EP2780562A1 - Delivery device for delivering a liquid additive out of a tank and method therefore - Google Patents

Delivery device for delivering a liquid additive out of a tank and method therefore

Info

Publication number
EP2780562A1
EP2780562A1 EP12783946.2A EP12783946A EP2780562A1 EP 2780562 A1 EP2780562 A1 EP 2780562A1 EP 12783946 A EP12783946 A EP 12783946A EP 2780562 A1 EP2780562 A1 EP 2780562A1
Authority
EP
European Patent Office
Prior art keywords
delivery
delivery duct
wall portion
flexible wall
delivery device
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP12783946.2A
Other languages
German (de)
French (fr)
Inventor
Georges Maguin
Cheikh Diouf
Sven Schepers
Jan Hodgson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Continental Automotive GmbH
Original Assignee
Emitec Gesellschaft fuer Emissionstechnologie mbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Emitec Gesellschaft fuer Emissionstechnologie mbH filed Critical Emitec Gesellschaft fuer Emissionstechnologie mbH
Publication of EP2780562A1 publication Critical patent/EP2780562A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
    • F01N3/2066—Selective catalytic reduction [SCR]
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
    • F01N3/36—Arrangements for supply of additional fuel
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/01—Adding substances to exhaust gases the substance being catalytic material in liquid form
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/02—Adding substances to exhaust gases the substance being ammonia or urea
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/14—Arrangements for the supply of substances, e.g. conduits
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/14—Arrangements for the supply of substances, e.g. conduits
    • F01N2610/1473—Overflow or return means for the substances, e.g. conduits or valves for the return path
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/14—Arrangements for the supply of substances, e.g. conduits
    • F01N2610/1486—Means to prevent the substance from freezing
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00—Fluid handling
    • Y10T137/0318—Processes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00—Fluid handling
    • Y10T137/8593—Systems
    • Y10T137/85978—With pump
    • Y10T137/86035—Combined with fluid receiver

Definitions

  • the invention relates to a delivery device for delivering a liquid additive out of a tank to an exhaust-gas treatment device.
  • Exhaust-gas treatment devices to which a liquid additive is supplied are widely used in particular also in the automotive field.
  • An exhaust-gas purification method particularly commonly implemented in such exhaust-gas treatment devices is the selective catalytic reduction (SCR) method in which nitrogen oxide compounds in the exhaust gas are converted with the aid of a reducing agent to form non-harmful substances (for example water, nitrogen and/or C02).
  • SCR selective catalytic reduction
  • the reducing agent is often supplied to such exhaust-gas treatment devices in the form of a liquid additive, in particular in the form of a urea-water solution.
  • a urea-water solution with a urea content of 32.5 per cent is available for this purpose under the trade name AdBlue ® .
  • a delivery device For the supply of the liquid additive to the exhaust-gas treatment device, a delivery device is generally required which transports the liquid additive from the tank to the exhaust-gas treatment device.
  • a delivery device should operate with the highest possible dosing accuracy, should be as cheap as possible and should have as long a service life as possible. If reducing agent is used as the liquid additive, it is a technical problem that such aqueous reducing agents freeze at temperatures that may arise during normal operation of a motor vehicle.
  • AdBlue ® commonly used as reducing agent for exhaust-gas purification freezes for example at -11 ° C.
  • the additive generally increases in volume. Said increase in volume can damage the delivery device. A delivery device should therefore if appropriate be con- structed such that it is not damaged by an increase in volume of the additive and by the associated ice pressure that is generated.
  • the invention relates to a delivery device for delivering a liquid additive out of a tank to an exhaust-gas treatment device, at least having a delivery duct with an overall volume and a pump arranged in the delivery duct, wherein the delivery duct has, downstream of the pump in a delivery direction, a flexible wall portion which, with an outer side situated opposite the delivery duct, bears against a stop when the pressure in the delivery duct lies in a predefined operating pressure range. On the outer side there is provided a spring element which is designed to deform the flexible wall portion such that the overall volume of the delivery duct is reduced in size when the pressure in the delivery duct is lower than a threshold pressure.
  • the delivery device preferably has a suction point at which the liquid additive can be sucked out of a tank.
  • a tank typically has an interior space, in which the liquid additive is stored, and a tank wall, which has a tank base and a tank top side and which delimits the interior space.
  • the suction point either may be in direct contact with the interior space of the tank or is connected via a line piece to the interior space of the tank.
  • the delivery device furthermore preferably has an outlet port.
  • the liquid additive is provided at the outlet port.
  • the outlet port is preferably connected via a line to an injection device.
  • the injection device may be arranged on an exhaust-gas treatment device and designed to supply the liquid additive into the exhaust-gas treatment device.
  • the injection device may comprise a nozzle for injecting the liquid additive into the exhaust- gas treatment device and/or a valve for controlling the amount of additive supplied into the exhaust-gas treatment device.
  • reducing agent or a reducing agent precursor which forms ammonia
  • aqueous urea solution is used as liquid additive.
  • the method of selective catalytic reduction is carried out using said reducing agent in an exhaust-gas treatment device.
  • the delivery device is preferably arranged directly on/in the tank for storing the liquid additive.
  • the delivery device is preferably arranged in a separate chamber arranged on or at least partially in the tank.
  • the exhaust-gas treatment device preferably comprises, in addition to the injection device, an SCR catalytic converter in which the SCR method can be carried out with the aid of a reducing agent which is provided as said liquid additive to the exhaust-gas treatment device.
  • the delivery duct preferably forms a portion of a flow path for the liquid additive from the tank to the exhaust-gas treatment device.
  • the overall volume of the delivery duct preferably refers to the volume which the delivery duct has in the delivery device and which is filled with the liquid additive during the operation of the delivery device.
  • the overall volume refers in particular to the volume which the delivery duct has downstream of the pump in the delivery direction of the liquid additive and which is filled with liquid additive.
  • the pump is connected to the delivery duct.
  • the pump preferably forms a portion of the delivery duct.
  • the pump divides the delivery duct into a suction portion from the suction point to the pump and a pressure portion from the pump to the outlet port.
  • the overall volume may in particular be formed only by the pressure portion of the delivery duct.
  • the pump has a movable pump element which can perform a delivery movement. By means of said delivery movement, the liquid additive is delivered through the pump.
  • the delivery duct has a duct wall.
  • the duct wall is preferably formed for the most part in the manner of a bore in a plate.
  • the flexible wall portion is preferably not fixedly connected to the plate, or not a fixed constituent part of the plate. Those wall portions of the delivery duct which are formed by the plate are, on the whole, rigid.
  • the flexible wall portion is preferably composed of a flexible material.
  • the flexible wall portion may be formed by a flexible diaphragm, for example.
  • the flexible wall portion or the flexible diaphragm may be formed for example from plastic, in particular from rubber.
  • the flexible wall portion is preferably reversi- bly/elastically deformable.
  • the flexible wall portion or the flexible diaphragm is preferably formed by an areal element.
  • Said areal element has a first surface and a second surface.
  • the first surface is directed toward the delivery duct and forms the flexible wall portion.
  • the second surface forms the outer side which is situated opposite the delivery duct and the first surface.
  • the stop against which the opposite outer side bears is formed for example by a cap element or a cover which makes contact with the outer side.
  • the spring element is preferably arranged between such a cap and the outer side of the flexible wall portion.
  • the operating pressure range lies preferably at pressures above 3 bar.
  • the operating pressure range lies particularly preferably between 5 bar and 10 bar and very particularly preferably between 7 bar and 9 bar.
  • the spring element is designed to push or press the flexible wall portion into the delivery duct or into the overall volume when the pressure in the delivery duct is lower than a threshold pressure.
  • the threshold pressure lies preferably below the lower limit of the operating pressure range, and therefore preferably below 3 bar.
  • the flexible wall portion may have a design which promotes a deformation.
  • the flexible wall portion may have provided on it corrugations which promote a deformation of the flexible wall portion.
  • the delivery unit is particularly advantageous if a return line branches off from the delivery duct downstream of the pump in the delivery direction (in the region of the pressure portion of the delivery duct), which return line can be closed off by a return valve.
  • the return line branches off from the pressure portion in order to be able, by means of the return valve, to ensure a release of pressure from the pressure portion if appropriate.
  • a return flow of liquid additive through the pump is prevented by the valve provided in the pump, as described further above.
  • a release of pressure from the pressure portion of the delivery duct through the pump is therefore prevented.
  • a release of pressure from the pressure portion through the outlet port would lead to a loss of liquid additive, because the additive discharged through the outlet port passes to the injection device.
  • a loss-free release of pressure is possible in particular through the return line.
  • the delivery device is particularly advantageous if there is arranged on the stop at least one force sensor which can measure the force exerted on the stop by the flexible wall portion.
  • a pressure in the delivery duct can thus be determined.
  • the flexible wall portion maintains its flexibility even when it is bearing against the stop.
  • the flexible wall portion then transmits (at all points) the force exerted by the pressure in the delivery duct directly to that region of the stop which is situated (directly) opposite.
  • the situation can be utilized in order, by means of a force sensor integrated in the stop, to carry out a measurement of the pressure in the delivery device or in the delivery duct of the delivery device.
  • the pressure sensor is preferably integrated into the stop so as to end flush with the stop.
  • the force sensor may also protrude slightly beyond the stop in order that a force exerted on the flexible wall portion is transmitted more easily to the force sensor.
  • the force actually acting on the force sensor is also defined by the surface area of the force sensor (or the surface area of the flexible wall portion pressing against the force sensor).
  • the surface area of the force sensor is multiplied by the pressure in the delivery duct in order to calculate the force exerted.
  • the surface area of the force sensor is preferably relatively small in relation to the overall surface area of the stop against which the flexible wall portion bears.
  • Said surface area of the sensor amounts to preferably at most 1/10, and particularly preferably at most 1/20, of the overall surface area of the stop.
  • Conventionally used force sensors measure an exerted force on the basis of a change in length or a deformation of an elastic material with a known modulus of elasticity. At the force sensor, therefore, a slight deformation of the flexible wall portion takes place even in the presence of the operating pressure in the delivery duct because the flexible wall portion deforms, in the region of the sensor, toward the sensor so as to transmit a force from the outer side to the force sensor.
  • the deformation is preferably as small as possible in order to ensure a small change in the overall volume of the delivery duct within the operating pressure range.
  • the force sensor is preferably formed by means of a piezo material and/or by means of a deformable (electrical) resistance.
  • a piezo material generates a different voltage according to how intensely it is deformed.
  • the electrical resistance changes as a function of a deformation.
  • the deformation is in each case proportional, based on the modulus of elasticity, to the acting force.
  • the generated electrical voltage is in each case proportional to the deformation.
  • An acting force can thus be converted into electrical voltage and evaluated by electronics.
  • the delivery device is particularly advantageous if the pump has a pump outlet and the delivery duct has a chamber downstream of the pump outlet in the delivery direction, the pump outlet opens into the chamber, and the flexible wall portion is arranged on the chamber opposite the pump outlet.
  • the chamber is in particular an extension of the delivery duct.
  • the chamber is preferably formed as a recess which is situated on a plate of the delivery device.
  • a portion of the delivery duct which extends from the pump outlet opens into the chamber.
  • a further portion of the delivery duct which extends to the outlet port branches off from the chamber. Since the chamber is provided as a recess in the plate, said chamber can be covered by an areal element which forms the flexible wall portion. This yields a particularly simple possibility for mounting the flexible wall portion of the delivery duct.
  • a cap which forms the stop can then be inserted in the described recess in the plate, at the outer side of the flexible element or material which forms the flexible wall portion.
  • the pump outlet of the pump is preferably aligned along a common axis with a pump inlet of the pump.
  • the additive exits the pump outlet as a pulsating flow with pressure fluctuations.
  • the described chamber is also advantageous from a flow aspect.
  • the pulsating flow from the pump outlet is homogenized in said chamber. This arises in particular on account of the enlarged volume of the chamber and/or the diversion of the flow which occurs when the additive exits the chamber again.
  • the chamber and the flexible wall portion are preferably arranged spatially on a common axis with the pump inlet and the pump outlet An axis running through the pump inlet and the pump outlet preferably inter- sects the chamber and the flexible wall portion.
  • the chamber is delimited by the flexible wall portion preferably on a side situated opposite the pump outlet or the pump.
  • the delivery device is particularly advantageous if the stop has a receptacle in which the spring element is accommodated when the flexible wall portion bears against the stop.
  • the receptacle makes it possible for the spring element to behave rig- idly when the pressure in the delivery duct lies in the operating pressure range.
  • the spring element is then accommodated entirely in the receptacle and, here, is preferably compressed.
  • the receptacle may be formed as a recess of the cap.
  • the receptacle may be formed for example as an annular groove in the cap, the diameter of which groove corresponds to the diameter of the spring and the depth of which groove is sufficient to completely accommodate the spring element in the compressed state.
  • the delivery device is also advantageous if the spring element exerts on the flexible wall portion a spring force which corresponds to a pressure of 0.2 to 1.0 bar in relation to the surface area of the flexible wall portion when the flexible wall portion bears against the stop.
  • the liquid additive can be forced out of the overall volume of the delivery duct of the delivery device even if a certain counter-pressure is acting on the delivery device from the outside.
  • the liquid additive should preferably be forced through a return line back into a tank.
  • the delivery device is preferably arranged on the base of a tank.
  • the pressure acting on the delivery duct or on the overall volume is defined substantially by the filling level in the tank if the delivery device is arranged on the tank base and a return valve in a return line which connects the delivery duct to the tank interior space is open.
  • a pressure of 0.2 to 1.0 bar then corresponds to the threshold pressure above which the overall volume in the delivery duct is reduced in size.
  • Said threshold pressure is preferably selected such that an adequate spacing from the operating pressure range is obtained and it is thus ensured, that the delivery device behaves substantially rigidly when the pressure lies in the operating pressure range and a reduction in size of the overall volume occurs only when an operational stoppage of the delivery device actually takes place and the return valve in a return line is open.
  • the spring force of the spring element required to ensure the above-specified values for the threshold pressure may be determined and fixed on the basis of the desired threshold pressure and the surface area of the flexible wall portion on which the spring element acts and which is exposed to the pres- sure in the delivery duct.
  • the outer side of the flexible wall portion is preferably connected to the environment via an exchange duct such that a pressure acting on the outer side of the flexible wall portion does not exert a force which distorts the behaviour (in particular the pressure-deformation characteristic curve) of the flexible wall portion.
  • a force exerted by the spring element on the flexible wall portion is if appropriate also taken into consideration in the determination of the pressure in the delivery duct.
  • a part of the pressure in the delivery duct may be compensated by the spring element such that the force sensor can measure only a part of the pressure.
  • To be able to measure the pressure in the duct it is necessary if appropriate to take into consideration that pressure component of the pressure measured by the force sensor which is compensated by the spring element.
  • Also claimed within the context of the invention is a method for compensating the formation of ice in a delivery device which has an overall volume, which is at least partially filled with liquid additive, of a delivery duct, wherein the method comprises at least the following steps:
  • the method according to the invention may be implemented or carried out in particular with the delivery device according to the invention.
  • the advantages and design features explained with regard to the described delivery device can be transferred analogously to the described method.
  • a compensation of the formation of ice refers here in particular to a compensation of the volume expansion which normally arises in conjunction with the formation of ice, or of the generated ice pressure of the additive.
  • the volume expansion is obtained by means of an increase in size of the volume provided for the additive.
  • the stoppage of the operation of a pump in step a) is usually associated with the stoppage of an internal combustion engine connected to an exhaust-gas treatment device, to the exhaust-gas treatment device of which internal combustion engine the delivery device is connected in order to supply the liquid additive.
  • the opening of the return valve in a return line in step b) normally takes place automatically.
  • the return valve is preferably designed as a solenoid valve which is closed when an electrical current is applied and which is open when no electrical current is applied.
  • an electrical current supply to the delivery device is preferably interrupted.
  • the return valve in the return line then opens automatically and produces a connection between the overall volume of the delivery duct and a tank through the return line. As a result of this, the pressure in the overall volume falls because the pressurized liquid additive in the delivery duct or in the overall volume can escape through the return line.
  • step c) the overall volume can then be reduced in size with relatively little force.
  • an active reduction in size means that a component of the delivery unit is provided for initiating or carrying out a process of reducing the size of the overall volume.
  • This may be realized for example by means of a spring which deforms a flexible wall portion of the delivery duct into the delivery duct.
  • a mechanically actuable device if appropriate with an electric drive
  • a slide element may be moved into the overall volume in order to reduce the size of the overall volume.
  • the liquid additive is, in step d), forced through the return valve and through the return line into the tank. There is a temporary flow of the liquid additive out of the overall volume through the return line and back into the tank.
  • a passive increase in size means in particular that the increase in size is not realized by means of an actively moved component of the delivery unit but rather is dependent on external circumstances (in the present case, the volume expansion of water-based additives when freezing occurs).
  • the compensation of the freezing or of the volume expansion which takes place when freezing occurs preferably takes place again by means (only) of a deformation of the flexible wall portion.
  • step e) preferably opposes the active deformation provided in step c).
  • steps a) - d) take place in the specified sequence when freezing occurs.
  • a motor vehicle having an internal combustion engine, an exhaust-gas treatment device for the purification of the exhaust gases of the internal combustion engine, a tank for a liquid additive, and a described delivery device which is designed to deliver the liquid additive from the tank to the exhaust-gas treatment device.
  • the delivery device of the motor vehicle is particularly advantageously also suitable for carrying out the described method.
  • Fig. 1 shows a sectional drawing of a delivery device
  • Fig. 2 shows a further sectional drawing of a delivery device
  • Fig. 3 shows a motor vehicle
  • Fig. 4 shows a diagram of the pressure in a delivery device
  • Fig. 5 shows a further design variant of a delivery device.
  • Figures 1 and 2 each illustrate different aspects of a delivery device 1.
  • the delivery device 1 Illustrated in each case is the delivery device 1, having a delivery duct 4 which extends from a suction point 17 to an outlet port 18.
  • the pump 5 Provided in the delivery duct 4 is the pump 5 which delivers the liquid additive through the delivery duct 4.
  • a chamber 16 is situated downstream of the pump 5 and downstream of the pump outlet 15.
  • the chamber 16 is a constituent part of the delivery duct 4.
  • the delivery duct 4 is arranged together with the chamber 16 in a plate 19.
  • the delivery duct 4 and the chamber 16 may for example be drilled or (if the plate 19 is formed as a cast part) cast into the plate 19.
  • the chamber 16 is delimited, on the side situated opposite the pump outlet, by a flexible wall portion 7.
  • Said flexible wall por- tion 7 therefore also forms a wall portion of the delivery duct 4.
  • the flexible wall portion 7 has a surface 23 by means of which it is in contact with the delivery duct 4 and with the chamber 16.
  • the delivery duct 4 together with its chamber 16 has an overall volume 20.
  • the flexible wall portion 7 is supported, on an outer side 29, against a stop 9.
  • the stop 9 may be formed for example by a cap which covers the flexible wall portion 7.
  • a force sensor 14 for determining a pressure in the delivery duct 4 or in the chamber or in the overall volume 20.
  • a spring element 8 Between the flexible wall portion 7 and the stop 9 there is situated a spring element 8.
  • a receptacle 30 is preferably provid- ed in which the spring element 8 can be accommodated when the flexible wall portion 7 bears against the stop 9.
  • the surface 23 of the flexible wall portion 7 is definitive for the force exerted on the spring element 8 by the pressure in the delivery duct 4.
  • the return line 26 can be opened and closed by means of a return valve 21.
  • Figure 1 illustrates the delivery device 1 when an operating pressure is prevailing in the overall volume 20.
  • the flexible wall portion 7 then bears against the stop 9.
  • Figure 2 illustrates the delivery device 1 when the pressure in the overall volume 20 is lower than a threshold pressure.
  • the spring element 8 is then expanded and the flexible wall portion 7 is deformed into the overall volume 20 or into the chamber.
  • the overall volume 20 is therefore reduced in size in figure 2.
  • Figure 3 shows a motor vehicle 24 having an internal combustion engine 25 and having an exhaust-gas treatment device 3 for the purification of the exhaust gases of the internal combustion engine 25.
  • an injection device 28 is provided on the exhaust-gas treatment device 3 by means of which liquid additive can be supplied into the exhaust-gas treatment device 3.
  • liquid additive is supplied to the injection device 28 from a tank 2 via a line 27 and a delivery device 1.
  • Figure 4 shows a diagram of a pressure in a delivery device.
  • the pressure in the delivery device is plotted on the horizontal axis 13.
  • the overall volume of the delivery device is plotted on the vertical volume axis 12. It is possible to see the operating volume which is constant in an operating pressure range 11 and which, during regular operation of the delivery device, forms the overall volume and is present in the delivery device. If the pressure falls below a threshold pressure 31, the overall volume decreases.
  • the threshold pressure 31 denotes the pressure beyond which an expansion of the spring element occurs.
  • Below the threshold pressure 31 the curve depicting the relationship between the pressure and the overall volume has a further bend. Said bend denotes the pressure at which an expansion of the spring is complete. Furthermore, the spring cannot press the flexible wall portion into the delivery duct.
  • FIG. 5 shows a further design variant of a delivery device 1.
  • Said delivery device 1 also has a base plate 19 in which is situated a delivery duct 4 for the delivery of liquid additive.
  • a pump 5 forms a portion of the delivery duct 4.
  • a return line 26 which branches off from the delivery duct 4 and which can be opened and closed by means of a return valve 21 in order to produce or break a connection from the delivery duct via a return line back into a tank.
  • the delivery duct 4 is designed such that horizontal portions (wherein horizontal is defined in relation to a preferred installation alignment of the delivery device in a motor vehicle) have in each case an angle of inclination 22 with respect to a horizontal alignment.
  • the angle of inclination 22 is preferably selected such that a flow path for an air bubble from any point of the delivery duct 4 to the return line 26 or to the return valve 21 is monotonously rising.
  • the angle of inclination 22 is preferably even selected such that such a flow path for an air bubble to the return valve 21 is monotonously rising even when the delivery device is in a slightly oblique position. Such an oblique position may arise during operation for example because the vehicle with the described delivery device is parked in an oblique position.
  • the angle of inclination 22 is preferably at least 2 ° and particularly preferably at least 5 ° . It is thus possible for oblique positions of up to 2 ° or even up to 5 ° to be compensated.
  • the concept of providing delivery ducts in a delivery device with an angle of inclination may also be implemented independently of the concept, described further above, of a delivery device having a flexible wall portion.
  • a delivery device having at least one delivery duct and having a pump for delivering reducing agent from a suction point in a tank to an outlet port, in which all the ducts in the delivery device are at an angle of at least 2 ° , such that from any point of the delivery duct, a flow path for an air bubble to a return valve exists which (in terms of the geodetic position of said air bubble) rises monotonously.
  • a delivery device may be supplemented as desired with further features from the description.

Abstract

The invention relates to a delivery device (1) for delivering a liquid additive out of a tank (2) to an exhaust-gas treatment device (3), at least having a delivery duct (4) with an overall volume (20) and a pump (5) arranged in the delivery duct (4), wherein the delivery duct (4) has, downstream of the pump (5) in a delivery direction (6), a flexible wall portion (7) which, with an outer side (29) situated opposite the delivery duct (4), bears against a stop (9) when the pressure in the delivery duct (4) lies in a predefined operating pressure range (11), wherein on the outer side (29) there is provided a spring element (8) which is designed to deform the flexible wall portion (7) such that the overall volume (20) is reduced in size when the pressure in the delivery duct (4) is lower than a threshold pressure (31). Furthermore, the invention also relates to a method for compensating the formation of ice in a delivery device.

Description

DELIVERY DEVICE FOR DELIVERING A LIQUID ADDITIVE
OUT OF A TANK AND METHOD THEREFORE
The invention relates to a delivery device for delivering a liquid additive out of a tank to an exhaust-gas treatment device. Exhaust-gas treatment devices to which a liquid additive is supplied are widely used in particular also in the automotive field. An exhaust-gas purification method particularly commonly implemented in such exhaust-gas treatment devices is the selective catalytic reduction (SCR) method in which nitrogen oxide compounds in the exhaust gas are converted with the aid of a reducing agent to form non-harmful substances (for example water, nitrogen and/or C02). The reducing agent is often supplied to such exhaust-gas treatment devices in the form of a liquid additive, in particular in the form of a urea-water solution. A urea-water solution with a urea content of 32.5 per cent is available for this purpose under the trade name AdBlue®.
For the supply of the liquid additive to the exhaust-gas treatment device, a delivery device is generally required which transports the liquid additive from the tank to the exhaust-gas treatment device. A delivery device should operate with the highest possible dosing accuracy, should be as cheap as possible and should have as long a service life as possible. If reducing agent is used as the liquid additive, it is a technical problem that such aqueous reducing agents freeze at temperatures that may arise during normal operation of a motor vehicle.
The urea-water solution AdBlue® commonly used as reducing agent for exhaust-gas purification freezes for example at -11 °C. In the case of motor vehicles, such low temperatures may arise in particular during long standstill periods in winter. As a liquid additive freezes, the additive generally increases in volume. Said increase in volume can damage the delivery device. A delivery device should therefore if appropriate be con- structed such that it is not damaged by an increase in volume of the additive and by the associated ice pressure that is generated.
Taking this as a starting point, it is an object of the present invention to as advantageously as possible solve, or at least lessen, the technical problems discussed. It is sought in particular to describe a particularly advantageous delivery device for delivering a liquid additive. Furthermore, it is sought to specify a particularly advantageous method for compensating the formation of ice in a delivery device.
Said objects are achieved by means of a delivery device according to the features of Claim 1 and also by means of a method according to the features of Claim 7. Further advantageous refinements of the invention are specified in the dependent claims. The features specified individually in the claims may be combined with one another in any desired technologically meaningful way and may be supplemented by explanatory facts from the description, with further design variants of the invention being specified. The invention relates to a delivery device for delivering a liquid additive out of a tank to an exhaust-gas treatment device, at least having a delivery duct with an overall volume and a pump arranged in the delivery duct, wherein the delivery duct has, downstream of the pump in a delivery direction, a flexible wall portion which, with an outer side situated opposite the delivery duct, bears against a stop when the pressure in the delivery duct lies in a predefined operating pressure range. On the outer side there is provided a spring element which is designed to deform the flexible wall portion such that the overall volume of the delivery duct is reduced in size when the pressure in the delivery duct is lower than a threshold pressure.
The delivery device preferably has a suction point at which the liquid additive can be sucked out of a tank. A tank typically has an interior space, in which the liquid additive is stored, and a tank wall, which has a tank base and a tank top side and which delimits the interior space. The suction point either may be in direct contact with the interior space of the tank or is connected via a line piece to the interior space of the tank. The delivery device furthermore preferably has an outlet port. The liquid additive is provided at the outlet port. The outlet port is preferably connected via a line to an injection device. The injection device may be arranged on an exhaust-gas treatment device and designed to supply the liquid additive into the exhaust-gas treatment device. The injection device may comprise a nozzle for injecting the liquid additive into the exhaust- gas treatment device and/or a valve for controlling the amount of additive supplied into the exhaust-gas treatment device.
In the described delivery device, preferably reducing agent (or a reducing agent precursor which forms ammonia) and particularly preferably aqueous urea solution is used as liquid additive. The method of selective catalytic reduction is carried out using said reducing agent in an exhaust-gas treatment device. The delivery device is preferably arranged directly on/in the tank for storing the liquid additive. The delivery device is preferably arranged in a separate chamber arranged on or at least partially in the tank. The exhaust-gas treatment device preferably comprises, in addition to the injection device, an SCR catalytic converter in which the SCR method can be carried out with the aid of a reducing agent which is provided as said liquid additive to the exhaust-gas treatment device.
The delivery duct preferably forms a portion of a flow path for the liquid additive from the tank to the exhaust-gas treatment device. The overall volume of the delivery duct preferably refers to the volume which the delivery duct has in the delivery device and which is filled with the liquid additive during the operation of the delivery device. The overall volume refers in particular to the volume which the delivery duct has downstream of the pump in the delivery direction of the liquid additive and which is filled with liquid additive. The pump is connected to the delivery duct. The pump preferably forms a portion of the delivery duct. The pump divides the delivery duct into a suction portion from the suction point to the pump and a pressure portion from the pump to the outlet port. The overall volume may in particular be formed only by the pressure portion of the delivery duct. It is preferable for at least one valve to be provided in the pump, which valve predefines a delivery direction of the liquid additive through the pump. For this reason, the liquid additive cannot flow through the pump counter to the delivery direction. Fur- thermore, the pump has a movable pump element which can perform a delivery movement. By means of said delivery movement, the liquid additive is delivered through the pump.
The delivery duct has a duct wall. The duct wall is preferably formed for the most part in the manner of a bore in a plate. The flexible wall portion is preferably not fixedly connected to the plate, or not a fixed constituent part of the plate. Those wall portions of the delivery duct which are formed by the plate are, on the whole, rigid. The flexible wall portion is preferably composed of a flexible material. The flexible wall portion may be formed by a flexible diaphragm, for example. The flexible wall portion or the flexible diaphragm may be formed for example from plastic, in particular from rubber. The flexible wall portion is preferably reversi- bly/elastically deformable. The flexible wall portion or the flexible diaphragm is preferably formed by an areal element. Said areal element has a first surface and a second surface. The first surface is directed toward the delivery duct and forms the flexible wall portion. The second surface forms the outer side which is situated opposite the delivery duct and the first surface. The stop against which the opposite outer side bears is formed for example by a cap element or a cover which makes contact with the outer side. The spring element is preferably arranged between such a cap and the outer side of the flexible wall portion.
The operating pressure range lies preferably at pressures above 3 bar. The operating pressure range lies particularly preferably between 5 bar and 10 bar and very particularly preferably between 7 bar and 9 bar. The spring element is designed to push or press the flexible wall portion into the delivery duct or into the overall volume when the pressure in the delivery duct is lower than a threshold pressure. The threshold pressure lies preferably below the lower limit of the operating pressure range, and therefore preferably below 3 bar. The flexible wall portion may have a design which promotes a deformation. For example, the flexible wall portion may have provided on it corrugations which promote a deformation of the flexible wall portion.
The delivery unit is particularly advantageous if a return line branches off from the delivery duct downstream of the pump in the delivery direction (in the region of the pressure portion of the delivery duct), which return line can be closed off by a return valve. The return line branches off from the pressure portion in order to be able, by means of the return valve, to ensure a release of pressure from the pressure portion if appropriate. A return flow of liquid additive through the pump is prevented by the valve provided in the pump, as described further above. A release of pressure from the pressure portion of the delivery duct through the pump is therefore prevented. A release of pressure from the pressure portion through the outlet port would lead to a loss of liquid additive, because the additive discharged through the outlet port passes to the injection device. A loss-free release of pressure is possible in particular through the return line. When the flexible wall portion deforms, the liquid additive which is displaced out of the delivery duct owing to the reduction in size of the overall volume can escape via the return line.
The delivery device is particularly advantageous if there is arranged on the stop at least one force sensor which can measure the force exerted on the stop by the flexible wall portion. A pressure in the delivery duct can thus be determined. The flexible wall portion maintains its flexibility even when it is bearing against the stop. The flexible wall portion then transmits (at all points) the force exerted by the pressure in the delivery duct directly to that region of the stop which is situated (directly) opposite. The situation can be utilized in order, by means of a force sensor integrated in the stop, to carry out a measurement of the pressure in the delivery device or in the delivery duct of the delivery device. The pressure sensor is preferably integrated into the stop so as to end flush with the stop. The force sensor may also protrude slightly beyond the stop in order that a force exerted on the flexible wall portion is transmitted more easily to the force sensor. During operation (when the flexible wall portion bears against the stop), the outer side of the flexible wall portion presses against the force sensor. The force actually acting on the force sensor is also defined by the surface area of the force sensor (or the surface area of the flexible wall portion pressing against the force sensor). The surface area of the force sensor is multiplied by the pressure in the delivery duct in order to calculate the force exerted. The surface area of the force sensor is preferably relatively small in relation to the overall surface area of the stop against which the flexible wall portion bears. Said surface area of the sensor amounts to preferably at most 1/10, and particularly preferably at most 1/20, of the overall surface area of the stop. Conventionally used force sensors measure an exerted force on the basis of a change in length or a deformation of an elastic material with a known modulus of elasticity. At the force sensor, therefore, a slight deformation of the flexible wall portion takes place even in the presence of the operating pressure in the delivery duct because the flexible wall portion deforms, in the region of the sensor, toward the sensor so as to transmit a force from the outer side to the force sensor. The deformation is preferably as small as possible in order to ensure a small change in the overall volume of the delivery duct within the operating pressure range.
The force sensor is preferably formed by means of a piezo material and/or by means of a deformable (electrical) resistance. A piezo material generates a different voltage according to how intensely it is deformed. In the case of a deformable resistance, the electrical resistance changes as a function of a deformation. The deformation is in each case proportional, based on the modulus of elasticity, to the acting force. The generated electrical voltage is in each case proportional to the deformation. An acting force can thus be converted into electrical voltage and evaluated by electronics. The delivery device is particularly advantageous if the pump has a pump outlet and the delivery duct has a chamber downstream of the pump outlet in the delivery direction, the pump outlet opens into the chamber, and the flexible wall portion is arranged on the chamber opposite the pump outlet.
The chamber is in particular an extension of the delivery duct. The chamber is preferably formed as a recess which is situated on a plate of the delivery device. A portion of the delivery duct which extends from the pump outlet opens into the chamber. A further portion of the delivery duct which extends to the outlet port branches off from the chamber. Since the chamber is provided as a recess in the plate, said chamber can be covered by an areal element which forms the flexible wall portion. This yields a particularly simple possibility for mounting the flexible wall portion of the delivery duct. A cap which forms the stop can then be inserted in the described recess in the plate, at the outer side of the flexible element or material which forms the flexible wall portion.
The pump outlet of the pump is preferably aligned along a common axis with a pump inlet of the pump. During delivery operation, the additive exits the pump outlet as a pulsating flow with pressure fluctuations. The described chamber is also advantageous from a flow aspect. The pulsating flow from the pump outlet is homogenized in said chamber. This arises in particular on account of the enlarged volume of the chamber and/or the diversion of the flow which occurs when the additive exits the chamber again.
The chamber and the flexible wall portion are preferably arranged spatially on a common axis with the pump inlet and the pump outlet An axis running through the pump inlet and the pump outlet preferably inter- sects the chamber and the flexible wall portion. The chamber is delimited by the flexible wall portion preferably on a side situated opposite the pump outlet or the pump. The delivery device is particularly advantageous if the stop has a receptacle in which the spring element is accommodated when the flexible wall portion bears against the stop.
Such a receptacle makes it possible for the spring element to behave rig- idly when the pressure in the delivery duct lies in the operating pressure range. The spring element is then accommodated entirely in the receptacle and, here, is preferably compressed. If the stop is formed by a cap, the receptacle may be formed as a recess of the cap. For a spring element designed as a spiral spring, the receptacle may be formed for example as an annular groove in the cap, the diameter of which groove corresponds to the diameter of the spring and the depth of which groove is sufficient to completely accommodate the spring element in the compressed state.
The delivery device is also advantageous if the spring element exerts on the flexible wall portion a spring force which corresponds to a pressure of 0.2 to 1.0 bar in relation to the surface area of the flexible wall portion when the flexible wall portion bears against the stop. By means of a force corresponding to such a pressure, the liquid additive can be forced out of the overall volume of the delivery duct of the delivery device even if a certain counter-pressure is acting on the delivery device from the outside. The liquid additive should preferably be forced through a return line back into a tank. The delivery device is preferably arranged on the base of a tank. The pressure acting on the delivery duct or on the overall volume is defined substantially by the filling level in the tank if the delivery device is arranged on the tank base and a return valve in a return line which connects the delivery duct to the tank interior space is open. A pressure of 0.2 to 1.0 bar then corresponds to the threshold pressure above which the overall volume in the delivery duct is reduced in size. Said threshold pressure is preferably selected such that an adequate spacing from the operating pressure range is obtained and it is thus ensured, that the delivery device behaves substantially rigidly when the pressure lies in the operating pressure range and a reduction in size of the overall volume occurs only when an operational stoppage of the delivery device actually takes place and the return valve in a return line is open. The spring force of the spring element required to ensure the above-specified values for the threshold pressure may be determined and fixed on the basis of the desired threshold pressure and the surface area of the flexible wall portion on which the spring element acts and which is exposed to the pres- sure in the delivery duct.
The outer side of the flexible wall portion is preferably connected to the environment via an exchange duct such that a pressure acting on the outer side of the flexible wall portion does not exert a force which distorts the behaviour (in particular the pressure-deformation characteristic curve) of the flexible wall portion.
A force exerted by the spring element on the flexible wall portion is if appropriate also taken into consideration in the determination of the pressure in the delivery duct. A part of the pressure in the delivery duct may be compensated by the spring element such that the force sensor can measure only a part of the pressure. To be able to measure the pressure in the duct, it is necessary if appropriate to take into consideration that pressure component of the pressure measured by the force sensor which is compensated by the spring element.
Also claimed within the context of the invention is a method for compensating the formation of ice in a delivery device which has an overall volume, which is at least partially filled with liquid additive, of a delivery duct, wherein the method comprises at least the following steps:
a) stoppage of the operation of a pump of the delivery device;
b) opening of a return valve of a return line which produces a connection between the delivery duct and a tank for the liquid additive; c) active reduction in size of the overall volume filled with liquid additive;
d) discharging of liquid additive through the return valve into the tank; and
e) passive increasing of the overall volume as the liquid additive in the delivery duct freezes.
The method according to the invention may be implemented or carried out in particular with the delivery device according to the invention. The advantages and design features explained with regard to the described delivery device can be transferred analogously to the described method. The same applies to the advantages and special configuration features of the method according to the invention described below, which can be transferred analogously to the delivery device according to the invention.
A compensation of the formation of ice refers here in particular to a compensation of the volume expansion which normally arises in conjunction with the formation of ice, or of the generated ice pressure of the additive. The volume expansion is obtained by means of an increase in size of the volume provided for the additive.
The stoppage of the operation of a pump in step a) is usually associated with the stoppage of an internal combustion engine connected to an exhaust-gas treatment device, to the exhaust-gas treatment device of which internal combustion engine the delivery device is connected in order to supply the liquid additive.
The opening of the return valve in a return line in step b) normally takes place automatically. The return valve is preferably designed as a solenoid valve which is closed when an electrical current is applied and which is open when no electrical current is applied. Upon the stoppage of operation, an electrical current supply to the delivery device is preferably interrupted. The return valve in the return line then opens automatically and produces a connection between the overall volume of the delivery duct and a tank through the return line. As a result of this, the pressure in the overall volume falls because the pressurized liquid additive in the delivery duct or in the overall volume can escape through the return line. In step c), the overall volume can then be reduced in size with relatively little force. Here, an active reduction in size means that a component of the delivery unit is provided for initiating or carrying out a process of reducing the size of the overall volume. This may be realized for example by means of a spring which deforms a flexible wall portion of the delivery duct into the delivery duct. It is however also possible, in a further embodiment of the method, for a mechanically actuable device (if appropriate with an electric drive) to actively reduce the size of the overall volume. For example, a slide element may be moved into the overall volume in order to reduce the size of the overall volume.
As a result of said deformation, the liquid additive is, in step d), forced through the return valve and through the return line into the tank. There is a temporary flow of the liquid additive out of the overall volume through the return line and back into the tank.
As long as the temperature (to which the delivery device is exposed) does not fall far enough to cause liquid additive to solidify into ice, the overall volume of the delivery duct does not change. If the temperature falls further and the formation of ice in the delivery duct of the delivery device begins, the overall volume increases in size again in step e) to the extent required for compensating the freezing. Here, a passive increase in size means in particular that the increase in size is not realized by means of an actively moved component of the delivery unit but rather is dependent on external circumstances (in the present case, the volume expansion of water-based additives when freezing occurs). The compensation of the freezing or of the volume expansion which takes place when freezing occurs preferably takes place again by means (only) of a deformation of the flexible wall portion. The deformation which occurs in step e) preferably opposes the active deformation provided in step c). For clarity, it is pointed out here again that (if this does not emerge from the above description itself) steps a) - d) take place in the specified sequence when freezing occurs.
Also proposed is a motor vehicle having an internal combustion engine, an exhaust-gas treatment device for the purification of the exhaust gases of the internal combustion engine, a tank for a liquid additive, and a described delivery device which is designed to deliver the liquid additive from the tank to the exhaust-gas treatment device.
The delivery device of the motor vehicle is particularly advantageously also suitable for carrying out the described method.
The invention and the technical field will be explained in more detail below on the basis of the figures. The figures show particularly preferred exemplary embodiments, to which the invention is however not restricted. In particular, note that the figures and in particular the illustrated proportions are merely schematic. In the figures:
Fig. 1: shows a sectional drawing of a delivery device;
Fig. 2: shows a further sectional drawing of a delivery device;
Fig. 3: shows a motor vehicle;
Fig. 4: shows a diagram of the pressure in a delivery device; and
Fig. 5: shows a further design variant of a delivery device.
Figures 1 and 2 each illustrate different aspects of a delivery device 1. A joint explanation of figures 1 and 2 will therefore be given first here. Illustrated in each case is the delivery device 1, having a delivery duct 4 which extends from a suction point 17 to an outlet port 18. Provided in the delivery duct 4 is the pump 5 which delivers the liquid additive through the delivery duct 4. In the delivery direction 6 illustrated in figure 1, a chamber 16 is situated downstream of the pump 5 and downstream of the pump outlet 15. The chamber 16 is a constituent part of the delivery duct 4. The delivery duct 4 is arranged together with the chamber 16 in a plate 19. The delivery duct 4 and the chamber 16 may for example be drilled or (if the plate 19 is formed as a cast part) cast into the plate 19. The chamber 16 is delimited, on the side situated opposite the pump outlet, by a flexible wall portion 7. Said flexible wall por- tion 7 therefore also forms a wall portion of the delivery duct 4. The flexible wall portion 7 has a surface 23 by means of which it is in contact with the delivery duct 4 and with the chamber 16. The delivery duct 4 together with its chamber 16 has an overall volume 20. The flexible wall portion 7 is supported, on an outer side 29, against a stop 9. The stop 9 may be formed for example by a cap which covers the flexible wall portion 7. In the stop 9 there may also be provided a force sensor 14 for determining a pressure in the delivery duct 4 or in the chamber or in the overall volume 20. Between the flexible wall portion 7 and the stop 9 there is situated a spring element 8. A receptacle 30 is preferably provid- ed in which the spring element 8 can be accommodated when the flexible wall portion 7 bears against the stop 9. The surface 23 of the flexible wall portion 7 is definitive for the force exerted on the spring element 8 by the pressure in the delivery duct 4. From the delivery duct 4 there preferably branches off a return line 26 which leads back into a tank for the liquid additive. The return line 26 can be opened and closed by means of a return valve 21.
Figure 1 illustrates the delivery device 1 when an operating pressure is prevailing in the overall volume 20. The flexible wall portion 7 then bears against the stop 9.
Figure 2 illustrates the delivery device 1 when the pressure in the overall volume 20 is lower than a threshold pressure. The spring element 8 is then expanded and the flexible wall portion 7 is deformed into the overall volume 20 or into the chamber. The overall volume 20 is therefore reduced in size in figure 2.
Figure 3 shows a motor vehicle 24 having an internal combustion engine 25 and having an exhaust-gas treatment device 3 for the purification of the exhaust gases of the internal combustion engine 25. Provided on the exhaust-gas treatment device 3 is an injection device 28 by means of which liquid additive can be supplied into the exhaust-gas treatment device 3. For this purpose, liquid additive is supplied to the injection device 28 from a tank 2 via a line 27 and a delivery device 1.
Figure 4 shows a diagram of a pressure in a delivery device. The pressure in the delivery device is plotted on the horizontal axis 13. The overall volume of the delivery device is plotted on the vertical volume axis 12. It is possible to see the operating volume which is constant in an operating pressure range 11 and which, during regular operation of the delivery device, forms the overall volume and is present in the delivery device. If the pressure falls below a threshold pressure 31, the overall volume decreases. The threshold pressure 31 denotes the pressure beyond which an expansion of the spring element occurs. Below the threshold pressure 31, the curve depicting the relationship between the pressure and the overall volume has a further bend. Said bend denotes the pressure at which an expansion of the spring is complete. Furthermore, the spring cannot press the flexible wall portion into the delivery duct.
Figure 5 shows a further design variant of a delivery device 1. Said delivery device 1 also has a base plate 19 in which is situated a delivery duct 4 for the delivery of liquid additive. Here, too, a pump 5 forms a portion of the delivery duct 4. It is also possible to see a return line 26 which branches off from the delivery duct 4 and which can be opened and closed by means of a return valve 21 in order to produce or break a connection from the delivery duct via a return line back into a tank. In the design variant of a delivery device according to figure 5, the delivery duct 4 is designed such that horizontal portions (wherein horizontal is defined in relation to a preferred installation alignment of the delivery device in a motor vehicle) have in each case an angle of inclination 22 with respect to a horizontal alignment. In this way, it is possible to prevent air bubbles from becoming trapped in the ducts. Such air bubbles can be conveyed out of the delivery device or out of the delivery duct only by means of an increased pressure, in particular also on account of capillary forces. The angle of inclination 22 is preferably selected such that a flow path for an air bubble from any point of the delivery duct 4 to the return line 26 or to the return valve 21 is monotonously rising. The angle of inclination 22 is preferably even selected such that such a flow path for an air bubble to the return valve 21 is monotonously rising even when the delivery device is in a slightly oblique position. Such an oblique position may arise during operation for example because the vehicle with the described delivery device is parked in an oblique position. The angle of inclination 22 is preferably at least 2° and particularly preferably at least 5°. It is thus possible for oblique positions of up to 2° or even up to 5° to be compensated.
The concept of providing delivery ducts in a delivery device with an angle of inclination may also be implemented independently of the concept, described further above, of a delivery device having a flexible wall portion. In particular, there is also specified here a delivery device having at least one delivery duct and having a pump for delivering reducing agent from a suction point in a tank to an outlet port, in which all the ducts in the delivery device are at an angle of at least 2°, such that from any point of the delivery duct, a flow path for an air bubble to a return valve exists which (in terms of the geodetic position of said air bubble) rises monotonously. Such a delivery device may be supplemented as desired with further features from the description. It is thereby possible, specifically for the field of application mentioned in the introduction, for the formation of gas bubbles in the ducts to be reduced, or for the migration of said gas bubbles in the delivery unit to be influenced in a targeted manner. It is thereby possible to obtain a reduction not only in pressure fluctuations but also for example in malfunctions in the delivery of the heating of frozen reducing agent and/or servicing and monitoring measures. List of reference
1 Delivery device
2 Tank
3 Exhaust-gas treatment device
4 Delivery duct
5 Pump
6 Delivery direction
7 Flexible wall portion
8 Spring element
9 Stop
10 Operating volume
11 Operating pressure range
12 Volume axis
13 Axis
14 Force sensor
15 Pump outlet
16 Chamber
17 Suction point
18 Outlet port
19 Plate
20 Overall volume
21 Return valve
22 Angle of inclination
23 Surface
24 Motor vehicle
25 Internal combustion engine
26 Return line
27 Line
28 Injection device
29 Outer side
30 Receptacle
31 Threshold pressure

Claims

Claims
1. Delivery device (1) for delivering a liquid additive out of a tank (2) to an exhaust-gas treatment device (3), at least having a delivery duct (4) with an overall volume (20) and a pump (5) arranged in the delivery duct (4), wherein the delivery duct (4) has, downstream of the pump (5) in a delivery direction (6), a flexible wall portion (7) which, with an outer side (29) situated opposite the delivery duct (4), bears against a stop (9) when the pressure in the delivery duct (4) lies in a predefined operating pressure range (11), wherein on the outer side
(29) there is provided a spring element (8) which is designed to deform the flexible wall portion (7) such that the overall volume (20) of the delivery duct (4) is reduced in size when the pressure in the delivery duct (4) is lower than a threshold pressure (31).
Delivery device (1) according to Claim 1, wherein a return line (26) which can be closed off by a return valve (21) branches off from the delivery duct (4) downstream of the pump (5) in the delivery direction (6).
Delivery device (1) according to one of the preceding claims, wherein at least one force sensor (14) is arranged on the stop (9), which force sensor can measure a force exerted on the stop (9) by the flexible wall portion (7), in order thereby to determine a pressure in the delivery duct (4).
Delivery device (1) according to one of the preceding claims, wherein the pump (5) has a pump outlet (15) and the delivery duct (4) has a chamber (16) downstream of the pump outlet (15) in the delivery direction (6), the pump outlet (15) opens into the chamber (16), and the flexible wall portion (7) is arranged on the chamber (16) opposite the pump outlet (15). Delivery device (1) according to one of the preceding claims, wherein the stop (9) has a receptacle (30) in which the spring element (8) is accommodated when the flexible wall portion (7) bears against the stop (9).
Delivery device (1) according to one of the preceding claims, wherein the spring element (8) exerts on the flexible wall portion (7) a spring force which corresponds to a pressure of 0.2 to 1.0 bar in relation to the surface area (23) of the flexible wall portion (7) when the flexible wall portion (7) bears against the stop (9).
Method for compensating the formation of ice in a delivery device (1) which has an overall volume (20), which is at least partially filled with liquid additive, of a delivery duct (4), having at least the following steps:
a) stoppage of the operation of a pump (5) of the delivery device
(1) ;
b) opening of a return valve (21) of a return line (26) which produces a connection between the delivery duct (4) and a tank
(2) for the liquid additive;
c) active reduction in size of the overall volume (20) filled with liquid additive;
d) discharging of liquid additive through the return valve (21) into the tank (2); and
e) passive increasing of the overall volume (20) as the liquid additive in the delivery duct (4) freezes.
Motor vehicle (24) having an internal combustion engine (25), an exhaust-gas treatment device (3) for the purification of the exhaust gases of the internal combustion engine (25), a tank (2) for a liquid additive, and a delivery device (1) according to one of Claims 1 to 7, which delivery device is designed to deliver liquid additive from the tank (2) to the exhaust-gas treatment device (3).
EP12783946.2A 2011-11-16 2012-10-31 Delivery device for delivering a liquid additive out of a tank and method therefore Withdrawn EP2780562A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102011118628 2011-11-16
PCT/EP2012/071530 WO2013072191A1 (en) 2011-11-16 2012-10-31 Delivery device for delivering a liquid additive out of a tank and method therefore

Publications (1)

Publication Number Publication Date
EP2780562A1 true EP2780562A1 (en) 2014-09-24

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EP12783946.2A Withdrawn EP2780562A1 (en) 2011-11-16 2012-10-31 Delivery device for delivering a liquid additive out of a tank and method therefore

Country Status (6)

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US (1) US20140245723A1 (en)
EP (1) EP2780562A1 (en)
JP (1) JP6148244B2 (en)
KR (1) KR101606762B1 (en)
CN (1) CN103930659A (en)
WO (1) WO2013072191A1 (en)

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KR101606762B1 (en) 2016-03-28
JP2015501899A (en) 2015-01-19
WO2013072191A1 (en) 2013-05-23
US20140245723A1 (en) 2014-09-04
RU2014123986A (en) 2015-12-27
KR20140082775A (en) 2014-07-02
JP6148244B2 (en) 2017-06-14
CN103930659A (en) 2014-07-16

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