JPS59101561A - Air-fuel ratio controller of engine - Google Patents

Abstract

PURPOSE:To ensure the prompt and accurate action of an exhaust sensor so as to smoothly perform closed loop control and consequently accurately perform open loop control, by heating the exhaust sensor before the closed loop control using the exhaust sensor is started to be performed. CONSTITUTION:A heating controller 25 for actuating a heating device 24 of an exhaust sensor 17 comprises a pulse generator circuit 27, which receives a trigger signal (a) at each time when the running time from a timer 26 reaches a prescribed value and generates a pulse-state heating instruction signal (b), heating circuit 28 which operates receiving the heating instruction signal (b) and generates a heating signal (c), and a power supply 29. The heating instruction signal (b) is input to also a timing circuit 22, which outputs a timing signal (d) after delay of a prescribed time, and a fuel control circuit 19 is switched from the open loop control condition to the closed loop control condition, further reset to the open loop control condition after continuing the closed loop control by the prescribed period set in the fuel control circuit 19 itself.

Description

DETAILED DESCRIPTION OF THE INVENTION The invention relates to an electronic air-fuel ratio control device that controls the air-fuel ratio of an engine to a state leaner than the stoichiometric air-fuel ratio.

Conventionally, an exhaust sensor is installed in the exhaust passage to detect the oxygen concentration in the exhaust gas, and based on the detection signal, the fuel supply amount is controlled in a closed loop so that the air-fuel ratio is close to the stoichiometric air-fuel ratio (14,7). , oxidation of HC and CO and NO by Wang Yuan
A system that smoothly performs the reduction of x is widely known.

On the other hand, there is a demand for setting the air-fuel ratio to a leaner state than the stoichiometric air-fuel ratio for the purpose of improving fuel efficiency and the like. However, when operating in lean conditions, the exhaust temperature decreases,
The minimum operating temperature of the exhaust sensor also decreases, making it difficult for the exhaust sensor to operate smoothly. Therefore, in this lean control, the above-mentioned closed pg control cannot be used as is.

Therefore, for a short predetermined period at predetermined intervals, closed-loop control is performed using an exhaust sensor to maintain the stoichiometric air-fuel ratio, and the correction value for correcting the fuel supply source ° in the lean direction at that time is memorized. A system is known in which, during periods other than the predetermined period, the amount of fuel supplied is open-loop controlled based on the above-mentioned corrected value so that the target air-fuel ratio is shifted toward the lean direction by a set value from the theoretical empty or internal ratio. (Refer to Japanese Unexamined Patent Publication No. 56-44434). According to this system, aging of the engine is detected through closed-loop control performed at predetermined intervals, and each time the above-mentioned correction value is replaced with a new value and recorded. Although open-loop control, that is, the advantage of accurate lean state control, is expected, in reality, when entering closed-loop control, the temperature of the exhaust gas does not rise rapidly, so the exhaust sensor is activated quickly. Since it does not operate, closed-loop control cannot be performed smoothly, and therefore, open-loop control cannot be performed accurately either.

This invention was made in order to eliminate the above-mentioned conventional drawbacks. By heating the exhaust sensor before the closed-loop control using the exhaust sensor begins, the present invention guarantees quick and accurate operation of the exhaust sensor and provides open-loop control. to be carried out smoothly,
As a result, it is an object of the present invention to provide an air-fuel ratio control device for an engine that allows accurate open-loop control.

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

In Figure 1, ■ is a 4-stroke gasoline engine,
The intake passage of this engine 11]2 has an air cleaner]3
and a fuel supply device 14 such as a fuel injection valve,
The exhaust passage 15 is provided with an exhaust sensor 17 that detects oxygen components in the exhaust gas 16. Reference numeral 19 denotes a fuel control circuit that controls the fuel supply system so that the air-fuel ratio of the intake air-fuel mixture becomes the stoichiometric air-fuel ratio (14, 7) based on the detection signal from the exhaust sensor 17 for a predetermined period at predetermined intervals. The fuel supply amount from 14 is controlled in a closed loop, and during periods other than the above-mentioned predetermined period, the target air-fuel ratio is shifted from the stoichiometric air-fuel ratio by the set value in the positive direction based on the correction value stored in the storage circuit 21. The amount of fuel supplied from the fuel supply device 14 is controlled in an open loop so that the switching between the closed loop and the open loop is performed by the timing circuit B. The closed-loop control is performed, for example, only for a few minutes each time the running time reaches a predetermined value.

Note that the meaning of "several minutes" here means that it is preferable that the correction j and E value Q(m), which will be described later, are all reinterpreted and corrected in each area (m-1 to m-9), so for this purpose, This is because it is considered that closed loop control only needs to be performed continuously for several minutes.

The storage circuit 21 stores a value obtained by correcting the fuel supply source during closed-loop control as the above-mentioned correction value in accordance with the engine operating state at the time of control. It is.

In the closed μm de control i, the fuel supply amount is controlled to achieve the stoichiometric air-fuel ratio based on the detection signal from the exhaust sensor 17. As shown in FIG. 2, the fuel supply amount is , increases and decreases in a zigzag pattern from lean to rich. ”
The peak and trough values of the bipedal fuel supply are K (],)
, K (2)..., and these K
('L) Using (Y= 1 to n), Q, + (b)
= Σ K(j,) / n x ai=1 o < a < i,.

seek. Here, α is a set value for correcting the air-fuel ratio to leaner than the stoichiometric air-fuel ratio.

The above Q, 0TI) is mapped to correspond to the engine operating state at the time of closed loop control, for example, as shown in Fig. 3, and is mapped to the engine speed and load, and then stored as a modified value. I'll keep it. These correction values Q(m) (m=1 to 9) are replaced with new values each time the above K(1) is updated through closed-loop control, so changes over time of the engine are absorbed and accurate A corrected value Q(ITI) is obtained.

During open loop control, the above correction value Q(Ill) is the first
9, the fuel supply amount from the fuel supply device 14 is controlled so as to obtain a target air-fuel ratio shifted in the lean direction by a set value from the stoichiometric air-fuel ratio.

The above configuration and operation are the same as those of the prior art, and the present invention is characterized by the provision of a heating device U for the exhaust sensor 17 and a heating control device 6 for operating the heating device U.

The heating control device δ receives a trigger signal a every time the running time reaches a predetermined value from an external timer that measures the running time, and generates a pulse-shaped heating command signal. The heating command signal 1], which is composed of a generating circuit I, a heating circuit circuit that operates upon receiving the heating command signal S and generates a heating signal C, and a power supply pair, is also input to the timing circuit η, Timing signal 1 after being delayed for a predetermined time
is output, the fuel control circuit 19 is switched from the open loop control state to the closed loop control state p1, and after continuing the closed loop control for a predetermined period set in the fuel control circuit 9 itself, the fuel control circuit 19 is switched to the open loop control state p1. Return to.

Each of the above signals 8. -d waveforms are shown in (A) to (0) in Fig. 4. ω in Fig. 4 shows the operation of the fuel control circuit 19 (Fig. 1). As is clear from FIG. 4, the timing signal 6
is delayed by a predetermined time t1 from the heating command signal d-, and in response to the timing signal d-, the fuel control circuit 19
is the predetermined period 1. As shown in FIG. 5, the fuel supply amount is increased compared to the open loop control to obtain the stoichiometric air-fuel ratio.

FIG. 4 (Heating signal C of Q is generated by activating the heating device shown in FIG. During closed-loop control, the temperature of the exhaust gas 16 reaches the minimum operating temperature, so the above-mentioned heating is not particularly necessary. Therefore, the above-mentioned heating signal C is set at a predetermined level from the start of closed-loop control. It is sufficient if there is enough time to operate the heating device U from before the start of the closed-loop control, but considering various errors, as shown in Figure 4 (Q), the time width ℃1 is changed to t+ <ts
It is preferable to set so that < t+ + tx.

As shown in FIG. 6, the heating device shown in FIG. It is energized by the heating signal C from the circuit and generates heat. The exhaust sensor 17 generates an electromotive force due to the difference in oxygen concentration between the inside of the exhaust passage [5] and the atmosphere, and outputs this as a detection signal θ. 16 Platinum thin film 31 for detecting oxygen concentration
, 32.

In the above configuration, the fuel control circuit shown in FIG. 1 normally performs the open-loop control described above, and from the stoichiometric air-fuel ratio to the target air-fuel ratio shifted by α in the lean direction. In this state, a timer measures the running time and outputs a trigger signal a every time this running time reaches a predetermined value.

In response to this trigger signal a, the heating control circuit bar/I/7
．． Generating circuit n operates and outputs a heating command signal. In response to this heating command signal), the heating circuit is activated, outputs the heating signal C, and for a predetermined period of time 1+ from the start of the closed loop control.
(See Figure 4) The separate heating devices are operated from +1iJ until immediately after the start of closed loop control, and the uh air sensor 17 in Figure 6 is activated.
The detection element/section 17a is heated.

During open loop control, the temperature of the exhaust gas 16 is below the minimum operating temperature (300'C) of the exhaust sensor 17, but the heating keeps the detection element section 17a above the minimum operating temperature. In this state, the timing circuit υ of FIG. 1 receives the heating command signal and outputs a timing signal d delayed by a predetermined time t, and switches the fuel control circuit 19 to closed loop control. The amount of fuel supplied from the fuel supply device 14 is controlled so that the stoichiometric air-fuel ratio is obtained. Therefore, when entering closed loop control, the exhaust sensor 17
Since the exhaust gas sensor 17 is already at or above the minimum operating temperature, the exhaust sensor 17 operates quickly and accurately, and close μm control is performed smoothly. Therefore, open-loop control can be performed accurately using the corrected value that corrects the fuel supply amount during closed-loop control.

As explained above, the present invention provides heating control that operates the heating device for heating the element portion 17a of the exhaust sensor 17 and the heating device for operating the heating device from a predetermined time tl before the start of the closed-loop control at least until the start of the closed-loop control. Since the exhaust sensor 17 is sufficiently heated when the closed loop control using the exhaust sensor 17 starts, the exhaust sensor I7 operates quickly and accurately, and the closed loop control is smoothly performed. As a result, open loop control can be performed accurately.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing an embodiment of the present invention, Fig. 2 is a characteristic diagram showing closed-loop control characteristics, and Fig. 3 is an explanation showing a mapping method of correction value Q(E) used in open-loop control. 4 is a signal waveform diagram showing signals of various parts, FIG. 5 is a characteristic diagram showing fuel supply amount in open loop control and closed loop control, and FIG. 6 is a longitudinal sectional view showing an exhaust sensor. 11...Engine, 14...Fuel supply device, 1G.
...Exhaust, 17...Exhaust sensor, 17a...Detection element section, 19...Fuel control circuit, 21...Memory circuit,
U...Heating device, δ...Heating control device, Q(m)・
...correction value, tl...predetermined time, t! ...predetermined period. 8 Peel ν1 2 Fig. 2 Fig. 3 Fig. 4 Fig. 5 II child 1111 t

Claims (1)

[Claims] (1) An exhaust sensor detects the components of engine exhaust gas, and the amount of fuel supplied is controlled in a closed loop so that the air-fuel ratio becomes the stoichiometric air-fuel ratio based on the detection signal from the exhaust sensor for a predetermined period every predetermined time. , during periods other than the above predetermined period, based on the correction values stored in the storage circuit,
and a fuel control circuit that controls the fuel supply amount by micrometers so that the target air-fuel ratio is shifted by a set value in the lean direction from the stoichiometric air-fuel ratio, and the memory circuit controls the fuel supply amount during the closed-loop control. An engine air-fuel ratio control device configured to store a corrected value as a corrected value corresponding to the engine operating state at the time of control includes a heating device that heats the element part of the exhaust sensor and a system for starting closed-loop control. An air-fuel ratio control device for an engine, comprising: a heating control device that operates the heating device from before a predetermined time until at least the start of closed-loop control.