阅读说明：本技术 废气净化系统及堆积量估计方法 (Exhaust gas purification system and deposit amount estimation method ) 是由 景山遊大 大石和贵 于 2018-06-12 设计创作，主要内容包括：本发明涉及能够估计排气通道中的白色生成物的堆积量的废气净化系统及堆积量估计方法。废气净化系统构成为在内燃机的排气通道中具备选择还原型催化装置、以及在选择还原型催化装置的上游侧喷射还原剂的还原剂喷射器。废气净化系统具备：温度获取部,获取在排气通道中通过的废气的温度；流量获取部,获取废气的流量；喷射量获取部,获取还原剂的喷射量；以及堆积量估计部,基于由温度获取部获取的温度、由流量获取部获取的流量、由喷射量获取部获取的喷射量,来估计来源于还原剂的白色生成物在排气通道中的堆积量。(the present invention relates to an exhaust gas purification system and a deposit amount estimation method capable of estimating the deposit amount of white products in an exhaust passage. The exhaust gas purification system is configured to include a selective reduction catalyst device and a reducing agent injector that injects a reducing agent upstream of the selective reduction catalyst device in an exhaust passage of an internal combustion engine. The exhaust gas purification system is provided with: a temperature acquisition unit that acquires the temperature of exhaust gas passing through the exhaust passage; a flow rate obtaining unit that obtains a flow rate of the exhaust gas; an injection amount acquisition unit that acquires an injection amount of the reducing agent; and a deposition amount estimation unit that estimates a deposition amount of a white product derived from the reducing agent in the exhaust passage based on the temperature acquired by the temperature acquisition unit, the flow rate acquired by the flow rate acquisition unit, and the injection amount acquired by the injection amount acquisition unit.)

1. An exhaust gas purification system including a selective reduction catalyst device and a reducing agent injector that injects a reducing agent upstream of the selective reduction catalyst device in an exhaust passage of an internal combustion engine, the exhaust gas purification system comprising:

A temperature acquisition unit that acquires the temperature of the exhaust gas passing through the exhaust passage;

A flow rate obtaining unit that obtains a flow rate of the exhaust gas;

An injection amount acquisition unit that acquires an injection amount of the reducing agent; and

And a deposition amount estimation unit that estimates a deposition amount of a white product derived from the reducing agent in the exhaust passage based on the temperature acquired by the temperature acquisition unit, the flow rate acquired by the flow rate acquisition unit, and the injection amount acquired by the injection amount acquisition unit.

2. An exhaust gas purification system as set forth in claim 1,

the deposition amount estimating unit estimates the deposition amount of the white product with reference to a deposition amount map that specifies in advance a relationship between the temperature of the exhaust gas, the flow rate of the exhaust gas, the injection amount of the reducing agent, and the deposition amount of the white product.

3. An exhaust gas purification system as set forth in claim 1,

The information processing apparatus includes an information unit that informs that the accumulation amount estimated by the accumulation amount estimation unit is equal to or greater than a predetermined amount.

4. A deposit amount estimation method in an exhaust gas purification system provided with a selective reduction type catalytic device and a reducing agent injector that injects a reducing agent upstream of the selective reduction type catalytic device in an exhaust passage of an internal combustion engine, the deposit amount estimation method comprising the steps of:

Acquiring a temperature of exhaust gas passing in the exhaust passage;

Acquiring the flow rate of the waste gas;

Acquiring the injection quantity of the reducing agent; and

Estimating a deposition amount of a white product derived from the reducing agent in the exhaust passage based on the acquired temperature, the acquired flow rate, and the acquired injection amount.

Technical Field

The present invention relates to an exhaust gas purification system and a deposit amount estimation method.

Background

As an exhaust gas purification system for purifying NOx in exhaust gas of a diesel engine mounted on a vehicle such as a truck or a bus, a Selective Catalytic Reduction (SCR) system has been developed in which NOx is reduced to nitrogen and water using urea water or the like as a reducing agent (see, for example, patent document 1).

In the selective catalytic reduction system, urea water stored in a urea water tank is supplied to an exhaust pipe upstream of a selective catalytic reduction device (SCR device), urea is hydrolyzed by the heat of exhaust gas to generate ammonia, and NOx is reduced by the ammonia with a catalyst in the selective catalytic reduction device. For example, an appropriate amount of urea water is injected from a urea water injector provided in an exhaust passage (exhaust pipe).

Disclosure of Invention

Problems to be solved by the invention

However, the following problems may occur due to the urea water injected into the exhaust pipe. That is, when the temperature of the exhaust gas is low (for example, 200 to 250 ℃), when the injection amount of the urea water is abnormally large, or when the injection of the urea water is continuously performed with a small flow rate of the exhaust gas, for example, during low load operation of the internal combustion engine, the hydrolysis of the urea water is insufficient, and a white product represented by cyanuric acid or the like generated during the hydrolysis of the urea water is deposited in a concave portion in the exhaust passage. If the white product is accumulated in the exhaust passage, for example, the following problems occur: the exhaust passage may be clogged, and the desired exhaust gas purification treatment may not be performed. If the amount of the white product deposited in the exhaust passage is known, measures for improving the deposition can be taken, but the deposition of the white product is not considered in the conventional art.

An object of the present invention is to provide an exhaust gas purification system and a deposit amount estimation method that can estimate the amount of white products deposited in an exhaust passage.

Means for solving the problems

An exhaust gas purification system according to the present invention is configured to include a selective reduction type catalytic device and a reducing agent injector that injects a reducing agent upstream of the selective reduction type catalytic device in an exhaust passage of an internal combustion engine, and includes:

a temperature acquisition unit that acquires the temperature of the exhaust gas passing through the exhaust passage;

A flow rate obtaining unit that obtains a flow rate of the exhaust gas;

An injection amount acquisition unit that acquires an injection amount of the reducing agent; and

and a deposition amount estimation unit that estimates a deposition amount of a white product derived from the reducing agent in the exhaust passage based on the temperature acquired by the temperature acquisition unit, the flow rate acquired by the flow rate acquisition unit, and the injection amount acquired by the injection amount acquisition unit.

a deposit amount estimation method according to the present invention is a deposit amount estimation method in an exhaust gas purification system including a selective reduction type catalytic device and a reducing agent injector that injects a reducing agent upstream of the selective reduction type catalytic device in an exhaust passage of an internal combustion engine, the deposit amount estimation method including the steps of:

Acquiring a temperature of exhaust gas passing in the exhaust passage;

Acquiring the flow rate of the waste gas;

acquiring the injection quantity of the reducing agent; and

Estimating a deposition amount of a white product derived from the reducing agent in the exhaust passage based on the acquired temperature, the acquired flow rate, and the acquired injection amount.

Effects of the invention

according to the present invention, the amount of white product deposited in the exhaust passage can be estimated.

Drawings

fig. 1 is a diagram showing a structure of a vehicle in the present embodiment.

fig. 2 is a diagram showing a change with time in the amount of white product deposited in the present embodiment.

Fig. 3 is a flowchart showing the deposition amount estimation processing in the present embodiment.

Detailed Description

Embodiments of the present invention will be described below with reference to the drawings. Fig. 1 is a diagram showing a structure of a vehicle 1 in the present embodiment. As shown in fig. 1, a vehicle 1 such as a truck or a bus is mounted with an internal combustion engine 10, an exhaust system 20, and a Control Unit 30 (specifically, an ECU (Electronic Control Unit)). The exhaust system 20 and the control unit 30 function as an exhaust gas purification system of the present invention.

First, the structure of the internal combustion engine 10 will be described. The internal combustion engine 10 is, for example, a diesel engine. In the combustion chamber 11 of the internal combustion engine 10, a fuel injection injector 13 injects fuel into the combustion chamber 11. Further, the fuel injection injector 13 may inject fuel into an intake port of the combustion chamber 11. The injection of fuel is controlled, for example, by an ECM (Engine Control Module) (not shown). The fuel in the combustion chamber 11 is compressed by the operation of the piston 19 and is combusted.

The valves 15 and 17 are configured to be openable and closable. By opening the intake valve 15, new air from the intake pipe 50 is drawn into the combustion chamber 11. Further, by opening the exhaust valve 17, exhaust gas generated by combustion of fuel in the combustion chamber 11 is sent to the exhaust system 20 (specifically, an exhaust pipe 21, corresponding to an exhaust passage of the present invention).

Next, the structure of the exhaust system 20 will be described. The exhaust system 20 has an exhaust pipe 21. Exhaust pipe 21 is mainly made of metal, and is provided, for example, in a lower portion of vehicle 1. Exhaust pipe 21 guides exhaust gas generated by combustion of fuel in internal combustion engine 10 to the atmosphere (outside the vehicle).

Further, various post-treatment devices are provided in the middle of the exhaust pipe 21 to purify (make harmless) the exhaust gas. In the present embodiment, as the aftertreatment device, a DOC (diesel oxidation catalyst, also referred to as an "oxidation catalyst") 23A, DPF (diesel particulate filter) 23B, SCR (corresponding to the selective reduction catalyst device of the present invention) 23C, RDOC (rear diesel oxidation catalyst) 23D is provided.

The DOC23A is formed by supporting rhodium, cerium oxide, platinum, alumina, and the like on a metal carrier. The DOC23A decomposes and removes Hydrocarbons (HC) and carbon monoxide (CO) contained in the exhaust gas. The DOC23A also has a function of oxidizing nitrogen monoxide (NO), which is a large part of NOx contained in exhaust gas, to generate nitrogen dioxide (NO)₂) The function of (c). By utilizing this function, combustion (PM regeneration) of PM (particulate matter) trapped in the DPF23B can be promoted, and the NOx purification efficiency of the SCR23C can be improved.

The exhaust pipe 21 is provided with a flow sensor 25 near the inlet of the DOC23A, for example. The flow rate sensor 25 detects the flow rate of the exhaust gas, and outputs a signal indicating the flow rate to the control unit 30.

The DPF23B is formed of a wall-flow filter (monolithic honeycomb) type in which the inlet and outlet of a channel (cell) of a honeycomb made of porous ceramic are alternately plugged. The DPF23B traps and removes Particulate Matter (PM) contained in exhaust gas.

A urea water injector 27 (also referred to as a dosing valve (dosing valve) corresponding to the reducing agent injector of the present invention) for injecting urea water (corresponding to the reducing agent of the present invention) is provided in the exhaust pipe 21 at a position downstream of the DPF23B (specifically, downstream in the flow direction of the exhaust gas) and upstream of the SCR 23C.

Further, the urea water injector 27 is more preferably disposed between the DPF23B and the SCR23C as close as possible to the DPF 23B.

In exhaust pipe 21, for example, a temperature sensor 29 is provided near the inlet of SCR 23C. The temperature sensor 29 is used for controlling the injection of the urea water, etc., detects the temperature of the exhaust gas, and outputs a signal indicating the temperature to the control unit 30.

The SCR23C has, for example, a cylindrical shape with a honeycomb carrier made of ceramic. The honeycomb wall surface is, for example, supported or coated with a catalyst such as zeolite or vanadium.

The SCR23C as described above is disposed downstream of the DPF23B in the exhaust pipe 21. Further, urea water as a reducing agent is injected by the urea water injector 27 between the DPF23B and the SCR23C in the exhaust pipe 21, and is supplied to the exhaust gas passing through the DOC23A and the DPF 23B. As a result, the urea water is hydrolyzed into ammonia. In the process of passing through SCR23C, the exhaust gas containing ammonia reacts with nitrogen oxides (i.e., NOx) by the action of a catalyst to become nitrogen and water (reduction reaction). Thereby, nitrogen oxides in the exhaust gas are purified.

here, hydrolysis occurs when the temperature of the exhaust gas passing through the SCR23C is equal to or higher than a predetermined temperature. Therefore, it is preferable that the urea water injector 27 supply the urea water to the exhaust gas in the exhaust pipe 21 when the temperature of the exhaust gas flowing into the SCR23C is equal to or higher than a predetermined temperature. Here, the injection of the urea water is controlled by a DCU (not shown). The predetermined temperature is determined as appropriate in consideration of the reaction temperature of ammonia and NOx, for example, by experiments and simulations at the design development stage of the exhaust system 20.

RDOC23D is a post-oxidation catalyst and has the same structure as DOC23A, and is disposed immediately downstream of SCR23C on exhaust pipe 21, immediately after SCR 23C.

RDOC23D primarily removes the missing ammonia by oxidizing it so that the missing ammonia is not released to the atmosphere in SCR23C without being used for the reduction reaction. Otherwise, RDOC23D may also have the same function as SCR 23C.

The water, nitrogen, and carbon dioxide generated by treating the exhaust gas by each of the above post-treatment devices are discharged to the atmosphere through a muffler (not shown) or the like.

The control Unit 30 includes a CPU (Central Processing Unit), a ROM (Read Only Memory) for storing a control program, a RAM (Random Access Memory), and other work Memory. The CPU reads out a control program from the ROM and develops it in the RAM, and controls execution of various processes in cooperation with the developed control program.

as shown in fig. 1, the control unit 30 includes: a temperature acquisition unit 31, a flow rate acquisition unit 32, an injection amount acquisition unit 33, a deposition amount estimation unit 34, and a notification unit 35.

The temperature acquisition unit 31 receives the signal output from the temperature sensor 29, and acquires the temperature of the exhaust gas passing through the exhaust pipe 21.

the flow rate acquisition unit 32 receives the signal output from the flow rate sensor 25, and acquires the flow rate of the exhaust gas passing through the exhaust pipe 21.

The injection amount obtaining unit 33 obtains the injection amount of the urea water injected by the urea water injector 27.

the deposition amount estimation unit 34 estimates the deposition amount of the white product derived from the urea water in the exhaust pipe 21 at the current time point based on the temperature acquired by the temperature acquisition unit 31, the flow rate acquired by the flow rate acquisition unit 32, and the injection amount acquired by the injection amount acquisition unit 33. The white product derived from the aqueous urea solution is cyanuric acid or the like generated at the time of hydrolysis of the aqueous urea solution.

In the present embodiment, the deposition amount estimating unit 34 estimates the deposition amount of the white product per predetermined time by referring to the deposition amount map 36, and the relationship between the temperature of the exhaust gas, the flow rate of the exhaust gas, the injection amount of the urea water, and the deposition amount of the white product is predetermined in the deposition amount map 36.

The accumulation amount map 36 is previously created through experiments or experiments, is stored in the RAM of the control unit 30, and is appropriately read out. In the deposit map 36, the amount of white product deposited is reduced as the temperature of the exhaust gas is increased. In the deposit map 36, the amount of white product deposited decreases as the flow rate of the exhaust gas increases. In the accumulation amount map 36, the amount of white product accumulation increases as the amount of urea water injected increases. In the present embodiment, each parameter (the temperature of the exhaust gas, the flow rate of the exhaust gas, and the injection amount of the urea water) is weighted in consideration of the degree of influence on the deposition of the white products.

The deposition amount estimating unit 34 estimates the deposition amount of the white product at the current time by integrating the deposition amount of the white product per predetermined time.

When the deposition amount at the current time estimated by the deposition amount estimation unit 34 is equal to or greater than the predetermined amount, the notification unit 35 notifies the driver of the fact. Here, the case where the deposition amount at the present time is equal to or more than the predetermined amount means a case where a large amount of white products are deposited in the exhaust pipe 21, and there is a possibility that, for example, the exhaust pipe 21 is clogged and the desired exhaust gas purification treatment cannot be performed.

Fig. 2 shows a temporal change in the deposition amount of the white product at the current time estimated by the deposition amount estimation unit 34. As shown in fig. 2, the amount of white product deposited at the current time increases and decreases with the passage of time, and becomes equal to or greater than a predetermined amount after a certain time.

In the present embodiment, the notification unit 35 prompts the driver to perform high-load operation by increasing the vehicle speed (for example, 80km or more) by lighting an indicator lamp provided near the driver's seat, or to perform manual regeneration by injecting fuel into the exhaust gas from an injector (not shown) provided in the exhaust pipe 21 to forcibly burn the PM. In the case of the vanadium system in which the DOC23A is not provided (that is, in the case where there is no temperature raising device and the temperature of the exhaust gas does not rise regularly), the notification unit 35 may prompt the driver to perform only the high-load operation.

Next, an example of the deposition amount estimation processing performed by the control unit 30 in the present embodiment will be described with reference to the flowchart in fig. 3.

First, the temperature acquisition unit 31 receives a signal output from the temperature sensor 29, and acquires the temperature of the exhaust gas passing through the exhaust pipe 21 (step S100). Next, the flow rate acquisition unit 32 receives the signal output from the flow rate sensor 25, and acquires the flow rate of the exhaust gas passing through the exhaust pipe 21 (step S120).

Next, the injection amount obtaining unit 33 obtains the injection amount of the urea solution injected by the urea solution injector 27 (step S140). Next, the deposition amount estimation unit 34 estimates the deposition amount of the white product derived from the urea water in the exhaust pipe 21 at the current time point, based on the temperature acquired by the temperature acquisition unit 31, the flow rate acquired by the flow rate acquisition unit 32, and the injection amount acquired by the injection amount acquisition unit 33 (step S160).

Next, the notification unit 35 determines whether or not the deposition amount at the current time estimated by the deposition amount estimation unit 34 is larger than a predetermined amount (step S180). If the accumulation amount at the current time point is not more than the predetermined amount as a result of the determination (no in step S180), control unit 30 ends the processing in fig. 3.

On the other hand, when the deposition amount at the current time is larger than the predetermined amount (step S180: "YES"), the notification unit 35 notifies the driver that the deposition amount at the current time estimated by the deposition amount estimation unit 34 is equal to or larger than the predetermined amount (step S200). The process in step S200 is completed and the process in fig. 3 ends.

As described above in detail, in the present embodiment, the exhaust gas purification system (the exhaust system 20 and the control unit 30) includes: a temperature acquisition unit 31 that acquires the temperature of the exhaust gas passing through the exhaust passage (exhaust pipe 21); a flow rate obtaining unit 32 for obtaining the flow rate of the exhaust gas; an injection amount obtaining unit 33 that obtains an injection amount of the urea water; and a deposition amount estimation unit 34 that estimates the deposition amount of the white product derived from the urea water in the exhaust passage based on the temperature acquired by the temperature acquisition unit 31, the flow rate acquired by the flow rate acquisition unit 32, and the injection amount acquired by the injection amount acquisition unit 33.

According to the present embodiment configured as described above, it is possible to estimate how much white product is accumulated in the exhaust passage, and therefore, it is possible to take appropriate measures (for example, high-load operation or manual regeneration) to improve the accumulation. As a result, it is possible to suitably prevent the possibility that the desired exhaust gas purification treatment cannot be performed due to clogging in the exhaust passage.

In the present embodiment, the deposition amount estimating unit 34 estimates the deposition amount of the white product by referring to the deposition amount map 36, and the relationship between the temperature of the exhaust gas, the flow rate of the exhaust gas, the injection amount of the urea water, and the deposition amount of the white product is defined in advance in the deposition amount map 36. With this configuration, the amount of white product deposited can be estimated accurately in a short time.

In the present embodiment, the notification unit 35 notifies that the deposition amount estimated by the deposition amount estimation unit 34 is equal to or greater than a predetermined amount. With this configuration, the driver can be notified when the amount of white product deposited is equal to or greater than the predetermined amount, that is, when there is a possibility that the desired exhaust gas purification process cannot be performed, and therefore the driver who has received the notification can promptly perform the high-load operation or the manual regeneration to remove the deposited white product.

In the above-described embodiment, the example in which the deposition amount estimation unit 34 estimates the deposition amount of the white product based on the temperature acquired by the temperature acquisition unit 31, the flow rate acquired by the flow rate acquisition unit 32, and the injection amount acquired by the injection amount acquisition unit 33 has been described, but the present invention is not limited to this. For example, the deposition amount estimation unit 34 may estimate the deposition amount of the white product based on the temperature acquired by the temperature acquisition unit 31, the flow rate acquired by the flow rate acquisition unit 32, and parameters (for example, the travel distance, the travel time, and the like) other than the injection amount acquired by the injection amount acquisition unit 33. This is because, from experiments or experiments performed in advance, the following tendency is known: the longer the running distance or the running time is, the larger the amount of the white product deposited becomes.

the above embodiments are merely examples of embodying the present invention, and the technical scope of the present invention should not be limited by these embodiments. That is, the present invention can be implemented in various forms without departing from the gist or main features thereof.

The present application is based on the japanese patent application (japanese patent application 2017-118604), filed on 16.6.2017, the content of which is hereby incorporated by reference.

Industrial applicability

The present invention is useful as an exhaust gas purification system and a deposition amount estimation method that can estimate the deposition amount of white products in an exhaust passage.

Description of the reference numerals

1 vehicle

10 internal combustion engine

11 combustion chamber

13 fuel injection injector

15 air inlet valve

17 exhaust valve

19 piston

20 exhaust system

21 exhaust pipe

23A DOC

23B DPF

23C SCR

23D RDOC

25 flow sensor

27 Urea water injector (reducing agent injector)

29 temperature sensor

30 control part

31 temperature acquisition part

32 flow rate acquisition unit

33 injection amount acquiring unit

34 accumulation amount estimating unit

35 informing part

36 pile-up mapping table

50 intake pipe