JP2004245122A - Cylinder control device of multiple-cylinder internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cylinder control device of a multiple-cylinder combustion engine in which the combustion state is stabilized and a low-temperature combustion state is established, and an optimal range of duty is substantially expanded. <P>SOLUTION: When a low-temperature combustion state is selected in a multiple-cylinder internal combustion engine in which a low-temperature combustion state and a normal combustion state are selectively switched, the number of cylinder to be actuated after fuel supply is set so that load for every actuated cylinder falls within a load region where the combustion state is stabilized without being affected by some disturbance such as variations in intake-air flow, and a low-temperature combustion state is attained. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a cylinder control device for a multi-cylinder internal combustion engine, which controls the number of cylinders to be operated in accordance with an operation state.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a multi-cylinder internal combustion engine, a cylinder control device of a multi-cylinder internal combustion engine that varies the number of cylinders to which fuel is supplied according to a load or a vehicle speed in order to improve fuel efficiency is known (for example, Patent Document 1) reference.).
[0003]
In addition, an exhaust gas recirculation passage for recirculating exhaust gas to the intake passage is provided, and the amount of recirculated exhaust gas when the amount of soot generated by the supply of the recirculated exhaust gas to the combustion chamber reaches a peak is increased. There is known an internal combustion engine that operates in a combustion state in which the amount of generated soot is suppressed by increasing the amount of recirculated exhaust gas supplied to a combustion chamber, that is, a so-called low-temperature combustion state (for example, See Patent Document 2.).
[0004]
[Patent Document 1]
JP-A-52-61636 [Patent Document 2]
JP-A-11-36923 [Patent Document 3]
Japanese Patent Application Laid-Open No. 05-163971
[Problems to be solved by the invention]
By the way, in order to set the combustion state to the low-temperature combustion state in the internal combustion engine, as described above, the amount of the recirculated exhaust gas supplied to the combustion chamber is made smaller than the amount of the recirculated exhaust gas at which the generation amount of soot becomes a peak. (For example, the EGR rate is set to approximately 55% or more). However, when the internal combustion engine is operating at a high load, the amount of intake air increases, so that the amount of recirculated exhaust gas supplied to the combustion chamber can be increased beyond the amount at which the amount of soot generation reaches a peak. Absent. Also, when the internal combustion engine is operating at a very low load, the intake air amount is very small, and it is difficult to perform stable combustion if the amount of recirculated exhaust gas supplied to the combustion chamber is increased. Become. Therefore, in the internal combustion engine, the load range in which the combustion state can be stably set to the low-temperature combustion state is limited.
[0006]
Therefore, an object of the present invention is to provide a technique capable of substantially expanding a load range in which a combustion state can be stably set to a low-temperature combustion state in a multi-cylinder internal combustion engine.
[0007]
[Means for Solving the Problems]
The present invention employs the following means in order to solve the above problems.
That is, according to the present invention, in a multi-cylinder internal combustion engine that selectively switches between a low-temperature combustion state and a normal combustion state, when the low-temperature combustion state is selected, the load of each cylinder to be operated is affected by disturbances such as slight intake air amount fluctuations. The number of cylinders for supplying and operating the fuel is set so that the combustion state is within a load range where the combustion state can be stably set to the low-temperature combustion state without being affected.
[0008]
More specifically, a cylinder control device for a multi-cylinder internal combustion engine according to the present invention,
It has a plurality of cylinders, and has exhaust recirculation means for recirculating a part of the exhaust gas to the intake system, soot which increases when the recirculated exhaust gas is supplied to the combustion chamber by the exhaust recirculation means. By increasing the amount of the recirculated exhaust gas supplied to the combustion chamber more than the amount of the recirculated exhaust gas when the generation amount reaches a peak, a low-temperature combustion state in which the generation amount of soot is suppressed. In a cylinder control device of a multi-cylinder internal combustion engine that selectively switches between a normal combustion state, which is a combustion state other than the low-temperature combustion state,
When selecting the low-temperature combustion state, an operation of setting the number of the working cylinders such that the load for each working cylinder is within a predetermined load region where the combustion state can be stably set to the low-temperature combustion state. It is characterized by having a cylinder number setting means.
[0009]
Here, the working cylinder is a cylinder to be operated, that is, a cylinder that supplies fuel.
[0010]
For example, in the multi-cylinder internal combustion engine according to the present invention, when the combustion state needs to be set to the low-temperature combustion state, the load for each working cylinder is set to a predetermined value that enables the combustion state to be stably set to the low-temperature combustion state. If it is smaller than the load range, the number of working cylinders is reduced.
[0011]
By reducing the number of working cylinders, the load on each working cylinder can be relatively increased. Therefore, it is possible to keep the load for each working cylinder within the predetermined load region while satisfying the required load for the entire engine.
[0012]
On the other hand, for example, in the multi-cylinder internal combustion engine according to the present invention, when the combustion state needs to be set to the low-temperature combustion state, the load for each working cylinder can stably set the combustion state to the low-temperature combustion state. If it is larger than the predetermined load range, the number of working cylinders is increased.
[0013]
By increasing the number of working cylinders, the load on each working cylinder can be relatively reduced. Therefore, similarly to the above, it is possible to keep the load for each working cylinder within the predetermined load range while satisfying the required load as the whole engine.
[0014]
As described above, according to the cylinder control device for a multi-cylinder internal combustion engine according to the present invention, by varying the number of working cylinders, the engine as a whole can satisfy the required load and reduce the load for each working cylinder to the predetermined load. It becomes possible to be within the area. Therefore, the load range in which the combustion state can be stably set to the low-temperature combustion state is expanded as the whole engine.
[0015]
In the cylinder control device for a multi-cylinder internal combustion engine according to the present invention, the load for each working cylinder may be the maximum load within a predetermined load region in which the combustion state can be stably set to the low-temperature combustion state. Alternatively, the number of working cylinders may be set.
[0016]
Generally, in an internal combustion engine, fuel efficiency tends to be improved during high-load operation. Therefore, by setting the load for each working cylinder to the maximum load within the predetermined load region, it becomes possible to stably set the combustion state to a low-temperature combustion state in a wider load region and to improve fuel efficiency. Can be done.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, specific embodiments of a cylinder control device for a multi-cylinder internal combustion engine according to the present invention will be described with reference to the drawings. Here, a case where the present invention is applied to a vehicle diesel engine will be described as an example.
[0018]
FIG. 1 is a diagram showing a schematic configuration of a multi-cylinder internal combustion engine according to the present invention.
[0019]
The internal combustion engine 1 shown in FIG. 1 is a diesel engine having four cylinders 2.
[0020]
The internal combustion engine 1 includes a fuel injection valve 3 for directly injecting fuel into a combustion chamber of each cylinder 2. Each fuel injection valve 3 is connected to a pressure accumulation chamber (common rail) 4 for accumulating fuel up to a predetermined pressure. A common rail pressure sensor 4a that outputs an electric signal corresponding to the pressure of the fuel in the common rail 4 is attached to the common rail 4.
[0021]
The common rail 4 communicates with a fuel pump 6 via a fuel supply pipe 5. The fuel pump 6 is a pump that operates using a rotational torque of an output shaft (crankshaft) of the internal combustion engine 1 as a driving source. A pump pulley 6a attached to an input shaft of the fuel pump 6 has an output shaft ( It is connected via a belt 7 to a crank pulley 1a attached to a crankshaft).
[0022]
In the fuel injection system configured as described above, when the rotation torque of the crankshaft is transmitted to the input shaft of the fuel pump 6, the fuel pump 6 rotates the rotation torque transmitted from the crankshaft to the input shaft of the fuel pump 6. The fuel is discharged at a pressure according to.
[0023]
The fuel discharged from the fuel pump 6 is supplied to a common rail 4 via a fuel supply pipe 5, accumulated in the common rail 4 to a predetermined pressure, and distributed to the fuel injection valves 3 of each cylinder 2. When a drive voltage is applied to the fuel injection valve 3, the fuel injection valve 3 opens, and as a result, fuel is injected from the fuel injection valve 3 into the combustion chamber of the cylinder 2.
[0024]
Next, an intake branch pipe 8 is connected to the internal combustion engine 1, and each branch pipe of the intake branch pipe 8 communicates with a combustion chamber of each cylinder 2 via an intake port (not shown).
[0025]
The intake branch pipe 8 is connected to an intake pipe 9, and the intake pipe 9 is connected to an air cleaner box 10. An air flow meter 11 that outputs an electric signal corresponding to a mass of intake air flowing through the intake pipe 9, a compressor housing 15 a of a centrifugal supercharger (turbocharger) 15, and an intake pipe 9 downstream of the air cleaner box 10. And an intercooler 16 for cooling the intake air which has been heated in the compressor housing 15a and has become high temperature.
[0026]
Further, at a portion of the intake pipe 9 located immediately upstream of the intake branch pipe 8, an intake throttle valve 13 for adjusting the flow rate of intake air flowing through the intake pipe 9 is provided. The intake throttle valve 13 is provided with an intake throttle actuator 14 which is configured by a stepper motor or the like and drives the intake throttle valve 13 to open and close.
[0027]
On the other hand, an exhaust branch pipe 18 is connected to the internal combustion engine 1, and each branch pipe of the exhaust branch pipe 18 communicates with a combustion chamber of each cylinder 2 via an exhaust port 30.
[0028]
The exhaust branch pipe 18 is connected to a turbine housing 15 b of the centrifugal supercharger 15. The turbine housing 15b is connected to the exhaust pipe 19. The exhaust pipe 19 is connected downstream to a muffler (not shown).
[0029]
In the middle of the exhaust pipe 19, an exhaust purification catalyst 20, such as an occlusion reduction type NOx catalyst or a selective reduction type NOx catalyst, is used to purify harmful gas components of nitrogen oxides (NOx) contained in exhaust gas. Are located.
[0030]
An exhaust pipe 19 upstream of the exhaust purification catalyst 20 has an air-fuel ratio sensor 23 that outputs an electric signal corresponding to the air-fuel ratio of the exhaust flowing through the exhaust pipe 19 and a sensor that responds to the temperature of the exhaust flowing through the exhaust pipe 19. And an exhaust gas temperature sensor 24 for outputting an electric signal.
[0031]
Further, the internal combustion engine 1 is provided with an exhaust gas recirculation device 40 for recirculating a part of the exhaust gas flowing through the exhaust system of the internal combustion engine 1 to the intake system. The exhaust gas recirculation device 40 includes an exhaust gas recirculation passage (EGR passage) 25 formed from the exhaust branch pipe 18 through the cylinder head to the gathering portion of the intake branch pipe 8, a solenoid valve, and the like. A flow control valve (EGR valve) 26 for adjusting the flow rate of exhaust gas (hereinafter, referred to as EGR gas) flowing in the EGR passage 25 according to the size, and the EGR passage provided in the EGR passage 25 upstream of the EGR valve 26. And an EGR cooler 27 for cooling the EGR gas flowing through the EGR gas 25.
[0032]
In the exhaust gas recirculation device 40 configured as described above, when the EGR valve 26 is opened, a part of the exhaust gas flowing in the exhaust branch pipe 18 passes through the EGR passage 25 and is cooled by the EGR cooler. It flows into the collecting portion of the intake branch pipe 8. The EGR gas flowing into the intake branch pipe 8 is distributed to the combustion chambers of the cylinders 2 while mixing with fresh air flowing from the upstream of the intake branch pipe 8, and the fuel injected from the fuel injection valve 3 is used as an ignition source. Burned.
[0033]
Here, the EGR gas contains an endothermic inert gas component such as water (H ₂ O) or carbon dioxide (CO ₂ ) that does not burn itself and is endothermic. When the EGR gas is contained in the air-fuel mixture, the combustion temperature of the air-fuel mixture becomes low, thereby suppressing the generation amount of nitrogen oxides (NOx).
[0034]
The internal combustion engine 1 configured as described above is provided with an electronic control unit (ECU: Electronic Control Unit) 35 for controlling the internal combustion engine 1. The ECU 35 is a unit that controls the operating state of the internal combustion engine 1 according to the operating conditions of the internal combustion engine 1 and the driver's requirements.
[0035]
Various sensors such as a common rail pressure sensor 4a, an air flow meter 11, an intake pipe pressure sensor 17, an air-fuel ratio sensor 23, an exhaust temperature sensor 24, a crank position sensor 33, and an accelerator opening sensor 36 are connected to the ECU 35 via electric wiring. The output signals of the various sensors described above are input to the ECU 35.
[0036]
On the other hand, the fuel injection valve 3, the intake throttle actuator 14, the EGR valve 26, and the like are connected to the ECU 35 via electric wiring, and the above-described components are controlled by the ECU 35.
[0037]
The ECU 35 includes a CPU, a ROM, a RAM, and the like, and performs feedback control of the air-fuel ratio of exhaust flowing into the exhaust purification catalyst 20 based on, for example, output signals of the air-fuel ratio sensor 23 and the exhaust temperature sensor 24. The ECU 35 calculates the engine speed based on the time interval at which the crank position sensor 33 outputs the pulse signal, and calculates the required load based on the output signal (accelerator opening) of the accelerator opening sensor 36 and the like. I do.
[0038]
Further, the ECU 35 controls the number of cylinders for injecting fuel and the fuel injection amount based on the engine speed, the required load, and the like.
[0039]
Further, the ECU 35 controls the combustion state in the combustion chamber to be selectively switched between a low-temperature combustion state and a normal combustion state. For example, when the low-temperature combustion execution condition is satisfied, the ECU 35 adjusts the opening degree of the EGR valve 26, and changes the amount of the EGR gas supplied to the combustion chamber to the amount of the EGR gas when the generation amount of soot reaches a peak. By setting the number to be larger than that, the combustion state in the combustion chamber is set to a low temperature combustion state. Examples of the low-temperature combustion execution conditions include a case where the exhaust gas purification catalyst 20 is recovered from SOx poisoning by setting the exhaust gas air-fuel ratio to a rich air-fuel ratio.
[0040]
Next, in the cylinder control device for a multi-cylinder engine according to the present embodiment, the control of the number of working cylinders for setting the number of cylinders for injecting fuel (hereinafter, referred to as working cylinders) will be described with reference to the flowchart shown in FIG. I do.
[0041]
The flowchart shown in FIG. 2 is a flowchart showing a working cylinder number control routine. This operating cylinder number control routine is a routine that is repeatedly executed by the ECU 35 at predetermined time intervals (for example, every time the crank position sensor 33 outputs a pulse signal), and is stored in a ROM provided in the ECU 35 in advance.
[0042]
In this working cylinder control routine, the ECU 35 first determines in S101 whether a low-temperature combustion execution condition has been satisfied.
[0043]
When it is determined in S101 that the low-temperature combustion execution condition is not satisfied, the ECU 35 proceeds to S104 and calculates a load region β per cylinder in which fuel efficiency is good based on the engine speed NE and the like.
[0044]
After calculating the load region β in S104, the ECU 35 proceeds to S105.
[0045]
In the S105, ECU 35, the load of each active cylinder, the with the calculated load region β in S104, as the overall engine meets the required load P, determines the number n ₂ of the hydraulic cylinder Then, the execution of this routine ends.
[0046]
On the other hand, if it is determined in 101 that the low-temperature combustion execution condition is satisfied, the ECU 35 proceeds to S102.
[0047]
As described above, in order to set the combustion state in the combustion chamber to the low-temperature combustion state, the amount of the EGR gas supplied to the combustion chamber must be larger than the amount of the EGR gas when the generation amount of soot reaches a peak. There is a need to. Therefore, the load range in which the combustion state can be stably set to the low-temperature combustion state is limited.
[0048]
Therefore, in S102, the ECU 35 calculates the load area α per cylinder in which the combustion state in the combustion chamber can be stably set to the low-temperature combustion state based on the engine speed NE. FIG. 3 shows a load region α per cylinder in which the combustion state can be stably set to the low-temperature combustion state.
[0049]
The ECU 35 that has calculated the load region α in S102 proceeds to S103, and the load of each working cylinder falls within the calculated load region α, and the number n of working cylinders is set so as to satisfy the required load P for the entire engine. Determine ₁ .
[0050]
For example, when the load for each working cylinder is smaller than the load region α, the number of working cylinders is reduced. By reducing the number of working cylinders, the load of each working cylinder can be relatively increased, so that the load of each working cylinder can be within the load range α.
[0051]
Further, for example, when the load of each working cylinder is larger than the load region α, the number of working cylinders is increased. By increasing the number of working cylinders, the load of each working cylinder can be relatively reduced, so that the load of each working cylinder can be within the load region α.
[0052]
In the S103, ECU 35 which determines the number _{n 1} of the working cylinder, terminates execution of this routine.
[0053]
According to the control of the number of working cylinders shown in this routine, when it is necessary to set the combustion state in the combustion chamber to a low-temperature combustion state, the load of each working cylinder is stabilized while maintaining the required load for the entire engine. As a result, the temperature can be set within a predetermined load region where a low-temperature combustion state can be achieved. Therefore, the load range in which the combustion state can be stably set to the low-temperature combustion state is expanded as the whole engine.
[0054]
Further, in the S103 in the present routine, ECU 35, the load of each active cylinder may determine the number n ₁ of the hydraulic cylinder so as to maximize the load in said load region α calculated in S102.
[0055]
Generally, in an internal combustion engine, fuel efficiency tends to be improved during high-load operation. Therefore, by setting the load of each working cylinder to the maximum load in the load region α, the combustion state can be stably changed to the low-temperature combustion state in a wider load region, and the fuel efficiency can be improved. I can do it.
[0056]
【The invention's effect】
According to the cylinder control device for a multi-cylinder internal combustion engine according to the present invention, the load for each working cylinder can be stably set to the low-temperature combustion state while stabilizing the combustion state in the combustion chamber while satisfying the required load as the whole engine. Since it can be within the possible predetermined load range, the combustion state can be stably set to the low-temperature combustion state in a wider load range as the whole engine.
[Brief description of the drawings]
1 is a diagram showing a schematic configuration of a multi-cylinder internal combustion engine according to the present invention; FIG. 2 is a flowchart showing a routine for controlling the number of working cylinders; FIG. 3 is a graph showing a low-temperature combustion stable region α;
1, internal combustion engine 1a, crank pulley 2, cylinder 3, fuel injection valve 4, common rail 5, fuel supply pipe 6, fuel pump 7, ... Belt 8 ... Intake branch pipe 9 ... Intake pipe 10 ... Air cleaner box 11 ... Air flow meter 13 ... Intake throttle valve 14 ... Intake throttle valve actuator 15 ... Centrifugal supercharger (turbocharger)
15a, compressor housing 15b, turbine housing 16, intercooler 17, intake pipe pressure sensor 18, exhaust branch pipe 19, exhaust pipe 20, exhaust purification catalyst 23, air-fuel ratio Sensor 24 Exhaust temperature sensor 25 EGR passage 26 EGR valve 27 EGR cooler 30 Exhaust port 33 Crank position sensor 35 ECU
36: accelerator opening sensor 40: exhaust gas recirculation device

Claims (2)

It has a plurality of cylinders, and has exhaust recirculation means for recirculating a part of the exhaust gas to the intake system, soot which increases when the recirculated exhaust gas is supplied to the combustion chamber by the exhaust recirculation means. By increasing the amount of the recirculated exhaust gas supplied to the combustion chamber more than the amount of the recirculated exhaust gas when the generation amount reaches a peak, a low-temperature combustion state in which the generation amount of soot is suppressed. In a cylinder control device of a multi-cylinder internal combustion engine that selectively switches between a normal combustion state, which is a combustion state other than the low-temperature combustion state,
When selecting the low-temperature combustion state, an operation of setting the number of the working cylinders such that the load for each working cylinder is within a predetermined load region where the combustion state can be stably set to the low-temperature combustion state. A cylinder control device for a multi-cylinder internal combustion engine, comprising: a cylinder number setting unit. 2. The multi-cylinder engine according to claim 1, wherein the number of operating cylinders setting unit sets the number of the operating cylinders such that a load for each of the operating cylinders has a maximum load within the predetermined load region. 3. A cylinder control device for an internal combustion engine.

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