JPH0370099B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a split operation controlled internal combustion engine.

In an internal combustion engine in which the engine load is controlled by a throttle valve, the fuel consumption rate worsens as the throttle valve opening becomes smaller. Therefore, in order to improve the fuel consumption rate, a split-operation control type internal combustion engine, in which some cylinders are deactivated during low-load engine operation and the remaining cylinders are operated at high load, is proposed, for example, in Japanese Patent Laid-Open No. 1983-1999. This method is known as described in Japanese Patent No. 69736. In this known internal combustion engine, the cylinders are divided into a first cylinder group A and a second cylinder group B, as shown in FIG. The second intake manifold 2 is connected, the first intake manifold 1 and the second intake manifold 2 are communicated with the atmosphere through a common throttle valve 3, and an intake cutoff valve 4 is connected to the intake air inlet of the first intake manifold 1. In addition, an exhaust recirculation valve 7 is provided in the exhaust recirculation passage 6 that connects the exhaust manifold 5 and the first intake manifold 1, and when the engine is operated at low load, fuel injection from the fuel injection valve 8 is stopped and the intake cutoff valve 4 is closed. The valves are closed and the exhaust recirculation valve 7 is opened to allow the second cylinder group B to operate under high load.On the other hand, during high load operation of the engine, fuel is injected from all fuel injection valves 8 and 9 and the intake cutoff valve 4 is opened. In addition, all cylinders A and B are closed by closing the exhaust recirculation valve 7.
It is designed to cause the engine to ignite. In this internal combustion engine, as mentioned above, when the engine is operated at low load, the intake cutoff valve 4 is closed and the exhaust recirculation valve 7 is opened, so that exhaust gas is circulated to the first cylinder group A via the exhaust recirculation passage 6. Therefore, pumping loss can be eliminated, and since the second cylinder group B is operated under high load at this time, the fuel consumption rate can be improved.

In such a split-operation controlled internal combustion engine, a three-way catalytic converter and an oxygen concentration detector are installed in the engine exhaust system, and the air-fuel ratio of the mixture supplied to the engine cylinders is theoretically determined based on the output signal of the oxygen concentration detector. In order to match the air-fuel ratio, it is necessary to accurately measure the amount of intake air.
As shown in the figure, an air flow meter K is installed upstream of the throttle valve 3 to measure the total amount of intake air. However, when the air flow meter K is installed upstream of the throttle valve 3 in this way, if the intake cutoff valve 4 is fully open and the same amount of intake air is being supplied to all cylinders, or if the intake cutoff valve 4 is fully closed. and second
The amount of intake air supplied to each cylinder can only be accurately measured when intake air is supplied only to cylinder group B. In other words, when the intake cutoff valve 4 is in a half-open state, the amount of intake air supplied to each cylinder can be accurately measured. Since it is not known in what proportion the intake air will be distributed to cylinder group A and second cylinder group B,
The amount of air supplied to each cylinder of cylinder group B cannot be determined accurately. In this way, the intake cutoff valve 4 becomes partially open when the intake cutoff valve 4 changes from fully closed to fully open, or from fully open to fully closed. Since the amount of intake air supplied to each cylinder cannot be determined accurately, the mixture supplied to each cylinder becomes either too rich or too lean, resulting in a problem of deterioration of exhaust emissions. In particular, the opening operation of the intake cutoff valve 4 is performed in order to prevent a sudden increase or decrease in the engine output.
Alternatively, if the valve closing operation is made slow, the exhaust emissions will become worse.

The present invention is capable of accurately measuring the amount of intake air supplied to each cylinder even when the intake cutoff valve is opening or closing, and predetermining the air-fuel ratio of the mixture supplied to each cylinder. It is an object of the present invention to provide an internal combustion engine that maintains an air-fuel ratio at a constant air-fuel ratio, thereby ensuring good exhaust emissions even when the number of operating cylinders is changed.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 2, 10 is the engine body, 11 is the first intake manifold, 12 is the second intake manifold,
13 is a surge tank, 14 is a first exhaust manifold, 15 is a second exhaust manifold, 16a, 16
b, 16c, 16d, 16e, and 16f indicate the first cylinder, the second cylinder, the third cylinder, the fourth cylinder, the fifth cylinder, and the sixth cylinder, respectively. Note that each of these cylinders is divided into a first cylinder group A consisting of cylinders 16a, 16b, and 16c, and a second cylinder group B consisting of cylinders 16d, 16e, and 16f. As can be seen from FIG. 2, the first intake manifold 11 and the first exhaust manifold 14 are connected to the first cylinder group A, and the second intake manifold 12 and the second exhaust manifold 15 are connected to the second cylinder group B. As shown in FIG. 2, each manifold branch pipe of the first intake manifold 11 and the second intake manifold 12 is connected to a fuel injection valve 17.
a, 17b are attached, and the solenoid of each of these fuel injection valves 17a, 17b is connected to an electronic control unit 18. On the other hand, the first exhaust manifold 1
4 and the second exhaust manifold 15 are partitioned by a common partition wall 19 at their outlet portions, and both the exhaust manifolds 14, 15 are separated within this partition wall 19.
An oxygen concentration detector 20 exposed within 15 is disposed. This oxygen concentration detector 20 is connected to the electronic control unit 18. Although not shown in the figure, the first
Exhaust manifold 14 and second exhaust manifold 1
A three-way catalytic converter is installed in the exhaust pipe connected to the outlet of the engine. First intake manifold 1
1 is an intake air inlet part 21, and each cylinder 16a, 16b, 16c branches from this intake air inlet part 21.
It has three manifold branch pipes each connected to the
The intake air inlet section 21 is connected to the surge tank 13. Similarly, the second intake manifold 12 has an intake air inlet section 22 and three manifold branch pipes branched from the intake air inlet section 22 and connected to the respective cylinders 16d, 16e, and 16f. Air inlet section 22 is connected to surge tank 13 .
An intake duct 2 is located approximately in the center of the surge tank 13.
3 is attached, and a throttle valve 24 is disposed within this intake duct 23. This throttle valve 2
4 is connected via a wire to an accelerator pedal provided in the driver's cabin of the vehicle. Furthermore, as shown in FIG. 2, an air flow meter 25 is installed in the intake duct 23.
is attached, and this air flow meter 25 is connected to the electronic control unit 18 via a lead wire (not shown).

The first intake manifold 1 as shown in FIG.
An intake cutoff valve 26 is disposed within the intake air inlet portion 21 of the intake air intake valve 1, and an arm 28 connected to a negative pressure diaphragm device 30 and a first changeover switch 29 are attached to a valve shaft 27 of the intake cutoff valve 26. As shown in FIG. 2, the negative pressure diaphragm device 30 has a pair of diaphragms 31 and 32 spaced apart from each other, and the inside of the negative pressure diaphragm device 30 is divided into a first Negative pressure chamber 33,
It is divided into three parts: a second negative pressure chamber 34 and an atmospheric pressure chamber 35. A compression spring 36 for pressing the diaphragm is inserted into the first negative pressure chamber 33, and a stopper 37 that is arranged to engage with the diaphragm 31 and can adjust the amount of displacement of the diaphragm 31 is provided in the housing of the negative pressure diaphragm device 30. be screwed on. Further, an engagement member 39 having an opening 38 is fixed on the surface of the diaphragm 31 exposed in the second negative pressure chamber 34.
A play coupling rod 40 having an enlarged head having a larger diameter than the aperture 38 and movable within the engagement member 39 is secured to the diaphragm 32. Additionally, a compression spring 41 is provided between the diaphragms 31 and 32.
is inserted and the diaphragm 32 is connected to the control rod 42.
It is connected to the tip of the arm 28 via. 1st
The negative pressure chamber 33 has a first electromagnetic switching valve 4 that can communicate with the atmosphere.
3. The second negative pressure chamber 34 is connected to the inside of the surge tank 13 via a throttle 46 and a negative pressure conduit 44, and the second negative pressure chamber 34 is connected to the inside of the surge tank 13 through a second electromagnetic switching valve 45 that can communicate with the atmosphere and a negative pressure conduit 47. connected to.
Note that, as shown in FIG. 2, a first one-way valve _F1 that allows flow only from the first electromagnetic switching valve 43 into the surge tank 13 is inserted into the negative pressure conduit 44, and the negative pressure conduit A second one-way valve F ₂ that allows flow only from the second electromagnetic switching valve 45 into the surge tank 13 is inserted into the surge tank 47 . On the other hand, the first changeover switch 29 has a movable contact 49 that rotates together with the valve shaft 27 of the throttle valve 26, and three fixed contacts 50, 51, and 52 that can make contact with the movable contact 49. , 51, 52 are connected to the electronic control unit 18. The movable contact 49 is connected to the fixed contact 50 when the throttle valve 26 is fully open.
When the throttle valve 26 is half open, it is connected to a fixed contact 51, and when the throttle valve 26 is fully closed, it is connected to a fixed contact 52.

On the other hand, the first exhaust manifold 14 upstream of the oxygen concentration detector 20 and the first intake manifold 11 downstream of the intake cutoff valve 26 are connected to each other by an exhaust gas recirculation passage 53. A type exhaust recirculation valve 54 is inserted. The exhaust gas recirculation valve 54 includes a negative pressure chamber 56 and an atmospheric pressure chamber 57 separated by a diaphragm 55.
A compression spring 58 for pressing the diaphragm is inserted inside. This negative pressure chamber 56 is connected to the inside of the surge tank 13 via a third electromagnetic switching valve 59 that can communicate with the atmosphere and a negative pressure conduit 60. A third one-way valve F ₃ is inserted which allows flow only inward. The solenoid of the third electromagnetic switching valve 59 and the solenoids of the first and second electromagnetic switching valves 43 and 45 are connected to the electronic control unit 18. A valve body 61 for controlling opening and closing of the exhaust gas recirculation passage 53 is disposed within the exhaust gas recirculation passage 53, and this valve body 61 is connected to the diaphragm 55 via a valve rod 62.
Further, the exhaust gas recirculation valve 54 includes a second changeover switch 63. The second changeover switch 63 includes a movable contact 64 connected to the diaphragm 55 and activated by movement of the diaphragm 55, and a pair of fixed contacts 65, 6 that can make contact with the movable contact 64.
6, and these fixed contacts 65, 66 are connected to the electronic control unit 18. The movable contact 64 is connected to the fixed contact 65 when the valve body 61 is closed, and is connected to the fixed contact 66 when the valve body 61 is opened. As shown in FIG. 2, a negative pressure sensor 67 is attached to the surge tank 13 in order to detect the engine load, and this negative pressure sensor 67 is connected to the electronic control unit 18. Although not shown in FIG. 2, a rotation speed sensor 72 (FIG. 3) is attached to the engine body 10.

FIG. 3 shows a circuit diagram of the electronic control unit 18. Referring to FIG. 3, the electronic control unit 18
consists of a digital computer, including a microprocessor (MPU) 80 that performs various arithmetic operations;
A random access memory (RAM) 81, a read-on memory (ROM) 82 in which control programs, calculation constants, etc. are stored in advance, an input port 83, and an output port 84 are interconnected via a bidirectional bus 85. Furthermore, the electronic control unit 18
A clock generator 86 is provided therein for generating various clock signals. As shown in FIG. 3, the rotation speed sensor 72, the first changeover switch 29, the second
The changeover switch 63 is connected to the input port 83 via corresponding buffer amplifiers 87, 88, and 89, respectively. In addition, the air flow meter 25 and the negative pressure sensor 67 are connected to the corresponding buffer amplifiers 90 and 91.
It is also connected to input port 83 via AD converters 92 and 93, and oxygen concentration detector 20 is connected to input port 83 via buffer 94 and comparator 95.

The air flow meter 25 outputs an output voltage proportional to the amount of intake air, and this output voltage is sent to the AD converter 9.
2, the data is converted into a corresponding binary number and then read into the MPU 80 via the input port 83 and bus 85. The rotation speed sensor 72 outputs continuous pulses with a period proportional to the engine rotation speed, and these continuous pulses are transmitted via the input port 83 and the bus 85.
Loaded into MPU80. Oxygen concentration detector 20
generates an output voltage of about 0.1 volt when the exhaust gas is in an oxidizing atmosphere, and when the exhaust gas is in a reducing atmosphere.
Generates an output voltage of about 0.9 volts. The output voltage of this oxygen concentration detector 20 is compared with a reference value of, for example, about 0.5 volts in a comparator 95,
For example, when the exhaust gas is in an oxidizing atmosphere, an output signal is generated at one output terminal of the comparator 95, and when the exhaust gas is in a reducing atmosphere, an output signal is generated at the other output terminal of the comparator 95. The output signal of comparator 95 is connected to input port 83 and bus 8.
5 to the MPU 80. The negative pressure sensor 67 outputs an output voltage proportional to the negative pressure inside the surge tank 13, and this output voltage is sent to the AD converter 93.
After being converted into a corresponding binary number at , it is read into the MPU 80 via the input port 83 and bus 85. The contact switching signals of the first changeover switch 29 and the second changeover switch 63 are read into the MPU 80 via the input port 83 and the bus 85.

The output port 84 is provided to operate the fuel injection valves 17a, 17b and the electromagnetic switching valves 43, 45, 59, and binary data is written to the output port 84 from the MPU 80 via the bus 85. The output terminals of output port 84 are connected to corresponding input terminals of down counters 96, 97 and latch 98. Each down counter 9
6 and 97 are provided to convert the binary data written from the MPU 80 into the corresponding time length, and these down counters 9
6 and 97 start counting down the data sent from the output port 84 in response to the clock signal from the clock generator 86, and when the count value reaches 0, the count is completed and a count completion signal is generated at the output terminal. Each S-R flip-flop 99,
Reset input terminals R of 100 are connected to the output terminals of down counters 96 and 97, respectively, and set input terminals S of S-R flip-flops 99 and 100 are connected to clock generator 86. These S-
The R flip-flops 99 and 100 are set by the clock signal of the clock generator 86 at the same time as the down count starts, and are reset by the counter completion signal of the corresponding down counters 96 and 97 when the down count is completed. Therefore, the output terminals Q of the S-R flip-flops 99, 100 are at a high level while the corresponding down counters 96, 97 are counting down. The output terminals Q of the S-R flip-flops 99 and 100 are connected to the fuel injection valves 17a of the first cylinder group A and the fuel injection valves 17b of the second cylinder group B via power amplification circuits 101 and 102, respectively. Therefore, while the down counters 96 and 97 are counting down, fuel is injected from the fuel injection valves 17a and 17b, respectively.
On the other hand, the data for controlling the electromagnetic switching valve written in the output port 84 is held by a latch 98, and the data held in the latch 98 causes the electromagnetic control valve 4 to
3, 45, and 59 are activated.

FIG. 4 and FIG. 5 show time charts for explaining the divided operation control method according to the present invention.
In FIGS. 4 and 5, each diagram from a to h indicates the following.

a: Output voltage of negative pressure sensor 67.

b: Control voltage applied to the solenoid of the first electromagnetic switching valve 43.

c: Control voltage applied to the solenoid of the second electromagnetic switching valve 45.

d: Control voltage applied to the solenoid of the third electromagnetic switching valve 59.

e: Control pulse applied to the fuel injection valve 17b of the second cylinder group B.

f: Control pulse applied to the fuel injection valve 17a of the first cylinder group A.

g: Opening degree of the intake cutoff valve 26.

h: Opening degree of the valve body 61 of the exhaust gas recirculation valve 54.

Note that FIG. 4 shows the transition from high load operation to low load operation, and FIG. 5 shows the transition from low load operation to high load operation.

Time T ₁ in FIG. 4 indicates a high load operation when the output voltage of the negative pressure sensor 67 is low. At this time, the fourth
As shown in FIG. b, the solenoid of the first electromagnetic switching valve 43 is deenergized, and therefore the first negative pressure chamber 33
communicates with the atmosphere via the first electromagnetic switching valve 43. At this time, as shown in FIG. 4c, the solenoid of the second electromagnetic switching valve 45 is also deenergized, and therefore the second negative pressure chamber 34 also
It communicates with the atmosphere through. As a result, both diaphragms 31 and 32 have moved furthest toward the atmospheric pressure chamber 35, and thus the intake cutoff valve 26 is fully open as shown in FIG. 4g. Furthermore, the time shown in Figure 4
At _T1 , the solenoid of the third electromagnetic switching valve 59 is deenergized, as shown in FIG. 4d, and therefore the negative pressure chamber 56 of the exhaust recirculation valve 54 is
9 to the atmosphere. In this way, the diaphragm 55 has moved furthest toward the atmospheric pressure chamber 57, and as a result, the valve body 61 completely closes the exhaust gas recirculation passage 53, as shown in FIG. 4h.

On the other hand, at this time, the MPU 80 shown in FIG. 2 calculates the engine rotation speed from the output pulse of the rotation speed sensor 72, and further calculates the basic fuel injection amount from this engine rotation speed and the output signal of the air flow meter 25. Furthermore, when a three-way catalyst is used, the purification efficiency is highest when the air-fuel ratio of the air-fuel mixture supplied into the engine cylinder reaches the stoichiometric air-fuel ratio; The fuel injection amount is calculated by correcting the basic fuel injection amount based on the output signal of the oxygen concentration detector 20 so that the fuel ratio approaches the stoichiometric air-fuel ratio. Data representing this fuel injection amount is written to the output port 84, and based on this data, pulses as shown in FIGS. 4e and 4f are sent to the fuel injection valves 17a of the first cylinder group A and the second cylinder It is applied to the group B fuel injection valves 17b. Therefore, during high-load engine operation, all fuel injection valves 17a,
Fuel is injected from 17b.

Next, if the high load operation is switched to the low load operation at time Ta in FIG. 4, the output voltage of the negative pressure sensor 67 will rise rapidly as shown in FIG. 4a. The MPU 80 determines that low load operation is occurring when the output voltage of the negative pressure sensor 67 becomes larger than the reference value Vr (Fig. 4 a), and as a result, the fourth
As shown in FIG. b, data to energize the solenoid of the first electromagnetic switching valve 43 is written to the output port 84. When the solenoid of the first electromagnetic switching valve 43 is energized in this way, the first negative pressure chamber 33 is
It is connected to the inside of the surge tank 13 via the first electromagnetic switching valve 43 and the one-way valve _F1 . At this time, since the one-way valve _F1 opens, the negative pressure in the surge tank 13 is introduced into the first negative pressure chamber 33 through the throttle 46, and as a result, the negative pressure in the first negative pressure chamber 33 increases. The diaphragm 31 is compressed by the compression spring 3 in order to gradually increase in size.
6 and moves toward the first negative pressure chamber 33 side. At this time, the engagement member 39 lifts the control rod 42 to engage the loose connection rod 40, thus causing the fourth
As shown in Figure g, the intake cutoff valve 26 gradually closes. On the other hand, when the negative pressure sensor 67 detects that the operation has changed from high load operation to low load operation, the feedback control of the air-fuel ratio by the oxygen concentration detector 20 is stopped, and at the same time, the air flow meter 25 and the negative pressure sensor 67 are activated. The fuel injection valve 1 is configured so that the air-fuel ratio of the air-fuel mixture supplied to the first cylinder group A and the second cylinder group B respectively becomes the stoichiometric air-fuel ratio based on the detection signal.
7a and the amount of fuel injected from the fuel injection valve 17b is controlled. That is, as the intake cutoff valve 26 gradually closes, the negative pressure in the surge tank 13 decreases, and if the engine speed is constant, the opening degree of the intake cutoff valve 26 and the negative pressure in the surge tank 13 decrease. There is a one-to-one relationship between them. Furthermore, if the engine speed is constant, the opening degree of the intake cutoff valve 26 has a one-to-one relationship with the allocation ratio of the intake air supplied to the first cylinder group A and the second cylinder group B, and therefore, the engine speed increases. If constant, there is a one-to-one relationship between the negative pressure in the surge tank 13 and the amount of intake air supplied to the second cylinder group B. Thus, if the relationship between the negative pressure in the surge tank 13 and the amount of intake air supplied to the second cylinder group B is known for each engine speed, it can be calculated from the engine speed and the negative pressure in the surge tank 13. Second
The amount of intake air supplied to cylinder group B can be determined. In the present invention, the relationship between the engine speed N, the negative pressure P in the surge tank 13, and the amount of intake air supplied to the second cylinder group B is determined in advance through experiments, and the relationship between the engine speed N, the negative pressure P in the surge tank The relationship with the amount of intake air supplied to the second cylinder group B is stored in the ROM 82 in advance. Therefore, the engine rotation speed N is calculated in the MPU 80 from the output signal of the rotation speed sensor 72, and the above-mentioned information stored in the ROM 82 is calculated based on the engine rotation speed N thus calculated and the output signal of the negative pressure sensor 67. The amount of intake air supplied to the second cylinder group B is calculated from the relationship. Furthermore, in the MPU 80, the amount of intake air supplied to the second cylinder group B is subtracted from the total amount of intake air determined from the output signal of the air flow meter 25, thereby reducing the amount of intake air supplied to the first cylinder group A. The amount is calculated. Next, in the MPU 80, the amount of intake air supplied to the first cylinder group A and the amount of intake air supplied to the second cylinder group B are used to calculate the air-fuel ratio necessary for the air-fuel ratio of the mixture supplied to each cylinder to reach the stoichiometric air-fuel ratio. The fuel injection amount is calculated,
Based on this calculation result, the fuel injection valves 17a and 17b are
Fuel is injected from. Such open-loop air-fuel ratio control is performed from time Ta to time in Figure 4.
It is carried out between Tb. During this time, intake cutoff valve 2
As can be seen from Figure 4g, valve 6 gradually closes, so the amount of intake air supplied to the first cylinder group A gradually decreases, and the amount of intake air supplied to the second cylinder group B gradually increases. do. Therefore, from time Ta to time Tb
During this period, the amount of fuel injected into the first cylinder group A gradually decreases as shown in FIG. 4f, and the amount of fuel injected into the second cylinder group B gradually decreases as shown in FIG. 4e. increases to

Next, when time Tb is reached in FIG. 4, the diaphragm 31 comes into contact with the stopper 37 and stops moving, and the intake cutoff valve 26 is maintained in a half-open state. In this way, the diaphragm 31 is connected to the stopper 37.
At the same time, the movable contact 49 of the first changeover switch 29 connects to the fixed contact 51, and the connection signal of the fixed contact 51 is read into the MPU 80.
As soon as this connection signal is issued, the MPU 80 writes data to stop the fuel injection of the first cylinder group A and data to energize the solenoid of the third electromagnetic switching valve 59 to the output port 86. 2nd at the same time
Air-fuel ratio feedback control for cylinder group B is started, and data indicating the fuel injection amount based on the output signal of oxygen concentration detector 20 is written to output port 84. As a result, when time Tb is reached, the fourth
As shown in Figure e, the amount of fuel injected from the fuel injection valve 17b of the second cylinder group B is increased, and the
As shown in FIG. f, fuel injection from the fuel injection valve 17a of the first cylinder group A is stopped. Further, since the solenoid of the third electromagnetic switching valve 59 is energized, the negative pressure chamber 56 of the exhaust recirculation valve 54 is connected to the inside of the surge tank 13 via the third electromagnetic switching valve 59 and the one-way valve _F3 . At this time, the one-way valve _F3 opens and negative pressure is applied to the negative pressure chamber 56, so the diaphragm 55 moves toward the negative pressure chamber 56 against the compression spring 58, and the valve body 61 Exhaust recirculation passage 53
Open the door. As a result, the exhaust gas in the first exhaust manifold 14 is recirculated into the first intake manifold 11 via the exhaust gas recirculation passage 53. Exhaust recirculation valve 54
When the valve body 61 fully opens the exhaust gas recirculation passage 53, the second valve body 61 fully opens the exhaust recirculation passage 53.
The movable contact 64 of the changeover switch 63 is the fixed contact 66
The connection signal of this fixed contact 66 is connected to the MPU
80. This time is indicated by time Tc in FIG. As soon as the connection signal of the fixed contact 66 is issued, the MPU 80 writes data to the output port 84 to energize the solenoid of the second electromagnetic switching valve 45. When the solenoid of the second electromagnetic switching valve 45 is energized in this manner, the second negative pressure chamber 34 is connected to the inside of the surge tank 13 via the negative pressure conduit 47 and the one-way valve _F2 . At this time, the one-way valve _F2 opens and the negative pressure inside the surge tank 13 is applied to the second negative pressure chamber 34, so that the diaphragm 3
2 moves toward the first negative pressure chamber 33 against the compression spring 41, and the control rod 42 is lifted, so that the intake cutoff valve 26 is moved as shown in FIG. 4g.
is fully closed.

As shown in FIGS. 4e to 4h, when the engine shifts from high-load operation to low-load operation, first the intake cutoff valve 26 is gradually closed to the half-open position, and during this time, the air is supplied to each cylinder. Since the air-fuel ratio of the air-fuel mixture is controlled to be the stoichiometric air-fuel ratio, the output torque of the first cylinder group A gradually decreases, and the output torque of the second cylinder group B gradually increases. As a result, the output torque can smoothly transition from high-load operation to low-load operation without abruptly decreasing. Furthermore, since the intake cutoff valve 26 is maintained in a half-open state until the exhaust gas recirculation action is started, pumping loss during transition from high-load operation to low-load operation can be eliminated.

On the other hand, in FIG. 5, time T ₂ indicates the time of low load operation, and time Ta indicates the time of transition from low load operation to high load operation. When low load operation is being performed, as indicated by time _T2 in _FIG . The second negative pressure chamber 34 of the negative pressure diaphragm device 30 is connected to the surge tank 13 via the one-way valve _F2 , and the negative pressure chamber 56 of the exhaust recirculation valve 54 is connected to the inside of the surge tank 13 via the one-way valve _F3 . It is connected inside the surge tank 13. Therefore, these first negative pressure chamber 33, second negative pressure chamber 34, and negative pressure chamber 5
The negative pressure in the surge tank 6 is maintained at the peak negative pressure generated in the surge tank 13 unless the electromagnetic switching valves 43, 45, and 59 are switched. Then the time
If the low load operation is switched to the high load operation at Ta, the output voltage of the negative pressure sensor 67 drops rapidly as shown in FIG. 5a. The MPU 80 determines that high load operation is occurring when the output voltage of the negative pressure sensor 67 becomes smaller than the reference value V _p . At this time, first, as shown in FIG. 5c, the solenoid of the second electromagnetic switching valve 45 is deenergized,
As a result, the second negative pressure chamber 34 is communicated with the atmosphere via the second electromagnetic switching valve 45, so the diaphragm 32 moves toward the atmospheric pressure chamber 35, and thus the fifth
As shown in Figure g, the intake cutoff valve 26 is opened to the half-open position. When the intake cutoff valve 26 is opened to the half-open position, the intake cutoff valve 26 is temporarily held in the half-open state. On the other hand, intake cutoff valve 2
6 is opened to the half-open position, the movable contact 49 of the first changeover switch 29 connects to the fixed contact 51, and this connection signal turns off the third solenoid changeover valve 59 as shown in FIG. 5d. Forced. As a result, the negative pressure chamber 56 of the exhaust recirculation valve 54 is communicated with the atmosphere via the third electromagnetic switching valve 59, so the diaphragm 55 moves toward the atmospheric pressure chamber 57, and the fifth
As shown in Figure h, the valve body 61
Close 3. When the valve body 61 is fully closed, the movable contact 64 of the second changeover switch 63 is connected to the fixed contact 65, and the connection signal from the fixed contact 65 causes the fifth
As shown in FIG. 5B, the first electromagnetic switching valve 43 is deenergized, and as shown in FIG. 5F, the fuel injection operation from the fuel injection valve 17a of the first cylinder group A is started. Furthermore, at this time, the feedback control by the oxygen concentration detector 20 is stopped, and the air flow meter 2 is adjusted so that the air-fuel ratio of the mixture supplied to the first cylinder group A and the second cylinder group B becomes the stoichiometric air-fuel ratio.
5 and the output signals of the negative pressure sensor 67, the amount of fuel injected from the fuel injection valves 17a and 17b is controlled.

Further, when the first electromagnetic switching valve 43 is deenergized, the first electromagnetic switching valve 43
Since the negative pressure chamber 33 is communicated with the atmosphere through the throttle 46, the diaphragm 31 is connected to the second negative pressure chamber 34.
5g, the intake cutoff valve 26 is gradually opened and fully opened, as shown in FIG. 5g.

In this way, when the engine shifts from low-load operation to high-load operation, the intake cutoff valve 26 is first half-opened, and then the valve body 61 of the exhaust recirculation valve 54 closes the exhaust recirculation passage 53, thereby eliminating pumping loss. Then, the intake cutoff valve 26 is gradually opened to the fully open position, and the output torque of the first cylinder group A is gradually increased, thereby making it possible to prevent the engine output from increasing rapidly.

FIG. 8 shows the relationship between the engine operating state and the negative pressure in the surge tank 13 in the embodiment shown in FIG. In FIG. 8, the chain line L indicates the case of partial cylinder operation, the chain line M indicates the case of full cylinder operation, and the horizontal axis P indicates the negative pressure (-mmHg) in the surge tank 13.
As shown in FIG. 8, when the partial cylinder operation L is performed, when the negative pressure in the surge tank 13 becomes smaller than _P1 , the operation shifts to the full cylinder operation,
At this time, the negative pressure inside the surge tank 13 becomes _P2 .
On the other hand, when the full cylinder operation M is performed, when the negative pressure in the surge tank 13 becomes greater than _P3 , the full cylinder operation shifts to partial cylinder operation, and at this time the negative pressure in the surge tank 13 becomes P3. It becomes ₄ .
If the negative pressure limit P ₁ at which partial cylinder operation is performed in FIG. 8 can be further reduced, partial cylinder operation can be performed until the engine load becomes higher, and the fuel consumption rate can thus be improved. . As described above, according to the present invention, the negative pressure in the first negative pressure chamber 33, the second negative pressure chamber 34, and the negative pressure chamber 56 can be maintained at the peak negative pressure generated in the surge tank 13 during partial cylinder operation. The negative pressures in the first negative pressure chamber 33, second negative pressure chamber 34, and negative pressure chamber 56 are maintained as they are unless the electromagnetic cutoff valves 43, 45, and 59 are operated. Therefore, the opening/closing control of the intake cutoff valve 26 and the exhaust recirculation valve 54 depends only on the operation of the electromagnetic cutoff valves 43, 45, and 59, and therefore the engine load is reduced when transitioning from partial cylinder operation to full cylinder operation. It can be made arbitrarily high.

Another embodiment is shown in FIG. In this embodiment, the first negative pressure chamber 33, the second negative pressure chamber 34, and the negative pressure chamber 56
are connected to a common negative pressure distribution pipe 110 via corresponding electromagnetic switching valves 43, 45, and 59, respectively, and negative pressure distribution pipe 110 is connected to a negative pressure control valve 111. As shown in FIG. 7, this negative pressure control valve 111 includes a first negative pressure chamber 113 and a second negative pressure chamber 114 separated by a diaphragm 112.
Negative pressure chamber 113 is connected to negative pressure distribution pipe 110 via negative pressure conduit 115 . A hollow pipe 116 protrudes into the first negative pressure chamber 113 , and this hollow pipe 116 is connected to the surge tank 13 via a negative pressure conduit 117 . This hollow tube 116 is controlled to open and close by a movable valve seat 118 supported by a diaphragm 112. Furthermore, an adjustment screw 1 is provided in the second negative pressure chamber 114.
A spring retainer 120 whose position is adjustable by 19 is provided, and a compression spring 121 is inserted between the valve seat 118 and the spring retainer 120.
In this embodiment, the pressure inside the first negative pressure chamber 113 is
When the pressure in the negative pressure chamber 114 becomes higher than the sum of the spring force of the compression spring 121, the diaphragm 112
The valve seat 118 opens the hollow tube 116. Therefore, in this embodiment as well, the first negative pressure chamber 3 is
3. The negative pressure in the second negative pressure chamber 34 and the negative pressure chamber 56 is maintained at a negative pressure greater than the peak negative pressure generated in the surge tank 13 by the spring force of the compression spring 121. Therefore, in this embodiment, the first negative pressure chamber 3
3. There is an advantage that the negative pressure in the negative pressure chamber 56 as well as the second negative pressure chamber 34 can be adjusted by the adjusting screw 119.

As described above, according to the present invention, the opening/closing operation of the intake cutoff valve cannot accurately determine the amount of intake air supplied to the first cylinder group and the second cylinder group only by the intake air amount detection device. Sometimes, the air-fuel ratio can be controlled to a predetermined air-fuel ratio by open-loop control of the air-fuel ratio based on the output signals of the intake air amount detection device, the negative pressure sensor, and the rotational speed sensor.

[Brief explanation of drawings]

FIG. 1 is a plan view schematically showing a conventional internal combustion engine, FIG. 2 is a plan view schematically showing an internal combustion engine according to the present invention, FIG. 3 is a circuit diagram of the electronic control unit shown in FIG. 5 is a diagram for explaining the divided operation control method according to the present invention, FIG. 6 is a diagram for explaining the divided operation control method according to the present invention, FIG. 6 is a plan view of another embodiment, and FIG. The figure is an enlarged plan sectional view of a part of FIG. 6, and FIG. 8 is a diagram showing the relationship between the engine operating state and the negative pressure in the surge tank. 11...First intake manifold, 12...Second intake manifold, 13...Surge tank, 14...
First exhaust manifold, 15... Second exhaust manifold, 17a, 17b... Fuel injection valve, 18... Electronic control unit, 24... Throttle valve, 26...
...Intake cutoff valve, 29...First selector switch, 30
...Negative pressure diaphragm device, 43...First electromagnetic switching valve, 45...Second electromagnetic switching valve, 53...Exhaust recirculation passage, 54...Exhaust recirculation valve, 59...Third electromagnetic switching valve, 63... ...Second changeover switch, F ₁ , F ₂ ,
_F3 ...One-way valve, 111...Negative pressure control valve.

Claims (1)

[Claims] 1 dividing the cylinders into a first cylinder group and a second cylinder group, connecting the first cylinder group and the second cylinder group to a common surge tank via a first intake passage and a second intake passage, respectively; An intake cutoff valve is provided in the first intake passage, the intake cutoff valve is closed during low engine load operation, and is opened during high engine load operation, and the first intake passage downstream of the intake cutoff valve and the engine exhaust passage An exhaust gas recirculation valve is provided in the exhaust gas recirculation passage connecting the engine, and the exhaust gas recirculation valve is opened when the engine is operating at a low load and closed when the engine is at a high load. In an internal combustion engine equipped with a fuel supply device that stops the supply of fuel and controls the supply of fuel to the second cylinder group and controls the supply of fuel to the first cylinder group and the second cylinder group during engine high load operation. , a switch capable of detecting the opening/closing operation of the intake cutoff valve, an intake air amount detection device capable of detecting the amount of intake air supplied to the surge tank, and a negative pressure capable of detecting the negative pressure inside the surge tank. a sensor, a rotational speed sensor capable of detecting engine rotational speed, and an oxygen concentration detector disposed in an engine exhaust passage, and detects the oxygen concentration when the intake cutoff valve is held in a closed state. The air-fuel ratio of the air-fuel mixture supplied to the second cylinder group is feedback-controlled to a predetermined air-fuel ratio based on the output signal of the device, and the oxygen concentration is detected when the intake cutoff valve is kept open. The air-fuel ratio of the air-fuel mixture supplied to the first cylinder group and the second cylinder group is feedback-controlled to a predetermined air-fuel ratio based on the output signal of the cylinder, and when the intake cutoff valve is opening/closing, Based on the intake air amount previously stored for one cylinder group as a function of the negative pressure in the surge tank and the engine speed, the output signal of the intake air amount detection device, the negative pressure sensor, and the rotation speed sensor is determined. The amount of intake air distributed and supplied to the first cylinder group and the second cylinder group is determined, and the air-fuel ratio of the mixture supplied to the first cylinder group and the second cylinder group is determined from the intake air amount to a predetermined air-fuel ratio. A split-operation controlled internal combustion engine with open-loop control.