Pumps – Motor driven – Including means utilizing pump fluid for augmenting cooling,...
Reexamination Certificate
2001-09-07
2003-09-02
Walberg, Teresa (Department: 3742)
Pumps
Motor driven
Including means utilizing pump fluid for augmenting cooling,...
C310S087000
Reexamination Certificate
active
06612815
ABSTRACT:
The invention relates to an electrically powered coolant pump in accordance with the preamble of claim 1.
Electrically powered coolant pumps are increasingly employed as drive elements for the cooling water circuit of an internal combustion engine in an automotive vehicle. In comparison with a pump of a conventional construction type which is coupled with the engine speed, these have the advantage of being able to convey cooling water independently of the engine speed and are thus, for example, also capable of conveying at standstill. One example for such a coolant pump is described in DE 296 18 558 U1. This pump has the form of a centrifugal pump whereby the coolant entering in an axial direction is radially deflected into a volute outlet passage and conveyed back into the internal combustion engine. The function of drive mechanism for the impeller of the centrifugal pump is in this example served by an electric motor flange-mounted to the internal combustion engine, which includes a stator and a rotor mounted therein on a hollow shaft. Between the rotor and the stator there is a shroud surrounded by cooling water. The electric motor or the shroud, respectively, is therefore located off the direction of flow of the coolant.
This design of a coolant pump does, however, present drawbacks: Thus the maximum rotational speed of the like wet-rotor pumps is generally limited to approx. 4,500 rpm so as to still be able to keep power losses low, in particular those due to the drag losses which steeply increase with the rotational speed.
In order to nevertheless be capable of providing the desired capacity, these known electrical coolant pumps therefore have correspondingly large dimensions. In addition, for the very reason of its design with a radially acting impeller, this coolant pump requires a considerable structural space so that the coolant may be deflected in a desired manner without excessively high friction losses occurring. The locations suited for installation of a coolant pump of this type are accordingly very limited, particularly in the engine room of an automotive vehicle. Particularly in the case of such an application the comparatively high weight of this design is moreover found to be a drawback, for here any additional weight units have a negative effect on consumption of the internal combustion engine. Traditionally a power-to-weight ratio of, e.g., approx. 1.1 kg/100 W is given.
The invention is therefore based on the object of further developing a coolant pump in accordance with the preamble of claim 1 in such a way that it allows for a high degree of liberty as regards the installation location, at low weight and a smaller demand for structural space.
This object is attained through an electrically powered coolant pump having the features of claim 1.
Thus in accordance with the invention it was particularly provided that the pump housing has an elongate shape and on the inlet side encloses the pump wheel and downstream therefrom encloses the electric motor, with an annular flow passage for the coolant being arranged between the pump housing and the outside of the electric motor, and with the electric motor being encapsulated against the coolant. This has the essential advantage that the coolant flows over the electric motor, as well, and very effective cooling of the electric motor is possible thanks to the large heat exchange area. The electric motor is retained in the pump housing with the aid of at least one web so that it may be driven.
In particular it was recognized in accordance with the invention that the losses of a pump generally increase at the fifth power of the wheel diameter. At the same time, however, the losses only increase at the third power of the rotational speed, for which reason the electric pump of the invention is designed so as to predominantly derive its power from rotational speed, i.e., it aims for higher rotational speeds than the prior art.
Other than in the prior art where the theoretical maximum rotational speed of the utilized pumps cannot be exploited for the named reasons, in accordance with the invention the entire performance spectrum of the electric motor can be utilized thanks to its arrangement in the coolant flow. Where maximum rotational speeds of approx . . . 4,500 rpm were still attainable in the prior art, rotational speeds of more than 12,000 rpm and in particular 15,000 rpm may for the first time also be attained with the electric pump of the invention.
The permanent water cooling of the electric motor's coil jacket obtained in accordance with the invention, and thus carrying off the heat losses of the electric motor through the steady flow of the coolant over the external shell of the motor, permits to obtain an optimized degree of usefulness. As a result, very high performances may be attained with a relatively small-sized motor.
This increased efficiency in comparison with the prior art moreover brings about a drastic improvement of the power-to-weight ratio to, e.g., approximately 350 g/100 W, which has a particularly advantageous effect with regard to the weight of the assembly.
At the same time, the electric motor as well as an optionally associated electronic control circuitry may be provided at very low cost.
On account of the high rotational speeds that are possible, the diameter of the pump wheel may moreover be kept small, so that the resulting losses may be reduced. At the same time this also allows for a substantially smaller size of the coolant pump of the invention in comparison with the prior art, thus expanding the possibilities of installation in an engine room etc. As the pump according to the invention moreover is designed as a so-called “inline pump”, it may particularly well be integrated into cooling circuits and is of extraordinarily universal use.
Although fuel delivery pumps in the form of “inline pumps” are also known in the field of automotive vehicles, in these the fuel flows through the magnet gap over the commutator of the electric motor, which makes them wet-rotor pumps. The maximum rotational speed of the electric motor is limited in fuel delivery pumps of this type because the drag losses strongly increase at elevated rotational speeds. These known fuel delivery pumps are designed with a view to applying high pressures on the fuel at relatively low rotational speeds. A dry-rotor motor may not enter into consideration here, for possibly occurring leakages into the hot rotor cavity might result in explosion.
In contrast, the present invention provides to furnish a coolant pump whereby large flow quantities may be conveyed at high rotational speeds, something that is not possible with the known fuel delivery pumps.
Advantageous developments of the invention result from the features of the subclaims.
Thus the electric motor may be followed downstream by an electronic control unit for driving the electric motor. As a result, it is advantageously possible to also obtain—besides a very compact design—permanent cooling of the electronic control unit through the coolant flowing past. The capacity of the coolant pump in accordance with the invention may therefore be further increased while the required installation space is decreased.
It is moreover also possible for the electronic control unit to include a metallic support member, the particularly good heat conductivity of which permits good discharge of the heat energy generated by the electronic components into the coolant.
It is furthermore advantageous if the pump wheel is an axial pump wheel. These allow for particularly high rotational speeds, so that the actual capacity of the electric motor, cooled by the coolant flowing through it in accordance with the invention, may be utilized particularly well.
As an alternative it is also possible for the pump wheel to be designed as a semiaxial pump wheel which is advantageous in particular applications, for example when it is necessary to overcome greater pumping heads.
If the external diameter of the pump wheel substantially corresponds to the internal diameter of a supply conduit to t
Amm Peter
Blaurock Frank
Pawellek Franz
Berkowitz Marvin C.
Fastovsky Leonid
GPM Gerate-und Pumpenbau GmbH
Nath Gary M.
Nath & Associates PLLC
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