JPH0318638A - Fuel control device for engine - Google Patents

Abstract

PURPOSE:To maintain the output performance of an engine by judging the evaporating characteristic of fuel and controlling the further increase of the fuel increase value in the specific operating region of the engine where the carburetion-atomization of fuel is lowered in the case of the fuel being of a low evaporating nature. CONSTITUTION:In a fuel supply means 50, the reference injection pulse set at an arithmetic circuit 51 is set, and when the acceleration state is judged at the operating state judging circuit 72 of a control means 70, the acceleration increase quantity correction circuit 62 of a fuel quantity increasing means 60 corrects the reference injection pulse width at a setting circuit 52 by a correction signal for increasing the fuel quantity at the time of acceleration and a correction signal from a fuel pressure control circuit 61 and sets the actual injection pulse width. When the fuel is judged to be of a low evaporating nature at a fuel judging circuit 71, the fuel quantity increasing means 60 outputs such a correction signal as to increase the fuel increase quantity value in the specific operating region of an engine where the carburetion-atomization of fuel is lowered. The output performance of the engine can be thus maintained.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a fuel control device for an engine.

(Prior Art) In automobile engines, during specific operating conditions, such as during startup or acceleration (this is when the amount of fuel set based on the engine speed and intake air amount is increased and corrected,
The aim is to improve starting performance or acceleration performance. For example, as a device for increasing the fuel amount during acceleration (acceleration increase), there is a device as shown in Japanese Patent Application Laid-Open No. 13933/1983.

(Problems to be Solved by the Invention) Generally speaking, in engines, it is possible to obtain an almost predetermined air-fuel ratio with both summer gasoline, which has relatively poor evaporation performance, and winter gasoline, which has relatively good evaporation performance. The fuel control system is set.

However, no matter how much the fuel control system is set up to handle both summer gasoline and winter gasoline,
For example, in a fuel control system that is designed to handle gasoline with particularly poor evaporation performance (hereinafter referred to as heavy fuel), which is mainly used for summer use, the proportion of gasoline that contributes to combustion is substantially reduced compared to the normal case. However, the amount of unburned gasoline increases.

This phenomenon occurs when starting an engine with low combustion chamber efficiency and poor gasoline evaporation (vaporization/atomization), resulting in a leaner air-fuel ratio, resulting in engine stop (hereinafter referred to as "engine stop") at the time of startup after startup. ), this results in various problems such as a decrease in engine speed during idling, engine stalling, and hesitation when starting.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an engine fuel control device that prevents the air-fuel ratio from becoming lean when using heavy fuel and maintains appropriate engine output. .

(Means for Solving the Problem) In the present invention, as a specific means for solving the problem, as shown in FIG. An in-pulse calculation circuit 5l, an actual injection pulse setting circuit 52 that performs various corrections on the basic injection amount to set the actual injection amount, and an injector drive circuit 53 that drives the injector 54 based on the actual injection pulse. A fuel supply means 50 comprising:
, a fuel pressure control circuit 6l that cuts the negative pressure of the pressure regulator (indicated as P/R) that adjusts the fuel supply pressure (hereinafter referred to as fuel pressure), increases the fuel pressure, and increases the amount of fuel supplied, and the fuel amount during acceleration. A fuel increasing means 60 includes an acceleration increase correction circuit 62 for increasing the amount of fuel, a fuel determining circuit 7l for determining the evaporation performance of the fuel, and an operating state determining circuit 72 for determining the operating state of the engine. The present invention is characterized by comprising a control means for causing the fuel increase means to further increase the fuel increase value in a specific operating range of the engine where the vaporization/atomization property of the fuel decreases when the fuel is evaporative. .

(Function) In the present invention, with such a configuration, when a low-evaporation fuel is used, in a specific operating range of the engine where the vaporization and atomization properties of the fuel are reduced, the amount of the supplied fuel is reduced. The amount of supplied fuel is increased by an amount corresponding to the amount of unevaporated fuel in order to compensate for the amount of unevaporated fuel corresponding to the generation rate of unevaporated fuel.

(Effects of the Invention) Therefore, according to the fuel control device for an engine of the present invention, the amount of supplied fuel is corrected to increase in accordance with the evaporation performance of the fuel, so even if the fuel has extremely poor evaporation performance, it will evaporate. The effect is that phosphorization of the air-fuel ratio due to performance is prevented, and the output performance of the engine can be maintained.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described based on FIGS. 2 to 6.

FIG. 2 shows an intake/exhaust system for an automobile engine 1 equipped with a fuel control device according to the present invention, in which reference numeral 2 designates an intake passage and 3 designates an exhaust passage.

A surge tank 4 is provided in the intake passage 2, and an injector 5 is provided downstream of the surge tank 4. On the other hand, on the upstream side of the surge tank 4, there is a throttle valve 6.7, an air flow meter 8, and an air cleaner 9.
are provided for each.

Further, the injector 5 is equipped with a pressure regulator lO for adjusting fuel pressure.

The fuel pressure of the pressure regulator IO is stabilized by the negative pressure chamber (not shown) of the pressure regulator 10.
This is done by controlling the negative pressure introduced into the three-way valve 1l. In this embodiment, as will be described later, when the fuel is heavy fuel, the fuel pressure is increased by cutting off the introduction of negative pressure into the negative pressure chamber.

Furthermore, reference numeral 12 is a control unit for controlling the fuel injection amount from the injector 5, and the control unit 12 includes an intake air temperature sensor l3 provided in the surge tank 4 as an injection amount control factor.
The intake air temperature is measured from the air flow meter 8, the engine temperature is measured from the water temperature sensor l4, and the atmospheric pressure is measured from the atmospheric pressure sensor l5.
The amount of intake air is determined by the sensor l6 installed in the exhaust passage 3.
In addition to inputting the air-fuel ratio signal from the rotation speed sensor 17 and the engine rotation speed from the rotation speed sensor 17, an idle switch signal and a neutral signal are also input.

The fuel control device configured in this way basically controls the fuel injection amount in accordance with the operating state of the engine based on the engine speed, intake air amount, etc. If the fuel is of high quality, this is determined based on a predetermined phenomenon of the engine (described later), and in that case, the amount of fuel corresponding to the unevaporated amount in the supplied fuel is increased to make the air-fuel ratio leaner. The engine output is maintained by preventing such occurrences.

Specifically, the aim is to prevent a decrease in engine output (including engine stalling) caused by heavy fuel in two cases: when starting the engine, immediately after starting, and during acceleration after starting. Hereinafter, specific control methods for each of these cases will be explained.

In this case, the engine output decreases during and immediately after starting, as shown in Fig. 4, when the engine speed suddenly drops after starting, and as shown in Fig. 5, when the engine stalls after starting and then restarts. There may be cases. In these cases, the actual fuel injection amount is increased by increasing the fuel pressure to prevent a decrease in engine output.

(b) First, in the former case, as shown in Figure (a), the engine's target rotation speed (curve 11,) and the limit rotation speed (curve 11, If the engine speed after startup falls below this limit, it is determined that the fuel is heavy (Fig.
), for a predetermined period, the pressure regulator 1
The introduction of negative pressure to 0 is stopped (negative pressure cut, see figure (c)), and the fuel pressure is increased. In this case, the negative pressure cut period is the period until the engine water temperature reaches the predetermined negative pressure cut return water temperature (the engine temperature at which fuel vaporization and atomization are good), as shown in Figure (d). It is said that The operating zone of the engine is divided into a starting zone when the engine speed rises and a normal zone thereafter, as shown in FIG. 2(e).

Therefore, in this case, conventionally, the engine speed is prevented from dropping significantly as shown by the broken line in FIG. It will be canceled.

(b) In the latter case, as shown in FIG. 5, when the engine stalls after starting (see (a) in the same figure), it is determined that the fuel is heavy fuel (see (b) in the same figure).

After determining the heavy fuel, the negative pressure cut is maintained until the engine water temperature reaches the predetermined return water temperature (see (d) in the same figure), and the engine is restarted during this period (see (c) in the same figure). (See figure (a)).

Therefore, in this case, as shown by the broken line in FIG. 3A, the engine will not stall again or the engine speed will drop significantly after restarting, and the transition to normal operation will be smooth.

Incidentally, the operating zone in this case is as shown in FIG. 2(e).

At the time of starting acceleration In this case, basically, as shown in Fig. 6, at the time of acceleration (
When the Ot sensor continues to output on the lean side for a predetermined period of time (see FIG. 10(e)), it is determined that the fuel is heavy fuel (see FIG. 2(b)).

At this time, the fuel injection amount itself is corrected to increase directly (see (c) and (d) in the same figure) to prevent a decrease in engine output due to a slope change in the air-fuel ratio and a shift in acceleration. There is.

Also, if the Ot sensor output sticks to the rich side at the next acceleration as a result of increasing the acceleration amount (in other words, when the engine temperature has increased and the fuel vaporization/atomization has improved, or if the acceleration amount itself has been increased too much) case), the increase value is reduced by a predetermined amount. This increase value is stored in memory and used during the next acceleration.

By performing such an increase correction, good starting acceleration is ensured even if the fuel used is heavy fuel.

Next, the actual control in each of the above cases will be explained based on the flowchart shown in FIG.

After starting the control, first, the gear position fa2 of the transmission is set as a control element.
GRIN, idle switch output, engine water temperature THW
, intake temperature T H A A , and start switch output are inputted (step Sl).

Next, start the engine (steps S2 and S3).
), read the engine rotation failure Ne after startup (step S
4) and the target engine speed N corresponding to the water temperature from the water temperature table in the memory. (Step S5)
. And this target rotation speed N. and the difference between the actual rotation speed Ne (
No Ne) and the predetermined rotation speed for heavy fuel determination (i.e.
The rotational speed Nl corresponding to the rotational speed difference between the curve a1 and the curve Q in FIG. 4(a) is compared (step S6).

As a result of the comparison, N + < N. -Ne, then
It is determined that the fuel used is not heavy fuel and no control is performed, but if N+>No Ne, fuel increase correction is performed by increasing the fuel pressure. That is, first, a timer is set (step S7), and a negative pressure cut to the pressure regulator 10 is executed within the set time (step S9). This negative pressure cut control substantially increases the amount of fuel and prevents the engine from stalling after starting or from excessively decreasing engine speed. Note that when the idle switch is turned on within this timer (transition state to the start acceleration state), the negative pressure cut control is stopped (step SIO) and the control moves to steps S+1 and subsequent steps.

After the time has elapsed or when transitioning to start acceleration as described above, control of the pressure regulator 10 is returned to normal control (step Sll) to prepare for acceleration control.

That is, first, the current operating state of the engine is O, and the sensor I6
Based on the output of , it is determined whether the air-fuel ratio is in a region where feedback control of the air-fuel ratio is performed (step S+2). Generally, feedback control is not performed during acceleration, but
Since this embodiment uses heavy fuel, feedback control is performed even during acceleration in order to maintain combustibility.

As a result of the determination, if the air-fuel ratio is not in the feedback region, the air-fuel ratio is fixed at a predetermined value (step S22).

On the other hand, in the feedback region, in the neutral state (step S13), and in the idle state (
Step S14) and not accelerating (Step S15)
), air-fuel ratio control is performed based on the O sensor output (step S23).

On the other hand, if the vehicle is in the feedback region and the vehicle is accelerating, it is determined whether or not the fuel used is heavy fuel from the perspective of preventing acceleration problems, and if it is heavy fuel, the fuel amount is increased for acceleration. .

That is, in step S16, the O sensor output is manually input, and it is determined whether or not the output is sticky (step S17).
). If the vehicle is in a stuck state, it is determined whether the state is lean or rich (step 818).

If the result of the determination is that the sticking is on the lean side, the sticking time is measured (step Sl9), and if this is longer than a predetermined time, the fuel used is heavy fuel, and therefore the acceleration amount is increased by a predetermined value. This prevents a decrease in engine output due to lean air-fuel ratio (step S2+).

On the other hand, if it is attached to the rich side,
The sticking time is measured (step S24), and if this is longer than a predetermined time, the acceleration increase is reduced by a predetermined value (step S26).

By performing the above-described control, both engine startability and starting acceleration are maintained well regardless of the evaporation performance of the fuel used.

[Brief explanation of drawings]

Fig. 1 is a functional block diagram of the present invention, Fig. 2 is a system diagram of a fuel control device according to an embodiment of the present invention, Fig. 3 is a control flowchart thereof, and Figs. 4 to 6 are control characteristic diagrams thereof. be. 1 ●●●● Engine 2... Intake passage 3... Exhaust passage 4... Surge tank 5... Injector 6.7... Throttle valve 8... Air flow meter 9. ...Air cleaner 10...Pressure regulator l1...Three-way valve l2...Control unit! 3...Intake temperature sensor l4...Water temperature sensor l5...Pressure sensor l6...Ot sensor l7...Rotation failure sensor

Claims (1)

[Claims] 1. A fuel supply means that supplies a predetermined amount of fuel in accordance with the operating state of the engine, a fuel increase means that increases the amount of fuel supplied from the fuel supply means as necessary, and determines the evaporation characteristics of the fuel. and control means for causing the fuel increase means to further increase the fuel increase value in a specific operating range of the engine where the vaporization and atomization properties of the fuel decrease when the fuel is a low-evaporability fuel. An engine fuel control device characterized by: