WO2018184694A1

WO2018184694A1 - Automotive gas flow pump

Info

Publication number: WO2018184694A1
Application number: PCT/EP2017/058403
Authority: WO
Inventors: Alessandro MALVASI
Original assignee: Pierburg Pump Technology GmbH
Current assignee: Pierburg Pump Technology GmbH
Priority date: 2017-04-07
Filing date: 2017-04-07
Publication date: 2018-10-11
Anticipated expiration: 2019-10-07
Also published as: DE112017007402T5

Abstract

The invention Is directed to n automotive gas flow pump (10) with a pump housing (14) and a pump wheel (20). The pump wheel (20) comprises a circular back side disk (26), a circular front side ring disk (24) defining a center pump wheel inlet opening (22) and numerous blades (30) connecting the back side disk (26) and the front side ring disk (24). The pump housing (14) comprises a front cover (15) substantially covering the front side ring disk (24) of the pump wheel (20). The pump wheel (20) is provided with an annular ring projection (40) axially projecting from the front side ring disk (24). The front cover (15) of the pump housing (14) is provided with a annular ring groove (17) corresponding with the annular ring projection (14) so that the annular ring projection (40) projects into the annular ring groove (17). Since the fluidic back flow through the gap between the pump housing front cover (15) and the pump wheel (20) Is reduced, the fluidic efficiency of the gas flow pump is increased.

Description

Automotive gas flow pump

The invention refers to an automotive gas flow pump, and preferably refers to a so called purge pump for pumping fuel vapor from an automotive fuel system to a vapor target, for example to a vapor accumulator or to a combustion device.

The gas flow pump is not a displacement pump, but is provided with a fast-rotating pump wheel generating a continuous flow with a relatively high flow-rate but with a relatively low pressure. A typical pump wheel is designed as a so-called impeller comprising a circular back side disk, a circular front side ring disk defining a centeric pump wheel inlet opening and numerous pump wheel blades connecting the back side disk and the front side ring disk with each other.

Since the pump wheel rotates with a relatively high rotational speed, even a small imbalance of the pump wheel requires a relatively large gap between the rotating pump wheel and the static pump housing to avoid a collision of the pump wheel with the housing. But a relatively large gap increases the fluidic backflow from the pump wheel outlet to the pump wheel inlet which causes a reduced fluidic efficiency of the gas flow pump.

It is an object of the invention to improve the fluidic efficiency of a fast- rotating gas flow pump.

This object is solved with an automotive gas flow pump with the features of main claim 1. The automotive gas flow pump according to the invention is provided with a pump wheel comprising a circular back side disk, comprising a circular front side ring disk defining the center pump wheel Inlet opening and comprising numerous pump wheel blades connecting the back side disk and the front side ring disk. The pump wheel is a so-called impeller.

The pump housing comprises a front cover substantially covering the front side ring disk of the pump wheel, The gap between the housing front cover and the front side ring disk of the pump wheel is the backflow path for the pumped gas from the high pressure side at the pump wheel outlet to the low pressure side at the pump wheel inlet.

The pump wheel is provided with an annular ring projection axially projecting from the front side ring disk of the pump wheel. The annular ring projection axially protrudes substantially in axial direction from the distal surface plane of the front side disk ring. The term 'axial' does not necessarily mean that the annular ring projection Is protruding exactly in axial direction but with a substantial axial component. The annular ring projection does not define the pump wheel inlet opening but is located with a radial distance of at least some millimeters from the pump wheel inlet opening.

The pump housing, in particular the front cover of the pump housing, is provided with an annular ring groove corresponding with the annular ring projection of the pump wheel so that the annular ring projection axially projects into the annular ring groove. The radial backflow path length between the gas outlet of the pump wheel and the gas inlet opening of the pump wheel defined by the gap between the housing front cover and the pump wheel's front side ring disk is thereby extended. Additionally the gap in the ring area can be manufactured with high precision so that the ring area gap can be provided with a relatively small gap width. The total fluldic resistance between the high-pressure side and the low pressure side is increased with the effect that the total fluidic backflow is reduced. Since the total fluid ic backflow is reduced, the fluldic efficiency of the gas flow pump is increased.

According to a preferred embodiment of the invention, the annular ring projection and the corresponding annular ring groove are positioned radially outwardly of the pump wheel Inlet opening and not adjacent to the pump wheel inlet opening. Preferably, the annular ring projection is provided within the outer half of the total radius of the pump wheel. According to a preferred embodiment of the invention, the annular ring projection and the corresponding annular ring groove together define a contact-free annular labyrinth seal.

Preferably, the annular ring projection is defined by an annular ring body with a substantially constant cross-section along the entire ring body circumference but with at least one balancing recess. In other words, the annular ring projection is provided with one or more recesse for balancing the pump wheel. After the production of the pump wheel, imbalance of the pump wheel Is determined in a suitable device, and the determined pump wheel imbalance Is reduced or neutralized by providing one or more balancing recess at a suitable location at the annular ring projection. The balancing recess can be provided as a radial bore or as any other kind of recess at the annular ring projection. Preferably, the balancing recess is provided at the distal axial front end of the annular ring body.

Since the fast-rotating pump wheel is balanced, the gap width between the pump housing front cover and the front side disk of the pump wheel can be reduced significantly so that the total f!uidic resistance of the gap between the high-pressure side and the low pressure side Is reduced significantly. As a result, the fluidic efficiency of the gas flow pump is improved. Preferably, the pump wheel is made out of plastic. A plastic pump wheel is relatively light and can be produced very cost-effectively, However, an injection molded pump wheel body typically has not a perfect contour accuracy which leads to imbalance of the individual plastic pump wheels. The imbalance of a pump wheel can be substantially corrected by providing suitable balancing recesses at the annular ring projection. As a result, the relatively light and balanced pump wheel allows to reduce the gap width between the housing front cover and the front side ring disk of the pump wheel to a very small value. As a result, the fluidic resistance of the gap is increased and the backflow between the high-pressure side and the low pressure side is reduced.

According to a preferred embodiment of the invention, an electric driving motor is provided for driving the pump wheel. The pump wheel is not mechanically driven by another rotating part of the automotive engine, but the pump has its own electric driving device. The gas flow pump can therefore be activated when a pump activity is needed and requested.

Preferably, the electric driving motor has a nominal pump speed of more than 10000 rpm. A relatively high nominal pump speed generates a relatively high gas flow and a relatively high pumping pressure and allows to thereby providing a very compact automotive gas flow pump.

According to a preferred embodiment, the gas flow pump is a fuel vapor pump, also known as a so-called purge pump, for pumping fuel vapor from a fuel circuit to a fuel vapor target.

One embodiment of the invention is described with reference to the drawings, wherein: figure 1 shows a schematic cross-section of an automotive gas flow pump including a pump housing and a pump wheel within the pump housing, figure 2 shows a perspective view of the pump wheel of figure 1, and figure 3 shows an enlarged detail of the labyrinth seal defined between the housing front cover and the front side ring disk of the pump wheel.

Figure 1 shows schematically an automotive gas flow pump 10 with a plastic pump housing 14, a plastic pump wheel 20 and an electric driving motor 12 directly driving the pump wheel 20. The gas flow pump 10 is a fuel vapor pump for pumping fuel vapor from a fuel circuit to a fuel vapor target, for example to a fuel vapor absorber or to a combustion section of an interna! combustion engine.

The electric driving motor 12 has a nominal rotational speed of between 30000 to 60000 rpm. A typical flow rate is 50 liters per minute. The typical pressure difference between the pump inlet and the pump outlet is 80 mbar.

The pump wheel 20 comprises a circular back side disk 26 and a circular front side ring disk 24 with a centric circular opening edge. The pump wheel 20 is provided with numerous pump wheel blades 30 connecting the back side disk 26 with the front side ring disk 24. A typical diameter of the pump wheel 20 is 40 mm. The pump housing 14 defines an axial centric pump In!et 13 being in-line with the pump wheel inlet opening 22 and defines an outlet volute 16 surrounding the pump wheel 20. The outlet volute 16 leads into a pump outlet which is not shown in the drawings. As can be seen in figures 1 and 3, the back side disk 26 of the pump wheel 20 Is lying In a cross plane. The front side ring disk 24 of the pump wheel 20 Is not exactly lying in a cross plane but is provided slightly conical. A cylindrical inlet opening collar 28 is provided at the circular inner edge of the front side ring disk 24. The opening collar 28 defines the centric pump wheel's inlet opening 22, A cylindrical annular ring projection 40 is provided at the front side ring disk 24. The annular ring projection 40 axlal!y projects from the front side ring disk 24. The annular ring projection 40 is an integral part of the front side ring disk 24. The radius RR of the annular ring projection 40 is larger than half of the total radius RW of the pump wheel 20. The annular ring projection 40 is positioned radially outwardly of the pump wheel inlet opening 22 and is positioned not adjacent to the pump wheel inlet opening 22.

As best can be seen in figures 1 and 3, the pump housing 14 comprises a front cover 15 substantially covering the front side ring disk 24 of the pump wheel 20. An annular ring groove 17 is provided at the inside surface of the housing front cover 15. The annular ring groove 17 corresponds with the annular ring projection 40 of the pump wheel 20 so that the annular ring projection 40 axially projects Into the annular ring groove 17 and thereby defines a contact-free annular labyrinth seal. The labyrinth seal gap has, seen in cross-section, a C-like course.

After the injection molding production process of the pump wheel 20, the pump wheel 20 can have a rotational imbalance. The pump wheel imbalance is compensated by providing one or more balancing recesses 44 at the front end 43 of the annular ring body 42 defining the annular ring projection 40. The size and the number of balancing recesses depends on the original imbalance of the pump wheel 20. The axial height H of the annular ring projection 40 above the surface of the front side ring disk 24 is between 1 mm and a few millimeters, for example 1,5 mm. The axial gap width Gl between the annular ring projection 40 and the housing front cover 15 within the annular ring groove 17 is 0,5 mm and the radial gap width G2 within the annular ring groove 17 is also about 0,5 mm.

Claims

C L A I M S

1. An automotive gas flow pump (10) with a pump housing (14) and a pump wheel (20),

the pump wheel (20) comprising a circular back side disk (26), a circular front side ring disk (24) defining a centric pump wheel inlet opening (22) and numerous blades (30) connecting the back side disk (26) and the front side ring disk (24),

the pump housing (14) comprising a front cover (15) substantially covering the front side ring disk (24) of the pump wheel (20),

wherein the pump wheel (20) is provided with an annular ring projection (40) axially projecting from the front side ring disk (24), and

wherein the pump housing front cover (15) is provided with an annular ring groove (17) corresponding with the annular ring projection (40) so that the annular ring projection (40) projects into the annular ring groove (17).

2. The automotive gas flow pump (10) of claim 1, wherein the annular ring projection (40) and the corresponding annular ring groove (17) are positioned radially outwardly of the and not adjacent to the pump wheel inlet opening (22).

3. The automotive gas flow pump (10) of one of the preceding claims, wherein the annular ring projection (40) and the corresponding annular ring groove (17) together define a contact-free annular labyrinth seal.

4. The automotive gas flow pump (10) of one of the preceding claims, wherein the annular ring projection (40) is defined by an annular ring body (42) with a substantially constant cross-section and with at least one balancing recess (44).

5. The automotive gas flow pump (10) of claim 4, wherein the balancing recess (44) is provided at the front end (43) of the annular ring body (42).

6. The automotive gas flow pump (10) of one of the preceding claims, wherein the annular ring projection (40) is provided within the outer half of the total radius (RW) of the pump wheel (20).

7. The automotive gas flow pump (10) of one of the preceding claims, wherein an electric driving motor (12) is provided for driving the pump wheel (20).

8. The automotive gas flow pump (10) of one of the preceding claims, wherein the pump wheel (20) is made out of plastic.

9. The automotive gas flow pump (10) of one of the preceding claims 7 to 8, wherein the electric driving motor (12) has a nominal rotational speed of more than 10000 rpm.

10. The automotive gas flow pump (10) of one of the preceding claims, wherein the pump (10) is a fuel vapor pump.