KR0169511B1 - Engine air-fuel ratio control system - Google Patents

Abstract

An object of the present invention is to enlarge the driving range of the line air-fuel ratio as much as possible without injuring the operability, and the polarity is higher than the theoretical air-fuel ratio depending on the driving condition detecting means 1 for detecting the engine driving condition and the driving conditions. The target air-fuel ratio setting means 2 which sets the target air-fuel ratio of the side, the line-in limit value setting means 3 which sets the limit value of the re-inward side of the air-fuel ratio according to the engine rotation speed, and compares the set target air-fuel ratio with a threshold value The air-fuel ratio selecting means 4 which selected the value of the side as a target air-fuel ratio, the fuel supply-amount calculation means 5 which calculates a fuel supply amount according to this target air-fuel ratio, and the fuel supply means which supplies fuel to an engine so that it may become a calculated fuel supply amount. (6) is provided.

Description

Air-fuel ratio control device of internal combustion engine

1 is a schematic structural diagram showing an embodiment of the present invention.

2 is a flowchart similarly showing the control operation.

3 is the same flowchart.

4 is the same flowchart.

5 is the same flowchart.

6 is an explanatory diagram showing a dividend map of seniority expenses.

7 is an explanatory diagram of a table in which the lower limit is set.

8 is a configuration diagram of the first invention.

9 is a block diagram of the second invention.

* Explanation of symbols for main parts of the drawings

1: driving condition detection means 2: target air-fuel ratio setting means

3: Rein limit setting means 4: Air-fuel ratio selection means

5 fuel supply amount calculation means 6 fuel supply means

7: Throttle fully closed state determination means

[Industrial use]

The present invention relates to an air-fuel ratio control apparatus for an internal combustion engine.

[Prior art]

In order to improve fuel efficiency and exhaust characteristics of an internal combustion engine, there is a line-in combustion engine which controls the mixer supplied to the engine less than the theoretical air-fuel ratio. While driving at the line-in air-fuel ratio improves fuel economy, it tends to cause problems in driving performance, so that the engine is temporarily unstable in driving conditions, for example, when driving, temporarily returns to the theoretical air-fuel ratio and prevents engine stops, or operates smoothly. (See Japanese Patent Application Laid-Open No. 61-187552).

[Problems to Solve Invention]

In this case, the target air-fuel ratio is set according to the driving region of the map divided by the engine load and the number of revolutions. When the target air-fuel ratio under driving conditions corresponding to idle driving is set to the theoretical air-fuel ratio, the surrounding area is also the theoretical air-fuel ratio. The area of the line air-fuel ratio is narrowed by that amount, and the effect of improving fuel economy is reduced.

In this regard, it is also considered to set the theoretical air-fuel ratio only when the idle air-fuel ratio is turned on in all driving areas including the idle driving condition and when the idle switch for detecting the fully closed state of the throttle is turned on. Even when the gear changes to return the pedal, if the throttle is completely closed, the air-fuel ratio is converted to the theoretical air-fuel ratio, and the unnecessary air-fuel ratio causes deterioration of fuel economy and exhaust characteristics.

Also, as in the above-described conventional example, one method is to set a constant delay time at the time of switching the air-fuel ratio, and to maintain the air-fuel ratio before the operating conditions change during the delay time at the time of gear change. The delay time may not be able to prevent the engine stop or unnecessary air fuel fluctuations.

For example, in case of gear change at low speed, the engine speed decreases to idle speed soon after returning Excel, but if the set delay time is too long, the re-air fuel ratio is maintained and engine stop or deterioration of driving performance is reduced. Occurs. On the other hand, if the delay time becomes too short, when it takes time to return to the idle rotation speed after returning Excel, as in the case of gear change at high rotation, the air-fuel ratio is unnecessary even though the rotation time is not idle even though it is not the idle rotation speed. It turns into the theoretical performance ratio. In such a constant delay time, it is not possible to accurately cope with gear changes under different conditions.

An object of the present invention is to solve such a problem, that is, to enlarge the operating area of the line-in air-fuel ratio without impairing the operability.

[Means for solving the problem]

In the first invention, as shown in Fig. 8, driving condition detecting means 1 for detecting an engine driving condition, target air-fuel ratio setting means 2 for setting a target air-fuel ratio rather than a theoretical air-fuel ratio according to the driving conditions; Rein limit value setting means 3 which sets the limit value of the rein side of an air-fuel ratio according to engine rotation speed, Air-fuel ratio selecting means 4 which compares the set target air-fuel ratio with a threshold value, and selects the value of either rich side as a target air-fuel ratio, and And fuel supply amount calculation means 5 for calculating a fuel supply amount according to the target air-fuel ratio, and fuel supply means 6 for supplying fuel to the engine so as to calculate the fuel supply amount.

In the second invention, in the first invention, the re-in limit setting means 3 is set near the theoretical air-fuel ratio near the idle rotational speed, and sets the air-fuel ratio that gradually changes to the liin side as the rotational speed is increased as the limit value.

In the third invention, as shown in Fig. 9, driving condition detecting means 1 for detecting an engine driving condition, target air-fuel ratio setting means 2 for setting a target air-fuel ratio rather than a theoretical air-fuel ratio according to the driving conditions; Rein limit value setting means for setting the limit value on the rein side of the air-fuel ratio according to the engine speed, judging means 7 for determining whether the throttle of the engine is in the fully closed state, and when the determination result is not in the completely closed state. The air-fuel ratio selecting means 8 selects the set target air-fuel ratio as it is, and compares the target air-fuel ratio with the threshold value and selects one of the rich side values as the target air-fuel ratio, and the fuel supply amount according to the selected target air-fuel ratio. The fuel supply amount calculation means 5 which calculates, and the fuel supply means 6 which supplies fuel to an engine so that it may calculate may be provided.

[Action]

In the first invention, the limit value of the rein side is set according to the engine speed, and when the target air-fuel ratio is the re-inward side than the limit, this limit value is set as the target air-fuel ratio. The deterioration of the driving performance is prevented, and in other areas, the target air fuel ratio set in accordance with the operating conditions is used so that the driving area of the line-in air fuel ratio is not unnecessarily reduced.

In the second invention, since the limit value on the rein side varies with the rotational speed, the air-fuel ratio can be gradually controlled toward the theoretical air-fuel ratio toward the rich side in response to the decrease in the rotational speed due to the complete closure of the excel when the gear is changed, and the sudden change of the air-fuel ratio is prevented. Therefore, smoothness and stability of operation can be secured.

In the third invention, the throttle is fully closed, and when the throttle is fully closed, the control unit selects and controls the air-fuel ratio of one of the reach side and the target air-fuel ratio according to the rotational speed, but when the throttle is not completely closed, what is the limit value? Nevertheless, the air-fuel ratio is controlled to be the target air-fuel ratio. Therefore, even if the rotational speed is close to the idle rotational speed, it is possible to maintain the line-in air-fuel ratio, such as during low-speed operation in which the throttle is a little open, thereby improving the fuel economy. If you're stepping on the accelerator, such as at low speeds, the clutches are linked even at low rotational speeds.

EXAMPLE

1 shows an embodiment of the present invention, reference numeral 11 denotes an engine, 12 an intake passage, 13 an exhaust passage, and an intake passage 12 downstream of a throttle valve (hereinafter simply referred to as a throttle) 14. It is located, the fuel injection valve 15 is installed. The fuel injection valve 15 disperses the fuel in accordance with the signal from the control unit 16 and supplies the engine 11 with a mixer of the air-in fuel ratio which is in principle thinner than the theoretical air-fuel ratio.

For this reason, in the control unit 16, the rotation speed sensor 17 which detects the engine speed, the air flow meter 18 which detects the intake air amount, or the throttle switch 19 which detects the fully closed state of the throttle valve 14 is carried out. The fuel injection amount is calculated so that a signal from the () is input and the target air-in fuel ratio is set according to the operating conditions based on these. In the area where driving conditions deteriorate, such as during idle driving, the air-fuel ratio is approached to the theoretical air-fuel ratio to maintain smooth driving performance. The control unit 16 also controls the air-fuel ratio to the target value based on the signal from the means for detecting the exhaust air-fuel ratio, which is not shown, and performs learning control.

Their control operations executed in the control unit 16 in accordance with the flowcharts of FIG. 2 to FIG. 5 will be described. In addition, in the following description, for the convenience of description about the controlled air fuel ratio, the term "air fuel ratio" which is a reciprocal of air fuel ratio and a contrast with the theoretical air fuel ratio (equivalent to theoretical air fuel ratio / performance cost) is used.

2 is a routine that is processed as a background job for setting a target fuel efficiency in accordance with the operating conditions. First, in step (1), it is determined whether or not the operating conditions are in the rein operation conditions. The operation area to be lean burned is set from each request such as the operability, and it is determined whether or not the current operation condition is in this condition. Then, in step (2), the map fuel consumption ratio Mdm1 is retrieved from the line-in fuel consumption ratio map MDm1L, and otherwise, from the line-in fuel consumption ratio map MDm1S. In addition, each fuel consumption ratio map is allocated by the engine load (fuel injection pulse width Tp) and the rotation speed Ne as shown in FIG. 6, and the target performance according to the operating conditions in the air-in fuel ratio and the air-in fuel ratio, respectively. The rain is set.

In step 4, this retrieved map air fuel ratio Mdm1 is exchanged with the target air fuel ratio Tdm1 and transferred to the control routine of FIG. 3 or FIG.

3 and 4 show different embodiments as jobs performed in synchronization with the reference signal for each rotation range or cylinder in order to calculate a correction value of the target fuel ratio, respectively, and will first be described in FIG.

The target air fuel ratio Tdm1 obtained in step 11 is compared with the corrected air fuel ratio Dm1 (corresponding to the current air fuel ratio) in step 12. If Dm1 is larger than Tdm1 (Dm1 ≥ Tdm1), the process proceeds to step 13, whereby the air-fuel ratio change rate Ddm1r is set to Dm1 _n-1 in the previous operation, considering that the target seniority ratio is larger (rich) than the current seniority ratio. In addition, in step 15, the upper limit of Dm1 is limited to Tdm1.

On the other hand, step 12, when Dm1 is smaller than Tdm1, sees that the target fuel consumption ratio is smaller (re-in) than the current fuel consumption ratio, and in step 14, the air _- fuel ratio change speed Ddm11 is subtracted from Dm1 _n-1 at the previous operation. In step 16 again, the lower limit of Dm1 is limited to Tdm1.

In this way, when the fuel consumption ratio is corrected in accordance with the target fuel consumption ratio, the flow advances to step 17 to search for a lower limit value (lin limit) Dm1i1m of the fuel consumption ratio prescribed according to the engine speed in the table of FIG. The Dm1i1m has a value of 1.0 corresponding to the theoretical air-fuel ratio when the engine speed is near the idle, and gradually changes to the rein side as the rotation speed increases, and is set to take a constant reinch above a predetermined rotation, and the stability limit at the rotation speed It is equivalent to line-in performance cost.

Then, in step 18, the corrected air fuel ratio Dm1 and the lower limit Dm1i1m are compared, and if the Dm1 side is smaller, that is, the air-fuel ratio, Dm1 is the lower side than the lower limit, the lower limit Dm1ilm is determined in step 19. Let it be corrected air fuel ratio Dm1. When the Dm1 side is large, the processing ends as it is.

In this way, Dm1 is compared with Dm1i1m, a rein limit set according to the number of revolutions at that time, and when the rein limit is on the rein side, the rein limit value is used as the air-fuel ratio as a control target to stabilize the operability. .

FIG. 4 is a flowchart of another embodiment and is equal to FIG. 3 until step 16. When the correction fuel ratio Dm1 is obtained, it is determined in step 21 whether the throttle is fully closed by the signal of the idle switch, and the idle state of the throttle full closing is shown. The process proceeds after the surface step 22, otherwise, the process is terminated by using Dm1 as a correction air fuel ratio.

When the throttle is fully closed, the lower limit value Dm1i1m of the line-in-fuel ratio according to the engine speed is searched in the table in the same manner as in the step 22, and in the step 23, the Dm1i1m and Dm1 are compared, In step 24, the process proceeds to Dm1 = Dm1i1m.

When the Dm1 side is larger (rich side), the processing ends as Dm1 with the corrected fuel consumption ratio as it is.

Therefore, in this embodiment, the comparison with the limit limit for safe driving is performed only when the throttle is completely closed in comparison with FIG. 3, otherwise Dm1 is used as the correction fuel ratio as it is.

In this way, the fuel injection amount is calculated along the flowchart of FIG. 5 while calculating the correction fuel ratio.

This operation is repeated every 10 ms, and in step 31, the control target air fuel ratio Tfbya is calculated as Tfbya = Dm1 + Ktw + Kas using the corrected air fuel ratio Dm1. Ktw is the increase in water temperature and Kas is the increase after starting. Ktw is the lower the water temperature and the larger Kas decreases with the elapsed time after starting. In step 32, the intake air amount Q, which is the output of the air flow meter, is A / D converted and linearized, and in step 33 the basic injection amount Tp at this intake air amount Q and the rotational speed N is Tp =. It calculates as K * Q / N, Avtp is calculated | required from this, and K is an integer.

In step 34, the fuel injection amount Ti is calculated by the following equation.

Ti = Avtp × Tfbya × Ktr × (α + αm) + Ts .... (1)

In addition, Ktr is an air-fuel ratio correction coefficient of overshowing, (alpha) is an air-fuel ratio feedback correction coefficient, and (alpha) m is an air-fuel ratio learning correction coefficient. However, the above formula has already been proposed in many applications by the present application and is well known.

Subsequently, it is determined whether the fuel injection condition is in an operating condition for cutting fuel injection in step 35, and the calculated fuel injection amount Ti is stored in an output register when the fuel injection condition is not. By storing Ts) in the output register, it is prepared for fuel injection at the next injection timing.

Therefore, in the first embodiment, the air-fuel ratio of the mixer supplied to the engine is basically controlled by the target re-in air-fuel ratio set by the operating conditions, and the target air-fuel ratio has a rein limit value corresponding to the re-air air-fuel ratio of the stability limit at the engine speed. If it is on the lean side than the re-in limit, the re-in limit is set as the target air-fuel ratio. For this reason, it is possible to reliably avoid the deterioration of driving performance while ensuring the maximum operating area at the line-in air-fuel ratio. For example, during idling operation, the air-fuel ratio required for stable combustion is controlled according to the rotational speed. Even if the throttle is temporarily abolished, it is set to an appropriate air-fuel ratio according to the decrease in the rotational speed, and the air-fuel ratio can be changed unnecessarily by increasing the air-fuel ratio when the gear is changed at a high rotational speed or the gear is changed at a low rotational speed. Engine stops due to delays can be reliably prevented.

In addition, the re-in limit value is set according to the rotation speed, and when the rotation speed gradually decreases at the time of gear change, the air-fuel ratio is gradually moved to the rich side to prevent sudden changes in the air-fuel ratio and maintain smooth rotation.

In the second embodiment, the comparison between the target air-fuel ratio and the rein limit value is carried out only when the throttle is completely closed, and in other driving stations, it is controlled based on the target air-fuel ratio. Therefore, when the throttle is not completely closed, the air-fuel ratio at the rotational speed is maintained at the re-in air-fuel ratio as it is at the re-in than the re-in limit. When the throttle is not completely closed, the clutch of the vehicle is still connected even if the driver stepped on the accelerator somewhat. Since it is possible to improve the fuel efficiency.

[Effects of the Invention]

According to the above, according to the first invention, if the limit value of the rein side is set according to the engine speed, and the target air-fuel ratio is the re-inward side than the limit value, in the operation (rotational) region where the engine stop or the like becomes problematic while the limit value is the target air-fuel ratio. Prevent the deterioration of driving performance by preventing the air-fuel ratio from being lower than the limit value, and by using the re-in air-fuel ratio set according to the operating conditions in other areas, it is possible to prevent unnecessary restriction of the driving area of the line-in air-fuel ratio, thereby avoiding deterioration of driving performance. Improve the effect.

In addition, according to the second invention, since the limit value on the rein side is changed according to the rotational speed, the air-fuel ratio can be gradually controlled toward the reach side to the theoretical air-fuel ratio in response to the decrease in the rotational speed accompanying the complete closure of the Excel when the gear is changed. In addition, the lubricity and stability of operation can be secured by preventing sudden changes in air-fuel ratio.

According to the third aspect of the present invention, the state of closing the throttle is determined, and when the throttle is fully closed, the control unit selects and controls the air-fuel ratio of one of the reach side and the target air-fuel ratio according to the rotational speed. However, the air-fuel ratio is controlled so as to be the target air-fuel ratio, so that the fuel economy is maintained by maintaining the air-fuel ratio when the engine speed does not reach the engine stop even when the driving performance is deteriorated during low speed operation in which the throttle is slightly open even when the rotation speed is close to the idle speed. Improves the effect of improvement.

Claims (3)

Operation condition detecting means for detecting the engine operating condition, target air fuel ratio setting means for setting a target air fuel ratio on the rein-side rather than the theoretical air fuel ratio according to the driving conditions, and a rein limit value for setting a limit value of the air-fuel ratio on the re-air side according to the engine revolutions. Means, an air-fuel ratio selecting means for comparing the set target air-fuel ratio with a threshold value, and selecting a value of one rich side as a target air-fuel ratio, a fuel supply amount calculating means for calculating a fuel supply amount according to the target air-fuel ratio, and a calculated fuel supply amount An air-fuel ratio control device for an internal combustion engine, comprising: a fuel supply means for supplying fuel to the engine. 2. An air-fuel ratio control apparatus for an internal combustion engine according to claim 1, wherein said rein limit value setting means sets the air-fuel ratio near the theoretical air-fuel ratio near the idle rotational speed and gradually changes to the rein side as the rotational speed increases. Operation condition detecting means for detecting the engine operating condition, target air fuel ratio setting means for setting a target air fuel ratio on the rein-side rather than the theoretical air fuel ratio according to the driving conditions, and a rein limit value for setting a limit value of the air-fuel ratio on the re-air side according to the engine revolutions. Means and means for determining whether the engine throttle is in the fully closed state, and if the determination result is not in the fully closed state, the set target air-fuel ratio is selected as it is; and in the fully closed state, the target air-fuel ratio is compared with the threshold value. Air-fuel ratio selecting means for selecting a value of one rich side as a target air-fuel ratio, fuel supply amount calculating means for calculating a fuel supply amount according to the selected target air-fuel ratio, and fuel supply means for supplying fuel to the engine so as to calculate the calculated fuel supply amount. An air-fuel ratio control device for an internal combustion engine, characterized in that it is provided.