JP2012072731A - Tractor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that, when a light-load operation is continued and a situation in which PM is deposited in a DPF is continued as a result, the operation may be interrupted because manual regeneration should be performed at a timing not intended by an operator.SOLUTION: In a tractor in which a diesel particulate filter 46b collecting particulate matter PM in exhaust gas and a diesel engine E are mounted, the tractor is provided with an operation mode selector 61. A light-load operation position is configured in the operation mode selector 61. When the light-load operation position is selected, the regeneration of the diesel particulate filter 46b is automatically performed. A puddling operation position is configured in the operation mode selector 61. When the puddling operation position is selected, the regeneration of the diesel particulate filter 46b is automatically performed.

Description

  The present invention relates to a tractor equipped with a diesel particulate filter and a diesel engine.

  In regenerating the diesel particulate filter (DPF), the DPF is regenerated by estimating the accumulation of particulate matter (PM) in the DPF by measuring the sound pressure of the exhaust gas (Patent Document 1). In addition to the sound pressure, a technique for detecting and reproducing the differential pressure across the DPF is well known.

JP 2007-132306 A

  In the technology as described above, the DPF is regenerated when the amount of PM in the DPF exceeds a predetermined amount. However, if the light load operation continues, the exhaust temperature does not rise, and the PM continues to accumulate. Since the DPF must be regenerated by interrupting the operation, the work efficiency has been reduced.

  The subject of this invention is providing the tractor 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 tractor equipped with the diesel particulate filter (46b) and the diesel engine (E) for collecting the particulate matter (PM) in the exhaust gas, the work mode selection means (61) is provided. The work mode selection means (61) is configured with a light load work position, and when the light load work position is selected, the diesel particulate filter (46b) is automatically regenerated. This is a characteristic tractor.

The operation of claim 1 automatically regenerates the diesel particulate filter (46b) when the light load work position is selected by the work mode selection means (61).
According to the second aspect of the present invention, in the tractor equipped with the diesel particulate filter (46b) for collecting the particulate matter (PM) in the exhaust gas and the diesel engine (E), the work mode selection means (61) is provided. The working mode selection means (61) comprises a scraping work position, and the diesel particulate filter (46b) is automatically regenerated when this scraping work position is selected. It is what.

  The operation of claim 2 automatically regenerates the diesel particulate filter (46b) when the work mode selection means (61) selects the lightly scraping work position.

  According to a third aspect of the present invention, in the tractor equipped with the diesel particulate filter (46b) for collecting the particulate matter (PM) in the exhaust gas and the diesel engine (E), the work mode selection means (61) is provided. The work mode selection means (61) is configured with a tow work position for performing a tow work traveling on the road, and when the tow work position is selected, the diesel particulate filter (46b) is automatically regenerated. The tractor is characterized in that it is configured as follows.

  The operation of claim 3 automatically regenerates the diesel particulate filter (46b) when the traction work position with a light load is selected by the work mode selection means (61).

  According to a fourth aspect of the present invention, the engine load detecting means (76) for detecting the load of the diesel engine (E) is provided, and the automatic regeneration of the diesel particulate filter (46b) is stopped when the engine load exceeds a predetermined value. The tractor according to claim 1, claim 2, or claim 3 is configured.

  In addition to the action of claim 1, 2 or 3, the action of claim 4 stops the automatic regeneration of the diesel particulate filter (46b) when the engine load exceeds a predetermined value.

  Since the present invention is configured as described above, according to the first aspect of the present invention, when light load work is continued, PM is deposited in the DPF (46b), but such a situation can be prevented. In addition, the frequency with which the work is interrupted and replayed can be reduced.

  According to the second aspect of the present invention, PM is accumulated in the DPF (46b) at the time of a lightly scraping operation, but such a situation can be prevented. In addition, the frequency with which the work is interrupted and replayed can be reduced.

  In the invention described in claim 3, PM is accumulated in the DPF (46b) at the time of load pulling work, but such a situation can be prevented. In addition, the frequency with which the work is interrupted and replayed can be reduced.

  In the invention according to claim 4, in addition to the effect of claim 1 or claim 2 or claim 3, since the load may be increased depending on the situation even in a light work, in such a case, the DPF ( By stopping the automatic regeneration of 46b), it is possible to prevent a decrease in engine speed and an engine stall.

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 Plan view of work mode selection dial Relationship diagram between intake air temperature and engine speed during manual regeneration Relationship between air pressure and engine speed during manual regeneration Manual regeneration permission flowchart Left side view of the tilted tractor Diesel engine perspective view Flow chart of DPF regeneration when the aircraft is tilted

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 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 incombustible material, 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-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.

  As the DPF regeneration operation for regenerating the DPF 46b, the exhaust gas temperature is raised by performing re-injection (after-injection) after the main injection, but the effect is enhanced when both the EGR valve 43 and the throttle valve 47 are throttled. . Also, depending on the PM deposition amount, either one may be performed. 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. The DPF 46b can be regenerated without performing after-injection of fuel (in order to increase the exhaust gas temperature), the number of after-injections can be reduced, and fuel consumption can be suppressed, which is good for the environment.

  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.

  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 prevent the maximum temperature from exceeding 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.

  When the differential pressure before and after the DPF 46b exceeds a predetermined value, the driver selects the regeneration mode of the DPF 46b after the work so that the DPF 46b is automatically regenerated, and the engine is automatically stopped after the DPF 46b is regenerated. To do. 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.
As described above, the DPF 46b needs to be regenerated, and there are manual and automatic regenerations. When the manual regeneration is in a specific condition (PM accumulation amount over a predetermined amount, pressure difference before and after the DPF over a predetermined value, etc.), a signal is sent from the ECU 100 to the CPU 100 on the tractor body side and the alarm lamp 60 on the tractor body side is turned on It encourages the driver to perform manual regeneration. In addition, automatic regeneration automatically regenerates the DPF 46b even when the vehicle is traveling or traveling when a specific condition (a predetermined amount of PM deposition amount or more, a pressure difference before and after the DPF exceeds a predetermined value). .

  Although there are various tractor operations described above, in the scraping operation, the load is low and the exhaust temperature is lowered, so that the DPF 46b is not regenerated and a large amount of PM is accumulated in the DPF 46b. In such a case, as described above, the manual regeneration may be performed after the work is completed by setting the differential pressure before and after the DPF 46b to a predetermined value or more. However, it may not be performed at night due to noise problems. is there. If the light load operation continues, the situation where PM accumulates in the DPF 46b continues, and as a result, manual regeneration must be performed when the operator does not intend, and the operation needs to be interrupted. .

  In view of this, the DPF 46b is automatically regenerated at the time of lightly scraping work. Specifically, work mode selection means (work mode selection dial) 61 is provided at an arbitrary position of the tractor (operable from the seat 17), and the work mode selection dial 61 is adjusted to the scraping work when performing the scraping work. Then, the intake valve 62 (FIG. 5) is throttled, the exhaust temperature rises, and the PM in the DPF 46b is burned out and removed. Even in the case of scraping work, the engine load may increase depending on the field conditions. In such a case, if the intake valve 62 is kept throttled, the engine speed decreases due to insufficient intake air amount. And engine stalls. For this reason, when the ECU 100 detects that the engine load is larger than a predetermined value, the intake valve 62 is returned to the original position. The engine load is detected by an engine load detecting means (engine load sensor) 76. As a method for detecting the engine load, there is a method for measuring the temperature of the exhaust gas. Further, in order to maintain the same rotational speed, there is a method of obtaining from the ratio between the fuel injection amount at no load and the fuel injection amount currently injected.

The work mode selection dial 61 is provided with a light load work position. When this position is selected, the DPF 46b is regenerated in the same manner as the scraping work.
The work mode selection dial includes a traction mode in which a trailer or the like is attached to the rear part of the tractor, a rotary mode in which the farm is cultivated or plowed, a 4-wheel drive 4WD mode, a 2-wheel drive There is a 2WD mode. In the traction mode, similarly to the scraping operation, when the operation mode selection dial 61 is set to the traction mode, the intake valve 62 is throttled to regenerate the DPF 46b. In the traction mode, because the road travels at a low speed, there are many situations in which the load is small and the exhaust temperature is low, so that the DPF 46b is regenerated.

  The manual regeneration conditions will be described. An intake air temperature sensor 63 (FIG. 5) is provided to determine the engine speed during manual regeneration based on the intake air temperature. This specific configuration is shown in FIG. Thus, when the temperature of the intake air is low, the activation temperature at which PM is removed can be reached quickly by increasing the engine speed and increasing the exhaust gas temperature. In addition, when the temperature of the intake air is high, it is possible to regenerate with low noise by reducing the engine speed, and also to save fuel.

  Moreover, you may comprise so that the engine speed at the time of manual regeneration may be changed according to external pressure. Tractors are effective because they are often used at high altitudes. The atmospheric pressure sensor 64 is installed on the cabin 14 (FIG. 3). When the altitude is high and the atmospheric pressure is low, the exhaust gas temperature is low because the oxygen concentration is low, and it is difficult to reach the activation temperature at which PM is removed. Therefore, as shown in FIG. 8, when the atmospheric pressure is low, the exhaust temperature is increased by increasing the engine speed during manual regeneration, so that the activation temperature at which PM is removed is reached quickly. When the atmospheric pressure is high, it is possible to regenerate with low noise by reducing the engine speed, and also to save fuel. Instead of the atmospheric pressure sensor 64, an altitude (altitude) may be detected. As an altitude detection method, there is a method of detecting a signal from GPS.

  In performing manual regeneration and automatic regeneration of the DPF 46b, the threshold value of the differential pressure of the exhaust gas before and after the DPF 46b is low during automatic regeneration and is high during manual regeneration. In addition, manual regeneration is not possible within the range of automatic regeneration. Manual regeneration is an act of specially operating and regenerating the engine other than at the time of running, so that extra fuel and time are required. That is, the configuration is performed only when PM cannot be completely removed by automatic regeneration.

  However, in consideration of the next day's work situation (light work), manual regeneration may be required during the work. Therefore, as shown in FIG. 9, the manual regeneration is permitted even when the PM accumulation amount is within the range of the automatic regeneration, and the engine is automatically stopped after the manual regeneration is completed. In this case, the manual regeneration is permitted when the remaining 20% of the PM accumulation amount threshold value during automatic regeneration is reached. This eliminates the need for performing manual regeneration by interrupting the work during the next day's work.

  A manual regeneration permission switch 66 that permits such manual regeneration is provided in the engine room 67. That is, since the manual regeneration permission switch 66 cannot be operated unless the bonnet 65 is opened, an inadvertent operation can be prevented.

  As shown in FIG. 10, the DPF 46 b is installed in the engine room 67. Specifically, as shown in FIG. 11, frames 68 and 69 are provided on the upper part of the engine E, and the lower part of the DPF 46 b is fixed to the frames 68 and 69 with bolts 70. Further, the engine E is provided with an inverted U-shaped frame 71, and the upper portion of the DPF 46 b is fixed to the frame 71 with an L-shaped bracket 72 and a bolt 73. Reference numeral 74 denotes a cooling fan, which is placed on the airframe so that the cooling fan 74 comes to the front of the airframe.

  Thus, although the DPF 46b is fixed to the engine E, there is a problem if the DPF 46b is regenerated with the entire tractor inclined greatly. When the DPF 46b is regenerated, the exhaust gas becomes hot, so depending on the direction of the exhaust gas, it may be affected by heat. Further, since the DPF 46b itself is also at a high temperature, if the aircraft is tilted, the removal of the PM inside the DPF 46b is affected. That is, if the DPF 46b is greatly inclined during regeneration, it is conceivable that the PM removal performance is degraded due to a change in the portion through which the exhaust gas passes.

  Therefore, a tilt sensor 75 (FIG. 10) is provided on the tractor body, and when the body is tilted by a predetermined value or more, the regeneration of the DPF 46b is restrained. FIG. 12 shows a flowchart thereof. Specifically, when the front / rear / left / right inclination of the aircraft is inclined by 5 degrees or more, the regeneration of the DPF 46b is checked.

  Each of the above-described embodiments is illustrated or described separately or mixed for easy understanding, but 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.

PM Granulated material E Diesel engine 1 Common rail 46b Diesel particulate filter (DPF)
61 Work mode selection means (work mode selection dial)
76 Engine load detection means (engine load sensor)

Claims (4)

  In a tractor equipped with a diesel particulate filter (46b) and a diesel engine (E) that collect particulate matter (PM) in exhaust gas, a work mode selection means (61) is provided, and the work mode selection means (61 ), And when the light load work position is selected, the diesel particulate filter (46b) is automatically regenerated.   In a tractor equipped with a diesel particulate filter (46b) and a diesel engine (E) that collect particulate matter (PM) in exhaust gas, a work mode selection means (61) is provided, and the work mode selection means (61 ) Is configured to automatically regenerate the diesel particulate filter (46b) when the scraping work position is selected.   In a tractor equipped with a diesel particulate filter (46b) and a diesel engine (E) that collect particulate matter (PM) in exhaust gas, a work mode selection means (61) is provided, and the work mode selection means (61 ) Is configured to automatically perform regeneration of the diesel particulate filter (46b) when the traction work position is selected and the traction work position is selected. Tractor.   An engine load detecting means (76) for detecting the load of the diesel engine (E) is provided, and the automatic regeneration of the diesel particulate filter (46b) is stopped when the engine load exceeds a predetermined value. The tractor according to claim 1, claim 2, or claim 3.

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