The Invention refers to an automotive electric evaporation pump with a gas suction port and a gas exhaust port.

Electric evaporation pumps are used in automobiles with a fuel tank for pumping fuel vapor from a fuel vapor source to a fuel vapor target. The fuel vapor source can be the fuel tank itself or can be a vapor absorbent unit, which is, for example, filled with active carbon as the absorbent media. Since the absorbent unit has a limited total absorbance capacity, the fuel vapor gas absorbed by the absorbent must be discharged from time to time. The discharge action Is provided by the electric evaporation pump which can be arranged fluidically between the vapor absorbent unit and the fuel vapor target which can be, for example, the gas inlet manifold of an internal combustion engine.

Alternatively, the evaporation pump is used to degas the cylinder cover or the crank case of the engine.

Different arrangements including a evaporation pump are described in DE 10 2011 051 828 Al and in US 5,931,141 A. The evaporation pump is generally a conventional gas pump. However, it has turned out that the lifetime of a conventional gas pump used as a evaporation pump is relatively short and the electric energy consumption is relatively high.

It Is an object of the invention to provide an evaporation pump with an increased lifetime and a reduced electric energy consumption.

This object is solved with an electric evaporation pump with the features of claim 1. The electric evaporation pump according to the invention is provided with a gas suction port and a gas exhaust port. The gas suction port can be fluidically connected to a fuel vapor source, for example to a fuel tank or to a fuel vapor absorbent unit. The gas exhaust port can be fluidically connected to a fuel vapor target, for example to a condensation unit or to a gas inlet manifold of an internal combustion engine.

The gas pump comprises a canned electric motor with a motor stator comprising at least two electromagnetic stator coils and with a rotor assembly comprising a pump wheel with pump wheel blades, a rotatable rotor shaft and a motor rotor. The motor rotor is preferably provided as a permanently magnetized rotor body. The gas pump is provided with a separation can arrangement which separates the motor stator provided in a gas-free section from the motor rotor in a gas section. In the gas section, the pumped gas is present. The gas-free section is fluidically separated by the separation can arrangement from the gas section so that no pumped gas is present in the gas-free section. The gas-free section can be filled with air but is fluidically isolated from the gas section where the pumped gas is present.

The gas pump is provided with a bearing means which is arranged in the gas section and which rotatably supports the motor rotor at a static pump housing or at a static pump frame. The bearing means can be a roller bearing or can be a friction bearing, or can be a combination of both bearing types. Preferably, the bearing means is provided with roller bearings because of the high rotational speed and the lack of bearing lubrication possibilities for a friction bearing.

The bearing means is provided with an axial gas passage. The axial bearing means gas passage can be realized by spaces and gaps between the neighboring roller elements of a roller bearing. Alternatively or additionally, the axial bearing means gas passage can also be provided as an axial groove or channel in a fixed part of the bearing means or in the static frame structure supporting of the bearing means. The rotor shaft is also provided with an axial gas passage and the pump wheel is provided with an axial gas outlet passage, preferably upstream of the pump wheel blades, so that a drying gas path through the bearing means, the shaft gas passage and the pump wheel gas outlet passage is realized. The pumped gas is flowing axially through the bearing means gas passage to the distal end of the gas section and then axially flows back in the direction of the pump wheel through the rotor shaft gas passage and finally through the pump wheel outlet passage.

The gas pressure at the center of the pump wheel where the gas outlet passage Is located is relatively low compared to the gas pressure radially outwardly of the pump wheel blades, when the rotor assembly is rotating. As a consequence, a drying path gas current is caused flowing from the area radially outwardly of the pump wheel blades to the pump wheel gas outlet passage in the center. The pump wheel is preferably provided as an impeller with an axial pump wheel inlet and a radial pump wheel outlet.

As long as the rotor assembly is rotating, a continuous gas current is caused in the drying gas path so that the gas section is continuously vented. As a consequence, no condensate or fuel or water can appear or remain in the gas section, In particular not in the hidden areas of the gas section. Since moisture and condensate is continuously avoided, corrosion in the gas section is significantly reduced and the mechanical rotation resistance is significantly reduced, as well.

Generally, the rotor shaft gas passage can be realized by one or more axial groove in the rotor shaft. According to a preferred embodiment, the shaft gas passage is defined by an axial shaft bore extending through the complete axial length of the rotor shaft.

Preferably, the pump wheel gas outlet passage is defined by an axial center opening in the pump wheel body. In the central area of the pump wheel, the gas pressure is relatively low so that an outlet opening in this area defining the fluidic end of the drying gas path is suitable to be used for generating a continuous drying gas path current. According to a preferred embodiment of the invention, an inlet gas passage of the drying gas path is defined by a circular gap between the rotatable pump wheel and a non-rotating part of the pump frame, of the pump housing or another static part of the pump. The pump wheel is preferably provided with a base disk from which the pump wheel blades axially project. The inlet gas passage of the drying path is preferably defined by a circular gap between the pump wheel base disk and another circular static part of the pump.

According to a preferred embodiment of the invention, the gas inlet passage defined by the pump wheel and a non rotating part of the pump frame or pump housing can be provided with a circular labyrinth sealing so that the total radial inlet flow is restricted and moderated to a maximum drying gas path rate which is sufficient to avoid condensation and moisture in the gas section.

Preferably, a motor rotor gas passage is defined by a circular gap between the motor rotor and the separation can arrangement. As an alternative or in addition to the circular gap, an axial groove provided In the separation can arrangement and/or in the motor rotor body can serve as a motor rotor gas passage.

Preferably, an electronic motor control is provided which is arranged axially between the motor stator and the pump wheel and which preferably surrounds the bearing means. The electronic motor control provides the electromagnetic stator coils with electric energy based on a commutation schema. The arrangement of the motor control electronics axially between the motor stator and the pump wheel allows a good mechanical protection of the electronics against environmental impact.

An embodiment of the invention is described with reference to the enclosed drawing, wherein the figure shows a longitudinal cross section of an electric evaporation pump with a drying gas path through the gas section of the electric motor. The figure shows an electric evaporation pump 10 for pumping fuel vapor from a fuel vapor source to a fuel vapor target, for example from a fuel vapor absorbent unit to an intake manifold of an internal combustion engine. The gas pump 10 is suitable for pumping gas but is not suitable for pumping a liquid. The gas pump 10 is provided with a pump housing 11 comprising an axial gas suction port 50 and a radial gas exhaust port 52. The gas pump 10 is provided with a pump section including an impeller pump wheel 18 and the ports 50,52, and with a motor section including an electric can motor 30 and a motor control 40. The motor control 40 including a printed circuit board 41 is arranged in a ring-like electronics chamber 83 axially between the pump section and the electric motor 30.

The pump housing 11 substantially comprises two separate parts, namely the motor section housing 12 and the pump section housing 14. Both section housings 12,14 are defined by massive plastic housing bodies 13, 15. The motor section housing 12 comprises and encloses numerous stator coils 33 of a motor stator 32. The stator coils 33 are embedded in the plastic motor housing body 13. The motor housing body 13 also defines the ring-like control electronics chamber 83 which houses the motor control 40. The motor control 40 Is defined by passive and active electronic elements on the printed circuit board 41.

The gas pump 10 is provided with a rota table rotor assembly 16 comprising a plastic pump wheel 18, an elastic coupling element 21, a metal rotor shaft 20 and a motor rotor 34 which is provided with a motor rotor body 80 with permanent magnets defining numerous magnetic rotor poles. The rotor shaft 20 co-rotatably supports the elastic coupling element 21 which directly supports the pump wheel 18. The elastic coupling element 21 allows the pump wheel 18 to tilt in a limited range so that blocking and jamming of the pump wheel 18 caused by solid particles can be avoided. The plastic pump wheel 18 is provided with numerous pump wheel blades 19 which axially project from a pump wheel base disk body 54 substantially arranged in a radial plane. The pump wheel base disk body 54 is provided with an axial center opening 57 in the axial center thereof which defines a drying gas outlet passage 55.

The rotor shaft 20 is defined by a metal rotor shaft body 22 which Is provided with an axial shaft bore 25 which defines an axial drying gas passage 24. The distal end of the shaft bore 25 defines a drying gas inlet opening 28 and the proximal end of the shaft bore 25 defines a drying gas outlet opening 26.

The rotor assembly 16 is rotatably supported by a bearing means 36 which comprises two roller bearings 37,38. The bearing means 36 is axially arranged between the motor rotor 34 and the pump wheel 18. The bearing means 36 is provided with an axial gas passage 70 which allows the pumped drying gas to flow axially through the bearing means 36. In case of the present roller bearings 37, 38 the axial gas passage is defined by the interspaces between the roller elements of the roller bearing 37, 38. Additionally, the bearing means 36 Is provided with a second axial gas passage defined by three axial grooves 106 which are provided in the cylindrical cylinder portion 84 of the can body 60. Even if the axial grooves 106 are not part of the roller bearings 37, 38, they also define axial bearing means gas passages in the sense of the patent claims. The axial gas passage grooves 106 transport 50% to 80% of the gas flowing through the drying gas path. This is to avoid a washing of the lubrication grease of the roller bearings 37,38.

The pump housing body 15 defines a pump volute 56 which radially surrounds the pump wheel 18 and fluidically leads into a radial pump outlet channel 53 which fluidically ends at the pump's gas exhaust port 52.

The gas pump 10 is provided with a separation can arrangement 82 which fluidically separates the motor stator 32 which is located in a gas-free section from the motor rotor assembly 16 which Is located in a gas section. In the gas section, the pumped gas is present, whereas in the gas-free section no pumped gas is present. However, another gas, as for example air, can be present in the gas-free section. In particular, the electronics chamber 83 is filled with air, but is not filled with pumped gas, The separation can arrangement 82 comprises the cylindrical Inner surface of the motor section housing body 13 and a separate metal sheet can body 60.

The can body 60 has a substantially cylindrical cylinder portion 84 and a ring disk portion 85 substantially lying In a radial plane. The circular edge 91 of the ring disk portion 85 of the can body 60 is clamped between corresponding flanges of the pump housing body 15 and the motor housing body 13. Both flanges are provided with a circular groove 87,89, respectively. In both circular grooves 87, 89 a sealing ring 88,90 is seated, respectively. The circular groove 87, 89, the circular sealing rings 88, 90 and the circular edge 91 of the ring disk portion 85 are axially aligned with each other so that a reliable sealing arrangement is realized.

The outer cylindrical surfaces of the roller bearings 37, 38 are fixed to the inner cylindrical surface of the separation can cylinder portion 84 by clamping. The outer surface of the separation can cylinder portion 84 is, in part, fixed to a cylindrical portion of the motor housing body 13 by clamping, as well. The fluidic sealing Is realized by a sealing ring 92 which is located between the outer surface of the separation can cylinder portion 84 and the inner cylindrical surface of the motor housing body 13.

The circular gap between the base disk 54 of the pump wheel 18 and the ring disk portion 85 of the can body 60 defines an circular inlet drying gas passage 77 of a drying gas path from the inlet drying gas passage 77 to the outlet drying gas passage 55. The circular gap is provided with a labyrinth sealing 100 which is defined by a circular axiai sealing land ring 102 at the back side of the disk portion 85 of the can body 60 and by a corresponding circular axial groove at the front side of the ring disk portion 85 of the can body 60. The labyrinth sealing 100 defines the maximum flow through the drying gas path so that the pneumatic shortcut defined by the drying gas path does not significantly affect the pneumatic efficiency of the gas pump 10.

The motor housing body 13 is, at Its cylindrical inner surface surrounding the motor rotor body 80, provided with one or more axial gas passage grooves 17 which allow an axial drying gas fiow to pass the motor rotor 34 in axial direction.

When the gas pump 10 is active, the electric can motor 30 rotates so that the pump wheel 18 is rotating, as well. The pump wheel pumps the gas which is fuel vapor axially through the axial gas suction port 50 and radially outwardly into the pump volute 56 from where the gas flows through the outlet channel 53 to the gas exhaust port 52.

The gas pressure in front of the pump wheel 18 is below the gas pressure in the pump volute 56. As a consequence, a drying gas flow is caused from the drying gas inlet passage 77 along the drying gas path to the drying gas outlet passage 55. The drying gas path comprises the circular drying gas inlet passage 77, the axial gas passages 70, 106 of the bearing means 36, the axiai gas passage grooves 17 at the motor housing body 13, the axial gas passage 24 of the rotor shaft 20 and the drying gas outlet passage 55 of the pump wheel 18.

As long as the pump wheel 18 is rotating, the pressure difference between the gas suction port 50 and the gas exhaust port 52 causes a drying gas flow through the drying gas path so that no relevant condensate of the pumped gas remains in the gas section of the gas pump 10.