JPH01177438A - Fuel control device for engine - Google Patents

Abstract

PURPOSE:To prevent an occurrence of an excess or shortage in fuel supply quantity by discriminating the degree of a bubble occurrence in fuel on the basis of a fuel temperature and a controlled variable related to the feedback control of an idling engine speed, and correcting the fuel supply quantity based upon the result of the discrimination. CONSTITUTION:At the time of an idle operation, the opening of a valve in a bypass passage 4 bypassing the throttle valve 3 of an air intake passage 2 is controlled with a feedback control means 5, thereby converging an engine speed to a target number of revolutions 8. Also, a fuel supply quantity is controlled via the adjustment of a fuel injection pulse for an injector 6 provided in the air intake passage 2 with a supply quantity control means 7, and the supply quantity control means 7 sets the fuel supply quantity on the basis of output from a fuel temperature detecting means 8. In this case, there is provided a discrimination means 9 for discriminating the bubble occurrence condition of fuel on the basis of a fuel temperature and a controlled variable related to the feedback control of an idling engine speed. And when a bubble appears, a correction means 10 is made to correct the fuel supply quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fuel control device for an engine that controls the amount of fuel supplied in response to changes in fuel temperature.

(Prior Art) Conventionally, for example, when the engine is stopped immediately after continued high-speed operation, the temperature of the fuel inside the fuel supply pipe increases due to the rise in the ambient temperature of the engine, causing bubbles to form inside. If the engine is restarted with bubbles generated, the amount of injected fuel will be reduced by the amount of bubbles even if the fuel is injected with the regular fuel injection pulse, resulting in a lean air-fuel ratio and poor startability. There is.

Therefore, for example, the fuel distribution pipe may be made of a heat insulating material to suppress the rise in fuel temperature and the generation of bubbles (see Japanese Patent Laid-Open No. 60-43163), or the engine water temperature and intake air temperature may be detected. 111JL to predict the degree of bubble generation in the fuel.In conditions where bubbles are generated, increase the fuel discharge amount by increasing the fuel pressure to compress the bubbles, improve the lean air-fuel ratio, and reduce the temperature. Techniques for improving quick startability are known.

(Problem to be Solved by the Invention) However, when performing fuel supply control in response to the generation of bubbles in the fuel as described above, for example, in the case of a mixed fuel of gasoline and alcohol, the temperature and temperature may vary depending on the alcohol concentration. If the characteristics of the degree of bubble generation change and the fuel supply amount is uniformly corrected in response to temperature changes as described above,
There is a problem in that correction corresponding to the actual amount of bubbles generated cannot be made, and the amount of fuel supplied may be in excess or insufficient relative to the required amount.

SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to provide a fuel control device for an engine that can perform fuel supply control corresponding to the actual state of bubble generation in response to temperature changes.

(Means for Solving the Problems) In order to achieve the above object, the fuel control device of the present invention includes a feedback means for feedback controlling the idle rotation speed to the target rotation speed during idling, and detects a temperature related to the fuel temperature. Regarding setting and controlling the fuel supply amount by the supply amount control means based on the signal of the temperature detection means,
Discrimination means receives the signals from the temperature detection means and the feedback means and determines the degree of bubble generation in the fuel based on a temperature related to the fuel temperature and a control amount related to feedback control of the idle rotation speed after starting; and a correction means for correcting the amount of fuel supplied by the supply amount control means based on the determination by the determination means.

FIG. 1 is a block diagram for clearly showing the configuration of the present invention.

Feedback means 5 is provided for controlling the idle speed of the engine 1 by, for example, adjusting the amount of bypass air by a bypass passage 4 that bypasses the throttle valve 3 of the intake passage 2. Feedback control is performed so that the target rotational speed is achieved.

On the other hand, the amount of fuel supplied to the engine, for example,
A supply amount control means 7 is provided which controls the fuel injection pulse by adjusting the fuel injection pulse for the injector 6 installed in the injector 6, and a signal from a temperature detection means 8 that detects a temperature related to the fuel temperature is input to the supply amount control means 7. and the temperature detection means 8
The fuel supply amount is set and controlled based on the signal.

Then, the signals of the temperature detection means 8 and the feedback means 5 are outputted to the discrimination means 9, and this discrimination means 9
The state of bubble generation in the fuel is determined based on a temperature related to the fuel temperature and a control amount related to feedback control of the idle speed after startup. In other words, feedback control of the idle speed when the temperature is such that bubbles are generated in the fuel is such that when bubbles are generated in the fuel and the idle speed decreases due to a reduction in the supplied fuel,
For example, the amount of bypass air is controlled to increase so as to increase the engine speed, and the greater the degree of bubble generation, the greater the control amount of feedback control changes, and the relationship between the state of fuel bubble generation and the control amount of feedback control is There is a correlation between the two, and the bubble generation characteristics due to temperature can be determined even with changes in fuel components. The determination result of the determination means 9 is output to a correction means 10, which corrects the amount of fuel supplied by the supply amount control means 7 in accordance with the bubble generation situation.

The temperature detecting means 8 detects the temperature related to the fuel temperature by indirectly detecting the fuel temperature by detecting temperatures such as engine ambient temperature and intake air temperature, or by directly detecting the fuel temperature. . Further, the correction of the fuel supply amount by the correction means 10 is performed by correcting the fuel injection amount by correcting the fuel injection pulse, correcting the fuel supply amount by changing the fuel pressure, etc.

(Function) In the above-mentioned fuel control device, the amount of fuel supplied to the engine is set and controlled by the supply amount control means so as to increase the amount of fuel supplied to the engine in response to a change in fuel temperature, for example, at a warm start. The bubble generation characteristics that change according to changes in components are determined from the feedback control of the idle rotation speed, and the fuel supply amount is corrected according to the temperature by the supply amount control means, and fuel control is performed according to the bubbles actually generated. I try to do this.

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 2 is an overall configuration diagram of a specific example.

An intake boat 21 and an exhaust boat 22 are opened in the combustion chamber 20 of the engine 1, and the openings of both boats 21 and 22 are opened and closed at predetermined timings by an intake valve 23 and an exhaust valve 24, respectively. The intake passage 2 that communicates with the intake boat 21 and supplies intake air to the combustion chamber 20 includes, from the upstream side, an air cleaner 26 and an intake air amount sensor 2 that measures the amount of intake air.
7. A throttle valve 3 is installed to control the amount of intake air, and a downstream side of the surge tank 29 is formed independently for each cylinder, and fuel is injected and supplied to the downstream side of the surge tank 29 toward the intake boat 21. An injector 6 is provided.

Further, a bypass passage 4 that bypasses the throttle valve 3 is provided, and a control valve 30 that adjusts the amount of bypass air is interposed in the bypass passage 4.

The amount of fuel supplied from the injector 6 to the engine 1 is controlled by a control signal (injection signal) sent from the control unit 31 to the injector 6. The control unit 31 also controls the idle rotation speed by controlling the amount of bypass air by operating the control valve 30 installed in the bypass passage 4.

The control unit 31 includes an engine 1.
In order to detect the operating state of the engine, an intake air amount signal from the intake air amount sensor 27, an intake air temperature signal from the intake air temperature sensor 33 disposed in the intake passage 2, and an idle switch 34 that detects the fully open state of the throttle valve 3 are used. , an idle signal from the engine, a water temperature signal from the water temperature sensor 35 that detects the engine cooling water temperature, and a crank angle signal from the crank angle sensor 36 (
An engine rotation signal) and a starter signal from a starter switch 37 are input to detect when the engine is started.

The control unit 3.1 controls the amount of fuel injection and the amount of bypass air in accordance with the operating state of the engine from various sensors. Fuel injection control corrects the basic injection amount for starting using intake air temperature and the like during cranking, and after starting, calculates the basic injection amount based on the intake air amount and engine rotational speed, and performs various corrections. Moreover, the bypass air control calculates the amount of bypass air according to the difference between the detected idle rotation speed and the target idle rotation speed, and performs idle rotation speed control by driving and controlling the control valve 30. In the fuel injection control during idling, the basic injection amount is determined based on the intake air amount and the engine speed, and the fuel injection amount is determined in response to the change in the intake air amount due to the bypass air amount control of the idling speed. The system grasps the state of bubble generation from the fuel injection amount and the intake air temperature, and performs control to make corrections corresponding to the bubble generation based on a preset fuel increase map corresponding to the fuel injection amount and intake air temperature.

Next, the processing of the control unit 31 will be explained based on the flowchart of FIG. This flowchart only shows fuel injection control, and idle rotation speed control is performed by conventionally known feedback control, so detailed explanation thereof will be omitted.

After starting, set the engine speed to N in step S1.

Various signals such as intake air amount Q1, intake air temperature Ta, and water temperature Tw are read, and in step S2, it is determined whether or not cranking is being performed depending on whether the starter signal is on or not. This judgment is Y
When cranking with ES, the detected engine rotation speed N changes to the starting judgment rotation speed N5t (for example, 500 rpm) in step S3.
m) Determine whether it is lower than If the determination in step S3 is YES and during cranking, the starting basic injection Jf
Read iTs (injection time) and set it to basic injection mTp. This basic injection amount Ts for starting is the engine water temperature Tv
The lower the engine water temperature Tv, the lower the injection JfiT.
s is set to increase. Also, step S
In step 5, read the intake air temperature correction JlCa from the intake air temperature table. Then, in step S14, battery voltage correction Tv
Other correction amounts such as , etc. are read in, the final injection amount To is calculated in step S15, and a fuel injection pulse is output to the injector 6 (31B).

On the other hand, if the determination in step S2 or S3 is No and after the engine is started (after cranking), the basic injection amount "rp-(Q/N) is determined based on the intake air ff1Q and the engine speed N in step S6. XK (K is a constant) is calculated. Then, in step S7, it is determined whether or not it is in an idle state.

If the determination in step S7 is YES and the engine is idling, the process proceeds to step S8 and the basic injection EtTp is set to a predetermined value Tp.
It is determined whether the value is larger than set. This predetermined value T p
set is an idle standard basic injection amount that indicates a normal value when no bubbles are generated in the fuel. In addition, the basic injection QTp is a value determined according to the intake air amount Q that changes by bypass air adjustment based on feedback control of the idle rotation speed during idling, and when air bubbles are generated, the intake air ff1Q increases. Correspondingly, the basic injection ff1Tp also takes a large value. If this basic injection amount Tp is greater than the predetermined value Tpset and the determination in step S8 is YES, the correction flag F is set to 1 in step S9.
while the basic injection mTp is set to a predetermined value Tpset.
Below, if the determination in step S8 is No, the correction flag F is reset to 0 in step SIO.

During this idling operation, the vapor correction value cb is read in step S11, and fuel correction corresponding to the generation of bubbles is performed. This vapor correction value cb is obtained based on a map as shown in FIG. 4, and the fuel increase rate is set corresponding to the basic injection amount Tp and intake air temperature Ta, and its setting characteristics are Basically, the intake air temperature Ta
increases in the bubble generation region, the increase rate is set to increase as the basic injection amount Tp increases and the intake air temperature Ta rises, and when the fuel temperature increases, the increase rate increases according to the degree of bubble generation. This is to perform fuel correction.

Further, if the determination in step S7 is NO and the vehicle is not idling, the process advances to step S12 and it is determined whether the correction flag F is set to 1 or not.

Then, if the correction flag F is set to 1 and the basic injection amount Tp is larger than the predetermined value T psct and is in the bubble generation region, the basic injection ff is set in step Sll.
The vapor correction value cb is read based on 1Tp and the intake air temperature Ta, and as described above, when the fuel temperature becomes high, fuel correction is performed according to the degree of bubble generation, so that the value gradually returns to the reference value.

Further, if the determination in step S12 is NO and the correction flag F is reset and no bubbles are generated, then in step S13 the intake air temperature correction amount Ca is read from a table in which correction coefficients are set according to the intake air temperature Ta. .

After reading the vapor correction value cb or the intake air temperature correction amount Ca for the intake air temperature as described above, step S
In L4, other correction amounts such as battery voltage correction iTv % high load increase Cen are read, and in step S15, the basic injection amount Tp is corrected to calculate the final injection amount To, and a fuel injection pulse is output to the injector ( S1
B).

According to the embodiment described above, during idling operation, the intake air amount changes in accordance with the generation of bubbles based on the bypass air amount control, and the air bubbles are determined from the value of the basic injection 17Tp that changes according to the intake air amount. For example, even if the bubble generation characteristics with respect to fuel temperature change due to changes in fuel composition, the magnitude of this basic injection mTp and the intake air temperature T
A vapor correction value is calculated in accordance with a, and the fuel supply amount is corrected in accordance with the actual degree of bubble generation, thereby improving startability and the like. Additionally, when transitioning from idling operation to another operating range, vapor correction is initially continued when transitioning from a state in which vapor correction was performed during idling operation to improve drivability due to increases in fuel temperature. It is something to do.

Note that in the above embodiment, vapor correction in a region where the fuel temperature becomes high is performed not by directly detecting the control amount of feedback control of the idle rotation speed, but by detecting the value of the basic injection amount Tp that changes accordingly. Although this is done by determining the state of bubble generation, it is also possible to grasp the state of bubble generation based on feedback control of the idle rotation speed from values such as intake negative pressure. The map will also be changed accordingly.

(Effects of the Invention) According to the present invention as described above, by detecting the control amount of the feedback control of the idle rotation speed during idling, the generation state of bubbles in the fuel is grasped, and based on this, the fuel supply amount is adjusted. By correcting this, even if the fuel composition changes due to the use of alcohol mixed fuel and the bubble generation characteristics change, fuel control can be performed according to the bubbles actually generated. This makes it possible to satisfactorily improve startability, etc., without supplying excess fuel more than necessary.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an engine fuel control device to clearly demonstrate the configuration of the present invention, Fig. 2 is an overall configuration diagram of a specific example engine, and Fig. 3 is a flowchart diagram to explain the operation of the control unit. , FIG. 4 is a map diagram showing an example of map settings when determining the vapor correction value. 1... Engine, 5... Feedback means, 7... Supply amount control means, 8...
・Temperature detection means, 9...Discrimination means, 10...
. . . Correction means, 31 . . . Control unit, 33 . . . Intake temperature sensor. Diagram 2 - Rule 5''#艮 1 (1

Claims (1)

[Claims] (1) In an engine fuel control device equipped with a feedback means for feedback controlling the idle rotation speed to a target rotation speed during idling, the engine includes a temperature detection means for detecting a temperature related to the fuel temperature, and a temperature detection means based on a signal from the temperature detection means. a supply amount control means for setting and controlling the fuel supply amount by using the temperature detection means and the feedback means;
a determining means for determining the state of bubble generation in the fuel based on a temperature related to the fuel temperature and a control amount related to feedback control of the idle rotation speed after starting; and the supply amount control based on the determination by the determining means. 1. A fuel control device for an engine, comprising: a correction means for correcting the amount of fuel supplied by the means.