JPS61164050A - Air-fuel ratio control device - Google Patents

Abstract

PURPOSE:To enable a control mode using a theoretical air-fuel ratio to be consistently maintained by learning, under specified conditions, a slice level which corresponds to a measured value by an O2 sensor when a control using a reference value at the slice level prepared in advance is put into practice, so that the learned value is to be used under subsequent operating conditions. CONSTITUTION:When an engine is in operation, CPU11 outputs, to a fuel injection valve 21, an air-fuel ratio control signal in accordance with a deviation obtained through comparing the output voltage of an O2 sensor 16 with a reference voltage at the slice level read-out through RAM14. In this case, while a control using a reference value at the slice level given in advance which corresponds to a measured value by an O2 sensor 16 is put into practice in operating conditions, a learning of a slice level which corresponds to a measured value by the O2 sensor 16 is also put into practice under specified conditions. After the end of the learning, the learned value is replaced by some of the contents of a slice level table so that the value is to be used under subsequent operating conditions. Said table is prepared in such a manner that the value of an electromotive voltage for the O2 sensor 16 is divided into, for example, 64, and then each value at the slice level corresponding to each of said values is recorded on the table as a learned value.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an air-fuel ratio υJ system for an automatic heavy-duty internal combustion engine.

[Conventional technique @]

For example, as shown in FIG. 7, this device detects the concentration of exhaust gas components (mainly oxygen) of the engine 1 with an 02 sensor 3 installed in the exhaust system 2, and outputs the output of the 02 sensor 3 and the slice level. The deviation is detected by the deviation detection circuit 4 (differential amplifier, comparator, etc.), and the control circuit 5 performs control according to the deviation. signal (for example, a proportional signal proportional to the deviation,
or an integral signal obtained by integrating the deviation), and based on that control signal, the fuel supply amount and air supply amount of the fuel temperature control device 6 (carburizer, fuel injection device, etc.) are additionally controlled (the fuel injection device is The air-fuel ratio of the air-fuel mixture supplied to the engine 1 is maintained at the set air-fuel ratio by controlling the operating noise (naturally, the operating noise is also controlled by other factors such as operating the throttle valve). If this set air-fuel ratio is set, for example, to the optimum operating point of the exhaust purification device 7 (catalyst device, reactor device, etc.), harmful components in the exhaust gas can be efficiently reduced under various operating conditions. For example, as an exhaust purification device, CO and HC oxidation and N
When using a three-way catalyst device that simultaneously reduces Ox, the set air-fuel ratio is set to a value close to the stoichiometric air-fuel ratio. However, in the air-fuel ratio control device as described above, the output of the O2 sensor 3 changes due to temperature changes, changes over time, etc., so there is a drawback that the actual air-fuel ratio deviates from the set air-fuel ratio. For example, in Fig. 8 showing the output characteristics of the O2 sensor 3, in order to set the set air-fuel ratio to Xl (for example, 14.8) at the normal value indicated by the solid line The voltage may be set to vl, but the maximum value of the output of the Oi sensor 3 tends to decrease and the minimum value tends to increase due to deterioration, as shown by Im@. Furthermore, at low temperatures, the internal impedance of the O2 sensor 3 becomes extremely large, so the output that can actually be taken out is as shown by the broken line @. Therefore, as shown in Japanese Patent Publication No. 5B-54456, the maximum and minimum values of the output of the Ox sensor are detected. The value obtained by dividing the two values at a predetermined ratio (for example, 0.6
) has already been proposed as the reference voltage of the slice level.

[Technical Issues] The key here is that the reference value of the slice level is constantly fed back and compared with the actual measurement value in the deviation detection circuit to extract the control signal, so it fluctuates depending on the operating condition and remains stable. There is no gender. In particular, in a process where the O2 sensor is not activated, substantially correct feedback control is not performed. [Object of the Invention] The present invention has been made based on the above circumstances, and even when the O2 sensor is not yet activated, such as in an aircraft,
The air-fuel ratio 1l is given a slice-level ml value based on past data, corrects the effects of oxygen sensor deterioration, etc., and maintains control at the stoichiometric air-fuel ratio at all times.
It is intended to provide a III device.

[Structure of the invention]

For this purpose, the present invention compares an O, t sensor that detects the concentration of engine exhaust gas components with a slice level reference voltage, and performs fuel metering control using a control signal based on the deviation. In the operating state, control is performed at a slice level corresponding to the actual measured value of the O2 sensor given in advance. The feature is that the slice level corresponding to the OL sensor measurement value is learned within predetermined conditions in that operating state, and the learning is completed and the contents of the slice level table are replaced so as to be used in the next operating state. It is something to do.

【Example】

Hereinafter, one embodiment of the present invention will be described in detail with reference to FIGS. 1 to 6. In the figure, reference numeral 11 denotes a central control unit, and the central control unit 11 inputs control information via an input board 12, processes it according to a program set in advance in the ROM 13, and stores it in the RAM 14 as control data. Write. This control data is given as a fixed slice level correction value. Further, the information in the RAM 14 is read out according to a program and is used for air-fuel ratio control via the output port 15. input boat 12
As is well known, the objects of data input to, for example, O, sensor 16. Air flow meter 17 installed in front of the throttle body. Engine water temperature sensor 18.
Throttle sensor 19. Such as the idle sensor 20. Further, the target of data output to the output port 15 is, for example, the fuel injection valve 21. This includes the throttle valve regulator 22 and the like. The analog signal from the Ox sensor 16 is digitized via the A/D converter 23 and input to the central control unit 11 as an output voltage signal every unit time. Further, in this embodiment, a series of data is written to the same URL before being written to the designated area 14a of the RAM 14.
The data is stored in an area 14b of the AM 14, and is replaced at a time in a predetermined area 14a of the RAM 14 under certain conditions (described in detail below). Therefore, when starting the engine, the predetermined area 14a of the RAM 14
The value of the initial slice level is stored in , and is compared with the output voltage of the 02 sensor 16, and the air-fuel ratio l1ltill signal is varied toward the rich side or the lean side based on the deviation. The output information is extracted from the RAM 14 in accordance with the value of the output voltage of the Oz sensor 1G at that time. For example, a value between the expected maximum value and minimum value is divided into 64 to define each output voltage range, and using this as an address, the memory contents are stored in 64 bytes in the predetermined area 14a. The main part of the present invention lies in the method of writing to the RAM 14 mentioned above. On the other hand, with the output voltage from the Ot sensor 16, the reference voltage of the required slice level or its correction value is read from the 7 dresses of the corresponding predetermined area 14a, and this is compared with the output voltage of the 02 sensor 16 to determine the control signal. On the other hand, the slice level reference voltage or its correction value is input to the other region 14b under the following conditions. If writing to this area 14b is a learning task, there are learning conditions for this. Now, when the output signal of the water temperature sensor 1B has a value indicating that warm-up has been completed and the idle sensor 20 is turned off and indicates that the operating state is to be entered, the 02 sensor 16 has already been activated and the normal It is determined that the operating state has started, and the following is performed. Now, if the data sampling period is To, then the output voltage Vx of the O2 sensor 1G, which fluctuates from moment to moment, is expressed as R-1:Vx (t -
To )≧vx (t)R-2: Vx (t
-2To)≧Vx (t-To)R=3:V
x (t −3To )≧Vx (t −2To
)RN:Vx(t-NTa)≧Vx(
t − (N=1) To ), yx (t − NTo ) is set to the rich signal V
Assume that the upper limit peak value VRp of R is R-1:Vx (t-To)≦VX(t)R-2
:Vx(t-2To)≦Vx(t-To
)R-3: Vx (t-3To)≦VX
(t −2To )R−N : Vx (t
−NTo ) ≦Vx(t −(N−1)T
o) When Vx (t −NTo ) is a lean signal v
It is assumed that the lower limit peak value VLI of L is the lower limit peak value VLI). When such a simple increase or decrease is realized a predetermined number of times r1, the data value is allowed to be taken in. In other words, when the above conditions are satisfied on a vibration waveform that changes arbitrarily without setting a reference value, it is defined as data that meets the rich/lean judgment criteria. This value indicates that VRp and VLp in VRp≧Vx (t - NTo > VLp≦VX (t - NTo) are maximum and minimum at the time of switching from simple increase to simple decrease or from simple decrease to simple increase. shows the value, but
The value close to the window width in the feedback region of Oz sensor 1G is VRp −−Vx (t−(N−r”) To
)VLD −=Vx (t −(N −r−) To
) (where r- can be freely selected from 1.2.). The voltage value when the difference between these values is divided by the required division ratio is
This is used as the reference value for the slice level. VL-VRI) ′”Q +VL11 ′(1-Q)
(However, q is the division ratio) The value obtained in this way is the 02 sensor 16 at that time.
The address corresponding to the output voltage value is written into another area 14b of the RAM 14. When the idle sensor 20 turns on, it is determined that learning has ended. The period from the start to the end of learning is shown in FIG. 3 in terms of the output voltage of the O2 sensor 16 and the passage of time. Within this section, the P-P period (period between peak VRp and peak VLp) such as sudden acceleration or sudden deceleration may be very short, but this is due to R
Since it is excluded from the condition of simple increase or decrease in times, it is excluded as noise, and therefore the obtained value ensures a stable slice level in a steady state. When learning is completed in this way, the contents of the other area 14 of the RAM 14 are converted to a predetermined area 14a. As a result, the slice level in the operating state that is performed again after or after the interruption is given by the newly rewritten contents of the predetermined area 14a of the RAM 14. In other words, the air-fuel ratio control is learned in the previous operation process, and the output information replaced by the predetermined area 14a Ic of the RAM 14 is taken out, and this is adopted as the reference value or correction value of the slice level, and the current 02 Compared with the output voltage of sensor 1G, the air-fuel ratio control signal is varied toward the rich side or the lean side. Note that if the RAM 14 is backed up, the learned value from the previous operation will already be in the RAM 14 when the engine is started, and this will be used as is. Note that in this embodiment, the output voltage of the Ot sensor 16 is set to 64
Divide it into, for example, ΔV-0.02V, and set the output value to OV~
Although the it range is set at 1.28 V, the number of divisions may be appropriately selected depending on the memory capacity, etc. Further, when rewriting from the area 14b to the area 14a, processing may be performed such that a weighted average or simple average with the value corresponding to the previous address is taken and the average is transferred to the area 14a. In addition, in this embodiment, when sudden acceleration or deceleration is performed during learning, the output value of the throttle sensor 19 is determined so as not to affect the slice level setting. It is preferable to prohibit reading of the output values of the sensor 1G during the time period. This makes it overrich. Overline input information can be removed, increasing reliability at the slice level. The process of peak value detection in slice level learning is shown in the flowchart of FIG. Here, in the first step S1, the output signal of the 02 sensor 16 is digitized and taken in as data Do. This data DO is written to the address Dl in the memory addresses Do to Dr prepared in advance in step S2. Next, in step S3, the initial value is set to N-0, and it is incremented by one (N+1→N), and then in step S4, memory addresses D (7-N) and D (6-N>
Compare the contents with. Here D (7-N>≧D C6
-N> does not hold, the process moves to step S5, and when it does, the process moves to step S6. Both steps85.
In 86, as initial M-5, M-1→M and M
+1 → M is executed, and in step S7 memory address D (
Shift the contents of 7-N) to the address of D (8-N). Then, in step S8, it is determined whether N==5 or not, and if N is 5, the process returns to step S3. In this way until memory address D! reaches N-5!
The contents from to D6 are shifted right one time. Next, in step S9, the contents of address D1 are changed to address D2.
will be shifted to. Here, if M = 10, the data at address Dτ is VRp (rich signal: MAX value), and if M-0, the data at address Dy is V
Lp (lean signal: MIN value). At this time, the data stored in the area 14b is the address D.
Instead of 7, the value of address D6 or address D5 may be taken. And M=0. Values other than M=10 indicate that simple increase and simple decrease during the five clocks have not been achieved. When address D7 is DT -0, the data is in an undefined state after reset, so a value such as M-3 is entered. In step 810, it is determined whether the address is DT-0 or not, and in step 511, M-3 is substituted. This is done because M needs to hold a value other than M-0°M-10. FIG. 5 shows a flowchart of the start of learning, completion of IR, and data import after the processing realized in the above flowchart. The flag Fo=Ft shown here indicates the value of the flag bit shown in FIG. Since the rich and lean barbs are repeated alternately, the actual measured value has a wave shape, so the flag Fo is rich. It is inverted depending on the lean detection result, and is switched to 0 on the rich side and 1 on the lean side. Also, Fl is
F2 is a flag indicating completion of initial value setting for lean, and F2 is a flag indicating completion of initial value setting for rich. Data ingestion is programmed to start from the rich side. Fs and F4 are initialization flags for backing up the RAM 14, Fs is a flag pit for checking the memory of the RAM 14 when the battery is turned on from off, and Fo is a flag pit for starting control (before start → O: !Fil start → 1), and FT is the flag pit of control end (before end → 1: end → 0). Therefore, the value of 7 lags Ft+Fz+Fa, , Fr is the initial value 0 before learning. In step S12, in order to check the starting point of learning, first check whether the rich initial value is set by checking whether the flag F2-1 is set (whether the rich flag is set or not).
Determine. If the flag is Fz-1, the process moves to step 313, and it is determined whether the next lean initial value has been set (or whether it is the flag F1-1 or output). Also step 8
If 7 lag Ft=1 is not set at 12, step 31
Move to 4. In step S14, it is determined whether or not M-10, and M-
If it is 10 (rich side data import condition), proceed to step 317, calculate R using the contents of address 07 as VRp (rich side peak value), and set 1/4 of it as RR8.
, RRE. Also, flag F2-1. Fo −0
As a result, we move on to the next step. In step 813, if the flag E1-1, step 8
If the flag F1=1 is not set, the process moves to step 81G. When it is determined in step 816 whether M≦0, if M-0 (lean side data acquisition condition), the process moves to step 818, and the contents of address D are set as VLp (lean side peak value) and L is seek,
1/4 of that is LLS. Assign to LLE. Also, flag F1=1. Fo=1 is set and the process moves to the next step. Here, moving from step 313 to step 815 means that after starting learning, VRp and VLp are
This shows that at least it has passed, indicating that the conditions for starting learning have already been met. Therefore, in step 815, it is determined whether or not M-0. If M-0 (lean side), the next step 31
At step 9, it is determined whether or not 7 lag Fo = O (whether or not the intake condition is on the lean side). If it is not M-0 in step 815, then step 82
0, it is determined whether it is M-10 or not, and if it is M-10 (rich side), in the next step 821, 7 lag Fo-1
A determination is made as to whether or not the intake condition is on the rich side. That is, in step S1'll, 820, it is determined whether the previous signal was on the rich side or the lean side based on whether the 7 lag Fo=1 or FO-0. For example, if 7 lag Fo = O in step 819 (rich side), the flag Fo = 1 is rewritten in the next step 825, and if 7 lag FO - 1 in step S21 (lean side), in the next step 322 Flag Fo = O to II! Change it. If the process moves from step 822 to step 323,
It is determined whether address D7≧R, and when this condition is satisfied, in step 824, address Or -e
R+ (15xRaax /16) + (Dt /
16) -I Rwax, Rsax /4-hRmax
X4 (that is, rich side detection). If the process moves from step 825 to step 826,
It is determined whether address DT≦L, and when this condition is satisfied, in step 827 address DT -)
L, (15X La+in /16) + (Dr
/1B)→ll+n, La1n /4-'Lli
n4 (that is, lean side detection). This is to convert the data to a resolution of 1/64. Here, the previous process Rmax/4→R*ax4 has already been executed. In the next step 828, L 1in4+ 2 <R ax4 is considered. Here, adding 2 to Llin4 and comparing it shows that when the difference between rich and lean is small, the learning start condition cannot be reached (here, reading errors at the start point due to small fluctuations in the measurement location are prevented do). If the conditions are satisfied in step 828, step 8
At 29, the learning control is entered with the flag F'e + F T-1, but otherwise, the data in the area 14a is used as the slice level table, and the value of the address (divided into 64) corresponding to the actual measured value of the Ot sensor 16 is fixed. As a slice level, the fuel is 51 as usual! This is to obtain a feedback signal for control. In step S30, it is determined whether the idle switch is off (in operation) or is warming up. If it is determined that the idle switch is on or that the aircraft is not in use, the process moves to step S31, but if the opposite is true, the stroke start condition is met, so the next step S32
Then, it is determined whether the vehicle is accelerating or not. If the vehicle is accelerating, the learning conditions are not met and learning control is not performed. Further, if the acceleration is not in progress, the process moves to step 833, and l
m1n4<LLS is compared, and if the condition is satisfied, Rmax4≧RR8 is also compared in step S34. When these are satisfied, in the next step 835 l-1in4→
LLS→LLE, flax4-+RR3-4RRE are loaded, and in step 83G, 02 sensor 1 at that time
6 electromotive force (Rmax4-L m1n4) x
O,6+ Rm1n4→R8 (LLS) is written, and the slice level is set for each address in the area 14b. When proceeding to step S31, it is determined whether the vehicle speed is v#O. If the vehicle speed is O, it is under the condition that learning is completed. Also, even if the vehicle speed is not 0. If it is neutral in the next step 337, it is assumed that the above conditions are met and the process moves to step S38. here,
l5in4>LLE is compared, and if the condition is satisfied, R*ax4≦RRE is also compared in step 839. When these are satisfied, in the next step 840 L 1
in4-+ LLE, Rmax4-+ RRS
is written, and in step 341, corresponding to the electromotive force of the 0□ sensor 16 at that time (F?, max4- Rain
4) x 0.6+ l m1n4-+ RE (RR
E), and the slice level is set for each of the seven addresses in the area 14b. Here, in steps 833 to 836, the writing address is (RR3>), and the slice level setting value is written to the area 14b using the lean side peak value as the address reference, whereas in steps 838 to 341,
It should be noted that the write address is (RR8), and the slice level setting value is written to the area 141) using the rich side peak value as the address reference. Note that after going through steps 814 and 817, or after determining that it is not M-0 in step 816, the RA
Through the initialization routine 42 of M14,
If even one of the 64 addresses contains a 0 value, the previously backed up value can be input to the address and used as the slice level for the air-fuel ratio control at the start. Also, whether to use the slice level table of the given operation start region as the reference value of the slice level, or to use the slice level table of the operation end region as the reference value as well (both are learned in the operation state, and the area 14b kl 14a) is operated via the routine shown in FIG. Here, it is determined in step 843 whether f8=1 (control start condition), and if the condition is satisfied, in the next step 344 it is determined whether the vehicle speed is equal to or less than V -1O2v. If the vehicle speed is V -1O2v or more, R8(L m1
n4) as a slice level, and the vehicle speed V −
If it is less than 1O2v, the next step 345 asks whether the idle switch 20 is on or off. If the idle switch 20 is off, R8 (m1n4) is used as the slice level, but if the idle switch 20 is on, the engine speed is set to 100 in step 846.
It is determined whether it is 0rp- or more. Engine speed is 1
000rp- or more, R8 (L m1n4) is used as the slice level, but if the engine speed is 11
If it is less than 000rp, RE (Riax4) will be used as the slice level. Effects of the Invention 1 The present invention has been described in detail above, and on the other hand, it is possible to perform air-fuel ratio 1-control in real time using the slice level reference value taken in advance.
When doing so, we imported a new reference value table based on the actual measured value of the 02 sensor within the specified conditions, and after learning, we prepared for the next operation using the previous slice level and MlllL. ! Even when the 02 sensor is not activated, the reference value of the slice level is given based on past data, and the air-fuel ratio ill mI at that stage is determined.
In addition, the above data is rewritten every time the operation is performed (from the beginning to the end of the amplitude fluctuation of the electromotive force of the 02 sensor), and corrections are made according to the degree of deterioration and activation of the 02 sensor. The effect is that control at the stoichiometric air-fuel ratio is maintained and the reference value is also stable.

[Brief explanation of drawings]

Figure #11 is a block diagram showing an embodiment of the present invention, Figure 2 is a diagram showing how the maximum value and minimum value of the oz sensor appear,
Figure 3 shows the start of data acquisition for slice level;
Figures 4 and 5 are flowcharts, Figure 6 is a diagram showing the contents of the flag bit, and Figure 7 is a diagram showing the contents of the flag bit. Example block diagram, Figure 8 is an output characteristic diagram of the O2 sensor,
FIG. 9 is a flowchart showing a routine for selecting a table depending on the driving situation. 11... Central control unit, 12... Input boat,
13...ROM, 14-RAM, 14a,
14b--area, 15--output boat, 16...
0□Sensor, 17...Air 70-meter, 18...
Water 2! ! Sensor, 19... Throttle sensor, 21.
...Fuel injection valve, 22...Regulator, 23...
A/D converter. Patent applicant: Fuji Heavy Industries Co., Ltd. Agent: Patent attorney: Makoto Kobashi Ukiyo Patent attorney: Susumu Murai I! ! Engraving of the surface (no change in content y 721:11 Fuwo Miro + 285 May 30, 1985 Commissioner of the Patent Office Gakudono Shiga1, Indication of the case 1985 Patent Application No. 0054072, Name of the invention blank) Fuel ratio control device 3° Relationship to the case of the person making the amendment Patent Applicant: 1-7-2-4 Nishi-Shinjuku, Shinjuku-ku, Tokyo, Agent 6, Date of amendment order: 6, Drawing plan subject to amendment 7, Amendment: Content

Claims (2)

[Claims] (1) The O_2 sensor that detects the concentration of engine exhaust gas components is compared with a reference voltage at the slice level, and fuel metering is controlled by a control signal based on the deviation. While controlling at the slice level corresponding to the actual measured value of the O_2 sensor, it also learns the slice level corresponding to the actual measured value of the O_2 sensor within the predetermined conditions of that operating state, and after the learning is completed, so as to use this in the next operating state. An air-fuel ratio control device characterized in that the contents of a slice level table are replaced. (2) The above slice level table is created by dividing the electromotive voltage value of the O_2 sensor into a predetermined number (for example, into 64 parts), and taking in the corresponding slice level value as a learning value, and then determining the electromotive force value of the O_2 sensor in the next operating state. Claim 1, characterized in that it is used as a voltage-compatible slice level.
The air-fuel ratio control device described in .