Exhaust gas purification device for internal combustion engines

Abstract

To provide an exhaust gas purification device for an internal combustion engine that can suppress ammonia slip during filter regeneration while avoiding deterioration of fuel efficiency. [Solution] An exhaust gas purification device 200 having a fuel supply unit 140, a filter 213, and an SCR catalyst 222 provided downstream of the filter to remove NOx contained in the exhaust gas by a reduction reaction with ammonia, comprising a flow rate adjustment unit for adjusting the intake air flow rate and exhaust air flow rate, a determination unit 191a for determining whether the amount of ammonia adsorbed on the SCR catalyst 222 is less than or equal to a determination value K, and a control unit 190, wherein after executing a first control, if the exhaust gas temperature T upstream of the filter 213 is greater than or equal to a first determination temperature T1 and the determination unit 191a determines that the amount of ammonia adsorbed P2 is less than or equal to a determination value K, the control unit 190 executes a second control to supply fuel according to the exhaust gas temperature T necessary to regenerate the filter 213.

Description

Technical Field

[0001] The present invention relates to an exhaust gas purification device for an internal combustion engine that purifies exhaust gas.

Background Art

[0002] Conventionally, an exhaust gas purification device that purifies exhaust gas (hereinafter sometimes simply referred to as "exhaust gas") discharged from an internal combustion engine has been known. This exhaust gas purification device includes a soot filter installed in an exhaust gas flow path from the internal combustion engine to collect particulate matter, a diesel oxidation catalyst installed upstream of the soot filter to promote oxidation of fuel, a diesel oxidation catalyst temperature sensor that detects the temperature of the diesel oxidation catalyst, a selective reduction catalyst installed downstream of the soot filter to reduce nitrogen oxides, and a urea water injector installed between the soot filter and the selective reduction catalyst to inject urea water into the exhaust gas discharged from the soot filter (see, for example, Patent Document 1).

[0003] The diesel engine described in Patent Document 1 performs a first control to remove hydrocarbons by raising the temperature of the diesel oxidation catalyst in order to maintain a state where the accumulation amount of hydrocarbons is below a predetermined limit amount, and a second control to stop or reduce the urea water from the urea water injector until the adsorption amount of ammonia on the selective reduction catalyst is reduced to a predetermined reduction target amount. It estimates the first time until the hydrocarbons accumulated in the soot filter reach a predetermined limit amount that causes white smoke, and the second time it takes for the adsorption amount of ammonia to reach the reduction target amount when the second control is performed from now on, and at the timing when the first time and the second time are the same length, immediately after performing the second control, the first control is performed. The reduction target amount in the second control is an appropriate amount at which slip of ammonia adsorbed on the selective reduction catalyst hardly occurs even when the selective reduction catalyst is heated.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] However, in the diesel engine described in Patent Document 1, in order to prioritize the avoidance of white smoke generation, there is a risk that a first control is performed to raise the temperature of the diesel oxidation catalyst, even though the soot filter has sufficient capacity to collect hydrocarbons. In other words, if the soot filter is not used to its limit of collection capacity, the collection capacity of the soot filter is not utilized sufficiently, and the frequency of unnecessary post-injection increases, which may result in a deterioration of fuel efficiency. That is, it is not easy to suppress ammonia slip during filter regeneration while avoiding a deterioration in fuel efficiency.

[0006] Therefore, the present invention aims to provide an exhaust gas purification device for an internal combustion engine that can suppress ammonia slip during filter regeneration while avoiding deterioration of fuel efficiency. [Means for solving the problem]

[0007] The exhaust gas purification device for an internal combustion engine of the first invention comprises a fuel supply unit that supplies fuel to a combustion chamber, a filter provided in an exhaust passage connected to the combustion chamber for collecting particulate matter contained in the exhaust gas, and a selective reduction catalyst provided downstream of the filter for removing nitrogen oxides contained in the exhaust gas by a reduction reaction with ammonia, and further comprises a flow rate adjustment unit that adjusts the intake air flow rate supplied to the combustion chamber and / or the exhaust gas flow rate joined to the intake air, a determination unit that determines whether the amount of ammonia adsorbed on the selective reduction catalyst is less than or equal to a predetermined determination value, and a control unit that controls the fuel supply unit and the flow rate adjustment unit, wherein, after the flow rate adjustment unit performs a first control to limit the intake air flow rate and / or the exhaust gas flow rate, if the determination unit determines that the exhaust gas temperature upstream of the filter is above a threshold and the amount of ammonia adsorbed on the selective reduction catalyst is less than or equal to the determination value, the control unit causes the fuel supply unit to perform a second control to supply fuel to the combustion chamber according to the exhaust gas temperature necessary to regenerate the filter.

[0008] According to the first invention, the nitrogen oxides in the exhaust sent to the selective reduction catalyst by the first control can be increased before determining the amount of ammonia adsorbed, and the ammonia adsorbed on the selective reduction catalyst can be oxidized and consumed without using fuel. As a result, the ammonia adsorbed on the selective reduction catalyst can be kept below the determination value, and the second control can be executed when the ammonia adsorbed on the selective reduction catalyst is below the determination value. Therefore, the particulate matter collection capacity of the filter can be maximized, the feasibility of filter regeneration can be increased, and the injection frequency of post-injection for filter regeneration can be suppressed. In other words, ammonia slip during filter regeneration can be suppressed while avoiding deterioration of fuel efficiency.

[0009] The second invention is characterized in that the flow rate adjustment unit includes an intake valve that adjusts the intake air flow rate supplied to the combustion chamber and an EGR valve that adjusts the exhaust air flow rate that is joined to the intake air, and the control unit closes the intake valve to a predetermined opening and fully closes the EGR valve during the first control.

[0010] According to the second invention, the amount of nitrogen oxides supplied to the selective reduction catalyst can be increased using an intake valve and an EGR valve without using fuel.

[0011] The third invention is characterized in that the determination unit determines a predetermined elapsed time from the execution of the first control, and the elapsed time indicates the time elapsed from the start of the execution of the first control.

[0012] According to the third invention, the amount of ammonia adsorbed on the selective reduction catalyst can be indirectly estimated using time as a parameter. This eliminates the need for direct measurement of the amount of ammonia deposited.

[0013] The fourth invention is characterized in that, during the second control, the control unit supplies a second target regeneration injection amount, which is less than the first target regeneration injection amount, to the combustion chamber before supplying a first target regeneration injection amount to the combustion chamber for regenerating the filter.

[0014] According to the fourth invention, a rapid increase in exhaust temperature of the exhaust gas directed toward the selective reduction catalyst can be suppressed. Therefore, even if the amount of ammonia adsorbed on the selective reduction catalyst is less than the estimated value, ammonia slip during the second control can be suppressed.

[0015] The fifth invention further comprises a urea water injection unit that injects urea water toward the exhaust gas, characterized in that, during the second control, the control unit controls the urea water injection unit to inject a second target amount of urea water, which is less than the first target amount of urea water, into the selective reduction catalyst before injecting a first target amount of urea water into the selective reduction catalyst.

[0016] According to the fifth invention, the amount of ammonia adsorbed on the selective reduction catalyst can be suppressed. Therefore, even if the amount of ammonia adsorbed on the selective reduction catalyst is greater than the estimated value, ammonia slip during the second control can be suppressed.

[0017] The sixth invention is characterized in that, in the first control, the control unit increases the opening degree of the intake valve when the flow rate adjustment unit restricts the intake valve and the EGR valve, and the determination unit determines that the temperature of the exhaust gas upstream of the filter is above a threshold and the amount of ammonia adsorbed on the selective reduction catalyst exceeds the determination value.

[0018] According to the sixth invention, if the ammonia reduction effect cannot be obtained by the first control, the deterioration of fuel efficiency can be suppressed by increasing the intake air flow rate.

[0019] The seventh invention is characterized in that the flow rate adjustment unit includes an intake valve that adjusts the intake air flow rate supplied to the combustion chamber and an EGR valve that adjusts the exhaust air flow rate that is joined to the intake air, the first control includes a third control that completely closes the EGR valve and a fourth control that closes the intake valve to a predetermined opening, the control unit executes the fourth control when the determination unit determines that the amount of ammonia adsorbed on the selective reduction catalyst is less than or equal to the determination value during the third control, and when the exhaust temperature upstream of the filter is above a threshold during the fourth control, the control unit executes the second control.

[0020] According to the seventh invention, the period during which the intake airflow is restricted can be shortened. Therefore, fuel efficiency can be improved.

[0021] The eighth invention further comprises a urea water injection unit for injecting urea water toward the selective reduction catalyst, the fuel supply unit further comprises a common rail for storing the fuel and a combustion injection unit for injecting the fuel from the common rail into the combustion chamber, and the control unit, when executing the first control, determines that the amount of ammonia adsorbed on the selective reduction catalyst exceeds the determination value, increases the pressure of the fuel stored in the common rail and stops injecting the urea water toward the selective reduction catalyst.

[0022] According to the eighth invention, nitrogen oxides in the exhaust gas can be increased, thereby reducing the amount of ammonia adsorbed by the selective reduction catalyst. [Effects of the Invention]

[0023] According to the present invention, it is possible to provide an exhaust gas purification device for an internal combustion engine that can suppress ammonia slip during filter regeneration while avoiding deterioration of fuel consumption.

Brief Description of the Drawings

[0024] [Figure 1] It is an overall configuration diagram showing an exhaust gas purification device for an engine according to Embodiment 1. [Figure 2] It is a block diagram showing the configuration of a control unit. [Figure 3] It is a graph showing the characteristics of post-injection amount. [Figure 4] It is a diagram showing a urea aqueous solution injection amount map. [Figure 5] It is a graph showing the characteristics of urea aqueous solution injection amount. [Figure 6] It is a graph showing the change in exhaust gas temperature. [Figure 7] It is a diagram showing the characteristics of a urea aqueous solution injection pattern. [Figure 8] It is a flowchart showing filter regeneration control processing. [Figure 9] It is a flowchart showing a second control process. [Figure 10] It is a flowchart showing urea aqueous solution injection control processing.

Modes for Carrying Out the Invention

[0025] Hereinafter, an embodiment of an exhaust gas purification device for an internal combustion engine according to the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and the description will not be repeated.

[0026] Referring to FIG. 1, an exhaust gas purification device 200 for an engine 100 of the present invention will be described. FIG. 1 is an overall configuration diagram showing an exhaust gas purification device 200 for an engine 100 according to Embodiment 1.

[0027] Engine 100 is, for example, a diesel engine. Engine 100 is mounted on the vehicle body as a power source for a tractor, for example. Engine 100 is configured as, for example, an inline four-cylinder engine. The rotational power generated by engine 100 is reduced by a transmission and transmitted to the drive wheels (neither of which are shown in the figure). Engine 100 corresponds to, for example, an "internal combustion engine". Note that engine 100 is not limited to a power source for a tractor. Engine 100 may also be a power source for other work vehicles (for example, a skid steer loader, etc.). As shown in Figure 1, engine 100 includes a combustion chamber 110, an intake manifold 120, an exhaust manifold 130, a fuel supply unit 140, an intake passage 150, an exhaust passage 160, an EGR device 170, a turbocharger 180, and a control unit 190.

[0028] The combustion chamber 110 burns fuel. For example, a combustion chamber 110 is provided in each of the four cylinders. The combustion chamber 110 is composed of a cylinder head that forms the upper wall, a cylinder block that forms the side wall, and a piston that moves back and forth vertically within the cylinder (none of which are shown in the diagram).

[0029] The intake manifold 120 supplies intake air to the combustion chamber 110. The intake manifold 120 is connected to the combustion chamber 110 of each cylinder. The intake manifold 120 has a single inlet and an intake port for each cylinder that supplies intake air to the combustion chamber 110. The intake manifold 120 is fixed to the intake side of the combustion chamber 110.

[0030] The exhaust manifold 130 discharges exhaust gas (hereinafter sometimes referred to as "exhaust") from the combustion chamber 110. The exhaust manifold 130 is connected to the combustion chamber 110 for each cylinder. The exhaust manifold 130 has an exhaust port for discharging exhaust from each cylinder and has a single collective outlet. The exhaust manifold 130 is fixed to the exhaust side of the combustion chamber 110.

[0031] The fuel supply unit 140 supplies fuel to the combustion chamber 110 of each cylinder. The fuel supply unit 140 supplies fuel to the combustion chamber 110 that corresponds to a target injection amount according to the operating conditions of the engine 100. As shown in Figure 1, the fuel supply unit 140 has a common rail 141 and a fuel injection unit 142.

[0032] The common rail 141 stores high-pressure fuel. The common rail 141 is a long, oval-shaped chamber extending in the direction of the cylinder arrangement. The common rail 141 is connected to a high-pressure pump via a pressure control valve (neither of which are shown). The common rail pressure, which is the pressure of the fuel in the common rail 141, is feedback-controlled via the pressure control valve to match, for example, a target common rail pressure corresponding to a target injection amount.

[0033] The fuel injection unit 142 is a nozzle that injects fuel from the common rail 141 into the combustion chamber 110. The fuel injection unit 142 is controlled to open and close and inject a fuel amount corresponding to the target injection amount into the combustion chamber 110. Specifically, a fuel injection unit 142 is provided for each combustion chamber 110, and the injection timing and injection duration are duty cycle controlled.

[0034] The turbocharger 180 utilizes exhaust energy to increase the amount of intake air filling the combustion chamber 110. The turbocharger 180 includes an intake compressor 181 and an exhaust turbine 182 connected coaxially to the intake compressor 181. The intake compressor 181 is located in the intake passage 150. The exhaust turbine 182 is located in the exhaust passage 160. In this embodiment, a heat shield (not shown) is placed between the turbocharger 180 and the cylinder head cover (not shown). The heat shield protects the harness around the cylinder head cover from heat generated by the exhaust.

[0035] The intake passage 150 takes in intake air from the outside. The intake passage 150 is formed in a pipe shape and is connected to the upstream end of the intake manifold 120. The intake passage 150 is equipped with an air cleaner (not shown), an intake compressor 181, and an intake valve 151 from the upstream side.

[0036] The intake valve 151 adjusts the intake airflow rate supplied to the combustion chamber 110. The intake valve 151 is, for example, a butterfly valve and is an electric throttle whose opening degree is electrically adjustable. The intake valve 151 is located between the intake compressor 181 and the intake manifold 120. The intake valve 151 corresponds to, for example, a "flow rate adjustment unit".

[0037] The exhaust passage 160 discharges exhaust gas from the combustion chamber 110. The exhaust passage 160 is formed in a pipe shape and is connected to the downstream end of the exhaust manifold 130. The exhaust passage 160 is equipped with an exhaust turbine 182 and an exhaust valve 161.

[0038] The exhaust valve 161 adjusts the exhaust flow rate discharged to the outside from the exhaust passage 160. The exhaust valve 161 is, for example, a butterfly valve and is controlled to open and close by the control unit 190. The more the exhaust valve 161 is operated to the closed side, the higher the exhaust pressure in the exhaust passage 160 can be increased.

[0039] The EGR device 170 mixes a portion of the exhaust gas into the intake air. The EGR device 170 suppresses the generation of nitrogen oxides (hereinafter sometimes referred to as "NOx") by reducing the amount of oxygen in the intake air supplied to the combustion chamber 110. However, if a high EGR rate is set, which increases the amount of exhaust gas mixed into the intake air, there is a risk of incomplete combustion due to insufficient oxygen in the intake air, so the EGR rate is adjusted according to the combustion state. The EGR device 170 includes an EGR pipe 171, an EGR valve 172, and an EGR cooler 173.

[0040] The EGR pipe 171 supplies exhaust gas to the intake passage 150. The EGR pipe 171 is formed in a pipe shape and connects the exhaust manifold 130 and the intake passage 150. One end of the EGR pipe 171 is connected to the exhaust manifold 130, and the other end is connected to a position between the intake manifold 120 and the intake valve 151.

[0041] The EGR valve 172 adjusts the exhaust gas flow rate that is joined to the intake air. The EGR valve 172 is located in the middle of the EGR pipe 171. The EGR valve 172 is, for example, a diaphragm valve that responds to the control pressure from a pressure control valve (not shown). The pressure control valve is driven by a duty cycle control command received from the control unit 190. The driving method of the EGR valve 172 is not limited to a diaphragm type; it may also be driven by a stepper motor. The harness of the EGR valve 172 is routed together with the harnesses of the crank angle and cam angle sensors (not shown) to the end of the cylinder arrangement direction where the timing belt (not shown) is not located. This prevents interference with the timing belt even if the harness sags. The EGR valve 172 corresponds to, for example, the "flow rate adjustment section".

[0042] The EGR valves 172 are arranged in pairs along the axis of a shaft (not shown), for example. The EGR valves 172 may become stuck to their seating surfaces due to condensation water generated inside the EGR pipe 171. Therefore, a protective plate with a larger diameter than the EGR valves 172 may be placed near each of the pair of EGR valves 172. Alternatively, a return portion may be provided that protrudes from the edge of the seating surface of one EGR valve 172 toward the other EGR valve 172. Furthermore, the edges of each EGR valve 172 may be made to overhang their respective seating surfaces. In addition, one or more grooves may be formed around the entire circumference of the shaft corresponding to the space between the pair of EGR valves 172. This can suppress the adhesion and mixing of condensed water.

[0043] The EGR cooler 173 cools the exhaust gas. More specifically, the EGR cooler 173 cools the exhaust gas (hereinafter sometimes referred to as "EGR gas") that is mixed with the intake air as it passes through the EGR pipe 171. The EGR cooler 173, for example, facilitates heat exchange between the EGR gas and the cooling water. Lowering the temperature of the EGR gas improves the efficiency of intake air filling the combustion chamber 110 and reduces the amount of NOx contained in the exhaust gas.

[0044] Furthermore, for work vehicles such as combine harvesters, which have a fixed operating season, the EGR valve 172 may become stuck to the valve seat (not shown) after being left unused for a long period of time after the end of the operating season. Therefore, if the period from the previous start to the current start is longer than a predetermined period, the EGR valve 172 may be fully opened. This can resolve the sticking of the EGR valve 172. Also, when the engine 100 is stopped, if the exhaust temperature is below a certain value and the engine 100's coolant temperature is below a certain value, the EGR valve 172 may be fully opened at the next start. This can resolve the sticking of the EGR valve 172 caused by condensation.

[0045] Next, the exhaust gas purification device 200 will be described with reference to Figure 1. The exhaust gas from the engine 100 flows from the exhaust manifold 130 through the exhaust turbine 182 of the turbocharger 180 to the exhaust passage 160. The exhaust gas purification device 200 takes in the exhaust gas flowing through the exhaust passage 160. As shown in Figure 1, the exhaust gas purification device 200 has, in order from the upstream side, a DPF device 210, a urea mixing unit 230, an SCR device 220, and an oxidizer injection unit 240.

[0046] The DPF device 210 collects and removes particulate matter (PM) contained in the exhaust gas. The DPF device 210 comprises a DPF case 211, a PM oxidation catalyst 212, and a filter 213.

[0047] The DPF case 211 houses the PM oxidation catalyst 212 and the filter 213. The DPF case 211 is positioned in the middle of the exhaust passage 160. The DPF case 211 receives exhaust gas from the exhaust passage 160 and discharges the purified exhaust gas back into the exhaust passage 160. The DPF case 211 is formed in a substantially cylindrical shape.

[0048] The PM oxidation catalyst 212 burns unburned substances. Specifically, the PM oxidation catalyst 212 is a catalyst for oxidizing unburned fuel, carbon monoxide, nitric oxide, etc., contained in the exhaust. The PM oxidation catalyst 212 is composed of platinum, etc. The oxidized unburned fuel, etc., becomes particulate matter and mixes into the exhaust.

[0049] The filter 213 collects particulate matter contained in the exhaust gas. The filter 213 is installed in the exhaust passage 160 connected to the combustion chamber 110 and collects particulate matter contained in the exhaust gas. The filter 213 is positioned downstream of the PM oxidation catalyst 212 and faces the PM oxidation catalyst 212. The filter 213 is, for example, a wall-flow type filter. Hereinafter, the amount of particulate matter collected by the filter 213 may be referred to as the PM deposit amount P1.

[0050] The SCR device 220 removes NOx contained in the exhaust gas. The SCR device 220 is located downstream of the DPF device 210. The SCR device 220 comprises an SCR case 221, an SCR catalyst 222, and an ammonia oxidation catalyst 223.

[0051] The SCR case 221 houses the SCR catalyst 222 and the ammonia oxidation catalyst 223. The SCR case 221 is positioned in the middle of the exhaust passage 160. The SCR case 221 receives exhaust gas from the exhaust passage 160 and discharges the purified exhaust gas back into the exhaust passage 160. The SCR case 221 is formed in a substantially cylindrical shape.

[0052] The SCR catalyst 222 adsorbs ammonia. Specifically, the SCR catalyst 222 is composed of materials such as zeolite and ceramic. The SCR catalyst 222 corresponds to, for example, a "selective reduction catalyst." The SCR catalyst 222 is installed downstream of the filter 213 and removes NOx contained in the exhaust gas through a reduction reaction with ammonia. Hereinafter, the amount of ammonia adsorbed on the SCR catalyst 222 may be referred to as "ammonia adsorption amount P2." Ammonia adsorption amount P2 is the amount of unreduced ammonia currently adsorbed on the SCR catalyst 222.

[0053] The ammonia oxidation catalyst 223 prevents the release of ammonia to the outside. Specifically, the ammonia oxidation catalyst 223 is a catalyst for oxidizing ammonia that is not adsorbed by the SCR catalyst 222, and ammonia that has been desorbed from the SCR catalyst 222. The ammonia oxidation catalyst 223 is composed of platinum or the like. The ammonia oxidation catalyst 223 converts ammonia into nitrogen, carbon monoxide, water, etc.

[0054] The urea mixing unit 230 generates ammonia in the exhaust gas flowing through the exhaust passage 160. The urea mixing unit 230 is located between the DPF device 210 and the SCR device 220. The urea mixing unit 230 includes a urea water injection unit 231, a water injection unit 232, a blower turbine 233, and a mixer unit 234.

[0055] The urea water injection unit 231 injects urea water towards the exhaust flowing through the exhaust passage 160. The urea water injection unit 231 includes a urea water injection nozzle 231a for injecting urea water, a urea water pump 231b, and a urea water tank 231c.

[0056] The urea water injection nozzle 231a is positioned near the downstream end of the DPF case 211. The injection timing and amount of urea water from the urea water injection nozzle 231a are controlled by the control unit 190. This causes the urea to hydrolyze and generate ammonia in the exhaust gas. The urea water injection nozzle 231a may also inject urea water directly towards the SCR catalyst 222. The urea water tank 231c stores the urea water. The urea water pump 231b pumps the urea water from the urea water tank 231c to the urea water injection nozzle 231a.

[0057] The water injection unit 232 injects water toward the urea water injection nozzle 231a. The water injection unit 232 includes a water injection nozzle 232a, a water pump 232b, and a water tank 232c. The water tank 232c stores water. The water pump 232b pumps water from the water tank 232c toward the water injection nozzle 232a.

[0058] The water injection nozzle 232a periodically sprays water toward the urea solution injection nozzle 231a. This suppresses the adhesion of the urea solution injection nozzle 231a caused by crystallization of the urea solution.

[0059] The blower turbine 233 facilitates exhaust from the DPF device 210. The blower turbine 233 generates airflow by rotating turbine-shaped blades, for example, using an electric motor. This reduces the exhaust pressure in the exhaust passage 160 and sends the exhaust downstream.

[0060] The mixer unit 234 agitates the airflow in the exhaust passage 160. The mixer unit 234 rotates a mixer equipped with, for example, agitation blades. After mixing the exhaust and ammonia, the mixer unit 234 guides the mixture toward the SCR device 220.

[0061] The oxidizer injection unit 240 injects an oxidizer toward the exhaust. The oxidizer injection unit 240 oxidizes residual ammonia contained in the exhaust. The oxidizer injection unit 240 includes an oxidizer injection nozzle 240a for injecting the oxidizer, an oxidizer pump 240b, and an oxidizer tank 240c.

[0062] The oxidant injection nozzle 240a injects oxidant towards the exhaust gas that has passed through the SCR device 220. This suppresses ammonia slip. The oxidant tank 240c stores the oxidant. The oxidant pump 240b pumps the oxidant from the oxidant tank 240c to the oxidant injection nozzle 240a.

[0063] Next, the control unit 190 will be described with reference to Figures 1 to 7. Figure 2 is a block diagram showing the configuration of the control unit 190. Figure 3 is a graph G1 showing the post-injection amount characteristics. Figure 4 is a diagram showing the urea solution injection amount map M. Figure 5 is a graph G2 showing the urea solution injection amount characteristics. Figure 6 is a graph G3 showing the change in exhaust temperature. Figure 7 is a diagram showing the characteristics of the urea solution injection pattern.

[0064] The control unit 190 is electrically connected to the sensor group. The control unit 190 receives detection signals detected by the sensor group. As shown in Figure 2, the sensor group includes a rotation speed sensor 301, an output sensor 302, a first pressure sensor 303, a second pressure sensor 304, an SCR temperature sensor 305, an exhaust temperature sensor 306, and a NOx concentration sensor 307. The first pressure sensor 303, the second pressure sensor 304, and the exhaust temperature sensor 306 are supported, for example, by a stay formed from a single plate. Connectors are fixed to this stay, for example, by spot welding. If the DPF device 210 is equipped with an inlet temperature sensor for the PM oxidation catalyst 212 and inlet / outlet temperature sensors for the filter 213, the three temperature sensors may be supported by the stay.

[0065] The rotational speed sensor 301 detects the rotational speed (r / min) of the engine 100. The output sensor 302 detects the output (kW) of the engine 100. As shown in Figures 1 and 2, the first pressure sensor 303 detects the exhaust pressure upstream of the DPF device 210. The second pressure sensor 304 detects the exhaust pressure downstream of the DPF device 210. The PM accumulation amount P1 deposited on the filter 213 is estimated using the differential pressure across the DPF device 210. The SCR temperature sensor 305 detects the temperature of the SCR catalyst 222. The exhaust temperature sensor 306 detects the temperature of the exhaust flowing through the exhaust passage 160. The exhaust temperature sensor 306 is located, for example, near the downstream end of the DPF case 211. The NOx concentration sensor 307 detects the concentration of NOx contained in the exhaust flowing through the exhaust passage 160. The NOx concentration sensor 307 is located, for example, near the downstream end of the SCR case 221.

[0066] Furthermore, the control unit 190 is electrically connected to the actuator group. The control unit 190 transmits control commands to the actuator group. The actuator group includes a fuel injection unit 142, an intake valve 151, an exhaust valve 161, an EGR valve 172, a urea water injection unit 231, a water injection unit 232, a blower turbine 233, a mixer unit 234, and an oxidizer injection unit 240. In other words, the control unit 190 controls the fuel supply unit 140 and the flow rate adjustment unit.

[0067] The control unit 190 includes an ECU (Engine Control Unit) 191 and a DCU (Dosing Control Unit) 192. In this embodiment, the ECU 191 and DCU 192 are configured separately and capable of communicating with each other, but the system is not limited to this configuration. The ECU 191 and DCU 192 may be controlled by a single processor. Hereinafter, the ECU 191 and DCU 192 may be collectively referred to as the "control unit 190".

[0068] The ECU191 includes a processor such as a CPU (Central Processing Unit) and an MPU (Micro Processing Unit). The ECU191's processor executes computer programs stored in a memory device (not shown) to control the actuator group. The memory device consists of ROM and RAM, etc.

[0069] The ECU 191 determines the target injection amount, injection timing, and injection duration for the main injection based on the operating conditions. The ECU 191 has a control map (not shown) defined based on the rotational speed and torque of the engine 100. Using the control map, the ECU 191 sets the duty cycle for operating the fuel injection unit 142 and transmits a control command for the main injection to the fuel injection unit 142.

[0070] The ECU 191 performs a first control. The first control is a control that limits the intake air flow rate supplied to the combustion chamber 110 or the exhaust air flow rate that merges with the intake air, or a control that limits both the intake air flow rate supplied to the combustion chamber 110 and the exhaust air flow rate that merges with the intake air. In this embodiment, the ECU 191 performs a first control that limits both the intake air flow rate and the exhaust air flow rate. During the first control, the ECU 191 outputs a control command to close the intake valve 151 to a predetermined opening and a control command to completely close the EGR valve 172. The execution of the first control increases the oxygen contained in the intake air and increases the generation of NO. In the case of the operation to close the intake valve 151 to a predetermined opening, for example, it may be closed to a constant opening from the current opening. Alternatively, as the operation to close to a predetermined opening, openings before and after the idling opening may be set in advance.

[0071] The ECU191 performs a second control. This second control involves post-injection, which heats the exhaust gas to forcibly incinerate and remove particulate matter collected by the filter 213 (see Figure 1). Post-injection is performed after the main injection. In post-injection, fuel is injected according to the exhaust gas temperature required to regenerate the filter 213. During the second control, the ECU191 outputs a control command to perform post-injection. The exhaust gas temperature required to regenerate the filter 213 is a temperature at which particulate matter can be incinerated, and is, for example, within a temperature range of 500°C to 650°C.

[0072] During the second control, the ECU 191 injects a post-injection amount corresponding to the target exhaust temperature. As shown in Figure 3, the ECU 191 typically injects a first post-injection amount F1 such that the characteristic L1 approaches linearly towards the target exhaust temperature E1 required to regenerate the filter 213. In this embodiment, the target exhaust temperature E1 is, for example, 600°C. The first post-injection amount F1 is the amount of fuel required to raise the exhaust temperature T flowing through the exhaust passage 160 to the target exhaust temperature E1. However, when the ammonia adsorption amount P2 is detected indirectly rather than directly, the actual amount of ammonia adsorbed on the SCR catalyst 222 may be greater than the estimated value. Indirect detection refers to estimating the ammonia adsorption amount P2 via a time parameter. If the actual amount of ammonia adsorbed on the SCR catalyst 222 is greater than the estimated value, a rapid increase in exhaust temperature can cause ammonia slip. The post-injection amount corresponds to, for example, the "target injection amount".

[0073] Before supplying the first post-injection amount F1 to the combustion chamber 110 for regenerating the filter 213, the ECU 191 supplies a second post-injection amount F2, which is less than the first post-injection amount F1, to the combustion chamber 110. As shown in graph G1 of Figure 3, when estimating the ammonia adsorption amount P2 with time as a parameter, the second post-injection amount F2 is injected to achieve the characteristic L2 shown by the dashed line. The second post-injection amount F2 performs post-injection targeting a target exhaust temperature E2 lower than the target exhaust temperature E1 until time t2, and has a temperature maintenance period from time t2 to time t3 to maintain the exhaust temperature. In this embodiment, the target exhaust temperature E2 is, for example, 500°C. After that, the second post-injection amount F2 performs post-injection targeting the target exhaust temperature E1. Note that although the temperature maintenance period of characteristic L2 was only for the target exhaust temperature E2, two or more temperature maintenance periods may be provided. In the case of characteristic L3, shown by the dashed line, before performing post-injection targeting the target exhaust temperature E1, a temperature maintenance period is provided between the target exhaust temperature E2 and a target exhaust temperature E3 that is lower than the target exhaust temperature E2. This suppresses a rapid rise in exhaust temperature T. In this embodiment, the target exhaust temperature E3 is, for example, 400°C.

[0074] The ECU191 has a determination unit 191a. The processor of the ECU191 executes a computer program stored in ROM and RAM, etc., and functions as the determination unit 191a.

[0075] The determination unit 191a determines that the amount of ammonia adsorbed on the SCR catalyst 222 is less than or equal to a predetermined determination value K. The determination value K is an index for determining the amount of ammonia adsorbed P2 at which ammonia slip does not occur even when post-injection is performed to regenerate the filter 213. The determination unit 191a also determines a predetermined elapsed time T3 from the start of the first control. The elapsed time is the time that has elapsed since the start of the first control. The predetermined elapsed time T3 is the determination time for determining that the amount of ammonia adsorbed P2 has been reduced to less than the determination value K by the execution of the first control. The predetermined elapsed time T3 is determined, for example, by experimental verification.

[0076] If, after executing the first control, the ECU 191 determines that the exhaust temperature T upstream of the filter 213 is equal to or greater than the first determination temperature T1 and that the determination unit 191a determines that the ammonia adsorption amount P2 is less than or equal to the determination value K, then the ECU 191 executes the second control. The first determination temperature T1 is the temperature at which the PM oxidation catalyst 212 is activated, and is, for example, included in the temperature range of 200°C to 250°C. The first determination temperature T1 corresponds to, for example, a "threshold."

[0077] The DCU192 includes a processor such as a CPU and an MPU. The DCU192's processor executes computer programs stored in a memory device (not shown) to control the actuator group. The memory device consists of ROM and RAM, etc.

[0078] The DCU192 determines the target injection amount, injection timing, and injection duration of urea solution based on the operating conditions. The DCU192 has a urea solution injection amount map M (see Figure 4) defined based on the rotational speed and torque of the engine 100. Based on the urea solution injection amount map M, the DCU192 transmits a control command for urea solution injection to the urea solution injection nozzle 231a.

[0079] As shown in Figure 4, in the urea solution injection amount map M, the urea solution injection amount is determined by the detected values ​​of engine speed (r / min) and engine output (kW). In the urea solution injection amount map M, the vertical axis is engine output and the horizontal axis is engine speed, and the urea solution injection amount is set for each point on the map M. A point on the map is determined by the detected values ​​of engine speed and engine output, and the first target urea solution injection amount f1 is determined so that it matches the set value of that point. In addition, the injection amount in the urea solution injection amount map M increases in proportion to the increase in engine output. Within the same engine output range, the injection amount increases more gradually as the engine speed increases. The numerical value of the injection amount is, for example, the amount injected in one (or one) injection from the urea solution injection nozzle 231a.

[0080] When controlling urea solution injection, the DCU192 injects a first target urea solution injection amount f1 set in the urea solution injection amount map M. As shown in graph G2 of Figure 5, the DCU192 normally injects urea solution to achieve a characteristic La that linearly approaches the first target urea solution injection amount f1. However, if the ammonia adsorption amount P2 is large, the injection of urea solution can cause ammonia slip. In particular, when the ammonia adsorption amount P2 is estimated using time as a parameter, the actual amount of adsorbed ammonia P2 may be greater than the estimated value.

[0081] During the second control, the DCU192 controls the urea solution injection unit 231 to inject a second target urea solution injection amount f2, which is less than the first target urea solution injection amount f1, into the SCR catalyst 222 before injecting the first target urea solution injection amount f1 into the SCR catalyst 222. As shown in Figure 5, when estimating the ammonia adsorption amount P2 with time as a parameter, the first target urea solution injection amount f1 is injected so that the characteristic Lb shown by the dashed line is obtained. Characteristic Lb is controlled so that the injection of urea solution is stopped until time tb, and then at time te the injection amount becomes the first target urea solution injection amount f1. In characteristics La and Lb, the injection amount increased linearly from the start of injection to the first target urea solution injection amount f1, but it may also be controlled in a stepwise manner. In the case of characteristic Lc shown by the dashed line, an injection of a second target urea solution injection amount f2, which is smaller than the first target urea solution injection amount f1, is provided before the injection of the first target urea solution injection amount f1, and an injection of a third target urea solution injection amount f3, which is smaller than the second target urea solution injection amount f2, is provided before the injection of the second target urea solution injection amount f2. This makes it possible to suppress ammonia slip during the second control.

[0082] The DCU192 calculates the rate of change of the exhaust gas temperature T flowing through the exhaust passage 160. As shown in Figure 6, the rate of change α of the exhaust gas temperature T at the start and end of urea water injection is determined. Based on the calculated rate of change α, the DCU192 determines the urea water injection pattern each time. As shown in Figure 7, the larger the rate of change α, the shorter the time interval between urea water injections is set, and the smaller the rate of change α, the longer the time interval between urea water injections is set. This optimizes the time interval between urea water injections and suppresses unnecessary urea water injection. As a result, problems such as clogging of the urea water injection nozzle 231a can also be prevented.

[0083] Next, the procedure for regenerating the filter 213 in the ECU 191 will be described with reference to the flowchart in Figure 8. Figure 8 is a flowchart of the filter regeneration control process. As shown in Figure 8, the process of the ECU 191 includes steps S1 to S9. Steps S1 to S9 are executed by the ECU 191's processor executing a computer program. The ECU 191 performs the filter regeneration control process at predetermined intervals.

[0084] As shown in the flowchart in Figure 8, in step S1, the ECU191 reads various information. The process then proceeds to step S2.

[0085] In step S2, the ECU 191 calculates the PM accumulation amount P1. The process then proceeds to step S3. The ECU 191 estimates the PM accumulation amount P1 of the filter 213 using the detected values ​​of the first pressure sensor 303 and the second pressure sensor 304.

[0086] In step S3, the ECU191 determines whether the PM accumulation amount P1 is greater than or equal to the DPF regeneration start determination value K1. If the ECU191 determines that the PM accumulation amount P1 is less than the DPF regeneration start determination value K1 (No in step S3), the process ends. If the ECU191 determines that the PM accumulation amount P1 is greater than or equal to the DPF regeneration start determination value K1 (Yes in step S3), the process proceeds to step S4.

[0087] In step S4, the ECU 191 executes the first control. The process proceeds to step S5. In the present embodiment, the ECU 191 activates a timer that counts the elapsed time since the start of the execution of the first control.

[0088] In step S5, the ECU 191 determines whether the exhaust temperature T is equal to or higher than the first determination temperature T1. If the ECU 191 determines that the exhaust temperature T is less than the first determination temperature T1 (No in step S5), the process returns to step S4. If the ECU 191 determines that the exhaust temperature T is equal to or higher than the first determination temperature T1 (Yes in step S5), the process proceeds to step S6.

[0089] In step S6, the ECU 191 calculates the ammonia adsorption amount P2. The process proceeds to step S7. In the present embodiment, the ammonia adsorption amount P2 is estimated based on the elapsed time since the start of the execution of the first control.

[0090] In step S7, the ECU 191 determines whether the ammonia adsorption amount P2 is equal to or less than the determination value K. If the ECU 191 determines that the ammonia adsorption amount P2 exceeds the determination value K (No in step S7), the process returns to step S4. If the ECU 191 determines that the ammonia adsorption amount P2 is equal to or less than the determination value K (Yes in step S7), the process proceeds to step S8.

[0091] In step S8, the ECU 191 executes the second control. The process proceeds to step S9.

[0092] In step S9, the ECU 191 determines whether the PM deposition amount P1 is less than the DPF regeneration end determination value K2 (<K1). If the ECU 191 determines that the PM deposition amount P1 is equal to or higher than the DPF regeneration end determination value K2 (No in step S9), the process returns to step S8. If the ECU 191 determines that the PM deposition amount P1 is less than the DPF regeneration end determination value K2 (Yes in step S9), the process ends. The counter of the timer is reset.

[0093] The procedure for the second control in step S8 will be described with reference to the flowchart in Figure 9. Figure 9 is a flowchart of the second control process. As shown in Figure 9, the processing of the ECU 191 includes steps S11 to S14. Steps S11 to S14 are executed by the processor of the ECU 191 executing a computer program.

[0094] As shown in the flowchart in Figure 9, in step S11, the ECU 191 determines whether or not the ammonia adsorption amount P2 has been determined based on the elapsed time since the start of the first control. If the ammonia adsorption amount P2 has not been determined based on the elapsed time since the start of the first control (No in step S11), the process proceeds to step S14. If the ammonia adsorption amount P2 has been determined based on the elapsed time since the start of the first control (Yes in step S11), the process proceeds to step S12.

[0095] In step S12, the ECU191 selects the second characteristic, characteristic L2 (see Figure 3). The process then proceeds to step S13. If characteristic L3 is set as the second characteristic, then characteristic L3 is selected.

[0096] In step S13, the ECU191 performs post-injection according to the selected characteristic and then terminates. If characteristic L2 is set as the second characteristic, it injects a second post-injection amount F2 corresponding to characteristic L2, and then injects a first post-injection amount F1. If characteristic L3 is set as the second characteristic, it injects a third post-injection amount F3 corresponding to characteristic L3, then injects a second post-injection amount F2, and then injects a first post-injection amount F1.

[0097] If the answer in step S11 is No, then in step S14, the ECU191 selects the first characteristic, characteristic L1 (see Figure 3). The process proceeds to step S13. In step S13, the ECU191 executes the first post-injection amount F1 and then terminates.

[0098] Next, the urea solution injection procedure in the DCU192 will be described with reference to the flowchart in Figure 10. Figure 10 is a flowchart of the urea solution injection control process. As shown in Figure 10, the process of the DCU192 includes steps S21 to S25. Steps S21 to S25 are executed by the DCU192 processor executing a computer program. The DCU192 periodically performs the urea solution injection control process independently of the filter regeneration control process.

[0099] As shown in the flowchart in Figure 10, in step 21, the DCU192 reads various information. The process then proceeds to step S22.

[0100] In step S22, the DCU192 determines whether the exhaust temperature T is equal to or greater than the first determination temperature T1. If the DCU192 determines that the exhaust temperature T is less than the first determination temperature T1 (No in step S22), the process ends. If the DCU192 determines that the exhaust temperature T is equal to or greater than the first determination temperature T1 (Yes in step S22), the process proceeds to step S23.

[0101] In step S23, the DCU192 performs urea water injection using the urea water injection nozzle 231a. In step S23, if the ammonia adsorption amount P2 is determined by the elapsed time from the start of the first control execution, the second characteristic, characteristic Lb (see Figure 5), is selected. Corresponding to characteristic Lb, the DCU192 stops injection for a predetermined time and then performs injection with the first target urea water injection amount f1 as the target injection amount. If characteristic Lc is set as the second characteristic, after executing the third target urea water injection amount f3 and the second target urea water injection amount f2, a stepwise injection is performed with the first target urea water injection amount f1 as the target injection amount. If the ammonia adsorption amount P2 is not determined by the elapsed time from the start of the first control execution, injection is performed with the first target urea water injection amount f1 as the target injection amount. The process proceeds to step S24.

[0102] In step S24, the DCU192 determines whether the exhaust temperature T is less than the first determination temperature T1. If the DCU192 determines that the exhaust temperature T is greater than or equal to the first determination temperature T1 (No in step S24), the process returns to step S23. If the DCU192 determines that the exhaust temperature T is less than the first determination temperature T1 (Yes in step S24), the process proceeds to step S25.

[0103] In step S25, the DCU192 determines whether the temperature of the SCR catalyst 222 is below the second determination temperature T2. If the DCU192 determines that the temperature of the SCR catalyst 222 is equal to or greater than the second determination temperature T2 (No in step S25), the process returns to step S23. If the DCU192 determines that the temperature of the SCR catalyst 222 is below the second determination temperature T2 (Yes in step S25), the process ends.

[0104] With the above configuration, the nitrogen oxides in the exhaust sent to the SCR catalyst 222 by the first control can be increased before determining the amount of ammonia adsorbed, and the ammonia adsorbed on the SCR catalyst 222 can be oxidized and consumed without using fuel. As a result, the ammonia adsorbed on the SCR catalyst 222 can be kept below the determination value K, and the second control can be executed when the ammonia adsorbed on the SCR catalyst 222 is below the determination value K. Therefore, the particulate matter collection capacity of the filter 213 can be maximized, the feasibility of filter regeneration can be increased, and the injection frequency of post-injection for regenerating the filter 213 can be suppressed. In other words, ammonia slip during filter 213 regeneration can be suppressed while avoiding deterioration of fuel efficiency.

[0105] The flow rate adjustment unit includes an intake valve 151 that adjusts the intake air flow rate supplied to the combustion chamber 110, and an EGR valve 172 that adjusts the exhaust gas flow rate that is joined to the intake air. During the first control, the ECU 191 closes the intake valve 151 to a predetermined opening and fully closes the EGR valve 172. This makes it possible to increase the amount of NOx sent to the SCR catalyst 222 using the intake valve 151 and the EGR valve 172 without using fuel.

[0106] The determination unit 191a determines a predetermined elapsed time from the execution of the first control, and the elapsed time indicates the time elapsed from the start of the execution of the first control. This allows the ammonia adsorption amount P2 to be indirectly estimated using time as a parameter. This eliminates the need for direct measurement of the amount of ammonia deposited.

[0107] During the second control phase, the ECU 191 supplies a second post-injection amount F2, which is less than the first post-injection amount F1, to the combustion chamber 110 before supplying the first post-injection amount F1 to regenerate the filter 213. This suppresses a rapid rise in the exhaust temperature T of the exhaust gas heading towards the SCR catalyst 222. Therefore, even if the ammonia adsorption amount P2 is greater than the estimated value, ammonia slip during the second control phase can be suppressed.

[0108] The system is further equipped with a urea solution injection unit 231 that injects urea solution toward the exhaust gas. During the second control, the DCU 192 controls the urea solution injection unit 231 to inject a second target urea solution injection amount f2, which is less than the first target urea solution injection amount f1, into the SCR catalyst 222 before injecting the first target urea solution injection amount f1 into the SCR catalyst 222. This suppresses the amount of ammonia adsorbed P2. Therefore, even if the amount of ammonia adsorbed on the SCR catalyst 222 is greater than the estimated value, ammonia slip during the second control can be suppressed. By setting the second target urea solution injection amount f2 to zero, the amount of ammonia adsorbed P2 can be reduced in a short time. Furthermore, control can be made easier by gradually increasing the second target urea solution injection amount f2.

[0109] Embodiments of the present invention have been described above with reference to the drawings. However, the present invention is not limited to the embodiments described above, and can be implemented in various forms without departing from the spirit of the invention. The drawings sometimes schematically show the components in order to facilitate understanding. The number of each component shown in the drawings may differ from the actual number due to the convenience of drawing creation. Furthermore, the components shown in the above embodiments are examples and are not particularly limiting, and various modifications are possible without substantially departing from the effects of the present invention.

[0110] (1) In this embodiment, the ECU 191 estimated the ammonia adsorption amount P2 based on the elapsed time since the start of the first control, but the disclosure is not limited thereto. NOx concentration sensors 307 may be placed upstream and downstream of the SCR device 220, respectively, and the ammonia adsorption amount P2 may be directly determined using the difference between the NOx inflow amount and the NOx outflow amount. It is also possible to use a combination of direct and indirect detection methods when detecting the ammonia adsorption amount P2. In this case, in the first control, the flow rate adjustment unit of the ECU 191 limits the intake valve 151 and the EGR valve 172. After limiting the intake valve 151 and the EGR valve 172, if the temperature of the exhaust gas upstream of the filter 213 is above the first determination temperature T1 and the determination unit 191a determines that the ammonia adsorption amount P2 exceeds the determination value K, the ECU 191 increases the opening of the intake valve 151. This makes it possible to suppress deterioration of fuel efficiency by increasing the intake flow rate when the ammonia reduction effect of the first control is not obtained.

[0111] Furthermore, when using both direct and indirect detection methods, if the determination unit 191a determines during the execution of the first control that the amount of ammonia adsorbed on the selective reduction catalyst P2 exceeds the determination value K, the ECU 191 may increase the pressure of the fuel stored in the common rail 141 and stop the injection of urea water into the SCR catalyst 222. This increases nitrogen oxides in the exhaust gas and reduces the ammonia adsorbed on the selective reduction catalyst. Alternatively, instead of increasing the pressure of the fuel stored in the common rail 141, the main injection may be advanced beyond the normal ignition timing. The injection amounts of the main injection, post-injection, or pre-injection for ignition may also be reduced below the normal value. This increases nitrogen oxides in the exhaust gas and reduces ammonia.

[0112] (2) In this embodiment, the intake valve 151 and the EGR valve 172 are restricted simultaneously, but the disclosure is not limited thereto. A time difference may be provided between the closing operations of the intake valve 151 and the EGR valve 172. In this case, for example, the first control includes a third control that completely closes the EGR valve 172 and a fourth control that closes the intake valve 151 to a predetermined opening, and the ECU 191 executes the fourth control if the determination unit 191a determines that the ammonia adsorption amount P2 is less than or equal to the determination value K during the third control, and executes the second control if the exhaust temperature T upstream of the filter 213 is greater than or equal to the first determination temperature T1 during the fourth control. This makes it possible to shorten the period during which the intake airflow is restricted. Therefore, fuel efficiency can be improved.

[0113] (3) In this embodiment, the execution of filter regeneration control was determined by comparing the PM accumulation amount P1 with the DPF regeneration start determination value K1, but manual regeneration may also be determined. For example, the cumulative time during which the temperature and exhaust flow rate in the exhaust passage 160 are lower than the determination value is added, and the cumulative time during which the temperature and exhaust flow rate in the exhaust passage 160 are higher than the determination value is subtracted to obtain a calculated value. If this calculated value is greater than the threshold, the operator is notified to start manual regeneration. Note that the downstream end temperature of the DPF device 210 may be used instead of the temperature and exhaust flow rate in the exhaust passage 160. This makes it possible to eliminate urea water crystals that accumulate in the exhaust passage 160.

[0114] Furthermore, the load factor of engine 100 is determined, and if the conditions are met—the load factor is below a predetermined value, the NOx concentration sensor 307 is above a predetermined value, and a predetermined period of time has elapsed since the last DPF regeneration—the operator is notified to start manual regeneration. Alternatively, instead of the condition that the NOx concentration sensor 307 is above a predetermined value, the rate of increase in the detected value of the NOx concentration sensor 307 may be used. This makes it easy to determine the timing of filter regeneration.

[0115] Furthermore, if the work vehicle is performing light load work and the intake air temperature of the engine 100 is below a certain value, automatic regeneration may be prohibited and the system may be notified to start manual regeneration. During manual regeneration, the regeneration time is extended every few manual regeneration cycles. This suppresses the deposition of hydrocarbons on the PM oxidation catalyst 212 and decomposes the precipitated urea water crystals.

[0116] (4) When manual regeneration is performed, for example, the conditions for success are that the parking brake is applied and the engine speed is maintained at a predetermined speed of 100, and the process is terminated after a predetermined judgment time has elapsed. However, a threshold smaller than the judgment time may be set, and the start of the process may be permitted when the PM accumulation amount P1 reaches the threshold. Specifically, when the PM accumulation amount P1 reaches the threshold, the operator is notified and the maintenance of the engine speed 100 is terminated. This allows the process to resume while DPF regeneration continues. [Explanation of Symbols]

[0117] 100...Engine, 110...Combustion chamber, 141...Common rail, 142...Fuel injection unit, 151...Intake valve, 172...EGR valve, 190...Control unit, 191...ECU, 191a...Determination unit, 192...DCU, 200...Exhaust gas purification device, 213...Filter, 222...SCR catalyst, 231a...Urea water injection nozzle

Claims

1. An exhaust gas purification device for an internal combustion engine, comprising: a fuel supply unit that supplies fuel to the combustion chamber; a filter provided in an exhaust passage connected to the combustion chamber for collecting particulate matter contained in the exhaust gas; and a selective reduction catalyst provided downstream of the filter for removing nitrogen oxides contained in the exhaust gas by a reduction reaction with ammonia, A flow rate adjustment unit that adjusts the intake air flow rate supplied to the combustion chamber and / or the exhaust air flow rate that is joined to the intake air, A determination unit that determines whether the amount of ammonia adsorbed on the selective reduction catalyst is less than or equal to a predetermined determination value, A control unit that controls the fuel supply unit and the flow rate adjustment unit. Equipped with, The control unit, An exhaust gas purification device for an internal combustion engine, wherein, after the flow rate adjustment unit performs a first control to limit the intake air flow rate and / or the exhaust air flow rate, if the determination unit determines that the exhaust gas temperature upstream of the filter is above a threshold and the amount of ammonia adsorbed on the selective reduction catalyst is below the determination value, the fuel supply unit performs a second control to supply fuel to the combustion chamber according to the exhaust gas temperature necessary to regenerate the filter.

2. The aforementioned flow rate adjustment unit is An intake valve that adjusts the intake air flow rate supplied to the combustion chamber, An EGR valve that adjusts the exhaust flow rate that is joined to the intake air, It has, The control unit, during the first control, The intake valve is closed to a predetermined opening, The exhaust gas purification device for an internal combustion engine according to claim 1, wherein the EGR valve is completely closed.

3. The determination unit determines a predetermined elapsed time from the execution of the first control, The exhaust gas purification device for an internal combustion engine according to claim 2, wherein the elapsed time indicates the time elapsed from the start of the execution of the first control.

4. The exhaust gas purification device for an internal combustion engine according to claim 3, wherein, during the second control, the control unit supplies a second target regeneration injection amount, which is less than the first target regeneration injection amount, to the combustion chamber before supplying a first target regeneration injection amount to the combustion chamber for regenerating the filter.

5. The system further includes a urea water injection unit that sprays urea water toward the exhaust, The exhaust gas purification device for an internal combustion engine according to claim 3, wherein, during the second control, the control unit controls the urea water injection unit to inject a second target urea water injection amount, which is less than the first target urea water injection amount, into the selective reduction catalyst before injecting the first target urea water injection amount into the selective reduction catalyst.

6. The control unit, In the first control, the flow rate adjustment unit restricts the intake valve and the EGR valve, The exhaust gas purification device for an internal combustion engine according to claim 3, wherein the opening of the intake valve is increased when the temperature of the exhaust gas upstream of the filter is above a threshold and the determination unit determines that the amount of ammonia adsorbed by the selective reduction catalyst exceeds the determination value.

7. The aforementioned flow rate adjustment unit is An intake valve that adjusts the intake air flow rate supplied to the combustion chamber, An EGR valve that adjusts the exhaust flow rate that is joined to the intake air, It has, The first control is, A third control that completely closes the EGR valve, A fourth control that closes the intake valve to a predetermined opening, Includes, The control unit, During the third control, if the determination unit determines that the amount of ammonia adsorbed on the selective reduction catalyst is less than or equal to the determination value, the fourth control is executed. The exhaust gas purification device for an internal combustion engine according to claim 1, wherein, during the fourth control, if the exhaust gas temperature upstream of the filter is above a threshold, the second control is executed.

8. The system further comprises a urea solution injection unit that injects urea solution toward the selective reduction catalyst, The aforementioned fuel supply unit is A common rail for storing the aforementioned fuel, A combustion injection unit that injects the fuel from the common rail into the combustion chamber. It further possesses, The control unit, The exhaust gas purification device for an internal combustion engine according to claim 1, wherein, during the execution of the first control, if the determination unit determines that the amount of ammonia adsorbed on the selective reduction catalyst exceeds the determination value, the pressure of the fuel stored in the common rail is increased and the injection of urea water into the selective reduction catalyst is stopped.

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