JPH03194149A - Fuel injection timing controller of engine - Google Patents

Abstract

PURPOSE:To improve a fuel consumption rate or exhaust surge performance by means of complete combustion by judging volatility of fuel to be used and controlling the injection timing of fuel to delay as the water temperature of an engine decreases in the case the volatility of the fuel is low. CONSTITUTION:In an ECU 40 which controls the fuel injection quantity of an injector according to an engine operation condition, a fuel judgement means 42 is provided to judge whether fuel currently used is light fuel, that is one with a proper volatility or not based on detection signals of an idle switch 29, an water temperature sensor 34 and an engine speed sensor 36. A timing variable means 44 is also provided to change a fuel injection timing to delay as an engine temperature decreases in the case the judgement result is inputted and the fuel is judged to be one with a low volatility. A control signal is outputted to injectors 30 from a fuel injection control means 46 based on a basic fuel injection timing or a changed fuel injection timing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for controlling fuel injection timing in an engine equipped with an electronically controlled fuel injection device.

[Conventional technology]

In an engine equipped with an electronically controlled fuel injection device, a signal is output to a fuel injection means such as an injector at a predetermined timing based on a detection signal from a crank angle sensor, etc., and fuel injection is thereby performed.

Here, the fuel injection timing is generally set at a certain time before the intake stroke so that the fuel is supplied into the engine in a sufficiently vaporized state.

However, when the engine temperature is low, even if the fuel is injected at the above timing, the fuel does not vaporize sufficiently and adheres to the intake valve and the inner wall of the intake pipe, resulting in the fuel not being sufficiently sent into the combustion chamber. There are cases. This phenomenon often occurs when so-called heavy fuels with low volatility are used, for example when using fuels whose volatility has been reduced by adding an anti-knock agent to increase the octane number. This is a major obstacle in performing good fuel injection control.

As a countermeasure, for example, as shown in Japanese Patent Application Laid-Open No. 60-222541, in the warm-up state where fuel adhesion is difficult to occur, fuel is injected during the expansion stroke before the intake stroke. After being completely vaporized by the heat near the intake valve, it is supplied into the fuel chamber for complete combustion.
On the other hand, in a cold engine operating state where the above-mentioned fuel adhesion is likely to occur, control is carried out such that fuel is injected at the beginning of the intake stroke and carried on the intake flow to carry the fuel to the combustion chamber while preventing the above-mentioned adhesion. It has been known.

[Problem to be solved by the invention]

In the above-mentioned engine, when a so-called light fuel with good volatility is used, even if the engine temperature is relatively low, the fuel naturally vaporizes and is less likely to adhere to the intake valve or the like. However, in the above device, even when such high-quality fuel is used, the injection timing is set late, so sufficient vaporization time is not secured, making it difficult to improve the fuel consumption rate and exhaust purification rate through complete combustion. At present, these effects are being sacrificed unnecessarily, resulting in a decline in engine performance.

In view of these circumstances, an object of the present invention is to provide a fuel injection timing control device for an engine that can always provide a good fuel supply without unduly impairing engine performance.

[Means to solve the problem]

The present invention provides a fuel injection timing control device for an engine that outputs a control signal to a fuel injection means based on a preset timing, thereby controlling the timing at which fuel is injected into the engine. a fuel determining means for determining whether the volatility of the fuel is good or bad; a water temperature detecting means for detecting the engine water temperature; The fuel injection device is provided with timing changing means that changes the fuel injection timing to be later as the water temperature is lower.

[For production]

According to the above configuration, when the volatility of the fuel used is good or when the engine is warmed up, the fuel injection timing is set to an earlier timing, for example, before the intake stroke. , sufficient vaporization time is ensured. Moreover, in this state, the fuel is easily vaporized, so even if the fuel is injected early, it is difficult for the fuel to adhere to the intake valve or the like.

On the other hand, when the volatility of the fuel used is low and the engine is in a cold state, the fuel injection timing is changed to a later stage, such as at the beginning of the intake stroke, so that the fuel is sufficiently Even if it is not vaporized, this fuel is carried smoothly into the combustion chamber by the intake air flow.

〔Example〕

FIG. 2 shows the overall configuration of an engine in one embodiment of the present invention. In the figure, 10 is an engine main body, each cylinder of which is provided with a piston 12, and above this piston 12 a combustion chamber 14 is formed. An intake valve 16, an exhaust valve 18, a spark plug 20, etc. are arranged at a position facing the combustion chamber 14, and an intake passage 22 and an exhaust passage 24 are connected to positions communicating with the intake valve 16 and exhaust valve 18, respectively. ing.

In the intake passage 22, an air flow meter 26 for detecting the intake air flow rate, a throttle valve 28, and an injector 30 for directly supplying fuel to the engine are arranged in this order. In this embodiment, the injector 30 is provided for each cylinder. There is. An idle switch 29 is provided near the throttle valve 28 and is turned on when the throttle valve 28 is fully closed, and the upstream and downstream parts of the throttle valve 28 are communicated through a bypass passage 31. ing.

Further, the exhaust passage 24 is provided with an 02 sensor 32 that detects the oxygen concentration in the exhaust gas, and the engine body 10 is provided with a water temperature sensor 34 that detects the engine water temperature. These 02 sensors 32 and water temperature sensors 34
, and detection signals from the idle switch 29, air flow meter 26, etc. are input to the ECU 40.

This ECU 40 has a functional configuration as shown in FIG.

In the figure, the fuel determining means 42 includes the idle switch 29, as will be explained in detail later in the flowchart of FIG.
, water temperature sensor 34, and engine speed sensor 36 (
Based on the detection signal (see FIG. 1), it is determined whether the fuel currently being used is a light fuel, that is, a fuel with good volatility.

When the fuel is determined to be light by the fuel determining means, the timing changing means 44 does not change the fuel injection timing, but changes the fuel injection timing to a preset basic fuel injection timing, specifically, the fifth fuel injection timing.
As shown by the solid line 51 in the time chart of the figure, the fuel is left in the middle of the exhaust stroke, which is before the intake stroke, and the fuel is determined to be heavy, that is, to have low volatility by the fuel determining means. In this case, as shown in the graph of FIG. 6, the lower the engine temperature, the later the fuel injection timing is changed.

The fuel injection control means 46 operates based on the basic fuel injection timing or the fuel injection timing changed by the timing changing means 44 and a detection signal from a crank angle sensor 38 (see FIG. 1) that detects the crank angle of the engine. Then, a control signal is output to each injector 30 at a predetermined timing to cause fuel injection to be performed.

Next, we will explain the details of the control actually performed by this device in the third section.
This will be explained with reference to the figure and the flowchart of FIG.

FIG. 3 shows the process of determining whether or not the fuel used is light. Here, a method is used to detect actual fluctuations in the engine speed in an idling state where there should be little fluctuation in the engine speed, and to determine the fuel level based on the results. That is, in this embodiment, before the vehicle actually starts, the volatility of the fuel is determined in advance.

First, various input signals are read in the ECU 40 (step S1), and it is determined whether the engine is currently in an idle state based on detection signals from the idle switch 29 and the like (step 82). The idle state here refers to a no-load idle state in which no external load such as a near conditioner is generated, and if a load such as the one described above is generated, the rotation speed will fluctuate due to this load. Therefore, it is excluded from the judgment conditions (N at step $2
o).

Furthermore, it is determined whether the engine water temperature is below 50°C, that is, whether the conditions are such that fuel adhesion is likely to occur (step S3), and if the condition is met, the rotational deviation ΔNe is calculated (step S4). .

This rotational deviation ΔNe is determined by the currently detected engine rotational speed Nei and the engine rotational speed N detected a certain time ago.
e (i-1), and when this rotational deviation ΔNe is large, it means that the rotational speed fluctuates greatly and unstable operation is being performed.

Therefore, if this rotational deviation ΔNe exceeds a preset value d (step S5), it is determined that the fuel being used is unstable heavy fuel, and the heavy flag is set to 1 (step S6). If the rotational deviation ΔNe is less than or equal to the above value d, it is determined that the fuel is a stable light fuel and the heavy flag is set to 0 (step S7).

After such a fuel determination is made, fuel injection timing control as shown in the flowchart of FIG. 4 is executed during actual operation based on the determination result. Note that, for convenience, only one of the first to fourth cylinders will be described here, but in this embodiment, similar control is performed for all cylinders (see the time chart in FIG. 5).

First, after various signals are read by the ECU 40 (step 511), a basic pulse TP corresponding to the basic fuel injection amount before being corrected is calculated (step 512).
). In this embodiment, the basic pulse TP is obtained by dividing the intake air amount Q detected by the air flow meter 26 by the engine rotational speed N and multiplying this by a constant coefficient K.

Next, various correction amounts such as the 02 feedback correction amount based on the detected value of the 02 sensor 32 are calculated (step 51).
3) The final pulse, that is, the pulse width of the signal actually output, is calculated from these correction amounts and the basic pulse TP (step 514). The above is the process of calculating the fuel injection amount.

0 Next, the injection timing by the injector 30 is set. First, check the currently set heavy flag, and if this heavy flag is 0 (step S1
5), that is, if the fuel is determined to be light fuel in the process shown in the flowchart of FIG. Then, as shown by the solid line 51 in the time chart of FIG. 5, the timing is set to correspond to the middle of the exhaust stroke (step S□7).

On the other hand, if the heavy flag is 1 (step S15
(YES), that is, when it is determined that the fuel used is heavy fuel, the actual injection timing is determined according to the engine water temperature, specifically, as shown in the graph of FIG. The lower the engine water temperature, the later the timing is changed (Step S6). As a result, for example, when the engine is in a warm-up state, the basic fuel injection timing corresponding to the middle of the exhaust stroke is set as the actual injection timing, similar to the timing set in step S17 above, and the engine is warmed up. When the engine is in a cold state, the timing corresponding to the beginning of the intake stroke is set as the injection timing, as shown by the two-dot chain line 52 in the time chart of FIG.

Thereafter, when the crank angle detected by the crank angle sensor 38 reaches the crank angle corresponding to the above-mentioned setting timing (step S]-8), the injector 30 is opened (step S□9), and the fuel is supplied to the predetermined level. is injected into the intake passage at the timing of

As described above, this device determines in advance whether the fuel used is light or heavy, and if the fuel is heavy, that is, has low volatility, the engine water temperature is low. Indeed, the injection timing is delayed, so in warm-up conditions, that is, when the fuel is relatively easy to vaporize due to engine temperature, the fuel is injected early to completely vaporize it, and then sent into the combustion chamber to completely vaporize it. While aiming to improve the fuel consumption rate and exhaust purification performance through combustion, the engine is in a cold state, that is, when the fuel is in the intake valve 16 or the intake passage 22.
In a state where the fuel tends to adhere to the inner wall, by injecting the fuel late and placing it on the intake air flow, it is possible to smoothly send the fuel into the combustion chamber without causing the above-mentioned adhesion.

On the other hand, if the fuel used is light, that is, if it is highly volatile and can be expected to naturally vaporize regardless of temperature, the above warming can be achieved by injecting the fuel at a consistently early timing. The effect of complete vaporization can be obtained in the same way as injection in the machine state.

Note that the timing specifically set in the present invention may be adjusted as appropriate depending on the configuration of the engine and the like. For example, if the fuel is light or the engine is warmed up, the fuel may be injected during the expansion stroke before the exhaust stroke, or if the fuel is heavy and the engine is cold, the fuel may be injected during the expansion stroke before the exhaust stroke. In some cases, fuel can be carried along with the intake air flow by injecting the fuel just before the intake stroke, ie, just before the intake valve opens.

In addition, in the present invention, the criteria for determining the volatility of fuel may be determined as appropriate, and regarding the determination means, the volatility may be detected directly using a sensor, etc., rather than by indirect means as described above. You can. For example, if the fuel is mixed with an anti-knock agent that impairs volatility,
Since this antiknock agent changes the refractive index of light, volatility can also be determined by detecting this refractive index with a sensor or the like.

Further, in the above embodiment, an injector 30 is arranged for each cylinder and the timing of each injector 30 is individually shifted, but the present invention is not limited to this.
For example, the present invention can also be applied to an air intake device in which a single injector is provided in a collective air intake device.

〔Effect of the invention〕

As described above, the present invention determines whether the volatility of the fuel used is good or not, and if the volatility of the fuel is low, the injection timing is delayed as the engine water temperature decreases. In warm-up conditions, when fuel is easily vaporized, the fuel is injected early to completely vaporize it, and then sent to the combustion chamber. This improves fuel consumption and exhaust purification through complete combustion, while also preventing the fuel from entering the intake air. In a cold engine state where fuel tends to adhere to the valves, the inner wall of the intake passage, etc., by injecting the fuel late and placing it on the intake air flow, it is possible to smoothly feed the fuel into the combustion chamber without causing the above-mentioned adhesion. Moreover, when the fuel is highly volatile, that is, when natural vaporization of the fuel can be expected, the fuel is injected at a predetermined timing regardless of the engine temperature, so there is no need to delay the injection timing more than necessary. By increasing the natural vaporization time, it is possible to ensure effects such as improvement in fuel consumption rate and exhaust purification due to complete combustion, similar to the warm-up state described above.

[Brief explanation of drawings]

FIG. 1 is a functional configuration diagram of an ECU provided in an engine according to an embodiment of the present invention, FIG. 2 is an overall configuration diagram of the engine, and FIGS. 3 and 4 show control operations performed by the ECU. FIG. 5 is a flowchart showing a time chart showing the fuel injection timing in the above engine, and FIG. 6 is a graph showing the relationship between engine temperature and fuel injection timing when the fuel is heavy in the same engine. 10... Engine body, 30... Injector, 3
4... Water temperature sensor, 40... ECU, 42... Fuel determining means, 44... Timing changing means, 46...
・Fuel injection control means.

Claims (1)

[Claims] 1. Volatization of the fuel used in an engine fuel injection timing control device that outputs a control signal to the fuel injection means based on a preset timing and thereby controls the timing of fuel injection into the engine. a fuel determining means for determining whether the volatility is good or bad; a water temperature detecting means for detecting the engine water temperature; and only when the fuel determining means determines that the volatility is poor, the water temperature detected by the water temperature detecting means is 1. A fuel injection timing control device for an engine, comprising: timing changing means for changing the fuel injection timing to a later value as the fuel injection timing becomes lower.