JP2001173431A - Exhaust emission control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control system with simple supplying means and spraying means for liquid reducing agent, easy to grasp the remaining amounts of the liquid reducing agent and compressed air, and capable of spraying the liquid reducing agent in small spray diameters while maintaining the density of the liquid reducing agent approximately constant. SOLUTION: In the exhaust emission control system 1, an injection nozzle 8 and a catalyst 3 for purifying exhaust gas is arranged on an exhaust passage 2 of an internal combustion engine in this order from the upstream side. The liquid reducing agent L is sprayed from the injection nozzle 8 and is supplied to the catalyst 3 to reduce and purify nitrogen oxides in exhaust gas G. The liquid reducing agent L is stored in an exchangeable cartridge 21. The injection nozzle 8 is constituted of an air assist type injection nozzle which sprays the liquid reducing agent L by compressed air A supplied from a compressed air supply source 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine and the like, in which a NOx reduction catalyst is provided in an exhaust passage of exhaust gas in order to reduce the amount of nitrogen oxide (NOx) in exhaust gas. The present invention relates to an exhaust gas purification system that purifies exhaust gas by utilizing a catalytic action by reducing NOx by adding a reducing agent.

[0002]

2. Description of the Related Art Nitrogen oxides (NO) contained in exhaust gas from diesel engines mounted on automobiles such as large and small commercial vehicles and passenger cars, ships and the like, and exhaust gas from combustion equipment and the like
In order to purify x), various exhaust gas purification systems that reduce nitrogen oxides by using a catalytic action have been put to practical use.

In particular, a three-way catalyst has been put to practical use in a gasoline engine for an automobile, and the result has been achieved. However, in a diesel engine, the three-way catalyst for a gasoline automobile has been used because of a high oxygen concentration in exhaust gas. There is a problem that it cannot be used directly.

Therefore, in a diesel engine, urea water or ammonia (NH ₃ ) is used for purifying nitrogen oxides.
The use of an SCR method using a selective catalytic reduction catalyst (SCR catalyst) using a reducing agent such as the above has been studied. This SCR
The method is a method in which a liquid reducing agent such as an aqueous urea solution, an aqueous ammonia solution, or liquid ammonia is injected into a high-temperature exhaust gas and brought into contact with a metal catalyst for denitration.

As shown in FIG. 6, in a conventional exhaust gas purification system 1B of the SCR method, an SCR catalyst 3 is provided in an exhaust passage 2 of an engine or the like, and an injection nozzle 8B is provided upstream of the SCR catalyst 3. The liquid reducing agent (aqueous reducing agent solution) L is supplied from the tank 4 to the mixing section 6 by the pump 5, while the compressed air (compressed air) A supplied from the air compressor 7 B is supplied to the mixing section 6. Then, it is sent to an injection nozzle (injector) 8B, and is sprayed on the upstream side of the SCR catalyst 3.

When the liquid reducing agent L is sprayed, it is atomized by pressurized air A using the principle of spraying,
The high-speed air collides with the sprayed liquid reducing agent L to make the sprayed particle diameter finer. Therefore, pressurized air A is required, so that an air compressor 7B is provided.

The injection hole 8B of the injection nozzle 8B
a into the exhaust passage 2 from the exhaust gas G
Nitrogen oxides are reduced and purified by the catalytic action of the SCR catalyst 3.

Further, in the exhaust gas purification system 1B, the controller (control unit) 9 controls the opening / closing valve of the injection nozzle 8B while confirming the remaining amount of the liquid reducing agent L by the capacity meter switch 4a provided in the tank 4. To adjust the spray volume. Then, when the remaining amount of the liquid reducing agent L decreases, this is detected by the capacity meter switch 4a, and the warning lamp 10B is turned on to urge the replenishment of the liquid reducing agent L.

The reduction action of this nitrogen oxide is 4NO + 4
NH ₃ + O ₂ = 4N ₂ + 6H ₂ O
The CR catalyst 3 is composed of a carrier such as alumina (aluminum oxide: Al ₂ O ₃ ), titania (titanium oxide: TiO ₂ ) or the like formed in a pellet or honeycomb shape.
t), vanadium oxide (V ₂ O ₅ ), iron oxide (Fe ₂ O ₅ )
₃ ), copper oxide (CuO), manganese oxide (Mn)
It is known to use an active material such as ₂ O ₃ ), chromium oxide (Cr ₂ O ₃ ), or molybdenum oxide (MoO ₃ ).

[0010]

However, since the liquid reducing agent tank is used while adding an aqueous solution like a washer tank, that is, a tank that can be added to the liquid reducing agent is used. In the case of a liquid reducing agent in which a reducing agent such as an aqueous ammonia solution is dissolved, the concentration of the aqueous solution of the reducing agent changes because water in the reducing agent evaporates.

That is, even after the filling, the concentration gradually increases due to the evaporation of the water in the reducing agent, and even when the liquid reducing agent at the beginning of the filling is added, the remaining aqueous solution immediately before the addition in the tank is removed. Since the concentration is increased by evaporation, the concentration after mixing is not constant.

Therefore, since the concentration of the reducing agent changes from time to time, it is difficult to control the concentration, it is not possible to supply an appropriate amount of the reducing agent, and the purification efficiency of the SCR catalyst is not stable. Alternatively, there is a problem that the exhaust gas is exhausted while the excess reducing agent is mixed in the exhaust gas, and the exhaust gas purification becomes insufficient.

Further, since the exhaust gas purification system 1B uses an air compressor, it is good when a large capacity air compressor is provided, such as a vehicle equipped with a large diesel engine. If the capacity of the air compressor is insufficient, or if the air compressor is not provided, it will be necessary to provide a new air compressor, so the weight of the equipment installed as this exhaust purification system will increase and the equipment will become complicated. Problem.

Further, since the air compressor needs to be driven by an engine, a motor or the like, the energy consumption of the engine or the motor increases, and the fuel efficiency of the vehicle deteriorates, and the problem of maintenance and management of the air compressor. Occurs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to provide an exhaust gas purification system for an internal combustion engine or the like using a catalyst, in which a liquid reducing agent supply means and a spray means are simple. It is another object of the present invention to provide an exhaust gas purification system in which the remaining amount of a liquid reducing agent or pressurized air can be easily grasped, and the concentration of the liquid reducing agent can be kept substantially constant to spray fine particles.

A further object is to accurately grasp the remaining amount of the liquid reducing agent or the pressurized air and issue a warning prompting the driver to change the supply source when the remaining amount is low, in a timely manner. It is an object of the present invention to provide an exhaust gas purification system that can perform the same.

[0017]

The exhaust gas purifying system for achieving the above object is configured as follows.

1) An injection nozzle and a catalyst for purifying exhaust gas are arranged in the exhaust passage of an internal combustion engine or the like in order from the upstream side, and a liquid reducing agent is sprayed from the injection nozzle and supplied to the catalyst, and the exhaust gas is exhausted. In an exhaust gas purification system that reduces and purifies nitrogen oxides in the liquid, the liquid reducing agent is stored in an exchangeable cartridge, and the injection nozzle is provided with the liquid reducing agent by pressurized air supplied from a pressurized air supply source. It is composed of an air-assist type spray nozzle that sprays in the form of a mist.

As this catalyst, there is an SCR catalyst or the like. In this SCR catalyst, a carrier is formed of Al ₂ O ₃ , TiO ₂ or the like, and a catalytic metal as an active substance is Pt, V ₂ O ₅ , Fe _2.
It can be formed of O ₃ , CuO, Mn ₂ O ₃ , Cr ₂ O ₃ , MoO ₃ or the like. Examples of the liquid reducing agent include a urea aqueous solution, an aqueous ammonia solution, and liquid ammonia.

The cartridge is a detachable container that replaces the entire container to supply a new liquid reducing agent. The hermetically sealed container prevents post-addition and prevents the liquid reducing agent from evaporating. Can be prevented and the concentration can be kept constant.

The cartridge used in the present exhaust gas purification system is filled with a known gas for pressurizing a liquid such as compressed air or other gas, for example, a paint spray can or a lubricant spray can. The liquid reducing agent may be supplied to the outside by gas pressure, or the liquid reducing agent in the cartridge may be supplied to the injection nozzle by a reducing agent supply pump provided outside.

The air-assist type injection nozzle refers to an injection nozzle that uses a high-pressure gas such as pressurized air (compressed air) to reduce the particle size to be sprayed and disperse it.

In the exhaust gas purifying system for an internal combustion engine having this configuration, the liquid reducing agent is supplied from the cartridge, and the compressed air is supplied from the pressurized air supply source. There is almost no change in the concentration of the solution, and it can be supplied to the catalyst by spraying with a stable concentration and a fine particle diameter.

Therefore, the exhaust purification system is simplified,
Further, since the reducing agent solution is supplied to the catalyst in an optimum amount accurately and in a state where chemical reaction is likely to occur, purification efficiency is improved.

In the exhaust gas purifying system, when the pressurized gas is not sealed in the cartridge, only the liquid pressure, the vapor pressure and the like need to be considered for the cartridge. In this case, the pressure of the pressurized gas is only supplied to the injection nozzle by the liquid reducing agent, and the spraying is performed by pressurized air. Therefore, the pressure of the pressurized gas may be low, so the structure of the cartridge itself is simple and lightweight. Becomes

2) In the exhaust gas purifying system for an internal combustion engine described above, the pressurized air supply source is formed by an air cylinder, and a warning is issued when the air pressure of the air cylinder falls below a predetermined warning pressure value. It is formed with pressure management means.

By forming the pressurized air supply source with an air cylinder, an air compressor and a drive source are not required,
The exhaust purification system is simplified, the weight increase is reduced, and the effect on fuel economy can be eliminated.

Further, by providing pressure management means,
Since the driver who receives the warning replaces the air cylinder at an appropriate time, the management of the pressurized air supply source is facilitated, and a decrease in the supply pressure of the pressurized air can be prevented.

This pressure management means receives a signal from the pressure sensor and a pressure sensor capable of detecting the pressure of the pressurized air in the air cylinder or the air supply line, and compares it with a preset warning pressure value. A simple configuration can be achieved by adding, to the controller, an arithmetic unit or a program that outputs a signal to a warning lamp, a sound generation device, or the like when the value becomes lower than the value.

3) In the exhaust gas purifying system for an internal combustion engine described above, a remaining amount detecting means for detecting a remaining amount of the liquid reducing agent in the cartridge, and when the remaining amount becomes equal to or less than a predetermined lower limit amount. It is formed with a warning generating means for generating a warning.

By providing the remaining amount detecting means and the warning generating means, the driver receiving the warning replaces the cartridge at an appropriate time, so that the management of the liquid reducing agent is facilitated and the supply of the liquid reducing agent is interrupted. Can be prevented.

The comparison between the remaining amount and the predetermined lower limit amount is as follows:
The comparison may be made directly with the weight of the liquid reducing agent, but the amount can be converted from this weight, for example, the capacity, the value of the detection signal (voltage value, etc.), the travel distance that can travel while consuming the liquid reducing agent, and the like. The comparison may be made by converted values, and the present invention includes these.

4) In the exhaust gas purifying system for an internal combustion engine, the remaining amount detecting means integrates a control signal for controlling the operation of the injection nozzle, and calculates the consumption amount of the liquid reducing agent from the integrated value. The calculation means is configured to calculate the remaining amount by calculation.

According to this configuration, since the consumption amount of the liquid reducing agent is calculated from the control signal for the injection nozzle, it is not necessary to newly provide a sensor, and this calculating means is provided to the controller of the internal combustion engine or the like. Since it can be provided by adding a program, it can be implemented relatively easily.

5) Alternatively, in the exhaust gas purification system for an internal combustion engine described above, the remaining amount detecting means may include a weight sensor for detecting a weight of the cartridge, and a remaining amount of the liquid reducing agent calculated from a signal from the weight sensor. It is composed of computing means that performs

According to this configuration, since the amount of the liquid reducing agent can be directly measured by the weight sensor, finer control with less error is possible.

6) Further, there is provided a replacement detecting means for detecting replacement of the cartridge, and when the replacement detecting means detects the replacement of the cartridge, the cartridge is transferred from the cartridge to the ejection nozzle for a predetermined time. The supply pipe for supplying the liquid reducing agent is configured to be evacuated.

This exchange detecting means can be formed by a switch or the like which is turned ON / OFF according to the presence or absence of the cartridge. The predetermined time for operating the injection nozzle is determined by the supply line of the liquid reducing agent (cartridge, injection hole, This is a time that is predetermined and input in advance to the controller.

When the liquid reducing agent in the cartridge is supplied to the injection nozzle by the pressure of the gas sealed in the cartridge, the air is released from the supply pipe by operating the injection nozzle for a predetermined time. When the liquid reducing agent in the cartridge is supplied to the injection nozzle by a reducing agent supply pump provided outside the cartridge, the operation is performed by operating the injection nozzle and the reducing agent supply pump for a predetermined time.

According to this configuration, since the replacement of the cartridge can be detected, the initial value serving as the reference for estimating the remaining amount can be accurately reset. In other words, the cartridge filling amount and concentration are accurately managed by the cartridge manufacturer so as to be a predetermined value in the quality control at the factory, and then shipped. Therefore, when the cartridge is replaced, the predetermined filling amount is used as the initial value of the reset. By using this, it is possible to more accurately estimate the remaining amount.

Further, since air is automatically vented when the cartridge is replaced, it is possible to prevent air from being caught in the supply line of the liquid reducing agent, and to always supply an appropriate amount of the liquid reducing agent in accordance with an instruction from the controller.

[0042]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an exhaust gas purification system according to the present invention will be described below with reference to the drawings.

As shown in FIGS. 1 and 2, the exhaust gas purifying systems 1 and 1A according to the present invention are provided with an SCR (selective catalytic reduction) catalyst 3 in an exhaust passage 2 of an engine or the like. An air-assist type injection nozzle (injector) 8 capable of spraying an aqueous urea solution L, which is one of the liquid reducing agents, is provided upstream of the nozzle.

In this SCR catalyst 3, the carrier is Al ₂ O ₃ ,
It is made of TiO ₂ or the like, and the catalytic metal as an activator is Pt,
V ₂ O ₅ , Fe ₂ O ₃ , CuO, Mn ₂ O ₃ , Cr ₂ O
₃ , MoO ₃ or the like.

A replaceable cartridge 21 in which an aqueous urea solution L is sealed and stored is provided.
This cartridge is detachably connected to the supply line 22 so that the cartridge
The urea aqueous solution L in 21 is supplied to the injection nozzle 8.

As a method of supplying the aqueous urea solution L to the injection nozzle 8, a pressurized gas P is sealed in a cartridge 21 as in the exhaust gas purification system 1 shown in FIG. There is a method of supplying the reducing agent supply pump 5 for supplying the aqueous urea solution L in the cartridge 21 to the injection nozzle 8 as in the exhaust gas purification system 1A shown in FIG. May be used.

Also, an air cylinder 7 is replaceably provided as a source of pressurized air for spraying, and pressurized air A is supplied from the air cylinder 7 to the injection nozzle 8, through an injection hole 8 a of the air assist type injection nozzle 8. The urea aqueous solution L is configured to be sprayed into the exhaust passage 2 under the control of a controller (control unit) 9.

The principle of spraying the aqueous urea solution L is the same as the principle of spraying.
Is sucked into the flow of the pressurized air A, blown off, atomized and sprayed.

The spraying is performed by controlling the opening and closing of the injection nozzle 8 by duty control so that the target spray amount calculated by the controller 9 with reference to various information of the engine and the like.

According to this configuration, the urea aqueous solution L can be supplied to the injection nozzle 8 by the pressurized gas P or the reducing agent supply pump 5 in the cartridge 21, and the urea aqueous solution L can be supplied by the pressurized air A obtained from the air cylinder 7. Can be atomized and sprayed.

Further, since the aqueous urea solution L is sealed in the cartridge 21, there is no change in concentration due to evaporation or the like, an appropriate amount of reducing agent can be supplied to the catalyst 3 at a stable concentration, and the purification efficiency can be kept good. it can.

[Management of Air Cylinder] When the pressure Pa of the pressurized air A of the air cylinder 7 as the pressurized air supply source decreases, the atomizing function of the spray of the injection nozzle 8 decreases. Gas purification efficiency deteriorates. For this purpose, the air pressure Pa of the air cylinder 7 is equal to a predetermined warning pressure value P.
A pressure management means for generating a warning when the value becomes w or less is provided.

The pressure management means is provided with a pressure sensor 34 provided in an air supply pipe 32 connecting the air cylinder 7 and the injection nozzle 8, and a detection value of the pressure sensor 34, and the air pressure Pa is set in advance. When the pressure becomes equal to or less than the predetermined warning pressure value Pw, a warning is generated by a warning lamp 10a, and the arithmetic unit 9a is configured to urge the driver to replace the air cylinder 7. The calculation unit 9a is usually incorporated in the controller 9.

As the warning pressure value Pw, a spraying limit pressure at which spraying becomes impossible is determined in advance by an experiment or the like, and a margin is set to some extent larger than the spraying limit pressure in consideration of the amount of consumption required until replacement. Let it be pressure value Pw.

By providing this pressure control means, before the air pressure Pa of the air cylinder 7 deviates from a predetermined pressure range in which fine particles can be formed, the exhaust gas purification efficiency deteriorates.
The warning lamp 10a can be turned on to warn the driver to replace the air cylinder 7. Therefore, the air cylinder 7 can be replaced at an appropriate time, and the pressurized air A having a sufficient pressure can be supplied, so that the deterioration of the exhaust gas purification efficiency can be prevented.

[Estimation of the Remaining Amount] Further, in order to estimate the remaining amount Ws of the aqueous urea solution L in the cartridge 21 and warn the driver or the like if necessary, it is constituted by a calculating means, a weight sensor 23 and the like. An exchange detecting means for detecting the exchange of the remaining amount and the cartridge 21 is provided, and performs the calculation and control according to the flow shown in FIGS.

By providing the remaining amount detecting means and the warning generating means, it is possible to grasp the accurate remaining amount Ws and to give a warning to the driver to display or replace the remaining amount Ws. Therefore, the cartridge 21 can be replaced at an appropriate time and the liquid reducing agent L can be supplied, so that interruption of the liquid reducing agent L can be prevented.

Further, the provision of the replacement detecting means for detecting replacement of the cartridge 21 allows the initial value of the remaining amount Ws to be reset to a predetermined value, so that the remaining amount Ws can be accurately estimated. When the exchange of the cartridge 21 is detected, the injection nozzle 8 is used when the pressurized gas P is sealed in the cartridge 21, and the injection nozzle 8 is used when the reducing agent supply pump 5 is used. By operating the pump 5 for a predetermined period of time, the air can be automatically removed from the supply pipe line 22, so that the air nozzle can be prevented from being caught and the injection nozzle 8 can be operated accurately.

[Estimation of Air Pressure and Remaining Amount (Part 1)] First, replacement detecting means 24 for detecting replacement of cartridge 21
The case in which is provided will be described.

The replacement detecting means 24 is a simple ON such that it becomes OFF when the empty cartridge 21 is removed and turns ON when a new cartridge 21 is installed.
It can be formed by the / OFF switch 24. In this case, the output from the switch 24 to the controller 9 changes from the OFF signal to the ON signal.
When the signal changes, it is determined that the replacement has been performed, and the initial value of the remaining liquid amount Ws is reset to a predetermined amount at the time of factory shipment. Note that ON and OFF may be reversed.

Further, in this configuration, the remaining amount detecting means includes:
The control signal of the controller 9 for controlling the operation of the injection nozzle 8 is integrated, and the consumption Wc of the liquid reducing agent L is calculated from the integrated value.
Is calculated to calculate the remaining amount Ws.

Therefore, the remaining amount detecting means can be provided only by adding a simple ON / OFF switch 24 and a new remaining amount calculating program, so that it is not necessary to newly provide an expensive sensor.

In this case, calculation and control are performed according to the flow of FIG. 3 is repeatedly called from the main control program at predetermined intervals, and when this flow starts, first, at step S11
Then, the remaining amount Ws of the aqueous urea solution L in the cartridge 21 is calculated.

The remaining amount Ws is calculated by subtracting the consumed weight Wc from the remaining amount (weight) Ws of the aqueous urea solution L before this flow is called. This consumed weight W
c is a duty (Dut) for controlling the opening and closing of the injection nozzle 8.
y) The duty ratio of the signal is integrated, the integrated value is converted into a spray amount, and the converted value is multiplied by the specific gravity of the aqueous urea solution L to obtain the value.

Next, at step S12, the air pressure Pa of the air cylinder 7 is detected by the pressure sensor 34. That is, the detection value of the pressure sensor 34 is taken.

Then, the flow proceeds to step S13, where it is determined whether or not the cartridge 21 has been replaced by the output of the replacement detecting means 24. If it is determined that the replacement has been performed (YES),
In step S14, the remaining amount Ws is initialized and reset to a predetermined amount, and in step S15, a signal for operating the injection nozzle 8 or the injection nozzle 8 and the reducing agent supply pump 5 for a predetermined time, for example, about several seconds. After the output, the supply pipe 22 is deflated, and the flow proceeds to step S16. If the cartridge 21 has not been replaced (NO), the flow directly proceeds to step S16.

The air bleeding of the supply line 22 is performed in order to prevent air from entering the supply line 22 when the cartridge 21 is replaced. In this case, an air release valve (not shown) may be provided, and the air release valve may be opened for a predetermined time.

Then, an operation for determining whether or not to give a warning for urging replacement of the cartridge 21 is performed. In this calculation, first, in step S16, a distance Dp that can be traveled without replacement is estimated from the current remaining amount Ws.
At 17, it is determined whether or not the travelable distance Dp has become smaller than the warning distance Dw which is a predetermined threshold value.

The travelable distance Dp is, for example, 60
The consumption Wa of the aqueous urea solution L per unit time when traveling at a constant reference speed of km / h (flatland) is estimated from data input in advance or data accumulated during actual traveling, and this consumption is estimated. It can be calculated by dividing the remaining amount Ws by the amount Wa, that is, by setting Dp = Ws / Wa. In addition, the warning distance Dw is a standard distance required for traveling before replacement, for example, 50 km.
And so on.

The travelable distance Dp is equal to the warning distance D.
If not less than w (NO), step S19
And if the following is true (YES), step S18
Then, the warning lamp 10b is turned on and the driver is informed of the cartridge.
Notify that the urea aqueous solution L in 21 is low,
Prompt for replacement.

Next, in step S19, it is determined whether or not the air pressure Pa of the air cylinder 7 is equal to or lower than a predetermined warning pressure value Pw. If the air pressure Pa is not equal to or lower than the warning pressure value Pw (N
In the case of O), the process returns to the main control as it is, and in the case of the following (YES), the warning lamp 10a is turned on in step S20, and the driver is supplied with the pressurized air A in the air cylinder 7. Informing that the fuel tank is running low
Prompt for replacement.

Then, the process returns and returns to the main control. The warning may be issued by voice instead of the warning lamps 10a and 10b, or the voice and the warning lamps 10a and 10b may be used together.

Further, the amount of the urea aqueous solution L estimated to be consumed when the vehicle travels over the warning distance Dw is reduced to a predetermined lower limit amount Wp.
Is calculated in advance as Step S16 and Step S17.
Instead, the remaining amount Ws may be directly compared with the predetermined lower limit value Wp, and when the remaining amount Ws becomes equal to or less than the predetermined lower limit amount Wp, the process may proceed to step S18 to generate a warning. it can.

[Estimation of Air Pressure and Remaining Amount (Part 2)] Next, the above-mentioned replacement detecting means 21 is not provided, and
A case in which a weight sensor 23 for measuring the weight of the cartridge 21 is provided, the weight of the cartridge 21 is measured, and the result is output to the controller 9 will be described.

When the weight sensor 23 is used, when the urea aqueous solution L is sufficiently left, the urea aqueous solution L is once removed and returned, or the used cartridge 21 having a residual amount different from the new amount is attached. In this case, it is possible to avoid erroneous estimation of the remaining amount, which is caused in such a case. In addition, since the amount of the liquid reducing agent L can be directly measured, finer control with less error can be performed.

In this case, calculation and control are performed according to the flow of FIG. 4 is repeatedly called from the main control program at predetermined intervals, and when started, first, in step S31, the total weight Cw of the cartridge 21 is detected, and the weight (pressurized gas Is subtracted to calculate the remaining amount Ws.

Next, in step S32, the air pressure Pa of the air cylinder 7 is detected by the pressure sensor 34.

Then, in step S33, it is determined whether or not the weight Cw is the same as that at the time of shipment from the factory, that is, whether or not the weight is equal to or more than a predetermined weight Co.
34, and outputs a signal for operating the injection nozzle 8 or the injection nozzle 8 and the reducing agent supply pump 5 for a predetermined period of time assuming that the cartridge 21 has been replaced.
If the result is (NO), it is determined that the cartridge 21 has not been replaced, and the process directly proceeds to step S35.

Then, in steps S35 to S37, an operation for determining whether or not to give a warning urging replacement of the cartridge 21 is performed. This operation is performed in steps S16 to S18 in the flow of FIG. The description is omitted here.

In steps S38 to S39, the air pressure Pa of the air cylinder 7 is checked and the air cylinder 7 is checked.
The warning about the replacement is also the same as steps S19 to S20 in the flow of FIG.

[Estimation of Air Pressure and Remaining Amount (Part 3)] Further, in order to detect whether or not the cartridge 21 has been replaced,
A case where both the replacement detecting means 24 and the weight sensor 23 for measuring the weight of the cartridge 21 are provided will be described.

The merit in this case is that if only the weight sensor 23 according to the flow of FIG. 4 is installed, the operation of the air bleeding nozzle 8 for a predetermined time is not repeated so that a new cartridge is used. High-precision weight sensor that can detect the difference between the weight of 21 and the weight after the air release operation
However, when the replacement detection means 24 is added as shown in the flow chart of FIG. 5, the ejection for bleeding is performed only based on the replacement detection means 24. It is only necessary to know Ws with some accuracy,
An inexpensive weight sensor 23 is sufficient, and an expensive weight sensor 23 is not required.

Further, since the cartridge maker controls the filling amount and the concentration of the cartridge 21 accurately so as to be a predetermined value in the quality control of the factory and ships the cartridge 21, the initial value of the remaining amount when the cartridge 21 is replaced is determined. By resetting to the predetermined value, the remaining amount can be more accurately estimated.

Then, in this case, calculation and control are performed according to the flow of FIG. 5 is repeatedly called from the main control program at predetermined intervals, and when started, in step S41, the total weight Cw of the cartridge 21 is detected by the weight sensor 23, and the
The remaining amount Ws is calculated by subtracting the weight of the main body (including the weight of the pressurized gas).

Next, in step S42, the air pressure Pa of the air cylinder 7 is detected by the pressure sensor 34.

Then, in step S43, it is determined whether or not the cartridge 21 has been replaced by the replacement detecting means. If it is determined that replacement has been performed (YES), the process proceeds to step S43.
At 44, a signal for operating the injection nozzle 8 or the injection nozzle 8 and the reducing agent supply pump 5 for a predetermined time is output.
The process proceeds to step S45, and if the cartridge 21 has not been replaced (NO), the process directly proceeds to step S45.

Then, in steps S45 to S47, a calculation is performed to determine whether or not a warning to urge replacement of the cartridge 21 is issued. This calculation is performed in steps S16 to S18 in the flow of FIG. The description is omitted here.

In steps S48 to S49, the air pressure Pa of the air cylinder 7 is checked and the air cylinder 7 is checked.
The warning about the replacement is also the same as steps S19 to S20 in the flow of FIG.

In the above description, purification of exhaust gas from an engine of an automobile or the like has been described as an example, and an aqueous urea solution has been described as an example of a liquid reducing agent. The present invention can be used for purification of exhaust gas of the present invention. Also, as for the liquid reducing agent, an aqueous solution in which the reducing agent such as the above-mentioned urea aqueous solution or aqueous ammonia solution is dissolved, or the reducing agent itself such as liquid ammonia is liquid. The present invention is not limited to only the above-described embodiment.

[0090]

As described above, according to the exhaust gas purification system of the present invention, the following effects can be obtained.

The liquid reducing agent is sealed in a replaceable cartridge, and the liquid reducing agent supplied from the cartridge is atomized by the pressurized air supplied from the pressurized air supply source. The particle size can be made very fine, and the purification performance of exhaust gas can be improved.

Further, since the liquid reducing agent is sealed in the cartridge, there is no change in the concentration of the liquid reducing agent due to evaporation of the reducing agent or the like, an appropriate amount of the reducing agent can be supplied to the catalyst at a stable concentration, and the purification efficiency can be improved. It keeps good and can prevent ammonia slip.

Therefore, since the liquid reducing agent can be made finer by the pressurized air, the exhaust gas can be efficiently purified and the liquid reducing agent is not wasted.

Further, since the pressurized air supply source is formed by an exchangeable air cylinder, the apparatus becomes simple and
Maintenance management is simplified, and there is no effect on fuel efficiency of the engine and the like.Furthermore, a pressure management means that generates a warning when the air pressure of the air cylinder falls below a predetermined warning pressure value is provided. The air cylinder can be replaced at an appropriate time before the temperature decreases, and the liquid reducing agent can always be supplied to the catalyst with high purification efficiency.

In addition, by providing the remaining amount detecting means and the warning generating means for the liquid reducing agent, the accurate remaining amount can be grasped, and the driver can be warned to display or replace the remaining amount. . Therefore, the liquid reducing agent can be reliably managed, and the cartridge can be replaced at an appropriate time and the liquid reducing agent can be supplied, so that it is possible to avoid the exhaust gas purification failure due to the interruption of the liquid reducing agent.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of a case where a cartridge containing a pressurized gas is used in an exhaust gas purification system according to the present invention.

FIG. 2 is a configuration diagram showing an embodiment when a reducing agent supply pump of the exhaust gas purification system according to the present invention is used.

FIG. 3 is a diagram showing a control flow of an exhaust gas purification system according to the present invention using a replacement detection unit for a cartridge.

FIG. 4 is a diagram showing a control flow of an exhaust gas purification system according to the present invention using a weight detection unit for a cartridge.

FIG. 5 is a diagram showing a control flow of the exhaust gas purification system according to the present invention using replacement detection means and weight detection means for the cartridge.

FIG. 6 is a configuration diagram showing a conventional exhaust gas purification system.

[Explanation of symbols]

 1, 1A Exhaust gas purification system 2 Exhaust passage 3 SCR catalyst (catalyst) 7 Air cylinder (pressurized air supply source) 8 Air-assist type injection nozzle 9 Controller (residual amount detecting means) 10a, 10b Warning lamp (warning generating means) 21 Cartridge 22 Supply line 23 Weight sensor (remaining amount detection means) 24 ON / OFF switch (replacement detection means) 34 Pressure sensor G Exhaust gas L Urea aqueous solution (liquid reducing agent) P Pressurized gas Pa Air pressure Pw Predetermined warning pressure Value Ws Remaining amount Wc Consumption amount Wp Predetermined lower limit amount

Continued on front page F-term (reference) 3G091 AA02 AA04 BA14 BA31 CA15 CA17 CB08 DB10 DC05 EA00 EA22 GA01 GA06 GB01W GB01X GB06W GB10W GB10X GB16X 4D048 AA06 AB02 AC03 AC04 BA07X BA23X BA25X BA26X BA28X BA30X BA35 DA01

Claims (6)

[Claims] 1. An injection nozzle and a catalyst for purifying exhaust gas are arranged in an exhaust passage of an internal combustion engine or the like in order from an upstream side, and a liquid reducing agent is sprayed from the injection nozzle and supplied to the catalyst to form an exhaust gas. In an exhaust purification system that reduces and purifies nitrogen oxides in the liquid, the liquid reducing agent is stored in an exchangeable cartridge, and the injection nozzle is configured to discharge the liquid reducing agent by pressurized air supplied from a pressurized air supply source. An exhaust gas purification system comprising an air-assist type injection nozzle that sprays in a mist state. 2. The apparatus according to claim 1, wherein said pressurized air supply source is formed by an air cylinder, and further comprises pressure management means for issuing a warning when the air pressure of said air cylinder falls below a predetermined warning pressure value. 2. The exhaust purification system according to 1. 3. The apparatus according to claim 1, further comprising: a remaining amount detecting unit configured to detect a remaining amount of the liquid reducing agent in the cartridge, and a warning generating unit configured to generate a warning when the remaining amount falls below a predetermined lower limit amount. The exhaust gas purification system according to claim 1. 4. A calculating means for calculating a remaining amount by integrating a control signal for controlling the operation of the injection nozzle, and calculating a consumption amount of the liquid reducing agent from the integrated value. The exhaust gas purification system according to claim 3, wherein: 5. The apparatus according to claim 1, wherein the remaining amount detecting means includes a weight sensor for detecting a weight of the cartridge, and a calculating means for calculating a remaining amount of the liquid reducing agent from a signal of the weight sensor. The exhaust purification system according to claim 3. 6. An exchange detecting means for detecting replacement of the cartridge, wherein when the replacement detection means detects replacement of the cartridge, the liquid reducing agent is supplied from the cartridge to the injection nozzle for a predetermined time. The exhaust gas purification system according to any one of claims 1 to 5, wherein air is removed from a supply pipe for supply.