JPH02181043A - Air-fuel ratio control device for electronic control fuel injection type engine - Google Patents

Abstract

PURPOSE:To make it possible to control air fuel ratio so as to meet its target even in utilizing an injector with large variations by deciding fuel injection quantity of respective injectors according to the detecting levels of intake air quantity, revolutions of an engine and air fuel ratio to control the injectors independently. CONSTITUTION:The detecting means of an intake air quantity sensor 8 measuring intake air Qa, a crank angle sensor 14, built in a distributor 12, detecting the revolutions N of an engine, O2 sensor detecting air fuel ratio A/F and so on are installed to input their output signals in a control unit 10, where an injection pulse duration Ti for supplying the fuel injection quantity suited to th operating conditions at that time is calculated independently for respective cylinders 24, based on respective signals inputted. During the calculated injection pulse duration Ti, fuel is injected for the corresponding cylinder 24 from an injector 22.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an air-fuel ratio control device, particularly an electronically controlled fuel injection type engine suitable for absorbing variations in air-fuel ratio that occur between a plurality of engine cylinders. The present invention relates to an air-fuel ratio control device.

[Conventional technology]

The fuel injection valve used in an electronically controlled fuel injection system is opened by a pulse signal given in synchronization with the rotation of the engine, and during the valve opening period, fuel at a predetermined pressure is injected into the engine cylinder. There is. Therefore, since the fuel injection amount is controlled by the pulse width of the immediate pulse signal, if this pulse @Tj is the control signal corresponding to the fuel injection amount, the pulse width Tj for obtaining the stoichiometric air-fuel ratio is determined by the following formula: Desired.

Ti = Tp - Kn・a + Ts TP: Base equivalent to the basic injection amount of fuel Main pulse width Kn: Various correction coefficients such as water temperature correction α: Air-fuel ratio feedback control air-fuel ratio feedback supplement for positive coefficient 13 = Ts: Fuel due to battery voltage fluctuation Correcting the injection amount change of the injection valve voltage correction for The basic pulse width TP is further expressed by the following equation.

Tp=to-Qa/N K: Constant, Qa: Intake air flow rate N: Engine rotational speed Air-fuel ratio control (λ control) is performed by providing an 02 sensor, for example, as an air-fuel ratio sensor in the exhaust system to check the actual air-fuel ratio. detect,
The slice level determines whether the air-fuel ratio is richer or leaner than the stoichiometric air-fuel ratio and is controlled.

For this reason, the air-fuel ratio feedback correction coefficient α is determined and the stoichiometric air-fuel ratio is maintained by changing this coefficient α.

The value of the air-fuel ratio feedback correction coefficient α is generally changed by proportional-integral control to perform stable control. That is, the output voltage of the 02 sensor is compared with the slice level voltage, and if the air-fuel ratio is rich (lean), it is first slightly lowered (raised) and then gradually lowered (raised). Controls the air-fuel ratio to make it leaner (richer). Also,
Under conditions where λ control is not performed, the coefficient α is clamped and each 1
The required air-fuel ratio is obtained by setting the species correction coefficient Kn. If the reference air-fuel ratio under λ control conditions, that is, the air-fuel ratio when α = 1, could be set to the stoichiometric air-fuel ratio (λ = 1), feedback control would not be necessary. It deviates from λ=1 due to variations in
Feedback control is performed. If the standard air-fuel ratio deviates from λ = 1, when the operating range changes significantly, the difference in the standard air-fuel ratio will be reduced to λ by feedback control.
It takes time to stabilize the value to 1.

Therefore, a system has been proposed that uses learning control to set the reference air-fuel ratio to λ=1, thereby eliminating deviations caused by the step in the reference air-fuel ratio during transient periods and improving control performance.

(For example, see JP-A-59-203828).

[Problem to be solved by the invention]

However, conventional air-fuel ratio control devices provide one air-fuel ratio sensor at the joint of the exhaust pipes of multiple engine cylinders, and detect the average air-fuel ratio of the entire engine, rather than the actual air-fuel ratio of each cylinder. It was designed to be controlled by feedback. Therefore, even if the air-fuel ratio of a specific cylinder deviates from that of other cylinders, it is impossible to detect this or to adjust the injection amount of an injector that injects and supplies fuel to that cylinder. Therefore, in order to achieve the desired control accuracy, high precision is required for controlling the injection amount of the injector that supplies fuel to each engine cylinder, and large variations are not allowed. The variation tolerance is required to be within ±3%.

SUMMARY OF THE INVENTION An object of the present invention is to propose an air-fuel ratio control device that can absorb the variation in injection amount of an injector even if the tolerance is large, and causes no practical problems.

[Means to solve the problem]

The present invention achieves the above object, and includes means for opening the intake air amount Qa of an engine equipped with a plurality of cylinders;
means for measuring the rotational speed N of the engine; a sensor for detecting the actual air-fuel ratio of the exhaust system for each cylinder of the engine; a plurality of injectors supplying fuel to each of the plurality of cylinders of the engine; The apparatus includes an arithmetic unit that determines the fuel injection amount of each of the injectors based on signals from the intake air amount measuring means, the air-fuel ratio sensor, and the rotational speed measuring means, and determines the fuel injection amount of each injector provided in each cylinder. The air-fuel ratio is changed independently according to the output signal of the arithmetic unit, and the air-fuel ratio is detected for each engine cylinder, and the fuel injection amount of the attached injector is controlled independently from other injectors. It becomes possible to do so.

〔Example〕

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of an engine and a fuel injection device to which the present invention is applied. The amount of air taken into the engine 4 that has been purified through an air filter 2 is adjusted by a throttle valve 6. As shown in FIG. The intake air amount sensor 8 is, for example, a hot wire air flow meter, and supplies a signal indicating the measured value Qa of the intake air amount to the control unit 10. On the other hand, a crank angle sensor 14 built into the distributor 12 generates a detection signal for the crank angle reference position and a pulse signal for every 1 degree of crank angle, and based on this, a signal indicating the rotation speed N detected by the signal processing device 16 is control unit 1
~10. The signal processing device 16 also generates a position signal PO8 indicating the crank position and a crank angle reference position signal R.
Generates F and supplies it to the control unit 10 1m t
7. ,l.

The control unit 10 includes an intake air flow rate signal Qa from the intake air amount sensor 8, an air-fuel ratio signal A/F from the Oz sensor 18, and a rotation speed N of the signal processing device 16, as well as an on-off signal ST of the starter switch. , water temperature sensor 20
Water temperature signal Tw from , reference signal RF, position signal pos
, the battery power supply voltage E is input. The control unit 10 calculates an injection pulse intensity Ti for supplying an amount of injected fuel suitable for the conditions, based on the intake air amount Qa, rotation speed N, etc. During the injection pulse width Ti commanded by the control unit 10, the injector 22
Inject fuel inside.

The fuel supplied from the fuel tank 26 is supplied to the fuel pump 28.
The oil is pressurized by the oil filter 30 and guided to the injector 22 through the oil filter 30. The injector 22 is attached to an intake pipe 32 of the engine 4, where the injected fuel is mixed with intake air and supplied into the corresponding cylinder 24 of the engine 4 via an intake valve 34. The fuel pressure regulator 36 adjusts the injection pressure of the injector according to the fuel tank pressure and the air pressure in the suction pipe.

As shown in FIG. 2, one injector 22 is provided for each cylinder of the engine 4.

For example, in the case of a four-cylinder engine, four injectors 22 are provided. Fuel injection is synchronized with the cycle of each cylinder of the engine, as shown in FIG. 3, and is performed slightly before the intake stroke. Therefore, the amount of fuel to be supplied to each cylinder is specified, and for example, No. 1, and the fuel injected by the injector 22 attached to one cylinder is No.

It is not inhaled into any cylinder other than 1 cylinder.

The fuel ignited and burned in the cylinder 24 of the engine 4 is sent to the exhaust pipe 38. The air-fuel ratio A/F of the exhaust gas is detected downstream of the collecting part of the exhaust pipes 38 of each cylinder.
A sensor 18 is attached and supplies a measured air-fuel ratio signal A/F to the control unit 10.

FIG. 2 is a block diagram for explaining the main functions of the engine shown in FIG. 1, in which the control unit 10 is an LSI 40. central processing unit 42, writable memory 44, stabilized power supply circuit 46, pump 28,
It includes intake and exhaust valves 48, an ignition device 50, a driver 52 that drives the injector 22, and the like. The memory 44 is used to set various coefficients, numerical values, etc. used when calculating the pulse width Ti that determines the fuel injection amount. RAM and ROM are used as the memory 44, and the learning results are reflected in the next calculation by modifying the contents of the RAM.

Figure 4 shows the characteristics of the 02 sensor. As is well known, the output voltage V O2 of the 02 sensor changes dramatically at λ=1, that is, the air-fuel ratio is 14.7. . VO21 indicates the output voltage when λ=1. Output voltage V
O2 is about 0.8V when the air-fuel ratio A/F is on the rich side, and about 0.2V when it is on the lean side.

FIG. 5 shows the characteristics of the injector, which injects fuel Qf proportional to the command pulse Ti.

In this case, the injection characteristics of the injector are expressed by the following equation.

Q f =Kn (Ti - Tsn) Tsn: Characteristic value Kn: Constant Therefore, the variation in the characteristics of the injector can be indicated by the variation in the characteristic value Tsn and the constant Kn, and in the embodiment of the present invention, it is ±5 to 10 %. Generally, this variation is ±3% or less, and the variation in the air-fuel ratio A/F of each cylinder is set to be maintained within an allowable range for engine combustion, but in the present invention, each cylinder Since the air-fuel ratio A/F is detected and controlled for each cylinder, even if there are variations in the injection amount, it is possible to absorb them. As described above, in the present invention, since variations of ±5 to 10% are allowed, the injector can be made without adjustment, and the injector manufacturing cost can be reduced by about 50%.

FIG. 6 is an explanatory diagram of the 02 feedback. When the engine is rotating steadily, the output voltage V O2 of the 02 sensor is determined based on the operating conditions of the engine, such as the rotation speed.
Output is periodically generated at a period to2 corresponding to the air flow rate, load, etc. As shown in FIG. 7, the period to2 becomes shorter as the air flow rate Qa and the engine speed N increase. Generally, this voltage V o x is VO with λ=1
When it is higher than 21, the air-fuel ratio A/F is rich, and vice versa, it is lean. The pulse width Ti varies by ΔTi in accordance with the output of the 02 sensor. This Ti+ΔT
The average value Ti1 of i is the pulse width that makes λ=1.

Fig. 6(c) shows the combustion cycle of each cylinder.
2 sensor switching period t. 2, the combustion cylinders are not necessarily synchronized. A plurality of engine cylinders burn in a predetermined order and emit exhaust gas, but if an 02 sensor is provided for each cylinder, each sensor output corresponds to each cylinder. When the only 02 sensor is installed at the exhaust pipe gathering part,
It is necessary to determine which cylinder the detection output corresponds to. Furthermore, if the 02 sensor is installed too far downstream of the exhaust valve, the exhaust gas from each cylinder will mix, and only the average air-fuel ratio can be detected, making it impossible to detect the air-fuel ratio of each cylinder. However, in this case, the installation of the 02 sensor can be done with the period t by appropriately selecting various conditions such as the distance between the position and the engine exhaust valve, the engine speed, and the air flow rate. 2 and the engine combustion cycle is possible. If selected in this way, the output of the 02 sensor will be synchronized with the particular cylinder being burned when the operating conditions are met. Therefore, if the rotation angle sensor detects the cylinder in the combustion cycle,
The air/fuel ratio is detected.

However, even if the period is not perfectly synchronized with the engine cycle, it is possible to determine which cylinder's output. For example, if the delay time from the exhaust cycle of the engine to when the 02 sensor output is obtained is known, it is possible to associate each engine with the 02 sensor output. Even in this case, it is necessary to appropriately select the engine conditions, the mounting position of the 02 sensor, and the distance between the engine exhaust valve and the engine exhaust valve so that exhaust gases from different cylinders do not mix.

FIG. 7 shows the switching period T of the 02 sensor. 2 is a diagram for explaining the tendency of To2 with respect to the combustion state of the engine, and To2 becomes shorter as Qa and N become larger. Therefore, the period T is synchronized with the cycle of the engine. 2 can be selected. Further, since this region is not important for exhaust gas, no problem will occur even if Oz feedback is intentionally stopped in this region and the A/F is fixed at λ=1.

FIG. 8 explains the state of the air-fuel ratio A/F in this region. When λ=1 for all cylinders from cylinders N011 to No. 4, the pulse is fixed at @Tj□. However, for example, if the flow rate of the injector installed in the NO, 1 cylinder is low and only this cylinder indicates lean, the combustion cycle and the detection cycle of the 02 sensor are synchronized under the above specific operating conditions, so the voltage It outputs an output lower than VO21 by ΔV o x, and it can be seen that the No. 1 cylinder is lean. This determination can be made for each cylinder based on the same theory, even if the number of lean cylinders increases to two, or if the engine shifts to the rich side.

By determining the A/F, the characteristic coefficients Tsn and Kn of the injector provided in each cylinder are determined as shown in FIG.
By setting , it becomes possible to control the cylinder A/F separately.

FIG. 10 shows a flowchart of an embodiment of the present invention. Conditions are set based on the engine conditions of the intake air amount Qa and the rotational speed N, and the engine combustion is controlled by the O2 sensor output output as described above. Define areas where synchronization can be achieved.

In this region, the engine cylinder outputs a pulse width Ti that should make λ=1. At this time, originally all cylinders should have approximately λ = 1, but if the characteristics of the injector installed in a particular cylinder are different, if the voltage V O2 is measured at the same timing for each cylinder,
It turns out that the output Vozn of a given cylinder is not λ=1. This signal detects which cylinder it is, and each corrects Tsn and Kn in small increments, and while going through the loop in Figure 10 several times, Ts and K are corrected so that λ=1 for all cylinders. The Rukoto.

〔Effect of the invention〕

As explained above, according to the present invention, the air-fuel ratio can be controlled to the target even if there are large variations in the injectors installed in each cylinder. You can explore the air-fuel ratio control device that can accomplish your goals.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of an air-fuel ratio control device showing one embodiment of the present invention, FIG. 2 is a block diagram for explaining its functions, FIG. 3 is a diagram for explaining the combustion cycle of an engine, and FIG.
The figure is a characteristic diagram of an O2 sensor, FIG. 5 is an injection characteristic diagram of an injector, and FIG. 6 is a characteristic diagram of an injector. Figure 7 is an explanatory diagram of air-fuel ratio feedback control, Figure 8 is a diagram to explain the output of the 02 sensor, Figure 9 is a diagram to explain the control constant of the injector, and Figure 10 is a diagram to explain the air-fuel ratio learning. It is a flowchart explaining the process. 4... Engine, 8... Intake air amount sensor, 10.
- Control unit, 18...02 sensor, 24... cylinder, 22... injector, 38... exhaust pipe. Isoiso Isoiro Chart Map

Claims (1)

[Claims] 1. Intake air amount Qa of an engine with multiple cylinders
means for measuring the rotational speed N of the engine, a sensor for detecting the actual air-fuel ratio of the exhaust system for each cylinder of the engine, and supplying fuel to each of the plurality of cylinders of the engine. multiple injectors,
The computer includes a calculation device that determines the fuel injection amount of each of the injectors based on the signals from the intake air amount measuring means, the air-fuel ratio sensor, and the rotation speed measuring means, and determines the fuel injection amount of each injector provided in each cylinder. An air-fuel ratio control device for an electronically controlled fuel injection engine, characterized in that the air-fuel ratio is controlled independently by an output signal of the arithmetic unit. 2. Intake air amount Qa of an engine with multiple cylinders
a means for measuring the rotational speed N of the engine; a plurality of O_2 sensors respectively provided in the exhaust pipes of the plurality of engine cylinders; and a plurality of O_2 sensors each supplying fuel to the plurality of engine cylinders. An arithmetic unit that determines the fuel injection amount of each of the injectors based on the signals from the injector, the intake air amount measuring means, the O_2 sensor, and the rotation speed measuring means, and the fuel injection of each injector provided in each cylinder is provided. An air-fuel ratio control device for an electronically controlled fuel injection engine, characterized in that the air-fuel ratio control device independently controls the amount by an output signal of the arithmetic device. 3. Intake air amount Qa of an engine with multiple cylinders
means for measuring the rotational speed N of the engine; one O_2 sensor provided at a gathering part of the exhaust pipes of the plurality of engine cylinders; a plurality of injectors that respectively supply fuel to the plurality of corresponding engine cylinders;
The apparatus includes a calculation device that determines the fuel injection amount of each of the injectors based on the signals from the intake air amount measuring means, the O_2 sensor, and the rotation speed measuring means, and determines the fuel injection amount of each injector provided in each cylinder. An air-fuel ratio control device for an electronically controlled fuel injection engine, characterized in that the air-fuel ratio control device is independently controlled by an output signal of the arithmetic device. 4. Intake air amount Qa of an engine with multiple cylinders
and each of a plurality of injectors that detects the rotational speed N of the engine and the actual air-fuel ratio of the exhaust system for each cylinder of the engine, and supplies the plurality of injectors to the plurality of cylinders of the engine according to the various quantities. The fuel injection amount of each injector provided in each cylinder is determined independently, and the tolerance of the variation in the injection amount of the injectors is ±5% to 10%. Features: Air-fuel ratio control device for electronically controlled fuel injection engines.