JPS635132A - Air-fuel ratio control device for number of cylinders control engine - Google Patents

Abstract

PURPOSE:To improve contrallability in two running modes, by a method wherein controllability in feedback control of an airfuel ratio during reduced number of cylinders running is set to a value different from that during total cylinder running. CONSTITUTION:Detecting values from an airflow meter 4, an intake air tempera ture sensor 5, a throttle sensor 7, an O2 sensor 11, a water temperature sensor 12, and a number of revolutions sensor 13 are inputted to an engine control unit 15, Based on the detecting values, a number of cylinders reducing means 101 closes a shutter valve 9, shutting off the feed of air to first-third cylinders through an on-off means 10 during low load running, and stops the feed of fuel to the cylinders to perform reduced number of cylinders running, An air-fuel ratio control means 102 computes a fundamental fuel injection amount from the number of revolutions and an intake air amount, and performs feedback control of an air-fuel ratio based on a detecting value from the O2 sensor 11 when a feedback control condition is established. Controllability of an air-fuel ratio during reduced number of cylinders running is set to a value different from that during total cylinder running.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention suspends the operation of some cylinders when the engine is under light load to perform cylinder reduction operation, and adjusts the air-fuel ratio of the air-fuel mixture to a preset air-fuel ratio. This invention relates to an air-fuel ratio control device for an engine that controls the number of cylinders and performs feedback control on the number of cylinders.

(Prior art) In general, when an engine is operated under a high load condition, fuel efficiency tends to improve. A cylinder number control engine is known in which the load on the remaining operating cylinders is relatively increased, thereby improving fuel efficiency in the light load range as a whole (see, for example, Japanese Patent Laid-Open No. 58-211567).

Further, in order to set the air-fuel ratio of the air-fuel mixture supplied to the engine to a target air-fuel ratio, there is known one that performs feedback control based on the output of an air-fuel ratio sensor. In addition, in accurately controlling the air-fuel ratio, for example, when transitioning from a non-feedback region to a feedback region,
In order to achieve the target air-fuel ratio in a short time, there is also known a learning control method in which the average value of feedback correction values in the previous feedback region is stored as a learning value, and this is used to perform control immediately after transition.

(Problem to be solved by the invention) By the way, when feedback control of the air-fuel ratio is performed in an engine with cylinder number control, even if the output of the air flow sensor is the same during full-cylinder operation and during reduced-cylinder operation, the injector Since the total injection amount is different and its characteristics are non-linear, the operating range is different, and the intake air flow changes, so the feedback correction amount is different from each other, and this is especially true for reduced-cylinder operation and full-cylinder operation. There will be a delay in the response of air-fuel ratio control when switching between the two. or.

As described above, even when learning control is performed, there is a problem that a single learning value does not meet the requirements for each cylinder reduction because the feedback correction amounts are different.

In view of the above, an object of the present invention is to provide an air-fuel ratio control device for an engine with a controlled number of cylinders, which has improved air-fuel ratio controllability both during reduced-cylinder operation and during full-cylinder operation.

(Means for Solving the Problems) The present invention solves the above-mentioned problems, and the details thereof will be explained below using FIG. 1 corresponding to an embodiment.

Operating state detecting means for detecting the operating state of the engine, such as an air flow meter 4, an intake air temperature sensor 5, a throttle sensor 7, and a water temperature sensor I2, and depending on the output of the operating state detecting means, operation of some cylinders is suspended when the engine is lightly loaded. an air-fuel ratio detecting means, for example, 02 sensor 11, which detects the air-fuel ratio of the air-fuel mixture supplied to the engine; This is based on the premise that the air-fuel ratio control means 102 is provided for performing feedback control on the fuel ratio, and the air-fuel ratio control means 102 receives the output of the cylinder reduction means 101 and controls the air-fuel ratio control means 102 during cylinder reduction operation and full cylinder operation. It has a correction means 103 that sets the control characteristics to mutually different values. Here, the control characteristic specifically indicates, for example, a correction value or learning value of a feedback control amount, a feedback control constant, etc.

(Function) Since the control characteristics of the air-fuel ratio control means 102 are corrected by the correction means 103 to be different depending on the reduced-cylinder operation and the full-cylinder operation, the controllability of the air-fuel ratio is improved during either operation. It increases.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

In Figure 1, 1 is a 6-cylinder engine with M cylinders,
An intake passage 2 and an exhaust passage 3 are connected.

In the intake passage 2, from the upstream side, an air flow meter 4, an intake temperature sensor 5, a throttle valve 6. A throttle sensor 7 for detecting the opening degree of the throttle sensor 7 and a surge tank 8 are arranged in this order, and the downstream side of the surge tank 8 is branched into branch roads 2a and 2b and communicates with each cylinder.

A shutter valve 9 is provided in each branch passage 2a communicating with the first to third cylinders, and the shutter valve 9 is opened and closed integrally by an opening/closing means 10.

11 is an 02 sensor as an air-fuel ratio detection means disposed in the exhaust passage 3; 12 is a water temperature sensor provided in the engine body for detecting the temperature of engine cooling water; and 13 is a rotation speed sensor for detecting the engine speed.

14 is an injector arranged in each branch passage 2a, 2b.

Reference numeral 15 denotes an engine control unit, which includes an operating state detection means for detecting the operating state of the engine, that is, an air flow meter 4.
, cylinder reduction means 101 that suspends operation of some cylinders when the engine is under light load in response to the outputs of the intake temperature sensor 5, throttle sensor 7, and water temperature sensor 12; Air-fuel ratio control means lO2 that receives the output of the 02 sensor 11 as a fuel ratio detection means and performs feedback control of the air-fuel ratio of the air-fuel mixture to a preset air-fuel ratio.
It is equipped with Further, in response to the output of the cylinder reduction means 101, the air-fuel ratio control means 102 receives the output from the cylinder reduction means 101 and controls the air-fuel ratio control means 102 during cylinder reduction operation and during all-cylinder operation.
correction means 103 for setting the control characteristics of the
has.

Next, the process flow of the engine control unit 15 will be explained with reference to FIGS. 2 to 5.

When starting, first, non-F/B is set by initialization.
Set the feedback judgment flag i to 0 to indicate whether or not the area has entered the F/B area (step SI), and set data values such as engine speed, intake air amount, throttle opening, temperature,
Read atmospheric pressure and engine cooling water temperature (step S2
).

Then, based on the engine speed and throttle opening, it is determined whether or not the engine is in the F/B region according to the F/B determination map shown in FIG. 4 (step Sa).

If it is a non-F/B area, a subroutine program (see FIG. 3) to be described later is executed (step S4), and the process returns to step Sl.

If it is in the F/B region, it is determined based on the engine speed and throttle opening whether it is an all-cylinder operating state or a reduced-cylinder operating state according to the operating state determination map shown in FIG. During cylinder operation, the operating state determination flag is set to 1 (step S6), and during reduced cylinder operation, the operating state determination flag is set to 2 (step S7), and then it is determined whether or not the feedback determination flag i=0 (step Ss). ), thereby determining whether or not the F/B area has been entered from the non-F/B area.

If the determination flag i=0, it means that the F/B area has been entered from the non-F/B area, so the feedback control term Cy
a. The learning correction term CLc is set to CF30(1) and CLco(I) which are stored in advance in step S12 (step S9), and at the start of air-fuel ratio control, that is, F/
Only for the first shot that enters area B, Cya and CLc that are stored above according to the operating condition, that is, CF[ during all cylinder operation.
Io (1) + cLco (1), and C during cylinder reduction operation.
Control using F2O(2)*CLCO(2).

Note that the learning correction term CL C is obtained by sampling the feedback control term CF8 using the following equation.

CLCj+t=CLcj+ (Σ(CF B M AX 0 CF 8 M I N)/
2) /4X+61 Here, CFBMAX is the maximum value of CF8, CF8MIN
is the minimum value of CFB.

Then, the value of the driving state determination flag I is stored as 0 in step S+o), the subroutine program shown in FIG. 3 is executed in step S++), and the feedback control term cFB and learning correction term CL in the current state are stored.
are respectively stored as C1Bo, r, rCLCO<r) (step 512), the feedback determination flag i is set to 1 (step 513), and the process returns to step S2.

- On the other hand, if i = O in the judgment/determination in step S8, it is determined whether the operating state determination flag ■ is ro, that is, the operating state S is the same as the previous time (same operating cylinders) (step 5I4). , 1 If the operating state is the same as the previous time, read the output value of the 02 sensor 11 (step S+
s), it is determined whether the air-fuel ratio is rich or low (step S's), and if it is rich, the feedback control term CFII is set to CF B - ΔC and step S
L? ), in the case of lean, the feedback control term CF B
fg Cy e+ΔC and moves to step 5ta), step SIO.

As shown in FIG. 3, the subroutine program calculates the basic injection amount τE2 using the following formula (step 521).

τE2 = / (N-U'') N is the engine speed, U is the intake air amount, and K takes different values depending on whether the engine is operating with all cylinders or with reduced cylinders.

Then, the fuel injection amount TP is calculated using the following equation (step 522).

Tp=f E2 (1+CF e+cLc)-+-r
a A TτB^↑ is the battery voltage corrected injection amount.

In the above embodiment, the feedback system flJ term CF 13
and the learning correction term CLC are stored together,
In addition, it is also possible to permanently store values determined experimentally in advance for the differences between all-cylinder operation and reduced-cylinder operation, and to use these values depending on all-cylinder operation and reduced-cylinder operation. good.

(Effects of the Invention) As described above, the present invention sets the control characteristics of the air-fuel ratio control means to different values during reduced-cylinder operation and during full-cylinder operation. Accurate control is possible during cylinder operation, improving air-fuel ratio control characteristics.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is an overall configuration diagram of an air-fuel ratio control device for an engine with cylinder number control, FIGS. 2 and 3 are flowcharts showing the flow of processing of the engine control unit, and FIG. is an explanatory diagram of the F/B region, FIG. 5 is an explanatory diagram of the all-cylinder operation region and reduced-cylinder operation region, and FIG. 6 is a diagram showing the relationship among the cylinder number control signal, shutter valve operation signal, and fuel injection signal. be. 1... Cylinder number control engine, 2... Intake passage, 3... Exhaust passage, 4... Air flow meter, 9... Shutter valve, 10
...Opening/closing means, 11...02 sensor,
14... Injector, 15... Engine control unit, 101... Cylinder reduction means, 10
2... Air-fuel ratio control means, 103... Correction means.

Claims (1)

[Claims] (1) An operating state detection means for detecting the operating state of the engine, a cylinder reduction means for suspending operation of some cylinders when the engine is under light load based on the output of the operating state detection means, and a cylinder reduction means for suspending operation of some cylinders when the engine is under light load. an air-fuel ratio detection means for detecting an air-fuel ratio;
The air-fuel ratio control means receives the output of the air-fuel ratio detection means and feedback-controls the air-fuel ratio of the air-fuel mixture to a preset air-fuel ratio. An air-fuel ratio control device for an engine with a controlled number of cylinders, comprising a correction means for setting control characteristics of the air-fuel ratio control means to different values during operation.