Regeneration system

Abstract

To supply fuel to an exhaust pipeline by using a simple configuration.SOLUTION: A regeneration system S includes: a filter 3 provided in an exhaust pipeline 35 for discharging exhaust gas of an engine 1 to outside and collecting substances included in exhaust gas; an exhaust valve control section 623 that opens an exhaust valve 42 in a first cylinder group 21 in a compression stroke of a partial cylinder of a plurality of cylinders of the engine 1; and an injection control section 624 that injects a second injection amount of fuel smaller than a first injection amount of fuel that is injected to a combustion chamber 242 of the first cylinder group 21 with the exhaust valve 42 closed in the compression stroke of the first cylinder group 21, to the combustion chamber 242 of the first cylinder group 21 with the exhaust valve 42 opened in the compression stroke.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a regeneration system for regenerating a filter that collects substances contained in exhaust gas.

Background Art

[0002] Techniques for regenerating a DPF (Diesel Particulate Filter) that collects soot and the like contained in exhaust gas are known. In Patent Document 1, when the accumulated soot and the like reach a predetermined amount, fuel (gas oil) is directly injected into the exhaust gas pipeline from an injection unit on the upstream side of the DPF, supplied, and the fuel is burned near the filter to incinerate the soot and the like collected on the filter to regenerate the filter. A technique is disclosed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in order to supply fuel into the exhaust gas pipeline on the upstream side of the filter, an injection unit for injecting fuel into the exhaust gas pipeline, a pipe for supplying fuel to the injection unit, a pump, etc. are required, and the configuration for supplying fuel into the exhaust gas pipeline has become complicated.

[0005] Therefore, the present invention has been made in view of these points, and an object thereof is to supply fuel to the exhaust gas pipeline with a simple configuration.

Means for Solving the Problems

[0006] In an aspect of the present invention, there is provided a regeneration system including a filter provided in an exhaust pipe for discharging the exhaust of an engine to the outside to collect substances contained in the exhaust, an exhaust valve control unit for controlling opening and closing of an exhaust valve of some of a plurality of cylinders of the engine during a compression process of the some of the cylinders, and an injection control unit for controlling an injection unit for injecting fuel into a combustion chamber of the some of the cylinders. The exhaust valve control unit opens the exhaust valve during the compression process of the some of the cylinders when removing the substances collected by the filter. The injection control unit injects fuel in a second injection amount, which is less than a first injection amount of fuel injected into the combustion chamber of the some of the cylinders when the exhaust valve is closed during the compression process of the some of the cylinders, into the combustion chamber of the some of the cylinders in a state where the exhaust valve is open during the compression process.

[0007] The injection control unit may inject the fuel in the second injection amount into the combustion chamber of the some of the cylinders in a state where the exhaust valve is open during the compression process at the same timing as the timing of injecting fuel into the combustion chamber of the some of the cylinders in a state where the exhaust valve is closed during the compression process.

[0008] The regeneration system may further include a turbine provided in the exhaust pipe of a supercharger for compressing fresh air supplied to the engine, a bypass pipe capable of supplying the exhaust of the some of the cylinders downstream of the turbine in the exhaust pipe from between the engine and the turbine in the exhaust pipe, and a flow path control unit for supplying the exhaust of the some of the cylinders to the bypass pipe when fuel is injected into the combustion chamber of the some of the cylinders in a state where the exhaust valve is open during the compression process.

[0009] The exhaust pipe includes a first pipe for supplying the exhaust of the some of the cylinders to the turbine and a second pipe for supplying the exhaust of other cylinders different from the some of the cylinders to the turbine. The bypass pipe may supply the exhaust of the some of the cylinders downstream of the turbine in the exhaust pipe from between the engine and the turbine in the first pipe.

[0010] A first reflux pipeline for refluxing the exhaust gas of the part of the cylinders to the intake pipeline of the engine, and a second reflux pipeline for refluxing the exhaust gas of the other cylinders to the intake pipeline, wherein when fuel is injected into the combustion chamber of the part of the cylinders in which the exhaust valve is open during the compression process, the flow path control unit may supply a part of the exhaust gas of the other cylinders to the second reflux pipeline to reflux it to the intake pipeline, and it is not necessary to supply the exhaust gas of the part of the cylinders to the first reflux pipeline.

[0011] When the injection control unit injects fuel into the combustion chamber of the part of the cylinders in which the exhaust valve is open during the compression process, the injection control unit may inject fuel with a fourth injection amount that is larger than a third injection amount of fuel injected into the combustion chamber of other cylinders different from the part of the cylinders in a state where the exhaust valve of the part of the cylinders is closed during the compression process of the part of the cylinders into the combustion chamber of the other cylinders.

[0012] When the exhaust valve opens during the compression process of the part of the cylinders, the injection control unit may inject fuel with the fourth injection amount that is larger than the third injection amount by an amount corresponding to the load generated in the engine in a state where the exhaust valve is open during the compression process of the part of the cylinders into the combustion chamber of the other cylinders.

[0013] When it is necessary to remove the substance collected by the filter, the engine speed is equal to or lower than a predetermined speed, and the indicated injection amount of fuel injected into the combustion chamber is equal to or lower than a predetermined value, the exhaust valve control unit may open the exhaust valve during the compression process of the part of the cylinders.

Advantages of the Invention

[0014] According to the present invention, there is an effect that fuel can be supplied to the exhaust pipeline with a simple configuration.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0016] The regeneration system S is a system for removing substances deposited on the filter 35 that collects substances contained in the exhaust gas of the engine 1. The configuration of the regeneration system S will be described with reference to FIGS. 1, 2, and 3. FIG. 1 is a diagram for explaining the configuration of the regeneration system S. FIG. 2 is a schematic diagram of the cylinder of the engine 1. FIG. 3 is a diagram for explaining the configuration of the engine control device 6. The regeneration system S includes the engine 1, a plurality of cylinders 2, an exhaust pipe 3, an engine control device 6, an intake pipe 12, and a filter 35. Each of the plurality of cylinders 2 has an exhaust valve 42 and an injection unit 43 that injects fuel into the combustion chamber 242 of the cylinder 2.

[0017] The engine 1 is an internal combustion engine that burns and expands a mixture of fuel and fresh air (air) to generate power. The engine 1 is, for example, a diesel engine mounted on an automobile or a ship. The plurality of cylinders 2 includes four cylinders: a first cylinder 211, a second cylinder 212, a third cylinder 213, and a fourth cylinder 214. Hereinafter, when it is not necessary to distinguish the first cylinder 211, the second cylinder 212, the third cylinder 213, and the fourth cylinder 214, they will be referred to as the cylinder 2. The first cylinder 211 and the fourth cylinder 214, which are some of the plurality of cylinders 2 of the engine 1, are the first cylinder group 21. The second cylinder 212 and the third cylinder 213, which are other cylinders different from some of the plurality of cylinders 2 of the engine 1, are the second cylinder group 22.

[0018] The cylinder 2 has an intake valve 41, an exhaust valve 42, an injection unit 43, and a piston 241. The intake valve 41 and the exhaust valve 42 are closed at the start of the operating cycle of the engine 1. First, when the piston 241 moves downward, the intake valve 41 opens, and fresh air is sucked into the cylinder 2 (intake process). Next, when the piston 241 reaches the bottom dead center, the intake valve 41 closes, and when the piston 241 rises to the top dead center, the air is compressed (compression process). Subsequently, fuel is injected by the injection unit 43, and the fuel mixed with the compressed and heated air burns, and the expanded combustion gas pushes the piston 241 down to the bottom dead center (combustion process). Then, due to inertia and expansion in other cylinders 2, when the piston 241 rises to the top dead center again, the exhaust valve 42 is opened, and the combustion gas is pushed out of the cylinder 2 and discharged into the exhaust pipeline 3 as exhaust gas (exhaust process).

[0019] The intake pipeline 12 is a pipeline that supplies fresh air to the engine 1. The intake pipeline 12 branches so as to correspond to each cylinder 2 and is a pipeline for supplying fresh air to each cylinder 2. An intercooler 143 is provided in the intake pipeline 12. The intercooler 143 cools the fresh air supplied to the engine 1. The intercooler 143 is a heat exchanger that cools the fresh air by exchanging heat between the cooling water of the engine 1 or the outside air and the fresh air.

[0020] The exhaust pipeline 3 is a pipeline that discharges the exhaust of the engine 1 to the outside. A turbine 162 of a supercharger 16 that compresses the fresh air supplied to the engine 1 is provided in the exhaust pipeline 3. The turbine 162 rotates when the exhaust passes through it. The turbine 162 is connected to a compressor 161 of the supercharger 16. The compressor 161 is provided in the intake pipeline 12. The compressor 161 rotates in conjunction with the rotation of the turbine 162 to compress and supercharge the fresh air.

[0021] The exhaust pipeline 3 has a first pipeline 31, a second pipeline 32, and a third pipeline 33. The first pipeline 31 is connected to the first cylinder group 21 and is a pipeline for supplying the exhaust of the first cylinder group 21 to the turbine 162. The second pipeline 32 is connected to the second cylinder group 22 and is a pipeline for supplying the exhaust of the second cylinder group 22 to the turbine 162. The third pipeline 33 is a pipeline for discharging the exhaust that has passed through the turbine 162 to the outside.

[0022] The first reflux pipeline 131 connects the first pipeline 31 and the intake pipeline 12 and is a pipeline for refluxing the exhaust of the first cylinder group 21 to the intake pipeline 12. An exhaust cooler 141 is provided in the first reflux pipeline 131. The exhaust cooler 141 is a heat exchanger that cools the exhaust of the first cylinder group 21 by exchanging heat between the exhaust of the first cylinder group 21 and the cooling water of the engine 1 or the outside air. A first control valve 151 is provided between the intake pipeline 12 and the exhaust cooler 141 in the first reflux pipeline 131. The first control valve 151 adjusts the flow rate of the exhaust of the first cylinder group 21 flowing into the intake pipeline 12. The first control valve 151 adjusts the flow rate of the exhaust of the first cylinder group 21 passing through the first control valve 151 by adjusting the area of the flow path when an adjustment valve that adjusts the area of the flow path operates under the control of the engine control device 6.

[0023] The second reflux pipeline 132 connects the second pipeline 32 and the intake pipeline 12 and is a pipeline for refluxing the exhaust of the second cylinder group 22 to the intake pipeline 12. An exhaust cooler 142 is provided in the second reflux pipeline 132. The exhaust cooler 142 is a heat exchanger that cools the exhaust of the second cylinder group 22 by exchanging heat between the exhaust of the second cylinder group 22 and the cooling water of the engine 1 or the outside air. A second control valve 152 is provided between the intake pipeline 12 and the exhaust cooler 142 in the second reflux pipeline 132. The second control valve 152 adjusts the flow rate of the exhaust of the second cylinder group 22 flowing into the intake pipeline 12. The second control valve 152 adjusts the flow rate of the exhaust of the second cylinder group 22 passing through the second control valve 152 by adjusting the area of the flow path when an adjustment valve that adjusts the area of the flow path operates under the control of the engine control device 6.

[0024] A purification device 34 and a filter 35 are provided in the third pipeline 33. The purification device 34 is provided between the turbine 162 and the filter 35. The purification device 34 purifies the exhaust gas of the engine 1. The purification device 34 is, for example, a Diesel Oxidation Catalyst (DOC), but is not limited thereto.

[0025] The filter 35 is provided downstream of the purification device 34 in the third pipeline 33. The filter 35 is, for example, a DPD (Diesel Particulate Diffuser). The filter 35 collects substances contained in the exhaust gas. The substances contained in the exhaust gas are, for example, particulate matter, and a specific example is soot. When the amount of substances collected by the filter 35 exceeds the allowable capacity that the filter 35 can collect, the collection performance of the filter 35 deteriorates. Therefore, when the amount of substances collected by the filter 35 exceeds the allowable capacity, it is necessary to execute a regeneration control to remove the substances collected by the filter 35 and regenerate the collection performance.

[0026] The bypass pipeline 36 is a pipeline capable of supplying the exhaust gas of the first cylinder group 21 downstream of the turbine 162 in the exhaust pipeline 3 from between the engine 1 and the turbine 162 in the exhaust pipeline 3. Specifically, the bypass pipeline 36 connects the first pipeline 31 and the third pipeline, and supplies the exhaust gas of the first cylinder group 21 downstream of the turbine 162 in the exhaust pipeline 3 from between the engine 1 and the turbine 162 in the first pipeline. In other words, the bypass pipeline 36 bypasses the turbine 162 in the exhaust gas of the first cylinder group 21.

[0027] The three-way valve 153 is provided at the branch point where the bypass pipeline 36 branches from the first pipeline 31. The three-way valve 153 switches whether to bypass the turbine 162 in the exhaust gas of the first cylinder group 21. Specifically, the three-way valve 153 switches whether to supply the exhaust gas of the first cylinder group 21 to the turbine 162 or to supply the exhaust gas of the first cylinder group 21 to the bypass pipeline 36.

[0028] The engine control device 6 is an ECU (Electronic Control Unit) that controls the engine 1. When the regeneration control of the filter 35 is necessary, the engine control device 6 supplies unburned fuel to the exhaust pipe 3 and burns it near the filter 35, so that the substances collected by the filter 35 can be removed by incineration. Hereinafter, the specific configuration of the engine control device 6 will be described.

[0029] The engine control device 6 includes a storage unit 61 and a control unit 62. The storage unit 61 is a storage medium including a ROM (Read Only Memory), a RAM (Random Access Memory), a hard disk, and the like. The storage unit 61 stores programs executed by the control unit 62.

[0030] The control unit 62 is a computing resource including a processor such as a CPU (Central Processing Unit). By executing the programs stored in the storage unit 61, the control unit 62 realizes functions as an acquisition unit 621, a determination unit 622, an exhaust valve control unit 623, an injection control unit 624, and a flow path control unit 625.

[0031] The acquisition unit 621 acquires information regarding the regeneration system S from a sensor group 11 that detects the information. For example, the sensor group 11 includes sensors that detect the pressures upstream and downstream of the filter 35 in the third pipe 33. The acquisition unit 621 acquires the pressures upstream and downstream of the filter 35 from the sensor group 11. Further, the sensor group 11 includes a sensor that acquires the rotational speed of the engine 1 and a sensor that acquires the temperature of the cooling water of the engine 1. The acquisition unit 621 acquires the rotational speed of the engine 1 and the temperature of the cooling water of the engine 1 from the sensor group 11.

[0032] The acquisition unit 621 acquires the indicated injection amount of the fuel to be injected into the combustion chamber 242. For example, the acquisition unit 621 acquires the indicated injection amount corresponding to the operation amount of the operation unit that controls the output of the engine 1. To give a specific example, when the engine 1 is mounted on a vehicle, the acquisition unit 621 acquires a larger indicated injection amount as the depression amount of the accelerator pedal, which is the operation unit, is larger. Further, the acquisition unit 621 may acquire the indicated injection amount corresponding to the required torque for the engine 1. In this case, the acquisition unit 621 acquires a larger indicated injection amount as the required torque is larger.

[0033] The determination unit 622 determines whether regeneration control for removing the substances collected by the filter 35 is necessary. The determination unit 622 determines whether regeneration control is necessary by determining whether the amount of substances collected by the filter 35 exceeds the allowable amount. When the amount of substances collected by the filter 35 exceeds the allowable amount, it becomes difficult for the exhaust gas to pass through the filter 35, so the pressure of the exhaust gas flowing upstream of the filter 35 increases, and the pressure of the exhaust gas flowing downstream of the filter 35 decreases. Therefore, when the amount of substances collected by the filter 35 exceeds the allowable amount, the difference between the pressures of the two exhaust gases increases. Thus, the determination unit 622 determines whether the amount of substances collected by the filter 35 exceeds the allowable amount based on the pressure difference between the pressure of the exhaust gas upstream of the filter 35 and the pressure of the exhaust gas downstream of the filter 35, and determines the necessity of regeneration control.

[0034] When the pressure difference is less than a predetermined pressure, the determination unit 622 determines that the amount of substances collected by the filter 35 does not exceed the allowable amount and regeneration control is unnecessary. The predetermined pressure may be determined by the performance and specifications of the filter 35 and experiments. When the pressure difference is equal to or greater than the predetermined pressure, the exhaust valve control unit 623 determines that the amount of substances collected by the filter 35 exceeds the allowable amount and regeneration control is necessary.

[0035] The exhaust valve control unit 623 controls the opening and closing of the exhaust valves 42 of the plurality of cylinders 2. The exhaust valve control unit 623 performs opening and closing control of the exhaust valves 42 of each of the plurality of cylinders 2 according to the process of the operation cycle of the engine 1. For example, when the regeneration control of the filter 35 is not required, the exhaust valve control unit 623 closes the exhaust valves 42 of the first cylinder group 21 during the compression process of the first cylinder group 21. In the following description, the first cylinder group 21 in a state where the exhaust valve 42 is closed during the compression process may be referred to as the first cylinder group 21 during normal operation.

[0036] When regeneration control is necessary, the exhaust valve control unit 623 opens the exhaust valves 42 of the first cylinder group 21 (the first cylinder 211 and the fourth cylinder 214) during the compression process of the first cylinder group 21. Specifically, when regeneration control is necessary and the substances collected by the filter 35 need to be removed, the exhaust valve control unit 623 opens the exhaust valves 42 of the first cylinder group 21 during the compression process of the first cylinder group 21. In this case, the exhaust valve control unit 623 closes the exhaust valves 42 of the second cylinder group 22 (the second cylinder 212 and the third cylinder 213) during the compression process of the second cylinder group 22. In the following description, opening the exhaust valves 42 of the first cylinder group 21 during the compression process of the first cylinder group 21 may be referred to as compression and release of the first cylinder group 21. Also, the first cylinder group 21 in a state where the exhaust valves 42 of the first cylinder group 21 are open during the compression process may be referred to as the first cylinder group 21 during compression and release.

[0037] The injection control unit 624 controls each injection unit 43 of the first cylinder group 21 and the second cylinder group 22 to control the injection of fuel into the combustion chambers 242 of the first cylinder group 21 and the second cylinder group 22. For example, the injection control unit 624 controls the injection unit 43 to inject fuel into the combustion chamber 242 of the first cylinder group 21 during compression and release. That is, the injection control unit 624 injects fuel into the combustion chamber 242 of the first cylinder group 21 where the temperature of the air-fuel mixture does not reach the combustible temperature due to the opening of the exhaust valve 42 during the compression process.

[0038] When the injection control unit 624 injects fuel into the combustion chamber 242 of the first cylinder group 21 at the time of compression release, it injects fuel in a second injection amount that is less than the first injection amount. The first injection amount is the amount of fuel to be injected into the combustion chamber 242 of the first cylinder group 21 during normal operation. The injection control unit 624 injects fuel in the second injection amount into the combustion chamber 242 of the first cylinder group 21 at the time of compression release at the same timing as the timing when fuel is injected into the combustion chamber 242 of the first cylinder group 21 during normal operation. In other words, when the injection control unit 624 injects fuel into the first cylinder group 21 at the time of compression release, similar to normal operation, it injects fuel N into the combustion chamber 242 of the first cylinder group 21 at the time of compression release when the piston 241 is near the top dead center (see FIG. 2).

[0039] Incidentally, although the combustion chamber 242 is designed such that an air flow is generated to suppress the adhesion of the fuel N injected during the compression process to the inner wall, it is not designed assuming that the fuel N is injected during the exhaust process. Therefore, the air flow generated in the combustion chamber 242 during the exhaust process is different from the air flow in the combustion chamber 242 during the compression process and does not become an air flow that suppresses the adhesion of the injected fuel N to the inner wall. As a result, when the fuel N is injected from the injection unit 43 into the combustion chamber 242 during the exhaust process, the fuel N may adhere to the inner wall of the combustion chamber 242. In this case, there is a risk that the fuel N adhering to the inner wall may mix into the lubricating oil that lubricates the piston 241 and cause the engine 1 to malfunction. On the other hand, the injection control unit 624 according to the present embodiment injects the fuel N into the injection unit 43 into the combustion chamber 242 during the compression process in the same manner as during normal combustion. By doing so, the fuel N injected into the combustion chamber 242 of the first cylinder group 21 at the time of compression release diffuses in the combustion chamber 242 and is mixed with the fresh air in the same manner as during normal operation. That is, the fuel N rides on the air flow generated in the combustion chamber 242 during the compression process, which suppresses the adhesion of the fuel N to the inner wall, and diffuses, so that the adhesion of the fuel N to the inner wall of the combustion chamber 242 is suppressed. As a result, the mixing of the fuel N into the lubricating oil that lubricates the piston 241 is suppressed, and thus the malfunction of the engine 1 is suppressed.

[0040] At this time, since the pressure in the combustion chamber 242 of the first cylinder bank 21 decreases by compressing and releasing the first cylinder bank 21, the temperature of the air compressed in the combustion chamber 242 is lower than the temperature at which the air-fuel mixture can burn. Therefore, when fuel N is injected into the combustion chamber 242 of the first cylinder bank 21 during compression release, the air-fuel mixture of fresh air and fuel N does not burn. Then, the air-fuel mixture is discharged from the combustion chamber 242 to the first pipeline 31 in an unburned state during the exhaust process of the first cylinder bank 21. That is, the injection control unit 624 can supply the unburned fuel N to the exhaust pipeline 3.

[0041] The air-fuel mixture of the unburned fuel N and air supplied to the first pipeline 31 merges with the exhaust of the second cylinder bank 22 in the third pipeline 33 and decomposes into hydrocarbons by the heat of the exhaust of the second cylinder bank 22. The hydrocarbons are supplied to the purification device 34 which is an oxidation catalyst. When the hydrocarbons are supplied to the purification device 34, the oxidation reaction of the purification device 34 is promoted and the hydrocarbons burn. Then, due to the combustion of the hydrocarbons, the temperature of the exhaust flowing into the filter 35 rises. Specifically, the temperature of the exhaust becomes a temperature (for example, 500 degrees Celsius) at which the substance (soot) collected by the filter 35 can be incinerated. When the exhaust at a temperature at which the substance collected by the filter 35 can be incinerated reaches the filter 35, the substance (soot, etc.) collected by the filter 35 is incinerated.

[0042] By the way, if the unburned fuel is refluxed to the intake pipeline 12, the amount of fuel reaching the filter 35 may decrease, and the combustion temperature may not reach a sufficient level to burn the substance collected by the filter 35. Also, if the unburned fuel is refluxed to the intake pipeline 12, there is a possibility that excessive fuel may be supplied to the combustion chamber 242 of the second cylinder bank 22.

[0043] Therefore, when fuel is injected into the combustion chamber 242 of the first cylinder group 21 during compression release, the flow control unit 625 does not supply the unburned fuel-air mixture discharged from the first cylinder group 21 to the first reflux pipeline 131. FIG. 4 is a diagram for explaining the exhaust flow discharged from cylinder 2. The white-filled arrows in FIG. 4 indicate the flow of the unburned fuel-air mixture discharged from the first cylinder group 21. The black-filled arrows in FIG. 4 indicate the exhaust flow discharged from the second cylinder group 22. The symbol with a cross in the circle indicates that no gas flows through the pipeline.

[0044] The flow control unit 625 closes the first control valve 151 to prevent the unburned fuel-air mixture from being supplied to the first reflux pipeline 131 and to prevent the unburned fuel-air mixture from flowing back into the intake pipeline 12. As shown in FIG. 4, the mixture indicated by the white-filled arrow does not flow toward the first reflux pipeline 131 at the branch point between the first pipeline 31 and the first reflux pipeline 131, but instead flows toward the three-way valve 153. Thereby, the flow control unit 625 can supply all of the unburned fuel-air mixture to the third pipeline 33 and suppress the supply of excessive fuel to the combustion chamber 242 of the second cylinder group 22.

[0045] When unburned fuel is supplied to the turbine 162, there is a risk that the turbine 162 may malfunction due to fuel adhering to the blades or motor of the turbine 162. Therefore, the flow control unit 625 does not supply unburned fuel to the turbine 162. Specifically, when fuel is injected into the combustion chamber 242 of the first cylinder group 21 during compression release, the flow control unit 625 causes the unburned fuel-air mixture discharged from the first cylinder group 21 to be supplied to the bypass pipeline 36. More specifically, the flow control unit 625 controls the three-way valve 153 to connect the first pipeline 31 and the bypass pipeline 36 and cut off the connection between the first pipeline 31 and the turbine 162, thereby causing the unburned fuel-air mixture discharged from the first cylinder group 21 to be supplied to the bypass pipeline 36.

[0046] As shown in FIG. 4, the air-fuel mixture indicated by the white-filled arrow does not go toward the turbine 162 and all passes through the three-way valve 153 and heads toward the bypass pipeline 36. By doing so, the unburned fuel-air mixture passes through the bypass pipeline 36 that bypasses the turbine 162 and reaches the filter 35. That is, the flow path control unit 625 can suppress the supply of the air-fuel mixture to the turbine 162.

[0047] The flow path control unit 625 does not cause the unburned fuel-air mixture to flow back to the engine 1, but causes the exhaust gas of the second cylinder group 22 to flow back to the engine 1. Specifically, the flow path control unit 625 supplies a part of the exhaust gas of the second cylinder group 22 to the second reflux pipeline 132 and causes it to flow back to the intake pipeline 12. More specifically, the flow path control unit 625 causes the exhaust gas of the second cylinder group 22 to flow back to the engine 1 by opening the second control valve 152 and supplying the exhaust gas of the second cylinder group 22 to the second reflux pipeline 132.

[0048] As shown in FIG. 4, the exhaust gas discharged from the second cylinder group 22 heads toward each of the second pipeline 32 and the second reflux pipeline 132 at a branch point where it branches from the second pipeline 32 to the second reflux pipeline 132. The exhaust gas flowing through the second pipeline 32 passes through the turbine 162 and reaches the third pipeline 33. The exhaust gas flowing through the second reflux pipeline 132 passes through the exhaust cooler 142 and the second control valve 152 and reaches the intake pipeline 12. Thereby, the flow path control unit 625 can reduce the oxygen concentration of the intake air (the mixture of fresh air and exhaust gas) supplied to the second cylinder group 22, so that the amount of nitrogen oxides generated during combustion in the combustion chamber 242 of the second cylinder group 22 can be reduced.

[0049] When the first cylinder group 21 is compression-released, a load is applied to the engine 1. That is, since a negative work is generated in the engine 1 because the expansion stroke is performed in a state where the pressure of the air in the combustion chamber has decreased, a load is applied to the engine 1. In order to make the output of the engine 1 the desired output when the first cylinder group 21 is compression-released, it is necessary to increase the amount of fuel injected into the second cylinder group 22.

[0050] Therefore, when the injection control unit 624 compresses and releases the first cylinder group 21, it injects fuel with a fourth injection amount that is more than the third injection amount into the combustion chamber 242 of the second cylinder group 22. The third injection amount is the amount of fuel injected into the combustion chamber 242 of the second cylinder group 22 when the first cylinder group 21 operates normally. Specifically, when compressing and releasing the first cylinder group 21, the injection control unit 624 determines the fourth injection amount according to the load generated in the engine 1. More specifically, when compressing and releasing the first cylinder group 21, the injection control unit 624 determines, as the fourth injection amount, a value obtained by adding the amount of fuel corresponding to the load generated in the engine 1 to the third injection amount. The injection control unit 624 controls the injection unit 43 to inject the determined fourth injection amount of fuel into the combustion chamber 242 of the second cylinder group 22.

[0051] In this way, the injection control unit 624 increases the amount of fuel injected into the second cylinder group 22 of the engine 1 under load when the first cylinder group 21 is compressed and released. Thereby, the injection control unit 624 can increase the amount of fuel injected into the combustion chamber 242 of the second cylinder group 22 without substantially increasing the output of the engine 1. As a result, the combustion temperature of the air-fuel mixture rises, so the exhaust temperature rises, and the unburned fuel discharged from the first cylinder group 21 can be easily burned in the exhaust pipe 3.

[0052] When the state of the engine 1 satisfies a predetermined condition, the engine control device 6 may execute the regeneration control of the filter 35. For example, when the rotational speed of the engine 1 is equal to or lower than a predetermined rotational speed, the number of combustion times per unit time is less than when the rotational speed is greater than the predetermined rotational speed. Therefore, the exhaust temperature is difficult to rise, and the substances collected by the filter 35 are difficult to burn. Thus, when the regeneration control of the filter 35 is necessary and the rotational speed of the engine 1 is equal to or lower than the predetermined rotational speed, the engine control device 6 executes the regeneration control of the filter 35. Specifically, when the regeneration control of the filter 35 is necessary and the rotational speed of the engine 1 is equal to or lower than the predetermined rotational speed, the exhaust valve control unit 623 compresses and releases the first cylinder group 21, and the injection control unit 624 injects fuel with a second injection amount into the first cylinder group 21 during compression and release.

[0053] The predetermined rotational speed may be appropriately determined according to the specifications and experiments of the engine 1. The specific value of the predetermined rotational speed is, for example, 2000 revolutions per minute in the case of a diesel engine, but it is not limited thereto. By injecting fuel into the first cylinder group 21 at the time of compression release, unburned fuel is supplied to the exhaust pipe 3. In this way, the engine control device 6 can appropriately execute the regeneration control of the filter 35 by supplying unburned fuel to the exhaust pipe 3 in a situation where the temperature of the exhaust is not likely to rise.

[0054] When the rotational speed of the engine 1 is greater than the predetermined rotational speed, the number of combustions per unit time is larger than when the rotational speed is less than or equal to the predetermined rotational speed. Therefore, the temperature of the exhaust is likely to rise, and the substances collected by the filter 35 are likely to burn. Therefore, even when the regeneration control of the filter 35 is necessary, the engine control device 6 does not execute the regeneration control of the filter 35 when the rotational speed of the engine 1 is greater than the predetermined rotational speed. When the regeneration control of the filter 35 is necessary and the state where the rotational speed of the engine 1 is greater than the predetermined rotational speed continues for a predetermined time, the engine control device 6 may execute the regeneration control of the filter 35.

[0055] When performing the regeneration control in a state where a large load is applied to the engine 1, an excessive load is applied to the engine 1. Therefore, the engine control device 6 executes the regeneration control of the filter 35 when the regeneration control of the filter 35 is necessary, the rotational speed of the engine 1 is less than or equal to the predetermined rotational speed, and the indicated injection amount is less than or equal to the determination threshold value. Specifically, when the regeneration control of the filter 35 is necessary, the rotational speed of the engine 1 is less than or equal to the predetermined rotational speed, and the indicated injection amount is less than or equal to the determination threshold value, the exhaust valve control unit 623 performs compression release on the first cylinder group 21, and the injection control unit 624 injects fuel in a second injection amount into the first cylinder group 21 at the time of compression release. Even when the regeneration control of the filter 35 is necessary and the rotational speed of the engine 1 is less than or equal to the predetermined rotational speed, the engine control device 6 does not execute the regeneration control of the filter 35 when the indicated injection amount is greater than the determination threshold value.

[0056] The determination threshold is smaller than the maximum injection amount that can be injected into the combustion chamber 242 of the engine 1. Specifically, the determination threshold is smaller than the maximum injection amount by a predetermined value. The predetermined value is determined, for example, based on the specifications and experiments of the engine 1. The specific value of the determination threshold N is one-fifth (equivalent to 20%) of the maximum injection amount M, but is not limited thereto. By doing so, the engine control device 6 can suppress the execution of the regeneration control in a state where a large load is applied to the engine 1, so that an excessive load can be prevented from being applied to the engine 1.

[0057] [Process for regenerating the filter 35] FIG. 5 is a flowchart showing an example of the flow of the process for regenerating the filter 35. The process for regenerating the filter 35 is executed at predetermined intervals during the operation of the engine 1. In other words, the process for regenerating the filter 35 is automatically executed while the vehicle equipped with the engine 1 is running. The predetermined interval may be determined as appropriate, for example, 1 minute, but is not limited thereto. Further, it is assumed that the acquisition unit 621 acquires the pressures of the exhaust gas upstream and downstream of the filter 35, the indicated injection amount of the engine 1, and the rotational speed of the engine 1.

[0058] The determination unit 622 determines whether or not regeneration control of the filter 35 is necessary (step S1). Specifically, when the pressure difference between the pressure of the exhaust gas upstream of the filter 35 and the pressure of the exhaust gas downstream of the filter 35 is less than the determination threshold, the exhaust valve control unit 623 determines that regeneration control is unnecessary. When the determination unit 622 determines that regeneration control is unnecessary (No in step S1), the process for regenerating the filter 35 is terminated.

[0059] When the pressure difference is equal to or greater than a predetermined pressure, the determination unit 622 determines that regeneration control is necessary. When the determination unit 622 determines that regeneration control is necessary (Yes in step S1), it determines whether or not the rotational speed of the engine 1 is equal to or lower than a predetermined rotational speed (step S2). When the rotational speed of the engine 1 is greater than the predetermined rotational speed (No in step S2), the determination unit 622 terminates the process for regenerating the filter 35 because the number of combustion times per unit time is large and the temperature of the exhaust gas tends to be high.

[0060] When the rotational speed of the engine 1 is equal to or lower than a predetermined rotational speed (Yes in step S2), the determination unit 622 determines whether the indicated injection amount is equal to or lower than a determination threshold value (step S3). When the indicated injection amount is greater than the determination threshold value (No in step S3), the determination unit 622 ends the process of regenerating the filter 35 because the amount of fuel to be injected is large and the engine 1 is under a large load.

[0061] When the indicated injection amount is equal to or lower than the determination threshold value (Yes in step S3), the exhaust valve control unit 623 performs compression release on the first cylinder group 21 (step S4). Specifically, the exhaust valve control unit 623 opens the exhaust valve 42 of the first cylinder group 21 during the compression process of the first cylinder group 21. The injection control unit 624 controls the injection unit 43 to inject fuel in a second injection amount into the combustion chamber 242 of the first cylinder group 21 at the time of compression release (step S5). The engine control device 6 repeatedly executes the processes from step S1 to step S5 until it is determined that the regeneration control of the filter 35 is unnecessary.

[0062] [Effect of the regeneration system S] As described above, when removing the substances collected by the filter 35, the regeneration system S opens the exhaust valve 42 of the first cylinder group 21, which is a part of the cylinders, during the compression process of the first cylinder group 21, and injects fuel in a second injection amount into the combustion chamber 242 of the first cylinder group 21 with the exhaust valve 42 of the first cylinder group 21 open. The second injection amount is less than the first injection amount injected into the combustion chamber 242 with the exhaust valve 42 closed during the compression process.

[0063] In this way, since the exhaust valve 42 opens during the compression process, the pressure in the combustion chamber 242 decreases and the temperature of the compressed air decreases. That is, the regeneration system S can inject fuel into the combustion chamber 242 in a state where the temperature of the compressed air is lower than the combustion temperature of the air-fuel mixture. The fuel injected into the combustion chamber 242 is discharged in an unburned state without burning in the combustion chamber 242 and is supplied to the exhaust pipe 3.

[0064] As described above, without adding an injection device for injecting fuel into the exhaust pipe 3, or pipes and pumps for supplying fuel to the injection device, the regeneration system S can supply unburned fuel to the exhaust pipe 3 with a simple configuration of opening the exhaust valve 42 during the compression process of the first cylinder bank 21 and injecting fuel into the first cylinder bank 21 with the exhaust valve 42 open. Then, the unburned fuel supplied to the exhaust pipe 3 burns in the exhaust pipe 3 before reaching the filter 35. The combustion of the fuel in the exhaust pipe 3 raises the temperature of the exhaust gas to the temperature at which the substances collected by the filter 35 burn. As a result, the substances (such as soot) collected by the filter 35 are incinerated and removed.

[0065] As mentioned above, the present invention has been described using embodiments. However, the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of the gist. For example, all or part of the device can be configured by functionally or physically dispersing and integrating it in any unit. Also, new embodiments resulting from any combination of multiple embodiments are included in the embodiments of the present invention. The effects of the new embodiments resulting from the combination have the effects of the original embodiments combined.

Explanation of Reference Numerals

[0066] S Regeneration system 1 Engine 11 Sensor group 12 Intake pipe 16 Supercharger 131 First reflux pipe 132 Second reflux pipe 141 Exhaust cooler 142 Exhaust cooler 143 Intercooler 151 First control valve 152 Second control valve 153 Three-way valve 161 Compressor 162 Turbine 2 Cylinder 21 First cylinder bank 22 Second cylinder bank 211 First cylinder 212 Second cylinder 213 Third cylinder 214 Fourth cylinder 241 Piston 242 Combustion chamber 3 Exhaust pipe 31 32 Second pipe 33 Third pipe 34 Purification device 35 Filter 36 Bypass pipe 41 Intake valve 42 Exhaust valve 43 Injection part 6 Engine control device 61 Memory part 62 Control part 621 Acquisition part 622 Judgment part 623 Exhaust valve control part 624 Injection control part 625 Flow path control part

Claims

1. A filter provided in an exhaust pipe for discharging the exhaust of an engine to the outside, for collecting substances contained in the exhaust, an exhaust valve control unit for controlling the opening and closing of the exhaust valves of some of the plurality of cylinders of the engine during the compression stroke of the some of the cylinders, an injection control unit for controlling an injection unit for injecting fuel into the combustion chambers of the some of the cylinders, comprising: when the exhaust valve control unit removes the substances collected by the filter, the exhaust valve control unit opens the exhaust valve during the compression stroke of the some of the cylinders, the injection control unit injects fuel in an amount less than a first injection amount of fuel injected into the combustion chambers of the some of the cylinders with the exhaust valve closed during the compression stroke of the some of the cylinders into the combustion chambers of the some of the cylinders with the exhaust valve open during the compression stroke, a regeneration system.

2. The injection control unit injects the fuel in the second injection amount into the combustion chambers of the some of the cylinders with the exhaust valve open during the compression stroke at the same timing as the timing at which the fuel is injected into the combustion chambers of the some of the cylinders with the exhaust valve closed during the compression stroke. The regeneration system according to Claim 1.

3. a turbine provided in the exhaust pipe of a supercharger for compressing fresh air supplied to the engine, a bypass pipe capable of supplying the exhaust of the some of the cylinders from between the engine and the turbine in the exhaust pipe to downstream of the turbine in the exhaust pipe, a flow path control unit for supplying the exhaust of the some of the cylinders to the bypass pipe when fuel is injected into the combustion chambers of the some of the cylinders with the exhaust valve open during the compression stroke. The regeneration system according to Claim 1.

4. The exhaust pipe includes a first pipe for supplying the exhaust of the some of the cylinders to the turbine and a second pipe for supplying the exhaust of other cylinders different from the some of the cylinders to the turbine, the bypass pipe supplies the exhaust of the some of the cylinders from between the engine and the turbine in the first pipe to downstream of the turbine in the exhaust pipe. The regeneration system according to Claim 3.

5. a first recirculation pipe for recirculating the exhaust of the some of the cylinders to the intake pipe of the engine, a second recirculation pipe for recirculating the exhaust of the other cylinders to the intake pipe. When fuel is injected into the combustion chambers of the part of the cylinders in which the exhaust valves are open during the compression process, the flow path control unit supplies a part of the exhaust gas of the other cylinders to the second reflux pipeline and refluxes it to the intake pipeline, and does not supply the exhaust gas of the part of the cylinders to the first reflux pipeline. The regeneration system according to claim 4.

6. When the injection control unit injects fuel into the combustion chambers of the part of the cylinders in which the exhaust valves are open during the compression process, the injection control unit injects fuel with a fourth injection amount, which is larger than a third injection amount of fuel injected into the combustion chambers of other cylinders different from the part of the cylinders in a state where the exhaust valves of the part of the cylinders are closed during the compression process of the part of the cylinders, into the combustion chambers of the other cylinders. The regeneration system according to claim 1.

7. When the exhaust valve opens during the compression process of the part of the cylinders, the injection control unit injects fuel with the fourth injection amount, which is larger than the third injection amount, into the combustion chambers of the other cylinders according to an amount corresponding to the load generated in the engine in a state where the exhaust valve of the part of the cylinders is open during the compression process of the part of the cylinders. The regeneration system according to claim 6.

8. When it is necessary to remove the substance collected by the filter, the engine speed is equal to or lower than a predetermined speed, and the indicated injection amount of fuel injected into the combustion chamber is equal to or lower than a predetermined value, the exhaust valve control unit opens the exhaust valve during the compression process of the part of the cylinders. The regeneration system according to claim 1.

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