Delivery unit

Description

BACKGROUND OF THE INVENTION

The invention relates to a delivery unit, in particular for delivering fuel, having a delivery pump which is driven by an electric motor, having an impeller wheel of the delivery pump, mounted between housing parts and is connected fixed in terms of rotation to a shaft which is driven by the electric motor, and having a support arrangement for the shaft in a housing part.

Such delivery units are frequently used in contemporary motor vehicles and are known from practice. In a known delivery unit, the shaft of the electric motor has a radial support arrangement in one of the housing parts of the delivery pump. A carbon bush is pressed into the housing part in order to provide radial support. The carbon bush has a bore corresponding to the shaft.

A disadvantage with the known delivery unit is that the bush can be damaged during mounting as a result of tilting of the bush or excessively large pressing-in forces. As a result, the delivery unit has a short service life. Furthermore, the carbon bush gives rise to very high mounting costs and material costs of the delivery unit.

The invention is based on the problem of configuring a delivery unit of the type mentioned at the beginning in such a way that it can be manufactured particularly cost-effectively and has a particularly long service life.

BRIEF DESCRIPTION OF THE INVENTION

This problem is solved according to the invention by virtue of the fact that a plastic casing of a rotor of the electric motor is fabricated in one piece with a bush which is arranged in the housing part, and that the housing part has a support shell for the bush.

As a result of this configuration, the radial support is produced directly by the housing part and the plastic casing which extends into the housing part. Thanks to the invention, there is no need for a carbon bush for the radial support. Since the plastic casing is present in any case in electric motors for contemporary delivery units, the delivery unit according to the invention requires a particularly small number of components. The delivery unit according to the invention can therefore be fabricated in a particularly cost-effective way.

With the known delivery unit, the shaft could have a flattened portion for entraining the impeller wheel fixed in terms of rotation. However, a further contribution to reducing the fabrication costs of the delivery unit according to the invention is made if the bush has a coupling for connection to the impeller wheel so as to be fixed in terms of rotation. As a result of this configuration, the shaft may be of cylindrical configuration in the region of the delivery pump. As a result of this configuration, the shaft does not transmit any torque since the torque is transmitted directly into the impeller wheel of the delivery pump by the plastic casing of the rotor of the electric motor. For this reason, no torsional forces are applied to the shaft so that it can be fabricated with a particularly small diameter, and thus a low weight.

According to another advantageous development of the invention, the coupling has a particularly simple structural design if the coupling of the bush has a lateral flattened portion for connection to the impeller wheel so as to be fixed in terms of rotation.

A lateral flattened portion of the bush frequently requires a very large installation space in the center of the impeller wheel. According to another advantageous development of the invention, the delivery pump can be made particularly compact if the coupling is designed to generate a positive lock between the axial faces of the bush and those of the impeller wheel.

A contribution to simplifying the structural design of the delivery unit according to the invention further is made if the axial faces of the bush and those of the impeller wheel have projections and recesses which correspond to one another. In addition, this permits the impeller wheel to be mounted in a position in the correct fashion in the delivery pump.

The bush could, for example, replace the shaft in the region of the delivery pump. The delivery unit according to the invention has, however, a high degree of stability if the bush is arranged on the shaft.

Rotors for electric motors of contemporary delivery units frequently have at least two plastic casings. According to another advantageous development of the invention, with such electric motors it is easily possible to ensure that the bush is reliably supported by the shaft if the bush is fabricated in one piece with an internal plastic casing, and a plurality of external plastic casings, of the rotor.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention permits numerous embodiments. In order to clarify its basic principle further, one of these embodiments is illustrated in the drawing and will be described below. Said drawing shows a longitudinal section through a delivery unit according to the invention in a single FIGURE.

The delivery unit has a delivery pump 2 which is driven by an electric motor 1. The delivery pump 2 is embodied as a side duct pump and is used to deliver fuel in a motor vehicle. The fuel is delivered by the delivery pump 2 in an axial fashion through an inlet duct 4 which is arranged in a housing part 3 to an outlet duct 6 which is arranged in a further housing part 5. An impeller wheel 7 of the delivery pump 2 is mounted axially between the housing parts 3, 5 and is connected fixed in terms of rotation to a shaft 8 of the electric motor 1. The electric motor 1 has a fixed stator 9 and a rotor 10 with the shaft 8. The rotor 10 has an internal plastic casing 11 and an external plastic casing 12. The inner plastic casing 11 is fabricated in one piece with a bush 13 which is arranged in one of the housing parts 5 of the delivery pump 2. The housing part 5 has a support shell 14 for the bush 13. As a result, the shaft 8 is mounted radially in the housing part 5. In the other housing part 3 of the delivery pump 2, a ball 15 is arranged as an axial bearing for the shaft 8. In order to connect the impeller wheel 7 of the delivery pump 2 to the rotor 10 of the electric motor 1 so as to be fixed in terms of rotation, a coupling 16 with projections 17 and recesses 18 which correspond to one another and which change over the circumference are arranged on the adjoining end sides of the bush 13 and of the impeller wheel 7. The projections 17 and recesses 18 engage one in the other and connect the impeller wheel 7 to the bush 13 in a positively locking fashion.