DE102019216898A1 - Emission control device - Google Patents

Abstract

[Task] It is possible to appropriately ensure the uniformity of the NOx / NH ratio depending on the flow rate of the urea water and the exhaust gas. [Solvent] The control by the electronic control unit 200 is such that the urea water injection through the urea water injection valve 4 Previously, the air inlet and outlet control valve 9 is gradually opened to gradually introduce a part of the exhaust gas into the partial flow bypass passage 7, and at the same time the wing angle of the small variable turbine 6 is changed to gradually increase the rotational speed of the small variable turbine 6 Increase, when the speed of the mixing turbine 5 exceeds a certain mixing start reference speed N, the mixing bypass channel 8 is completely closed by the mixing control valve 10 and then the injection of urea water is started by the urea water injection valve 4.

Description

[Technical field]

The present invention relates to an exhaust gas cleaning device, in particular for cleaning NOx (nitrogen oxide) discharged from an internal combustion engine by means of a reducing agent and a catalyst for selective catalytic reduction (SCR: Selective Catalytic Reduction), in which an increased cleaning efficiency or the like is achieved.

[State of the art]

It is generally known that as one of the NOx reduction systems of a kind of an internal combustion engine, namely the diesel engine, a urea SCR system as an exhaust gas purification device for decomposing the NOx contained in exhaust gas by a reaction with the ammonia (NH ₃ ) in harmless nitrogen (N ₂ ) and water (H ₂ O) is used.

As a relatively important factor of the factors contributing to an increase in the NOx purification efficiency in an exhaust gas purification device formed from the urea SCR system, the uniformity of the NOx / NH ₃ ratio can be mentioned.
The ammonia (NH ₃ ) atomized in the exhaust pipe is mixed with the nitrogen oxide contained in the exhaust gas, it being preferred that the mixing state be as uniform as possible. The NOx / NH ₃ ratio is the uniformity of the mixing state.

As a measure to increase the uniformity of the NOx / NH ₃ ratio, z. For example, the method is generally known that a plate-like component called a stirrer for stirring the urea water and the nitrogen oxide is arranged in the exhaust pipe, downstream of the urea water injection valve (see, for example, patent literature 1 or the like).

The plate-like component referred to as a stirrer is designed such that a plurality of cutout-like small tongues are provided on a flat plate-like component crossing the exhaust pipe and enclose a certain angle with the direction of flow of the exhaust gas flowing in the exhaust pipe. According to this structure, when the urea water and the nitrogen oxide flow through the cut-out areas, the flows through the small tongues are mixed up and thus stirred together, thereby producing a highly uniform mixing state.

[Older technical literature]

[Patent literature]

[Patent Literature 1] JP Patent Laid-Open No. 2009-24655

SUMMARY OF THE INVENTION

OBJECT OF THE INVENTION

However, since the stirrer mentioned above has no movable area and is mechanically fastened in its overall structure, there is no stirring corresponding to the flow rate of the urea water and the exhaust gas. Therefore, it is believed that it is difficult to maintain a steady state at an appropriate level.

The present invention is based on the above-mentioned circumstances. The object of the invention is to provide an exhaust gas cleaning device in which the uniformity of the NOx / NH ₃ ratio can be ensured in a suitable manner depending on the flow rate of the urea water and the exhaust gas.

[Means for Solving the Task]

In order to achieve the above object of the present invention, the exhaust gas purification device, in which the injection of urea water in an SCR catalytic converter is controlled by an electronic control unit and thereby enables the nitrogen oxide emitted by an internal combustion engine mounted on a vehicle to be cleaned, is constructed according to the invention in such a way that
that in an exhaust pipe between a urea water injection valve for injecting urea water and the SCR catalytic converter, a mixing turbine of a mixing device, which is formed from a small variable turbine and the mixing turbine, each with interconnected rotary shafts and used to mix urea water and nitrogen oxide, and a before and behind the mixing turbine, the bypass duct bypassing the exhaust pipe is provided, that a mixing control valve is provided at a connection position of the exhaust pipe and the mixing bypass duct on the side of the urea water injection valve,
that a partial flow bypass duct is provided, through which a part of the exhaust gas in the exhaust pipe is divided upstream of a supercharger arranged in the exhaust pipe and is returned to the downstream side of the supercharger, the small variable turbine being provided in the partial flow bypass duct and upstream of the partial flow bypass duct an air inlet and air outlet control valve is provided in the connection position with the exhaust pipe,
that the electronic control unit is constructed in such a way that the electronic control unit, prior to the injection of urea water through the urea water injection valve, gradually opens the air inlet and outlet control valve in order to gradually introduce part of the exhaust gas into the partial flow bypass duct and at the same time the wing angle of the small variable turbine changes to gradually increase the rotating speed of the small variable turbine, wherein when the speed of the mixing turbine exceeds a certain reference speed, the mixture bypass passage is fully closed by the mixture control valve, and then the injection of urea water through the urea water injection valve is started becomes.

Effects of the Invention

According to the present invention, the exhaust gas purification device is constructed in such a way that, unlike conventional passive stirrers, a turbine operated exclusively for mixing is rotated by exhaust gas energy. As a result, the effect can be achieved that an exhaust gas purification device can be provided in which the uniformity of the NOx / NH ₃ ratio is considerably increased and which therefore has good purification efficiency.
It is not only provided that part of the exhaust gas is divided as a partial flow only if exhaust gas is required for the mixing turbine, but also that depending on the partial flow rate, the blade angle of the variable turbine of the supercharger is adjusted, as a result of which the condition caused by the partial flow Fluctuation of the supercharged pressure is damped. This minimizes influences on the control of the supercharged pressure and at the same time increases the uniformity of the NOx / NH ₃ ratio.

Figure list

• [ 1 ] is a construction view showing a construction example of the exhaust gas purification device according to the embodiment of the present invention.
• [ 2nd ] is a flowchart for a subroutine to show the operations of the operation control performed by the exhaust gas purification device according to the embodiment of the present invention.
• [ 3rd ] shows schematic representations for schematically explaining the changes in the main part state when performing the operation control on the exhaust gas purification device according to the embodiment of the present invention, wherein 3 (A) FIG. 2 is a schematic illustration for schematically showing the change in the command signal corresponding to the command for injecting urea water generated inside the electronic control unit, FIG. 3 (B) FIG. 2 is a schematic illustration for schematically showing the open and closed state of the air inlet and air outlet control valve, FIG. 3 (C) FIG. 2 is a schematic diagram for schematically showing the change in the supercharged pressure, 3 (D) FIG. 2 is a schematic diagram for schematically showing the change in the wing angle of the variable turbine; and 3 (E) is a schematic diagram for schematically showing the change in the rotational speed of the mixing turbine.

Embodiment of the Invention

An embodiment of the present invention will now be described with reference to FIG 1 to 3rd explained.
The present invention is not limited to the components, the arrangement types or the like explained below and can be varied in various ways within the scope of the essence of the present invention.
First, a construction example of the exhaust gas purification device according to the embodiment of the present invention will be described with reference to FIG 1 explained. According to the embodiment of the present invention, the exhaust gas purification device is made of a Diesel Oxidation Catalyst (DOC) 2, which is in an exhaust pipe 1 is arranged at a suitable position, a catalyst for selective catalytic reduction (SCR) 3, a urea water injection valve 4th , a mixing device 100 and an electronic control unit 200 for operating control of the mixing device 100 and the like. Formed as main constituent elements.

The exhaust gas purification device is specifically explained below. In the exhaust pipe 1 are the diesel oxidation catalyst 2nd and the SCR catalyst 3rd arranged from the upstream side to the downstream side in this order.
According to the embodiment of the present invention is a so-called urea SCR system with the SCR catalyst 3rd educated.
That is the urea water injection valve 4th for injecting urea water into the exhaust pipe 1 at a suitable position, upstream of the SCR catalytic converter 3rd provided, and between the urea water injection valve 4th and the SCR catalyst 3rd is the mixing device 100 for sufficient distribution of urea water in the exhaust pipe 1 intended.

According to the embodiment of the present invention, besides the exhaust gas purification device 501 a charger 502 , as explained next.
That is the charger 502 designed such that a variable turbine 51 in the exhaust pipe 1 in a suitable position upstream of the diesel oxidation catalyst 2nd a compressor is provided 52 that with the rotating shaft of the variable turbine 51 is connected in a suction pipe 50 is provided in a suitable position and the charger 502 has a generally known structure from these main constituent elements.

According to the embodiment of the present invention, the mixing device 100 , as explained next.
The mixing device 100 is from a mixing turbine 5 , a small variable turbine 6 , a partial flow bypass duct 7 , a mix bypass channel 8th , an air inlet and outlet control valve 9 and a mixture control valve 10th educated.

The partial flow bypass channel 7 is provided to be an appropriate one of the variable turbine 51 upstream position of the exhaust pipe 1 with a suitable from the variable turbine 51 connect downstream position. At one end of the partial flow bypass channel 7 , namely one from the variable turbine 51 upstream facing the exhaust pipe 1 adjoining area is the air inlet and outlet control valve 9 intended.
Furthermore, the small variable turbine 6 in the partial flow bypass channel 7 provided at a suitable position.

The small variable turbine 6 shows the structure of the variable turbine 51 essentially the same structure. Namely, the small variable turbine 6 a plurality of movable wings (not shown). The amount of exhaust gas flowing into the turbine (not shown) can be adjusted by changing the relative directions and the spacing of the mutually adjacent movable blades, as a result of which the rotational speed can be adjusted.

The moving blades (not shown) of the small variable turbine 6 are through the electronic control unit 200 adjustable.
The rotating shaft (not shown) of the small variable turbine 6 is with the rotary shaft (not shown) of the mixing turbine explained below 5 mutually connected.

The mixing turbine 5 is in the exhaust pipe 1 at an appropriate position between a downstream side of the urea water injection valve 4th and the SCR catalyst 3rd intended.
The mixing turbine 5 differs from the small variable turbine mentioned above 6 and has no movable blades, but has attached turbine blades (not shown).

The mixing turbine 5 is rotated by direct exposure to exhaust gas and can at the same time by the torque of the small variable turbine mentioned above 6 be rotated, as explained in more detail below.
Near the mixing turbine 5 is a rotation sensor 11 provided by which the rotational speed of the mixing turbine 5 is detectable. The detection signal is sent to the electronic control unit 200 entered.

The mix bypass channel 8th is provided to be suitable from the mixing turbine 5 upstream position of the exhaust pipe 1 with a suitable one from the mixing turbine 5 connect downstream position.
At the connection area of the mixture bypass channel 8th and the exhaust pipe 1 is the mixture control valve 10th intended.

According to the embodiment of the present invention, the mixture control valve 10th the construction of a so-called three-way valve.
Through the mixture control valve 10th can the diesel oxidation catalyst 2nd Exhaust gas flowing through in two directions, namely to the side of the mixing turbine 5 and the side of the mix bypass channel 8th , can be divided.

The mixture control valve 10th has the structure that z. B. with a large degree of valve opening to the side of the mixing turbine 5 the valve opening degree to the side of the mixture bypass channel 8th becomes small, so that when the valve opening degree is fully open to the side of the mixing turbine 5 the valve opening degree to the side of the mixture bypass channel 8th fully closed, i.e. 0%.
If, contrary to the above example, the valve opening degree to the side of the mixture bypass channel 8th is increased, the valve opening degree to the side of the mixing turbine 5 on the other hand, proportionally reduced.

The air inlet and outlet control valve 9 and the mixture control valve 10th are also designed so that the opening and closing of the valves, as explained later, by the electronic control unit 200 to be controlled.
The valve opening degree of the at the upstream end of the partial flow bypass channel 7 provided air inlet and outlet control valve 9 is through the electronic control unit 200 adjustable, making the Amount of that from the exhaust pipe 1 into the partial flow bypass channel 7 incoming exhaust gas is adjustable.
The valve opening degree of the at the upstream end of the mixture bypass channel 8th provided mixing control valve 10th is through the electronic control unit 200 adjustable, reducing the amount of exhaust pipe 1 into the mix bypass channel 8th incoming exhaust gas is adjustable.

The electronic control unit 200 is z. B. mainly from a microcomputer with a well-known structure, memory elements (not shown) such as RAM, ROM or the like. And input and output interface circuits (not shown) formed as the main constituent elements.

In the electronic control unit 200 in addition to the detection signal of the aforementioned rotation sensor 11 Various sensors or the like, not shown. Detected signals required for the operational control of the vehicle, e.g. B. with respect to the atmospheric pressure, the engine speed, the pedal opening degree, the temperature of the engine cooling water or the like. Entered.
The above various in the electronic control unit 200 Input detection signals are mainly used for the injection control of urea water and are used for the operation control or the like explained later. The exhaust gas purification device according to the embodiment of the present invention.

Next are those from the electronic control unit 200 performed steps for operating control of the exhaust gas purification device 501 according to the embodiment of the present invention with reference to the in 2nd Flowchart shown for a subroutine explained.
Above all, it is assumed that the electronic control unit 200 According to the embodiment of the present invention, the electronic control unit 200 an operation control of the supercharger which is the same as the conventional operation control 502 and an operation control of the exhaust gas purification device which is the same as the conventional operation control and which controls the injection by the urea water injection valve 4th causes, can perform.

Will the treatment by the electronic control unit 200 started, it is first determined whether there is a command to inject urea water (see step S110 in 2nd ).
As explained above, it is assumed that the electronic control unit 200 according to the embodiment of the present invention performs a conventional basic control for the exhaust gas purification device. Here, the command to inject urea water based on this conventional control for the exhaust gas purification device inside the electronic control unit 200 generated when a urea water injection on the SCR catalytic converter 3rd is required.

Will in step S110 determines that a command to inject urea water has been generated (is present) (in the case of YES), the process proceeds to the next step S120 continue. If it is determined that no command to inject urea water has been generated (is present) (in the case of NO), the work process proceeds to the step explained below S180 continue.
In step S120 a gradual opening of the air inlet and air outlet control valve is started and at the same time an adjustment of the wing angle is carried out.

In the operation control of the exhaust gas purification device 501 according to the embodiment of the present invention, the small variable turbine 6 rotated through part of the exhaust gas. This requires the air inlet and outlet control valve 9 to open, thereby part of the exhaust gas in the partial flow bypass channel 7 initiate. The partial flow of the exhaust gas is allowed through the air inlet and outlet control valve 9 as far as possible no external interference factor for the control of the supercharged pressure by the supercharger 502 represent.
Therefore, the valve opening degree of the air inlet and air outlet control valve 9 According to the embodiment of the present invention, it is not immediately changed over to the required valve opening degree, but is gradually increased to the required valve opening degree.

In addition to the gradual opening of the air inlet and air outlet control valve 9 also an adjustment of the wing angle (adjustment of the wing angle) of the variable turbine 51 performed, thereby reducing the speed of rotation of the variable turbine 51 by reducing the in the variable turbine 51 equalize incoming exhaust gas.

Then the injection amount of urea water and the exhaust gas flow rate are calculated (see step S130 in 2nd ).
The calculation of the injection amount of the urea water and the exhaust gas flow rate is not specific to the present invention, but is performed based on the conventional operation control of the exhaust gas purification device.
The urea water injection amount is the amount of the urea water injection valve 4th urea water to be injected, which is normally calculated on the basis of the amount of nitrogen oxide released, depending on the exhaust gas flow rate and the operating state or the like.

Since the required injection amount of the urea water differs depending on the specifications or the like of the vehicle, it is preferable to take the required injection amount of the urea water into consideration the specifications or the like of the vehicle is calculated on the basis of experiment results and simulation results by means of a predetermined operating formula, a diagram or the like.
The flow rate of the exhaust gas is e.g. B. based on the detection value by an air flow meter (not shown), by an EGR valve (not shown) or the like. Calculated by a well-known calculation formula or the like.

Then the rotation of the small variable turbine is set (see step S140 in 2nd ).
The speed of rotation of the small variable turbine 6 due to the in step S130 To increase the calculated injection amount of the urea water and the flow rate of the exhaust gas, an adjusting device (not shown) for adjusting the wing angle by the electronic control unit 200 driven, whereby the wing angle is adjusted to a suitable wing angle.

The setting of the wing angle is carried out in such a way that the wing angle is changed gradually until that by the rotation sensor 11 recorded speed of the mixing turbine 5 the full opening reference speed N _up exceeds (see step S150 in 2nd ).
The full opening reference speed N _up is preferably determined based on experiment results, simulation results or the like, based on the point of view of whether the rotation state is suitable for reaching the mixing state in which the urea water injected by the urea water injection is sufficiently distributed and appropriately mixed with the exhaust gas.
Regarding the setting of the valve opening degree of the air inlet and outlet control valve 9 and the adjustment of the wing angle of the variable turbine 51 it is desirable to subject the respective manipulated values to filter processing in order to mitigate the change in the degree of valve opening and the change in the wing angle and in this way in practice not to cause a sensitive reaction in the transition region.

Will in step S150 determines that the speed of the mixing turbine 5 the mix start reference speed N _up exceeds (in the case of YES), the mix bypass channel 8th fully closed (see step S160 in 2nd ).
Namely, in the mixture control valve 10th the degree of valve opening to the side of the mixing bypass channel 8th to 0% and the valve opening degree to the side of the mixing turbine 5 set to 100%. As a result, the mix bypass channel 8th fully closed so that all of the diesel oxidation catalyst 2nd exhaust gas flowing into the mixing turbine 5 flows in.

Then the injection of urea water is started (see step S170 in 2nd ).
Namely, the urea water injection valve 4th driven to a certain amount of urea water into the exhaust pipe 1 to inject.
The injected urea water flows together with exhaust gas into the mixing turbine 5 and is by the mixing turbine in a sufficiently rotated state 5 distributed and stirred. As a result, nitrogen oxide (NOx) and ammonia (NH ₃ ) are mixed sufficiently (mixture) and then flow into the SCR catalytic converter 3rd a. Therefore, the uniformity of the NOx / NH ₃ ratio in the SCR catalyst 3rd significantly increased compared to a conventional exhaust gas purification device, which ensures a high purification efficiency.

Will in the above step S110 determines that there is no command to inject urea water (in the case of NO), a gradual closure of the air inlet and outlet control valve is started (see step S180 in 2nd ).
Namely, the valve opening degree of the air inlet and outlet control valve 9 , from the aforementioned gradual opening of the air inlet and outlet valve in step S120 conversely, gradually reduced so as not to have an external disturbing factor for the control of the supercharged pressure by the supercharger 502 to represent, and finally the air inlet and outlet control valve 9 fully closed.
The gradual closure of the air inlet and outlet control valve 9 is performed after determining whether the speed of the mixing turbine 5 _falls below the mixture completion reference speed N _dw (see step S190 in 2nd ). Incidentally, it is both possible that the aforementioned mix start reference speed N _up and the mixture completion reference speed N _{dw is the} same value or different values from each other.

The mixture completion reference speed N _dw is preferably determined from the point of view of whether the rotation state for introducing everything into the mixing turbine 5 exhaust gas flowing into the mixture bypass duct 8th is suitable, based on experiment results, simulation results or the like.

Will in step S190 determines that the speed of the mixing turbine 5 falls below the mixture completion reference speed N _dw (in the case of YES), the mixture bypass channel 8th fully open (see step S200 in 2nd ).
Namely, in the mixture control valve 10th the degree of valve opening to the side of the mixing bypass channel 8th to 100% and the valve opening degree to the side of the mixing turbine 5 set to 0%. As a result, the duct becomes the side of the mixing turbine 5 fully closed so that all of the diesel oxidation catalyst 2nd Exhaust gas flowing into the mixture bypass channel 8th flows in and without flowing through the mixing turbine 5 in the SCR catalyst 3rd flows in.

Below, all of the operations of the exhaust gas purification device according to the embodiment of the present invention will be described with reference to FIG 3rd explained in rough outline.
If a command to inject urea water is generated due to the conventional operation control of the exhaust gas purification device (see the time instant at time t1 in 3 (A) ), the valve opening degree of the air inlet and air outlet control valve 9 gradually increased (see step S120 in 2nd and the vicinity of time t1 in 3 (B) ). At the same time, the wing angle of the variable turbine 51 set to reduce the rotation of the variable turbine 51 through the partial flow of the exhaust gas into the partial flow bypass duct 7 compensate (see step S120 in 2nd and 3 (D) ).

Although the opening of the air inlet and outlet control valve 9 is a factor that can lead to a fluctuation in the supercharged pressure, according to the embodiment of the present invention, the blade angle of the variable turbine 51 depending on the size of the valve opening degree of the air inlet and air outlet control valve 9 adjusted, causing the fluctuation of the supercharged pressure through the opening of the air inlet and outlet control valve 9 is minimized as a whole (see 3 (C) ).
In 3 (C) The change in the target boost pressure is represented by a dotted characteristic curve, and the change in the actual boost pressure is represented by a solid characteristic curve.

By adjusting the wing angle of the small variable turbine 6 the rotation speed is increased (see step S140 in 2nd ). Exceeds the speed of rotation of the mixing turbine 5 the mix start reference speed N _up (see step S150 in 2nd and the vicinity of time t3 in 3 (E) ), the mix bypass channel 8th through the mixture control valve 10th fully closed (see step S160 in 2nd ).
As a result, everything flows through the diesel oxidation catalyst 2nd exhaust gas flowing into the mixing turbine 5 and urea water injection starts (see step S170 in 2nd ).

After the urea water injection command is completed, the valve opening degree of the air intake and exhaust control valve 9 gradually reduced (see step S180 in 2nd and the course from time t5 in 3 (B) ). Falls below the speed of rotation of the mixing turbine 5 the mix completion reference speed N _dw , becomes the mix bypass channel 8th through the mixture control valve 10th fully open (see steps S190 and S200 in 2nd and 3 (B) and 3 (E) ).
As a result, everything flows through the diesel oxidation catalyst 2nd Exhaust gas flowing into the mixture bypass channel 8th and flows through the mixing turbine without flowing through 5 in the SCR catalyst 3rd a.

[Industrial uses]

The present invention can be applied to an exhaust gas purification device with a urea SCR system in which it is desired that the uniformity of the NOx / NH ₃ ratio be appropriately ensured depending on the flow rate of the urea water and the exhaust gas.

Reference list

2nd

Diesel oxidation catalyst

3rd

SCR catalytic converter

4th

Urea water injection valve

5

Mixing turbine

6

small variable turbine

7

Partial flow bypass duct

8th

Mix bypass channel

9

Air inlet and outlet control valve

10th

Mixing control valve

100

Mixing device

200

electronic control unit

501

Emission control device

502

Supercharger

Claims (2)

Exhaust gas purification device in which the injection of urea water in an SCR catalytic converter is controlled by an electronic control unit and thereby enables cleaning of the nitrogen oxide emitted by an internal combustion engine mounted on a vehicle, characterized in that in an exhaust pipe between a urea water injection valve for the injection of urea water and the SCR catalytic converter, a mixing turbine of a mixing device, which is formed from a small variable turbine and the mixing turbine, each with rotating shafts connected to one another, and is used for mixing urea water and nitrogen oxide, and a mixing bypass duct that bypasses the exhaust pipe in front and behind the mixing turbine that on a At the connection position of the exhaust pipe and the mixing bypass passage on the side of the urea water injection valve, a mixing control valve is provided that a partial flow bypass passage is provided through which a part of the exhaust gas in the exhaust pipe is divided upstream of a supercharger arranged in the exhaust pipe and returned to the downstream side of the supercharger The small variable turbine is provided in the partial flow bypass duct and an air inlet and air outlet control valve is provided upstream of the partial flow bypass duct at the connection position with the exhaust pipe, such that the electronic control unit is constructed such that the electronic control unit, the injection preceded by urea water through the urea water injection valve, the air inlet and outlet control valve gradually opens to gradually introduce a portion of the exhaust gas into the partial flow bypass passage, and at the same time the wing angle of the small variable door bine changes to gradually increase the speed of rotation of the small variable turbine, wherein when the speed of the mixing turbine exceeds a certain reference speed, the mixture bypass passage is fully closed by the mixture control valve and then the injection of urea water through the urea water injection valve is started. Exhaust gas purification device after Claim 1 , characterized in that the electronic control unit is constructed in such a way that when the urea water injection through the urea water injection valve ends, the electronic control unit gradually reduces the valve opening degree of the air inlet and air outlet control valve and, if the speed of the mixing turbine falls below a certain reference speed, the mixture Bypass channel through the mixture control valve opens fully, thereby stopping the inflow of exhaust gas into the mixing turbine.

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