JP2020193616A - Engine system - Google Patents

Abstract

To provide an engine system capable of early activating a catalyst.SOLUTION: A control device for an engine system selects a temperature increase mode when a selective reduction type catalyst is in an inactive state. In the temperature increase mode, the control device for the engine system increases fuel injection amount so that output torque of an engine becomes request torque while executing a temperature increase opening/closing operation that comprises a first opening/closing operation for opening a valve in an expansion stroke and a second opening/closing operation for opening the valve through a valve closing period at least part of which is included in an exhaust stroke and in which the first opening/closing operation includes larger maximum lift amount and a longer valve opening period than those of the second opening/closing operation.SELECTED DRAWING: Figure 5

Description

The present invention relates to an engine system.

For example, as in Patent Document 1, an engine system using an engine is equipped with an exhaust purification device having a catalyst that adds a reducing agent to the exhaust gas and reduces NOx of the exhaust gas by using the added reducing agent. Has been done.

JP-A-2019-007351

In the exhaust gas purification device described above, it is desired to activate the catalyst at an early stage in order to effectively purify the exhaust gas at the time of cold start of the engine.
An object of the present invention is to provide an engine system capable of activating a catalyst at an early stage.

The engine system that solves the above problems includes an engine having an exhaust valve that can change the opening / closing timing of opening and closing the combustion chamber, an exhaust purification device having a catalyst that purifies the exhaust gas from the engine, and a control that controls the engine. An engine system including a device, wherein the control device has an acquisition unit that acquires a required torque from a driver and a state of the catalyst, and the engine so that the output torque of the engine becomes the required torque. The mode selection unit includes a fuel injection amount control unit that controls the fuel injection amount to the exhaust gas, a mode selection unit that selects a control mode of the engine system, and a valve control unit that controls the opening and closing of the exhaust valve. When the catalyst is in an inactive state, a temperature rise mode is selected as the control mode, and in the temperature rise mode, the valve control unit opens the exhaust valve during the expansion stroke. The first heated exhaust operation is more than the second heated exhaust operation, which is composed of a second temperature rising exhaust operation in which the exhaust valve is opened after a valve closing period including at least a part of the exhaust stroke. A temperature-increasing exhaust operation with a large maximum lift and a long valve opening period is performed.

According to the above configuration, in the expansion stroke, the exhaust gas flows out from the combustion chamber by the first temperature raising exhaust operation, so that an output loss occurs in the engine. Further, in the exhaust stroke, the exhaust gas remaining in the combustion chamber at the completion of the first temperature raising exhaust operation is compressed during the valve closing period, so that an output loss occurs in the engine. Therefore, the fuel injection amount required to realize the required torque can be increased by the amount of the output loss of the engine.

Further, the exhaust gas flowing out of the combustion chamber during the execution of the first temperature raising exhaust operation is an exhaust gas having a higher enthalpy than the exhaust gas flowing out of the combustion chamber without executing the first temperature raising exhaust operation. Therefore, the exhaust gas having a high enthalpy can be supplied to the exhaust purification device during the execution of the first temperature raising exhaust operation. In addition, the first temperature-increasing exhaust operation has a larger maximum lift amount than the second temperature-increasing exhaust operation, and the valve opening period is long, so that more high enthalpy exhaust gas can be supplied to the exhaust purification device. it can.

Further, the exhaust gas remaining in the combustion chamber when the first temperature-rising exhaust operation is completed is compressed during the valve closing period and then discharged from the combustion chamber by the second temperature-heating exhaust operation. Therefore, it is possible to suppress an increase in the EGR rate due to exhaust recirculation based on the backflow of the exhaust gas, so-called internal EGR (Exhaust Gas Recirculation). As a result, the amount of fresh air taken in by the engine increases, so that a higher enthalpy exhaust gas can be supplied to the exhaust purification device.

That is, according to the above configuration, when the catalyst is in an inactive state, the exhaust energy supplied to the exhaust purification device can be effectively increased while satisfying the required torque of the driver. As a result, the catalyst can be activated at an early stage.

In the engine system, it is preferable that the mode selection unit selects the temperature rise mode when the required torque is equal to or less than the selection permission value.
According to the above configuration, it is possible to suppress an excessive increase in the fuel injection amount required to secure the required torque of the driver in the temperature rising mode. As a result, the amount of unburned fuel contained in the exhaust gas can be reduced in the temperature rising mode.

In the engine system, the first temperature raising / exhausting operation may be an opening / closing operation in which the exhaust valve opens 40 ° CA or later after the compression top dead center.
If the angle is retarded larger than the compression top dead center, the fuel injected by the injector reaches the inner wall surface of the cylinder and easily mixes with the lubricating oil, and the EGR gas supplied to the cylinder and the mixed gas of the intake air cannot be mixed. Burning becomes difficult. Therefore, the fuel injection is controlled so that the air-fuel mixture of the mixed gas of EGR gas and intake air and the fuel injected by the injector, which is generally supplied to the cylinder, burns before 40 ° CA after the compression top dead center. To. Therefore, according to the above configuration, it is possible to reduce the amount of unburned fuel contained in the exhaust gas flowing out of the combustion chamber by the first temperature raising exhaust operation.

In the engine system, the second temperature raising / exhausting operation may be an opening / closing operation in which the exhaust valve closes before the intake valve that opens / closes the combustion chamber opens.
According to the above configuration, it is possible to prevent the exhaust gas flowing out of the combustion chamber from flowing into the combustion chamber again when the intake valve is opened. As a result, the exhaust gas flows out of the combustion chamber and the pressure in the combustion chamber decreases, so that the amount of fresh air increases. As a result, the amount of exhaust gas supplied to the catalyst can be increased, so that the exhaust energy can be increased.

In the engine system, the first temperature raising exhaust operation is preferably an exhaust operation in which the exhaust valve closes in the expansion stroke.
According to the above configuration, the amount of exhaust gas remaining in the combustion chamber at the completion of the first temperature raising / exhausting operation is larger than that in the case where the first temperature rising / exhausting operation is completed after the expansion stroke. As a result, the output loss of the engine during the valve closing period until the second temperature rising exhaust operation is started becomes large, so that the fuel injection amount for satisfying the required torque can be further increased. As a result, the exhaust energy supplied from the engine to the exhaust purification device can be increased more effectively.

In the engine system, the first temperature rising exhaust operation is preferably an opening / closing operation having a shorter valve opening period than the normal exhaust operation in the normal mode, which is the control mode when the catalyst is in the active state.

According to the above configuration, it is possible to increase the amount of exhaust gas remaining in the combustion chamber at the completion of the first temperature rise exhaust operation while supplying the exhaust gas having high enthalpy to the exhaust purification device by the first temperature rise exhaust operation. .. As a result, the output loss of the engine during the valve closing period until the second temperature rising exhaust operation is started becomes larger, so that the fuel injection amount for satisfying the required torque can be further increased. As a result, the exhaust energy supplied from the engine to the exhaust purification device can be further effectively increased.

In the engine system, the first temperature rising exhaust operation may be an opening / closing operation in which the exhaust valve closes in the exhaust stroke.
According to the above configuration, the amount of high enthalpy exhaust gas supplied to the exhaust purification device can be increased as compared with the case where the first temperature rising exhaust operation is completed in the expansion stroke, and the first temperature rising exhaust operation is completed. Sometimes the amount of exhaust gas remaining in the combustion chamber can be reduced. Thereby, the internal EGR can be effectively suppressed. As a result, the decrease in exhaust energy due to the increase in the EGR rate can be effectively suppressed.

In the engine system, the engine further includes an intake valve capable of changing the opening / closing timing of opening and closing the combustion chamber, and the second temperature rising exhaust operation includes an exhaust top dead center in the first half of the valve opening period. It is an opening / closing operation, and the valve control unit is configured to be able to control the opening / closing timing of the intake valve. The opening / closing operation of the intake valve is opened after the completion of the second temperature raising / exhausting operation in the temperature rising mode. It is advisable to perform a temperature rise intake operation with valve timing.

According to the above configuration, the output loss of the engine increases as the compression period of the exhaust gas in the exhaust stroke becomes longer. Therefore, the fuel injection amount required to realize the required torque is further increased. Further, by opening the intake valve after the completion of the second temperature rising exhaust operation, it is possible to suppress the exhaust gas from flowing back to the intake side, and it is possible to make the engine inhale more intake air. From these things, the exhaust energy supplied to the exhaust purification device can be increased.

In the engine system having the above configuration, the heating intake operation may be an opening / closing operation in which the normal exhaust operation in the normal mode, which is the control mode when the catalyst is in the active state, is retarded. According to the above configuration, a sufficient amount of intake air can be sucked into the engine by the temperature raising intake operation.

The figure which shows the schematic structure of the engine system in 1st Embodiment. The figure which shows typically an example of the cross-sectional structure of the engine in the vicinity of a cylinder in 1st Embodiment. A functional block diagram showing an example of a functional configuration of an engine system in the first embodiment. The flowchart which shows an example of the mode selection process in 1st Embodiment. The figure which shows an example of the relationship between the crank angle of a normal exhaust operation and a temperature rise exhaust operation, and a lift amount in 1st Embodiment. In the first embodiment, it is a graph which shows the result of the simulation which compared the normal mode and the temperature rise mode, (a) the graph which shows an example of the result of comparing the exhaust gas temperature when the engine rotation speed is 800 rpm. , (B) A graph showing an example of the result of comparing the exhaust gas temperature when the engine speed is 1080 rpm, and (c) A graph showing an example of the result of comparing the exhaust energy when the engine speed is 800 rpm. (D) The graph which shows an example of the result of having compared the exhaust energy when the engine speed is 1080 rpm. The figure which shows an example of the relationship between the crank angle and a lift amount of a normal exhaust operation and a temperature rise exhaust operation in a 2nd Embodiment. In the second embodiment, it is a graph which shows the result of the simulation which compared the normal mode and the temperature rise mode, (a) the graph which shows an example of the result of comparing the exhaust gas temperature when the engine speed is 800 rpm. , (B) A graph showing an example of the result of comparing the exhaust energy when the engine speed is 800 rpm. The figure which shows the schematic structure of the engine system in 3rd Embodiment. The figure which shows typically an example of the cross-sectional structure of the engine in the vicinity of a cylinder in 3rd Embodiment. In the third embodiment, a functional block diagram showing an example of a functional configuration of an engine system. The flowchart which shows an example of the mode selection process in 3rd Embodiment. In the third embodiment, the figure which shows an example of the relationship between the crank angle of a normal exhaust operation and a temperature rise exhaust operation, and a lift amount.

(First Embodiment)
A first embodiment of the engine system will be described with reference to FIGS. 1 to 6. First, a schematic configuration of the engine system will be described with reference to FIG.

As shown in FIG. 1, the engine system includes a diesel engine 10 (hereinafter referred to as an engine 10). The engine 10 includes an engine block 12 having a plurality of cylinders 11. Fuel is injected into each cylinder 11 from an injector 13 to which fuel of a predetermined pressure is supplied from a common rail. The intake manifold 14 and the exhaust manifold 15 are connected to the engine block 12. An intake passage 16 through which air taken in by the engine 10 flows is connected to the intake manifold 14, and an exhaust passage 17 through which the exhaust gas discharged by the engine 10 flows is connected to the exhaust manifold 15.

As shown in FIG. 2, the engine block 12 has a cylinder block 12A in which the cylinder 11 is formed and a cylinder head 12B connected to the cylinder block 12A. The cylinder head 12B closes the opening of the cylinder 11 formed in the cylinder block 12A. The engine 10 has a piston 20 that is housed so as to be movable up and down with respect to each cylinder 11. The space surrounded by the cylinder block 12A, the cylinder head 12B, and the piston 20 is a combustion chamber 21 in which the injector 13 injects fuel and the fuel is burned. The piston 20 is connected to the crankshaft 23 shown in FIG. 1 via a connection rod 22. The crankshaft 23 is rotationally driven by the piston 20 moving up and down in the cylinder 11. The cylinder head 12B is formed with an intake port 25 connected to the intake manifold 14 and an exhaust port 26 connected to the exhaust manifold 15 for each cylinder 11.

The engine 10 has an intake valve 27 and an exhaust valve 28. The intake valve 27 is driven by the intake side valve mechanism 29, and opens and closes the combustion chamber 21 with respect to the intake manifold 14 by opening and closing the intake port 25. The exhaust valve 28 is driven by the exhaust side valve mechanism 30, and opens and closes the exhaust port 26 to open and close the combustion chamber 21 with respect to the exhaust manifold 15. The exhaust side valve mechanism 30 is a variable valve mechanism configured so that the opening / closing timing including the lift amount of the exhaust valve 28 can be changed. The exhaust side valve mechanism 30 may be a cam switching type variable valve mechanism, or may be a variable valve mechanism whose lift amount and opening / closing timing can be changed by an electronically controlled actuator.

As shown in FIG. 1, the engine system includes a turbocharger 35. The turbocharger 35 has a compressor 36, an intercooler 37, and a turbine 38. The compressor 36 and the intercooler 37 are arranged in the intake passage 16. The compressor 36 compresses the air that has passed through the air cleaner 39, and the intercooler 37 cools the air compressed by the compressor 36. The turbine 38 is arranged in the exhaust passage 17. The turbine 38 uses the exhaust energy, which is the energy of the exhaust gas, to rotate the compressor 36.

The engine system includes an EGR (Exhaust Gas Recirculation) device 40. The EGR device 40 is configured to be able to execute an external EGR that recirculates exhaust gas from the exhaust side to the intake side through the EGR passage 41 that connects the exhaust manifold 15 and the intake passage 16. The EGR passage 41 is provided with an EGR cooler 42 and an EGR valve 43. When the EGR valve 43 is in the open state, a mixed gas of EGR gas and intake air is supplied to the cylinder 11 as a working gas. When the EGR valve 43 is in the closed state, intake air is supplied to the cylinder 11 as a working gas. In the cylinder 11, the air-fuel mixture of the working gas and the fuel injected by the injector 13 burns. The exhaust gas from the cylinder 11 flows into the exhaust passage 17 through the exhaust manifold 15 and then flows into the turbine 38. The ratio of EGR gas to the working gas sucked by the engine 10 is called the EGR rate.

The engine system includes an exhaust gas purification device 45. Exhaust gas that has passed through the turbine 38 flows into the exhaust purification device 45. The exhaust gas purification device 45 has an addition unit 46 and a selective reduction catalyst 47. The selective reduction catalyst 47 is housed in the enlarged diameter portion 17A constituting the exhaust passage 17.

The adding unit 46 adds a reducing agent to the exhaust gas flowing into the enlarged diameter portion 17A. The addition unit 46 includes a reducing agent passage 49 connected to a tank 48 for storing the reducing agent. A pump 50 is arranged in the reducing agent passage 49. The pump 50 pumps the reducing agent in the tank 48 to the addition valve 51 at a predetermined pressure. The addition valve 51 is an electronically controlled injection valve having a built-in valve mechanism, and adds a reducing agent to the exhaust gas when the valve mechanism is in the open state.

The selective reduction catalyst 47 reduces NOx contained in the exhaust gas to nitrogen and water by using the reducing agent added by the addition unit 46. The selective reduction catalyst 47 is, for example, a flow-through type monolith carrier made of ceramic or stainless steel having excellent heat resistance, in which various catalyst metals are held. The selective reduction catalyst 47 is in an active state when the catalyst temperature Tc, which is the temperature thereof, is within a predetermined temperature range. The lower limit of this temperature range is the lower limit active temperature TcL.

An example of the selective reduction catalyst 47 is a urea SCR catalyst. In this case, the addition unit 46 adds urea water as a reducing agent, and the selective reduction catalyst 47 reacts ammonia obtained by hydrolyzing urea water with NOx contained in the exhaust gas to reduce NOx to nitrogen or water. .. The selective reduction catalyst 47 is configured by allowing the monolith carrier to hold various catalyst metals such as copper-based, iron-based, and vanadium-based. The selective reduction catalyst 47 has, for example, a temperature range of 150 ° C. to 350 ° C. as an active temperature.

The exhaust purification device 45 has a filter for capturing particulate matter contained in the exhaust gas, a pre-stage oxidation catalyst for oxidizing the unburned fuel contained in the exhaust gas, and the like upstream of the addition valve 51 in the exhaust passage 17. You may have. Further, the exhaust purification device 45 may have a post-stage oxidation catalyst or the like that oxidizes ammonia or the like contained in the exhaust gas that has passed through the selective reduction catalyst 47 downstream of the selective reduction catalyst 47 in the exhaust passage 17. .. Further, the exhaust purification device 45 may include, as the selective reduction catalyst 47, a catalyst that reduces NOx using light oil as a fuel of the engine 10 as a reducing agent, a so-called HC-SCR catalyst.

The engine system is equipped with various sensors. The engine system includes a crank angle sensor 55, a catalyst temperature sensor 56, and an accelerator opening sensor 57. The crank angle sensor 55 detects the crank angle, which is the rotation angle of the crankshaft 23 driven by the engine 10. The catalyst temperature sensor 56 detects the catalyst temperature Tc, which is the temperature of the selective reduction catalyst 47. The accelerator opening sensor 57 detects the accelerator opening ACC based on the amount of depression of the accelerator pedal 57a operated by the driver. The various sensors output signals indicating the detected values to the control device 60 that controls the engine system in an integrated manner.

The control device 60 will be described with reference to FIGS. 3 to 6. The control device 60 can be configured as a circuit including one or more dedicated hardware circuits such as an ASIC, one or more processors operating according to a computer program (software), or a combination thereof. The processor includes a CPU and a memory such as a RAM and a ROM, and the memory stores a program code or a command configured to cause the CPU to execute a process. Memory or computer-readable media includes any available medium accessible by a general purpose or dedicated computer.

As shown in FIG. 3, the control device 60 has an acquisition unit 61, a mode selection unit 62, a fuel injection control unit 63, an EGR control unit 64, an addition control unit 65, and a functional unit that functions by executing various computer programs. It has a valve control unit 66.

The acquisition unit 61 acquires various information through an input interface (not shown). The acquisition unit 61 acquires the crank angle based on the detection signal output by the crank angle sensor 55. The acquisition unit 61 acquires the catalyst temperature Tc as the state of the selective reduction catalyst 47 based on the detection signal output by the catalyst temperature sensor 56. The acquisition unit 61 acquires the accelerator opening ACC based on the detection signal output by the accelerator opening sensor 57. Further, the acquisition unit 61 calculates the engine speed Ne based on the amount of change in the crank angle, and acquires the required torque L from the driver based on the calculated engine speed Ne and the accelerator opening ACC.

The mode selection unit 62 selects the control mode of the engine system. The mode selection unit 62 executes a mode selection process for selecting a control mode for fuel injection by the injector 13 and exhaust operation of the exhaust valve 28 based on various information acquired by the acquisition unit 61. The mode selection unit 62 selects a normal mode or a temperature rise mode through the mode selection process. The temperature raising mode is a control mode in which the exhaust energy supplied to the exhaust purification device 45 is increased to prioritize the temperature rise of the selective reduction catalyst 47. The normal mode is a control mode in which the heat retention of the selective reduction catalyst 47 and the reduction of fuel consumption are prioritized over the temperature rise of the selective reduction catalyst 47.

The mode selection process executed by the mode selection unit 62 will be described with reference to FIG. The mode selection unit 62 repeatedly executes the mode selection process while the engine 10 is operating.
As shown in FIG. 4, in the mode selection process, the mode selection unit 62 determines whether or not the required torque L based on the accelerator opening ACC and the engine speed Ne acquired by the acquisition unit 61 is equal to or less than the selection permission value L1. Is determined (step S101). The selection permission value L1 is an upper limit value of the required torque L capable of executing the temperature rising mode, and the details thereof will be described later.

When the required torque L is equal to or less than the selection permission value L1 (step S101: YES), the mode selection unit 62 determines whether or not the catalyst temperature Tc acquired by the acquisition unit 61 is less than the lower limit active temperature TcL (step). S102). When the catalyst temperature Tc is less than the lower limit active temperature TcL (step S102: YES), the mode selection unit 62 selects the temperature rising mode (step S103) and temporarily ends a series of processes. On the other hand, when the required torque L is larger than the selection permission value L1 (step S101: NO) and when the catalyst temperature Tc is equal to or higher than the lower limit active temperature TcL (step S102: NO), the mode selection unit 62 sets the normal mode. Select (step S104) to temporarily end a series of processes.

As shown in FIG. 3, the fuel injection control unit 63 controls fuel injection by each injector 13 by outputting a control signal through an output interface (not shown). The fuel injection control unit 63 controls fuel injection by each injector 13 based on the accelerator opening ACC and engine speed Ne acquired by the acquisition unit 61, the control mode selected by the mode selection unit 62, and the like. The fuel injection control unit 63 holds a fuel map in which the fuel injection amount is defined for each accelerator opening degree ACC and engine speed Ne in a predetermined area of the memory. The fuel injection control unit 63 holds a normal map 67, which is a fuel map used in the normal mode, and a temperature rise map 68, which is a fuel map used in the temperature rise mode, in a predetermined area of the memory. The fuel injection control unit 63 controls the fuel injection amount by using the fuel map corresponding to the control mode selected by the mode selection unit 62.

The EGR control unit 64 controls the opening degree of the EGR device 40, specifically, the EGR valve 43, by outputting a control signal through an output interface (not shown). The EGR control unit 64 controls the EGR valve 43 based on the control mode selected by the mode selection unit 62, and controls the amount of EGR, which is the amount of EGR gas. When the control mode is the normal mode, the EGR control unit 64 controls the opening degree of the EGR valve 43 so that the exhaust gas is recirculated by the amount of EGR suitable for the operating state of the engine 10 at that time. When the control mode is the temperature rising mode, the EGR control unit 64 prohibits the external EGR by keeping the EGR valve 43 in the closed state.

The addition control unit 65 controls the opening and closing of the addition unit 46 of the exhaust gas purification device 45, specifically, the addition valve 51, by outputting a control signal through an output interface (not shown). The addition control unit 65 controls the addition amount and addition timing of urea water by the addition valve 51 based on the control mode selected by the mode selection unit 62. When the control mode is the normal mode, the addition control unit 65 controls the opening and closing of the addition valve 51 so that an amount of urea water suitable for the operating state of the engine 10 at that time is added. When the control mode is the temperature rise mode, the addition control unit 65 prohibits the addition of urea water by keeping the addition valve 51 in a closed state.

The valve control unit 66 controls the opening / closing operation of the exhaust valve 28 through the exhaust side valve mechanism 30 by outputting a control signal through an output interface (not shown). The valve control unit 66 controls the lift amount and opening / closing timing of the exhaust valve 28 based on the control mode selected by the mode selection unit 62. The valve control unit 66 causes the exhaust valve 28 to perform a normal exhaust operation in the normal mode. The valve control unit 66 causes the exhaust valve 28 to perform a temperature rise exhaust operation in the temperature rise mode.

The normal exhaust operation and the temperature rising exhaust operation will be described with reference to FIG. The crank angle shown in FIG. 5 indicates a crank angle with reference to the compression top dead center (= 0 ° CA), which is the top dead center of the compression stroke. Further, the description in parentheses shown below indicates the crank angle shown in FIG.

As shown in FIG. 5, in the normal exhaust operation, the valve is opened shortly before reaching the expansion bottom dead center (= 180 ° CA), which is the bottom dead center of the expansion stroke, and the exhaust is on the exhaust, which is the top dead center of the exhaust stroke. It is an opening / closing operation that closes the valve near the dead center (= 360 ° CA).

The temperature-increasing exhaust operation is composed of a first temperature-heating exhaust operation that opens the valve during the expansion stroke and a second temperature-heating exhaust operation that opens at least a part of the valve after a valve closing period included in the exhaust stroke.
The first temperature-rising exhaust operation is an exhaust operation in which the maximum lift amount is larger and the valve opening period is longer than that of the second temperature-heating exhaust operation. The first temperature rising exhaust operation is an opening / closing operation in which the valve opening time is earlier and the valve opening period is shorter than the normal exhaust operation. For example, the first temperature rising exhaust operation is set to less than half of the normal exhaust operation for each of the maximum lift amount and the valve opening period. The first heating / exhausting operation is an opening / closing operation in which the valve is opened 40 ° CA or later after the compression top dead center (= 0 ° CA), which is the top dead center of the compression stroke, and is closed in the expansion stroke.

The second heated exhaust operation is an opening / closing operation in which the valve is opened in the latter half of the exhaust stroke and closed before the intake valve 27 is opened near the exhaust top dead center (= 360 ° CA). For example, in the second temperature raising / exhausting operation, each of the maximum lift amount and the valve opening period is set to half or less of the first temperature rising / exhausting operation.

The operation of the temperature rising exhaust operation of the first embodiment will be described.
During the execution of the first temperature rising exhaust operation, a part of the exhaust gas in the combustion chamber 21 becomes a choked flow and flows out to the exhaust port 26 without pressing the piston 20. That is, during the execution of the first temperature raising exhaust operation, an output loss (hereinafter referred to as an outflow loss) is generated in the engine 10 by the amount of the exhaust gas flowing out from the combustion chamber 21. Further, the exhaust gas remaining in the combustion chamber 21 when the first temperature rising exhaust operation is completed is compressed by the piston 20 during the valve closing period between the first temperature rising exhaust operation and the second temperature rising exhaust operation. This causes an output loss (hereinafter referred to as a compression loss) in the engine 10. The temperature rise map 68 held by the fuel injection control unit 63 is a fuel injection that satisfies the driver's required torque L after adding the above-mentioned outflow loss and compression loss based on the results of experiments and simulations performed in advance. The amount is specified. That is, the temperature rise map 68 defines a value equal to or higher than the value specified in the normal map 67 for the same address based on the accelerator opening degree ACC and the engine speed Ne. As a result, the exhaust energy supplied to the exhaust purification device 45 in the temperature rising mode can be increased as compared with the normal mode under the condition that the required torque L is the same.

On the other hand, if the fuel injection amount required to realize the required torque L is excessively increased, the amount of unburned fuel contained in the exhaust gas will increase. In this respect, in the mode selection process described above, the selection permission value L1 is set as the upper limit value of the required torque L that can execute the temperature rising mode. The selection permission value L1 is set to a value that can realize the required torque L while reducing the unburned fuel contained in the exhaust gas. The selection permission value L1 is set to a value at which the operating state of the engine 10 is determined to be a low load state, for example, in the normal mode, based on the results of experiments and simulations performed in advance.

The exhaust gas flowing out of the combustion chamber 21 during the execution of the first temperature raising exhaust operation does the work of pushing the piston 20 more than the exhaust gas discharged from the combustion chamber 21 without executing the first temperature rising exhaust operation. Exhaust gas with high enthalpy as much as it is not. Therefore, the exhaust gas having a higher enthalpy can be supplied to the exhaust purification device 45 during the execution of the first temperature raising exhaust operation. Moreover, since the first temperature-increasing exhaust operation has a larger maximum lift amount than the second temperature-increasing exhaust operation and the valve opening period is a long opening / closing operation, a larger amount of high enthalpy exhaust gas can be exhausted. Can be supplied to. As a result, the exhaust energy supplied to the exhaust purification device 45 can be effectively increased.

The exhaust gas remaining in the combustion chamber 21 when the first temperature-rising exhaust operation is completed flows out from the combustion chamber 21 to the exhaust port 26 by the second temperature-heating exhaust operation. Thereby, the pressure of the combustion chamber 21 at the exhaust top dead center can be reduced, and the increase in the EGR rate due to the EGR based on the backflow of the exhaust gas, that is, the so-called internal EGR, can be suppressed. As a result, the amount of fresh air taken in by the engine 10 increases, so that a higher enthalpy exhaust gas can be supplied to the exhaust purification device 45 during the execution of the first temperature raising exhaust operation.

During the execution of the first temperature rising exhaust operation, the exhaust gas having a high enthalpy flows into the turbine 38 of the turbocharger 35, so that the turbocharger 35 can be efficiently driven. Further, by compressing the exhaust gas during the valve closing period between the first temperature rising exhaust operation and the second temperature rising exhaust operation, the temperature of the exhaust gas flowing out from the combustion chamber 21 in the second temperature rising exhaust operation A certain exhaust temperature can be raised. As a result, the turbocharger 35 can be driven efficiently. By efficiently driving the turbocharger 35 in this way, the amount of air taken in by the engine 10 increases, and the exhaust energy can be further increased.

An example of the result of comparing the exhaust gas temperature and the exhaust energy in the normal mode and the temperature rising mode will be described with reference to FIG.
As shown in FIG. 6A, when the engine 10 is driven in a no-load state (idling state) at an engine speed Ne of 800 rpm, the exhaust gas temperature in the temperature rise mode is larger than the exhaust gas temperature in the normal mode. It was found to rise. As shown in FIG. 6B, when the engine 10 is driven in a no-load state where the engine speed Ne is 1080 rpm, the exhaust gas temperature in the temperature rising mode may rise significantly with respect to the exhaust gas temperature in the normal mode. Admitted.

As shown in FIG. 6C, when the engine 10 is driven in a no-load state where the engine speed Ne is 800 rpm, it is recognized that the exhaust energy in the temperature rise mode is significantly higher than the exhaust energy in the normal mode. It was. As shown in FIG. 6D, when the engine 10 is driven in a no-load state where the engine speed Ne is 1080 rpm, it is recognized that the exhaust energy in the temperature rise mode is significantly higher than the exhaust energy in the normal mode. It was.

The effect of the first embodiment will be described.
(1-1) Since the exhaust energy supplied to the exhaust purification device 45 is increased by the temperature raising exhaust operation as compared with the normal mode, the temperature of the selective reduction catalyst 47 can be raised at an early stage.

(1-2) The temperature rising mode is selected when the required torque L is equal to or less than the selection permission value L1. As a result, the unburned fuel contained in the exhaust gas can be reduced in the temperature rising mode.
(1-3) In the first heating and exhausting operation, the valve opening time is set after 40 ° CA after the compression top dead center. According to such a configuration, it is possible to reduce the amount of unburned fuel contained in the exhaust gas flowing out of the combustion chamber 21 by the first temperature raising exhaust operation.

(1-4) In the second temperature raising / exhausting operation, the valve closing time is set before the intake valve 27 that opens and closes the combustion chamber 21 opens. According to such a configuration, it is possible to prevent the exhaust gas flowing out of the combustion chamber 21 from flowing into the combustion chamber 21 again when the intake valve 27 is opened. As a result, it is possible to suppress the internal EGR caused by the exhaust gas remaining in the combustion chamber 21 when the first temperature rising exhaust operation is completed.

(1-5) The first temperature raising / exhausting operation is an opening / closing operation of closing the valve in the expansion stroke. According to such a configuration, the amount of exhaust gas remaining in the combustion chamber 21 at the completion of the first temperature raising / exhausting operation can be increased as compared with the case where the first temperature rising / exhausting operation is completed in the exhaust stroke. As a result, the compression loss of the engine 10 becomes large, so that the fuel injection amount for the output torque of the engine 10 to satisfy the required torque L can be increased. As a result, the exhaust energy supplied from the engine 10 to the exhaust purification device 45 can be increased more effectively.

(1-6) The first temperature rising exhaust operation is an opening / closing operation having a shorter valve opening period than the normal exhaust operation which is the opening / closing operation in the normal mode. According to such a configuration, it is possible to increase the amount of exhaust gas remaining in the combustion chamber 21 when the first temperature rising exhaust operation is completed while supplying the exhaust gas having high enthalpy to the exhaust purification device 45 by the first opening / closing operation. .. As a result, the compression loss of the engine 10 becomes larger, so that the fuel injection amount for satisfying the required torque L can be further increased. As a result, the exhaust energy supplied from the engine 10 to the exhaust purification device 45 can be further effectively increased.

(1-7) The engine system is equipped with a turbocharger 35. Therefore, in the temperature rise mode, the turbocharger 35 can be efficiently driven by the exhaust gas flowing out of the combustion chamber 21 in the second temperature rise exhaust operation. As a result, the exhaust energy can be further increased.

(Second Embodiment)
A second embodiment of the engine system will be described with reference to FIGS. 7 and 8. The engine system of the second embodiment has the same main configuration as the control device of the engine system of the first embodiment. Therefore, in the second embodiment, the parts different from the first embodiment will be described in detail, and the same parts as those in the first embodiment will be designated by the same reference numerals, and the detailed description thereof will be omitted.

As shown in FIG. 7, the temperature-increasing exhaust operation includes a first temperature-increasing exhaust operation that opens the valve during the expansion stroke and a second temperature-heating exhaust operation that opens the valve after a valve closing period in which at least a part of the valve is included in the exhaust stroke. Consists of.
The first temperature raising / exhausting operation is an opening / closing operation in which the maximum lift amount is larger and the valve opening period is longer than that of the second temperature rising / exhausting operation. In the first heated exhaust operation, the valve opening time is earlier than the normal exhaust operation, and the valve is opened 40 ° CA or later after the compression top dead center (= 0 ° CA), which is the compression stroke, in the exhaust stroke. It is an opening / closing operation that closes the valve. The first temperature raising exhaust operation is an opening / closing operation in which the normal exhaust operation is advanced.

The second heated exhaust operation is an opening / closing operation in which the valve is opened in the latter half of the exhaust stroke and closed before the intake valve 27 is opened near the exhaust top dead center (= 360 ° CA). For example, in the second temperature raising / exhausting operation, each of the maximum lift amount and the valve opening period is set to 1/4 or less of the first temperature rising / exhausting operation.

The operation of the temperature rising exhaust operation of the second embodiment will be described.
In the temperature-increasing exhaust operation of the second embodiment, the amount of high enthalpy exhaust gas flowing out from the combustion chamber 21 during the execution of the first temperature-increasing exhaust operation is increased as compared with the temperature-increasing exhaust operation of the first embodiment. Can be done. As a result, the amount of high enthalpy exhaust gas supplied to the exhaust purification device 45 can be increased. Further, since the exhaust gas remaining in the combustion chamber 21 at the completion of the first temperature raising exhaust operation is reduced, it is possible to suppress the pressure increase in the combustion chamber 21 during the valve closing period. As a result, it is possible to suppress an increase in the EGR rate due to the exhaust gas remaining in the combustion chamber 21 when the first temperature rising exhaust operation is completed. The temperature-increasing exhaust operation of the second embodiment is a temperature-heating / exhaust operation capable of effectively suppressing an increase in the EGR rate due to the internal EGR, although the compression loss is smaller than that of the temperature-heating / exhaust operation of the first embodiment. ..

An example of the result of comparing the exhaust gas temperature and the exhaust energy in the normal mode and the temperature rising mode will be described with reference to FIG.
As shown in FIG. 8A, when the engine 10 is driven in a no-load state (idling state) at an engine speed Ne of 800 rpm, the exhaust gas temperature in the temperature rise mode is compared with the exhaust gas temperature in the normal mode. Was found to rise significantly. Further, as shown in FIG. 8B, when the engine 10 is driven in a no-load state where the engine speed Ne is 800 rpm, the exhaust energy is significantly increased in the temperature rising mode with respect to the exhaust energy in the normal mode. Was recognized.

The effect of the second embodiment will be described.
(2-1) The same effects as (1-1) to (1-4) and (1-7) described in the first embodiment can be obtained.

(2-2) In the first temperature rising exhaust operation, the valve closing time is set in the exhaust stroke. According to such a configuration, the exhaust gas remaining in the combustion chamber 21 at the completion of the first temperature raising / exhausting operation can be reduced as compared with the case where the first temperature rising / exhausting operation is completed in the expansion stroke. As a result, the pressure rise in the combustion chamber 21 during the valve closing period is suppressed, so that the decrease in exhaust energy due to the internal EGR can be effectively suppressed.

(2-3) The first temperature raising exhaust operation is an opening / closing operation in which the normal exhaust operation is advanced. According to such a configuration, a larger amount of high enthalpy exhaust gas can be supplied to the exhaust purification device 45 as compared with the case where the first temperature rising exhaust operation is completed in the expansion stroke.

(Third Embodiment)
A third embodiment of the engine system will be described with reference to FIGS. 9 to 13. The engine system of the third embodiment has the same main configuration as the engine system of the first embodiment. Therefore, in the third embodiment, the parts different from the first embodiment will be described in detail, and the same parts as those in the first embodiment will be designated by the same reference numerals, and the detailed description thereof will be omitted. The main difference is the mode selection process and the opening / closing operation of the intake valve 27 and the exhaust valve 28 in the temperature rising mode.

The schematic configuration of the engine system will be described with reference to FIGS. 9 and 10.
As shown in FIGS. 9 and 10, in addition to the engine system described in the first embodiment, the engine system includes an exhaust throttle valve 52, an operation switch S, an exhaust gas temperature sensor 58, and a vehicle speed sensor 59. There is.

The exhaust throttle valve 52 is arranged between the addition valve 51 in the exhaust passage 17 and the turbine 38 of the turbocharger 35. The exhaust throttle valve 52 is configured so that the cross-sectional area of the flow path of the exhaust passage 17 can be changed. The exhaust throttle valve 52 functions as an exhaust brake, which is one of the auxiliary brakes, by reducing the cross-sectional area of the flow path of the exhaust passage 17 and increasing the exhaust resistance. The auxiliary brake is configured to operate when the driver-operable actuation switch S is in the on state. The operation switch S outputs an operation signal indicating an operation status to the control device 60.

The exhaust gas temperature sensor 58 detects the exhaust gas temperature Tex, which is the temperature of the exhaust gas flowing into the selective reduction catalyst 47. The vehicle speed sensor 59 detects the vehicle speed v, which is the speed of the vehicle. The exhaust gas temperature sensor 58 and the vehicle speed sensor 59 output a signal indicating the detected vehicle speed v to the control device 60.

As shown in FIG. 11, the acquisition unit 61 acquires the exhaust gas temperature Tex based on the detection signal output by the exhaust gas temperature sensor 58, and acquires the vehicle speed v based on the detection signal output by the vehicle speed sensor 59. The acquisition unit 61 acquires the operation status of the operation switch S.

Through the mode selection process, the mode selection unit 62 selects a control mode for fuel injection by the injector 13, intake operation of the intake valve 27, exhaust operation of the exhaust valve 28, and operation of the exhaust throttle valve 52. The mode selection unit 62 selectively selects a control mode from the temperature rise mode, the heat retention mode, the brake mode, and the normal mode. The heat retention mode is a control mode for holding the catalyst temperature Tc of the selective reduction catalyst 47 at or above the lower limit active temperature TcL. The brake mode is a control mode in which the opening and closing of the intake valve 27 and the exhaust valve 28 are controlled to generate a braking force by the compression release brake.

In addition to the normal map 67 and the temperature rise map 68, the fuel injection control unit 63 holds a heat retention map 69, which is a fuel map used in the heat retention mode, in a predetermined area of the memory. In the brake mode, the fuel injection control unit 63 executes fuel cut control for temporarily stopping fuel injection according to the engine speed Ne.

The valve control unit 66 controls the opening / closing operation of the intake valve 27 through the intake side valve mechanism 29, and controls the opening / closing operation of the exhaust valve 28 through the exhaust side valve mechanism 30. The valve control unit 66 controls the opening / closing timing including the lift amount for each of the intake valve 27 and the exhaust valve 28 based on the control mode selected by the mode selection unit 62.

The valve control unit 66 causes the intake valve 27 to perform a normal intake operation in the normal mode, a temperature rise intake operation in the temperature rise mode, a heat retention intake operation in the heat retention mode, and a brake intake operation in the brake mode. The valve control unit 66 causes the exhaust valve 28 to perform a normal exhaust operation in the normal mode, a temperature rise exhaust operation in the temperature rise mode, a heat retention exhaust operation in the heat retention mode, and a brake exhaust operation in the brake mode.

Further, the control device 60 has an exhaust brake control unit 70 as a functional unit that functions by executing various computer programs. The exhaust brake control unit 70 controls the exhaust throttle valve 52. The exhaust brake control unit 70 controls the exhaust throttle valve 52 to the operating state when the control mode is in the brake mode, and controls the exhaust throttle valve 52 to the non-operating state when the control mode is different from the brake mode.

The mode selection process executed by the mode selection unit 62 will be described with reference to FIG.
As shown in FIG. 12, in the mode selection process, the mode selection unit 62 determines whether or not the catalyst temperature Tc acquired by the acquisition unit 61 is equal to or higher than the lower limit active temperature TcL (step S201).

When the catalyst temperature Tc is less than the lower limit active temperature TcL (step S201: NO), in the mode selection unit 62, for example, the engine load EL based on the required torque L and the engine speed Ne is equal to or less than the temperature rise selection load EL1. Whether or not it is determined (step S202). The temperature rise selective load EL1 is set to a value at which the unburned fuel contained in the exhaust gas is suppressed even if the fuel injection amount is increased, and the torque L required from the driver can be realized. The temperature rise selective load EL1 is set based on the results of experiments and simulations performed in advance. The temperature rising selective load EL1 is preferably set from a value of, for example, 20% or less, and one example thereof is 15%. When the engine load EL is equal to or less than the temperature rise selection load EL1 (step S202: YES), the mode selection unit 62 selects the temperature rise mode (step S203) and temporarily ends a series of processes.

In step S201, when the catalyst temperature Tc is equal to or higher than the lower limit active temperature TcL (step S201: YES), the mode selection unit 62 determines whether or not the exhaust gas temperature Tex acquired by the acquisition unit 61 is the heat retention temperature Tex1 or higher. Determine (step S204). The heat retention temperature Tex1 is a temperature at which it is highly likely that the catalyst temperature Tc will drop to the lower limit active temperature TcL when exhaust gas having a temperature lower than that temperature is supplied to the selective reduction catalyst 47 for a predetermined period. is there. The heat retention temperature Tex1 is set so as to be, for example, a value equal to or higher than the lower limit active temperature TcL, and the lower the detection value of the outside air temperature sensor that detects the outside air temperature as one of the various sensors provided in the engine system, the higher the value. May be good. The lower the outside air temperature, the higher the heat retention temperature Tex1, so that an appropriate heat retention temperature Tex1 can be set according to the traveling environment at that time. As a result, it is more reliably suppressed that the catalyst temperature Tc drops to the lower limit active temperature TcL.

When the exhaust gas temperature Tex is less than the heat retention temperature Tex1 (step S204: NO), the mode selection unit 62 determines whether or not the engine load EL is the heat retention selection value EL2 or less (step S205). The heat retention selective value EL2 is a value at which the engine load EL is determined to be a light load, for example, in an idling state. The heat retention selection value EL2 is set to a value lower than that of the temperature rise selection load EL1. When the engine load EL is equal to or less than the heat retention selection value EL2 (step S205: YES), the mode selection unit 62 selects the heat retention mode (step S206) and temporarily ends a series of processes. That is, in the heat retention mode, the exhaust gas temperature Tex is in a state where the catalyst temperature Tc is likely to reach the lower limit active temperature TcL (step S204: NO), and the engine load EL is in a light load, so that the exhaust gas is exhaust gas. This mode keeps the catalyst temperature Tc at a temperature higher than the lower limit active temperature TcL in a state where the temperature Tex is unlikely to rise (step S205: YES).

On the other hand, when the exhaust gas temperature Tex is the heat retention temperature Tex1 or more (step S204: YES), the mode selection unit 62 determines whether or not the accelerator opening ACC acquired by the acquisition unit 61 is 0% or more (step S204: YES). Step S207).

When the accelerator opening ACC is less than 0% (step S207: NO), that is, when the required torque L is at the deceleration required torque requiring deceleration, does the mode selection unit 62 satisfy the operating conditions of the auxiliary brake? It is determined whether or not (step S208). The operating condition is that when the accelerator opening ACC is less than 0%, the operating switch S is in the ON state and the vehicle speed v is equal to or higher than the operating speed v1. The operating speed v1 is set to a vehicle speed v on which the braking force of the auxiliary brake effectively acts. An example of the operating speed v1 is 30 km / h.

When the operating condition is satisfied (step S208: YES), the mode selection unit 62 selects the brake mode (step S209) and temporarily ends a series of processes. In the brake mode, the control device 60 controls the intake side valve mechanism 29 and the exhaust side valve mechanism 30 so that the compression release brake, which is one of the auxiliary brakes, operates. Further, the control device 60 controls the exhaust throttle valve 52 in the closing direction so that the exhaust brake, which is one of the auxiliary brakes, operates.

On the other hand, when the accelerator opening ACC is 0% or more (step S207: YES), the engine load EL is not less than or equal to the temperature rise selective load EL1 (step S202: NO), and the engine load EL is not less than or equal to the heat retention selective value EL2. (Step S205: NO) If the operating condition of the auxiliary brake is not satisfied (step S208: NO), the mode selection unit 62 selects the normal mode (step S210) and temporarily ends a series of processes.

With reference to FIG. 13, the temperature-increasing exhaust operation, which is the opening / closing operation of the exhaust valve 28, and the temperature-increasing intake operation, which is the opening / closing operation of the intake valve 27, will be described. The crank angle shown in FIG. 13 indicates a crank angle with reference to the compression top dead center (= 0 ° CA), which is the top dead center of the compression stroke. Further, the description in parentheses shown below indicates the crank angle shown in FIG.

As shown in FIG. 13, the temperature-increasing exhaust operation includes a first temperature-increasing exhaust operation that opens the valve during the expansion stroke and a second temperature-heating exhaust operation that opens at least a part of the valve after a valve closing period included in the exhaust stroke. Consists of.
The first temperature-rising exhaust operation is an exhaust operation in which the maximum lift amount is larger and the valve opening period is longer than that of the second temperature-heating exhaust operation. The first temperature rising exhaust operation is an opening / closing operation in which the valve opening time is earlier and the valve opening period is shorter than the normal exhaust operation. For example, the first temperature rising exhaust operation is set to less than half of the normal exhaust operation for each of the maximum lift amount and the valve opening period. The first heating / exhausting operation is an opening / closing operation in which the valve is opened 40 ° CA or later after the compression top dead center (= 0 ° CA), which is the top dead center of the compression stroke, and is closed in the expansion stroke.

The second temperature-rising exhaust operation is, for example, an opening / closing operation in which each of the maximum lift amount and the valve opening period is set to half or less of the first temperature-heating exhaust operation. The second temperature rising exhaust operation is an opening / closing operation including the exhaust top dead center (= 360 ° CA) in the first half of the valve opening period. The first half of the opening / closing operation is the period from valve opening to reaching the maximum lift.

The temperature-increasing intake operation is an opening / closing operation in which the normal intake operation is retarded so that the intake valve 27 opens after the end of the second temperature-heating exhaust operation. The temperature-increasing intake operation is preferably an opening / closing operation in which the maximum lift position is before the suction bottom dead center (= 540 ° CA), that is, the suction bottom dead center is included in the first half of the valve opening period. According to such a configuration, since the period during which the intake valve 27 is open in the intake stroke is longer than when the maximum lift position is set after the suction bottom dead center, more intake air can be supplied to the cylinder 11. Can be imported into.

The operation of the temperature rising exhaust operation of the third embodiment will be described.
In the temperature-increasing exhaust operation of the third embodiment, a larger compression loss can be obtained because the valve closing period in the exhaust stroke is longer than that of the temperature-increasing exhaust operation of the first embodiment. Therefore, since the amount of fuel injection required to satisfy the required torque L from the driver is increased, the exhaust energy supplied to the exhaust purification device 45 can be increased as compared with the first embodiment.

Further, the temperature rise intake operation is a retardation of the normal intake operation so that the intake valve 27 does not open during the opening / closing operation of the second temperature temperature exhaust operation. Therefore, a sufficient amount of air can be sucked into the cylinder 11 while suppressing the exhaust gas from being discharged from the cylinder 11 to the intake manifold 14 during the execution of the second temperature raising exhaust operation.

Here, the excess air rate may temporarily decrease during the transitional period when the opening / closing operation of the exhaust valve 28 is switched. This is because the switching of the opening / closing operation of the exhaust valve 28 is not completed only by the advance angle and the retard angle of the normal opening / closing operation, but the exhaust gas is discharged from the cylinder 11 by changing the opening / closing timing and the lift amount. It is caused by becoming difficult.

Therefore, the fuel injection control unit 63 temporarily reduces the fuel injection amount during a transient period (for example, about two cycles) in which the opening / closing operation of the exhaust valve 28 is switched to the temperature raising exhaust operation. For example, the fuel injection control unit 63 may hold a transitional period map, which is a fuel map for the transitional period, in a predetermined area of the memory, and calculate the fuel injection amount based on the held transitional period map. Further, for example, the fuel injection control unit 63 may calculate the fuel injection amount by correcting the fuel injection amount derived using the normal map 67 in the decreasing direction.

The effect of the third embodiment will be described.
(3-1) The same effects as (1-1) to (1-7) described above can be obtained.
(3-2) The second temperature rising exhaust operation includes the exhaust top dead center in the first half of the valve opening period. As a result, the compression period of the exhaust gas becomes longer, and a larger compression loss can be obtained. As a result, the amount of fuel injection for satisfying the required torque L increases, so that the exhaust energy supplied to the exhaust purification device 45 can be further increased. Further, in the second temperature rising exhaust operation, the exhaust valve 28 opens in a state where the exhaust gas in the cylinder 11 is sufficiently compressed, so that the exhaust gas remaining in the cylinder 11 after the second temperature rising exhaust operation is released. Can be reduced.

(3-3) The temperature rise intake operation has a valve opening time of the intake valve 27 after the second temperature temperature exhaust operation. As a result, the amount of intake air required for raising the catalyst temperature Tc can be secured while preventing the inflow of exhaust gas into the intake manifold 14 due to the opening of the intake valve 27.

(3-4) The temperature raising intake operation is an opening / closing operation in which the normal intake operation is retarded. Therefore, the amount of intake air required for raising the catalyst temperature Tc can be more reliably secured. Further, for example, since it is possible to switch to the temperature rise intake operation by using the intake cam phaser whose phase of the intake camshaft can be changed, the intake operation can be switched under a simple configuration.

(3-5) The fuel injection control unit 63 temporarily reduces the fuel injection amount during the transitional period in which the opening / closing operation of the exhaust valve 28 switches from the normal exhaust operation to the temperature raising exhaust operation. Therefore, it is possible to suppress a decrease in the excess air rate due to switching of the opening / closing operation of the exhaust valve 28.

The above-described first to third embodiments can be modified and implemented as follows. The first to third embodiments and the following modified examples can be implemented in combination with each other within a technically consistent range.

-In the third embodiment, the temperature rise intake operation is not limited to the opening / closing operation in which the normal intake operation is retarded. For example, the temperature raising intake operation may be an opening / closing operation in which the lift amount and the valve opening period are different from those of the normal intake operation.

-In the first and third embodiments, the first temperature raising exhaust operation may be an opening / closing operation in which the maximum lift amount is the same as the normal exhaust operation and the valve opening period is short. Further, the first temperature raising exhaust operation may be an opening / closing operation in which the maximum lift amount is smaller than that in the normal exhaust operation and the valve opening period is the same length.

-In the first to third embodiments, the second temperature rising exhaust operation may be configured such that the intake valve 27 is opened and then the exhaust valve 28 is closed.
-In the first to third embodiments, the first heating and exhausting operation may be opened in the expansion stroke, and may be opened by 40 ° CA after the compression top dead center.

-In the first to third embodiments, the mode selection unit 62 may select the temperature rise mode on the condition that the catalyst temperature Tc is equal to or less than the lower limit catalyst temperature TcL.
-In the first and second embodiments, when the catalyst temperature Tc is equal to or lower than the lower limit catalyst temperature TcL and the required torque L is 0 (a state in which the driver does not depress the accelerator pedal 57a), the mode selection unit 62 is used. The temperature rise mode may be selected only for. That is, the temperature rising mode may be selectably configured when the engine 10 is in the idling state. According to such a configuration, since the temperature rising mode is selected when the exhaust energy of the engine 10 is small and the exhaust gas temperature is low in the normal mode, the increase in the exhaust energy and the rise in the exhaust gas temperature can be efficiently performed. It can be carried out.

The fuel injection control unit 63 may have a configuration in which the fuel injection amount can be increased in the temperature rise mode as compared with the normal mode, and is not limited to the configuration in which the normal map 67 and the temperature rise map 68 are held as the fuel map. For example, the fuel injection control unit 63 is configured to increase the fuel injection amount by correcting the fuel injection amount specified in the normal map 67 according to the operating state of the engine 10 at that time in the temperature rise mode. You may.

When the exhaust gas purification device 45 has a plurality of catalysts, the determination regarding the catalyst temperature Tc in the mode selection process may be made based on the catalyst temperature located at the uppermost stream. According to such a configuration, at least the catalyst located at the most upstream can act. Further, the determination regarding the catalyst temperature Tc may be made based on the catalyst temperature of the catalyst selected in advance from the plurality of catalysts. According to such a configuration, the catalyst can act on a preselected catalyst.

The engine system may not include at least one of the turbocharger 35 and the EGR device 40.
-The engine 10 is not limited to a diesel engine, and may be a gasoline engine or a gas engine.

10 ... Engine, 11 ... Cylinder, 12 ... Engine block, 12A ... Cylinder block, 12B ... Cylinder head, 13 ... Injector, 14 ... Intake manifold, 15 ... Exhaust manifold, 16 ... Intake passage, 17 ... Exhaust passage, 17A ... Expansion Diameter, 20 ... Piston, 21 ... Combustion chamber, 22 ... Connection rod, 23 ... Crank shaft, 25 ... Intake port, 26 ... Exhaust port, 27 ... Intake valve, 28 ... Exhaust valve, 29 ... Intake side valve mechanism, 30 ... Exhaust side valve mechanism, 35 ... Turbocharger, 36 ... Compressor, 37 ... Intercooler, 38 ... Turbine, 39 ... Air cleaner, 40 ... EGR device, 41 ... EGR passage, 42 ... EGR cooler, 43 ... EGR valve, 45 ... Exhaust gas recirculation device, 46 ... Addition part, 47 ... Selective reduction catalyst, 48 ... Tank, 49 ... Reducing agent passage, 50 ... Pump, 51 ... Addition valve, 52 ... Exhaust throttle valve, 55 ... Crank angle sensor, 56 ... catalyst temperature sensor, 57 ... accelerator opening sensor, 57a ... accelerator pedal, 58 ... exhaust gas temperature sensor, 59 ... vehicle speed sensor, 60 ... control device, 61 ... acquisition unit, 62 ... mode selection unit, 63 ... fuel injection control Unit, 64 ... EGR control unit, 65 ... addition control unit, 66 ... valve control unit, 67 ... normal map, 68 ... temperature rise map, 69 ... heat retention map, 70 ... exhaust brake control unit.

Claims (9)

An engine with an exhaust valve that can change the opening and closing timing of opening and closing the combustion chamber,
An exhaust purification device having a catalyst for purifying the exhaust gas from the engine,
An engine system including a control device for controlling the engine.
The control device is
An acquisition unit that acquires the required torque from the driver and the state of the catalyst, and
A fuel injection amount control unit that controls the fuel injection amount to the engine so that the output torque of the engine becomes the required torque.
A mode selection unit for selecting the control mode of the engine system and
A valve control unit that controls the opening and closing of the exhaust valve is provided.
The mode selection unit selects a temperature rise mode as the control mode when the catalyst is in an inactive state.
In the temperature rise mode, the valve control unit opens the exhaust valve after a first temperature rise exhaust operation in which the exhaust valve opens in the expansion stroke and a valve closing period in which at least a part thereof is included in the exhaust stroke. An engine system composed of a second temperature-rising exhaust operation and performing a temperature-heating / exhaust operation in which the first temperature-heating / exhaust operation has a larger maximum lift amount and a longer valve opening period than the second temperature-heating / exhaust operation. The engine system according to claim 1, wherein the mode selection unit selects the temperature rise mode when the required torque is equal to or less than the selection permission value. The engine system according to claim 1 or 2, wherein the first temperature-increasing exhaust operation is an opening / closing operation in which the exhaust valve opens after 40 ° CA after the compression top dead center. The engine system according to any one of claims 1 to 3, wherein the second temperature raising / exhausting operation is an opening / closing operation in which the exhaust valve closes before the intake valve that opens / closes the combustion chamber opens. The engine system according to any one of claims 1 to 4, wherein the first temperature raising / exhausting operation is an opening / closing operation in which the exhaust valve closes in the expansion stroke. The engine system according to claim 5, wherein the first temperature raising / exhausting operation is an opening / closing operation having a shorter valve opening period than the normal exhaust operation in the normal mode, which is the control mode when the catalyst is in the active state. The engine system according to any one of claims 1 to 4, wherein the first temperature raising exhaust operation is an opening / closing operation in which the exhaust valve closes in the exhaust stroke. The engine further includes an intake valve that can change the opening / closing timing of opening / closing the combustion chamber.
The second temperature rising exhaust operation is an opening / closing operation including the exhaust top dead center in the first half of the valve opening period.
The valve control unit is configured to be able to control the opening / closing timing of the intake valve, and as the opening / closing operation of the intake valve, the valve opening time is set after the completion of the second temperature rising / exhausting operation in the temperature rising mode. The engine system according to any one of claims 1 to 7, which performs a warm intake operation. The engine system according to claim 8, wherein the temperature raising intake operation is an opening / closing operation in which the normal exhaust operation in the normal mode, which is the control mode when the catalyst is in the active state, is retarded.