JPS63129146A - Air-fuel ratio control device for engine - Google Patents

Abstract

PURPOSE:To continually improve control accuracy of air-fuel ratio, by equipping a control device with a heater ability detecting means, which detects heater ability of an exhaust sensor with heater, and a correcting means which receives an output from the heater ability detecting means correcting a feedback control signal in a control means. CONSTITUTION:If ability of a heater decreases due to its break or the like, the output characteristic of an exhaust sensor 18 changes in accordance with an exhaust temperature, but a feedback control signal of a control means 25 is corrected by a correcting means 26 so that the change of said output characteristic is compensated. Consequently, air-fuel ratio of a mixture is controlled in good accuracy to the target air-fuel ratio in accordance with an operative condition even when the heater causes its break or the like.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to the air-fuel ratio control system of an engine, and uses an exhaust sensor with a heater to directly feedback the air-fuel ratio of the air-fuel mixture to a predetermined value. Concerning improvements made to the above.

(Conventional technology) Conventionally, this type of air-fuel ratio control! As an II\r device, for example, as disclosed in Japanese Patent Application Laid-Open No. 60-79133, an exhaust sensor with a heater is placed in the exhaust passage of the engine to detect the air-fuel ratio of the air-fuel mixture based on the oxygen concentration component in the exhaust gas. Based on the output of this exhaust sensor, the injector is feedback-controlled so that the air-fuel ratio of the mixture reaches the target value, and the heater is used to control the exhaust so that the output characteristics of the exhaust sensor remain constant regardless of the exhaust gas temperature. Sensors that heat the sensor are known.

By the way, in an air-fuel ratio control device that uses an exhaust sensor with a heater as described above, if the heater is disconnected and the exhaust gas level is low, the reversal of the exhaust sensor output from the rich side to the lean side will be delayed. First, since the air-fuel ratio is detected to have a rich tendency, the air-fuel ratio of the air-fuel mixture deviates from the target air-fuel ratio to a lean tendency.

Therefore, in order to solve this problem, in the above cited example, when the heater is disconnected, the exhaust sensor output level at that time is memorized, and from then on, the air-fuel ratio of the mixture is feedback-controlled based on this output value, and the exhaust sensor This is intended to reduce the reduction in control efficiency due to fluctuations in output characteristics.

(Problem to be solved by the invention) However, in the above-mentioned conventional device, after the heater is disconnected, the feedback control ull signal remains constant ((fixed to the mouth, so the feedback control The air-fuel ratio cannot be controlled in response to changes in conditions.

The present invention has been made in view of this point, and its purpose is to reduce the heater's ability to cut off. ! The purpose is to improve the control accuracy of the air-fuel ratio by appropriately setting the feedback control signal while making use of the output of the exhaust sensor even when the air-fuel ratio decreases due to i1 or the like.

(Means for solving the problem) In order to achieve the above object, the present invention sets feedback control No. 13 based on the output of the exhaust sensor and corrects this feedback control signal according to the heater capacity. be.

Specifically, the solution taken by the present invention, as shown in FIG. , a heater-equipped exhaust sensor 18 for detecting the air-fuel ratio of the air-fuel mixture supplied to the engine; and receiving the output of the heater-equipped exhaust sensor 18, the air-fuel ratio adjusting means 8 is adjusted so that the air-fuel ratio of the engine is at the target level. The provision of 1-control means 25 for feedback control is referred to as 1rl. and a heater capacity detection means 20 for detecting the heater capacity of the heater-equipped exhaust sensor 18, and a correction means for receiving the output of the heater capacity detection means 20 and correcting the feedback ii control signal to the control means 25 J3. 26 etc.

(Function) Due to the above combination, in the present invention, the ability of the heater 21 is
1vi line etc., the output characteristics of the exhaust sensor 18 fluctuate depending on the exhaust humidity.
Since the feedback control signal No. 5 is corrected, the air-fuel ratio of the air-fuel mixture is accurately controlled to the target air-fuel ratio in accordance with the operating state even when the heater is disconnected.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 2 shows an engine equipped with an air-fuel ratio control device according to the present invention, in which 1 is an engine, 2 is a combustion chamber whose volume is variable by a piston 4 inserted into a cylinder 3 of the engine 1 so as to be movable; 5 is an intake passage with one end communicating with the combustion chamber 2 and the other end opening into the combustion chamber 2 for supplying intake air to the engine 1; 6 with one end opening into the combustion chamber 2; If! ! It is an exhaust passage whose end is open to the atmosphere to discharge exhaust gas, and in the middle of the intake passage 5 there is a throttle valve 7 that controls the amount of intake air, and a throttle valve 7 that controls the amount of intake air, and on the downstream side of the throttle valve 7 that supplies fuel to the engine 1. A fuel injection valve 8 is provided as an air-fuel ratio adjusting means for injecting and supplying fuel, and an intake valve 9 is provided at the frontage of the intake passage 5 to the combustion chamber 2, and an intake valve 9 is provided at the frontage of the intake passage 5 to the combustion chamber 2. Exhaust valves 10 are disposed at the frontage to the combustion chamber 2, respectively. Furthermore, an ignition plug 11 is disposed at the top of the combustion chamber 2 to ignite the air-fuel mixture within the combustion chamber 2.

Further, 15 is an air 70-sensor that detects the amount of intake air on the upstream side of the throttle valve T7 of the intake passage 5, 16 is an air gap sensor that detects the opening degree of the throttle valve 7, and 17 is an air sensor that detects the amount of intake air on the upstream side of the throttle valve T7 of the intake passage 5. An engine hybrid sensor that detects a greenhouse; 18 is an exhaust sensor with a heater that is installed in the exhaust passage 7 and detects the air-fuel ratio of the air-fuel mixture based on the oxygen component in the exhaust gas; 19 is a rotational speed sensor that detects the engine rotational speed; It is a built-in distributor, and the above air 7
The operating state of the engine 1 is detected by the 0-sensor 15 and the distributor 19. As shown in FIG. 3, the heater-equipped exhaust sensor 18 has a heater that is energized when the exhaust gas leakage is low, heats the sensor element, and compensates its output characteristics at a constant level regardless of the exhaust gas length of 1 m. 21 is built-in. The heater 21 is connected to a battery 23 via a heater sensor 20 and a relay 22, which serve as heater capability detection means for detecting voltage applied to the heater. And the above-mentioned sensors 15 to 20
Each detection signal is input to a controller 24, and the controller 24 controls the fuel injection valve 8, spark plug 11, and relay 22, respectively.

Next, the operation of the controller 24 will be explained based on the flowchart of FIG. 4. First, after initialization is performed in step S1, signals from various sensors 15 to 20 are inputted in step S3, and in step S3, signals from various sensors 15 to 20 are inputted. A basic fuel injection pulse width Tp corresponding to the operating state of the engine 1 is calculated, and step S
In step 4, it is determined whether the air-fuel ratio is in a zone where feedback control is required. If the answer is No, which is not in the feedback zone, then in step $5, the fuel injection pulse width T is calculated by T-Tp x Ck using the forest fuel injection pulse width Tp and a constant correction coefficient Ck'.

On the other hand, when YES is in the feedback zone,
In step 36, as shown in FIG.
is in the heater control zone where the exhaust gas temperature is low, and if NO is not in the heater control zone, in step S7, the proportional it, +11 & 0 constant in the feedback control is set to C, and the integral control constant is set to C', In step SI2, it is determined whether or not the output of the exhaust sensor 18 is larger than a set value corresponding to the target air-fuel ratio, and when the rich judgment is larger than the set value, the above-described process is performed in step S13 in order to shift the air-fuel ratio to lean. Ratio VA control constant C and integral control constant C' in step S7
When the exhaust sensor 18 output is smaller than the above-mentioned setting value and is determined to be lean, the proportional control constant of the above-mentioned step SA is calculated in step Sj4 in order to shift the air-fuel ratio to rich. The feedback correction coefficient a C'F B is calculated based on C and the integral control constant C', and in step S If YES, it is determined in step s8 whether or not the voltage applied to the heater is O in order to determine whether or not the heater 21 is disconnected. When the voltage applied to the heater is O (YES), it is determined that the heater 21 is disconnected, and in step S9, as shown in FIG.
The proportional control constant and the integral control constant in the case of 1 are set to A and A', respectively, which are larger than the above C1C'. Then, in accordance with the output of the exhaust sensor 18 in step S12, when a rich judgment is made, a feedback correction coefficient CFe4rv4 is calculated based on the proportional control constant C and the integral control window ac' in step S13, while a rich judgment is made. In this case, in step S14, the feedback correction coefficient C is calculated based on A and A' which are larger than the above c and c'.
Determine FB and set fuel injection pulse width T in step S+s.
Calculate. In other words, the output characteristic of the exhaust sensor 18 fluctuates due to the inoperation of the heater 21, and feedback control is performed in a state where the air-fuel ratio is detected as having a rich tendency, so that the second fuel ratio tends to become lean. Since the proportional ili control constant and the slope of the integral 1111IOII constant are increased when performing feedback control t211 to make the air-fuel ratio rich, the air-fuel ratio of the air-fuel mixture is controlled to the target air-fuel ratio v1 more effectively.

Also, in step Ss above, the voltage applied to the heater is not O.
When o, it is determined that the wire 21 is not disconnected, and the process proceeds to step S I++. At this step S IQ, in order to determine a change in heater capacity, it is determined whether or not the heater application 'R' is lower than the set value. judge. When the heater applied voltage is NO higher than the set value, it is determined that the heater capacity has not changed, and the process proceeds to step 87, where the same control as when the engine 1 is not in the heater control zone is performed, while the heater applied voltage is 8Q. ``b lower than 7k la YES
In this case, it is determined that the heater capacity has decreased due to a decrease in battery voltage, etc., and in step S11, as shown in FIG. 7, the proportional control constant and The integral control constants are set to B and B', which are smaller than A and A' and larger than c and c', respectively, according to the heater applied voltage, and the feedback correction coefficient CF is set in step S14.
l11 is +*U, and the fuel injection pulse width T is determined in step S+s. In other words, the output characteristics of the exhaust sensor 18 fluctuate due to a decrease in the performance of the heater 21, and feedback control is performed in a state where the air-fuel ratio is detected to have a rich tendency, so the air-fuel ratio tends to increase. Since the slopes of the proportional control constant 1j133 and the integral control constant when performing feedback control to bring the air-fuel ratio to a ridge are appropriately increased, the air-fuel ratio of the air-fuel mixture is precisely controlled to the target air-fuel ratio.

In the above flow, step S7. S13゜SL4
and S+s, 1III control means receives the output of the heater-equipped exhaust sensor 18 and controls the fuel injection valve 8 (air-fuel ratio adjustment means) with feedback so that the air-fuel ratio of the engine 1 becomes 1Keyum α. 25, and the heater sensor 2 is configured in steps S3 and S o.
The correction means 26 receives the output of the heater capacity detection means 0 and corrects the feedback control signal in the control means 25.

In the above example of authority, the control is applied in response to fluctuations in the output characteristics of the exhaust sensor 18 caused by disconnection of the heater 21 or reduction in performance.
The slice level of the exhaust sensor 18, that is, the exhaust sensor 18, is corrected as shown in FIG. 8 when the heater 21 is disconnected, and as shown in FIG. 9 when its performance is reduced. The setting 11n that separates the rich side and the lean side of the air-fuel ratio depending on the output of the engine may be set to a large value.

In addition, the heater 21 (Fig. 10 at the time of 17i,
When the performance of J5 decreases, as shown in Fig. 11, the delay time, that is, the time provided from when the output of the IJI sensor 18 is reversed from the ridge side to the lean side until the feedback correction coefficient is reversed, is increased. You can also do this.

(Effects of the Invention!!) As explained above, according to the engine air-fuel ratio control device of the present invention, one finger force of the heater that heats the exhaust sensor (responsively, the feedback ff+'l ln II ( Since No. i is made to be heavy-duty, the air-fuel ratio of the air-fuel mixture can be accurately controlled to the target air-fuel ratio without being affected by the heater capacity.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of the present invention. Figures 2 to 11
The figures show an actual MA example of the present invention, Fig. 2 is an overall strategic configuration diagram, Fig. 3 is a diagram showing the 1st air sensor and heater, Fig. 4 is a sized flowchart showing the operation of the control unit, and Fig. 5 is a diagram showing the operation of the control unit. Figure 6 is an explanatory diagram showing the heater control zone, Figure 6 is an explanatory diagram showing the control constant when the heater is disconnected, Figure 7 is an explanatory diagram showing the control constant when the heater capacity is reduced, and Figures 8 and 9 are FIGS. 10 and 11 are explanatory diagrams showing the slice level characteristics when the heater is disconnected and when the heater capacity is decreased, respectively. FIGS. 10 and 11 are explanatory diagrams showing the dilator time characteristics when the heater is disconnected and the heater capacity is decreased, respectively. DESCRIPTION OF SYMBOLS 1... Engine, 8... Fuel injection valve, 18... Exhaust sensor with heater, 20... Heater sensor, 21...
- Heater, 24... Controller, 25... Control means, 26... Correction means. Patent applicant Mazda Motor Corporation 2-i-'j-
”-゛ Representative Patent Attorney 1)
Hiro C' - - - Fig. 3 Fig. 1 Fig. 7 Fig. 6 Heater 6p applied voltage Fig. 9 Fig. 8 Fig. 11 Fig. 10 Fig. 1 Fig. 7 Fig. 6

Claims (1)

[Claims] (1) An air-fuel ratio adjusting means for adjusting the air-fuel ratio of the air-fuel mixture supplied to the engine; an exhaust sensor with a heater that is disposed in the exhaust passage of the engine and detects the air-fuel ratio of the air-fuel mixture supplied to the engine; a control means that receives an output of the exhaust sensor with a heater and performs feedback control on the air-fuel ratio adjusting means so that the air-fuel ratio of the engine reaches a target value; and a heater capacity detection means that detects the heating capacity of the exhaust sensor with a heater; An air-fuel ratio control device for an engine, comprising: correction means for receiving the output of the heater capacity detection means and correcting a feedback control signal in the control means.