JP2585037B2 - Engine fuel control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to an engine fuel control apparatus, and more particularly to an improved fuel control apparatus for correcting a high load increase for lowering exhaust gas temperature.

(Prior art)

Generally, in an engine for an automobile or the like, a problem of thermal fatigue of the exhaust system may occur when the exhaust system is in a high-rotation high-load operation state where the temperature is high. Therefore, conventionally, assuming a driver who performs the most severe driving, control is performed so as to increase the air-fuel ratio by increasing the amount of fuel in order to lower the exhaust gas temperature in the high load operation state.

Fig. 5 shows the prior art for determining the set temperature of the exhaust system in consideration of the reliability limit of the exhaust system. The set temperature T _EX of the exhaust system is set from the cumulative number of uses and the exhaust system reliability limit, and the correction amount of the high load increase correction is set based on the set temperature T _EX . Since the thermal fatigue of the exhaust system progresses due to thermal shock caused by repetition of high / low temperature changes, the exhaust system reliability limit decreases as the cumulative number of times of high load use increases.

For example, in Japanese Patent Publication No. Sho 60-11220, a fuel correction amount (increase correction or decrease correction) is set and stored in accordance with the rotational speed and the load state, and the fuel correction amount is stored in accordance with the operation state of the engine. A fuel control device is disclosed in which a fuel correction amount is read out to perform fuel correction.

[Problems to be solved by the invention]

As in the above prior art, the exhaust system set temperature T is set based on the exhaust system reliability limit, assuming a driver who performs severe driving.
_{When EX} is set, as can be seen from Fig. 5, when the cumulative number of times of high load use is small, that is, when the mileage is shorter than 100,000 km or when the mileage is long, the frequency of high load use is high. When a driver with a small number of motors is operated, the exhaust system set temperature T _EX has a considerable margin with respect to the exhaust system reliability limit. In other words, since the exhaust system set temperature _TEX is too low, unnecessary high load increase correction is performed.

[Means for solving the problem]

The engine fuel control device according to the present invention is configured such that, in an engine in which the amount of fuel is increased and corrected in a high load state in which the temperature of the exhaust system is high, the fuel is controlled in accordance with an increase in the cumulative number of times of the high load state. A correction control means for increasing the correction amount of the increase correction is provided.

[Action]

In the engine fuel control device according to the present invention, the correction control means increases the correction amount of the fuel increase correction in accordance with an increase in the number of times of accumulation in the high load state where the temperature of the exhaust system becomes high.

In other words, the thermal fatigue of the exhaust system progresses as the cumulative number of times of the high load state increases, and the exhaust temperature at the exhaust reliability limit decreases, so the exhaust temperature is increased by increasing the correction amount of the fuel increase correction. I try to lower it. Therefore, it is possible to prevent the temperature of the exhaust system from rising above the exhaust temperature at the exhaust system reliability limit and to suppress the thermal fatigue of the exhaust system while preventing the fuel efficiency from being deteriorated by the unnecessary fuel increase correction.

〔The invention's effect〕

According to the fuel control device for an engine according to the present invention, as described above, by providing the correction control means, it is possible to prevent deterioration of fuel consumption over the entire service life of the engine and to reduce thermal fatigue (thermal degradation) of the exhaust system. ) Can be suppressed.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows the entire configuration of a vertical engine E for a motor vehicle and a fuel control device thereof. A combustion chamber 4 is formed by a cylinder block 1, a cylinder head 2, and a piston 3, and a spark plug is provided in the cylinder head 2. 5, an intake port 6 is opened and closed by an intake valve 7 and an exhaust port 8 is opened and closed by an exhaust valve 9. An air cleaner 11 is provided at an upstream end of an intake passage 10 extending from the intake port 6. An air flow meter 1, a throttle valve 13, and a surge tank 14 are provided in this order from the upstream side, and an injector 15 that injects fuel toward the intake port 6 is provided downstream of the intake passage 10.

A catalyst converter 17 is provided in an exhaust passage 16 extending from the exhaust port 8.

As sensors for controlling the fuel of the engine E, the air flow meter 12 mounted upstream of the intake passage 10 is used.
And an intake air temperature sensor 18, an exhaust gas temperature sensor 19 mounted upstream of the exhaust passage 16, a water temperature sensor 20 for detecting a cooling water temperature of a water jacket, and a crankshaft rotation angle signal, i.e., a crank angle, incorporated in the distributor 21. A crank angle sensor 21a for outputting a signal (including an engine speed signal) and an idle switch 13a for detecting that the throttle valve 13 is substantially fully closed at the time of idling are provided. The signals and the signals from the ignition switch 22 and the starter switch 23 are input to the control unit 24.

The control unit 24 includes a waveform shaping circuit that shapes the waveform of the engine speed signal, an intake air amount signal from the air flow meter 12, an exhaust temperature signal from the exhaust temperature sensor 19, an intake temperature signal from the intake temperature sensor 18, and a water temperature sensor. A / D converter for A / D conversion of water temperature signal from 20, input / output interface, CPU (central processing unit) and ROM (read only
A microcomputer comprising a memory) and a RAM (random access memory), a drive circuit for driving the injector 15 in accordance with a control signal from the microcomputer, a drive circuit for outputting an ignition drive signal to the dithostributor 21, and the like. .

In the ROM of the microcomputer, at least a control program for fuel control, which will be described later, and a map and a table accompanying the control are previously input and stored.
M is a temporary storage memory (memory,
Counters, flags, etc.).

First, the outline of the fuel control will be described with reference to FIG. 4. After the start of use of a new vehicle, the exhaust system becomes hot and the cumulative number of times of using a high load (however, strictly, high rotation and high load) increases. Exhaust system thermal fatigue progresses, and the exhaust system reliability limit decreases as shown in the figure. Therefore, as the cumulative number of times of high load use increases, the exhaust system set temperature T _n
(However, n = 1, 2, 3,...) Is controlled so as to be reduced stepwise. Then, set the exhaust temperature to the exhaust system set temperature for each stage.
In order to maintain _Tn or less, the correction amount of the fuel high load increase correction is increased in accordance with the increase in the cumulative number of times of high load use, and the air-fuel efficiency is controlled to be rich.

Hereinafter, the fuel control routine executed by the control unit 24 will be described with reference to the flowcharts of FIGS. In the figure, Si (i = 1, 2, 3,...)
Are the respective steps. It is assumed that the counter n is set to n = 1 and the counter m is set to m = 0 in advance when the vehicle is in a new vehicle state as a premise of the main routine of FIG.

When the control is started upon turning on the ignition switch 22, initialization such as resetting the flag k to k = 0 and clearing the memory of the RAM is executed (S1). T signal is read (S
2), then the exhaust gas temperature T is determined whether the exhaust system is larger than the set temperature T _n of each stage (S3). As shown in FIG. 4, the set temperature _Tn is set in advance so as to gradually decrease as the cumulative number of times of high load use increases, and is stored in the ROM in a table using n as a parameter. . When the return to S2 also T> T _n when not the result T> T _n of the determination flag k indicating that in a high-load use is set (S4), whether the next ignition switch 22 is turned OFF Judged (S5), when it is ON, return to S2 and OFF
When the flag k is set, it is determined whether or not the flag k is set (S6). When the flag k is not 1, the process returns to S2. When the flag k is 1, the counter m for counting the cumulative number of times of high load use in each stage. Is incremented by 1 (S7), then it is determined whether or not the count value m of the counter m is larger than the set value _m0 (S8). When m> _mo is not satisfied, the process returns to S2, and when m> _mo , In order to switch the stage, the counter n indicating the stage is incremented by 1 (S9), and then the ROM in which the correction value C _ER of the high load increase correction is set.
The map g (n) is rewritten and stored (S10), and S
Return to 2. The map g (n) is set so that the correction value C _ER increases as n increases. Note that the above control routine continues for a predetermined time (for example, one second) measured by the soft timer even after the ignition switch 22 is turned off, and is temporarily terminated after the predetermined time has elapsed. It is restarted when the next ignition switch 22 is turned on. That is, consistent control is executed until the new vehicle is used and then scrapped. Exhaust system set temperature T _n according to the degree of the accumulated number of high-load use as in the fourth diagram the control described above are set stepwise, high-load increase amount corresponding to the exhaust system set temperature T _n of the stages _Will be set. The routine shown in FIG. 2 is repeated every predetermined subtle time.

Next, the high load increase correction value determined by the above control
By adding a C _ER is illustrated by Figure 3 for a routine for controlling the fuel injection amount. However, the routine of FIG. 3 is performed at a predetermined timing (for example, the explosion TD) based on the crank angle signal.
This is executed in the interrupt processing every C).

First, when the interrupt process is started, the air flow meter
The engine speed N, a water temperature signal from the water temperature sensor 20, and a water temperature signal from the intake temperature sensor 18, which are separately calculated and stored in the memory based on the signal of the intake air amount Q from 12 and the engine speed signal from the crank angle sensor 21a. And the exhaust temperature signal from the exhaust temperature sensor 19 are read (S20).
Basic fuel injection quantity T _P is calculated by the equation T _P = K · Q / N and then based on the intake air amount Q and the engine speed N and the predetermined constant K (S21). However, the basic fuel injection amount _TP is determined in advance by using the engine speed N and the intake air amount Q as parameters.
You may make it read from the map stored in M. Then, the exhaust gas temperature T is determined whether the exhaust system is larger than the set temperature T _n of each stage (S22). The set temperature T _n is read from the ROM tables as a parameter similarly to the n.
Then, it is not necessary to high-load increase amount correction when not under a high-load increase amount correction value C _ER is the map g (n) from the read rare (S23) The T> T _n when the T> T _n and C _ER = 0 setting is (S24), then based on the water temperature and intake air temperature other correction value C is calculated from the respective predetermined arithmetic expression or a table (S25), then a final injection amount T _I which is injected from the injector 15 is basic injection It is determined by summing the amount T _P and the high-load increase correction value C _ER and another correction value C (S26), at a predetermined timing determined then based on the crank angle signal, via the injector drive circuit driving pulse corresponding to the final injection amount T _I to the injector 15 is output fuel injection final injection amount T _I runs Te (S27), returns to the main routine of Figure 2.

The exhaust system reliability limit shown in FIG. 4 in the above embodiment can guarantee a guaranteed mileage of 100,000 km even when a relatively severely driven driver operates.

Although the above-mentioned exhaust system reliability limit is a characteristic that linearly decreases according to an increase in the number of times of high load use, the exhaust system reliability limit may be a characteristic that nonlinearly reduces,
In this case, the set value m _o for each stage is not fixed, and a different set value m _i (i = 1, 2, 3,...) May be used for each stage.

In the routine shown in FIG. 2, when a high-load state (high-speed high-load operation state) where T> _Tn is detected one or more times from when the ignition switch 22 is turned ON to OFF, each step is performed. Is controlled so that the counter m indicating the cumulative number of times of high load use is incremented by one, but at least once during a predetermined operation time (for example, one hour).
> It counter m for each comprising a high-load condition of T _n may be incremented by 1, T during the operation period> T _n
The counter m may be incremented by one each time the high load state of the above is continued for a predetermined time (for example, 15 minutes).

In the fuel control device according to the above embodiment, the correction value C _ER of the high load increase correction for lowering the exhaust gas temperature is increased in accordance with the increase in the cumulative number of times of high load use. Since the correction value C _ER does not need to be set unnecessarily large, it is possible to prevent deterioration of fuel efficiency.

In particular, in vehicles used by drivers who drive calmly, such as female drivers, the frequency of high-load conditions is very low, and the cumulative number of times of high-load use increases only gradually. Become.

Further, it is possible to prevent the exhaust temperature from rising to the exhaust system reliability limit over the entire service life of the vehicle, and to suppress the thermal fatigue of the exhaust system.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 to FIG. 4 show an embodiment of the present invention. FIG. 1 is an overall configuration diagram of an automobile vertical engine and its fuel control device. FIG. 3 is a flowchart of a main routine of fuel control, FIG. 3 is a flowchart of an interrupt processing routine of fuel injection amount control, FIG. 4 is an explanatory diagram for explaining a relationship between an accumulated number of times of high load use and an exhaust system set temperature, 5
The figure is equivalent to FIG. 4 according to the prior art. 19 …… Exhaust gas temperature sensor, 22 …… Ignition switch, 24
……control unit.

Continuation of the front page (56) References JP-A-63-61736 (JP, A) JP-A-63-147942 (JP, A) JP-A-63-61735 (JP, A) JP-A-61-55340 (JP, A) , A)

Claims (1)

(57) [Claims] In an engine in which the amount of fuel is increased and corrected in a high load state where the temperature of the exhaust system becomes high, the correction amount of the increase correction is increased in accordance with an increase in the number of times of accumulation in the high load state. A fuel control device for an engine, comprising a correction control means for increasing the amount of fuel.