WO2014086518A1

WO2014086518A1 - Metering device

Info

Publication number: WO2014086518A1
Application number: PCT/EP2013/070874
Authority: WO
Inventors: Christian Bayer; Volker Reusing; Chris Weirauch
Original assignee: Robert Bosch Gmbh
Priority date: 2012-12-03
Filing date: 2013-10-08
Publication date: 2014-06-12
Also published as: DE102012222040A1

Abstract

The invention relates to a metering device for a medium into a line, in particular for fuel into an exhaust pipe (1) upstream of an oxidation catalyst, comprising a supply system (2), a metering unit (5) for the medium into the line, wherein between the supply system (2) and the metering unit (5) a throttle (12) is arranged. According to the invention, a metering device and a method for operating a metering device are disclosed, which keep the effects of pressure fluctuations in the metering device on a quantity of a medium introduced into a line by a metering unit (5) of the metering device at a low level. This is achieved, because the throttle is a variable throttle (12).

Description

Title:

Eindosierungsvornchtung

The present invention relates to a metering device for a medium in a line, in particular for fuel in an exhaust pipe upstream of an oxidation catalyst, comprising a supply device and a metering unit for the medium in the conduit, wherein between the

Supply device and the metering unit, a throttle is arranged. Furthermore, the invention relates to a method for operating such a Dososvornchtung.

State of the art

Such a dosing device is known from DE 10 2008 040 463 A1. This metering apparatus is for metering fuel into an exhaust pipe of an internal combustion engine upstream of an engine

Exhaust pipe built-in oxidation catalyst designed. The

Einosierungsvornchtung has a supply device that the

Supplying fuel from a tank to a metering unit, which in turn meters the supplied fuel and supplies the metered quantity to the injection unit, which feeds the fuel into the exhaust pipe.

Alternatively, the optionally existing supply device of the high pressure pump of the injection system of the corresponding internal combustion engine can be used for fuel supply.

Such a dosing device is used primarily in internal combustion engines to effect a reduction of harmful exhaust gas components in the exhaust gas of the internal combustion engine. This includes that one

Regeneration of harmful exhaust gas components receiving devices, such as a soot filter, must be made possible. So has such Einosierungsvornchtung next to a connected to a storage tank supply means a metering unit and an injection unit with an injection valve, which is installed in an exhaust pipe of the internal combustion engine and wherein injected through the injection valve fuel in the exhaust pipe to regenerate, for example, a diesel particulate filter. That's it

Injector valve preferably disposed in front of an oxidation catalyst and injects a precisely metered amount of fuel before the oxidation catalyst in the exhaust pipe. As a result, the exhaust gas temperature rises when flowing through the oxidation catalyst significantly, so that in the downstream

Particle filter stored soot burns off. By varying the flow rate of fuel through the metering device controlled by the metering unit, the temperature change in the exhaust gas line caused by the injected fuel is varied according to current requirements.

It is an object of the present invention to provide a metering apparatus and method for operating a metering apparatus which minimizes the effects of pressure variations in the metering apparatus on an amount of a medium introduced into a conduit from a metering unit of the metering apparatus.

Disclosure of the Invention Advantages of the Invention

This object is achieved in that the throttle is a variable throttle. The corresponding method for operating the metering device provides that a between the supply device and the

Adjusting unit arranged variable throttle is adjusted so that between the supply device and the metering unit, a low pressure drop and at least approximately constant pressure prevails. This refinement and this method are based on the knowledge that the pressure of the medium in the supply device can be subject to considerable fluctuations, so that it is both just above the permissible minimum inlet pressure and significantly above the permissible maximum inlet pressure to the metering unit lies. This results in high pressure in the supply device, a very large overflow, which must be returned via a dedicated return line in a tank. Cause is that the

Diameter of the throttle before the metering unit must be chosen so large that at minimum pressure in the supply device at a

closed in the return line built-in overflow valve of one of the metering unit downstream injection device

Pressure drop caused by the amount of injected fuel flowing through must be so small that the minimum inlet pressure to the metering unit is not undershot. A correspondingly large diameter has the consequence that, if a large pressure drop is required, because the pressure in the supply device is well above the maximum permissible supply pressure to the metering unit, a large amount flow back into the tank via the throttle and thus via the overflow valve got to. This amount is unnecessarily promoted, or can not be provided depending on the delivery of a pump associated with the supply device. Since according to the invention, the throttle in front of the metering unit with an example variable

Diameter or throttle cross-section is performed, depending on the required pressure drop, a larger or smaller diameter can be adjusted. Thus, it is possible to keep the pressure drop sufficiently small at a low pressure in the supply device, without causing a large overflow at high supply pressure. Here is the embodiment of the invention or the

inventive method suitable for all media to be fed into a line. However, the object of the invention is preferably used in an exhaust aftertreatment system of an internal combustion engine, in which fuel is injected into an exhaust line of the internal combustion engine upstream of an oxidation catalyst to achieve the effects described above by means of the dosing device.

In a further development of the invention, the throttle is inserted into a connecting line between the supply device and the metering unit.

In principle, the variable throttle can also be installed in the supply device or the metering unit. The installation in the connecting line between the mentioned components has proved to be particularly useful.

In a further development of the invention, the variable throttle is a switchable

Stage throttle and / or the variable throttle has a continuously adjustable throttle cross-section. In the design of the throttle as a stage throttle, this preferably has two flow cross sections, between which can be switched. In the embodiment of the throttle with a continuously adjustable throttle cross section, the adjustment of the flow cross-section via a suitable actuator, for example via an electromagnet. In this case, the throttle and the function of a shut-off valve or the correspondingly controlled shut-off valve can take over the function of the throttle. Normally, the shut-off valve completely shuts off or enables the supply of fuel to the metering unit.

In a further embodiment of the invention, an overflow device is arranged downstream of the throttle. The overflow device is in turn in another embodiment, an overflow valve or a Überströmdrossel. Furthermore, the overflow device in the connecting line between the supply device and the metering unit or directly into the

Be integrated with the metering unit. In the case of integration of the overflow in the metering unit, this may be mounted in front of a built-in metering valve or between the shut-off valve and a downstream metering valve of the metering unit. In the case of the formation of the overflow as Überströmdrossel always flows at low pressure always a certain amount of the medium back into a return. Due to the variable throttle in the inlet to the metering unit, however, this amount can be kept as low as possible in all operating points.

In the event that the variable throttle the switching valve - or vice versa - replaced, the throttle can also be formed by a high-frequency modulated switching valve, by constantly opening and closing of the switching valve or by a variation of the ratio of the open and closed time of the switching valve a variable throttle is modeled. Further advantageous embodiments of the invention are the

Drawing description can be seen in the embodiments illustrated in the figures of the invention are described in more detail.

Brief description of the drawings

Show it:

Figure 1 shows a schematic representation of a first embodiment of a

Dosing device according to the invention,

FIG. 2 a schematic representation of a second embodiment of a metering device according to the invention,

3 shows a schematic representation of a third embodiment of a

Dosing device according to the invention,

Figure 4 shows a schematic representation of a fourth embodiment of a

Dosing device according to the invention, and

Figure 5 shows a schematic representation of a fifth embodiment of a metering device according to the invention.

Embodiments of the invention

Figure 1 shows a schematic representation of a metering device for fuel in an exhaust pipe 1 of an internal combustion engine. Of the

Internal combustion engine is preferably supplied by means of a common rail injection system fuel, in particular with diesel fuel, and is operated as a self-igniting internal combustion engine. The internal combustion engine has an exhaust system with an exhaust pipe 1, through which the resulting in the combustion of fuel and combustion air exhaust gases are derived. To reduce harmful components of the exhaust gas, an exhaust aftertreatment device is installed in the exhaust pipe 1, for example, a

Oxidation catalyst and an oxidation catalyst downstream Soot filter included. In the soot filter are in the exhaust gas of the

Internal combustion engine entrained soot deposited, which must be disposed of as needed. For this purpose, by means of a metering device fuel into the exhaust pipe 1, which causes chemical reactions in the oxidation catalyst, which cause, inter alia, a temperature increase of the exhaust gas. This temperature increase of the exhaust gas triggers a burning off process of the deposited soot in the particle filter, so that the particle filter is regenerated again. The metering device has a supply device 2, which, for example by means of a pump fuel from a tank 3, the

Preferably, the fuel tank of the internal combustion engine is in one

Connecting line 4 between the supply device 2 and a

Metering unit 5 promotes. The metering unit 5 determines the amount of fuel that is supplied to an injection unit 6 and in particular has an injection valve 7, which has at least one opening into the exhaust pipe 1 injection opening. During operation of the metering device is thus controlled or controlled fuel through the injection valve 7 in the

Injected exhaust pipe 1.

The metering unit 5 has on the input side an electrically actuated switching valve 8, the electrical actuation of which is reproduced by the symbols shown below the switching valve. To the switching valve 8 includes a pressure and temperature sensor 9, whose signal line with a

Control device for the metering device is connected. On the

Pressure and temperature sensor 9 follows downstream in a fuel cell crossing the metering unit a metering valve 10, which in turn is electrically operated. With the metering valve 10, the injection unit 6 and the injection valve 7 supplied amount of fuel is adjusted. To the metering valve 10 includes a pressure sensor 1 1, which measures the pressure of the fuel, wherein the corresponding signal is again guided to the control device and evaluated in this. Alternatively, a system with only one or no pressure sensor is possible. In this case, the pressure information necessary for the dosage and diagnosis must be derived from other available sensor signals. Between the supply device 2 with the pump is in the

Connecting line 4 to the metering unit 5, the inventively constructed variable throttle 12 installed, which also - as can be controlled electrically or electromagnetically by the reproduced below the throttle 12 symbols. In this case, the throttle 12 may be formed so that the throttle cross section or the flow area can be adjusted continuously through the throttle 12 or the throttle 12 is as

Stage throttle formed in the example, two flow cross-sections are fixed adjustable. Optionally, the throttle is also designed so that the setting of more than two flow cross sections is possible.

Downstream of the throttle 12, an overflow line 13 branches off from the connecting line 4, wherein an overflow valve 14 is installed in the overflow line 13. The overflow line 13 in turn opens into the tank. 3

With the throttle 12, depending on the required pressure drop in the

Connecting line 4 are set a larger or smaller diameter, so that it is possible at a low of the

Supply device 2 provided fuel pressure to keep the pressure drop sufficiently small, without being at a high of the

Supply device 2 generated supply pressure a large

Overflow is caused, which must be passed through the overflow 13 and the spill valve 14 back into the tank 3.

In the embodiment according to FIG. 2, the overflow line 13 and the overflow valve 14 are integrated into the metering unit 5 upstream of the switching valve 8, the tank 3 and a corresponding tank line

are of course arranged outside the metering unit. The further construction and the further function of this exemplary embodiment, as with the still following figures (with the exception of the differences described), are identical to those previously described with reference to FIG

Eindosierungsvorrichtung. In the embodiment according to FIG. 3, the overflow line 13 and the overflow valve 14 are arranged between the switching valve 8 and the metering valve 10 in front of the pressure and temperature sensor 9.

In the exemplary embodiment according to FIG. 4, the overflow line 13, instead of an overflow valve, has an overflow throttle 15, which is arranged in front of or inside the metering unit 5. In this case, even at low pressure, a certain amount of fuel always flows back into the tank 3 via the overflow line 13. In this variant, the throttle 12 can also be designed as a fixed throttle if the inlet pressure is only subject to slight fluctuations. Only in this case, the diameter of the throttle 12 and the overflow throttle 15 can be optimally matched to each other. In particular, in this embodiment, the throttle 12 may also be integrated into the metering unit 5.

In the embodiment according to FIG. 5, the variable throttle 12 is integrated in the switching valve 8. In this case, the switching valve 8 forming the throttle 12 is designed as a valve with a variable flow cross-section, which can be set correspondingly electrically or electromagnetically. For example, but also an existing switching valve 8 can be controlled modulated high frequency, so that by constant opening and closing of the switching valve 8, the variable throttle 12 is modeled.

It should be noted that in the context of the invention, any combinations of the described embodiments are optionally possible and provided only with Teilmarkmalen.

Claims

claims

1 . Metering device for a medium in a line, in particular for fuel in an exhaust pipe (1) upstream of a

Oxidation catalyst, comprising a supply device (2), a metering unit (5) for the medium in the line, wherein between the

Supply device (2) and the metering unit (5) a throttle (12) is arranged,

characterized in that the throttle (12) is a variable throttle (12).

2. metering device according to claim 1,

characterized in that the throttle (12) in a connecting line (4) between the supply device (2) and the metering unit (5) is inserted.

3. metering device according to claim 1 or 2,

characterized in that the throttle (12) is a switchable stage throttle.

4. metering device according to one of claims 1 to 3, characterized in that the throttle (12) has a continuously adjustable throttle cross-section.

5. metering device according to one of the preceding claims, characterized in that downstream of the throttle (12) has a

Overflow device is arranged.

6. metering device according to claim 5,

characterized in that the overflow device is an overflow valve (14).

7. metering device according to claim 5,

characterized in that the overflow device is an overflow throttle (15).

8. metering device according to one of claims 5 to 7, characterized in that the overflow in the

Connecting line (4) is inserted.

9. metering device according to one of claims 5 to 7, characterized in that the overflow device is integrated in the metering unit (5).

10. A method for operating a metering device for a medium in a line, in particular for fuel in an exhaust pipe (1)

upstream of an oxidation catalyst comprising a

Supply device (2) and a metering unit (5) for the medium in the line, wherein between the supply device (2) and the metering unit (5), a throttle is arranged,

characterized in that between the supply device (2) and the metering unit (5) arranged variable throttle (12) is adjusted so that between the supply device (2) and the metering unit (5) has a low pressure drop and at least approximately constant pressure.