Patent Publication Number: US-2010119391-A1

Title: Centrifugal Pump Comprising a Spiral Housing

Description:
The invention relates to a centrifugal pump having a spiral housing. The invention further relates to the use of the centrifugal pump. Centrifugal pumps having spiral housings are known. DE 103 47 302 A1 describes a two-part spiral housing for a centrifugal pump, which is of optimized design from the point of view of fluid mechanics. Such centrifugal pumps are generally driven by an electric motor, the stator of the electric motor being arranged in a dry chamber and the rotor in a wet chamber. The rotor therefore turns in the wet chamber, flowing around which is the medium to be pumped. The dry chamber and the wet chamber are here divided by a separately arranged can, the disadvantage being that it is necessary to arrange sealing elements between the one part of the spiral housing and the can in order to avoid liquid or vapor from the wet chamber getting into the dry chamber. Over prolonged operating times, that is to say as the seal gradually becomes porous, or when subjected to vibrations acting on the centrifugal pump, it is often not possible to avoid larger quantities of liquid getting into the dry chamber and flooding it. This then results in more serious damage to the stator and to electronic components, which in addition to the stator are also situated in the dry chamber. 
     The object of the invention, therefore, is to create a centrifugal pump having a spiral housing, in which liquid from the wet chamber enclosing the rotor is entirely prevented from entering the dry chamber, and consequently flooding the dry chamber. 
     The object of the invention is achieved by a centrifugal pump having a spiral housing, which comprises a first housing part and a second housing part, the area of the second housing part remote from the inlet E of the inflowing medium being of tubular design and its outline delimited for internal accommodation of the rotor in the wet chamber N, a stator being arranged in the dry chamber T externally surrounding the second housing part in the area of the rotor, wherein a cover is arranged on the tubular outline of the second housing part, a first seal, which is connected to the surroundings on at least one side remote from the wet chamber N, being arranged between the cover and the second housing part. The area of the second housing part remote from the inlet E of the inflowing medium is of tubular design and therefore assumes the function of a can, the additional separate arrangement of which, however, can be completely dispensed with. The first seal is connected to the surroundings on at least one side remote from the wet chamber N. This means that at least one part of the seal is in direct contact with the surrounding air, or that if the need arises a liquid flowing out via the seal can pass directly into the surroundings. It has surprisingly emerged that in this way it is possible to entirely prevent liquid from the wet chamber N getting into the dry chamber T, and thereby to prevent flooding of the dry chamber T. The connection of the first seal to the surroundings advantageously ensures that should the first seal start to decompose after prolonged operating times, some of the liquid can be released directly into the surroundings and therefore does not get into the dry chamber T. In this way damage to the stator and damage to other electrical components in the dry chamber T can advantageously be avoided. 
     In a preferred development of the invention the first seal is connected to the surroundings by ducts or passages in or on the cover. This represents a relatively easy and straightforward way of connecting the first seal to the surroundings, which allows the advantageous use of various sealing elements as first seal. 
     In a further preferred development of the invention the stator is externally surrounded by a motor housing, and a second seal is arranged between the motor housing and the second housing part in the area of its tubular outline. This advantageously serves to prevent even slight quantities of vapor getting into the dry chamber T. This measure therefore advantageously serves to keep the dry chamber T absolutely dry. This is of advantage particularly where the flowing medium contains corrosive constituents. 
     In a further preferred development of the invention an O-ring seal is in each case provided as first seal and as second seal. It may be advantageous here to arrange the first seal and the second seal in the form of an O-ring directly opposite on the second housing part, although this is not absolutely essential. The first seal in the form of an O-ring is then arranged on the inside wall of the tubular outline of the second housing part. The second seal is then arranged in the form of an O-ring on the outside wall of the tubular outline of the second housing part. This measure facilitates the manufacture of the centrifugal pump. 
     In a further preferred development of the invention the second housing part comprises a first bearing and the cover comprises a second bearing for rotatable mounting of the rotor. The cover may in this case itself form the second bearing, or it merely serves to accommodate such a bearing. It is advantageous here that the additional arrangement of a special bearing race inside the centrifugal pump can be dispensed with. 
     In a further preferred development of the invention the outer area of the second housing part has an outline of curved longitudinal section perpendicular to the direction of flow of the medium flowing in from the inlet E. The precise profile of the curved outline is in this case of an engineered design to optimize the fluid mechanics. This is an especially advantageous way of minimizing the overall space required for the centrifugal pump. 
     The invention finally relates to the use of the centrifugal pump as a coolant centrifugal pump in a motor vehicle. Coolant centrifugal pumps in motor vehicles have to function perfectly over prolonged operating times, there being an absolute need to avoid flooding of the dry chamber T. The use of the centrifugal pump as a coolant centrifugal pump in a motor vehicle is therefore particularly advantageous. 
    
    
     
       The invention will be explained in more detail below by way of example and with reference to the drawing ( FIG. 1  to  FIG. 3 ). 
         FIG. 1  shows a longitudinal, three-dimensional section through the centrifugal pump. 
         FIG. 2  shows a longitudinal, three-dimensional section through the centrifugal pump in the form of an exploded diagram. 
         FIG. 3  shows a longitudinal, three-dimensional section through a centrifugal pump according to the state of the art. 
     
    
    
       FIG. 1  shows a centrifugal pump in longitudinal, three-dimensional section. The centrifugal pump comprises a spiral housing, which comprises a first housing part  1  and a second housing part  2 , the area of the second housing part  2  remote from the inlet E of the inflowing medium being of tubular design and its outline delimited for internal accommodation of the rotor  3  in the wet chamber N. The flowing medium is here illustrated by the bold arrow. A stator  4  is arranged in the dry chamber T externally surrounding the second housing part  2  in the area of the rotor  3 . A cover  5  is arranged on the tubular outline of the second housing part  2 , a first seal  6 , which is connected to the surroundings on at least one side remote from the wet chamber N, being arranged between the cover  5  and the second housing part  2 . The first seal  6  is here connected to the surroundings by ducts  5 ′ on the cover  5 . The stator  4  is externally surrounded by a motor housing  7 . A second seal  8  is arranged between the motor housing  7  and the second housing part  2  in the area of its tubular outline. The first seal  6  and the second seal  8  are each provided in the form of an O-ring seal. The second housing part  2  has a first bearing  2 * and the cover  5  has a second bearing  5 * for rotatable mounting of rotor  3 . This makes it possible to dispense entirely with an additional bearing race. The outer area of the second housing part  2  has an outline  2 ** of curved longitudinal section perpendicular to the direction of flow of the medium flowing in from the inlet E. If the first seal  6  becomes porous after prolonged operating times, for example, the liquid passes via the first seal  6  into the ducts  5 ′, which constitute the connection to the surroundings. The liquid is therefore given off directly to the surroundings, which is illustrated by the light arrow. This makes it impossible for liquid to pass from the wet chamber N, in which the rotor  3  is arranged, into the dry chamber T, so that flooding of the dry chamber T is entirely prevented. The arrangement of the second seal  8  also serves to prevent slight traces of escaping vapor getting into the dry chamber T, which is especially advantageous where the liquid contains corrosive fractions. This therefore makes it possible to keep the dry chamber T completely dry. 
       FIG. 2  shows the centrifugal pump in longitudinal, three-dimensional section in the form of an exploded diagram. In one area the second housing part  2  is of tubular design and its outline delineated for internal accommodation of the rotor  3 . The first seal  6  and the second seal  8  are in each case embodied as O-ring seals. 
       FIG. 3  shows a longitudinal, three dimensional section through a centrifugal pump according to the state of the art. The centrifugal pump according to the state of the art has a spiral housing, which comprises a first housing part  1   b  and a second housing part  2   b.  Liquid medium to be pumped, represented by the bold arrow, passes through the inlet Eb into the wet chamber Nb, in which the rotor  3   b  is rotatably mounted. A stator  4   b  is externally arranged in the dry chamber Tb in the area of the rotor  3   b.  The dry chamber Tb is here closed off from the surroundings by a motor housing  7   b.  In the state of the art the wet chamber Nb is separated from the dry chamber Tb by the disadvantageous arrangement of a can  9   b,  it being possible under certain circumstances for liquid to get into the dry chamber Tb from the wet chamber Nb owing to a disadvantageous arrangement of a sealing ring  10   b,  which has to be arranged between the can  9   b  and the second housing part  2   b.  This then results in a disadvantageous flooding of the dry chamber Tb, which may happen, for example, if the centrifugal pump is subjected to heavier vibrations in operation. The possible ingress of liquid into the dry chamber Tb is illustrated by the light arrow. The possible flooding of the dry chamber Tb results directly in damage to the stator  4   b  and other electronic components (not shown), which is prevented by the centrifugal pump according to the invention.