JPS5859332A - Air-fuel ratio control device in internal-combustion engine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to an air-fuel ratio control device for an internal combustion engine.

An example of an oxygen SN detector that can be used in a gaseous oxygen concentration detector is an oxygen concentration detector using an oxygen ion conductive solid electrolyte such as zirconia, as described in JP-A-52-72286. is omniscient. In this oxygen concentration detector, a thin film serving as a cathode is placed on one surface of a zirconia plate, and a thin film serving as an anode is coated on the other surface of the zirconia plate, and a voltage is applied between the cathode and the anode. Then, after the oxygen molecules that came into contact with the cathode and were given electrons pass through the zirconia plate, K
1K to emit electrons at the anode] 1k from the anode
A current directed toward liK is generated, and this current value is compared to the number of oxygen molecules passing through the zirconia plate, that is, the partial pressure of oxygen in the gas that contacts the cathode Kll.The oxygen degree can be determined from this current value. I can do it. When the 9-lever oxygen a degree detector is installed in the engine exhaust passage, the oxygen concentration in the exhaust passage will be detected.
j[Vt can be detected, and therefore the air-fuel ratio of the 6c+supplied mixture O in the engine syringe can be known. Since this oxygen concentration detector detects the oxygen concentration in the exhaust passage, it can detect the air-fuel ratio when the air-fuel mixture supplied into the engine cylinder is a lean air-fuel mixture.

On the other hand, when no voltage is applied between the anode and cathode of the zirconia plate in this oxygen concentration detector, the oxygen concentration in the gas that contacts one surface of the zirconia plate and the gas that contacts the other surface of the zirconia plate An electromotive force is generated due to the difference in the concentration of oxygen in the engine cylinder, and this property can be used to determine whether the air-fuel mixture supplied into the engine cylinder is higher than the stoichiometric air-fuel ratio. Internal combustion engines have a core wall that adjusts the air-fuel ratio of the air-fuel mixture supplied into the engine cylinders to the stoichiometric air-fuel ratio or to a lean mixture depending on the engine operating condition.
Therefore, by using the oxygen concentration detector as described above, the air-fuel ratio can be precisely controlled over a wide range.

The object of the present invention is to provide an air-fuel ratio control system that can accurately control the air-fuel ratio of the air-fuel mixture supplied into an engine cylinder over a wide range using the oxygen concentration detector described above. .

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 1, 1 is an engine body, 2 is a cylinder block, 3Fi is a piston that reciprocates within the cylinder block 2, 4 is a cylinder head fixed on the cylinder block 2, and 5 is a piston 3 and a cylinder bed. Combustion chamber formed between 4, 6L spark plug placed in combustion chamber s, 7 intake/-1'+8 intake valve, 9 exhaust/-), 1
0t; i Indicate the exhaust valve. The intake I-door is connected to a common surge tank 12 via a branch pipe 11, while the exhaust port 9 is connected to an exhaust w-nifold 13. Each branch pipe 11
Each of the fuel injection valves 15 is provided with a fuel injection valve 15 that is controlled by an output signal from an electronic control unit 14, and fuel is injected from these fuel injection valves 15 toward the corresponding intake port 7. The surge tank 12 is connected via an intake pipe 16 (not shown).
7. Connected to the air cleaner and inside this intake pipe 16. Nine throttle valves 17 are arranged connected to the throttle valve.

A negative pressure expander 18 is installed inside the surge tank 12,
Negative pressure dragon 118 lined up with TC11 rotation speed sensor 19 Hiro electronic control equipment 14KIII! be done. On the other hand, Tsumugi Oxygen I & Degree Detection 112G is installed on PI3,
This oxygen concentration detector 20 is connected to an electronically controlled L et 14°. The oxygen 11 degree detector 20, as shown in FIG.
The porous septic 22 is disposed in the exhaust gas flow.

In addition, a thin gold film for the anode and a thin platinum film for the cathode are coated on the inner surface and outer surface of the oxygen ion conductive surrounding electrolyte 210! These platinum thin film beams 1123
m and 23b to the switching circuit 24. As shown in the 211th IK, there are three switching circuits 24 and 3 O switching switches 25m and 28b.

2s, an electric current 61121, and a resistor 27, and as described later, a 4r changeover switch 25m,! 5 to 2! ! *
are simultaneously controlled. Changeover switch 28aa lead * 23aK connection: a moving contact and a pair of fixed contacts.
, from f to one side selector switch zsbq output terminal 28
It consists of a movable contact g connected to m, and a pair of fixed contacts f. Further, the changeover switch 26c has a movable contact connected to the output terminal 28b and a pair of fixed contacts 1. Consists of m. Changeover switch 26m fixed contact/Hiro changeover switch 2
5. Connected to the fixed contact l of the Hibiki 1. The fixed contact m of the changeover switch 25c is connected to the lead @23b. In addition, the fixed contact of the changeover switch 25m and the changeover switch 2! A power supply 26 and a resistor 27 are connected in series between the fixed contact m of s@, and the connection point between the power supply 26 and the resistor 27 is connected to the fixed contact hKII of the changeover switch 25b(1).

When the changeover switches 25m, 25b, 25* are in the connected state as shown in Fig. 2, the power wires 23m, 23b are
The voltage of the power supply 26 is applied between them.

At this time, oxygen molecules in the exhaust gas are absorbed by the porous ceramic 22.
Oxygen ion conductive facepiece electrolyte 2
After reaching the cathode platinum thin film of No. 1 and given electrons here, the oxygen molecules pass through the W1 element ion conductive solid electrolyte 21 and then contact the anode platinum thin film of the Ik element ion conductive solid electrolyte 21. A stain flow is generated by emitting electrons.

Figure 5 shows oxygen concentration tP in exhaust gas (weight/9 cents)
This relationship is shown by and generated current A (mm). As shown in Fig. 5, it can be seen that the generated current is approximately proportional to the oxygen concentration. Note that if the oxygen concentration in the exhaust gas is known, the air-fuel ratio supplied into the engine cylinder can be determined, and this air-fuel ratio t is represented by the horizontal axis A/F in FIG. Therefore, it can be seen from FIG. 5 that if the generated current is known, the air-fuel ratio of the air-fuel mixture supplied into the engine cylinder can be detected. In addition,! As shown in Figure 2, the output terminals 28 m + 28 b are resistors 2
Since it is connected to both ends of 70, output terminals 28m and 28b
A voltage proportional to the generated current is generated between them, and therefore, the vertical axis in FIG. 5 can be considered to represent the output voltage vt. A state in which the output voltage V is proportional to the degree of curvature in this manner is called a first detection state.

On the other hand, as shown by the broken line in FIG.
The second detection state is a state in which the 5 m movable contact d is connected to the fixed contact f, the movable contact g of the changeover switch 25b is connected to the fixed contact f, and the movable contact k of the changeover switch 25c is connected to the fixed contact mK*. That's what it means.

At this time, the lead wires 23m and 23b are connected directly to the output terminals 2 and 8.
a w 28 b K connected, lead i! lI23
m.

No voltage is applied between 23b. At this time, the difference between the oxygen concentration in the exhaust manifold 13 and the oxygen concentration in the atmosphere, that is, the oxygen concentration between the gases in contact with both sides of the oxygen ion conductive solid electrolyte 21, causes a difference between both sides of the oxygen ion conductive solid electrolyte 21. A voltage as shown in FIG. 6 is generated. In FIG. 6, the vertical axis V shows the voltage, and the axis A/F shows the air-fuel ratio. Therefore, in the second detection state, if the air-fuel ratio is smaller than the stoichiometric air-fuel ratio by 8, then the output terminals 28m and 28b are connected to 09< When the direct output voltage is generated and the air-fuel ratio is also large (as compared to the stoichiometric air-fuel ratio), the output terminal 28a.

It can be seen that an output voltage of about 0.1° is generated between 28b and 28b. In this way, in the second detection state, it is possible to detect whether the air-fuel ratio is larger or smaller than the stoichiometric air-fuel ratio.

FIG. 3 shows the electronic control unit 14. Referring to FIG. 3, the electronic control unit 14 includes a digital computer, a microprocessor (MPU) 3G that performs various arithmetic processes, and a random access memory (R).
AM) 31, read-only memory (ROM) 32 in which control programs, calculation constants, etc. are stored in advance.
, input/-) 33 as well as output ports 34 are interconnected via a bidirectional path 35. Furthermore, a clock generator 36 is provided within the electronic control unit 14 to generate various clock signals. As shown in FIG. 3, negative pressure sensor 18 is connected to input port 33 via buffer 37 and wholesale converter 38t. The negative pressure sensor 18 generates an output voltage proportional to the negative pressure generated in the surge tank 12, that is, the intake pipe negative pressure P, and this output voltage is applied to the AD converter 3.
B, the binary number is converted into a corresponding binary number, and this binary number is sent to the MPU 3G via the input port 33 and /# bus 35.
is input. On the other hand, rotation speed sensor 19 Hiro buffer 39
It is connected to the input port 33 via. This rotation speed sensor 19 generates a /# Lus tube every time the engine crankshaft rotates by a predetermined crank angle, and this /4 Lus is inputted to the MPU ao via an input port 33 and a path 35. In MPo 3 G, the engine speed is calculated from the output pulse of the rotation speed sensor 19. Further, the output terminal of the oxygen 111 degree detector 20 is connected to the switching circuit 24 as described above, and this switching circuit 24 is connected to the amplifier 40 and the AD
To input port 33 via converter 41! 1m! be done.

The output voltage of the switching circuit 24 is converted into a corresponding binary number in a digital converter 41, and this binary number is input to the WSO via an input 33 and a path 35. In addition,! !
Actual in Figure 5! Output voltage V and air-fuel ratio A/F shown in 1
The related company is stored in advance in the RCmI 32 in the form of a function or welfare data table.

Output Baud 134 company switching jII & circuit 240 each switching switch?
25m, 26b, 25e, and the data for operating the fuel injection valve 15 are provided. 3G via bus 35. The output terminal of the output port 34 is connected to the switching circuit 2 on the one hand.
4 and an input terminal of a down counter 43 on the other hand.

Therefore, each changeover switch 25m, 25b, 25c is controlled to be switched to either the first detection state or the second detection state based on the data input to the output port 34. On the other hand, the down counter 43. is provided to convert the binary data written from the hard U3G into the corresponding time length, and this down counter 43 counts down the data sent from the output port 34. starting with a clock signal of clock generator 36;
When the count value reaches 0, the count is completed and a count completion signal is generated at the output terminal. Reset of S-R flip-flop 44 Connected to the output terminal of human power leakage RU down counter 43, and set input of S-R flip-flop f44 A terminal sh is connected to the clock generator 36. This S
The -R flip-flop counter 44 is set by the clock signal from the clock generator 36 at the same time as the down count starts, and is reset by the count completion signal from the down counter 43 when the down count is completed. Therefore, the output terminal Q of the 8-R7 circuit f707'44 is at a high level while the down count is being performed.
The output terminal Q of Gll 77' 44 is a power amplification circuit 45
It can be seen that the fuel injection valve 15 is connected to the fuel injection valve 15 through the t-t, so that the fuel injection valve 15 is energized while the down counter 43 is counting down.

Next, the operation of the alternating/twisting ratio control device according to the present invention will be explained with reference to FIG. Referring to FIG. 184, first, in step 50, the negative pressure sensor 18 and the rotation speed sensor 1 are
A target air-fuel ratio is set from the output signal of 9. This target air-fuel ratio is stored in advance in 10M32 as a function of intake pipe negative pressure P and engine speed N, for example, as shown in FIG. Note that the ott* value in Figure @7 indicates the air-fuel ratio. Therefore, in step 50, the target air-fuel ratio is calculated from the relationship shown in FIG. As can be seen from Fig. 7, this target value becomes the stoichiometric air-fuel ratio when the engine rotation @N is approximately 1G 00 r, p, III, and is very low, and when the I hill is higher than 4000 r, p, m. When the engine speed N is between 1000 r, p, m and 4000 r, p, m, the air-fuel ratio is on the lean side as shown by a single value. After the target air-fuel ratio is determined in step 50, the basic fuel injection time τ0 is set to 1 in step 51.

This basic fuel injection time is a sufficient time to form a mixture with an air-fuel ratio as shown in Fig. 7, and this basic fuel injection time τ is the same as that shown in Fig. 7 in the intake pipe. ROM 3 in the form of a map as a function of negative pressure P and engine speed N
2 has a memory leak. Next, in Stella f52, it is determined whether or not the target air-fuel ratio is on the extremely lean side, and if the target air-fuel ratio is on the lean side, the process proceeds to step 53. Step 53
Now, the changeover switch 25a of the changeover circuit 24.

25b and 25c are switched to the first detection state as shown in FIG. Next, in Stella f54, the target output voltage value V of the switching circuit 24 is calculated from the relationship shown in FIG. Next, at step 55, the current output voltage value V of the switching circuit 20 is the target voltage value V.

) is also determined to be small or not. In step 55, it is determined that the current output voltage value V is not smaller than the target voltage value V. If it is determined that the current output voltage value V is not smaller than the target voltage value V, in step 56, a constant value α is added to the correction coefficient f, and the addition result is set as f. Proceed to.

On the other hand, Stella! In step 55, when it is determined that the current output voltage value V is smaller than the target voltage value V, a constant value β is subtracted from the correction coefficient f in Stella 7''58, and after setting the subtraction result to f, Proceed to step 57. In Stella 7'' 57, the basic fuel injection time τ is multiplied by the correction coefficient f to calculate the fuel injection time τ, and fuel is injected from the fuel injection valve 15 for the required time corresponding to this fuel injection time rK. be done. FIG. 8 shows the output voltage V of the switching circuit 24 and the correction coefficient f.
shows the change in The output of the switching circuit 24 as shown in FIG.

When the voltage V becomes larger than the target voltage value V, that is, when the air-fuel ratio becomes larger than the target air-fuel ratio, the correction coefficient at is increased by α, so that the fuel injection amount is increased. When the output voltage V becomes smaller than the target voltage value V, that is, when the air-fuel ratio becomes smaller than the target air-fuel ratio, the correction body if is reduced by β, and thus the fuel injection t is reduced.

On the other hand, if it is determined in Stella f52 that the target air-fuel ratio is not on the lean side, that is, if the target air-fuel ratio is the stoichiometric air-fuel ratio as shown by the hatching in FIG. 7, the process proceeds to step 59. In step 59, each of the changeover switches 25m and 25b of the changeover circuit 24.

25c to switch to the second detection state shown by the broken line.Next, in the Stella f60, the output voltage V of the switching circuit 24
It is determined whether or not is smaller than the reference voltage Vr shown in FIG. sg6. Note that this reference voltage Vr is set in advance to R
Stored within OM 32. When it is determined in step 60 that the output voltage ■ of the switching circuit 24 is smaller than the reference voltage Vr, that is, when the air-fuel ratio is larger than the stoichiometric air-fuel ratio, the corrector lI! tKr
are added, and let the addition result be f. Therefore, at this time, the fuel injection time τ is gradually increased. on the other hand,
When it is determined that the output voltage V of the switching circuit 24 is not smaller than the reference voltage Vr in Stella 7''60, that is, when the air-fuel ratio is smaller than the stoichiometric air-fuel ratio, Stella f62 is selected.
δ is subtracted from the correction body at, and the subtraction result is set as f. Therefore, at this time, the fuel injection time i is gradually increased. In this way, the air-fuel ratio is controlled to the stoichiometric 9-fuel ratio.

As described above, according to the present invention, the air-fuel ratio of the air-fuel mixture supplied into the engine cylinder can be precisely controlled to the target air-fuel ratio, whether the target air-fuel ratio is the stoichiometric 9-fuel ratio or the lean air-fuel ratio. be able to. Furthermore, there is an advantage that such 9-fuel ratio control can be performed using only one oxygen concentration detector.

[Brief explanation of the drawing]

Fig. 111 is a side sectional view of the internal combustion engine according to the present invention, Fig. 2 is a circuit diagram of the switching circuit of the oxygen concentration detector, Fig. 3 is a circuit diagram of the company's electronic control system, and Fig. 4 is a circuit diagram of the air-fuel ratio control device. 70-char to explain the operation of )% II! Figure 6 shows the output voltage of the oxygen concentration detector in the second detection state, Figure 7 shows the target air-fuel ratio. , Stripe 8 is a diagram showing a change in correction body excess. 12...Surge tank, 13...Exhaust manifold,
14... Electronic control unit, 15... Fuel injection valve,
17...S0 sottle valve, 18...Negative pressure upper sensor, 19
...Rotational speed sensor, 20...Oxygen concentration detector, Patent applicant Toyota Motor Corporation Patent sales agent Akira Aoki Patent attorney Kazuyuki Nishidate Patent attorney Yoshi 1) Tadashi Patent attorney Yamaguchi Akihito Figure 1 Figure 2 'IPJ4 Zuzai Mi VR/ Figure 5 Figure 6〉

Claims (1)

[Claims] An oxygen concentration detector capable of detecting the quality of oxygen in the exhaust passage is installed in the engine exhaust passage, and the air-fuel ratio of the air-fuel mixture supplied into the engine cylinder is controlled based on the output signal of the oxygen concentration detector. In the air-fuel ratio control device, the above oxygen 1
A first detection state in which the detector generates an output voltage proportional to the oxygen degree S in the exhaust passage; and a second detection state in which the detector generates an output voltage indicating whether the air-fuel ratio is greater than the stoichiometric air-fuel ratio. It is equipped with a switching circuit that can switch the detection status lIK for any time, and also controls the air-fuel ratio according to the operating status of the machine 11.
! 2! Should I use the fuel ratio or lean 111M? ! An air-fuel ratio control device for an internal combustion engine, comprising a storage means tA storing information on whether the fuel ratio should be set, and controlling the switching of the detected state by operating the switching circuit based on the stored information.