JP2010053806A - Work mode switching device of tractor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve so that an engine for agricultural work machine sufficiently exerts torque adaptability to various work modes. <P>SOLUTION: A tractor is mounted with a common rail type diesel engine, and is provided with a mode changeover switch 1 for allocating a plurality of work modes of using a high torque map A corresponding to a high load and a plurality of work modes of using a low torque map B corresponding to an ordinary load so as to be switchable in response to the work content. In the work mode of performing plowing work, the high torque map A and the low torque map B are respectively switchably arranged in response to the work content. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a work mode switching device for a tractor, and belongs to a field such as a tractor equipped with a common rail diesel engine that switches work modes sorted by a torque map according to work contents.

  Conventionally, an electronic governor-controlled marine internal combustion engine has been known. In this case, as a maximum torque control method, in order to avoid damage to the internal combustion engine, the maximum torque obtained at each rotational speed is The rack position for setting the fuel injection amount of the electronic governor is controlled by setting the torque to be lower than the allowable maximum torque, but in this state where the maximum torque is suppressed, This is a fatal problem for fishing boats that require early arrival at the time of fishing or landing after catching, since the amount of reduction will increase and the boat speed will drop significantly.

Therefore, regarding the setting map of the maximum rack position with respect to the engine speed in the electronic governor-controlled internal combustion engine, a standard map in which the maximum rack position is set so as to keep the limit torque lower than the engine allowable maximum torque and the engine allowable maximum torque are obtained. Two maps of the special map with the maximum rack position set are recorded so that the map can be arbitrarily switched, the control time of the internal combustion engine by the special map is limited, and the control of the internal combustion engine by the standard map is possible. There have been disclosed things that make it impossible to switch to a special map for a certain period of time after returning.
(For example, see Patent Document 1)
In general, work machine engines are often operated in an overload, low-load, or no-load condition, and there is a large fluctuation in the external load, resulting in an instantaneous transition from an overload condition to a no-load condition. Conversely, a transition from an unloaded state to an overloaded state frequently occurs during work. For example, in a tiller engine as a farming machine, when it is changed from a tilled state to a non-plowed state by a rotary device, it becomes a no-load state from the rated load and the rated rotational speed in an instant. When the device is in a tilled state at a stretch from the idle state, the load increases suddenly and sometimes overloads, so if the fuel injection amount is not adjusted in response to the increase, an engine stall will occur. There is a risk.

Therefore, it has been determined that the load state discriminating unit and the load state discriminating unit are medium load / high load, which discriminates whether the engine operating state is medium load / high load or low load / no load. In response to the feedback control unit that performs feedback control based on the air / fuel ratio based on the medium load / high load map and the load state determination unit determines that the load is low / no load, the feedback control is canceled. And an open control means for setting the injection amount by open control based on a low load / no load map in which the target air-fuel ratio on the fuel rich side is set. (For example, see Patent Document 2)
Japanese Patent Laid-Open No. 11-270359 JP 2000-274280 A

  However, as described above, in the electronic governor-controlled internal combustion engine, the standard map in which the maximum rack position is set so as to keep the limit torque lower than the engine allowable maximum torque and the maximum rack position so as to obtain the engine allowable maximum torque. In response to the determination that the operating state is medium load / high load on the engine that controls engine operation using the two special maps and the tiller engine, the medium load / high load map is displayed. Control of engine operation based on control based on air-fuel ratio based on and control based on air-fuel ratio on the fuel-rich side based on low-load / no-load map in response to determination of low load / no load In either case, it is possible to switch between two torque modes, low torque and high torque. Rukumodo alone, the type of work as the engine for agricultural machines have diversified, is insufficient torque adaptability to various working modes, there is a risk that hinder the good working performance.

  Therefore, the present invention is to improve the torque adaptability to various working modes as an engine for agricultural machines, thereby obtaining good working performance.

  According to the first aspect of the present invention, in a tractor equipped with a common rail type diesel engine, a plurality of work modes using a high torque map (A) for high loads and a plurality of low torque maps (B) for normal loads are used. The tractor is characterized in that a mode changeover switch (1) is provided which is assigned so as to be switchable according to the work content.

  With such a configuration, the mode changeover switch (1), which is arranged at an appropriate position of the tractor and assigns a plurality of work modes based on the high torque map (A) and a plurality of work modes based on the low torque map (B). The high torque map (A) for the high load work mode with a large load factor, and the low torque map (B) with low fuel consumption with the injection timing advanced for the normal load work mode. By switching to the side according to the work content, the optimum work mode based on the high torque map (A) or the low torque map (B) can be selected.

  The invention according to claim 2 is characterized in that the high torque map (A) and the low torque map (B) are provided so as to be switchable according to the work contents in the work mode for performing the tillage work. It is set as the structure of the tractor of 1 description.

  With such a configuration, during a plowing operation on a tractor, the high torque map (A) side is applied to a high torque map (A) side when the load factor is large, and the low torque map (B) side with low fuel consumption is advanced in the injection timing during a normal work load. Further, by switching according to the work contents, the tilling work can be performed without being affected by the work load.

  In the first aspect of the invention, as described above, the mode changeover switch (1) arranged at an appropriate position of the tractor is arranged on the high torque map (A) side for a plurality of work modes at a high load with a large load factor. In addition, the high torque map (A) or the high torque map (A) or Since it is possible to select an optimal work mode based on the low torque map (B), when the load factor increases in the low torque mode as in the conventional case, the rotational speed decreases, causing trouble in work performance and fuel efficiency. Good work performance and fuel efficiency can be obtained with excellent torque adaptability to various work modes without being worsened.

  In the invention of claim 2, as described above, at the time of tillage work on a tractor, a high torque map (A) corresponding to a high load with a large load factor and a low torque due to low fuel consumption by advancing the injection timing corresponding to a normal load Since it can be switched to the map (B) according to the work contents, when the load factor becomes large in the low torque mode as in the conventional case, the rotational speed is reduced, causing trouble in work performance and fuel efficiency. There is no deterioration, and the tilling work can be performed with good fuel efficiency without being affected by the work load.

  In a tractor equipped with a common rail diesel engine, switch between multiple work modes that use a high torque map A for high loads and multiple work modes that use a low torque map B for normal loads, depending on the work content. A mode change-over switch 1 assigned as possible is provided. In a tractor equipped with the common rail diesel engine, a high torque map A and a low torque map B are provided so as to be switchable according to the work contents in a work mode in which a tilling work is performed.

Embodiments of the present invention will be described below with reference to the drawings.
As shown in the system diagram of FIG. 3 for the common rail type diesel engine E, the common rail type (accumulation type fuel injection method) is a common rail 10 (accumulation pressure) that is supplied by adjusting the fuel injection to each cylinder to the required pressure. Room).

  The fuel in the fuel tank 11 is sucked into the high pressure pump 13 driven by the engine E through the fuel filter 12 through the suction passage, and the high pressure fuel pressurized by the high pressure pump 13 is guided to the common rail 10 through the discharge passage 14. It is stored.

  The high-pressure fuel in the common rail 10 is supplied to the injectors 17 corresponding to the number of cylinders through the high-pressure fuel supply passages 16, and the injectors 17 are opened for each cylinder based on commands from the engine control unit 18 (hereinafter referred to as ECU). Then, the high pressure fuel is injected and supplied into each combustion chamber of the engine E, and surplus fuel (return fuel) in each injector 17 is led to a common fuel return passage 20 by each fuel return pipe 19, and this fuel return passage. 20 is returned to the fuel tank 11.

  Further, a pressure control valve 21 is provided in the high-pressure pump 13 for controlling the fuel pressure (common rail pressure) in the common rail 10, and this pressure control valve 21 is sent from the high-pressure pump 13 to the fuel tank 11 by a duty signal from the ECU 18. This adjusts the flow area of the fuel return passage 20 for surplus fuel to the common rail, so that the common rail pressure can be controlled by adjusting the amount of fuel discharged to the common rail 10 side.

  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 21 so that the common rail pressure detected by the rail pressure sensor 22 matches the target common rail pressure. .

  The ECU 18 of the common rail diesel engine E in the agricultural machine has a droop control in which the output fluctuates due to the fluctuation of the rotation speed in the relationship between the rotation speed and the output torque, and the rotation speed is constant even if the load fluctuates, and the output depends on the load. There are three types of control modes: isochronous control that changes and heavy load control that raises the number of revolutions and raises the output when isochronous control approaches the load limit.

  Droop control is used when traveling without farming. For example, when the traveling speed is reduced or stopped by applying a brake, the engine speed decreases as the traveling load increases. Therefore, it is possible to safely reduce or stop the traveling speed.

  Isochronous control is used when performing normal farming work.For example, if a tractor is cultivated and the cultivated land is hard and resistance is applied to the cultivating blade, and if it is a combine, there is a lot of harvest during harvesting. Even when it increases, the output fluctuates and maintains the rotation speed, so that the operator can operate easily.

  Heavy load control is used especially when farming near the load limit.For example, when plowing with a tractor, engine output is usually at the normal limit even when encountering hard cultivated land. The work will not be interrupted.

  Conventionally, in a diesel engine, it is known to perform pilot injection that injects a small amount of fuel in a pulse manner prior to main injection, thereby shortening the ignition delay and reducing the so-called knocking noise peculiar to the diesel engine. .

  This pilot injection is performed once or twice before the main injection. However, by using the system of the common rail 10, the state of the pilot injection is changed according to the state of the engine. The generation of white smoke or black smoke due to noise reduction or incomplete combustion can be suppressed.

  In the common rail type diesel engine E, as shown in the overall configuration of FIG. 4, a cylinder head 5 is disposed on an upper portion of a cylinder block 4 that supports a crankshaft 3, an oil pan 6 is disposed on a lower portion, and a gear train is disposed on a front portion. An internally mounted gear case 7 and a cooling fan 8 are provided, and a flywheel 9 is provided at the rear.

  An intake manifold 23 is connected to the intake side of the cylinder head 5, the common rail 10 is mounted and disposed near the lower side thereof, and the high-pressure pump 13 driven by the gear case 7 is disposed and disposed below the common rail 10. The injector 17 is fitted and arranged on the upper surface of the cylinder head 5.

  A tractor T equipped with a common rail type diesel engine E has a front wheel 31 and a rear wheel 32 at the front and rear portions of the fuselage, as shown in the overall configuration of FIG. The transmission is appropriately changed by 30 transmissions and transmitted to the front wheels 31 and the rear wheels 32.

  A steering handle 35 is supported on a handle post 34 in the cabin 33 and a seat 36 is provided behind the handle post 34 in the cabin 33. Below the handle 35, the advancing direction of the aircraft is switched to the front-rear direction. A forward / reverse lever 37 is provided. When the forward / reverse lever 37 is moved forward, the aircraft moves forward, and when it is moved backward, it moves backward. The rotary device 38 is connected by a link 39 at the rear of the machine body.

  As shown in FIGS. 1 and 2, the panel 29 located on the upper portion of the handle post 34 has a high torque map A area corresponding to a high load ratio and a 4WD work mode 1a at the time of 4WD drive. Only the front wheel speed-up turning mode 1b for driving the front wheels 31, the heavy tillage work mode 1c at high load, etc., and the low load map B in the low torque map B with the fuel injection timing corresponding to the normal load, A mode change-over switch 1 assigned with a normal tillage work mode 1d at the time, a loader mode 1e for performing loader work, a travel mode 1f for performing normal travel, and the like is arranged.

  With such a configuration, the mode changeover switch 1 located on the panel 29 allows the 4WD work mode 1a, the front wheel accelerated turning mode 1b, and the heavy tillage, which are arranged in the region of the high torque map A, depending on the work contents. The work mode 1c and the like are switched at the appropriate time to correspond to the work mode at the time of high load, and the normal tillage work mode 1d, the loader mode 1e, the traveling mode 1f, etc. arranged in the region of the low torque map B are switched at the appropriate time to the normal load. Since it is possible to select an optimum work mode based on the high torque map A or the low torque map B by corresponding to the current work mode, when the load factor becomes large in the low torque mode as in the prior art, the rotational speed This will not interfere with work performance and fuel efficiency, and will exhibit excellent torque adaptability. It can be obtained a good working performance and fuel efficiency.

  In addition, it has a system that corresponds to the work mode by selectively switching between two maps of high torque and low torque, calculates a map suitable for work from the two maps according to the load factor, and control by this calculated map I don't see anything to do.

  Therefore, the tractor T equipped with the common rail type diesel engine E has a system corresponding to the work mode by selectively switching the two torque modes by the high torque map A and the low torque map B as described above. By configuring the target torque map suitable for the work based on the load factor information such as the depth, a target torque map suitable for the work is calculated based on the load factor information as shown in the flowchart of FIG. When it is necessary to change the map by calculation, the selection map is switched from the two maps to the optimum map suitable for the work, and the control is performed using this optimum map. Efficiency can be improved.

  In addition, it has a system that corresponds to the work mode by selectively switching between two maps of high torque and low torque. In the torque mode of low torque, the load factor becomes high, resulting in a decrease in the rotational speed and the like. There were difficulties.

  Therefore, the tractor T equipped with the common rail type diesel engine E has a system corresponding to the work mode by selectively switching the two torque modes by the high torque map A and the low torque map B as described above. When the rate is greater than a certain value, it is possible to automatically switch to the torque mode based on the high torque map A, and as shown in the flowchart of FIG. However, when the load factor becomes a certain value or more according to the load factor information, it automatically switches to the high torque map A and performs control to improve fuel efficiency during work, thereby reducing fuel consumption during work and automatic torque map. Efficiency can be improved by switching.

  In addition, there is a system that corresponds to the work mode by selectively switching between two maps of high torque and low torque. If you can find a rotation control method (droop control, isochronous control) or torque curve by CAN communication Absent.

  Therefore, the tractor T equipped with the common rail type diesel engine E has a system corresponding to the work mode by selectively switching the two torque modes by the high torque map A and the low torque map B as described above. When the engine speed is controlled by isochronous control and the engine speed is changed during turning or reversing, it is switched to droop control by CAN communication and the engine speed can be controlled by the accelerator opening instruction. To configure.

  With such a configuration, as shown in the flowchart of FIG. 8, the initial setting value is transmitted by a CAN message, and when the change by the CAN is approved, as shown in the diagram of FIG. The control method, torque curve, and the like are changed, and completion of the change is returned by a CAN message. As described above, the engine speed, the rotation control method (droop control, isochronous control), the torque curve, and the like can be selected by CAN communication. Therefore, the engine can be controlled by an appropriate control method depending on the work mode.

  In addition, when the load suddenly decreases during turning of the tractor, etc., the engine speed increases to the maximum no-load speed, resulting in high-speed turning. It was.

  For this reason, in the tractor T equipped with the common rail diesel engine E, the average engine speed is calculated by checking the working state, and when the rise of the rotary device 38 is detected during turning, a sudden load is applied. The engine speed which is going to increase to the maximum no-load speed due to the reduction is configured to be controllable so as to become the average speed during the work.

  With such a configuration, as shown in the flowchart of FIG. 10 and the diagram of FIG. 11, when the average engine speed is calculated by checking and confirming the working state, and when the rise of the rotary device 38 is detected during turning, etc. If the engine speed that is going to increase to the maximum no-load speed by suddenly reducing the load is not droop control or automatic accelerator control where the output fluctuates due to fluctuations in the speed, it is controlled to be the average speed at the time of work. When the operation is started again, the engine speed can be controlled to the normal rotation state. As described above, since it is possible to perform control so that the average rotational speed during work is reduced when the load is suddenly reduced, it is possible to reduce a sense of incongruity and improve operability.

  In addition, when the engine speed is a low speed such as 1000 rpm or less, the injection timing is usually advanced by giving priority to the engine startability, but at the time of start in a loaded state of 1000 rpm or less during normal operation. Since the combustion state is different from that in the case where the injection timing is advanced, the fuel efficiency is worsened, and the engine torque is reduced and the stickiness does not occur.

  For this reason, in the tractor T equipped with the common rail diesel engine E, when the engine is not in the start mode, when the engine speed is 1000 revolutions or less and the command injection quantity is a certain value or more, the injection timing is retarded. As shown in the flowchart of FIG. 12, when the engine state is not in the start mode, the engine speed is confirmed to be 1000 rpm or less, and the command injection amount is a certain value or more. Is confirmed, the main injection timing is retarded. In this way, when the rotation decreases when using low rotation, such as when starting from the top or slow tillage, the fuel injection rate is retarded to improve fuel economy and increase the engine torque to prevent further decrease in rotation. Can do.

  In addition, when the engine speed is low, such as 1000 rpm or less, usually the engine startability is prioritized and the injection pattern, for example, pilot ignition with good ignition, is performed. When the rotational speed decreases due to a load or the like, smoke is likely to be generated, and pilot injection is not suitable for controlling this smoke.

  For this reason, in the tractor T equipped with the common rail type diesel engine E, when the engine is not in the start mode, when the engine speed is 900 rotations or less and the command injection amount is a certain value or more, the injection pattern is changed from pilot injection. By switching to after injection, as shown in the flowchart of FIG. 13, when the engine speed is not in the start mode by checking the engine state, the engine speed is confirmed to be 900 rpm or less, and the indicated injection amount is constant. When the value is confirmed to be greater than or equal to the value, after injection can be turned on by turning off pilot injection.

  With regard to this after-injection, conventionally, in common rail engines, the number of injections per cycle is limited to 2 to 3 from the viewpoint of nozzle durability, so even if after-injection is set on the ECU map, pilot injection In general, pilot injection is prioritized and after-injection is not performed. Therefore, as described above, after the pilot injection is simply turned OFF, the preset after-injection is turned ON. As described above, when the rotation is reduced at the time of low rotation such as top start or slow tillage, the amount of smoke generated can be greatly reduced by switching from pilot injection to after injection that is effective in suppressing smoke.

  Further, in the tractor T equipped with the common rail diesel engine E, when the accelerator opening degree 100% continues for 2 seconds or more, the after injection amount is set to substantially the entire amount, and otherwise, the after injection amount is set to about 60%. With this configuration, as shown in the flowchart of FIG. 14, during the normal operation in which the after injection amount is about 60%, when the opening degree 100% continues for 2 seconds or more by checking the accelerator opening amount, the after injection amount is reduced. Set the total amount.

  By performing such after-injection, there is an effect of suppressing smoke, and by further increasing the after-injection amount, the injection amount is dispersed in one cycle, and as a result, the injection period is extended. As a result, Nox is reduced. In this way, when the rotation fluctuation is small, such as during work, the after-injection amount is increased, and nox reduction is emphasized. In situations where smoke is likely to occur, such as on the road, the after-injection amount is reduced and smoke suppression is emphasized. By sorting by purpose, exhaust gas can be made cleaner.

  Further, as shown in the diagram of FIG. 15, in the fuel injection of the engine, since it is difficult to apply a torque limit (injection amount restriction) at normal temperature, smoke is suppressed by using the accelerator filter together with the torque limit. However, when the temperature is low, the command injection amount at the time of accelerator 0% increases due to increased engine friction and fuel cooling, etc., so torque limit is easily applied and smoke is not applied without applying an accelerator filter. Is suppressed. However, in such a case, when the accelerator is depressed, the accelerator filter is added together with the torque limit, and the accelerator response is further deteriorated.

  Therefore, in the tractor T equipped with the common rail type diesel engine E, the accelerator filter coefficient k set according to the water temperature is set to 0 (no correction) when it is 0 degrees C or less as shown in the diagram of FIG. ), The coefficient is set to 1 when the temperature is 60 degrees C or more, and the coefficient is formed by linearly connecting 0 to 1 when the temperature is 0 to 60 degrees C. As shown in the flowchart of FIG. The water temperature is monitored at the time of start-up, and the accelerator filter coefficient k is determined and changed according to the state of the water temperature. In this way, since the injection amount limitation by the torque limit itself acts as an accelerator filter at low temperatures, the accelerator response can be improved by reducing or releasing the accelerator filter, and smoke is suppressed because the accelerator filter is applied at room temperature. be able to.

  In addition, in the rotation control at the time of turning of the combine, there is no one that controls the engine speed by isochronous control by supporting the accelerator opening by CAN communication.

  Therefore, in a combine equipped with a common rail type diesel engine E, the rotation speed is controlled by isochronous control for the entire rotation range at the time of operation, and the accelerator opening is changed by CAN communication at the time of dredging or turning, so that the engine speed is adjusted. With the configuration to be changed, the engine speed can be kept constant by controlling the vehicle speed based on the load factor information.

  With such a configuration, as shown in the flowchart of FIG. 18, when isochronous control is performed in the entire rotation range, transmission is performed using a CAN message. As shown in the diagram of FIG. While making the change, the vehicle speed can be controlled by checking the load factor, and the engine speed can be kept constant. The completion of this change is returned as a CAN message. As described above, the engine speed can be kept constant by controlling the engine speed by CAN communication by the whole area isochronous control and keeping the vehicle speed constant by the load factor information.

  Further, in an engine having an EGR system, when the engine operating state suddenly changes, a time lag occurs until the optimum EGR driving state is reached. One of the problems caused by this time lag is a phenomenon in which the amount of intake air temporarily becomes short and black smoke is discharged or the output is reduced.

  Therefore, in an agricultural machine such as a tractor T or a combine equipped with a common rail diesel engine E having an electronically controlled EGR, as shown in FIG. 20, an exhaust manifold 24 connected to the exhaust side of the cylinder head 5 of the engine E, a turbo excess The exhaust turbine side 25 a of the feeder 25 is connected by an exhaust path 26, and the compressor 25 b side of the turbocharger 25 and the intake manifold 23 are connected by an intake path 28 via an intercooler 27. And the middle of the intake path 28 are connected by the EGR path 40 and disposed.

  An EGR valve 41 for adjusting the EGR rate is arranged on the EGR gas introduction side connecting the EGR path 40 to the exhaust path 26, and the EGR valve 41 is connected to the ECU 18 so as to be electrically controllable.

  With such a configuration, the vehicle behavior in which the engine load greatly changes due to the start of tillage work, the start of cutting work, turning operation, etc. is foreseeed and detected by the image of the position sensor, acceleration sensor, in-vehicle camera, etc. Then, the EGR valve 41 can be autonomously controlled in advance on the side where the EGR rate is lowered by using the detected signal as a trigger.

  As shown in the diagram of FIG. 21 (a), the conventional time lag is reduced even when the load becomes large and the engine speed rapidly decreases during full load work due to the autonomous prior control of the EGR rate. As shown in the diagram of Fig. 21 (b), the time lag from the large EGR control state with a large amount of black smoke emission to the optimal EGR control state can be reduced. Therefore, black smoke emission and output reduction can be suppressed.

  It can also be used for general vehicles including agricultural machines such as tractors and combines.

The top view which shows the state of the mode switch which switches the work mode each arrange | positioned to the area | region of a high torque map and a low torque map. The diagram which shows the relationship between each torque and engine speed in a high torque map and a low torque map. The system figure which shows the pressure accumulation type fuel injection diesel engine by a common rail. The side view which shows the whole structure in a common rail type diesel engine. The side view which shows the whole structure in a tractor. The flowchart which shows the procedure which calculates a torque map with a load factor and switches to an optimal map. The flowchart which shows the procedure of switching to a high torque map automatically, when a load factor becomes more than a fixed value at the time of the operation | work by a low torque map. The flowchart which shows the procedure which transmits an initial setting value by CAN communication, and changes an accelerator opening degree, a rotation control method, a torque curve, etc. The diagram which shows the state of the isochronous control by the accelerator opening degree, and the droop control in the relationship between the torque and engine speed in a high and low torque map. The flowchart which shows the procedure which calculates the average engine speed by confirmation of a work state, and performs control which becomes the average speed at the time of work, when load reduces rapidly. The diagram which shows the rotation control state of this proposal with respect to the conventional rotation rise state when load reduces rapidly from the average rotation speed at the time of work. 7 is a flowchart showing a procedure for retarding the injection timing when the engine speed is 1000 rpm or less and the command injection amount is a certain value or more in a mode other than the start mode. 7 is a flowchart showing a procedure for turning on after-injection by turning off pilot injection when the engine speed is 900 rpm or less and the command injection amount is a certain value or more in a mode other than the start mode. The flowchart which shows the procedure which makes the after injection amount from about 60% to substantially the full amount when the accelerator opening degree 100% continues for 2 seconds or more during normal work. The diagram which shows the state which becomes easy to apply a torque limit at the time of low temperature with respect to normal temperature. The diagram which shows the state which sets an accelerator filter coefficient according to the height of water temperature. The flowchart which shows the procedure which determines and changes an accelerator filter coefficient with the state of water temperature. The flowchart which shows the procedure which changes the accelerator opening by CAN communication at the time of isochronous control by a combine, confirms a load factor, and controls vehicle speed. The diagram which shows the state of an accelerator opening in the relationship between a torque and an engine speed. Schematic which shows the state which has arrange | positioned the EGR valve in the EGR path | route which connects the intake path and exhaust path | route of a diesel engine. (A) The diagram which shows the conventional EGR control state in case a load becomes large during a full load operation and a sudden decrease in engine speed occurs.

    (B) The diagram which shows the EGR control state of this proposal in case a load becomes large during a full load operation | work and the engine speed falls rapidly.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mode change switch 1a 4WD work mode 1b Front wheel acceleration turning mode 1c Heavy tillage work mode 1d Normal tillage work mode 1e Loader mode 1f Travel mode A High torque map B Low torque map

Claims (2)

  In a tractor equipped with a common rail diesel engine, the work contents include a plurality of work modes using a high torque map (A) for high loads and a plurality of work modes using a low torque map (B) for normal loads. A tractor characterized in that a mode change switch (1) is provided so as to be switchable according to the condition.   2. The tractor according to claim 1, wherein the high torque map (A) and the low torque map (B) are provided so as to be switchable in accordance with work contents in a work mode in which a tilling work is performed.

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