JP2021131068A - Exhaust emission control device and vehicle - Google Patents

Abstract

To provide an exhaust emission control device and a vehicle, capable of actualizing early activation of a NOx removal catalyst.SOLUTION: The exhaust emission control device includes: a first NOx removal catalyst provided on the upstream side in the flowing direction of exhaust gas; a second NOx removal catalyst provided on the downstream side further than the first NOx removal catalyst; a heat release part provided between the first NOx removal catalyst and the second NOx removal catalyst; a reductant supply device for supplying reductant on the upstream side of the first NOx removal catalyst; and a control part for controlling the heat release part and the reductant supply device. The control part allows the heat release part to start the heat release to raise the temperature of the exhaust gas right after starting an internal combustion engine, and then allows the reductant supply device to start the injection of the reductant when the temperature of the exhaust gas on the downstream side of the second NOx removal catalyst exceeds a threshold value.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to an exhaust gas purification device and a vehicle for purifying exhaust gas.

Conventionally, there is known an exhaust purification device in which a plurality of NOx purification catalysts for reducing NOx in the exhaust gas are provided in an exhaust pipe through which the exhaust gas discharged from the internal combustion engine flows.

For example, Patent Document 1 discloses an exhaust purification device in which a heating device for heating the exhaust gas flowing between the NOx purification catalyst on the upstream side and the NOx purification catalyst on the downstream side is arranged.

Japanese Unexamined Patent Publication No. 2019-132168

However, in the exhaust gas purification device of Patent Document 1, there is room for improvement in the activation of the NOx purification catalyst.

An object of one aspect of the present disclosure is to provide an exhaust gas purification device and a vehicle capable of activating a plurality of NOx purification catalysts at an early stage.

The exhaust gas purification device according to one aspect of the present disclosure includes a first NOx purification catalyst provided on the upstream side in the flow direction of the exhaust gas discharged from the internal combustion engine, and the first NOx purification catalyst in the flow direction of the exhaust gas. A second NOx purification catalyst provided on the downstream side, a heat radiating portion provided between the first NOx purification catalyst and the second NOx purification catalyst, and the first NOx purification catalyst. It has a reducing agent supply device that supplies a reducing agent on the upstream side, and a control unit that controls the operation of each of the heat dissipation unit and the reducing agent supply device. The control unit is immediately after the start of the internal combustion engine. The reducing agent supply device starts heat dissipation to the heat radiating unit in order to raise the temperature of the exhaust gas, and then when the temperature of the exhaust gas on the downstream side of the second NOx purification catalyst exceeds a predetermined threshold value. Starts the injection of the reducing agent.

The vehicle according to one aspect of the present disclosure includes an exhaust gas purification device according to one aspect of the present disclosure.

According to the present disclosure, a plurality of NOx purification catalysts can be activated at an early stage.

Schematic diagram showing the configuration of the exhaust gas purification device according to the embodiment of the present disclosure. A flowchart showing the operation of the control unit according to the embodiment of the present disclosure.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

The configuration of the exhaust gas purification device 100 according to the embodiment of the present disclosure will be described with reference to FIG. FIG. 1 is a schematic view showing an example of the configuration of the exhaust gas purification device 100 of the present embodiment.

The exhaust gas purification device 100 is a device mounted on a vehicle (not shown) to purify exhaust gas discharged from an internal combustion engine (not shown). In the present embodiment, the case where the internal combustion engine is a diesel engine will be described as an example, but the present invention is not limited to this, and the internal combustion engine may be, for example, a gasoline engine. Further, the exhaust gas purification device 100 is not limited to the internal combustion engine of a vehicle, and can be applied to, for example, a ship or a stationary internal combustion engine.

As shown in FIG. 1, the exhaust gas purification device 100 includes a control unit 10, a first catalytic converter 11, and a second catalytic converter 12.

The control unit 10 controls the injection amount and injection timing of urea water (an example of a reducing agent) in the urea water injection devices 2 and 8, and on / off of the power supply to the heat dissipation unit 4. Examples of the control unit 10 include an ECU (Electronic Control Unit).

In FIG. 1, the dotted arrow indicates a control signal output from the control unit 10 to the heat radiating unit 4 and the urea water injection devices 2 and 8. Further, in FIG. 1, the arrow of the alternate long and short dash line indicates a signal output from the temperature sensor 14 described later to the control unit 10.

The details of the operation of the control unit 10 will be described later with reference to FIG.

The first catalytic converter 11 and the second catalytic converter 12 are provided in series in the exhaust pipe 1.

The upstream end (left side in the drawing) of the exhaust pipe 1 is connected to, for example, the downstream end of the exhaust manifold (not shown) of a diesel engine. The exhaust gas discharged from the exhaust manifold flows through the exhaust pipe 1 from the left side to the right side in the drawing. In FIG. 1, the solid arrow indicates the flow direction of the exhaust gas.

The first catalyst converter 11 is a housing (case) that can be attached to and detached from the exhaust pipe 1. For example, the first catalytic converter 11 is provided at a position closer to the diesel engine than the second catalytic converter 12.

In the first catalytic converter 11, the urea water injection device 2, the SCR (Selective Catalytic Reduction) 3, the heat radiating unit 4, the SCR 5, and the temperature sensor 14 are housed in series in order from the upstream side.

The urea water injection device 2 (an example of a reducing agent supply device) is a device that injects urea water (an example of a reducing agent) into the first catalytic converter 11. The urea water injected by the urea water injection device 2 is hydrolyzed. Ammonia generated thereby (an example of a substance generated from the reducing agent) is supplied to SCRs 3 and 5. As described above, the injection amount and injection timing of urea water are controlled by the control unit 10.

SCR3 (an example of a first NOx purification catalyst) and SCR5 (an example of a second NOx purification catalyst) are catalysts that reduce NOx in exhaust gas to nitrogen by ammonia generated from urea water.

The carrier of SCR3 and the carrier of SCR5 may be the same or different. As the carrier, a metal (for example, stainless steel), ceramics (for example, silicon carbide or cordylite) or the like can be used.

The heat radiating unit 4 is, for example, a member (for example, stainless steel, ceramics, etc.) that dissipates heat by supplying electric power from a battery (not shown). The heat radiation of the heat radiating unit 4 heats the exhaust gas flowing between the SCR 3 and the SCR 5. As a result, the temperature of SCR5 tends to rise. As described above, the control unit 10 controls the on / off of the power supply to the heat dissipation unit 4.

The temperature sensor 14 is provided on the downstream side of the SCR 5. The temperature sensor 14 periodically detects the temperature of the exhaust gas that has passed through the SCR 5, and outputs a signal (see the arrow of the alternate long and short dash line in the figure) indicating the temperature (hereinafter referred to as the detected temperature) to the control unit 10.

The second catalyst converter 12 is a housing (case) that can be attached to and detached from the exhaust pipe 1. The second catalytic converter 12 is provided at a position farther from the diesel engine than the first catalytic converter 11.

In the second catalytic converter 12, DOC (Diesel Oxidation Catalyst) 6, DPF (Diesel Particulate Filter) 7, urea water injection device 8, SCR9, and ASC (Ammonia Slip Catalyst) 13 are housed in series in order from the upstream side. There is.

DOC6 is a catalyst that oxidizes nitric oxide and hydrocarbons in exhaust gas.

DPF7 is a filter that collects and removes particulate matter (PM) in exhaust gas.

The urea water injection device 8 is a device that injects urea water into the second catalytic converter 12. The urea water injected by the urea water injection device 8 is hydrolyzed. Ammonia generated thereby is supplied to SCR9. As described above, the injection amount and injection timing of urea water are controlled by the control unit 10.

SCR9 is a catalyst that reduces NOx in exhaust gas to nitrogen by ammonia generated from urea water.

The active temperature range of SCR9 is higher than, for example, the active temperature range of SCR3 and SCR5.

Further, the SCR9 may use a metal (for example, stainless steel) as a carrier or a ceramic (for example, silicon carbide or cordylite) as a carrier.

ASC13 (an example of a decomposition catalyst) is a catalyst that oxidizes and decomposes ammonia that cannot be completely consumed by SCR9. This makes it possible to prevent ammonia from being discharged into the atmosphere.

The configuration of the exhaust gas purification device 100 has been described above.

Next, the operation of the control unit 10 will be described with reference to FIG. FIG. 2 is a flowchart showing an example of the operation of the control unit 10. The flow shown in FIG. 2 is started immediately after the start of the diesel engine, for example.

First, the control unit 10 starts supplying electric power to the heat radiating unit 4, and causes the heat radiating unit 4 to start heat radiating (step S1).

Next, the control unit 10 determines whether or not the detected temperature notified from the temperature sensor 14 exceeds a predetermined threshold value (step S2).

The threshold value is, for example, the lower limit of the active temperature range of SCR5. Alternatively, the threshold value may be, for example, the smaller of the lower limit value of the active temperature range of SCR3 and the lower limit value of the active temperature range of SCR5.

If the detection temperature does not exceed the threshold value (step S2: NO), the flow returns to step S2. That is, the control unit 10 again determines whether or not the detected temperature exceeds the threshold value.

On the other hand, when the detection temperature exceeds the threshold value (step S2: YES), the control unit 10 causes the urea water injection device 2 to start the injection of urea water (step S3). At this time, the control unit 10 may start the urea water injection device 8 to inject urea water.

The operation of the control unit 10 has been described above.

Next, the action and effect of the exhaust gas purification device 100 will be described below.

The exhaust purification device 100 starts radiating heat from the heat radiating unit 4 immediately after starting the diesel engine, and starts injecting urea water from the urea water injection device 2 when the temperature of the exhaust gas on the downstream side of the SCR 5 exceeds the threshold value. It is characterized by that.

Therefore, the SCR3 on the upstream side raises the temperature early due to the exhaust gas, and the SCR5 on the downstream side raises the temperature early due to the heat radiation of the heat radiating unit 4, so that the entire SCR3 and 5 can be activated at an early stage. Further, since the injection of urea water is started when the temperature of the exhaust gas on the downstream side of SCR5 exceeds the threshold value (in other words, when both SCR3 and 5 are in the active state), the urea water is not wasted. Can be sprayed.

Further, in the exhaust gas purification device 100, the SCRs 3, 5 and SCR9 having different active temperature ranges are housed in separate housings (for example, the first catalyst converter 11 and the second catalyst converter 12). Therefore, the second catalytic converter 12 can be provided at a position away from the diesel engine where a sufficient installation space can be secured. Therefore, the size of the SCR9 housed in the second catalytic converter 12 can be increased, and the NOx purification efficiency can be further improved.

Further, in the exhaust gas purification device 100, a urea water injection device 2 is provided corresponding to SCR3 and 5, and a urea water injection device 8 is provided corresponding to SCR9. Therefore, hydrolysis can be promoted in each of the first catalytic converter 11 and the second catalytic converter 12, and NOx can be efficiently purified in each of SCRs 3, 5 and 9.

Further, in the exhaust gas purification device 100, the DOC6 and the DPF7 are provided in the second catalyst converter 12. Therefore, it is possible to more reliably oxidize carbon monoxide and hydrocarbons and collect particulate matter.

Further, in the exhaust gas purification device 100, the first catalyst converter 11 and the second catalyst converter 12 can be independently attached to and detached from the exhaust pipe 1. Therefore, maintenance and the like become easy.

The action and effect of the exhaust gas purification device 100 have been described above.

The present disclosure is not limited to the above-described embodiment, and can be appropriately modified and implemented without departing from the spirit of the present disclosure. Hereinafter, each modification will be described.

In the embodiment, all the components shown in FIG. 1 are collectively referred to as an exhaust gas purification device 100, but among the components shown in FIG. 1, the urea water injection device 2, SCR3, 5, the heat radiating unit 4, and the heat radiating unit 4 are used. The control unit 10 may be referred to as an exhaust gas purification device 100.

Further, in the embodiment, the case where the exhaust gas purification device 100 includes the second catalyst converter 12 has been described as an example, but the present invention is not limited to this. For example, the exhaust gas purification device 100 may not include the DOC6, the DPF7, the urea water injection device 8, the SCR9, the ASC13, and the second catalytic converter 12 among the components shown in FIG.

Further, in the embodiment, the case where the urea water injection device 2, the SCR3, 5, the heat radiating unit 4, and the temperature sensor 14 are housed in the first catalyst converter 11 has been described as an example, but the present invention is not limited thereto. For example, the urea water injection device 2, the SCR3, 5, the heat radiating unit 4, and the temperature sensor 14 may be provided in the exhaust pipe 1 without being housed in the first catalyst converter 11.

Further, in the embodiment, the case where the first catalytic converter 11 does not include the ASC has been described as an example, but the present invention is not limited to this. For example, the first catalytic converter 11 may be provided with an ASC on the downstream side of the SCR5. This makes it possible to reduce the amount of ammonia in the exhaust gas flowing out of the first catalytic converter 11. Therefore, ammonia is supplied to DOC6, and it is possible to suppress the oxidation of ammonia in DOC6. As a result, the generation of NOx due to the oxidation of ammonia generated from the urea water can be suppressed.

Further, in the embodiment, the case where the urea water injection device 2 is provided only on the upstream side of the SCR3 in the first catalyst converter 11 has been described as an example, but the present invention is not limited to this. For example, the first catalytic converter 11 may further include a urea water injection device between the heat radiating unit 4 and the SCR 5 in addition to the urea water injection device 2. Thereby, the NOx purification efficiency in SCR5 can be further improved.

Further, in the embodiment, the case where the NOx purification catalyst is SCR3, 5 and 9 has been described as an example, but the present invention is not limited to this. Instead of SCR3, 5 and 9, other selective reduction catalysts, NOx adsorption catalysts, or three-way catalysts may be used. In that case, a reducing agent other than urea water (for example, a hydrocarbon or the like) may be used.

Each modification has been described above. In addition, each modification may be carried out in combination.

The exhaust gas purification device and vehicle of the present disclosure are useful for early activation of a NOx purification catalyst that purifies exhaust gas.

1 Exhaust pipe 2, 8 Urea water injection device 3, 5, 9 SCR
4 Heat dissipation part 6 DOC
7 DPF
10 Control unit 11 1st catalytic converter 12 2nd catalytic converter 13 ASC
14 Temperature sensor 100 Exhaust gas purification device

Claims (7)

A first NOx purification catalyst provided on the upstream side in the flow direction of the exhaust gas discharged from the internal combustion engine, and
A second NOx purification catalyst provided on the downstream side of the first NOx purification catalyst in the flow direction of the exhaust gas,
A heat radiating unit provided between the first NOx purification catalyst and the second NOx purification catalyst,
A reducing agent supply device that supplies a reducing agent on the upstream side of the first NOx purification catalyst, and
It has a heat radiating unit and a control unit that controls the operation of each of the reducing agent supply devices.
The control unit
Immediately after starting the internal combustion engine, the heat radiating portion is started to dissipate heat in order to raise the temperature of the exhaust gas.
After that, when the temperature of the exhaust gas on the downstream side of the second NOx purification catalyst exceeds a predetermined threshold value, the reducing agent supply device is started to inject the reducing agent.
Exhaust purification device. The threshold is
This is the lower limit of the active temperature range of the second NOx purification catalyst.
The exhaust purification device according to claim 1. The reducing agent supply device, the first NOx purification catalyst, the heat radiating portion, and a housing for accommodating the second NOx purification catalyst in series are further included.
The exhaust gas purification device according to claim 1 or 2. The first NOx purification catalyst and the second NOx purification catalyst are selective reduction catalysts that promote the reduction of the NOx by the substance generated from the reducing agent.
The exhaust purification device according to claim 3. The housing further houses a decomposition catalyst that decomposes the substance on the downstream side of the second NOx purification catalyst.
The exhaust purification device according to claim 4. The reducing agent is urea water.
The substance is ammonia,
The exhaust purification device according to claim 4 or 5. A vehicle provided with the exhaust gas purification device according to any one of claims 1 to 6.

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