JP2020165416A - Tractor - Google Patents

Abstract

To correct the opening of an EGR valve to reduce the occurrence of soot.SOLUTION: In a tractor equipped with a diesel engine (E) having an EGR circuit (44) that reduces part of exhaust gas to a suction side, the EGR circuit (44) is provided with an EGR valve (43) that adjusts a reduction amount of exhaust gas, an air amount sensor (70) is provided on the suction side of an engine, and the EGR valve (43) is configured to be closed for a predetermined time during the operation of the engine. When a detected value of the air amount sensor (70) changes during this predetermined time, the tractor is configured to control the EGR valve (43) according to the changed amount of air.SELECTED DRAWING: Figure 6

Description

The present invention relates to a tractor that is an agricultural machine, and more particularly to a tractor having a reduction rate control configuration of an engine EGR circuit.

A technique for controlling the opening degree of an EGR valve to suppress soot is disclosed (see, for example, Patent Document 1).

JP-A-2002-70655

In the technique described in the above-mentioned publication, the EGR valve is controlled to suppress soot, but there is no function of checking whether the EGR valve opening is correct at the present time.
An object of the present invention is to solve the above-mentioned problems.

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

That is, in the invention according to claim 1, in a tractor equipped with a diesel engine (E) having an EGR circuit (44) that returns a part of the exhaust gas to the intake side, the exhaust gas is reduced to the EGR circuit (44). An EGR valve (43) for adjusting the amount is provided, an air amount sensor (70) is provided on the intake side of the engine, and the EGR valve (43) is closed for a predetermined time during the engine operation. The tractor is characterized in that the EGR valve (43) is controlled according to the changed air amount when the detected value of the air amount sensor (70) changes.
In the invention according to claim 2, when the changed air amount increases more than a specified value, the EGR becomes lower than the opening degree of the EGR valve (43) before closing the EGR valve (43). The tractor according to claim 1, wherein the valve (43) is configured to open after the predetermined time.

2. The invention according to claim 3 is characterized in that the EGR valve (43) is configured to be closed for a predetermined time until the changed air amount does not increase more than a specified value. It is the described tractor.

Since the present invention is configured as described above, the EGR valve opening degree at the present time can be modified.

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 diagram of intake system and exhaust system EGR valve opening and intake amount time chart Flow chart of altitude estimation Flow chart in playback prohibited mode

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

FIG. 1 is an overall configuration diagram of a pressure-accumulation 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 that accumulates high-pressure fuel corresponding to the injection pressure, the pressure sensor 2 attached to the common rail 1, and the fuel pumped from the fuel tank 3 and pumps the fuel to the common rail 1. A high-pressure pump 4, a fuel injection nozzle 6 that injects high-pressure fuel accumulated in the common rail 1 into the cylinder 5 of the engine E, a control device (ECU) that controls the operation of the high-pressure pump 4, the fuel injection nozzle 6, and the like. Consists of. The ECU is an abbreviation for an engine control unit.
As described above, the common rail 1 injects fuel into 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 by the discharge passage 8. It is stored and stored.
The high-pressure fuel in the common rail 1 is supplied to the fuel injection nozzles 6 for the number of cylinders by each high-pressure fuel supply passage 9, and the fuel injection nozzle 6 operates in each cylinder based on the command from the ECU 100, and the high-pressure fuel is supplied to the engine E. The surplus fuel (return fuel) in each fuel injection nozzle 6 is injected and supplied into each of the silunder 5 chambers, is guided to the common return passage 10 by each return passage 10, and is returned to the fuel tank 3 by the return passage 10.
Further, a pressure control valve 11 is provided in the high pressure pump 4 in order to control the fuel pressure (common rail pressure) in the common rail 1, and the pressure control valve 11 is provided from the high pressure pump 4 to the fuel tank 3 by a duty signal from the ECU 100. The flow path area of the return passage 10 of the surplus fuel to 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 the 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 a structure.
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 traveling mode A, normal working mode B, and heavy working mode C in relation to the rotation speed and the output torque. It has a control mode.
The driving mode A is a droop control in which the output also fluctuates due to fluctuations in the engine speed. It is used when traveling on the move without farming. For example, when the brake is applied to reduce or stop the traveling speed, the engine speed decreases as the traveling load increases, so that the traveling speed can be reduced or stopped safely.
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 if the load fluctuates. It is used when performing normal farm work. For example, in the case of a tractor, the cultivated land is hard during tilling work and resistance is applied to the tilling blade, and in the case of a combine, the output fluctuates and the rotation speed is maintained even when the load increases due to a large amount of harvested material during harvesting work. It's time.
In the heavy work mode C, as in the normal work mode B, in addition to isochronous control in which the engine speed is constant and the output is changed according to the load even if the load fluctuates, the speed is increased to output when the load limit is approached. It is a control with a heavy load control that raises. In particular, it is used when farming near the load limit. For example, when cultivating with a tractor, especially when encountering hard cultivated land, the engine output increases beyond the normal limit, so the work is not interrupted and efficient work is possible. ..
These work modes A, B, and C are the operation of the work mode changeover switch that can switch each work mode A, B, C, or the shift operation of the traveling speed change lever of the agricultural work vehicle (tractor, combine, rice transplanter, etc.). Alternatively, the work clutch (rotary for a tractor, cutting section and threshing section for a combine harvester) is configured to switch by turning on and off.
In the diesel engine E, it is possible to shorten the ignition delay, reduce the knocking noise peculiar to the diesel engine E, and reduce the noise by performing the pilot injection in which a small amount of fuel is injected in a pulsed manner prior to the main injection. The configuration is as follows.
This pilot injection was performed only once or twice before the main injection, but by using the accumulator fuel injection device of the common rail 1, the pilot injection is performed according to the situation of the engine E. It becomes possible to reduce noise and suppress the generation of white smoke or black smoke due to incomplete combustion. In addition, the amount of nitrogen oxides in the exhaust gas is reduced by performing pilot injection in which a small amount of fuel is pulsedly injected prior to the main injection.

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 state in which the cabin 14 shown in FIG. 3 is omitted is shown.

The tractor is provided with front wheels 12, 12 and rear wheels 13, 13 at the front and rear parts of the airframe, and the rotational power of the engine E mounted on the front part of the airframe is appropriately decelerated by a transmission in the transmission case T, and these front wheels 12 , 12 and the rear wheels 13, 13.

A steering handle 16 is supported by a handle post 15 in the cabin 14 at the center of the fuselage, and a seat 17 is provided behind the steering handle 16. Below the steering handle 16, a forward / backward lever 18 for switching the traveling direction of the aircraft in the front-rear direction is provided. When the forward / backward lever 18 is moved forward, 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 / backward lever 18 with the handle post 15 interposed therebetween, and an accelerator for adjusting the engine speed is similarly provided at the right corner of the step floor 19. The pedals 23 and the left and right rear wheels 13 and 13 are provided with left and right brake pedals 24L and 24R for operating the brakes. A clutch pedal 20 is provided at the left corner of the step floor 19.

Further, the main shift lever 26 is located on the left front portion of the seat 17, and the auxiliary shift lever 27 capable of selecting any of low speed, medium speed, high speed and neutral positions is located behind the main shift lever 26, and the PTO shift lever 28 is further to the right side thereof. 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 depth lever 30 for automatically setting the tilling depth of the field, and a 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 working machine 21 are arranged. The backup switch 34 automatically raises the working machine 21 when the machine is moving backward. The work machine 21 is configured to be connected to the rear of the machine body by a link 22. The tractor drives the work machine 21 to run the machine body, thereby performing work such as tilling in the field. Reference numeral 21a is a hydraulic cylinder for raising and lowering the working machine 21.

FIG. 5 is a schematic view of intake and exhaust into the cylinder 5 of the engine, and is an example 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. 39 is an intake valve and 40 is a piston. Reference numeral 48 denotes a cam, which opens and closes the intake / exhaust valves 39 and 41 via the rocker arm 49.
The exhaust gas burned in the cylinder 5 passes through the exhaust manifold 42 from the exhaust valve 41, and then is discharged by driving the supercharger TB with the exhaust turbine 45 of the supercharger TB.

This diesel engine has an EGR (exhaust gas recirculation device) circuit 44 for mixing a part of exhaust gas into the intake side. The EGR circuit is configured to reduce the amount of oxygen (O2) by mixing a part of the exhaust gas into the intake side to reduce the generation of nitrogen oxide Nox. However, if the EGR rate rises 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 the exhaust pipe 55 on the downstream side of the aftertreatment device 46, which will be described later, to the intake pipe 56 on the upstream side of the intake turbine 36 of the turbocharger TB. Further, an EGR cooler 57 is provided in the middle of the EGR circuit 44. The amount of exhaust gas returned into the cylinder 5 changes depending on how the EGR valve 43 is opened and closed.

The exhaust gas after passing through the exhaust turbine 45 passes through the aftertreatment device 46 and is discharged to the atmosphere from the muffler 50. 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 chamber, and the diesel particulate filter (DPF) is for collecting the granulated substance (PM). The EGR valve 43 and the throttle valve 47 are configured to be controlled by the ECU 100. The aftertreatment device 46 may be composed of only the diesel particulate filter (DPF) 46b. If the oxidation catalyst (DOC) is provided, the incombustible substance is burned, so that the exhaust gas becomes cleaner.

If the temperature of the exhaust gas of the DPF46b is low (low load) for a long time, PM is accumulated and there is a concern that the capacity of the DPF46b is lowered. Therefore, if a throttle valve 47 is provided on the lower side of the aftertreatment device 46 and the throttle valve 47 is throttled, the pressure in the DPF 46b is kept high, so that the temperature also rises. As a result, the DPF46b can be regenerated due to the influence of the high temperature. That is, when the high-temperature exhaust gas passes through the DPF46b, the PM existing in the DPF46b is burnt off and the DPF46b is regenerated.

In the DPF regeneration operation for regenerating the DPF 46b, both the EGR valve 43 and the throttle valve 47 are throttled. Then, the gas temperature in the DPF46b is raised in combination with the retard (retard) of the fuel injection timing so that the DPF46b enters the regeneration. As a result, after-injection of fuel (to raise the exhaust gas temperature) becomes unnecessary, and the number of after-injections can be reduced, so that fuel consumption can be suppressed, which is good for the environment.

As a condition for performing such a DPF regeneration operation, a pressure sensor 52 is provided on the upper side of the aftertreatment device 46, and a pressure sensor 53 is also provided on the lower side of the aftertreatment device 46, and the pressure difference is equal to or larger than a predetermined value. In this case, PM is accumulated in the DPF46b and becomes a resistance, so the DPF regeneration operation is performed. Further, instead of the pressure sensor 52, the pressure sensor 58 may be provided between the DOC 46a and the DPF 46b.

Further, if the state of entering the DPF regeneration operation continues for a long time, it becomes an overheated state and the DPF46b is damaged. Therefore, a temperature sensor 59 is provided on the lower side of the aftertreatment 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 returned.

In normal operation, the EGR valve 43 and the throttle valve 47 are controlled at the same time so that the EGR amount is appropriately controlled. In particular, by having the throttle valve 47, the gas temperature in the DPF 46b can be kept high.

The above-mentioned configuration eliminates the need for an intake throttle. That is, since the intake side pressure is high in an engine with a supercharger, it is necessary to provide an exhaust throttle valve or an intake throttle in order to secure the amount of EGR gas and control in conjunction with the EGR valve, but such a system is unnecessary. It becomes.

Further, since the exhaust gas downstream of the DPF46b is taken out, it becomes 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 reducing NOx becomes large.

As described above, in the DPF forced regeneration mode in which the DPF regeneration operation is performed, the exhaust throttle valve 47 is throttled, and the EGR valve 43 is fully closed by ON-OFF control. Therefore, since the exhaust gas is not reduced, NO increases, and this NO is converted to NO2 by the oxidation catalyst (DOC) 46a, and the regeneration of DPF46b is promoted.

Further, when the engine rotation shifts to low idle during the forced regeneration of the DPF46b, 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 value detected by the temperature sensor 59 rises above a predetermined value.

When the throttle valve 47 is throttled to perform forced regeneration of the DPF 46b, the engine speed is set to a low speed to increase the amount of oxygen supplied, and the exhaust gas flow velocity is reduced to facilitate the temperature rise. However, when the engine speed is changed to low idle or its vicinity during regeneration, soot burns rapidly due to an increase in the amount of oxygen supplied and a decrease in the flow velocity. As a result, the temperature may rise rapidly and the DPF46b may be damaged. Therefore, it is necessary to control the soot so that the maximum temperature does not exceed the allowable temperature.

Therefore, when the temperature sensor 59 exceeds a predetermined value, the engine speed is increased to the medium speed range. As a result, the flow velocity of the exhaust gas is increased, so that the maximum temperature is lowered and damage to the DPF46b can be prevented. Further, if the value of the predetermined value of the temperature sensor 59 is controlled in the vicinity of the limit value, the DPF 46b can be efficiently regenerated.

When raising the engine speed to the medium speed range, the engine speed may be increased to the maximum speed range and then decelerated to the medium speed range. As a result, the exhaust gas once flows at the maximum speed, so that preheating is performed. It becomes possible to prevent the DPF46b from being heated and exceeding the threshold temperature.

Further, during the forced regeneration of the DPF46b, 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 to shift to the medium speed range. The post injection is restarted at. As a result, a sudden rise in the exhaust gas temperature can be suppressed, so that damage to the DPF46b can be prevented.

When the differential pressure before and after DPF46b exceeds a predetermined value, the driver automatically regenerates the DPF46b by selecting the reproduction mode of the DPF46b with the selection switch 67 after the work, and automatically stops the engine after the reproduction of the DPF46b. Configure to do. The differential pressure before and after the DPF46b is monitored by the pressure sensors 58 and 53. When the differential pressure before and after the DPF46b immediately before the engine is stopped is equal to or higher than a predetermined value, a warning lamp or an alarm is used to notify the driver, and the driver operates a switch (not shown) for reproducing the DPF46b by himself / herself.
Then, even when the engine key is in the off position, by selecting the reproduction mode, the engine maintains the rotation in the idling state and executes the reproduction of the DPF46b. When the differential pressure around DPF46b becomes less than a predetermined value, the engine is automatically stopped.

As a result, the DPF46b can be automatically regenerated and the engine can be stopped even after the work is completed, so that the driver can perform other work away from the machine.
When the DPF46b is regenerated, as shown in FIG. 5, the intake air may be configured to be sent from the pipeline 61 to the upstream side of the DPF46b. That is, when the DPF46b is regenerated, the valve 60 may be opened to send the air on the intake side on the upstream side of the turbocharger TB having a large amount of oxygen to the upstream side of the DPF46b. As a result, the reproduction efficiency is improved.

Further, the temperature of the DPF 46b may be monitored by the temperature sensors 62 and 59, and the temperature rise during regeneration may be confirmed in three steps. First, the intake air is throttled (not shown), and the temperature rise is confirmed in the throttled state of the intake air. Next, the first post injection is performed to confirm the temperature rise. At this point, if the temperature before and after the DPF46b has not reached 250 degrees, a further temperature rise cannot be expected even if the second post injection is performed, so the reproduction is temporarily interrupted. Of course, if the temperature is 250 degrees or higher, the second post injection is performed to regenerate the DPF46b.

As shown in FIG. 5, an air-fuel ratio sensor 63 is provided on the downstream side of the DPF 46b. When the DPF46b is regenerated by performing post injection, if the fuel injection amount is too large, the fuel efficiency deteriorates, and if it is too small, the temperature does not rise and the regeneration cannot be performed. 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, the fuel consumption becomes appropriate and the DPF46b can be regenerated. Further, instead of the air-fuel ratio sensor 63, the pressure value in the intake manifold may be fed back.

In the case of a plurality of cylinders, the combustion of some cylinders may be stopped when the DPF46b is regenerated as described above. In this way, by stopping the combustion of some cylinders, even if the friction of the engine is the same, the load per cylinder may be increased to raise the exhaust temperature.

In the EGR valve 43, soot and HC adhere to the EGR valve 43 and are integrated with water such as dew 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 sticks, 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 during the after-run after the engine is stopped to remove the viscous liquid, the EGR valve 43 does not stick even if the engine cools.
Next, in an engine with an EGR circuit 44, a configuration for preventing an increase in PM will be described. An air amount sensor 70 is provided on the intake side, and the EGR valve 43 is closed for a short time (about 0.5 seconds) during operation. At this time, the value of the air amount sensor 70 increases, and the EGR rate when the EGR valve 43 is closed for a short time (about 0.5 seconds) during operation is obtained from this increase. The EGR valve 43 is controlled so as to obtain the obtained EGR rate.
Specifically, when the amount of air increases from the specified value, the EGR rate is too high, so the current EGR rate is controlled to be low. That is, the EGR valve 43 is configured to open after a predetermined time so that the opening degree is lower than the opening degree of the EGR valve 43 before closing the EGR valve 43. Then, the above-mentioned control is repeated until the amount of air does not increase more than the specified value.
As a result, it is possible to prevent an increase in soot (PM) due to an excessive EGR rate, and it is possible to prolong the regeneration cycle of DPF46b.
When the pressure of the pressure sensor 58 on the upstream side of the DPF 46b is lower than the specified value, the EGR valve 43 is fully opened.
When the pressure value of the pressure sensor 58 rises to a predetermined value, the opening degree of the EGR valve 43 is set to about 50%. In this way, a map showing the relationship between the pressure value of the pressure sensor 58 and the opening degree of the EGR valve 43 is registered in the ECU 100, and the opening degree of the EGR valve 43 is controlled according to the pressure. As a result, it is possible to prevent an excessive supply of EGR gas when PM is deposited in the DPF46b, and it is possible to reduce the generation of soot (PM). Therefore, the regeneration frequency of the DPF46b is reduced, the fuel consumption required for regeneration can be reduced, and the life of the DPF is extended.
Instead of the pressure, the PM accumulation amount may be estimated and calculated in the DFP46b to control the opening degree of the EGR valve 43. The amount of PM deposited in the DFP46b is estimated and calculated from the flow rate of the exhaust gas, the fuel flow rate, and the DPF temperature.
Further, a NOx sensor 74 may be provided on the downstream side of the DPF 46b, and the opening degree of the EGR valve 43 may be controlled by the value of the NOx sensor 74. Further, the opening degree of the EGR valve 43 may be controlled by detecting the pressure in the inlet manifold.
The above-mentioned EGR valve 43 is provided on the downstream side of the EGR cooler 57, but may be provided as the EGR valve 71 on the upstream side of the EGR cooler 57. In this case, the shutter valve 72 and the temperature sensor 73 are provided between the EGR valve 71 and the EGR cooler 57.
Excessive cooling in the EGR cooler 57 may result in the generation of incomplete combustion products due to condensed water. Therefore, when the temperature sensor 73 detects a low exhaust gas temperature (specified value), the shutter valve 72 is temporarily closed. Then, when the exhaust gas temperature becomes higher than the specified value by the temperature sensor 73, the shutter valve 72 is opened. This makes it possible to prevent the generation of incomplete combustion products due to condensed water.
The flowchart of FIG. 7 shows an abnormality detection method in highlands.
The altitude A is calculated by comparing the current boost pressure value (the exhaust pressure value is estimated from the DPF differential pressure value to correct the boost pressure value) and the reference boost pressure value in the lowland. In addition, the altitude B estimated from the atmospheric pressure value is calculated, and if the value of altitude A and the value of altitude B are different beyond the range of the error, the boost pressure sensor and the differential pressure sensor of DPF (upstream side sensor and downstream side sensor) The side sensor) and the atmospheric pressure sensor are judged to be abnormal, and the operator is notified. As a result, it is possible to prevent the occurrence of a fatal engine failure.
As described above, the DPF46b is automatically regenerated, but the boost pressure is increased during the automatic regeneration. As a result, the fuel injection amount increases and the exhaust temperature rises, so that the regeneration efficiency of the DPF is improved.
A case where a reproduction prohibition mode for prohibiting reproduction of DFP is installed will be described (FIG. 8). The time in the regeneration prohibition mode is counted, and when the ratio of the regeneration prohibition mode operation time to the total operation time reaches a predetermined value or more, the threshold value of the PM accumulation amount at which the DPF regeneration is started is lowered. As a configuration, the regeneration is performed from an earlier stage than usual.
By calculating the ratio of the regeneration prohibition mode operation time, it is possible to judge whether or not there is a high possibility that the regeneration is prohibited. Therefore, if the ratio is high, reduce the PM accumulation amount of the DPF that starts regeneration. Therefore, the possibility of performing regeneration increases. This makes it possible to reduce the possibility that the PM amount of the DPF will be in an over-deposited state due to the reproduction prohibition mode.

It can also be used for other work vehicles such as agricultural work machines such as tractors and combines.

E Diesel engine 43 EGR valve 44 EGR circuit 70 Air volume sensor

Claims (3)

In a tractor equipped with a diesel engine (E) having an EGR circuit (44) that returns a part of the exhaust gas to the intake side, the EGR circuit (44) is provided with an EGR valve (43) that adjusts the amount of exhaust gas reduction. An air amount sensor (70) is provided on the intake side of the engine, the EGR valve (43) is closed for a predetermined time during engine operation, and the detection value of the air amount sensor (70) is measured during this predetermined time. A tractor characterized in that it is configured to control the EGR valve (43) according to the changed amount of air when it changes. When the changed amount of air increases more than the specified value, the EGR valve (43) is opened for the predetermined time so that the opening degree is lower than the opening degree of the EGR valve (43) before closing the EGR valve (43). The tractor according to claim 1, wherein the tractor is configured to be opened later. The tractor according to claim 2, wherein the EGR valve (43) is configured to be closed for a predetermined time until the changed air amount does not increase more than a specified value.

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