WO2019223927A1

WO2019223927A1 - Fluid-conveying device for a freezable fluid, metering system and method for operating a fluid-conveying device

Info

Publication number: WO2019223927A1
Application number: PCT/EP2019/058811
Authority: WO
Inventors: Yihao Zhu; Ralf Gragen; Mohan Kumar Kuppusamy
Original assignee: Robert Bosch Gmbh
Priority date: 2018-05-23
Filing date: 2019-04-08
Publication date: 2019-11-28
Also published as: DE102018208112A1

Abstract

The invention relates to a fluid-conveying device (1) for a freezable fluid, in particular for an aqueous urea solution for the post-treatment of exhaust gases of an internal combustion engine, comprising a compression chamber (2), an inlet valve (3) for connecting the compression chamber (2) to a fluid tank (4), and an outlet valve (5) for connecting the compression chamber (2) to a metering module (6). According to the invention, the inlet valve (3) and the outlet valve (5) are designed as electrically actuatable, normally closed valves. The invention also relates to a metering system comprising a conveying device of this type, as well as a method for operating a fluid-conveying device of this type.

Description

description

Title:

Fluid delivery device for a freezable fluid, dosing system and method for

Operating a fluid delivery device

The invention relates to a fluid delivery device for a free-flowing fluid, in particular for an aqueous urea solution for the aftertreatment of exhaust gases of an internal combustion engine, having the features of the preamble of claim 1. The invention further relates to a metering system with such a fluid delivery device and a method for operating a corresponding fluid delivery device.

In the after-treatment of exhaust gases of an internal combustion engine, an aqueous urea solution is metered into an exhaust gas tract of the internal combustion engine. The aqueous urea solution causes the formation of ammonia in the exhaust tract, which reacts with the nitrogen oxides contained in the exhaust gas in a downstream catalyst to harmless nitrogen and water. This process is also known as selective catalytic reduction. The nitrogen oxide emissions of

Internal combustion engine, in particular in a diesel fuel operated

Internal combustion engine, can be significantly reduced in this way.

However, a disadvantage of the aqueous urea solution is that it at

Temperatures of less than -11 ° C freezes and expands. In order to protect lines and components of a metering system filled with aqueous urea solution from ice pressure, they are emptied when the internal combustion engine is at a standstill.

State of the art

The published patent application DE 10 2007 057 446 A1 discloses a fluid delivery device for freezing liquids, such as, for example, a urea-water solution, which can be emptied by reversing the conveying direction. The conveyor, preferably a pump, has for this purpose a valve device with a first and a second check valve and a pneumatic or electric

controllable actuator on. When controlling the actuator, the reverse direction of the two check valves changes, so that the urea-water solution in the for

Main conveying direction is promoted reverse direction.

Based on the above-mentioned prior art, the present invention has for its object to provide a fluid delivery device for a freezable fluid, which is operable in a main conveying direction and in a direction opposite to the main conveying direction, to allow a back suction of fluid.

The fluid delivery device should be as simple as possible, in particular a separate valve for reversing the conveying direction should be saved. In addition, a variation of the flow rate should be possible.

The object is achieved by the fluid delivery device with the features of claim 1, the metering system with the features of claim 5 and the method for operating a fluid delivery device with the features of

Claim 6. Advantageous developments of the invention are the respective

Subclaims refer.

Disclosure of the invention

The proposed fluid delivery device for a freezable fluid, in particular for an aqueous urea solution for the aftertreatment of exhaust gases

Internal combustion engine, comprising a compression chamber, an inlet valve for

Connection of the compression chamber with a fluid tank and an outlet valve for connecting the compression chamber with a metering module. According to the invention, the inlet valve and the outlet valve are electrically operated, de-energized

closed valves executed.

In contrast to the prior art, therefore, the inlet valve and the outlet valve in the delivery mode are not actuated by the applied fluid pressure, but actively activated. The inlet valve and the outlet valve can thus targeted be opened or closed. To reverse the direction of the

To effect fluid delivery, therefore, only the control of the two valves must be changed. In the suction mode, instead of the inlet valve

Exhaust valve opened, allowing fluid from the dosing module back into the

Compression space is sucked. Is the compression space with fluid from the

Dosing module filled, the exhaust valve is closed to then open the inlet valve. The sucked-back fluid is then conveyed back into the fluid tank via the inlet valve.

The active control of the intake valve and the exhaust valve also has the advantage that in each case over the opening time, the opening duration and / or the closing time, the delivery rate of the fluid flow rate is adjustable. This means that the flow rate can be varied as needed.

The fluid delivery device can also be constructed comparatively simple. For example, this may be a simple pump, which itself knows only one conveying direction. Because if necessary, the reversal of the conveying direction is effected by means of the actively controllable valves, which is the inlet valve and the outlet valve. A separate valve for reversing the conveying direction is not required. Correspondingly simple, accordingly, the drive of the pump can be carried out.

In each case, an actuator is assigned to the inlet valve and the outlet valve, so that both valves can be electrically actuated or controlled independently of one another. The actuator may for example be designed as a magnetic actuator or piezoelectric actuator. The electrical actuation by means of such an actuator has the advantage that the heat generated during operation of the actuator for heating the fluid can be used so that it thaws faster at low temperatures or does not even freeze.

Further preferably, the inlet valve and the outlet valve each have a reciprocating valve member which is biased by the spring force of a spring in the direction of a valve seat. Closing the inlet valve and the Exhaust valve can therefore be effected in a simple manner by means of the spring force of the respective spring.

The compression space preferably has a movable boundary wall which is formed by a reciprocating piston or an elastically deformable membrane. Accordingly, this may in particular be a piston pump or a diaphragm pump in the case of the fluid delivery device. These are particularly robust and compact at the same time. The drive can be easily by a rotating drive or Hubmitel, for example a

Solenoids, are effected.

Since the preferred field of application of the fluid delivery device according to the invention is the exhaust aftertreatment, a metering system for metering in a free-flowing fluid, in particular an aqueous urea solution, into a

Exhaust tract of an internal combustion engine proposed. The proposed

Metering system comprises a fluid tank, a metering module and a fluid delivery device according to the invention. The fluid delivery device is arranged between the fluid tank and the metering module in order to convey fluid from the fluid tank in the direction of the metering module during the delivery operation. With the help of the metering module, the fluid can then be metered into an exhaust tract of an internal combustion engine. When turned off

Internal combustion engine, the fluid delivery device according to the invention can be used to empty the dosing system to prevent damage by ice pressure.

In addition, a method for operating a fluid delivery device for a freezable fluid, in particular for an aqueous urea solution to

Aftertreatment of exhaust gases of an internal combustion engine proposed. The

Fluid delivery device comprises a compression chamber, an inlet valve for connecting the compression chamber with a fluid tank and an outlet valve for connecting the compression chamber with a metering module. According to the invention, the intake valve and the exhaust valve are electrically operated alternately in the conveying mode. This means that the inlet valve and the outlet valve are each actively activated in the delivery mode of the fluid delivery device, so that in particular the opening can be effected independently of the applied fluid pressure. To fill the compression chamber, the inlet valve is initially actively activated or opened while the exhaust valve remains closed. In this way, in the suction operation of the fluid conveyor fluid from the fluid tank in the

Suction compression space. After filling the compression space and closing the inlet valve, the outlet valve is opened to supply the fluid to the dosing module. To change the conveying direction to fluid from the

The metering module is sucked back into the fluid tank, the intake valve and the exhaust valve are electrically operated in reverse order in alternation. Instead of the inlet valve, the outlet valve is initially activated or opened while the inlet valve remains closed. In this way, in the suction operation of the fluid conveyor fluid from the dosing back into the

Suction compression space. Subsequently, the outlet valve is closed and the inlet valve is opened, so that the fluid is conveyed from the compression space back into the fluid tank.

For carrying out the method, in particular the inventive

Can be used fluid delivery, since the inlet valve and exhaust valve are actively controlled.

Preferably, the inlet valve and the check valve are each electrically actuated by an actuator, preferably a magnetic actuator or a piezoelectric actuator. Since each valve is assigned its own actuator, these can be controlled independently of each other. Furthermore, depending on the Bestrom ungsart - the effective direction of an actuator can be changed to assist the closing of a valve, while the other valve is opened via the other actuator. The heat generated when using a magnetic actuator or a piezoelectric actuator can also be used to heat the fluid, so that it thaws at low temperatures or does not even freeze.

By energizing an actuator is preferably a reciprocating valve member of the intake valve or the exhaust valve against the spring force of a spring lifted from a valve seat. The spring force of the spring can then be used to close the intake valve or exhaust valve. By reversing the direction of action of the actuator closing can also be actively supported. In the conveying mode of the fluid delivery device, the delivery rate is preferably set via the beginning, the duration and / or the end of the energization of the actuators, in particular of the actuator assigned to the inlet valve. For example, the opening of the intake valve may be delayed. Alternatively or additionally, the

Closing time of the intake valve are moved so that the intake valve is closed only after completion of the suction phase. That way, one becomes

Subset of the fluid from the compression chamber via the inlet valve pushed out again, so that the flow rate is reduced. The flow rate is thus adjustable as needed.

The actuators, in particular the actuator associated with the inlet valve, are preferably energized offset in time from the reversal of the direction of movement of the compression space delimiting a movable boundary wall. The direction of movement of the boundary wall determines whether the fluid delivery device is in the suction phase or in the delivery phase. In the suction phase, the boundary wall performs a movement which leads to an increase in the volume of the compression space. In the conveying phase, the boundary wall moves in the reverse direction and thus leads to a reduction of the volume. This changes the pressure conditions in the compression chamber. Because the inlet valve and the

Each exhaust valve are actively controlled, the opening and closing of the valves can be effected regardless of the position of the boundary wall and thus regardless of the prevailing fluid pressure in the compression chamber. Thus, it is possible to effect the opening and / or closing offset in time, in particular delayed.

The movable boundary wall can be formed by a reciprocating piston or by an elastically deformable membrane. In the case of a membrane, the opening of the valves that is offset in time from the reversal of the direction of movement of the membrane, in particular delayed, uses the fact that the membrane can initially reorient itself.

The movement of the boundary wall is preferably effected by a rotating drive or by lifting means, for example a lifting magnet. For example, the rotary drive may be a cam or eccentric drive via which a piston is moved back and forth. This drive form has proven itself in fluid conveyors. The reciprocating movements of a piston or a membrane can also be effected in a simple manner by means of a lifting magnet. The drive types mentioned are robust and easy and inexpensive to implement.

A preferred embodiment of the invention will be described below with reference to the drawings. These show:

1 is a schematic representation of a dosing system,

2 shows a schematic representation of the fluid delivery device of the metering system of FIG. 1 during the suction phase during conveying in the main conveying direction, FIG.

3 shows a schematic representation of the fluid delivery device of FIG. 2 during the delivery phase during conveying in the main conveying direction, FIG.

2 during the suction phase during conveying in a conveying direction opposite to the main conveying direction, FIG.

2 during the conveying phase during conveying in a conveying direction opposite to the main conveying direction, FIG.

6 shows a section through the conveying device of the dosing system of FIG. 1, and FIG. 7 shows a diagram for clarifying the control strategy of the valves. Detailed description of the drawings

The dosing system shown schematically in FIG. 1 comprises a fluid tank 4, in which a freezable fluid, in the present case an aqueous urea solution for

Exhaust gas aftertreatment, is stored. The fluid tank 4 is via a first

Fluid line 16 is connected to a fluid conveyor 1. Of the Fluid delivery device 1 leads a further fluid line 17 to a metering module 6, by means of which the fluid in an exhaust gas tract 18 of an internal combustion engine (not shown) can be metered.

Based on the following figures, the fluid conveying device 1 of

Dosing of Fig. 1 and its operation described in more detail.

The fluid delivery device 1 shown in FIG. 2 has a compression space 2 whose volume can be changed. With increasing volume, the fluid delivery device 1 is in a suction phase, with decreasing volume in a delivery phase.

During the suction phase, fluid is sucked out of the fluid tank 4 into the compression space 2 via an opened inlet valve 3. At the same time, an exhaust valve 5 is closed. To open the inlet valve 3, an actuator 7 is energized, which causes an opening force which is greater than the spring force of a force acting in the closing direction of the spring 11 of the inlet valve 3. Thus, the valve opens and releases a valve seat 13, via which the fluid can flow into the compression space 2. In this way, the compression space 2 fills with the fluid.

During the delivery phase, shown in FIG. 3, the energization of the actuator 7 is terminated so that the spring 11 closes the inlet valve 3. To open the

Exhaust valve 5, an actuator 8 is now energized, which causes an opening force which is greater than the spring force of a force acting in the closing direction spring 12 of

Exhaust valve 5 is. Thus, the outlet valve 5 opens and releases a valve seat 14, via which the fluid can flow out of the compression space 2 in the direction of the dosing module 6.

When the internal combustion engine is switched off, the dosing system is emptied in order to prevent damage by ice pressure at low temperatures, since the aqueous urea solution freezes at temperatures below -11 ° C. The emptying is with the help of

Inlet valve 3 and the exhaust valve 5 causes by these are actively driven in reverse order. For emptying, the outlet valve 5 is opened during a suction phase of the fluid delivery device 1, shown in FIG. 4, so that fluid flows back into the compression space 2 via the fluid line 17 and the valve seat 14. Opening the

Exhaust valve 5 is effected by energizing its associated actuator 8, which provides the required opening force. The inlet valve 3 remains closed during this time.

During the subsequent delivery phase, shown in FIG. 5, the inlet valve 3 is opened when the outlet valve 5 is closed. For this purpose, the actuator 7 associated with the inlet valve 3 is energized. When the inlet valve 3 is open, the fluid flows from the compression space 2 via the valve seat 13 and the fluid line 16 back into the fluid tank 4.

A possible embodiment of the fluid delivery device 1 shown only schematically in FIGS. 1 to 5 can be seen in FIG. The compression chamber 2 is the volume change by a movable

Limiting wall 15 limited, which in the present case is formed by an elastically deformable membrane. The compression chamber 2 is on the one hand via an actively controllable inlet valve 3 and a fluid line 16 with a fluid tank 4 (not shown) connectable. On the other hand, the compression chamber 2 via an actively controllable outlet valve 5 and a fluid line 17 with a metering module (not shown) connectable. For active control, both valves 3, 5 each have an actuator 7, 8, which is embodied here as a magnetic actuator. When energizing an actuator 7, 8, a magnetic field is generated, the magnetic force acts on a reciprocating valve member 9, 10 in such a way that it against the

Spring force of an associated spring 11, 12 is lifted from a valve seat 13, 14. Valve seat side, the valve members 9, 10 are each provided with a sealing body 19, 20 made of an elastomeric material to optimize the sealing seat.

The drive strategy according to the invention will be explained again with reference to FIG. The curve 21 shows the cyclical reciprocating movements of the

Compression space 2 delimiting boundary wall 15. While the curve 21 is increasing, the fluid delivery device 1 is in a suction phase, with decreasing curve 21 in a delivery phase. During a suction phase, the inlet valve 3 actively open while the exhaust valve 5 remains closed, so that the compression chamber 2 fills with fluid from the fluid tank 4. To open the

Inlet valve 3, the actuator 7 is energized, the energization with a slight time delay or shortly after entering the suction phase takes place (see curve 22).

During the subsequent delivery phase, the outlet valve 5 is opened while the inlet valve 3 remains closed in order to supply the fluid from the compression space 2 to the dosing module 6. To open the exhaust valve 5, the actuator 8 is energized, the energizing de actuator 8 only after the energization of the actuator 7 has been completed (see curve 23). This means that the actuators 7, 8 are each energized alternately and at time intervals.

In order to effect a reversal of the conveying direction, the curves 22, 23 need only be reversed.

Claims

claims

1. fluid conveying device (1) for a freezable fluid, in particular for an aqueous urea solution for the aftertreatment of exhaust gases

An internal combustion engine, comprising a compression chamber (2), an inlet valve (3) for connecting the compression chamber (2) to a fluid tank (4) and a

Exhaust valve (5) for connecting the compression chamber (2) with a

Dosing module (6),

characterized in that the inlet valve (3) and the outlet valve (5) are designed as electrically actuated, normally closed valves.

2. fluid delivery device (1) according to claim 1,

characterized in that the inlet valve (3) and the outlet valve (5) in each case an actuator (7, 8) is assigned, preferably as a magnetic actuator or

Piezoelectric actuator is executed.

3. fluid delivery device (1) according to claim 1 or 2,

characterized in that the inlet valve (3) and the outlet valve (5) each have a reciprocating valve member (9, 10) biased by the spring force of a spring (11, 12) in the direction of a valve seat (13, 14) is.

4. fluid conveying device (1) according to one of the preceding claims,

characterized in that the compression space (2) has a movable

Boundary wall (15) which is formed by a reciprocating piston or an elastically deformable membrane.

5. metering system for metering a freezable fluid, in particular an aqueous urea solution, into an exhaust tract of an internal combustion engine, comprising a fluid tank (4), a metering module (6) and a fluid delivery device (1) according to one of the preceding claims.

6. A method for operating a fluid conveying device (1) for a freezable fluid, in particular for an aqueous urea solution for after-treatment of exhaust gases of an internal combustion engine, comprising a compression chamber (2), an inlet valve (3) for connecting the compression chamber (2) to a fluid tank ( 4) and an outlet valve (5) for connecting the compression space (2) with a metering module (6),

characterized in that in the conveying operation, the inlet valve (3) and the outlet valve (5) are electrically operated alternately and the inlet valve (3) and the outlet valve (5) are electrically operated alternately in reverse order to change the conveying direction.

7. The method according to claim 6,

characterized in that the inlet valve (3) and the check valve (5) in each case by an actuator (7, 8), preferably a solenoid actuator or a piezoelectric actuator, electrically actuated, preferably by the energization of an actuator (7, 8) on a - And herbewegliches valve member (9, 10) against the spring force of a spring (11, 12) from a valve seat (13, 14) is lifted.

8. The method according to claim 6 or 7,

characterized in that in the conveying mode over the beginning, the duration and / or the end of the energization of the actuators (7, 8), in particular of the inlet valve (3) associated actuator (7), the delivery rate is set.

9. The method according to any one of claims 6 to 8,

characterized in that the actuators (7, 8), in particular the the

Inlet valve (3) associated actuator (7), offset in time to the reversal of

Direction of movement of the compression space (2) limiting movable boundary wall (15) are energized.

10. The method according to any one of claims 6 to 9,

characterized in that the movement of the boundary wall (15) by a rotating drive or by lifting means, for example a lifting magnet, is effected.