JP4447142B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust gas purification device for an internal combustion engine that purifies exhaust gas discharged from the internal combustion engine.
[0002]
[Prior art]
A selective reduction type NOx catalyst that reduces or decomposes harmful NOx with a reducing agent in an oxygen-excess atmosphere is an exhaust gas discharged from an internal combustion engine (for example, a diesel engine or a lean burn gasoline engine) that can burn at a lean air-fuel ratio. Often used as an exhaust purification device for purifying NOx.
[0003]
The reduction catalyst requires a reducing agent, and a technique using solid urea as a reducing agent has been developed. As an example of the means for discharging the solid urea in the storage device, there is a reducing agent supply device described in JP 2000-27626 A.
[0004]
In the apparatus disclosed in Japanese Patent Laid-Open No. 2000-27626, there is disposed a pulverizing means including a spring member fixed to the upper wall of the storage device and a pulverizing mechanism fixed to the lower end portion of the spring member. The crushing mechanism has a plurality of crushing arms extending radially from the vertical bar to the vicinity of the side wall of the storage device, and the lower tip of the vertical bar extends inward from the bottom wall of the storage device. The guide member is guided so as to be slidable in the vertical direction. When supplying urea to the storage device, the spring member of the pulverizing means is not buried in urea so that it can freely expand and contract.
[0005]
Urea tends to be agglomerated in the storage device, but when such a crushing means is arranged in the storage device, the crushing mechanism guided so as to be slidable in the vertical direction by the guide member causes the spring member to move due to vehicle vibration. In order to vibrate up and down, the mass of urea is crushed throughout the storage device. Thereby, the pulverized urea in the storage device can be discharged continuously.
[0006]
[Problems to be solved by the invention]
However, the apparatus disclosed in Japanese Patent Application Laid-Open No. 2000-27626 requires a spring member and a crushing mechanism to discharge the solid reducing agent from the storage apparatus, and the storage apparatus is complicated. Further, there is no specific supply means for the solid reducing agent discharged from the solid reducing agent storage device.
[0007]
In particular, when a solid reducing agent is used after being liquefied, if a reducing agent such as molten urea remains in the supply path, if the temperature decreases with time, these solidify again and are supplied next time. May not be possible.
[0008]
Therefore, it is desired to provide an apparatus that can reliably supply a predetermined amount of reducing agent to a position upstream of the selective reduction type NOx catalyst.
[0009]
The present invention has been made in view of such problems, and the problem to be solved by the present invention is that it is small and excellent in controllability, and is heated upstream from a selective reduction type NOx catalyst by heating and melting a solid reducing agent. Another object of the present invention is to provide an exhaust gas purifying apparatus capable of supplying a predetermined amount to the exhaust gas passage.
[0010]
[Means for Solving the Problems]
The present invention employs the following means in order to solve the above problems. That is, the present invention provides a selective reduction type NOx catalyst that is provided in an exhaust gas passage of an internal combustion engine and that reduces or decomposes NOx in the presence of an ammonia-derived reducing agent,
A solid reducing agent storage means for storing a solid reducing agent;
A heating and melting means for heating and melting the solid reducing agent;
A melt reducing agent storage means for storing the melt reducing agent derived from the solid reducing agent storage means;
A melt reducing agent supply means for supplying the melt reducing agent to the exhaust gas passage upstream of the selective reduction type NOx catalyst;
A melting reducing agent supply amount calculating means for calculating a supply amount of the melting reducing agent supplied by the melting reducing agent supply means according to an operating state;
And a reducing agent heating control means for controlling the heating and melting means based on the reducing agent supply amount calculated by the melting and reducing agent supply amount calculating means.
[0011]
The required amount of the solid reducing agent stored in the solid reducing agent storage means is calculated according to the operating conditions, and is heated and melted by the heating and melting means installed at the bottom of the solid reducing agent storage means, and the molten reducing agent storage means Stored in. The stored molten reducing agent is supplied to the exhaust passage upstream of the selective reduction type NOx catalyst by the reducing agent supply means.
[0012]
In the present invention, the melting reducing agent storage means is provided with detecting means for detecting the remaining amount of the melting reducing agent, the remaining amount of the melting reducing agent detected by the detecting means, and the melting reducing agent supply amount calculating means. The reducing agent heating control means can be controlled such that the reducing agent supply amount calculated by the above is equal.
[0013]
By controlling the melting amount of the solid reducing agent and the supply amount of the melting reducing agent as described above, the molten reducing agent remaining without being used becomes solid again in the apparatus, and the melting reducing agent in the apparatus Can be blocked.
In the present invention, the heating temperature of the heating and melting means can be set to a temperature at which the solid reducing agent is not altered.
[0014]
Moreover, in this invention, the temperature holding means which hold | maintains the temperature of the said melt | dissolution reducing agent preservation | save means to the temperature which a solid reducing agent does not change can be provided.
[0015]
The heater surface temperature when melting the solid reducing agent is preferably in the range of about 133 degrees Celsius to 200 degrees Celsius. This is because urea is unlikely to deteriorate in this temperature range.
[0016]
In the present invention, since the flow rate of the liquid reducing agent is controlled, the apparatus can be reduced in size and simplified, and the controllability is good, so that the supply amount of the reducing agent can be controlled with high accuracy.
[0017]
Examples of the internal combustion engine include an in-cylinder direct injection type lean burn gasoline engine and a diesel engine.
[0018]
Examples of the selective reduction NOx catalyst include a catalyst in which a transition metal such as Cu is ion-exchanged and supported on zeolite, a catalyst in which a noble metal is supported on zeolite or alumina, a titania / vanadium catalyst, and the like.
[0019]
The reducing agent can be easily taken out from the solid reducing agent storage means by forming a spherical shape, for example. An example of the reducing agent is urea.
[0020]
The heating and melting means may be a heater installed on the bottom surface of the solid reducing agent storage means.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of an exhaust gas purification apparatus for an internal combustion engine according to the present invention will be described below based on the drawings of FIGS. In addition, each embodiment described below is an aspect in which the present invention is applied to a vehicle driving diesel engine.
[0022]
Air is introduced into the combustion chamber 2 of each cylinder of the vehicle diesel engine 1 through the air cleaner 3 from the intake pipe 4 and fuel is injected into the combustion chamber 2 from the fuel injection valve 5. Burns at fuel ratio. In FIG. 1, reference numeral 6 denotes a piston.
[0023]
Exhaust gas exhausted from each combustion chamber 2 is exhausted into the atmosphere through an exhaust pipe 7 downstream thereof, a NOx catalytic converter 8, and an exhaust pipe 9 downstream of the NOx catalytic converter 8. The NOx catalytic converter 8 contains a zeolite-silica-based or TiN selective reduction type NOx catalyst 10 that reduces or decomposes NOx in the presence of a reducing agent.
[0024]
In order to purify NOx in the exhaust gas by the selective reduction type NOx catalyst 10, the presence of a reducing agent is necessary. For this reason, the exhaust purification device has an exhaust pipe 7 upstream of the NOx catalytic converter 8. A reducing agent adding device (reducing agent adding means) 11 for adding a reducing agent is provided.
[First Embodiment]
A first embodiment of an exhaust gas purification apparatus for an internal combustion engine according to the present invention will be described with reference to FIGS.
[0025]
FIG. 2 shows the reducing agent addition apparatus 11 in the present embodiment. This is to liquefy a large number of solid urea A formed in a spherical shape as a reducing agent and then supply it into the exhaust pipe 7. The reducing agent adding device 11 includes a storage container 12 for storing solid urea A, and a heater 31 installed on the inner bottom surface 12 c of the storage container 12. The inner bottom surface 12c where the heater 31 is installed is formed so as to incline so that the discharge port 12d is at the lowest position and descends toward the center.
[0026]
The solid urea A can be prevented from sticking to each other and becoming a large lump by coating with an anti-sticking agent.
[0027]
Since the solid urea A has a property of absorbing moisture and fixing easily, the storage container 12 can be provided with a dehumidifying means such as silica gel (not shown). In this case, the dehumidifying means 15 can be configured as a container containing silica gel or the like so as to communicate with the storage container 12 to which the solid urea A is supplied via the passage 15a.
[0028]
A communication passage 12e is connected to the discharge port 12d of the storage container 12, and a liquid urea storage chamber 13 is installed below the communication passage 12e. A melt reducing agent is disposed below the liquid urea storage chamber 13. A conveyance path 33 is provided. The addition control valve 14 is connected to the melt reducing agent conveyance path 33.
[0029]
The storage container 12 has a reducing agent inlet 12a at an upper portion thereof, and the reducing agent inlet 12a can be opened and closed by a lid 12b. There is a discharge port 12 d at the center of the bottom surface of the storage container 12, which communicates with the liquid urea storage chamber 13.
[0030]
As shown in FIG. 2, the inclined bottom surface 12 c includes a heater 31 that heats the surface, and the heater 31 is energized and controlled by the ECU 16.
[0031]
The liquid urea storage chamber 13 stores the liquid urea U supplied from the upper storage container 12 through the communication path 12e. The liquid urea U is added to the exhaust pipe 7 with the flow rate controlled by the addition control valve 14.
[0032]
The addition control valve 14 has a needle valve 14a at the tip, and a communication path 12c from the liquid urea storage chamber 13 is connected to a supply path 14d through which an axial valve body 14c penetrates in the axial direction. It is guided by the support 14e so that it can reciprocate. At the rear end of the addition control valve 14, a stopper 14f mounted on the rear portion of the penetrating valve body 14c is provided, which is locked to the rear end surface of the main body of the addition control valve 14. A solenoid 37 is disposed behind the stopper 14f, and when it is excited, the stopper 14f is pulled backward. A seal 14b is provided on the outer peripheral surface of the support 14e of the valve body 14c so that the supplied liquid urea U does not leak.
[0033]
Since the reducing agent addition device 11 has the above-described configuration, the solid urea A is heated and melted by the heater 31, and the heated and melted solid urea A is liquefied and flows down the lower surface 12c, from the discharge port 12d. It continuously falls into the liquid urea storage chamber 13. The flow rate of the liquid urea U is controlled by the addition control valve 14 and is added into the exhaust pipe 7. That is, the opening / closing time of the addition control valve 14 is duty ratio controlled by the ECU 16, thereby controlling the flow rate and addition timing of the liquid urea U.
[0034]
More specifically, the solenoid 37 of the addition control valve 14 is excited by energization according to a command from the ECU 16, the stopper 14f moves rearward, and the valve body 14c moves rearward along with this, and the needle valve 14a at the distal end is moved. When is opened, a predetermined amount of urea is added into the exhaust passage for a predetermined time during the valve opening.
[0035]
On the other hand, when the energization to the solenoid 37 is stopped, the stopper 14f is returned to the original position by the spring 38, the needle valve 14a is closed, and the addition of urea is completed.
[0036]
Between the addition control valve 14 and the liquid urea storage chamber 13, a pump (not shown) that pressurizes the liquid urea U and sends it to the pressure regulator, and the liquid urea U is kept at a constant pressure in the pressure regulator. There is provided a pressure regulator 39 that pressurizes the pressure.
[0037]
By the way, the heating source such as the electric heater 31 provided in the solid urea storage container 12 is at an optimum temperature (for example, 133 ° C. to 3 ° C.) at which the solid urea A is liquefied and stored in the liquid urea storage chamber 13 as a liquid. The heating state is controlled by the ECU 16 so as to be 230 ° C. This is because when the solid urea A is heated to a temperature higher than the optimum temperature, it may be gasified without being liquefied. However, the temperature may be set to 230 ° C. or higher if there is no inconvenience such as deterioration or gasification of solid urea.
[0038]
Further, the storage container 12 is provided with a remaining amount sensor 17 (FIG. 1) for detecting the remaining amount of the solid urea A. The remaining amount sensor 17 outputs an output signal proportional to the detected remaining amount of the solid urea A to the ECU 16. Output to.
[0039]
When an input signal indicating a predetermined remaining amount value (hereinafter referred to as an alarm remaining amount value) is input from the remaining amount sensor 17, the ECU 16 lights the alarm lamp 23 of the meter panel 22, and the solid urea A Notify that the remaining amount is low.
[0040]
Further, when the ECU 16 receives an input signal indicating a lower limit value lower than the alarm remaining amount value from the remaining amount sensor 17, the ECU 16 stops the operation of the reducing agent adding device 11 and fully closes the addition control valve 14. Then, the addition of the liquid urea U is stopped.
[0041]
On the other hand, the exhaust pipe 7 upstream of the NOx catalytic converter 8 is provided with an incoming gas temperature sensor 19 for detecting the temperature of the exhaust gas flowing into the NOx catalytic converter 8, and an output signal proportional to the detected incoming gas temperature. Is output to the ECU 16.
[0042]
The ECU 16 is composed of a digital computer, and includes a ROM (Read Only Memory), a RAM (Random Access Memory), a CPU (Central Processor Unit), an input / output port, and an output port that are connected to each other via a bidirectional bus. In addition to performing basic control such as fuel injection amount control, in this embodiment, addition amount control of liquid urea U and energization control of the heater 31 are performed.
[0043]
For these controls, an input signal from the air flow meter 20 is input to the input port of the ECU 16 via the A / D converter. The air flow meter 20 outputs an output signal proportional to the intake air amount to the ECU 16, and the ECU 16 calculates the intake air amount based on the output signal of the air flow meter 20.
[0044]
The exhaust pipe 7 upstream of the NOx catalytic converter 8 is provided with a NOx sensor 21 that detects the amount of NOx flowing into the NOx catalytic converter 8, and outputs an output signal proportional to the detected NOx amount to the ECU 16.
[0045]
The ECU 16 calculates the target addition amount of the liquid urea U necessary for purifying NOx based on the detected NOx amount, calculates the energization time of the heater 31 corresponding to this target addition amount, and energizes the heater 31. . Further, the duty ratio of the addition control valve 14 that obtains a flow rate corresponding to the target addition amount is calculated, and the addition control valve 14 is controlled by the duty ratio. Since only the necessary amount of solid urea A is liquefied and added in this way, the excess liquid urea U remaining in the apparatus 11, particularly the liquid urea storage chamber 13, is solidified again and clogged in the apparatus. Can be prevented.
[0046]
Next, the operation of the exhaust gas purification apparatus for the internal combustion engine will be described. As described above, the ECU 16 performs energization control of the heater 31 and duty ratio control of the addition control valve 14 according to the operating state of the engine 1, that is, according to the NOx emission amount, and an appropriate amount is set in the exhaust pipe 7. Add liquid urea U. As a result of being heated by the exhaust gas, the liquid urea U added into the exhaust pipe 7 is immediately vaporized to become a reducing gas (ammonia gas) and flows into the NOx catalytic converter 8 together with the exhaust gas.
[0047]
The reducing gas reduces or decomposes NOx contained in the exhaust gas on the selective reduction type NOx catalyst 10. The purified exhaust gas is discharged to the atmosphere through the exhaust pipe 9.
[0048]
The selective reduction type NOx catalyst 10 has a property that the NOx purification rate is low when the exhaust gas temperature is equal to or lower than a predetermined temperature, and the NOx purification rate is rapidly increased when the exhaust gas temperature exceeds the predetermined temperature. Therefore, even if the reducing gas is added when the exhaust gas temperature is low, the added reducing gas passes through the NOx converter 8 without being used for the NOx reduction reaction and is released to the atmosphere. Therefore, in this embodiment, when the incoming gas temperature detected by the incoming gas temperature sensor 19 is equal to or lower than the predetermined temperature, the ECU 16 controls the addition control valve 14 to be fully closed, thereby stopping the addition of the liquid urea U. Therefore, leakage of reducing gas is prevented in advance.
[0049]
In the above-described embodiment, the NOx sensor for detecting the NOx concentration of the exhaust gas is provided in the exhaust pipe 7 upstream of the NOx catalytic converter 8, and the NOx concentration detected by the NOx sensor and the air flow meter 20 are used for detection. The NOx emission amount is calculated from the intake air amount. Instead of this, the relationship between the operating state of the engine 1 and the NOx emission amount is mapped in advance, and the actual individual values are referenced with reference to this map. The NOx emission amount in the engine operating state may be estimated and calculated.
[0050]
Further, the time taken to supply all of the molten reducing agent stored in the liquid urea storage chamber 13 and the addition control valve 14 into the exhaust pipe 7 is obtained by heating and melting the solid reducing agent with the heater 31 and adding the control valve 14. Reducing agent storage capacity and heater of the liquid element storage chamber 13, the addition control valve 14, and the molten reductant transfer passage 33 from the liquid element storage chamber 13 to the addition control valve 14 so as to be longer than the time required for the transfer. You may make it set 31 reducing agent melting performance.
[0051]
Further, the solid reducing agent may be added to the exhaust pipe 7 after all of the solid reducing agent has been melted, but the amount of addition and the amount of addition are always grasped, and the addition is started simultaneously with melting, and finally the calculated amount and amount of addition are Feedback control may be performed so as to be the same.
[0052]
Next, a flow chart of reducing agent supply by this reducing agent supply device will be described.
[0053]
In step 100, the ECU 16 calculates a target addition amount of liquid urea U necessary for purifying NOx based on the detected NOx amount.
[0054]
After the calculation, the process proceeds to step 101, where the heater for heating the solid urea is energized to liquefy the solid urea, and the target amount of liquid urea U is generated. The generated liquid urea U is stored in the liquid urea storage chamber 13 (step 102).
[0055]
Next, in step 103, it is determined whether it is time to add liquid urea U as a reducing agent into the exhaust pipe 7. If it is the addition time, the routine proceeds to step 104 where liquid urea U is added into the exhaust pipe 7. On the other hand, if it is not the addition time, the process returns to step 102 and the liquid urea U is stored in the liquid urea storage chamber 13. In step 103, it is determined again whether it is the addition time. If it is the addition time, liquid urea U is added.
[0056]
In the exhaust purification apparatus of this embodiment, the solid urea A as described above is heated and liquefied to form liquid urea U, and a predetermined amount of this liquid urea U is added into the exhaust pipe 7 by the addition control valve 14. In this case, the amount of heat required to liquefy the solid urea can be smaller than the amount of heat required to vaporize the solid urea, so that the heating source (electric heater) is smaller than using gasified urea. That's it. In addition, since liquid urea U is produced by directly liquefying solid urea, it becomes 100% concentration and precise addition amount control is required, but because the controlled object is liquid, not addition control, The valve 14 can sufficiently control the flow rate with high accuracy.
[Second Embodiment]
Next, a second embodiment of the exhaust gas purification apparatus for an internal combustion engine according to the present invention will be described. FIG. 3 shows a reducing agent addition apparatus 30 in the present embodiment. The solid urea A as the reducing agent is liquefied and supplied into the exhaust pipe 7 as in the first embodiment and the apparatus.
[0057]
The storage container 12 has a reducing agent input port 12a on the top surface, and a discharge port 12d at the bottom thereof, which communicates with the liquid urea storage chamber 13 through the communication path 12e. A lattice-shaped heater 31 is installed at the discharge port 12 d, and solid urea A is heated and melted by the heater 31. The generated liquid urea U flows down into the liquid urea storage chamber 13 from the discharge port 12d and is stored.
[0058]
A predetermined amount of this liquid urea U is added into the exhaust pipe 7 by the addition control valve 14. In addition, as in the case of the first embodiment, the addition control valve 14 is duty ratio-controlled by the ECU 16 for the opening and closing time, thereby controlling the flow rate and addition timing of the liquid urea U.
[0059]
In this embodiment, in the liquid urea storage chamber 13 in which the liquid urea U is stored, a liquid amount sensor 32 that detects a melting reducing agent, and an ECU 16 that controls the heater 31 based on a signal from the liquid amount sensor 32. Is provided.
[0060]
The liquid amount sensor 32 outputs the detected remaining amount of liquid urea U to the ECU 16 as an output signal. When the ECU 16 receives an input signal indicating a predetermined remaining amount value from the melt reducing agent detection means 32, the ECU 16 energizes the heater 31 to melt the solid urea A into liquid urea U, which is converted into the liquid urea storage chamber 13. To flow down.
[0061]
The predetermined remaining amount value, that is, the threshold value, is the liquid urea until the solid urea A is liquefied and added from the storage chamber 12 through the liquid urea storage chamber 13 to the exhaust pipe 7 from the addition control valve 14. The value is such that U does not disappear (the liquid urea storage chamber 13 does not become empty), and the liquid urea U of this value is always stored in the liquid urea storage chamber 13. Preserving a large amount of liquid urea U must be avoided because the liquid urea re-solidifies due to a temperature drop over time. However, if the liquid urea storage chamber 13 is emptied, the NOx reduction action by the selective reduction type NOx catalyst 10 stops, and there is a risk that NOx in the exhaust gas is released into the atmosphere. .
[0062]
Therefore, considering the time until the solid urea A is melted by heating and becomes liquid urea U and is added into the exhaust pipe 7, it is replenished when the level of the liquid urea U becomes lower than the threshold value. In this way, since the next reducing agent is added before the liquid urea U solidifies, the liquid urea U does not remain in the liquid urea storage chamber 13 for a long time.
[0063]
The liquid amount sensor 32 serving as a means for detecting the remaining amount of liquid urea U outputs a signal to the ECU 16 when the liquid urea U falls below a predetermined level, or the remaining amount of liquid urea U in the liquid urea storage chamber 13. Can always be used.
[0064]
Note that when the solid urea A is liquefied, the temperature of the heater 31 is controlled by the ECU 16 so that the temperature becomes an optimum temperature (for example, 133 to 200 ° C. within a range in which no alteration of urea occurs).
[0065]
The liquid urea storage chamber 13 is provided with a temperature sensor 18 for detecting the liquid temperature of the liquid urea U. The temperature sensor 18 outputs an output signal proportional to the detected liquid temperature of the liquid urea U to the ECU 16.
[0066]
On the other hand, the exhaust pipe 7 upstream of the NOx catalytic converter 8 is provided with an incoming gas temperature sensor 19 for detecting the temperature of the exhaust gas flowing into the NOx catalytic converter 8, and an output signal proportional to the detected incoming gas temperature. Is output to the ECU 16.
[0067]
In this embodiment, the ECU 16 performs the addition control of the liquid urea U and the energization control of the heater 31. For these controls, the input signal from the air flow meter 20 is supplied to the input port of the ECU 16 as A. Input via / D converter. Thus, the air flow meter 20 outputs an output signal proportional to the intake air amount to the ECU 16, and the ECU 16 calculates the intake air amount based on the output signal of the air flow meter 20.
[0068]
Further, the exhaust pipe 7 upstream of the NOx catalytic converter 8 is provided with a NOx sensor 21 that detects the amount of NOx flowing into the NOx catalytic converter 8, and outputs an output signal proportional to the detected NOx amount to the ECU 16.
[0069]
The ECU 16 calculates a target addition amount of the liquid urea U necessary for purifying NOx based on the detected NOx amount, and until the amount of the liquid urea U detected by the liquid amount sensor 32 becomes equal to this calculated value. The heater 31 is energized to melt the solid urea. Further, the duty ratio of the addition control valve 14 that obtains a flow rate corresponding to the target addition amount is calculated, and the addition control valve 14 is controlled by the duty ratio.
[0070]
Next, the flow chart of reducing agent supply by this apparatus will be described with reference to FIG.
[0071]
First, at step 200, the ECU 16 calculates a target addition amount of liquid urea U necessary for purifying NOx based on the detected NOx amount.
[0072]
In step 201, the amount of liquid urea U detected by the liquid amount sensor 32 is compared with the amount of urea stored in the liquid urea storage chamber 13. If the stored amount of liquid urea U is less than the target addition amount, the process proceeds to step 201, where the heater 31 is energized until the stored amount of liquid urea U becomes equal to the target addition amount, and the solid urea A is liquefied to liquid. Urea U is supplied to the liquid urea storage chamber 13.
[0073]
On the other hand, if the amount of liquid urea U stored is larger than the target addition amount, the liquid urea U is not replenished.
[0074]
Next, in step 203, it is determined whether or not it is time to add liquid urea U as a reducing agent into the exhaust pipe 7. If it is the addition time, the process proceeds to step 204 where liquid urea U is added. On the other hand, if it is not the addition time, the process jumps to step 208 and the liquid urea U is stored in the liquid urea storage chamber 13.
[0075]
When the liquid urea U is added in step 204, the process proceeds to step 205 and the remaining amount is detected. In step 206, it is determined whether or not the remaining amount is equal to or less than the threshold value. This is saved at step 208.
[0076]
On the other hand, if the liquid urea is not less than or equal to the threshold value, the process jumps to step 208 to store the liquid urea U.
[0077]
In the exhaust gas purifying apparatus of the present invention, only a necessary amount of solid urea is liquefied and added each time depending on the operating condition in this way, so that excess liquid urea U remaining in the apparatus is solidified. It is possible to prevent clogging of the device.
[0078]
Further, it is possible to prevent the liquid urea U in the apparatus from being used up and the shortage of the liquid reducing agent before the solid urea is liquefied and can be added to the exhaust pipe 7.
[0079]
【The invention's effect】
As described above, according to the exhaust gas purification apparatus for an internal combustion engine according to the present invention, the solid urea is stored, liquefied and used, thereby miniaturizing and simplifying the apparatus, and reducing the supply amount of the reducing agent with high accuracy. Can be controlled.
[0080]
In the present invention, since the required amount of the melt reducing agent is supplied in accordance with the operating condition of the internal combustion engine, the amount required for the selective reduction type NOx catalyst among the stored solid reducing agents is increased each time. It is heated and melted. Therefore, it is possible to prevent excess melt reducing agent remaining in the exhaust purification device from becoming solid again and clogging the device, and causing inconvenience in the next supply of reducing agent.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an internal combustion engine exhaust gas purification apparatus according to the present invention.
FIG. 2 is a diagram showing a schematic configuration of a reducing agent addition apparatus according to the first embodiment of the present invention.
FIG. 3 is a diagram showing a schematic configuration of a reducing agent addition apparatus according to a second embodiment of the present invention.
FIG. 4 is a diagram showing a flowchart of adding a reducing agent in the first embodiment.
FIG. 5 is a diagram showing a flowchart of adding a reducing agent in the second embodiment.
[Explanation of symbols]
1 Diesel engine (internal combustion engine)
7 Exhaust pipe
8 NOx catalytic converter
9 Exhaust pipe (exhaust passage)
10 Selective reduction type NOx catalyst
11 Reducing agent addition device
12 Storage container
13 Liquid urea storage room
14 Addition control valve (supply amount control means)
16 ECU
17 Remaining sensor
18 Temperature sensor
19 Gas temperature sensor
20 Air flow meter
21 NOx sensor
22 Meter panel
23 Alarm lamp
31 Heater
32 Liquid sensor
33. Melting agent transport passage

Claims (4)

A selective reduction type NOx catalyst which is provided in an exhaust gas passage of an internal combustion engine and reduces or decomposes NOx in the presence of a reducing agent derived from ammonia;
A solid reducing agent storage means for storing a solid reducing agent;
A heating and melting means for heating and melting the solid reducing agent;
A melt reducing agent storage means for storing the melt reducing agent derived from the solid reducing agent storage means;
A melt reducing agent supply means for supplying the melt reducing agent to the exhaust gas passage upstream of the selective reduction type NOx catalyst;
A melting reducing agent supply amount calculating means for calculating a supply amount of the melting reducing agent supplied by the melting reducing agent supply means according to an operating state;
Reducing agent heating control means for controlling the heating and melting means based on the reducing agent supply amount calculated by the melting and reducing agent supply amount calculating means;
An exhaust gas purifying device for an internal combustion engine, comprising: The melting reducing agent storage means is provided with detecting means for detecting the remaining amount of the melting reducing agent, the remaining amount of the melting reducing agent detected by the detecting means, and the reduction calculated by the melting reducing agent supply amount calculating means. 2. The exhaust gas purifying device for an internal combustion engine according to claim 1, wherein the reducing agent heating control means is controlled so that the amount of the agent supplied becomes equal. The exhaust gas purifying device for an internal combustion engine according to claim 1 or 2, wherein the heating temperature of the heating and melting means is set to a temperature at which the solid reducing agent does not change. The exhaust gas purifying device for an internal combustion engine according to any one of claims 1 to 3, further comprising temperature holding means for holding the temperature of the melting reducing agent storage means at a temperature at which the solid reducing agent does not change.

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