JP2016217301A - Ammonia generator and ammonia generation control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To purify NOx even at a low exhaust gas temperature region by operating a selective reduction catalyst device from a lower temperature region without being dependent on an exhaust gas temperature.SOLUTION: An ammonia generator 20 includes a main body 201 installed at a rear stage of a urea water injection device 18, having an introduction part 20a for feeding exhaust gas, a discharging part 20b for discharging exhaust gas, and a first flow passage part 21a and a second flow passage 22a each of which is separated to each other and communicated with the introduction part 20a and the discharging part 20b. The ammonia generator 20 includes a heater 30 arranged at the first flow passage 21a, and a first changing-over part 25 arranged at the introduction part 20a of the main body 201 and capable of changing over a flowing passage for the exhaust gas between the first flow passage part 21a and the second flow passage part 22a.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an ammonia generator and an ammonia generation control device.

  In order to comply with the regulations regarding the exhaust gas (exhaust gas) component of the internal combustion engine in recent years, various exhaust gas purification devices are arranged in the exhaust pipe path of the internal combustion engine. Among these exhaust gas purification devices, a selective reduction catalyst (SCR) device is known as a device for reducing and purifying NOx. The SCR device reduces and purifies NOx by ammonia generated by hydrolyzing urea water as a reducing agent and a NOx reduction catalyst. In order to hydrolyze urea water, a temperature of about 200 degrees is required, and when exhaust gas is used as a heat source, or when a heat source for hydrolyzing urea water is disposed in the exhaust passage If the exhaust gas temperature is low, there is a problem that urea water cannot be hydrolyzed. Therefore, a technique has been proposed in which heat for disposing the heat of the reducing agent is not lost even when the exhaust gas temperature is low by disposing the heat source outside the exhaust passage (for example, Patent Document 1). ). Further, a technique has been proposed in which urea water is hydrolyzed using gas entropy by providing a side flow through which exhaust gas flows and supplying urea water to the side flow (Patent Document 2).

JP 2014-159776 A JP 2014-514828 A

  However, the conventional technique is a technique for providing a temperature environment in which urea water can be hydrolyzed by compensating for heat loss due to the flow of exhaust gas, or a technique for effectively utilizing the thermal energy of exhaust gas. In contrast, recent internal combustion engines have the fact that the exhaust gas temperature hardly exceeds the temperature at which urea water can be hydrolyzed due to the improvement in combustion efficiency.

  Therefore, it is desired that the selective catalytic reduction device is made to function from a lower temperature range and NOx is purified even in a lower exhaust gas temperature range without depending on the exhaust gas temperature.

  The present invention has been made to solve the above-described problems, and can be realized as the following aspects.

  A 1st aspect provides the ammonia generator arranged in the back | latter stage of urea water supply part in the exhaust passage of an internal combustion engine. An ammonia generator according to a first aspect is in communication with an introduction part for introducing exhaust gas, an exhaust part for exhausting the exhaust gas, and the introduction part and the exhaust part. A main body having a first flow path section and a second flow path section, a heater disposed in the first flow path section, and the exhaust section disposed on the introduction section side of the main body. A first switching unit capable of switching a gas flow path between the first flow path unit and the second flow path unit.

  According to the ammonia generator according to the first aspect, the NOx can be purified even in a low exhaust gas temperature range by allowing the selective catalytic reduction device to function from a lower temperature range without depending on the exhaust gas temperature.

  The ammonia generator according to the first aspect is further arranged at a side of the discharge part in the main body, and a second switch capable of switching so as to close the first flow path part or the second flow path part. A part may be provided. In this case, the first channel portion or the second channel portion can be further separated from each other.

  In the ammonia generator according to the first aspect, the heater may include a holding unit capable of holding urea water supplied by the urea water supply unit. In this case, urea water can be held in the heater.

  The ammonia generator according to the first aspect may further include a second urea water supply unit capable of directly supplying urea water to the first flow path unit in the main body. In this case, urea water can be directly supplied to the first flow path portion.

  A second aspect provides an ammonia generation control device. An ammonia generation control device according to a second aspect includes a main body that is disposed in an exhaust passage of an internal combustion engine and has a first flow path portion and a second flow path portion that are separated from each other, and an exhaust gas in the main body. A urea water supply section for supplying urea water disposed on the introduction side of the heater, a heater disposed on the first flow path section, and a flow of the exhaust gas disposed on the introduction side of the main body. A switching section capable of switching a path between the first flow path section and the second flow path section, and a flow path of the exhaust gas when the operating state of the internal combustion engine is the first operating state. And a control unit that controls the switching unit so as to switch to the second flow path unit.

  According to the ammonia generation control device according to the second aspect, the selective reduction catalyst device can function from a lower temperature range without depending on the exhaust gas temperature, and NOx can be purified even in a lower exhaust gas temperature range.

  In the ammonia generation control device according to the second aspect, the first operation state may be an operation state in which the heater is operated, or an operation state in which the urea water is hydrolyzed. In this case, the heater can be operated without being in contact with the flow of the exhaust gas, and the urea water can be hydrolyzed.

  In the ammonia generation control device according to the second aspect, the first operating state may be an operating state in which the temperature of the exhaust gas is higher than a predetermined temperature. In this case, the exhaust gas can be flowed without going through a heater.

  In the ammonia generation control device according to the second aspect, the control unit further controls the supply of urea water by the urea water supply unit and the operation of the heater. In the first operating state, the control unit includes: After switching the flow path of the exhaust gas to the second flow path section and operating the heater, the flow path of the exhaust gas is switched to the first flow path section and the urea water supply section Urea water may be supplied to the first flow path portion. In this case, the heater can be operated without being exposed to the exhaust gas, and urea water can be supplied to the operating heater.

  In the ammonia generation control device according to the second aspect, the control unit further controls the supply of urea water by the urea water supply unit and the operation of the heater. In the first operating state, the control unit includes: The flow path of the exhaust gas is switched to the first flow path section, and urea water is supplied to the first flow path section by the urea water supply section, and urea water for the first flow path section After the supply of is completed, the flow path of the exhaust gas may be switched to the second flow path section to operate the heater. In this case, the supplied urea water can be hydrolyzed by the heater without being exposed to the flow of the exhaust gas.

  The ammonia generation control device according to the second aspect can also be realized as an ammonia generation device control method and an ammonia generation device control program.

It is explanatory drawing which shows roughly the vehicle provided with the ammonia generator used in 1st Embodiment. It is an external appearance perspective view which shows schematic structure of the ammonia generator which concerns on 1st Embodiment. FIG. 3 is a schematic cross-sectional view of the ammonia generator according to the first embodiment, cut along line 3-3 shown in FIG. 2. It is explanatory drawing which shows the operation state of the ammonia generator which concerns on 1st Embodiment at the time of a cold start. It is explanatory drawing which shows the operation state of the ammonia generator which concerns on 1st Embodiment at the time of warming-up. It is explanatory drawing which shows the operation state of the ammonia generator which concerns on 1st Embodiment at the time of warming-up. It is explanatory drawing which shows the operation state of the ammonia generator which concerns on 1st Embodiment at the time of warming-up. It is explanatory drawing which shows the operation state of the ammonia generator which concerns on 1st Embodiment in the normal time. It is a block diagram which shows roughly the electrical connection between the electrical components in a vehicle provided with the ammonia generator which concerns on 1st Embodiment. It is a flowchart which shows the process routine for controlling operation | movement of the ammonia generator in 1st Embodiment. It is explanatory drawing which shows the operation state of the ammonia generator which concerns on 2nd Embodiment at the time of warming-up. It is explanatory drawing which shows the operation state of the ammonia generator which concerns on 2nd Embodiment at the time of warming-up. It is a flowchart which shows the process routine for controlling operation | movement of the ammonia generator in 2nd Embodiment. It is explanatory drawing which shows the modification of the ammonia generator which concerns on 1st and 2nd embodiment. It is explanatory drawing which shows the modification of an ammonia generator.

  As an aspect of a vehicle including an exhaust gas purification system including an ammonia generator according to the present invention, a vehicle including a diesel engine (internal combustion engine) will be described below as an example. FIG. 1 is an explanatory diagram schematically showing a vehicle including an ammonia generator used in the first embodiment.

First embodiment:
The vehicle 500 includes a diesel engine (hereinafter referred to as “engine”) 510, four wheels 520, and the exhaust gas purification system 10. An ammonia generator 20 according to this embodiment is provided in the exhaust gas purification system 10. The engine 510 uses light oil as fuel, outputs driving force by the explosive combustion of the fuel, and the exhaust system is equipped with exhaust gas containing NOx (nitrogen oxide) and PM (particulate matter) accompanying the explosive combustion. The exhaust gas is discharged to the atmosphere through the exhaust gas purification system 10. The engine 510 is provided with a first temperature sensor 191 that detects the temperature of the coolant that cools the engine 510. Note that the vehicle configuration shown in FIG. 1 used in the first embodiment can be similarly used in other embodiments.

The exhaust gas purification system 10 includes various exhaust gas purification devices on an exhaust pipe 11 (exhaust pipe line). The exhaust pipe 11 is connected to the engine 510 via the manifold 11a on the engine 510 side (upstream side of the exhaust gas flow), and includes a muffler end pipe 11b on the most downstream side of the exhaust gas flow. The purification system includes a diesel oxidation catalyst (DOC) 12, a diesel particulate filter (DPF) 13, an ammonia generator 20, a selective reduction catalyst (SCR) device 14, and an ammonia slip diesel oxidation catalyst (NH) from the upstream side of the exhaust gas flow. ₃ DOC) 15 is provided on the exhaust pipe 11. A fuel injection device 17 may be disposed upstream of the DOC 12 on the exhaust pipe 11. A urea water injection device 18 is disposed upstream of the ammonia generator 20. A temperature sensor 192 is disposed on the exhaust side of the DPF 13 of the exhaust gas purification system 10. In addition to this, the temperature sensor 192 may be disposed in, for example, the ammonia generator 20 and the SCR device 14. The term “on the exhaust pipe” in the present embodiment means both the inside of the exhaust pipe and the middle of the exhaust pipe (which constitutes a part of the exhaust pipe).

The diesel oxidation catalyst 12 supports a noble metal such as platinum (Pt) or palladium (Pd) as a catalyst, and oxidizes carbon monoxide (CO) and hydrocarbon (HC), which are unburned gas components contained in the exhaust gas. Then, it is converted into carbon dioxide (CO ₂ ) and water (H ₂ O), and nitric oxide (NO) contained in the exhaust gas is oxidized to be converted into nitrogen dioxide (NO ₂ ).

The diesel particulate filter 13 is a filter that collects particulate matter (PM) contained in the exhaust gas through a fine gap of porous ceramics or metal, and in a broad sense is an aspect of the exhaust gas purification device. In the present specification, focusing on PM collection, it is treated as a first particulate collection filter. A metal catalyst such as platinum is applied to the porous surface, and the diesel particulate filter 13 has a particulate matter in an atmosphere of 250 to 300 ° C. in the presence of NOx produced by the diesel oxidation catalyst 12. It is naturally regenerated by causing a chemical reaction with the catalyst and converting it to carbon dioxide (CO ₂ ) and water (H ₂ O). The diesel particulate filter 13 supplies fuel to the diesel oxidation catalyst 12 directly from the engine 510 via the fuel injection device 17 or through an exhaust stroke, and catalytically combusts fuel-derived hydrocarbons to increase the exhaust temperature. It can also be regenerated by forced regeneration in which the particulate matter collected at 450 ° C. or higher is oxidized.

In addition to the type in which particulate matter is physically collected and the particulate matter is oxidized by catalytic combustion of hydrocarbons, the DPF 13 generates low-temperature plasma in the plasma generator and activates mainly O _3. A plasma DPF that generates seeds, supplies the generated active species to the DPF, and converts (oxidizes) particulate matter components such as HC and C into H ₂ O and CO ₂ may be used. In the plasma DPF, the particulate matter can be oxidized without using fuel, but the particulate matter is not collected in the physical form, so the amount of active species corresponding to the amount of the particulate matter to be processed in advance. Therefore, it is required to design a plasma generating apparatus so as to be able to generate the above.

The selective reduction catalyst (SCR) device 14 is a device that includes a NOx reduction catalyst that carries a zeolite-based catalyst or a vanadium-based catalyst and selectively reduces NOx. The SCR device generally removes NOx components in exhaust gas by ammonia (NH ₃ ) generated through the thermal decomposition and hydrolysis reaction of urea water supplied in the previous stage of the SCR device, and a NOx reduction catalyst. Convert to nitrogen (N ₂ ) and water (H ₂ O). Therefore, the SCR device that receives the supply of urea water cannot obtain a desired NOx reduction function unless it is at an appropriate temperature, for example, 200 ° C. or higher, in order to obtain ammonia from the urea water.

  The ammonia generator 20 is disposed downstream of the urea water injector 18 (on the downstream side of the exhaust gas flow) and includes a heater 30 therein. The ammonia generator 20 heats the urea water injected from the urea water injector 18 by the heater 30 and hydrolyzes it to generate ammonia (generate ammonia). The produced ammonia is supplied to the SCR device 14 and used as a reducing agent for reducing NOx.

  The ammonia slip / diesel oxidation catalyst 15 supports the same catalyst as the diesel oxidation catalyst 12 and oxidizes and decomposes ammonia that has not been subjected to the reaction in the SCR device 14 to generate nitrogen or NOx.

  The ammonia generator 20 according to the first embodiment used in the exhaust gas purification system 10 will be described in detail below. FIG. 2 is an external perspective view showing a schematic configuration of the ammonia generator according to the first embodiment. FIG. 3 is a schematic cross-sectional view of the ammonia generator according to the first embodiment, taken along line 3-3 shown in FIG.

  The ammonia generator 20 includes a case 201 (main body), a first flow path pipe 21, a second flow path pipe 22, a heat insulating material 23, a first flow path switching valve 25, a second flow path switching valve 26, and A heater 30 is provided. The case 201 is made of stainless steel or a steel plate that has been subjected to an antioxidant treatment. The first flow path pipe 21 defines a first flow path section 21a through which exhaust gas flows, and the second flow path pipe 22 defines a second flow path section 22a through which exhaust gas flows. The passage tube 21 and the second passage tube 22 are arranged in parallel. The case 201 includes an introduction portion 20a for introducing exhaust gas into the inside and a discharge portion 20b for discharging the exhaust gas to the outside. The introduction part 20a communicates with the first flow path pipe 21 and the second flow path pipe 22, and the discharge part 20b communicates with the first flow path pipe 21 and the second flow path pipe 22. In addition, although the 1st flow path pipe 21 and the 2nd flow path pipe 22 have a hollow rectangular shape, you may have a cylindrical shape and another shape.

  A urea water injection device 18 that injects urea water into the inside of the ammonia generation device 20 is disposed in the front stage of the introduction unit 20a. The urea water injection device 18 is a device for supplying urea water stored in a urea water tank (not shown) to the introduction unit 20a (ammonia generator 20). The urea water injection device 18 desirably supplies urea water in an atomized state in consideration of conversion to ammonia, and is supplied at a high pressure by opening and closing the injection hole by an electromagnetic or piezo-type actuator. Achieving urea water injection or injection stop. The urea water injection device 18 may be disposed at a position where urea water can be supplied to the first flow path pipe 21 and the second flow path pipe. For example, the urea water injection apparatus 18 is disposed in the introduction portion 20a. May be. In the example of FIG. 1, it arrange | positions at the connection part which connects the ammonia generator 20 and DPF13 which are upstream from the introduction part 20a. Since the ammonia generator 20 according to the first embodiment is a device that generates ammonia by receiving the supply of urea water, it must receive the supply of urea water, but does not include a urea water injection device as a configuration. Alternatively, urea water supplied from a separate urea water injection device may be converted into ammonia.

  The first flow path switching valve 25 has a flow path pipe (flow path) through which exhaust gas flows between the first flow path pipe 21 and the second flow path pipe 22 on the introduction portion 20 a side of the case 201. Provided for switching. That is, the first flow path switching valve 25 allows the exhaust gas to flow through the first flow path pipe 21 (first flow path section 21a) (first flow path pipe 21 (first flow path section 21a). ) Is opened), the second flow path tube 22 (second flow path portion 22a) is closed, and the exhaust gas is allowed to flow through the second flow path tube 22 (second flow path portion 22a) ( In the case of opening the second flow channel tube 22 (first flow channel portion 22a), the first flow channel tube 21 (first flow channel portion 21a) is closed.

  The second flow path switching valve 26 closes a flow path pipe (flow path) through which exhaust gas does not flow on the discharge portion 20b side of the case 201, and forms a closed space 21b (see FIG. 4) in the flow path pipe. Is provided. As will be described later, this closed space can function as a space for temporarily storing the generated ammonia. When the exhaust gas flows through the first flow path pipe 21 (first flow path section 21a), the second flow path switching valve 26 has a second flow path pipe 22 (second flow path section 22a). ), And when the exhaust gas flows through the second flow path pipe 22 (second flow path section 22a), the first flow path pipe 21 (first flow path section 21a) is closed.

  As the first and second flow path switching valves 25 and 26, as shown in the drawing, switching is performed to selectively switch the flow path by swinging a plate-shaped valve body around an axis provided at one end. A valve, a switching valve that selectively switches the flow path by rotating a rotary valve body having an internal communication passage around one axis, and a flow path that is selectively switched by a linear movement of the plate-shaped valve body A switching valve or the like can be used. As an actuator for driving the valve body, a motor such as a stepping motor, an electromagnetic actuator, or a fluid actuator such as air or oil can be used. As will be described later, the flow paths may not be switched selectively, that is, exclusively, and the first and second flow path pipes 21 may be used as the first flow path switching valve 25. , 22 leads the exhaust gas introduced from the introduction part 20a to the second flow path switching valve 26 so as to discharge to both the first and second flow path pipes 21, 22. It is required to guide the exhaust gas to the portion 20b. The first and second flow path switching valves 25 and 26 may be provided for the flow path pipes 21 and 22, respectively. In this case, the flow rate of the exhaust gas flowing through the other channel pipe can be adjusted after closing one channel pipe. That is, the flow rate of the outside air gas in each channel pipe can be controlled independently.

  In the example of FIGS. 2 and 3, the heater 30 has a rectangular shape in which the first flow path pipe 21 has a rectangular shape. The cross-sectional shape may be provided, for example, a shape having a circular spiral cross-section. The heater 30 may be a heater disposed in the first flow path tube 21, or may be integrally formed on the inner wall surface of the first flow path pipe 21. The heater 30 may be formed by laminating a plurality of metal flat plates or corrugated plates or metal flat plates and corrugated plates, and the plate material itself may generate heat when energized. In this case, a drilling process is performed on at least a part of the metal plate material in order to increase the heat generation surface area and to realize the urea water holding portion 30a that holds the urea water supplied by the urea water injection device 18. Alternatively, it is desirable that a process such as an uneven process is performed. In FIG. 3, the urea water holding part 30 a is illustrated only on a part of the surface of the heater 30 in order to simplify the illustration. The space between the plate members stacked close to each other can also function as a urea water holding unit that holds the urea water supplied by the urea water injection device 18. The urea water holding unit 30a holds the urea water by fine perforations and surface tension at the surface irregularities.

  As the heater 30, a plurality of heaters having a rod shape and arranged in the first flow path pipe 21 along the flow direction of the exhaust gas may be used. Even in the case of having a rod-like shape, a urea water holding part can be realized by performing uneven processing on the surface (outer surface) of the heater. In this embodiment, the heater 30 is a resistance heating element (heating member) that is not covered with an insulating material and generates heat when the member is energized, and is a nichrome wire, a copper wire, or a tungsten wire. It may be a linear metal plate such as stainless steel, copper, aluminum, or the like, and a resistance heating element disposed in a case covered with a powdered inorganic insulator such as magnesia. It may be a heater provided, that is, a heater generally called a heater. Depending on the application, a non-metallic material such as silicon carbide or carbon having a small heat capacity may be used as the heater 30.

  The heater 30 according to the present embodiment can also function as a heat storage body. For example, when the heater 30 has an aspect having a spiral cross section by laminating plate materials, when the plate material has a rectangular solid shape by laminating, the metal plate materials are sensible heat. Since it can function as a heat storage member, it functions as a heat storage body having a predetermined heat capacity.

  Further, a heat storage body may be provided separately from the heater 30. An internal flow that allows the exhaust gas to flow inside is provided in a soot that is an integral heat storage body in which the heat storage body is disposed across the cross section of the first flow path pipe 21 (cross section orthogonal to the flow direction of the exhaust gas). It is required to have a road. The heater 30 may be included in the heat storage body, or may be arranged in series or in parallel with the heat storage body. The heat storage body may have a shape that matches the shape of the first flow path pipe 21 or may have another shape. As the heat accumulator, a ceramic material having an internal flow path, a metal powder sintered body, a metal honeycomb, an expanded metal, or the like can be used. The internal flow path may be a flow path that is intentionally formed, for example, a straight flow path, or may be a flow path that is formed by a gap formed due to the properties of the material, for example, a coasting flow path. . Further, the internal channel can also function as a urea water holding part.

  A heat insulating material 23 is disposed or filled between the first flow path pipe 21 and the second flow path pipe 22 and the case 201. As the heat insulating material 23, for example, a ceramic sheet material, a cylindrical hard ceramic material, a foamable ceramic material, or the like is used. By providing the heat insulating material 23, the heat conduction amount to the metal case 201 can be suppressed, and the heat retention efficiency of the particulate collection device 20 can be maintained at a desired level. The case 201 may be provided with a double wall structure that sandwiches an air layer in order to further improve heat insulation.

  Mode of switching the first and second flow path switching valves 25 and 26 according to the operating state of the internal combustion engine and mode of hydrolysis of urea water by the heater 30, that is, the ammonia generator according to the first embodiment 20 operation | movement aspects are demonstrated with reference to FIGS. FIG. 4 is an explanatory diagram showing an operating state of the ammonia generator according to the first embodiment at the time of cold start. FIG. 5 is an explanatory diagram showing an operating state of the ammonia generator according to the first embodiment during warm-up. FIG. 6 is an explanatory diagram showing an operating state of the ammonia generator according to the first embodiment during warm-up. FIG. 7 is an explanatory diagram showing an operating state of the ammonia generator according to the first embodiment during warm-up. FIG. 8 is an explanatory view showing an operating state of the ammonia generator according to the first embodiment at the normal time.

  In the present embodiment, the cold start state, the warm-up state, and the normal state are considered as the operation state of the internal combustion engine (engine). The cold start state means a state at the start of engine start in a state where the coolant temperature and oil temperature of the engine are lower than the warm-up completion temperature. The warm-up state means an operating state of the engine after the cold start until the engine coolant temperature and oil temperature reach the warm-up completion temperature. The normal state is an operating state of the engine after the engine coolant temperature and the oil temperature reach the warm-up completion temperature, and the exhaust gas temperature is higher than the temperature at the time of cold start and warm-up (predetermined) It means an operating state (higher than temperature). Note that the engine coolant temperature and the oil temperature warm-up completion temperature may be appropriately determined for each engine. From the viewpoint of the present embodiment, the exhaust gas purifying device including the SCR device 14 purifies the engine. The engine coolant temperature and oil temperature when exhaust gas having a temperature that can exhibit an action is discharged may be used as the warm-up completion temperature.

  When the engine is in a cold start state, as shown in FIG. 4, the first flow path switching valve 25 closes the first flow path pipe 21, and exhausts the exhaust gas from the engine 510. It is switched so as to lead to the second flow path tube 22, that is, the second flow path portion 22a. The second flow path switching valve 26 is switched so as to close the first flow path pipe 21 and make the first flow path pipe 21 a closed space 21b. The exhaust gas temperature at the time of cold start is low, and when the exhaust gas comes into contact with the heater 30, the temperature of the heater 30 may decrease. Therefore, at the time of cold start, the first flow path pipe 21 (first flow path portion 21a) is a closed space 21b, and the heater 30 and the exhaust gas are not brought into contact with each other.

  When the engine is in a warm-up state, as shown in FIGS. 5 to 7, the operating state of the first and second flow path switching valves 25, 26, the operating state of the heater 30, and The operating state of the urea water injection device 18 changes. Note that the engine operating state is the first operating state: a state in which the heater 30 is operated (heat generation), a state in which urea water is hydrolyzed (converting urea water to ammonia), and an exhaust gas temperature is a predetermined temperature. Means a state in which at least one of the higher states. The state where the heater 30 is operated and the state where the urea water is hydrolyzed appears when the engine is warmed up, and the state where the exhaust gas temperature is higher than the predetermined temperature appears during normal operation after the engine is warmed up.

  After the cold start, the engine is in a warm-up state. When the engine is in a warm-up state, first, as shown in FIG. 5, the first flow path switching valve 25 closes the second flow path pipe 22 and is introduced from the engine 510 through the introduction portion 20a. The exhaust gas is switched so as to be guided to the first flow path pipe 21, that is, the first flow path portion 21a. The second flow path switching valve 26 closes the second flow path pipe 22, and guides the exhaust gas led to the first flow path pipe 21, that is, the first flow path portion 21a, to the discharge portion 20b. Can be switched to. In this state, the urea water injection device 18 injects a predetermined amount of urea water. As a result, the injected urea water is guided to the heater 30 together with the exhaust gas, and at least a part of the urea water adheres to the surface of the heater 30 as shown by the dot pattern (the urea water holding portion provided in the heater 30). 30a). The injection amount of urea water may be determined as appropriate depending on, for example, the exhaust gas temperature and the engine load. The injection amount increases as the exhaust gas temperature increases and the engine load increases.

  When the supply of urea water by the urea water injection device 18 is completed, as shown in FIG. 6, the first flow path switching valve 25 closes the first flow path pipe 21, and exhausts the exhaust gas from the engine 510 to the second. It is switched so as to guide to the flow path pipe 22. The operating state of the engine shown in FIG. 6 is the first operating state, in which urea water is hydrolyzed (urea water is converted to ammonia). In addition, since the heater 30 is operated, it may be said that the heater 30 is in a state of operating (generating heat). The second flow path switching valve 26 is switched so as to close the first flow path pipe 21 and confine the heater 30 in the closed space 21b. In this state, the heater 30 is turned on to be in a heated state, and the urea water attached (held) to the heater 30 is converted into ammonia to generate ammonia. The temperature realized by the heater 30 is a required temperature for hydrolyzing urea water, for example, 200 degrees or more. Since the ammonia generator 20 in this embodiment is provided with the 2nd flow-path switching valve 26 which plugs the downstream of the 1st flow-path pipe 21, the produced | generated ammonia is hold | maintained in the closed space 21b.

  When the conversion from urea water to ammonia (generation of ammonia) by the heater 30 is completed, as shown in FIG. 7, the first flow path switching valve 25 closes the second flow path pipe 22, and from the engine 510 The exhaust gas introduced through the introduction part 20a is switched so as to be guided to the first flow path pipe 21. The second flow path switching valve 26 is switched so as to close the second flow path pipe 22 and guide the exhaust gas guided to the first flow path pipe 21 to the discharge portion 20b. As a result, the ammonia held in the closed space 21b formed in the first flow path pipe 21 is supplied to the SCR device 14 together with the exhaust gas. Since the exhaust gas supplied to the SCR device 14 is heated by the heater 30, the NOx reduction reaction in the SCR device 14 can be promoted. The end of the conversion from urea water to ammonia can be determined, for example, based on whether or not a predetermined period required for converting the supplied urea water into ammonia has elapsed. This required period may always be constant, or may be a period changed by the coolant temperature, the exhaust gas temperature, the outside air temperature, or the like. Generally, the required period can be shortened as the coolant temperature, the exhaust gas temperature, the outside air temperature, and the like increase. In FIG. 7, the heater 30 is energized. However, the energization of the heater 30 may be stopped if a sufficient amount of ammonia can be supplied.

  In the present embodiment, an ammonia generator 20 is provided in front of the SCR device 14, and the ammonia generated by the ammonia generator 20 is supplied to the SCR device 14. The NOx reduction function can be exhibited from a low temperature range.

  When the engine operating state reaches the normal state after the warm-up operation state, the first flow path switching valve 25 closes the first flow path pipe 21 and exhausts from the engine 510 as shown in FIG. The gas is switched to guide the gas to the second channel tube 22. The engine operating state shown in FIG. 8 is the first operating state, that is, the exhaust gas temperature is higher than a predetermined temperature. The second flow path switching valve 26 is switched so as to close the first flow path pipe 21. The energization to the heater 30 is stopped, and the heating by the heater 30 is finished. The urea water injection device 18 injects urea water as necessary. As a result, the injected urea water is led to the SCR device 14 together with the exhaust gas whose temperature is higher than that after the cold start and during warm-up, and is converted into ammonia by hydrolysis.

  FIG. 9 is a block diagram schematically showing electrical connection between electrical components in a vehicle including the ammonia generator 20 according to the first embodiment. The vehicle 500 includes an alternator (generator) 40 that is driven by the driving force of the engine 510. The engine 510 includes an engine-side pulley 511 for providing the alternator 40 with a driving force (output) extracted from a crankshaft (not shown). The alternator 40 includes an alternator-side pulley 401 to which a driving force provided from the engine 510 is input. The engine-side pulley 511 and the alternator-side pulley 401 are mechanically connected by a belt 512, and the driving force of the engine 510 is transmitted to the alternator 40 via the belt 512.

  The vehicle 500 includes a urea water injection device 18, a first flow path switching valve 25, a second flow path switching valve 26, a vehicle auxiliary machine 41, a battery 42, a control unit 60, a first relay 61, and a second relay. 62, a first temperature sensor 191 and a second temperature sensor 192 are provided. The first flow path switching valve 25 and the second flow path switching valve 26 have the above-described configuration, and are connected to the control unit 60 through a control signal line. The actuator is activated by a control signal from the control unit 60. By driving the valve body, the flow path of the exhaust gas is switched to the first flow path pipe 21, the second flow path pipe 22, or the first and second flow path pipes 21 and 22. In the present specification, a configuration including the control unit 60, various sensors, and the ammonia generator 20 is referred to as an ammonia generation controller 20a.

  The control unit 60 functions as a control unit for generating ammonia in the ammonia generator 20. The control unit 60 not only controls opening / closing of the first and second flow path switching valves 25 and 26 (flow pipe opening / closing control) but also urea water injection control (injection on / off) by the urea water injection device 18. The ammonia generator 20 is controlled by executing off control) and energization control for the heater 30 (operation / non-operation control of the heater 30).

  The vehicle auxiliary machine 41 is an auxiliary machine that is used in conjunction with vehicle travel that is driven (consumes electric power) by the electric power output from the alternator 40 or the electric power stored in the battery 42. This applies to navigation systems and electric heaters.

  The output terminal of the alternator 40 is electrically connected to the heater 30 via the first relay 61 and is also electrically connected to the vehicle auxiliary machine 41 via the second relay 62, It is electrically connected to the plus terminal (+) of the battery 42 via the total 64. A DC / DC converter for stepping up or stepping down the voltage may be arranged on the wiring path from the alternator 40 to the vehicle auxiliary equipment 41 and the battery 42. The ground-side terminals of the alternator 40, the vehicle auxiliary machine 41, and the heater 30 are electrically connected to the negative terminal (−) of the battery 42 through the body ground.

  The first relay 61 is a switch for turning on or off the heater 30, that is, switching between supply and interruption of power to the heater 30. The second relay 62 is a switch that switches between supplying and shutting off the electric power generated by the alternator 40 with respect to both the auxiliary machine 41 and the battery 42. The first and second relays 61 and 62 are connected to the control unit 60 via a control signal line, and are turned on (closed) or turned off (open) by a control signal from the control unit 60. The ammeter 64 provides the detected output current of the battery 42 to the control unit 60 via the signal line. The first temperature sensor 191 is used to detect the temperature of the coolant that cools the engine 510, and the second temperature sensor 192 is used to detect the temperature of the exhaust gas introduced into the exhaust gas purification device 10. Both are used and are connected to the control unit 60 by signal lines.

  The operation control of the ammonia generator 20 in the first embodiment will be described with reference to FIG. FIG. 10 is a flowchart showing a processing routine for controlling the operation of the ammonia generator according to the first embodiment. This processing routine is executed by the control unit 60 repeatedly at a predetermined timing and time interval. The control unit 60 includes at least an input / output interface (not shown) for exchanging control signals and detection signals with a central processing unit (CPU), a memory, and external devices.

  The control unit 60 starts this processing routine when the vehicle is started, and detects the operating state of the engine by various sensors provided in the vehicle. The start of the vehicle means that the ignition key position is switched to the on position, and the ignition key position is switched to the start position, that is, a state before the engine 510 is started. For example, the control unit 60 detects the vehicle temperature based on input signals input from a first temperature sensor 191 that detects a coolant temperature, a second temperature sensor that detects an exhaust gas temperature, an outside air temperature sensor, and an oil temperature sensor. It can be determined whether or not the operating state is a cold start state, a warm-up state, or a normal state. The cold start state generally means a state in which the temperature of the engine 510 (coolant temperature) is equal to or lower than the outside air temperature, and is normally in the cold start state at the first engine start in a day. The warm-up state means an operating state until the coolant temperature and the oil temperature reach predetermined temperatures. For example, the temperature at which the clearance between the piston and the cylinder is the desired dimension, and the oil is The temperature at which the lubricating performance (viscosity) is exhibited is used as the predetermined temperature.

  The control unit 60 determines whether or not the operating state of the engine is in a cold start state (step S100). If the control unit 60 determines that the engine operating state is in the cold start state (step S100: Yes), the control unit 60 turns off the first relay 61 (step S102). That is, the heater 30 is electrically disconnected from the alternator 40 and the battery 42 and does not generate heat (activate). The control unit 60 closes the first flow path pipe 21 (first flow path portion 21a) (step S104), and returns to the detection of the operating state. When the first flow path pipe 21 is closed, the control unit 60 transmits a control signal to the first flow path switching valve 25 and the second flow path switching valve 26, and as shown in FIG. The valve positions of the first flow path switching valve 25 and the second flow path switching valve 26 are switched so as to close the flow path pipe 21. As a result, the introduction part 20a and the second flow path pipe 22 (second flow path part 22a) communicate with each other, and the introduced exhaust gas flows through the second flow path part 22a and is guided to the discharge part 20b. . That is, the heater 30 is not exposed to the flow of exhaust gas, and the hydrolysis of urea water by the heater 30 described below can be efficiently performed. The control unit 60 determines whether or not the engine is in a cold start state at any timing before and after the engine start after the ignition key position is switched to the on position. Also good.

  When it is determined that the engine operating state is not in the cold start state (step S100: No), the control unit 60 determines whether the engine operating state is in the warm-up state (step S106). ). When the control unit 60 determines that the operating state of the engine is in the warm-up state (step S106: Yes), the control unit 60 turns off the first relay 61 (step S108), and the heater 30, the alternator 40, and The electrical connection with the battery 42 is cut off, and the heater 30 is deactivated. The control unit 60 closes the second flow path portion 22a (step S110), and causes the urea water injection device 18 to inject urea water (step S112). Specifically, the control unit 60 transmits a control signal to the first flow path switching valve 25 and the second flow path switching valve 26, and as shown in FIG. The valve positions of the first flow path switching valve 25 and the second flow path switching valve 26 are switched so as to close the second flow path portion 22a). As a result, the introduction part 20a and the first flow path pipe 21 (first flow path part 21a) communicate with each other, and the introduced exhaust gas flows through the first flow path part 21a and is guided to the discharge part 20b. . The urea water supplied to the introduction part 20a by the urea water injection device 18 is guided to the first flow path part 21a by the exhaust gas, and at least a part of the urea water adheres to the heater 30 and is held. As described above, it is desirable that the heater 30 is formed with the urea water holding part 30a, and the urea water guided to the heater 30 is held in the urea water holding part 30a by the surface tension.

  When the injection of the predetermined amount of urea water is completed, the control unit 60 closes the first flow path portion 21a (step S114) and turns on the first relay 61 (step S116). The control unit 60 transmits a control signal to the first flow path switching valve 25 and the second flow path switching valve 26, and as shown in FIG. 6, the first flow path portion 21a is closed. The valve positions of the second flow path switching valve 25 and the second flow path switching valve 26 are switched. As a result, a closed space 21b that is closed (defined) by the first and second flow path switching valves 25 and 26 is formed in the first flow path pipe 21 (first flow path portion 21a). Is done. When the first relay 61 is turned on in this state, the alternator 40 and the heater 30 are electrically connected, and the electric power generated by the alternator 40 is supplied to the heater 30. The heater 30 that is supplied with electric power generates heat, heats the urea water held therein, and generates ammonia by hydrolysis. Since the heater 30 exists in the closed space 21b defined by the first and second flow path switching valves 25 and 26, the generated (generated) ammonia is held in the closed space 21b.

  The control unit 60 closes the second flow path portion 22a after the time for converting the total amount of urea water held in the heater 30 or a predetermined amount or more into ammonia has elapsed (step S118), and the operation state Return to detection. The control unit 60 transmits a control signal to the first flow path switching valve 25 and the second flow path switching valve 26, and as shown in FIG. 7, the first flow path section 22a is closed so as to close the first flow path section 22a. The valve positions of the second flow path switching valve 25 and the second flow path switching valve 26 are switched. As a result, the introduction part 20a and the first flow path part 21a communicate with each other, and the introduced exhaust gas flows through the first flow path part 21a and is guided to the discharge part 20b. The exhaust gas flowing through the first flow path portion 21a promotes the flow of ammonia held in the first flow path portion 21a (closed space 21b), and the held ammonia flows into the SCR via the discharge portion 20b. Supplied to the device 14. Since ammonia is supplied to the SCR device 14 instead of urea water, the SCR device 14 can realize NOx reduction in a lower exhaust gas temperature range. It should be noted that the time during which the total amount of urea water held in the heater 30 or a predetermined amount or more is converted to ammonia is the volume of the closed space 21b, the heat generation performance of the heater 30, and the amount of urea water that can be held by the heater 30. It may be determined experimentally by such as.

  When it is determined that the engine operating state is not in the warm-up state (step S106: No), the control unit 60 determines that the engine operating state is in the normal state and turns off the first relay 61. (Step S120). When the first relay 61 is turned off, the electrical connection between the heater 30, the alternator 40, and the battery 42 is interrupted, and the heater 30 is inactivated. The control unit 60 closes the first flow path portion 21a (step S122), injects urea water by the urea water injection device 18 (step S124), and returns to the detection of the operating state. The control unit 60 transmits a control signal to the first flow path switching valve 25 and the second flow path switching valve 26, and as shown in FIG. 8, the first flow path portion 21a is closed so as to close the first flow path portion 21a. The valve positions of the second flow path switching valve 25 and the second flow path switching valve 26 are switched. As a result, the introduction part 20a and the first flow path pipe 21 (first flow path part 21a) communicate with each other, and the introduced exhaust gas flows through the first flow path part 21a and is guided to the discharge part 20b. . The urea water supplied to the introduction part 20a by the urea water injection device 18 is guided to the second flow path part 22a by the exhaust gas, and is supplied to the SCR device 14 together with the exhaust gas through the discharge part 20b. The temperature of the exhaust gas in the normal state is equal to or higher than a predetermined temperature, and urea water can be converted into ammonia by the amount of heat of the exhaust gas.

  According to the ammonia generator 20 according to the first embodiment described above, urea water is held in the heater 30, and the first flow switching valve 25 and the second flow switching valve 26 perform the first flow. By closing the passage 21a, a closed space 21b that encloses the heater 30 is formed, and the heater 30 generates heat. Therefore, ammonia can be efficiently generated from urea water without being affected by the temperature and flow of the exhaust gas. That is, it is possible to convert the entire amount of urea water into ammonia while reducing the amount of power required for the heat generation of the heater 30, and the ammonia supply amount to the SCR device 14 can be stabilized. Further, since ammonia can be held in the closed space 21b, unnecessary ammonia leakage can be prevented or suppressed, and the amount of ammonia supplied to the SCR device 14 can be adjusted. Furthermore, since the ammonia slip / diesel oxidation catalyst 15 is provided in the subsequent stage of the ammonia generator 20, even if ammonia leaks out of the closed space 21b, it is not released outside the vehicle.

  According to the ammonia generator 20 according to the first embodiment, ammonia is supplied to the SCR device 14 instead of urea water, so that the temperature range is lower than the operating temperature conventionally required for the operation of the SCR device 14. Thus, NOx reduction can be realized. That is, in the conventional method of supplying urea water to the SCR device, the temperature of the SCR device itself, the temperature at which the exhaust gas temperature supplied to the SCR device hydrolyzes urea water to generate ammonia, for example, 200 degrees, It was required to be. On the other hand, the NOx reduction catalyst provided in the SCR device increases the amount of ammonia required for reduction and reduces the NOx reduction rate (reduction rate), but has the ability to reduce NOx from a lower temperature, for example, about 120 degrees. Have. Therefore, by using the ammonia generator 20 according to the first embodiment and supplying ammonia directly to the SCR device 14 instead of urea water, it becomes possible to supply the amount of ammonia necessary for low-temperature reduction, NOx reduction can be realized in a lower operating temperature range.

  It is known that the temperature of exhaust gas exhausted from the engine 510 tends to be lower than 200 degrees when traveling in an urban area, that is, in a low / medium load operation region, with improvement in combustion efficiency and fuel saving. Yes. If the ammonia generator 20 according to the first embodiment is used, NOx reduction can be performed even in the low and medium load operation region, and exhaust gas purification can be realized in a wider operation region as compared with the conventional case.

  Generally, the amount of ammonia that can be adsorbed by the SCR device (NOx reduction catalyst) tends to increase as the SCR device temperature decreases. When ammonia is supplied to the low temperature SCR device 14, the supplied ammonia is SCR. It is adsorbed by the device 14. Therefore, even when the exhaust gas temperature is low, the amount of ammonia required for NOx reduction can be provided.

  According to the ammonia generator 20 according to the first embodiment, when ammonia is supplied to the SCR device 14, the exhaust gas heated by the heater 30 via the first flow path pipe 21 is Supplied to the SCR device 14. Therefore, even in the low and medium load operation region, it is possible to supply the exhaust gas having a higher temperature to the SCR device 14 without being affected by the low-temperature exhaust gas that does not pass through the heater 30, and NOx reduction in the SCR device 14. Efficiency can be improved.

Second embodiment:
With reference to FIGS. 11-13, the ammonia generator 20 which concerns on 2nd Embodiment is demonstrated. FIG. 11 is an explanatory diagram showing an operating state of the ammonia generator according to the second embodiment during warm-up. FIG. 12 is an explanatory view showing an operating state of the ammonia generator according to the second embodiment during warm-up. FIG. 13 is a flowchart showing a processing routine for controlling the operation of the ammonia generator according to the second embodiment. This processing routine is executed by the control unit 60 repeatedly at a predetermined timing and time interval. The ammonia generator 20 according to the second embodiment is different from the procedure in the ammonia generator 20 according to the first embodiment in the procedure for generating ammonia, but each component is the same as that in the first embodiment. Since it is the same as that of the ammonia generator 20 concerned, the same code | symbol is attached | subjected and description of each component is abbreviate | omitted.

  Since some of the operating states of the ammonia generator 20 according to the second embodiment are the same as the operating states of the ammonia generator 20 according to the first embodiment, detailed description thereof is omitted. When the engine is in a cold start state, as shown in FIG. 4, the first flow path switching valve 25 closes the first flow path pipe 21, and exhausts the exhaust gas from the engine 510. It is switched so as to lead to the second flow path pipe 22. The second flow path switching valve 26 is switched so as to close the first flow path pipe 21 and make the first flow path pipe 21 a closed space 21b.

  When the engine is in a warm-up state, as shown in FIGS. 11 and 12, the operating state of the first and second flow path switching valves 25, 26, the operating state of the heater 30, and The operating state of the urea water injection device 18 changes. In addition, in the ammonia generator 20 which concerns on 2nd Embodiment, after making the heater 30 heat | fever-generate, after the urea water is supplied in the point to which urea water is supplied, it is the 1st which makes the heater 30 heat-generate. This is different from the ammonia generator 20 of FIG. In addition, the heater 30 may be provided with the urea water holding | maintenance part 30a similarly to 1st Embodiment.

  Also in the second embodiment, the operation state of the engine is in the first operation state is a state in which the heater 30 is operated (heat generation), a state in which urea water is hydrolyzed (converting urea water into ammonia), It means a case where the exhaust gas temperature is at least one of a state higher than a predetermined temperature. The state where the heater 30 is operated and the state where the urea water is hydrolyzed appears when the engine is warmed up, and the state where the exhaust gas temperature is higher than the predetermined temperature appears during normal operation after the engine is warmed up.

  After the engine operating state becomes a warm-up state, the first and second flow path switching valves 25 and 26, the heater 30, and the urea water injection device 18 of the ammonia generator 20 according to the second embodiment. Adopts the operating state shown in FIG. That is, the first flow path switching valve 25 is switched so as to close the first flow path pipe 21 and guide the exhaust gas from the engine 510 to the second flow path pipe 22. The second flow path switching valve 26 is switched so as to close the first flow path pipe 21 and confine the heater 30 in the closed space 21b. In this state, the heater 30 is turned on and enters a heated state. The operating state of the engine shown in FIG. 11 is a first operating state, that is, a state in which the heater 30 is operated (heat generation). In the second embodiment, urea water is not held in the heater 30 (no dot pattern is attached), and the energization of the heater 30 is energization for preheating. The preheating is performed for a predetermined time until the temperature of the heater 30 or the temperature in the closed space 21b reaches a required temperature for hydrolyzing urea water, for example, 200 degrees or more. The predetermined time may be determined in advance based on the performance of the heater 30, the volume of the closed space 21b, and may be corrected in consideration of the outside air temperature and the like.

  When the predetermined time elapses after the heater 30 is energized, as shown in FIG. 12, the first flow path switching valve 25 closes the second flow path pipe 22 and connects the introduction part 20a from the engine 510. The exhaust gas thus introduced is switched so as to be guided to the first flow path pipe 21, that is, the first flow path portion 21a. The second flow path switching valve 26 closes the second flow path pipe 22, and guides the exhaust gas led to the first flow path pipe 21, that is, the first flow path portion 21a, to the discharge portion 20b. Can be switched to. In this state, the urea water injection device 18 injects a predetermined amount of urea water. As a result, the injected urea water is guided to the heater 30 together with the exhaust gas, and at least a part thereof is heated by the heater 30 and converted into ammonia by hydrolysis. Ammonia generated by the conversion from the urea water is supplied to the SCR device 14 together with the exhaust gas. Since the exhaust gas supplied to the SCR device 14 is heated by the heater 30, the NOx reduction reaction in the SCR device 14 can be promoted. The injection amount of urea water may be determined as appropriate depending on, for example, the exhaust gas temperature and the engine load. The injection amount increases as the exhaust gas temperature increases and the engine load increases.

  In the present embodiment, an ammonia generator 20 is provided in front of the SCR device 14, and the ammonia generated by the ammonia generator 20 is supplied to the SCR device 14. The NOx reduction function can be exhibited from a low temperature range.

  When the operating state of the engine is changed to the normal state through the warm-up state, the first and second flow path switching valves 25 and 26, the heater 30, and the urea of the ammonia generator 20 according to the second embodiment. The water injection device 18 takes the operation state shown in FIG. The engine operating state shown in FIG. 8 is the first operating state, that is, the exhaust gas temperature is higher than a predetermined temperature.

  Operation control of the ammonia generator 20 in the second embodiment will be described with reference to FIG. This processing routine is executed by the control unit 60 repeatedly at a predetermined timing and time interval.

  The control unit 60 starts this processing routine when the vehicle is started, and detects the operating state of the engine by various sensors provided in the vehicle. The detection of the operating state of the engine has been described in the first embodiment.

  The control unit 60 determines whether or not the operating state of the engine is in a cold start state (step S200). When it is determined that the engine operating state is in the cold start state (step S200: Yes), the control unit 60 turns off the first relay 61 (step S202). That is, the heater 30 is electrically disconnected from the alternator 40 and the battery 42 and does not generate heat (activate). The control unit 60 closes the first flow path portion 21a (step S204), and returns to the detection of the operating state. When the first flow path portion 21a is closed, the control unit 60 transmits a control signal to the first flow path switching valve 25 and the second flow path switching valve 26, as shown in FIG. The valve positions of the first flow path switching valve 25 and the second flow path switching valve 26 are switched so as to close the flow path pipe 21. As a result, the introduction part 20a and the second flow path part 22a communicate with each other, and the introduced exhaust gas flows through the second flow path part 22a and is guided to the discharge part 20b.

  When it is determined that the engine operating state is not in the cold start state (step S200: No), the control unit 60 determines whether the engine operating state is in the warm-up state (step S206). ). When the control unit 60 determines that the operating state of the engine is in the warm-up state (step S206: Yes), the control unit 60 closes the first flow path portion 21a (step S208), and the first relay 61 Is turned on (step S210). Specifically, the control unit 60 transmits a control signal to the first flow path switching valve 25 and the second flow path switching valve 26, and as shown in FIG. The valve positions of the first flow path switching valve 25 and the second flow path switching valve 26 are switched so as to be closed. As a result, a closed space 21b closed (defined) by the first and second flow path switching valves 25 and 26 is formed in the first flow path portion 21a. When the first relay 61 is turned on in this state, the alternator 40 and the heater 30 are electrically connected, and the electric power generated by the alternator 40 is supplied to the heater 30. The heater 30 that is supplied with electric power generates heat, and preheating is performed.

  When the energization time for the heater 30 elapses for a predetermined time, the control unit 60 closes the second flow path portion 22a (step S212). The control unit 60 causes the urea water injector 18 to inject urea water (step S214), and returns to the detection of the operating state. Specifically, the control unit 60 transmits a control signal to the first flow path switching valve 25 and the second flow path switching valve 26, and the urea water injector 18, and as shown in FIG. The valve positions of the first flow path switching valve 25 and the second flow path switching valve 26 are switched so as to block the second flow path portion 22a, and urea water is injected from the urea water injection device 18. As a result, the introduction part 20a and the first flow path part 21a communicate with each other, and the introduced exhaust gas flows through the first flow path part 21a and is guided to the discharge part 20b. The urea water supplied to the introduction part 20a by the urea water injection device 18 is led to the first flow path part 21a by the exhaust gas, and is hydrolyzed by the heater 30 that generates heat by preheating, Ammonia is generated. The generated ammonia is guided to the discharge unit 20b by the exhaust gas and supplied to the SCR device 14. Also in the present embodiment, ammonia is supplied to the SCR device 14 instead of urea water, so the SCR device 14 can achieve NOx reduction in a lower exhaust gas temperature range.

  If it is determined that the engine operating state is not in the warm-up state (step S206: No), the control unit 60 determines that the engine operating state is in the normal state and turns off the first relay 61. (Step S216). When the first relay 61 is turned off, the electrical connection between the heater 30, the alternator 40, and the battery 42 is interrupted, and the heater 30 is inactivated. The control unit 60 closes the first flow path portion 21a (step S218), injects urea water by the urea water injection device 18 (step S220), and returns to the detection of the operating state. The control unit 60 transmits a control signal to the first flow path switching valve 25 and the second flow path switching valve 26, and as shown in FIG. 8, the first flow path portion 21a is closed so as to close the first flow path portion 21a. The valve positions of the second flow path switching valve 25 and the second flow path switching valve 26 are switched. As a result, the introduction part 20a and the first flow path part 21a communicate with each other, and the introduced exhaust gas flows through the first flow path part 21a and is guided to the discharge part 20b. The urea water supplied to the introduction part 20a by the urea water injection device 18 is guided to the second flow path part 22a by the exhaust gas, and is supplied to the SCR device 14 together with the exhaust gas through the discharge part 20b. The temperature of the exhaust gas in the normal state is equal to or higher than a predetermined temperature, and urea water can be converted into ammonia by the amount of heat of the exhaust gas.

  According to the ammonia generator 20 according to the second embodiment described above, the SCR device 14 can be used in a temperature range lower than that of the prior art in the same manner as when the ammonia generator 20 according to the first embodiment is used. NOx reduction can be realized.

  In the ammonia generator 20 according to the second embodiment, since the urea water supply process to the heater 30 is not required, the number of times of switching the first and second flow path switching valves 25 and 26 can be reduced.

  According to the ammonia generator 20 according to the second embodiment, since the preheating of the heater 30 is executed in the closed space 21b, the heating can be efficiently performed without being affected by the exhaust gas temperature and the exhaust gas flow. The vessel 30 can generate heat. In addition, when ammonia is supplied to the SCR device 14, exhaust gas that has passed through the first flow path pipe 21 is supplied to the SCR device 14, so that the influence of low-temperature exhaust gas that does not pass through the heater 30 is affected. Therefore, the exhaust gas having a higher temperature can be supplied to the SCR device 14 without receiving the NOx, and the NOx reduction efficiency in the SCR device 14 can be improved.

  According to the ammonia generator 20 according to the second embodiment, since the conversion from urea water to ammonia is executed at the timing when ammonia is supplied to the SCR device 14, NOx depends on the operating state of the engine 510. The amount of ammonia required for the reduction can be dynamically provided.

Variations:
(1) The ammonia generator 20 according to the first and second embodiments shown in FIG. 2 and FIG. 3 includes a first flow path pipe 21 and a second flow path pipe 22 arranged in parallel in the horizontal direction. However, as shown in FIG. 14, the first flow path pipe 21 and the second flow path pipe 22 arranged in the vertical direction may be provided. FIG. 14 is an explanatory view showing a modification of the ammonia generator according to the first and second embodiments. For example, when there is no mounting space in the horizontal direction, the ammonia generator 20 according to the first and second embodiments can be mounted on the vehicle by finding the mounting space in the vertical (vertical) direction. FIG. 14 shows the ammonia generator 20 including the above-described heat storage body 31 that can be provided in addition to the heater 30.

(2) In each of the above embodiments, by arranging a DC / DC converter between the first relay 61 and the second relay 62, the electric power generated by the alternator 40 can be reduced to the heater 30 without being stepped down. Can be supplied. As a result, it is possible to improve the heating performance of the heater 30 and to provide a necessary amount of heat in a shorter time.

(3) In the above embodiments, the second flow path switching valve 26 may not be provided. That is, since the contact between the exhaust gas flow and the heater 30 is prevented by the first flow path switching valve 25, the problem of heat loss due to the heater 30 coming into contact with the exhaust gas can be avoided.

(4) In each of the above embodiments, in addition to the urea water injection device 18, as shown in FIG. 15, a second urea water injection device 18a that directly injects urea water into the closed space 21b may be provided. . FIG. 15 is an explanatory view showing a modification of the ammonia generator. In this case, in 1st Embodiment, the process for supplying the urea water shown in FIG. 5 to the heater 30 is abbreviate | omitted, and it transfers to the state shown in FIG. 6 directly from the cold start state shown in FIG. Thus, the number of operations of the first and second flow path switching valves 25 and 26 can be reduced. In the first and second embodiments, it is possible to reduce the amount of urea water adhering to the first flow path pipe 21 and to prevent or suppress the temperature drop of the urea water due to the exhaust gas having a low temperature. be able to. Furthermore, urea water can be supplied to the first channel pipe 21 independently of the operating states of the first and second channel switching valves 25 and 26. Note that FIG. 15 illustrates a mode in which the urea water injection device 18 already mentioned is arranged in the introduction portion 20a.

(5) In each of the above embodiments, the ammonia generator 20 has a rectangular box shape. However, the ammonia generator 20 may have a redundant shape that is folded back multiple times from the introduction part 20a to the discharge part 20b. It may have a cylindrical shape. Moreover, in each said embodiment, although the ammonia generator 20 extended linearly was demonstrated as an example, the ammonia generator 20 is arrange | positioned in the direction where one part structure or piping cross | intersects another structure or piping. And may be applied to a purification system formed in a folded shape. For example, it is applied to a purification system having a folded shape having a parallel part arranged parallel to the ground when mounted on the vehicle and a crossing part intersecting the parallel part, and shortening the length in the flow direction of exhaust gas. Also good. The intersecting portion may be a vertical portion perpendicular to the ground, and may be a purification system having a bulk in the vertical direction. In this case, the ammonia generator 20 may be arranged in either the parallel part or the intersecting part.

  As mentioned above, although this invention was demonstrated based on the Example and the modification, Embodiment mentioned above is for making an understanding of this invention easy, and does not limit this invention. The present invention can be changed and improved without departing from the spirit and scope of the claims, and equivalents thereof are included in the present invention. For example, the technical features in the embodiments and the modifications corresponding to the technical features in each embodiment described in the summary section of the invention are to solve some or all of the above-described problems, or In order to achieve part or all of the effects, replacement or combination can be performed as appropriate. Further, if the technical feature is not described as essential in the present specification, it can be deleted as appropriate.

DESCRIPTION OF SYMBOLS 10 ... Exhaust gas purification system 11 ... Exhaust pipe 11a ... Manifold 11b ... Muffler end pipe 12 ... Diesel oxidation catalyst 13 ... Diesel particulate filter 14 ... Selective reduction catalyst (SCR) device 15 ... Diesel oxidation catalyst 17 ... Fuel injection device 18 ... Urea Water injection device 18a ... second urea water injection device 191 ... first temperature sensor 192 ... second temperature sensor 20 ... ammonia generator 20a ... introduction portion 20b ... discharge portion 201 ... case 21 ... first flow path tube 21a ... 1st flow path part 21b ... Closed space 22 ... 2nd flow path pipe 22a ... 2nd flow path part 23 ... Heat insulating material 25 ... 1st flow path switching valve 26 ... 2nd flow path switching valve DESCRIPTION OF SYMBOLS 30 ... Heater 30a ... Urea water holding | maintenance part 31 ... Heat storage body 40 ... Alternator 401 ... Alternator side pulley 41 ... Auxiliary machine 42 ... Battery 50 ... vehicle 510 ... diesel engines 511 ... engine side pulley 512 ... belt 520 ... wheel 60 ... control unit 61 ... first relay 62 ... second relay 64 ... ammeter

Claims (10)

In the exhaust passage of the internal combustion engine, an ammonia generator disposed at the rear stage of the urea water supply unit,
An introduction portion for introducing exhaust gas, a discharge portion for discharging the exhaust gas, a first flow path portion that is in communication with the introduction portion and the discharge portion, and is separated from each other; A main body having a flow path portion;
A heater disposed in the first flow path portion;
A first switching unit disposed on the introduction unit side of the main body and capable of switching a flow path of the exhaust gas between the first flow path unit and the second flow path unit;
An ammonia generator comprising: The ammonia generator according to claim 1 further comprises:
An ammonia generator, comprising: a second switching unit that is disposed on a side of the discharge unit in the main body and is switchable so as to block the first channel unit or the second channel unit. The ammonia generator according to claim 1 or 2,
The said heater is an ammonia generator which has a holding | maintenance part which can hold | maintain the urea water supplied by the said urea water supply part. The ammonia generator according to any one of claims 1 to 3, further comprising:
An ammonia generator, wherein the main body includes a second urea water supply unit capable of directly supplying urea water to the first flow path unit. An ammonia generation control device,
A main body disposed in an exhaust passage of the internal combustion engine and having a first flow path portion and a second flow path portion separated from each other;
A urea water supply unit that supplies urea water disposed on the exhaust gas introduction side of the main body;
A heater disposed in the first flow path portion;
A switching unit disposed on the introduction side of the main body and capable of switching a flow path of the exhaust gas between the first channel unit and the second channel unit;
A control unit that controls the switching unit to switch the flow path of the exhaust gas to the second flow path unit when the operating state of the internal combustion engine is the first operating state;
An ammonia generation control device comprising: In the ammonia generation control device according to claim 5,
The ammonia generation control device, wherein the first operation state is an operation state in which the heater is operated. In the ammonia generation control device according to claim 5,
The first operation state is an ammonia generation control device in which the urea water is hydrolyzed. In the ammonia generation control device according to claim 5,
The ammonia generation control device, wherein the first operation state is an operation state in which the temperature of the exhaust gas is higher than a predetermined temperature. In the ammonia generation control device according to claim 6,
The control unit further controls the supply of urea water by the urea water supply unit and the operation of the heater,
In the first operating state, the control unit switches the flow path of the exhaust gas to the second flow path section, operates the heater, and then changes the flow path of the exhaust gas to the first flow path. An ammonia generation control device that switches to a flow path section and causes the urea water supply section to supply urea water to the first flow path section. In the ammonia generation control device according to claim 7,
The control unit further controls the supply of urea water by the urea water supply unit and the operation of the heater,
In the first operation state, the control unit switches the flow path of the exhaust gas to the first flow path unit, and supplies urea water to the first flow path unit by the urea water supply unit. After the supply of urea water to the first flow path part is completed, the ammonia generation control device that switches the flow path of the exhaust gas to the second flow path part and operates the heater.

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