JP2010053795A - Diesel engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently regenerate a diesel particulate filter in a postprocessing device arranged in an exhaust passage of exhaust gas. <P>SOLUTION: This diesel engine includes: a supercharger TB; and an exhaust gas postprocessing device 46 having the diesel particulate filter 46b for collecting particulate matter PM in at least the exhaust gas, on the downstream side of an exhaust turbine 45 of the supercharger TB, and is constituted so as to regenerate the diesel particulate filter 46b by throttling a throttle valve 47 on the downstream side of the postprocessing device 46 when detecting that differential pressure between pressure sensors 52 and 53 arranged on the upstream side and the downstream side of the diesel particulate filter 46b is pressure of a predetermined value or more. The engine is also provided with an engine control unit 100 for making control so as to reduce an engine speed up to the vicinity of a low idle speed after a predetermined time, and to open the throttle valve 47. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a diesel engine equipped with an aftertreatment device for treating exhaust gas.

In regenerating the diesel particulate filter (DPF), the pressure before and after the DPF is detected, and when the pressure exceeds a predetermined value, the throttle valve is throttled to increase the temperature of the DPF to regenerate the DPF. However, a control technique for lowering the engine speed to near the low idle speed at the same time is not disclosed (for example, see Patent Document 1).
JP 2005-90359 A

    In the technology as described above, if the engine speed remains high even if the throttle valve is throttled, it takes time for the DPF temperature to rise to a recyclable temperature because the exhaust gas flow rate is fast. Especially in the cold winter season, the temperature may not rise to a recyclable temperature.

  The subject of this invention is providing the diesel engine which eliminates the above malfunctions.

The above object of the present invention is achieved by the following configuration.
That is, in the invention described in claim 1, diesel that traps at least the particulate matter (PM) in the exhaust gas on the lower side of the supercharger (TB) and the exhaust turbine (45) of the supercharger (TB). In a diesel engine having an exhaust gas aftertreatment device (46) having a particulate filter (46b), pressure sensors (52), (53) provided on the upstream side and the downstream side of the diesel particulate filter (46b). When a pressure greater than a predetermined value is detected, the throttle valve (47) on the downstream side of the post-processing device (46) is throttled to regenerate the diesel particulate filter (46b). The engine control unit (10 ) Is obtained by a diesel engine, characterized in that the provided.

    The action of claim 1 is that the burned exhaust gas exits from the cylinder, but the diesel particulate filter (46b) constituting a part of the aftertreatment device (46) removes the particulate matter (PM) in the exhaust gas. Collect. However, if the low load state continues for a long time, the granulated material (PM) becomes accumulated and clogs. The clogged state is measured by the pressure sensors (52) and (53), and when the pressure difference exceeds a predetermined value, the throttle valve 47 is throttled. Then, the exhaust gas temperature in the diesel particulate filter (46b) rises due to the resistance of the diesel particulate filter (46b).

    Further, after a predetermined time, the engine speed is lowered to near the low idle speed and the throttle valve (47) is opened. As a result, the flow rate of the exhaust gas decreases and the exhaust gas temperature further increases. However, in order to increase the temperature appropriately, the throttle valve (47) is opened. In such a series of flows, (PM) is burned out by the high-temperature exhaust gas, and the diesel particulate filter (46b) is regenerated.

  In the invention according to claim 2, when the values of the temperature sensors (58), (59) for detecting the temperature of the diesel particulate filter (46b) exceed a predetermined value, the engine speed is reduced to the middle speed range. The diesel engine according to claim 1, wherein the diesel engine is configured to be raised.

  The effect of claim 2 is that in addition to the effect of claim 1, when the values of the temperature sensors (58) and (59) for detecting the temperature of the diesel particulate filter (46b) exceed a predetermined value, the engine speed is reduced. Increase to speed range. As a result, the exhaust gas flow rate is increased, the temperature is lowered, and a sudden temperature increase of the diesel particulate filter (46b) can be prevented.

Since the present invention is configured as described above, in the invention according to claim 1, the regeneration time of the diesel particulate filter (46b) can be shortened.
In the second aspect of the invention, in addition to the effect of the first aspect, the rapid temperature rise of the diesel particulate filter (46b) can be prevented, so that the diesel particulate filter (46b) can be prevented from being damaged. .

The best mode for carrying out the present invention will be described.
FIG. 1 is an overall configuration diagram of a pressure accumulation type fuel injection device. The accumulator fuel injection device is applied to, for example, a multi-cylinder diesel engine, but may be a gasoline engine. The accumulator fuel injection device pressurizes the common rail 1 accumulating high-pressure fuel corresponding to the injection pressure, the pressure sensor 2 attached to the common rail 1, and the fuel pumped up from the fuel tank 3, and pumps the fuel to the common rail 1. A high-pressure pump 4, a fuel injection nozzle 6 for injecting high-pressure fuel accumulated in the common rail 1 into the cylinder 5 of the engine E, a control device (ECU) for controlling the operation of the high-pressure pump 4 and the fuel injection nozzle 6 Consists of ECU is an abbreviation for engine control unit.

Thus, the common rail 1 injects fuel to each cylinder 5 of the engine E, and makes the fuel supply a required pressure.
The fuel in the fuel tank 3 is sucked into the high-pressure pump 4 driven by the engine E through the fuel filter 7 through the suction passage, and the high-pressure fuel pressurized by the high-pressure pump 4 is guided to the common rail 1 through the discharge passage 8. Stored.

    The high-pressure fuel in the common rail 1 is supplied to the fuel injection nozzles 6 for the number of cylinders through the high-pressure fuel supply passages 9, and the fuel injection nozzles 6 are operated to the respective cylinders based on commands from the ECU 100. The surplus fuel (return fuel) from each fuel injection nozzle 6 is guided to a common return passage 10 by each return passage 10 and returned to the fuel tank 3 by this return passage 10.

    In addition, a pressure control valve 11 is provided in the high-pressure pump 4 to control the fuel pressure (common rail pressure) in the common rail 1. The pressure control valve 11 is connected to the fuel tank 3 from the high-pressure pump 4 by a duty signal from the ECU 100. The flow area of the return passage 10 for surplus fuel to the fuel is adjusted, whereby the amount of fuel discharged to the common rail 1 side can be adjusted to control the common rail pressure.

    Specifically, the target common rail pressure is set according to the engine operating conditions, and the common rail pressure is feedback-controlled through the pressure control valve 11 so that the common rail pressure detected by the rail pressure sensor 2 matches the target common rail pressure. It is configured.

    As shown in FIG. 2, the ECU 100 of the diesel engine E having the common rail 1 in the work vehicle (agricultural work machine) has three types of modes, a travel mode A, a normal work mode B, and a heavy work mode C in relation to the rotational speed and the output torque. The configuration has a control mode.

    The traveling mode A is droop control in which the output also varies with the variation of the engine speed. It is used when traveling without farming. For example, when the traveling speed is reduced or stopped by applying a brake, the engine speed decreases with an increase in the traveling load, so that the traveling speed can be safely reduced or stopped.

    The normal work mode B is isochronous control in which the engine speed is constant and the output is changed according to the load even when the load varies. It is used for normal farm work. For example, if it is a tractor, it is when the cultivated land is hard during plowing work and resistance is applied to the plowing blade. Is the time.

    In the heavy work mode C, in addition to the isochronous control in which the engine speed is constant and the output is changed according to the load even when the load fluctuates in the same manner as the normal work mode B, the engine speed is increased when the load is close to the limit. This is a control with heavy load control that increases In particular, it is used when farming near the load limit. For example, when plowing with a tractor, the engine output increases beyond the normal limit even when encountering hard cultivated land, so work can be performed efficiently without interruption. .

    These work modes A, B, and C are operations of a work mode changeover switch that can switch between the work modes A, B, and C, or a shift operation of a traveling speed change lever of a farm vehicle (tractor, combine, rice transplanter, etc.) Alternatively, it is configured to be switched by an on / off operation or the like of a work clutch (rotary if it is a tractor, and mowing part or threshing part if it is a combine).

    In diesel engine E, pilot injection that injects a small amount of fuel in a pulse manner prior to main injection makes it possible to shorten the ignition delay, reduce the knocking noise peculiar to diesel engine E, and reduce noise It has a simple structure.

    This pilot injection is performed only once or twice before the main injection. By using the accumulator fuel injection device of the common rail 1, pilot injection is performed according to the situation of the engine E. Thus, it becomes possible to reduce the noise and the generation of white smoke or black smoke due to incomplete combustion. Further, by performing pilot injection in which a small amount of fuel is pulse-injected prior to main injection, the amount of nitrogen oxides in the exhaust gas is reduced.

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

  The tractor includes front wheels 12 and 12 and rear wheels 13 and 13 at the front and rear portions of the fuselage, and the rotational power of the engine E mounted on the front portion of the fuselage is appropriately decelerated by a transmission in the transmission case T so that the front wheels 12 , 12 and the rear wheels 13, 13.

  A steering handle 16 is supported on the handle post 15 in the cabin 14 at the center of the body, and a seat 17 is provided behind the steering handle 16. A forward / reverse lever 18 is provided below the steering handle 16 to switch the advancing direction of the aircraft to the front / rear direction. When the forward / reverse lever 18 is moved to the front side, the aircraft moves forward, and when it is moved backward, the aircraft moves backward.

    An accelerator lever 25 for adjusting the engine speed is provided on the opposite side of the forward / reverse lever 18 with the handle post 15 in between, and an accelerator for similarly adjusting the engine speed is provided at the right corner of the step floor 19. The pedal 23 and left and right brake pedals 24L, 24R for operating the left and right rear wheels 13, 13 are provided. A clutch pedal 20 is provided at the left corner of the step floor 19.

  The main transmission lever 26 is located at the left front portion of the seat 17, the auxiliary transmission lever 27 capable of selecting any of the low speed, medium speed, high speed and neutral positions is located behind the main transmission lever 26, and further on the right side thereof is the PTO transmission lever 28. Is provided. Further, on the right side of the seat 17, a position lever 29 for setting the height of the working machine 21 (rotary or the like), an automatic tilling lever 30 for automatically setting the tilling depth of the field, and the working machine 21 after these levers. The right-up switch 31 and the right-down switch 32 are arranged, and then the automatic horizontal switch 33 and the backup switch 34 of the work machine 21 are arranged. The backup switch 34 automatically raises the work machine 21 when the machine moves backward. The work machine 21 has a configuration in which a link 22 is connected to the rear of the machine body. The tractor performs work such as tillage in the field by driving the work machine 21 and running the machine body. 21a is a hydraulic cylinder which raises and lowers the working machine 21.

  FIG. 5 is a schematic diagram of intake and exhaust into the cylinder 5 of the engine, which is an embodiment of a four-cycle diesel engine. The air supercharged by the intake turbine 36 of the supercharger TB passes through the intake turbine 36 and the intercooler 37 from the air cleaner 35 and is sent from the intake manifold 38 into the cylinder 5. Reference numeral 39 is an intake valve, and 40 is a piston. A cam 48 opens and closes the intake and exhaust valves 39 and 41 via a rocker arm 49.

The exhaust gas combusted in the cylinder 5 passes through the exhaust manifold 42 from the exhaust valve 41 and is then discharged by driving the supercharger TB with the exhaust turbine 45 of the supercharger TB.
This diesel engine has an EGR (exhaust gas recirculation device) circuit 44 for mixing a part of the exhaust gas into the intake side. In the EGR circuit, a part of the exhaust gas is mixed into the intake side to reduce the amount of oxygen (O2), thereby reducing the generation of nitrogen oxide Nox. However, if the EGR rate increases too much, the amount of oxygen decreases and incomplete combustion occurs. Therefore, it is necessary to adjust the EGR rate according to the combustion state. This adjustment is performed by the EGR valve 43. The EGR circuit 44 connects between an exhaust pipe 55 on the downstream side of a post-processing device 46 described later and an intake pipe 56 on the upstream side of the intake turbine 36 of the supercharger TB. In addition, an EGR cooler 57 is provided in the middle of the EGR circuit 44. The amount of exhaust gas reduced into the cylinder 5 varies depending on how the EGR valve 43 is opened and closed.

  The exhaust gas that has passed through the exhaust turbine 45 passes through the aftertreatment device 46 and is discharged from the muffler 50 into the atmosphere. The post-processing device 46 includes an oxidation catalyst (DOC) 46a and a diesel particulate filter (DPF) 46b.

    The oxidation catalyst (DOC) burns the incombustible material chamber, and the diesel particulate filter (DPF) is for collecting the granulated material chamber (PM). The EGR valve 43 and the throttle valve 47 are controlled by the ECU 100. The post-processing device 46 may be composed of only a diesel particulate filter (DPF) 46b. If an oxidation catalyst (DOC) is provided, the non-combustible material burns, resulting in cleaner exhaust gas.

  When the state of the exhaust gas is low (low load) continues for a long time, the DPF 46b has a concern that PM will accumulate and the capacity may be reduced. Therefore, a throttle valve 47 is provided on the lower side of the post-processing device 46, and when the throttle valve 47 is throttled, the pressure in the DPF 46b is kept high, so the temperature also rises. This makes it possible to regenerate the DPF 46b due to the influence of a high temperature. That is, when exhaust gas having a high temperature passes through the DPF 46b, the DPF 46b is regenerated by burning off the PM present in the DPF 46b.

  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 DPF 46b is raised together with the retard (retard) of the fuel injection timing so that the DPF 46b starts to be regenerated. This eliminates the need for fuel after-injection (in order to increase the exhaust gas temperature) or reduces the number of after-injections, so that the amount of fuel consumption can be suppressed and the environment is good.

  As a condition for performing such a DPF regeneration operation, the pressure sensor 52 is provided on the upper side of the post-processing device 46, the pressure sensor 53 is provided on the lower side of the post-processing device 46, and this pressure difference is a predetermined value or more. Then, since PM accumulates in the DPF 46b and becomes a resistance, the DPF regeneration operation is performed.

  Further, if the state in which the DPF regeneration operation is started continues for a long time, the DPF 46b is damaged due to an overheating state. Therefore, a temperature sensor 59 is provided on the lower side of the post-processing device 46, and when the value of the temperature sensor 59 exceeds a predetermined value, the DPF regeneration operation is stopped and the normal operation is resumed.

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

  With the configuration as described above, an intake throttle is not required. In other words, since the intake side pressure is high in an engine with a supercharger, an exhaust throttle valve or an intake throttle is required to secure the amount of EGR gas, and control in conjunction with the EGR valve is required, but such a system is unnecessary. It becomes.

  Further, since the exhaust gas downstream of the DPF 46b is taken out, it is possible to prevent the performance deterioration caused by the dirt of the supercharger TB. And since EGR gas is cooled by the EGR cooler 57, an effect becomes large with respect to NOx reduction.

  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 throttled and the EGR valve 43 is fully closed by 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.

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

  When the DPF 46b is forcibly regenerated by restricting the throttle valve 47, the engine speed is reduced to increase the supply oxygen amount, and the exhaust gas flow rate is decreased to increase the temperature easily. However, when the engine speed is changed to low idle or in the vicinity thereof during regeneration, soot burns rapidly due to an increase in the amount of supplied oxygen and a decrease in the flow velocity. As a result, the temperature may rise rapidly and the DPF 46b may be damaged. Therefore, it is necessary to manage the soot 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 a medium speed range. As a result, the flow rate of the exhaust gas is increased, so that the maximum temperature is lowered and damage to the DPF 46b can be prevented. Further, when the predetermined value of the temperature sensor 59 is controlled in the vicinity of the limit value, the DPF 46b can be efficiently regenerated.

  In order to increase the engine speed to the middle speed range, it may be configured to once increase to the maximum speed and then decelerate to the middle speed range, so that the exhaust gas once flows at the maximum speed. For example, it is possible to prevent the DPF 46b from being heated and exceeding the threshold temperature.

  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. Then, post-injection is resumed. Thereby, since the rapid rise in the exhaust gas temperature can be suppressed, damage to the DPF 46b can be prevented.

  As shown in FIG. 6, the plate 61 is provided at the inlet portion of the oxidation catalyst 46 a of the post-processing device 46, and the fan 60 is rotatably provided at the center portion of the plate 61. As a result, the fan 60 is rotated by the flow of the exhaust gas, so that the exhaust gas is diffused and the exhaust gas concentration becomes uniform, and abnormal combustion during regeneration due to the uneven collection of PM can be prevented.

  The fan 60a in FIG. 7 is an embodiment in which the fan itself is elongated in the longitudinal direction in which the exhaust gas flows. In FIG. 8, a conical plate 62 is provided at the inlet of the oxidation catalyst 46a, and a plurality of holes are provided. As a result, the flow of exhaust gas becomes uniform, and abnormal combustion during regeneration due to uneven collection of PM can be prevented. Further, as shown in FIG. 9, the shape of the entrance portion of the oxidation catalyst 46a may be conical. Further, as shown in FIG. 10, a plate 63 may be provided on the upstream side of the oxidation catalyst 46a, and when the hole 64 is provided in the plate 63, a larger diameter hole may be formed toward the outer peripheral portion.

  As a method for operating the regeneration of the DPF 46b, a configuration as shown in FIG. 11 may be used. That is, a position for forcibly regenerating the DPF 46b is provided in front of the engine stop position of the engine start key 65. When the forced regeneration position is set, the DPF 46b is automatically regenerated, and the engine is automatically stopped after the regeneration. As described above, the forced regeneration is determined by notifying the driver with a monitor or the like when the pressure difference between the pressure sensors 52 and 53 exceeds a predetermined value. When there is no forced regeneration position, the forced regeneration is configured at the engine stop position. In this case, fuel is wasted if forced regeneration is always performed. Therefore, a switch for determining whether or not forced regeneration is possible is provided. When this switch is on, the DPF 46b is regenerated at the conventional engine stop position.

  FIG. 12 shows a coping method when the soot in the DPF 46b is ignited and abnormally burned. A digestive tract 69 is connected in the aftertreatment device 46, and the cooling water of the reserve tank 67 of the radiator 66 flows through the digestive tract 69. When the temperature sensors 58 and 59 detect that abnormal combustion has occurred in the post-processing device 46, the digestion valve 68 is opened and digested. Thereby, it becomes possible to prevent the abnormal combustion in the post-processing device 46 from spreading to the entire body.

  FIG. 13 shows a configuration in which the temperature of the exhaust gas flowing through the tail pipe 70 is lowered. Since the DPF 46b exhausts a considerably high temperature exhaust gas, there is a risk of a fire if a substance with high ignitability adheres to the tail pipe 70. Therefore, the temperature of the tail pipe 70 itself is lowered by connecting the pipe 71 to the tail pipe 70 and sending air in the atmosphere from the pipe 71 into the tail pipe 70. In particular, in an agricultural machine, if dust or the like is entangled or accumulated on the tail pipe 70, it is ignited and dangerous, but such a problem can be prevented.

  As shown in FIG. 14, a part of the air cooled by the intercooler 37 is sent to the upstream side or downstream side of the post-processing device 46. That is, the cooling air is taken from the pipe line 72 and connected to the upstream side of the post-processing device 46 through the valve 74 and the pipe line 74. In addition, the valve 75 is connected to the downstream side of the post-processing device 46 via the pipe 73.

The valve 75 is closed except during regeneration of the DPF 46b. However, it may be opened when the exhaust temperature rise is detected to lower the exhaust temperature.
At the time of regeneration of the DPF 46b, if the values of the temperature sensors 58 and 59 described above are normal values, the valve 75 is opened so that the cooling air is sent to the downstream side of the post-processing device 46. Thereby, the temperature rise of a muffler etc. can be suppressed now. Further, when the values of the temperature sensors 58 and 59 become abnormally high during the regeneration of the DPF 46b, the valve 75 is opened so that the cooling air is sent to the upstream side of the post-processing device 46. Thereby, it becomes possible to suppress a rapid temperature rise of the DPF 46b, and to prevent the DPF 46b from being damaged.

    It can be used for farm vehicles such as tractors and combiners as well as general vehicles.

Overall configuration diagram of accumulator fuel injection system Diagram showing the relationship between engine speed and output torque in control mode Left side view of tractor Top view of tractor Schematic diagram of intake and exhaust systems Side view of post-processing device and partial front view of the interior Side view of aftertreatment device Side view of aftertreatment device Side view of aftertreatment device Side view of aftertreatment device Plan view of engine key Schematic diagram of post-processing equipment Schematic diagram of post-processing equipment Schematic diagram of intake and exhaust systems

Explanation of symbols

TB Supercharger PM Granulated material 46 Exhaust gas aftertreatment device 46b Diesel particulate filter (DPF)
47 Throttle valve 52, 53 Pressure sensor 58, 59 Temperature sensor 100 Engine control unit (ECU)

Claims (2)

  Exhaust gas having a supercharger (TB) and a diesel particulate filter (46b) that collects at least particulate matter (PM) in the exhaust gas on the lower side of the exhaust turbine (45) of the supercharger (TB) In a diesel engine equipped with an aftertreatment device (46), a pressure difference between pressure sensors (52) and (53) provided on the upstream side and the downstream side of the diesel particulate filter (46b) exceeds a predetermined value. When detected, the throttle valve (47) on the downstream side of the post-processing device (46) is throttled to regenerate the diesel particulate filter (46b), and after a predetermined time, the engine speed is reduced to near the low idle speed. An engine control unit (100) for performing control to open the throttle valve (47) is provided. Le engine.   When the value of the temperature sensors (58) and (59) for detecting the temperature of the diesel particulate filter (46b) exceeds a predetermined value, the engine speed is increased to a medium speed range. The diesel engine according to claim 1, wherein

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