JP2021113540A - Engine system - Google Patents

Abstract

To achieve both the prevention of the production of condensed water in an EGR device and the prevention of the deterioration of NOx catalyst activity in a post-treatment device.SOLUTION: An engine system comprises; a NOx catalyst 78; an exhaust emission recirculation device 55; a first heater 77 arranged at a side downstream of a branch part 33A branched from an exhaust emission recirculation passage 56 of an exhaust passage 33 and at a side upstream of the NOx catalyst 78; a second heater 59 arranged at a side upstream of a cooler 58 of the exhaust emission recirculation passage 56; a catalyst temperature rise control part for controlling a rise of a catalyst temperature for raising the temperature of the NOx catalyst 78 up to an activation temperature by raising a temperature of the first heater 77 when the temperature of the NOx catalyst 78 is lower than the activation temperature; and a condensed water production prevention control part for controlling the prevention of the production of condensed water which raises a temperature of an exhaust emission recirculation gas up to a dew point temperature by raising a temperature of the second heater 59.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to an engine system, and more particularly to an engine system including an exhaust gas recirculation device and an aftertreatment device having a NOx catalyst for purifying NOx (nitrogen oxides).

Conventionally, an exhaust gas recirculation (EGR) device has been known in which at least a part of the exhaust gas of an engine is returned to an intake system to reduce NOx. The EGR device includes a high-pressure EGR device that recirculates EGR gas from the exhaust system on the upstream side of the turbocharger's turbine to the intake system on the downstream side of the compressor of the turbocharger, and an exhaust system on the downstream side of the turbocharger's turbine. A low-pressure EGR device that recirculates EGR gas to the intake system on the upstream side of the compressor of the turbocharger is known.

In the low-pressure EGR apparatus, corrosive condensed water may be generated by condensing the water contained in the EGR gas with an EGR cooler or the like. Then, the generated condensed water may erode the EGR cooler, the EGR passage, and the like. For example, in Patent Document 1, a heater is provided on the upstream side of the branch portion of the exhaust passage with the EGR passage, and the exhaust heated by the heater is returned to the EGR passage to remove condensed water condensing on the EGR cooler or the like. The technology to be used is disclosed.

Japanese Unexamined Patent Publication No. 2012-215142

By the way, in order to prevent corrosion of the EGR passage and the like due to condensed water, the heater is operated from the start of the engine to raise the temperature of the EGR gas higher than the dew point temperature to prevent the generation of condensed water. It is desirable to do. Further, in order to reduce the NOx emission amount, it is desirable to operate the heater from the start of the engine to control the catalyst temperature rise to raise the catalyst temperature of the NOx catalyst to the active temperature range at an early stage.

In the technique described in Document 1, the heater is provided on the upstream side of the branch portion between the exhaust passage and the EGR passage. For this reason, if the condensate water generation prevention control and the catalyst temperature rise control are performed in parallel, the heat of the heater is dispersed in the EGR passage and the exhaust passage, respectively, and there is a possibility that these controls cannot be efficiently compatible with each other. There is. On the other hand, if the EGR passage is blocked and the temperature rise of the NOx catalyst is prioritized, the EGR device cannot be operated until the catalyst temperature reaches the active temperature, which may lead to deterioration of the exhaust emission performance.

The technique of the present disclosure has been made in view of the above circumstances, and an object of the present invention is to achieve both prevention of generation of condensed water in an EGR apparatus and prevention of deterioration of NOx catalytic activity in an aftertreatment apparatus.

The technique of the present disclosure is provided in an intake passage that circulates the intake air to be introduced into the engine, an exhaust passage that circulates the exhaust gas discharged from the engine, and a NOx catalyst that purifies the NOx in the exhaust. An exhaust recirculation device having an exhaust recirculation passage that branches off from the exhaust passage on the upstream side of the NOx catalyst and joins the intake passage, and a cooler provided in the exhaust recirculation passage, and the exhaust passage. A first heater provided on the downstream side of the branch portion of the exhaust gas recirculation passage and on the upstream side of the NOx catalyst, and a second heater provided on the upstream side of the exhaust gas recirculation passage with the cooler. The NOx catalyst temperature acquisition unit that acquires the temperature of the NOx catalyst, the exhaust gas recirculation gas state amount acquisition unit that acquires the state amount of the exhaust gas recirculation gas flowing through the exhaust gas recirculation passage, and the NOx acquired. When the temperature of the catalyst is lower than the predetermined active temperature of the NOx catalyst, the temperature of the NOx catalyst is raised to the active temperature by raising the temperature of the first heater. When the temperature of the exhaust gas recirculation gas is estimated to be lower than the dew point temperature based on the control unit and the acquired state amount, the second heater is raised to raise the temperature of the exhaust gas recirculation gas. It is characterized by including a condensed water generation prevention control unit that implements a condensed water generation prevention control that raises the temperature to the dew point temperature.

Further, when the acquired temperature of the NOx catalyst is lower than the active temperature and the temperature of the exhaust gas recirculation gas is estimated to be lower than the dew point temperature based on the acquired state quantity. It is preferable that the catalyst temperature rise control and the condensed water generation prevention control are performed in parallel.

Further, an oxidation catalyst provided in the exhaust passage to oxidize unburned fuel in the exhaust and a particulate matter provided in the exhaust passage downstream of the oxidation catalyst to collect particulate matter in the exhaust. The filter, the third heater provided on the upstream side of the exhaust passage with respect to the filter, and the unburned fuel are supplied to the oxidation catalyst, and the temperature of the third heater is raised to deposit on the filter. It is preferable to further include a filter regeneration control unit that performs filter regeneration control for burning and removing the particulate matter.

Further, a supercharger having a turbine provided in the exhaust passage and driven by exhaust and a compressor provided in the intake passage and integrally rotatably connected to the turbine is further provided, and the exhaust is provided. The recirculation device is preferably a low-pressure exhaust recirculation device that branches from the exhaust passage on the downstream side of the turbine and joins the intake passage on the upstream side of the compressor.

According to the technique of the present disclosure, it is possible to achieve both prevention of generation of condensed water in the EGR apparatus and prevention of deterioration of NOx catalytic activity in the aftertreatment apparatus.

It is a schematic overall block diagram which shows the intake / exhaust system of the engine which concerns on this embodiment. It is a schematic functional block diagram which shows the control device which concerns on this embodiment, and the related peripheral configuration. It is a chart diagram explaining the catalyst temperature rise control by the control apparatus which concerns on this embodiment. It is a chart diagram explaining the condensate generation prevention control by the control device which concerns on this embodiment. It is a chart diagram explaining the filter reproduction control by the control apparatus which concerns on this embodiment.

Hereinafter, the engine system according to the present embodiment will be described based on the attached drawings. The same parts have the same reference numerals, and their names and functions are also the same. Therefore, detailed explanations about them will not be repeated.

FIG. 1 is a schematic overall configuration diagram showing an intake system and an exhaust system of the engine system according to the present embodiment.

The engine 10 mainly has a cylinder head CH and an engine main body portion each of which is composed of a cylinder block, a crankcase, or the like (not shown). A plurality of cylinders C are provided in the cylinder block, and a piston (not shown) is housed in each cylinder C so as to be reciprocating. The piston is connected to the crankshaft 11 via a connecting rod, a crankarm, or the like (not shown), and the reciprocating motion of the piston is converted into a rotary motion and transmitted to the crankshaft 11.

The engine 10 is not limited to the in-line multi-cylinder engine shown in the illustrated example, and may be a V-type engine, a horizontally opposed engine, or the like. Further, the engine 10 is not limited to a multi-cylinder engine, and may be a single-cylinder engine.

The crankshaft 11 is provided with a drive pulley 12. An alternator 15 is connected to the drive pulley 12 via a belt 13 and a driven pulley 14. The electric power generated by the alternator 15 is stored in the vehicle-mounted battery 16 according to the state of charge (SOC), or is supplied to an electrical component (not shown). The rated voltage of the vehicle-mounted battery 16 may be either 24V or 12V.

An intake manifold 20 that distributes intake air to an intake port (not shown) is provided on the side portion of the cylinder head CH on the intake side. The air cleaner 21, the upstream intake passage 22, the compressor 42 of the supercharger 40, the downstream intake passage 23, and the like are connected to the intake manifold 20 in this order from the intake upstream side. The downstream intake passage 23 is provided with an intercooler 24 for cooling the intake air pumped by the compressor 42. The intercooler 24 may be either a water-cooled type or an air-cooled type.

An exhaust manifold 30 is provided on the exhaust side of the cylinder head CH to collect the exhaust gas discharged from each cylinder C via an exhaust port (not shown). In the exhaust manifold 30, in order from the exhaust upstream side, the upstream exhaust passage 31, the turbine 41 of the supercharger 40, the first connection exhaust passage 32, the pre-stage post-treatment device 60, the second connection exhaust passage 33, and the post-stage post-treatment device 70 , Downstream exhaust passage 34 and the like are connected. The second connection exhaust passage 33 is provided with an exhaust valve 35 whose exhaust flow rate can be adjusted. The downstream exhaust passage 34 is provided with a silencer, a tail pipe, and the like (not shown). When the turbine housing of the turbocharger 40 is directly connected to the exhaust manifold 30, the upstream exhaust passage 31 may be omitted. The opening / closing operation of the exhaust valve 35 is controlled in response to a command from the control device 100.

The supercharger 40 includes a turbine 41 driven by exhaust gas and a compressor 42 integrally rotatably connected to the turbine 41 by a turbo shaft 43. The supercharger 40 is not limited to the conventional type shown in the illustrated example, and may be a variable capacitance type having variable wings.

A wastegate mechanism 45 is provided in the exhaust system between the exhaust manifold 30 and the pretreatment device 60. The wastegate mechanism 45 includes a bypass passage 46 that communicates the upstream side and the downstream side of the turbine 41, a wastegate valve 47 provided in the bypass passage 46, and an actuator 48 that operates the wastegate valve 47 by boost pressure. I have.

The high-pressure EGR device 50 includes a high-pressure EGR passage 51, a high-pressure EGR valve 52 capable of adjusting the amount of EGR gas, and a high-pressure EGR cooler 53 for cooling the EGR gas. The high-pressure EGR passage 51 branches from the exhaust manifold 30 (or the upstream exhaust passage 31) and joins the downstream intake passage 23 on the downstream side of the intercooler 24. The high-pressure EGR cooler 53 may be either a water-cooled type or an air-cooled type. The opening / closing operation of the high-pressure EGR valve 52 is controlled in response to a command from the control device 100.

The low-pressure EGR device 55 (an example of the exhaust gas recirculation device of the present disclosure) comprises a low-pressure EGR passage 56, a low-pressure EGR valve 57 capable of adjusting the amount of EGR gas, a low-pressure EGR cooler 58 for cooling the EGR gas, and an EGR gas. It is provided with an EGR heater 59 that raises the temperature.

The low-pressure EGR passage 56 (an example of the exhaust gas recirculation passage of the present disclosure) branches from the second connection exhaust passage 33 and joins the upstream intake passage 22. The low-pressure EGR cooler 58 (an example of the cooler of the present disclosure) may be either a water-cooled type or an air-cooled type.

The EGR heater 59 (an example of the second heater of the present disclosure) is provided in the low pressure EGR passage 56 on the upstream side (second connection exhaust passage 33 side) of the low pressure EGR cooler 58. The EGR heater 59 is an electric heater capable of raising the temperature of the EGR gas flowing through the low-pressure EGR passage 56 by being energized, and the energization is controlled in response to a command from the control device 100. The opening / closing operation of the low pressure EGR valve 57 is controlled in response to a command from the control device 100.

The pre-stage post-treatment device 60 has an oxidation catalyst 62, a pre-stage post-treatment heater 63, and a filter 64 in this order from the upstream side of the exhaust gas.

The oxidation catalyst 62 is formed by supporting a catalyst component or the like on the surface of a ceramic carrier such as a cordierite honeycomb structure, and oxidizes HC and CO contained in the exhaust gas. When unburned fuel (HC) is supplied by post-injection by an in-cylinder injector (not shown) of the engine 10 or exhaust pipe injection of an exhaust pipe injector (not shown), the oxidation catalyst 62 oxidizes the unburned fuel (HC) to increase the exhaust temperature. Raise.

The pre-stage post-processing heater 63 (an example of the third heater of the present disclosure) is an electric heater capable of raising the temperature of the exhaust gas flowing into the filter 64 by being energized, and is energized in response to a command from the control device 100. Be controlled.

The filter 64 is formed, for example, by arranging a large number of cells partitioned by a porous partition wall along the flow direction of exhaust gas, and alternately sealing the upstream side and the downstream side of these cells. .. The filter 64 collects particulate matter (PM) in the exhaust gas in the pores and surface of the partition wall, and when the amount of PM deposited reaches a predetermined amount, the filter regeneration is carried out to burn and remove it. Will be done. Note that the filter regeneration may be performed at predetermined intervals, such as when the cumulative mileage from the previous filter regeneration execution reaches a predetermined threshold distance.

The post-stage post-treatment device 70 includes a urea water injection device 71, a post-stage post-treatment heater 77, a selective catalytic reduction catalyst (hereinafter referred to as SCR catalyst) 78, and an ammonia slip catalyst 79 in this order from the upstream side of the exhaust gas.

The urea water injection device 71 supplies the urea water tank 72 that stores the urea water, the strainer 73 that is immersed in the urea water in the urea water tank 72 to remove foreign matter, and the supply pipe 74 connected to the strainer 73. It includes a urea water pump 75 that is provided in the pipe 74 and pumps urea water from the urea water tank 72, and a urea water injector 76 that injects the urea water supplied from the supply pipe 74 into the second connection exhaust passage 33. ..

The urea water injected from the urea water injector 76 is hydrolyzed by exhaust heat and water vapor in the exhaust to produce ammonia (NH3), which is supplied to the SCR catalyst 78 on the downstream side as a reducing agent.

The post-stage post-treatment heater 77 (an example of the first heater of the present disclosure) is an electric heater capable of raising the temperature of the exhaust gas flowing into the SCR catalyst 78 by being energized, and is an electric heater capable of raising the temperature of the exhaust gas flowing into the SCR catalyst 78 in response to a command from the control device 100. Energization is controlled.

The SCR catalyst 78 (an example of the NOx catalyst of the present disclosure) is formed by supporting zeolite or the like on, for example, a porous ceramic carrier. The SCR catalyst 78 adsorbs ammonia supplied as a reducing agent from the urea water injector 76, and selectively reduces and purifies NOx from the exhaust gas passing by the adsorbed ammonia.

The ammonia slip catalyst 79 is formed by supporting an oxidation catalyst component or the like on the surface of a ceramic carrier such as a honeycomb structure, and has a function of decomposing (oxidizing) ammonia slipped downstream from the SCR catalyst 78. Have.

The intake air flow sensor (hereinafter referred to as MAF sensor) 91 acquires the intake air flow rate q introduced from the air cleaner 21 into the upstream intake passage 22. The outside air temperature sensor 92 acquires the temperature of the outside air. The boost pressure sensor 93 acquires the pressure (boost pressure) of the intake air pumped by the compressor 42. The first exhaust temperature sensor 94 is provided immediately downstream of the filter 64, and acquires the temperature of the exhaust gas that has passed through the filter 64 (hereinafter, simply referred to as the filter temperature). The first exhaust temperature sensor 94 may be provided immediately downstream of the oxidation catalyst 62. The differential pressure sensor 95 is provided upstream and downstream of the filter 64, and acquires the front-rear differential pressure P of the filter 64. The second exhaust temperature sensor 96 is provided immediately downstream of the SCR catalyst 78, and acquires the temperature of the exhaust gas flowing through the SCR catalyst 78 (SCR catalyst outlet temperature). The EGR temperature sensor 97 is provided in the low-pressure EGR passage 56, and acquires the _{EGR gas temperature T EGR flowing into the low-pressure EGR cooler 58.} The EGR humidity sensor 98 is provided in the low-pressure EGR passage 56, and acquires the _{EGR gas humidity H EGR flowing into the low-pressure EGR cooler 58.} The sensor values of each of these sensors 91 to 98 are transmitted to the electrically connected control device 100.

The arrangement and number of sensors are not limited to the illustrated examples, and an exhaust temperature sensor may be further provided on the inlet side of the SCR catalyst 78.

FIG. 2 is a schematic functional block diagram showing the control device 100 and related peripheral configurations according to the present embodiment.

The control device 100 is, for example, a device that performs calculations such as a computer, and is a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an input port, and an output connected to each other by a bus or the like. It has a port and executes a control program.

Further, the control device 100 causes the SCR catalyst temperature estimation unit 110, the EGR gas dew point temperature estimation unit 120, the catalyst temperature rise control unit 130, the condensed water generation prevention control unit 140, and the filter regeneration control unit 150 by executing the control program. Functions as a equipped device. Each of these functional elements will be described as being included in the control device 100, which is integrated hardware in the present embodiment, but any part of these may be provided in separate hardware.

The SCR catalyst temperature estimation unit 110 (an example of the NOx catalyst temperature acquisition unit of the present disclosure) has an SCR catalyst temperature corresponding to the internal temperature of the SCR catalyst 78 based on the SCR catalyst outlet temperature transmitted from the second exhaust temperature sensor 96. Estimate the _TSCR. The SCR catalyst temperature T _SCR may be estimated based on the inlet temperature and the outlet temperature of the SCR catalyst 78 as long as the temperature sensor is also provided on the inlet side of the SCR catalyst 78. Further, SCR catalyst temperature T _SCR is an engine speed sensor and an accelerator opening sensor (not shown), it may be estimated based on the operating state of the engine 10 acquired by the MAF sensor 91 and the like. SCR catalyst temperature _{T SCR} estimated by the SCR catalyst temperature estimating unit 110 is transmitted to the catalyst Atsushi Nobori control unit 130.

The EGR gas dew point temperature estimation unit 120 (an example of the exhaust gas recirculation gas state amount acquisition unit of the present disclosure) is an EGR gas temperature T _EGR transmitted from the EGR temperature sensor 97 and an EGR gas humidity H transmitted from the EGR humidity sensor 98. based on the _EGR, estimating a dew point temperature _{T dEW} of EGR gas flowing into the low-pressure EGR cooler 58. The dew point temperature T _DEW may be estimated based on the operating state of the engine 10 according to the engine speed, the accelerator opening degree, the EGR flow rate, etc., the outside air temperature, and the like. The EGR flow rate may be acquired based on the intake air flow rate q and the EGR rate (command value from the control device 100). The outside air temperature may be acquired by the outside air temperature sensor 92. _{The dew point temperature T DEW} estimated by the EGR gas dew point temperature estimation unit 120 is transmitted to the condensed water generation prevention control unit 140.

The catalyst temperature rise control unit 130 energizes the post-stage post-treatment heater 77 when the _{SCR catalyst temperature T SCR} transmitted from the SCR catalyst temperature estimation unit 110 is less than a predetermined active temperature T _{ACT (for example, about 200 ° C.).} , SCR catalyst temperature T The catalyst temperature rise control that raises the _SCR to the active temperature _{TACT is performed.} The amount of energization in the catalyst temperature rise control may be feedback-controlled based on the deviation between the _{SCR catalyst temperature T SCR} and the active temperature T _{ACT transmitted from the SCR catalyst temperature estimation unit 110.}

As described above, the temperature of the exhaust gas flowing into the SCR catalyst 78 due to the heat generation of the post-stage post-treatment heater 77 arranged on the downstream side of the branch portion 33A (see FIG. 1) between the second connection exhaust passage 33 and the low-pressure EGR passage 56. By executing the catalyst temperature rise control for raising the temperature of the SCR catalyst 78, the temperature of the SCR catalyst 78 is directly raised without losing heat to the low pressure EGR passage 56 side even if it is executed in parallel with the control for preventing the generation of condensed water, which will be described later. can do. This makes it possible to improve the exhaust emission performance of the engine 10. The catalyst temperature rise control ends when the SCR catalyst temperature T _SCR reaches the active temperature T _ACT.

The condensed water generation prevention control unit 140 energizes the EGR heater 59 when the _{EGR gas temperature T EGR transmitted from the EGR temperature sensor 97 is less than the dew point temperature T DEW} transmitted from the EGR gas dew point temperature estimation unit 120. _{, The EGR gas temperature T EGR} of the low pressure EGR passage 56 is raised to the dew point temperature T _DEW to prevent the generation of condensed water. The amount of energization in the condensed water generation prevention control may be feedback-controlled based on the deviation between the _{EGR gas temperature T EGR transmitted from the EGR temperature sensor 97 and the dew point temperature T DEW} transmitted from the EGR gas dew point temperature estimation unit 120. ..

In this way, the condensed water that raises the _{EGR gas temperature T EGR} flowing through the low-pressure EGR passage 56 due to the heat generated by the EGR heater 59 arranged on the upstream side (branch portion 33A side) of the low-pressure EGR passage 56 with respect to the low-pressure EGR cooler 58. By executing the generation prevention control, the EGR gas can be directly heated without losing heat to the second connection exhaust passage 33 side even if it is executed in parallel with the catalyst temperature rise control described above. .. This makes it possible to prevent the generation of condensed water in the low-pressure EGR cooler 58, the low-pressure EGR passage 56, and the like. The control for preventing the generation of condensed water _{ends when the EGR gas temperature T EGR} reaches the dew point temperature T _DEW.

The filter regeneration control unit 150 determines when the front-rear differential pressure P transmitted from the differential pressure sensor 95 reaches a predetermined upper limit differential pressure, or the interval from the previous filter regeneration execution (for example, cumulative mileage or cumulative mileage). ) Reaches a predetermined interval, or when a predetermined execution condition is satisfied, filter regeneration control for burning and removing PM accumulated on the filter 64 is performed.

In the present embodiment, the filter regeneration control unit 150 filters by using both the heater heating control that heats the pretreatment heater 63 and the fuel injection control by the post injection of the in-cylinder injector and the exhaust pipe injection of the exhaust pipe injector. Execute playback control.

Specifically, the filter regeneration control unit 150 performs heater heating control so that the filter temperature transmitted from the first exhaust temperature sensor 94 becomes a predetermined first target temperature lower than the PM combustion temperature. The energization amount in the heater heating control may be feedforward controlled based on a preset target energization amount.

Further, the filter regeneration control unit 150 performs fuel injection control so that the filter temperature transmitted from the first exhaust temperature sensor 94 becomes the PM combustion temperature. The fuel injection amount of the post injection and the exhaust pipe injection in the fuel injection control may be feedback controlled based on the deviation between the PM combustion temperature and the filter temperature acquired by the first exhaust temperature sensor 94.

In this way, by executing the heater heating control in combination with the fuel injection control, it is possible to effectively reduce the total fuel consumption consumed for filter regeneration. In the filter regeneration control, the front-rear differential pressure P transmitted from the differential pressure sensor 95 drops to a predetermined lower limit differential pressure, the total fuel injection amount reaches a predetermined upper limit injection amount, or the filter regeneration control starts. It ends when the elapsed time from is reached the upper limit time.

Next, the flow of the catalyst temperature rise control, the condensed water generation prevention control, and the filter regeneration control according to the present embodiment will be described with reference to FIGS. 3, 4, and 5. Each of these control routines is started, for example, at the same time as the ON operation of the ignition switch.

FIG. 3 is a chart diagram for explaining the flow of the catalyst temperature rise control process according to the present embodiment.

In step S100, it is determined whether or not the SCR catalyst temperature T _{SCR is lower} than the active temperature T ACT. If the SCR catalyst temperature T _SCR is less than the active temperature T _ACT (Yes), this control proceeds to step S110. On the other hand, when the SCR catalyst temperature T _SCR is equal to or higher than the active temperature T _ACT (No), this control repeats the determination process of step S100.

In step S110, the catalyst temperature rise control for raising the temperature of the exhaust gas flowing into the SCR catalyst 78 is executed by energizing the post-stage post-treatment heater 77.

Next, in step S120, it is determined whether or not _{the SCR catalyst temperature T SCR} has risen to the active temperature T _ACT. If the SCR catalyst temperature T _SCR has not risen to the active temperature T _ACT (No), this control is returned to the process of step S110. On the other hand, when the SCR catalyst temperature T _SCR rises to the active temperature T _ACT (Yes), this control is then returned.

FIG. 4 is a chart diagram illustrating a flow of processing for controlling the generation of condensed water according to the present embodiment.

In step S200, it is determined whether or not the EGR gas temperature T _EGR is less than the dew point temperature T _DEW. If the EGR gas temperature T _EGR is less than the dew point temperature T _DEW (Yes), this control proceeds to step S210. On the other hand, when the EGR gas temperature T _EGR is equal to or higher than the dew point temperature T _DEW (No), this control repeats the determination process in step S200.

In step S210, by energizing the EGR heater 59, the condensate water generation prevention control for raising _{the EGR gas temperature T EGR of the low pressure EGR passage 56 is executed.}

Next, in step S220, it is determined whether or not _{the EGR gas temperature T EGR} has risen to the dew point temperature T _DEW. If the EGR gas temperature T _EGR has not risen to the dew point temperature T _DEW (No), this control is returned to the process of step S210. On the other hand, when the EGR gas temperature T _EGR rises to the dew point temperature T _DEW (Yes), this control is then returned.

FIG. 5 is a chart diagram illustrating a flow of processing for filter regeneration control according to the present embodiment.

In step S300, the execution condition of the filter regeneration is satisfied, in which the front-rear differential pressure P transmitted from the differential pressure sensor 95 reaches a predetermined upper limit differential pressure, or the interval from the previous filter regeneration execution reaches a predetermined interval. Determine whether or not to do so. When the execution condition of the filter reproduction is satisfied (Yes), this control proceeds to step S310. On the other hand, when the execution condition is not satisfied (No), this control repeats the determination process of step S300.

In step S310, fuel injection control by post-injection of the in-cylinder injector and exhaust pipe injection of the exhaust pipe injector, and heater heating control for energizing the pre-stage post-processing heater 63 are executed.

In step S320, it is determined whether or not the filter reproduction end condition is satisfied. If the filter reproduction end condition is not satisfied (No), this control is returned to the process of step S310. On the other hand, when the end condition of the filter reproduction is satisfied (Yes), this control is then returned.

According to the present embodiment described in detail above, a post-stage post-treatment heater 77 is provided on the downstream side of the exhaust gas from the branch portion 33A, and an EGR heater 59 is provided on the upstream side of the low pressure EGR cooler 58 of the low pressure EGR passage 56, respectively, and an SCR catalyst is provided. When the temperature T _SCR is less than the active temperature T _ACT , the catalyst temperature rise control that energizes the post-stage post-treatment heater 77, and when the EGR gas temperature T _EGR is less than the dew point temperature T _DEW , the condensed water that energizes the EGR heater 59. It is configured to perform occurrence prevention control. As a result, for example, when the engine is started, the activation of the SCR catalyst 78 and the prevention of the generation of condensed water in the low-pressure EGR cooler 58 or the like can be effectively performed in parallel, and the exhaust emission performance is ensured. It is possible to prevent the low-pressure EGR cooler 58 and the like from being eroded by the condensed water.

The present disclosure is not limited to the above-described embodiment, and can be appropriately modified and implemented without departing from the spirit of the present disclosure.

For example, in the above embodiment, the pre-stage post-treatment heater 63 is provided on the downstream side of the oxidation catalyst 62 of the pre-stage post-treatment device 60, but is provided on the upstream side of the oxidation catalyst 62 of the pre-stage post-treatment device 60. When the oxidation catalyst temperature _TDOC is lower than a predetermined activity temperature (for example, about 200 ° C.), the catalyst temperature rise control for energizing the pre-stage post-treatment heater 63 may be performed. In this case, the catalyst temperature rise control by the combustion control of the engine becomes unnecessary, and the fuel efficiency can be improved.

Further, in the above embodiment, the EGR heater 59 has been described as being provided in the low pressure EGR passage 56, but the EGR heater 59 may be provided in the high pressure EGR passage 51.

10 Engine 22 Upstream intake passage 23 Downstream intake passage 31 Upstream exhaust passage 32 First connection exhaust passage 33 Second connection exhaust passage 34 Downstream exhaust passage 40 Supercharger 41 Turbine 42 Compressor 43 Turbo shaft 55 Low-pressure EGR device (exhaust recirculation device) )
56 Low pressure EGR passage (exhaust gas recirculation passage)
57 Low pressure EGR valve 58 Low pressure EGR cooler (cooler)
59 EGR heater (second heater)
60 Pre-stage post-treatment device 62 Oxidation catalyst 63 Pre-stage post-treatment heater (third heater)
64 Filter 70 Post-stage post-treatment device 71 Urea water injection device 77 Post-stage post-treatment heater (first heater)
78 SCR catalyst (NOx catalyst)
79 Ammonia slip catalyst 100 Controller 110 SCR catalyst temperature estimation unit (NOx catalyst temperature acquisition unit)
120 EGR gas dew point temperature estimation unit (exhaust gas recirculation gas state quantity acquisition unit)
130 Catalyst temperature rise control unit 140 Condensed water generation prevention control unit 150 Filter regeneration control unit

Claims (4)

The intake passage that circulates the intake air to be introduced into the engine,
An exhaust passage that circulates the exhaust gas discharged from the engine, and
A NOx catalyst provided in the exhaust passage to purify NOx in the exhaust,
An exhaust gas recirculation device having an exhaust recirculation passage branching from the exhaust passage on the upstream side of the NOx catalyst and joining the intake passage, and a cooler provided in the exhaust recirculation passage.
A first heater provided on the downstream side of the exhaust passage with the exhaust recirculation passage and on the upstream side of the NOx catalyst.
A second heater provided on the upstream side of the cooler of the exhaust gas recirculation passage, and
A NOx catalyst temperature acquisition unit that acquires the temperature of the NOx catalyst,
An exhaust gas recirculation gas state amount acquisition unit that acquires the state amount of the exhaust gas recirculation gas flowing through the exhaust gas recirculation passage, and an exhaust gas recirculation gas state amount acquisition unit.
When the acquired temperature of the NOx catalyst is lower than the predetermined active temperature of the NOx catalyst, the catalyst temperature rise control for raising the temperature of the NOx catalyst to the active temperature by raising the temperature of the first heater. The catalyst temperature rise control unit to be implemented and
When the temperature of the exhaust gas recirculation gas is estimated to be lower than the dew point temperature based on the acquired state quantity, the temperature of the exhaust gas recirculation gas is changed to the dew point by raising the temperature of the second heater. An engine system characterized by being equipped with a condensed water generation prevention control unit that implements condensed water generation prevention control for raising the temperature to a temperature. When the acquired temperature of the NOx catalyst is lower than the active temperature and the temperature of the exhaust gas recirculation gas is estimated to be lower than the dew point temperature based on the acquired state quantity, the catalyst The engine system according to claim 1, wherein the temperature rise control and the condensed water generation prevention control are performed in parallel. An oxidation catalyst provided in the exhaust passage to oxidize unburned fuel in the exhaust,
A filter provided downstream of the oxidation catalyst in the exhaust passage and collecting particulate matter in the exhaust,
A third heater provided on the upstream side of the exhaust passage with respect to the filter, and
A filter regeneration control unit that performs filter regeneration control for burning and removing the particulate matter deposited on the filter by supplying the unburned fuel to the oxidation catalyst and raising the temperature of the third heater. The engine system according to claim 1 or 2, further comprising. A supercharger having a turbine provided in the exhaust passage and driven by exhaust gas and a compressor provided in the intake passage and rotatably connected to the turbine is further provided.
The exhaust gas recirculation device is a low-pressure exhaust gas recirculation device that branches from the exhaust passage on the downstream side of the turbine and joins the intake passage on the upstream side of the compressor. The engine system according to any one item.

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