Control device of engine

Abstract

To provide a control device of an engine which is suppressed in a torque shock.SOLUTION: A control device of an engine comprises a control part for controlling air excess ratios of N-numbers of cylinders by controlling suction air amounts and fuel injection amounts of the N-numbers (N is an integer larger than 2) of the cylinders, and a determination part for determining whether or not there arises a requirement for switching the air excess ratio which is controlled to λ1 to λ2 which is different from λ1. When a determination by the determination part is affirmative, the control part controls the air excess ratio so that a ratio of L-times of combustion strokes at λ2 occupied in continuous K-numbers (K is an integer larger than N) of the combustion strokes is increased to M steps (M is an integer larger than N) up until reaching 100% from 0%.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an engine control device. [Background technology]

[0002] In a four-cylinder engine, there is a case where it is required to switch from a first air-fuel ratio to a second air-fuel ratio. In this case, the air-fuel ratios of two cylinders are switched from the first air-fuel ratio to the second air-fuel ratio. After that, the air-fuel ratios of the remaining two cylinders are switched from the first air-fuel ratio to the second air-fuel ratio. This makes it possible to suppress torque shock compared to a case where the air-fuel ratios of all cylinders are switched to the second air-fuel ratio at the same time (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-172356 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above technology, there is a risk of a torque shock occurring when the air-fuel ratios of the two cylinders are switched to the second air-fuel ratio.

[0005] SUMMARY OF THE PRESENT EMBODIMENTS Accordingly, an object of the present invention is to provide an engine control device that suppresses torque shock. [Means for solving the problem]

[0006] The above object can be achieved by an engine control device comprising: a control unit that controls each of N (an integer greater than 2) cylinders by controlling the intake air amount and fuel injection amount of each of the N cylinders; and a judgment unit that judges whether or not there is a request to switch each of the excess air ratios controlled to λ1 to λ2 different from λ1, wherein when a positive judgment is made by the judgment unit, the control unit controls each of the excess air ratios so that a proportion of L combustion strokes at λ2 out of K (an integer greater than N) consecutive combustion strokes increases in M ​​(an integer greater than N) steps from 0% to 100%.

[0007] When L is other than 1, other than K, and a divisor of K, the control unit may execute the combustion stroke at λ2 at equal intervals.

[0008] When J obtained by subtracting L from K is other than 1, is other than K, and is a divisor of J, the control unit may execute the combustion stroke at λ1 at equal intervals.

[0009] One of the excess ratios λ1 and λ2 may be 1.0 or more, and the other of the excess ratios λ1 and λ2 may be 1.5 or more, the N may be 4 or more, and the M may be 5 or more. Effect of the Invention

[0010] According to the present invention, it is possible to provide an engine control device that suppresses torque shock. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic configuration diagram of an engine system. [Diagram 2] FIG. 2 is a flowchart illustrating an example of the air excess ratio switching control. [Diagram 3] FIG. 3 is a timing chart illustrating the transition process. [Figure 4] 4A to 4D are explanatory diagrams showing the combustion strokes of λ1 and λ2 in the transition process. [Diagram 5] 5A and 5B are explanatory diagrams showing the combustion strokes of λ1 and λ2 in the transition process in the modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] [Outline of engine system configuration] 1 is a schematic diagram of an engine system 1. The engine system 1 includes an engine 10, an intake passage 12 and an exhaust passage 22 connected to the engine 10, and an ECU (Electric Control Unit) 30 that controls the engine 10. The engine 10 is a four-cylinder in-line gasoline engine having cylinders #1 to #4, but is not limited to this type of engine. The engine 10 may be, for example, a diesel engine. The number of cylinders of the engine 10 is not limited to four.

[0013] The intake passage 12 is provided with a throttle valve 13 for adjusting the intake air amount Ga. The air taken in from the intake passage 12 flows into each combustion chamber 16 of a plurality of cylinders 14. Each of the cylinders #1 to #4 is provided with an in-cylinder injection valve 18 for injecting fuel and a spark plug 20 for generating a spark discharge. The in-cylinder injection valve 18 injects fuel directly into the combustion chamber 16. In addition to the in-cylinder injection valve 18, or instead of the in-cylinder injection valve 18, a port injection valve may be provided. In the combustion chamber 16, the mixture of air and fuel is burned. The mixture burned is discharged to the exhaust passage 22 as exhaust. The exhaust passage 22 is provided with a three-way catalyst 24 for purifying the exhaust. Furthermore, a gasoline particulate filter (GPF) 26 is provided downstream of the three-way catalyst 24 in the exhaust passage 22. The GPF 26 collects particulates in the exhaust.

[0014] The ECU 30 controls the throttle valve 13, the in-cylinder injection valve 18, and the spark plug 20 to control the output of the engine 10. At this time, the ECU 30 refers to the air-fuel ratio detected by an air-fuel ratio sensor 40 provided upstream of the three-way catalyst 24, the output signal of a crank angle sensor 42, and the intake air amount Ga detected by an air flow meter 44. The ECU 30 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and a rewritable non-volatile memory, and the CPU executes programs stored in the ROM to control the above-mentioned controlled variables.

[0015] Furthermore, as will be described in detail later, the ECU 30 controls the intake air amount Ga by the throttle valve 13 and the fuel injection amount Q by each in-cylinder injection valve 18 to control the excess air ratio λ of each of the cylinders #1 to #4. The excess air ratio λ can be expressed as air-fuel ratio / stoichiometric air-fuel ratio. The excess air ratio λ is greater than 1, indicating that the air-fuel ratio of the mixture is leaner. The excess air ratio λ is controlled by the ECU 30 in accordance with the required output of the engine 10. The CPU, RAM, ROM, and non-volatile memory of the ECU 30 functionally realize a determination unit and a control unit. The ECU 30 is an example of an engine control device.

[0016] [Air excess ratio switching control] FIG. 2 is a flowchart illustrating the excess air ratio switching control. This control is repeatedly executed at a predetermined cycle while the ignition is on. The ECU 30 judges whether or not there is a request to switch to λ2 while each excess air ratio is controlled to λ1 (step S1). λ1 and λ2 are different values. One of λ1 and λ2 is 1.0 or more. The other of λ1 and λ2 is 1.5 or more. That is, if there is a request to switch from one of lean combustion and stoichiometric combustion to the other, it is judged as Yes in step S1. Also, if there is a request to change the excess air ratio while continuing lean combustion, it is judged as Yes in step S1. Step S1 is an example of a process executed by the judgment unit. If the answer is No in step S1, this control ends.

[0017] If the answer is Yes in step S1, the ECU 30 executes a transition process (step S2). The transition process is a process in which the excess air ratios of the cylinders #1 to #4 are controlled so that the ratio R of L combustion strokes at λ2 to K consecutive combustion strokes in the engine 10 increases in M ​​steps from 0% to 100%. K is an integer larger than the number of cylinders N. L is an integer. M is an integer larger than N. R is a value that indicates the ratio of L to K as a percentage. In this embodiment, the cases of N=4, K=10, M=5, and L=2, 4, 6, 8, and 10 will be described. Step S2 is an example of a process executed by the control unit.

[0018] [Transition process] FIG. 3 is a timing chart illustrating the transition process. FIG. 3 shows the transition of the intake air amount Ga and the output P. The example of FIG. 3 shows a case where there is a request to switch from λ1 to λ2 due to a request to increase the output of the engine 10. That is, the example of FIG. 3 shows a case where λ2 is smaller than λ1. The example of FIG. 3 shows a case where the air excess ratios of the cylinders #1 to #4 are switched by changing the fuel injection amount Q for each of #1 to #4 while controlling the intake air amount Ga to be constant. FIGS. 4A to 4D are explanatory diagrams showing the combustion strokes of λ1 and λ2 in the transition process. The vertical axis shows the cylinders #1 to #4, and the horizontal axis shows the number of combustion strokes. In FIGS. 4A to 4D, the combustion stroke at λ1 is shown by a dotted line, and the combustion stroke at λ2 is shown by a solid line.

[0019] When the transition process is started at time t1, the first process is executed. As shown in FIG. 4A, in the first process, L=2, R=20%. Here, combustion is performed in the order of cylinders #1, #3, #4, and #2. In the example of FIG. 4A, the excess air ratios in the first and sixth combustion strokes are switched to λ2. The first and sixth combustion strokes are performed in #1 and #3, respectively. Note that, before the transition process is started, the excess air ratios in cylinders #1 to #4 are controlled to λ1, so L=0, R=0%.

[0020] At time t2, the second process is executed. As shown in FIG. 4B, L=4 and R=40% in the second process. In the example of FIG. 4B, the air excess ratios in the second, fifth, seventh, and tenth combustion strokes are switched to λ2. The second, fifth, seventh, and tenth combustion strokes are performed in cylinders #3, #1, #4, and #3, respectively.

[0021] At time t3, the third process is executed. As shown in FIG. 4C, in the third process, L=6 and R=60%. In the example of FIG. 4C, the air excess ratios in the second, third, fifth, sixth, eighth, and ninth combustion strokes are switched to λ2. The second, third, fifth, sixth, eighth, and ninth combustion strokes are performed in cylinders #3, #4, #1, #3, #2, and #1, respectively.

[0022] At time t4, the fourth process is executed. As shown in FIG. 4D, L=8 and R=80% in the fourth process. In the example of FIG. 4D, the excess air ratios in the second to fifth and seventh to tenth combustion strokes are switched to λ2. The second to fifth combustion strokes are performed in cylinders #3, #4, #2, and #1, respectively. The seventh to tenth combustion strokes are performed in cylinders #4, #2, #1, and #3, respectively. For each of the first to fourth processes, the K combustion strokes may be executed in only one cycle or over multiple cycles. Also, the first to fourth processes may be executed in different cycles.

[0023] At time t5, the excess air ratios of all cylinders #1 to #4 are switched to λ2, L=10, and R=100%. As described above, R increases in five stages: R=20%, 40%, 60%, 80%, and 100%. This suppresses torque shock during the transition process.

[0024] For example, assume that the excess air ratio is switched to λ2 for each of cylinders #1 to #4 in sequence. In this case, N=M=4, and R=25%, 50%, 75%, and 100%. In this way, R increases in four stages depending on the number of cylinders. For this reason, there is a risk of torque shock increasing compared to the above embodiment. In the above embodiment, R can be increased in multiple stages regardless of the number of cylinders, and torque shock is further suppressed.

[0025] Here, it is considered to gradually change each excess air ratio of all cylinders #1 to #4 from the above-mentioned λ1 to λ2 in order to suppress the torque shock. However, such a gradual change of the excess air ratio may increase the amount of NOx emissions. For example, from the theoretical air-fuel ratio to a predetermined lean air-fuel ratio, the oxidation of nitrogen in the air is promoted due to the increase in combustion temperature and the excess oxygen concentration, and the amount of NOx emissions increases. If the air-fuel ratio becomes even higher, the combustion temperature decreases and the amount of NOx emissions decreases. In this way, when the excess air ratio is gradually changed from λ1 to λ2, the air-fuel ratio passes through a region where the amount of NOx emissions increases. In the transition processing of this embodiment, each excess air ratio of cylinders #1 to #4 is controlled to λ1 or λ2, and the air-fuel ratio does not pass through a region where the amount of NOx emissions increases. Therefore, the amount of NOx emissions is suppressed while suppressing the torque shock.

[0026] In the first process shown in FIG. 4A, K=10 and L=2 as described above. Here, 2 is other than 1, other than 10, and is a divisor of 10. In the first process, the first and sixth combustion strokes are switched to λ2. Here, four combustion strokes at λ1 are executed between the first and sixth combustion strokes. That is, in the first process, the combustion strokes at λ2 are executed at equal intervals. In this way, since L is a divisor of K, the combustion strokes at λ2 can be executed at equal intervals. This suppresses torque shock when the first process is executed.

[0027] In the fourth process shown in FIG. 4D, K=10 and L=8 as described above. If the number of combustion strokes at λ1 is J, then J=2. Here, 2 is other than 1, other than 10, and is a divisor of 10. In the fourth process, the first and sixth combustion strokes are maintained at λ1. Here, four combustion strokes at λ2 are executed between the first and sixth combustion strokes. That is, in the fourth process, the combustion strokes at λ1 are executed at equal intervals. Since L is a divisor of K in this way, the combustion strokes at λ2 can be executed at equal intervals. This suppresses torque shock when the fourth process is executed.

[0028] 3 illustrates an example of the transition process when the intake air amount Ga is constant, but is not limited to this. In addition, when there is a request to increase the output of the engine 10, the intake air amount Ga may be increased to an upper limit value while maintaining the excess air ratio constant, and then the transition process may be executed while maintaining the intake air amount Ga at the upper limit value.

[0029] In the above embodiment, the ratio R is increased in five stages, but this is not limiting. For example, the ratio R may be increased in ten stages. K is not limited to 10. K may be any number greater than the number of cylinders N. For example, K may be 5. In this case, the ratio R is increased in five stages.

[0030] [Variations] Next, the transition process in a V6 engine will be described. In a V6 engine, cylinders #1, #3, and #5 are provided in the left bank, and cylinders #2, #4, and #6 are provided in the right bank. Combustion occurs in the order of cylinders #1, #2, #3, #4, #5, and #6. In this modification, N=6, K=10, M=7, and L=1, 2, 4, 5, 7, 8, and 10. The ratio R increases in seven stages, which is more than the number of cylinders N. This suppresses torque shock. Figures 5A and 5B are explanatory diagrams showing the combustion strokes of λ1 and λ2 in the transition process in the modification.

[0031] FIG. 5A illustrates the case where R=20%. In the example of FIG. 5A, the first and sixth combustion strokes are switched to λ2. The first and sixth combustion strokes are performed at #1 and #6, respectively. In this process, the combustion strokes at λ2 are performed at equal intervals. This suppresses torque shock.

[0032] FIG. 5B illustrates the case where R=80%. In the example of FIG. 5B, the excess air ratios in the second to fifth and seventh to tenth combustion strokes are switched to λ2. If the number of combustion strokes in λ1 is J, then J=2. Here, 2 is a number other than 1, a number other than 10, and a divisor of 10. In this process, the combustion strokes in λ1 are executed at equal intervals. This suppresses torque shock when this process is executed.

[0033] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention described in the claims. [Explanation of symbols]

[0034] 10 Engine 18 In-cylinder injection valve 22 Exhaust passage 30 ECU (engine control unit, judgment unit, control unit)

Claims

1. a control unit that controls an intake air amount and a fuel injection amount of each of N (N is an integer equal to or greater than 2) cylinders to control an excess air ratio of each of the N cylinders; a determination unit that determines whether or not there is a request to switch each of the air excess ratios controlled to λ1 to λ2 different from the λ1, When a positive determination is made by the determination unit, the control unit controls each of the air excess ratios so that the proportion of L combustion strokes at λ2 out of K consecutive combustion strokes (an integer greater than N) increases in M ​​(an integer greater than N) steps from 0% to 100%.

2. 2. The engine control device according to claim 1, wherein when L is other than 1, other than K, and is a submultiple of K, the control unit executes the combustion stroke at λ2 at equal intervals.

3. 2. The engine control device according to claim 1, wherein when J obtained by subtracting L from K is other than 1, is other than K and is a submultiple of J, the control unit executes the combustion stroke at λ1 at equal intervals.

4. One of the excess ratios λ1 and λ2 is 1.0 or more, The other of the excess ratios λ1 and λ2 is 1.5 or more, The N is 4 or more, 4. The engine control device according to claim 1, wherein said M is 5 or more.

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