JP2011007151A - Exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize trouble caused by clogging of an injection nozzle.SOLUTION: An electric heater 200 is disposed around the injection nozzle 120, and a circumference of the electric heater 200 is covered by heat insulating material 202. A temperature sensor TS5 passing through the heat insulating material 202 and the electric heater 200 are disposed near the injection nozzle 120, and detects temperature Ta representing temperature of an inside of the injection nozzle 120. The electric heater 200 eliminates or prevents the injection nozzle 120 from clogging by heating the injection nozzle 120, and melting or gasifying crystal of reducing agent RA solidifying in the injection nozzle 120. The heat insulating material 202 inhibits heat radiation from the electric heater 200 and increases heating efficiency of the electric heater 200.

Description

  The present invention is an exhaust emission control device used for an engine such as a gasoline engine or a diesel engine of an industrial vehicle or the like, and an exhaust gas that reduces and removes nitrogen oxide (NOx) in the exhaust gas using a urea aqueous solution as a reducing agent. The present invention relates to a purification device, and more particularly, to a technique for automatically eliminating clogging of a urea water injection nozzle.

As this type of exhaust purification device, there is a device in which a reduction catalyst is arranged in an exhaust system of an engine, and a reducing agent is supplied from an injection nozzle provided in an exhaust passage upstream of the reduction catalyst. NOx in the exhaust gas is purified into harmless components by contacting the reducing agent and promoting the reduction reaction in the reduction catalyst.
The reduction reaction is a reduction reaction between NOx and ammonia. For example, urea aqueous solution, ammonia aqueous solution, or other reducing agent aqueous solution is used as a reducing agent that efficiently generates ammonia.

  The reducing agent is stored in the storage tank at room temperature, and the required amount is supplied from the storage tank to the injection nozzle through the passage based on the operating state of the engine, that is, the exhaust temperature, NOx emission amount, etc. Depending on the operating condition, clogging may occur in the passage and the injection hole.

  Therefore, in the exhaust emission control device described in Patent Document 1, clogging is detected by the internal pressure of the injection nozzle, and at that time, the urea water supply is stopped, cooling of the injection nozzle is suppressed, and clogging occurs when the exhaust gas temperature rises. Is determined to have been resolved.

JP 2005-113687 A

  In the exhaust purification device of Patent Document 1, when the engine has been in an idling state or a low load state for a long time, it takes a long time to raise the exhaust temperature in the vicinity of the injection nozzle, during which unpurified NOx is discharged. Will be. At this time, the desired purification performance of the exhaust purification device cannot be obtained.

  An exhaust emission control device according to the present invention includes a reduction catalyst disposed in an exhaust passage of an engine, an injection nozzle that injects a reducing agent upstream of the reduction catalyst in the exhaust passage, and a heater that heats the injection nozzle. A condition determination unit that determines whether or not a condition for clogging the injection nozzle (hereinafter, clogging condition) is satisfied, and a heating control unit that starts a heating operation of the heater when the clogging condition is satisfied. It is characterized by providing.

  According to the present invention, obstacles due to clogging of the injection nozzle can be minimized.

1 is a configuration diagram showing an embodiment of an exhaust emission control device according to the present invention. The block diagram which shows the reducing agent supply apparatus of FIG. The flowchart which shows control of the electric heater of FIG. The flowchart which shows the other control of an electric heater. The longitudinal section which shows the detail of the injection nozzle of FIG. The longitudinal section which shows the modification of an injection nozzle. The longitudinal section which shows the other modification of an injection nozzle. The longitudinal section which shows the further another modification of an injection nozzle. The longitudinal section which shows the further another modification of an injection nozzle.

Embodiments of an exhaust emission control device according to the present invention will be described below in detail with reference to the accompanying drawings.
-First embodiment-
1 to 3 are views for explaining an exhaust emission control device according to the first embodiment. As shown in FIG. 1, the exhaust gas EG of the engine 100 such as an industrial vehicle is discharged from the manifold 102 to the atmosphere via the exhaust passage 104.

  An exhaust emission control device used for such an engine is provided with an oxidation catalyst (not shown), a particulate filter (not shown), and a reduction for NOx, which are sequentially arranged in the exhaust passage 104 of the engine 100 from upstream to downstream. A catalyst 110, an oxidation catalyst (not shown), a NOx sensor (not shown) arranged upstream in the vicinity of the reduction catalyst 110, and an injection nozzle 120 that injects the reducing agent RA upstream from the reduction catalyst 110. Then, nitrogen oxides (NOx) discharged from the engine 100 are removed. The injection nozzle 120 is disposed on the side surface of the exhaust passage 104 so that the tip thereof does not protrude into the exhaust passage 104 so as not to hinder the flow of the exhaust gas EG.

  The reduction catalyst 110 reduces and purifies NOx in the exhaust gas EG with a reducing agent RA. For example, a zeolite-type active component is supported on a monolith type catalyst carrier having a cross-sectional honeycomb shape made of ceramic cordieride. Yes. The active component is activated when the reducing agent RA is supplied, and effectively purifies NOx into a harmless substance.

  A reducing agent supply device 130 is connected to the injection nozzle 120, and the reducing agent supply device 130 sucks the reducing agent RA from the storage tank 140 through the supply pipe 132 and sends it to the injection nozzle 120.

  As the reducing agent RA, an aqueous urea solution, an aqueous ammonia solution, or the like is used, and when an aqueous urea solution is used, it is heated and hydrolyzed by the exhaust gas EG in the exhaust passage 104 to generate ammonia. The generated ammonia reacts with NOx in the exhaust gas EG in the reduction catalyst 110 to be purified into water and harmless gas.

  The exhaust passage 104 is provided with an exhaust temperature sensor TS1 that detects the temperature Tg of the exhaust gas EG upstream of the injection nozzle 120, and the reducing agent supply device 130 contains the reducing agent RA that is supplied to the injection nozzle 120. A flow rate sensor TS2 for detecting the flow rate is provided. Based on the detection signal from the flow sensor TS2, clogging of the injection nozzle 120 can be detected.

  On the other hand, the engine 100 is provided with a rotation speed sensor TS3 for detecting the rotation speed Ne and a load sensor TS4 for detecting the load F. The load sensor TS4 detects the fuel injection amount of the engine 100, the accelerator pedal opening, the hydraulic pump pressure, and the like. The stop state of the engine 100 can be detected based on the detection signal of the rotation sensor TS3, and the idling state and the stop state of the engine 100 can be detected based on the detection signal of the load sensor TS4.

  An electric heater 200 is disposed around the spray nozzle 120, and the electric heater 200 is covered with a heat insulating material 202. In the vicinity of the injection nozzle 120, a temperature sensor TS5 penetrating the heat insulating material 202 and the electric heater 200 is disposed, and a temperature Ta representing the temperature inside the injection nozzle 120 can be detected.

  The electric heater 200 heats the injection nozzle 120 and melts or vaporizes the crystal of the reducing agent RA solidified in the injection nozzle 120, thereby eliminating or preventing clogging of the injection nozzle 120. The heat insulating material 202 suppresses heat radiation from the electric heater 200 and increases the heating efficiency of the electric heater 200.

The exhaust temperature sensor TS1, the flow rate sensor TS2, the rotation speed sensor TS3, the load sensor TS4, and the temperature sensor TS5 are connected to the control unit 150. The control unit 150 controls the reducing agent supply device 130, the electric heater 200, the engine 100, and others. To do.
The control unit 150 includes, for example, a computer, and the computer CPU and system memory perform various controls. For example, the electric heater 200 is controlled by a heating control unit 152 realized by a computer. A timer 154 built in the computer is used for time measurement described later.

  As shown in FIG. 2, the reducing agent supply device 130 controls the booster pump 136 provided in the supply pipe 132 for boosting the reducing agent RA and the flow rate Q of the reducing agent RA on the downstream side of the booster pump 136. The flow rate sensor TS <b> 2 is disposed on the downstream side of the supply valve 138.

  The reducing agent supply device 130 includes a reducing agent supply control circuit 134 that controls the booster pump 136, the supply valve 138, and the flow rate sensor TS2. The reducing agent supply control circuit 134 controls the booster pump 136 and the supply valve 138 while being controlled by the control unit 150, and supplies the reducing agent RA with an appropriate flow rate to the injection nozzle 120. The reducing agent supply control circuit 134 adjusts the flow rate Q by controlling the booster pump 136 and the supply valve 138 based on the flow rate Q detected by the flow rate sensor TS2.

  When the flow rate Q detected by the flow rate sensor TS2 is less than a predetermined value, the control unit 150 determines that clogging has occurred and stops the supply of the reducing agent RA by the reducing agent supply device 130. Further, the control unit 150 heats the engine when the engine is idling and the exhaust gas temperature Tg detected by the exhaust temperature sensor TS5 is lower than the melting point (melting temperature) T1 of the reducing agent RA (132 degrees Celsius for urea). The electric heater 200 is operated by the control unit 152 and heated so that the heater temperature Ta ≧ melting point T1. Thereby, the injection nozzle 120 is heated, the reducing agent RA solidified inside is melted, and clogging is eliminated.

  The reason why the engine is in an idling state as a condition for operating the electric heater 200 is that the injection nozzle 120 is highly likely to be heated by the exhaust gas EG when the engine 100 is under load. This is because the possibility of clogging 120 is low.

When the engine 100 is stopped and the temperature Tg of the exhaust gas EG is higher than the freezing point (crystallization temperature) T2 (100 degrees Celsius for urea) of the reducing agent RA, the reducing agent RA stays inside the injection nozzle 120. In such a case, the reducing agent RA may crystallize inside the injection nozzle 120 due to a temperature drop thereafter. On the other hand, when the exhaust gas temperature Tg is equal to or higher than the boiling point (vaporization temperature) T3 (360 degrees Celsius for urea) of the reducing agent RA, the reducing agent RA is vaporized and discharged from the exhaust passage 104, thereby causing clogging. Unlikely.
Therefore, when the freezing point T2 <exhaust gas temperature Tg <boiling point T3, the control unit 150 operates the electric heater 200 by the heating control unit 152 to heat the heater so that the heater temperature Ta ≧ the boiling point T3.

As shown in FIG. 3, the control unit 150 functions as the heating control unit 152 by the control program stored in the built-in ROM, and executes the following steps.
This program is activated when the ignition switch is operated to the accessory position or the on position.

  Step S301: First, it is determined whether or not the engine 100 is stopped based on the output signal of the rotation sensor TS3. When the engine 100 is in a stopped state, the process proceeds to step S311. When the engine 100 is in an operating state, the process proceeds to step S302.

  Step S302: It is determined whether or not the injection nozzle 120 is clogged based on the output signal of the flow sensor TS2. When the flow rate of the urea water is equal to or lower than the predetermined value based on the output signal of the flow rate sensor TS2, it is determined that clogging has occurred, and the process proceeds to step S303. If it is determined in step S302 that no clogging has occurred, the process proceeds to step S310.

  Step S303: Supply of the reducing agent RA is stopped by the reducing agent supply device 130, and the process proceeds to Step S304.

  Step S304: If it is determined that the injection nozzle 120 is clogged while the engine is operating, it is determined whether or not the engine 100 is idling based on the output signal of the load sensor TS4. When it is in the idling state, the process proceeds to step S305, and when it is not in the idling state (during load operation), the process returns to step S301.

  Step S305: When it is determined that the injection nozzle 120 is clogged and in an idling state, it is determined whether or not the temperature Tg of the exhaust gas EG is lower than the melting point T1 based on the output signal of the exhaust temperature sensor TS1. When Tg <T1, the process proceeds to step S306, and when Tg ≧ T1, the process returns to step S301.

  Step S306: When it is determined that the temperature Tg of the exhaust gas EG is lower than the melting point T1, the electric heater 200 is operated, and the process proceeds to Step S307.

  Step S307: It is determined whether or not the temperature Ta of the electric heater 200 has become higher than the melting point T1 based on the output signal of the temperature sensor TS5. When Ta> T1, the process proceeds to step S308, and when Ta ≦ T1, the process returns to step S306. Thus, heating is continued until the temperature of the injection nozzle 120 is raised to the melting point T1.

  Step S308: The timer 154 measures the time for which heating of the electric heater 200 is continued after Ta> T1, and then proceeds to step S309. As a result, the injection nozzle 120 can be continuously heated at the melting point T1, and clogging can be reliably eliminated.

Step S309: Stop the electric heater 200 and return to Step S301.

  Step S310: When it is determined in step S302 that the injection nozzle 120 is not clogged, the supply of the reducing agent RA is resumed, and the process of FIG. 3 is completed.

  Step S311: If it is determined in step S301 that the engine is not in operation, the process proceeds to step S311. Based on the output signal of the exhaust temperature sensor TS1, the temperature Tg of the exhaust gas EG is higher than the crystallization temperature T2, and It is determined whether or not the boiling point is lower than T3. When T2 <Tg <T3, the process proceeds to step S312, and when Tg ≦ T2 or Tg ≧ T3, the process is ended as it is.

  Step S312: When it is determined that the temperature Tg of the exhaust gas EG is higher than the crystallization temperature T2 and lower than the boiling point T3, the electric heater 200 is operated, and the process proceeds to Step S313.

  Step S313: It is determined whether Ta> T3. When Ta> T3, the process proceeds to step S314. When Ta ≦ T3, the process returns to step S312. Thus, the heating is continued until the temperature of the spray nozzle 120 is raised to the boiling point T3.

Step S314: The timer 154 measures the time during which heating of the electric heater 200 is continued after Ta> T3, and then proceeds to step S315. Thereby, the injection nozzle 120 is continuously heated at the vaporization temperature T3, and clogging can be reliably eliminated.
Thereafter, the processing of the entire control program is terminated.

According to the exhaust emission control device of the first embodiment described above, the following operational effects can be obtained.
(1) When clogging of the injection nozzle 120 is detected, the injection nozzle 120 is heated so that the clogging is eliminated. Therefore, clogging can be reliably eliminated. And when clogging has not occurred, the heater is not operated, so that energy consumption for the heater can be saved.

(2) When clogging of the injection nozzle 120 is detected, the temperature of the injection nozzle 120 is equal to or higher than the melting point T1 of the reducing agent when the exhaust gas temperature Tg is lower than the melting point (melting temperature) T1 of the reducing agent in the idling state. Since the electric heater 200 is operated as described above, the reducing agent solidified in the injection nozzle 120 can be reliably melted.
Since the idling state is added as a condition for operating the electric heater 200, the electric heater 200 is operated only when the possibility of clogging due to the exhaust gas temperature Tg is low, and energy consumption for the electric heater 200 is reduced. Can do.

(3) When the engine 100 is stopped, if the exhaust gas temperature Tg is equal to or higher than the freezing point T2 of the reducing agent and less than the vaporization temperature T3 that can vaporize the solidified reducing agent, the temperature of the injection nozzle 120 is solidified. The electric heater 200 is operated so that the temperature becomes higher than the temperature at which the reducing agent can be vaporized. Therefore, it can be prevented that the exhaust gas temperature Tg decreases after the engine stops and the reducing agent is solidified by the injection nozzle 120. That is, clogging of the injection nozzle 120 can be prevented.

-Second embodiment-
As shown in FIG. 4, the temperature sensor TS5 is omitted, and steps S307 and S313 in the flowchart of FIG. 3 are omitted, and a simpler configuration and processing can be employed. That is, the following steps may be executed by the control unit 150.

  Steps S401 to S406: The same processing as steps S301 to S306 is executed. The contents have been described with reference to FIG.

  Step S407: The electric heater 200 is operated for a predetermined time. However, unlike step S308, a heating time during which the injection nozzle 120 is reliably higher than the melting point T1 is obtained in advance, and the heating time is measured by the timer 154. That is, the electric heater 200 operates regardless of the temperature Ta. When the predetermined heating time has elapsed, the process proceeds to step S408.

Step S408: The electric heater 200 is stopped as in step S309.
Steps S409 to S411: The same processes as in steps S310 to S411 are executed. The contents have been described with reference to FIG.

  Step S412: The electric heater 200 is operated for a predetermined time. However, unlike step S314, a heating time during which the injection nozzle 120 is reliably higher than the boiling point T3 is obtained in advance, and the heating time is measured by the timer 154. That is, the electric heater 200 operates for a sufficient heating time regardless of the temperature Ta. When the predetermined heating time has elapsed, the process proceeds to step S413.

  Step S413: The electric heater 200 is stopped similarly to step S315, and the processing of the entire control program is ended.

According to the exhaust gas purification apparatus of the second embodiment described above, the following effects can be obtained in addition to the operational effects obtained by the exhaust gas purification apparatus according to the first embodiment.
(1) When the temperature Tg detected by the exhaust temperature sensor TS5 is equal to or lower than the melting point T1 of the reducing agent RA, the heating controller 152 operates the electric heater 200 for a predetermined time, and heats so that Ta ≧ T1. Therefore, it is not necessary to manage the temperature of the injection nozzle 120, and the program is simplified.

Below, the shape of the injection nozzle 120 is demonstrated according to FIGS.
As shown in FIG. 5, the injection nozzle 120 is formed, for example, by opening a plurality of holes 120 </ b> H on the tip side wall of a pipe whose tip is blocked. Thus, the manufacturing cost of the injection nozzle 120 can be reduced by processing the pipe to form the injection nozzle 120.

The electric heater 200 is disposed so as to surround the injection nozzle 120 while being slightly separated from the injection nozzle 120. The heat insulating material 202 is disposed so as to cover the electric heater 200 while being in close contact with the electric heater 200.
By separating the electric heater 200 from the injection nozzle 120, maintenance of the injection nozzle 120 and the electric heater 200 is facilitated.

  The temperature sensor TS5 is disposed so that the tip thereof is close to the injection nozzle 120 while penetrating through the heat insulating material 202 and the through hole 204 formed in the electric heater 200. The temperature sensor TS5 can be inserted into and removed from the through hole 204, and maintenance of the temperature sensor TS5 is easy.

FIG. 6 shows a modification of the injection nozzle 120. In the modification of FIG. 6, the electric heater 200 is in close contact with the injection nozzle 120. Other configurations are the same as those in FIG.
By bringing the electric heater 200 into close contact with the injection nozzle 120, the injection nozzle 120 can be heated more efficiently than the configuration of FIG.

FIG. 7 shows another modification of the injection nozzle 120. In the modification of FIG. 7, the injection nozzle 120 is formed by a tip-shaped spherical pipe. Thereby, the injection direction of the reducing agent RA can be set in various directions such as an oblique direction along the flow of the exhaust gas EG, and an effective supply of the reducing agent RA is possible.
Also in FIG. 7, the electric heater 200 is in close contact with the injection nozzle 120.

FIG. 8 shows another modification of the injection nozzle 120. In the modification of FIG. 8, the injection nozzle 120 is formed by a sphere 122, and a pipe 124 is connected to the sphere 122. Thereby, compared with FIG. 7, the injection direction of the reducing agent RA can be set more variously, and the effective supply of the reducing agent RA is possible. Thus, the injection nozzle 120 is not limited to the nozzle shape, and various shapes can be adopted.
The electric heater 200 is in close contact with the sphere 122 and the pipe 124.

FIG. 9 shows another modification of the injection nozzle 120. In the modification of FIG. 9, the injection nozzle 120 is formed by a thick pipe 126, and the temperature sensor TS <b> 5 is embedded in the wall surface of the pipe 126. Thereby, the temperature sensor TS5 can detect the temperature in the injection nozzle 120 more precisely.
The electric heater 200 is in close contact with the sphere 122 and the pipe 124.

The exhaust emission control device according to the present invention can be implemented with the following modifications.
(1) In the exhaust purification apparatus described above, the electric heater 200 is operated when the following three conditions (a) to (c) are satisfied while the engine is operating.
(A) The injection nozzle 120 is clogged,
(B) the engine is idling;
(C) the exhaust gas temperature is lower than the melting point (melting temperature) T1 of the reducing agent,
However, when the injection nozzle 120 is clogged, it is possible to operate the electric heater 200 unconditionally regardless of the operating state of the engine and the exhaust gas temperature Tg, thereby simplifying the device configuration and control processing.

(2) Although the clogging of the injection nozzle 120 is detected by detecting the flow rate of the urea aqueous solution, a pressure sensor for detecting the pressure of the urea aqueous solution is disposed instead of the flow rate sensor, and the pressure of the injection nozzle 120 is determined by the pressure. A clog may be detected.

(3) After the clogging of the injection nozzle 120 was detected, the operation of the heater 200 was controlled by determining the conditions under which the urea water solidified and clogged during engine operation. However, the heater may be operated on the condition that the clogging of the injection nozzle 120 is detected by the flow sensor or the pressure sensor during engine operation.

(4) When the engine is stopped, the electric heater 200 is operated when the exhaust gas temperature Tg is equal to or higher than the freezing point T2 of the reducing agent and lower than the vaporization temperature T3 that can vaporize the solidified reducing agent. However, whenever the engine is stopped, the temperature of the injection nozzle 120 may be controlled to be equal to or higher than the vaporization temperature T3 that can vaporize the solidified reducing agent.

  Although the above embodiment demonstrated a gasoline engine and a diesel engine, this invention is applicable to the arbitrary exhaust gas purification apparatuses which purify | clean exhaust gas with a reducing agent.

EG Exhaust gas TS1 Exhaust temperature sensor TS2 Flow rate sensor TS3 Rotation sensor TS4 Load sensor TS5 Temperature sensor RA Reductant 100 Engine 104 Exhaust passage 110 Reduction catalyst 120 Injection nozzle 130 Reductant supply device 150 Control unit 152 Heating control unit 154 Timer 200 Electric heater

Claims (5)

A reduction catalyst disposed in the exhaust passage of the engine;
An injection nozzle for injecting a reducing agent upstream of the reduction catalyst in the exhaust passage;
A heater for heating the spray nozzle;
Condition determining means for determining whether or not a condition for clogging the injection nozzle (hereinafter, clogging condition) is satisfied;
When the clogging condition is satisfied, heating control means for starting the heating operation of the heater;
An exhaust emission control device comprising: The exhaust emission control device according to claim 1,
The clogging condition is a condition in which the exhaust gas temperature is lower than the melting point of the reducing agent (hereinafter referred to as the melting temperature),
A temperature detecting means for detecting the exhaust gas temperature;
The exhaust gas purifying apparatus according to claim 1, wherein the condition determining means determines that the clogging condition is satisfied when the exhaust gas temperature is lower than a melting point of the reducing agent (hereinafter referred to as a melting temperature). The exhaust emission control device according to claim 1,
The clogging condition is a condition in which the exhaust gas temperature during engine idling is less than the melting point of the reducing agent (hereinafter referred to as the melting temperature),
Idling determination means for determining whether or not the engine is idling;
Temperature detecting means for detecting the exhaust gas temperature,
The condition determination means determines that the clogging condition is satisfied when the engine is in an idling state and the exhaust gas temperature is lower than a melting point of the reducing agent (hereinafter referred to as a melting temperature). A featured exhaust purification device. The exhaust emission control device according to any one of claims 1 to 3,
Clogging detection means for determining whether or not the injection nozzle is clogged,
The exhaust emission control device characterized in that the heating control means operates the heater on condition that the clogging of the injection nozzle is detected by the clogging detection means. The exhaust emission control device according to claim 1,
The clogging condition is a condition in which the exhaust gas temperature is a temperature between the crystallization temperature of the reducing agent and the vaporization temperature when the engine is stopped.
Stop determination means for determining whether or not the engine is stopped;
A timer for detecting an operation time of the heater by the heating control means;
The condition determining means determines that the engine stop heating condition is satisfied when the exhaust gas temperature is between the crystallization temperature of the reducing agent and the vaporization temperature when the engine is stopped.
The heating control means starts the operation of the electric heater when the heating condition when the engine is stopped is satisfied, and stops the operation of the electric heater after a predetermined time elapses after the start of heating. Exhaust gas purification device.

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