Fluid pump

This is a National Phase Application in the United States of International Patent Application No. PCT/EP2006/009763 filed Oct. 10, 2006, which claims priority on German Patent Application No. 10 2005 054.027.9, filed Nov. 11, 2005. The entire disclosures of the above patent applications are hereby incorporated by reference.

The invention is directed to a fluid pump for internal combustion engines, comprising an electric motor with a rotor arranged in a motor housing and a stator, the rotor being arranged on a drive shaft at least in a manner secured against rotation, an impeller fastened on the drive shaft, at least one set of guide vanes arranged behind the impeller in the flow direction of the fluid to be conveyed, and a pump housing enclosing the motor housing, the impeller and the guide vanes and at which a pressure port and an intake port are arranged opposite the axial ends.

Fluid pumps for internal combustion engines are used especially as coolant pumps in the cooling circuit. Whereas, in the past, a direct coupling with the engine speed existed and the pumps were driven by belt or chain drives, more recent engines increasingly use electric variable speed coolant pumps with a can, so as to realize a modern thermal management. Thus, an excessive delivery rate can be prevented, so that, for example, the internal combustion engine can be heated up faster after a cold start. The delivery rate can be controlled according to the actually required cooling capacity.

Such a pump is known, for example, from MTZ No. 11, vol. 2005 (p. 872-877). This electric coolant pump comprises an EC motor as the drive unit and has a pump head with an axial inlet and a tangential outlet. The components and especially the housing parts used therein are rather large for the power input of the pump, since a relatively large drive motor has to be used.

Thus, US 2002/0106290 A1 discloses an electric fluid pump of semi-axial construction, whereby, with the same power input to the electric motor, the electric motor can be made smaller to obtain higher speeds, so that the same delivery rate can be obtained with a more compact structure. It comprises a completely enclosed electromotor with a guide vanes provided at the outer side thereof. However, behind the guide vanes, seen in the flow direction, obstacles are formed that hinder the establishing of the electric contacting to the electronic unit. On the impeller side, the entire motor is sealed with gaskets from the environment. It is at least debatable whether such a sealing at the rotating parts is sufficient.

The pump housing is bipartite and has various steps and through holes for electric contacting. Depending on the desired maximum delivery rate, different electric motors and housings must be designed.

Likely, a completely irrotational flow is not achieved due to the rather short guide vanes. Further, the pressure loss due to the passages of the electric contacts is rather high so that the gain in the power input of the electric motor is partly thwarted by the pressure losses occurring.

DE 202 01 183 U1 discloses an axial pump with an electric motor enclosed by a housing part having straight supporting ribs intended to serve as a guide vanes. Due to their straight design, the pressure loss is very high. In addition, it is most probable that an irrotational flow is not achieved with this structure.

It is therefore an object of the invention to achieve an irrotational outflow with pressure losses as small as possible and to thereby increase the efficiency while reducing the package size. Further, various maximum delivery rates are to be achieved, while using the same housing parts.

This object is achieved by providing a pressure-side motor housing part with a conduction device. This conduction device allows to obtain an almost completely irrotational flow so that the kinetic energy of the tangential component of the flow velocity is converted into pressure energy with low friction losses. This increases the efficiency of the fluid pump. Thus, in order to obtain an unaltered delivery rate, it is also possible to reduce the overall size of the electric motor.

In a further developed embodiment, the conduction device is formed by recirculation vanes manufactured integrally with the pressure-side motor housing part and formed on the surface thereof, so that no additional components are required and an irrotational flow with little loss of energy is guaranteed. The recirculation vanes serve to convert the tangential flow component into an axial flow component without any significant pressure losses. The efficiency is increased and the number of components is reduced.

Preferably, the pressure-side motor housing part is tapered in the flow direction and surrounded by a correspondingly shaped pressure-side pump housing part. Thus, the radial ends of the recirculation vanes are delimited by the pump housing, so that it is reliably prevented that the vanes are flown over.

It is advantageous to form grooves in the pressure-side pump housing part, the radial ends of the recirculation vanes extending into these grooves. This again reduces the flow resistance by preventing an overflowing of the vanes and defines the position of the motor housing part with respect to the pump housing part, so that, in turn, assembly errors are avoided, since the grooves serve as guiding grooves upon assembly.

In a further developed embodiment, the pressure-side motor housing part is adapted to be slid into a receiving opening of an axially adjoining motor housing part by slipping the pressure-side pump housing part onto the pressure-side motor housing part, with interposition of a gasket, wherein the pressure-side motor housing part is fixed by fastening the pressure-side pump housing part at a pump housing part situated radially outward with respect to the axially adjoining motor housing part. Accordingly, no fastening elements have to be used to fasten the pressure-side motor housing part. The fastening of the pump housing part alone guarantees for a tight fastening of the motor housing, so that the assembly effort is reduced.

Preferably, the pressure-side pump housing part has a flange via which the fluid pump can be fastened to an internal combustion engine. Due to the simplicity of the pump housing parts, the pressure port can be made integrally with the flange, so that the fluid pump can be flange-mounted directly on a motor housing, for example, without additional intermediate lines.

It is particularly advantageous if a plurality of fluid pumps are connected in series via a flange connection, the flanges being formed at the pressure-side pump housing part of the first pump and a suction-side pump housing part of a downstream pump. It is possible to provide a series connection without additional components, allowing to realize a higher required maximum volume flow. This becomes possible especially because of the irrotational flow in the outlet port caused by the conduction device. Thus, it is possible, in a restricted package space, to achieve a different delivery flow with different motor sizes, without any redesigning and without changing the components. Thereby, costs can be reduced.

Thus, a fluid pump is provided that supplies an irrotational flow at the outlet and operates with negligible pressure losses by friction and the like. This increases the efficiency, since a large part of the kinetic energy is actually converted into pressure energy. A series connection allows to obtain various delivery rates with the same components in a compact space.

An embodiment of the invention is illustrated in the drawing and will be detailed hereinafter.