JP2019100275A - Exhaust gas temperature raising device - Google Patents

Abstract

To provide an exhaust gas temperature raising device capable of more effectively raising an exhaust gas temperature in comparison with a conventional one, while keeping the same deceleration feeling as that in a conventional device in an accelerator-off time.SOLUTION: An exhaust gas temperature raising device includes: an exhaust brake 14 (exhaust throttle valve) disposed at the middle of an exhaust pipe 11 and capable of continuously adjusting an opening; and a control device 15 executing an exhaust gas temperature raising mode according to the necessity to raise an exhaust gas temperature by applying load resistance to a diesel engine 1 by throttling the exhaust brake 14 to the proper opening during traveling, and continuing fuel injection so that torque corresponding to pumping loss by the throttling is generated, without returning the throttling of the exhaust brake 14 even when an accelerator-off is detected during the execution.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an exhaust gas temperature raising device in which exhaust gas temperature is raised by narrowing an exhaust gas throttle valve to give load resistance to an engine.

  Conventionally, diesel engines are equipped with a selective reduction catalyst provided with the property of selectively reacting NOx (nitrogen oxide) with a reducing agent even in the presence of oxygen in the middle of an exhaust pipe through which exhaust gas flows, A necessary amount of reducing agent is added on the upstream side of the selective reduction catalyst so that the reducing agent can be reduced on NOx in the exhaust gas over the selective reduction catalyst, thereby reducing the concentration of NOx emission. There is something that

On the other hand, in the field of industrial exhaust gas denitration treatment in plants etc., the effectiveness of the method of reducing and purifying NOx using ammonia (NH ₃ ) as a reducing agent is already widely known, but in the case of automobile In recent years, non-toxic urea water has been widely used as a reducing agent because it is difficult to ensure safety when traveling by loading ammonia itself.

That is, if urea water is added to the exhaust gas on the upstream side of the selective reduction catalyst, the heat of the exhaust gas hydrolyzes the urea water into ammonia and carbon dioxide according to the following equation, and the exhaust gas over the selective reduction catalyst The NOx contained therein is well reduced and purified by ammonia.
[Chemical formula 1]
(NH ₂ ) ₂ CO + H ₂ O → 2 NH ₃ + CO ₂

  However, with this type of selective reduction catalyst, NOx in the exhaust gas can not be satisfactorily reduced and purified by ammonia unless the bed temperature has risen to a predetermined activation temperature. However, in a situation where the engine is being warmed up, the bed temperature of the selective reduction catalyst is still too low to start addition of urea water, and during this time there is a risk that the NOx emissions can not be sufficiently reduced. There is.

  For this reason, conventionally, the exhaust gas temperature raising mode is performed to achieve exhaust gas temperature rise by closing the exhaust gas throttle valve provided in the middle of the exhaust pipe during idle stop to give load resistance to the engine, thereby warming up the engine In this way, if the exhaust throttle valve is closed during idle stop and load resistance is given to the engine, the amount of fuel injection corresponding to the load resistance is increased, and the exhaust temperature rises. As the exhaust resistance of the engine increases, intake air having a relatively low temperature is less likely to flow into the cylinder, and the remaining amount of exhaust gas having a relatively high temperature is increased. The air is compressed in the next compression stroke to reach an explosion stroke, which further increases the exhaust temperature. In many cases, a diesel engine is equipped with an open / close exhaust brake in the middle of the exhaust pipe, which can be diverted to an exhaust throttle valve to perform exhaust gas temperature rise.

  In addition, there exist following patent document 1 grade | etc., As a prior art literature information relevant to this invention.

Unexamined-Japanese-Patent No. 2003-193824

  However, in exhaust gas temperature rise performed by diverting the conventional open / close exhaust brake to the exhaust throttle valve, only limited application during idle stop is possible, so in recent years, stepless operation using an electric actuator etc. It has been studied to adopt an exhaust brake whose opening degree can be adjusted and divert it to an exhaust throttle valve, and to conduct exhaust throttle even while traveling by this exhaust brake to achieve exhaust temperature rise. Because it is necessary to release the exhaust brake so that the feeling does not change from the past, in the case of operation where there are many opportunities for accelerator off (no injection) accompanying acceleration / deceleration, in addition to the decrease in exhaust temperature due to the stop of fuel injection There is a problem that the temperature of the catalyst bed, which is about to warm up, is rapidly lowered by the fact that the cooled intake air that has not passed through flows into the selective reduction catalyst in large quantities as it is.

  The present invention has been made in view of the above-described circumstances, and it is an object of the present invention to provide an exhaust gas temperature raising device capable of achieving more effective exhaust gas temperature rise while maintaining the same degree of deceleration feeling as before in the accelerator off There is.

  The present invention is an exhaust throttle valve equipped in the middle of an exhaust pipe and capable of adjusting the degree of opening steplessly, and reducing the exhaust throttle valve to an appropriate opening degree while traveling to raise the exhaust gas by giving a load resistance to the engine. If necessary, the exhaust temperature raising mode for increasing the temperature is executed, and fuel is generated so that the torque corresponding to the pumping loss due to the narrowing is generated without returning the narrowing of the exhaust throttle valve even if the accelerator off is detected during the execution. And a control device for continuing the injection.

  In this way, when the exhaust gas temperature raising mode is executed by the control device during traveling immediately after a cold start, etc., the exhaust throttle valve is narrowed to an appropriate opening degree, and the load resistance of the engine is reduced. While the torque decrease due to this load resistance is compensated by the increase of the fuel injection amount and effective exhaust temperature rise is achieved, the narrowing of the exhaust throttle valve is maintained even if the accelerator is turned off during its execution. Since fuel injection is continued so that a torque corresponding to the pumping loss due to the narrowing is generated, a situation where a large amount of cooled intake air not passing the combustion stroke flows into the post-treatment device in the middle of the exhaust pipe does not occur. It is possible to rapidly raise the post-processing device to the required temperature, and it is possible to maintain the same deceleration feeling as before when the accelerator is released.

  Further, when the present invention is more specifically implemented, the exhaust brake is used as the exhaust throttle valve, and under the condition that the exhaust brake switch is detected to be turned on by the driver, the accelerator is released with priority given to the normal brake control. Preferably, the control unit is configured to stop fuel injection at the same time, so that it is possible for the driver to return to normal braking control when he wants to use the exhaust brake as a true auxiliary brake. It is possible to prevent unreasonable situations such as continuation of fuel injection in an operating condition where braking is desired.

  Furthermore, in the present invention, the deceleration is calculated based on the engine speed at the time of disengaging the clutch in conjunction with the gear change in the exhaust temperature raising mode, and the deviation between the calculated value and the specified value of the deceleration is detected to raise the exhaust. Preferably, the control device is configured to learn and correct the fuel injection amount when the accelerator is off in the warm mode, and in this case, the operation error related to the fuel injection amount of the injector and the exhaust throttle amount of the exhaust throttle valve It is possible to correct the variation due to deterioration or to eliminate the difference between the actual deceleration degree and the prescribed deceleration degree, and to maintain the still-following sense of deceleration more reliably.

  According to the exhaust gas temperature raising device of the present invention described above, the following various excellent effects can be obtained.

  (I) According to the invention of claim 1 of the present invention, the exhaust gas temperature raising mode in which the exhaust gas temperature is raised by executing the load resistance on the engine by narrowing the exhaust gas throttle valve to an appropriate opening during traveling is executed. In doing so, the exhaust gas temperature rise can be made more effective than before while maintaining the same feeling of deceleration at the time of accelerator off, so that the aftertreatment device in the middle of the exhaust pipe can be rapidly raised to the required temperature. For example, when the aftertreatment device is a NOx reduction catalyst, the NOx reduction catalyst can be promptly raised to the activation temperature during running immediately after a cold start to exhibit a favorable NOx reduction effect, and When the post-processing device is a particulate filter, forced regeneration of the particulate filter can be completed early and surely.

  (II) According to the invention described in claim 2 of the present invention, even when the exhaust brake is diverted as the exhaust throttle valve, normal brake control is performed under the condition that ON of the exhaust brake switch by the driver is detected. Since priority is given to stopping fuel injection at the accelerator off, when the driver wants to use the exhaust brake as the original auxiliary brake, it can return to normal brake control, and the fuel can be used in the operating condition where braking is desired. Unreasonable situations such as continued injection can be avoided in advance.

  (III) According to the invention described in claim 3 of the present invention, the deceleration is calculated based on the engine speed at the time of the disconnection of the clutch accompanying the gear change in the exhaust temperature raising mode, and the calculation value and the definition of the deceleration Since the deviation from this value is detected to learn and correct the fuel injection amount at the time of accelerator off in the exhaust temperature rise mode, operation errors and deterioration related to the fuel injection amount of the injector and the exhaust throttle amount of the exhaust throttle valve It is possible to correct the variation and eliminate the deviation between the actual deceleration degree and the prescribed deceleration degree, and thereby maintain the more consistent sense of deceleration.

BRIEF DESCRIPTION OF THE DRAWINGS It is a whole systematic diagram which shows an example of the form which implements this invention. It is a flowchart explaining the control procedure of the control apparatus of FIG. It is a flowchart regarding learning correction | amendment of the fuel injection quantity at the time of accelerator off. It is a graph which shows the comparison with this example of a form and existing technology according to item.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows an example of the exhaust gas temperature raising device according to the present invention, and reference numeral 1 in FIG. 1 shows a diesel engine equipped with a turbocharger 2. The intake air 4 led from the air cleaner 3 is an intake pipe 5. The intake air 4 is sent to the compressor 2a of the turbocharger 2 and pressurized by the compressor 2a is sent to the intercooler 6 to be cooled, and the cooled intake air 4 is led to the intake manifold 7 for diesel It is distributed to each cylinder 8 (an example of in-line 6 cylinders is illustrated in FIG. 1) of the engine 1.

  Further, the exhaust gas 9 discharged from each cylinder 8 of the diesel engine 1 is sent to the turbine 2 b of the turbocharger 2 through the exhaust manifold 10 and is sent out to the exhaust pipe 11 after driving the turbine 2 b. The exhaust pipe 11 is equipped with a particulate filter 12 and a selective reduction catalyst 13 as a post-treatment device.

  And, in the example shown here, an exhaust brake 14 whose opening degree can be adjusted steplessly by an electric actuator or the like is provided immediately after the turbine 2b, and this exhaust brake 14 is The exhaust brake 14 is utilized as an exhaust throttle valve independently from the operation to enhance the braking force, and the exhaust brake 14 is narrowed down while traveling by the control device 15 to give load resistance to the diesel engine 1 to thereby raise the exhaust temperature. The mode is made to be able to execute.

  Here, the control device 15 operates the accelerator sensor 16 for detecting the accelerator opening, the rotation sensor 17 for detecting the engine rotational speed, the water temperature sensor 18 for detecting the engine water temperature, and the exhaust brake 14 as an auxiliary brake. Further, detection signals from various sensors (not shown) are inputted.

  On the other hand, the control device 15 outputs control signals to the injectors 20 (only one cylinder 8 is shown in FIG. 1) of the diesel engine 1 and the exhaust brake 14 to drive the exhaust brake 14. If necessary, the exhaust gas temperature raising mode for raising the exhaust gas temperature is performed by narrowing down to an appropriate opening degree to give load resistance to the diesel engine 1, and the exhaust gas is detected even if accelerator off is detected during the execution. The fuel injection is continued to generate a torque corresponding to the pumping loss due to the narrowing of the brake 14 without returning the narrowing of the brake 14.

  Incidentally, reference numeral 21 in FIG. 1 denotes an EGR flow path for extracting a part of the exhaust gas 9 from the exhaust manifold 10 and guiding it to the inlet of the intake manifold 7, and 22 denotes a normally closed EGR valve which opens the EGR flow path 21 when necessary. , 23 each show an EGR cooler for cooling the exhaust gas 9 to be recirculated.

  Further, FIG. 2 shows a specific control procedure in the control unit 15. First, when it is confirmed in step S1 that the engine start mode (starting condition in which the cell is cranked) is confirmed, the next step is performed. The process proceeds to step S2, and the determination of step S1 is repeated until it is not confirmed.

  In the next step S2, the exhaust brake switch 19 at the driver's seat is on, or the switch of the conventionally known compression pressure release engine brake (only the exhaust brake switch 19 is shown in FIG. 1) is on. When it is confirmed that any switch is on, it is determined that the driver has a clear request for auxiliary brake operation, and the process proceeds to the next step S3 to enter the auxiliary brake mode.

  Then, in step S4, the engine rotational speed is A [rpm] (A is an arbitrary compatible value) or more, and the vehicle speed is B [km / h] (B is an arbitrary compatible value) or more (vehicle is During traveling), when it is confirmed that the gear position is not neutral or reverse, the clutch is in the connected state, and the accelerator opening is 0% (the accelerator is not depressed), the operation goes to the next step S5 The process proceeds to step S4 in which the determination in step S4 is repeated until all are confirmed.

  In the next step S5, the auxiliary brake (the exhaust brake 14 or the compression pressure release engine brake) is operated based on the switch confirmed in the previous step S2, and fuel injection is stopped as usual. . At this time, the EGR valve 22 is fully closed so that the effectiveness of the auxiliary brake is not impaired.

  On the other hand, if it is determined in the previous step S2 that neither switch is on, it is assumed that the driver does not have a clear request for auxiliary brake operation, and the normal traveling mode is set in the next step S6. It is determined whether or not [° C.] (C is an arbitrary compatible value) or less, and if the engine water temperature exceeds C [° C.], the process proceeds to step S8 and the normal control mode is entered to fully open the exhaust brake 14 Normal governor control (fuel injection amount control for the number of revolutions of the diesel engine 1 and the accelerator opening degree) is performed as it is.

  However, if it is determined in step S7 that the engine water temperature is equal to or lower than C [° C.], it is determined that the diesel engine 1 is still cold and that the exhaust temperature raising mode needs to be executed. In step S10, the governor control is switched to the exhaust temperature raising mode, and the stepless exhaust throttle control of the exhaust brake 14 is performed.

  That is, as described above, the exhaust temperature is raised by narrowing the exhaust brake 14 to an appropriate opening degree while driving to give the load resistance to the diesel engine 1, and the exhaust gas is detected even if accelerator off is detected during its execution. Control is performed such that fuel injection is continued so as to generate a torque corresponding to the pumping loss due to the squeezing without returning the squeezing of the brake 14.

  Here, in the present embodiment, it is intended to correct the variation due to the operation error and deterioration related to the fuel injection amount of the injector 20 and the exhaust throttle amount of the exhaust brake 14, and is accompanied by the gear change in the exhaust temperature raising mode. In anticipation of disconnection of the clutch, the instantaneous deceleration at the time of disconnection of the clutch is calculated based on the engine speed, and the deviation between the calculated value and the specified value of deceleration is detected to accelerate the accelerator in exhaust temperature rise mode. The fuel injection amount at the time is learned and corrected, and for example, control as shown in the flowchart of FIG. 3 is performed.

  That is, in the control of learning correction shown by the flowchart in FIG. 3, first, at step S11, the engine rotational speed is from D [rpm] (D is any suitable value) to E [rpm] (E is any suitable value) When it is in the range, that the accelerator opening is 0% (the accelerator is not depressed), and all the clutch is in the disengaged state, the process proceeds to the next step S12, and the reference decrease for each determined rotation speed The speed (a map calculation value from the engine speed and the engine water temperature) is calculated, and the actual deceleration (actually measured value by the rotation sensor) for each determined rotation speed is calculated.

  Then, after the deviation (deceleration deviation) between the reference deceleration and the actual deceleration is calculated in the next step S13, the basic injection amount (the map calculation value from the engine speed) is calculated in the next step S14. At the same time, the learning correction injection amount (map calculation value from the engine speed and the deceleration deviation) is calculated, and the fuel injection amount at the time of accelerator off at step S15 (calculation value obtained by adding the learning correction injection amount to the basic injection amount) Is calculated.

However, when the deceleration deviation obtained in the previous step S13 is less than the disturbance level F [r / s ² ] (F is an arbitrary adaptation value), the learning correction injection amount in step S14 is not updated and the previous time By adopting the values again, the robustness is enhanced.

  Incidentally, when calculating the learning correction injection amount in step S14, the previous value of the deceleration deviation is adopted through step S16 unless all the conditions are satisfied in the determination in step S11 above. .

  Thus, in the case where the exhaust gas temperature raising device is configured as described above, the control device 15 indicates that the diesel engine 1 is still cold and it is necessary to execute the exhaust gas temperature raising mode during traveling immediately after a cold start. If the engine temperature rise mode is executed by the control unit 15, the exhaust brake 14 is narrowed to an appropriate opening degree to give a load resistance to the diesel engine 1, and the torque reduction due to this load resistance is a fuel injection The exhaust gas temperature is compensated by the increase of the amount to achieve effective exhaust temperature rise, while the narrowing of the exhaust brake 14 is maintained even if the accelerator is turned off during the execution, and the torque corresponding to the pumping loss due to the narrowing is generated. As the fuel injection is continued, the cooled intake air 4 that has not passed the combustion stroke is directly added to the selective reduction catalyst 13 (NOx reduction catalyst) in the middle of the exhaust pipe 11 as it is. The situation where it does not flow does not occur, and it becomes possible to rapidly raise the selective reduction catalyst 13 to the required temperature, and it is possible to maintain the same feeling of deceleration at the time of accelerator off as before.

  FIG. 4 shows an example of the present embodiment in a transient state immediately after a cold start (refer to a curve shown by a solid line in all items in FIG. 4) and a curve shown by a dashed line in all items in FIG. The comparison with と) is shown in the graph according to item, and in any case, exhaust brake 14 is narrowed to an appropriate opening during traveling to give exhaust resistance to the diesel engine 1, thereby aiming to raise the exhaust temperature. However, while the exhaust throttle opening degree is returned to fully open when the accelerator is released in the existing technology, in the present embodiment, the exhaust throttle opening degree is kept fully closed when the accelerator is released. In this case, the driver may feel an unexpected sense of deceleration, but in the present embodiment, the pumping loss due to the narrowing-down of the exhaust brake 14 is not returned even when the accelerator is released. The fuel injection is continued so that the torque corresponding to the engine torque is generated, so the transition of the engine torque is almost unchanged from the existing technology, and as a result, the exhaust temperature can be raised more efficiently than the existing technology. It is possible.

  Therefore, according to the above-described embodiment, the accelerator brake 14 is narrowed to an appropriate opening during driving to apply load resistance to the diesel engine 1 to execute the exhaust gas temperature rise mode for raising the exhaust gas temperature. Since the exhaust gas temperature can be increased more effectively than before while maintaining the same feeling of deceleration as before, the selective reduction catalyst 13 (NOx reduction catalyst) can be rapidly raised to the activation temperature, and urea is not shown. The addition of urea water by the water addition valve can be started earlier than before.

  Further, particularly in the present embodiment, under the condition that the exhaust brake switch 19 is detected to be turned on by the driver, the fuel injection at the accelerator off is stopped by giving priority to the normal brake control. When it is desired to use the exhaust brake 14 as an original auxiliary brake, it is possible to return to normal brake control, and it is possible to prevent an unreasonable situation such as continuation of fuel injection under an operating condition where braking is desired.

  Moreover, when the clutch is disengaged in the exhaust temperature raising mode, the deceleration is calculated based on the engine speed, and the deviation between the calculated value and the specified value of the deceleration is detected to detect the acceleration in the exhaust temperature raising mode. Since the fuel injection amount at the OFF time is learned and corrected, the variation due to the operation error and deterioration related to the fuel injection amount of the injector 20 and the exhaust throttle amount of the exhaust brake 14 is corrected, and the actual deceleration degree and the specified deceleration With this, it is possible to more reliably maintain the usual sense of deceleration as it is.

  Also, the case has been described above where the exhaust gas temperature raising mode is performed for the purpose of raising the selective catalytic reduction catalyst 13 to the activation temperature early. However, in this type of exhaust gas temperature raising mode, the particulate filter 12 is It can also be used in the case of forced regeneration.

  That is, when the exhaust purification of the diesel engine 1 is intended, it is not sufficient to remove only the NOx in the exhaust gas 9, and the particulate filter 12 is also used for the particulate matter contained in the exhaust gas 9. However, when this type of particulate filter 12 is adopted, particulates are appropriately burned and removed before the exhaust resistance increases due to clogging, and forced regeneration of the particulate filter 12 is required. It is necessary to

  For this reason, an oxidation catalyst is supported on the particulate filter 12 and fuel is added to the upstream exhaust gas 9 at the stage where the amount of particulate deposition has increased, thereby forcing regeneration of the particulate filter 12. If the exhaust gas temperature raising mode as described above is executed at the time of forced regeneration of such particulate filter 12, forced regeneration of particulate filter 12 is completed early and surely even in an operating condition where exhaust temperature is low. Can.

  The exhaust gas temperature raising device of the present invention is not limited to only the above-described embodiment, and the aftertreatment device may be a NOx reduction catalyst such as a selective reduction type catalyst if it requires an exhaust gas temperature raising mode. Of course, it may be a particulate filter, and various changes may be made without departing from the scope of the present invention.

1 Diesel engine (engine)
9 exhaust gas 11 exhaust pipe 12 particulate filter (post-treatment device)
13 Selective reduction type catalyst (post-treatment device)
14 Exhaust brake (exhaust throttle valve)
15 Control Device 16 Accelerator Sensor 19 Exhaust Brake Switch 20 Injector

Claims (3)

  An exhaust throttle valve equipped in the middle of the exhaust pipe and capable of adjusting the opening steplessly, and the exhaust throttle valve which narrows down to an appropriate opening degree during traveling to give a load resistance to the engine, thereby raising exhaust gas temperature The temperature raising mode is executed as necessary, and fuel injection is continued so that the torque corresponding to the pumping loss due to the narrowing is generated without returning the narrowing of the exhaust throttle valve even if the accelerator off is detected during the execution. An exhaust temperature raising device comprising: a control device.   The control device is configured to stop fuel injection at accelerator off by giving priority to normal brake control under conditions where the exhaust brake is diverted as the exhaust throttle valve and the driver's turn on of the exhaust brake switch is detected. The exhaust gas temperature raising device according to claim 1, characterized in that:   Deceleration is calculated based on the engine speed at the time of disengaging the clutch in the exhaust temperature rise mode, and the deviation between the calculated value and the specified value of deceleration is detected, and the accelerator is off in exhaust temperature rise mode The exhaust gas temperature raising device according to claim 1 or 2, wherein the control device is configured to learn and correct the fuel injection amount.

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