JP4163926B2 - Exhaust white smoke prevention device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust white smoke prevention device.
[0002]
[Prior art]
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). 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. It has been done conventionally.
[0003]
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.
[0004]
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 exhaust temperatures that are high enough for the particulates to self-combust. For example, an appropriate amount for alumina loaded with platinum A catalyst regeneration type particulate filter in which an oxidation catalyst formed by adding a rare earth element such as cerium is integrally supported is being put to practical use.
[0005]
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.
[0006]
[Problems to be solved by the invention]
However, since this type of particulate filter has a porous honeycomb structure, it is highly moisturizing and can store a large amount of moisture. Therefore, when the idling state where the exhaust temperature is low continues for a long time. In addition, when the mist-like moisture in the exhaust gas is collected by the particulate filter and accumulated in a large amount, when the vehicle starts running and the exhaust gas rises, the moisture accumulated in the particulate filter suddenly increases. There is a possibility that a large amount of water vapor is generated by evaporating, and this becomes white smoke and is discharged to the rear of the vehicle.
[0007]
That is, when the water accumulated in the particulate filter evaporates to become white smoke, not only the water vapor is visualized in relation to the outside air temperature to become white smoke but also unburned gas contained in the exhaust gas. Fuel and oil are decomposed into HC particles of an appropriate size by causing a halfway oxidation reaction on the oxidation catalyst of the particulate filter, and white smoke is produced by attaching water vapor to the HC particles as a nucleus. Since it is contained, the white smoke of water vapor having nuclei of HC particles is not preferable because it has a characteristic that it does not easily disappear in the atmosphere.
[0008]
By the way, such a situation where the idling state continues for a long time is, for example, when a route bus running in the city center is caught in a heavy traffic jam, or a route bus that arrives at the end point turns back to the next If you are waiting with the engine running in preparation (when passengers are seated and waiting, it is necessary to continue operating air conditioning such as cooling), or long-distance transportation trucks are on highways, etc. It is assumed that there is a break (nap) with the engine running in the parking (when it is desired to continue operating an air conditioner such as cooling).
[0009]
Incidentally, the problem of white smoke of exhaust gas at the start of traveling after the idling state as described above continues for a long time is also taken up in the following patent document 1 which is an unpublished prior application.
[0010]
[Patent Document 1]
Japanese Patent Application No. 2002-88508 [0011]
The present invention has been made in view of the above-described circumstances, and relates to a vehicle equipped with a catalyst regeneration type particulate filter in the middle of an exhaust pipe, and relates to a white exhaust gas at the start of running after a long idling state continues. The purpose is to prevent smoke.
[0012]
[Means for Solving the Problems]
The present invention is an exhaust white smoke prevention device intended for a vehicle equipped with a catalyst regeneration type particulate filter in the middle of an exhaust pipe, an idling determination means for determining that the vehicle is in an idling state, An exhaust gas temperature raising means for raising the exhaust gas temperature to a predetermined temperature or more upstream from the curate filter, and a first temperature sensor for measuring the intake air temperature, the idling determination means can continue the idling state for a predetermined time or more. When confirmed, a predetermined interval is determined based on the temperature detected by the first temperature sensor, and the exhaust gas temperature raising means is operated intermittently.
[0013]
Thus, in this way, when the idling determination means confirms the continuation of the idling state for a predetermined time or more, the exhaust gas temperature raising means at a predetermined interval determined based on the temperature detected by the first temperature sensor. Is operated intermittently, and the exhaust gas is heated to a predetermined temperature or higher on the upstream side of the particulate filter.Therefore, before the idling state continues for a long time and a large amount of water is accumulated in the particulate filter, the particulate filter The catalyst bed temperature of the curate filter is raised early, the oxidation catalyst is activated, and the particulate filter is heated by the reaction heat generated by oxidizing the collected particulates and unburned fuel in the exhaust gas. As a result, moisture in the particulate filter is released as water vapor.
[0014]
At this time, the amount of water vapor evaporated from the particulate filter is small, and since the catalytic activity is high, oxidation treatment of unburned fuel, oil, etc. proceeds efficiently, and water vapor is likely to adhere due to a halfway oxidation reaction. Since a situation in which a large amount of HC particles is generated is avoided, white smoke of the exhaust gas discharged to the rear of the vehicle is prevented.
[0015]
Moreover, the exhaust temperature raising means is operated intermittently at a predetermined interval, and this interval is appropriately adjusted based on the intake air temperature detected by the first temperature sensor. Therefore, the exhaust temperature raising means is operated with the minimum necessary operation by shortening the interval when the outside air temperature is substantially equal to the intake air temperature or by extending the interval when the outside air temperature is low. As a result, the operating cost required for the operation of the exhaust gas temperature raising means is suppressed as much as possible.
[0016]
In the present invention, the rotation sensor for detecting the engine speed, the load sensor for detecting the engine load, the neutral switch for detecting that the gear position is in the neutral position, and the side brake being pulled The idling determination means can be configured by a combination with any one or more of the side brake switch to detect and the vehicle speed sensor to detect the vehicle speed.
[0017]
Further, in the present invention, a second temperature sensor for detecting the exhaust gas temperature may be provided, and the exhaust gas temperature raising means may be feedback controlled based on the temperature detected by the second temperature sensor. The exhaust gas temperature raising means can be appropriately controlled so that the detected temperature of the second temperature sensor can be used as a substitute value for the catalyst bed temperature of the particulate filter, so that the catalyst bed temperature can reliably rise to the target temperature. .
[0018]
Further, the exhaust temperature raising means, an exhaust throttle means for appropriately reducing the exhaust flow rate, a fuel injection device that injects fuel into each cylinder of the engine, and outputs a closing operation command to the exhaust throttle means when operating, Control that outputs to the fuel injection device a fuel injection command for increasing the injection amount per main injection in order to increase the number of revolutions during normal idling and adding after injection at a combustible timing immediately after the main injection It is possible to configure with a device.
[0019]
In this way, when the exhaust flow rate is throttled by the exhaust throttle means that has received a closing operation command from the control device, the exhaust gas temperature is increased by boosting the exhaust gas upstream of this, and the exhaust resistance is reduced. As a result of the increase, the intake of relatively low temperature exhaust gas becomes difficult to flow into the cylinder, and the residual amount of exhaust gas having a relatively high temperature increases. The exhaust temperature can be further increased by being compressed in the compression stroke and reaching the explosion stroke, and at the same time, the amount of injection per main injection is increased on the engine side to increase the number of revolutions. Exhaust temperature is increased by increasing the input amount, and furthermore, combustion at a timing when it is difficult to convert the fuel from after-injection to output, lowering the thermal efficiency of the engine, So that the increase in the exhaust temperature increasing amount of heat is not used for the power of the heat it can be achieved. Note that the exhaust throttle means may be configured by also using an exhaust brake.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0021]
1 to 3 show an example of an embodiment for carrying out the present invention. In FIG. 1, reference numeral 1 denotes a diesel engine equipped with a turbocharger 2, and intake air 4 guided from an air cleaner 3 is an intake pipe 5. And the intake air 4 pressurized by the compressor 2a is sent to the intercooler 6 to be cooled, and the intake air 4 further flows from the intercooler 6 to the intake manifold 7. It is guided and distributed to each cylinder 8 of the diesel engine 1 (the case of in-line 6 cylinders is illustrated in FIG. 1).
[0022]
Further, the exhaust gas 9 discharged from each cylinder 8 of the diesel engine 1 is sent to the turbine 2b of the turbocharger 2 through the exhaust manifold 10, and the exhaust gas 9 that has driven the turbine 2b passes through the exhaust pipe 11. It is designed to be discharged outside the vehicle.
[0023]
Further, in the middle of the exhaust pipe 11, a catalyst regeneration type particulate filter 12 integrally carrying an oxidation catalyst is mounted and mounted on a filter case 13, and is shown in an enlarged view in FIG. Thus, this particulate filter 12 has a porous honeycomb structure made of ceramic, and the inlets of the respective flow paths 12a partitioned in a lattice pattern are alternately sealed, and the flow paths in which the inlets are not sealed. About 12a, the exit is sealed, and only the exhaust gas 9 which permeate | transmitted the porous thin wall 12b which divides each flow path 12a is discharged | emitted downstream.
[0024]
A temperature sensor 14 that measures the temperature of the exhaust gas 9 that has passed through the particulate filter 12 as a substitute value for the catalyst bed temperature is provided at the outlet of the filter case 13, and a temperature signal 14 a of the temperature sensor 14 is provided. Is input to a control device 15 constituting an engine control computer (ECU: Electronic Control Unit).
[0025]
Since this control device 15 also serves as an engine control computer, it is also responsible for control related to fuel injection. More specifically, the control device 15 detects an accelerator opening as a load of the diesel engine 1 ( A fuel injection device that injects fuel into each cylinder 8 of the diesel engine 1 based on an accelerator opening signal 16a from the load sensor) and a rotation speed signal 17a from the rotation sensor 17 that detects the engine rotation speed of the diesel engine 1. A fuel injection signal 18 a is output to the engine 18.
[0026]
Here, the fuel injection device 18 is composed of a plurality of injectors 19 provided for each cylinder 8, and the electromagnetic valves of these injectors 19 are appropriately controlled to open by the fuel injection signal 18a. The injection timing (valve opening timing) and the injection amount (valve opening time) are appropriately controlled.
[0027]
Further, a temperature sensor 20 for measuring the temperature of the intake air 4 is provided between the air cleaner 3 and the compressor 2a in the intake pipe 5, and a detection signal 20a of the temperature sensor 20 is also input to the control device 15. It has become so.
[0028]
In the control device 15, the fuel injection signal 18a in the normal mode is determined based on the accelerator opening signal 16a and the rotation speed signal 17a. When the continuation of the state is confirmed, a predetermined interval (about 30 minutes to 4 hours) is determined based on the temperature detected by the temperature sensor 20, and the normal mode is switched to the temperature rising mode intermittently. When the mode is switched to the temperature mode, as shown in FIG. 3, the compression top dead center (crank angle 0 °) so as to execute the control (about 450 to 1500 rpm) for increasing the rotation speed from the normal idling (about 450 rpm). In addition to increasing the amount of injection per main injection that was performed in the vicinity, at the timing at which combustion is possible immediately after the main injection Fuel injection signal 18a for injection pattern so as to add a lid injection (fuel injection command) are outputted.
[0029]
Further, an exhaust brake 21 capable of adjusting the opening degree is provided at an appropriate position upstream of the particulate filter 12 to narrow down the flow path of the exhaust pipe 11 to an appropriate opening degree. 15, the opening degree is controlled by an opening degree command signal 21 a from 15, but in this embodiment, when the temperature raising mode is selected by the control device 15, the original operation with respect to the exhaust brake 21 is performed. The exhaust brake 21 can be used as an exhaust throttle means for raising the exhaust temperature as will be described later.
[0030]
Here, a supplementary description will be given of the switching of the control device 15 from the normal mode to the temperature raising mode. The control device 15 includes the temperature sensors 14 and 20, the accelerator sensor 16, and the rotation sensor 17 described above. In addition, detection signals 22a and 23a from a neutral switch 22 for detecting that the gear position is in the neutral position, a side brake switch 23 for detecting that the side brake is being pulled, and a vehicle speed sensor 24 for detecting the vehicle speed, respectively. And a vehicle speed signal 24a are input, and based on these signals, it is determined whether or not the vehicle is in an idling state, and when it is confirmed that the idling state continues for a predetermined time or more, the temperature sensor 20 The temperature rising mode is intermittently released from the normal mode at a predetermined interval determined based on the detected temperature. Switches are adapted to be executed to.
[0031]
More specifically, the rotation sensor 17 confirms that the engine speed is within a relatively low predetermined rotational speed range, the accelerator sensor 16 confirms that the accelerator is off (load is zero), and the neutral switch 22 changes the gear position to the neutral position. If it is confirmed that there is a side brake applied by the side brake switch 23 and the vehicle speed sensor 24 confirms that the vehicle speed is zero, the control device determines that the current driving state is in the idling state. 15 is determined.
[0032]
Here, the determination of the idling state does not necessarily require all signals from these sensors and switches, but at least the rotation sensor 17, the accelerator sensor 16, the neutral switch 22, the side brake switch 23, the vehicle speed. It is possible to configure the idling determination means by combining with any one or more of the sensors 24.
[0033]
For operation in the temperature raising mode in the control device 15, the detected temperature of the temperature sensor 14 is used as a substitute value for the catalyst bed temperature of the particulate filter 12, and the catalyst bed temperature is surely set to the target temperature (about 150 to 300 ° C). ) Feedback control can be applied so as to rise to.
[0034]
Thus, when the operation control of this embodiment is performed by such a control device 15, the idling determination means comprising the rotation sensor 17, the accelerator sensor 16, the neutral switch 22, the side brake switch 23, and the vehicle speed sensor 24 is used for a predetermined time or more. When the continuation of the idling state is confirmed, the control device 15 intermittently switches from the normal mode to the temperature raising mode at a predetermined interval determined based on the temperature detected by the temperature sensor 20, and the fuel injection device from the control device 15 A fuel injection signal 18a (fuel injection command) having an injection pattern that increases the injection amount per main injection toward the engine 18 and adds after injection at a combustible timing immediately after the main injection is output.
[0035]
That is, by increasing the injection amount per main injection, the amount of energy input increases, the exhaust temperature rises, and the fuel by after-injection burns at a timing when it is difficult to convert it to output. The thermal efficiency of the engine 1 decreases, and the amount of heat not used for power out of the calorific value of the fuel increases, thereby increasing the exhaust temperature.
[0036]
Further, when switching from the normal mode to the temperature raising mode is performed, the exhaust flow rate is narrowed down by the exhaust brake 21 that has received the closing operation command from the control device 15, and the upstream exhaust gas 9 is boosted. The exhaust temperature is raised.
[0037]
In other words, the following relational expression is established between the temperature T of the exhaust gas 9, the exhaust pressure P, and the flow rate V:
P · V / T = constant, and if the exhaust pressure P is increased and the exhaust pressure P is increased to keep the flow rate V constant, the temperature T of the exhaust gas 9 will increase greatly with respect to a predetermined operating state. become.
[0038]
In addition, since the exhaust resistance of the diesel engine 1 is increased, the intake air 4 having a relatively low temperature is difficult to flow into the cylinder 8, and the residual amount of the exhaust gas 9 having a relatively high temperature is increased. Even if the air in the cylinder 8 containing a large amount of the exhaust gas 9 is compressed in the next compression stroke and reaches the explosion stroke, the exhaust temperature is further increased.
[0039]
If the exhaust gas 9 is intermittently heated to a predetermined temperature or higher when continuation of the idling state for a predetermined time or more is confirmed in this way, a large amount of moisture can be absorbed by the idling state continuing for a long time. Before being accumulated in the curative filter 12, the catalyst bed temperature of the particulate filter 12 is raised early to activate the oxidation catalyst, and the collected particulates and unburned fuel in the exhaust gas 9 are oxidized. As a result, the particulate filter 12 is heated to a high temperature by the reaction heat, and as a result, the moisture in the particulate filter 12 is released as water vapor.
[0040]
At this time, the amount of water vapor evaporated from the particulate filter 12 is small, and since the catalytic activity is high, the oxidation treatment of unburned fuel, oil, etc. proceeds efficiently, and the water vapor adheres due to a halfway oxidation reaction. Since a situation in which many HC particles having an easily sized particle are generated is avoided, white smoke of the exhaust gas 9 discharged to the rear of the vehicle is prevented.
[0041]
Moreover, the temperature raising mode of the control device 15 is operated intermittently at a predetermined interval, and this interval is appropriately adjusted based on the temperature of the intake air 4 detected by the temperature sensor 20. Therefore, the exhaust brake 21 and the fuel injection device can be reduced by shortening the interval when the outside air temperature is substantially equal to the temperature of the intake air 4 or by extending the interval when the outside air temperature is low. It is possible to operate the exhaust gas temperature raising means composed of 18 and the control device 15 with the minimum necessary operation, and the operation cost required for the operation of the exhaust gas temperature raising means is suppressed as much as possible.
[0042]
Therefore, according to the above embodiment, regarding the vehicle equipped with the catalyst regeneration type particulate filter 12 in the middle of the exhaust pipe 11, the exhaust gas 9 is not white smoked at the start of running after the idling state has continued for a long time. In addition, the operating cost required for the operation of the exhaust gas temperature raising means comprising the exhaust brake 21, the fuel injection device 18 and the control device 15 can be suppressed to the minimum necessary.
[0043]
Further, a temperature sensor 14 for detecting the exhaust temperature is provided on the outlet side of the particulate filter 12, and feedback control is performed based on the temperature detected by the temperature sensor 14. Therefore, the temperature detected by the temperature sensor 14 is determined as the particulate temperature. As an alternative value of the catalyst bed temperature of the filter, the exhaust gas temperature raising means can be appropriately controlled so that the catalyst bed temperature can surely rise to the target temperature.
[0044]
Furthermore, the exhaust gas temperature raising means is realized by effectively utilizing the existing exhaust brake 21, the fuel injection device 18, and the control device 15 without newly providing special incidental equipment. The cost required for the means can be greatly reduced, and the temperature of the exhaust gas 9 can be raised efficiently and reliably.
[0045]
In addition, the exhaust white smoke prevention device of the present invention is not limited to the above-described embodiment, and actively burns and removes the collected particulates in the particulate filter in the idling state where the exhaust temperature is low. It can be used as a reproducing means, and in determining the idling state, another signal such as a clutch signal may be considered for the purpose of more reliable determination. When narrowing down the appropriate location of the exhaust flow path, it is not always necessary to use an exhaust brake, and an exhaust throttle valve may be separately provided in the middle of the exhaust pipe, and the scope not departing from the gist of the present invention. Of course, various changes can be made.
[0046]
【The invention's effect】
According to the exhaust white smoke prevention device of the present invention described above, various excellent effects as described below can be obtained.
[0047]
(I) According to the first and second aspects of the present invention, the exhaust gas at the start of traveling after the idling state continues for a long time, with respect to a vehicle equipped with a catalyst regeneration type particulate filter in the middle of the exhaust pipe. It is possible to prevent the gas from becoming white smoke, and to suppress the operating cost required for the operation of the exhaust gas temperature raising means to the minimum necessary.
[0048]
(II) According to the invention described in claim 3 of the present invention, the detected temperature of the second temperature sensor is used as a substitute value for the catalyst bed temperature of the particulate filter, and the catalyst bed temperature is reliably increased to the target temperature. The exhaust temperature raising means can be appropriately controlled to obtain.
[0049]
(III) According to the inventions described in claims 4 and 5 of the present invention, the exhaust gas temperature raising means can be realized by using existing equipment as effectively as possible without newly providing special incidental equipment. The cost required for the exhaust gas temperature raising means can be greatly reduced, and the temperature of the exhaust gas can be raised efficiently and reliably.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of an embodiment for carrying out the present invention.
FIG. 2 is a cross-sectional view showing details of the particulate filter of FIG.
FIG. 3 is a graph showing a rotational speed control pattern by the control device of FIG. 1;
[Explanation of symbols]
1 Diesel engine (engine)
4 Intake 5 Intake pipe 8 Cylinder 9 Exhaust gas 11 Exhaust pipe 12 Particulate filter 14 Temperature sensor (second temperature sensor)
15 Control device (exhaust temperature raising means)
16 Accelerator sensor (load sensor: idling determination means)
17 Rotation sensor (idling determination means)
18 Fuel injection device (exhaust throttle means: exhaust temperature raising means)
20 Temperature sensor (first temperature sensor)
21 Exhaust brake (exhaust temperature raising means)
22 Neutral switch (idling determination means)
23 Side brake switch (idling determination means)
24 Vehicle speed sensor (idling determination means)

Claims (5)

An exhaust white smoke prevention device for a vehicle equipped with a catalyst regeneration type particulate filter in the middle of an exhaust pipe, and an idling determination means for determining that the vehicle is in an idling state, and upstream of the particulate filter The exhaust gas temperature raising means for raising the exhaust gas temperature to a predetermined temperature or higher and a first temperature sensor for measuring the intake air temperature, and when the idling determination means confirms that the idling state continues for a predetermined time or longer. An exhaust white smoke prevention device characterized in that the exhaust temperature raising means is operated intermittently by determining a predetermined interval based on the temperature detected by the first temperature sensor. A rotation sensor that detects the engine speed, a load sensor that detects the engine load, a neutral switch that detects that the gear is in the neutral position, a side brake switch that detects that the side brake is being pulled, and a vehicle speed 2. The exhaust white smoke prevention device according to claim 1, wherein the idling determination means is configured by a combination with any one or more of the vehicle speed sensors for detecting the engine. The exhaust gas according to claim 1 or 2, further comprising a second temperature sensor for detecting an exhaust gas temperature, wherein the exhaust gas temperature raising means is feedback controlled based on a temperature detected by the second temperature sensor. White smoke prevention device. The exhaust temperature raising means appropriately restricts the exhaust flow rate, the fuel injection device for injecting fuel to each cylinder of the engine, and outputs a closing operation command to the exhaust throttle means during its operation, A control device that outputs a fuel injection command to the fuel injection device to increase the injection amount per main injection in order to increase the rotational speed from idling and to add after injection at a combustible timing immediately after the main injection; The exhaust smoke whitening prevention device according to any one of claims 1, 2, and 3, characterized by comprising: The exhaust white smoke prevention device according to claim 4, wherein the exhaust throttle means comprises an exhaust brake.

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