JP2019100244A - Tractor - Google Patents

Abstract

To enhance NOx reduction effect, and prevent an EGR valve from being fastened.SOLUTION: A tractor mounted with a Diesel engine having an EGR circuit for reducing part of exhaust gas to a suction side is characterized in that the EGR circuit is composed of a low-pressure side EGR circuit 44 where pressure of the exhaust gas is low and a high-pressure side EGR circuit 74 where the pressure of the exhaust gas is high. The tractor is also characterized in that the low-pressure side EGR circuit 44 is configured to connect an exhaust pipe 55 on a downstream side of a posttreatment device 46 and a suction pipe 56 on an upstream side of a supercharger TB, and the high-pressure side EGR circuit 74 is configured to connect an exhaust pipe 75 on a downstream side of an exhaust manifold 42 and a suction pipe 76 on an upstream side of a suction manifold 38.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a tractor that is an agricultural machine, and more particularly to a tractor having a configuration for efficiently reducing NOx and preventing the EGR valve of an EGR circuit from sticking.

There is disclosed a technology of an engine provided with a high pressure side EGR circuit in which an exhaust pipe on the downstream side of an exhaust manifold and an intake pipe on the upstream side of an intake manifold are connected (for example, see Patent Document 1).

JP, 2016-3601, A

The above-described technology has a problem that the NOx reduction efficiency is low because only one EGR circuit is configured. In addition, when the amount of unburned fuel in the exhaust gas increases, there is a problem that the EGR valve is stuck after the engine is stopped.
An object of the present invention is to provide a tractor equipped with a diesel engine which eliminates the above-mentioned problems.

  The above object of the present invention is achieved by the following constitution.

That is, in the invention according to claim 1, in a tractor mounted with a diesel engine (E) having an EGR circuit for reducing a part of exhaust gas to the intake side, the EGR circuit is a low pressure side EGR circuit having low exhaust gas pressure. According to another aspect of the present invention, there is provided a tractor characterized by comprising the high pressure side EGR circuit (74) in which the pressure of the exhaust gas and the exhaust gas are high.
In the invention according to claim 2, the low pressure side EGR circuit (44) is connected by connecting between the exhaust pipe (55) on the downstream side of the post-processing device (46) and the suction pipe (56) on the upstream side of the turbocharger (TB). A high pressure side EGR circuit (74) by connecting the exhaust pipe (75) downstream of the exhaust manifold (42) and the intake pipe (76) upstream of the intake manifold (38). It is set as the tractor of Claim 1.

  In the invention according to claim 3, an unburned fuel sensor (78) for detecting unburned fuel in exhaust gas is provided, and the high pressure of the high pressure side EGR circuit (74) is detected when the detected value of unburned fuel becomes equal to or greater than a predetermined value. The tractor according to claim 2, wherein the EGR valve (74a) is fully closed.

Since the present invention is configured as described above, in the inventions according to claims 1 and 2, the NOx reduction effect is increased.
According to the third aspect of the present invention, it is possible to prevent the high pressure EGR valve from sticking after the engine is stopped.

Overall Configuration of Accumulator Fuel Injection System Diagram showing the relationship between engine speed and output torque in the control mode Left side view of the tractor Top view of the tractor Schematic of intake and exhaust system Flow chart Flow chart Diagram showing change in soot deposition amount in DPF Diagram showing change in soot deposition amount in DPF Flow chart Flow chart Schematic of intake and exhaust system Schematic of intake and exhaust system

  The best mode for carrying out the present invention will be described.

FIG. 1 is an entire configuration diagram of a pressure accumulation type fuel injection device. The accumulator fuel injection device is applied to, for example, a multi-cylinder diesel engine, but may be a gasoline engine. Then, the pressure accumulation type fuel injection device pressurizes the common rail 1 for accumulating high pressure fuel corresponding to the injection pressure, the pressure sensor 2 attached to the common rail 1, and the fuel drawn up from the fuel tank 3 and pumps it 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 a cylinder 5 of the engine E, a control unit (ECU) for controlling the operation of the high pressure pump 4 and the fuel injection nozzle 6 etc. It consists of The ECU is an abbreviation of an engine control unit.
As described above, the common rail 1 injects the fuel to the cylinders 5 of the engine E, and makes the fuel supply pressure required.
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 by the suction passage, and the high pressure fuel pressurized by the high pressure pump 4 is conducted to the common rail 1 by the discharge passage 8 It is stored.
The high pressure fuel in the common rail 1 is supplied to the fuel injection nozzles 6 for the number of cylinders by the high pressure fuel supply passages 9, and the fuel injection nozzles 6 operate on each cylinder based on the command from the ECU 100. The surplus fuel (return fuel) at each fuel injection nozzle 6 is introduced into the common return passage 10 by each return passage 10 and returned to the fuel tank 3 by this return passage 10.
The high pressure pump 4 is provided with a pressure control valve 11 for controlling the fuel pressure in the common rail 1 (common rail pressure). The pressure control valve 11 receives the fuel tank 3 from the high pressure pump 4 according to a duty signal from the ECU 100. The flow passage area of the return passage 10 for surplus fuel is adjusted, whereby the fuel discharge amount 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 engine operating conditions, and the common rail pressure is feedback controlled via 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 has composition.
As shown in FIG. 2, the ECU 100 of the diesel engine E having the common rail 1 in a working vehicle (agriculture work machine) has three types of traveling mode A, normal operation mode B and heavy operation mode C in relation to the rotational speed and output torque. The configuration has a control mode.
The traveling mode A is the droop control in which the output also varies with the variation of the engine speed. It is used when traveling without traveling in farming. For example, when the traveling speed is reduced or stopped by applying a brake, the engine rotational speed decreases with an increase in the traveling load, so that the traveling speed can be safely reduced or stopped.
The normal operation mode B is isochronous control in which the engine speed is constant even if the load changes and the output is changed according to the load. It is used when performing normal agricultural work. For example, in the case of a tractor, it is when the cultivated land is hard during the tilling operation and resistance is applied to the tilling blade, and if it is a combine, the output fluctuates and the rotational speed is maintained even when the load of the harvest increases during the harvesting operation. It is time.
The heavy operation mode C is the same as the normal operation mode B. In addition to isochronous control that changes the output according to the load at constant engine speed even if the load fluctuates, the engine speed is increased when the load limit is reached. It is the control which added heavy load control which raises. In particular, it is used when performing farming work near the load limit. For example, when carrying out a tillage operation with a tractor, especially when hard tillage is encountered, the engine output increases beyond the normal limit, so work is not interrupted and efficient work is possible. .
In these operation modes A, B and C, operation of the operation mode changeover switch capable of switching each operation mode A, B and C, or shift operation of the traveling shift lever of an agricultural work vehicle (tractor, combine, rice transplanter, etc.) Alternatively, it is configured to be switched by the on / off operation or the like of a working clutch (in the case of a tractor, it is a rotary, and in the case of a combine, it is a reaper or a threshing part).
In the diesel engine E, by performing pilot injection in which a small amount of fuel is injected in a pulsed manner prior to the main injection, the ignition delay can be shortened, knock noise specific to the diesel engine E can be reduced, and noise can be reduced. Configuration.
Although this pilot injection was performed once or twice before the main injection, by using the pressure accumulation type fuel injection device of the common rail 1, the pilot injection according to the condition of the engine E It is possible to reduce the generation of white smoke or black smoke due to noise reduction and incomplete combustion. In addition, by performing pilot injection in which a small amount of fuel is injected in a pulsed manner prior to the main injection, the amount of nitrogen oxides in the exhaust gas can be reduced.

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

  The tractor is provided with front wheels 12, 12 and rear wheels 13, 13 on the front and rear of the machine body, and the rotational power of the engine E mounted on the front of the machine body is appropriately reduced by the transmission in the transmission case T. , 12 and the rear wheels 13, 13.

A steering wheel 16 is supported at the steering wheel post 15 in the cabin 14 at the center of the airframe, and a seat 17 is provided behind the steering wheel 16. Below the steering wheel 16, a forward / backward advancing lever 18 is provided to switch the traveling direction of the vehicle in the front-rear direction. When the forward and reverse lever 18 is moved forward, the machine moves forward, and when it is moved backward, the vehicle moves backward.
In addition, an accelerator lever 25 for adjusting the engine speed is provided on the opposite side of the front-back lever 18 across the steering wheel post 15, and an accelerator for adjusting the engine speed is similarly provided at the right corner of the step floor 19. The pedals 23 and left and right brake pedals 24L, 24R for operating the brakes on 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 shift lever 26 is located on the left front side of the seat 17 and there is an auxiliary shift lever 27 located behind the PTO shift lever 27 which can select any one of low, medium, high and neutral positions. Is provided. Furthermore, on the right side of the seat 17, there are a position lever 29 for setting the height of the working machine 21 (rotary etc.), an automatic plowing lever 30 for automatically setting the tillage depth of the field, and the working machine 21 behind these levers. The right raising switch 31 and the right lowering switch 32 are disposed, and the automatic horizontal switch 33 and the backup switch 34 of the working machine 21 are disposed thereafter. The backup switch 34 automatically raises the work implement 21 when the machine is in reverse. The work implement 21 is configured to be connected to the rear of the machine by a link 22. The tractor drives the working machine 21 to run the machine to perform operations such as tilling in a field. Reference numeral 21 a denotes a hydraulic cylinder that raises and lowers the work machine 21.

FIG. 5 is a schematic view of intake and exhaust into the cylinder 5 of the engine, which is an embodiment of a four-stroke diesel engine. The air supercharged by the intake turbine 36 of the turbocharger TB is sent from the air cleaner 35 through the intake turbine 36 and the intercooler 37 to the cylinder 5 from the intake manifold 38. 39 is an intake valve and 40 is a piston. A cam 48 opens and closes the intake and exhaust valves 39 and 41 through the rocker arm 49.
The exhaust gas burned in the cylinder 5 is configured to be discharged by driving the supercharger TB by the exhaust turbine 45 of the supercharger TB after passing through the exhaust manifold 42 from the exhaust valve 41.

  This diesel engine has an EGR (exhaust gas recirculation device) circuit 44 for mixing a part of the exhaust gas on the intake side. By mixing a part of the exhaust gas to the intake side in the EGR circuit, the amount of oxygen (O2) is reduced to reduce the generation of nitrogen oxide Nox. However, if the EGR rate rises too much, conversely, the amount of oxygen decreases to cause incomplete combustion, so it is necessary to adjust the EGR rate depending on the combustion state. This adjustment is performed by the EGR valve 43. The EGR circuit 44 connects between an exhaust pipe 55 downstream of the post-processing device 46 described later and a suction pipe 56 upstream of the intake turbine 36 of the turbocharger TB. Further, an EGR cooler 57 is provided in the middle of the EGR circuit 44. Depending on the degree of opening and closing of the EGR valve 43, the amount of reduction of the exhaust gas into the cylinder 5 changes.

Exhaust gas after passing through the exhaust turbine 45 passes through the aftertreatment device 46 and is exhausted from the muffler 50 to the atmosphere. The aftertreatment device 46 is composed of an oxidation catalyst (DOC) 46a and a diesel particulate filter (DPF) 46b.
The oxidation catalyst (DOC) burns the incombustible material chamber, and the diesel particulate filter (DPF) is for collecting particulate matter (PM). The EGR valve 43 and the throttle valve 47 are controlled by the ECU 100. The post-treatment device 46 may be constituted only by the diesel particulate filter (DPF) 46b. If an oxidation catalyst (DOC) is provided, the non-combustible substance burns, resulting in a cleaner exhaust gas.

  In the DPF 46b, when the exhaust gas temperature is low (low load) for a long time, PM may be accumulated, and the performance may be reduced. Therefore, a throttling valve 47 is provided on the lower side of the post-processing device 46. When the throttling valve 47 is squeezed, the pressure in the DPF 46b is held high, and the temperature also becomes high. As a result, the DPF 46b can be regenerated due to the influence of high temperature. That is, when the high temperature exhaust gas passes through the DPF 46b, the PM present in the DPF 46b is burned off to regenerate the DPF 46b.

  As a 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 (retarding angle) of the fuel injection timing so that the DPF 46b enters regeneration. As a result, after injection (after raising the exhaust gas temperature) of the fuel becomes unnecessary and the number of after injections can be reduced, the fuel consumption can be suppressed, which is good for the environment.

  As a condition for performing such DPF regeneration operation, a pressure sensor 52 is provided on the upper side of the post-processing device 46, and a pressure sensor 53 is also provided on the lower side of the post-processing device 46. At this time, the PM is accumulated in the DPF 46b to be a resistance, so the DPF regeneration operation is performed. Further, instead of the pressure sensor 52, a pressure sensor 58 may be provided between the DOC 46a and the DPF 46b.

  In addition, if the state in which the DPF regeneration operation is started continues for a long time, the overheat state occurs, and the DPF 46b is damaged. 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 maintained high.

  The configuration as described above eliminates the need for the intake throttle. That is, since the intake side pressure is high in an engine with a supercharger, an exhaust throttle valve or intake throttle is required to secure the amount of EGR gas, and control interlocking with the EGR valve is required, but such a system is unnecessary. It becomes.

  In addition, since the exhaust gas downstream of the DPF 46b is taken out, it is possible to prevent the performance deterioration due to the contamination of the turbocharger TB. Then, since the EGR gas is cooled by the EGR cooler 57, the effect on NOx reduction is enhanced.

  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 narrowed, and the EGR valve 43 is fully closed by the 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.

  In addition, when the engine rotation shifts to low idle during 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 detected value by the temperature sensor 59 has risen to a predetermined value or more.

  When the DPF 46b is forcedly regenerated by throttling the throttle valve 47, the engine speed is lowered to increase the supplied oxygen amount, and the exhaust gas flow rate is decreased to facilitate the temperature rise. However, if the engine speed is changed to or near low idle during regeneration, the increase in the amount of supplied oxygen and the decrease in the flow velocity cause the soot to burn rapidly. As a result, the temperature may rise rapidly and the DPF 46 b may be damaged. Therefore, it is necessary to control the temperature which prevents the maximum temperature from exceeding the allowable temperature.

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

  In order to raise the engine speed to the medium speed range, the engine speed may be once raised to the maximum speed and then decelerated to the medium speed range, whereby the exhaust gas flows once at the maximum speed, so preheating is possible. Thus, the DPF 46b can be prevented 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. The post injection is restarted at As a result, a rapid rise in the exhaust gas temperature can be suppressed, and damage to the DPF 46b can be prevented.

When the differential pressure before and after the DPF 46b becomes equal to or higher than a predetermined value, the driver selects the regeneration mode of the DPF 46b with the selection switch 67 after work to automatically regenerate the DPF 46b and automatically stop the engine after regeneration of the DPF 46b. Configure to The differential pressure before and after the DPF 46 b is monitored by the pressure sensors 58, 53. If the pressure difference across DPF 46b immediately before the stop of the engine is equal to or more than a predetermined value, a warning lamp or an alarm is notified, and the driver operates a switch (not shown) that regenerates the DPF 46b.
Then, even if the engine key is in the off position, by selecting the regeneration mode, the engine keeps its rotation in the idling state, and regeneration of the DPF 46b is performed. When the differential pressure before and after the DPF 46b becomes equal to or less than a predetermined value, the engine is automatically stopped.

As a result, the regeneration of the DPF 46b and the engine stop can be performed automatically even after the work is completed, so that the driver can perform other work away from the machine.
When the DPF 46b is regenerated, as shown in FIG. 5, the air on the intake side may be sent from the pipeline 61 to the upstream side of the DPF 46b. That is, when the regeneration of the DPF 46b is performed, the valve 60 may be opened to send the air on the intake side upstream of the turbocharger TB having a large amount of oxygen to the upstream side of the DPF 46b. This improves the reproduction efficiency.

  Also, the temperature of the DPF 46b may be monitored by the temperature sensors 62, 59, and the temperature rise during regeneration may be confirmed in three steps. First, intake throttling (not shown) is performed, and temperature rise confirmation in the throttling state of the intake is performed. Next, the first post injection is performed to check the temperature rise. At this point in time, if the temperature before and after DPF 46b has not reached 250 ° C., no further temperature rise can be expected even if the second post injection is performed, so regeneration is temporarily interrupted. Of course, if the temperature 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 downstream of the DPF 46b. In the case where the post injection is performed to regenerate the DPF 46b, if the fuel injection amount is too large, the fuel efficiency will deteriorate. If the fuel injection amount is too small, the temperature will not rise and the regeneration will not be possible. Therefore, the value of the air-fuel ratio sensor 63 is fed back to the ECU 100 to determine the injection amount. As a result, appropriate fuel consumption can be achieved, and regeneration of the DPF 46b becomes possible. Further, instead of the air-fuel ratio sensor 63, a pressure value in the intake manifold may be fed back.

  When the DPF 46b is regenerated as described above, in the case of a plurality of cylinders, combustion of some of the cylinders may be stopped. As described above, by stopping the combustion of some of the cylinders, the engine friction may be the same or the load per cylinder may be increased to raise the exhaust temperature.

  In the EGR valve 43, soot and HC adhere and are integrated with moisture such as condensation to form a viscous liquid. In such a state, the EGR valve 43 operates, but when the engine is stopped and the engine cools, the viscous liquid may stick, and when the engine is restarted, the EGR valve 43 may not move. In order to solve such a problem, the EGR valve 43 is provided with a cleaning function. That is, by forcibly operating the EGR valve 43 to remove the viscous liquid during afterrun after the engine is stopped, the EGR valve 43 does not stick even if the engine is cooled.

A high pressure side EGR circuit 74 is provided to the EGR circuit 44 (low pressure side EGR circuit). That is, two EGR circuits are provided. The high pressure side EGR circuit 74 is configured to connect the exhaust pipe 75 on the downstream side of the exhaust manifold 42 and the intake pipe 76 on the upstream side of the intake manifold 38, and the high pressure side EGR circuit 74 is provided with a high pressure EGR valve 74a. Then, the ratio of the low pressure side EGR circuit 44 and the high pressure side EGR circuit 74 is increased by the rotation of the PTO shaft 77 (see FIG. 3) of the tractor and the depth of plow (engine load factor) to obtain two EGR circuits. By reducing the NOx at this point, it is possible to reduce NOx efficiently. The rotation of the PTO shaft 77 is from 1st to 5th, and the plow depth is from shallow to deep in five steps of 1 to 5. Although this combination works, the load on the engine is determined by the field conditions (dry or wet). The load factor detection of the engine is calculated from the engine performance curve in the ECU 100, the engine speed, and the current fuel injection amount.
However, the measured value of NOx is detected by the NOx sensor 77 rather than the engine load factor, and the accuracy is improved if the EGR rates of the two systems are controlled based on the detected value.
When the unburned fuel sensor 78 for detecting unburned fuel increases the amount of unburned fuel, the high pressure EGR valve 74a of the high pressure side EGR circuit 74 is fully closed, and the high pressure side EGR circuit 74 is not used. The EGR reduction is performed only by the circuit 44. Thereby, the sticking of the high pressure EGR valve 74a can be prevented. As shown in FIG. 7, an EGR selection switch 79 may be provided so that the low pressure side EGR circuit 44 or the high pressure side EGR circuit 74 can be selected in advance.
In the DPF 46b described above, as shown in FIG. 8, the soot combustion promotion control area S1 is set in front of the forced regeneration area S. S0 is a normal operation area. In the soot combustion promotion control area S1, the EGR rate is lowered to increase the amount of NOx, and the soot is easily burned by the catalyst. When the soot decreases by a predetermined amount (the difference between the pressure sensor values before and after DPF is equal to or less than a predetermined value), the EGR opening degree is returned to the original value. Alternatively, it is configured to be restored after a predetermined time (for example, after 30 minutes). This makes it possible to interrupt the work and reduce the situation of forced regeneration.
In FIG. 9, the exhaust temperature rise region S3 is set in front of the forced regeneration region S2. The specific configuration of the exhaust temperature rise region S3 is to increase the common rail pressure and to delay the fuel injection timing. When the exhaust temperature rises, the combustion of the soot is promoted. When the soot decreases by a predetermined amount (the difference between the pressure sensor values before and after DPF is equal to or less than a predetermined value), the common rail pressure and the fuel injection timing are returned to the original state. Alternatively, it is configured to be restored after a predetermined time (for example, after 60 minutes). This makes it possible to interrupt the work and reduce the situation of forced regeneration. In addition, deterioration of fuel consumption can be prevented.

  FIG. 10 shows a soot confirmation method based on the differential pressure before and after the DPF 46b. The differential pressure at no load is monitored, and when the fuel injection amount, the cooling water temperature, and the exhaust temperature (DPF temperature) are under predetermined conditions, the differential pressure value of the DPF with respect to the current soot amount is more than expected. , Forced regeneration (manual regeneration) is performed. This can prevent an increase in the amount of clogged soot in the DPF 46b.

  FIG. 11 shows a configuration in which a plurality of DPF manual regeneration methods are provided. An arbitrary mode can be selected according to the work situation of the worker, and each mode is distinguished by the difference in post injection amount, timing, and regeneration end judgment.

  In the time priority mode M1, the DPF regeneration time is prioritized over the fuel consumption, and the post injection is performed so that the DPF differential pressure necessary for resuming operation can be immediately obtained.

  The fuel consumption priority mode M2 suppresses the fuel consumption amount consumed by the post injection more than the time required for the DPF regeneration.

  In the regeneration priority mode M3, there is no change in DPF regeneration (different pressure before and after) per unit time, and regeneration is performed until the DPF differential pressure becomes an initial value.

In the time selection mode M4, the operator arbitrarily selects the time for regeneration operation. (If regeneration is not performed within the selected time, regeneration operation is performed again)
As a result, even when forced regeneration (manual regeneration) is required, the forced regeneration (manual regeneration) mode can be selected according to the worker's work status, so that the burden on the operator can be reduced.

  The selection of the time priority mode M1, the fuel consumption priority mode M2, the regeneration priority mode M3, and the time selection mode M4 is configured by selecting with independent switches 84a, 84b, 84c, 84d. Each of these switches is configured to light up when one of the modes is selected by pressing. In addition, as shown in FIG. 4, these switches are provided on any of the meter panel, the right operation panel, and the left operation panel.

  Further, the selection of the time priority mode M1, the fuel consumption priority mode M2, the reproduction priority mode M3, and the time selection mode M4 may be configured as a switch of the dial 85 by turning the dial 85. In this case, the selected mode portion is configured to light up.

  When the vehicle is stopped to perform forced regeneration (manual regeneration) of the DPF 46b, a high temperature exhaust gas is discharged, which may cause a fire. Therefore, as shown in FIG. 12, the heat exchanger 80 is provided in the exhaust pipe downstream of the DPF 46b. The engine cooling water piping is connected to the heat exchanger 80 from the hose between the engine E and the radiator 81, and the flow path is switched by the valve 82. When the vehicle is stopped and forced regeneration (manual regeneration) is performed, the valve 82 is switched to circulate the cooling water through the heat exchanger 80. As a result, the temperature of the exhaust gas is reduced, so that the occurrence of a fire can be prevented. By extracting the cooling water to the heat exchanger 80 upstream of the radiator 81 and returning it to the upstream of the radiator 81, it is possible to prevent the high temperature cooling water from entering the engine E.

  FIG. 13 shows another configuration of FIG. 12 described above. A heat exchanger 80 is provided in parallel with the exhaust pipe downstream of the DPF 46b. A heat exchanger 80 is provided on the hose between the engine E and the radiator 81. The heat exchanger 80 and the exhaust pipe are connected, and the valve 83 switches the flow of the exhaust gas. When the vehicle is stopped and forced regeneration (manual regeneration) is performed, the valve 83 is switched to flow exhaust gas into the heat exchanger 80.

  In the case of forced regeneration (manual regeneration) of the DPF 46b, if the outside air temperature is high, the temperature around the DPF 46b may increase, which may cause thermal deterioration to peripheral devices. Therefore, it is important to install a temperature sensor around the DPF 46b and keep the value of the temperature sensor substantially constant. Therefore, the temperature around the DPF 46b is uniformly maintained by correcting and controlling the post injection amount.

It can be used for general vehicles as well as agricultural machines such as tractors and combine harvesters.

E Diesel engine 44 Low pressure side EGR circuit 46 Post-processing device 55 Exhaust pipe 56 downstream of post-processing device Intake pipe 74 upstream of supercharger Intake pipe 74 high pressure side EGR circuit 74a High pressure EGR valve 75 Exhaust pipe downstream of exhaust manifold 76 Intake manifold Upstream intake pipe 78 Unburned fuel sensor

Claims (3)

  In a tractor equipped with a diesel engine (E) having an EGR circuit that reduces part of the exhaust gas to the intake side, the EGR circuit is low in exhaust gas pressure and the exhaust gas pressure is high. A tractor characterized by comprising a high pressure side EGR circuit (74).   A low pressure side EGR circuit (44) is configured by connecting between the exhaust pipe (55) on the downstream side of the post-processing device (46) and the suction pipe (56) on the upstream side of the turbocharger (TB). 42) The tractor according to claim 1, characterized in that a high pressure side EGR circuit (74) is configured by connecting the exhaust pipe (75) on the downstream side and the intake pipe (76) on the upstream side of the intake manifold (38). .   An unburned fuel sensor (78) for detecting unburned fuel in the exhaust gas is provided, and the high pressure EGR valve (74a) of the high pressure side EGR circuit (74) is fully closed when the detected value of unburned fuel exceeds a predetermined value. The tractor according to claim 2, characterized in that it is in a state.

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