JP2008180110A - Exhaust emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To always supply reducing agent even right after starting an engine 2, in an exhaust emission control device 1 purifying exhaust gas exhausted from a vehicular engine 2 by reducing agent. <P>SOLUTION: This exhaust emission control device 1 is provided with a heater 16 heating urea water by electric power, and an ECU 17 controlling power feed to the heater 16. The ECU 17 is formed to allow power to be fed to the heater 16 from another power source (an on-vehicle power source 20 or an external power source 21) other than a vehicle driving power source 19. Thereby, power can be fed to the heater 16 even during stop of the engine 2 disabling power feed from the vehicle driving power source 19. Thereby, the heater 16 can heat the urea water even during stop of the engine 2, whereby the ECU 17 can control power feed to the heater 16 to melt the urea water right after starting the engine 2. Thereby, the urea water can be always supplied even right after the start of the engine 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust emission control device for purifying exhaust gas from a vehicle engine.

  2. Description of the Related Art Conventionally, exhaust gas purification apparatuses that reduce and purify nitrogen oxide (NOx) contained in exhaust gas of a vehicle engine with a reducing agent are known. This reducing agent is, for example, urea water, and ammonia (NH 3) generated by the decomposition of urea generates a harmless nitrogen (N 2) or water (H 2 O) through a reduction reaction with NO x by a catalyst. Purified.

By the way, the conventional exhaust emission control device discloses a technique for preventing the coagulation of the reducing agent during engine operation by heating the reducing agent with engine cooling water or an electric heater (see, for example, Patent Document 1). However, according to the technique described in Patent Document 1, it is impossible to prevent the reducing agent from coagulating after the engine is stopped. Further, after the next engine start, the reducing agent is exhausted until the solidified reducing agent melts. Can not be supplied against. For this reason, when the outside air temperature is low, NOx may not be purified immediately after the engine is started.
Japanese Patent Laid-Open No. 2004-324651

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an exhaust purification device that purifies exhaust gas discharged from a vehicle engine with a reducing agent. It is to be able to supply.

[Means of Claim 1]
The exhaust emission control device according to claim 1 purifies exhaust gas from a vehicle engine with a reducing agent, and includes a heating unit that heats the reducing agent with electric power, and a control unit that controls power supply to the heating unit. Prepare. The control means is provided so as to be able to supply power to the heating means from another power source other than the vehicle driving power source that supplies power for driving the vehicle.

As a result, it is possible to supply power to the heating means even when the engine is stopped, which makes it impossible to supply power from the vehicle drive power source. For this reason, since the heating means can heat the reducing agent even when the engine is stopped, the control means can control the power supply to the heating means so that the reducing agent is melted immediately after the engine is started. As described above, in the exhaust gas purification apparatus that purifies the exhaust gas discharged from the vehicle engine with the reducing agent, the reducing agent can always be supplied even immediately after the engine is started.
The separate power source is, for example, an in-vehicle power source other than the vehicle driving power source, an external power source that can be powered by a plug-in, or the like.

[Means of claim 2]
The exhaust emission control device according to claim 2 includes melting detection means for detecting that the reducing agent is melted. And a control means controls the electric power feeding to a heating means according to the input obtained from a melting detection means.
Thereby, since the heating means can heat the reducing agent depending on whether the reducing agent is melted or not, the coagulation of the reducing agent can be prevented without consuming excessive power.

[Means of claim 3]
According to the exhaust purification device of the third aspect, the melting detection means is a flow path temperature detection means for detecting the temperature of the flow path of the reducing agent, and an outside air temperature detection means for detecting the outside air temperature.
Thereby, the control means can control the heating means in consideration of the outside air temperature as well as the temperature of the reducing agent in the flow path. For this reason, the reliability with respect to the coagulation | solidification prevention of the reducing agent in an exhaust gas purification apparatus can be improved.

[Means of claim 4]
According to the exhaust emission control device of the fourth aspect, the control means controls the power supply to the heating means so that the reducing agent maintains a molten state after the engine is stopped.
Thus, the reducing agent can be kept in a molten state until the next engine start, so that the reducing agent can be reliably supplied immediately after the next engine start.

[Means of claim 5]
According to the exhaust purification device of the fifth aspect, the control means controls the power supply to the heating means so that the reducing agent solidified after the engine is stopped is melted before the engine is started.
As a result, the reducing agent can be melted before the next engine start, so that the reducing agent can be reliably supplied immediately after the next engine start.

[Means of claim 6]
According to the exhaust emission control device of the sixth aspect, the control means controls the power supply to the heating means based on the next engine start timing inputted by the occupant.
Thereby, the control means can set the power supply start time to the heating means by calculating backward from the next engine start time. For this reason, the reducing agent can be melted before the next engine start without consuming excessive power.

[Means of Claim 7]
According to the exhaust emission control device of the seventh aspect, when the next start time of the engine is not input by the occupant, the control means supplies the heating means so that the reducing agent maintains a molten state after the engine is stopped. Control the power supply.
Thereby, even when there is no input of the next engine start time, the reducing agent can be maintained in a molten state until the next engine start.

  The exhaust emission control device of the best mode 1 purifies exhaust gas from a vehicle engine with a reducing agent, and includes heating means for heating the reducing agent with electric power, and control means for controlling power supply to the heating means. . The control means is provided so as to be able to supply power to the heating means from another power source other than the vehicle driving power source that supplies power for driving the vehicle.

  In addition, the exhaust gas purification device includes melting detection means for detecting that the reducing agent is melted. And a control means controls the electric power feeding to a heating means according to the input obtained from a melting detection means. According to this exhaust gas purification apparatus, the melting detection means is a flow path temperature detection means for detecting the temperature of the flow path of the reducing agent, and an outside air temperature detection means for detecting the outside air temperature.

  Further, the control means controls the power supply to the heating means so that the reducing agent solidified after the engine is stopped is melted before the engine is started. That is, the control means controls the power supply to the heating means based on the next engine start timing input by the occupant. Further, the control means controls the power supply to the heating means so that the reducing agent maintains a molten state after the engine is stopped when the next engine start timing is not inputted by the occupant.

[Configuration of Example 1]
The configuration of the exhaust emission control device 1 according to the first embodiment will be described with reference to FIG.
The exhaust emission control device 1 purifies nitrogen oxide (NOx) contained in exhaust gas from the engine 2 of the vehicle with a reducing agent. The reducing agent is, for example, urea water, and ammonia (NH3) generated by decomposition of urea reacts with NOx by a catalyst to generate harmless nitrogen (N2) and water (H2O), thereby purifying NOx. Is done.

  That is, the exhaust purification device 1 promotes the NOx reduction reaction by the first oxidation catalyst device 3 that promotes the oxidation reaction that oxidizes nitric oxide (NO) contained in the exhaust gas to form nitrogen dioxide (NO2), and NH3. A reduction catalyst device 4, a second oxidation catalyst device 5 that promotes an oxidation reaction of unreacted NH 3 that has flowed out of the reduction catalyst device 4, and a urea water supply device 6 that supplies urea water to the exhaust gas, NOx is purified mainly by the catalytic action of the reduction catalyst device 4.

  Here, the urea water supply device 6 includes, for example, a tank 9 for storing urea water, a pump 10 for sucking and discharging urea water from the tank 9, an addition valve 12 for injecting urea water into the exhaust pipe 11, and a pump A supply pipe 13 for guiding urea water from 10 to the addition valve 12 is provided. The addition valve 12 is mounted so as to protrude into the exhaust pipe 11 upstream of the reduction catalyst device 4 and downstream of the first oxidation catalyst device 3. Thereby, the urea water injected from the addition valve 12 is atomized and spreads in the exhaust gas and flows into the reduction catalyst device 4.

The exhaust emission control device 1 includes a heater 16 as a heating unit that heats urea water with electric power, and an electronic control unit (ECU) 17 as a control unit that controls power supply to the heater 16.
The heater 16 is a well-known electric heater, and the tank 9, the pump 10, and the supply pipe are among the devices and members that constitute the portion where the urea water flows (that is, the urea water (reducing agent) flow path). It is equipped so that 13 can be heated.

  The ECU 17 is a well-known microcomputer including a storage device such as a CPU, a ROM, and a RAM, an input device, an output device, and the like that perform a control function and an arithmetic function. The ECU 17 is provided so as to be able to supply power to the heater 16 from another power source other than the vehicle driving power source 19 that supplies power for driving the vehicle. The separate power source is an in-vehicle power source 20 other than the vehicle driving power source 19 or an external power source 21 that can be powered by plug-in.

  Further, the ECU 17 detects the temperature of the urea water stored in the tank 9, the urea water temperature sensor 23 that detects the level of the urea water stored in the tank 9, and the outside air temperature detection that detects the outside air temperature. A detection value is input from the outside air temperature sensor 25 or the like as a means, and power supply to the heater 16 is controlled according to these detection values.

  Here, the urea water temperature sensor 23 functions as a flow path temperature detecting means for detecting the temperature of the flow path of the urea water, and also as a melting detection means for detecting that the urea water is melted together with the outside air temperature sensor 25. Function. That is, the ECU 17 determines whether the urea water is melted or predicts the time when the urea water is solidified according to detection values obtained from the urea water temperature sensor 23, the outside air temperature sensor 25, and the like. The power supply to the heater 16 after the engine 2 is stopped is controlled.

That is, the ECU 17 controls power supply to the heater 16 so that the reducing agent solidified after the engine 2 is stopped is melted before the engine 2 is started (see FIG. 2A).
For example, when the next start time (scheduled engine start time) of the engine 2 is input by the occupant, the ECU 17 determines the time (melting time) necessary for melting the reducing agent by the scheduled engine start time as the urea water temperature. Calculation is performed according to detection values obtained from the sensor 23, the outside air temperature sensor 25, and the like.

  Then, the ECU 17 turns on the heater 16 from another power source (that is, the in-vehicle power source 20 or the external power source 21) at the energization start timing calculated backward from the scheduled engine start timing and the melting time. Further, when the engine 2 is started, the ECU 17 turns off the energization of the heater 16 from another power source, and turns on the energization of the heater 16 from the vehicle drive power source 19 as necessary.

Further, the ECU 17 controls power supply to the heater 16 so that the reducing agent maintains a molten state after the engine 2 is stopped (see FIG. 2B).
For example, the ECU 17 obtains, from the urea water temperature sensor 23, the outside air temperature sensor 25, and the like, the time when the reducing agent starts coagulation after the engine 2 is stopped (coagulation start time) when the scheduled engine start time is not input by the occupant. It calculates according to the detected value.

  Then, the ECU 17 turns on the power to the heater 16 from another power source when the coagulation start time comes. Further, when the engine 2 is started, the ECU 17 turns off the energization of the heater 16 from another power source, and turns on the energization of the heater 16 from the vehicle drive power source 19 as necessary.

[Control Method of Example 1]
A control method by the exhaust emission control device 1 according to the first embodiment will be described with reference to a flowchart shown in FIG.
First, in step S1, the urea water temperature sensor 23, the urea water amount sensor 24, and the outside air temperature sensor 25 obtain the detected values of the temperature of the urea water, the water level of the urea water, and the outside air temperature, respectively. In step S2, it is determined whether there is an input of the scheduled engine start time. If there is an input of the scheduled engine start time (YES), the process proceeds to step S3, and if there is no input of the scheduled engine start time (NO), the process proceeds to step S4.

  In step S3, the melting time is calculated based on the detected values of the temperature of the urea water, the water level of the urea water, and the outside air temperature. In step S4, the melting time is calculated based on the detected values of the temperature of the urea water, the water level of the urea water, and the outside air temperature. Calculate the coagulation start time. In step S5, the energization start time is obtained. That is, when the melting time is calculated, the energization start timing is calculated backward from the scheduled engine start timing and the melting time, and when the solidification start timing is calculated, the solidification start timing is set as the energization start timing.

  In step S6, it is determined whether or not the energization start time has arrived. If the energization start time has arrived (YES), the process proceeds to step S7, where energization from another power source to the heater 16 is turned on. If it has not arrived (NO), it waits until the energization start time arrives.

  Next, in step S8, it is determined whether or not the engine 2 has been started. If the engine 2 is started (YES), the process proceeds to step S9 to turn off the power from the separate power source to the heater 16, and the engine 2 is started. If not (NO), it waits until the engine 2 starts.

  Next, in step S10, the urea water temperature sensor 23, the urea water amount sensor 24, and the outside air temperature sensor 25 again obtain the detected values of the temperature of the urea water, the water level of the urea water, and the outside air temperature, respectively. In step S11, based on the detected values of the temperature of the urea water, the water level of the urea water, and the outside air temperature, it is determined whether or not the urea water may be solidified again. If it is determined that there is a possibility of solidifying again (YES), the process proceeds to step S12, the energization from the vehicle driving power source 19 to the heater 16 is turned on, and if it is determined that there is no possibility of solidifying again (NO), step S10. Return to.

  Next, in step S13, it is determined whether or not the engine 2 is stopped. If the engine 2 is stopped (YES), the control flow is terminated. If the engine 2 is not stopped (NO), the process proceeds to step S10. Return.

[Effect of Example 1]
The exhaust emission control device 1 according to the first embodiment includes a heater 16 that heats urea water with electric power, and an ECU 17 that controls power supply to the heater 16. The ECU 17 is provided so that power can be supplied to the heater 16 from another power source other than the vehicle drive power source 19.
As a result, power can be supplied to the heater 16 even while the engine 2 is stopped, where power supply from the vehicle drive power supply 19 is impossible. For this reason, since the heater 16 can heat urea water even when the engine 2 is stopped, the ECU 17 can control power supply to the heater 16 so that the urea water is melted immediately after the engine 2 is started. . As described above, urea water can always be supplied immediately after the engine 2 is started.

Further, the exhaust purification device 1 includes a urea water temperature sensor 23, a urea water amount sensor 24, and an outside air temperature sensor 25 as melting detection means, and the ECU 17 receives inputs obtained from the urea water temperature sensor 23, the urea water amount sensor 24, and the outside air temperature sensor 25. The power supply to the heater 16 is controlled accordingly.
As a result, the ECU 17 can determine whether the urea water is melted and control the power supply to the heater 16, so that the urea water can be prevented from coagulating without consuming excessive power. . In addition, since the ECU 17 can control the heater 16 in consideration of the outside air temperature as well as the temperature of the urea water in the flow path, the reliability of the reducing agent coagulation prevention in the exhaust purification device 1 is increased.

  Further, when the scheduled engine start time is input by the occupant, the ECU 17 sets the energization start time to the heater 16 by calculating backward from the scheduled engine start time. For this reason, urea water can be melted by the next engine start time without consuming excessive power.

  In addition, when the scheduled engine start time is not input by the occupant, the ECU 17 calculates the solidification start time, and sets the solidification start time as the energization start time. For this reason, even when there is no input of the scheduled engine start time, the urea water can be maintained in a molten state until the next engine start.

[Modification]
According to the exhaust gas purification apparatus 1 of the first embodiment, the ECU 17 supplies the heater 16 to the heater 16 so that the urea water is maintained in the melted state until the next engine start only when the scheduled engine start time is not input by the occupant. Although the power supply is controlled, the power supply to the heater 16 may be controlled so that the urea water is maintained in a molten state until the next engine start regardless of whether the engine start scheduled time is input.

  Further, according to the exhaust gas purification apparatus 1 of the first embodiment, the ECU 17 controls the power supply to the heater 16 based on the detection values obtained from the urea water temperature sensor 23, the urea water amount sensor 24, and the outside air temperature sensor 25. 16 may be performed based on detection values obtained from the urea water temperature sensor 23 and the outside air temperature sensor 25, or may be performed based on detection values obtained from the urea water amount sensor 24 and the outside air temperature sensor 25. . Furthermore, the power supply to the heater 16 may be controlled based on a detection value obtained from any one of the urea water temperature sensor 23 and the outside air temperature sensor 25.

It is a block diagram of an exhaust emission control device. (A) is a time chart showing the energization state from each power source to the heater when there is an input of the scheduled engine start time, and (b) is the energization from each power source to the heater when there is no input of the engine scheduled start time. It is a time chart which shows a condition. It is a flowchart which shows the control flow by an exhaust gas purification apparatus.

Explanation of symbols

1 Exhaust purification device 2 Engine 9 Tank (reducing agent flow path)
10 Pump (reducing agent flow path)
13 Supply piping (reducing agent flow path)
16 Heater (heating means)
17 ECU (control means)
19 Power source for vehicle drive 20 On-vehicle power source (separate power source)
21 External power supply (separate power supply)
23 Urea water temperature sensor (melting detection means, flow path temperature detection means)
24 Urea water quantity sensor (melting detection means)
25 Outside air temperature sensor (melting detection means, outside air temperature detection means)

Claims (7)

In an exhaust purification device that purifies exhaust gas from a vehicle engine with a reducing agent,
Heating means for heating the reducing agent with electric power;
Control means for controlling the power supply to the heating means,
The exhaust gas purification apparatus according to claim 1, wherein the control means is provided so as to be able to supply power to the heating means from another power source other than a vehicle driving power source that supplies power for driving the vehicle. The exhaust emission control device according to claim 1,
Equipped with a melting detection means for detecting that the reducing agent has melted,
The exhaust gas purification apparatus according to claim 1, wherein the control means controls power feeding to the heating means in accordance with an input obtained from the melting detection means. The exhaust emission control device according to claim 2,
The exhaust gas purification apparatus, wherein the melting detection means is a flow path temperature detection means for detecting a temperature of the flow path of the reducing agent and an outside air temperature detection means for detecting an outside air temperature. The exhaust emission control device according to any one of claims 1 to 3,
The exhaust gas purification apparatus according to claim 1, wherein the control means controls power supply to the heating means so that the reducing agent maintains a molten state after the engine is stopped. The exhaust emission control device according to any one of claims 1 to 3,
The exhaust gas purification apparatus according to claim 1, wherein the control means controls the power supply to the heating means so that the reducing agent solidified after the engine is stopped is melted before the engine is started. The exhaust emission control device according to claim 5,
The exhaust gas purification apparatus according to claim 1, wherein the control means controls power supply to the heating means based on a next start timing of the engine input by a passenger. The exhaust emission control device according to claim 6,
The control means controls the power supply to the heating means so that the reducing agent maintains a molten state after the engine is stopped when the next start timing of the engine is not input by a passenger. Exhaust purification device.

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