Pump, pump system and water-bearing household appliance

Abstract

A pump (1) for a water-bearing household appliance (100) is provided. The pump (1) comprises a shaft (2) extending in an axial direction (A), a bearing bushing (3) configured to rotatably support the shaft (2) about the axial direction (A), a drive (4) configured to rotate the shaft (2), and a seal (5) configured to seal against the shaft (2). The seal (5) is arranged in a sealing area (6) of the shaft (2), and the drive (4) is arranged in a drive area (7) of the shaft (2) opposite the bearing bushing (3). The bearing bushing (3) has at least one passage (8) configured to connect the sealing area (6) with the drive area (7). A pump system and a water-bearing household appliance are also provided.

Description

[0001] The invention relates to a pump, a pump system for a water-bearing household appliance and a water-bearing household appliance.

[0002] Laundry treatment equipment typically uses drain pumps to pump out or transfer fluids such as lye or cleaning solutions. These pumps are often designed using the wet rotor principle, meaning that the pump's rotor (usually magnetic) is located within the fluid being pumped. This wet rotor design eliminates the need for costly mechanical seals with increased friction, which would otherwise separate the working fluid from the drive. A canned housing, in which the rotor is supported by bearings, for example, separates the pumped medium from the electrical drive, thus creating a barrier between the wet and dry areas.To improve the rotor's running characteristics, for lubrication and cooling, and to prevent unwanted vibration and / or noise, the canned tube is sealed to the fluid being pumped with a radial shaft seal. This allows the use of a water-oil emulsion in the drive system, which improves the rotor's performance and protects the drive bearing from particles in the pumped fluid. Simple radial rubber seals are typically used as shaft seals, featuring sealing lips or providing additional sealing through spring tension. Circumferential coil springs within the rubber seal further enhance its sealing properties.

[0003] During operation, the lubricant and coolant film initially applied between such seals and the drive shaft can be reduced or removed due to thermal influences or axial shaft misalignment caused by pressure differences between the working medium and the working area or bearing area in the canned tube. As a result, the coefficient of friction between the rubber of the seal and the steel of the shaft can change, typically increasing. The rubber seal is subjected to increased friction, which may involve not only sliding friction but also, very briefly, a temporary state of static friction before reverting to sliding friction. This can lead to a continuous alternation between sliding and static friction, a so-called stick-slip effect.In the stick-slip effect, the rubber seal adheres to the shaft by friction, rotates with the shaft over a few degrees or minutes of arc, and deforms elastically until, due to the rotational (tangential) stresses of the component, sliding friction is re-established between the rubber and the steel. The seal then rotates or springs back to its original position. If this cycle of alternating between static and sliding friction repeats itself with a constant sequence, a disturbance frequency can develop in this resonant circuit, with the oscillation period corresponding precisely to the time between sliding friction, static friction, and renewed sliding friction. Frequencies of several hundred hertz (Hz) up to several kilohertz (kHz) are typically reached. This stick-slip effect leads to unpleasant noise and additional undesirable material wear, or accelerated component deterioration.

[0004] EP 3 135 921 A1 relates to a water pump unit in which a rotating shaft is mounted by a holding element in such a way as to reduce vibrations and noise generation.

[0005] Therefore, the object of the invention is to provide a pump, a pump system and a water-bearing household appliance which can avoid unwanted noise generation caused by the pump drive.

[0006] This problem is solved by a pump having the features of claim 1, a pump system having the features of claim 10 and a water-bearing household appliance having the features of claim 11.

[0007] According to one aspect of the present invention, a pump for a water-bearing household appliance is provided. The pump comprises a shaft extending in an axial direction, a bearing bushing configured to rotatably support the shaft about the axial direction, a drive configured to rotate the shaft, and a seal configured to seal against the shaft, wherein the seal is arranged in a sealing area of ​​the shaft and the drive is arranged in a drive area of ​​the shaft opposite the bearing bushing, and wherein the bearing bushing has at least one passage configured to bring the sealing area into communication with the drive area.

[0008] Compared to the prior art, the bearing bushing can be continuous from the drive area to the bearing area (for example, achieved through predominantly axial channels). In other words, a fluid can pass through the bearing bushing (for example, in the axial direction). Thus, the bearing bushing can be designed to be continuous for fluid flow. Consequently, the seal that seals the drive area and the area where the pump shaft is supported against the fluid being pumped can be lubricated even during pump operation. More precisely, a fluid can flow from the drive area to the seal. This reliably prevents the stick-slip effect and the associated vibration and noise generation. Furthermore, the service life of the seal can be increased, as continuous lubrication of the seal can be ensured.Furthermore, the seal can be protected from being additionally exposed to tangential high-frequency stresses and strains.

[0009] The water-using appliance could be a laundry treatment machine or a washer-dryer. It is also conceivable that the water-using appliance could be a dishwasher. The pump could be a radial centrifugal pump and could have a synchronous pump drive.

[0010] The shaft can be a cylindrical element that extends rotationally symmetrically around its axis in the axial direction. The shaft can be made of a metal alloy, particularly steel. Preferably, the shaft has a circular cross-section. The circular cross-section of the shaft has a radius extending in a radial direction. The axis of the shaft is preferably perpendicular to the circular cross-section of the shaft. Furthermore, the axis of the shaft can be perpendicular to the radial direction of the shaft. Preferably, the shaft is designed to be driven by rotation. For this purpose, the shaft can have a driven end at which the shaft is driven, and a driving end at which the shaft drives another element (for example, an impeller). The driven end can be opposite the driving or driven end. The driven end can be located within the drive area.The driving end can be located beyond the sealing area. The shaft can extend through both the driving and sealing areas. For example, the shaft can have a diameter of 3 mm to 3.5 mm, but larger diameters are also possible.

[0011] A bearing bushing can be an element for supporting a shaft, such as a plain bearing bushing. A bearing bushing can have the form of a hollow cylinder. For example, the bearing bushing can be made of steel, bronze, metal, a plastic, or a fiber-reinforced plastic. The bearing bushing can be designed to support a shaft rotatably around its axis within the pump. In particular, the bearing bushing can be a plain bearing bushing. In a plain bearing, the two parts moving relative to each other (e.g., the bearing bushing and the shaft) can be in direct contact. The bearing bushing can be an integral or one-piece component. The bushing can be designed to support the shaft rotatably within a housing (e.g., a canned tube). The bearing bushing can be fixed to the housing so that the shaft can rotate relative to the bearing bushing. Furthermore, the pump or...The pump drive may include an additional bearing bushing, which can be located within the drive area. This allows the shaft to be supported at two points. For example, the bearing bushing may be designed to fix, position, or hold the seal.

[0012] A drive can be a device for generating a rotational motion and a rotationally acting torque. Furthermore, the drive can be designed to transmit the electromagnetic rotational motion (rotating field) to the shaft. Preferably, the drive is designed to rotate the shaft. The drive can be an electric motor. The motor can be an asynchronous motor. Alternatively, the motor can be a permanent magnet synchronous motor. This allows for a particularly simple pump design. In the synchronous motor, a constantly magnetized rotor can be driven synchronously by a rotating magnetic field in a stator. Preferably, the synchronous motor's movement is synchronous with the applied alternating voltage. Thus, no direct mechanical contact (mechanical coupling) between the rotor and stator is necessary. This allows for an advantageously sealed pump.The rotor can, for example, be located within the drive area. The drive area can be sealed off from the stator. A drive area can be understood as a section of the shaft that incorporates a drive. In other words, the drive area can extend axially along the shaft. Furthermore, a drive area can be understood as the section of the shaft that is located opposite the sealing area with respect to the bearing bushing. The drive area can be directly adjacent to the sealing area.

[0013] The seal can be an element designed to prevent or limit unwanted material transfer from one side of the seal to another. The seal can comprise EPDM (ethylene propylene diene monomer rubber), NBR (acrylonitrile butadiene rubber), SBR (styrene butadiene rubber), FKM (fluorocarbon rubber), and / or CR (chloroprene rubber). Unwanted material transfer can be the passage of a liquid and / or gas through the seal. In one embodiment of the present invention, the seal serves to prevent the ingress of the fluid to be pumped into the working area, drive area, or sealing area. Furthermore, the seal can be designed to prevent the escape of fluid from the working area and / or the sealing area into the fluid to be pumped. The pump can have a housing. The housing can have an opening through which the shaft extends.The seal can be positioned within this opening so that the opening is essentially sealed by the seal and the shaft. In other words, the seal can close a gap between the shaft and an edge of the opening (i.e., seal against the shaft). Thus, the seal can be designed to prevent fluid from passing from an area outside the housing (e.g., from the pump pressure chamber) into the housing (e.g., the slotted housing of a wet-rotor drive). The seal can be positioned so that it is fixed to the drive housing (e.g., the slotted tube). The shaft can rotate relative to the seal. This allows for relative movement between the shaft and the seal, which is accompanied by a frictional torque due to the component contact, i.e., the friction between the components. Furthermore, the seal can be designed to at least partially accommodate the bearing bushing.In other words, the seal can extend along the axial direction and at least partially surround the bearing bushing. The bearing bushing can thus bear against the seal. This allows for a particularly reliable seal of the housing (e.g., a split tube), since the load radially transferred by the bearing bushing acts on the seal, thereby improving the sealing effect between the housing and the seal. This often eliminates the need for clamping elements in the seal. As a result, the seal design can be particularly simple. Furthermore, the seal can have a radially inward-facing projection in the area where it contacts the bearing bushing. The bearing bushing can have a corresponding radial recess that is in contact with this projection.Thus, axial displacement of the bearing bushing towards the seal or the drive housing (slotted tube) can be prevented or reduced using simple means.

[0014] The seal can define the sealing area. The sealing area can extend along the shaft (i.e., in the axial direction). The sealing area can be limited by the sealing point between the seal and the shaft and the bearing bushing. Furthermore, the section of the shaft opposite the drive area with respect to the bearing bushing can also be considered a sealing area.

[0015] The fluid or medium can be a liquid, a gas, or a mixture that can reduce friction between the shaft and the bearing bushing and / or cool the shaft, the bearing bushing, and / or a rotor. The fluid can also be suitable for preventing or reducing corrosion of the shaft and / or the bearing bushing. Furthermore, it can include a component designed to prevent the fluid from freezing. The fluid can be a lubricant, a coolant, a corrosion inhibitor, and / or an antifreeze. The fluid can also be an aqueous solution or a water-oil emulsion, which then possesses damping properties to reduce vibration noise of the rotor assembly. Finally, the fluid can be two-phase and a liquid-air mixture.The fluid can be stored in a reservoir within the pump, the reservoir being designed to release a portion of the fluid to the bearing bushing during pump operation. Additionally or alternatively, the fluid can be provided in the drive section.

[0016] The passage can be an opening, channel, or through-hole in the bearing bushing, extending axially similarly to the shaft bore in the bearing bushing, but not arranged concentrically to the shaft bore. A passage can have a cylindrical shape. The passage can extend along a central axis and thus follow a direction vector that has predominantly axial components. The passage can have a circular, elliptical, or rectangular cross-section. The passage can be designed to bring the sealing area into communication with the drive area. Communication can be understood, in particular, as fluidic communication. Accordingly, a fluid can be transported through the bearing bushing, usually predominantly in an axial direction. Transport of a fluid can be understood as any movement of the fluid, in particular flowing or streaming of the fluid.The fluidic communication, enabled by at least one passage, has the advantage that the fluid can be distributed across the various areas of the shaft, ensuring lubrication, cooling, corrosion protection, and / or frost protection for other components in different parts of the pump. In other words, the fluid can flow from the drive area to the sealing area. This ensures a low coefficient of friction between the seal and the shaft over the entire service life of the water-bearing household appliance. Furthermore, the stick-slip effect and the associated unpleasant vibrations and noise can be avoided.

[0017] According to one embodiment, the at least one passage is designed such that a fluid can flow from the drive area through the bearing bushing into the sealing area or from the sealing area into the drive area. Preferably, the fluid enters the passage in the bearing bushing in the drive area and exits the passage on the opposite side of the bearing bushing. This allows the fluid to reach the seal and reduce friction between the seal and the shaft. Furthermore, the fluid can lubricate and cool the contact area between the shaft and the seal. Additionally, a fluid, which may include a corrosion inhibitor and / or antifreeze, can be evenly distributed over the entire length of the shaft in both the sealing and working areas, thus protecting the shaft over a large area from corrosion and / or frost, as well as from heat generation due to friction at the seal.

[0018] According to a further embodiment, at least one passage extends through the bearing bushing at a constant distance in the radial direction relative to the shaft. The radial direction can be perpendicular to the axial direction. The distance between the central axis of the at least one passage and the axis of the shaft can be constant. In other words, the radial distance can be constant along the axis of the shaft. Several passages can be present, each passage having the same constant distance from its central axis to the axis of the shaft. The same distance between the central axis of the passage and the axis of the shaft can also be maintained if the passage extends through the bearing bushing in a curved path relative to the shaft. In other words, the passage can extend at a constant radial distance from the bearing bore (i.e.,to the shaft) and additionally possess a tangential component of the passage alignment vector, thus resembling a thread (further details follow below). Preferably, the at least one passage can be arranged parallel to the shaft. This has the advantage that a fluid can travel from the drive area to the sealing area and vice versa via a short or very short path. This enables bidirectional fluid transport. Furthermore, this embodiment has the advantage that the bearing bushing with the at least one passage can be manufactured simply and cost-effectively.

[0019] According to a further embodiment, the at least one passage extends at a variable distance from the shaft. This variable distance can be a variable radial distance. A variable distance can be understood to mean that the central axis of the passage is skew to the axis of the shaft. Skew means that the central axis of the passage and the axis of the shaft neither intersect nor are parallel to each other. Multiple passages can be present. These multiple passages can have the same variable distance from the axis of the shaft or different variable distances from the axis of the shaft. Due to the rotation of the shaft and, if applicable, other components, radial pressure fields with varying local pressures can build up.Furthermore, due to the axial misalignment of the passages, different pressures can prevail at different radial distances (i.e., radii) of the passage openings. This pressure difference in radial extent can cause a flow of fluid to build up through the passage from the larger radius to the smaller radius.

[0020] The at least one passage with a variable distance from the shaft axis offers the advantage of allowing the direction of fluid flow to be controlled. The variable distance of this passage can be selected so that the fluid flows exclusively or primarily from the drive area to the sealing area, or vice versa. This allows, for example, a specific pressure to be built up in the sealing area. As a result, the fluid can be reliably forced between the seal and the shaft, and the sealing properties of the seal can be improved.

[0021] According to a further embodiment, at least one passage is open towards the shaft. This at least one passage can be open radially along its entire length. Thus, the fluid passing through the passage can come into direct contact with the shaft, even in the area of ​​the bearing bushing. This allows for effective or even more effective lubrication and / or cooling of the shaft between the bearing bushing and the shaft.

[0022] According to a further embodiment, the at least one passage is partially open towards the shaft. The passage can have one or more sections in which the fluid comes into direct contact with the shaft. Furthermore, the passage can have one or more sections closed towards the shaft, in which the fluid does not come into direct contact with the shaft. This prevents the shaft from entering the passage(s). In other words, the closed sections of the at least one passage prevent the shaft from entering or becoming trapped in the passage and blocking it, for example, in the case of increased bushing wear.

[0023] According to another embodiment, the bearing bushing has one to thirteen passages, preferably three to seven. With multiple passages, it has been shown that sufficient fluid can be conveyed into the sealing area to adequately wet and lubricate the seal. Three to seven passages have proven particularly advantageous, as a uniform flow of fluid was observed. Furthermore, sufficient pressure was established in the sealing area within this range, providing mechanical support for the seal. The more passages there are, the greater the amount of fluid that can pass through the bearing bushing.

[0024] According to a further embodiment, the at least one passage has a diameter of at least 1.0 mm, preferably at least 1.5 mm. This allows the fluid to be transported from the drive area to the sealing area to a sufficient extent for lubricating the seal. With smaller diameters, unfavorable flow resistance can occur in the passages, potentially impeding fluid transport. In the diameter range of at least 1.5 mm, it was observed that the bearing bushing was able to absorb radial forces from the shaft very effectively without deformation, despite the passages. In other words, very good mechanical strength of the bearing bushing can be ensured.

[0025] According to a further embodiment, the bearing bushing has at least two passages with different diameters. Differently sized passages ensure both a sufficient fluid flow rate through the bearing bushing and, consequently, particularly good mechanical stability. This is especially advantageous at high shaft speeds and thus increased loads on the bearing bushing. It is also advantageous that the bearing bushing maintains symmetry with respect to a plane passing through its axis. This ensures sufficient strength for the bearing bushing.

[0026] According to a further embodiment, at least one passage is arranged such that the angle between the passage and the shaft axis is 1° to 45°, preferably 5° to 20°. Preferably, the angle between the passage and the shaft axis is understood to be the angle between the central axis of the passage and the shaft axis. This has the advantage that the direction of fluidic communication can be influenced. The angle between the centerline of the at least one passage and the shaft axis can be selected such that the fluid can flow from the drive area to the sealing area, or vice versa, solely by specifying the direction of rotation of the rotor in accordance with the axial inclination of the passages or the passage itself. In this way, not only can hydraulic communication be realized between the drive and sealing areas, but even a fluid flow can be initiated by the rotor rotation.Furthermore, the angle between the axes can influence the amount of fluid that can pass through the passages of the bearing bushing. A large angle reduces the amount of fluid that can pass through the bearing bushing, or is even conveyed, whereas a shallow angle can increase the amount of fluid that can pass through the bearing bushing. However, no dependence or flow rate amplification on the rotor's direction of rotation can be derived from this. With a larger angle, the passage length can be increased, which can also increase the frictional resistance or flow resistance within the passage. Additionally, by arranging at least one passage at an angle, inlet losses at the upstream end of the passage can be reduced, as the opening cross-section is then increased perpendicular to the bearing bushing.In other words, the opening area of ​​at least one passage to the drive area and / or sealing area can be enlarged, making it particularly easy for the fluid to enter at least one passage.

[0027] According to a further embodiment, at least two passages are provided, arranged so that they intersect or cross each other. Two intersecting passages can touch at least one point without their center axes touching. In the case of two crossing passages, the center axes can touch at one point. A fluid volume entering a first passage and another fluid volume entering a second passage can come into contact in the area where the first and second passages intersect. This allows for improved mixing of the fluid and prevents the separation of the fluid's components, for example, water and oil in the case of a water-oil emulsion.

[0028] According to a further embodiment, at least two passages are provided, arranged so that they neither intersect nor cross each other. "At least two passages that do not intersect" can be understood to mean that the at least two passages do not touch each other. "Two passages that do not cross" can be understood to mean that the center axes of the passages are arranged at an angle to each other. This has the advantage that potential flow resistances caused by the mixing of fluid volumes in the area where different passages intersect can be avoided. Furthermore, this has the advantage that effective and rapid fluidic communication can be achieved, which can then be designed, for example, for different operating points, so that a different inclination of the passage axis is optimally specified for each different operating point.

[0029] Preferably, at least one passage extends through the bearing bushing in a substantially helical shape. A substantially helical passage can be understood to mean that the shape of the at least one passage is substantially similar to a helix. In other words, the central axis of the passage can extend around the shaft through the bearing bushing in the form of a helix. The passage, which extends in a helical shape (e.g., screw or thread form), can have a constant pitch around the shaft, so that there is a constant deflection of the predominantly axially extending passage axis relative to the bearing axis in a tangential direction in the cylindrical coordinate system. The advantage of a helical passage is that the pitch of the helix can be selected such that the fluid is guided along the helix, thus preventing undesirable turbulence of the fluid upon contact with the bearing bushing.to a single passage. Furthermore, the helical shape has the advantage that the direction of fluidic communication can be defined. Depending on the direction of rotation of the helix and the choice of the direction of rotation of a rotor or shaft, the fluid can either flow only from the drive area to the sealing area, but not from the sealing area to the drive area, or only from the sealing area to the drive area, but not from the drive area to the sealing area. Preferably, the at least one helical passage and the shaft have the same direction of rotation, so that the transport of the fluid is supported by the rotation of the shaft. The helical shape enables efficient fluidic communication. The helical passage can be designed in a screw-like form, so that virtually all threads have the same pitch. Alternatively, the helical passage can be implemented with a variable pitch.One embodiment would promote fluid transport in which the passage axis has a steeper inclination at the inlet and beginning of the channel, which then decreases with further axial extension. This reduces the passage length through the sliding bearing bushing compared to a constant inclination. The prevailing shaft rotation allows for the generation of dynamic pressure within the at least one helical passage, further enhancing fluid transport. In other words, varying the radial distance between the passage axis and the bearing bushing axis allows the passage axis to take on a tangential shape, resulting in a helical form.

[0030] Preferably, the axial extent of the passages is not extended by tangential components, so that flow resistance is not negatively affected. Consequently, the angle of the passage axis relative to the shaft axis can be between 5 and 20°. The longitudinal axis of the passage need not be radially inclined, but can instead have an inclination that is tangential in cylindrical coordinates, thus creating a quasi-helical shape for the passage.

[0031] According to a further aspect of the present invention, a pump system is provided comprising a pump according to one of the above embodiments and an impeller arranged on the side of the shaft with respect to the bearing bushing in the sealing area and provided such that it is rotatable together with the shaft. The impeller (rotor) can be a rotating body enclosed in an annular, tubular, or cylindrical housing, particularly for a pump for a water-bearing household appliance. Preferably, the impeller is designed and arranged on the shaft such that the impeller is driven to rotate when the shaft is driven to rotate. Furthermore, the impeller is designed to increase the pressure in a medium to be pumped in a pump chamber. Preferably, the impeller has several straight or curved blades or ribs that can rotate in the fluid to be pumped.

[0032] According to a further aspect of the present invention, a water-bearing household appliance is provided, comprising at least one pump according to one of the above embodiments. In particular, the water-bearing household appliance can be a washing machine or a washer-dryer.

[0033] According to a further aspect of the present invention, a method for guiding fluid through a bearing bushing is provided, wherein the method comprises providing a pump according to one of the above embodiments, driving the shaft so that it rotates about an axial direction, and conveying fluid through the at least one passage in the bearing bushing so that the fluid passes from the working area into the sealing area. Preferably, the fluid lubricates the seal in the sealing area, particularly in the contact area between the seal and the shaft. Thus, sliding friction between the seal and the shaft can be reduced and / or static friction effects between the shaft and the seal can be completely eliminated, which can lead to a slip-slide effect between the shaft and the seal. Preferably, the method further comprises supplying fluid to the working area. The fluid can be supplied from a reservoir.This ensures sufficient fluid is present in the working area, even if fluid has leaked into the sealing area. This guarantees adequate lubrication in both areas.

[0034] According to one embodiment of the invention, a pump is provided with a bearing bushing, wherein the bearing bushing is designed as a radial sliding bearing bushing. The sliding bearing bushing can be a hollow cylinder. The fluid can be transported through the bearing bushing via largely axially extending passages (e.g., grooves or channels with variable flow cross-section, preferably a circular flow cross-section) on the outer surface of the sliding bearing cylinder. Additionally or alternatively, the fluid can be transported through the bearing bushing via largely axially extending passages (e.g., grooves or channels with variable flow cross-section, preferably a circular flow cross-section) on the inner surface of the sliding bearing cylinder. Thus, the fluid can be transported through the bearing bushing virtually at the bearing friction surface.The fluid is transported through bores or channels with variable flow cross-sections (preferably round flow cross-sections) through a wall of the sliding bearing bushing. Thus, the passages can be integrated as channels within the bearing bushing. A combination of the above measures is also conceivable to achieve even better fluid transport into the sealing area.

[0035] Furthermore, the invention relates to the use of a pump according to one of the above embodiments in a water-bearing household appliance. The water-bearing household appliance is preferably a washing machine or a washer-dryer.

[0036] The advantages and effects mentioned in connection with the device also apply analogously to the method, and vice versa. Individual features of different embodiments can be combined with other features or other embodiments to form new embodiments. The aforementioned advantages and effects of the features also apply to the new embodiments.

[0037] In the following, embodiments of the present invention are described in detail with reference to the accompanying figures. Figure 1 shows a schematic and perspective representation of a pump according to an embodiment of the present invention. Figure 2 is a schematic representation of part of a pump according to an embodiment of the present invention. Figure 3 is a schematic representation of part of a pump according to a further embodiment of the present invention. Figure 4is a schematic and perspective view of a bearing bushing of a pump according to an embodiment of the present invention. Figure 5 Figure 1 is a schematic representation of a bearing bushing of a pump according to a further embodiment of the present invention. Figure 6 Figure 1 is a schematic representation of a bearing bushing of a pump according to a further embodiment of the present invention.

[0038] Figure 1Figure 1 is a schematic and perspective longitudinal section view of a pump drive 1 according to an embodiment of the present invention. The pump 1 comprises a drive 4, which is provided in a drive area 7. The drive 4 is designed to rotate a shaft 2 about an axis (hereinafter referred to as the axial direction A). The shaft 2 is supported by a bearing bushing 3 (also referred to as the first bearing bushing 3) and a second bearing bushing 9. The drive 4 is a permanent magnet synchronous drive. More precisely, the drive 4 is a permanent magnet synchronous drive based on the so-called wet rotor principle. The shaft 2 is arranged in a canned tube 12. The canned tube 12 is designed to be virtually fluid-tight, as it is sealed to the fluid-carrying pump pressure chamber by a spring-loaded radial shaft seal. The canned tube 12 can also be referred to as the housing.Inside the can 12, a water-oil emulsion is used to improve the operating characteristics of the drive 4 and the shaft 2. Thus, a fluid or medium (the so-called can liner filling, lubricating and cooling medium) is located in the working area 7. The working area 7 is bounded by the bearing bushing 3 and the bearing bushing 9. Furthermore, the pump 1 includes a seal 5, which is designed to seal against the shaft 2. In other words, the can 12 has an opening through which the shaft 2 extends. The opening 13 is sealed by the seal 5 in such a way that no fluid can enter the can 12 from the outside (pump pressure chamber) into the can 12, nor can any fluid pass through the seal 5 from the inside (can 12) to the outside (pump pressure chamber). The area of ​​the shaft 2 in which the seal 5 is located is referred to as the sealing area 6.In other words, the sealing area 6 is defined between the sealing point between shaft 2 and seal 5 and the bearing bushing 3. The seal 5 is in direct contact with the shaft 2 and thus primarily seals the canned tube filling, preventing its loss, even though the drive is essentially designed as a "wet-rotor" design. The seal 5 is held against the canned tube 12, either by its mounting or by its axial press-fit. Therefore, the shaft 2 can move relative to the seal 5 during operation. Further axially along the shaft 2, away from the sealing area 6, an impeller 11 is arranged, which is rotatably mounted within a pump chamber or pressure chamber. Operation of the shaft 2 rotates the impeller 11, generating a pumping effect in the pump 1 based on the principle of a radial centrifugal pump (i.e., a continuously operating turbomachine).In the present embodiment, no seals are provided between the impeller (wheel) 11 and the seal 5, so that the seal 5 can come into contact with the fluid to be pumped (for example, a mixture of laundry detergent and water). Thus, normally neither the fluid from the working area 7 nor the fluid to be pumped from the pump pressure chamber is present between the seal 5 and the bearing bushing 3. The present invention provides at least one passage 8 in the bearing bushing 3 (in . Figure 1(not shown) is designed to bring the working area 7 into communication with the sealing area 6 to enable fluid transport. This allows the fluid medium to flow from the working area 7 into the sealing area 6. As a result, the seal 5 can be lubricated from the inside, so that the contact area between the seal 5 and the shaft 2 can be lubricated by the fluid from the sealing area 7. This prevents the switching between sliding and static friction, as the static friction effects are completely eliminated. Furthermore, the sliding friction, in the form of the coefficient of sliding friction, is significantly reduced. Consequently, the stick-slip effect and thus corresponding interference frequencies can be prevented. This enables particularly quiet operation of the pump 1.

[0039] Figure 2 is a schematic longitudinal section view of a section of pump 1. In Figure 2The sealing area 6 is shown enlarged. In contrast, only a portion of the working area 7 is shown. In the present embodiment, the bearing bushing 3 has a radially extending recess on its outer circumference, into which a corresponding projection of the seal 5 engages. Thus, the bearing bushing 3 can be held by the seal 5. More precisely, the bearing bushing 3 can be secured against axial displacement in this way. This enables a particularly simple pump design. Furthermore, in the Figure 2 In the cross-sectional view shown, a passage 8 is visible. Figure 2 The left area is the area facing the pump pressure chamber.

[0040] Figure 3This represents a further embodiment of the present invention. In this embodiment, the seal 5 has a double sealing lip on the side facing the pump pressure chamber. This allows the slotted tube 12 to be sealed particularly reliably against the pump pressure chamber. Otherwise, this embodiment is similar to the one described in Figure 2 depicted embodiment.

[0041] Figure 4 Figure 1 is a perspective and schematic representation as a side view of a bearing bushing according to an embodiment of the present invention. The bearing bushing has at least one passage 8 that runs along its outer circumference. In an installed or operating state, the fluid can thus flow from the working area 7 to the sealing area 6. The passage 8 is partially formed by the bearing bushing 3 and partially by the slotted tube 12 (in Figure 4 (not shown) formed.

[0042] Figure 5 is a bearing bushing 3 in a rear view according to a further embodiment of the present invention. The in Figure 5 The bearing bushing 3 shown has four passages 8. The bearing bushing 3 is in Figure 5 The embodiment is shown in a view essentially along the axial direction A. Furthermore, it can be seen that the passages 8 are provided in the bearing bushing 3 such that they are arranged on the inner hollow cylindrical surface of the bearing bushing 3. In other words, the passages 8 are open towards the shaft 2. This ensures that the fluid from the drive area 7 flows along the shaft 2 on its way to the sealing area 6 and can also exert its effect between the bearing bushing 3 and the shaft 2. For example, the fluid can comprise a lubricant, a coolant, a corrosion inhibitor, and / or an antifreeze, and introduce these effects precisely at the contact point between the shaft and the plain bearing.

[0043] Figure 6 Figure 1 shows another perspective and schematic view of a bearing bushing 3 from the rear side according to a further embodiment of the present invention. The bearing bushing 3 of the present invention also has 7 passages 8. In the present embodiment, the passages 8 are formed solely by the bearing bushing 3. In other words, no other elements, such as the shaft 2 or the spacer tube 12, are required to form the respective passage 8. This allows fluid transport from the drive area 7 to the sealing area 6 to be integrated into the sliding bearing bushing without any additional components.

[0044] In summary, the embodiments of the present invention prevent the stick-slip effect because the passages 8, which extend predominantly axially through the bearing bushing 3, allow the seal 5 to be lubricated and / or cooled from the drive side as well, thus completely eliminating the static friction effect between the shaft and the seal. In other words, a constant, low coefficient of friction for sliding friction can be ensured between the friction partners (i.e., between the seal 5 and the shaft 2), so that static friction effects are completely eliminated. Furthermore, consistent temperature and lubrication properties between the friction partners can be ensured even during prolonged operation of the pump 1.

Claims

1. Pump (1) for a water-conducting household appliance (100), comprising: a shaft (2) extending in an axial direction (A), a bearing bushing (3) which is configured to support the shaft (2) in a rotatable manner about the axial direction (A), a drive (4) which is configured to drive the shaft (2) in a rotating manner and a seal (5) which is configured to seal against the shaft (2), wherein the seal (5) is arranged in a sealing region (6) of the shaft (2) and the drive (4) is arranged in a drive region (7) of the shaft (2) which lies opposite the bearing bushing (3), and characterised in that the bearing bushing (3) has at least one passage (8) which is configured to bring the sealing region (6) into communication with the drive region (7).

2. Pump (1) according to claim 1, wherein the at least one passage (8) is configured such that a fluid from the drive region (7) can reach the sealing region (6) through the bearing bushing (3).

3. Pump (1) according to claim 1 or 2, wherein the fluid comprises a lubricant, a coolant, an anti-corrosion agent and / or an anti-freeze.

4. Pump (1) according to one of the preceding claims, wherein at least one passage (8) extends at a constant distance through the bearing bushing (3) in the radial direction (R) with respect to the shaft (2).

5. Pump (1) according to one of the preceding claims, wherein at least one passage (8) extends at a variable distance through the bearing bushing (3) in the radial direction (R) with respect to the shaft (2).

6. Pump (1) according to one of the preceding claims, wherein at least one passage (8) to the shaft (2) is open at least in sections.

7. Pump (1) according to one of the preceding claims, wherein at least one passage (8) is arranged such that it has an angle between the passage (8) and the axial direction (A) of the shaft (2) of between 1 ° and 45 °, preferably of between 5 ° and 20 °.

8. Pump (1) according to one of the preceding claims, wherein at least two passages (8) are provided and are arranged such that they intersect or cross one another.

9. Pump (1) according to one of the preceding claims, wherein at least one passage (8) extends through the bearing bushing (3) in a substantially helix-like manner.

10. Pump system (10), comprising a pump (1) according to one of the preceding claims, and an impeller (11) which is arranged on the shaft (2) on the side of the sealing region (6), with respect to the bearing bushing (3), and is provided such that it can be rotated together with the shaft (2).

11. Water-conducting household appliance (100), comprising at least one pump (1) according to one of claims 1 to 9.

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