JP2022011307A - Exhaust emission control system - Google Patents

Abstract

To properly remove a reductant agent after stoppage of an internal combustion engine.SOLUTION: An exhaust emission control system S includes: an injection unit 41 for injecting a reductant agent into an exhaust pipe; a supply pipe for supplying a reductant agent into the injection unit 41; an air supply unit for supplying air into the supply pipe; an injection degree acquisition unit 122 for acquiring a reductant agent injection degree by the injection unit 41 before stoppage of an internal combustion engine at the time of the stoppage of the internal combustion engine; and a supply control unit 123 for controlling such that the larger the acquired injection degree, the larger the amount of air to be supplied to the supply pipe after the stoppage of the internal combustion engine or the longer the time to supply air.SELECTED DRAWING: Figure 2

Description

The present invention relates to an exhaust purification system that purifies exhaust gas by injecting a reducing agent into an exhaust pipe through which exhaust gas flows.

The exhaust pipe of the internal combustion engine is provided with a reducing agent injection device that injects a reducing agent that purifies the exhaust gas. In the reducing agent injection device, the reducing agent in the tank is supplied to the injection unit via the supply pipe, and the injection unit injects the reducing agent into the exhaust pipe.
Some reducing agent injection devices remove the reducing agent remaining in the supply pipe by supplying air into the supply pipe for a predetermined time after the internal combustion engine is stopped.

Japanese Unexamined Patent Publication No. 2016-128678

By the way, depending on the operating condition before the internal combustion engine is stopped, the reducing agent may not be completely removed even if air is supplied to the supply pipe at a predetermined time. In this case, the residual water content of the reducing agent may evaporate and the injection portion may be clogged.

Therefore, the present invention has been made in view of these points, and an object thereof is to appropriately remove the reducing agent after the internal combustion engine is stopped.

One aspect of the present invention is an exhaust purification system that injects a reducing agent for purifying the exhaust gas into an exhaust pipe through which exhaust gas generated from an internal combustion engine flows, and the reducing agent is applied to the exhaust pipe. An injection unit for injecting, a supply pipe for supplying the reducing agent to the injection unit, an air supply unit for supplying air to the supply pipe, and the injection unit before the internal combustion engine is stopped when the internal combustion engine is stopped. The larger the injection degree acquisition unit that acquires the injection degree of the reducing agent and the injection degree acquired by the injection degree acquisition unit, the larger the amount of air supplied to the supply pipe after the internal combustion engine is stopped. Provided is an exhaust gas purification system including a supply control unit for increasing the supply time of the air.

Further, the injection degree acquisition unit may acquire the injection degree within a predetermined time before the internal combustion engine is stopped when the internal combustion engine is stopped.

Further, the injection degree acquisition unit acquires the injection amount of the reducing agent as the injection degree before the internal combustion engine is stopped, and the supply control unit has a large injection amount acquired by the injection degree acquisition unit. The amount of air supplied to the supply pipe after the internal combustion engine is stopped may be increased, or the air supply time may be lengthened.

Further, the injection degree acquisition unit acquires the injection time of the reducing agent as the injection degree before the internal combustion engine is stopped, and the supply control unit has a long injection time acquired by the injection degree acquisition unit. The amount of air supplied to the supply pipe after the internal combustion engine is stopped may be increased, or the air supply time may be lengthened.

Further, the exhaust gas purification system further includes an outside air temperature acquisition unit that acquires the outside air temperature when the internal combustion engine is stopped, and the supply control unit is described so that the lower the outside air temperature acquired by the outside air temperature acquisition unit, the lower the outside air temperature. The amount of air supplied to the supply pipe after the internal combustion engine is stopped may be increased, or the air supply time may be lengthened.

Further, the exhaust purification system is provided in the supply pipe to a mixing unit that mixes the reducing agent and the air, a first valve that controls the flow of the reducing agent to the mixing unit, and the mixing unit. A second valve for controlling the flow of air is further provided, and the supply control unit closes the first valve and opens the second valve after the internal combustion engine is stopped. The air supply unit may supply the air to the mixing unit.

According to the present invention, there is an effect that the reducing agent can be appropriately removed after the internal combustion engine is stopped.

It is a schematic diagram which shows the structure of the exhaust gas purification system S which concerns on one Embodiment. It is a block diagram which shows the detailed structure of the control device 100. It is a schematic diagram for demonstrating the supply amount of air according to the injection degree. It is a flowchart for demonstrating the operation example of the urea water injection apparatus 40.

<Structure of exhaust purification system>
The configuration of the exhaust gas purification system S according to the embodiment of the present invention will be described with reference to FIG. 1.

FIG. 1 is a schematic diagram showing a configuration of an exhaust gas purification system S according to an embodiment. As shown in FIG. 1, the exhaust purification system S includes an engine 10, an exhaust passage 20, a DPF (Diesel Particulate Filter) 30, a urea water injection device 40, an air supply unit 50, and an SCR (Selective Catalytic Reduction; It has a selective reduction catalyst) device 60, a sensor group 70, and a control device 100. The exhaust gas purification system S is mounted on a vehicle such as a truck and purifies the exhaust gas of the engine 10. Here, the exhaust purification system S purifies the exhaust gas flowing through the exhaust passage 20 with urea water which is a reducing agent.

The engine 10 is an internal combustion engine that generates power by burning and expanding a mixture of fuel and intake air (air). The engine 10 is a 4-cylinder diesel engine here, but the engine 10 is not limited to this, and may be an engine other than the 4-cylinder engine.

The exhaust passage 20 is an exhaust pipe connected to the engine 10 and exhausts the exhaust gas of the engine 10 to the outside of the vehicle. The exhaust passage 20 through which the exhaust gas flows is provided with a DPF 30, a urea water injection device 40, and an SCR device 60.

The DPF 30 is a filter that collects particulate matter (PM) contained in the exhaust gas. The DPF 30 is made of, for example, a honeycomb body made of metal or ceramics.

The urea water injection device 40 is provided between the DPF 30 and the SCR device 60, and injects urea water into the exhaust passage 20. The urea water injected by the urea water injection device 40 is hydrolyzed by the heat of the exhaust gas flowing through the exhaust passage 20, and ammonia is generated. Ammonia is used to cause a reduction reaction of NOx in the exhaust gas. Thus, urea water is also a precursor that produces ammonia.

In the present embodiment, the urea water injection device 40 mixes urea water and air and injects them into the exhaust passage 20. As a result, the particle size of the urea water becomes finer, so that the exhaust gas can be efficiently purified. As shown in FIG. 1, the urea water injection device 40 includes an injection unit 41, a urea water tank 42, a urea water supply pipe 43, a urea water side pump 44, a urea water side valve 45, and a mixing unit 46. Has.

The injection unit 41 injects urea water into the exhaust passage 20. The injection unit 41 injects urea water to the upstream side of the SCR device 60 in the exhaust passage 20. The urea water tank 42 is a storage unit for accommodating urea water. The urea water supply pipe 43 supplies urea water to the injection unit 41. The urea water supply pipe 43 is a pipe connecting the urea water tank 42 and the injection unit 41, and is a flow path through which urea water flows.

The urea water side pump 44 is provided in the urea water supply pipe 43, and sends out urea water from the urea water tank 42 toward the injection unit 41. The urea water side valve 45 is a valve that can be opened and closed provided in the urea water supply pipe 43, and when in the open state, urea water passes through the mixing unit 46 and flows to the injection unit 41. That is, the urea water side valve 45 controls the flow of urea water to the mixing unit 46.

The mixing unit 46 is provided in the urea water supply pipe 43, and mixes urea water and air. Here, the mixing unit 46 is a chamber (space) provided at the connection portion between the urea water supply pipe 43 and the air supply pipe 52. The urea water and air mixed in the mixing unit 46 flow to the injection unit 41 and are injected from the injection unit 41.

The air supply unit 50 supplies air to the urea water supply pipe 43. The air supply unit 50 supplies, for example, pressurized air to the urea water supply pipe 43 and mixes it with the urea water. Further, the air supply unit 50 supplies air to the urea water supply pipe 43 in order to sweep out the urea water remaining in the urea water supply pipe 43 when the engine 10 is stopped. For example, when the vehicle stops idling, urea water remains in the urea water supply pipe 43, so that air is supplied to the urea water supply pipe 43 when the engine 10 such as the idling stop is stopped. As shown in FIG. 1, the air supply unit 50 includes an air tank 51, an air supply pipe 52, an air side pump 53, and an air side valve 54.

The air tank 51 is an accommodating portion for accommodating air. The air-side pump 53 obtains power from the engine 10 and fills the air tank 51 with air. The air supply pipe 52 is a pipe connecting the air tank 51 and the mixing portion 46, and is a flow path through which air flows.

The air side valve 54 is a valve that can be opened and closed provided in the air supply pipe 52, and the air in the air tank 51 flows to the mixing portion 46 when the air tank 51 is in the open state. That is, the air side valve 54 controls the flow of air to the mixing unit 46. In the present embodiment, the air side valve 54 corresponds to the second valve, and the urea water side valve 45 corresponds to the first valve.

The SCR device 60 is a device that converts NOx in the exhaust gas into harmless nitrogen by a reduction reaction. The SCR device 60 has a reduction catalyst 62 that promotes a reduction reaction between ammonia and NOx. Ammonia generated from urea water is adsorbed on the reduction catalyst 62. The reduction catalyst 62 reduces NOx to nitrogen and water by the adsorbed ammonia, and reduces the emission of NOx.

The sensor group 70 detects the state of the exhaust gas purification system S and the like. For example, the sensor group 70 includes a sensor that detects the presence or absence of operation of the engine 10. Further, the sensor group 70 includes a temperature detection sensor (for example, the temperature detection sensor 72 shown in FIG. 2) that detects the temperature of the outside air. The sensor group 70 outputs the detection result to the control device 100.

The control device 100 controls the operation of the exhaust gas purification system S. The control device 100 controls the operation of the urea water injection device 40 based on the detection result of the sensor group 70. For example, when the engine 10 is stopped, the control device 100 supplies air to the urea water supply pipe 43 to remove the urea water remaining in the urea water supply pipe 43. Then, although the details will be described later, the control device 100 controls the supply amount or supply time of air to the urea water supply pipe 43 after the engine 10 is stopped according to the injection degree of the urea water before the engine 10 is stopped. do. As a result, for example, when the injection amount or injection time of urea water before the engine 10 is stopped is long, the urea supply amount is increased after the engine 10 is stopped, or the air supply time is lengthened. Urea water in the water supply pipe 43 can be appropriately removed.

<Detailed configuration of control device>
An example of the detailed configuration of the control device 100 will be described with reference to FIG.
FIG. 2 is a block diagram showing a detailed configuration of the control device 100. The control device 100 has a storage unit 110 and a control unit 120.

The storage unit 110 includes, for example, a ROM (Read Only Memory) and a RAM (Random Access Memory). The storage unit 110 stores programs and various data for execution by the control unit 120. For example, the storage unit 110 stores various information used for air supply processing after the engine 10 is stopped.

The control unit 120 is, for example, a CPU (Central Processing Unit). The control unit 120 controls the operation of the exhaust gas purification system S by executing the program stored in the storage unit 110. In the present embodiment, the control unit 120 functions as an injection control unit 121, an injection degree acquisition unit 122, a supply control unit 123, and an outside air temperature acquisition unit 124.

The injection control unit 121 controls the injection of urea water by the injection unit 41. For example, the injection control unit 121 injects urea water into the injection unit 41 during the operation of the engine 10. The injection control unit 121 controls the injection amount and injection time of urea water.

The injection degree acquisition unit 122 acquires the injection degree of urea water by the injection unit 41. The injection degree acquisition unit 122 acquires the injection degree of urea water by the injection unit 41 before the engine 10 is stopped when the engine 10 is stopped. When the injection degree acquisition unit 122 detects the stop of the engine 10 by the sensor group 70 (FIG. 1), the injection degree acquisition unit 122 acquires the injection degree of urea water before the engine 10 is stopped. The injection degree acquisition unit 122 acquires the injection degree based on, for example, the injection amount and the injection time controlled by the injection control unit 121 before the engine 10 is stopped. The injection degree acquisition unit 122 outputs the acquired injection degree to the supply control unit 123.

When the engine 10 is stopped, the injection degree acquisition unit 122 acquires the injection degree of urea water within a predetermined time before the engine 10 is stopped. That is, the injection degree acquisition unit 122 acquires the injection degree of urea water immediately before the engine 10 is stopped.

The injection degree acquisition unit 122 can acquire the injection amount of urea water as the injection degree before the engine 10 is stopped. Specifically, the injection degree acquisition unit 122 acquires the injection amount of urea water within a predetermined time before the engine 10 is stopped. Further, the injection degree acquisition unit 122 can acquire the injection time of urea water as the injection degree before the engine 10 is stopped. Specifically, the injection degree acquisition unit 122 acquires the injection time of urea water within a predetermined time before the engine 10 is stopped. The injection degree acquisition unit 122 may acquire both the injection amount and the injection time.

The supply control unit 123 controls the supply of urea water and air injected by the injection unit 41. For example, the supply control unit 123 operates the urea water side pump 44 to supply urea water and operates the air side pump 53 to supply air while the engine 10 is operating. Further, the supply control unit 123 controls the supply amount of urea water by opening and closing the urea water side valve 45. Similarly, the supply control unit 123 controls the supply amount or supply time of air by opening and closing the air side valve 54.

After the engine 10 is stopped, the supply control unit 123 supplies air without supplying urea water. Specifically, after the engine 10 is stopped, the supply control unit 123 closes the urea water side valve 45 and opens the air side valve 54, and supplies air to the air supply unit 50 to the mixing unit 46. Let me. As a result, the urea water remaining in the urea water supply pipe 43 when the engine 10 is stopped (for example, when idling is stopped) can be removed by the air supplied after the engine 10 is stopped.

The supply control unit 123 controls the amount of air supplied after the engine 10 is stopped, based on the injection degree acquired by the injection degree acquisition unit 122 when the engine 10 is stopped. The greater the degree of injection before the engine 10 is stopped, the greater the amount of urea water remaining in the urea water supply pipe 43. Therefore, the supply control unit 123 adjusts the supply amount of air for removing the urea water remaining in the urea water supply pipe 43 according to the injection degree of the urea water before the stop, instead of keeping it constant. ..

FIG. 3 is a schematic diagram for explaining the amount of air supplied according to the degree of injection. As shown in FIG. 3, the supply control unit 123 increases the amount of air supplied to the urea water supply pipe 43 after the engine 10 is stopped, as the injection degree acquired by the injection degree acquisition unit 122 is larger. For example, the supply control unit 123 increases the amount of air supplied to the urea water supply pipe 43 after the engine 10 is stopped as the amount of urea water injected by the injection degree acquisition unit 122 before the engine 10 is stopped increases. Let me. Further, the supply control unit 123 increases the amount of air supplied to the urea water supply pipe 43 after the engine 10 is stopped as the injection time of the urea water acquired by the injection degree acquisition unit 122 before the engine 10 is stopped is longer. Let me. As a result, the urea water in the urea water supply pipe 43 is appropriately adjusted by adjusting the supply amount of the air supplied to the urea water supply pipe 43 after the engine 10 is stopped according to the injection degree before the engine 10 is stopped. Can be removed. In FIG. 3, it is decided that the larger the injection degree, the larger the air supply amount, but the larger the injection degree, the longer the air supply time may be.

The outside air temperature acquisition unit 124 acquires the outside air temperature from the detection result of the temperature detection sensor 72 that detects the temperature of the outside air. For example, the outside air temperature acquisition unit 124 acquires the outside air temperature when the engine 10 is stopped. The outside air temperature acquisition unit 124 outputs the acquired outside air temperature information to the supply control unit 123.

The supply control unit 123 controls the amount of air supplied to the urea water supply pipe 43 according to the outside air temperature acquired by the outside air temperature acquisition unit 124. When the outside air temperature is low, there is a high possibility that urea water remains in the urea water supply pipe 43 as compared with the case where the outside air temperature is high. Therefore, the supply control unit 123 increases the amount of air supplied to the urea water supply pipe 43 after the engine 10 is stopped, or lengthens the air supply time, as the outside air temperature acquired by the outside air temperature acquisition unit 124 is lower. Let me. As a result, it is possible to effectively suppress the residual urea water due to the outside air temperature.

<Operation example of urea water injection device>
An operation example of the urea water injection device 40 will be described with reference to FIG.

FIG. 4 is a flowchart for explaining an operation example of the urea water injection device 40. This flowchart starts from the place where the engine 10 is operating.

First, the injection control unit 121 of the control device 100 injects urea water into the exhaust passage 20 through which the exhaust gas generated from the engine 10 flows (step S102). At this time, the urea water supplied from the urea water tank and the air supplied from the air tank are mixed by the mixing unit 46 and then injected from the injection unit 41.

After that, the control device 100 determines whether or not the engine 10 has stopped (step S104). If it is determined in step S104 that the engine 10 has stopped (Yes), the injection control unit 121 stops the injection of urea water (step S106).

Next, the injection degree acquisition unit 122 acquires the injection degree of urea water before the engine 10 is stopped (step S108). For example, the injection degree acquisition unit 122 acquires the injection amount and injection time of urea water within a predetermined time before the engine 10 is stopped. The injection degree acquisition unit 122 can acquire the injection degree from the injection control of urea water by the injection control unit 121 before the engine 10 is stopped.

Next, the supply control unit 123 goes to the urea water supply pipe 43 in order to remove the urea water remaining in the urea water supply pipe 43 after the engine 10 is stopped, based on the injection degree acquired by the injection degree acquisition unit 122. The air supply amount of (step S110) is set. The supply control unit 123 sets a larger amount of air supply after the engine 10 is stopped as the degree of injection of urea water before the engine 10 is stopped (for example, the amount of urea water injected and the injection time) is larger. The supply control unit 123 may set a long air supply time instead of setting the air supply amount.

Next, after the engine 10 is stopped, the supply control unit 123 supplies air to the urea water supply pipe 43 for the supply amount or supply time set in step S110 (step S112). The supplied air is discharged from the injection unit 41 while pushing out the urea water remaining in the urea water supply pipe 43. As a result, the urea water remaining in the urea water supply pipe 43 is removed.

<Effect in this embodiment>
The exhaust gas purification system S of the present embodiment described above acquires the degree of urea water injection by the injection unit 41 before the engine 10 is stopped when the engine 10 is stopped. Then, the exhaust purification system S increases the amount of air supplied to the urea water supply pipe 43 after the engine 10 is stopped, or lengthens the air supply time, as the degree of injection of the acquired urea water increases.
The greater the degree of injection of urea water before the engine 10 is stopped, the greater the amount of urea water remaining in the urea water supply pipe 43. Therefore, the greater the injection degree of urea water before stopping, the larger the amount of air supplied after the engine 10 is stopped, or the longer the air supply time, so that the urea water remaining in the urea water supply pipe 43 can be removed. Can be removed properly.

Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes can be made within the scope of the gist. be. For example, all or part of the device can be functionally or physically distributed / integrated in any unit. Also included in the embodiments of the present invention are new embodiments resulting from any combination of the plurality of embodiments. The effect of the new embodiment produced by the combination has the effect of the original embodiment together.

10 Engine 20 Exhaust passage 41 Injection part 43 Urea water supply pipe 45 Urea water side valve 46 Mixing part 50 Air supply part 54 Air side valve 122 Injection degree acquisition part 123 Supply control part 124 Outside temperature acquisition part S Exhaust purification system

Claims (6)

An exhaust purification system that injects a reducing agent for purifying the exhaust gas into the exhaust pipe through which the exhaust gas generated from the internal combustion engine flows.
An injection unit that injects the reducing agent into the exhaust pipe,
A supply pipe that supplies the reducing agent to the injection unit,
An air supply unit that supplies air to the supply pipe,
When the internal combustion engine is stopped, an injection degree acquisition unit that acquires the injection degree of the reducing agent by the injection unit before the internal combustion engine is stopped, and an injection degree acquisition unit.
The larger the injection degree acquired by the injection degree acquisition unit, the larger the supply amount of the air to the supply pipe after the internal combustion engine is stopped, or the supply control unit that prolongs the supply time of the air.
Equipped with an exhaust purification system. When the internal combustion engine is stopped, the injection degree acquisition unit acquires the injection degree within a predetermined time before the internal combustion engine is stopped.
The exhaust purification system according to claim 1. The injection degree acquisition unit acquires the injection amount of the reducing agent as the injection degree before the internal combustion engine is stopped.
The supply control unit increases the supply amount of the air to the supply pipe after the internal combustion engine is stopped, or lengthens the supply time of the air, as the injection amount acquired by the injection degree acquisition unit increases. Let,
The exhaust purification system according to claim 1 or 2. The injection degree acquisition unit acquires the injection time of the reducing agent as the injection degree before the internal combustion engine is stopped.
The supply control unit increases the amount of air supplied to the supply pipe after the internal combustion engine is stopped, or lengthens the air supply time, as the injection time acquired by the injection degree acquisition unit becomes longer. Let,
The exhaust gas purification system according to any one of claims 1 to 3. Further provided with an outside air temperature acquisition unit that acquires the outside air temperature when the internal combustion engine is stopped.
The supply control unit increases the amount of air supplied to the supply pipe after the internal combustion engine is stopped, or lengthens the air supply time, as the outside air temperature acquired by the outside air temperature acquisition unit is lower. Let,
The exhaust gas purification system according to any one of claims 1 to 4. A mixing unit provided in the supply pipe for mixing the reducing agent and the air,
A first valve that controls the flow of the reducing agent to the mixing portion,
A second valve for controlling the flow of the air to the mixing portion is further provided.
After the internal combustion engine is stopped, the supply control unit closes the first valve and opens the second valve, and causes the air supply unit to supply the air to the mixing unit.
The exhaust gas purification system according to any one of claims 1 to 5.

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