FUEL SUPPLY CONTROL SYSTEM FOR V-TYPE TWO-CYLINDER GENERAL PURPOSE ENGINE

Abstract

A fuel supply control system for a V-type two-cylinder general purpose engine according to the present disclosure, in a V-type two-cylinder general purpose engine including one fuel injection valve in a throttle body disposed upstream via an intake manifold connected to a cylinder head of each cylinder, changes an injection frequency or an operation timing of the fuel injection valve in accordance with an engine operation state detected by a detection unit.

Claims

1. A fuel supply control system for a V-type two-cylinder general purpose engine, comprising a fuel injection valve in a throttle body disposed upstream via an intake manifold connected to a cylinder head of each cylinder, wherein, in the fuel supply control system, an injection frequency or an operation timing of the fuel injection valve is changed in accordance with an engine operation state detected by a detection unit.

2. The fuel supply control system for a V-type two-cylinder general purpose engine according to claim 1, wherein the detection unit to detect the engine operation state includes an intake pressure sensor, an engine rotation sensor, an engine temperature sensor, and an oxygen sensor.

3. The fuel supply control system for a V-type two-cylinder general purpose engine according to claim 1, wherein in a case where an injection frequency of the fuel injection valve is once or twice, and a shift criteria is shifted from once to twice, an OR condition is applied, and in a case where the injection frequency of the fuel injection valve is shifted from twice to once, an AND condition is applied.

4. The fuel supply control system for a V-type two-cylinder general purpose engine according to claim 1, wherein in a case where an injection frequency of the fuel injection valve is twice, an injection is performed from an exhaust stroke to an intake stroke of each cylinder, and in a case where an injection frequency of the fuel injection valve is once, the injection starts in the middle of the intake stroke of each cylinder.

5. The fuel supply control system for a V-type two-cylinder general purpose engine according to claim 2, wherein in a case where an injection frequency of the fuel injection valve is once or twice, and a shift criteria is shifted from once to twice, an OR condition is applied, and in a case where the injection frequency of the fuel injection valve is shifted from twice to once, an AND condition is applied.

6. The fuel supply control system for a V-type two-cylinder general purpose engine according to claim 2, wherein in a case where an injection frequency of the fuel injection valve is twice, an injection is performed from an exhaust stroke to an intake stroke of each cylinder, and in a case where an injection frequency of the fuel injection valve is once, the injection starts in the middle of the intake stroke of each cylinder.

7. The fuel supply control system for a V-type two-cylinder general purpose engine according to claim 3, wherein in a case where an injection frequency of the fuel injection valve is twice, an injection is performed from an exhaust stroke to an intake stroke of each cylinder, and in a case where an injection frequency of the fuel injection valve is once, the injection starts in the middle of the intake stroke of each cylinder.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0019] FIG. 1 is a sectional view illustrating a V-type two-cylinder general purpose engine to practice the present invention;

[0020] FIG. 2 is a simple block circuit diagram illustrating an operation state of a fuel injection by each type of sensors in the V-type two-cylinder general purpose engine illustrated in FIG. 1;

[0021] FIG. 3 is a diagram describing an example of the AND theory according to an embodiment of the present invention;

[0022] FIG. 4 is a diagram describing an example of the OR theory according to the embodiment of the present invention;

[0023] FIG. 5 is a relation diagram from an exhaust stroke to an intake stroke of each cylinder in the case where an injection frequency of a fuel injection valve according to the embodiment of the present invention is once and twice;

[0024] FIG. 6 is a relation diagram between a fuel injection flow rate and a fuel injection width in the embodiment of the present invention; and

[0025] FIG. 7 is a view describing a conventional example.

DETAILED DESCRIPTION

[0026] Next, a preferred embodiment of the present invention will be described.

[0027] Regarding an embodiment of the present invention, a configuration is same as in the V-type two-cylinder general purpose engine 2 illustrated in FIG. 1. One fuel injection valve 6 is included in the throttle body 5 disposed upstream via the intake manifold 4 connected to the cylinder heads 31 and 31 of the cylinders 3 and 3.

[0028] Then, in the embodiment, as illustrated in FIG. 2, a detection signal from an intake pressure sensor, an engine rotation sensor, an engine temperature sensor, and an oxygen sensor which is a detection unit to detect an engine operation state is received by an ECU, and an injection frequency or an operation timing of a fuel injection valve is changed in accordance with predetermined conditions.

[0029] Further, more specifically, engine load information is detected by the intake pressure sensor, and the ECU reflects the signal to a valve opening time of the fuel injection valve. In addition, an engine stroke is identified by the rotation sensor, and an injection is performed at a predetermined injection timing. The engine temperature sensor measures an engine warming-up state and is used to correct an extension of a valve opening time of an injection valve, for example, at cold start. As described above, the oxygen sensor is used to detect a concentration of a combustion exhaust gas during theoretical air-fuel ratio control.

[0030] In particular, in the control system, an injection frequency of a fuel injection valve is once or twice. As illustrated in FIG. 3, an engine operation is performed at an injection pattern in which an injection is performed once when three conditions are satisfied (an AND condition): when a load is light, in other words, when it is determined that a valve opening time of the fuel injection valve is short with respect to a predetermined threshold (or a value of an intake pressure sensor is low); when an rotation speed is an arbitrary speed; and when an engine is not in a transient response state (acceleration and deceleration).

[0031] Further, as illustrated in FIG. 4, when even one of the three conditions is not satisfied (an OR condition), the injection pattern is shifted to a pattern in which an injection is performed twice. As a result, a stable engine operation is realized without entering an immovable area on a small flow rate side of a fuel injection valve. Further, one type of the fuel injection valve can be used in small to large displacement engines.

[0032] FIG. 5 illustrates a preferred embodiment indicating a relation between an injection timing and an injection time when an injection is performed twice and once in intake/exhaust strokes of each cylinder. FIG. 6 indicates a relation between a fuel injection flow rate and a fuel injection width. A flow rate of a fuel injection valve is designed with a specification in which a maximum flow rate is required in engine variations. In the case where the fuel injection valve is used in the largest engine, an injection is performed twice in the whole of an engine operation area. In the case where the fuel injection valve is used in small or middle-sized engines, the injection is performed twice in an operation area in which relatively a large amount of fuels in a medium load area and a high load area is required. In a light load area, a flow rate during a minimum driving time of the injection valve which intermittently injects and supplies a fuel is excessively increased with respect to a required flow rate of an engine. Therefore, an engine operation becomes difficult. Specifically, a flow rate of a fuel to be supplied to each cylinder needs to be reduced.

[0033] Therefore, although a fuel has been injected and supplied twice to each cylinder, a fuel supply frequency is reduced to once, and a fuel is supplied to each cylinder at a total flow rate. As a result, a valve opening time of an injection valve can be extended to an available time.

[0034] An injection timing is synchronized with past intake timings of cylinders, and fuel supply is started in the middle to the end of an intake stroke of one of the cylinders. While forming an appropriate mixing ratio with respect to the cylinder, a valve close time with respect to another cylinder is also controlled. Consequently appropriate fuel supply is performed. As a result, a valve opening time of an injection valve certainly extends when an injection is performed once in comparison with the case where the injection is performed twice, and the same-type of a fuel injection valve can be used for middle and small-sized engines.

[0035] In an operation area with light to medium loads when the injection is performed once, an operation is performed at a theoretical air-fuel ratio. Consequently, a theoretical air-fuel ratio feedback control is performed by an oxygen sensor disposed in an exhaust pipe, and a stable engine operation is realized.

[0036] On the other hand, it is considered that the fuel injection valve is used in middle and small-sized engines, and the whole of an operation area is controlled by injecting once. However, generally an engine is often set in a state in which a fuel concentration is increased in comparison with a theoretical air-fuel ratio with medium to high loads in which output is needed. In this case, the theoretical air-fuel ratio feedback control using an oxygen sensor cannot be performed, and open loop control is performed.

[0037] In the case of the open loop control, a fuel injection valve operates based on a valve opening command from a rotation signal. Therefore, an injection timing may be changed due to each variation factor including an assembly variation of a rotation sensor on an engine side and a working variation of an engine cam.

[0038] The change during the opening loop control similarly affects in the case where an injection frequency is once in the case where the injection frequency is twice.

[0039] However, when the injection frequency is once, the change generally affects, in other words, directly affects a fuel supply amount to both cylinders. When the injection frequency is twice, the change is slightly caused between exhaust strokes or intake strokes of each cylinder and does not much affect the cylinder.

[0040] Therefore, in comparison with the case where the whole area is controlled by injecting once, when the injection is performed once in a light load area only in which the theoretical air-fuel ratio feedback control is effective, and the injection is performed twice in medium to high load area, a robustness is highly kept with respect to a manufacturing variation on an engine parts side.