JPH0229845B2 - - 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, and the fuel injection time from the fuel injection valves 8 and 9 is controlled based on the output signal of the air flow meter K. However, in this internal combustion engine, as shown in FIG. A fuel injection pressure regulating valve V responsive to negative pressure is provided to control the pressure difference between the fuel pressure in the fuel supply pipe M and the negative pressure in the intake passage downstream of the throttle valve 3 to be constant. It's summery. Therefore, in this internal combustion engine, for example, when the intake cutoff valve 4 is closed from the fully open state to the fully closed state when transitioning from high load operation to low load operation, the negative pressure generated in the first intake manifold 1 is The negative pressure in the second intake manifold 2, that is, the negative pressure in the negative pressure chamber E of the fuel injection pressure regulating valve V, becomes greater than the negative pressure in the fuel supply pipe M and the negative pressure in the first intake manifold 1. Since the pressure difference between the fuel injection pressure and the fuel injection pressure becomes larger than a constant pressure predetermined by the fuel injection pressure regulating valve V, a problem arises in that a rich mixture is supplied to the first cylinder group A.

The present invention provides a system in which the air-fuel ratio of the air-fuel mixture supplied to the first cylinder group is predetermined even while the first cylinder group is transitioning from the idle state to the idle state or from the idle state to the idle state. It is an object of the present invention to provide an internal combustion engine that maintains the air-fuel ratio at a constant air-fuel ratio, thereby ensuring good exhaust emissions even when changing the number of operating cylinders.

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 FIGS. 2 and 3, fuel injection valves 17a and 17b are attached to each manifold branch pipe of the first intake manifold 11 and the second intake manifold 12. The solenoid is connected to an electronic control unit 18. On the other hand, the first exhaust manifold 14 and the second exhaust manifold 15
are separated by a common partition wall 19 at their outlet portions, and an oxygen concentration detector 20 exposed within both exhaust honifolds 14 and 15 is disposed within this partition wall 19. This oxygen concentration detector 20 is connected to the electronic control unit 18. Although not shown in the figure, a three-way catalytic converter is installed in the exhaust pipes connected to the outlet portions of the first exhaust manifold 14 and the second exhaust manifold 15. The first intake manifold 11 has an intake air inlet part 21, and branches from this intake air inlet part 21 to each cylinder 16a,
It has three manifold branch pipes connected to ports 16b and 16c, respectively, and 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 branches from this intake air inlet section 22 to each cylinder 16d, 16.
It has three manifold branch pipes connected to e and 16f, respectively, and the intake air inlet 22 is connected to the surge tank 1.
Connected to 3. An intake duct 23 is attached to approximately the center of the surge tank 13, and a throttle valve 24 is disposed within the intake duct 23. This throttle valve 24 is connected to an accelerator pedal provided in the vehicle cab. Furthermore, as shown in FIG. 3, an air flow meter 2 is installed in the intake duct 23.
5 is attached, and this air flow meter 25 is connected to the electronic control unit 18 via a lead wire (not shown). As can be seen from FIG. 2, the first intake manifold 11 and the second intake manifold 12 have substantially symmetrical shapes with respect to the axis of symmetry S that is perpendicular to the longitudinal direction of the engine body 10, and The duct 23 is arranged approximately on this axis of symmetry S. Further, the surge tank 13 also has a substantially symmetrical shape with respect to the axis of symmetry S.

As shown in FIGS. 2 and 3, an intake cutoff valve 26 is disposed within the intake air inlet portion 21 of the first intake manifold 11, and the valve shaft 2 of the intake cutoff valve 26
7 is attached with an arm 28 connected to the negative pressure diaphragm device 30 and a first changeover switch 29. As shown in FIG. 3, 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, second negative pressure chamber 34 and atmospheric pressure chamber 3
It is divided into 5 parts. 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 engaging member 39 having an opening 38 is fixed on the surface of the diaphragm 31 exposed in the second negative pressure chamber 34, and has a diameter larger than the opening 38 and inside the engaging member 39. A loose coupling rod 40 with a movable enlarged head is secured to the diaphragm 32. A compression spring 41 is inserted between the diaphragms 31 and 32, and the diaphragm 32 is connected to the tip of the arm 28 via a control rod 42. The first negative pressure chamber 33 includes a first electromagnetic switching valve 43, a throttle 46, and a negative pressure conduit 44 that can communicate with the atmosphere.
The second negative pressure chamber 34 is connected to the inside of the surge tank 13 via a second electromagnetic switching valve 45 that can communicate with the atmosphere.
It is also connected to the inside of the surge tank 13 via a negative pressure conduit 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, connected to the fixed contact 51 when the throttle valve 26 is half open, and connected to the fixed contact 52 when the throttle valve 26 is fully closed. Ru.

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. The solenoid of the third electromagnetic switching valve 59 and the solenoids of the first and second electromagnetic switching valves 43 and 45 are controlled by the electronic control unit 18.
connected to. A valve body 61 that controls opening and closing of the exhaust gas recirculation passage 53 is disposed within the exhaust gas recirculation passage 53.
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. This second changeover switch 63 has a movable contact 64 connected to the diaphragm 55 and actuated by movement of the diaphragm 55, and a pair of fixed contacts 65, 66 that can come into contact with the movable contact 64. Contacts 65, 66 are connected to 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. Incidentally, as shown in FIG. 3, a negative pressure sensor 67 for detecting the engine load is attached to the surge tank 13, and this negative pressure sensor 67 is connected to the electronic control unit 18. Additionally, as shown in FIG. 2, an exhaust gas recirculation device consisting of a recirculation exhaust gas flow control valve 73 and a recirculation exhaust gas conduit 69 is provided. The exhaust gas inlet 70 of the recirculating exhaust gas conduit 69 is connected to the first exhaust manifold 14 upstream of the oxygen concentration detector 20, and the exhaust gas outlet 71 of the recirculating exhaust gas conduit 69 is located approximately on the axis of symmetry S. It is connected inside the surge tank 13. Although not shown in FIGS. 2 and 3, a rotation speed sensor 72 (FIG. 4) is attached to the engine body 10 to detect the engine rotation speed.

On the other hand, as shown in FIG. 3, the fuel injection valve 17a of the first cylinder group A is connected to the fuel tank 79 via the first fuel supply pipe 80.
A first fuel injection pressure regulating valve 82 is provided. Further, the fuel injection valve 17b of the second cylinder group B is connected to the fuel tank 79 via the second fuel supply pipe 81,
A second fuel injection pressure regulating valve 8 is connected to the second fuel supply pipe 81.
3 is provided. The first fuel injection pressure regulating valve 82 and the second fuel injection pressure regulating valve 83 each have a fuel chamber b and a negative pressure chamber C separated by a diaphragm a,
A compression spring d for pressing the diaphragm is inserted into the negative pressure chamber C. The fuel chamber b has a fuel inlet port e and a fuel outlet port f, and a valve g that controls opening and closing of the fuel inlet port e is connected to the diaphragm a. On the other hand, the fuel outlet port f is connected to the fuel tank 79 via fuel return conduits 84 and 85, respectively. Further, the first fuel supply pipe 80 and the second fuel supply pipe 81 are provided with fuel supply pumps 87 and 88 driven by a drive motor 86 common to both husband and wife.

As shown in FIG. 3, the negative pressure chamber C of the first fuel injection pressure regulating valve 82 is connected to the inside of the first intake manifold 11 downstream of the intake cutoff valve 26 via a negative pressure conduit 89. When the pressure difference between the pressure in the fuel chamber b and the negative pressure in the negative pressure chamber C becomes larger than a constant pressure determined by the spring force of the compression spring d, the valve body g of the first fuel injection pressure regulating valve 82 opens the fuel inlet. The port e is opened, and when it becomes small, the fuel inlet port e is opened. Therefore, the pressure difference between the pressure of the fuel supplied to the fuel injection valve 17a and the negative pressure in the intake manifold 11 is maintained constant regardless of the opening degree of the intake cutoff valve 26, and thus the fuel is injected from the fuel injection valve 17a. The amount of fuel injected will be proportional to the fuel injection time. On the other hand, the negative pressure chamber C of the second fuel injection pressure regulating valve 83 is connected to the inside of the surge tank 13 via a negative pressure conduit 90, and is similarly supplied to the fuel injection valve 17b by the second fuel injection pressure regulating valve 83. The pressure difference between the fuel pressure and the negative pressure in the intake manifold 12 is held constant. Therefore, the amount of fuel injected from the fuel injection valve 17b is proportional to the fuel injection time.

FIG. 4 shows a circuit diagram of the electronic control unit 18. Referring to FIG. 4, the electronic control unit 18
consists of a digital computer with a microprocessor (MPU) 20 that performs various arithmetic operations.
0, random access memory (RAM) 201,
A read-only memory (ROM) 202 in which control programs, calculation constants, etc. are stored in advance, an input port 203, and an output port 204 are connected to each other via a bidirectional path 205. Furthermore,
A clock generator 206 is provided within the electronic control unit 18 for generating various clock signals.
As shown in FIG.
Buffer amplifiers 207, 208, 209 to which the changeover switch 29 and the second changeover switch 63 correspond, respectively.
is connected to input port 203 via. Also,
The air flow meter 25 and negative pressure sensor 67 are connected to the corresponding buffer amplifiers 210, 211 and AD.
Input port 203 via converters 212, 213
The oxygen concentration detector 20 is connected to the input port 203 via a buffer amplifier 214 and a comparator 215.

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 2.
After being converted into a corresponding binary number at 12, it is sent to the MPU 2 via an input port 203 and a bus 205.
00. The rotational speed sensor 72 generates an output pulse representing the engine rotational speed, and this output pulse is transmitted via the input port 203 and the bus 205.
Loaded into MPU200. Oxygen concentration detector 2
0 generates an output voltage of about 0.1 volt when the exhaust gas is in an oxidizing atmosphere, and generates an output voltage of about 0.9 volt when the exhaust gas is in a reducing atmosphere. The output voltage of this oxygen concentration detector 20 is determined by a comparator 21.
5, an output signal is generated at one output terminal of the comparator 215 when the exhaust gas is in an oxidizing atmosphere, and an output signal is generated at one output terminal of the comparator 215 when the exhaust gas is in a reducing atmosphere.
An output signal is generated at the other output terminal of 15. The output signal of comparator 215 is input to input port 203.
It is also read into the MPU 200 via the bus 205. The negative pressure sensor 67 outputs an output voltage proportional to the negative pressure inside the surge tank 13, and this output voltage is converted into a corresponding binary number by the AD converter 213 and then sent to the MPU 200 via the input port 203 and bus 205. Loaded. The contact switching signals of the first changeover switch 29 and the second changeover switch 63 are read into the MPU 200 via the input port 203 and the bus 205.

Output port 204 is fuel injection valve 17a, 17b
It is also provided to operate the electromagnetic switching valves 43, 45, and 59, and binary data is written to this output port 204 from the MPU 200 via the bus 205. The output terminals of output port 204 are connected to the corresponding input terminals of down counters 216, 217 and latch 218. Each down counter 216, 217 is provided to convert the binary data written from the MPU 200 into the corresponding time length, and these down counters 216, 217 convert the data sent from the output port 204. A down count is started by a clock signal from the clock generator 206, and when the count value reaches 0, the count is completed and a count completion signal is generated at the output terminal. The reset input terminal R of each S-R flip-flop 219, 220 is connected to a down counter 216, 21, respectively.
The set input terminals S of the S-R flip-flops 219 and 220 are connected to the clock generator 206. These S-R flip-flops 219 and 220 are connected to the clock generator 2.
It is set by the clock signal 06 at the same time as the start of down counting, and is reset by the counter completion signal of the corresponding down counters 216 and 217 when the down counting is completed. Therefore, the output terminals Q of the S-R flip-flops 219 and 220 are at a high level while the corresponding down counters 216 and 217 are counting down. S-
Output terminal Q of R flip-flop 219, 220
are the first through power amplifying circuits 221 and 222, respectively.
Fuel injection valve 17a of cylinder group A and second cylinder group B
Therefore, while the down counters 216 and 217 are counting down, fuel is injected from the fuel injection valves 17a and 17b, respectively. On the other hand, the electromagnetic switching valve control data written to the output port 204 is held by the latch 218, and the electromagnetic control valves 43, 45, 59 are operated by the data held by the latch 218.

FIG. 5 and FIG. 6 show time charts for explaining the divided operation control method according to the present invention.
In FIGS. 5 and 6, 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. 5 shows the transition from high load operation to low load operation, and FIG. 6 shows the transition from low load operation to high load operation.

Time T ₁ in FIG. 5 indicates a high load operation when the output voltage of the negative pressure sensor 67 is low. At this time, the fifth
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. Further, at this time, as shown in FIG. 5c, the solenoid of the second solenoid 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. 5g. Furthermore, the time shown in Figure 5
At _T1 , the solenoid of the third solenoid switching valve 59 is deenergized, as shown in FIG.
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. 5h.

On the other hand, at this time, the MPU 200 shown in FIG. 4 calculates the engine rotation speed from the output pulse of the rotation speed sensor 72, and further calculates the basic fuel injection amount from the 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 204, and based on this data, pulses as shown in FIG. 5e and FIG. It is applied to the group B fuel injection valves 17b.
Therefore, during high-load engine operation, all fuel injection valves 17
Fuel is injected from a and 17b.

Next, if the high load operation is switched to the low load operation at time Ta in FIG. 5, the output voltage of the negative pressure sensor 67 will rise rapidly as shown in FIG. 5a. In the MPU 200, when the output voltage of the negative pressure sensor 67 becomes larger than the reference value Vr (Fig. 5a), it is determined that the operation is under low load, and as a result, as shown in Fig. 5b, the first electromagnetic switching valve Data to energize the solenoid 43 is written to the output port 204. When the solenoid of the first electromagnetic switching valve 43 is energized in this way, the first negative pressure chamber 33 is
6 and a first electromagnetic switching valve 43 into the surge tank 13 . As a result, the first negative pressure chamber 3
Since the negative pressure inside 3 gradually increases, the diaphragm 31 moves toward the first negative pressure chamber 33 against the compression spring 36. At this time, the engagement member 39 lifts the control rod 42 into engagement with the loose coupling rod 40, thus gradually closing the intake shutoff valve 26 as shown in FIG. 5g. On the other hand, the negative pressure sensor 67
When it is detected 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 feedback control of the air-fuel ratio by the oxygen concentration detector 20 is stopped, and at the same time, the The amount of fuel injected from the fuel injection valves 17a and 17b is controlled 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. 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 intake cutoff valve 26
The opening degree of the surge tank 13 has a one-to-one relationship with the allocation ratio of supply intake air to the first cylinder group A and the second cylinder group B. Therefore, if the engine speed is constant, the negative pressure in the surge tank 13 and the second cylinder group There is a one-to-one relationship with the amount of intake air supplied to cylinder group B. In this way, 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, the relationship between the engine speed and the surge tank 13 can be determined.
The amount of intake air supplied to the second cylinder group B can be determined from the negative pressure inside. In the present invention, the engine speed N, the negative pressure P in the surge tank 13, and the second cylinder group B
The relationship between 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, and the amount of intake air supplied to the second cylinder group B is stored in the ROM 202 in advance. ing. Therefore, the engine rotation speed N can be determined from the output signal of the rotation speed sensor 72.
The amount of intake air supplied to the second cylinder group B is calculated in the MPU 200 and based on the above-mentioned relationship stored in the ROM 202 based on the calculated engine speed N and the output signal of the negative pressure sensor 67. Calculated. Furthermore, in the MPU 200, 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. Therefore, the rotation speed sensor 7
2. Negative pressure sensor 67 and air flow meter 25
constitutes a detection device that detects 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. Next, in the MPU 200, 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 time is calculated, and fuel is injected from the fuel injection valves 17a and 17b based on the calculation result. Such open-loop air-fuel ratio control is performed between time Ta and time Tb in FIG. During this time, the intake cutoff valve 26 gradually closes as shown in FIG.
The amount of intake air supplied to cylinder group B gradually increases. Therefore, between time Ta and time Tb, the amount of fuel injected into the first cylinder group A gradually decreases as shown in FIG. 5f, and the amount of fuel injected into the second cylinder group A gradually decreases as shown in FIG.
The amount of fuel injected into the cylinder group gradually increases. At this time, as described above, each fuel injection valve 17a, 17
Since the amount of fuel injected from b is exactly proportional to the fuel injection time, the air-fuel ratio of the air-fuel mixture supplied to the first cylinder group A and the second cylinder group B can be maintained at the stoichiometric air-fuel ratio.

Next, when time Tb is reached in FIG. 5, 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 200.
As soon as this connection signal is issued, the MPU 200 writes data to stop fuel injection in the first cylinder group A and data to energize the solenoid of the third electromagnetic switching valve 59 to the output port 204. At the same time, air-fuel ratio feedback control for the second cylinder group B is started, and therefore data indicating the fuel injection amount based on the output signal of the oxygen concentration detector 20 is transmitted to the output port 204.
will be written to. As a result, when time Tb is reached, the amount of fuel injected from the fuel injection valve 17b of the second cylinder group B is increased, as shown in FIG. 5e.
As shown in FIG. 5f, 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 gas recirculation valve 54 is connected to the inside of the surge tank 13 via the third electromagnetic switching valve 59 . As a result, negative pressure is applied in 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 opens the exhaust gas recirculation passage 53. 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. When the valve body 61 of the exhaust gas recirculation valve 54 fully opens the exhaust gas recirculation passage 53, the movable contact 64 of the second changeover switch 63 connects to the fixed contact 66, and a connection signal from the fixed contact 66 is read into the MPU 200. This time is indicated by time Tc in FIG. As soon as this fixed contact 66 connection signal is issued, the MPU 200
writes data to energize the solenoid of the second electromagnetic switching valve 45 to the output port 204. When the solenoid of the second electromagnetic switching valve 45 is energized in this way, the second negative pressure chamber 34 is connected to the inside of the surge tank 13 via the negative pressure conduit 47, and thus the inside of the second negative pressure chamber 34 is Negative pressure is applied to the As a result, the diaphragm 32 resists the compression spring 41 and the first negative pressure chamber 33
5g, and the control rod 42 is thus lifted so that the intake shutoff valve 26 is fully closed, as shown in FIG. 5g.

As shown in FIGS. 5e to 5h, when the engine shifts from high-load operation to low-load operation, the intake cutoff valve 26 is first 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. 6, time Ta indicates a transition from low load operation to high load operation. At this time, first, as shown in FIG. 6c, the solenoid of the second electromagnetic switching valve 45 is deenergized, and as a result, the second negative pressure chamber 34 is communicated with the atmosphere via the second electromagnetic switching valve 45. Therefore, the diaphragm 32 moves toward the atmospheric pressure chamber 35, and the intake cutoff valve 26 is opened to the half-open position as shown in FIG. 6g. 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, when the intake cutoff valve 26 is opened to the half-open position, the first changeover switch 2
The movable contact 49 of 9 connects to the fixed contact 51, and this connection signal causes the third
The electromagnetic switching valve 59 is deenergized. As a result, the negative pressure chamber 56 of the exhaust gas recirculation valve 54 is communicated with the atmosphere via the third electromagnetic switching valve 59, and the diaphragm 55 moves toward the atmospheric pressure chamber 57, as shown in FIG. 6h. Valve body 61 closes exhaust gas recirculation passage 53. When the valve body 61 is fully closed, the second changeover switch 63
A movable contact 64 is connected to a fixed contact 65, and a connection signal from the fixed contact 65 deenergizes the first electromagnetic switching valve 43 as shown in FIG. 6b and as shown in FIG. 6f. Thus, the fuel injection action 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 25 and the negative pressure are 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. Fuel injection valve 17 based on the output signal of sensor 67
The fuel injection time from a 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.
In this way, the intake cutoff valve 26 gradually opens and fully opens as shown in FIG. 6g.

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.

Another embodiment is shown in FIG. In this embodiment, a first surge tank 100 common to the first cylinder group A
and a second surge tank 1 common to the second cylinder group B.
01 is provided. The first surge tank 100 is connected to the first cylinder group A via branch pipes 102, 103, 104.
The fuel injection valves 17 are connected to the cylinders 16a, 16b, and 16c, and the fuel injection valves 17 are connected to the branch pipes 102, 103, and 104, respectively.
a is attached. On the other hand, the second surge tank 10
1 is connected to cylinders 16d, 16e, 16f of the second cylinder group B via branch pipes 105, 106, 107, and a husband and wife fuel injection valve 17b is attached to each branch pipe 105, 106, 107. A first fuel injection pressure regulating valve 82 is provided in a first fuel supply pipe 80 common to the fuel injection valves 17a, and a negative pressure chamber C of this first fuel injection pressure regulating valve 82 is connected to a first fuel injection pressure regulating valve 82 via a negative pressure conduit 108. 1 surge tank 100. On the other hand, a second fuel injection pressure regulating valve 83 is provided in a second fuel supply pipe 81 common to the fuel injection valves 17b, and a negative pressure chamber C of this second fuel injection pressure regulating valve 83 is connected to a second fuel supply pipe 81 through a negative pressure conduit 109. and is connected to the second surge tank 101. 1st
The surge tank 101 is connected to a first air flow meter 111 via an intake duct 110, and a first throttle valve 1 connected to an accelerator pedal 112.
13 is disposed within the intake duct 110. on the other hand,
The second surge tank 101 is connected to a second air flow meter 114 via an intake duct 113, and a second throttle valve 116 controlled by an opening/closing control valve 115 is disposed within the intake duct 113. The opening/closing control valve 115 has a negative pressure chamber 118 isolated from the atmosphere by a diaphragm 117.
The tip of the arm 119 fixed to the throttle shaft of the second throttle valve 116 is connected to the diaphragm 117.
connected to. The negative pressure chamber 118 is connected on the one hand to the first surge tank 100 via a negative pressure conduit 120 and on the other hand to the atmosphere via an air bleed control valve 121 . Furthermore, as shown in FIG. 7, the throttle shafts of the first throttle valve 113 and the second throttle valve 116 are connected to potentiometers 122, 123, respectively, and the output signals of these potentiometers 122, 123 are transmitted to the electronic control unit. 18 is input. Further, each exhaust manifold 14, 15 has an oxygen concentration detector 20, respectively.
The output signals of these oxygen concentration detectors 20a and 20b are input to the electronic control unit 18.

In this embodiment, when the engine is operated under high load, the opening degree of the second throttle valve 116 is equal to that of the first throttle valve 113.
Air bleed control valve 1
The duty ratio of the pulse applied to the solenoid 21, that is, the negative pressure in the negative pressure chamber 118 of the opening/closing control valve 115 is controlled. Next, when the operating state of the engine shifts from high load operation to low load operation, the air bleed control valve 1 is activated by the output signal of the electronic control unit 18.
The duty ratio of the pulse applied to the throttle valve 21 is controlled to gradually close the second throttle valve 116 to a fully closed state. When the second throttle valve 116 is fully closed, the supply of fuel from the fuel injection valve 17b is stopped, and then the second throttle valve 116 is rapidly opened to the fully open position. Therefore, only air is supplied to the second cylinder group B at this time. On the other hand, when the engine operating state shifts from low load operation to high load operation, the second throttle valve 116 is first opened from the fully open position to the fully closed position, and then the fuel injection valve 17 is opened from the fully open position to the fully closed position.
The injection action of fuel from b starts, then from the second
The throttle valve 116 is gradually opened to an opening equal to the opening of the first throttle valve 113.
In this embodiment as well, the pressure difference between the pressure of fuel supplied to the fuel injection valves 17a of the first cylinder group A and the negative pressure in the first surge tank 100, and the pressure difference between the pressure of the fuel supplied to the fuel injection valves 17a of the first cylinder group A, and the pressure of the fuel supplied to the fuel injection valves 17b of the second cylinder group B are determined. Since the pressure difference between the fuel pressure and the negative pressure in the second surge tank 101 is always kept constant, the second throttle valve 116
Even while the throttle valve 116 is closed to the fully closed position or while the second throttle valve 116 is opened from the fully closed position, the air-fuel mixture supplied to the first cylinder group A and the second cylinder group B is The fuel ratio can be made to match the stoichiometric air-fuel ratio.

As described above, according to the present invention, the pressure difference between the negative pressure in the intake passage where fuel is to be injected and the fuel injection pressure can be kept constant regardless of the operating state of the engine. It can be made exactly proportional to time. As a result, the air-fuel ratio of the mixture supplied to the first cylinder group and the second cylinder group when the engine transitions from high-load operation to low-load operation or from low-load operation to high-load operation can be calculated theoretically. Since open-loop control can be performed to maintain an air twist ratio, deterioration of exhaust emissions can be prevented.

[Brief explanation of drawings]

FIG. 1 is a plan view schematically showing a conventional internal combustion engine, FIG. 2 is a plan view of an internal combustion engine according to the present invention, and FIG. 3 is a plan view schematically showing the internal combustion engine of FIG.
4 is a circuit diagram of the electronic control unit of FIG. 3, FIG. 5 is a diagram for explaining the divided operation control method according to the present invention, and FIG. 6 is a diagram for explaining the divided operation control method according to the present invention. FIG. 7 is a plan view schematically showing another embodiment of the internal combustion engine. 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, 80... ...First fuel supply pipe, 81...Second
fuel supply pipe.

Claims (1)

[Claims] 1. A cylinder is divided into a first cylinder group and a second cylinder group, and a first fuel injection valve group is arranged in a first intake passage connected to the first cylinder group, and the second cylinder group A second fuel injection valve group is disposed in a second intake passage connected to the engine, and fuel is supplied from the first fuel injection valve group and the second fuel injection valve group during high engine load operation, and the first fuel An air or exhaust gas inflow control valve is provided in the first intake passage upstream of the injection valve group to stop the supply of fuel from the first fuel injection valve group when the engine is operating at low load, and to control the flow of air or exhaust gas into the first cylinder group. A split operation control type internal combustion engine configured to supply the above-mentioned number of cylinders is provided with a detection device for detecting the amount of intake air supplied to the first cylinder group and the amount of intake air supplied to the second cylinder group. Fuel supply passages to the first fuel injection valve group and the second fuel injection valve group are provided separately, and the first fuel supply passage connected to the first fuel injection valve group is connected to the first intake passage downstream of the inflow control valve. A first fuel injection pressure regulating valve responsive to negative pressure is provided to maintain a constant pressure difference between the fuel pressure in the first fuel supply passage and the negative pressure in the first intake passage; A second fuel injection pressure regulating valve that responds to the negative pressure in the second intake passage is provided in the second fuel supply passage connected to the group, so that the fuel pressure in the second fuel supply passage and the negative pressure in the second intake passage are adjusted. The pressure difference between the pressure and the pressure is maintained constant, and when transitioning from high-load operation to low-load operation and from low-load operation to high-load operation, the first cylinder is The fuel injection time from the first fuel injection valve group and the second fuel injection valve group is controlled in an open loop so that the air-fuel ratio of the air-fuel mixture supplied to the first fuel injection valve group and the second cylinder group becomes the target air-fuel ratio. Controlled internal combustion engine.