Engine control device

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 a switch from a first air-fuel ratio to a second air-fuel ratio is required. 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 when the air-fuel ratios of all cylinders are switched to the second air-fuel ratio simultaneously (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-172356 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 INVENTION It is therefore an object of the present invention 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 including: a control unit that controls the intake air amount and fuel injection amount of each of N cylinders, thereby controlling the excess air ratio of each of the N cylinders (an integer greater than 2); and a determination unit that determines whether or not there is a request to switch each of the excess air ratios, which is controlled to λ1, to λ2, which is different from λ1, wherein, when a positive determination is made by the determination unit, the control unit controls each of the excess air ratios so that a 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%.

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

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

[0011] [Figure 1] FIG. 1 is a schematic diagram of the engine system. [Figure 2] FIG. 2 is a flowchart illustrating an example of the excess air ratio switching control. [Figure 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. [Figure 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 INVENTION

[0012] [Engine system overview] 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 that adjusts the intake air amount Ga. Air drawn in through 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 that injects fuel and a spark plug 20 that generates a spark discharge. The in-cylinder injection valve 18 injects fuel directly into the combustion chamber 16. A port injection valve may be provided in addition to or instead of the in-cylinder injection valve 18. In the combustion chamber 16, a mixture of air and fuel is burned. The burned mixture is discharged to an exhaust passage 22 as exhaust. A three-way catalyst 24 that purifies exhaust gas is provided in the exhaust passage 22. 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 particulate matter in the exhaust.

[0014] The ECU 30 controls the throttle valve 13, the in-cylinder injection valves 18, and the spark plugs 20 to control the output of the engine 10. In doing so, 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), RAM (Random Access Memory), ROM (Read Only Memory), and a rewritable non-volatile memory, and the CPU executes programs stored in the ROM to control the above-mentioned control variables.

[0015] As will be described in detail later, the ECU 30 controls the air excess ratio λ of each of the cylinders #1 to #4 by controlling the intake air amount Ga by the throttle valve 13 and the fuel injection amount Q by each in-cylinder injection valve 18. The air excess ratio λ can be expressed as air-fuel ratio / stoichiometric air-fuel ratio. The air excess ratio λ greater than 1 indicates a leaner air-fuel ratio of the mixture. The air excess 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] [Excess air 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 determines whether or not there is a request to switch each excess air ratio to λ2 while it is controlled to λ1 (step S1). λ1 and λ2 are different values. One of λ1 and λ2 is 1.0 or greater. The other of λ1 and λ2 is 1.5 or greater. That is, if there is a request to switch from one of lean combustion and stoichiometric combustion to the other, the determination in step S1 is Yes. Also, if there is a request to change the excess air ratio while continuing lean combustion, the determination in step S1 is Yes. Step S1 is an example of processing executed by the determination unit. If the determination in step S1 is No, 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 for controlling the excess air ratio of each of cylinders #1 to #4 so that the proportion R of L combustion strokes at λ2 among K consecutive combustion strokes in the engine 10 increases in M ​​steps from 0% to 100%. K is an integer greater than the number of cylinders N. L is an integer. M is an integer greater than N. R is a value that indicates the proportion 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 in FIG. 3 illustrates a case where a switch from λ1 to λ2 is required due to a request to increase the output of the engine 10. That is, the example in FIG. 3 illustrates a case where λ2 is smaller than λ1. The example in FIG. 3 illustrates a case where the excess air 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 at λ1 and λ2 during the transition process. The vertical axis indicates the cylinders #1 to #4, and the horizontal axis indicates the number of combustion strokes. In FIGS. 4A to 4D, the combustion stroke at λ1 is indicated by a dotted line, and the combustion stroke at λ2 is indicated by a solid line.

[0019] When the transition process starts at time t1, the first process is executed. As shown in FIG. 4A, in the first process, L=2 and R=20%. Here, combustion occurs 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 starts, the excess air ratios in cylinders #1 to #4 are controlled to λ1, so L=0 and R=0%.

[0020] At time t2, the second process is executed. As shown in FIG. 4B, in the second process, L=4 and R=40%. In the example of FIG. 4B, the excess air 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 excess air 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 are switched to λ2 in the second to fifth and seventh to tenth combustion strokes. 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. Note that for each of the first to fourth processes, K combustion strokes may be performed in only one cycle, or may be performed over multiple cycles. Furthermore, the first to fourth processes may be performed in different cycles.

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

[0024] For example, consider a case where 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. This may increase torque shock compared to the previous embodiment. In the previous embodiment, R can be increased in multiple stages regardless of the number of cylinders, further suppressing torque shock.

[0025] Here, in order to suppress torque shock, it is conceivable to gradually change the excess air ratios of all cylinders #1 to #4 from the above-mentioned λ1 to λ2. However, such a gradual change in the excess air ratio may increase NOx emissions. For example, from the stoichiometric air-fuel ratio to a predetermined lean air-fuel ratio, the increase in combustion temperature and the excess oxygen concentration promote the oxidation of nitrogen in the air, increasing NOx emissions. At a higher air-fuel ratio, the combustion temperature decreases and NOx emissions decrease. When the excess air ratio is gradually changed from λ1 to λ2 in this way, the air-fuel ratio passes through a region where NOx emissions increase. In the transition processing of this embodiment, the excess air ratios of cylinders #1 to #4 are controlled to λ1 or λ2, and the air-fuel ratio does not pass through a region where NOx emissions increase. Therefore, torque shock is suppressed while NOx emissions are also suppressed.

[0026] In the first process shown in FIG. 4A, as described above, K=10 and L=2. Here, 2 is a number other than 1, a number other than 10, and 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. As described above, 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, as described above, K=10 and L=8. If the number of combustion strokes at 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 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. Because L is a divisor of K, 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 the present invention is not limited to this. Furthermore, when an output increase request is made to the engine 10, the intake air amount Ga may be increased to an upper limit value while maintaining a constant excess air ratio, 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 as long as it is 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 located on the left bank, and cylinders #2, #4, and #6 are located on the right bank. Combustion occurs in the order of cylinders #1, #2, #3, #4, #5, and #6. In this modified example, N=6, K=10, M=7, and L=1, 2, 4, 5, 7, 8, and 10. The ratio R increases over 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 this modified example.

[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 ratio is switched to λ2 in the second to fifth and seventh to tenth combustion strokes. If the number of combustion strokes at 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 at 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 as defined 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

[Claim 1] a control unit that controls an intake air amount and a fuel injection amount of each of N (an integer of 2 or more) 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 λ1, When the determination unit makes a positive determination, the control unit controls each of the excess air ratios so that the ratio of the number of combustion strokes at λ2 to the number of consecutive K (an integer greater than N) combustion strokes increases in M ​​(an integer greater than N) steps from 0% to 100%; One of λ1 and λ2 is 1.0 or more, and the other of λ1 and λ2 is 1.5 or more, said N is 4, said M is 5, and said K is 10; The N cylinders are first, second, third, and fourth cylinders, In each stage, the combustion stroke is performed in the order of the first cylinder, the third cylinder, the fourth cylinder, the second cylinder, the first cylinder, the third cylinder, the fourth cylinder, the second cylinder, the first cylinder, and the third cylinder; In the first stage, the excess air ratios in the first and sixth combustion strokes are controlled to the λ2, and the excess air ratios in the second to fifth and seventh to tenth combustion strokes are controlled to the λ1. In the second stage, the excess air ratios in the second, fifth, seventh, and tenth combustion strokes are controlled to the λ2, and the excess air ratios in the first, third, fourth, sixth, eighth, and ninth combustion strokes are controlled to the λ1, In a third stage, the excess air ratios in the second, third, fifth, sixth, eighth, and ninth combustion strokes are controlled to the λ2, and the excess air ratios in the first, fourth, seventh, and tenth combustion strokes are controlled to the λ1, In the fourth stage, the excess air ratios in the second to fifth and seventh to tenth combustion strokes are controlled to the λ2, and the excess air ratios in the first and sixth combustion strokes are controlled to the λ1. In the fifth stage, each excess air ratio is controlled to λ2 in all combustion strokes. Engine control device.

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