JP7234830B2 - work vehicle - Google Patents

Description

The present invention relates to a work vehicle equipped with a diesel particulate filter, a hydraulic continuously variable transmission, and a loader .

During DPF regeneration, when deceleration is detected, the DPF is warmed by a heater (see, for example, Patent Document 1).

JP 2013-108433 A

Techniques such as those described above require a separate heater, which is costly.
SUMMARY OF THE INVENTION An object of the present invention is to provide a work vehicle equipped with a diesel engine that eliminates the problems described above.

The above object of the present invention is achieved by the following configuration.
That is, in the invention according to claim 1, in a work vehicle equipped with a diesel particulate filter (46b) that collects particulate matter (PM) in exhaust gas, a hydraulic continuously variable transmission, and a diesel engine, A loader (70) is attached to the front part of the machine body of the work vehicle, and when the height of the loader (70) is a predetermined height or more and the hydraulic pressure value of the hydraulic continuously variable transmission is a predetermined value or more, the diesel engine The working vehicle is characterized in that it is configured to regenerate the particulate filter (46b) .

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Since the present invention is configured as described above, there are more chances of regeneration in the loader mounting machine.

Overall configuration diagram of an accumulator fuel injection system Diagram showing relationship between engine speed and output torque depending on control mode left side view of tractor top view of tractor Schematic diagram of intake system and exhaust system Right side view of tractor with loader flowchart diagram time chart diagram flowchart diagram flowchart diagram time chart diagram Time chart diagram of injection pattern flowchart diagram Fuel system diagram Fuel system diagram

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

FIG. 1 is an overall configuration diagram of an accumulator fuel injection system. The accumulator fuel injection device is applied to, for example, a multi-cylinder diesel engine, but may be applied to a gasoline engine. The pressure accumulator fuel injection device includes a common rail 1 that accumulates high-pressure fuel corresponding to the injection pressure, a pressure sensor 2 attached to the common rail 1, and a fuel tank 3 that pumps up fuel from a fuel tank 3 and pressurizes the fuel to the common rail 1. A high-pressure pump 4, a fuel injection nozzle 6 for injecting the high-pressure fuel accumulated in the common rail 1 into the cylinder 5 of the engine E, a control device (ECU) for controlling the operation of the high-pressure pump 4 and the fuel injection nozzle 6, etc. consists of ECU is an abbreviation for engine control unit.
Thus, the common rail 1 injects fuel into each cylinder 5 of the engine E to bring the fuel supply to the 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 intake passage. He is stored.
The high-pressure fuel in the common rail 1 is supplied to the fuel injection nozzles 6 corresponding to the number of cylinders through each high-pressure fuel supply passage 9, and the fuel injection nozzles 6 of each cylinder are operated based on commands from the ECU 100, and the high-pressure fuel is supplied to the engine E. Excess fuel (return fuel) at each fuel injection nozzle 6 is led to a common return passage 10 through each return passage 10 and returned to the fuel tank 3 through this return passage 10.
A pressure control valve 11 is provided in the high pressure pump 4 to control the fuel pressure in the common rail 1 (common rail pressure). By adjusting the passage area of the return passage 10 for the surplus fuel to the common rail 1, it is possible to control the common rail pressure by adjusting the amount of fuel discharged to the common rail 1 side.
Specifically, a 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 is configured.
As shown in FIG. 2, the ECU 100 of the diesel engine E having the common rail 1 in the work vehicle (agricultural work machine) operates in three modes: a travel mode A, a normal work mode B, and a heavy work mode C in terms of the relationship between the rotation speed and the output torque. It is configured to have a control mode.
Driving mode A is a droop control in which the output fluctuates as the engine speed fluctuates. It is used when traveling without doing farm work. For example, when the running speed is decelerated or stopped by applying the brakes, the engine speed decreases as the running load increases, so the running speed can be decelerated or stopped safely.
The normal work mode B is isochronous control in which the engine speed is constant even if the load fluctuates and the output is changed according to the load. It is used for normal farm work. For example, in the case of a tractor, resistance is applied to the plowing blade when the land is hard during plowing work, and in the case of a combine harvester, output fluctuates and the number of rotations is maintained even when the load increases due to the large amount of harvested material during harvesting work. It is time.
Heavy work mode C is similar to normal work mode B. In addition to isochronous control that changes the output according to the load at a constant engine speed even if the load fluctuates, when the load approaches the limit, the speed is increased and the output is increased. This is a control with heavy load control that raises In particular, it is used when agricultural work is performed near the load limit. For example, when plowing with a tractor, even if a particularly hard field is encountered, the engine output increases beyond the normal limit, enabling efficient work without interrupting the work. .
These work modes A, B, and C are operated by operating a work mode selector switch that can switch between the work modes A, B, and C, or by operating a travel gear shift lever of an agricultural vehicle (tractor, combine, rice transplanter, etc.), Alternatively, it is configured to be switched by on/off operation of a work clutch (rotary in the case of a tractor, and reaping section and threshing section in the case of a combine harvester).
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, it is possible to shorten the ignition delay, reduce the knocking sound peculiar to the diesel engine E, and reduce noise. configuration.
This pilot injection was performed only once or twice before the main injection. By changing the state of , it is possible to reduce noise and suppress the generation of white smoke or black smoke due to incomplete combustion. Further, by performing a pilot injection in which a small amount of fuel is pulse-injected prior to the main injection, the amount of nitrogen oxides in the exhaust gas is reduced.

FIG. 3 shows a side view of a work vehicle (tractor) equipped with a diesel engine having the 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 has front wheels 12, 12 and rear wheels 13, 13 at the front and rear parts of the body. , 12 and rear wheels 13, 13.

A steering handle 16 is supported on a handle post 15 in the cabin 14 at the center of the aircraft body, and a seat 17 is provided behind it. Below the steering handle 16, a forward/backward lever 18 is provided for switching the forward/backward direction of the machine body. When the forward/reverse lever 18 is moved forward, the fuselage moves forward, and when it is moved backward, the fuselage moves backward.
An accelerator lever 25 for adjusting the engine speed is provided on the opposite side of the forward/reverse lever 18 across the handle post 15, and an accelerator for adjusting the engine speed is provided at the right corner of the step floor 19. A pedal 23 and left and right brake pedals 24L and 24R for applying brakes to the left and right rear wheels 13 and 13 are provided. A clutch pedal 20 is provided at the left corner of the step floor 19 .

A main gearshift lever 26 is located in front of the left side of the seat 17, an auxiliary gearshift lever 27 which can select any of low speed, medium speed, high speed and neutral position is located behind it, and a PTO gearshift lever 28 is located on 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 (such as a rotary) and an automatic plowing depth lever 30 for automatically setting the plowing depth of the field. A right raising switch 31 and a right lowering switch 32 are arranged, and an automatic leveling switch 33 and a backup switch 34 of the working machine 21 are further arranged after that. The backup switch 34 automatically raises the work implement 21 when the machine body moves backward. The working machine 21 is configured to be connected to the rear of the machine body by a link 22 . The tractor performs work such as plowing in a field by driving the working machine 21 to make the machine body travel. A hydraulic cylinder 21a moves the work machine 21 up and down.

FIG. 5 is a schematic diagram of the intake and exhaust into the cylinder 5 of the engine, which is an example of a four-cycle diesel engine. The air supercharged by the intake turbine 36 of the supercharger TB passes from the air cleaner 35 through the intake turbine 36 and the intercooler 37 and is sent from the intake manifold 38 into the cylinder 5 . 39 is an intake valve and 40 is a piston. A cam 48 opens and closes the intake and exhaust valves 39 and 41 via a rocker arm 49 .
Exhaust gas combusted in the cylinder 5 passes through an exhaust manifold 42 from an exhaust valve 41, and then is discharged by driving the supercharger TB with an exhaust turbine 45 of the supercharger TB.

This diesel engine has an EGR (exhaust gas recirculation device) circuit 44 for mixing part of the exhaust gas into the intake side. The EGR circuit mixes part of the exhaust gas into the intake side to reduce the amount of oxygen (O2), thereby reducing the generation of nitrogen oxides Nox. However, if the EGR rate rises too much, the amount of oxygen will decrease, resulting in incomplete combustion. Therefore, it is necessary to adjust the EGR rate according to the combustion state. This adjustment is performed by the EGR valve 43 . The EGR circuit 44 connects between an exhaust pipe 55 on the downstream side of an aftertreatment device 46 and an intake pipe 56 on the upstream side of the intake turbine 36 of the supercharger TB. Also, an EGR cooler 57 is provided in the middle of the EGR circuit 44 . The amount of exhaust gas returned to the cylinder 5 changes depending on how the EGR valve 43 is opened or closed.

After passing through the exhaust turbine 45, the exhaust gas passes through the aftertreatment device 46 and is discharged from the muffler 50 into 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 chamber, and the diesel particulate filter (DPF) collects particulate matter (PM). The EGR valve 43 and throttle valve 47 are configured to be controlled by the ECU 100 . The post-treatment device 46 may be composed only of a diesel particulate filter (DPF) 46b. If an oxidation catalyst (DOC) is provided, incombustible substances are burned, resulting in cleaner exhaust gas.

If the temperature of the exhaust gas is low (low load) continues for a long period of time, the DPF 46b is likely to be deteriorated due to accumulation of PM. Therefore, if a throttle valve 47 is provided on the downstream side of the post-processing device 46 and the throttle valve 47 is throttled, the pressure in the DPF 46b is kept high and the temperature also rises. Thereby, regeneration of the DPF 46b becomes possible due to the influence of the high temperature. That is, when high-temperature exhaust gas passes through the DPF 46b, the DPF 46b is regenerated by burning off the PM present in the DPF 46b.

As the DPF regeneration operation for regenerating the DPF 46b, both the EGR valve 43 and the throttle valve 47 are throttled. Together with retarding the fuel injection timing, the gas temperature in the DPF 46b is increased so that the DPF 46b enters regeneration. This eliminates the need for after-injection of fuel (to raise the temperature of the exhaust gas) and reduces the number of times of after-injection, which reduces fuel consumption and is good for the environment.

As a condition for performing such a DPF regeneration operation, a pressure sensor 52 is provided on the upstream side of the aftertreatment device 46, a pressure sensor 53 is provided on the downstream side of the aftertreatment device 46, and the pressure difference is equal to or greater than a predetermined value. When this happens, PM is accumulated in the DPF 46b and becomes a resistance, so the DPF regeneration operation is performed. Further, instead of the pressure sensor 52, a configuration may be adopted in which a pressure sensor 58 is provided between the DOC 46a and the DPF 46b.

Further, if the DPF regeneration operation continues for a long time, the DPF 46b will be damaged due to overheating. Therefore, a temperature sensor 59 is provided downstream of the aftertreatment device 46, and when the value of this temperature sensor 59 exceeds a predetermined value, the DPF regeneration operation is stopped and normal operation is resumed.

In normal operation, the EGR valve 43 and the throttle valve 47 are simultaneously controlled to appropriately control the EGR amount. In particular, by having the throttle valve 47, the gas temperature in the DPF 46b can be kept high.

By adopting the configuration as described above, an intake throttle becomes unnecessary. That is, since the intake side pressure is high in an engine with a supercharger, an exhaust throttle valve or an intake throttle is provided to secure the amount of EGR gas, and control in conjunction with the EGR valve is required, but such a system is unnecessary. becomes.

In addition, since the exhaust gas is taken out downstream of the DPF 46b, it is possible to prevent the performance from deteriorating due to dirt on the supercharger TB. Since the EGR gas is cooled by the EGR cooler 57, the effect of reducing NOx is increased.

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 reduction of the exhaust gas is not performed, NO increases, and this NO is converted to NO2 by the oxidation catalyst (DOC) 46a, thereby promoting regeneration of the DPF 46b.

Further, when the engine speed 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, the fact that the detected value by the temperature sensor 59 rises above a predetermined value may be added to the conditions.

When performing forced regeneration of the DPF 46b by throttling the throttle valve 47, the engine speed is lowered to increase the amount of oxygen supplied, and the flow velocity of the exhaust gas is reduced, thereby making it easier to raise the temperature. However, when the engine speed is changed to low idle or its vicinity during regeneration, soot is rapidly burned due to the increase in the amount of supplied oxygen and the decrease in flow velocity. As a result, the temperature may rise rapidly and damage the DPF 46b. Therefore, it is necessary to manage the soot so that the maximum temperature does not exceed the allowable temperature.

For this reason, when the temperature sensor 59 exceeds a predetermined value, the engine speed is increased to the middle speed range. As a result, the flow velocity of the exhaust gas increases, the maximum temperature decreases, and damage to the DPF 46b can be prevented. Also, by controlling the predetermined value of the temperature sensor 59 near the limit value, the DPF 46b can be efficiently regenerated.

When the engine speed is increased to the middle speed range, it may be configured so that it is once increased to the maximum speed range and then decelerated to the middle speed range. Thus, it is possible to prevent the DPF 46b from being heated and exceeding the threshold temperature.

Also, during forced regeneration of the DPF 46b, when the engine speed is shifted to low idle as described above, the post-injection is interrupted, the engine speed is increased to the maximum speed, and the stage is shifted to the middle speed range. , the post injection is restarted. As a result, a rapid rise in 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 exceeds a predetermined value, the driver selects the regeneration mode of the DPF 46b with the selection switch 67 after the work, and the DPF 46b is automatically regenerated, and after the DPF 46b regeneration, the engine is automatically stopped. configured to Pressure sensors 58 and 53 monitor the differential pressure across the DPF 46b. When the differential pressure across the DPF 46b immediately before the engine is stopped is greater than or equal to a predetermined value, a warning lamp or alarm is issued, and the driver himself/herself operates a switch (not shown) for regenerating the DPF 46b.
By selecting the regeneration mode even when the engine key is turned off, the engine keeps rotating in the idling state and the DPF 46b is regenerated. 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 DPF 46b can be automatically regenerated and the engine can be stopped even after the work is finished, so that the driver can leave the machine and perform other work.
When the DPF 46b is regenerated, as shown in FIG. 5, the air on the intake side may be sent from the conduit 61 to the upstream side of the DPF 46b. That is, when the DPF 46b is to be regenerated, the valve 60 may be opened to send air on the intake side upstream of the supercharger TB, which has a large amount of oxygen, to the upstream side of the DPF 46b. Thereby, the reproduction efficiency is improved.

Also, 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 this throttled state of the intake air. Next, the first post-injection is performed to check the temperature rise. At this point, if the temperature before and after the DPF 46b does not reach 250 degrees, the temperature cannot be expected to rise further even if the second post-injection is performed, so the regeneration is temporarily interrupted. Of course, if the angle 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. When the post-injection is performed to regenerate the DPF 46b, if the fuel injection amount is too large, the fuel consumption 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, appropriate fuel consumption can be achieved, and the DPF 46b can be regenerated. Also, instead of the air-fuel ratio sensor 63, the 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 may be stopped in some of the cylinders. In this way, by stopping combustion in 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 and are combined with moisture 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 solidifies, and when the engine is restarted, the EGR valve 43 may not operate. In order to solve such problems, 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 the after-run after the engine is stopped, the EGR valve 43 will not stick even when the engine cools down.

FIG. 6 shows a tractor with a loader 70 attached to the front of the fuselage. As conditions for automatic regeneration of the DPF 46b, an embodiment of a tractor equipped with a loader 70 and a hydraulic continuously variable transmission (HST) will be described.

As shown in the flowchart of FIG. 7 and the time chart of FIG. 8, when the height of the loader 70 reaches or exceeds a predetermined height, the automatic regeneration control mode of the DPF 46b is entered and automatic regeneration is performed. This enables efficient automatic regeneration by performing automatic regeneration periodically.

When the loader 70 is ascending, work is normally in progress and the exhaust gas temperature is high, so there is no problem with DPF regeneration. Therefore, when automatically regenerating the DPF, the exhaust gas temperature is also checked at the same time, and if the exhaust gas temperature is equal to or higher than a predetermined temperature, automatic regeneration is performed. This ensures that the DPF is regenerated.

Further, as shown in the flowchart of FIG. 9, in a tractor equipped with a hydraulic continuously variable transmission (HST), in addition to detecting that the loader 70 is above a predetermined height, the hydraulic pressure value of the HST is detected and the HST The DPF is automatically regenerated when the hydraulic pressure value of is equal to or higher than a predetermined value. When the hydraulic pressure value of the HST is high, it means that the exhaust gas temperature is inevitably high because it is under running load, and efficient regeneration is possible.

In the EGR cooler 57 described above, the cooling water of the engine is used to cool the exhaust gas. However, if the cooling is excessive, the temperature of the exhaust gas is rapidly decreased, resulting in condensed water from the exhaust gas being circulated to the intake side. Therefore, when the temperature of the cooling water is equal to or higher than a predetermined value (approximately 60 degrees), the EGR valve 43 is opened to activate the EGR function. A cooling water temperature sensor 71 for detecting the cooling water temperature is provided at a position immediately before the EGR cooler 57 . As a result, since the generation of condensed water is suppressed, the generation of sticking substances generated by mixing of the condensed water and soot is also suppressed, so that the EGR valve 43 is prevented from becoming difficult to move or sticking. can.

An inclination sensor 72 (Fig. 3) is provided on the machine body, and if the downhill running during forward movement continues for a predetermined time or longer, the injection pattern is changed and after-injection is performed so that the temperature in the exhaust pipe does not drop. . In this case, after-injection increases fuel consumption, so the actual exhaust temperature is measured by a temperature sensor 59 (FIG. 5), and after-injection is performed when the exhaust temperature is below a predetermined value.

Further, instead of the temperature sensor 59, a state in which no fuel is injected may continue for a predetermined time or longer. This is because the decrease in the exhaust gas temperature can be predicted to some extent by the non-injection state of fuel continuing for a predetermined time or longer. The fuel injection state is always grasped by the ECU 100 because the fuel injection nozzle 6 of each cylinder is operated based on a command from the ECU 100 . FIG. 10 shows a flow chart, FIG. 11 shows a time chart, and FIG. 12 shows an injection pattern.

If there is no fuel injection on a long downhill while moving forward, the temperature of the exhaust gas will drop and condensed water will form, which may adversely affect the sensors. , the generation of condensed water and its effects can be prevented.

Further, if a long downward slope during forward movement continues during the automatic regeneration of the DPF 46b, the automatic regeneration control will be interrupted due to the decrease in the exhaust gas temperature.

Therefore, in such a case, the exhaust brake 73 (FIG. 5) is configured to operate. FIG. 13 shows a flow chart of exhaust brake operation. The exhaust brake 73 is a resistance plate 73a provided in the exhaust pipe 55, and the resistance plate 73a narrows the portion through which the exhaust gas flows in the exhaust pipe 55 when the accelerator pedal is stopped. As a result, the release of the exhaust gas into the atmosphere becomes slow, causing resistance to running, resulting in an increase in the engine load and a decrease in exhaust gas temperature.

Next, FIGS. 14 and 15 will be described.

The upstream and downstream sides of the fuel filter 74 are connected by a first bypass circuit 75, and a check valve 76 is provided in this circuit.

14, the negative pressure by the fuel filter 74 is small, so the check valve does not open, and the fuel that has passed through the fuel filter 74 from the fuel tank 3 is supplied to the engine E. As shown in FIG.
When the check valve shown in FIG. 15 is actuated, the wax component in the fuel (light oil) precipitates, resulting in poor fluidity and increased pressure loss due to the fuel filter 74, resulting in insufficient fuel supply and poor engine startability. Getting worse.
Therefore, as the pressure loss due to the fuel filter 74 increases, the check valve 76 of the first bypass circuit 75 opens, fuel is smoothly supplied to the engine E, and deterioration of startability due to insufficient fuel supply can be prevented. .
A return pipe 79 from the engine E and the upstream side of the fuel filter 74 are connected by a second bypass circuit 77, and a check valve 78 is provided in this circuit. Since the temperature of the fuel returned from the engine E has risen, part of the fuel whose temperature has risen is supplied into the fuel filter 74 to dissolve the light oil wax component in the fuel filter 74 .

PM Particulate Matter 46b Diesel Particulate Filter (DPF)
59 temperature sensor 72 tilt sensor

Claims (1)

In a work vehicle equipped with a diesel particulate filter (46b) that collects particulate matter (PM) in exhaust gas, a hydraulic continuously variable transmission, and a diesel engine, a loader (70 ), and the diesel particulate filter (46b) is regenerated when the height of the loader (70) is a predetermined height or more and the hydraulic pressure value of the hydraulic continuously variable transmission is a predetermined value or more. A working vehicle, characterized in that it is configured to

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