JP2016089728A - engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine enabling switching between a normal mode and an SCR heating mode at appropriate timing.SOLUTION: An engine includes an urea water injection section, an SCR catalyst and a control section. The urea water injection section injects urea water to a route to which exhaust gas is discharged. The SCR catalyst removes nitrogen oxide from exhaust gas passing there by taking in ammonia obtained from urea injected by the urea water injection section. The control section enables switching between a normal mode and an SCR heating mode of increasing a temperature of the SCR catalyst, and switches a mode from the SCR heating mode to the normal mode on the basis of a passage time from the start of the engine.SELECTED DRAWING: Figure 7

Description

  The present invention relates to an engine that injects urea water to reduce nitrogen oxides contained in exhaust gas.

  Conventionally, an engine that purifies NOx (nitrogen oxide) contained in exhaust gas by using selective catalytic reduction (SCR) has been known. This type of engine includes a urea water injection unit that injects urea water and an SCR catalyst. The urea water injection unit injects urea water into a path through which the exhaust gas passes. Urea contained in the urea water is hydrolyzed to ammonia by touching high-temperature exhaust gas. The SCR catalyst is made of a material such as zeolite or ceramic that adsorbs ammonia. NOx contained in the exhaust gas is reduced by touching the SCR catalyst that has adsorbed ammonia, and changes into nitrogen and water. Thereby, the amount of NOx emission can be suppressed. Patent Documents 1 and 2 disclose this type of technology.

  In Patent Document 1, if the temperature of the SCR catalyst is lower than a predetermined value, the SCR catalyst cannot sufficiently remove NOx in the exhaust gas, and that the urea water is not sufficiently hydrolyzed in a situation where the exhaust gas temperature is low. An SCR system that takes into account is disclosed. In this SCR system, control is performed to increase the temperature around the SCR catalyst by delaying the fuel injection timing (increasing the retard amount). The retard amount is determined based on the atmospheric pressure, the outside air temperature, and the cooling water temperature in addition to the engine speed and the injection amount.

  The SCR system of Patent Document 2 controls the injection amount of urea water based on the detection amount of NOx sensors arranged upstream and downstream of the SCR catalyst. However, the NOx sensor cannot detect NOx with high accuracy since the ambient temperature is low for a while after being activated. Therefore, the SCR system of Patent Document 2 controls the injection amount of urea water without using the NOx sensor after the engine is started. Specifically, the injection amount of urea water is determined based on the atmospheric pressure, the outside air temperature, and the cooling water temperature in addition to the engine speed and the injection amount.

Japanese Patent No. 555076 JP 2013-72391 A

  However, in Patent Document 1, since there is no concept of heating the SCR catalyst by switching modes, the retard amount is calculated even when heating of the SCR catalyst is unnecessary, for example. When the heating of the SCR catalyst is not required, the retard amount becomes zero, but the calculation itself is performed, so that the processing amount increases.

  Patent Document 2 only describes that preliminary heating control is performed, and does not disclose a start condition or a cancellation condition for preliminary heating control.

  The present invention has been made in view of the above circumstances, and a main object thereof is to provide an engine capable of switching between a normal mode and an SCR heating mode at an appropriate timing.

Means and effects for solving the problems

  The problems to be solved by the present invention are as described above. Next, means for solving the problems and the effects thereof will be described.

  According to an aspect of the present invention, an engine having the following configuration is provided. That is, this engine includes a urea water injection unit, an SCR catalyst, and a control unit. The urea water injection unit injects urea water into a path through which exhaust gas passes. The SCR catalyst is disposed in a path through which the exhaust gas passes, and removes nitrogen oxides contained in the passing exhaust gas by taking in ammonia obtained from urea injected by the urea water injection unit. The control unit can switch between a normal mode and an SCR heating mode in which the temperature of the SCR catalyst is increased, and switches from the SCR heating mode to the normal mode based on an elapsed time from engine start. .

  Thereby, since the temperature of the SCR catalyst is usually low at the time of engine start, it is possible to switch to the normal mode at an appropriate timing by using the elapsed time from engine start. Further, since the temperature of the SCR catalyst is raised by switching the mode, the processing amount in the normal mode can be reduced.

  The engine preferably has the following configuration. That is, this engine includes an SCR catalyst temperature sensor that detects the temperature of the SCR catalyst. The controller switches between the normal mode and the SCR heating mode based on the temperature of the SCR catalyst.

  Thereby, the mode can be switched at an appropriate timing by using the temperature of the SCR catalyst that is directly related to the amount of adsorption of ammonia.

  In the engine, the temperature at which the normal mode is switched to the SCR heating mode is preferably lower than the temperature at which the SCR heating mode is switched to the normal mode.

  This can prevent frequent switching between the normal mode and the SCR heating mode.

  In the engine, the control unit preferably switches between the normal mode and the SCR heating mode based on a detection result of a value related to the surrounding environment or an engine operating state.

  Thus, the mode can be switched in consideration of exhaust gas regulations by using the surrounding environment. Further, by using the engine operating state, the mode can be switched in consideration of the exhaust gas temperature.

1 is a perspective view of an engine according to an embodiment of the present invention. The side view by the side of the intake manifold of an engine. Explanatory drawing which shows typically the flow of the intake and exhaust of an engine. The block diagram which concerns on engine control. Explanatory drawing which shows the name and timing of fuel injection typically. The table | surface which shows an example of the process performed in normal mode and SCR heating mode. The flowchart which shows the process which switches normal mode and SCR heating mode. The graph which shows the example in which a mode switches when two mode switching temperatures are set. The flowchart which shows the process which switches a normal mode and SCR heating mode, when two mode switching temperatures are set. The table | surface which shows an example of the control performed in normal mode, 1st SCR heating mode, and 2nd SCR heating mode. The table | surface which compares the characteristic of 1st SCR heating mode and 2nd SCR heating mode. The graph which compares the temperature rising capability of the SCR catalyst of normal mode, 1st SCR heating mode, and 2nd SCR heating mode. The flowchart which shows the control in the case of performing SCR heating mode based on the information set beforehand. The flowchart which shows the control in the case of switching SCR heating mode based on the information acquired from the sensor group. The side view which shows a mode that the engine of this embodiment was applied to the tractor. The top view which shows a mode that the engine of this embodiment was applied to the tractor. The side view which shows a mode that the engine of this embodiment was applied to the combine. The top view which shows a mode that the engine of this embodiment was applied to the combine. The side view which shows a mode that the engine of this embodiment was applied to the skid steer loader. The top view which shows a mode that the engine of this embodiment was applied to the skid steer loader.

  Next, embodiments of the present invention will be described with reference to the drawings. First, a basic configuration of the engine 100 of the present embodiment will be described with reference to FIGS. 1 to 5. The engine 100 is a diesel engine and is mounted on an agricultural machine such as a tractor and a construction machine such as a skid steer loader.

  As shown in FIGS. 1 and 2, an oil pan 1 is disposed at the lower part of the engine 100. The oil pan 1 is a container-like part for storing engine oil. A cylinder block 2 is disposed above the oil pan 1. A piston, a crankshaft, and the like are disposed inside the cylinder block 2. A cylinder head 3 is disposed on the upper side of the cylinder block 2. The cylinder head 3 is attached with an injector for injecting fuel into the combustion chamber.

  A cooling fan 4 is disposed on the side surface of the cylinder block 2. The cooling fan 4 has a large number of blades, and wind can be generated by rotating these blades. A radiator 5 is disposed at a position facing the cooling fan 4. The radiator 5 has a circulation path for circulating the cooling water. The cooling fan 4 can cool the cooling water by applying wind to the radiator 5. As shown in the block diagram of FIG. 4, engine 100 includes a cooling water temperature sensor 81 that detects the temperature of the cooling water and outputs it to an ECU (Engine Control Unit) 80.

  As shown in FIG. 4, the ECU 80 includes a control unit 80a and a storage unit 80b. The control unit 80a includes a CPU (not shown) and the like. As shown in FIG. 4, the control unit 80a sends control commands to various actuators of the actuator group based on information from the various sensors of the sensor group, and performs various parameters (for example, The fuel injection amount, the air intake amount, the exhaust gas reduction amount, etc.) are controlled.

  The storage unit 80b includes an unillustrated ROM, RAM, and the like. The storage unit 80b stores various programs and a plurality of control information set in advance regarding the control of the engine 100.

  A flywheel housing 6 is disposed on the side surface of the cylinder block 2 opposite to the cooling fan 4. A flywheel is disposed inside the flywheel housing 6. The power of engine 100 is taken from the flywheel.

  As shown in FIGS. 1 to 3, the engine 100 includes an intake portion 11, a supercharger 12, an intake pipe connection portion 13, an intake throttle (intake throttle device) 14, and an intake manifold as intake system members. 15.

  The suction part 11 sucks in gas from the outside via an air cleaner described later. As shown in FIG. 4, engine 100 includes an atmospheric pressure sensor 82 that detects atmospheric pressure and outputs it to ECU 80.

  As shown in FIG. 3, the supercharger 12 includes a turbine wheel 12a and a compressor wheel 12b. The turbine wheel 12a is configured to rotate using exhaust gas. The compressor wheel 12b is connected to the same shaft 12c as the turbine wheel 12a, and rotates with the rotation of the turbine wheel 12a. Thus, by rotating the compressor wheel 12b, air can be compressed and forced intake can be performed.

  The gas sucked by the supercharger 12 is supplied to the intake manifold 15 via an unillustrated intake pipe, an intake pipe connecting portion 13 shown in FIG. 2, and an intake throttle 14 shown in FIG. The intake throttle 14 includes a throttle valve. The intake throttle 14 can change the amount of gas supplied to the intake manifold 15 (that is, the combustion chamber) by adjusting the opening of the throttle valve. The opening degree of the throttle valve is controlled by the ECU 80.

  The intake manifold 15 divides the supplied gas into a number corresponding to the number of cylinders (four in this embodiment) and supplies it to the combustion chamber. In addition, an intake air temperature sensor 84 is attached to the intake manifold 15 as shown in FIG. The intake air temperature sensor 84 detects the temperature of the gas in the intake manifold 15 and outputs it to the ECU 80.

  As shown in FIG. 2, a common rail 22 is disposed below the intake manifold 15. The common rail 22 stores the fuel supplied from the fuel pump 21 at a high pressure, and supplies the fuel to an injector 23 (fuel injection device, see FIG. 3) arranged in the cylinder head.

  The injector 23 injects fuel into the combustion chamber at a predetermined timing. The injector 23 is configured to perform main injection near the top dead center (TDC) as shown in FIG. Further, the injector 23 can perform pre-injection for noise reduction immediately before the main injection, or can perform pilot injection for NOx reduction and noise reduction at a timing before the pre-injection. The injector 23 performs post-injection for the purpose of reducing PM, promoting purification of exhaust gas, and increasing the temperature immediately after the main injection, or post-injection for the purpose of increasing the temperature at a later timing of the after-injection. Can be done. The injector 23 includes an injector solenoid valve 24 (see FIG. 4). The injector solenoid valve 24 is opened and closed at a timing according to an instruction from the ECU 80 to inject fuel into the combustion chamber.

  When the fuel injected into the combustion chamber burns, the piston can be driven up and down to rotate the crankshaft. The engine 100 includes an engine rotation speed detection sensor 83 that detects the engine rotation speed (rotation speed, rotation speed per predetermined time). The engine speed detection sensor 83 outputs the detected engine speed to the ECU 80.

  As shown in FIGS. 1 to 3, the engine 100 includes an exhaust manifold 31, an EGR device 32, and an exhaust gas purification device 40.

  The exhaust manifold 31 collectively supplies exhaust gases generated in the plurality of combustion chambers to the turbine wheel 12 a of the supercharger 12. An exhaust temperature sensor 85 is attached to the exhaust manifold 31. The exhaust temperature sensor 85 detects the temperature of the gas in the exhaust manifold 31 and outputs it to the ECU 80. A part of the gas that has passed through the exhaust manifold 31 is supplied to the EGR device 32 and the rest is supplied to the exhaust gas purification device 40.

  The EGR device 32 includes an EGR cooler 33, an EGR pipe 34, and an EGR valve 35. The EGR cooler 33 cools the exhaust gas recirculated to the intake system. The EGR pipe 34 recirculates the exhaust gas cooled by the EGR cooler 33 to the intake system. Further, the EGR device 32 can change the amount of exhaust gas supplied to the intake manifold 15 by adjusting the opening degree of the EGR valve 35. The valve opening degree of the EGR valve 35 is controlled by the ECU 80.

  The exhaust gas purification device 40 includes a DPF device 50 and an SCR device 60. The engine 100 includes a support base 41, a case fixing body 42, and a case fastening band 43 as members that support and fix the exhaust gas purification device 40.

  The support base 41 is a rectangular member that is disposed at the top of the cylinder head 3 and has an edge bent downward. The case fixing body 42 is disposed at the upper part of the support base 41 and contacts the lower part of the DPF device 50 and the SCR device 60. The case fastening band 43 is a flexible member configured to be attachable to the case fixing body 42. The DPF device 50 and the SCR device 60 are fixed by sandwiching the DPF device 50 and the SCR device 60 between the case fixing body 42 and the case fastening band 43.

  The DPF device 50 removes particulate matter (PM) contained in the exhaust gas. The DPF device 50 includes a DPF case 51, an oxidation catalyst 52, and a filter 53.

  The DPF case 51 is a substantially cylindrical hollow member, in which an oxidation catalyst 52 and a filter 53 are disposed. The oxidation catalyst 52 is made of platinum or the like, and is a catalyst for oxidizing (combusting) unburned fuel, carbon monoxide, nitrogen monoxide and the like contained in the exhaust gas. The filter 53 is configured as a fall flow type filter, for example, and collects particulate matter contained in the exhaust gas treated by the oxidation catalyst 52.

  Further, an oxidation catalyst temperature sensor 86, a filter temperature sensor 87, and a differential pressure sensor 88 are attached to the DPF case 51. The oxidation catalyst temperature sensor 86 detects the temperature in the vicinity of the inlet of the DPF case 51 (the exhaust upstream side of the oxidation catalyst 52) and outputs it to the ECU 80. The filter temperature sensor 87 detects the temperature between the oxidation catalyst 52 and the filter 53 (upstream side of the filter 53) and outputs the detected temperature to the ECU 80. The differential pressure sensor 88 detects a pressure difference between the upstream side of the filter 53 (downstream side of the oxidation catalyst 52) and the downstream side of the filter 53, and outputs it to the ECU 80.

  The exhaust gas that has passed through the DPF device 50 is sent to the SCR device 60 via the DPF outlet pipe 44, the urea mixing pipe 45, and the SCR inlet pipe 46. The DPF outlet pipe 44 is connected to the downstream end of the DPF device 50. An upstream NOx sensor 89 that detects the NOx concentration of the exhaust gas is attached to the DPF outlet pipe 44. The upstream NOx sensor 89 outputs the detected NOx concentration to the ECU 80.

  The urea mixing pipe 45 is connected so as to be substantially perpendicular to the DPF outlet pipe 44. The longitudinal direction of the urea mixing tube 45 is parallel to the longitudinal directions of the DPF device 50 and the SCR device 60. In the vicinity of the upstream end of the urea mixing tube 45, a urea water injection unit 47 is attached. The urea water injection unit 47 includes a urea water injection nozzle 47a that injects urea water, and a urea water injection pipe 47b that supplies urea water to the urea water injection nozzle 47a. By injecting urea water into the urea mixing tube 45, urea is hydrolyzed and ammonia is generated.

  In the urea water injection unit 47, the presence or absence and the injection amount of urea water are controlled by a DCU (Dosing Control Unit) 95. For example, when the temperature of the exhaust gas has passed the temperature at which urea is hydrolyzed into ammonia, the DCU 95 starts injection of urea water. One control device may have the functions of the ECU 80 and the DCU 95.

  The SCR device 60 removes NOx contained in the exhaust gas introduced through the SCR inlet pipe 46. The SCR device 60 includes an SCR case 61, an SCR catalyst 62, and a slip catalyst 63.

  The SCR case 61 is a substantially cylindrical hollow member, in which the SCR catalyst 62 and the slip catalyst 63 are arranged. The SCR catalyst 62 is made of a material such as ceramic that adsorbs ammonia. Ammonia generated by the urea water injection unit 47 injecting the urea water is adsorbed on the SCR catalyst 62. NOx contained in the exhaust gas is reduced by touching the SCR catalyst 62 that has adsorbed ammonia, and changes into nitrogen and water.

  The slip catalyst 63 is a catalyst such as platinum that oxidizes ammonia, and oxidizes ammonia to change it into nitrogen and water. The slip catalyst 63 is a catalyst that prevents the ammonia that has been desorbed from the SCR catalyst 62 and not adsorbed by the SCR catalyst 62 from being released to the outside. The exhaust gas passes through the slip catalyst 63, passes through a predetermined exhaust pipe, and is then discharged to the outside. By providing the urea water injection unit 47 and the SCR catalyst 62 as described above, NOx contained in the exhaust gas can be removed.

  An SCR catalyst temperature sensor 90 is attached upstream of the SCR catalyst 62. The SCR catalyst temperature sensor 90 detects the temperature immediately upstream of the SCR catalyst 62 (hereinafter referred to as “SCR catalyst temperature”) and outputs the detected temperature to the ECU 80. The method for detecting the SCR catalyst temperature is arbitrary, and a temperature sensor may be provided downstream of the SCR catalyst 62 and the detected value may be used, or temperature sensors may be provided upstream and downstream to average the detected values. Etc. may be used. Moreover, you may correct | amend the detected value obtained from these temperature sensors based on an engine driving | running state etc.

  A downstream NOx sensor 91 is attached to the downstream side of the slip catalyst 63. The downstream NOx sensor 91 outputs the detected NOx concentration to the ECU 80.

  Next, the normal mode and the SCR heating mode will be described. First, the difference in processing performed between the normal mode and the SCR heating mode will be described with reference to FIG.

  As described above, it is known that when the SCR catalyst temperature is low, the SCR catalyst 62 cannot sufficiently remove NOx in the exhaust gas. Therefore, the engine 100 of the present embodiment has an SCR heating mode that effectively increases the SCR catalyst temperature in addition to the normal mode. The SCR heating mode is a mode in which the temperature of the exhaust gas (and hence the SCR catalyst temperature) is increased by controlling the injector 23, the intake throttle 14, and the like.

  FIG. 6 shows processing specifically performed in each mode. In the normal mode, pre-injection and main injection are performed. On the other hand, in the SCR heating mode, in addition to pre-injection and main injection, retard control (control to delay the injection timing of main injection), after-injection, and post-injection are performed. Processing for reducing the inhalation amount is performed.

  By performing retard control, after-injection, and post-injection, energy that does not directly contribute to the output of engine 100 increases, so the temperature of the exhaust gas can be raised. In addition, when performing retard control, the combustion in a combustion chamber may become unstable.

  However, since the post-injection injects fuel at a timing slightly delayed from the main injection, and thus hardly affects the combustion of the main injection, the temperature of the exhaust gas can be appropriately increased. Furthermore, even if the SCR device 60 is disposed at a position away from the cylinder block 2, the SCR catalyst temperature can be effectively increased.

  Further, by controlling the intake throttle 14 to reduce the intake amount of the outside air, the heat capacity of the exhaust gas can be lowered, so that the temperature of the SCR catalyst can be raised more quickly. Note that the table shown in FIG. 6 is an example, and in the SCR heating mode, if the temperature of the exhaust gas can be raised as compared with the normal mode, the processing performed in each mode can be appropriately changed.

  In this embodiment, the parameters of each process (specifically, the retard amount of the retard control, the injection timing and the injection amount of the after injection and the post injection, and the throttle amount of the intake throttle) are basically constant. Thereby, compared with the structure which changes injection quantity and retard amount according to a condition, the processing amount in SCR heating mode can be reduced.

  Furthermore, in the present embodiment, since the normal mode and the SCR heating mode are clearly separated, for example, as compared with a configuration in which the amount of retard is calculated even when heating of the SCR catalyst is unnecessary as in Patent Document 1, Processing can be simplified.

  Next, processing for switching between the normal mode and the SCR heating mode will be described with reference to FIGS.

  Since the SCR catalyst temperature can be effectively increased by using the SCR heating mode, the NOx emission amount can be reduced. However, in the SCR heating mode, fuel consumption is increased because fuel is consumed to raise the temperature of the exhaust gas. Therefore, it is preferable to switch between the normal mode and the SCR heating mode at an appropriate timing.

  In this regard, in the present embodiment, the normal mode and the SCR heating mode are switched based on various indices as shown in FIG. This will be specifically described below. In this embodiment, the SCR heating mode is performed when all of the conditions indicated by S101 to S106 are satisfied. However, the SCR heating mode is configured when some of the conditions are satisfied. You can also.

  In S101, a condition based on atmospheric pressure is set. This is because the restriction of exhaust gas is relaxed when the altitude is high (that is, when the atmospheric pressure is low). The ECU 80 determines whether or not the atmospheric pressure detected by the atmospheric pressure sensor 82 satisfies the condition shown in S101. The ECU 80 uses the normal mode when determining that the condition of S101 is not satisfied (S108), and performs the process of S102 when determining that the condition of S101 is satisfied.

  In S102, a condition based on the intake air temperature is set. This is because the restriction of exhaust gas is relaxed in a cold region (that is, when the intake air temperature is low). The ECU 80 determines whether or not the intake air temperature detected by the intake air temperature sensor 84 satisfies the condition shown in S102. The ECU 80 uses the normal mode when determining that the condition of S102 is not satisfied (S108), and performs the process of S103 when determining that the condition of S102 is satisfied. Note that the atmospheric pressure and the intake air temperature correspond to “values related to the surrounding environment”.

  In S103, a condition based on the cooling water temperature is set. This is because the temperature of the cooling water is difficult to increase when the temperature of the exhaust gas is low. The ECU 80 determines whether or not the coolant temperature detected by the coolant temperature sensor 81 satisfies the condition shown in S103. The ECU 80 uses the normal mode when it is determined that the condition of S103 is not satisfied (S108), and performs the process of S104 when it is determined that the condition of S103 is satisfied.

  In S104, a condition based on the engine operating state (specifically, the fuel injection amount and the engine speed) is set. This is because the temperature of the exhaust gas can be estimated according to the engine operating state. For example, when the engine speed is drastically decreased, the temperature of the exhaust gas obtained from the engine operating state may deviate from the actual exhaust gas temperature (there is a time lag until the temperature decreases). A time condition is also set. The ECU 80 determines whether the set fuel injection amount, the engine speed detected by the engine speed detection sensor 83, and the elapsed time satisfy the condition shown in S104. The ECU 80 uses the normal mode when determining that the condition of S104 is not satisfied (S108), and performs the process of S105 when determining that the condition of S104 is satisfied.

  In S105, a condition based on the elapsed time after completion of engine start is set. This is because the temperature of the engine 100 is low immediately after the engine 100 is started. In the present embodiment, it is determined that the start is completed when the engine speed becomes equal to or higher than a predetermined value. The ECU 80 determines whether or not the elapsed time since the start is determined to satisfy the condition of S105. The ECU 80 uses the normal mode when determining that the condition of S105 is not satisfied (S108), and performs the process of S106 when determining that the condition of S105 is satisfied.

  In S106, conditions based on the SCR catalyst temperature are set. The ECU 80 determines whether or not the SCR catalyst temperature detected by the SCR catalyst temperature sensor 90 satisfies the condition indicated by S106. When it is determined that the condition of S106 is not satisfied, the ECU 80 uses the normal mode (S108), and when it is determined that the condition of S106 is satisfied, the ECU 80 performs heating using the SCR heating mode (S107).

  The method for determining whether or not the conditions described above are satisfied is arbitrary and can be changed as appropriate. For example, the altitude may be measured using a GPS receiver instead of the atmospheric pressure sensor. Further, completion of starting of engine 100 may be determined based on the time from the start.

  The numerical values of the conditions shown in FIG. 7 are an example. Also, the numerical value of the condition may be changed according to the condition. For example, when the outside air temperature (intake air temperature) is low, the elapsed time after completion of starting may be lengthened. Further, the SCR catalyst temperature condition may be changed based on altitude (atmospheric pressure) and outside air temperature (intake air temperature).

  Next, an example in which two types of temperatures for switching modes (hereinafter referred to as mode switching temperatures) are set when the mode is switched based only on the SCR catalyst temperature will be described with reference to FIGS. 8 and 9. .

  If the mode switching temperature from the normal mode to the SCR heating mode is the same as the mode switching temperature from the SCR heating mode to the normal mode, if the temperature fluctuates near the mode switching temperature, Will switch frequently.

  Therefore, in this embodiment, as shown in FIG. 8, the mode switching temperature from the normal mode to the SCR heating mode is 200 ° C., and the mode switching temperature from the SCR heating mode to the normal mode is 240 ° C. Specific processing will be described below.

  If the ECU 80 is in the normal mode (Yes in S201 of FIG. 9) and the SCR catalyst temperature is 200 ° C. or lower (Yes in S202), the ECU 80 shifts to the SCR heating mode (S203). On the other hand, when the ECU 80 is in the SCR heating mode (No in S201 of FIG. 9), if the SCR catalyst temperature is 240 ° C. or higher (Yes in S204), the ECU 80 shifts to the normal mode (S205). .

  Next, a configuration having the first SCR heating mode and the second SCR heating mode will be described with reference to FIGS. First, the difference between the two SCR heating modes will be described with reference to FIGS.

  FIG. 10 shows processing specifically performed in each mode. As shown in FIG. 10, the first SCR heating mode and the second SCR heating mode differ only in whether or not control related to the EGR device is performed. Specifically, only in the first SCR heating mode, a process of controlling the EGR device 32 (EGR valve 35) and returning the exhaust gas to the intake manifold 15 (hereinafter referred to as an exhaust gas recirculation process) is performed.

  FIG. 11 is a table comparing the merits and demerits of the first SCR heating mode and the second SCR heating mode. As shown in FIG. 11, the temperature increase capability of the SCR catalyst is higher in the second SCR heating mode than in the first SCR heating mode. This is because when the exhaust gas recirculation process is performed, a gas having a low oxygen concentration is sent to the combustion chamber, so that the combustion temperature decreases. Therefore, as shown in FIG. 12, the normal mode has the lowest temperature increase capability, the first SCR heating mode has the highest temperature increase capability, and the second SCR heating mode has the highest temperature increase capability.

  Furthermore, the amount of PM non-adhering to the DPF device 50 is smaller in the second SCR heating mode than in the first SCR heating mode. This is because in the first SCR heating mode, soot is likely to occur because the combustion temperature is low.

  On the other hand, generation of NOx can be suppressed by performing the exhaust gas recirculation process. Therefore, in the first SCR heating mode, the amount of NOx to be removed is smaller than in the second SCR heating mode. Thereby, in the 1st SCR heating mode, consumption of urea water can be held down rather than the 2nd SCR heating mode. Similarly, in the first SCR heating mode, the number of post injections and the like can be reduced as compared with the second SCR heating mode, so that the fuel consumption can also be reduced.

  Considering the above, it is preferable to use the second SCR heating mode when it is important to quickly raise the temperature of the SCR catalyst and to suppress the NOx emission amount early. On the other hand, when it is important to reduce the consumption of urea water and fuel, it is preferable to use the first SCR heating mode.

  As a first method of utilizing the engine 100 capable of executing the first SCR heating mode and the second SCR heating mode, which SCR heating mode is used is specified in advance (for example, at the time of factory shipment). There is a way to continue using that mode.

  Specifically, the preferred SCR heating mode is determined based on the use environment, the use area, and in which machine the machine is mounted. For example, when used at high altitudes, it is preferable to designate the first SCR heating mode because the restriction of exhaust gas is relaxed. In addition, since it is difficult to raise the SCR catalyst temperature when the SCR device 60 is far from the cylinder block, it is preferable to designate the second SCR heating mode.

  The information designated in this way is written in the storage unit 80b of the ECU 80. The ECU 80 reads the SCR heating mode to be used with reference to the contents of the storage unit 80b after the engine is started (S301 in FIG. 13). Then, the ECU 80 controls the engine while switching between the normal mode and the read SCR heating mode (S302).

  As a second method of using the engine 100 capable of executing the first SCR heating mode and the second SCR heating mode, the first SCR heating mode and the second SCR heating mode are switched in real time based on information from sensors and the like. There is a way.

  Specifically, the ECU 80 acquires the detection result from the sensor group after the engine is started (S401). The ECU 80 determines whether to use the first SCR heating mode or the second SCR heating mode based on the detection result of the sensor group (S402). For example, when the current position is a highland or a cold region, it is preferable to use the first SCR heating mode because the restriction of exhaust gas is relaxed. In addition, since it is necessary to significantly increase the SCR catalyst temperature immediately after the engine is started, it is preferable to use the second SCR heating mode when the elapsed time from the engine start is not more than a predetermined value.

  Then, the ECU 80 controls the engine while switching between the normal mode and the determined SCR heating mode (S403). As described above, by enabling execution of the first SCR heating mode and the second SCR heating mode, it is possible to perform appropriate heating according to the use environment, the use region, the mounted target, and the like.

  Next, an example in which the engine 100 described above is applied to an agricultural machine and a construction machine will be described. In the following description, “left side”, “right side” and the like simply mean the left side and the right side in the direction in which the vehicle moves forward.

  First, the tractor 110 including the engine 100 will be described with reference to FIGS. 15 and 16. The tractor 110 is a work vehicle for agricultural work, and can be equipped with various work machines (attachments) such as a rotary, a loader, a plow, a box scraper, and the like to perform various work using the work machine. it can.

  The tractor 110 includes a vehicle body 111, a pair of left and right front wheels 112, and a pair of left and right rear wheels 113. A bonnet 114 is arranged at the front of the vehicle body 111, and the engine 100 is arranged inside the bonnet 114.

  A radiator 5 is arranged inside the bonnet 114 and opposite the cooling fan 4. An air cleaner 122 is arranged inside the bonnet 114. The air cleaner 122 removes dust and the like contained in the sucked outside air.

  A mission case 115 is disposed between the pair of left and right rear wheels 113. The output of the engine 100 is shifted by the transmission in the transmission case 115 and transmitted to the rear wheel 113 and the work machine.

  At the rear of the mission case 115, a lower link 116, a top link 117, and a PTO shaft 118 are arranged. In addition, on the upper part of the mission case 115, the work implement is connected to the lower link 116 and the top link 117 and is driven by the PTO shaft 118.

  A cabin 119 for an operator to board is disposed above the mission case 115 and behind the hood 114. A driver's seat is provided inside the cabin 119, and a number of operating tools for an operator to operate are provided in the vicinity of the driver's seat.

  A urea water tank 120 and a fuel tank 121 are disposed below the cabin 119. The urea water tank 120 is connected to the urea water injection nozzle 47a by a urea water injection pipe 47b.

  Next, with reference to FIG.17 and FIG.18, the combine 130 provided with said engine 100 is demonstrated. The combine 130 is configured as a so-called self-removing combine. A crawler section 132 for running the machine body 131 is provided below the machine body 131 of the combine 130. Further, the combine 130 is provided with a cutting part 133 in front of the machine body 131 for cutting off the stock of rice grains and wheat.

  The cutting unit 133 includes a plurality of weed bodies and a cutting blade. The plurality of herbaceous bodies define a width for harvesting the culm or scoop up the culm in a fallen state. The cereal buds inserted between the weeds are cut and cut near the root by a cutting blade.

  Further, the cutting unit 133 is connected to the body 131 of the combine 130 via a lifting mechanism (not shown). This elevating mechanism is configured to be able to drive the mowing unit 133 up and down. Thereby, according to the inclination of a farm field, etc., the height of the cutting part 133 can be adjusted to an appropriate height, and cutting can be performed appropriately.

  A threshing device 134 is provided behind the mowing unit 133 and on the left side of the combine 130. The threshing apparatus 134 threshs the cereals harvested by the reaping unit 133. A sorting device 135 is provided below the threshing device 134. The sorting device 135 sorts and takes out the grains threshed by the threshing device 134.

  A Glen tank 136 is provided behind the cutting unit 133 and on the right side of the combine 130. Glen tank 136 stores the grains selected by sorting device 135. The grain stored in the Glen tank 136 is discharged to the outside by the discharge auger 137.

  A cabin 138 for an operator to board is disposed in front of the Glen tank 136. Inside the cabin 138, a driver's seat is provided, and a number of operating tools for an operator to operate are provided in the vicinity of the driver's seat.

  An engine 100 is disposed below the cabin 138. A radiator 5 is disposed opposite the cooling fan 4 of the engine 100. Further, a pre-cleaner 139 is disposed behind the cabin 138. Dust and the like are removed from the outside air sucked from the precleaner 139 through an unillustrated air cleaner. A urea water tank 140 is disposed near the engine 100.

  In addition, a waste chain 141 is provided behind the threshing device 134 and the sorting device 135. The waste chain 141 conveys the waste from which the grain has been removed from the grain straw to the rear. The waste conveyed by the waste chain 141 is cut into an appropriate length by the waste cutter device 142 provided at the rear of the combine 130 and discharged outside the machine.

  Next, a skid steer loader 150 including the engine 100 will be described with reference to FIGS. 19 and 20. The skid steer loader 150 is configured to load a loader device 151 to be described later and perform a loader operation. A pair of left and right crawler units 152 are mounted on the skid steer loader 150. A bonnet 153 is disposed above the crawler unit 152.

  An engine 100 is disposed inside the bonnet 153. A radiator 5 is disposed inside the hood 153 and opposite the cooling fan 4 of the engine 100. A urea water tank 154 is disposed inside the hood 153 and in front of the engine 100.

  A hydraulic pump 155 and a transmission device 156 are disposed in front of the engine 100. The power of the engine 100 is transmitted to the crawler unit 152 via the transmission device 156.

  In front of the hood 153, a cabin 157 on which an operator is boarded is disposed. A driver's seat is provided inside the cabin 157, and a number of operating tools for operation by an operator are provided in the vicinity of the driver's seat.

  In addition, the loader device 151 is capable of rotating to a loader post 158 disposed on both left and right sides, a pair of left and right lift arms 159 rotatably connected to the top of each loader post 158, and a tip end of the lift arm 159. And a bucket 160 connected to.

  Between each loader post 158 and the lift arm 159, a lift cylinder 161 for rotating the lift arm 159 up and down is provided. A bucket cylinder 162 for rotating the bucket 160 up and down is provided between the lift arm 159 and the bucket 160. When the operator operates an operation tool (not shown), the hydraulic pressure of the hydraulic pump 155 is controlled. Thereby, the lift cylinder 161 or the bucket cylinder 162 expands and contracts, and the lift arm 159 or the bucket 160 rotates. The operator can carry out work such as earth and sand in this way.

  As described above, the engine 100 of the present embodiment includes the urea water injection unit 47, the SCR catalyst 62, and the control unit 80a. The urea water injection unit 47 injects urea water into a path (urea mixing pipe 45) through which the exhaust gas passes. The SCR catalyst 62 is disposed in a path through which the exhaust gas passes, and removes nitrogen oxides contained in the exhaust gas passing through the SCR catalyst 62 by taking in ammonia obtained from urea injected by the urea water injection unit 47. To do. The control unit 80a can switch between the normal mode and the SCR heating mode in which the temperature of the SCR catalyst 62 is increased, and switches from the SCR heating mode to the normal mode based on the elapsed time from the engine start.

  Thereby, since the temperature of the SCR catalyst 62 is usually low at the time of engine start, it is possible to switch to the normal mode at an appropriate timing by using the elapsed time from the engine start. Further, since the mode is switched to raise the temperature of the SCR catalyst 62, the processing amount in the normal mode can be reduced.

  Further, the engine 100 of the present embodiment includes an SCR catalyst temperature sensor 90 that detects the temperature of the SCR catalyst 62. The controller 80a switches between the normal mode and the SCR heating mode based on the temperature of the SCR catalyst 62.

  Thereby, the mode can be switched at an appropriate timing by using the temperature of the SCR catalyst that is directly related to the amount of adsorption of ammonia.

  In the engine 100 of the present embodiment, the temperature at which the normal mode is switched to the SCR heating mode is lower than the temperature at which the SCR heating mode is switched to the normal mode.

  This can prevent frequent switching between the normal mode and the SCR heating mode.

  Further, the control unit 80a of the engine 100 according to the present embodiment switches between the normal mode and the SCR heating mode based on the detection result of the value related to the surrounding environment or the engine operating state.

  Thus, the mode can be switched in consideration of exhaust gas regulations by using the surrounding environment. Further, by using the engine operating state, the mode can be switched in consideration of the exhaust gas temperature.

  The preferred embodiment of the present invention has been described above, but the above configuration can be modified as follows, for example.

  In the above embodiment, the DPF device 50 and the SCR device 60 are located at the top of the engine 100, but the arrangement of the DPF device 50 and the SCR device 60 is arbitrary. May be. Further, in this specification, even if the DPF device 50 and the SCR device 60 are separated from the cylinder block 2, they are included in the “engine” including them.

  The positions of the various sensors are examples, and can be changed as appropriate. For example, the intake temperature sensor 84 may be disposed upstream of the intake manifold 15 (for example, upstream of the compressor wheel 12b), and the exhaust temperature sensor 85 may be disposed downstream of the exhaust manifold 31. .

  Although the example which applies this invention to the diesel engine provided with a supercharger was shown above, this invention is applicable also to a naturally aspirated diesel engine.

14 Intake throttle (intake throttle device)
23 Injector (fuel injection device)
32 EGR device 47 Urea water injection unit 50 DPF device 60 SCR device 61 SCR case 62 SCR catalyst 63 Slip catalyst 80 ECU
95 DCU
100 engine

Claims (4)

A urea water injection unit that injects urea water into a path through which exhaust gas passes;
An SCR catalyst that is disposed in a path through which exhaust gas passes and that removes nitrogen oxides contained in the exhaust gas that passes through by taking in ammonia obtained from urea injected by the urea water injection unit;
A control unit that can switch between a normal mode and an SCR heating mode that raises the temperature of the SCR catalyst, and that switches from the SCR heating mode to the normal mode based on an elapsed time from engine startup;
An engine comprising: The engine according to claim 1,
An SCR catalyst temperature sensor for detecting the temperature of the SCR catalyst;
The engine, wherein the controller switches between the normal mode and the SCR heating mode based on a temperature of the SCR catalyst. The engine according to claim 2,
The engine for switching from the normal mode to the SCR heating mode is lower than the temperature for switching from the SCR heating mode to the normal mode. The engine according to any one of claims 1 to 3,
The engine, wherein the control unit switches between the normal mode and the SCR heating mode based on a detection result of a value related to the surrounding environment or an engine operating state.

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