JP6479642B2 - EGR system - Google Patents

Description

  The present invention relates to an EGR system that recirculates exhaust gas of an internal combustion engine of a moving body to an intake side. Specifically, the present invention relates to a configuration for reducing the adverse effects of unburned fuel components on the EGR system.

  Conventionally, an internal combustion engine having an EGR system that recirculates exhaust gas to the intake side is known. Patent Document 1 discloses this type of internal combustion engine. The EGR system provided in the internal combustion engine (diesel engine) of Patent Document 1 determines the opening of an EGR valve (EGR valve) provided in an EGR passage that connects an exhaust side passage and an intake side passage with an EGR control unit ( Whether or not to operate the EGR system is switched by controlling by the EGR control means). The EGR control unit is configured to place the EGR system in a non-operating state (specifically, to close the EGR valve) when the idling state of the internal combustion engine continues for a predetermined time.

Japanese Patent Laying-Open No. 2015-31171

  However, in the configuration of Patent Document 1 described above, when the internal combustion engine is switched from the idling state to the normal operating state, the exhaust gas component is caused by the influence of unburned fuel components accumulated in the exhaust side passage during the idling state. The concentration of the unburned fuel component will temporarily increase. When this high-concentration unburned fuel component enters the EGR passage by opening the EGR valve at the start of the normal operation state, the unburned fuel component is condensed on the inner surface of the EGR passage, around the EGR valve, or the like. As a result, smooth recirculation of exhaust gas to the intake side may be hindered. Further, when the unburned fuel component is condensed on the inner surface of the EGR passage or the like, a sulfur component (soot or the like) may be deposited on the porous surface to cause sulfuric acid corrosion of the EGR passage.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to reduce adverse effects of unburned fuel components of exhaust gas on the EGR system in the EGR system.

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 EGR system having the following configuration is provided. That is, this EGR system recirculates the exhaust gas of the moving body internal combustion engine to the intake side. The EGR system includes an EGR passage, an EGR valve, an EGR control unit, an idling duration acquisition unit, and a delay time calculation unit. The EGR passage connects an exhaust-side passage and an intake-side passage of the internal combustion engine. The EGR valve is provided in the EGR passage, and can adjust the amount of EGR recirculated to the intake side of the exhaust gas by changing the opening degree. The EGR control unit controls the opening degree of the EGR valve. The idling duration acquisition unit acquires a duration of an idling state of the internal combustion engine. The delay time calculation unit calculates a valve opening delay time that is a time from when the internal combustion engine is switched from the idling state to a normal operation state until the EGR valve that is closed in the idling state starts to be opened, It calculates based on the acquisition result of the said idling continuation time acquisition part. The EGR control unit starts opening the EGR valve at a timing delayed by the valve opening delay time after the internal combustion engine is switched from the idling state to the normal operation state. The delay time calculation unit estimates the amount of unburned fuel components accumulated in the exhaust-side passage during the idling state based on the acquisition result of the idling duration acquisition unit, and starts normal operation. The time estimated to take until the amount of the unburned fuel component estimated to be accumulated in the exhaust-side passage decreases to below the threshold value is calculated as the valve opening delay time.

Thereby, the following effects are produced. That is, in general, when the engine is switched from the idling state to the normal operation state, the concentration of the unburned fuel component in the exhaust gas temporarily changes due to the influence of the unburned fuel component accumulated in the exhaust side passage during the idling state. To increase. Considering this point, in the configuration of the present invention, when the idling state is switched to the normal operation state, the EGR valve that was closed in the idling state is not immediately started to open, but by the delay time calculation unit. The EGR valve is opened after being delayed by the calculated valve opening delay time. Thereby, it can suppress that an unburned fuel component has a bad influence on an EGR system by condensing in an EGR channel | path. In addition, when the engine is switched from the idling state to the normal operation, the EGR valve is opened after the amount of unburned fuel components accumulated in the exhaust-side passage during the idling state is sufficiently reduced. Become. Therefore, it is possible to reliably prevent the high-concentration unburned fuel component from entering the EGR passage, and to further reduce the adverse effect of the unburned fuel component on the EGR system.

  In the EGR system, it is preferable that the delay time calculation unit calculates the valve opening delay time such that the longer the duration of the idling state acquired by the idling duration acquisition unit, the longer.

  Thereby, the following effects are produced. That is, generally, the longer the idling state duration, the greater the amount of unburned fuel component that accumulates in the exhaust-side passage. In consideration of this point, the duration of the idling state is shortened by controlling so that the longer the duration of the idling state, the longer it takes to start opening the EGR valve that was closed in the idling state. In some cases, the period during which the EGR system is not operated can be shortened. Thereby, the period when an EGR system does not function substantially can be shortened, and the situation where a lot of nitrogen oxides are contained in exhaust gas can be controlled.

  In the EGR system, the EGR control unit opens the fully closed EGR valve at a timing delayed by the valve opening delay time after the internal combustion engine is switched from the idling state to the normal operation state. It is preferable to control the state.

  Thus, when the adverse effect of the unburned fuel component on the EGR system is reduced, the EGR valve can be fully opened at once, and the EGR system can be immediately operated to the maximum extent. As a result, it is possible to maintain a state where the amount of nitrogen oxides contained in the exhaust gas is reduced (a state where the EGR system is operating) over a wide range of operation time.

The schematic diagram showing the composition of the engine provided with the EGR system concerning one embodiment of the present invention typically. The block diagram which shows the main electrical structures of an engine. The figure which showed the area | region (idling area | region) judged to be in an idling state when it sees by the relationship between an engine speed and fuel injection quantity by hatching. The flowchart which shows the process performed by ECU for control of an EGR valve. The graph which showed the time (valve opening delay time) after starting normal driving | operating until it starts opening an EGR valve in relation to idling continuation time. The graph which showed the time change of the density | concentration of the unburned fuel component contained in exhaust gas when normal driving | operation is started after idling.

  Next, embodiments of the present invention will be described with reference to the drawings. First, an engine 1 that is an internal combustion engine including the EGR system 70 of the present embodiment will be described with reference to FIG. FIG. 1 is a schematic view schematically showing a configuration of an engine 1 including an EGR system 70 according to an embodiment of the present invention. In a circle indicated by a two-dot chain line in the drawing, The structure of is shown.

  The engine 1 of this embodiment shown in FIG. 1 is mounted on a tractor (agricultural work vehicle, work vehicle) that is a moving body, and serves as a drive source for the tractor. The engine 1 includes an engine main body 10, a fuel injection device 20, an EGR device (exhaust gas recirculation device) 30, an exhaust turbine supercharger 40, an exhaust purification device 50, and an ECU that controls the engine 1 ( Engine control unit) 60. The EGR device 30 is a part of the EGR system 70 of the present embodiment.

  In the present embodiment, the engine 1 is configured as an in-line four-cylinder diesel engine. The engine main body 10 includes a cylinder block and a cylinder head as main structures, and is configured by assembling various components thereto. Four cylinders 11 are formed in the cylinder block. A combustion chamber 12 is formed inside each cylinder 11, and a piston 13 is slidably disposed in the combustion chamber 12. The piston 13 is connected to a crankshaft 14 that is an output shaft of the engine 1 via a rod 19.

  The engine main body 10 includes an intake manifold 15 and an exhaust manifold 16. An intake pipe 17 is connected to the intake manifold 15 as an intake side passage for introducing intake air into the intake manifold 15. An exhaust pipe 18 is connected to the exhaust manifold 16 as an exhaust side passage through which exhaust gas from the exhaust manifold 16 is discharged.

  The fuel injection device 20 includes an injector 21 corresponding to each cylinder 11. The fuel pumped by a fuel injection pump (not shown) is distributed to the injector 21 via a common rail (not shown). The electronic control valve provided in the injector 21 is electrically connected to the ECU 60 so that an appropriate amount of fuel is injected from the injector 21 into the combustion chamber 12 at an appropriate timing. By injecting fuel into the combustion chamber 12, the piston 13 reciprocates in the cylinder 11 by the propulsive force obtained from the explosion after the intake and compression stroke in the combustion chamber 12, and the reciprocating motion of the piston 13 moves the rod 19. Thus, it is converted into a rotational motion of the crankshaft 14 to obtain power.

  The EGR device 30 includes an EGR pipe 31 as an EGR passage, an EGR cooler 32, and an EGR valve 33. The EGR pipe 31 connects the intake pipe 17 and the exhaust pipe 18, and a part of the exhaust gas is recirculated (recirculated) to the intake air via the EGR pipe 31. The EGR valve 33 is provided inside the EGR pipe 31, and the EGR valve 33 is electrically connected to an EGR control unit 61 (see FIG. 2) of the ECU 60. The EGR control unit 61 is a part of the EGR system 70 of the present embodiment. Specifically, the EGR valve 33 can be configured by, for example, an electromagnetic flow control valve. By appropriately adjusting (changing) the opening degree of the EGR valve 33 by the EGR control unit 61, the amount of exhaust gas recirculated to the intake side (hereinafter referred to as “EGR amount”) is adjusted.

  The supercharger 40 includes a turbine 41 that is rotated by exhaust gas that flows through the exhaust pipe 18, and a compressor 42 that rotates integrally with the turbine 41. The compressor 42 is disposed inside the intake pipe 17, and the intake air is compressed by the rotation of the compressor 42 and is sent into the cylinder 11 through the intake manifold 15.

  The exhaust purification device 50 is provided at the outlet of the exhaust pipe 18. The exhaust purification device 50 includes, for example, a DOC (diesel oxidation catalyst) 51 and a DPF (diesel particulate filter) 52. The exhaust gas is purified by passing through the exhaust purification device 50 and then discharged to the outside.

  Next, with reference to FIG. 2, the electrical configuration and control configuration of the engine 1 will be described. FIG. 2 is a block diagram showing the main electrical configuration of the engine 1.

  The ECU 60 is configured as a computer including a CPU, a ROM, a RAM, and the like, and various data such as control programs and control parameters are stored in the ROM. The ECU 60 acquires information from various sensors and the operation tool of the tractor, and performs control related to the engine 1 based on these information.

  By loading the above-described program stored in the ROM into the RAM and executing it by the CPU, the ECU 60 can be operated as the EGR control unit 61, the idling duration acquisition unit 62, the delay time calculation unit 63, and the like. it can. Further, in the present embodiment, as the various sensors described above, an engine speed sensor 9 that detects the engine speed of the engine 1, a fuel injection amount sensor 22 that detects the fuel injection amount of the fuel injection device 20, and an EGR valve An opening detection sensor 34 that detects the opening of 33 is electrically connected to the ECU 60.

  Hereinafter, the configuration of each part of the control system of the engine 1 will be described in more detail. As shown in FIG. 2, the ECU 60 includes an idling region calculation unit 64, an engine speed acquisition unit 65, a fuel injection amount, in addition to the EGR control unit 61, the idling duration acquisition unit 62, and the delay time calculation unit 63 described above. An acquisition unit 66 and an idling state determination unit 67 are provided.

  The EGR control unit 61 can open or close the EGR valve 33 at a desired speed by transmitting a signal to the EGR valve 33. Thereby, for example, the opening degree of the EGR valve 33 can be changed and set to a desired opening degree (target opening degree) while balancing the pressure on the upstream side and the downstream side of the EGR valve 33. By doing so, the flow path cross-sectional area of the EGR pipe 31 can be set appropriately, and the EGR amount can be adjusted.

The idling area calculation unit 64 calculates an area in which it is determined that the operating state of the engine 1 is in an idling state when viewed with two parameters of the engine speed and the fuel injection amount. The idling area calculation unit 64 of the present embodiment acquires information indicating that the engine 1 is used in the tractor, and calculates an idling area (idling area) in consideration of this. Specifically, the low speed side threshold value N _a and the high speed side threshold value N _{b of} the engine speed determined to be in the idling state, and the low injection amount side threshold value of the fuel injection amount determined to be in the idling state. F _a (N) and a threshold F _b (N) on the high injection amount side are calculated (see FIG. 3). Note that the threshold value F _a (N) on the low injection amount side and the threshold value F _b (N) on the high injection amount side of the fuel injection amount are obtained as functions having the engine speed N as an input variable. However, in addition to information on the usage of the engine 1 (for example, information indicating that the engine 1 is used for the tractor in the present embodiment), other information such as the intake air temperature is also taken into consideration. The idling area may be calculated. In FIG. 3, a region that is determined to be in the idling state (idling region) when viewed in relation to the engine speed and the fuel injection amount is indicated by hatching.

  Although not shown in FIG. 3, an appropriate hysteresis is provided at the boundary of the idling area calculation unit 64. Thereby, even when the operating state of the engine 1 fluctuates slightly near the boundary of the idling region, frequent switching between the idling state and the other state can be prevented.

  The engine speed acquisition unit 65 shown in FIG. 2 acquires information on the engine speed of the engine 1 detected by the engine speed sensor 9.

  The fuel injection amount acquisition unit 66 acquires information on the fuel injection amount of the fuel injection device 20 detected by the fuel injection amount sensor 22.

The idling state determination unit 67 determines whether or not the engine 1 is in an idling state when the current operation (operation) state of the engine 1 is viewed with two parameters of the engine speed and the fuel injection amount. Specifically, in the present embodiment, (i) the current engine speed N acquired by the engine speed acquisition unit 65 satisfies N _a ≦ N ≦ N _b , and (ii) the fuel injection amount acquisition unit 66 The acquired current fuel injection amount F satisfies F _a (N) ≦ F ≦ F _b (N), and (iii) N _a ≦ N ≦ N _b and F _a (N) ≦ F ≦ F _b (N ) At the same time, it is determined whether or not it has continued for a predetermined time. When all of the above (i) to (iii) are satisfied, the idling state determination unit 67 determines that the current operating state of the engine 1 is the idling state.

  Note that it is known that when the idling state determination unit 67 determines that the current operating state of the engine 1 is the idling state, the exhaust gas has a low temperature (in the idling state, the exhaust gas has a low temperature). In order to prevent unburned fuel components (components derived from unburned fuel) contained in the EGR system 30 from flowing into the EGR device 30 and condensing to adversely affect the EGR system 70, the EGR valve 33 is closed and the EGR system is closed. 70 is to be deactivated. Details of this control will be described later.

  The idling duration acquisition unit 62 acquires the time during which the idling state continues (hereinafter referred to as “idling duration”) based on the determination result of the idling state determination unit 67.

  When the idling state determination unit 67 determines that the engine 1 is no longer in the idling state, the delay time calculation unit 63 calculates the time until the EGR valve 33 that has been closed during the idling state starts to open. 62 is calculated based on the acquired idling duration time. The control of the valve opening timing of the EGR valve 33 will be described in detail later.

  Next, processing performed by the ECU 60 for controlling the EGR valve 33 will be described in detail with reference to FIG. FIG. 4 is a flowchart showing processing performed by the ECU 60.

  When the flow of FIG. 4 starts, the engine speed acquisition unit 65 of the ECU 60 acquires the engine speed N detected by the engine speed sensor 9, and the fuel injection amount acquisition unit 66 detects by the fuel injection amount sensor 22. A fuel injection amount F is acquired (step S101).

Subsequently, as described in the above conditions (i) to (iii), the idling state determination unit 67 of the ECU 60 determines that the engine speed N acquired in step S101 satisfies N _a ≦ N ≦ N _b and the fuel It is determined whether or not the state in which the injection amount F satisfies F _a (N) ≦ F ≦ F _b (N) continues for a predetermined time or more (step S102). In other words, when the operation (operation) state of the engine 1 is viewed with two parameters of the engine speed and the fuel injection amount, the engine speed N is included in the idling area calculated by the idling area calculation unit 64 from a predetermined time before to the present time. And whether or not the state in which the fuel injection amount F is included continues.

  If it is determined in step S102 that the operating state of the engine 1 is included in the idling region for a predetermined time or longer, the idling state determination unit 67 of the ECU 60 determines that the operating state of the engine 1 is in the idling state. It is determined that there is (step S103). In this case, the EGR control unit 61 of the ECU 60 determines whether or not the state immediately before the engine 1 is the idling state (step S104).

  If it is determined in step S104 that the state of the immediately preceding engine 1 is not the idling state, it means that the engine 1 is switched from the non-idling state to the idling state. Therefore, the EGR control unit 61 causes the unburned fuel component (component derived from the unburned fuel) contained in the exhaust gas to flow into the EGR device 30 at a low temperature (because of the idling state) and condense. In order to suppress adverse effects on the system 70, the EGR valve 33 is controlled so that the EGR valve 33 is immediately fully closed (step S105). Further, the idling duration acquisition unit 62 of the ECU 60 resets the idling duration to zero (step S106). Thereafter, the process returns to step S101.

  If it is determined in step S104 that the engine 1 is idling immediately before and now, the processes in steps S105 and S106 are not performed. Instead, the idling continuation time acquisition unit 62 of the ECU 60 performs an idling continuation time count-up process (step S107). Thereafter, the process returns to step S101.

  If it is determined in step S102 that the operating state of the engine 1 is not included in the idling region, or if it is included, the state does not continue for a predetermined time or longer, the idling state determination unit 67 of the ECU 60 It is determined that the operation state 1 is not the idling state (step S108). In this case, the EGR control unit 61 of the ECU 60 determines whether or not the state immediately before the engine 1 is the idling state (step S109).

  If it is determined in step S109 that the immediately previous state of the engine 1 is the idling state, it means that the engine 1 is switched from the idling state to the non-idling state. Therefore, the delay time calculation unit 63 of the ECU 60 sets the idling continuation time calculated by the idling continuation time acquisition unit 62 in step S107 or the like as the time to wait without opening the EGR valve 33 that has been closed during the idling state. Based on the calculation (step S110). More specifically, the delay time calculation unit 63 is the time from the start of normal operation until the EGR valve 33 starts to open (the time for which the valve opening should be delayed. Hereinafter, it may be referred to as the valve opening delay time). Is calculated using the idling duration.

  The relationship between the idling duration time and the valve opening delay time of the EGR valve 33 calculated by the delay time calculation unit 63 is shown in a graph in FIG. As shown in FIG. 5, the valve opening delay time is determined to be longer as the idling duration time is longer. This is due to the following reason.

  FIG. 6 is a graph showing the change over time in the concentration of the unburned fuel component that is included in the exhaust gas and discharged when normal operation is started after various changes in the idling duration time. As shown in FIG. 6, unburned fuel components accumulated in the exhaust-side passage (for example, the exhaust pipe 18) during the idling state are discharged together with the exhaust gas when the idling state is switched to the normal operation. The amount to be increased greatly immediately after the start of normal operation, but thereafter decreases with the passage of time. The peak of the amount of unburned fuel component emission becomes larger as the duration of the previous idling state is longer (that is, the more unburned fuel component deposited as described above in the idling state). The time until the discharge amount (discharge concentration) decreases to a predetermined value also becomes longer. In consideration of such a tendency, in the present embodiment, the amount of unburned fuel components accumulated in the exhaust-side passage (exhaust pipe 18 and the like) during the idling state is estimated and normal operation is started. The time estimated to take until the amount of the unburned fuel component estimated to be accumulated in the exhaust-side passage decreases to below the threshold is obtained as the valve opening delay time. Is generated in advance and stored in the delay time calculation unit 63. The control information (specifically, a table) is expressed in relation to the idling duration time. Note that this control information is not limited to a table, and may be expressed by a function, for example, as long as the relationship illustrated in FIG. 5 can be expressed. The delay time calculation unit 63 of the ECU 60 acquires the valve opening delay time corresponding to the idling duration time by referring to this table.

  Thereafter, the EGR control unit 61 of the ECU 60 maintains the fully closed state of the EGR valve 33 until the valve opening delay time obtained in step S110 has elapsed (step S111). When the valve opening delay time elapses, the EGR control unit 61 sets the EGR valve 33 to the fully open state at a high speed (for example, at the maximum speed) (step S112), and then performs the normal operation of the EGR valve 33 to adjust the EGR amount. Is controlled (step S113). Thereafter, the process returns to step S101.

  If it is determined in step S109 that the state of the immediately preceding engine 1 is not the idling state, it means that the engine 1 is continuing the non-idling state (normal operating state). In this case, the processing of step S110 to step S112 is skipped, and normal control of the EGR valve 33 is performed to adjust the EGR amount (step S113). Thereafter, the process returns to step S101.

  According to the above flow, in this embodiment, when the operating state of the engine 1 becomes a normal operation state, the EGR valve 33 does not start to be opened immediately, but the EGR valve 33 starts to be opened after being delayed by the valve opening delay time. Yes. In addition, the valve opening is delayed until the influence of the unburned fuel component accumulated in the exhaust pipe 18 is sufficiently reduced (until the content of the unburned fuel component becomes less than the threshold), depending on the idling duration time. The valve opening delay time is made different. Accordingly, it is possible to suppress the EGR system 70 from being adversely affected by the unburned fuel component contained in the exhaust gas while shortening the time during which the EGR system 70 is not operated as much as possible according to various situations. .

  That is, for example, when an operation to start work on a tractor in which the engine 1 is idling is performed and the engine 1 shifts to a normal operation, from the viewpoint of reducing the amount of nitrogen oxides contained in the exhaust gas only. It is desirable to operate the EGR system 70 as soon as possible. However, generally, when the engine 1 is switched from the idling state to the normal operation state, the concentration of the unburned fuel component in the exhaust gas is reduced due to the influence of the unburned fuel component accumulated in the exhaust pipe 18 during the idling state. It will increase temporarily. When this high-concentration unburned fuel component enters the EGR device 30 by opening the EGR valve 33 at the start of a normal operation state, the unburned fuel component is in the inner surface of the EGR pipe 31 or around the EGR valve 33. In some cases, the exhaust gas may be condensed to prevent the smooth return of exhaust gas to the intake side. Furthermore, when the unburned fuel component is condensed on the inner surface of the EGR pipe 31 or the like, the sulfur component (soot or the like) is deposited in a porous state on the EGR pipe 31 and the sulfuric acid corrosion of the EGR device 30 may be caused. Therefore, in the EGR system 70 of the present embodiment, the timing for opening the EGR valve 33 is delayed (delayed) until the amount of unburned fuel components accumulated in the exhaust pipe 18 decreases. As a result, the EGR system 70 can be well protected from unburned fuel components.

  As described above, the EGR system 70 of the present embodiment recirculates the exhaust gas of the engine 1 of the tractor (not shown) to the intake side. This EGR system 70 includes an EGR pipe 31, an EGR valve 33, an EGR control unit 61, an idling duration acquisition unit 62, and a delay time calculation unit 63. The EGR pipe 31 connects a passage on the exhaust side of the engine 1 and a passage on the intake side. The EGR valve 33 is provided in the EGR pipe 31 and can adjust the amount of EGR recirculated to the intake side of the exhaust gas by changing the opening degree. The EGR control unit 61 controls the opening degree of the EGR valve 33. The idling duration acquisition unit 62 acquires the duration of the idling state of the engine 1. The delay time calculation unit 63 calculates the valve opening delay time that is the time from when the engine 1 is switched from the idling state to the normal operation state until the EGR valve 33 that has been closed in the idling state starts to open. Calculation is based on the acquisition result of the duration acquisition unit 62. The EGR control unit 61 starts opening the EGR valve 33 at a timing delayed by the valve opening delay time after the engine 1 is switched from the idling state to the normal operation state.

  Thereby, the following effects are produced. That is, generally, when the engine 1 is switched from the idling state to the normal operating state, the concentration of the unburned fuel component in the exhaust gas due to the influence of the unburned fuel component accumulated in the exhaust pipe 18 or the like during the idling state. Increases temporarily. In view of this point, in the above configuration, when the idling state is switched to the normal operation state, the EGR valve 33 that was closed in the idling state is not immediately started to open, but the delay time calculation unit 63 The EGR valve 33 starts to open after being delayed by the valve opening delay time calculated by the above. Thereby, it can suppress that an unburned fuel component condenses in the EGR pipe | tube 31 etc. and exerts a bad influence on the EGR system 70.

  Further, in the EGR system 70 of the present embodiment, the delay time calculation unit 63 is based on the acquisition result of the idling continuation time acquisition unit 62, and the unburned fuel accumulated in the exhaust side passage such as the exhaust pipe 18 during the idling state. The amount of the fuel component is estimated, and it takes from the start of normal operation until the amount of the unburned fuel component estimated to be accumulated in the exhaust-side passage such as the exhaust pipe 18 decreases below the threshold value. Is calculated as the valve opening delay time.

  As a result, when the idling state is switched to the normal operation, the EGR valve 33 is operated after the amount of the unburned fuel component accumulated in the exhaust side passage such as the exhaust pipe 18 during the idling state is sufficiently reduced. Will be opened. Therefore, it is possible to reliably prevent the high-concentration unburned fuel component from entering the EGR pipe 31 and the like, and to further reduce the adverse effect of the unburned fuel component on the EGR system 70.

  In the EGR system 70 of the present embodiment, the delay time calculation unit 63 calculates the valve opening delay time so that the idling state duration acquired by the idling duration acquisition unit 62 increases as the duration time increases.

  Thereby, the following effects are produced. That is, generally, the longer the duration of the idling state, the greater the amount of unburned fuel component that accumulates in the exhaust-side passage such as the exhaust pipe 18. Considering this point, the duration of the idling state is controlled so that the longer the duration of the idling state, the longer the time until the EGR valve 33 that has been closed in the idling state starts to open is controlled. If it is short, the period during which the EGR system 70 is not operated can be shortened. Thereby, the period when the EGR system 70 does not substantially function can be shortened, and the situation where a large amount of nitrogen oxide is contained in the exhaust gas can be suppressed.

  Further, in the EGR system 70 of the present embodiment, the EGR control unit 61 performs the EGR in the fully closed state at a timing delayed by the valve opening delay time after the engine 1 is switched from the idling state to the normal operation state. Control is performed so that the valve 33 is fully opened.

  As a result, when the adverse effect of the unburned fuel component on the EGR system 70 is reduced, the EGR valve 33 can be fully opened at once and the EGR system 70 can be immediately operated to the maximum extent. As a result, it is possible to maintain a state where the amount of nitrogen oxides contained in the exhaust gas is reduced (a state where the EGR system is operating) over a wide range of operation time.

  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 engine 1 is a diesel engine. However, the present invention is not limited to this, and the present invention can be applied to a gasoline engine, for example. Further, the number and arrangement of cylinders are not limited to the in-line 4-cylinder type of the above embodiment.

  In the above-described embodiment, the idling state determination unit 67 determines whether or not the engine 1 is in the idling state by viewing the current operation (operation) state of the engine 1 with the two parameters of the engine speed and the fuel injection amount. It was supposed to be. However, the method of determining the idling state is not limited to this. For example, instead of this, whether or not the accelerator of the tractor is operated is detected by the accelerator position sensor, and the idling state is determined based on the detection result. It may be determined whether or not there is.

  The idling area calculated by the idling area calculation unit 64 is not limited to the area shown in FIG. 3 but can be changed according to the situation or the like.

  In the above embodiment, in the control information (table) shown in FIG. 5, the time from the start of normal operation until the EGR valve 33 starts to open (the valve opening delay time) increases as the idling duration time increases. It is determined to increase at an accelerated rate. However, the present invention is not necessarily limited to this, and instead, for example, the valve opening delay time may be determined to increase linearly as the idling duration time increases.

  In the above embodiment, when the EGR valve 33 starts to be opened after the valve opening delay time calculated by the delay time calculation unit 63 has elapsed after the normal operation is started, for example, the EGR valve 33 is opened at the maximum speed. ing. However, the present invention is not limited to this, and the EGR valve 33 may be opened at a desired speed in consideration of the pressure balance between the upstream side and the downstream side of the EGR valve 33. Alternatively, when the EGR valve 33 starts to be opened after the valve opening delay time calculated by the delay time calculation unit 63 has elapsed, the valve opening speed or opening degree of the EGR valve 33 is determined according to the calculated valve opening delay time. May be corrected as appropriate.

  In the above embodiment, the engine 1 is provided with the supercharger 40. However, the present invention is not necessarily limited to this, and the present invention can be applied to an engine that does not include the supercharger 40. Can do.

  In the above embodiment, the moving body on which the engine 1 is mounted is a tractor. However, the present invention is not limited to this. For example, instead of this, the moving body can be another agricultural work vehicle such as a combine, or can be a non-agricultural work vehicle such as a truck or a forklift. Or it can be a ship or the like.

1 Engine 31 EGR Pipe 33 EGR Valve 61 EGR Control Unit 62 Idling Duration Acquisition Unit 63 Delay Time Calculation Unit 70 EGR System

Claims (3)

In an EGR system that recirculates exhaust gas of a moving internal combustion engine to the intake side,
An EGR passage connecting an exhaust-side passage and an intake-side passage of the internal combustion engine;
An EGR valve provided in the EGR passage and capable of adjusting an EGR amount recirculated to an intake side of exhaust gas by changing an opening degree;
An EGR control unit for controlling the opening of the EGR valve;
An idling duration acquisition unit for acquiring a duration of an idling state of the internal combustion engine;
A valve opening delay time that is a time from when the internal combustion engine is switched from the idling state to the normal operation state until the EGR valve that was closed in the idling state starts to open is determined by the idling duration acquisition unit. A delay time calculation unit for calculating based on the acquisition result;
With
The EGR control unit starts opening the EGR valve at a timing delayed by the valve opening delay time after the internal combustion engine is switched from the idling state to the normal operation state ,
The delay time calculation unit estimates the amount of unburned fuel components accumulated in the exhaust-side passage during the idling state based on the acquisition result of the idling duration acquisition unit, and starts normal operation. From the above, it is calculated as the valve opening delay time that is estimated to be taken until the amount of the unburned fuel component estimated to be accumulated in the exhaust-side passage decreases to less than a threshold value. EGR system to do. The EGR system according to claim 1 ,
The delay time calculation unit calculates the valve opening delay time such that the longer the duration of the idling state acquired by the idling duration acquisition unit, the longer the valve opening delay time. The EGR system according to claim 1 or 2 ,
The EGR control unit controls the EGR valve in the fully closed state to be fully opened at a timing delayed by the valve opening delay time after the internal combustion engine is switched from the idling state to the normal operation state. An EGR system characterized by that.

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