JP2002213280A - Fuel supply controller for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure the start of an engine with a required minimum quantity of fuel to prevent deterioration in fuel economy and emission performance. SOLUTION: During the initial stage of startup cranking, fuel is supplied in a basic fuel quantity tsb which is defined according to the temperature Tw of engine cooling water at that time, and an incremental amount dt of fuel is additionally supplied after a predetermined period of time Ta determined according to the cooling water temperature has elapsed since the start of this starting operation. Such incremental control enables the engine to be started for complete ignition in a short time without wasteful fuel supply, as compared with a conventional technique which effects incremental correction of fuel from the initial stage of startup.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply control device for an engine, and more particularly, to a fuel supply control at the time of starting.

[0002]

2. Description of the Related Art In order to ensure the startability of an engine at a low temperature, control for increasing the fuel supply amount in accordance with the cooling water temperature is generally performed. However, since the starting time from the start of cranking to the complete explosion varies among individuals due to the effects of engine friction, etc., increasing the fuel only based on the water temperature may result in excess or deficiency of the actual required fuel amount. is there. FIG. 1 shows the relationship between the starting fuel amount and the starting time. As shown in the figure, up to a certain amount of fuel, the starting time becomes shorter when the amount of fuel is large. It becomes longer and wastes fuel. FIG. 2 shows the relationship between the starting fuel amount and the exhaust emission. In the case where the fuel amount is too large, mainly the incomplete combustion takes place. Emissions worsen. As described above, an excess or deficiency of the starting fuel from an appropriate amount may cause deterioration of fuel efficiency and emission performance. On the other hand, in consideration of the influence of engine friction, there has been proposed an engine which optimizes the fuel amount at the time of starting by reducing the amount of fuel increase as the rotation rise at the time of cranking becomes faster (Japanese Patent Laid-Open No. Hei 8- No. 14080).

[0003] However, especially at low temperatures, the combustion in each cycle of the engine is not stable, so that the engine rotation often causes a complete explosion while repeatedly rising and falling, and it is difficult to accurately detect the engine rotation and the rise in rotation. is there. For this reason, according to the conventional start-up control described above, for example, when a temporary increase in the engine speed is detected, the increased fuel cost is reduced, and the movement of the engine speed rising to complete the explosion is suppressed. On the contrary, there is a possibility that the startability is deteriorated.

The present invention has been made in view of such conventional problems, and has as its object to provide a fuel supply amount control device capable of surely starting an engine with a minimum necessary fuel amount. I have.

[0005]

According to a first aspect of the present invention, there is provided a starting basic fuel amount determining means for determining a basic fuel amount at the time of starting an engine, and a fuel supply means for supplying the determined starting fuel amount to the engine. A temperature detection means for detecting an engine temperature, a start detection means for detecting a start operation of the engine, and a correction amount determination for determining an increase correction amount of the basic fuel amount at the time of start. Means, time measuring means for measuring the time elapsed from the start of the start operation, increase start time determination means for determining the supply start time for the increase correction according to the engine temperature, and after the start operation, the increase correction amount And an increased fuel supply means for starting supply of the fuel for the increased correction when a supply start time has elapsed.

According to a second aspect of the invention, the basic fuel amount and the increase correction amount in the above invention are determined according to the engine temperature.

According to a third aspect of the invention, the amount of the increase correction of each of the above inventions is periodically increased until the initial value of the initially determined correction amount reaches the time of complete explosion.

According to a fourth aspect of the present invention, the limit value for the increase correction in the third invention is set according to the engine temperature, and when the limit value is reached, the increase for the increase correction is terminated.

According to a fifth aspect of the present invention, the supply start timing of the amount of the increase correction according to the first aspect of the invention is set to be longer than a predetermined standard start time according to the engine temperature.

[0010]

[Operation and Effect] In each of the inventions following the first invention,
At the beginning of starting cranking, fuel is supplied with the basic fuel amount determined according to the engine temperature at that time,
Only when a certain period of time has elapsed since the start of the starting operation, the fuel supply for the increased amount is performed. Such control makes it possible to completely start the engine without performing useless fuel supply as compared with the related art in which the fuel increase correction is performed from the beginning of the start. In particular, depending on the state of the engine at the start, such as the presence of residual fuel in the intake passage and the state of lubricating oil, the basic fuel amount alone may lead to a complete explosion in the start.In such a case, it is not possible to supply the increase correction amount. Since it does not, the amount of fuel required for starting is minimized.

Since the start time of the supply of the increased amount of fuel is determined according to the engine temperature, for example, by setting a longer time as the temperature becomes lower, it is possible to obtain a large friction and take a long time to complete explosion of the engine under low temperature conditions. By optimizing the fuel supply start timing, exhaust emission and fuel efficiency can be further improved.

In general, the time required for starting the engine changes according to the engine temperature such as the cooling water temperature, and the starting time tends to be longer at a lower temperature. Therefore, as shown in the second invention, the basic fuel amount and the increase correction amount are increased. If the minute is also determined according to the engine temperature, the starting control can be performed more accurately.

The fuel for the increased amount of correction may be set to a fixed value in accordance with the engine temperature or the like. However, as shown in the third invention, a predetermined amount of correction before the complete explosion is reached. If the initial value is increased periodically, for example, in synchronization with the rotation of the engine, it is possible to further reduce the increased fuel supply amount until the complete explosion. In this case, as shown in the fourth invention, a limit value corresponding to the engine temperature is provided in the increase correction amount so that the maximum value of the increase amount does not exceed the limit value. Emission deterioration can be more reliably prevented.

On the other hand, since the starting characteristics of the engine tend to be determined to some extent depending on the model and the specifications, a standard starting time according to the engine temperature is determined by experiments and the like.
As described as the fifth invention, by setting the supply start timing for the increase correction to be equal to or longer than the standard start time based on the standard start time, the start control can be performed in accordance with the characteristics of the engine. Can be optimized.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 shows a mechanical configuration of the embodiment of the present invention. 1 is an engine control unit composed of a microcomputer and its peripheral devices,
It has functions as various means of the control system of the present invention.
That is, the control unit 1 mainly controls the fuel injection amount and the ignition timing of the engine 2 based on various operation state signals. The basic detection amounts for engine control are an intake air amount signal from the air flow meter 3 and an engine rotation speed signal from the crank angle sensor 4. For the fuel injection amount, a basic value determined from these signals is used as the coolant temperature or the like. The signal value is determined by correcting according to the exhaust oxygen concentration or the like. 5 is a water temperature sensor that detects the cooling water temperature as an engine temperature, 6 is an exhaust sensor that detects exhaust oxygen concentration,
7, an injector for injecting fuel into the engine 2;
Is an ignition plug, and 9 is a throttle valve. Reference numeral 10 denotes a key switch as start detection means for detecting a starter operation by a driver.

Next, the control of the fuel supply amount at the time of starting by the control unit 1 will be described with reference to a flow chart shown in FIG. FIG. 4 shows a control routine for increasing fuel at start-up, which is started as an interrupt condition for an engine start operation by the key switch 10, for example, as part of an engine control routine that is periodically executed. When starting the engine, the key switch 10 is normally turned on to start cranking by the starter.
This routine is terminated when it is detected that the key switch 10 has been returned to the ON position again in the background of the present routine, or when a complete explosion condition described later is satisfied, in the background of this routine. I do.

First, in step 1 (hereinafter referred to as "S1"), the engine coolant temperature Tw is detected by the coolant temperature sensor 5.
Is detected. Next, at S2, based on the water temperature Tw, the basic fuel amount tsb at the time of starting, the increase start timing Ta, and the increase limit value dtm.
ax is determined, and a timer value T for measuring an elapsed time from the start of the start operation and a fuel increase dt are initialized.

The basic fuel amount tsb and the increase limit value dtm
The values of ax and the initial increase dt correspond to the tendency that the starting time becomes longer as the temperature becomes lower, and as shown in FIG. (However, Figure 3
Shows only the change tendency of the fuel amount with respect to the water temperature Tw, and the actual value given for each water temperature is different.) Further, the increase start timing Ta is determined by searching a table that gives a slightly longer time than the standard start time Ts of the engine at the water temperature Tw according to the water temperature Tw, as shown in FIG. 6, for example. The standard starting time Ts is
As described above, this is the time required until the complete explosion of the engine, which is experimentally determined in advance according to the model and specifications of the engine.

In S3, the basic fuel amount tsb is supplied from the injector 7, and then in S4, the basic fuel amount tsb is supplied.
A complete explosion judgment is made under the supply condition of b. The complete explosion is determined, for example, when it is detected that the engine rotation exceeds a predetermined reference value by a signal from the crank angle sensor 4 or when the key switch 10 is returned to the ON position while the engine rotation is continuing. It is detected by a known method such as when it is detected. When it is detected that a complete explosion has occurred, this routine is terminated and control is transferred to fuel supply control after starting.

If the explosion has not been completed, it is determined in the next S5 whether or not the elapsed time T after the start has reached the increase start timing Ta. When T ≧ Ta is not satisfied, the starting cranking with the basic fuel amount tsb in S3 is repeated.

If T ≧ Ta in S5, this is the case where the basic fuel amount tsb was not supplied and the complete explosion was not reached. In the next S6, the value obtained by adding the increment tad to the initial increase dt is used. Set as increase. Since the increment dt is increased periodically, for example, synchronously with the engine rotation until the engine completely explodes, the increment dt is increased in the next step S7.
It is determined whether or not dt, which is the integration result of ad, does not exceed the limit value dtmax. If it does, dt is reduced to dt in S8.
Max is set so that the amount is not increased any more, thereby preventing over-enrichment.

In S9, the fuel of the increased amount dt set as described above is added to the basic fuel amount tsb and fuel is supplied from the injector 7. In S10, the complete explosion determination under the fuel supply in S9 is performed. Do. If the explosion has not been completed, the process returns to S6, and the increment dt is incremented by t with the limit value dtmax as an upper limit.
The operation of supplying the fuel amount to which ad has been added is repeated.
If a complete explosion has occurred, this routine is terminated, and control is transferred to fuel supply control after starting.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing a general relationship between a starting fuel amount and a starting time.

FIG. 2 is a characteristic diagram showing a general relationship between a starting fuel amount and exhaust emission.

FIG. 3 is a schematic diagram of a mechanical configuration according to an embodiment of the present invention.

FIG. 4 is a flowchart showing processing contents of an embodiment relating to control of the present invention.

FIG. 5 is a characteristic diagram showing a setting tendency of a basic fuel amount tsb, an increase limit value dtmax, and an initial increase amount dt with respect to a water temperature Tw.

FIG. 6 is a characteristic diagram showing a setting tendency of an increase start time Ta with respect to a water temperature Tw.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine control unit 2 Engine 3 Air flow meter 4 Crank angle sensor 5 Water temperature sensor 6 Exhaust sensor 7 Injector 8 Intake passage 9 Throttle valve 10 Key switch

Claims (5)

[Claims] An engine fuel supply control device comprising: a starting basic fuel amount determining means for determining a basic fuel amount at the time of engine start; and a fuel supply means for supplying fuel to the engine with the determined starting fuel amount. , A temperature detecting means for detecting an engine temperature, a start detecting means for detecting a start operation of the engine, a correction amount determining means for determining an increase correction amount of the basic fuel amount at the time of starting, and an elapsed time from the start of the starting operation Time-measuring means for measuring the fuel supply amount; increasing-start-time determining means for determining the supply start timing for the increase correction according to the engine temperature; and, after the start operation, when the supply start time for the increase correction elapses, the increase is performed. A fuel supply control device for an engine, comprising: an increased fuel supply means for starting supply of a fuel for a correction. 2. The fuel supply control device for an engine according to claim 1, wherein the basic fuel amount and the increase correction amount are each determined according to the engine temperature. 3. The fuel supply control for an engine according to claim 1, wherein the increase correction amount periodically increases an initial value of the correction amount initially determined until a complete explosion occurs. apparatus. 4. The fuel supply control device for an engine according to claim 3, wherein the limit value for the increase correction is set according to the engine temperature, and when the limit value is reached, the increase for the increase correction is terminated. . 5. The engine fuel supply control device according to claim 1, wherein the supply start timing is set to be equal to or longer than a predetermined standard start time according to the engine temperature.