equivalent to this, such as crank chamber pressure, scavenging passage internal pressure, etc.
The present invention includes such things.

The present invention is also applicable to a 4-stroke engine,
The amount of intake air may be detected by means such as an air flow meter.

(Effects of the Invention) As described above, the present invention thins out the number of injections so that injection is performed less than this number of cycles within multiple cycles of the engine during low load operation when the injection amount is small (i.e., low load operation). Since the fuel pressure is lowered in response to an increase in intake negative pressure, it is possible to perform highly accurate control of minute injection amounts without reducing the injection time width of the injector. Therefore, there is no need to use expensive injection valves.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of an embodiment of the present invention, FIG. 2 is an injection timing diagram of an injection valve, and FIG. 3 is a characteristic diagram showing the injection amount M with respect to operating conditions. DESCRIPTION OF SYMBOLS 10... Engine, 40... Fuel injection valve, 42... Fuel pressure regulator, 47... Pipe as negative pressure detection means, 62... Control device.

Claims (1)

[Scope of Claims] A fuel injection engine equipped with a control device that determines an injection amount according to an amount of intake air, comprising: negative pressure detection means for detecting intake negative pressure; and a fuel pressure regulator that lowers the fuel pressure supplied to the engine, and the control device opens the injection valve at a predetermined timing within one cycle of the engine during high/medium load operation, and changes the valve opening time width according to the injection amount, A fuel injection type engine characterized in that during low load operation, the fuel injection valve is opened a number of times less than this number of cycles within a plurality of engine cycles.