JPH041182B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an engine control device.

[Prior art]

In recent years, vehicle engines have been equipped with air-fuel ratio sensors in their exhaust systems to detect the concentration of specific components, such as oxygen concentration, in the exhaust gas, in order to improve fuel efficiency and take measures against exhaust gas. Feedback control of the air-fuel ratio of the air-fuel mixture is performed. As an example, conventionally, an air-fuel ratio sensor of the type that reverses its output at a set air-fuel ratio, such as the stoichiometric air-fuel ratio, is used, and in a specific operating range of the engine, the air-fuel mixture is feedback-controlled to the set air-fuel ratio based on the sensor output. On the other hand, there are some systems that control the air-fuel mixture to a predetermined air-fuel ratio, such as a lean or rich air-fuel ratio, by supplying a preset fuel according to the amount of intake air outside a specific operating range of the engine.

However, in fuel injection valves that have recently been widely used as fuel supply devices, due to their mechanism, the characteristics of the fuel injection amount with respect to the fuel injection pulse are not linearly specified, which is the required characteristic. If fuel injection is performed simply by applying a fuel injection pulse corresponding to the amount of intake air to the fuel injection valve, the problem arises that the air-fuel ratio of the air-fuel mixture actually supplied to the engine deviates from the above-mentioned predetermined air-fuel ratio. be.

Conventionally, as a method to solve such a problem, as shown in, for example, Japanese Utility Model Application Publication No. 59-49739, a corrected fuel injection pulse that provides a predetermined air-fuel ratio is determined and stored in advance. There is a method of reading a corrected fuel injection pulse according to the amount of intake air and injecting fuel accordingly. However, in this method, the above-mentioned air-fuel ratio sensor is of a type that detects only the set air-fuel ratio,
Since it is not possible to detect whether or not the required fuel injection amount can be obtained even with the above corrected fuel injection pulse, errors occur in the corrected fuel injection pulse due to individual differences in fuel injectors and changes over time, resulting in poor air-fuel ratio control. Accuracy may not be obtained.

In addition, conventional methods for controlling the air-fuel ratio of an engine include feedback control of the air-fuel ratio of the air-fuel mixture based on the output of an air-fuel ratio sensor, and learning the correction value at that time, as shown in Japanese Patent Application Laid-Open No. 55-96339. When this operating state is entered in memory, the fuel supply amount is first controlled using the learned and memorized correction value, and then the air-fuel ratio of the air-fuel mixture is feedback-controlled, thereby adjusting the air-fuel ratio during transient operation. Methods are known to reduce fluctuations.

And in the engine control device mentioned above,
It is conceivable to adopt the concept of the air-fuel ratio control method described above, and to correct the corrected fuel injection pulse outside the specific operating range of the engine by reflecting the correction value of the feedback control in the specific operating range. With this method, it is possible to determine the state of deviation between the required characteristics of the fuel injection pulse and fuel injection amount and the actual characteristics from the correction values of the feedback control, so it is possible to deal with individual differences and secular changes in the characteristics of the fuel injectors. However, the operating conditions in which the feedback control correction values are learned may be significantly different from the operating conditions in which they are used, and in such cases, there is a risk that satisfactory air-fuel ratio control accuracy may still not be ensured. .

[Purpose of the invention]

SUMMARY OF THE INVENTION In view of these problems, it is an object of the present invention to provide an engine control device that can improve air-fuel ratio control accuracy.

[Structure of the invention]

In the engine control device described above, one way to improve the air-fuel ratio control accuracy is to perform feedback control of the air-fuel ratio for a predetermined period of time even outside a specific operating range, and then use the feedback control correction value determined at that time to It is considered that the fuel injection amount should be controlled to the amount after a predetermined period of time has elapsed.

However, in this case, the actual air-fuel ratio deviates from the original required air-fuel ratio during feedback control outside a specific operating range, and for example, in an enriched region such as during high-load operation, the actual air-fuel ratio deviates from the required air-fuel ratio to the lean side. This may cause knotting.

Therefore, the present invention provides an engine control device that performs feedback control of the air-fuel ratio in a specific operating range of the engine, and supplies a preset fuel according to the amount of intake air outside the specific operating range. Even outside the operating range, the fuel supply control is stopped according to the intake air amount to perform feedback on the air-fuel ratio for a predetermined period of time. The air-fuel ratio is controlled based on the corrected value, and various factors governing the combustion state are corrected in a direction that suppresses deterioration of drivability during feedback control outside the specified operating range. As shown in the functional block diagram of FIG. 1, this invention detects the set air-fuel ratio of the air-fuel mixture supplied to the engine with the air-fuel ratio adjusting means 25, and determines the operating state of the engine with the operating state setting means 26. a first operating state in which the operation should be performed at the stoichiometric air-fuel ratio based on the output of the air-fuel ratio detection means 25;
The air-fuel ratio is set to a second operating state in which the air-fuel ratio is to be operated at a different air-fuel ratio from the air-fuel ratio in the first operating state, and the air-fuel ratio adjusting means 27 receives the output of the operating state setting means 26 and changes the air-fuel ratio to the output of the air-fuel ratio detecting means 25. On the other hand, the stopping means 50 receives the output of the operating state setting means 26 and controls the air-fuel ratio adjusting means 27 at a predetermined time in the second operating state of the engine. and correct at least one of the fuel or the air-fuel ratio to achieve the stoichiometric air-fuel ratio based on the output of the air-fuel ratio detection means 25, and the storage means 28 stores the correction value at that time,
After the learning control means 29 is in the second operating state and a predetermined period of time has elapsed until the correction value is stored in the storage means 28, the learning control means 29 adjusts the air-fuel ratio to the second value based on the correction value stored in the storage means 28. During the predetermined period of time during which the air-fuel ratio is controlled to the stoichiometric air-fuel ratio in the second operating state, the correction means 30 adjusts the combustion state of the engine using something other than fuel and air. Various controlling factors are corrected to prevent deterioration of drivability.

〔Example〕

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

2 to 6 show an engine control device according to an embodiment of the present invention. 2 and 3, 1 is an engine, a throttle valve 3 is disposed in the middle of an intake passage 2 of the engine 1, and a fuel injection valve 4 is disposed in the intake passage 2 on the downstream side of the throttle valve 3.
is provided. Intake passage 2 of this engine 1
An EGR device 6 is provided between the exhaust passage 5 and the exhaust passage 5. In this EGR device 6, one end of an EGR passage 7 is connected to the exhaust passage 5, and the other end is connected to the intake passage 2. An EGR valve 8 is interposed in the middle of the EGR passage 7. An actuator 9 is provided to drive it. Further, a spark plug 11 is attached to the engine 1 so as to face the combustion chamber 10 .

In the figure, 12 is a throttle opening sensor that detects the opening of the throttle valve 3, 13 is a negative pressure sensor that detects the intake negative pressure downstream of the throttle, 14 is a crank angle sensor that detects the rotation angle of the crankshaft, and 15 is a 16 is _a water temperature sensor that detects the engine cooling water temperature; 17 is a crank that calculates the engine speed from the output of the crank angle sensor 14; Angle/rotation speed conversion circuit, 18 is an A/D converter that A/D converts each output of the throttle opening sensor 12, negative pressure sensor 13, O ₂ sensor 15, and water temperature sensor 16, 19 is a CPU 20, RAM 2
1 and ROM 22, and controls the fuel injection amount, ignition timing, and EGR amount. The RAM 21 stores input information and the calculation results of the CPU 20, and the ROM
22 stores programs for arithmetic processing of the CPU 20 shown in FIGS. 4 to 6.

Then, the CPU 20 determines the basic fuel injection amount according to the engine speed and intake air amount, and in the engine feedback control region, performs feedback correction on the basic fuel injection amount according to the output of the O ₂ sensor 15 to perform actual fuel injection. The air-fuel ratio of the air-fuel mixture is feedback-controlled to the set air-fuel ratio by injecting and supplying the actual injection amount of fuel to the fuel injection valve 4, and in the enrichment region, which is a non-feedback control region of the engine, By feedback-correcting the basic fuel injection amount according to the O ₂ sensor output at a predetermined time during operation, the air-fuel ratio of the air-fuel mixture is feedback-controlled to the set air-fuel ratio, and the correction value at that time is used as the learning value of the pulse width characteristic table. After that, the basic fuel injection amount is corrected using the learned value and the fuel increase correction value to obtain the actual fuel injection amount, and the fuel injection valve 4 is injected and supplied with the actual injection amount of fuel to adjust the air-fuel mixture. It controls the air-fuel ratio to a predetermined air-fuel ratio.

Further, the CPU 20 determines a basic ignition timing according to the engine speed and intake air amount, and normally causes the spark plug 11 to ignite at this basic ignition timing, and during a predetermined time in the enrichment region, The ignition control based on the engine speed and intake air amount is stopped, the basic ignition timing is retarded by a predetermined amount, and a control signal is applied to the actuator 9 of the EGR valve 8 to cause EGR to be introduced.

In the above configuration, the spark plug 11, EGR device 6, and CPU 20 serve as the correction means 30 shown in FIG. 1, and the CPU 20 and RAM 21 serve as the storage means 28 shown in FIG. Further, the CPU 20 realizes the functions of the operating state setting means 26, the air-fuel ratio adjusting means 27, the learning control means 29, and the stopping means 50 shown in FIG.

Next, the operation will be explained using FIGS. 4 to 7. Here, FIG. 4 is a flowchart of the background routine of the CPU 20, FIGS. 5a and 5b are flowcharts of the first and second interrupt routines of the CPU 20, respectively, and FIG. A more detailed flowchart of the value calculation step 44 is shown in FIG. 7, which shows the fuel injection amount and pulse width characteristics to explain the operation of the CPU 20.
In Fig. 7, the broken line a is the characteristic before learning, and the solid line b
are characteristics after learning, and Z1 to Z6 are learning areas.

When the engine starts, the CPU 20 first sets the learning request slug to "1" (step 31), and then
The input data of engine speed, intake negative pressure, throttle opening, cooling water temperature, and O ₂ sensor output are read (step 32), and basic information is calculated according to the engine speed and intake air pressure, which is a parameter of intake air amount. The ignition timing and basic fuel injection amount are calculated (steps 33, 34), and then it is determined whether the learning conditions for the injection valve characteristics are satisfied (step 35). Here, the learning condition for the injection valve characteristics means that the engine operating range is a feedback control range where the temperature of the engine is above a predetermined coolant temperature or an enrichment range where the temperature of the coolant is above a predetermined level. Also, the feedback control area is
This refers to a state in which the engine is in a transient state, in an enrichment region, or not at startup, and the enrichment region is determined by the engine speed and throttle opening.

First, when the engine is started or when the coolant temperature is below a predetermined value, the CPU 20 makes a negative determination in step 35 described above, and proceeds to enrich region determination step 36, feedback control region determination step 37, and cooling water temperature. After passing through the determination step 38, the pulse width of the fuel injection pulse is determined from the above-mentioned basic fuel injection amount (step 39), and the process returns to the above-mentioned step 32, and the processes of the above-mentioned steps 32 to 39 are repeated.

Next, when the engine enters the feedback control region with a predetermined coolant temperature or higher, the CPU 20 determines whether the learning request flag is "1" (step 40),
Since the learning request flag is "1" until learning is completed, it is determined YES in step 40, and then after determining whether or not it is in the enriched area (step 40).
41) The basic fuel injection amount is feedback-corrected based on the output of the O ₂ sensor 15 using a conventionally known method (step 42), and the pulse width of the fuel injection pulse is determined from the corrected fuel injection amount. (Step 43), calculates the learning value of the injection valve characteristics (Step 44), and after determining whether learning has been completed for all learning areas Z1 to Z6 (Step
45), the process returns to step 32 described above, and thus feedback correction of the fuel injection amount and calculation of the learned value of the injection valve characteristics are performed.

Furthermore, when the engine reaches the enrichment region where the temperature of the cooling water is higher than the predetermined temperature, the CPU 20 executes the step 32 described above.
~Go through routes 35, 40, 41 and say YES on step 41
After determining that this is the case and applying a control signal to the actuator 9 of the EGR valve 8 and retarding the basic ignition timing obtained above by a predetermined amount (step 46), the process proceeds through the path of steps 42 to 45 described above, and thus fuel injection is performed. In addition to performing feedback correction of the amount, the learned value of the injection valve characteristics is calculated, and at the same time, the EGR
will be introduced and the ignition timing will be corrected.

In this way, the feedback control of the fuel injector and the calculation of the learned value of the injector characteristics are performed, and when learning is completed for all learning areas Z1 to Z6, the CPU 20 determines YES in step 45 mentioned above and starts learning. Clear the request flag (step 47),
Return to step 32 above, and if the engine is in the feedback control region, step 32 to
Proceeding through routes 38, 48, and 39, feedback correction of the fuel injection amount is performed based on the learned value of the above-mentioned injector characteristics and the O ₂ sensor output (step 48), and if the engine is in the enriched region, Proceed through steps 32 to 36, 49, 37, and 39, and perform enrichment correction of the fuel injection amount based on the learning value of the above-mentioned injector characteristics obtained by feedback control in the enrichment region and the enrichment correction coefficient. (Step 49).

Furthermore, while executing the background routine processing described above, at a predetermined timing, for example, when the engine crank angle reaches TDC, the CPU executes the first interrupt routine processing shown in FIG. 5a, After setting the pulse width determined in the background routine in the timer (not shown) of the injector drive system (step 50), the process returns to the background routine, and the fuel injector 4
A fuel injection pulse with the above-mentioned pulse width is applied to the engine, and an amount of fuel corresponding to the operating condition is injected and supplied to the engine (see broken line b and solid line a in Figure 7), and the air-fuel ratio of the mixture changes before learning is completed. The air-fuel ratio is controlled to an air-fuel ratio that can be detected by the O ₂ sensor 15, and after learning is completed, the air-fuel ratio is controlled to an air-fuel ratio that can be detected by the O ₂ sensor 15 in the feedback control region, and to a predetermined air-fuel ratio in the enrichment region. When the engine crank angle reaches 60 degrees BTDC, the CPU executes the second interrupt routine shown in Figure 5b, and sets the ignition timing determined in the background routine to the ignition control system's timer (not shown). (Step 51), the process returns to the background routine, whereby the spark plug 11 normally ignites at the ignition timing that corresponds to the operating condition, and when performing feedback control in the enrich region. In this case, ignition is performed even when the ignition timing is retarded by a predetermined amount depending on the operating state.

Next, more detailed processing of the learning value calculation step 44 for the injection valve characteristics will be explained with reference to FIG. At the learning value calculation step 44, the CPU 20 first determines learning areas Z1 to Z6 according to the basic fuel injection amount and determines whether they are the same learning area (step 52).
If the learning area changes, set the set value n to the learning counter N and clear the learning register Reg (step 53), then proceed to step 54.
Also, if the learning areas are the same, go directly to step 54.
Then, the feedback correction coefficient is accumulated and stored in the learning register Reg, and then the count value of the learning counter N is decremented by 1 and it is determined whether it is zero or not.
55), when this reaches zero, the cumulative total of the feedback correction coefficients, which is the value stored in the learning counter Reg, is divided by the set value n, and the average value of the feedback correction coefficients is calculated.
Find AVE (step 56) and select this learning area Z1~
The learned value of the injector characteristic corresponding to Z6 is rewritten with the average value AVE of the feedback correction coefficient (step 57), the area Z1 to Z6 where learning has been performed is memorized (step 58), and this learned value calculation step 44 This will end the process.

In the device of this embodiment as described above, in the enrichment region of the engine, feedback control is performed on the air-fuel ratio at the beginning of operation in that region, and then the fuel injection amount is corrected using the correction value at that time, so that the feedback control region Compared to the case where the correction value is used, a more accurate correction value corresponding to the operating state of the engine can be learned, and as a result, the accuracy of air-fuel ratio control in this enriched region can be greatly improved.

In addition, this device retards the engine's ignition timing and introduces EGR during feedback control in the enrichment region, so the air-fuel ratio of the mixture is controlled to a value different from the predetermined air-fuel ratio. The occurrence of knocking can be suppressed and engine drivability can be guaranteed.

In the above embodiment, the air-fuel ratio of the air-fuel mixture is controlled by adjusting the fuel injection amount, but this may be done by adjusting the intake air, or by adjusting both the fuel injection amount and the intake air. You can do it like this. Further, the fuel supply device may be a carburetor instead of a fuel injection valve. Furthermore, only one of the ignition timing control and the introduction of EGR may be performed during feedback control in the enrichment region, and in any case, the combustion control factors may be set to a value higher than the normal value in a direction that prevents deterioration of drivability. All you have to do is shift it.

Further, in the above embodiment, the case where the non-feedback control region is an enrich region has been described, but it may be a lean control region or an idle region.

〔Effect of the invention〕

As described above, according to the present invention, the air-fuel ratio is feedback-controlled in a specific operating range of the engine, and a preset fuel is supplied according to the intake air amount outside the specific operating range. In the device, the fuel supply control according to the intake air amount is stopped even in other than the above-mentioned specific operating range, and feedback of the air-fuel ratio is performed for a predetermined time, and after a predetermined time has elapsed until the correction value is stored, The stored correction value is used to control the air-fuel ratio, and when feedback control is performed outside the above-mentioned specific operating range, various factors governing the combustion state are corrected in a direction that suppresses deterioration of drivability. This has the effect of improving controllability of the air-fuel ratio and preventing deterioration of drivability during learning.

[Brief explanation of drawings]

FIG. 1 is a functional block diagram showing the configuration of the present invention.
2 and 3 are both schematic configuration diagrams of an engine control device according to an embodiment of the present invention, FIG. 4 is a flowchart of a background routine of the CPU 20 in the above device, and FIGS. 5 a and b
6 shows a flowchart of the first and second interrupt routines of the CPU 20, FIG. 6 shows a more detailed flowchart of the learning value calculation step 44 in the background routine, and FIG. FIG. 3 is a diagram showing injection amount/pulse width characteristics before and after learning for explaining the operation of the CPU 20. FIG. 25...Air-fuel ratio detection means, 26...Operating state setting means, 27...Air-fuel ratio adjustment means, 28...Storage means, 29...Learning control means, 30...Correction means, 50...Stopping means, 1 ...Engine, 6...
EGR device, 11... Spark plug, 15... O ₂ sensor, 20... CPU, 21... RAM.

Claims (1)

[Scope of Claims] 1. Air-fuel ratio detection means for detecting a predetermined air-fuel ratio of the air-fuel mixture supplied to the engine; an operating state setting means for setting the first operating state and a second operating state in which the operation is to be performed at an air-fuel ratio different from the air-fuel ratio in the first operating state; air-fuel ratio adjusting means for correcting at least one of the fuel or the air to achieve the stoichiometric air-fuel ratio based on the output of the detection means; a stopping means for stopping the control to the air-fuel ratio corresponding to the second operating state; and a stopping means for stopping the control to the air-fuel ratio corresponding to the first operating state in response to the output of the stopping means; storage means for controlling and correcting at least one of the fuel or the air-fuel ratio to achieve the stoichiometric air-fuel ratio based on the output of the air-fuel ratio detection means and storing the correction value; and a storage means for storing the correction value in the second operating state. a learning control means for controlling the air-fuel ratio to an air-fuel ratio corresponding to the second operating state based on the correction value stored in the storage means; An engine characterized in that it is provided with a correction means for correcting various factors governing the combustion state of the engine other than fuel and air in a direction to suppress deterioration of drivability during the predetermined period of time during which the air-fuel ratio is controlled to the stoichiometric air-fuel ratio. control device.