JPS58575B2 - Fuel supply cylinder number control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel supply cylinder number control device that accurately sets an air-fuel ratio when switching the cylinder number in a device that changes the fuel supply cylinder number according to engine load. .

In general, when an engine is operated under a high load condition, fuel efficiency tends to be better.For this reason, when a multi-cylinder engine is operated under a low engine load condition, fuel supply to some groups of cylinders is stopped. An engine with cylinder number control was devised in which operation is stopped by doing so, and the load per unit of the remaining operating cylinder group is increased by that amount, thereby improving overall fuel efficiency.

On the other hand, as a measure against engine exhaust, a three-way catalyst is installed in the exhaust system, and the oxygen concentration in the exhaust gas is detected and the air-fuel ratio is feedback-controlled to a nearly rational air-fuel ratio. A system is known that efficiently oxidizes NOx and reduces NOx at the same time, but when this system is applied to the above-mentioned engine with controlled number of cylinders,
During partial cylinder operation when some cylinder groups are inactive, the oxygen concentration in the exhaust gas differs from the gas composition of the actual combustion cylinder and becomes extremely rich, so feedback control of the air-fuel ratio is not performed properly. A situation may arise.

In order to avoid such inconveniences, 1. For example, an oxygen sensor and a three-way catalyst may be installed in the exhaust passages divided into groups corresponding to each group of active cylinders and inactive cylinders to control the air-fuel ratio. Oxygen sensors and three-way catalysts are installed in the combined exhaust passage of the cylinder group and in the exhaust passage of only the operating cylinders upstream thereof, and the same control is performed while switching the sensor output taken as control input depending on the operating state. Systems such as the following were considered.

Incidentally, when the number of cylinders to which fuel is supplied changes, the engine torque may fluctuate, which may cause a reduction in driving feeling, especially during slow acceleration or slow deceleration.

Conventionally, in order to reduce engine torque fluctuations as much as possible, the air-fuel ratio is temporarily varied at the moment the number of operating cylinders changes to reduce torque fluctuations.

In other words, in a 6-cylinder engine, when switching from 3-cylinder to 6-cylinder operation, the air-fuel ratio is temporarily leaner, and conversely, when switching from 6-cylinder to 3-cylinder operation, the air-fuel ratio is enriched to prevent a decrease in output torque. By suppressing this, torque fluctuations were prevented.

However, for example, when switching from 3-cylinder operation to 6-cylinder operation while accelerating by rapidly pressing the accelerator, or when switching from 6-cylinder operation to 3-cylinder operation while suddenly decelerating the engine by fully closing the accelerator. when.

Even if you try to reduce fluctuations in engine torque by changing the air-fuel ratio, there are cases where the change in torque due to a large change in the accelerator pedal is greater.

In such a case, although the desired effect of preventing torque fluctuations cannot be achieved, the effect of functional deterioration on the three-way catalyst increases.

The present invention has been made in view of the above, and relates to an engine in which a predetermined air-fuel ratio is set when changing the number of cylinders.

In order to ensure proper exhaust purification, there is provided a fuel supply cylinder number control device that does not change the air-fuel ratio as described above even if the number of operating cylinders changes during sudden acceleration or sudden deceleration. .

Hereinafter, embodiments will be described based on the drawings.

Figure 1 shows an overall block diagram. 1 in Figure 1 is a fuel supply cylinder number control circuit (hereinafter referred to as the C8 circuit), which controls the number of fuel supply cylinders based on the engine load signal (using a fuel injection pulse signal, which will be described later). Let me give you an example.

For example, an operating cylinder number signal is output so that six cylinder operation is performed in a medium-high load range and three cylinder operation is performed in a low load range.

2 is a fuel injection control circuit (hereinafter referred to as EGI circuit), which basically sends a fuel injection pulse signal based on an engine intake air amount signal and a rotational speed signal to fuel injection valve #1.
．． #2. #3. The fuel is supplied to #4, #5, and #6, but since correction is performed based on the feedback signal from the air-fuel ratio control circuit 3, the amount of fuel to be injected is determined so that it almost reaches the stoichiometric air-fuel ratio. .

Note that this air-fuel ratio control circuit 3 performs feedback control of the air-fuel ratio based on the output of an oxygen sensor 4 installed in the engine exhaust system, and as will be described later, it controls the air-fuel ratio when the number of operating cylinders changes. The switching signal is the air-fuel ratio changing circuit 5
When inputting from .

Feedback control is stopped during that period, and switching of the air-fuel ratio from the stoichiometric air-fuel ratio to the rich side or lean side, which is normal feedback control, is not prevented.

The air-fuel ratio changing circuit 5 detects the signals from the VC8 circuit 1, that is, the signals of bi-level "1" instructing 6-cylinder operation and low-level "0" instructing 3-cylinder operation.
When switching from "1" to "0", a signal is output that enriches the air-fuel ratio for a certain period of time, and conversely, when switching from "0" to "1", a signal that also makes the air-fuel ratio lean is output. output, and in principle suppresses engine torque fluctuations that occur when changing the number of cylinders.

The fuel injection signal from the EGI circuit 2 is supplied to the fuel injection valves #1 to #3 via a gate circuit (AND circuit) 7 that opens and closes depending on the signal from the VC8 circuit 1. Since the fuel is directly supplied to the fuel injection valves 4 to #6, #4 to #6 become a cylinder group that is always in operation, and the other cylinder group #1 to #3 have ■C808 circuit output power of "1".
Fuel injection is performed only when

Next, an air-fuel ratio change stop circuit 9 is provided so as to cancel the air-fuel ratio change command from the air-fuel ratio change circuit 5 when there is a significant change in engine load even when the number of cylinders changes.

The air-fuel ratio change/stop circuit 9 determines whether the engine load is very high or low based on, for example, the pulse width of the fuel injection signal.

In such a case, even if the number of cylinders is switched (changed), the air-fuel ratio is not temporarily changed to prevent deterioration in exhaust performance.

FIG. 2 shows a specific example of this air-fuel ratio change/stop circuit 9.

Mono-multi M1 and M2 each use the fuel injection pulse signal Pw as a trigger pulse, and set the standard pulse width P on the high load side.
It outputs WH and a reference pulse PWL on the low load side.

■1. ■2. ■3 is a sign inverter and a flip-flop F
The J terminal of F1 is input with the output of the monomulti M1, and the output of the sign inverter 1 is input into the output terminal of the monomulti M1, and the output of the monomulti M2 and the sign inverter are input into the J terminal of the flip-flop FF2, respectively. Input from device ■3 is input.

The fuel injection pulse signal pw is input to the C terminals of flip-flops FF1 and FF2 via a sign inverter 2,
Therefore, as shown in the time chart of FIG. 3, the Q output of the flip-flop FF1 outputs a bilevel "1" when the pulse width of Pw is smaller than the output pulse PWH of the monomulti M1, and The Q output of FF2 is the output pulse PW of the mode multi M2.
When the pulse width of Pw is smaller than that of L, bilevel ゛°
Outputs 1”.

These flip-flops FF1. The Q output and Q output of FF2 are output to the air-fuel ratio changing circuit 5 through the OR circuit OR, and are used as bi-level signals when the load is large and when the load is small.
1'' stops changing the air-fuel ratio.

With the above configuration, a fuel injection signal having a pulse width set in the EGI circuit 2 is sent to the fuel injection valves +1 to ≠3 and 41-4 to ≠6 provided at each intake port of the engine. is supplied after being corrected by the air-fuel ratio control circuit 3, and thereby fuel is injected and supplied so that the air-fuel ratio becomes approximately the stoichiometric air-fuel ratio.

Therefore, in principle, combustion of the air-fuel mixture at the stoichiometric air-fuel ratio is performed, and the three-way catalyst device (not shown) reacts appropriately in this state to efficiently purify CO, HC, and NOx.

On the other hand, ■When the C8 circuit 1 determines that the engine load state is light, a low level "0" signal, which is a 3-cylinder signal, is input to the AND circuit 7, so that ≠1.
The gate is closed to the fuel injection valves with values of ~≠3, and no injection signal is supplied to them.

As a result, the operation is switched to the remaining 3-cylinder operation with +4 to ≠6.

Note that the C8 circuit 1 outputs a bi-level signal "1" which is the 6 cylinder signal in the middle and high load range, so at this time the AND circuit 7 opens and can supply fuel injection signals to +1 to 43. Cylinder operation is performed.

By the way, when the number of cylinders is changed like this, the VC
8 The output of the circuit 1 is detected, and the air-fuel ratio changing circuit 5 commands the EGI circuit 2 to change the air-fuel ratio for a certain short period of time from the time of this change, and changes the engine torque when changing the number of cylinders. Suppress as much as possible.

This command is output via the air-fuel ratio control circuit 3, and the feedback control during this period is stopped, and the corrected air-fuel ratio signal is
The fuel is sent directly from the I circuit 2 to the fuel injection valve.

However, this air-fuel ratio changing circuit 5 operates only.

When there is no release signal from the air-fuel ratio change stop circuit 9.

In other words, when changing the number of cylinders, excluding cases where there is a large change in engine load due to other factors such as a large change in the amount of depression of the accelerator pedal, and if there is a large change in load before or after that, the empty Based on the output from the fuel ratio change stop circuit 9, the air-fuel ratio is no longer temporarily changed.

In other words, when you press the accelerator pedal hard and accelerate suddenly from 3-cylinder operation, the switch is immediately made to 6-cylinder operation, but in such cases, the engine load increases significantly, so it is difficult to change the number of cylinders. Not only does the accompanying torque fluctuation (increase) cause no problem at all in terms of driving feeling, but rather the torque increase is necessary, so temporarily reducing the air-fuel ratio would go against the requirements.

Similarly, when decelerating by suddenly releasing the accelerator pedal during 6-cylinder operation, a command is issued to stop changing the air-fuel ratio.
To prevent the air-fuel ratio from becoming richer when switching to 3 cylinders.

This is because if the air-fuel ratio is increased at the time of switching even though it is necessary to assist the deceleration operation with an engine brake or the like, the torque will increase and characteristics different from the required characteristics will be obtained.

In this way, according to the present invention, when switching the number of fuel supply cylinders, the air-fuel ratio is temporarily changed to compensate for output fluctuations, except during slow acceleration or slow deceleration, which tend to deteriorate the driving feeling. This has the excellent effect of preventing deterioration of exhaust performance and loss of fuel efficiency due to this air-fuel ratio change at the time of switching, and improving driving performance during sudden acceleration and deceleration.

[Brief explanation of drawings]

The figures show an embodiment of the present invention, in which Fig. 1 is an overall block diagram, Fig. 2 is a block diagram of an air-fuel ratio change/stop circuit,
Figure 3 is the time chart. 1...Fuel supply cylinder number control circuit, 2...
・Fuel injection control circuit, 3...Air-fuel ratio control circuit,
5...Air-fuel ratio change circuit, 9...Air-fuel ratio change stop circuit.

Claims (1)

[Claims] 1. A fuel supply device that controls a fuel supply amount, a cylinder number control circuit that performs partial cylinder operation by cutting off a fuel supply signal from the fuel supply device to a predetermined group of cylinders depending on the engine load, and a fuel supply cylinder. In a multi-cylinder engine equipped with an air-fuel ratio changing circuit that changes the air-fuel ratio to a different air-fuel ratio from the air-fuel ratio controlled during normal air-fuel ratio control, when the engine load is higher than a predetermined high load or a predetermined low load, An engine load determination circuit that determines whether the fuel supply signal is below the load based on the fuel supply signal described above, and an air-fuel ratio change stop circuit that suspends changing the air-fuel ratio of the air-fuel ratio change circuit in accordance with the determination by the engine load determination circuit. A fuel supply cylinder number control device characterized by the following.