The invention relates to a vane pump with a pump housing having a sleeve-shaped housing body, a bottom, and a cover, with the bottom and the cover axially closing the housing body, a rotor arranged eccentrically in the housing body and rotatably mounted in the bottom and cover, and one or more vanes which are mounted in the rotor for movement in axial direction.
Vane pumps are known in many configurations. They are intended to seal gaseous media, to produce a negative pressure, or to transport gaseous or liquid media. In these vane pumps, a rotor is eccentrically arranged in the pump housing and has several vanes which are movably mounted so as to form between the vanes and between the rotor and the inner circumferential surface of the pump housing forming the stator, work spaces that have continuously changing volumes, i.e. expand and contract. The vanes are hurled outwards by the centrifugal force when the rotor rotates and sweep on the inner circumferential surface of the pump housing. As a result, the respective work space is sealed against the neighboring work spaces. The sealing action is assisted by wetting the surface of the components with lubricating oil. This lubricating oil also serves to reduce frictional forces so that the power loss of the pump is reduced. It is considered disadvantageous however that the transported fluid becomes necessarily wetted with lubricant and possibly has to be cleaned before being either used again or released into the atmosphere. Moreover, lubricant is consumed.
The invention is based on the object to provide a vane pump which exhibits a lesser consumption of lubricant and in which the transported fluid is free of lubricant.
In accordance with the invention, this object is attained by a vane pump of the afore-described type by providing each vane at its axial end faces with bearing pins which engage in the bottom and the cover.
In the vane pump according to the invention, the vane is not only mounted in the rotor for movement in radial direction so as to be able to oscillate in radial direction in relation to the rotor in accordance with the eccentric disposition of the rotor in the pump housing but also has bearing pins which engage in the bottom and the cover so that the vane can be deliberately controlled via these bearing pins. This is possible because the bottom and the cover are stationary and the bearing pins revolve in the bottom and the cover.
For that purpose, the bottom and the cover have each a guideway for the bearing pins, with the bearing pins engaging in the guideways free of clearance or at slight clearance. Preferably, the guideways are configured as groove, with the guideway exhibiting in particular a circular shape and lying in coaxial relationship to the inner circumferential surface of the housing body. As a result, the vanes always assume a defined position in relation to the inner circumferential surface of the housing body. This has the advantage that this position is assumed even when the rotor does not revolve. As a result, when the rotation speeds are low and thus the centrifugal force is also small, it is ensured that the vanes still assume a defined position so that optimum transport results are achieved, already when the rotation speeds are low. This is of advantage e.g. when starting a combustion engine and the vane pump operates as lubricant pump. In this case, the lubricant is transported already at the start of the engine and not when higher rotation speeds are involved.
In a preferred exemplary embodiment, the bearing pin is formed by a bolt mounted in the vane. As a result, the vane can be produced as usually, for example as injection-molded part or a die-case part, which needs only to be provided with the bearing pin. The latter may, for example, be injected directly into the injection-molded part.
According to a refinement, the free end of the bolt, which end extends axially beyond the vane, supports a bearing, in particular a deep groove ball bearing. This deep groove ball bearing engages in the guideway and revolves in the bottom and the cover. Preferably, the deep groove ball bearing is self-lubricating so that the need for an additional lubrication can be omitted.
An essential feature of the invention resides in the presence of a gap between the radially outer vane tip and the inner circumferential surface of the housing body. This gap ensures that no frictional forces can establish between vane and housing body so that the vane is not exposed to wear on one hand, and the power loss of the pump is small on the other hand. The gap lies hereby at a range between 5 μm to 100 μm, and in particular between 10 μm and 50 μm.
In the event a complete sealing is desired or required, a sealing bar may be arranged on the radially outer vane tip. In an exemplary embodiment, a groove extends in the radially outer vane tip in length direction of the vane and receives a sealing bar which projects beyond the vane tip. This sealing bar is floatingly supported in the groove so as to be able to execute relative movements in relation to the vane. When the rotor rotates, this sealing bar is forced or hurled against the inner circumferential surface of the housing body to thereby completely seal the work space. As the weight of the sealing bar is virtually negligible in comparison to the vane, the frictional forces are minimal.
Preferably, the sealing bar is made of metal, especially light metal or of a plastic which is fiber-reinforced for example. Such sealing bars have a slight weight on one hand and are sufficiently wear-resistant on the other hand.
Preferably, the vane pump according to the invention is operated in the absence of lubricant, i.e. running dry. This has the advantage that the transported medium is not contaminated so that the need for oil separator or the like at the outlet of the vane pump is eliminated.
Further advantages, features and details of the invention are set forth in the sub-claims and the following description which describes in greater detail a particularly preferred exemplified embodiment with reference to the drawing. The features illustrated in the drawing and set forth in the description and the claims may be relevant individually or in any combination
The drawing shows in:
FIG. 1 a perspective view of the vane pump according to the invention;
FIG. 2 a side view in direction of the arrow II according to FIG. 1;
FIG. 3 a perspective view according to FIG. 1 with detached housing cover;
FIG. 4 a section IV-IV according to FIG. 2;
FIG. 5 a section V-V according to FIG. 4;
FIG. 6 a section VI-VI according to FIG. 4; and
FIG. 7 a perspective view of a vane, cut open in part.
FIG. 1 depicts a vane pump 10 which essentially includes a housing body 12 with cooling fins 14, a bottom 16 with fastening brackets 18, and a cover 20 with a fastening bracket 22. Further shown are outlet and inlet openings 24 and 26 in the cover 20 as well as a flange 28 for attachment of a (not shown) drive which is connected to a driveshaft 30.
As can be seen from FIG. 3, the housing body 12 has a substantially sleeve-like configuration in surrounding relationship to a rotor 32 which is mounted eccentrically in the housing body 12 and from which the driveshaft 30 projects out. The rotor 32 is substantially cylindrical in shape and provided with receiving slots 34 which extend in axial direction and have open edges at the circumference of the rotor 32 and the end faces thereof. Moreover, the rotor 32 is provided with a multiplicity of axial bores 36 and 38, with the bores 38 lying at the base of the receiving slots 34 and the bores 36 lying between the receiving slots 34. These bores 36 and 38 reduce the weight of the rotor 32 and thus its moment of inertia. Vanes 40 are located in the receiving slots 34 and mounted in such a way as to be able to move in radial direction. Two adjacent vanes 40, the circumferential surface 42 of the rotor 32, and the inner circumferential surface 44 of the housing body 12 form each a work space 46 in which the trapped fluid is transported from the inlet opening 26 to the outlet opening 24.
As can be seen from FIG. 4, the inlet opening 26 and the outlet opening 24 are connected via overflow channels 48 in the housing body 12 having crescent-shaped inlets and outlets 50 and 52 feeding into the work spaces 46.
FIG. 5 clearly shows that the work spaces 46 permanently expand and contract and that the vanes 40 project more or less far into the receiving slots 34 of the rotor 32.
FIG. 7 shows such a vane 40 which is provided on both its end faces 54 with bearing pins 56 that are formed by bolts 58 which engage in the vanes 40 and project beyond the end face 54 and which support a bearing 60, for example a deep groove ball bearing 62.
As can be seen from FIG. 6, the cover 20 has a guideway 66 configured in the shape of a groove 64 for guiding the deep groove ball bearing 62. The groove 64 thus forms a forced control for the vanes 40 as the groove 64 lies coaxially to the inner circumferential surface of the housing body 12 and thus eccentrically to the rotor 32 and the driveshaft 30 thereof. The position of the guideway 66 and the radial extent of the vanes 40 as well as the position thereof in the rotor 32 are so dimensioned that the vane tip 68 (FIG. 7) has a constant distance to the inner circumferential surface 44 of the housing body 12 in the range of 5 μm to 100 μm. The guideway 66 is thus situated such as to ensure this gap or distance to the inner circumferential surface 44, with consideration that the vanes 40 although radially arranged in the rotor 32 are inclined to the orthogonal in relation to the housing body 12, in particular the inner circumferential surface 44 thereof. This means that the inner circumferential surface 44 and/or the guideway 66 has or have a configuration which deviates from the circular shape as the gap is constantly of same size. The gap may also fluctuate within certain limits.
FIG. 7 further shows that the vane tip 68 has a groove 70 which extends in length direction of the vane 40 and in which a sealing bar 72 is placed and slightly extends beyond the vane tip 68. The sealing bar 72 floats in the groove 70 and is able to move especially in direction of the inner circumferential surface 44 of the housing body 12. The sealing bar 72 has the task to bridge and seal the gap between the vane 40 and the inner circumferential surface 44 of the housing body 12. The gap is effectively closed, in particular when the gap continuously changes, and it is ensured that the vane tip 68 does not touch the inner circumferential surface 44 of the housing body 12. As the sealing bar 72 is made of plastic in particular, the weight is low so that the frictional forces become negligibly small. Moreover, the sealing bar 72 can easily be exchanged.