JP2584299B2 - Electronically controlled fuel injection device for internal combustion engine - Google Patents

Description

The present invention relates to an electronically controlled fuel injection device for an internal combustion engine.

<Prior Art> In a conventional electronically controlled fuel injection device for an internal combustion engine, an intake air flow rate Q detected by a hot wire air flow meter is used.
And the engine speed N calculated based on the signal from the crank angle sensor, the basic fuel injection amount Tp (= K · Q / N; K
Is a constant), which is appropriately corrected according to the operating state at that time, and the final fuel injection amount Ti (= Tp · COEF + Ts; C)
OEF defines various correction coefficients, and Ts defines the voltage correction), outputs a fuel injection pulse with a pulse width corresponding to Ti to the electromagnetic fuel injection valve at a predetermined timing synchronized with the engine rotation, and supplies it to the engine intake system. Injecting the optimal amount of fuel.

When the engine is started, separately from the above fuel injection control, the fuel injection amount Ti (= f
(Tw)), and at the same time as the start of cranking, that is, at a predetermined timing in synchronization with the first reference signal output from the crank angle sensor, as shown in FIG. And fuel is injected by the fuel injection valve (see Japanese Utility Model Laid-Open No. 63-123742).

<Problems to be solved by the invention> By the way, the fuel injection pulse width and the cooling water temperature at the time of engine start
The relationship with Tw is, as shown in FIG. 6, when the cooling water temperature Tw is low, that is, at the time of a so-called cold start, the fuel injection pulse width is wide, that is, the fuel injection amount is relatively large.
When the cooling water temperature Tw increases, the fuel injection pulse width becomes narrow, that is, the fuel injection amount decreases.

Further, the fuel is injected into the engine intake system by the fuel injection valve. As a property of the fuel, the viscosity is relatively high at a low temperature, and decreases at a high temperature. Since the fuel pressure (for example, 2.55 kg / cm ² ) is applied, immediately after the engine stops, if the fuel circulates and the fuel temperature inside the fuel injector rises, the sealability of the fuel injector deteriorates, Fuel dripping from the fuel injection valve causes fuel leakage and accumulates in the engine intake passage.

Further, as described above, since the fuel injection amount at the time of engine start is set by the cooling water temperature Tw, at a relatively low temperature where the fuel injection amount is relatively large, the presence of the leaked and accumulated fuel does not significantly affect the fuel injection amount. At the time of high temperature restart, the fuel injection amount is small, so the proportion of accumulated fuel becomes large, the effect is large, and the air-fuel ratio is greatly enriched. there were.

That is, even if a fuel injection pulse corresponding to the cooling water temperature Tw at the time of starting is output, it is impossible to predict the amount of fuel dripped into the intake passage, so that an air-fuel ratio suitable for starting can be obtained. Will not be.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described conventional problems, and has as its object to improve startability at the time of high-temperature restart.

<Means for Solving the Problems> To achieve the above object, in the present invention, as shown in FIG. 1, a fuel injection valve a is provided in an engine intake system, and fuel is supplied at a predetermined timing synchronized with engine rotation. An electronically controlled fuel injection device for an internal combustion engine having a fuel injection control means for injecting, wherein an engine start time detection means c for detecting an engine start time when a start switch is ON, and an engine temperature detection means d for detecting an engine temperature And a starting fuel injection amount setting unit e for setting a fuel injection amount according to the engine temperature detected by the engine temperature detecting unit d at the time of engine start detected by the engine start detecting unit c. And the following means are provided.

That is, at the time of engine start detected by the engine start time detecting means c, based on the engine temperature detected by the engine temperature detecting means d, a high temperature restart determining means f for determining whether or not the engine is in a high temperature restart state. A start elapsed time measuring means g for measuring an elapsed time from when the engine start time is first detected by the engine start time detecting means c; and an elapsed time measured by the start elapsed time measuring means g. In the high-temperature restart state determined by the high-temperature restart determining means f, which is determined by the high-temperature restart determining means f, the period determining means h that determines whether or not the period is the first preset period of the start switch ON period by comparing the Fuel injection stopping means i for stopping fuel injection only during the first preset period of the start switch ON period determined by the period determining means h.

<Operation> According to the above configuration, the high-temperature restart determining means determines whether or not the engine is in the high-temperature restart state based on the cooling water temperature or the like at the time of starting, and the start switch is turned on by the period determining means.
It is determined whether it is the first preset period (constant rotation or constant time, etc.) of the period. Then, when it is determined that the engine is in the high-temperature restart state, the fuel injection by the fuel injection valve is stopped by the fuel injection stop means only during the first preset period of the start switch ON period, so that the engine intake passage is stopped. The fuel accumulated in the engine is once scavenged, then the fuel injection is started, and the engine can be started with an appropriate air-fuel ratio. Therefore, the startability of the engine at the time of high temperature restart can be improved.

<Example> An example of the present invention will be described below.

In FIG. 2, air is sucked into the engine 1 through an air cleaner 2, an intake duct 3, a throttle chamber 4, and an intake manifold 5.

A throttle valve 6, which is linked to an accelerator pedal (not shown), is provided in the throttle chamber 4 to control the intake air flow rate.

A fuel injection valve 7 is provided for each cylinder in the intake manifold 5 or the intake port of the engine 1. The fuel injection valve 7 is an electromagnetic fuel injection valve. The solenoid is energized by a fuel injection pulse from the control unit 8 and is opened by being supplied with a predetermined pressure (for example, 2.55kg / c
The fuel adjusted to m ² ) is injected and supplied to the engine 1. In addition to the multi-point injection system as in the present embodiment, a single-point injection system in which a single fuel injection valve is provided in common for all cylinders may be used.

Further, the control unit 8 receives input signals from various sensors, performs an arithmetic processing by a built-in microcomputer in accordance with a fuel injection control routine of FIG. 3 described later, determines a fuel injection amount, and sets a pulse width corresponding to the fuel injection amount. Is output to the fuel injection valve 7 at a predetermined timing in synchronization with the rotation of the engine 1.

As the various sensors, a hot wire air flow meter 9 is provided in the intake duct 3 and outputs a voltage signal corresponding to the intake air flow rate Q.

Further, a crank angle sensor 10 is provided, for example, by being incorporated in a distributor (not shown), and outputs a position signal every 1 ° or 2 ° and a reference signal every 180 ° in the case of four cylinders. Here, the engine speed N can be calculated by measuring the number of position signals generated within a predetermined time or the period of the reference signal.

The throttle valve 6 is provided with a potentiometer type throttle sensor 11, and the throttle valve opening TVO
And outputs a signal corresponding to.

Further, a water temperature sensor 12 is provided on a water jacket of the engine 1 and outputs a signal corresponding to the cooling water temperature Tw.
This water temperature sensor 12 is used as engine temperature detecting means.

Further, the control unit 8 is supplied with an operating power supply and a voltage of a battery 13 for detecting a power supply voltage via an ignition switch 14a and a start switch 14b of an engine key 14.

Next, a fuel injection control routine executed by the microcomputer in the control unit 8 will be described with reference to FIG.

In step 1 (referred to as S1 in the figure, the same applies hereinafter),
Various data such as the intake air flow rate Q and the engine speed N are inputted, and in step 2, a basic fuel injection amount Tp (= K · Q / N; K is a constant) is calculated.

In step 3, various corrections are added to the final fuel injection amount Ti (= Tp · COFE + Ts; COEF is a correction coefficient, Ts
Is calculated for the voltage correction) to set a normal fuel injection amount.

In step 4, it is determined whether or not the engine is at the start based on ON / OFF of the start switch 14b, and steps 5 to 7 are executed only at the time of the start (when it is ON).

In step 5, the engine cooling water temperature Tw representing the engine temperature
From the starting fuel injection amount CSP called a cold start pulse, and in the next step 6, it is determined whether the CSP is greater than the fuel injection amount Ti calculated in step 3,
Only when it is larger, the process proceeds to step 7 and CSP is substituted for Ti.

Here, step 4 corresponds to engine start detection means, and steps 5 to 7 correspond to start fuel injection amount setting means.

In step 8, the signal from the crank angle sensor 10 is monitored to determine whether or not the injection timing is a predetermined injection timing every two reference signals.
Proceed to the following.

In step 9, ON / O of the start switch 14b is again performed.
Based on the FF, it is determined whether or not it is at the time of starting.

When not starting (when the start switch 14b is off)
Proceeding to step 13 as it is, a fuel injection pulse having a pulse width of Ti is output to the fuel injection valve 7 to perform fuel injection.

Therefore, steps 8 and 13 correspond to fuel injection control means.

At startup (when the start switch 14b is ON), the process proceeds to step 10, engine coolant temperature Tw is determined whether or not a predetermined value T ₀ or more, when the Tw ≦ T _0, a time of hot restart So
Proceed to step 11, otherwise proceed to step 13.

Here, step 9 corresponds to the engine start time detecting means,
Step 10 corresponds to the high temperature restart determination means.

At the time of high temperature restart, first, at step 11, 1 is added to the counter C, and at step 12, it is determined whether or not the value of the counter C is 2 or less. Therefore, this routine ends without executing the fuel injection of step 13.

When the value of the counter C is 3 or more, step
Proceeding to 13, the fuel injection amount Ti determined in step 3 or step 7 is output, and this routine ends. That is, at this time, since the engine has exceeded the fuel injection stop engine,
The injection fuel will be executed.

Here, step 11 corresponds to a start elapsed period measuring unit, step 12 corresponds to a period determining unit, and a branch portion for ending this routine without executing the fuel injection from step 12 to step 13 is a fuel injection stopping unit. Is equivalent to

Thus, at the time of high temperature restart, in this example, the fuel injection for two injections (for two rotations of the engine) is stopped for a preset period, the fuel in the intake passage is scavenged, and an indefinite amount of fuel leaks and drops. Even after that, it is possible to reliably create a startable air-fuel ratio thereafter.

In addition, if the ignition during the stop of the fuel injection is performed as usual, the fuel may explode only by the fuel dripping in the intake passage, so that the deterioration of the startability can be minimized.

Note that the period during which fuel injection is stopped may be defined by the engine speed or by time (for example, 1.0 sec).

When the engine speed is defined, it is preferable to stop fuel injection during two engine revolutions as in the present embodiment, and in the case of a four-cylinder engine, as shown in FIG.

Further, in the present embodiment, to determine the high-temperature restart state, at the time of starting the engine, it was determined based on the engine cooling water temperature Tw, but based on the fuel temperature in the pipe, the fuel injection was stopped,
It goes without saying that it may be determined whether or not to perform scavenging.

<Effects of the Invention> As described above, according to the present invention, it is determined whether or not the engine is at a high temperature restart. At that time, the fuel injection can be stopped for a predetermined period. The effect of being able to prevent the poor startability due to excess fuel by purging once is obtained.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing the configuration of the present invention, FIG. 2 is a system diagram showing one embodiment of the present invention, FIG. 3 is a flowchart showing control contents, and FIG. FIG. 5 is a diagram showing a conventional injection timing at the time of starting, and FIG. 6 is a diagram showing a relationship between a cooling water temperature and a fuel injection pulse width. 1 ... engine, 7 ... fuel injection valve, 8 ... control unit, 9 ... air flow meter, 10 ... crank angle sensor, 12 ... water temperature sensor, 14 ... engine key, 14a ...
… Ignition switch, 14b …… start switch

Claims (1)

(57) [Claims] 1. An electronically controlled fuel injection device for an internal combustion engine, comprising: a fuel injection valve in an engine intake system; and fuel injection control means for injecting fuel at a predetermined timing synchronized with engine rotation. Engine start time detecting means for detecting an engine start time which is ON, engine temperature detecting means for detecting an engine temperature, and the engine temperature detected by the engine temperature detecting means at the time of engine start detected by the engine start moving time detecting means. Starting fuel injection amount setting means for setting the fuel injection amount according to the engine temperature, wherein at the time of engine start detected by the engine start detection means, the engine temperature detected by the engine temperature detection means A high-temperature restart determining means for determining whether or not the engine is in a high-temperature restart state, based on an elapsed time from when the engine start time is first detected by the engine start time detecting means; The elapsed time measured by the start elapsed time measuring means and the preset elapsed time measured by the start elapsed time measuring means, and whether or not the start switch ON period is the first predetermined time period is determined. In the high-temperature restart state determined by the high-temperature restart determination unit, only the first preset period of the start switch ON period determined by the period determination unit,
An electronically controlled fuel injection device for an internal combustion engine, comprising: fuel injection stopping means for stopping fuel injection.