Output controlling method and device for internal combustion engines

Abstract

A method of and a device for controlling the output of an internal combustion engine, in which a mixture in an amount corresponding to the amount required for the full load operation of the engine is caused to flow into each cylinder in the suction stroke, even in the case of partial load operation, and, in the compression stroke, the amount of mixture required for the particular load of the engine is remained in the cylinder and the remaining part thereof is caused to flow back into the suction system from the cylinder.

Description

BACKGROUND OF THE INVENTION

This invention relates generally to the control of the output of internal combustion engines, and particularly to a method of and a device for controlling the output of internal combustion engines, in which a mixture once sucked into each cylinder in an amount corresponding to the amount required for the full load operation of the engine, even in the case of partial load operation, is partially caused to flow back into the suction pipe in the compression stroke, the amount of mixture flowing back into the suction pipe being controlled thereby to control the output of the engine.

The output of internal combustion engines, e.g. reciprocating internal combustion engines, has generally been controlled by a throttle valve which is provided in the suction pipe between the suction valve and the carburetor Venturi at a location downstream of said carburetor Venturi and which is opened and closed by the accelerator pedal operatively interlocked therewith.

The conventional internal combustion engines of the type described have had the following disadvantages: Namely, (1) the amount of the residual gas is large because the combustion gas is sucked into the suction system under the effect of the vacuum pressure occurring in said suction system during the overlapping period of the opening strokes of the suction valve and exhaust valve; (2) a fluctuation of the vacuum pressure in the suction stroke under varying load on the engine results in a fluctuation of the amount of liquid fuel in the suction pipe and control of the air fuel ratio during the period of this fluctuation is difficult; (3) in the suction stroke, the vacuum pressure in the suction pipe increases the pumping loss; and (4) the throttle valve closes the suction pipe at the deceleration of the engine, so that a shortage of the intake air results and unburned gases are released into the atmosphere.

SUMMARY OF THE INVENTION

According to the present invention, an amount of mixture corresponding to the amount required for the full load operation of the engine, even in the case of partial load operation, is sucked into each cylinder in the suction stroke and, in the compression stroke, the mixture is partially caused to flow back into the suction pipe according to the load on the engine, whereby the output of the engine is controlled.

To this end, according to the invention each cylinder of the engine is provided with at least two ports which are respectively communicated with the suction pipe and opened and closed by valve means and the like, and a conduit communicating at least one of said ports with the suction pipe is provided therein with a throttle valve whose opening is controlled by an output controlling mechanism such as an accelerator pedal and a conduit communicating at least one other port with the suction pipe is used for passing an amount of mixture corresponding to the amount required for the full load operation of the engine, in the suction stroke the amount of mixture corresponding to the amount required for the full load operation being sucked into the cylinder from said latter port and, in the compression stroke, said latter port being closed and the mixture in the cylinder being partially caused to flow back into the suction pipe from said former port according to the degree of opening of said throttle valve, whereby the output of the engine is controlled.

An object of the invention is to provide a method of and a device for controlling the output of internal combustion engines, which does not make the internal pressure of the suction pipe extremely low, which minimizes the pumping loss and which prevents the exhaust gas from being sucked into the suction system under the effect of the vacuum pressure in said suction system.

Another object of the invention is to provide a method of and a device for controlling the output of internal combustion engines, which increases the amount of mixture in proportion to the amount of residual gas at the deceleration of the engine from a high speed phase of operation and does not cause misfire.

Still another object of the invention is to provide a method of and a device for controlling the output of internal combustion engines, which maintains the amount of mixture supplied from the suction port constant independently of the fluctuation of the load on the engine, which reduces to a minimum the fluctuation of the amount of liquid fuel passing in the suction pipe and facilitates control of the air fuel ratio.

Still another object of the invention is to provide a method of and a device for controlling the output of internal combustion engines, which prevents misfire or after-burning at the start of deceleration due to overpitch arising from the gasification of liquid fuel and which prevents overheating of an exhaust gas purifying device when such device is used with the engine.

A further object of the invention is to provide a method of and a device for controlling the output of internal combustion engines, which during operation of the engine under low loads, causes the mixture to recirculate repeatedly between the suction system and the cylinder, whereby the atomization of the mixture is promoted, the combustion chamber of the cylinder is cooled by the recirculating mixture, the suction gas temperature and therefore the highest combustion temperature is lowered owing to the reduced pumping loss, and the discharge of NOx is decreased.

An additional object of the invention is to provide a method of and a device for controlling the output of internal combustion engines, in which during the compression stroke, the compressed gas is caused to flow back into the suction system from the cylinder, whereby swirling of the gas in the combustion chamber is enhanced, the combustion rate is increased and thereby the efficiency of the engine is increased.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 3 are sectional views of a reciprocating four-cycle internal combustion engine in which the present invention is embodied, FIG. 1 being a view of the engine in the suction stroke, FIG. 2 being a view of the engine in the compression stroke, and FIG. 3 being a view of the engine in the exhaust stroke;

FIG. 4 is a characteristic diagram illustrating the operations of the valves of the internal combustion engine shown in FIGS. 1 to 3; and

FIG. 5 is an indicator diagram (P-V diagram) of the internal combustion engine.

DESCRIPTION OF THE PREFERRED EMBODIMET

With reference to FIGS. 1 to 3, a cylinder head 1A of a cylinder 1 of an internal combustion engine is provided with a suction port 2A, a suction valve 2 for opening and closing said port 2A, an exhaust port 3A, an exhaust valve 3 for opening and closing said port 3A, a back-flow port 4A and a back-flow valve 4 for opening and closing said port 4A.

A conduit 5A diverged from a suction pipe 5 is connected to the back-flow port 4A and the suction pipe 5 is connected to the suction port 2A.

The conduit 5A is provided therein with a throttle valve 6 by which the flow in said conduit is controlled. The throttle valve 6 is operatively interlocked with an output controlling mechanism, such as an accelerator pedal, (not shown) to be operated thereby in such a manner that it is angularly displaced in a closing direction as the load on the engine increases and in an opening direction as the load on the engine decreases. Reference numeral 7 designates a piston.

The suction valve 2, the exhaust valve 3 and the back-flow valve 4 respectively are operated by operating means, such as cams, (not shown) which are operatively interlocked with the output shaft of the engine, in the manner shown in the characteristic diagram of FIG. 4. In the characteristic diagram of FIG. 4, the axis of abscissa is scaled by the crank angle .theta. of the engine and the axis of ordinate by the valve lift h, and the curve A represents the operational characteristic of the exhaust valve 3, the curve B the operational characteristic of the suction valve 2 and the curve C the operational characteristic of the back-flow valve 4. Namely, the exhaust valve 3 starts opening from a point immediately before the piston 7 reaches its bottom dead center I of the piston 7 and is closed at a point immediately after the piston 7 reaches its top dead center I. The suction valve 2 starts opening at a point immediately before the piston 7 reaches its top dead center I and is closed at a point immediately after the piston reaches its bottom dead center II. The back-flow valve 4 starts opening at a point immediately before the piston reaches its bottom dead center II and is closed at a point about 130.degree. of the crank angle from the bottom dead center II of the piston, the lift of said valve being largest at a point where the crank angle is 60.degree..

Now, the operation of the internal combustion engine described above will be described.

The suction valve 2 is opened at the point immediately before the piston 7 reaches its top dead center (TDC) and a mixture is sucked into the cylinder 1. The volume of the mixture is the same as that required at the full load operation of the engine, even in the case of not full load operation, and the pressure thereof is the atmospheric pressure (or the pressure of supercharged mixture when a supercharger is used). The flow-back valve 4 is opened at the point immediately before the piston 7 moving down from its top dead center I reaches its bottom dead center (BDC) II and closed at the point when the piston 7 advances from its bottom dead center II about 130.degree. in terms of the crank angle. The suction valve 2 is closed at the point immediately after the piston reaches its bottom dead center II. Thus, it will be understood that the mixture in the cylinder 1 is forced back into the conduit 5A and suction pipe 5 through the back-flow port 4A in an amount according to the degree of opening of the throttle valve 6 in the initial stage of the compression stroke. (No mixture is forced back into the conduit 5A when said conduit is closed by the throttle valve 6.)

As a consequence, the engine generates an output corresponding to the amount of mixture remaining in the cylinder I and operates along the P-V curve shown in the diagram of FIG. 5.

The mixture forced back into the conduit 5A is partially or entirely sucked into the cylinder 1 at the next suction stroke through the suction pipe 5 and the suction port 2A and the mixture thus sucked is further partially recirculated in the passage formed by the cylinder 1, the conduit 5A and the suction pipe 5.

Although in the embodiment described and illustrated herein the opening and closing of the suction port 2A and the back-flow port 4A are effected by means of valves, it should be understood that the same may be effected by any other means. It should also be understood that while the present invention has been described herein as applied to a four-cycle reciprocating internal combustion engine, it is generally applicable to other types of internal combustion engine, including a reciprocating two-cycle internal combustion engine or rotary piston engine.

Claims

I claim:

1. A method of controlling the output of a four-cycle internal combustion engine, comprising supplying an amount of mixture corresponding to the amount required at the full-load operation of the engine into a cylinder of the engine at the suction stroke, and at the compression stroke causing an amount of mixture in excess to the amount required for operation of the engine to flow back from the cylinder into a suction pipe by the action of the piston in said cylinder, said mixture in excess being delivered only to the suction pipe coupled to the corresponding cylinder and being substantially confined for use within said corresponding cylinder, whereby the output of the engine is controlled.

2. The method of claim 1 wherein:

said amount caused to flow back is controlled by throttling said flow-back of said excess mixture such that the amount of said flow-back entering a conduit communicating with said suction pipe is controlled, said throttling of said flow-back being achieved by a throttle disposed within said conduit.

3. A device for controlling the output of an internal combustion engine comprising a suction port from which an amount of mixture corresponding to the amount required for the full load operation of the engine is supplied into a cylinder, a back-flow port provided separately from said suction port, a conduit communicating the cylinder with a suction pipe through the back-flow port in a direct fashion such that substantially all of said mixture delivered through said conduit to said suction pipe is supplied to said cylinder corresponding to said conduit and suction pipe, said back-flow port being opened only at a specific stage of the compression stroke of the engine, and a throttle valve provided in the conduit and being operated such that said throttle is angularly displaced in a closing direction as the load on the engine is increased.

4. The device of claim 3 wherein:

said internal combustion engine is a four cycle engine; and

said back-flow port is opened during the compression cycle between bottom dead center and 130.degree. after bottom dead center, said back-flow port having a maximum opening at 60.degree. after bottom dead center.

5. The device of claim 3 wherein:

said suction pipe and said conduit are exterior to the walls of said cylinder.