Engine System

Abstract

To suppress emission of environmental load components even when a catalyst is not activated.SOLUTION: An engine system includes; an engine having a first cylinder, a second cylinder, and a connection port for connecting the first cylinder and the second cylinder in series; and a control device for controlling the engine. The control device has one or a plurality of processors, and one or a plurality of memories connected to the processors. The processor executes processing including: controlling the engine so that a fuel is burnt in a rich atmosphere in the first cylinder and the fuel is burnt in a stoichiometric atmosphere in the second cylinder in a cold state of the engine; and controlling the second cylinder to be in an intake stoke when the first cylinder is in an exhaust stroke, and introducing exhaust air of the first cylinder to the second cylinder via the connection port.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] For example, Patent Document 1 discloses an engine in which a branch pipe branching from an exhaust pipe of a cylinder on the exhaust stroke is connected to an intake pipe of a cylinder on the intake stroke. In this engine, the exhaust gas from the cylinder on the exhaust stroke is supplied to the cylinder on the intake stroke. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Jitszen No. 59-196566 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the engine is cold, from when the engine is started until the catalyst is activated, the catalyst that purifies the exhaust gas is not activated. Therefore, when the engine is cold, environmentally hazardous components such as hydrocarbons (HC), carbon monoxide (CO), soot (PM or PN), and nitrogen oxides (NOx) may be emitted into the atmosphere. The emission of environmentally hazardous components when the engine is cold is caused, for example, by fuel injected into the cylinder adhering to the wall surface of the combustion chamber. When the temperature of the wall surface of the combustion chamber is low, liquid fuel adhering to the wall surface is difficult to vaporize, and this fuel adhesion causes the emission of the environmentally hazardous components. However, the technology described in Patent Document 1 above was unable to address this problem.

[0005] Therefore, an object of the present invention is to provide an engine system that can suppress emissions of environmentally hazardous components even if the catalyst is not activated. [Means for solving the problem]

[0006] In order to solve the above problem, an engine system according to one embodiment of the present invention comprises: an engine having a first cylinder, a second cylinder, and a connection port connecting the first cylinder and the second cylinder in series; a catalyst provided in an exhaust passage connected to the engine; a valve mechanism that opens and closes the exhaust valve of at least the first cylinder; a control device for controlling the engine; Equipped with The control device one or more processors; one or more memories coupled to said processor; and The processor: The period from when the engine is started until the temperature of the catalyst reaches or exceeds the lower limit temperature at which the catalyst is activated. Controlling the engine so that fuel is burned in a rich atmosphere in the first cylinder and fuel is burned in a stoichiometric atmosphere in the second cylinder when the engine is in a cold state; closing the exhaust valve of the first cylinder by the valve mechanism; controlling the second cylinder to an intake stroke when the first cylinder is in an exhaust stroke, and introducing the exhaust gas from the first cylinder into the second cylinder through the connecting port; Execute the process including. [Effects of the Invention]

[0007] According to the present invention, it is possible to suppress the emission of environmentally hazardous components even if the catalyst is not activated. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of an engine system according to this embodiment. [Figure 2] FIG. 2 is a schematic diagram of the engine system showing the first and second cylinders in vertical cross section. [Figure 3] FIG. 3 is a schematic plan view of the first and second cylinders as viewed from above. [Figure 4] FIG. 4 is a diagram illustrating the stroke in each cylinder. [Figure 5] FIG. 5 is a diagram illustrating a special operation. [Figure 6] FIG. 6 is a diagram illustrating a normal operation. [Figure 7] FIG. 7 is a time chart illustrating the time progression of the control of the engine by the control device. [Figure 8] FIG. 8 is a flowchart illustrating the flow of the operation of the control device. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Specific dimensions, materials, numerical values, etc. shown in the embodiments are merely examples for facilitating understanding of the invention and do not limit the present invention unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are designated by the same reference numerals to avoid redundant explanation, and elements not directly related to the present invention are not shown.

[0010] 1 is a schematic diagram showing the configuration of an engine system 1 according to this embodiment. The engine system 1 includes an engine 10 and a control device 12. The engine 10 is mounted on, for example, a vehicle.

[0011] Engine 10 is, for example, a horizontally opposed engine and has a right bank 20 and a left bank 22. Engine 10 has four cylinders: A cylinder 30a, B cylinder 30b, C cylinder 30c, and D cylinder 30d. For example, A cylinder 30a and C cylinder 30c are provided in the right bank 20 of the horizontally opposed engine, and B cylinder 30b and D cylinder 30d are provided in the left bank 22 of the horizontally opposed engine. Alternatively, A cylinder 30a and C cylinder 30c may be provided in the left bank 22, and B cylinder 30b and D cylinder 30d may be provided in the right bank 20. Furthermore, A cylinder 30a, B cylinder 30b, C cylinder 30c, and D cylinder 30d may be collectively referred to simply as cylinders.

[0012] Here, cylinder C 30c in the right bank 20 is designated as the first cylinder, and cylinder A 30a in the right bank 20 is designated as the second cylinder. Cylinder D 30d in the left bank 22 is designated as the first cylinder, and cylinder B 30b in the left bank 22 is designated as the second cylinder. Engine 10 has a connection port 32 that connects the first and second cylinders in series. Connection port 32 communicates the combustion chamber of the first cylinder with the combustion chamber of the second cylinder. Specifically, cylinder C 30c, which is the first cylinder, and cylinder A 30a, which is the second cylinder, are connected by connection port 32 in the right bank 20, and cylinder D 30d, which is the first cylinder, and cylinder B 30b, which is the second cylinder, are connected by connection port 32 in the left bank 22.

[0013] The engine 10 has an intake valve 40, an exhaust valve 42, a first valve 44, a second valve 46, and a valve train 48. As will be described later, the intake valve 40 is provided in an intake port, and the exhaust valve 42 is provided in an exhaust port. The first valve 44 is provided on the first cylinder side of the connection port 32, and the second valve 46 is provided on the second cylinder side of the connection port 32. The valve train 48 opens and closes the intake valve 40, the exhaust valve 42, the first valve 44, and the second valve 46.

[0014] The control device 12 includes one or more processors 52 and one or more memories 54 connected to the processors 52. The memory 54 includes a ROM in which programs and the like are stored, and a RAM as a work area. The processor 52 of the control device 12 cooperates with the programs stored in the memory 54 to control the engine 10. The operation of the control device 12 will be described in detail later.

[0015] Fig. 2 is a schematic diagram of the engine system 1 showing the first and second cylinders in vertical cross section. Fig. 3 is a schematic plan view of the first and second cylinders as seen from above. In Figs. 2 and 3, C cylinder 30c and A cylinder 30a are shown as the first and second cylinders. Note that D cylinder 30d and B cylinder 30b are not shown because they have the same configuration as C cylinder 30c and A cylinder 30a.

[0016] The engine 10 includes a cylinder block 60, pistons 62, connecting rods 64, and a cylinder head 66. The C-cylinder 30c and the A-cylinder 30a are formed in the cylinder block 60. A piston 62 is housed in each cylinder. The piston 62 is connected to a crankshaft (not shown) via the connecting rod 64.

[0017] The cylinder head 66 is disposed on the opposite side of the cylinder block 60 from the crankshaft. The cylinder head 66 is disposed on each cylinder so as to cover the upper opening of each cylinder, and is connected to the cylinder block 60. A combustion chamber 68 is a space surrounded by the inner surfaces of the cylinders, the inner surface of the cylinder head 66, and the crown surface of the piston 62.

[0018] The cylinder head 66 has an intake port 70 and an exhaust port 72 for each cylinder. Specifically, the intake port 70 of the C cylinder 30c is connected to the combustion chamber 68 of the C cylinder 30c through an opening 74. The exhaust port 72 of the C cylinder 30c is connected to the combustion chamber 68 of the C cylinder 30c through an opening 76. The intake port 70 of the A cylinder 30a is connected to the combustion chamber 68 of the A cylinder 30a through the opening 74. The exhaust port 72 of the A cylinder 30a is connected to the combustion chamber 68 of the A cylinder 30a through the opening 76.

[0019] The intake valve 40 is provided in the intake port 70 and opens and closes an opening 74 of the intake port 70. When the opening 74 of the intake port 70 is opened by the intake valve 40, air is introduced into the combustion chamber 68 through the intake port 70. The exhaust valve 42 is provided in the exhaust port 72 and opens and closes an opening 76 of the exhaust port 72. When the opening 76 of the exhaust port 72 is opened by the exhaust valve 42, gas within the combustion chamber 68 is discharged through the exhaust port 72.

[0020] The connection port 32 is formed in the cylinder head 66. The first valve 44 is provided on the C cylinder 30c side of the connection port 32 and opens and closes an opening 80 on the C cylinder 30c side. The second valve 46 is provided on the A cylinder 30a side of the connection port 32 and opens and closes an opening 82 on the A cylinder 30a side. As will be described later, when the first valve 44 and the second valve 46 are opened, exhaust from the C cylinder 30c (first cylinder) is introduced through the connection port 32 into the combustion chamber 68 of the A cylinder 30a (second cylinder).

[0021] As shown in FIG. 3 , the C cylinder 30c has one opening 74 for the intake port 70 and one opening 76 for the exhaust port 72. The opening 74 for the intake port 70 of the C cylinder 30c is eccentric with respect to the central axis of the C cylinder 30c. The opening 76 for the exhaust port 72 of the C cylinder 30c is located on the opposite side of the central axis of the C cylinder 30c from the intake port 70. Similarly, the A cylinder 30a has one opening 74 for the intake port 70 and one opening 76 for the exhaust port 72. The opening 74 for the intake port 70 of the A cylinder 30a is eccentric with respect to the central axis of the A cylinder 30a. The opening 76 for the exhaust port 72 of the A cylinder 30a is located on the opposite side of the central axis of the A cylinder 30a from the intake port 70.

[0022] An opening 80 of the connection port 32 on the C cylinder 30c side is located in the gap between the opening 74 of the intake port 70 and the opening 76 of the exhaust port 72 in the C cylinder 30c, and is positioned closer to the A cylinder 30a. An opening 82 of the connection port 32 on the A cylinder 30a side is located in the gap between the opening 74 of the intake port 70 and the opening 76 of the exhaust port 72 in the A cylinder 30a, and is positioned closer to the C cylinder 30c.

[0023] As shown in FIG. 2, the cylinder head 66 is provided with an injector 84 and a spark plug 86 for each cylinder. The injector 84 is arranged with its nozzle facing the combustion chamber 68. The injector 84 injects fuel such as gasoline into the combustion chamber 68 at a predetermined timing. The spark plug 86 is arranged with its electrode facing the combustion chamber 68. The spark plug 86 ignites a mixture of air and fuel in the combustion chamber 68 at a predetermined timing to cause combustion. This combustion causes the piston 62 to reciprocate in the axial direction of the cylinder. The crankshaft rotates in accordance with the reciprocating motion of the piston 62.

[0024] Figure 4 is a diagram explaining the strokes in each cylinder. Each cylinder repeats the following strokes in the order of intake stroke, compression stroke, power stroke, and exhaust stroke. To prevent the same stroke from overlapping in each cylinder, the strokes in each cylinder are shifted relative to each other.

[0025] Specifically, when cylinder A 30a is on its intake stroke, cylinder B 30b is on its power stroke, cylinder C 30c is on its exhaust stroke, and cylinder D 30d is on its compression stroke. When cylinder A 30a is on its compression stroke, cylinder B 30b is on its exhaust stroke, cylinder C 30c is on its intake stroke, and cylinder D 30d is on its power stroke. When cylinder A 30a is on its power stroke, cylinder B 30b is on its intake stroke, cylinder C 30c is on its compression stroke, and cylinder D 30d is on its exhaust stroke. When cylinder A 30a is on its exhaust stroke, cylinder B 30b is on its compression stroke, cylinder C 30c is on its power stroke, and cylinder D 30d is on its intake stroke.

[0026] That is, when the first cylinder, C cylinder 30c, is on an exhaust stroke, the second cylinder, A cylinder 30a, is on an intake stroke. Similarly, when the first cylinder, D cylinder 30d, is on an exhaust stroke, the second cylinder, B cylinder 30b, is on an intake stroke.

[0027] When the first cylinder is on its exhaust stroke, the control device 12 causes the valve operating mechanism 48 to open the first valve 44 and the second valve 46. As a result, the exhaust gas from the first cylinder on its exhaust stroke is introduced into the second cylinder on its intake stroke through the connecting port 32. By controlling the second cylinder so that it is on its intake stroke when the first cylinder is on its exhaust stroke, the control device 12 can smoothly introduce the exhaust gas from the first cylinder into the second cylinder.

[0028] As shown in FIG. 2, the engine system 1 has an exhaust flow path 90, a catalyst 92, and an exhaust port 94. The exhaust flow path 90 is connected to the exhaust port 72 of the A-cylinder 30a, which is the second cylinder. Although not shown, the exhaust flow path 90 is also connected to the exhaust port 72 of the C-cylinder 30c, which is the first cylinder. The catalyst 92 is provided in the exhaust flow path 90. Specifically, the catalyst 92 is provided closer to the exhaust port 94 than the position where the exhaust flow path 90 extending from the A-cylinder 30a and the exhaust flow path 90 extending from the C-cylinder 30c join together. Exhaust gas discharged from the exhaust port 72 of the A-cylinder 30a flows through the exhaust flow path 90 and the catalyst 92 and is discharged from the exhaust port 94. The catalyst 92 purifies the exhaust gas flowing through the exhaust flow path 90.

[0029] The engine system 1 has an air-fuel ratio sensor 100 and a water temperature sensor 102. The air-fuel ratio sensor 100 is provided in the exhaust flow path 90 between the A-cylinder 30a and the catalyst 92. The air-fuel ratio sensor 100 detects the air-fuel ratio of the exhaust gas flowing through the exhaust flow path 90. The water temperature sensor 102 is provided in the flow path of the coolant that cools the engine 10, and detects the water temperature, which is the temperature of the coolant.

[0030] The control device 12 acquires the detection results of the air-fuel ratio sensor 100 and the water temperature sensor 102. The control device 12 controls the amount of fuel injected by the injector 84 based on the air-fuel ratio acquired from the air-fuel ratio sensor 100. The control device 12 estimates the temperature of the catalyst 92 based on the water temperature acquired from the water temperature sensor 102. Hereinafter, the temperature of the catalyst 92 may be referred to as the catalyst temperature.

[0031] The control device 12 switches the operation mode of the engine 10 between a normal operation mode and a special operation mode according to the estimated catalyst temperature. The normal operation mode is an operation mode in which the engine 10 operates without supplying exhaust gas from the first cylinder to the second cylinder. The special operation mode is an operation mode in which the engine 10 operates while supplying exhaust gas from the first cylinder to the second cylinder. Hereinafter, the operation of the engine 10 in the normal operation mode may be referred to as normal operation, and the operation of the engine 10 in the special operation mode may be referred to as special operation.

[0032] Figure 5 is a diagram illustrating the special operation. Figure 5 shows cylinder C 30c and cylinder A 30a as the first and second cylinders. The special operation is an operation in which the valve mechanism 48 opens and closes the first valve 44 and the second valve 46 according to the strokes of the first and second cylinders, respectively, to supply exhaust gas from the first cylinder to the second cylinder.

[0033] Although not shown, the valve train 48 includes a stop valve mechanism that can keep the exhaust valve 42 of the first cylinder closed. The stop valve mechanism may be, for example, a mechanism that stops the rotation of a cam, or a mechanism that causes the cam to swing free against a rocker arm, or any known technology may be applied.

[0034] In the special operation, as indicated by a cross A10 in Figure 5, the stop valve mechanism of the valve train 48 closes the opening 76 of the exhaust port 72 of the first cylinder. In contrast, the opening 74 of the intake port 70 of the first cylinder and the opening 80 of the connecting port 32 on the first cylinder side are opened and closed according to the stroke of the first cylinder. In addition, the opening 74 of the intake port 70 of the second cylinder, the opening 76 of the exhaust port 72 of the second cylinder, and the opening 82 of the connecting port 32 on the second cylinder side are opened and closed according to the stroke of the second cylinder.

[0035] When the first cylinder is on its intake stroke, air is introduced into the first cylinder through the intake port 70, as indicated by the solid arrow A12. When the first cylinder is on its exhaust stroke, exhaust gas from the first cylinder is supplied to the second cylinder through the connecting port 32, as indicated by the dashed-dotted arrow A14. When the first cylinder is on its exhaust stroke, the second cylinder is on its intake stroke. When the second cylinder is on its intake stroke, exhaust gas from the first cylinder is supplied to the second cylinder as described above, and air is introduced into the second cylinder through the intake port 70, as indicated by the solid arrow A16. When the second cylinder is on its exhaust stroke, exhaust gas from the second cylinder is discharged through the exhaust port 72, as indicated by the dashed-dotted arrow A18. In this way, the first and second cylinders are interconnected during this special operation.

[0036] Generally, before the engine 10 is started, the catalyst temperature is below a predetermined temperature. The predetermined temperature is set, for example, to the lower limit temperature at which the catalyst 92 is activated. When a predetermined time has elapsed since the engine 10 was started, the catalyst 92 is heated by the exhaust gas from the engine 10, and the catalyst temperature becomes equal to or higher than the predetermined temperature. Here, the period from when the engine 10 is started until the catalyst temperature becomes equal to or higher than the predetermined temperature is sometimes referred to as when the engine 10 is in a cold state. The special operation is performed when the engine 10 is in a cold state, when the catalyst temperature is below the predetermined temperature. In other words, the special operation is performed when the catalyst 92 is not activated.

[0037] When the catalyst temperature is below a predetermined temperature, the engine 10 has not yet warmed up, and therefore the temperature of the wall surface of the combustion chamber 68 of each cylinder is relatively low. When the temperature of the wall surface of the combustion chamber 68 of a cylinder is low, the fuel adhering to the wall surface is difficult to vaporize, and the fuel on the wall surface is not sufficiently mixed with the air, resulting in incomplete combustion of the fuel on the wall surface. This results in the generation of hydrocarbons (HC), carbon monoxide (CO), and soot (PM or PN). Hydrocarbons, carbon monoxide, and soot are environmentally hazardous components that may impose a burden on the environment if emitted into the atmosphere.

[0038] Furthermore, when fuel is burned in a stoichiometric atmosphere and the combustion temperature is relatively high, nitrogen oxides (NOx) are generated. Nitrogen oxides are environmentally hazardous components that may cause a burden on the environment if emitted into the atmosphere.

[0039] As a comparative example, there is an engine system in which, when the engine is cold, exhaust gas from the first cylinder is not supplied to the second cylinder, and the exhaust gas from the first cylinder is discharged from the exhaust port 72. Because the catalyst 92 is not activated when the engine is cold, the engine system of this comparative example may emit the above-mentioned environmentally hazardous components such as hydrocarbons, carbon monoxide, soot, and nitrogen oxides into the atmosphere.

[0040] In contrast, the control device 12 of the engine system 1 of this embodiment controls the engine 10 in a special operation when the engine 10 is cold. In the special operation, the control device 12 controls the engine 10 so that fuel is burned in a rich atmosphere in the first cylinder and in a stoichiometric atmosphere in the second cylinder. The rich atmosphere has a higher fuel ratio than the stoichiometric atmosphere. In the special operation, the control device 12 introduces exhaust gas from the first cylinder into the second cylinder through the connection port 32.

[0041] During the special operation, the control device 12 injects fuel from the injector 84 to create a rich atmosphere in the first cylinder. As a result, hydrocarbons, carbon monoxide, and soot are likely to be generated in the first cylinder not only from the incomplete combustion of fuel that has reached the wall of the combustion chamber 68 of the first cylinder, but also from the combustion of fuel that has not reached the wall. Hydrocarbons, carbon monoxide, and soot are also unburned fuel.

[0042] However, because the first cylinder has a rich atmosphere, nitrogen oxides are less likely to be generated in the first cylinder, and therefore exhaust gas containing a large amount of unburned fuel such as hydrocarbons, carbon monoxide, and soot, but with a reduced nitrogen oxide content, is introduced from the first cylinder to the second cylinder.

[0043] During the special operation, the control device 12 does not inject fuel from the injector 84 of the second cylinder, and instead uses unburned fuel supplied from the first cylinder to create a stoichiometric atmosphere in the second cylinder. The unburned fuel supplied from the first cylinder is sufficiently vaporized. Therefore, the unburned fuel supplied can be completely burned in the second cylinder. Furthermore, by not injecting fuel from the injector 84 of the second cylinder, the generation of additional unvaporized fuel can be suppressed. Therefore, incomplete combustion of fuel can be suppressed in the second cylinder.

[0044] Furthermore, the exhaust gas from the first cylinder contains a large amount of inert gas, such as the unburned fuel described above. The inert gas in the exhaust gas from the first cylinder reduces the combustion temperature in the second cylinder compared to when the exhaust gas from the first cylinder is not supplied. Although the second cylinder maintains a stoichiometric atmosphere, the reduced combustion temperature in the second cylinder reduces the generation of nitrogen oxides in the second cylinder.

[0045] As a result, exhaust gas containing reduced amounts of hydrocarbons, carbon monoxide, soot, and nitrogen oxides is discharged from the second cylinder into the exhaust flow path 90.

[0046] During special operation, the catalyst temperature is below a predetermined temperature, and the catalyst 92 is not activated. However, because exhaust gas with reduced contents of hydrocarbons, carbon monoxide, soot, and nitrogen oxides flows through the exhaust flow path 90, even if the catalyst 92 is not activated, it is possible to suppress environmentally harmful components emitted into the atmosphere from the exhaust port 94.

[0047] The control device 12 controls the fuel injection amount of the injector 84 of the first cylinder so that the air-fuel ratio measured by the air-fuel ratio sensor 100 becomes stoichiometric. As a result, the second cylinder is controlled to a stoichiometric atmosphere. Furthermore, because the exhaust gas from the first cylinder makes the second cylinder a stoichiometric atmosphere, the control device 12 ultimately controls the first cylinder to a rich atmosphere.

[0048] The control device 12 previously controlled the injector 84 of the second cylinder not to inject fuel. However, the control device 12 may inject fuel from the injector 84 of the second cylinder, provided that the first cylinder is in a rich atmosphere and the second cylinder is in a stoichiometric atmosphere. Because exhaust gas from the first cylinder is supplied to the second cylinder, even if fuel is injected into the second cylinder, the amount of fuel injected into the second cylinder is relatively small. Therefore, in this configuration, incomplete combustion in the second cylinder can be suppressed more effectively than in a configuration in which exhaust gas from the first cylinder is not supplied to the second cylinder. As a result, this configuration also suppresses the environmental load components emitted into the atmosphere from the exhaust port 94 when the engine 10 is cold.

[0049] Figure 6 is a diagram illustrating normal operation. In Figure 6, the C cylinder 30c and the A cylinder 30a are shown as the first and second cylinders. In normal operation, the valve mechanism 48 closes the first valve 44 and the second valve 46, preventing the exhaust gas from the first cylinder from being supplied to the second cylinder.

[0050] Although not shown, the valve stop mechanism of the valve train is configured to be able to keep the first valve 44 and the second valve 46 closed, similar to the exhaust valve 42 of the first cylinder.

[0051] In normal operation, as indicated by the cross A20 in Figure 6, the stop valve mechanism of the valve train 48 closes the opening 80 of the connecting port 32 on the first cylinder side and the opening 82 of the connecting port 32 on the second cylinder side. In contrast, the opening 74 of the intake port 70 of the first cylinder and the opening 76 of the exhaust port 72 of the first cylinder are opened and closed according to the stroke of the first cylinder. Similarly, the opening 74 of the intake port 70 of the second cylinder and the opening 76 of the exhaust port 72 of the second cylinder are opened and closed according to the stroke of the second cylinder.

[0052] When the first cylinder is on its intake stroke, air is introduced into the first cylinder through intake port 70, as indicated by solid arrow A22. When the first cylinder is on its exhaust stroke, exhaust gas from the first cylinder is discharged through exhaust port 72, as indicated by dashed-dotted arrow A24. When the second cylinder is on its intake stroke, air is introduced into the second cylinder through intake port 70, as indicated by solid arrow A26. When the second cylinder is on its exhaust stroke, exhaust gas from the second cylinder is discharged through exhaust port 72, as indicated by dashed-dotted arrow A28. Thus, during normal operation, the first and second cylinders operate independently of each other.

[0053] The normal operation is performed when the catalyst temperature is equal to or higher than a predetermined temperature, i.e., when the catalyst is activated.

[0054] Furthermore, in the special operation, fuel is not injected from the injector 84 of the second cylinder, but in the normal operation, fuel is injected from the injector 84 of the second cylinder, and the fuel injected from the injector 84 is burned.

[0055] In addition, in the special operation, the first cylinder is set to a rich atmosphere and the second cylinder is set to a stoichiometric atmosphere, but in the normal operation, the atmospheres of the first cylinder and the second cylinder may be set to any atmosphere depending on the driving situation of the vehicle, etc. Since the normal operation is performed when the catalyst 92 is activated, even if environmental load components are emitted from the first or second cylinder during the normal operation, the environmental load components are purified by the catalyst 92.

[0056] Figure 7 is a time chart illustrating the time progression of the control of the engine 10 by the control device 12. A solid line A30 in Figure 7 shows an example of the time progression of the catalyst temperature. A dashed-dotted line A32 in Figure 7 shows a predetermined temperature Tth, which is a threshold for switching the operation mode of the engine 10.

[0057] Assume that the engine 10 is started at timing t0 in FIG. 7. At timing t0, the catalyst temperature is at temperature T0, which is lower than predetermined temperature Tth, so the catalyst 92 is not activated. Also, because the catalyst temperature is lower than predetermined temperature Tth at timing t0, the control device 12 sets the operation mode of the engine 10 to a special operation mode. This controls the first cylinder to a rich atmosphere and the second cylinder to a stoichiometric atmosphere. Because the engine 10 is controlled in a special operation, it is possible to suppress environmental load components from being emitted into the atmosphere from the exhaust port 94, even if the catalyst 92 is not activated.

[0058] After time t0, the catalyst 92 is gradually heated by the exhaust gas from the engine 10. At time t1, the catalyst temperature reaches or exceeds a predetermined temperature Tth. When the catalyst temperature reaches or exceeds the predetermined temperature, the catalyst 92 is activated. At time t1, when the catalyst temperature reaches or exceeds the predetermined temperature Tth, the control device 12 switches the operation mode of the engine 10 from the special operation mode to the normal operation mode. The atmospheres of the first and second cylinders during normal operation can be any atmosphere. Because the catalyst 92 is activated, the environmental load components emitted from the engine 10 are purified by the catalyst 92.

[0059] Fig. 8 is a flowchart illustrating the flow of operations of the control device 12. The control device 12 executes the series of processes shown in Fig. 8 at predetermined interrupt timings that occur at predetermined control cycles while the engine 10 is stopped.

[0060] When a predetermined interrupt timing arrives, the control device 12 determines whether or not the engine 10 has been started (S10). If the engine 10 is stopped (NO in S10), the control device 12 ends the series of processes.

[0061] When the engine 10 is started (YES in S10), the control device 12 derives the catalyst temperature based on the water temperature measured by the water temperature sensor 102 (S11). Note that the catalyst 92 may be provided with a temperature sensor that directly detects the catalyst temperature, and the control device 12 may directly obtain the catalyst temperature using the temperature sensor.

[0062] Next, the control device 12 determines whether the catalyst temperature is equal to or higher than a predetermined temperature (S12). If the catalyst temperature is lower than the predetermined temperature (NO in S12), the control device 12 closes the exhaust valve 42 of the first cylinder using the valve mechanism 48 (S13) and performs a special operation on the engine 10 (S14). The control device 12 then returns to step S11 to again derive and compare the catalyst temperature. This allows the special operation to continue until the catalyst temperature reaches or exceeds the predetermined temperature. In the special operation, the first cylinder is set to a rich atmosphere, the second cylinder is set to a stoichiometric atmosphere, and the exhaust gas from the first cylinder is supplied to the second cylinder.

[0063] If the catalyst temperature is equal to or higher than the predetermined temperature in step S12 (YES in S12), the control device 12 releases the closed state of the exhaust valve 42 of the first cylinder (S15). As a result, the exhaust valve 42 of the first cylinder opens and closes according to the stroke of the first cylinder. Next, the control device 12 closes the first valve 44 and the second valve 46 using the valve mechanism 48 (S16), operates the engine 10 normally (S17), and ends the series of processes.

[0064] As described above, in the engine system 1 of this embodiment, the processor 52 executes a process to control the engine 10 so that, when the engine 10 is cold, the first cylinder burns fuel in a rich atmosphere and the second cylinder burns fuel in a stoichiometric atmosphere. Furthermore, when the engine 10 is cold, the processor 52 executes a process to control the second cylinder to an intake stroke when the first cylinder is on an exhaust stroke, and to introduce the exhaust gas from the first cylinder into the second cylinder through the connection port 32. As a result, unburned fuel contained in the exhaust gas from the first cylinder is burned in the second cylinder, and the generation of nitrogen oxides in the second cylinder is suppressed, so that exhaust gas with reduced environmental load components is emitted from the second cylinder.

[0065] Therefore, according to the engine system 1 of this embodiment, even if the catalyst 92 is not activated, it is possible to suppress the emission of environmental load components into the atmosphere.

[0066] While the present invention has been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to such embodiments. It is clear that those skilled in the art can conceive of various modifications and alterations within the scope of the claims, and it is understood that such modifications and alterations also fall within the technical scope of the present invention.

[0067] For example, in the above embodiment, the first cylinder, the second cylinder, and the connecting port 32 are provided in both the right bank 20 and the left bank 22 of the horizontally opposed engine. However, the first cylinder, the second cylinder, and the connecting port 32 may be provided in only one of the right bank 20 and the left bank 22 of the horizontally opposed engine. Furthermore, the engine 10 is not limited to a horizontally opposed engine, and may be any type of engine, such as a V-engine.

[0068] In the above embodiment, the first cylinder is provided with one intake port 70, one exhaust port 72, and one connecting port 32. However, the first cylinder may be provided with two intake ports 70, one exhaust port 72, and one connecting port 32. In the above embodiment, the second cylinder is provided with one intake port 70, one exhaust port 72, and one connecting port 32. However, the second cylinder may be provided with one intake port 70, two exhaust ports 72, and one connecting port 32. [Explanation of symbols]

[0069] 1 Engine System 10 Engine 12 Control device 20 Right Bank 22 Left Bank 30a A cylinder 30b B cylinder 30c C cylinder 30d D-cylinder 32 connection ports 44 First valve 46 Second valve 48 Valve train 52 processors 54 memory 72 Exhaust port 90 Exhaust flow path 92 Catalyst

Claims

1. an engine having a first cylinder, a second cylinder, and a connection port connecting the first cylinder and the second cylinder in series; a catalyst provided in an exhaust passage connected to the engine; a valve mechanism that opens and closes an exhaust valve of at least the first cylinder; a control device for controlling the engine; Equipped with The control device one or more processors; one or more memories coupled to the processor; and The processor: controlling the engine so that fuel is burned in a rich atmosphere in the first cylinder and fuel is burned in a stoichiometric atmosphere in the second cylinder when the engine is in a cold state, which is a period from when the engine is started until the temperature of the catalyst reaches or exceeds a lower limit temperature at which the catalyst is activated; closing the exhaust valve of the first cylinder by the valve mechanism; controlling the second cylinder to an intake stroke when the first cylinder is in an exhaust stroke, and introducing the exhaust gas from the first cylinder into the second cylinder through the connecting port; An engine system that performs processing including:

2. The processor: controlling the engine to inject fuel into the first cylinder and not inject fuel into the second cylinder when the engine is cold; The engine system of claim 1 , wherein the engine system performs a process including:

3. The processor, switching an operation mode of the engine between a normal operation mode in which the engine is operated without supplying exhaust gas from the first cylinder to the second cylinder and a special operation mode in which the engine is operated while supplying exhaust gas from the first cylinder to the second cylinder, according to the temperature of the catalyst; The engine system according to claim 1 or 2, wherein the engine system executes a process including the steps of:

4. a first valve capable of opening and closing an opening of the connection port on the first cylinder side; a second valve capable of opening and closing an opening of the connection port on the second cylinder side; Furthermore, the valve mechanism opens and closes the first valve and the second valve; The processor: If the temperature of the catalyst is lower than the lower limit temperature, the special operation mode is executed, and the first valve and the second valve are opened and closed by the valve mechanism according to the strokes of the first cylinder and the second cylinder, respectively, to operate the engine while supplying the exhaust gas of the first cylinder to the second cylinder; If the temperature of the catalyst is equal to or higher than the lower limit temperature, the normal operation mode is executed, the first valve and the second valve are closed by the valve mechanism, and the engine is operated normally without supplying exhaust gas from the first cylinder to the second cylinder. The engine system of claim 3 , wherein the engine system executes a process including:

5. the engine is a horizontally opposed engine, 5. The engine system according to claim 1, wherein the first cylinder and the second cylinder are provided on either one or both of a left bank and a right bank of the horizontally opposed engine.

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