Abstract:
A side-channel blower for an internal combustion engine includes a flow housing, an impeller which rotates in the flow housing, a drive unit which drives the impeller, a housing wall with a radially delimiting housing wall, impeller blades arranged in a radially outer region of the impeller, a radial gap arranged between the impeller and the housing wall, an inlet, an outlet, and two flow channels. The housing wall radially surrounds the impeller. The impeller blades open in a radially outward direction. The two flow channels connect the inlet to the outlet and are fluidically connected to one another via intermediate spaces between the impeller blades. An interruption zone is arranged between the outlet and the inlet which interrupts the two flow channels in a peripheral direction. A radial interrupting gap is arranged between the impeller and the radially delimiting housing wall in the entire interruption zone.

Description:
CROSS REFERENCE TO PRIOR APPLICATIONS 
       [0001]    This application is a U.S. National Phase application under 35 U.S.C. §371 of International Application No. PCT/EP2015/079414, filed on Dec. 11, 2015 and which claims benefit to German Patent Application No. 10 2015 100 214.0, filed on Jan. 9, 2015. The International Application was published in German on Jul. 14, 2016 as WO 2016/110371 A1 under PCT Article 21(2). 
     
    
     FIELD 
       [0002]    The present invention relates to a side-channel blower for an internal combustion engine comprising a flow housing, an impeller that is rotatably arranged in the flow housing, impeller blades that are formed in the radially outer region of the impeller and are open in the radially outward direction, a radial gap between the impeller and a housing wall that radially surrounds the impeller, an inlet and an outlet, as well as two flow channels for a gas which connect the inlet to the outlet and which are formed axially opposite the impeller blades in the flow housing, the ducts being fluidically connected to one another via intermediate spaces between the impeller blades, a drive unit for driving the impeller, and an interruption zone which is located between the outlet and the inlet and in which the flow channels are interrupted in the peripheral direction. 
       BACKGROUND 
       [0003]    Side-channel blowers or pumps have previously been described. In a vehicle, they serve, for example, to convey fuel, to blow secondary air into the exhaust system, or to convey hydrogen for PEM fuel cell systems. The drive is usually effected by an electric motor whose output shaft has the impeller arranged thereon. Side-channel blowers have previously been described in which only one flow channel is formed on an axial side of the impeller in a housing part, as well as side-channel blowers formed with a flow channel on either axial side of the impeller, in which case both flow channels are in fluid communication with each other. In such a side-channel blower, one of the flow channels is most often formed in a housing part which serves as a cover, while the other flow channel is formed in the housing part to which the drive unit is typically mounted, on the shaft of which the impeller is arranged to rotate therewith. The impeller is designed at its periphery so that it forms one or two circumferential vortex ducts together with the flow channel or the flow channels surrounding the impeller. 
         [0004]    In side-channel blowers with two axially opposite vortex ducts, the impeller blades are divided axially across a radial section into two sections which are respectively assigned to the opposite flow channel. Pockets are formed between the impeller blades in which, when the impeller rotates, the fluid conveyed is accelerated by the impeller blades in the circumferential direction as well as in the radial direction so that a circulating vortex flow is generated in the flow channel. With impeller blades of a radially open design, an overflow from one flow channel to the other most often occurs via the gap between the radial end of the impeller and the radially opposite housing wall. 
         [0005]    In order to obtain the best possible conveyance or pressure increase, different measures have been taken in conveying gases and liquids which are due to the different behavior of compressible and incompressible or slightly compressible media when they are conveyed. 
         [0006]    The generation of noise should also be taken into account when conveying in side-channel blowers since acoustically disturbing pressure surges occur at the beginning of the interruption zone immediately after a medium has flowed over each impeller blade because compressed gas is still present in the pockets between the impeller blades, which gas has not been completely expelled via the outlet and is suddenly accelerated against the walls of the interruption zone when it reaches that zone. This causes significantly increased noise emissions. 
         [0007]    Various outlet contours and designs of the interruption zone have previously been described for this reason. For example, DE 10 2010 946 870 A1 describes a side-channel blower in which recesses are formed behind the outlet in the radially delimiting housing wall which extend in the circumferential direction for several times the distance between the blades so that the interruption zone is formed in a stepped manner at the housing wall. The generation of noise may well be improved thereby, however, with such a design, the interruption zone extends over a circumferential angle of more than 60°, whereby the possible delivery rate and thus the efficiency of the blower is decreased since a shorter path is available for increasing pressure. The radial interrupting gap for preventing a short-circuit flow from the outlet directly to the inlet via the interruption zone is also merely about 0.3 mm. As a consequence, if such a blower is used in internal combustion engines at outside temperatures below the freezing point, condensates in the gap may freeze and block the impeller. Very accurate tolerances must further be observed during production and assembly so as to prevent contact between the impeller and the housing wall. 
         [0008]    A side-channel pump is also described in DE 691 01 249 T2 whose interruption zone is significantly shortened. To still prevent an overflow and to minimize noise generation, various measures are taken, which, however, are based on the assumption that an overflow occurs in the region of the closed disc of the impeller. To avoid an overflowing of the interruption zone, the radial gap between the impeller and the housing wall is kept as small as possible, whereby problems in manufacture are again caused due to tolerances that must be observed, and a significant generation of noise occurs in the interruption zone as the gas leaves the impeller in the radial direction. 
       SUMMARY 
       [0009]    An aspect of the present invention is to provide a side-channel blower with which the feed rate or the feed pressure of known side-channel blowers or comparable size is maintained, while the necessary tolerances can still be significantly increased in order to facilitate manufacture. An aspect of the present invention is to thereby prevent the formation of ice bridges in the blower and to make the blower less susceptible to the accumulation of dirt. An aspect of the present invention is also to prevent an overflowing of the interruption zone and if possible to reduce the generation of noise. 
         [0010]    In an embodiment, the present invention provides a side-channel blower for an internal combustion engine which includes a flow housing, an impeller configured to rotate in the flow housing, a drive unit configured to drive the impeller, a housing wall comprising a radially delimiting housing wall, impeller blades arranged in a radially outer region of the impeller, a radial gap arranged between the impeller and the housing wall, an inlet, an outlet, and two flow channels for a gas. The housing wall is configured to radially surround the impeller. The impeller blades are configured to open in a radially outward direction. A respective one of the two flow channels is respectively formed axially opposite to the impeller blades in the flow housing. The two flow channels are configured to connect the inlet to the outlet and to be fluidically connected to one another via intermediate spaces between the impeller blades. An interruption zone is arranged between the outlet and the inlet. The interruption zone is configured to interrupt the two flow channels in a peripheral direction. A radial interrupting gap is arranged between the impeller and the radially delimiting housing wall in the entire interruption zone. The radial interrupting gap is 0.005 to 0.03 times a diameter of the impeller. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The present invention is described in greater detail below on the basis of embodiments and of the drawings in which: 
           [0012]      FIG. 1  shows a sectional side view of a side-channel blower according to the present invention; 
           [0013]      FIG. 2  shows a perspective view of a detail of the impeller of the side-channel blower in  FIG. 1 ; and 
           [0014]      FIG. 3  shows a perspective view of a bearing housing of the side-channel blower in  FIG. 1  according to the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    Contrary to expectations, such an optimization in conveying compressible media is achieved with a side-channel blower in which a radial interruption gap between the impeller and the radially delimiting housing wall in the entire interruption zone is 0.005 to 0.003 times the impeller diameter. This corresponds to an increase of the gap by a factor of two to ten as compared to known designs, whereby the susceptibility to the formation of ice or to contaminating substances in the gas conveyed is reduced significantly and manufacture is clearly simplified due to the low tolerances which must be observed. At the same time, no restriction of the delivery rate is expected since, given this distance, the gap acts as a dynamic gas seal with the pressure in the gap being sufficiently increased. 
         [0016]    In an embodiment of the present invention, the interruption zone can, for example, merely extend over an angle between 20° and 40° of the total circumference of the flow housing. Due to the extension of the flow channels resulting therefrom, no restriction occurs with respect to the delivery rate and the efficiency. The area available for possible accretions and ice formation is also reduced. 
         [0017]    In an embodiment of the present invention, the impeller blades can, for example, be formed in a V-shape, as seen in cross section, so that, with respect to the rotary axis, the impeller blades are inclined in the direction of rotation and extend in the direction of their opposite flow channel. At the same time, the impeller is formed to be open both in the axial and in the radial direction in the radially outer region so that gas is gathered in the axial center of the blade and is accelerated, which has proven beneficial to the formation of the spiral flow, a constant exchange being possible between the two flow channels. A very high pressure is generated in the radial gap with this impeller design which prevents a short-circuit flow from the inlet to the outlet, as with the use of a dynamic gas seal. A leakage with the resulting reduction in delivery rate is thereby reliably avoided. 
         [0018]    An optimal inclination of the blades with respect to the rotary axis is 5° to 20° in the direction of rotation of the impeller. A particularly high efficiency is obtained with such an angle since an optimal pressure is achieved on the inner side of the blades. 
         [0019]    In an embodiment of the present invention, in their radially outer end region, the impeller blades can, for example, be formed so that they are inclined in the direction of rotation of the impeller with respect to the intermediate region of the impeller blades adjoining the end region on the radially inner side. An additional acceleration is thereby generated as the medium is moved radially outward, whereby the pressure generated in the gap is further increased, thereby improving the sealing effect. 
         [0020]    In an embodiment of the present invention, the radial end region of the impeller blades can, for example, be inclined by 5° to 20° in the direction of rotation with respect to the radial direction, and the adjacent intermediate region of the impeller blades can, for example, be inclined by 5° to 20° against the direction of rotation with respect to the radial direction. An optimized feed pressure of the blower with the resulting sealing effect and an improvement of the delivery rate are obtained with these pitch angles. 
         [0021]    In this embodiment of the impeller, in connection with the rather wide gap in the interruption zone, it has additionally proven beneficial if the outlet extends tangentially from the flow channels in the flow housing and has a circular cross section that substantially corresponds to the cross section of the flow channels. This embodiment reduces the noise emissions generated, in particular by allowing a distribution of the flow in the gap due to the wide gap. 
         [0022]    In an embodiment of the present invention, a partition wall can, for example, be formed at the height of the connection between the two legs of the V-shaped impeller blades, which partition wall extends radially over the intermediate region of the impeller blades that adjoins the end region. Pressure losses are thereby prevented that are caused by the two gas flows from the two flow channels axially converging at the radially inner edge of the impeller blades or the flow channels, respectively, and improves the formation of the two vortex flows, thereby again increasing the pressure in the gap and thus improving the sealing effect. 
         [0023]    A side-channel blower is thus provided in which, compared to previously described side-channel blowers for compressible media, a high pressure is generated in the gap, while the feed rate is maintained, whereby a counter pressure against a short-circuit flow is generated in the gap, as with the use of a gas seal. The impeller and the housing can be manufactured with larger tolerances, thereby reducing manufacturing costs. The susceptibility to accretions, foreign matter, and ice bridge formation is clearly reduced when compared to known designs. 
         [0024]    An embodiment of a side-channel blower according to the present invention is illustrated in the drawings and will be described below. 
         [0025]    The side-channel blower illustrated in  FIG. 1  has a bipartite flow housing formed by a bearing housing  10  and a housing cover  12  fastened thereto, for example, by screws. An impeller  16  is supported in the bearing housing  10 , the impeller  16  being rotatable by a drive unit  14 . The compressible medium conveyed reaches the interior of the side-channel blower via an axial inlet  18  formed in the housing cover  12 . 
         [0026]    The medium then flows from the inlet  18  into two substantially annular flow channels  20 ,  22 , of which the first flow channel  20  is formed in the bearing housing  10  in the central opening  24  of which a bearing  26  of a drive shaft  28  of the drive unit  14  is also arranged, the impeller  16  being fastened on the drive shaft  28 , and the second flow channel  22  being formed in the housing cover  12 . The air leaves via a tangential outlet  30  formed in the bearing housing  10 . 
         [0027]    The impeller  16  is arranged between the housing cover  12  and the bearing housing  10  and has impeller blades  32  along its circumference which extend from a disc-shaped central part  34  that is fastened on a drive shaft  28  forming an rotary axis X of the impeller  16 , the two flow channels  20 ,  22  being formed axially opposite the blades. A sealing from the two flow channels  20 ,  22  to the interior of the impeller  16  is obtained by circumferential corresponding webs  36  and grooves  38  in the housing parts  10 ,  12  and the disc-shaped central part  34  of the impeller  16 . 
         [0028]    The impeller blades  32  of the impeller  16  have a radially outer end region  40 , as well as a radially adjoining intermediate region  42  arranged between the disc-shaped central part  34  and the radially outer end region  40 . In this intermediate region  42 , the impeller blades  32  are divided by a radially extending partition wall  44  into a first row axially opposite the first flow channel  20  and a second row axially opposite the second flow channel  22  so that two vortex ducts are formed that are each formed by a respective one of the two flow channels  20 ,  22  and the part of the impeller blades  32  facing the respective one of the two flow channels  20 ,  22 . No separation exists in the radially outer end region  40  so that an exchange of medium between the two flow channels  20 ,  22  is possible in this region. 
         [0029]    The two flow channels  20 ,  22  arranged in the bearing housing  10  and in the housing cover  12  have a substantially constant width and extend over an angle of about 330° in the bearing housing  10  and in the housing cover  12 . 
         [0030]    The outer diameter of the two flow channels  20 ,  22  is slightly larger than the outer diameter of the impeller  16  which is, for example, about 85 mm, so that a fluidic connection between the two flow channels  20 ,  22  also exists outside the outer circumference of the impeller  16 . A radial gap  52  of 3 to 6 mm in dimension is thus formed between the radially delimiting housing wall  54  and the radial end of the impeller  16 , where a correspondingly larger impeller  16  requires a correspondingly larger radial gap  52  as well. Pockets  56 , which are open radially outwards, are thus formed between the impeller blades  32 , in which pockets  56  the medium is accelerated so that the pressure of the medium is increased over the length of the two flow channels  20 ,  22 . 
         [0031]    In the shown embodiment, the impeller blades  32  are inclined, with respect to the radial direction Z, in the intermediate region  42  by an angle of about 10° against the direction of rotation of the impeller  16 . In the adjoining radially outer end region  40 , the impeller blades  32  are inclined by an angle of 20° in the direction of rotation, compared to the intermediate region  42 , or they extend in this radially outer end region  40  by an angle of 10° in the direction of rotation with respect to the radial direction Z. This causes an additional acceleration of the medium during the rotation of the impeller  16  at a speed of about 12,000 to 24,000 rpm. 
         [0032]    The impeller blades  32  are also V-shaped over their entire substantially radial extension, when seen in cross section, i.e., when cut perpendicularly to the circumferential direction or the direction of rotation Y, so that each leg of each impeller blade  32  is assigned to its opposite flow channel  20 ,  22  and the radially extending partition wall  44  is arranged between the legs in the intermediate region  42 . Compared to a vector extending in parallel with the rotary axis X, each leg is inclined by about 15° in the direction of rotation of the impeller  16  and is formed to extend towards the opposite flow channel  20 ,  22 . In other words: the axial ends of the two legs are each leading with respect to the point at which the two legs join each other. 
         [0033]    When the impeller  16  is rotated by the drive unit  14 , the gas from the two flow channels  20 ,  22  enters the pockets  56  in the radially inner intermediate region  42 . A maximum accumulation of the gas occurs in the central region of each of the impeller blades  32  due to the rotation and the shape of the impeller blades  32 . This accumulated gas is then accelerated outwards via the axially central region, the inclination of the radially outer end region  40  generating an additional acceleration exceeding that caused by the normal rotational speed. With this pressure, the gas is accelerated towards the radially delimiting housing wall  54 , which is correspondingly arranged at a distance of 3 to 6 mm from the outer circumference of the impeller  16 , so that a larger space is available for deflection towards the two flow channels  20 ,  22 . The two flow channels  20 ,  22  are then flowed through again from radially outside to the inside. The gas thereafter again enters the pockets  56  to be accelerated once more. A helical movement is thus obtained along each of the two flow channels  20 ,  22  from the inlet  18  to the outlet  30 . This leads to a good delivery rate of the blower. 
         [0034]    The outlet  30  has a circular cross section, whereby the cross section available for outflow from each of the pockets  56  gradually decreases during a rotation of the impeller  16 . 
         [0035]    As the impeller  16  rotates, the impeller blades  32  are thereafter moved over an interruption zone  58  extending over an angle of about 30° between the inlet  18  and the outlet  30 . The zone interrupts the two flow channels  20 ,  22  and prevents a short-circuit flow from the inlet  18  to the outlet  30  against the direction of rotation of the impeller  16 . For this purpose, wall surfaces  60 ,  62  are formed at the height of the impeller blades  32  in parallel with the impeller  16  between the inlet  18  and the outlet  30  in the bearing housing  10  and the housing cover  12 , which wall surfaces  60 ,  62  interrupt the two flow channels  20 ,  22 , wherein a gap as small as possible exists between these wall surfaces  60 ,  62  and the axially opposite impeller blades  32  of the impeller  16 . 
         [0036]    According to the present invention, a radial interrupting gap  64  is formed between the radially delimiting housing wall  54  and the outer circumference of the impeller  16 , the width of the radial interrupting gap being about 0.5 to 2.5 mm. This radial interrupting gap  64  is thus clearly larger than the conventional gaps of about 0.3 mm in this region. It is also possible to make this radial interrupting gap  64  correspondingly larger when the impeller  16  is designed to have a larger size. When the impeller blades  32  pass over the interruption zone  58 , a part of the residual gas can at first flow from the pockets  56  to the outlet  30  via the interruption zone  58 , whereby the generation of noise is reduced compared to designs with narrower gaps. The residual gas is conveyed centrally toward the radially delimiting housing wall  54  at a high velocity due to the high acceleration caused by the shape of the impeller blades  32 . A pressure is thereby caused in the radial interrupting gap  64  which has a sealing effect with respect to the inlet  18  so that the radial interrupting gap  64  acts like a dynamic gas seal. A short-circuit flow from the inlet  18  directly to the outlet  30  is largely suppressed by this pressure. 
         [0037]    A side-channel blower for compressible media is thus provided which can be manufactured with clearly less strict tolerances since the gap in the region of the interruption can be significantly larger, while a sufficient sealing from the inlet towards the outlet  30  still exists. The manufacturing costs and the assembly costs are reduced correspondingly. Due to the greater distance between the rotating and the stationary parts and the larger angular range of the interruption, the susceptibility to the formation of ice and to the accumulation of dirt is also reduced. High differential pressures are generated due to the path length of the flow channels, by which the effect of a dynamic gas seal is obtained in the interrupting gap without having to expect limitations with respect to the delivery rates. 
         [0038]    It should be clear that various modifications can be made to the embodiment of the side-channel blower described without leaving the protective scope of the main claim. For example, the drive, the inlet and the outlet, the interruption and outlet contours or the fastening and sealing structures can be modified. Further modifications are also conceivable. Reference should also be had to the appended claims.