JP2008223612A - Exhaust emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent abrupt change in the operational status of accessories by performing a regeneration control of a particulate filter when the accessories are used in a working special purpose vehicle. <P>SOLUTION: An exhaust emission control device is applied for a working special purpose vehicle. In the working special purpose vehicle, engine power is taken in an idling state through a power take-off device 14 to drive a hydraulic pump 15 (auxiliary machine), a hydraulic lift type high-place work bench 20 (installation equipment) is operated, to do the work, by the drive of the hydraulic pump 15. In the exhaust emission control device, under a condition where at least one of a connection signal 16a of the power take-off device 14 and an operation signal 22a of the high-place work bench 20 is input to a control device 9, a fuel injection signal 10a (regeneration control command) of a regeneration mode is not output from the control device 9. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust emission control device.

  Particulate matter (particulate matter) discharged from diesel engines is mainly composed of carbonaceous soot and SOF (Soluble Organic Fraction) consisting of high-boiling hydrocarbon components. Furthermore, the composition contains a small amount of sulfate (mist-like sulfuric acid component). As a measure to reduce this type of particulates, a particulate filter is installed in the middle of the exhaust pipe through which the exhaust gas flows. Has been performed conventionally.

  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, but in normal diesel engine operating conditions, there are few opportunities to obtain an exhaust temperature that is high enough for particulates to self-combust, so a catalyst regeneration type that integrally supports an oxidation catalyst. A particulate filter is used.

  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 used, the trapped amount exceeds the particulate processing amount in the operation region where the exhaust temperature is low, so such a low exhaust gas. If the operation state at the temperature continues, there is a possibility that the particulate filter will fall into an over trapped state without the regeneration of the particulate filter proceeding well.

  Therefore, a flow-through type oxidation catalyst is separately arranged in front of the particulate filter, and fuel is added to the exhaust gas upstream of the oxidation catalyst at the stage where the amount of particulate accumulation has increased. It is considered to perform forced regeneration.

  That is, the fuel (HC) added on the upstream side of the particulate filter undergoes an oxidation reaction while passing through the preceding oxidation catalyst, and the catalyst bed of the particulate filter immediately after the inflow of exhaust gas heated by the reaction heat. The temperature is raised, the particulates are burned out, and the particulate filter is regenerated.

  As a specific means for performing this type of fuel addition, post-injection is added at the timing of non-ignition later than the compression top dead center following the main injection of fuel performed near the compression top dead center. What is necessary is just to add a fuel in gas.

As prior art document information related to the forced regeneration of such a particulate filter, there are the following Patent Document 1 and Patent Document 2 by the same applicant as the present invention.
JP 2003-155915 A Japanese Patent Application No. 2003-222040

  However, when performing the regeneration control as described above, for example, the vehicle seems to be a specially equipped vehicle for work (special equipment for work) such as an aerial work vehicle equipped with a hydraulic lift type high work platform as a mounting facility. In such a case, the engine power may be used as auxiliary power for a hydraulic pump or the like for purposes other than traveling. Therefore, when such auxiliary equipment is used, regeneration control by fuel addition is automatically executed. As a result, the operating state of the engine suddenly changes, and the operating state of auxiliary equipment such as a hydraulic pump also suddenly changes, which may hinder work using the bodywork equipment.

  That is, in this type of specially equipped vehicle for work, an auxiliary machine is used in an idling stopped state. When performing regeneration control of the particulate filter in such an idling state, the temperature and flow rate of the exhaust gas are used. It is difficult to remove particulates satisfactorily because it is too low, and by increasing the injection amount per main injection, the rotational speed is increased compared to normal idling, thereby increasing the energy input and exhausting. Since it is necessary to add control to raise the gas temperature and flow rate to a level suitable for regeneration control, post-injection is added to the operation of the auxiliary machine after the rotation speed is increased from that during normal idling. There was concern about unexpected driver fluctuations.

  For example, if the specially equipped vehicle for work is an aerial work vehicle, there are cases where it is desired to slowly raise and lower the work platform while maintaining a low idling speed. In such a case, regeneration of the particulate filter is possible. When control starts and the rotation speed increases, the operating state of auxiliary equipment such as hydraulic pumps suddenly changes, and there is a concern that the lifting speed of the work platform at a high altitude will change suddenly and hinder the work. Yes.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to prevent the operating state of the auxiliary machine from changing suddenly by performing regeneration control of the particulate filter when the auxiliary machine is used in the specially equipped vehicle for work.

  The present invention is applied to a specially equipped vehicle for work in which engine power is taken out in an idling state via a power take-off device, an auxiliary machine is driven, and the bodywork is operated by driving the auxiliary machine. It is an exhaust purification device, and it is necessary to regenerate the particulate filter by burning and removing the collected particulate filter, which is equipped with an oxidation catalyst in the previous stage and interposed in the middle of the exhaust pipe When this occurs, a post-injection is added at the timing of non-ignition later than the compression top dead center following the main injection of fuel to the fuel injection device of the engine near the compression top dead center, and the post injection in the idling state Only at the time of execution, a regeneration control command is issued to increase the injection amount per main injection in order to increase the engine speed than during normal idling. And a regeneration control command is not output from the control device under the condition that at least one of the connection signal of the power take-off device and the operation signal of the bodywork equipment is input to the control device. It is characterized by comprising.

  Thus, in this way, regeneration control from the control device to the fuel injection device under the condition that at least one of the connection signal of the power take-off device and the operation signal of the bodywork equipment is input to the control device. Since the output of the command is blocked, the engine power is taken out in the idling state via the power take-off device, and the regeneration control due to the addition of post-injection or the increase in the rotational speed is not applied under the situation where the auxiliary machine is driven. A situation in which the operating state of the vehicle suddenly changes and the operating state of the auxiliary machine also changes suddenly does not occur.

  In other words, if the connection signal is input to the control device by turning on the PTO switch of the power take-off device at the driver's seat, it is clear that the accessory is driven by the engine power through the power take-off device. This type of power take-off device can be connected to a mechanical connection form in which the power take-off device is connected manually by an external operation, or a power take-off device can be connected by either a driver's PTO switch or an external manual operation. Since there is a dual-purpose type, there may be a case where it cannot be confirmed by the control device that the auxiliary device is in use only by depending on the connection signal of the power take-off device.

  However, in the present invention, there is no connection signal for the power take-off device because the operation signal when operating the bodywork equipment is also checked without depending on only the connection signal for the power take-off device. However, if an operation signal when the bodywork equipment is operated externally is input, it is possible to confirm with the control device that the auxiliary machine is in use.

  On the other hand, when it is necessary to regenerate the particulate filter during normal driving, post-injection is executed by the fuel injection device in accordance with a regeneration control command from the control device, and unburned fuel added to the exhaust gas thereby. The oxidation reaction occurs on the oxidation catalyst on the front stage of the particulate filter, and the catalyst bed temperature of the particulate filter immediately after is raised by the inflow of exhaust gas heated by the reaction heat, so that the particulates in the particulate filter are It is forcibly removed by combustion.

  Further, when it is necessary to regenerate the particulate filter in the idling state where the power take-off device is in the non-operating state, post-injection is executed by the fuel injection device in response to a regeneration control command from the control device. Then, the injection amount per main injection is increased, and the engine speed becomes higher than that during normal idling.

  As a result, the temperature and flow rate of the exhaust gas are raised to a level suitable for regeneration control, and unburned fuel added to the exhaust gas undergoes an oxidation reaction on the oxidation catalyst in the preceding stage of the particulate filter, and the reaction heat The catalyst bed temperature of the particulate filter immediately after is raised by the inflow of the exhaust gas whose temperature has been raised in step 1, and the particulates in the particulate filter are forcibly burned off.

  According to the exhaust gas purification apparatus of the present invention described above, regeneration control by adding post-injection or increasing the rotational speed does not take place under the situation where the engine power is taken out in an idling state via the power take-off device and the auxiliary machine is driven. Therefore, this regeneration control can reliably avoid a situation in which the engine operating state suddenly changes and the auxiliary operating state suddenly changes. It is possible to achieve an excellent effect that it is possible to prevent problems such as sudden changes in the operation of the equipment and hindering work.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIGS. 1 to 3 show an example of an embodiment for carrying out the present invention. In the exhaust purification apparatus of the present embodiment shown in FIG. 1, a hydraulic lift type high work platform is provided as a bodywork equipment. The example is applied to an aerial work vehicle (specially equipped vehicle for work), in the middle of an exhaust pipe 4 through which exhaust gas 3 discharged from a diesel engine 1 (engine) through an exhaust manifold 2 circulates. A catalyst regeneration type particulate filter 6 provided with an oxidation catalyst 5 in the previous stage is held by a filter case 7 and interposed.

  That is, a particulate filter 6 as schematically shown in FIG. 2 is accommodated in the inside of the filter case 7, and this particulate filter 6 has a porous honeycomb structure made of ceramic, and has a lattice structure. The inlets of the respective flow paths 6a partitioned in a shape are alternately sealed, and the outlets of the flow paths 6a whose inlets are not sealed are sealed. Only the exhaust gas 3 that has permeated through the porous thin wall 6b is discharged to the downstream side, and a flow as shown in FIG. A through-type oxidation catalyst 5 is provided as an accessory.

  A pressure sensor 8 is provided on the inlet side of the filter case 7, and a pressure signal 8a of the pressure sensor 8 is input to a control device 9 constituting an engine control computer (ECU: Electronic Control Unit). In this control device 9, based on the pressure signal 8a from the pressure sensor 8, the pressure difference between the inlet side and the outlet side of the particulate filter 6 (the pressure loss on the outlet side is preset in advance) is within an allowable range. If the pressure difference exceeds the allowable range, it is determined that it is necessary to regenerate the particulate filter 6 due to an increase in the accumulated amount of particulates.

  There are various ways of estimating the amount of accumulated particulates, and the basic amount of particulates generated based on the current operating state of the diesel engine 1 is estimated. Is multiplied by a correction factor that takes into account various conditions related to the generation of particulates, and the final generation amount is obtained by subtracting the particulate processing amount in the current operating state, and this final generation amount is obtained moment by moment. It is also possible to estimate the accumulated amount of particulates by integrating.

  Further, since the control device 9 also serves as an engine control computer, it is also responsible for control relating to fuel injection. More specifically, the control device 9 detects an accelerator opening as a load of the diesel engine 1. Fuel injection for injecting fuel into each cylinder of the diesel engine 1 based on an accelerator opening signal 11a from the engine 11 (load sensor) and a rotation speed signal 12a from the rotation sensor 12 that detects the engine rotation speed of the diesel engine 1 A fuel injection signal 10 a is output to the device 10.

  Here, the fuel injection device 10 is composed of a plurality of injectors provided for each cylinder, and the solenoid valve of each injector is appropriately controlled to be opened by the fuel injection signal 10a, and the fuel injection timing. (Valve opening timing) and injection amount (valve opening time) are appropriately controlled.

  On the other hand, in the control device 9, the fuel injection signal 10a in the normal mode is determined based on the accelerator opening signal 11a and the rotation speed signal 12a. On the other hand, it is necessary to perform regeneration control of the particulate filter 6. In this case, the normal mode is switched to the regeneration mode, and the post-injection is performed at the non-ignition timing later than the compression top dead center following the main injection of fuel performed near the compression top dead center (crank angle 0 °). The fuel injection signal 10a of the injection pattern is determined.

  That is, when post-injection is performed at a non-ignition timing later than the compression top dead center following main injection, unburned fuel (mainly HC: hydrocarbon) is added to the exhaust gas 3 by this post-injection. This unburned fuel undergoes an oxidation reaction on the preceding oxidation catalyst 5 on the surface of the particulate filter 6, and the catalyst bed temperature rises due to the reaction heat, and the particulates in the particulate filter 6 are burned. Will be 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.

  In other words, when the particulate filter 6 is forcibly regenerated when the idling is stopped, the temperature and flow rate of the exhaust gas 3 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 3 to a level suitable for forced regeneration.

  Further, in addition to the control for increasing the rotational speed of the diesel engine 1, after-injection may be performed at a combustible timing immediately after the main injection if necessary. Thus, the combustion immediately after the main injection is performed. If after-injection is performed at a possible 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 1 and increasing the amount of heat that is not used for power out of the calorific value of fuel This makes it possible to further increase the exhaust temperature.

  Although not specifically shown in FIG. 1, in addition to the accelerator sensor 11 and the rotation sensor 12 described above, a neutral switch for detecting that the gear position is in the neutral position and a side brake are pulled. Detection signals from the side brake switch for detecting the vehicle speed and the vehicle speed sensor for detecting the vehicle speed are also input to the control device 9, and whether or not the vehicle is in an idling state is determined based on these detection signals. It is determined by the control device 9.

  That is, in the control device 9, it is confirmed by the rotation sensor 12 that the rotation speed is within a relatively low predetermined rotational speed range, the accelerator sensor 11 confirms that the accelerator is off (load is zero), and the neutral position is set by the neutral switch. When it is confirmed that the vehicle is in the position, it is confirmed that the side brake is applied by the side brake switch, and the vehicle speed is confirmed to be zero by the vehicle speed sensor, it is determined that the current driving state is in the idling state. It is like that.

  Note that the determination of the idling state does not necessarily require all signals from these sensors and switches, and at least one of the rotation sensor 12, the accelerator sensor 11, the neutral switch, the side brake switch, and the vehicle speed sensor. The idling determination means can be configured by a combination of heels, and further another signal such as a clutch signal may be considered for the purpose of more reliable determination.

  In the specially equipped vehicle for work as shown in FIG. 1, a power take-off device 14 is provided on the side surface of the transmission 13, and power can be taken out from the countershaft gear of the transmission 13 through the gear train. The power extracted from the transmission 13 is output from the output shaft of the power take-off device 14 to the hydraulic pump 15 (auxiliary machine). Is performed inside the power take-off device 14.

  However, in addition to the transmission PTO method as described above, various methods such as a flywheel PTO method in which power is extracted from the gear provided on the flywheel at the front of the transmission 13 are adopted for the engine power extraction method. Is possible.

  On the other hand, the instrument panel in the cab is provided with a PTO switch 16 for taking out the engine power through the power take-off device 14 and driving the hydraulic pump 15, and the PTO switch 16 is turned on. Thus, the PTO command signal 14a is output from the control device 9 that has received the connection signal 16a to the power take-off device 14 and the output of the power take-off device 14 is turned on, while the external accelerator 17 installed separately outside the cab is provided. Is to be effective.

  That is, the external accelerator 17 is configured to operate the special-purpose accelerator sensor 18 outside the cab with the special-purpose lever 19, and the external accelerator opening signal 18a from the special-purpose accelerator sensor 18 when the PTO switch 16 is turned on. Is electrically activated in the control device 9 as a control signal for the diesel engine 1 so that the rotational speed of the diesel engine 1 can be controlled outside the cab without stepping on the accelerator pedal in the cab.

  Further, a hydraulic lift type aerial work platform 20 provided as a bodywork facility in the aerial work vehicle (working specially equipped vehicle) shown in FIG. 1 is supplied with hydraulic pressure supplied from a hydraulic pump 15 constituting an auxiliary machine. However, the raising / lowering operation is directly performed via the operation lever 22 by an operator placed on the work platform 20 at a high place. The control device 9 that receives the operation signal 22a from the operation lever 22 controls a hydraulic system (not shown) so that the boom 21 is raised and lowered.

  And in the said control apparatus 9, the connection signal 16a from the PTO switch 16 which shows that the power take-off apparatus 14 is connected, and the operation signal 22a from the operation lever 22 which performs the raising / lowering operation of the aerial work platform 20 The fuel injection signal 10a (in the regeneration mode under the condition that at least one of them is input, that is, under the condition that the engine power is taken out in the idling state via the power take-off device 14 and the hydraulic pump 15 is driven. Interlock is applied so that the regeneration control command is not output, and more specifically, the combustion injection control is not switched from the normal mode to the regeneration mode.

  Thus, in this way, the control device 9 is operated under a condition in which at least one of the connection signal 16a of the power take-off device 14 and the operation signal 22a of the work platform 20 is input to the control device 9. Since the output of the fuel injection signal 10a in the regeneration mode from the engine to the fuel injection device 10 is blocked, the engine power is taken out in an idling state via the power take-off device 14 and the hydraulic pump 15 is driven in the post-injection state. Thus, the regeneration control due to the addition of the engine speed or the increase in the rotational speed is not applied, and the operation state of the diesel engine 1 is suddenly changed and the operation state of the hydraulic pump 15 is not suddenly changed.

  That is, if the connection signal 16a is input to the control device 9 by turning on the PTO switch 16 of the power take-off device 14 at the driver's seat, the hydraulic pump 15 is driven by the engine power via the power take-off device 14. Obviously, this type of power take-off device 14 has a mechanical connection configuration in which the power take-off device 14 is connected manually by an external operation, or an external PTO switch 16 in the driver's seat. A case in which the power take-off device 14 can be connected even by manual operation exists, and the control device 9 cannot confirm that the hydraulic pump 15 is in use only by relying on the connection signal 16a of the power take-off device 14 Can happen.

  However, in this embodiment, the operation signal 22a when operating the aerial work platform 20 externally is also checked without depending on only the connection signal 16a of the power take-off device 14, so that the power take-off Even if there is no connection signal 16a for the device 14, if the operation signal 22a when the aerial work platform 20 is operated externally is input, the control device 9 confirms that the hydraulic pump 15 is in use. Is possible.

  On the other hand, when it is necessary to regenerate the particulate filter 6 during normal travel, post-injection is executed by the fuel injection device 10 in response to a fuel injection signal 10a (regeneration control command) in the regeneration mode from the control device 9. As a result, the unburned fuel added to the exhaust gas 3 undergoes an oxidation reaction on the oxidation catalyst 5 in the preceding stage of the particulate filter 6 and the particulate filter immediately after the exhaust gas 3 heated by the reaction heat flows in. The catalyst bed temperature of 6 is raised and the particulates are forcibly burned off.

  Further, when it is necessary to regenerate the particulate filter 6 in the idling state in which the power take-off device 14 is inactive, the regeneration mode fuel injection signal 10a (regeneration control command) from the control device 9 is used. While the fuel injection device 10 performs post injection, the injection amount per main injection is increased, and the rotational speed of the diesel engine 1 becomes higher than that during normal idling.

  As a result, the temperature and flow rate of the exhaust gas 3 are raised to a level suitable for regeneration control, and unburned fuel added to the exhaust gas 3 undergoes an oxidation reaction on the oxidation catalyst 5 at the front stage of the particulate filter 6. The inflow of the exhaust gas 3 heated by the reaction heat raises the catalyst bed temperature of the particulate filter 6 immediately after that, thereby forcibly removing the particulates.

  Therefore, according to the above-described embodiment, the regeneration control due to the addition of the post injection or the increase in the rotational speed is not applied under the situation where the engine power is taken out in the idling state via the power take-off device 14 and the hydraulic pump 15 is driven. Therefore, it is possible to reliably avoid a situation in which the operation state of the diesel engine 1 suddenly changes and the operation state of the hydraulic pump 15 is suddenly changed by this regeneration control, and the operation state of the hydraulic pump 15 is suddenly changed. Therefore, it is possible to prevent problems such as a sudden change in the ascending / descending speed of the aerial work platform 20 and hindering work.

  The exhaust emission control device of the present invention is not limited to the above-described embodiment. The specially equipped vehicle for work is not necessarily limited to an aerial work vehicle, and the hydraulic equipment of the lift system is also used for the bodywork equipment. It is possible to appropriately adopt a device other than the base, and it is possible to appropriately employ a device other than the hydraulic pump as an auxiliary machine, and further increase the exhaust gas during the regeneration control of the particulate filter. Of course, it is possible to use a means for reducing the exhaust flow rate or the intake flow rate for the purpose of increasing the temperature, and other various modifications can be made without departing from the scope of the present invention. .

It is the schematic which shows an example of the form which implements this invention. It is sectional drawing which shows typically the structure of the particulate filter of FIG. FIG. 2 is a perspective view showing a part of the oxidation catalyst of FIG.

Explanation of symbols

1 Diesel engine (engine)
Reference Signs List 3 exhaust gas 4 exhaust pipe 5 oxidation catalyst 6 particulate filter 9 control device 10 fuel injection device 10a fuel injection signal (regeneration control command)
14 Power take-off device 15 Hydraulic pump (auxiliary machine)
16 PTO switch 16a Connection signal 20 Platform work place (mounting equipment)
22 Operation lever 22a Operation signal

Claims (1)

  An exhaust emission control device for application to a specially equipped vehicle for work that takes out engine power in an idling state via a power take-off device, drives an auxiliary machine, and operates the bodywork equipment by driving the auxiliary machine. When a catalyst regeneration type particulate filter equipped with an oxidation catalyst in the previous stage and interposed in the middle of the exhaust pipe and when it is necessary to regenerate the particulate filter by removing the collected particulates by combustion Normal only when post-injection is performed at the time of non-ignition timing after the main injection of fuel performed near the compression top dead center and non-ignition timing later than the compression top dead center for the fuel injection device of the engine. To output a regeneration control command to increase the injection amount per main injection in order to increase the engine speed from the idling of the engine And a regeneration control command is not output from the control device under the condition that at least one of the connection signal of the power take-off device and the operation signal of the bodywork equipment is input to the control device. An exhaust purification device characterized by that.

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