JP2012159018A - Working vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently regenerate a DPF (Diesel Particulate Filter) according to the situation.SOLUTION: A working vehicle is configured to mount a diesel particulate filter 46b for collecting a particulate matter PM in exhaust gas and a diesel engine E, and to perform regeneration control for removing the particulate matter PM in the diesel particulate filter 46b. The working vehicle is provided with a second exhaust passage 71 having a combustion chamber 73 upstream from the diesel particulate filter 46b, and is provided with a first exhaust passage 70 having a valve 72 so as to bypass the second exhaust passage 71. When the vehicle is operated without regeneration of the diesel particulate filter 46b, the valve 72 is fully opened.

Description

  The present invention relates to a work vehicle equipped with a diesel engine equipped with a diesel particulate filter (DPF) for removing particulate matter (PM) in an exhaust system.

  When granulated material (PM) accumulates inside the DPF, it is necessary to remove (regenerate) by raising the exhaust gas temperature. However, if the temperature of the DPF itself is low, regeneration is not performed efficiently and regeneration is poor. Therefore, a burner combustion chamber having a fuel injection nozzle and an ignition plug is provided on the upstream side of the DPF. When the amount of PM in the DPF increases, the burner is ignited to raise the exhaust gas temperature, and the PM in the DPF is heated at a high exhaust gas temperature. It is the structure which burns away (for example, refer patent document 1).

JP-A-8-260944

  In the known technology, if a high load acts on the engine and the exhaust gas temperature becomes too high, the fuel injection nozzle for DPF regeneration may be damaged by heat from the exhaust gas.

  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 invention according to claim 1, the diesel particulate filter (46b) and the diesel engine (E) for collecting the particulate matter (PM) in the exhaust gas are mounted, and the diesel particulate filter (46b) In a work vehicle configured to perform regeneration control to remove the particulate matter (PM), a second exhaust passage (71) having a combustion chamber (73) is provided upstream of the diesel particulate filter (46b). The work vehicle is characterized in that a first exhaust passage (70) having a valve (72) is provided so as to bypass the exhaust passage (71).

Exhaust gas passes through either one or both of the second exhaust passage (71) and the first exhaust passage (70) depending on conditions.
According to a second aspect of the present invention, there is provided the work vehicle according to the first aspect, wherein the valve (72) is fully opened during an operation in which the diesel particulate filter (46b) is not regenerated. Is.

  When the diesel particulate filter (46b) is not regenerated, the valve (72) is fully opened. The exhaust gas passes through both the second exhaust passage (71) and the first exhaust passage (70).

  In the third aspect of the invention, when the operation is performed to stop the work vehicle and regenerate the diesel particulate filter (46b) at the idling engine speed, the valve (72) is fully closed, and the combustion chamber ( 73. The work vehicle according to claim 1, wherein fuel is injected from a fuel injection nozzle (74) provided in 73) and energized to an ignition glow plug (75). .

  During the operation of stopping the work vehicle and regenerating the diesel particulate filter (46b) at the idling engine speed, the valve (72) is fully closed. The exhaust gas passes only through the second exhaust passage (71). Then, the fuel is injected from the fuel injection nozzle (74) to energize the ignition glow plug (75).

  The exhaust gas temperature sensor (92) for detecting the temperature of the exhaust gas is provided upstream of the diesel particulate filter (46b), and the detected value of the exhaust gas temperature sensor (92) is within a predetermined range. When inside, the valve (72) is partially closed to induce a part of the exhaust gas to the combustion chamber (73) and to inject fuel from the fuel injection nozzle (74). Item No. 1 is a working vehicle.

  When the detected value of the exhaust gas temperature sensor (92) falls within a predetermined range, the valve (72) is partially closed to induce a part of the exhaust gas to the combustion chamber (73). The exhaust gas passes through both the second exhaust passage (71) and the first exhaust passage (70). Then, fuel is injected from the fuel injection nozzle (74).

  Since the present invention is configured as described above, in the first aspect of the present invention, by selecting the second exhaust passage (71) or the first exhaust passage (70) as the exhaust gas passage according to the situation, the efficiency can be improved. A good DPF (46b) can be regenerated.

  In the second aspect of the invention, in addition to the effect of the first aspect, the exhaust gas is opened to the second exhaust passage (71) by fully opening the valve (72) when the diesel particulate filter (46b) is not regenerated. And the first exhaust passage (70), the exhaust gas temperature passing through the fuel injection nozzle (74) side becomes relatively low. As a result, the fuel injection nozzle (74) is less affected by thermal damage from the high-temperature exhaust gas.

  In the third aspect of the invention, in addition to the effect of the first aspect, in the operation of stopping the work vehicle and regenerating the diesel particulate filter (46b) at the engine speed in the idling state, all the valves (72) are set. Since the fuel is injected from the fuel injection nozzle (74) provided in the combustion chamber (73) and energized to the glow plug (75) for ignition, compared with the post injection performed after the main injection. Since the fuel burns in the vicinity of the DPF (46b), the particulate matter (PM) is burned off when the exhaust gas of higher temperature passes through the DPF (46b), and the regeneration of the DPF (46b) is good. To be done. Since the fuel burns near the DPF (46b), the amount of fuel used can be reduced as compared with post-injection, and further, it is possible to prevent the problem that the unburned fuel is mixed into the oil.

  In the invention of claim 4, in addition to the effect of claim 1, when the detected value of the exhaust gas temperature sensor (92) falls within a predetermined range, the valve (72) is partially closed to partially remove the exhaust gas. Since the fuel is guided to the combustion chamber (73) and the fuel is injected from the fuel injection nozzle (74), the DPF (46b) is not clogged with a large amount of PM, that is, a situation in which no particularly rapid regeneration is required. However, since the high-temperature exhaust gas passes through the DPF (46b) according to specific conditions, (PM) is removed, the frequency of forced regeneration can be reduced, and the amount of fuel used can be suppressed.

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 (A) Schematic diagram of exhaust system (during normal operation), (b) Schematic diagram of exhaust system (during DPF regeneration operation) Schematic diagram of exhaust system (during DPF regeneration operation within a specified exhaust temperature range) Schematic diagram of intake and exhaust systems (A) Schematic diagram of exhaust system (when soot emissions are high), (b) Schematic diagram of exhaust system (when soot emissions are low) Flowchart of EGR valve control and DPF regeneration Flow chart of tilling depth control during automatic regeneration Cross section of DPF Cross section of tractor engine room Cross section of DPF Schematic diagram of cooling water flow

The best mode for carrying out the present invention will be described.
In addition, although each Example described later is illustrated or described separately or mixed for easy understanding, these can be combined in various ways, and can be configured according to their description order and expression. -The action and the like are not limited, and there are of course cases where a synergistic effect is produced.

  FIG. 1 is an overall configuration diagram of a pressure accumulation type fuel injection device. The accumulator type 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 that accumulates 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, the fuel injection nozzle 6 and the like 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.
The 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) burns the incombustible chamber, and the diesel particulate filter (DPF) is for collecting the particulate matter (PM). The EGR valve 43 and the throttle valve 47 are controlled by the ECU 100. The post-processing device 46 may be composed of only a diesel particulate filter (DPF) 46b. If an oxidation catalyst (DOC) is provided, the non-combustible material burns, resulting in cleaner exhaust gas.

  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, a throttle valve 47 is provided on the lower side of the post-processing device 46, and when the throttle valve 47 is throttled, the pressure in the DPF 46b is kept high, so 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. Moreover, it is good also as a structure which provides the pressure sensor 58 between DOC46a and DPF46b instead of the pressure sensor 52. FIG.

  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.

  With the configuration as described above, an intake throttle is not required. In other words, since the intake side pressure is high in an engine with a supercharger, an exhaust throttle valve or an intake throttle is required to secure the amount of EGR gas, and control in conjunction with the EGR valve is required, but such a system is unnecessary. It becomes.

  Further, since the exhaust gas downstream of the DPF 46b is taken out, it is possible to prevent the performance deterioration caused by the dirt of the supercharger TB. And since EGR gas is cooled by the EGR cooler 57, an effect becomes large with respect to NOx reduction.

  As described above, in the DPF forced regeneration mode in which the regeneration operation of the DPF is performed, the exhaust throttle valve 47 is throttled and the EGR valve 43 is fully closed by ON-OFF control. Therefore, NO is increased because the exhaust gas is not reduced, and this NO is converted to NO2 by the oxidation catalyst (DOC) 46a, and regeneration of the DPF 46b is promoted.

  Further, when the engine rotation shifts to low idle during the forced regeneration of the DPF 46b, the EGR valve 43 is fully opened. Since the temperature sensor 59 is provided on the downstream side of the DPF 46b, it may be added to the condition that the detection value by the temperature sensor 59 has risen to a predetermined value or more.

  When the DPF 46b is forcibly regenerated by restricting the throttle valve 47, the engine speed is reduced to increase the supply oxygen amount, and the exhaust gas flow rate is decreased to increase the temperature easily. However, when the engine speed is changed to low idle or in the vicinity thereof during regeneration, soot burns rapidly due to an increase in the amount of supplied oxygen and a decrease in the flow velocity. As a result, the temperature may rise rapidly and the DPF 46b may be damaged. Therefore, it is necessary to manage the soot that the maximum temperature does not exceed the allowable temperature.

  For this reason, when the temperature sensor 59 exceeds a predetermined value, the engine speed is increased to a medium speed range. As a result, the flow rate of the exhaust gas is increased, so that the maximum temperature is lowered and damage to the DPF 46b can be prevented. Further, when the predetermined value of the temperature sensor 59 is controlled in the vicinity of the limit value, the DPF 46b can be efficiently regenerated.

  In order to increase the engine speed to the middle speed range, it may be configured to once increase to the maximum speed and then decelerate to the middle speed range, so that the exhaust gas once flows at the maximum speed. For example, it is possible to prevent the DPF 46b from being heated and exceeding the threshold temperature.

  Further, during the forced regeneration of the DPF 46b, when the engine speed is shifted to low idle as described above, the post-injection is interrupted, and then the engine speed is increased to the maximum speed and shifted to the medium speed range. Then, post-injection is resumed. Thereby, since the rapid rise in the exhaust gas temperature can be suppressed, damage to the DPF 46b can be prevented.

  When the differential pressure across the DPF 46b exceeds a predetermined value, the driver selects the regeneration mode of the DPF 46b after the operation with the selection switch 67, so that the DPF 46b is automatically regenerated. After the DPF 46b is regenerated, the engine is automatically stopped. To be configured. The differential pressure across the DPF 46b is monitored by pressure sensors 58 and 53. If the differential pressure across the DPF 46b immediately before the engine stops is equal to or greater than a predetermined value, a warning lamp or alarm notifies the driver, and the driver operates a switch (not shown) for regenerating the DPF 46b.

  Even when the engine key is in the cut position, since the regeneration mode is selected, the engine keeps rotating in the idling state and performs regeneration of the DPF 46b. When the differential pressure before and after the DPF 46b falls below a predetermined value, the engine is automatically stopped.

Thus, even after the work is completed, the DPF 46b can be automatically regenerated and the engine can be stopped, so that the driver can leave the machine and perform other work.
When the DPF 46b is regenerated, the intake side air may be sent from the pipe 61 to the upstream side of the DPF 46b as shown in FIG. That is, when the DPF 46b is regenerated, the valve 60 may be opened so that the intake air on the upstream side of the turbocharger TB having a large amount of oxygen is sent to the upstream side of the DPF 46b. Thereby, the reproduction efficiency is improved.

  Alternatively, the temperature of the DPF 46b may be monitored by the temperature sensors 62 and 59, and the temperature increase during regeneration may be confirmed in three steps. First, the intake is throttled (not shown), and the temperature rise in the throttled state of intake is confirmed. Next, the first post injection is performed to check the temperature rise. At this time, if the temperature before and after the DPF 46b does not reach 250 degrees, further temperature rise cannot be expected even if the second post-injection is performed. Therefore, the regeneration is temporarily interrupted. Of course, if it is 250 degrees or more, the second post injection is performed to regenerate the DPF 46b.

  As shown in FIG. 5, an air-fuel ratio sensor 63 is provided on the downstream side of the DPF 46b. When the post-injection is performed to regenerate the DPF 46b, if the fuel injection amount is too large, the fuel consumption is deteriorated. If the fuel injection amount is small, the temperature does not increase and the regeneration cannot be performed. Therefore, the injection amount is determined by feeding back the value of the air-fuel ratio sensor 63 to the ECU 100. As a result, the fuel consumption becomes appropriate and the DPF 46b can be regenerated. Further, instead of the air-fuel ratio sensor 63, a pressure value in the intake manifold may be fed back.

  When regenerating the DPF 46b as described above, in the case of a plurality of cylinders, the combustion of some cylinders may be stopped. Thus, by stopping the combustion of some cylinders, the exhaust temperature may be increased by increasing the load per cylinder even if the engine friction is the same.

  FIG. 6 will be described. A first exhaust passage 70 and a second exhaust passage 71 are formed on the upstream side of the aftertreatment device 46. A valve 72 is provided in the first exhaust passage 70. A combustion chamber 73 is provided in the second exhaust passage 71, and a fuel injection nozzle 74 for injecting fuel and an ignition glow plug 75 are provided in the combustion chamber 73.

  FIG. 6A shows a state during normal operation, and the valve 72 is fully opened. At this time, the exhaust gas flows through both the first exhaust passage 70 and the second exhaust passage 71. Accordingly, the amount of exhaust gas flowing through the second exhaust passage 71 is reduced. Thereby, the fuel injection nozzle 74 can be protected from the heat of the exhaust gas.

  FIG. 6B shows a case where the DPF 46b is forcibly (manually) regenerated (the airframe is stopped. The engine speed is idling. Post injection is performed after the main injection). Gas is guided to the combustion chamber 73. Then, the fuel is injected from the fuel injection nozzle 74 and the ignition glow plug 75 is energized to ignite the fuel. As a result, the fuel burns near the DPF 46b as compared with the post-injection performed after the main injection, so that the granulated material PM is burned off when the higher-temperature exhaust gas passes through the DPF 46b, and the regeneration of the DPF 46b is performed. It will be done well. Since the fuel burns near the DPF 46b, the amount of fuel used can be reduced as compared with post-injection, and further, it is possible to prevent a problem that unburned fuel is mixed into the oil.

  The forced regeneration of the DPF 46b is performed in a state where the airframe is stopped because there is a possibility that the PM clogged state in the DPF 46b is saturated and the DPF 46b is damaged when the airframe is further driven.

  FIG. 7 shows a state in which a certain amount of load (about 20% to 40%) is applied to the engine during traveling (whether working or non-working). The load is detected by the load calculation means 91 (FIG. 5). Specifically, the load is calculated by using the maximum fuel injection amount Q1 that can maintain the set engine speed R as a denominator, and the current fuel injection amount Q2 that is used to actually maintain the engine speed R. As a numerator, the load factor is calculated.

  Thus, when a certain load (about 20% to 40%) is acting on the engine, the valve 72 is partially closed (approximately 50%) to induce a part of the exhaust gas to the combustion chamber 73. That is, the amount of exhaust gas flowing through the second exhaust passage 71 is increased. Then, fuel is injected from the fuel injection nozzle 74. Even if the ignition glow plug 75 is not energized, a certain amount of load is applied to the engine, so the exhaust temperature is high, and thus the fuel is ignited. As a result, even when the DPF (46b) is not clogged with a large amount of PM, that is, particularly in the situation where rapid regeneration is not required, the hot exhaust gas passes through the DPF (46b) under certain conditions (PM). Is removed, the frequency of forced regeneration can be reduced, and the amount of fuel used can be reduced.

  Further, the above-described control may be performed by the temperature of the exhaust gas instead of the load calculating means 91. The exhaust gas temperature sensor 92 is provided on the upstream side of the post-processing device 46. If the exhaust gas temperature sensor 92 detects that the exhaust gas temperature is in a range between a predetermined value (T1) and a predetermined value (T2), the valve 72 is partially closed (approximately 50%) and a part of the exhaust gas is discharged. To the combustion chamber 73. Similarly, the fuel is injected from the fuel injection nozzle 74 and the ignition glow plug 75 is not energized. As a result, the high-temperature exhaust gas passes through the DPF 46b, so that PM is removed, and the frequency of forced regeneration as shown in FIG. 6B can be reduced, and the amount of fuel used can be suppressed.

The exhaust gas temperature T1 is a temperature at which fuel is ignited when fuel is injected from the fuel injection nozzle 74, and the exhaust gas temperature T2 is a temperature at which the fuel injection nozzle 74 is not damaged.
FIG. 8 shows a configuration in which an air flow sensor 76 and an intake throttle valve 77 are provided upstream of the supercharger TB. Then, the intake air amount is monitored during the forced regeneration of the DPF 46b, and the air-fuel ratio is calculated from the air amount and the fuel injection amount. When the air-fuel ratio is large, the intake throttle opening of the intake throttle valve 77 is decreased, and when the air-fuel ratio is small, the intake throttle opening of the intake throttle valve 77 is increased. Thereby, it is possible to prevent the unburned fuel from being excessively mixed into the exhaust gas, and the post-treatment device 46 is quickly heated by mixing an appropriate amount of unburned fuel into the exhaust gas.

  FIG. 9 shows a bypass circuit 78 for the post-processing device 46, and a throttle valve 79 is provided in the bypass circuit 78. FIG. 9A shows a condition where there is a lot of soot discharge, that is, a low speed and high load state, and the exhaust gas is purified by closing the throttle valve 79. FIG. 9B shows a condition when the soot discharge is low (exhaust gas regulation clear), and the throttle valve 79 is opened. As a result, the amount of soot that accumulates on the DPF 46b decreases, and the frequency of forced regeneration decreases. Further, when the exhaust gas bypass circuit 78 flows, it is possible to suppress deterioration in fuel consumption due to DPF 46b pressure loss.

  FIG. 10 is a flowchart for manually regenerating the DPF 46b. When the intake air temperature is low, the EGR valve 43 of the EGR circuit 44 (FIG. 5) is opened to raise the exhaust gas temperature. As a result, the DPF 46b can be regenerated at a higher temperature, the regeneration time is shortened, and the fuel consumption is improved.

  When the DPF 46b is regenerated, it is performed under the above-described conditions (differential pressure before and after the DPF, etc.), but may be configured to be estimated and not actually measured. That is, the DPF 46b is regenerated by estimating the PM accumulation amount in the DPF 46b from the engine speed, fuel injection amount, and time. And in estimating PM accumulation amount, it is set as the structure which considered the driving | running | working on the inclined land of a tractor. Specifically, the tractor is provided with an inclination sensor, and the PM accumulation amount is corrected with a correction map during uphill traveling and downhill traveling. A value calculated at a specific ratio is added during uphill traveling, and a value calculated at a specific ratio is subtracted during downhill traveling. This makes it possible to accurately estimate the PM accumulation amount.

  When the tractor performs automatic regeneration of the DPF 46b during work travel, when the exhaust gas temperature during work decreases, the working machine 21 such as a rotary is automatically lowered (a manual lowering may be promoted) to increase the tilling depth. Deepen the engine load. This configuration is shown in the flowchart of FIG. Thereby, automatic reproduction can be continued.

  FIG. 12 shows a cross-sectional view of the post-processing device 46. An arrow K is a normal flow of exhaust gas, and an arrow K1 is a flow in the outside air direction. A return circuit 80 returns a part of the exhaust gas to the upstream side of the aftertreatment device 46. A switching valve 81 is provided at the branch direction of the outside air direction and the return circuit 80. At the time of regeneration of the DPF 46b, if the exhaust gas temperature is low, the regeneration time of the DPF 46b becomes long. Therefore, when the exhaust gas temperature is low, the switching valve 81 is switched to return a part of the exhaust gas to the upstream side of the post-processing device 46. As a result, the regeneration time of the DPF 46b can be shortened, and the post injection and the post injection amount for increasing the exhaust temperature can be reduced. Moreover, you may comprise so that exhaust gas temperature may be raised with the heating wire 82. FIG.

  Reference numeral 83 shown in FIG. 5 is an intake side heater, and reference numeral 84 is an exhaust side heater. During manual regeneration of the DPF 46b, the exhaust temperature is raised by energizing the intake side heater 83 and the exhaust side heater 84, and the exhaust temperature is raised by applying a load to the engine using the power generation load of the generator. The configuration. As a result, the amount of fuel used for manual regeneration of the DPF 46b can be reduced without greatly changing the basic configuration of the engine. Further, since the post injection and the post injection amount are reduced, the amount of engine lubricating oil diluted by the post injection is also reduced. Both the intake side heater 83 and the exhaust side heater 84 may be provided, or one of them may be provided.

  FIG. 13 shows the engine E, the radiator 85, and the radiator fan 86 mounted on the frame 87 at the front of the tractor. A post-processing device 46 is mounted above the engine E. The post-processing device 46 is arranged such that its longitudinal direction is the front-rear direction of the machine body.

  FIG. 14 shows a cross section of the post-processing device 46. The outer peripheral surface of the post-processing device 46 is configured to be covered with a plate 88. As a result, the cooling air generated by the radiator fan 86 passes between the post-processing device 46 and the plate 88. Therefore, it is possible to prevent an excessive increase in temperature of the post-processing device 46 and to prevent adverse effects on peripheral devices.

  Since the radiator fan 86 is rotated by the motor 86a, the rotational speed of the radiator fan 86 can be controlled. Normally, the cooling water temperature is controlled to be around 76 degrees, but when the DPF 46b is forcibly regenerated, the cooling water temperature is controlled to be around 90 degrees. As a result, the exhaust temperature rises to assist the regeneration of the DPF 46b, and the regeneration time is shortened. Also, post injection and post injection amount are reduced.

  FIG. 15 is a schematic diagram showing the flow of cooling water. A cooling water passage is formed between the engine E and the radiator 85, and the cooling water is circulated by the water pump 89. Reference numeral 90 denotes a thermostat valve disposed at the outlet portion of the radiator 85. Normally, the thermostat valve 90 opens and the cooling water circulates at a water temperature of about 80 degrees, but when regenerating the DPF 46b, the thermostat valve 90 is throttled to inhibit the flow of the cooling water and the cooling water temperature is set to about 90 degrees. It is set as the structure which raises to. As a result, the exhaust temperature rises to assist the regeneration of the DPF 46b, and the regeneration time is shortened. Also, post injection and post injection amount are reduced.

  Further, when the DPF 46b is regenerated, the operating temperature of the thermostat valve 90 itself may be variable up to about 90 degrees.

PM Granulated material E Diesel engine
46b Diesel particulate filter (DPF)
70 First exhaust passage 71 Second exhaust passage 72 Valve 73 Combustion chamber 74 Fuel injection nozzle 75 Glow plug for ignition 92 Exhaust gas temperature sensor

Claims (4)

  A diesel particulate filter (46b) that collects particulate matter (PM) in exhaust gas and a diesel engine (E) are installed, and regeneration that removes particulate matter (PM) in the diesel particulate filter (46b) is performed. In the work vehicle configured to control, a second exhaust passage (71) having a combustion chamber (73) is provided on the upstream side of the diesel particulate filter (46b) so as to bypass the second exhaust passage (71). A work vehicle comprising a first exhaust passage (70) having a valve (72).   The work vehicle according to claim 1, wherein the valve (72) is fully opened during an operation in which the diesel particulate filter (46b) is not regenerated.   In the operation of stopping the work vehicle and regenerating the diesel particulate filter (46b) at the engine speed in the idling state, the valve (72) is fully closed and the fuel injection provided in the combustion chamber (73) 2. The work vehicle according to claim 1, wherein fuel is injected from a nozzle (74) to energize an ignition glow plug (75).   An exhaust gas temperature sensor (92) for detecting the temperature of the exhaust gas is provided upstream of the diesel particulate filter (46b). When the detected value of the exhaust gas temperature sensor (92) falls within a predetermined range, the valve (72) The work vehicle according to claim 1, wherein a part of the exhaust gas is guided to the combustion chamber (73) and fuel is injected from the fuel injection nozzle (74).

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