GB2576925A

GB2576925A - A pump module for a dosing system and a non-return valve assembly therefor

Info

Publication number: GB2576925A
Application number: GB1814559.9A
Authority: GB
Inventors: Zhou Larry; Wang Fei; Shi Brice
Original assignee: Delphi Technologies IP Ltd
Current assignee: Delphi Technologies IP Ltd
Priority date: 2018-09-07
Filing date: 2018-09-07
Publication date: 2020-03-11
Anticipated expiration: 2038-09-07
Also published as: WO2020049131A1; GB2576925B; GB201814559D0

Abstract

A pump module (20, fig 1) for an SCR dosing system (2, fig 1) provides reagent to an exhaust system (6, fig 1), with an SCR catalyst (16, fig 1), of an internal combustion engine (4, fig 1). A pump assembly (32, fig 2) pumps regent through a supply line (26, fig 1) from a tank (18, fig 1) to a dosing module (22, fig 1) and pumps excess reagent through a return line (28, fig 1) back to the tank. A non-return valve assembly (36, fig 2) within the return line has a first body (52, fig 5) comprising a valve seat 64 at the end of an inlet passage 60, and a second body (56, fig 5) comprising an outlet passage 70. A valve chamber 84 defined between the first and second bodies is in fluidic communication with the inlet and outlet passages. A deformable valve member 54 within the valve chamber deforms between a closed position, biased into engagement with the valve seat to seal the inlet passage, and an open position, held from the valve seat to permit a flow of reagent through the valve chamber from the inlet passage to the outlet passage.

Description

(54) Title of the Invention: A pump module for a dosing system and a non-return valve assembly therefor Abstract Title: A pump module for a dosing system and a non-return valve assembly therefor (57) A pump module (20, fig 1) for an SCR dosing system (2, fig 1) provides reagent to an exhaust system (6, fig 1), with an SCR catalyst (16, fig 1), of an internal combustion engine (4, fig 1). A pump assembly (32, fig 2) pumps regent through a supply line (26, fig 1) from a tank (18, fig 1) to a dosing module (22, fig 1) and pumps excess reagent through a return line (28, fig 1) back to the tank. A non-return valve assembly (36, fig 2) within the return line has a first body (52, fig 5) comprising a valve seat 64 at the end of an inlet passage 60, and a second body (56, fig 5) comprising an outlet passage 70. A valve chamber 84 defined between the first and second bodies is in fluidic communication with the inlet and outlet passages. A deformable valve member 54 within the valve chamber deforms between a closed position, biased into engagement with the valve seat to seal the inlet passage, and an open position, held from the valve seat to permit a flow of reagent through the valve chamber from the inlet passage to the outlet passage.

At least one drawing originally filed was informal and the print reproduced here is taken from a later filed formal copy.

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A PUMP MODULE FOR A DOSING SYSTEM AND A NON-RETURN VALVE ASSEMBLY THEREFOR

FIELD OF THE INVENTION

This invention relates to a pump module for a selective catalytic reduction (SCR) dosing system and in particular to a non-return valve assembly for the pump module.

BACKGROUND

An SCR dosing system is configured to provide a reagent, such as urea, to an exhaust gas stream of an internal combustion engine. The SCR dosing system generally comprises a tank module for storing reagent, a pump module and a dosing module comprising an atomiser for injecting reagent into the exhaust gas stream. Once the dosing is complete, the system is purged to move unused reagent back to the tank module. Any unused reagent left in the system after the system has been purged could crystallise causing parts of the system to clog-up. This can result in pressure fluctuations within the system and affect its dosing accuracy and/ or damage the system.

It is against this background that the invention has been devised.

STATEMENTS OF INVENTION

According to an aspect of the invention, there is provided a pump module for an SCR dosing system arranged to provide reagent to an exhaust gas stream of an internal combustion engine having an exhaust system with a SCR catalyst, the pump module comprising a pump assembly configured to pump regent through a supply line from a tank module to a dosing module and to pump excess reagent through a return line back to the tank module, wherein the pump module further comprises a non-return valve assembly positioned within the return line, the nonreturn valve assembly comprising: a first body comprising an inlet passage and a valve seat positioned at the end of the inlet passage; a second body comprising an outlet passage; a valve chamber defined between the first body and the second body, the valve chamber being in fluidic communication with the inlet and outlet passages; and, a deformable valve member received within the valve chamber, wherein the deformable valve member is configured to deform between a closed position, in which it is biased into engagement with the valve seat to seal the inlet passage, and an open position, in which it is held from the valve seat to permit a flow of reagent through the valve chamber from the inlet passage to the outlet passage when the pump assembly is pumping reagent through the supply line from the tank module to the dosing module.

Preferably, the deformable valve member of the non-return valve assembly is held between a surface of the first body and a surface of the second body.

Preferably, the deformable valve member of the non-return valve assembly comprises an elongate diaphragm arranged to traverse the end of the inlet passage.

Preferably, the inlet and outlet passages of the non-return valve assembly are eccentrically arranged relative to each other.

Preferably, the first body of the non-return valve assembly comprises a first plate section in which the inlet passage is formed and the second body of the nonreturn valve assembly comprises a second plate section in which the outlet passage is formed, wherein the first plate section is arranged above the second plate section to define the valve chamber and wherein the deformable valve member is clamped between a lower surface of the first plate section and an upper surface of the second plate section.

Preferably, the upper surface of the second plate section comprises a cavity in which the outlet passage is formed.

Preferably, the second plate section comprises an abutment means comprising an abutment surface configured to limit movement of the deformable valve member.

Preferably, the abutment means is located within the cavity in the upper surface of the second plate section.

Preferably, the lower surface of the first plate section of the non-return valve assembly comprises a cavity configured to receive the deformable valve member.

Preferably, the first body of the non-return valve assembly comprises a first cylindrical cap and the second body comprises a second cylindrical cap, the second cylindrical cap being received within the first cylindrical cap to define the valve chamber.

Preferably, the first cylindrical cap comprises a stop member configured to limit the extent to which the second cylindrical cap is received within the first cylindrical cap.

According to another aspect of the invention, there is provided a SCR dosing system for providing regent to an exhaust gas stream of an internal combustion engine having an exhaust system with a SCR catalyst comprising a pump module according to the previous aspect.

BRIEF DESCRIPTION OF DRAWINGS

The above and other aspects of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a schematic view of a SCR dosing system for use with the present invention;

Figure 2 is a schematic view of a pump module for use in the SCR dosing system of Figure 1;

Figure 3 is an illustration of a section of the pump module of Figure 2 showing the general arrangement of a pressure chamber and a non-return valve assembly;

Figure 4 is an example of a known non-return valve assembly;

Figure 5 is an exploded perspective view of a non-return valve assembly in accordance with the invention for use in the pump module of Figure 2;

Figure 6a is an underside view of a first body of the non-return valve assembly of Figure 5;

Figures 6b is a cross-sectional view of the first body of Figure 6a;

Figures 7a is an upper perspective view of a second body of the non-return valve assembly of Figure 5;

Figure 7b is a cross-sectional view of the second body of Figure 7a;

Figure 8 is a cross-sectional view of the non-return valve assembly of Figure 5;

Figure 9a is a cross-sectional view of the non-return valve assembly of Figure 5 when the pump module of Figure 2 is operating in a first operational state; and,

Figure 9b is a cross-sectional view of the non-return valve assembly of Figure 5 when the pump module of Figure 2 is operating in a second operational state.

In the drawings, like features are denoted by like reference signs.

SPECIFIC DESCRIPTION

The following description refers to the accompanying drawings that show, by way of illustration, specific details and embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilised and structural changes may be made without departing from the scope of the invention as defined in the appended claims. Moreover, references in the following description to “upper”, “lower” or any other terms having an implied orientation are not intended to be limiting, and refer only to the orientation of the features as shown in the accompanying drawings.

Figure 1 is a schematic illustration of a selective catalytic reduction dosing system (hereinafter, “the SCR dosing system”), generally designated by 2. The SCR dosing system 2 is operable to inject a quantity of reagent or reductant into an exhaust gas stream emitted from an internal combustion engine 4 (hereinafter, “the engine 4”). In this embodiment, the engine 4 is a compression-ignition combustion engine. An exhaust system, generally designated by 6, is coupled to the engine 4 for conveying exhaust gas emissions therefrom. The exhaust system 6 comprises first, second and third exhaust portions 8, 10, 12, together with a diesel particulate filter 14, disposed between the first and second exhaust portions 8, 10, and a selective catalytic reduction catalyst 16 (hereinafter, “the SCR catalyst 16”), disposed between the second and third exhaust portions 10, 12. The exhaust system 6 may also include a diesel oxidation catalyst (not shown) placed upstream from the diesel particulate filter 14, between the engine 4 and the first exhaust portion 8. During operation of the engine 4, exhaust gas emissions from the engine 4 enter the first exhaust portion 8, via the diesel oxidation catalyst if present, and pass through the diesel particulate filter 14, followed by the SCR catalyst 16 before exiting the exhaust system 6 via the third exhaust portion 12.

The SCR dosing system 2 generally comprises a tank module 18 for storing a supply of a suitable reagent, such as urea, a pump module 20 and a dosing module 22 operatively connected to the second exhaust portion 10. The dosing module 22 typically comprises an atomiser 23 for injecting reagent into the exhaust gas stream upstream of the SCR catalyst 16. The SCR dosing system 2 further comprises a series of connecting pipes through which reagent can pass under pressure created by the pump module 20, along with a dosing control unit 24 (hereinafter, “the DCU 24”) operatively coupled to the tank module 18, the pump module 20 and the dosing module 22. The connecting pipes comprises a supply line 26, connecting the tank module 18 to the dosing module 22 via the pump module 20, and a return line 28 for returning excess reagent from the pump module 20 to the tank module 18. The DCU 24 is operable to control the injection of reagent into the exhaust gas stream and the flow of reagent through the supply and return lines 26, 28, according to a reagent dosing strategy, and may comprise a processing means, such as a microprocessor, and a memory means for storing different reagent dosing strategies. The DCU 24 receives signals from various engine and vehicle mounted sensors, including an engine control unit (not shown), and uses these signals to determine an appropriate reagent dosing strategy. Alternatively, the functionality of the DCU 24 may instead be provided by the engine control unit. It will be appreciated by the skilled reader that Figure 1 is a very simplified schematic illustration that includes only the primary features of the SCR dosing system 2 and that, in practice, the SCR dosing system 2 would include a myriad of additional components in addition to those shown and described herein so as to ensure a reliable operation of the SCR dosing system 2. For example, the tank module 18 and/ or the supply line 26 may include heaters to regulate the temperature of the reagent. However, these additional components are not central to the invention, and so have not been described in any detail.

As mentioned above, the DCU 24 is operable to control the flow of reagent through the supply and return lines 26, 28, under pressure created by the pump module 20, according to a reagent dosing strategy. Figure 2 is a schematic illustration of the pump module 20, which generally comprises a filter assembly 30, a pump assembly 32 and a pressure chamber 34, all of which are connected by the supply line 26 which has been divided four sections, 26a, 26b, 26c, 26d, and a non-return valve assembly 36. The pump module 20 is operable according to two operational states, a first operational state being followed by a second operational state. In the first operational state, the pump module 20 is configured to provide pressurised reagent to the dosing module 22 for delivery to the exhaust gas stream. In this operational state, reagent is pumped according to a reagent dosing strategy, by the pump assembly 32, from the tank module 18 to the pump module 20 through the supply line 26a. On reaching the pump module 20, the reagent passes through the filter assembly 30, which captures any particulates carried within the reagent, and is then pumped through the pump assembly 32. From there, the reagent is pumped further along the supply line 26c to the pressure chamber 34 from where some of the reagent continues along the supply line 26d to the dosing module 22 for delivery to the exhaust gas stream, and excess reagent enters the return line 28 to be pumped back to the tank module 18. The non-return valve assembly 36 is located between the pressure chamber 34 and the return line 28, and permits reagent to enter the return line 28 when the pump module 20 is operating in the first operational state.

Once the delivery of the reagent to the exhaust gas stream is complete, the pump module 20 is operable, according to the second operational state, to purge the SCR dosing system 2 by pumping the remaining reagent back through the supply line 26 to the tank module 18. In this operational state, the non-return valve assembly 36 closes, preventing reagent from entering the pressure chamber 34 from the return line 28 and creating a vacuum in the supply line 26c to purge reagent in the dosing module 22. The SCR dosing system 2 is shutdown following the second operational state, ready to be used again as necessary.

Figures 3a and 3b show the general arrangement of the pressure chamber 34 and the non-return valve assembly 36 in more detail and illustrate the difference between the flow of reagent depending on whether the pump module 20 is operating in the first or second operational state respectively. When the pump module 20 is operating in the first operational state, as shown in Figure 3a, reagent is pumped from the supply line 26c into the top of the pressure chamber 34. From here, the reagent continues along the supply line 26d to the dosing module 22 and enters the return line 28, as permitted by the non-return valve assembly 36, to be pumped back to the tank module 18. The non-return valve assembly 36 is configured to open, allowing reagent to flow into the return line 28 from the pressure chamber 34, once the pressure in the pressure chamber 34 exceeds a predetermined threshold, and functions to improve the dosing accuracy of the dosing module 22 by reducing pressure fluctuations, caused by the pump assembly 32 and the dosing module 22, for example, and improve the efficiency with which the SCR dosing system 2 is purged.

When the pump module 20 is operating in the second operational state, as shown in Figure 3b, reagent is sucked from the pressure chamber 34 and the supply lines 26c, 26d by the pump assembly 32. This decreases the pressure in the pressure chamber 34, closing the non-return valve assembly 36 to prevent reagent being sucked from the return line 28 back into the pressure chamber 34.

Figure 4 shows a known non-return valve assembly 36 for use in the pump module 20. The non-return valve assembly 36 includes a sealing ball 38 arranged to engage, under the biasing force of a spring 40, a valve seat 42 formed in a body 44 of the non-return valve assembly 36. The spring 40 is housed in a socket 46, and the body 44 comprises a throttle orifice 48 for controlling the flow of reagent from the pressure chamber 34. When the pump module 20 is operating in the first operational state, supplying pressurised reagent to the dosing module 22, pressurised reagent flows though the throttle orifice 48 from the pressure chamber 34 into a gap 50 formed between the sealing ball 38 and the body 44 to exert an opening force on the sealing ball 38.

When the opening force exceeds the biasing force provided by the spring 40, the sealing ball 38 is lifted from the valve seat 42, permitting reagent to flow past the non-return valve assembly 36 and enter the return line 28. When the pump module 20 is operating in the second operational state, the biasing force of the spring 40, together with the low pressure in the pressure chamber 34, urges the sealing ball 38 into contact with the valve seat 42, preventing reagent in the return line 28 from entering the pressure chamber 34. Once the SCR dosing system 2 has been purged of reagent, it is shutdown ready to be used again as necessary. During this period, any reagent adhered to the spring 40 and/ or held within the socket 46 begins to crystallise as water within the reagent begins to evaporate. This causes the non-return valve assembly 36 to clog-up, which delays, or in the worst case prevents, its opening when the pump module 20 enters a subsequent first operational state. This can lead to pressure fluctuations in the supply line 26, reducing the dosing accuracy of the dosing module 22.

Figure 5 shows a non-return valve assembly in accordance with an embodiment of the invention, generally designated by 51, comprising a first body 52, an elastically deformable valve member 54, in the form of an elongate diaphragm, and a second body 56. In this embodiment, the first and second bodies 52, 56 are in the form of first and second cylindrical caps respectively, the second cylindrical cap being configured to be received within the first cylindrical cap. This embodiment also includes an O-ring 58 arranged to be received over the second body 56 to perform a sealing function around the non-return valve assembly 36 when positioned in the return line 28.

Figures 6a and 6b show underside and cross-sectional views of the first body 52 respectively, which comprises a concentric inlet passage 60 formed in a first plate section 62 of the first body 52 and a valve seat 64 positioned at the end of the inlet passage 60. The underside of the first plate section 62 defines a lower surface 66 comprising a cavity 68 configured to receive the deformable valve member 54.

Figures 7a and 7b show upper perspective and cross-sectional views of the second body 56 respectively, which comprises an outlet passage 70, in the form of a throttle orifice, eccentrically positioned relative to the inlet passage 60 of the first body 52 when the non-returned valve assembly 51 is assembled. The second body 56 further comprises a second plate section 72 defining an upper surface 74 of the second body 56. The upper surface 74 comprises a concentric cavity 76, within which the outlet passage 70 is formed, and an abutment means 78, in the form of a post, comprising an abutment surface 80. The abutment means 78 is centrally located within the cavity 76, defining an annular passage 82 connected to the outlet passage 70.

Figure 8 shows an assembled cross-sectional view of the non-return valve assembly 51, with the second body 56 received within the first body 52, such that the first plate section 62 is arranged above the second plate section 72 defining a valve chamber 84 therebetween. Specifically, the valve chamber 84 is defined by the lower surface 66 of the first plate section 62 and the upper surface 74 of the second plate section 72, such that the inlet passage 60 opens into the valve chamber 84, and the valve chamber 84 contracts into the outlet passage 70. The first body 52 comprises an internal annular stop member 86, for limiting the extent to which the second body 56 is received with the first body 52. The deformable valve member 54 is held within valve chamber 84, with its ends clamped between the lower surface 66 of the first plate section 62 and the upper surface 74 of the second plate section 72, and is configured to traverse the cavity 76 in the upper surface 74 of the second plate section 72. The deformable valve member 54 is biased, by its elasticity, into engagement with the valve seat 64 to seal the inlet passage 60.

When the pump module 20 is operating in the first operational state, as shown in Figure 9a, pressurised reagent flows through the inlet passage 60 from the pressure chamber 34 to exert an opening force on the deformable valve member 54. When the opening force exceeds the biasing force provided by the elasticity of the deformable valve member 54, the deformable valve member 54 lifts from the valve seat 64, permitting reagent to flow into the valve chamber 84, past the deformable valve member 54. From there, the reagent flows into the annular passage 82 and leaves the non-return valve assembly 51 to the return line 28 via the outlet passage 70, which functions as a throttle for controlling the flow of reagent from the pressure chamber 34. The deformable valve member 54 is arranged to abut the abutment surface 80 when it lifts from the valve seat 64 in order to limit its deformation. When the pump module 20 is operating in the second operational state, as shown in Figure 9b, the biasing force of the deformable valve member 54, together with the low pressure in the pressure chamber 34, urges the deformable valve member 54 into contact with the valve seat 64, preventing any reagent in the return line 28 from entering the pressure chamber 34. Once the SCR dosing system 2 has been purged of reagent, it is shutdown ready to be used again as necessary. During this period, any reagent left in the non-return valve assembly 51 is leaked by the outlet passage 70 into the return line 28. This ensures that no reagent is present in the non-return valve assembly 51 when the SCR dosing system 2 is shutdown, thereby preventing the non-return valve assembly 51 from becoming clog-up as described in relation to the known non-return valve assembly 36.

It will be appreciated by a person skilled in the art that the invention could be modified to take many alternative forms to that described herein, without departing from the scope of the appended claims. For example, the abutment means 78 could be removed. Also, the deformable valve member 54 is shown herein as an elongate diaphragm, but it could also be a deformable ball arranged to compression under the pressure in the pressure chamber 34 to lift from the valve seat 64, permitting reagent to flow from the pressure chamber 34 into the valve chamber 84.

References used:

SCR dosing system 2

Internal combustion engine 4

Exhaust system 6

First exhaust portion 8

Second exhaust portion 10

Third exhaust portion 12

Diesel particulate filter 14

SCR catalyst 16 Tank module 18 Pump module 20 Dosing module 22 Atomiser 23 Dosing control unit 24 Supply line 26

Return line 28

Filter assembly 30

Pump assembly 32

Pressure chamber 34

Non-return valve assembly 36

Sealing ball 38

Spring 40

Valve seat 42

Body 44

Socket 46

Throttle orifice 48

Gap 50

Non-return valve assembly 51

First body 52

Deformable valve member 54

Second body 56

O-ring 58

Inlet passage 60

First plate section 62

Valve seat 64

Lower surface 66

Cavity 68

Outlet passage 70

Second plate section 72

Upper surface 74

Cavity 76

Abutment means 78

Abutment surface 80

Annular passage 82

Valve chamber 84

Annular stop member 86

Claims

CLAIMS:

1. A pump module (20) for an SCR dosing system (2) arranged to provide reagent to an exhaust gas stream of an internal combustion engine (4) having an exhaust system (6) with a SCR catalyst (16), the pump module (20) comprising a pump assembly (32) configured to pump regent through a supply line (26) from a tank module (18) to a dosing module (22) and to pump excess reagent through a return line (28) back to the tank module (18), wherein the pump module (20) further comprises a non-return valve assembly (36) positioned within the return line (28), the non-return valve assembly (36) comprising:

a first body (52) comprising an inlet passage (60) and a valve seat (64) positioned at the end of the inlet passage (60);

a second body (56) comprising an outlet passage (70);

a valve chamber (84) defined between the first body (52) and the second body (56), the valve chamber (84) being in fluidic communication with the inlet and outlet passages (60, 70); and, a deformable valve member (54) received within the valve chamber (84), wherein the deformable valve member (54) is configured to deform between a closed position, in which it is biased into engagement with the valve seat (64) to seal the inlet passage (60), and an open position, in which it is held from the valve seat (64) to permit a flow of reagent through the valve chamber (84) from the inlet passage (60) to the outlet passage (70) when the pump assembly (32) is pumping reagent through the supply line (26) from the tank module (18) to the dosing module (22).

2. A pump module (20) according to claim 1, wherein the deformable valve member (54) of the non-return valve assembly (36) is held between a surface (66) of the first body (52) and a surface (74) of the second body (56).

3. A pump module (20) according to any preceding claim, wherein the deformable valve member (54) of the non-return valve assembly (36) comprises an elongate diaphragm arranged to traverse the end of the inlet passage (60).

4. A pump module (20) according to any preceding claim, wherein the inlet and outlet passages (60, 70) of the non-return valve assembly (36) are eccentrically arranged relative to each other.

5. A pump module (20) according to any preceding claim, wherein the first body (52) of the non-return valve assembly (36) comprises a first plate section (62) in which the inlet passage (60) is formed and the second body (56) of the non-return valve assembly (36) comprises a second plate section (72) in which the outlet passage (70) is formed, wherein the first plate section (62) is arranged above the second plate section (72) to define the valve chamber (84) and wherein the deformable valve member (54) is clamped between a lower surface (66) of the first plate section (62) and an upper surface (74) of the second plate section (72).

6. A pump module (20) according to claim 5, wherein the upper surface (74) of the second plate section (72) comprises a cavity (76) in which the outlet passage (70) is formed.

7. A pump module (20) according to claim 5 or 6, wherein the second plate section (72) comprises an abutment means (78) comprising an abutment surface (80) configured to limit movement of the deformable valve member (54).

8. A pump module (20) according to claim 7 when dependent on claim 6, wherein the abutment means (78) is located within the cavity (76) in the upper surface (74) of the second plate section (72).

9. A pump module (20) according to any one of claims 5 to 8, wherein the lower surface (66) of the first plate section (62) of the non-return valve assembly (36) comprises a cavity (68) configured to receive the deformable valve member (54).

10. A pump module (20) according to any preceding claim, wherein the first body (52) of the non-return valve assembly (36) comprises a first cylindrical cap and the second body (56) comprises a second cylindrical cap, the second cylindrical cap being received within the first cylindrical cap to define the valve chamber (84).

11. A pump module (20) according to claim 10, wherein the first cylindrical cap comprises a stop member (86) configured to limit the extent to which the second cylindrical cap is received within the first cylindrical cap.

12. A SCR dosing system (2) for providing regent to an exhaust gas stream of an internal combustion engine (4) having an exhaust system (6) with a SCR catalyst (16) comprising a pump module (20) according to any preceding claim.

Intellectual

Property

Office

Application No:

GB1814559.9

Examiner:

Rachel Smith