JPH0256499B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an air-fuel ratio control device for an engine that detects the air-fuel ratio of the engine from exhaust gas components and controls the air-fuel ratio based on the detected output.

[Prior art]

As a method of controlling the air-fuel ratio of the engine, the oxygen concentration in the exhaust gas is detected by an oxygen gas sensor (hereinafter referred to as an O ₂ sensor), and the amount of fuel supplied to the engine is feedback-controlled based on the value obtained by integrating the output of the sensor. It is commonly done. However, with this method alone, there is a problem that during transient operation of the engine, if the basic air-fuel ratio changes faster than the above-mentioned integral processing, the air-fuel ratio control cannot keep up and the exhaust gas deteriorates. As a countermeasure for this, a deviation in the air-fuel ratio is detected from the result of the above integral processing for each state of the engine, a correction coefficient corresponding to this value is stored in memory, and a correction coefficient corresponding to each state of the engine and the above Learning control has been proposed to control the amount of fuel supplied to the engine based on the results of integral processing.
In this case, the feedback control described above cannot be performed in the open loop zone which requires an air-fuel ratio higher than the stoichiometric air-fuel ratio, and therefore the learning control cannot be performed. For this reason, it is conceivable to control the air-fuel ratio in the open loop zone using a correction coefficient for the closed loop zone in which the feedback control is performed in the vicinity of the open loop zone. However, normally in the closed loop zone, exhaust gas recirculation control (EGR control)
is also performed at the same time, and EGR control is not performed in the open loop zone, so there is a possibility that the above-mentioned correction coefficient will be affected by the EGR control, resulting in a problem in which the air-fuel ratio in the open loop zone cannot be properly controlled.

[Summary of the invention]

The present invention has been made to solve the above-mentioned problems, and includes providing an area adjacent to the open loop zone in the closed loop zone where exhaust gas recirculation is not always performed, and adjusting the correction coefficient in the area to adjust the open loop zone to the open loop zone. The air-fuel ratio of the engine is controlled appropriately.

[Embodiments of the invention]

The present invention will be described below with reference to an embodiment shown in the drawings. FIG. 1 shows an example of the configuration of the present invention.
The engine 1 takes in air for combustion through an air cleaner 21, an intake pipe 2, and a throttle valve 23 provided in the middle of the intake pipe 2. The fuel necessary for the engine 1 is supplied by an injector 22 provided upstream of a throttle valve 23, and the amount of fuel supplied is controlled by controlling the opening time of the injector 22. The control device 4 is a pressure sensor 2
4. Water temperature sensor 2 that detects the cooling water temperature of engine 1
The operating zone determining means 41 determines the operating zone of the engine 1 based on the output of the engine 5, controls the EGR control valve 12, and directs a portion of the exhaust gas flowing through the exhaust pipe 3 of the engine 1 via the EGR passage 13 to the intake pipe 2. The output of the pressure sensor 24 that controls whether or not the flow flows downstream of the throttle valve 23 and converts the pressure downstream of the throttle valve 23 in the intake pipe 2 into voltage and the rotation speed that converts the rotation speed of the engine 1 into a pulse signal. Based on the output of the sensor 11, the driving time determining means 42 determines the injector 2.
Determine the driving time T ₀ of No. 2. The driving time correcting means 43 calculates the driving time based on the output of the driving zone detecting means 41 and the output of the _O2 sensor 31, which is installed at the collecting part of the exhaust pipe 3 and detects the oxygen concentration in the exhaust gas.
T ₀ is corrected, and the injector 22 is controlled by the drive time control means 44.

FIG. 2 shows details of the configuration of the control device 4. The filter 45 smoothes the output of the pressure sensor 24, the interface 46 converts the output of the water temperature sensor 25 into voltage, and the filter 47 smoothes the output of the O ₂ sensor 3.
Smooth the output of 1. The AD converter 48 sequentially converts the outputs of the filters 45, 47 and the interface 46 into digital values and outputs them to the microprocessor 53. Comparator 49 is rotation sensor 11
The output of the D flip-flop 50 is waveform-shaped and output to the clock terminal of the D flip-flop 50. D flip flop 5
The output of 0 becomes "L" level in synchronization with the rise of the output of the comparator 49, and the output of the microcomputer 5
output a first interrupt signal to the first interrupt terminal of 3;
It is preset to the "H" level by the microcomputer 53, and then becomes the "L" level in response to a cycle corresponding to the rotational speed of the engine 1.
The counter 51 counts the output of the oscillator 52 while the output of the D flip-flop 50 is at "L" level, and the microcomputer 53 calculates the rotational speed N of the engine 1 from this counted value _T0 . The timer 58 outputs an interrupt signal to the second interrupt terminal of the microcomputer 53 at fixed time intervals (for example, 5 msec). The microcomputer 53 has a ROM60,
It has a built-in RAM 61, executes processing according to a program stored in the ROM 60, and stores a part of the processing results in the nonvolatile RAM 59. non-volatile
The RAM 59 retains its stored contents even when the power of the control device 4 is turned off, and for example, an EEPROM x 2804A manufactured by Xiko Corporation may be used. The timer 54 counts the output of the oscillator 55 in accordance with the set value output by the microprocessor 53, creates a pulse width corresponding to the output of the drive time correction means 43, and uses the driver 56 to control the injector 22.
to drive. The drive time control means 44 includes:
A timer 54, an oscillator 55, and a driver 56 are included. The driver 57 drives the EGR control valve 12 based on the output of the microcomputer 53.

Next, the operation of the microcomputer 53 is controlled by the third
The explanation will be given according to the flowchart shown in the figure. Control device 4
When power is supplied to the microcomputer 53
In step 70, the RAM 61, output signals, etc. are set to the initial state. Next, the operation zone determination operation in steps 72 to 78 and 84 is performed. At step 71,
If t ₀ seconds have elapsed, proceed to step 72; otherwise, wait until t ₀ seconds have elapsed. t ₀ seconds is counted and created by the second interrupt processing routine that is processed every 5 msec. AD converter 48 in step 72
The outputs of the pressure sensor 24, water temperature sensor 25, and _O2 sensor 31 are sequentially converted into digital values by
Store in RAM61. These stored data are respectively pressure data P, water temperature data W, and _O2 data A.
shall be. At step 73, count value of counter 51
From T ₀ and constant C, calculate the rotation speed N as N=C/T ₀ . In step 74, the operating zone is divided into six zones Z ₁ to _{Z 6} as shown in Fig. 4, and it is determined in which zone the engine is being operated based on the predetermined rotational speed Na and the predetermined pressures Pa and Pb of the intake pipe 2. judge. Here, operating zones Z ₁ to _{Z 4} are closed loop zones, and Z ₅ and Z ₆ are open loop zones. In step 75, the operating zone _t0 seconds before and the current operating zone are compared, and if they do not match, the integrated value SI of the integral value I is set to zero in step 76, and if they match, the process proceeds to step 77. If the pressure data P is smaller than Pb in step 77, the process proceeds to step 78; if it is larger, the process proceeds to step 84. At step 78,
The EGR control valve 12 is turned on, a part of the exhaust gas is recirculated to the intake pipe 2, and in step 79, the drive time _T0 of the injector 22 is set to the pressure data P and the rotation speed N when the EGR control valve 12 is turned on. ROM60 as shown in Figure 5 in advance.
In step 80, if the water temperature data W is smaller than a predetermined value, that is, if the water temperature is high, the process proceeds to step 81; otherwise, the process proceeds to step 88. Step 79 and step 85 are drive time determining means. Next, a driving time correction operation is performed in steps 81 to 97. In step 81, O ₂
If data A is smaller than a predetermined value (for example, equivalent to 0.5V), it is determined to be lean, otherwise it is determined to be rich,
If it is lean, a constant _L1 is added to the integral value I in step 82, and if it is rich, a constant L1 is added from the integral value I in step 83.
Subtract L ₂ to get the new integral value. Next step
At step 89, compare the judgment result (lean or rich) of O ₂ data _{A 0} seconds before t with the current judgment result, and if the result is reversed (rich to lean or lean to rich), the integrated value SI is changed to step 90. The integral value I is added and the process proceeds to step 91; otherwise, the process proceeds to step 95. In step 91, it is determined whether the integral value I has been added 8 times to the integrated value SI. If it has been added 8 times, in step 92 the integrated value SI/8 is set as the correction amount _K1 , and in step 93, the integrated value SI is added to the integrated value SI. 0, and in step 94, set the correction amount _K1 to RAM5.
It is stored at the address corresponding to the driving zone determined in step 74 of 9.

Here, when the operating zone is Z ₃ in FIG. 4, the correction amount K 1 is stored in the address corresponding to zone Z ₅ of RAM 59, and when the operating zone is Z ₄ , the correction amount K ₁ is stored in the address corresponding to zone Z ₆ of RAM 59. Correction amount to the address corresponding to
Remember K ₁ . Therefore, the correction amounts stored in the RAM 59 for zones Z ₃ and Z ₅ and zones Z ₄ and Z ₆ are the same. After storing the correction amount in RAM59, step
Go to 95.

Also, if the judgment result of _O2 data A is not reversed in step 89, the process advances to step 95 and
If 8 times have not been added in step 91, proceed to step 95. In step 95, the correction amount in the RAM 59 corresponding to the zone determined in step 74 is read out and set as the correction amount _K2 , and in step 96, the integral value I is added to the correction amount _K2 to obtain the correction coefficient _K3 , and in step 97, the above Drive time T ₀ is multiplied by correction coefficient K ₃ , drive time T ₁
Then, in step 98, this driving time data _T1 is set in the timer 54, and the process returns to step 71. If the pressure data P is greater than the predetermined value Pb in step 77, the EGR control valve 12 is turned OFF in step 84.
The recirculation of exhaust gas is stopped, and in step 85, the operating time _T0 of the injector 22 is changed to the EGR control valve 1.
2 is OFF, the pressure data P and rotation speed N are selected from the data previously stored in the ROM 60 as shown in Fig. 6, and if the pressure data is greater than Pa in Fig. 4 at step 86, the drive time T is selected. ₀
is multiplied by the enrichment coefficient KE to lengthen the driving time _T0 by a predetermined percentage to obtain a new driving time _T0 , and in step 88, the integral value I is set to zero and the process proceeds to step 88. If the pressure data P is less than or equal to Pa in step 86, the process advances to step 80.

The drive time control operation starts with the timer 54 in step 98.
A driving time T ₁ is set, and every time an interrupt signal is input to the first interrupt terminal, that is, in synchronization with the rotation of the engine 1, the microcomputer 53 triggers the timer 54 to reach the driving time T _1. corresponding period,
This is done by driving the injector 22.

_{The above} process will be explained with reference _{to FIG .}
Based on the output of 1, the integral value I is increased or decreased in steps 82 and 83, and the peak value of the integral value I is increased or decreased in steps 82 and 83.
89 to 94, the average value of the integral value I is stored in the RAM 59 as the correction amount for each zone, and this correction amount and the integral value I
Then, in steps 95 to 97, the air-fuel ratio of the engine 1 is controlled to be close to the stoichiometric air-fuel ratio by correcting the drive time _T0 . Since an air-fuel ratio richer than the stoichiometric air-fuel ratio is required in the operating zones Z ₅ and Z ₆ , it is not possible to correct the drive time T ₀ using the integral value I, and therefore the above-mentioned correction amount cannot be calculated. Therefore, in step 94, for operation zone _Z5 , the correction amount of operation zone _Z3 adjacent to this zone is changed to operation zone Z5.
Operating zone Z ₄ adjacent to this zone for Z ₆
Correction data is stored in the RAM 59 so that the correction amount is used.

Here, the correction amount _K1 is gradually corrected by the integral value I, and the integral value I gradually approaches zero, and the correction amount
_K1 is a value for correcting the air-fuel ratio of the engine 1 to the stoichiometric air-fuel ratio. When exhaust gas recirculation control is performed, a deviation occurs in the air-fuel ratio of the engine 1 due to this control, but in operating zones Z ₃ and Z ₄ , the EGR control valve 12 is turned OFF to stop exhaust gas recirculation, so that the exhaust gas Correction amount when excluding the influence of reflux control
K ₁ can be detected, and by applying the correction amount K ₁ at this time to the operating zones Z ₅ and Z ₆ , the air-fuel ratio of the engine 1 can be adjusted to the stoichiometric air-fuel ratio if the process in step 87 is not performed. Therefore, the air-fuel ratio can be corrected appropriately using the enrichment coefficient KE in step 87.

In the above embodiment, the operating zones are divided based on the rotational speed and the pressure of the intake pipe 2, but they may be divided based on the rotational speed and the opening degree of the throttle valve 23.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, in a system that determines the amount of fuel supplied to the engine based on the rotational speed and intake pipe pressure, exhaust gas recirculation adjacent to the open loop zone is not performed constantly within the closed loop zone. By providing a region, determining a correction coefficient from the integral value in this region, and applying this correction coefficient to the open loop zone, there is an effect that the air-fuel ratio in the open loop zone can be controlled with high accuracy.

Furthermore, even if the O ₂ sensor fails midway through the closed loop zone and the air-fuel ratio cannot be controlled using the integral value I, the air-fuel ratio can be properly controlled using the correction amount.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a block diagram showing details of the control device 4, Fig. 3 is a flowchart showing control of the microcomputer 53, and Fig. 4 is an explanation of the operation zone. Figure, Figure 5, Figure 6
The figure is a diagram showing driving time data of the injector 22. In the figure, 1 is the engine, 2 is the intake pipe, 3 is the exhaust pipe, 11 is the rotation sensor, 12 is the EGR control valve,
22 is an injector, 24 is a pressure sensor, 25
31 is a water temperature sensor, 31 is an O ₂ sensor, 48 is an AD converter, 51 is a counter, 53 is a microcomputer, 54 and 58 are timers, and 56 and 57 are drivers.

Claims (1)

[Claims] 1. An integral processing step that integrates the output signal of the air-fuel ratio sensor that detects the air-fuel ratio based on the exhaust gas components of the engine, and a correction amount that is corrected based on the integral information obtained in this integral processing step, which is stored in a non-volatile memory. an amnestic step for storing the information in the memory;
A means for controlling the air-fuel ratio of the engine based on the integral information subjected to the integral processing and the stored correction amount is provided, and the operating range of the engine is divided into a closed loop zone where the integral processing step is performed and an open loop zone where the step is not performed. The method is divided into zones and performs exhaust gas recirculation control in the closed loop zone, wherein an area is provided in the closed loop zone adjacent to the open loop zone where the exhaust gas recirculation is not performed at all times,
An air-fuel ratio control device for an engine, characterized in that the air-fuel ratio in the open loop zone is controlled based on the correction amount in the region.