JPH06105061B2 - Air-fuel ratio control method for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention controls the amount of fuel supplied to an internal combustion engine so that the internal combustion engine can always be operated under optimum conditions. Regarding the method.

[Prior Art] Conventionally, the amount of fuel supplied to an internal combustion engine mounted on a vehicle or the like is controlled in order to operate the engine under optimal conditions. The same is true at the time of starting the internal combustion engine, and the injection time of the fuel injection device is appropriately set so as to execute the supply of the amount of fuel according to the starting characteristics of the internal combustion engine.

However, in 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 has a high temperature due to causes such as high load long-time operation of the internal combustion engine. When the vapor is generated, the fuel is not supplied only for the vapor even during the same injection time, resulting in a considerably lean air-fuel mixture (hereinafter referred to as lean) compared to the predetermined air-fuel ratio. . This phenomenon is particularly a problem at the time of starting the internal combustion engine, and the fuel is not sufficiently supplied for starting the internal combustion engine, so that the engine cannot be started or the idle state may become unstable even if the engine is started.

Therefore, JP-A-56-81230 or JP-A-57-107 is used.
As disclosed in Japanese Patent No. 41, there is a device for increasing the fuel injection amount for a predetermined time when starting the internal combustion engine in a state where the fuel temperature is high, or a device for increasing the fuel injection amount according to the fuel temperature. Proposed.

[Problems to be Solved by the Invention] However, even the above-mentioned apparatus has the following problems, which are not yet sufficient.

In other words, the vapor generated in the fuel pipe varies from the one generated near the fuel injection valve in various internal combustion engine systems and its usage conditions to the one generated near the fuel tank side. The amount of time given is not uniquely defined. Therefore, it is not possible to determine whether or not the vapor portion has completely disappeared from the fuel pipe by simply increasing the fuel injection amount based only on the time elapsed from the start, and the vapor is still in the fuel pipe. If the increase in fuel injection amount is stopped despite remaining, vapor lock may occur.Conversely, if the time for continuing the increase is too long, the air-fuel ratio becomes abnormally rich and fuel consumption and emission deteriorate. There was a problem of inviting.

Also, in the case of executing the increase of the fuel injection amount according to the fuel temperature, the relationship between the fuel temperature and the amount of vapor generated is not unique, and the same as above, depending on the internal combustion engine system and its usage condition. Since it is not possible to determine at what point of time the generated vapor is ejected into the combustion chamber of the internal combustion engine, there is the same problem as described above.

[Object of the Invention] The present invention has been made to solve the above problems,
By correcting the fuel injection amount according to the vapor generated in the fuel pipe, the fuel injection amount when the vapor is generated is accurately corrected to improve the starting characteristics and idle stability, and to improve the fuel economy. It is an object of the present invention to provide an air-fuel ratio control method for an internal combustion engine that achieves good emission and emission.

[Means for Solving the Problems] According to the configuration of the present invention for achieving the above object, as shown in the basic configuration diagram of FIG. 1, fuel is injected and supplied from a fuel injection valve to operate an internal combustion engine. In an air-fuel ratio control method for an internal combustion engine using an electronically controlled fuel injection device, when the internal combustion engine is started (P1), it is determined whether the fuel temperature is equal to or higher than a predetermined temperature (P2), and the temperature is equal to or higher than the predetermined temperature. When it is determined that the fuel injection amount of the internal combustion engine is increased, the amount increased by the increase control is gradually decreased in accordance with the increase in the rotation speed of the internal combustion engine (P3). The gist is the air-fuel ratio control method.

[Operation] The determination of the fuel temperature at the time of starting of the present invention is to determine whether or not the condition is such that vapor is generated in the fuel pipe.
Therefore, the method is not limited to the method of directly detecting the fuel temperature at the time of starting and comparing it with a predetermined value, but a method of estimating the fuel temperature by detecting the temperature of the cooling water of the internal combustion engine or the temperature of the intake air may be used.

It should be noted that the fact that the internal combustion engine is starting is performed by detecting a state in which the ignition key is turned on, a state in which the rotation speed of the internal combustion engine is low, and the like.

When the fuel temperature at the time of starting the internal combustion engine is determined to be equal to or higher than the predetermined value by the above method, the control for increasing the fuel injection amount according to the rotational speed of the internal combustion engine is performed if the rotational speed is low. The amount of fuel injection is increased, and the decrease in the rotational speed of the internal combustion engine caused by the large amount of vapor and the lean air-fuel ratio is prevented. The increase amount is obtained by using a map stored in the storage means or by calculation from a relational expression including the rotation speed. Further, the relationship between the rotation speed and the increase amount is optimally selected for each internal combustion engine system. As a method of increasing the amount, either a method of lengthening the time for executing the fuel injection or a method of increasing the injection pressure of the fuel injection may be used. Then, the amount of increase by the increase control is gradually decreased as the engine speed increases.

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

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

1 is a gasoline engine body, 2 is a piston, 3 is a spark plug, 4 is an exhaust manifold, 5 is an exhaust manifold 4
An oxygen sensor for detecting the residual oxygen concentration in the exhaust gas, 6 a fuel injection valve for injecting fuel into the intake air of the gasoline engine body 1, 7 an intake manifold, 8 sent to the gasoline engine body 1. An intake air temperature sensor that detects the temperature of intake air, 9 a water temperature sensor that detects the water temperature of the gasoline engine cooling water, 10 a throttle valve that adjusts the intake air amount of the gasoline engine 1, 11 that detects the opening of the throttle valve 10. Is a throttle sensor, 14 is an air flow meter for measuring the amount of intake air, and 15 is a surge tank for absorbing the pulsation of intake air.

16 is an igniter that outputs the high voltage required for ignition,
17 is an igniter that is linked to a crankshaft (not shown).
Distributor 18 that distributes the high voltage generated in 16 to the ignition plugs 3 of each cylinder, and 18 is installed in the distributor 17 and outputs a pulse signal of 24 pulses for one rotation of the distributor 17, that is, two rotations of the crankshaft. A sensor, 19 is a cylinder discrimination sensor that outputs a pulse signal for one revolution of the distributor 17, 20 is an electronic control circuit, 21 is a key switch, and 22 is a starter motor. Reference numeral 26 denotes a vehicle speed sensor which is interlocked with the wheels and transmits a pulse signal corresponding 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 performs processing for controlling operation of various devices, 31 indicates a control program and initial data. Read-only memory (hereinafter simply RO
M), 32 is a random access memory (hereinafter simply referred to as RAM) in which data input to the electronic control circuit 20 and data necessary for arithmetic control are temporarily read and written, and 33 is a key switch 21 turned off. Backup random access memory (hereinafter simply referred to as backup RAM) as a non-volatile memory backed up by a battery so as to retain data necessary for subsequent operation of the internal combustion engine, 34 to 3
7 is a buffer for the output signal of each sensor, 38 is a multiplexer that selectively outputs the output signal of each sensor to the CPU 30, 39
Is an A / D converter that converts analog signals to digital signals, 4
0 is an input / output port for sending each sensor signal to the CPU 30 via the buffer or via the buffer, the multiplexer 38 and the A / D converter 39 and outputting the control signal of the multiplexer 38 and the A / D converter 39 from the CPU 30. Is represented.

41 is a buffer for sending the output signal of the oxygen sensor 5 to the comparator 42, and 43 is the rotation angle sensor 18 and the cylinder discrimination sensor.
The shaping circuit for shaping the waveform of the output signal of 19 is shown. The output of the throttle opening sensor 11 and the operation signal of the key switch 21 are sent to the CPU 30 by the input / output port 46 directly or via the buffer 41 and the like.

Further, 47 and 48 represent drive circuits for driving the fuel injection valve 6 and the igniter 16 by a signal from the CPU 30 via the output ports 49 and 50, respectively. In addition, 51 is a bus line that serves as a passage for signals and data, 52 is a CPU 30, ROM31, RAM3
It represents a clock circuit that sends a clock signal that becomes the control timing at a predetermined interval to 2nd and the like.

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

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

First, the processing of the starting air-fuel ratio control routine of FIG. 4A will be described step by step.

This routine is interrupted by the CPU 30 when the key switch 21 is turned on when the gasoline engine 1 is started.

When the processing of this routine is started, step 100 is executed and it is determined based on the output of the throttle opening sensor 11 whether or not the throttle valve 10 is in the fully closed state. If this is not the case, this routine ends.

In step 110, the gasoline engine 1 is used as one method for estimating the fuel temperature supplied to the gasoline engine 1.
The temperature of the cooling water is detected and determined. 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 if it is lower than this, this routine is ended.

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

Therefore, the operating condition of the gasoline engine 1 when step 130 is executed is immediately after the ignition key is turned on, the accelerator has not been operated yet, and the water temperature TW
> 85 ° C., intake air temperature TA> 65 ° C., that is, when restarting at high temperature. This step is executed only under such a special condition, and is one of the correction coefficients of the basic fuel injection amount (fuel injection time) Tp described later. Set Fhot to "0.5". By this processing, as will be described later, the fuel injection time can be extended and the desired fuel injection amount increase control can be performed.

In the following step 140, in order to detect the current starting state of the gasoline engine 1, the average rotational speed ANE of the gasoline engine 1 is calculated based on the output of the rotation angle sensor 18. At the time of starting, as is well known, the rotational speed of the gasoline engine 1 shows a large fluctuation. Therefore, in this step, the time required for the gasoline engine 1 to rotate 16 times is measured, and the average rotational speed ANE of the gasoline engine 1 is calculated from the value.

In the next step 150, the correction coefficient Fhot is changed based on the calculated average rotational speed ANE. Average speed
Those who say that ANE rises, that is, gasoline engine 1
It means that the fuel injection amount executed to improve the starting characteristics and to correct the air-fuel ratio that was lean by the vapor amount was sufficient. . Therefore, the correction coefficient Fhot is made smaller as the average rotational speed ANE of the gasoline engine 1 increases.

FIG. 4 (B) shows a graph showing the relationship (f) between the average rotational speed ANE and the correction coefficient Fhot. The gasoline engine system of this embodiment has an average engine speed ANE of the gasoline engine 1 executed by the starter motor of 250 [rpm] and an idle engine average speed ANE of the gasoline engine 1 of 750 [rpm], which is experimentally optimum. The correction coefficient Fhot is obtained.

As a result, fuel can be supplied according to the operation of the gasoline engine 1.

In the following step 160, it is determined whether or not the correction coefficient Fhot is "0". That is, the average speed ANE is 800 in the previous step.
It becomes [rpm] and the correction coefficient Fhot is set to "0" as shown in FIG. 4 (B), and the vapor of the fuel of the gasoline engine 1 is exhausted, and it is judged that the engine is in the normal idle state. Here, the average engine speed AN of the gasoline engine 1 is still
When E is not 800 [rpm] and it is judged that the fuel vapor is not removed, the routine returns to step 140 and the same processing is repeated thereafter, and the average rotational speed ANE is 800 [rpm], that is, Fho
If t is "0", all the processes of this routine are completed.

Fuel injection for determining the actual fuel injection amount (fuel injection time) T shown in FIG. 5, which is executed in synchronization with the rotational speed of the gasoline engine 1, using the correction coefficient Fhot determined as described above. The time T determination routine is processed.

When the CPU 30 enters the processing of this routine, step 200 is first executed, the rotational speed NE of the gasoline engine 1 and the intake air amount Q are calculated based on the outputs of the rotation angle sensor 18 and the air flow meter 14, and then step 210 is executed. To be processed.

In step 210, the load Q / NE is calculated from the operation information of these two basic gasoline engines 1, and the basic fuel injection amount (basic fuel injection time) Tp, which is the optimum fuel supply amount for that load, is stored in the ROM 31. Search from the map in.

In the following step 220, the correction coefficient K of the basic fuel injection amount Tp is calculated based on the information from various sensors that are easily implemented in the gasoline engine system. For example, the correction coefficient K is calculated by integrating various correction values such as the correction coefficient learned from the operation state of the gasoline engine 1 up to the previous time, the warm-up state of the gasoline engine, the air-fuel ratio feedback correction coefficient by the output of the oxygen sensor 5, and the like. Is done.

Then, in the next step 230, the correction coefficient K obtained as described above and the flowchart of FIG. 4 (A) are obtained.
Actual fuel injection amount from Fhot (fuel injection time)
T is calculated using the following formula.

T = Tp × (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 ends.

In this way, the fuel injection amount T stored in the RAM 32 is appropriately read by another fuel injection execution routine, and the fuel injection corresponding to the fuel injection amount T is executed from the fuel injection valve 6 to the gasoline engine 1 to obtain the desired value. The gasoline engine 1 can be operated with the air-fuel ratio of.

As is clear from the above description, when the air-fuel ratio control method of the present embodiment determines that the fuel of the gasoline engine 1 is at a predetermined temperature or higher, the fuel injection of 50
Extend the fuel injection time to increase the fuel consumption by% (step 13
0). Then, the amount of increase is detected by detecting the number of revolutions of the gasoline engine 1 and appropriately reduced as the number of revolutions increases (step 150).

Therefore, when the fuel temperature is high and vapor is generated, the process for increasing the fuel injection amount is executed, so that the fuel suitable for the starting characteristics of the gasoline engine 1 is supplied to make the starting good and the vapor decreases. When the fuel supply to the gasoline engine 1 increases and the rotation speed increases, the fuel injection time is reduced according to the increase in the rotation speed. That is, when the fuel supply amount of the gasoline engine 1 is lower than the desired value due to the occurrence of vapor and the rotation speed of the gasoline engine 1 does not increase, the fuel injection amount increasing processing is continued, and the rotation speed of the gasoline engine 1 is increased by the increasing processing. Is increased and starts to be started, the fuel amount is decreased and it is possible to prevent the excessive fuel from being supplied to the gasoline engine 1.

Because it is a way to perform such a good fueling,
The starting characteristics of the gasoline engine 1 are good, and moreover, there is an effect that fuel consumption is improved in order to prevent excessive fuel supply, and deterioration of emission is also prevented.

[Advantages of the Invention] As described above with reference to the embodiments, the method of controlling the air-fuel ratio of the internal combustion engine of the present invention, when the fuel temperature at the start of the internal combustion engine is equal to or higher than a predetermined value, This is a method characterized by executing the increase control and gradually decreasing the increase amount by the increase control in accordance with the increase of the engine speed.

Therefore, while increasing the fuel supply amount with respect to the amount of vapor in the fuel pipe to improve the starting characteristics of the internal combustion engine,
When the internal combustion engine starts to start and the number of revolutions increases, the fuel supply amount is reduced by the increase amount in order to prevent the fuel supply amount from being excessive. This decrease in the amount of increase is performed gradually according to the engine speed, so that the engine speed does not suddenly rise or fall. As a result, neither excessive fuel is supplied even if the vapor is eliminated, or the fuel increase is not stopped even though the vapor remains.

As a result, the internal combustion engine has a good starting and subsequent idle stability, and is an excellent air-fuel ratio control method that can prevent deterioration of fuel consumption and emission due to excessive fuel supply.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of the present invention, FIG. 2 is a configuration schematic diagram of an embodiment, FIG. 3 is a block diagram of a control device thereof, and FIG. 4 (A) is a flow chart of the starting air-fuel ratio control,
FIG. 5B is a graph showing the relationship between the rotational speed and the correction coefficient Fhot, and FIG. 5 is a flowchart for determining the fuel injection time. 1 …… Gasoline engine 6 …… Fuel injection valve 8 …… Intake air temperature sensor 9 …… Water temperature sensor 14 …… Air flow meter 18 …… Rotation angle sensor 20 …… Electronic control circuit

Claims (1)

[Claims] 1. An air-fuel ratio control method for an internal combustion engine using an electronically controlled fuel injection device for injecting fuel from a fuel injection valve to operate the internal combustion engine, wherein a fuel temperature is above a predetermined temperature when the internal combustion engine is started. When it is determined that the temperature is equal to or higher than the predetermined temperature, the fuel injection amount of the internal combustion engine is controlled to increase, and the amount increased by the increase control is gradually increased in accordance with the increase in the rotation speed of the internal combustion engine. An air-fuel ratio control method for an internal combustion engine, which is characterized by reducing the amount.