KR101719403B1 - Method for operating a metering apparatus - Google Patents

Abstract

The present invention relates to a method of operating a metering device (1) for providing a liquid additive. At a minimum, the metering device comprises at least one pump 2 for pumping the additive from the tank 3 to the pressure accumulator 4, and an additive present in the pressure accumulator 4 in a metered manner A designed metering valve 5 and a check valve 6. The additive present in the pressure accumulator 4 can be guided back to the tank 3 by the check valve. In the present method, a metering request is first made in step a). Subsequently, the pump 2 is started in step b) to generate the pressure in the pressure accumulator 4. Thereafter, the pressure in the pressure accumulator 4 is set to the required metering pressure 8. The liquid additive is then dispensed by the metering valve 5 in step d).

Description

[0001] METHOD FOR OPERATING A METERING APPARATUS [0002]

The present invention relates to a method of operating a dosing apparatus for providing a liquid additive. The dosing device may be used, for example, to supply a liquid additive to an exhaust gas treatment device, wherein in the exhaust gas treatment device, the liquid additive is used for purifying the exhaust gas of a movable internal combustion engine Is used.

BACKGROUND ART [0002] Exhaust gas treatment apparatuses to which liquid additives are supplied have been increasingly widely used in recent years. An exhaust gas purifying method, which is typically practiced in such an exhaust gas treating apparatus, is a selective catalytic reduction (SCR) method in which the nitrogen oxide compound of the exhaust gas is reduced with the aid of a reducing agent. The reducing agent is usually supplied to the exhaust gas treatment device in the form of a liquid additive. Particularly commonly used liquid additives in this context are urea-aqueous solutions. Urea-aqueous solutions with an element content of 32.5% are marketed under the trade name AdBlue ^® and are widely used. The urea-aqueous solution is merely a reducing agent precursor and is converted to ammonia (reducing agent) in the exhaust gas either outside the exhaust gas (in the reactor provided for this purpose) or in the exhaust gas treatment apparatus (under the action of the exhaust gas). The nitrogen oxide compound in the exhaust gas is then reduced with ammonia in the presence of the SCR catalytic converter to form non-hazardous substances (water, CO ₂ and nitrogen). The present invention is particularly used in such technical fields.

A dosing device for providing a liquid additive (urea-aqueous solution) can take the simplest configuration possible and is durable, maintenance-free and cost-effective. At the same time, it is desirable that the dosing accuracy of the dosing device is particularly excellent. In any case, the amount of the liquid additive required for the conversion of the pollutant component of the exhaust gas can be set in a particularly accurate manner. Moreover, overdosing can be prevented in an effective manner.

With this as a starting point, the object of the present invention is to solve or at least alleviate the technical problems highlighted with respect to the prior art. Particularly advantageous methods of operation of the urea-atomizing machine are proposed in particular.

The object of the invention is achieved by a method according to the characterizing part of claim 1. Other advantageous embodiments of the invention are specified in the dependent claims. Features that are individually specified in the claims may be combined with each other in any technologically meaningful manner, and other features of the invention may be supplemented by exemplary matters in a specific situation.

The present invention relates to a method of operating a dosing device for providing a liquid additive, in particular an urea-aqueous solution.

The dosing device is:

At least one pump for transferring the additive from the tank to the pressure accumulator,

A dosing valve designed to supply an additive present in said pressure accumulator in a dosing manner, and

And a return valve that allows the additive present in the pressure accumulator to be discharged back to the tank.

The operating method of the dosing device includes at least the steps described below:

a) confirming the dosing request,

b) actuating the pump to generate pressure in the pressure accumulator,

c) setting the pressure in the pressure accumulator to a dosing pressure, and

d) dispensing the additive through the dosing device.

The dosing device is particularly preferably used for dosing of a reducing agent (or dosing of a reducing agent precursor such as urea-aqueous solution) such as a liquid additive to an exhaust gas treating apparatus of an internal combustion engine. The pump is preferably a diaphragm pump or a piston pump. The feed rate of the pump is preferably not adjusted. This means that no electrical regulator or controller is provided to allow the flow rate of the additive transferred by the pump to be set accurately. The tank is preferably connected to the pump through a suction line and the pump can draw liquid out of the tank through the suction line. The pressure accumulator is preferably disposed downstream of the pump when viewed in the direction of flow of the liquid additive from the tank to the dosing valve. The pressure produced by the pump then appears in the pressure accumulator. The pressure accumulator may take the form of, for example, a flexible line that expands when the liquid additive is delivered to the flexible line under pressure by the pump. The dosing valve is preferably an electrically controlled solenoid valve which can be opened and closed by an electric drive, wherein the opening time of the dosing valve presupposes the amount of liquid additive supplied. The pressure accumulator is also connected by a return valve. The return valve is preferably connected back to the tank via the return line so that the liquid additive present in the pressure accumulator can be discharged back into the tank.

The confirmation of the dosing request in step a) preferably includes an acknowledgment of the electrical signal from the engine controller and the electrical signal indicates a dosing request. For example, the engine controller transmits a signal corresponding to a specific flow rate of the required liquid additive. The signal is detected or confirmed as a dosing request. During step a), it is preferable that the pressure appearing in the pressure accumulator is low such that adjustment of the dosing request is not possible. It is preferred that during step a) the pressure in the pressure accumulator is less than 2 bar, particularly preferably less than 1 bar, and very particularly preferably less than 0.5 bar. In step b), the pump is actuated to produce a pressure in the pressure accumulator such that adequate dosing can be performed by the dosing valve. In order to create pressure, a diaphragm pump or a piston pump is preferably operated by a stroke between two pump strokes and 10 pump strokes. The number of pump strokes required to create the pressure required for the pressure accumulator is determined by the pressure differential between the pressure during step a) and the dosing pressure (step b) and by the flexibility of the pressure accumulator. The greater the flexibility of the pressure accumulator, the more liquid additives can be transferred to the pressure accumulator, creating the required pressure. The greater the pressure difference, the more liquid additive can be delivered to the pressure accumulator. The pressure produced as a result of the start-up of the pump in step b) is preferably between 3 and 10 bar, particularly preferably between 5 and 10 bar, and very particularly preferably between 6 and 8 bar to be. The pressure produced by the pump in step b) is typically slightly greater than the dosing pressure required to effect precise dosing by the dosing valve. This is because the pump is not preferably adjusted. This does not cause the pump to start when a certain pressure is achieved, but instead, after the pump is started, the pump continues to operate, regardless of the magnitude of the pressure appearing in the pressure accumulator (the pressure acting against the pump) It means that it works.

In one embodiment of the disclosed method, operation of the pump is terminated only when the pressure in the pressure accumulator is large such that the pump can not generate a further pressure increase in the pressure accumulator.

The method is particularly preferred if the method steps a) to d) are repeatedly carried out during operation of the dosing device. The method is more preferred if the pressure is reduced by a return valve which is particularly open, for the setting of the pressure in step c). Therefore, it is preferable that the return valve is opened so as to set a precise pressure required in the pressure accumulator so that highly precise dosing can be performed by the dosing valve.

It is preferred that step b) occurs continuously during step c). The return valve is kept open and the pump is started. Because of the return flow of the liquid additive through the return valve, the pressure in the pressure accumulator remains constant.

The method is even more preferred if at least steps c) and d) are carried out at least partially parallel to each other. It is particularly preferred that steps b), c) and d) occur at least partially in parallel.

In order to distribute the liquid additive through the dosing valve in step d), the dosing valve is opened. The liquid additive then flows to the liquid additive consumer outside the pressure accumulator through the dosing valve. The consumer of the liquid additive is preferably an exhaust gas treatment device, and the method of selective catalytic reduction in the exhaust gas treatment device is carried out using a liquid additive. Preferably, the method steps b) and c) continue to occur during the execution of step d). During step d), the pump maintains the activated state and continues to transfer the liquid additive to the pressure accumulator. During step d), the return valve remains open and the pressure in the pressure accumulator reaches a value between, for example, 5 bar and 10 bar, for example the dosing pressure required for dosing operation of 7 bar As shown in Fig. Here, it is preferred that the return valve is not always open, but instead it is opened in a pressure-controlled manner every time the pressure in the pressure accumulator exceeds the dosing pressure. In any case, the pressure in the pressure accumulator is repeatedly adjusted to the dosing pressure during dispensing of the additive through the dosing valve in each case.

For dispensing of the additive in step d), the dosing valve need not be continuously opened. Also, the dosing request identified in step a) can be distributed into several pulses. Here, the pulses correspond in each case to one opening process and one closing process of the dosing valve.

If the method is repeatedly carried out during operation of the dosing machine, it is preferred that the pump is not actuated in each case after method step d). The pump is then restarted only when a new dosing request is identified in the new step a). In particular, the pump does not operate continuously during operation of the transfer line and during operation of the vehicle, and the dosing device is placed in the vehicle and instead the pump is normally started only when there is a dosing request.

The process is more advantageous if, after process step d), the process steps described below are carried out:

e) lowering the pressure in the pressure accumulator.

Method step e) is preferably also repeatedly carried out with method steps a) to d).

As a result of lowering the pressure in the pressure accumulator in step e), the pressure accumulator makes it possible to reduce the load between the two dosing requests. The durability of the dosing device can be reduced in this way. In one embodiment, the pressure accumulator can actively relieve the load. The return valve diverged from the pressure accumulator can be actively opened in step e) if necessary to allow escape of the liquid additive from the pressure accumulator and thus the pressure in the pressure accumulator . The return valve may be identical to the return valve used in method step c) and may additionally be actively opened in step e). However, also during step e), an additional return valve may be provided to actively open and preferably be arranged to be disposed in a parallel second return line from the pressure accumulator to the tank.

In another embodiment of the method of the present invention, active abatement of the load can be achieved by the pump of the transfer unit. In step e), the pump is arranged to transfer the liquid additive outside the pressure accumulator and back to the tank, such that the pressure in the pressure accumulator is reduced and thus the pressure accumulator alleviates the load , It can be operated if necessary to counter the transport direction.

A pressure accumulator also allows passive relief of the load. To this end, the leakage flow of the liquid additive can flow back to the tank through the pump in step e) and / or via the return valve, which results in a pressure drop in the pressure accumulator. In the case of a passive relief of the load in step e), the pressure in the pressure accumulator drops relatively slowly because the leakage flow is generally relatively small. The effect of the leaking pressure on pressure in the pressure accumulator during dosing in step d) can be very large in other respects.

It is also contemplated that the return valve is a manual open valve, and that the open pressure of the open valve corresponds to the dosing pressure.

The return valve is preferably a manual open valve and the manual open valve is open at a predetermined or predetermined critical pressure, wherein the critical pressure corresponds to the dosing pressure (the pressure at which the additive is dosed). The return valve preferably comprises a valve body and a valve spring for applying a preload to the valve body. The return valve is opened when the force exerted on the return valve by the liquid additive present in the pressure accumulator exceeds the spring force of the spring at the return valve. The use of a return valve of this type enables the realization of a particularly inexpensive dosing device, since the (electric) drive is not required for the dosing valve and, furthermore, the control unit is not required for the control of the return valve .

The dosing device may be operated without an electrically driven dosing valve and / or without a (active) control unit of the return valve.

Moreover, the method of the present invention is advantageous if the return valve is an active open valve with a valve actuation, in which case a pressure sensor is placed on the pressure accumulator and the return valve is in the control unit step c) Controlled by the control unit, with the aid of the valve drive, in order to set the pressure in the accumulator to the required dosing pressure.

The valve actuation portion may be, for example, an electromagnet that forces the armature at the return valve, and the force may cause the return valve to open and / or close. The pressure sensor may take the form of, for example, an electrical pressure sensor, which measures the pressure in the pressure accumulator and transmits the measured value to the control unit as an electrical signal. The pressure information is then processed in the control unit to specify whether the check valve is open and / or closed (regulating loop).

The method of the present invention is also advantageous if the pump has at least one pump valve and pump chamber that preforms the transfer direction. The pump chamber preferably has a pump moving portion imparted to the pump chamber by a diaphragm or pump piston. In a preferred embodiment, two pump valves are provided and are placed upstream and downstream of the pump chamber, as shown in the flow direction of the liquid additive from the tank to the dosing valve and taking up the respective manual opening configuration.

In another embodiment, only a single pump valve is provided. The single pump valve is then preferably provided downstream of the pump chamber as seen in the flow direction. The pump piston is then designed to vent the liquid additive in the pump chamber through the pump valve during a subsequent transfer movement (discharge movement). Replenishment flow of the liquid additive into the pump chamber occurs during the return movement of the pump piston in a direction opposite to the subsequent transfer movement. Pumps of this type are described, for example, in DE 10 2008 010 073 B4, especially in FIGS. 2 and 3 and in the description relating to paragraphs [0038] to [0051], which are incorporated herein by reference .

The method according to the present invention is particularly preferably used in a pressure accumulator in the case of a dosing device which does not have a pressure sensor for electrically monitoring the pressure in the pressure accumulator. In this case, the pressure in the pressure accumulator is exclusively set by the return valve. The return valve preferably operates mechanically.

The present invention also relates to an exhaust gas treatment device for use in an automobile having an internal combustion engine, an exhaust gas treatment device for purifying the exhaust gas of the internal combustion engine, and a dosing device, wherein the liquid additive is supplied to the exhaust gas treatment device And the dosing device is set and designed to operate in accordance with the methods described herein. The automobile is preferably a passenger car or a large transporter. The internal combustion engine is preferably a diesel internal combustion engine. The exhaust gas treatment device preferably comprises an SCR catalytic converter for carrying out the method of selective catalytic reduction. Like liquid additives, the exhaust gas treatment device is preferably supplied as a reducing agent, particularly an urea-aqueous solution, upstream of the SCR catalytic converter. Thereafter, by the reducing agent, the method of selective catalytic reduction is carried out in the exhaust gas treating apparatus for the purpose of reducing the nitrogen oxide compound in the exhaust gas in an effective manner.

The invention and the technical field are described in more detail below on the basis of the drawings. It should be understood that the drawings particularly point out the preferred embodiments of the present invention, but the present invention is not limited to these preferred embodiments. In particular, it will be appreciated that the figures and particularly the figures shown are only schematic.

1 is a view of a dosing machine having a tank and an exhaust gas treatment device together,
2 is a view of a dosing machine of another embodiment having a tank and an exhaust gas treatment device together,
3 is a view of a vehicle equipped with a dosing device,
Figure 4 is a first diagram of the sequence of the method according to the invention, and
Figure 5 is a second diagram of the sequence of the method according to the invention.

1 is a view showing a dosing machine 1 including a tank 3 and an exhaust gas treatment machine 11 together. The dosing device 1 extracts the liquid additive (urea-aqueous solution) from the tank 3 at the extraction point 17. A transfer line 18 initially extending to the pump 2 extends from the extraction point 17. From the pump 2 the transfer line 18 extends forward to the dosing valve 5 and the liquid additive is supplied by the dosing valve to the exhaust gas flow 13 in the exhaust gas treatment device 11 . The liquid additive is transferred from the tank 3 to the dosing valve 5 via the transfer line 18 due to the transfer action of the pump 2. The pressure accumulator 4 is disposed downstream of the pump 2 when viewed in the transport direction from the tank 3 to the dosing valve 5. The pressure accumulator 4 may be partly formed by the transfer line 18, for example, by a transfer line 18 in the form of a flexible hose. The return line 12 branches off from the pressure accumulator 4 and goes back to the tank 3. The return valve 6 is disposed in the return line 12. By means of a dosing device of this type, the method according to the invention can be carried out in a particularly advantageous manner.

Most of the parts of the dosing device according to Fig. 2 correspond to the device according to Fig. A valve driving part 19 is additionally provided in the present invention, and the return valve 6 can be opened and closed by the valve driving part. The pressure accumulator 4 is connected by a pressure sensor 20, and the pressure in the pressure accumulator 4 can be measured by the pressure sensor. Pressure information determined by the pressure sensor 20 is passed to the control unit 21 and processed in the control unit. The control unit 21 can open and close the return valve 6 as required by the valve drive 19. [

3 is a view showing an automobile 9 provided with an internal combustion engine 10 and an exhaust gas processing device 11 and the exhaust gas of the internal combustion engine 10 can be purified by the exhaust gas processing device . The exhaust gas of the internal combustion engine 10 flows as the exhaust gas flow 13 through the exhaust gas processing device 11. [ A dosing valve (5) is provided on the exhaust gas treatment device (11), and the liquid additive can be supplied to the exhaust gas treatment device (11) by the dosing valve. The liquid additive is fed from the tank (3) to the dosing valve (5) by the dosing device (1).

Figure 4 is a first flow diagram of a method according to the present invention. The time axis 14 and the pressure axis 15 are shown in the figure. During the method according to the invention, the pressure profile 16 is shown for the time axis 14. The pressure profile 16 represents the pressure in the pressure accumulator of the described dosing device. In step a), the pressure in the pressure accumulator is at a low constant damping pressure level (e.g., 2 bar or less). During step a), the dosing request is confirmed. If the dosing request is confirmed, then in step b), the pressure in the pressure accumulator is increased by the actuation of the pump, as described above. The pressure profile 16 rises sharply. In step b), the pressure is increased to such an extent that it partially exceeds the dosing pressure 8. By opening the return valve in step c), the pressure is set to the dosing pressure 8 as described above. Thereafter, in step d), dispensing of the liquid additive is effected through a dosing valve, in which case the liquid additive is present at dosing pressure 8. Then step e) is carried out, in which the pressure in the pressure accumulator falls again. The pressure profile 16 is preferably reduced again from step a) to dormant pressure 7. (E. G., By a return transfer action by the pump or by an active opening of the return valve) is not required. Also in step e), the pressure is suitable if it falls off manually (for example because of a leak flow through the return valve or via a pump).

5 is a diagram showing the process steps a), b), c), d) and e). It will be appreciated that this method step can be repeatedly executed at regular intervals in a loop manner.

1 dosing device 2 pump
3 Tank 4 Pressure accumulator
5 dosing valve 6 return valve
7 dormant pressure 8 dosing pressure
9 Automobile 10 Internal combustion engine
11 Exhaust gas treatment equipment 12 Return line
13 Exhaust gas flow 14 hour axis
15 Pressure Axis 16 Pressure Profile
17 Extraction point 18 Transfer line
19 Valve drive part 20 Pressure sensor
21 control unit

Claims (9)

A method of operating a dosing device (1) for providing a liquid additive,
At least one pump for conveying the additive from the tank 3 to the pressure accumulator 4 and a dosing valve 5 designed to provide the additive present in the pressure accumulator 4 in a dosing manner And a return valve (6) for allowing the additive present in the pressure accumulator (4) to be discharged to the tank (3) again,
a) confirming the dosing request;
b) actuating the pump (2) to produce a pressure in the pressure accumulator (4);
c) setting the pressure in the pressure accumulator (4) to a dosing pressure (8);
d) dispensing the additive through the dosing valve (5) while maintaining the pressure set in the pressure accumulator (4); And
e) after step d), lowering the pressure in the pressure accumulator (4). < Desc / Clms Page number 13 > The method according to claim 1,
Method steps a) to d) are repeatedly performed in a loop manner during operation of the dosing device (1). The method according to claim 1,
A method for operating the dosing device (1) for providing a liquid additive in which the return valve (6) is opened, in order to set the pressure in step c). 4. The method according to any one of claims 1 to 3,
Wherein at least steps c) and d) are carried out at least partly in parallel with each other. delete 4. The method according to any one of claims 1 to 3,
Wherein the return valve (6) is a manual open valve and the opening pressure of the open valve corresponds to the dosing pressure. 4. The method according to any one of claims 1 to 3,
Wherein the return valve 6 is an active open valve with a valve actuation 19 wherein the pressure sensor 20 is disposed on the pressure accumulator 4 and the return valve 6 is in an actuated state in step c , Which is controlled by the control unit (21) with the aid of a valve drive (19) to set the pressure in the pressure accumulator (4) to the dosing pressure (8) A method of operating the dosing device (1). 4. The method according to any one of claims 1 to 3,
Characterized in that the pump (2) comprises a pump chamber (7) and at least one pump valve (8) predetermining the transport direction (12). An exhaust gas treatment apparatus (11) for purifying exhaust gas of an internal combustion engine (10) and a dosing device (1), comprising an internal combustion engine (10) A vehicle (9) in which a liquid additive can be supplied to the device (11) and the dosing device is designed and set to operate in accordance with the method according to any one of claims 1 to 3.

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