Circulating pump

In order to provide a circulating pump, comprising a stator, a rotor, a bearing device with a convex bearing member and at least one concave bearing shell, via which the rotor is mounted for rotation, and an impeller which is connected non-rotatably to the rotor, which has improved lubrication possibilities and/or with which any axial lifting of the impeller can be prevented in an effective manner, it is provided for a shaft element to be connected non-rotatably to the rotor and non-rotatably to the impeller and for the shaft element to be guided through the bearing member and to be rotatable relative to the bearing member.

BACKGROUND OF THE INVENTION

The invention relates to a circulating pump, comprising a stator, a rotor, a bearing device with a convex bearing member and at least one concave bearing shell, via which the rotor is mounted for rotation, and an impeller which is connected non-rotatably to the rotor.

EP 1 593 852 A2 discloses a circulating pump and a method for the fluid lubrication of a spherical bearing in an electric motor. The circulating pump comprises an electric motor which has a rotor and a stator, wherein the rotor is mounted on a spherical bearing which has a sliding member with a convex, spherical surface and a bearing pan with a concave, spherical surface and which is lubricated by fluid. A flow guide for conducting lubricating fluid through a lubrication area between the sliding member and the bearing pan is separate from a gap between stator and rotor.

A bearing device with a convex bearing member and a concave bearing shell (bearing pan), which have respective spherical surfaces which face one another, is also designated as a spherical bearing.

SUMMARY OF THE INVENTION

In accordance with an embodiment of the invention a circulating pump is provided which has a reduced flow through the gap between rotor and stator and/or with which any axial lifting of the impeller can be prevented in an effective manner.

In accordance with an embodiment of the invention, in a circulating pump a shaft element is connected non-rotatably to the rotor and non-rotatably to the impeller and the shaft element is guided through the bearing member and can be rotated relative to the bearing member.

As a result of the provision of an additional shaft element which connects the impeller to the rotor, the rotor can, with respect to flow, be decoupled from a flow in an impeller chamber. In this case, a flow of fluid to be pumped through a gap of air at the rotor is no longer necessary to effect fluid lubrication of the bearing device. As a result, on the other hand, magnetic particles, which can be contained in the fluid to be pumped, may be prevented from reaching the rotor and being able to settle thereon. The depositing of magnetic particles on the rotor can lead to a seizing of the circulating pump.

As a result of the provision of the shaft element, it is, in principle, also possible to bring about the sliding mounting of the spherically concave bearing shell on the bearing member (sliding member), which is spherically convex at least in sections, outside the rotor. As a result, the rotor can be of a more simple configuration.

It is also possible, as a result, to provide a bearing device which is supported on the bearing member in two directions via two bearing shells.

The bearing member has, in particular, a (continuous) recess, in which the shaft element is (rotatably) positioned. The recess is, for example, a cylindrical recess which extends between oppositely located pole areas of the bearing member. When the convex bearing member is of a spherical design, the recess is preferably aligned coaxially to a direction of the diameter, wherein this direction of the diameter is preferably at right angles to an equatorial plane of the bearing member.

The shaft element has, in particular, a greatest external diameter which is smaller than a smallest internal diameter of the recess. A gap is formed between the shaft element and walls of the recess which makes a free rotatability in the recess possible. It has proven to be favorable when the width of the gap is at least 0.5 mm.

It is favorable when the shaft element has a recessed area with a reduced diameter in the region of an exit area through the recess. For example, the shaft element has an annular recess. As a result, the shaft element is prevented from striking an edge of the bearing member which is formed by the recess. Such edges are, particularly when the convex bearing member is a ceramic element, generally very sensitive to impact. When the shaft element tilts in the recess, the shaft element meets the wall of the recess outside the edge and cannot strike the edge. Such recessed areas are formed by the recess, in particular, at the oppositely located exit areas; in this respect, one exit area is located in an impeller chamber and the other exit area is located in a rotor chamber. It is also possible for the width of a gap between the shaft element and a recess in the bearing member to be so large that the shaft element does not touch the bearing member even with a maximum tilting of the impeller. In this case, the rotor strikes “outside” before the shaft element strikes.

The shaft element is preferably designed to be cylindrical in at least one section, with which it is guided through the bearing member. As a result, the recess may be produced in a simple manner.

It is favorable when the bearing member is arranged between a bearing shell, which is fixed to the impeller, and a fixing area of the shaft element on the rotor. As a result, a non-rotatable connection between the rotor and the impeller may be realized in a simple manner, wherein the impeller is then mounted directly on the bearing member and the rotor is, on the other hand, mounted “indirectly” on the bearing member via the connection. In addition, it is also possible for the rotor to also be slidingly mounted directly on the bearing member via an additional bearing shell.

It is particularly advantageous when the bearing member is held non-rotatably by a holder which is arranged above the rotor facing the impeller. The holder may be fixed in position with respect to a housing of the circulating pump in a simple manner. It can, at the same time, be used as a separating element in order to separate a rotor chamber from an impeller chamber, for example, in a fluid-tight manner or at least separate them in such a manner that larger magnetic particles cannot pass into the rotor chamber.

It is particularly advantageous when a rotor chamber is provided, in which the rotor is arranged so as to be rotatable, and an impeller chamber is provided, in which the impeller is arranged so as to be rotatable, wherein the rotor chamber and the impeller chamber are separated from one another by a separating element. The separating element separates the rotor chamber from the impeller chamber in such a manner that no magnetic particles of a minimum size can pass into the rotor chamber. This can be achieved, for example, in that the separating element separates the rotor chamber from the impeller chamber in a completely fluid-tight manner. It is, however, also possible, in principle, for an exchange of fluid to be possible between the impeller chamber and the rotor chamber, wherein corresponding exchange openings must then have a diameter which does not allow magnetic particles of a “critical size” to pass into the rotor chamber.

It is favorable when the separating element is arranged at the level of the bearing member and, in particular, is arranged in such a manner that it holds the bearing member for the purpose of fixing it in position at or in the vicinity of an equatorial plane. As a result, a relatively large, spherical area is provided on the bearing member as a sliding surface for the spherical, concave bearing shell. It is then also possible, in principle, for a bearing shell, which slides on the bearing member, to be arranged on the rotor itself, in addition.

It is favorable when the separating element is designed as a holder for the bearing member. As a result, the number of components which are required for the construction of the circulating pump can be kept low. As a result of the separating element, the impeller chamber may be separated from the rotor chamber and the bearing member is fixed in position by the separating element at the same time.

It is favorable when a bearing shell (which is spherically concave), which is connected non-rotatably to the impeller and which is mounted on the bearing member, is arranged between the separating element and the impeller with respect to an axial direction. This results in a simple construction and advantageous lubrication possibilities may be realized.

The separating element decouples the rotor chamber from a lubrication chamber of the bearing device, through which fluid for the lubrication is transported during operation of the circulating pump and so, at least not directly, fluid to be pumped can flow from the lubrication chamber into the rotor chamber and a flow circuit is thereby formed. As a result, no magnetic particles can pass into the rotor chamber via the lubrication chamber.

In this respect, it is possible for the separating element to be designed to be fluid-tight or have at the most one or more openings between the impeller chamber and the rotor chamber, the diameter of which is at the most 0.3 mm. When the separating element is designed to be completely fluid-tight, no exchange of fluid can take place between the impeller chamber and the rotor chamber, i.e. no fluid to be pumped can pass into the rotor chamber and, therefore, no magnetic particles, which are contained in the fluid to be pumped, can pass into the rotor chamber. In principle, a flow of fluid in the rotor chamber can be desirable in order to be able to discharge heat more effectively. The discharge of heat takes place by way of a transfer of heat to fluid to be pumped in the impeller chamber. It may then be desirable to form a flow of fluid in the rotor chamber. When fluid is to be filled into the rotor chamber (first filling) from the impeller chamber, magnetic particles of a critical size must be prevented from reaching the rotor chamber as a result of a correspondingly small design of the at least one opening. When the diameter of a corresponding opening is at the most 0.3 mm, this penetration of magnetic particles into the rotor chamber can be prevented in an effective manner.

It is advantageous when the separating element has a rib structure. The rib structure can face the impeller chamber and/or the rotor chamber. The surface area of the separating element is increased as a result of the rib structure. As a result, the surface area, via which a transfer of heat can take place, is increased. A more effective cooling action can then be achieved. A rib structure can also increase the rigidity of the separating element. As a result, the characteristic frequency spectrum of the rotating system can be modulated. As a result of a rib structure which is designed accordingly, the characteristic frequency spectrum can, in particular, be modulated such that a lowest characteristic frequency is below and, in particular, far below 600 Hz.

In one embodiment, at least one seal is arranged between the separating element and a separating cap which surrounds the rotor. Such a seal is provided, in particular, when the separating element is designed to be fluid-tight in order to screen off the rotor chamber completely from the impeller chamber with respect to the penetration of fluid. As a result, a closed rotor chamber is provided, wherein no exchange of fluid with the impeller chamber is possible.

It is then favorable when the rotor chamber is previously filled with fluid. For example, a prior filling with a mixture of water and glycol is provided. This fluid serves as a heat transfer fluid for the more effective discharge of heat from the stator as primary heat source via the rotor to the impeller chamber.

In one embodiment, a lubrication chamber for the bearing device is separated with respect to fluid from an impeller chamber, in which the impeller rotates. The lubrication chamber is then coupled to the rotor chamber. The rotor chamber is, as a result, a reservoir for lubricant. No fluid to be pumped is then used as lubrication fluid. Instead of this, an internal lubricant circuit is provided. As a result, an effective lubrication of the bearing device can be achieved even in the case of abrasive fluids to be pumped.

It is provided, in particular, for the shaft element to have at least one channel, via which fluid can flow from the lubrication chamber to the rotor chamber, in which the rotor rotates. The shaft element has, in particular, a corresponding hollow channel in order to make this possible. Lubricant fluid from the rotor chamber can then be used to lubricate the corresponding bearing device. This is separated from the impeller chamber with respect to fluid so that the penetration of abrasive particles into the lubrication chamber is prevented, wherein an effective fluid lubrication of the bearing device is ensured.

The at least one bearing shell is, in particular, sealed in the direction of the impeller chamber in order to prevent the penetration of fluid to be pumped into the lubrication chamber and, therefore, also into the rotor chamber.

The at least one bearing shell advantageously has channels, via which fluid which flows around the shaft element through a gap at the bearing member can be supplied to the at least one channel of the shaft element. As a result, a circuit for a stream of lubricant between the rotor chamber and the lubrication chamber is made possible in order to bring about an effective fluid lubrication of the bearing device.

It is, in addition, favorable when a friction pump is formed by the rotor which rotates in a rotor chamber and this friction pump drives a flow of lubricant through the lubrication chamber. This friction pump generates the necessary difference in pressure to drive lubricant from the rotor chamber through the lubrication chamber at the bearing device.

In one embodiment, a holder for the bearing member is mounted on a modulating element for the characteristic frequencies of the rotating system. This modulating element provides for a decoupling of vibration. It is designed, for example, as a rubber bearing. A characteristic frequency spectrum can be modulated by a corresponding selection. On the other hand, the generation of noise can be optimized, as a result.

In particular, the lowest characteristic frequency is set to a value below 600 Hz via the modulating element and is set, in particular, to a value far below 600 Hz.

In one embodiment, an additional separating element is provided which is arranged between a holder for the bearing member and the impeller and which has a central opening, through which the bearing member can be acted upon with fluid. The separating element is arranged such that fluid from a high pressure area of the circulating pump can be decoupled. A low pressure area is located in the region around the bearing member. As a result, fluid can be sprayed onto the bearing member. As a result, an effective lubrication is achieved and, in particular, an emergency lubrication is realized when, for example, the fluid to be pumped contains a high proportion of gas.

At least one fluid channel is formed, in particular, between the additional separating element and the holder and at least one opening, which points into a high pressure area of an impeller chamber, is arranged at the additional separating element. As a result, fluid may be coupled out of the high pressure area and sprayed onto the bearing member in order to make an effective lubrication and, in particular, emergency lubrication possible.

In one embodiment, a blade structure is arranged on the rotor. As a result, a difference in pressure may be generated in a rotor chamber as a result of rotation of the rotor and this leads to a mechanical axial force on the rotor. This is oriented in the direction of the stator and causes a holding force component in an axial direction. This holding force component increases the axial holding force for the rotor at the bearing device. In principle, the dynamic pressure during operation of the circulating pump can cause the impeller to lift away from the bearing member, in particular in the case of high discharge heads. This is counteracted by the blade structure at the rotor.

In one embodiment, a first bearing shell, which is mounted on the bearing member, and a second bearing shell, which is mounted on the bearing member, are provided, wherein the first bearing shell is connected non-rotatably to the impeller and the second bearing shell is connected non-rotatably to the rotor. As a result, the rotor may be supported directly on the spherically convex bearing member and the impeller may be supported directly on the spherically concave bearing shell. This can have various advantages depending on the configuration. For example, an additional mechanical holding force for preventing any lifting of the impeller may be generated or the lifting of the impeller may be prevented completely as a result.

The first bearing shell and the second bearing shell are, in particular, arranged at oppositely located pole areas of the bearing member. As a result, the combination consisting of rotor and impeller may, to a certain extent, be clamped to the bearing member.

A section of the shaft element, which is guided through the bearing member, then extends, in particular, between the first bearing shell and the second bearing shell. As a result, a bearing device may be realized which has spaced, oppositely located, spherical sliding surfaces.

It is favorable, in addition, when the shaft element is guided through the first bearing shell and the second bearing shell. As a result, it may be connected non-rotatably to the rotor and the impeller in an effective manner.

In one embodiment, the second bearing shell is supported on the rotor via a spring device. The spring device exerts an additional force in the direction of the stator, i.e., the second bearing shell is tensioned. There is, as a result, an additional mechanical holding force for preventing the lifting of the impeller.

In an alternative embodiment, the first bearing shell is supported on the impeller via a spring device. In this case, a main bearing, via which the rotor is mounted so as to be rotatable, is formed via the second bearing shell and the corresponding pole area of the bearing member. The second bearing shell acts “from below” on the bearing member, i.e., on a pole area which is located opposite the pole area which is in direct contact with the first bearing shell fixed in position on the impeller. Any lifting of the impeller is prevented, as a result. The first bearing shell ensures that the impeller-rotor combination is clamped at the bearing member and supports the system consisting of rotor and impeller during any start, stop and standstill and, in general, in situations, in which the hydraulic force is smaller than the magnetic holding force which acts in the direction of the stator. The spring device facilitates a simple producibility, wherein greater tolerances are made possible.

It may be provided for a seal to be arranged in the recess between a wall of the recess and the shaft element. The seal can, in principle, be arranged on the shaft element and, in particular, rotate with it or it can be arranged on the wall of the recess and the shaft element can rotate contrary to it. A mixed form is also possible, with which the seal can be entrained by the shaft element and, in this respect, rotate with a rotary speed which is, on average, less than the rotary speed of the shaft element. The rotor chamber may be additionally sealed by such a seal; no fluid can then pass into the rotor chamber from the impeller chamber or the lubrication chamber through a gap between the wall of the recess and the shaft element.

It is also possible for the concave bearing shell to have a sealing area in relation to the recess for the shaft element. As a result, an impeller chamber is separated from the rotor chamber in a fluid-tight manner via the bearing shell. Fluid from the impeller chamber, which is used for the lubrication of the bearing unit, is prevented from passing into the recess and, therefore, into the rotor chamber. Accordingly, the bearing shell has an inner edge which has a sealing effect. This inner edge periphery area is lubricated at the most incompletely. It can, however, be subject to wear and tear only at a contact surface on the convex bearing member and forms, as a result, a terminal element which is adequately sealed in the direction of the recess.

The following description of preferred embodiments serves to explain the invention in greater detail in conjunction with the drawings.

DETAILED DESCRIPTION OF THE INVENTION

The embodiment of a circulating pump according to the invention, which is shown inFIG. 1in a schematic sectional illustration and designated as10, comprises an electric motor12with a stator14and a rotor16. The rotor16can be turned (rotated) about an axis of rotation18.

The rotor16generates, in particular, a magnetic field. The rotor16comprises for this purpose one or more magnetic elements20and, in particular, permanent magnet elements. The stator14comprises one or more coil windings (not shown in the drawings). For example, a magnetic field which changes with respect to time is generated at the stator14and, as a result, the magnetic force between the rotor16and the stator14changes, whereby the rotary movement of the rotor16is driven.

A separating cap22is associated with the stator14and the rotor16and this separates the stator14from the rotor16in a fluid-tight manner. The separating cap22has a spherical area24. It has, for example, the shape of a cut-off spherical shell.

The rotor16is likewise of a spherical design with a spherical area26which faces the spherical area24of the separating cap22. A gap28(gap of air) is located between the spherical area26of the rotor16and the separating cap22.

The rotor16is rotatable in a rotor chamber30, wherein the rotor chamber30is located in an interior space of the separating cap22.

The rotor chamber30is limited upwards by a separating element32. The separating element32is supported on the separating cap22and, for example, connected to it. In this respect, a seal in the shape, for example, of an O-ring can, as will be explained in greater detail below, be arranged on the supporting area of the separating element32against the separating cap22.

The rotor chamber30is designed to be rotationally symmetric to an axial axis34of the circulating pump10. When the rotor16is not inclined, the axis of rotation18coincides with the axial axis34.

The separating element32is designed as a holder36for a spherically convex bearing member38. For this purpose, the holder36comprises an opening40which lies concentrically to the axial axis34. The bearing member38is seated in this opening. The bearing member38is, in particular, a bearing ball which is produced, for example, from a ceramic material. It is held in the opening40of the separating element32in an equatorial plane42.

The bearing member38has a (central) recess (opening)44which extends between poles46a,46bwhich are located opposite one another (in relation to the equatorial plane42).

A shaft element48is guided through the recess44. This shaft element48is, in particular, of a cylindrical design. The recess44is of a hollow cylindrical design. The shaft element48is connected non-rotatably to the rotor16via a connecting area50. It has an area which is located in the recess44. It projects beyond the recess44with an additional area52.

The bearing member38is held non-rotatably by the holder36in relation to a housing54of the circulating pump10. The shaft element48is guided through the recess44so as to be rotatable. During a rotation of the rotor16relative to the stator14(and, therefore, also relative to the housing54) the area of the shaft element48located in the recess44rotates relative to the recess44about the axis of rotation18.

A gap58is formed between a wall56of the recess44and the shaft element48. The shaft element48has, in this respect, an external diameter which is smaller than the internal diameter of the recess44. A width of the gap58is predetermined by the difference between this internal diameter and this external diameter.

The width of the gap is selected in one embodiment such that the shaft element48does not touch the wall56and the rotor16strikes beforehand in the maximum possible or admissible inclined position of the rotor16relative to the axial axis34of the shaft element48. Further on, a variation will be explained in conjunction withFIG. 11, with which the shaft element has a recessed area.

The width of the gap58is, in particular, at least 0.5 mm.

An impeller chamber60is formed above the rotor chamber30, limited by the housing54. An impeller62is arranged for rotation in this impeller chamber60, wherein an axis of rotation of the impeller62is the axis of rotation18.

The impeller62is connected non-rotatably to the area52of the shaft element48.

In addition, a bearing shell64, which has a spherically convex area66, is seated non-rotatably on the impeller62. The bearing shell64is placed on the bearing member38with this convex area66in the region of the pole46b.

The bearing shell64is produced, for example, from graphite.

The shaft element48passes through the bearing shell64by way of a corresponding recess.

The bearing shell64is of a spherical design in the concave area66(hollow spherical section). The concave area66forms a spherical sliding surface68.

The bearing shell64is connected non-rotatably to the impeller62by means of a connecting element70which comprises, for example, the bearing shell64. An annular channel72is formed between a base of the connecting element70and the bearing shell64and this extends as far as the area52of the shaft element48.

One or more channels74, which are aligned at least approximately parallel to the axial axis34, open into the annular channel72. These channels74are connected to one or more channels76which open into a hollow space78of the impeller62.

Flow paths are provided by the annular channel72and the channels74,76, through which fluid can flow along the sliding surface68into the hollow space78. As a result, a lubrication chamber80is provided. The bearing member38with the bearing shell64forms a bearing device82, via which the rotor16is mounted for rotation relative to the stator14. The bearing device82may be lubricated via the lubrication chamber80by way of fluid to be pumped which is intended to be conveyed by the circulating pump10.

The separating element32separates the rotor chamber30from the lubrication chamber80. The impeller chamber60is separated from the rotor chamber30via the separating element32. When fluid is conveyed via rotation of the impeller62, the fluid is not pumped through the gap28. As a result, the problem is avoided of magnetic particles being able to settle in the gap28and lead to a blockage.

The conveyance of lubricant through the lubrication chamber80is brought about solely through the impeller chamber60without participation of the rotor chamber30.

In principle, fluid can enter the recess44via the annular channel72in the case of the circulating pump10. Since the fluid is, however, at the same level of pressure as the fluid in the gap28, a reduced number of magnetic particles can, as a result, pass into the rotor chamber30.

The separating element32is produced from a heat-conductive material and in particular, from a metallic material in order to be able to discharge heat from the stator14via the rotor chamber30into the impeller chamber60and, from there, by means of fluid to be pumped.

In a variation of one embodiment, the separating element32is provided with a rib structure84which faces the impeller chamber60. The rib structure84increases the surface area of the separating element32and, therefore, the heat discharging surface area. It is also possible for a rib structure to be arranged in the direction of the rotor chamber30.

In principle, it is favorable when the gap28is filled with fluid in order to make a greater transfer of heat to the separating element32possible. For example, the rotor chamber30is filled beforehand (for example, with a mixture of water and glycol).

The solution according to the invention functions as follows:

The rotor16is driven by an electric motor by way of the electromagnetic interaction with the stator14when this is acted upon with current. It rotates about the axis of rotation18. The impeller62is connected non-rotatably to the rotor16via the shaft element48and so the impeller62is driven by the rotation of the rotor and, as a result, a difference in pressure in relation to the conveyance of fluid is generated.

The rotor16is mounted for rotation via the bearing device82. The shaft element48passes through the bearing member38. The bearing member38is located between the bearing shell64and the connecting area50to the rotor16. The rotor16is supported on the bearing device82to a certain extent from above. This support “from above” is made possible by the shaft element48which passes through the bearing member38.

As a result, it is possible to separate the rotor chamber30from the lubrication chamber80in a fluid-tight manner via the separating element32or at least separate them such that magnetic particles (which can be contained in the fluid to be pumped) are prevented from passing into the rotor chamber30. As a result of the separating element32, the lubrication chamber80is in direct effective fluid contact with the impeller chamber60and is not in direct effective fluid contact with the rotor chamber30. Lubricant (fluid to be pumped) need not, as a result, flow in the gap28.

At least an “uninhibited” flow of fluid to be pumped (lubricant) through the gap28is no longer possible. As a result, magnetic particles can no longer be deposited on the rotor16or this deposit is prevented to a considerable extent.

The rotor16and the bearing device82form a combination. In the case of any replacement of the rotor, the entire combination consisting of rotor and bearing device is exchanged.

Lubricant flows through the lubrication chamber80and, in this respect, follows the difference in pressure generated as a result of rotation of the impeller62. InFIG. 1, the flow of lubricant is indicated by arrows. This flow of lubricant avoids the rotor chamber30.

In one variation of the circulating pump10which is shown schematically inFIG. 2in a sectional view, wherein the same reference numerals are used for the same elements, a seal86is arranged in the recess44between the wall56and the shaft element48and interrupts the flow of fluid to be pumped (and, therefore, also of lubricant) from the lubrication chamber80or from the impeller chamber60to the rotor chamber30completely.

In the embodiment shown, the seal86is arranged on the shaft element48, for example, in the vicinity of the equatorial plane42. The seal86is designed such that a rotation of the shaft element48about the axis of rotation18is possible, wherein it rotates with the shaft element48and, in particular, is arranged non-rotatably on it.

When a complete fluid-tightness of the rotor chamber30is intended to be achieved, the separating element32is also preferably arranged in relation to the separating cap22via a seal88, for example, in the form of an O-ring in order to make a through flow of fluid in this area impossible.

In order to obtain a good discharge of heat during operation of the corresponding circulating pump, the gap28and all the other intermediate spaces in the rotor16are preferably filled beforehand with a fluid, such as, for example, a mixture of water and glycol.

In another variation, which is shown schematically inFIG. 3, a stationary seal90is arranged in the recess44and is fixed to the wall56. The shaft element48rotates relative to this seal90.

The circulating pumps according toFIGS. 2 and 3otherwise function like the circulating pump according toFIG. 1.

In a further variation of the circulating pump10which is shown schematically inFIG. 4, wherein the same reference numerals are used for the same elements, a separating element92is provided instead of the separating element32, which is arranged and designed to be fluid-tight, and this separating element92has one or more openings94from the impeller chamber60into the rotor chamber30. The openings94have a diameter which is small enough so that magnetic particles with a specific critical size cannot pass into the rotor chamber30. For example, the diameter of such an opening94is at the most 0.3 mm large and, in particular, this diameter is at the most 0.2 mm. An opening94is produced, for example, by way of laser machining.

It is possible for fluid to be pumped to enter the rotor chamber30and, therefore, for this to be filled with fluid to be pumped (first filling) through an opening94. As a result, an improved cooling effect is achieved in order to allow a better discharge of heat from the rotor16. In addition, it is not necessary for the rotor chamber30to be filled beforehand at the works.

The opening or openings94are preferably arranged where the difference in pressure between the impeller chamber60and the rotor chamber30is minimized. For example, one or several openings94are arranged in the vicinity of the bearing member38.

It is also possible for a larger opening to be arranged at the separating element92, at which a filter element is then arranged which filters out larger magnetic particles (for example, with a size of 0.2 mm or more).

Otherwise, the circulating pump functions as described above.

In a further variation of the circulating pump10which is shown schematically inFIG. 5, the separating element32is mounted on the separating cap22via a modulating element96or is arranged directly on the stator14. The modulating element96serves to modulate the characteristic frequencies of the rotating system consisting of rotor16and impeller62. The modulating element96is, for example, an annular rubber bearing. It serves to decouple and, in particular, decouple the separating element32from the stator14with respect to vibration.

An optimization of noise generation may be achieved by selecting the modulating element96accordingly. For example, a main characteristic frequency may be set in a frequency range considerably below 600 Hz.

In this respect, it is, in principle, possible to also modulate the characteristic frequencies by designing the separating element92accordingly. For example, the separating element92can be reinforced by ribs.

The characteristic frequency spectrum of the circulating pump10can be modulated by the modulating element96in a targeted manner and be brought into a desired range at least with respect to the strongest characteristic mode.

A second embodiment of a circulating pump according to the invention, which is shown schematically in a sectional view inFIG. 6and designated as98, comprises a stator and a rotor which are, in principle, of the same construction as in the circulating pump10. The same reference numerals are used for the same elements. Again, a bearing device is provided with a bearing member38which has a continuous recess44. This bearing member38is held via a holder36which separates a rotor chamber30from an impeller chamber60and, in particular, separates them in a fluid-tight manner.

A shaft element100is guided through the recess44and this is connected non-rotatably to the rotor16. The shaft element100is, in addition, connected non-rotatably to an impeller102, wherein the arrangement is, in principle, the same as that described in conjunction with the circulating pump10.

The corresponding bearing device comprises a concave bearing shell104which is placed on the bearing member38.

A channel106is arranged at the shaft element100which is parallel to a direction of longitudinal extension of the shaft element100. The shaft element100has a hollow cavity in the area of the channel106.

The channel106opens into the rotor chamber30, wherein it opens into a hollow space108which is part of the rotor chamber30.

The bearing shell104is, on the other hand, held on the impeller102via a connecting element110. The connecting element110is designed such that a lubrication chamber112for the fluid lubrication of the corresponding bearing device is not in effective fluid communication with the impeller chamber60.

One or more channels114are arranged in the bearing shell104and these are oriented at least approximately axially. They open in one direction into a surface area of the bearing shell104, with which this is placed on the bearing member38. At their other end, the channel or channels114open into an annular chamber116, wherein the annular chamber is, on the other hand, in effective fluid communication with the channel106in the shaft element100. Instead of an annual chamber116, a plurality of channels can also be provided which connect the channel106of the shaft element100to the channel or channels114.

The bearing shell104has a spherical area118which is arranged between the impeller chamber60and an opening area of the channel or channels114. This spherical area118is designed such that the channel or channels114are separated with respect to the impeller chamber60so as to be fluid-tight, i.e., the spherical area118is designed as a sealing area.

Furthermore, the bearing shell104has a spherical area120which extends between the opening area of the channel or channels114and the gap58between the recess44and an outer contour of the shaft element100. A flow path for fluid to be pumped as lubricant is formed via this spherical area120.

The gap28between the recess44and the outer contour of the shaft element100opens into an area122of the rotor chamber30. As a result, lubricating fluid can pass from the rotor chamber30into the gap58.

The lubrication chamber112is decoupled from the impeller chamber60. An “internal lubrication” of the bearing device may be realized which is separate from the transport of the medium to be pumped.

A friction pump is formed in the rotor chamber30via the rotating rotor16. For this purpose, the separating element32is sealed via a seal124so that no exchange of fluid with the impeller chamber60can take place.

The friction pump results in the region of the gap58in a pressure p1which is greater than a pressure p2in the hollow space108. As a result, lubricant (fluid) is moved. This passes through the gap28into the recess44and via the spherical area120and the channel or channels114into the annular chamber116. It then flows through the channel106into the hollow space108. The hollow space108, on the other hand, is in effective fluid communication with the gap58. This results in a flow circuit, in which lubricating fluid is transported between the bearing shell104and the bearing member38, wherein no exchange with the impeller chamber60can take place as a result of the design of the spherical area118.

As a result, magnetic particles can also be prevented from passing into the rotor chamber30or abrasive particles from passing into the lubrication chamber.

In order to form this internal lubricant circuit, a first filling with, for example, a mixture of water and glycol is necessary.

Otherwise, the circulating pump98functions like the circulating pump10.

A third embodiment of a circulating pump according to the invention, which is shown schematically inFIG. 7in a sectional illustration and designated as126, is, in principle, of the same design as the circulating pump10. The same reference numerals are used for the same elements.

An additional separating element128, for example in the form of a separating plate, is arranged above the separating element32. This additional separating element128follows the separating element32in its shape, wherein it does not touch the bearing member38. In the area of the bearing member38, the separating element128has an area130which encloses the bearing member38. The area130thereby encloses a central opening132of the separating element128, via which the bearing member38can be acted upon and, in particular, can be sprayed with fluid.

One fluid channel134(at least) is formed between the additional separating element128and the separating element32(which forms the holder for the bearing member38). In particular, the intermediate space between the separating element128and the separating element32forms a continuous fluid channel.

One or more openings136, via which an effective fluid connection between the at least one fluid channel134and the impeller chamber60is achieved, are arranged in the separating element128in an outer area. Fluid to be pumped can pass into the at least one fluid channel134via the opening or openings136.

The opening136is arranged in an area, in which the pressure in the fluid to be pumped is greater than around the bearing member38. As a result, as mentioned above, the bearing member38can be acted upon directly with fluid to be pumped between the bearing shell104and the connecting area to the separating element32. As a result, an emergency lubrication may be realized or the lubrication of the corresponding bearing device may be improved. Lubrication may also be realized when the fluid to be pumped contains a high proportion of gas since fluid to be pumped can be sprayed on as lubricant.

Otherwise, the circulating pump126functions like the circulating pump10.

A fourth embodiment of a circulating pump according to the invention, which is shown schematically inFIG. 8and designated as138, is, in principle, of the same design as the circulating pump10. The same reference numerals are used for the same elements.

The circulating pump138differs from the circulating pump10in the design of the rotor. A rotor140is provided which has an area142with a blade structure144. The blade structure144is arranged below the separating element32and faces it.

The blade structure144comprises a plurality of vane profiles or ribs which rotate with the rotation of the rotor140in the rotor chamber30. The corresponding profiles are designed such that the blade structure144influences an axial force which acts on the combination consisting of impeller62and rotor140.

As a result of the rotation of the impeller62in the impeller chamber60, fluid to be pumped exerts an axially acting hydraulic force on the impeller62which is directed away from the stator14. This force has the tendency to lift the bearing shell64away from the bearing member38. In the case of greater discharge heads, there is, in principle, the risk of the impeller62lifting away.

Fluid is located in hollow cavities of the rotor140which are interconnected in an effective fluid manner. In this respect, this may be fluid to be pumped which enters gradually during operation and provides for the filling or it may be a prior filling. As a result of the blade structure144on the rotor140, an increase in pressure is brought about in the rotor chamber30and this generates a holding force component in an axial direction, wherein this axial force acts on the stator14. As a result, a mechanical holding force, which reduces the risk of lifting, is generated via the rotor blades in addition to the magnetic holding force between the rotor16and the stator14(and, in particular, an iron portion of the stator14).

Otherwise, the circulating pump138functions as described above.

A fifth embodiment of a circulating pump according to the invention, which is shown schematically inFIG. 9in a sectional illustration and designated as146, comprises a bearing device148with a convex bearing member. The same reference numerals are used for the same elements as those of the circulating pump10. The bearing member is, therefore, designated as38. A spherically concave first bearing shell152is mounted on the bearing member38at a first pole area150a. The first bearing shell152is positioned in an impeller chamber60which is, in principle, of the same design as the impeller chamber60of the circulating pump10. An impeller62rotates in this impeller chamber60.

The bearing member38has a recess, through which a shaft element154is guided which is connected non-rotatably to the impeller62.

The impeller chamber60is separated from a rotor chamber156, in which a rotor158is arranged for rotation. A separating element32which corresponds to the separating element32of the circulating pump10separates the rotor chamber156from the impeller chamber60. It also holds the convex bearing member38.

A spherically concave second bearing shell160is arranged in the rotor chamber156and is supported on a second pole area150bof the convex bearing member38. The first pole area150aand the second pole area150bare located axially opposite one another.

The shaft element154passes through a recess162of the second bearing shell160and is connected non-rotatably to the rotor158.

The second bearing shell160is supported on the rotor158by a spring device164. The spring device164is formed, in particular, by a plate spring166or by a set of plate springs. Plate springs have the advantage that their characteristic line can be set in a defined manner.

The spring device164is designed such that it exerts a tensioning force on the second bearing shell160in an axial direction towards the stator (not shown inFIG. 9). The direction of the force is indicated inFIG. 9by the reference numeral168.

The second bearing shell160is held non-rotatably on the rotor158by a connecting element170. The connecting element170is designed, for example, in the shape of a beaker and the second bearing shell160is fixed in position in an interior space of the connecting element170. An annular channel172is formed between the connecting element170and a rear side of the second bearing shell160which faces away from a spherical area of the second bearing shell and the annular channel is in effective fluid communication with the gap28between the shaft element154and the wall56of the recess44.

One or more channels174lead from the annular channel172through the connecting element170into a hollow cavity176of the rotor chamber156. As a result, the annular channel172is in effective fluid communication with the rotor chamber156.

The first bearing shell152which is of a concave design has a spherical sliding surface, via which it is mounted on the spherically convex bearing member38. Fluid to be pumped serves as lubricant for this bearing, wherein the lubricant path is the same as that described in conjunction with the circulating pump10.

The second bearing shell160likewise has a concave spherical sliding area, with which it is seated on the second pole area150bof the convex spherical bearing member38. This bearing is lubricated by fluid from the rotor chamber156as lubricant which can flow in a flow path through the gap28.

The spring device164is set such that it exerts a tensioning force in the direction of the stator which is, for example, in the order of magnitude of 10 N. This tensioning force is part of an axial holding force which prevents any lifting of the impeller62in the case of great discharge heads. As a result of the provision of an elastic spring device164, the bearing member38is not securely “rigidly” clamped between the first bearing shell152and the second bearing shell160but rather an axial flexibility is realized. As a result, the installation is made easier and the tolerance requirements for the production of the circulating pump146are reduced.

A sixth embodiment of a circulating pump according to the invention, which is shown schematically inFIG. 10in a sectional illustration and designated as178, comprises a bearing device180with a spherical bearing member38, on which a first concave bearing shell184is placed in a first pole area182a. A concave second bearing shell186, which slides on the bearing member38, is arranged at an oppositely located second pole area182b.

The second bearing shell186is connected non-rotatably to a rotor188. A shaft element190is connected non-rotatably to the rotor188and is guided through a recess44in the bearing member38, is guided through the first bearing shell184and connected non-rotatably to an impeller192. The impeller is, on the other hand, rotatable in an impeller chamber60.

The first bearing shell184is connected non-rotatably to the impeller192. The first bearing shell184is supported on the impeller192via a spring device194. The spring device194comprises, in particular, a plate spring or a set of plate springs. The distance between the first bearing shell184and the impeller192can be varied via the elastic spring device194.

The mounting of the rotor188via the second bearing shell186on the convex bearing member38forms a main bearing for the rotatable mounting of the rotor188. Any lifting of the impeller192relative to the rotor188is prevented by this support “from below”. The mounting via the first bearing shell184exerts a counterforce which axially fixes the position of the rotor188and, therefore, also the position of the impeller192. The system consisting of rotor188and impeller192may be borne via the bearing which is formed by means of the first bearing shell184and the bearing member38in situations, in which the hydraulic force is smaller than the magnetic holding force. The magnetic holding force acts in the direction of the stator14. This is particularly relevant during any start, stop and standstill.

The part bearing, which is formed via the second bearing shell186and the second pole area182bof the bearing member38, prevents any lifting of the impeller192in an axial direction completely. As a result, a mechanical securing against lifting is realized and so a magnetic holding force for preventing the lifting is no longer necessary.

A magnetic holding force is proportional to the sinus β between a radial direction at right angles to the axis of rotation18and the effective direction of the magnetic holding force which is, on the other hand, determined by the interaction between the stator and the rotor188(the stator is not shown inFIG. 10). Since the main bearing mentioned above provides for the axial holding force, the angle β can, in principle, be selected to be optionally small.

The torque is proportional to cos β. When the angle β is selected to be small, a high torque is obtained.

High torques can, therefore, be realized as a result of the circulating pump178, wherein the impeller192is secured against lifting.

The rotor188and, therefore, the impeller192, too, is axially fixed via the “counter mounting” by means of the first bearing shell184. The spring device194enables the installation to be made easier and the tolerance requirements to be kept low.

The lubrication of the bearing device180is brought about, in principle, via fluid which can be made available to sliding surfaces of the bearing device180through corresponding channels and gaps.

A variation of the circulating pump10, which is shown schematically inFIG. 11and designated as196, comprises a shaft element198which has recessed areas200,202which are axially spaced. The recessed areas200,202are formed by annular recesses which are coaxial to an axis of the shaft element198. In the region of the recessed areas202, the shaft element198has a smaller external diameter than outside the recessed areas202(and, in particular, smaller than in that part of the shaft element198which is located between the recessed areas200and202).

The shaft element198exits from the bearing member38in respective exit areas204and206. The recess44at the bearing member38has respective annular edges208,210.

The recessed areas200,202are each arranged at the exit areas204,206of the shaft element108so as to be located opposite the edges208and210, respectively.

The bearing member38is particularly sensitive to impact at the edges208,210, particularly when it is a ceramic member. As a result of the recessed areas200,202, the shaft element198is prevented from striking the edges208,210, which are sensitive to impact, during tilting of the rotor16.

It is possible for the shaft element198to successfully strike the wall56of the recess4in an area which is spaced sufficiently from the edges208,210.

In this embodiment, which can also be used in all the other circulating pumps described, a limitation of the tilting of the rotor60by the shaft element198striking within the recess44is possible.

In a variation of one embodiment, a bearing shell212is provided (FIG. 11) which has an edge area214towards the recess44which has a sealing effect in relation to the recess44. As a result, fluid from the impeller chamber cannot pass into the recess44and, therefore, into the rotor chamber30.

The bearing shell212slides on the bearing ball38via this edge area214(inner edge). This edge area214can wear out only on the spherical contact surface on the bearing member38. When no lubrication or along a minimum lubrication is present, it also forms a relatively tight terminating element towards the recess44and, therefore, towards the rotor chamber30.

The edge area214forms a continuous area for the purpose of the fluid-tight delimitation of the rotor chamber30in relation to the impeller chamber60at the recess44.

A flow path216for fluid to be pumped as lubricant for the corresponding bearing device is shown schematically inFIG. 11. The lubricant flows between the bearing ball38and an outer area of the bearing shell212into one or more channels218. The edge area214provides for a seal in relation to the recess44.

Otherwise, the circulating pump196functions as described above.