JP2014190287A - Exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control device that does not cause an operational failure in an engine even if regeneration of a particulate filter is conducted during extraction of the power of a diesel engine for driving a hydraulic pump.SOLUTION: An exhaust emission control device 9 installed in a crane truck 1 includes: an exhaust pipe 4 for leading an exhaust gas 5 from an engine 2 to the outside; a particulate filter 7; a fuel injection device 14 that regenerates the particulate filter 7 by adding a fuel when a deposition amount of particulate exceeds a predetermined amount; and an exhaust brake 17 that raises an exhaust temperature by reducing a flow rate of the exhaust in the exhaust pipe 4. When the regeneration of the particulate filter 7 is conducted by the fuel injection device 14 while the hydraulic pump 22 is used, in the exhaust brake 17, a valve 16 is closed to reduce the flow rate of the exhaust in the exhaust pipe 4 so that the regeneration of the particulate filter 7 is supported. When the hydraulic pressure of the hydraulic pump 22 becomes higher than a first threshold, the valve 16 is opened.

Description

  The present invention relates to an engine that generates power, a power take-off that extracts engine power for driving a hydraulic pump, an exhaust pipe that guides exhaust gas from the engine to the outside, and exhaust gas flow by narrowing the exhaust flow rate of the exhaust pipe. The present invention relates to an exhaust purification device that is mounted on a specially equipped vehicle including an exhaust throttle means for raising the temperature.

  Particulate matter (particulate matter) discharged from a diesel engine is mainly composed of soot made of carbonaceous matter and SOF content (Soluble Organic Fraction) made of high-boiling hydrocarbon components. The composition contains a small amount of sulfate (mist-like sulfuric acid component). Conventionally, as a measure for reducing this kind of particulates, a particulate filter is provided in the middle of an exhaust pipe through which exhaust gas flows.

  This type of particulate filter has a porous honeycomb structure made of a ceramic such as cordierite, and the inlets of the flow paths partitioned in a lattice pattern are alternately sealed, and the inlets are not sealed. About the flow path, the exit is sealed, and only the exhaust gas which permeate | transmitted the porous thin wall which divides each flow path is discharged | emitted downstream.

  Then, the particulates in the exhaust gas are collected and deposited on the inner surface of the porous thin wall, so that the particulates are appropriately burned and removed before the exhaust resistance increases due to clogging. It is necessary to regenerate. However, since there are few opportunities to obtain exhaust temperatures that are high enough for particulates to self-combust under normal diesel engine operating conditions, for example, an appropriate amount of rare earth elements such as cerium on alumina-supported platinum A catalyst regeneration type particulate filter in which an oxidation catalyst formed by adding a catalyst is integrally supported is employed.

  That is, if such a catalyst regeneration type particulate filter is employed, the oxidation reaction of the collected particulates is promoted to lower the ignition temperature, and the particulates can be burned and removed even at an exhaust temperature lower than the conventional one. It becomes possible.

  However, even when such a catalyst regeneration type particulate filter is adopted, the trapped amount exceeds the particulate processing amount in the operation region where the exhaust temperature is low, and thus such a low exhaust gas. If the operating condition at temperature continues, there is a risk that the particulate filter will not regenerate well and the particulate filter will fall into an over-collected state, and at the stage where the accumulated amount of particulates has increased, it will be upstream of the particulate filter. It is considered to forcibly regenerate the particulate filter by adding fuel to the exhaust gas on the side.

  In other words, if fuel is added upstream from the particulate filter, the added fuel undergoes an oxidation reaction on the oxidation catalyst of the particulate filter, and the heat of the reaction raises the catalyst bed temperature to burn out the particulate. Thus, regeneration of the particulate filter is achieved.

  In addition, the exhaust brake is operated and the exhaust flow rate flowing through the exhaust pipe is throttled by the valve, thereby increasing the pumping loss of the engine and increasing the fuel injected to maintain the engine rotation. As the exhaust temperature rises and the exhaust resistance increases, the intake of the relatively low temperature is difficult to flow into the cylinder, and the residual amount of the relatively high temperature exhaust gas increases. The exhaust temperature is further increased by the air in the cylinder containing a large amount of gas being compressed in the next compression stroke and reaching the explosion stroke.

  An invention for regenerating this type of particulate filter is disclosed, for example, in Patent Document 1 below.

Japanese Patent Application No. 2004-150415

  However, when the particulate filter is automatically regenerated when the amount of accumulated particulates exceeds a predetermined amount, a problem occurs depending on the type of vehicle. That is, it is a specially equipped vehicle such as a crane vehicle having a power take-off for extracting the power of the diesel engine. The extracted power is used for the operation of a hydraulic pump that operates the crane.

  Since crane trucks operate a hydraulic pump by the power of the diesel engine, when regeneration is automatically performed when the hydraulic pump is used, the fuel injection amount is reduced in order for the diesel engine to maintain its operating speed. Increase. However, there is a risk that misfire and engine stop may occur because sufficient air cannot be taken in to burn fuel by operating the exhaust brake.

  The present invention relates to an exhaust emission control device for a specially equipped vehicle in which regeneration of a particulate filter is automatically performed when the amount of accumulated particulate matter exceeds a predetermined amount, and the power of a diesel engine is being taken out for driving a hydraulic pump. Another object of the present invention is to provide an exhaust emission control device that does not cause a problem in engine operation even when regeneration is performed.

The present invention relates to an exhaust emission control device mounted on a specially equipped vehicle including an engine that generates power and a power take-off that extracts the power of the engine for driving a hydraulic pump.
An exhaust pipe that guides exhaust gas from the engine to the outside, a particulate filter that is disposed in the exhaust pipe and collects particulates in the exhaust gas, and automatically when the accumulated amount of the particulates exceeds a predetermined amount Fuel addition means for regenerating the particulate filter by adding fuel to the exhaust gas, and exhaust throttle means for raising the exhaust temperature by narrowing the exhaust flow rate of the exhaust pipe. The exhaust throttle means throttles the exhaust flow rate of the exhaust pipe to assist regeneration of the particulate filter when the fuel addition means is executed when the hydraulic pump is used, and the hydraulic pressure of the hydraulic pump is reduced. The exhaust gas flow rate narrowing is released when it becomes higher than the first threshold value.

  In the exhaust purification apparatus, it is preferable that the exhaust throttle means throttles the exhaust flow rate when the hydraulic pump is in use and the hydraulic pressure of the hydraulic pump is equal to or lower than a second threshold value that is lower than the first threshold value.

  ADVANTAGE OF THE INVENTION According to this invention, even if regeneration of a particulate filter is performed automatically while taking out the motive power of a diesel engine for the drive of a hydraulic pump, it can prevent that a malfunction arises in operation | movement of an engine. .

It is the schematic which shows an example of the specially equipped vehicle of this invention. It is a flowchart figure which shows the process of a control apparatus.

  Hereinafter, the form for implementing this invention is demonstrated with reference to FIG. FIG. 1 is a schematic view showing an example of a specially equipped vehicle on which the exhaust emission control device of the present invention is mounted. The specially equipped vehicle shown in FIG.

  The crane vehicle 1 flows the exhaust gas 5 from the diesel engine 2 (engine) through the exhaust manifold 3 to the exhaust pipe 4 and discharges it to the outside. Inside the muffler 6 of the exhaust pipe 4 is accommodated a catalyst regeneration type particulate filter 7 that integrally carries an oxidation catalyst. The particulate filter 7 is held by the filter case 8. The filter case 8 forms an outer cylinder of the muffler 6. The exhaust purification device 9 includes an exhaust pipe 4, a muffler 6 having a particulate filter 7 and a filter case 8, and an exhaust brake 17 having a valve 16.

  The particulate filter 7 has a porous honeycomb structure made of ceramic, and the inlets of the respective flow paths partitioned in a lattice pattern are alternately sealed. The outlet is sealed, and only the exhaust gas 5 that has permeated through the porous thin wall partitioning each flow path is discharged downstream.

  A temperature sensor (temperature detection means) 10 that measures the temperature of the exhaust gas 5 introduced into the particulate filter 7 as a substitute value of the catalyst bed temperature is disposed at the inlet portion (inlet side) of the filter case 8. . The detection signal 10 a of the temperature sensor 10 is input to the control device 11.

  The control device 11 includes an engine control unit (ECU: Electronic Control Unit). The engine control unit is a microcontroller that comprehensively controls the control of the operation of the diesel engine 2 using an electronically controlled auxiliary device.

  And the control apparatus 11 performs control regarding the fuel injection of the fuel injection apparatus (fuel addition means) 14 which injects a fuel into each cylinder of the diesel engine 2. FIG. The control device 11 includes an accelerator opening signal 12a from an accelerator sensor 12 (load sensor) that detects the accelerator opening as a load of the diesel engine 2, and a rotation speed from a rotation sensor 13 that detects the engine speed of the diesel engine 1. Based on the signal 13a, a fuel injection signal 14a is output to the fuel injection device 14 for injecting fuel into each cylinder of the diesel engine 2, and when the fuel injection signal 14a is output, The operation state is always grasped by the control device 11.

  Here, the fuel injection device 14 has a plurality of injectors installed in each cylinder, and the solenoid valves of these injectors are appropriately controlled to open by the fuel injection signal 14a, and the fuel injection timing and injection amount are controlled. Is properly controlled. And the control apparatus 11 determines the fuel injection signal 14a of a normal mode based on the accelerator opening signal 12a and the rotation speed signal 13a.

  The control device 11 automatically regenerates the particulate filter 7 when the particulate accumulation amount in the particulate filter 7 exceeds a predetermined amount. Specifically, the control device 11 extracts the rotational speed of the diesel engine 2 based on the rotational speed signal 13a from the rotational sensor 13, and determines the fuel injection signal 14a based on the accelerator opening signal 12a from the accelerator sensor 12. The fuel injection amount, which is sometimes known, is extracted, and the basic generation amount of particulates based on the current operating state of the diesel engine 2 is estimated from the particulate generation map based on the rotation speed and the injection amount, Multiply the basic generation amount by a correction factor that takes into account various conditions related to the generation of particulates, and subtract the particulate processing amount in the current operating state to obtain the final generation amount. The accumulated amount of particulate matter is accumulated every moment to estimate the accumulated amount of particulates, and this accumulated amount is a predetermined target value. It has from the normal mode to perform switching to the reproduction mode when it is estimated that reached.

  When the control device 11 is switched from the normal mode to the regeneration mode, the main injection of fuel performed near the compression top dead center (crank angle 0 °) is followed by the post injection at the non-ignition timing later than the compression top dead center. A fuel injection signal 14 a having such an injection pattern is transmitted to the fuel injection device 14.

  That is, when post-injection is performed at the non-ignition timing later than the compression top dead center following main injection, unburned fuel (mainly HC: hydrocarbon) is added to the exhaust gas 5 by this post-injection. As a result, the unburned fuel undergoes an oxidation reaction on the oxidation catalyst on the surface of the particulate filter 7, the catalyst bed temperature rises due to the reaction heat, and the catalyst bed temperature of the particulate filter (PF) 7 becomes predetermined. When a predetermined time (time required for regeneration) elapses above the temperature, the particulates in the particulate filter 7 are burned and removed.

  However, if the vehicle is in an idling state when switching to the regeneration mode, the main injection that was performed near the compression top dead center (crank angle 0 °) to increase the rotational speed compared to the normal idling The amount of injection is increased.

  That is, when the particulate filter 7 is forcibly regenerated when the idling is stopped, the temperature and flow rate of the exhaust gas 5 are too low to perform good combustion removal of the particulates. By increasing the injection amount, the rotational speed is increased from that during normal idling, thereby increasing the amount of energy input and raising the temperature and flow rate of the exhaust gas 5 to a level suitable for forced regeneration.

  Further, in addition to the control for increasing the rotational speed of the diesel engine 2, after injection may be performed at a combustible timing immediately after the main injection as necessary. If the after-injection is performed at a proper timing, the fuel of the after-injection is burned at a timing that is difficult to be converted to output, thereby lowering the thermal efficiency of the diesel engine 2 and increasing the amount of heat that is not used for power out of the heat generated by the fuel. It is possible to further increase the exhaust temperature.

  Moreover, the control apparatus 11 has an idling determination means for determining whether or not the crane vehicle 1 is in an idle state. Specifically, although not shown in FIG. 1, in addition to the accelerator sensor 12 and the rotation sensor 13 described above, a neutral switch for detecting that the gear position is in the neutral position and a side brake are applied. A detection signal from a side brake switch for detecting that the vehicle is running and a vehicle speed sensor for detecting the vehicle speed are also input to the control device 11, and based on these detection signals, it is determined whether or not the crane vehicle 1 is in an idling state. It has become.

  The controller 11 confirms that the rotation sensor 13 is in a relatively low predetermined rotational speed range, the accelerator sensor 12 confirms that the accelerator is off (the load is zero), and the gear position is in the neutral position by the neutral switch. When it is confirmed that the side brake is being pulled by the side brake switch and the vehicle speed sensor confirms that the vehicle speed is zero, it is determined that the current driving state is the idling state. Yes.

  An exhaust brake (exhaust throttle means) 17 including a valve 16 that narrows the exhaust flow rate from the diesel engine 2 is disposed upstream of the particulate filter 7. The exhaust brake 17 is normally used as an auxiliary brake that increases the exhaust pressure in the exhaust pipe 4 by restricting the exhaust flow rate of the exhaust pipe 4 by the valve 16 and increases the pumping loss applied to the diesel engine 2 to suppress the rotational speed. It is done.

  However, in the embodiment for carrying out the present invention, the exhaust brake 17 will be described as a means for further raising the exhaust temperature while the crane 1 is idling when the regeneration mode is selected by the control device 11. The valve 16 of the exhaust brake 17 is controlled to be opened / closed by an opening / closing command signal 17 a from the control device 11. Here, closing the valve of the exhaust brake 17 indicates that the exhaust flow rate is reduced, and opening the valve indicates that the exhaust flow rate is reduced.

  The crane vehicle 1 includes a power take-off 21 on the side surface of the transmission 20. The power take-off 21 is a mechanism for taking out the power of the diesel engine 2 from the countershaft gear of the transmission 20 through the gear train. The power extracted from the transmission 20 is output for driving the hydraulic pump 22 from the output shaft of the power take-off device 21.

  Here, the instrument panel in the cab is provided with a PTO switch 23 for taking out the power of the diesel engine 2 through the power take-off 21 and driving the hydraulic pump 22.

  When the PTO switch 23 is turned on, the control device 11 receives an on signal 23 a and outputs a PTO command signal 21 a to the power take-off 21. When the power take-off 21 receives the PTO command signal 21a, the output is turned on, and the external accelerator 24 separately installed outside the cab is activated.

  The external accelerator 24 is configured to operate an external accelerator sensor 25 outside the cab with a lever 26, and an external accelerator opening signal 25 a from the external accelerator sensor 25 is controlled by the diesel engine 2 when the PTO switch 23 is turned on. The signal is electrically activated in the control device 11 as a signal, and the rotational speed of the diesel engine 2 can be controlled outside the cab without stepping on the accelerator pedal in the cab.

  Here, when the PTO switch 23 is on, the control device 11 determines that the crane 1 is in an idling state. Therefore, when the regeneration of the particulate filter 7 is executed, the control device 11 controls the valve 16 to restrict the flow path of the exhaust pipe 4.

  When the PTO switch 23 is turned on and the hydraulic pump 22 is operated by the power extracted from the diesel engine 2 by the power take-off 21, the hydraulic oil sucked from the hydraulic oil tank becomes pressure oil, and the hydraulic cylinder or The crane 27 is operated by being guided to a hydraulic motor and changed to a reciprocating motion or a rotational motion, respectively.

  The oil pressure of the hydraulic pump 22 is measured by the oil pressure gauge 28, and the oil pressure value 28 a is sequentially transmitted to the control device 11. When the control device 11 determines that the regeneration of the particulate filter 7 has been executed and the hydraulic pressure has become higher than the first threshold value, the control device 11 turns the valve 16 of the exhaust brake 17 so that the diesel engine 2 does not malfunction such as misfire or engine stop. Control to open. Specifically, an open / close command signal 17a is transmitted to the exhaust brake 17, and the valve 16 is opened to release the exhaust brake 17.

  Further, when the regeneration of the particulate filter 7 is executed, the control device 11 turns on the PTO switch 23 (the hydraulic pump is in use), and the hydraulic pressure of the hydraulic pump 22 is lower than the first threshold. In the following cases, an open / close command signal 17a is transmitted to the exhaust brake 17 so as to close the valve 16, and the exhaust brake 17 is operated.

  The operation of the present invention will be described with reference to FIGS. FIG. 2 is a flowchart showing processing of the control device. As shown in FIG. 2, in step S1, the control device 11 sets the fuel injection of the fuel injection device 14 to the normal mode, and proceeds to step S2. In step S2, the control device 11 determines whether or not the calculated value of the particulate integrated amount is equal to or greater than a predetermined value (target value). If the calculated value is equal to or greater than the predetermined value, the control device 11 proceeds to step S3. The injection is set to the regeneration mode, and the process proceeds to step S4. In step S2, if the calculated value of the particulate cumulative amount is smaller than the predetermined value, the process returns to step S2.

  In step S4, the control device 11 determines whether the PTO switch 23 is ON and the hydraulic pressure of the hydraulic pump 22 is equal to or lower than the second threshold value. If so, the process proceeds to step S5 and the valve 16 of the exhaust brake 17 is opened / closed. By closing the transmission of the signal 17a, the exhaust flow rate of the exhaust pipe 4 is reduced, and the process proceeds to step S6. In step S4, when the PTO switch 23 is ON and the hydraulic pressure of the hydraulic pump 22 does not fall below the second threshold value, the control device 11 proceeds to step S8.

  In step S6, if the hydraulic pressure of the hydraulic pump 22 is greater than or equal to the first threshold value, the control device 11 proceeds to step S7, opens the valve 16 of the exhaust brake 17 by transmitting an open / close command signal 17a, and proceeds to step S8. . In step S6, when the hydraulic pressure of the hydraulic pump 22 is lower than the first threshold value, the process proceeds to step S8.

  In step S8, when the catalyst bed temperature of the particulate filter (PF) 7 is equal to or higher than a predetermined temperature and a predetermined time (time required for regeneration) has elapsed, it is assumed that the regeneration is completed, and the process returns to step 1 and fuel injection is performed again. Normal mode is set. In step S8, if the catalyst bed temperature of the particulate filter (PF) 7 is equal to or higher than the predetermined temperature and the predetermined time has not elapsed, that is, if regeneration is not completed, the process proceeds to step S4.

  According to the present invention, in the exhaust gas purification apparatus 9 for a specially equipped vehicle in which regeneration of the particulate filter is automatically performed when the accumulated amount of the particulate matter exceeds a predetermined amount, the power of the diesel engine is driven by the hydraulic pump 22. Therefore, even if regeneration of the exhaust gas is automatically executed during extraction, if the hydraulic pressure of the hydraulic pump 22 is equal to or higher than the first threshold, the valve 16 of the exhaust brake 17 is opened by the control device 11 and the exhaust brake 17 Since the operation is released, it is possible to prevent malfunction of the diesel engine 2 such that misfire and engine stop occur because sufficient air for burning fuel cannot be sucked by the operation of the exhaust brake 17.

  Further, according to the present invention, the first threshold value used for the determination value for opening the valve 16 of the exhaust brake 17 and the second threshold value used for the determination value for closing the valve 16 of the exhaust brake 17 are different values having a width. Is used. Thus, by providing a range between the hydraulic pressure value for closing the valve 16 and the hydraulic pressure value for closing, the hydraulic pressure value before and after the first threshold value is detected when the determination is made only with the first threshold value, and accordingly the valve 16 Can be prevented from continuously opening and closing and the operation of the exhaust brake 17 becoming unstable.

  The specially equipped vehicle is not limited to the above-described embodiment. For example, although the crane vehicle 1 is exemplified as the specially equipped vehicle, the present invention is not limited to this, and any specially equipped vehicle including the hydraulic pump 22 may be used. For example, a hydraulic excavator may be used.

  Further, although an example of the accumulated amount of particulates has been described, the present invention is not limited to this, and the accumulated amount of particulates may be estimated using a method other than the estimation method exemplified in the specification. .

  Moreover, although the fuel addition means was demonstrated with the fuel-injection apparatus 14 which injects a fuel into each cylinder of the diesel engine 2, it is not limited to this. For example, an addition nozzle that injects fuel into the filter case 8 and upstream of the particulate filter 7 may be provided separately.

  The idling state is determined by using the accelerator sensor 12, the rotation sensor 13, the neutral switch, the side brake switch, and the vehicle speed sensor, but all signals from these sensors and switches are necessary. However, the idling determination means can be configured by a combination of at least the accelerator sensor 12, the rotation sensor 13, and the neutral switch, the side brake switch, or the vehicle speed sensor. Further, another signal such as a clutch signal may be taken into consideration for the purpose of more reliable determination.

  Further, although the exhaust throttle means has been described in the form using the exhaust brake 17, it is not limited to this, and an exhaust throttle valve may be separately provided in the middle of the exhaust pipe 4.

  Further, the method of taking out the engine power has been described in the transmission PTO method, but is not limited to this. Various systems such as a flywheel PTO system in which power is extracted from a gear provided on a flywheel at the front of the transmission 20 can be employed.

  Moreover, although the case where operation with respect to the hydraulic pump 22 is performed with the external accelerator 24 has been described as an example, a vehicle in which the hydraulic pump 22 can be operated with an accelerator pedal within the cab, or an idle volume within the cab. In the case of a vehicle that can be operated with a throttle button (manually adjusting the idling speed during warm-up operation, etc.), these accelerator pedal and idle volume operation signals are referred to as the external accelerator opening signal 25a. Similarly, this may be detected in the control device 11 as an operation input to the hydraulic pump 22.

  Further, for convenience of explaining the case where exhaust gas regeneration is automatically performed while the power of the diesel engine is taken out for driving the hydraulic pump 22, step 4 in FIG. 2 is designated as “PTO switch 23 ON and hydraulic pressure”. As described in “The hydraulic pressure of the pump 22 is equal to or lower than the second threshold value”, it is naturally assumed that regeneration is performed even during normal idling without using the hydraulic pump. When the mobile crane 1 does not use the hydraulic pump 22, it proceeds from step S4 to step S5.

  The exhaust emission control device of the present invention can be variously modified without departing from the gist of the present invention.

1 Crane truck (special equipment)
2 Diesel engine (engine)
4 exhaust pipe 5 exhaust gas 7 particulate filter 9 exhaust purification device 14 fuel injection device (fuel addition means)
17 Exhaust brake (exhaust throttle means)
21 Power take-off 22 Hydraulic pump

Claims (2)

An exhaust emission control device mounted on a specially equipped vehicle comprising: an engine that generates power; and a power take-off that extracts the power of the engine for driving a hydraulic pump,
An exhaust pipe for guiding exhaust gas from the engine to the outside;
A particulate filter disposed in the exhaust pipe for collecting particulates in the exhaust gas;
Fuel addition means for regenerating the particulate filter by automatically adding fuel when the amount of accumulated particulate matter exceeds a predetermined amount;
An exhaust throttle means for raising the exhaust temperature by narrowing the exhaust flow rate of the exhaust pipe,
The exhaust throttle means throttles the exhaust flow rate of the exhaust pipe so as to assist regeneration of the particulate filter when the fuel addition means is executed when the hydraulic pump is used, and the hydraulic pressure of the hydraulic pump is first An exhaust emission control device, wherein the exhaust gas flow restriction is released when the value is higher than the threshold value.   2. The exhaust according to claim 1, wherein the exhaust throttle means throttles an exhaust flow rate when the hydraulic pump is in use and the hydraulic pressure of the hydraulic pump is equal to or lower than a second threshold value that is lower than a first threshold value. Purification equipment.

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