JP2010229959A - Diesel engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To purify exhaust gas in a wide range and prevent deterioration of second oxidation catalyst due to high temperature. <P>SOLUTION: This diesel engine is equipped with an aftertreatment device comprising an oxidation catalyst and a diesel particulate filter collecting particulate matter in exhaust gas at a downstream side of a supercharger. In the diesel engine, a bypass route is constituted in an exhaust pipe at an upstream side of an exhaust gas turbine of the supercharger, the second oxidation catalyst is provided in the bypass route, a throttle valve making exhaust gas flow in a bypass route direction is provided, an EGR valve performing EGR reduction and an EGR circuit connecting an exhaust pipe at an upstream side of the throttle valve and an intake pipe at an upstream side of an intake manifold are provided, and exhaust gas is made to pass through the second oxidation catalyst by closing the throttle valve when the EGR valve is opened to return part of exhaust gas to the intake side. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a diesel engine equipped with a diesel particulate filter and an oxidation catalyst.

  In the exhaust system of a diesel engine, an oxidation catalyst (DOC) and a diesel particulate filter (DPF) are provided. (For example, refer to Patent Document 1).

JP 2008-75610 A

  During regeneration of the DPF, the exhaust valve is closed and the exhaust gas temperature is raised to activate the aftertreatment device, that is, the oxidation catalyst (DOC) and the diesel particulate filter (DPF). Then, the unburned fuel is made to flow along with the exhaust gas by post-injection, burned by the oxidation catalyst (DOC), the temperature in the DPF is raised, the soot and particulate matter (PM) in the DPF are burned and burned in the atmosphere Fly.

  However, if the temperature on the upstream side of the aftertreatment device is low, the unburned fuel by post injection cannot be heated by post injection because the catalyst of the oxidation catalyst (DOC) is not in an active state. When the load is light, the exhaust temperature does not become high, and the DPF becomes clogged. Since automatic regeneration of the DPF cannot be performed unless the temperature is higher than a predetermined level, it is necessary to manually regenerate the DPF.

  The subject of this invention is providing the work vehicle carrying the diesel engine which eliminates the above malfunctions.

The above object of the present invention is achieved by the following configuration.
That is, in the first aspect of the present invention, the aftertreatment device 46 including the diesel particulate filter 46b and the oxidation catalyst 46a for collecting the particulate matter PM in the exhaust gas is provided on the downstream side of the supercharger TB. In this diesel engine, a bypass path 64 is formed in the exhaust pipe 63 upstream of the exhaust turbine 45 of the supercharger TB, a second dioxide catalyst 65 is provided in the bypass path 64, and the throttle for flowing exhaust gas in the direction of the bypass path 64 A valve 66 is provided, an EGR circuit 44 that connects the exhaust pipe 63 upstream of the throttle valve 66 and the intake pipe 38a upstream of the intake manifold 38, and an EGR valve 43 that performs EGR reduction are provided, and the EGR valve 43 is opened. When a part of the exhaust gas is being reduced to the intake side, the throttle valve 66 is closed to allow the exhaust gas to pass through the second dioxide catalyst 65. It thus constructed is obtained by a diesel engine, characterized in.

  According to the first aspect of the present invention, since the exhaust gas temperature is high in the high load region, there is no need for the second oxidation catalyst (DOC) 65. In this region, the EGR valve 43 is closed to ensure the output. The throttle valve 66 works with the EGR valve 43 and uses the circuit of the second oxidation catalyst (DOC) 65 when the EGR valve 43 is opened. That is, when the EGR valve 43 is opened and a part of the exhaust gas is being reduced to the intake side, the throttle valve 66 is closed and the exhaust gas passes through the second dioxide catalyst 65.

  According to a second aspect of the present invention, in the diesel engine according to the first aspect, the second dioxide catalyst 65 has a smaller shape than the oxidation catalyst 46a disposed on the downstream side of the supercharger TB. Is.

  The action of the second aspect is the same as that of the first aspect, and the second dioxide catalyst 65 has a smaller shape than the oxidation catalyst 46a disposed on the downstream side of the supercharger TB.

  Since the present invention is configured as described above, the exhaust gas temperature is high in the high load region in the invention according to the first aspect, so there is no need for the second CO2 catalyst (DOC) 65. In this region, EGR is required to secure output. Close the valve 43. The throttle valve 66 works with the EGR valve 43 and uses the circuit of the second oxidation catalyst (DOC) 65 when the EGR valve 43 is opened. As a result, a temperature rise effect for exhaust gas purification and DPF 46b regeneration in a wide range is obtained, and catalyst deterioration due to the high temperature of the second dioxide catalyst (DOC) 65 can be prevented.

  In the invention according to claim 2, in addition to the effect of claim 1, the second dioxide catalyst 65 has a smaller shape than the oxidation catalyst 46a disposed downstream of the supercharger TB. Compact configuration is possible.

Overall configuration diagram of accumulator fuel injection system Diagram showing the relationship between engine speed and output torque in control mode Left side view of tractor Top view of tractor Schematic diagram of intake and exhaust systems Left side view of tractor front Left side view of part of tractor (A) Left side view of engine and partial rear view (b) Left side view of engine and partial rear view Front view of post-processing equipment Left side view of part of tractor (A) Left side view of a part of the tractor (b) Schematic view of a part of the tractor (A) Engine left side view (b) Plan view of the aftertreatment device (A) Engine left side view (b) Plan view of the aftertreatment device Schematic diagram of intake and exhaust systems Relationship between accelerator lever opening and output voltage

The best mode for carrying out the present invention will be described.
FIG. 1 is an overall configuration diagram of a pressure accumulation type fuel injection device. The accumulator fuel injection device is applied to, for example, a multi-cylinder diesel engine, but may be a gasoline engine. The accumulator fuel injection device pressurizes the common rail 1 accumulating high-pressure fuel corresponding to the injection pressure, the pressure sensor 2 attached to the common rail 1, and the fuel pumped up from the fuel tank 3, and pumps the fuel to the common rail 1. A high-pressure pump 4, a fuel injection nozzle 6 for injecting high-pressure fuel accumulated in the common rail 1 into the cylinder 5 of the engine E, a control device (ECU) for controlling the operation of the high-pressure pump 4 and the fuel injection nozzle 6 Consists of ECU is an abbreviation for engine control unit.

Thus, the common rail 1 injects fuel to each cylinder 5 of the engine E, and makes the fuel supply a required pressure.
The fuel in the fuel tank 3 is sucked into the high-pressure pump 4 driven by the engine E through the fuel filter 7 through the suction passage, and the high-pressure fuel pressurized by the high-pressure pump 4 is guided to the common rail 1 through the discharge passage 8. Stored.

  The high-pressure fuel in the common rail 1 is supplied to the fuel injection nozzles 6 for the number of cylinders through the high-pressure fuel supply passages 9, and the fuel injection nozzles 6 are operated to the respective cylinders based on commands from the ECU 100. The surplus fuel (return fuel) from each fuel injection nozzle 6 is guided to a common return passage 10 by each return passage 10 and returned to the fuel tank 3 by this return passage 10.

  In addition, a pressure control valve 11 is provided in the high-pressure pump 4 to control the fuel pressure (common rail pressure) in the common rail 1. The pressure control valve 11 is connected to the fuel tank 3 from the high-pressure pump 4 by a duty signal from the ECU 100. The flow area of the return passage 10 for surplus fuel to the fuel is adjusted, whereby the amount of fuel discharged to the common rail 1 side can be adjusted to control the common rail pressure.

  Specifically, the target common rail pressure is set according to the engine operating conditions, and the common rail pressure is feedback-controlled through the pressure control valve 11 so that the common rail pressure detected by the rail pressure sensor 2 matches the target common rail pressure. It is configured.

  As shown in FIG. 2, the ECU 100 of the diesel engine E having the common rail 1 in the work vehicle (agricultural work machine) has three types of modes, a travel mode A, a normal work mode B, and a heavy work mode C in relation to the rotational speed and the output torque. The configuration has a control mode.

  The traveling mode A is droop control in which the output also varies with the variation of the engine speed. It is used when traveling without farming. For example, when the traveling speed is reduced or stopped by applying a brake, the engine speed decreases with an increase in the traveling load, so that the traveling speed can be safely reduced or stopped.

  The normal work mode B is isochronous control in which the engine speed is constant and the output is changed according to the load even when the load varies. It is used for normal farm work. For example, if it is a tractor, it is when the cultivated land is hard during plowing work and resistance is applied to the plowing blade. Is the time.

  In the heavy work mode C, in addition to the isochronous control in which the engine speed is constant and the output is changed according to the load even when the load fluctuates in the same manner as the normal work mode B, the engine speed is increased when the load is close to the limit. This is a control with heavy load control that increases In particular, it is used when farming near the load limit. For example, when plowing with a tractor, the engine output increases beyond the normal limit even when encountering hard cultivated land, so work can be performed efficiently without interruption. .

  These work modes A, B, and C are operations of a work mode changeover switch that can switch between the work modes A, B, and C, or a shift operation of a traveling speed change lever of a farm vehicle (tractor, combine, rice transplanter, etc.) Alternatively, it is configured to be switched by an on / off operation or the like of a work clutch (rotary if it is a tractor, and mowing part or threshing part if it is a combine).

  In diesel engine E, pilot injection that injects a small amount of fuel in a pulse manner prior to main injection makes it possible to shorten the ignition delay, reduce the knocking noise peculiar to diesel engine E, and reduce noise It has a simple structure.

  This pilot injection is performed only once or twice before the main injection. By using the accumulator fuel injection device of the common rail 1, pilot injection is performed according to the situation of the engine E. Thus, it becomes possible to reduce the noise and the generation of white smoke or black smoke due to incomplete combustion. Further, by performing pilot injection in which a small amount of fuel is pulse-injected prior to main injection, the amount of nitrogen oxides in the exhaust gas is reduced.

  FIG. 3 shows a side view of a tractor equipped with a diesel engine having the common rail 1 as described above, and FIG. 4 shows a plan view thereof. In the plan view, the cabin 14 shown in FIG. 3 is omitted.

  The tractor includes front wheels 12 and 12 and rear wheels 13 and 13 at the front and rear portions of the fuselage, and the rotational power of the engine E mounted on the front portion of the fuselage is appropriately decelerated by a transmission in the transmission case T so that the front wheels 12 , 12 and the rear wheels 13, 13.

  A steering handle 16 is supported on the handle post 15 in the cabin 14 at the center of the body, and a seat 17 is provided behind the steering handle 16. A forward / reverse lever 18 is provided below the steering handle 16 to switch the advancing direction of the aircraft to the front / rear direction. When the forward / reverse lever 18 is moved to the front side, the aircraft moves forward, and when it is moved backward, the aircraft moves backward.

  An accelerator lever 25 for adjusting the engine speed is provided on the opposite side of the forward / reverse lever 18 with the handle post 15 in between, and an accelerator for similarly adjusting the engine speed is provided at the right corner of the step floor 19. The pedal 23 and left and right brake pedals 24L, 24R for operating the left and right rear wheels 13, 13 are provided. A clutch pedal 20 is provided at the left corner of the step floor 19.

  The main transmission lever 26 is located at the left front portion of the seat 17, the auxiliary transmission lever 27 capable of selecting any of the low speed, medium speed, high speed and neutral positions is located behind the main transmission lever 26, and further on the right side thereof is the PTO transmission lever 28. Is provided. Further, on the right side of the seat 17, a position lever 29 for setting the height of the working machine 21 (rotary or the like), an automatic tilling lever 30 for automatically setting the tilling depth of the field, and the working machine 21 after these levers. The right-up switch 31 and the right-down switch 32 are arranged, and then the automatic horizontal switch 33 and the backup switch 34 of the work machine 21 are arranged. The backup switch 34 automatically raises the work machine 21 when the machine moves backward. The work machine 21 has a configuration in which a link 22 is connected to the rear of the machine body. The tractor performs work such as tillage in the field by driving the work machine 21 and running the machine body. 21a is a hydraulic cylinder which raises and lowers the working machine 21.

  FIG. 5 is a schematic diagram of intake and exhaust into the cylinder 5 of the engine, which is an embodiment of a four-cycle diesel engine. The air supercharged by the intake turbine 36 of the supercharger TB passes through the intake turbine 36 and the intercooler 37 from the air cleaner 35 and is sent from the intake manifold 38 into the cylinder 5. Reference numeral 39 is an intake valve, and 40 is a piston. A cam 48 opens and closes the intake and exhaust valves 39 and 41 via a rocker arm 49.

The exhaust gas combusted in the cylinder 5 passes through the exhaust manifold 42 from the exhaust valve 41 and is then discharged by driving the supercharger TB with the exhaust turbine 45 of the supercharger TB.
This diesel engine has an EGR (exhaust gas recirculation device) circuit 44 for mixing a part of the exhaust gas into the intake side. In the EGR circuit, a part of the exhaust gas is mixed into the intake side to reduce the amount of oxygen (O2), thereby reducing the generation of nitrogen oxide Nox. However, if the EGR rate increases too much, the amount of oxygen decreases and incomplete combustion occurs. Therefore, it is necessary to adjust the EGR rate according to the combustion state. This adjustment is performed by the EGR valve 43. The EGR circuit 44 connects between an exhaust pipe 55 on the downstream side of a post-processing device 46 described later and an intake pipe 56 on the upstream side of the intake turbine 36 of the supercharger TB. In addition, an EGR cooler 57 is provided in the middle of the EGR circuit 44. The amount of exhaust gas reduced into the cylinder 5 varies depending on how the EGR valve 43 is opened and closed.

  The exhaust gas that has passed through the exhaust turbine 45 passes through the aftertreatment device 46 and is discharged from the muffler 50 into the atmosphere. The post-processing device 46 includes an oxidation catalyst (DOC) 46a and a diesel particulate filter (DPF) 46b.

  The oxidation catalyst (DOC) 46a burns the incombustible material chamber, and the diesel particulate filter (DPF) is for collecting the granulated material (PM). The EGR valve 43 and the throttle valve 47 are controlled by the ECU 100. The post-treatment device 46 may be constituted only by a diesel particulate filter (DPF) 46b. If an oxidation catalyst (DOC) 46a is provided, the non-combustible material burns, so that the exhaust gas becomes cleaner.

  When the state of the exhaust gas is low (low load) continues for a long time, the DPF 46b has a concern that PM will accumulate and the capacity may be reduced. Therefore, if the throttle valve 47 on the lower side of the post-processing device 46 is controlled to throttle the throttle valve 47, the pressure in the DPF 46b is kept high, and the temperature also rises. This makes it possible to regenerate the DPF 46b due to the influence of a high temperature. That is, when exhaust gas having a high temperature passes through the DPF 46b, the DPF 46b is regenerated by burning off the PM present in the DPF 46b.

  In the DPF regeneration operation for regenerating the DPF 46b, both the EGR valve 43 and the throttle valve 47 are throttled. Then, the gas temperature in the DPF 46b is raised together with the retard (retard) of the fuel injection timing so that the DPF 46b starts to be regenerated. This eliminates the need for fuel after-injection (in order to increase the exhaust gas temperature) or reduces the number of after-injections, so that the amount of fuel consumption can be suppressed and the environment is good.

  As a condition for performing such a DPF regeneration operation, the pressure sensor 52 is provided on the upper side of the post-processing device 46, the pressure sensor 53 is provided on the lower side of the post-processing device 46, and this pressure difference is a predetermined value or more. Then, since PM accumulates in the DPF 46b and becomes a resistance, the DPF regeneration operation is performed.

  Further, if the state in which the DPF regeneration operation is started continues for a long time, the DPF 46b is damaged due to an overheating state. Therefore, a temperature sensor 59 is provided on the lower side of the post-processing device 46, and when the value of the temperature sensor 59 exceeds a predetermined value, the DPF regeneration operation is stopped and the normal operation is resumed.

  In normal operation, the EGR valve 43 and the throttle valve 47 are simultaneously controlled to appropriately control the EGR amount. In particular, by having the throttle valve 47, the gas temperature in the DPF 46b can be kept high.

  The exhaust gas exhausted from the cylinder chamber 5 passes through the exhaust pipe 63 toward the exhaust turbine 45 of the supercharger TB, and forms a bypass path 64 in the middle of the exhaust pipe 63. A catalyst (DOC) 65 is provided. The second dioxide catalyst (DOC) 65 has a smaller size than the oxidation catalyst (DOC) 46a in the post-processing device 46.

  Then, when unburned fuel is flowed by post injection or the like, the throttle valve 66 is closed so that the exhaust gas flows to the bypass path 64. Then, a part of unburned fuel is oxidized at the second dioxide catalyst (DOC) 65 and the temperature of the unburned fuel is increased. Furthermore, since the remaining unburned fuel is oxidized by the oxidation catalyst (DOC) 46a and further rises in temperature, the combustion of the PM collected in the DPF 46b is promoted and the regeneration of the DPF 46b becomes possible quickly. .

Further, the throttle part 67 is provided immediately downstream of the second dioxide catalyst (DOC) 65. As a result, the exhaust resistance increases and the rise in the exhaust gas temperature is promoted.
Although the temperature sensor 59 is provided on the lower side of the post-processing device 46, the temperature sensor 70 is also provided on the upstream side of the post-processing device 46. When the temperature of the temperature sensor 70 is, for example, 250 ° C. or less, the unburned fuel by the post injection cannot be heated by the post injection because the catalyst of the DOC 46a is not sufficiently activated.

  During a light load operation such as a tractor, the exhaust temperature does not become high and the DPF 46b is clogged. The automatic regeneration mode of the DPF 46b can only be performed at a temperature of 250 ° C. or higher, and manual regeneration must be performed.

  In such a state, the above-described throttle valve 66 is closed and automatic regeneration is performed using the second dioxide catalyst (DOC) 65. In this way, by using the second dioxide catalyst (DOC) 65, automatic regeneration of the DPF 46b is possible, and manual regeneration of the DPF 46b is not necessary.

  The EGR circuit 44 and the EGR cooler 57 described above may be provided between the intake pipe 38a on the upstream side of the intake manifold 38 and the exhaust pipe 63. In such a configuration, since the exhaust gas temperature is high in the high load region, there is no need for the second oxidation catalyst (DOC) 65. In this region, the EGR valve 43 is closed to ensure the output. The throttle valve 66 works with the EGR valve 43 and uses the circuit of the second oxidation catalyst (DOC) 65 when the EGR valve 43 is opened. As a result, a temperature rise effect for exhaust gas purification and DPF 46b regeneration in a wide range is obtained, and catalyst deterioration due to the high temperature of the second dioxide catalyst (DOC) 65 can be prevented.

  Further, the throttle valve 66 is configured to use the circuit of the second dioxide catalyst (DOC) 65 when the opening degree is small in conjunction with the throttle valve 71 on the intake side. As a result, a temperature rise effect for exhaust gas purification and DPF 46b regeneration in a wide range is obtained, and catalyst deterioration due to the high temperature of the second dioxide catalyst (DOC) 65 can be prevented.

  FIG. 6 shows the arrangement of the post-processing device 46 in the tractor. An engine room 72 that stores the engine E and a processing chamber 73 that stores the post-processing device 46 are configured separately. When the second bonnet 75 is opened, the processing chamber 73 is opened, and when the first bonnet 74 is opened, the engine room 72 is opened. The processing chamber 73 is supported by a mount 76. When the first bonnet 74 is opened, if the connection between the post-processing device 46 and the engine E is released, the processing chamber 73 rises together with the first bonnet 74. This facilitates inspection and maintenance of the post-processing device 46 and reduces the vibration by the mount 76. Further, as shown in FIG. 7, the post-processing device 46 may be provided below the step floor 19 of the cabin. 77 is a muffler. As a result, the influence of the cooling air from the cooling fan 78 on the post-processing device 46 can be reduced. In such an arrangement, the post-processing device 46 is not so far from the exhaust manifold of the engine E, so that the temperature of the exhaust gas passing through the post-processing device 46 can be prevented from being lowered, and the regeneration of the DPF 46b is not adversely affected.

  Further, as shown in FIG. 8A, a stay may be erected from the engine E to support the post-processing device 46. Alternatively, the frame 80 may be erected from the body frame 81 and connected by the plate 82, and the post-processing device 46 may be supported from the plate 82. Further, as shown in FIG. 9, hooks 83 are provided on the plate 82 side and the post-processing device 46 side, respectively, and the post-processing device 46 is suspended by a soft ring 84 between these hooks 83 and 83. May be. A flexible pipe 85 connects the engine E and the post-processing device 46. Thereby, the vibration of the post-processing device 46 is reduced.

  FIG. 10 shows a DPF 46b having a large diameter and a short overall length and an engine E arranged as far forward as possible. The DPF 46 b is supported in front of the cabin frame 88 and is connected to the engine E by the flexible pipe 89. The cabin frame 88 is supported by a vibration isolator (rubber, damper, etc.) 91 with respect to the airframe. 12 is a front wheel and 90 is a bonnet. As a result, the heavy DPF 46b can be easily isolated.

  FIG. 11A is a side view of the engine E and the cabin 14, and FIG. 11B is a schematic view of the cabin 14 and the post-processing device 46 as viewed from above (engine E is omitted). The oxidation catalyst (DOC) 46a and the DPF 46b are integrated in a casing 93 and arranged in front of the engine E, and the oxidation catalyst (DOC) 46a and the DPF 46b are arranged in the left-right direction of the machine body. The exhaust from the engine E is passed through the frame 14a on the front side of the cabin 14 to exhaust the exhaust gas into the atmosphere. Conventionally, a battery is mounted in front of the engine E, but inspection and maintenance are facilitated by arranging the post-processing device 46 (oxidation catalyst (DOC) 46a and DPF 46b) in this place. By arranging the battery 92 in the space below the cabin 14, inspection and maintenance of the battery 92 from the side of the machine body is facilitated.

  12 (a) and 12 (b), the DPF 46b and the silencer 94 are arranged in parallel above the engine E. FIG. At this time, the silencer 94 is arranged on the cooling fan 95 side so that the cooling air from the cooling fan 95 of the radiator 96 does not directly hit the DPF 46b. Thereby, the cooling air from the cooling fan 95 does not hit the DPF 46b, so that the temperature drop of the DPF 46b can be suppressed, and the adverse effect on the regeneration of the DPF 46b is reduced. However, some of the cooling air that has passed around the silencer 94 is directed toward the DPF 46b along the silencer 94 as it is.

  Therefore, the DPF 46b and the silencer 94 may have shapes as shown in FIGS. 13 (a) and 13 (b). That is, the shape of the silencer 94 may be changed so as to cover the DPF 46b (half-moon shape). In this case, the cooling air from the cooling fan 95 does not hit the DPF 46b as much as possible.

  FIG. 14 will be described. In the case of an engine provided with the EGR circuit 44, if the amount of EGR gas is less than the appropriate value, NOx emission increases, and if the amount of EGR gas is greater than the appropriate value, soot emission increases. That is, the internal pressure of the intake manifold 38 changes depending on the degree of clogging of the air cleaner, and the internal pressure of the exhaust manifold 42 changes depending on the degree of clogging of the DPF 46b. As described above, since the EGR rate changes depending on the state of the intake / exhaust parts, it is necessary to control the opening degree of the EGR valve 43 in accordance with the change in the EGR rate.

  Therefore, an exhaust gas amount sensor (air flow sensor) 86 is provided to monitor the exhaust gas amount. Then, during operation, the EGR valve 43 is momentarily closed, the increase amount is calculated from the exhaust gas amount monitor, and the instantaneous EGR rate is predicted from the increase amount of the exhaust gas amount. The opening degree of the EGR valve 43 is controlled based on the prediction result. Thereby, since the accuracy of the EGR rate can be improved, the emission is improved. Further, an increase in soot due to excessive EGR can be prevented, and the regeneration cycle of the DPF 46b can be lengthened. As another method for predicting the EGR rate, the exhaust gas amount sensor (air flow sensor) 86 and a lambda sensor (air-fuel ratio sensor) 87 provided on the upstream side of the supercharger TB may be used.

  In addition, by accurately estimating the clogging of the soot and granulated material (PM) inside the DPF 46b, the regeneration cycle of the DPF 46b can be appropriately performed. Specifically, pressure sensors are provided before and after the DPF 46b and before and after the DOC 46a. The ratio of the pressure difference between the DPF 46b and the pressure difference between the DOC 46a and the pressure difference between the DOC 46a (P1 ratio) and the degree of clogging of particulate matter (PM) to the DPF 46b. Can be estimated. (The P1 ratio is substantially the same if the amount of accumulation in the DPF 46b is the same, whether it is a high load with a large exhaust gas flow rate or a low load with a low exhaust gas flow rate.

  Further, a diffusion plate (not shown) is provided at the inlet portion of the DPF 46b so that the exhaust gas becomes uniform. However, the ratio of the differential pressure across the diffusion plate and the differential pressure across the DPF 46b ( (P2 ratio).

  In order to increase the rotation speed of the engine E, there is an accelerator lever in addition to the pedal. The output voltage changes with the opening degree of the accelerator lever, and the engine rotation speed is changed according to the output voltage value. This relationship diagram is shown in FIG.

  In the relationship graph between the opening degree of the accelerator lever and the output voltage value, the signal line L1 and a signal line L2 that is ½ of the signal line L1 are used. In the case of a single unit, engine control cannot be performed due to circuit disconnection or short circuit. However, by having two signal lines L1 and L2 as described above, mutual diagnosis is possible and signal reliability is improved. . For example, even if a clearly strange signal is input during normal control on the signal line L1, if the signal on the signal line L2 is normal, normal control is performed on the signal line L2 to maintain engine rotation normally. It is possible to continue operation. The signal line L2 may be a signal line L2a as indicated by a dotted line.

  In addition, there is no sudden change because the accelerator lever is operated manually, but when there is an obvious sudden change, the engine voltage is controlled while maintaining the output voltage value at the time of the sudden change. By doing so, it becomes possible to prevent sudden changes in the engine speed.

  It can be used for farm vehicles such as tractors and combiners as well as general vehicles.

PM Granulated substance TB Supercharger 38 Intake manifold 38a Intake pipe 43 EGR valve 44 EGR circuit 45 Exhaust turbine 46 Aftertreatment device 46a Oxidation catalyst (DOC)
46b Diesel particulate filter (DPF)
63 Exhaust pipe 64 Bypass path 65 Second dioxide catalyst 66 Throttle valve

Claims (2)

  An aftertreatment device (46) comprising a diesel particulate filter (46b) and an oxidation catalyst (46a) for collecting particulate matter (PM) in the exhaust gas is provided on the downstream side of the supercharger (TB). In the diesel engine, a bypass path (64) is formed in the exhaust pipe (63) upstream of the exhaust turbine (45) of the supercharger (TB), and the second dioxide catalyst (65) is provided in the bypass path (64). A throttle valve (66) for flowing exhaust gas in the direction of the bypass path (64) is provided, and an exhaust pipe (63) on the upstream side of the throttle valve (66) and an intake pipe (38a) on the upstream side of the intake manifold (38) The EGR circuit (44) for connecting the EGR valve and the EGR valve (43) for performing EGR reduction are provided, and the throttle valve is opened when the EGR valve (43) is opened to reduce part of the exhaust gas to the intake side. (66 Diesel engine, characterized by being configured to pass the exhaust gas to close the second oxidation catalyst (65).   The diesel engine according to claim 1, wherein the second dioxide catalyst (65) has a smaller shape than an oxidation catalyst (46a) disposed downstream of the supercharger (TB).

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