JPS6123841A - Air-fuel ratio controlling method in internal-combustion engine - Google Patents

Abstract

PURPOSE:To improve a starting characteristic ever so better, by increasing a fuel injection quantity as much as commensurate to an engine speed if fuel temperature is more than the specified value in time of engine starting. CONSTITUTION:At a step P1, that whether an internal-combustion engine is in time of starting or not is discriminated. Then, at a step P2, that whether fuel temperature is more than the specified one or not is discriminated as well. If it is in time of starting and the fuel temperature is above the specified value, a fuel injection quantity is increased according to an engine speed at a step P3. With this constitution, a starting characteristic in the engine is improved.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an air-fuel ratio control for an internal combustion engine that can control the amount of fuel supplied to the internal combustion engine and constantly operate the internal combustion engine under optimal conditions. Regarding the method.

[Prior Art] Conventionally, the amount of fuel supplied to an internal combustion engine mounted on a vehicle or the like has been controlled in order to operate the engine under optimal conditions. The same is true when starting the internal combustion engine, and the injection time of the fuel quantity control device is appropriately set in order to supply an amount of fuel that corresponds to the starting characteristics of the internal combustion engine.

However, with the method of determining the amount of fuel to be supplied to the internal combustion engine in proportion to the injection time of the fuel injection device, the fuel in the fuel pipe of the fuel injection device is at a high temperature due to reasons such as high-load long-term operation of the internal combustion engine. In such cases, when paper is generated, fuel is not supplied for the same amount of paper even if the injection time is the same, resulting in a mixture that is much leaner than the desired air-fuel ratio (g, called lower lean). It becomes.

This phenomenon is particularly problematic when starting the internal combustion engine, and there is a possibility that sufficient fuel may not be supplied to start the internal combustion engine, making it impossible to start, or even if it does start, the idling state may become unstable.

Therefore, as disclosed in JP-A-56-81230 or JP-A-57-10741, when starting an internal combustion engine with fuel at a high temperature,
Devices that increase the amount of fuel injection for a predetermined period of time and devices that increase the amount of fuel injection in accordance with fuel temperature have been proposed.

[Problems to be Solved by the Invention] However, the above-mentioned apparatus also has the following problems, and is still not satisfactory.

In other words, the paper generated in the fuel piping varies depending on the various internal combustion engine systems and their usage conditions, from those generated very close to the fuel injection valve to those generated near the fuel tank side, so paper ejects. The time required for this is not uniquely determined. Therefore, by simply increasing the amount of fuel injection based on the time elapsed since startup, it is not possible to determine whether or not the paper has completely disappeared from the fuel pipe; If you stop increasing the amount of fuel injection OA even though it remains in the piping, there is a possibility that paper lock will occur.
On the other hand, if the amount of fuel continues to be increased for a long time, the air-fuel ratio becomes abnormally rich, resulting in a problem of deterioration of fuel efficiency and emissions.

In addition, fuel injection according to fuel temperature! ) The relationship between the fuel temperature and the amount of paper generated is not unambiguous, and similarly to the above, the timing at which paper is generated depends on the internal combustion engine system and its usage conditions. Since it is not possible to determine whether or not the fuel is ejected into the combustion chamber of the internal combustion engine, the problem is the same as that described above.

[Object of the invention] The present invention has been made to solve the above problems,
Fuel injection ffl according to paper generated in fuel piping
An air-fuel ratio control method for an internal combustion engine that improves starting characteristics and idling stability by accurately correcting the fuel injection amount when paper is generated by executing the correction, and improves fuel efficiency and emissions. is intended to provide.

[Means for Solving the Problems] The configuration of the present invention to achieve the above object is as shown in the basic configuration diagram of FIG. In an air-fuel ratio control method for an internal combustion engine using a controlled fuel injection device, at the time of starting the internal combustion engine (Pl), it is determined whether the fuel temperature is above a predetermined temperature (P2), and if the fuel temperature is above the predetermined temperature (P2). The air-fuel ratio control method for an internal combustion engine is characterized in that when the determination is made, the fuel injection amount of the internal combustion engine is increased and the amount of increased control is decreased in accordance with an increase in the rotational speed of the internal combustion engine (P3). What is the gist?

[Operation] The fuel temperature determination at the time of startup of the present invention is to determine whether or not there is a condition where paper is generated in the fuel pipe.

Therefore, the method is not limited to directly detecting the fuel temperature at startup and comparing it with a predetermined value, but may also be a method of detecting the temperature of the cooling water of the internal combustion engine, the temperature of the intake air, etc., and estimating the fuel temperature.

Note that the fact that the internal combustion engine is starting is determined by detecting a state in which the ignition key is turned on, a state in which the rotational speed of the internal combustion engine is low, or the like.

The increase control of the fuel injection amount according to the rotational speed of the internal combustion engine, which is executed when the fuel temperature at the time of starting the internal combustion engine is determined to be equal to or higher than a predetermined value using the above method, means This increases the amount of fuel injected, and prevents the internal combustion engine's rotational speed from decreasing due to a lean air-fuel ratio due to a large amount of paper. The amount of increase is determined by using a map stored in the storage means or by calculation from a relational expression including the number of revolutions. Furthermore, the relationship between the rotational speed and the amount of increase is selected optimally for each internal combustion engine system. The method for increasing the amount of fuel may be either by lengthening the time it takes to perform fuel injection or by increasing the injection pressure of fuel injection.

EXAMPLES Hereinafter, in order to explain the present invention more specifically, the present invention will be described in detail with reference to Examples.

[Example] First, FIG. 2 is an explanatory diagram showing a gasoline engine and its peripheral equipment to which the method of the present invention is applied.

1 is the gasoline engine body, 2 is the piston, 3 is the spark plug, 4 is the exhaust manifold, 5 is the exhaust manifold 4
6 is a fuel injection valve that injects fuel into the intake air of the gasoline engine body 1, 7 is an intake manifold, and 8 is an intake valve that is sent to the gasoline engine body 1. An intake air temperature sensor 9 detects the temperature of the air, a water temperature sensor 9 detects the temperature of gasoline engine cooling water, a throttle valve 10 adjusts the intake air amount of the gasoline engine 1, and 11 detects the opening degree of the throttle valve 10. Throttle valve-11
Reference numeral 4 represents an air 70 meter that measures the amount of intake air, and 15 represents a surge tank that absorbs pulsation of the intake air.

16 is an igniter that outputs the high voltage necessary for ignition; 17 is a distributor that is linked to a crankshaft (not shown) and distributes the high voltage generated by the igniter 16 to the spark plugs 3 of each cylinder; and 18 is a distributor 17 A rotation angle sensor 19 is attached to the distributor 17 and outputs 24 pulse signals for one revolution of the distributor 17, that is, two revolutions of the crankshaft.
20 is an electronic control circuit, 21 is a key switch, and 22 is a starter motor. 26 represents a vehicle speed sensor that is linked to the axle and transmits a pulse signal according to the vehicle speed.

Next, FIG. 3 shows a block diagram of the electronic control circuit 20 and its related parts.

30 is a central processing unit (hereinafter simply referred to as CPU) that inputs and calculates data output from each sensor according to a control program and also performs processing for controlling the operation of various devices; 31 is a central processing unit that inputs and calculates data output from each sensor; A read-only memory (hereinafter simply referred to as ROM) in which data is stored; 32 a random access memory (hereinafter simply referred to as RAM) in which data input to the electronic control circuit 20 and data required for arithmetic control are temporarily read and written; ), 33 is when the key switch 21 is turned off.
[Backup random access memory (non-volatile memory backed up by a battery) to retain data necessary for further operation of the internal combustion engine]
34 to 37 are buffers for the output signals of each sensor; 38 is a multiplexer that selectively outputs the output signal of each sensor to CPL 30;
39 is an A/D converter that converts an analog signal into a digital signal; 40 is an A/D converter that sends each sensor signal to the CPU 30 via a buffer or via a buffer, a multiplexer 38 and an A/D converter 39; and a multiplexer 38 from the CPU 30; , represents an input/output port that outputs a control signal of the A/D converter 39.

41 converts the output signal of the oxygen sensor 5 into the comparator 4.
2, a buffer 43 represents a shaping circuit that shapes the waveforms of the output signals of the rotation angle sensor 18 and the cylinder discrimination sensor 19. The output of the throttle opening sensor 11 and the operation signal of the key switch 21 are sent to the CPU 3 via an input/output port 46 directly or via a buffer 41 or the like.
Sent to 0.

Additionally, 47.48 connects to CP via output port 49.50.
Fuel injection valve 6 and igniter 1 are activated by the signal from U30.
6 respectively represent the drive circuits that drive 6. Also 5
1 is a path line for signals and data, 52 is a CP
It represents a clock circuit that sends a clock signal serving as a control timing to U30, ROM 31, RAM 32, etc. at predetermined intervals.

Next, the control program of this embodiment will be explained.

FIG. 4(A) and FIG. 5 are flowcharts of this embodiment.

First, the processing of the starting air-fuel ratio control routine shown in FIG. 4 (A>) will be explained step by step.

This routine interrupts CPU 3° when the key switch 21 is turned on when the gasoline engine 1 is started.

When the process of this routine is started, step 100 is executed, and it is determined whether the throttle valve 10 is fully open based on the output of the throttle interval sensor 11, and if it is fully open, the next step 110 is executed. Otherwise, this routine ends.

In step 110, the humidity of the cooling water of the gasoline engine 1 is detected and determined as one method for estimating the temperature of the fuel supplied to the gasoline engine 1. Then, in this step, when the output of the water temperature sensor 9 is higher than 85° C., the process proceeds to the next step 120, and when it is lower than 85° C., the routine ends.

In step 120, the humidity of the intake air of the gasoline engine 1, which is another information for estimating the fuel temperature, is detected.
Discern. At this time, if the output of the intake temperature t-sensor 8 is higher than 65° C., the process proceeds to the next step 130, and if it is lower than that, the routine ends.

Therefore, the operating status of the gasoline engine 1 when step 130 is executed is that the ignition key has just been turned ON, the accelerator has not been operated yet, the water ITW>85°C, and the intake IT△>65°C. ℃, when restarting at a high temperature. This step is executed only under such special conditions, and Fho, which is the correction coefficient for the basic fuel injection amount (fuel injection time) Tp, which will be described later.
Set t to ro, 5J. As will be described later, this process allows the fuel injection time to be extended and a desired additional amount of fuel to be injected.

In the following step 140, in order to detect the current starting state of the gasoline engine 1, the average rotation speed ANE of the gasoline engine 1 is calculated based on the output of the rotation angle sensor 18. As is well known, the rotational speed of the gasoline engine 1 shows large fluctuations during startup. Therefore, in this step, the time required for the gasoline engine 1 to rotate 16 times is measured, and from that value, the average rotation speed AN of the gasoline engine 1 is calculated.
It calculates E.

In the next step 150, this calculated average rotation speed A
Based on NE, the correction coefficient Fhot is changed.

People say that the average rotational speed ANE increases.
In other words, gasoline engine 1! If! This suggests that the increase in fuel injection amount was sufficient to improve the starting characteristics and to correct the air-fuel ratio, which was lean by the amount of vapor. Therefore, as the average rotational speed ANE of the gasoline engine 1 increases, the correction coefficient Fhot is successively made smaller.

Figure 4 (B) shows this average rotational speed ANE and correction coefficient Fho.
A graph showing the relationship (f) with t is shown. In the gasoline engine system of this embodiment, the average rotational speed ANE of the gasoline engine 1 executed by the starter motor is 250 [rp1
11], idle average speed AN of gasoline engine 1
E is 750 [rto+I], and the optimum correction coefficient F hot was experimentally determined.

This makes it possible to supply fuel according to the operation of the gasoline engine 1.

In the following step 160, it is determined whether the correction coefficient Fhot is equal to rOJ. That is, in the previous step, the average rotation speed A
NE becomes 800 [rpm] and the correction coefficient Fhot becomes the fourth
As shown in Figure (B), it is set to "0", and it is determined that the gasoline engine 1 has run out of fuel paper and is in a normal idling state.

At this point, if it is determined that the average rotational speed of the gasoline engine 1 has not reached NE of 800 [rl)m], the process returns to step 140 and repeats the same process. However, when the average rotational speed NE is 800 [rpm], that is, when Fhot is rOJ, all processing of this routine is completed.

Determine the correction coefficient determined as described above (the actual fuel injection time shown in FIG. 5, which is executed in synchronization with the rotation speed of the gasoline engine 1, using :hot). A fuel injection time determination routine is then processed.

When the CPU 30 enters the processing of this routine, step 200 is first executed, and the rotation speed NE of the gasoline engine 1 and the intake air ff1Q are calculated based on the outputs of the rotation angle sensor 18 and the air flow meter 14, and the next step 210 is executed.
It is used for processing.

In step 210, the load Q/NE is calculated from these two basic operation information of the gasoline engine 1, and then the basic fuel injection amount (basic fuel injection time) Tp, which is the optimal fuel supply amount for the load, is stored in the ROM. 3' Search from the map in 1.

In the following step 220, a correction coefficient K for the basic fuel injection amount Tp is calculated based on information from various sensors provided in the gasoline engine system. for example,
The correction coefficient learned from the previous operating state of the gasoline engine 1, the warm-up state of the gasoline engine, and the oxygen sensor 5
The correction coefficient is calculated as a total of various correction values such as the air-fuel ratio feedback correction coefficient based on the output.

Then, in the next step 230, the fuel injection amount (fuel injection time) to be actually executed is calculated using the following formula from the correction coefficient obtained as described above and Fhot obtained in the flowchart of FIG. 4 (A>). It is calculated using

T=Tp x (K+Fhot) In the next step 240, the fuel injection amount T calculated in the previous step 230 is stored in the RAM 32, and the processing of this routine is ended.

The fuel injection amount T stored in the RAM 32 in this way
is read out by another fuel injection execution routine as appropriate, and fuel injection corresponding to the fuel injection amount is executed from the fuel injection valve 6 to the gasoline engine 1, thereby making it possible to operate the gasoline engine 1 at a desired air-fuel ratio. It is.

As is clear from the detailed description above, the air-fuel ratio control method of this embodiment, when it is determined that the fuel in the gasoline engine 1 is at a predetermined temperature or higher, controls the fuel injection to
Extend fuel injection time to increase by 0% (Step 1)
30). Then, the increased amount is determined by detecting the rotational speed of the gasoline engine 1, and is reduced as appropriate according to the increase in the rotational speed (step 150).

Therefore, when the fuel temperature is high and paper is generated, the fuel injection amount is increased, so fuel suitable for the starting characteristics of the gasoline engine 1 is supplied, and the starting is smooth, and the paper is reduced. If the fuel supply to the gasoline engine 1 is large (and the rotation speed increases), the fuel injection time is reduced as the rotation speed increases. In other words, paper is generated and the amount of fuel supplied to the gasoline engine 1 is reduced to the desired amount. When the rotation speed of the gasoline engine 1 is lower than the value and the rotation speed of the gasoline engine 1 does not increase, the process of increasing the fuel injection amount is continued, and when the rotation speed of the gasoline engine 1 increases due to the increase process and starts to start, the fuel amount is decreased until it becomes excessive. This makes it possible to prevent fuel from being supplied to the gasoline engine 1.

Because it's such a great way to run a fuel supply.
The starting characteristics of the gasoline engine 1 are improved, and since excessive fuel supply is prevented, fuel efficiency is improved, and deterioration of emissions can also be prevented.

[Effects of the Invention] As described above with reference to the embodiments, the air-fuel ratio control method for an internal combustion engine according to the present invention is capable of controlling the air-fuel ratio according to the rotational speed of the internal combustion engine when the fuel temperature at the time of starting the internal combustion engine is equal to or higher than a predetermined value. This method is characterized by executing control to increase the fuel injection amount.

Therefore, the starting characteristics of the internal combustion engine are improved by increasing the amount of fuel supplied relative to the amount of paper in the fuel pipe, and
When the internal combustion engine starts to start and increases its rotational speed, the amount of fuel supplied is reduced in order to prevent an excessive amount of fuel supplied.

This provides an excellent air-fuel ratio control method that allows the internal combustion engine to have good starting and subsequent idling stability, and to prevent deterioration of fuel efficiency and emissions due to excessive fuel supply.

[Brief explanation of drawings]

Fig. 1 is a basic configuration diagram of the present invention, Fig. 2 is a schematic configuration diagram of an embodiment, Fig. 3 is a block diagram of its control device, and Fig. 4 (
A) is a flowchart of the air-fuel ratio control at the time of starting, (B,
) The figure shows the rotation speed and correction coefficient Fh. A graph showing the relationship with t, and FIG. 5 shows a flowchart for determining the fuel injection time. 1...Gasoline engine 6...Fuel injection valve 8...Intake temperature sensor 9...Water temperature sensor 14...J aphrometer 18...Rotation angle sensor 20...Electronic control circuit

Claims (1)

[Scope of Claims] In an air-fuel ratio control method for an internal combustion engine using an electronically controlled fuel injection device that operates the internal combustion engine by injecting fuel from a fuel injection valve, the fuel temperature is equal to or higher than a predetermined temperature when the internal combustion engine is started. and when it is determined that the temperature is higher than a predetermined temperature, the fuel injection amount of the internal combustion engine is increased and the amount of fuel injection is decreased in response to an increase in the rotational speed of the internal combustion engine. Features: Air-fuel ratio control method for internal combustion engines.