GB2145470A

GB2145470A - Internal-combustion engine control

Info

Publication number: GB2145470A
Application number: GB08420941A
Authority: GB
Inventors: Shigeo Sakurai
Original assignee: Mikuni Corp
Current assignee: Mikuni Corp
Priority date: 1983-08-17
Filing date: 1984-08-17
Publication date: 1985-03-27
Also published as: CA1230275A; DE3430347A1; GB2145470B; FR2550822A1; GB8420941D0; JPS6043135A

Abstract

A fuel feed amount controlling method for internal combustion engines comprising a step in which a required air flow volume and a time constant of the first-order lag until the injected fuel is actually sucked into the cylinder of the engine are estimated from the trodden amount of an accelerator pedal, the number of revolutions of the engine and a load to be applied to the engine and a step in which, when the accelerator pedal is trodden down, the fuel feed amount is determined in consideration of the time constant of the first-order lag of the fuel to the first-order lag of the air flow volume to be actually sucked into the cylinder, in order to prevent the uncomfortable shock at the time of acceleration or deceleration and improve the accelerating and decelerating performances.

Description

SPECIFICATION Fuel feed amount controlling method for internal combustion engines Background of the invention a) Field of the invention: This invention relates to a method of controlling a fuel feed amount in an internal combustion engine.

b) Description of the prior art: It is generally known that, in an internal combustion engine, even if the throttle valve is instantaneously fully opened or closed, the flow volume of air to be sucked into the cylinder will vary with the first-order lag having a time constant. In order to explain this point in detail, for example, as shown in Fig.) if the air flow volume in a suction bore controlled by a throttle valve 1 is represented by OAv, the air flow volume in a manifold 2 is represented by QAm, the air flow volume sucked into a cylinder 3 is represented by QAE, the volume of the manifold 2 is represented by Vm, the absolute pressure within the manifold 2 is represented by Pm, the volume of the cylinder 3 is represented by Vc, the number of revolutions of the engine is represented by N and the case of a 4-cylinder engine is considered, QAE = pVc x 60 x 2 60 Pm = Pm x 1.193 = KPm Po 760 (760 mmHg at 23 C.) ## QAE = K.Pm VcN/30........................(1) Also, QAm = PVm = KPmVm dPm (2) .-.QAm = KVm at dt Also, QAm = QAv - QAE ....................(3) Therefore, from the formulae (1), (2) and (3), dPm VcN ...... (4) KVm at = QAv - KPm 30 Hence, Pm = 30 QAv - Vm30 dPm ....(5) KVcN VcN dt That is to say, even in case the air flow volume QAv within the suction bore varies instantaneously, the absolute pressure Pm within the manifold will vary with the first-order lag having a time constant of Vm30 VcN Therefore, the air flow volume QA (= OAE) sucked into the cylinder 3 will vary with the firstorder lag in reverse proportion to the absolute pressure Pm within the manifold.

Therefore, for example, in one of the conventional fuel feed amount controlling methods wherein, as shown by the dotted line in Fig. 2, the fuel injecting amount from the injector is varied directly in response to the variation of the trodden amount of the accelerator pedal, there has been a problem that, at the time of acceleration or deceleration, the air-fuel ratio of the gaseous mixture and the output torque of the engine will vary so quickly as to give an uncomfortable shock to the operator.On the other hand, in another method wherein, as shown by the one-point chain line in Fig. 2, the fuel injecting amount from the injector is varied in reverse proportion to the absolute pressure Pm within the manifold 2, there has been a problem that, particularly, at the time of a low rotation of the engine, a time lag will be produced in the operation of the accelerator pedal and the accerlatability and deceleratability will be low.

Summary of the Invention In view of the above mentioned circumstances, a primary object of the present invention is to provide a fuel feed amount controlling method wherein the uncomfortable shock at the time of acceleration or deceleration can be prevented and the accelerating and decelerating performances can be improved.

According to the present invention, this object is attained by a method wherein a required air flow volume and a time constant of the first-order lag until the injected fuel is actually sucked into the cylinder are estimated from the trodden amount of the accelerator pedal, the number of revolutions of the engine and the load on the engine and, when the accelerator pedal is trodden down, the fuel feed amount is determined in consideration of the time constant of the first-order lag of the fuel to the first-order lag of the air flow volume to be actually sucked into the cylinder thereby to obtain a proper air-fuel ratio.

Brief description of the drawings Figure 1 is a schematic view showing the variation of the air volume flowing into the cylinder from the manifold with the position; Figure 2 is a graph showing the variation characteristics of the fuel feed amount by the conventional fuel feed amount controlling system; Figure 3 is a view showing a controlling pattern of an embodiment of the fuel feed controlling method according to the present invention; and Figure 4 is a graph showing variation characteristics of the fuel feed amount by the above mentioned embodiment.

Description of the preferred embodiment The present invention shall be explained in the following on the basis of one embodiment shown in Figs. 3 and 4. Fig. 3 shows the controlling pattern of the method of the present invention. In case the operator treads down the accelerator pedal, for example, from the point A (or1, QF1) to the point B (OA2, QF2) in Fig. 2, the trodden amount, the number of revolutions of the engine at the point A and the magnitude of the load on the engine will be detected by various sensors, the required air flow volume, that is, the air flow volume QA2 at the point B and a time constant of the first-order lag until the injected fuel is actually sucked into the cylinder 3 will be estimated and then, the fuel feed amount (the injected fuel amount from the injector) will be varied from QF, to QF2 in consideration of the estimated time constant of the first-order lag of the fuel to the air flow volume having the above mentioned first-order lag. This is represented by a formula as follows; OFn=(0F2-OF1)(1 -r) + OF1 (0 < r < 1) (6) wherein n represents a number of injections. Therefore, the variation of the fuel feed amount QF will be as illustrated by the dotted line in Fig. 4. If the value of the constant r is varied, the variation curve of the fuel feed amount QF will also vary and therefore the air-fuel ration will be able to be freely set. Thus, by properly selecting .he variation curve of the fuel feed amount OF, the uncomfortable shock at the time of acceleration and deceleration can be prevented and the accelerating and decelerating performances can be improved.

Claims

1. A fuel feed amount controlling method for internal combustion engines, characterized by comprising a step in which a required air flow volume and a time constant of the first-order lag until the injected fuel is actually sucked into the cylinder of the engine are estimated from the trodden amount of an accelerator pedal, the number of revolutions of the engine and load to be applied to the engine, and a step in which, when the accelerator pedal is trodden down, the fuel feed amount is estimated is consideration of the time constant of the first-order lag of said fuel to the first-order lag of the air flow volume to be actually sucked into said cylinder.

2. A fuel feed amount controlling method for internal combustion engines substantially as hereinbefore described with reference to the accompanying drawings.