Abstract:
A side-channel blower for an internal combustion engine includes a flow housing, an impeller which rotates in the flow housing, a housing wall which surrounds the impeller, a drive unit which drives the impeller, 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, two flow channels which connect the inlet to the outlet, and an interruption zone arranged between the outlet and the inlet which interrupts the two flow channels in a peripheral direction. The impeller blades 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 impeller blades each comprise a V-shaped cross-section.

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/EP2015/079420, filed on Dec. 11, 2015 and which claims benefit to German Patent Application No. 10 2015 100 215.9, filed on Jan. 9, 2015. The International Application was published in German on Jul. 14, 2016 as WO 2016/110373 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 which open in a radially outward direction, a radial gap between the impeller and a housing wall that radially surrounds the impeller, an inlet and an outlet, 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 side 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 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]    U.S. Pat. No. 6,422,808 B1 describes a side-channel blower for a compressible fluid to increase conveying pressure comprising an impeller enclosed by a flow housing with two side channels, the flow housing having a fluid inlet and a fluid outlet. Blades are arranged along the periphery of the impeller that extend in an axial and a radial direction and which have a radially inner section inclined oppositely to the direction of rotation of the rotor, as well as a radial outer section inclined in the direction of rotation of the rotor, and which convey fluid from the inlet to the outlet as the rotor rotates. The blades each have a chamfer at the radially inner section. 
         [0008]    A side-channel blower is also described in U.S. Pat. No. 5,299,908 B1 whose impeller blades extend straightly in a radial direction, but are inclined towards the opposite side channel with respect to the direction of rotation. A radial partition wall is, however, arranged between these two axial blade parts to prevent an overflow from one duct to the other via the impeller. Only a radially outer part of the blades is further formed opposite the flow channel. 
         [0009]    Blades that are inclined and separated from each other in such a manner have also been previously described from an impeller of a side-channel pump for an incompressible medium. This impeller also has a radially limiting side wall. 
         [0010]    All these blowers and pumps are not, however, optimal in view of their feed rate and in view of the possible pressure increase, respectively. 
       SUMMARY 
       [0011]    An aspect of the present invention is to provide a side-channel blower with which the feed rate or the feed pressure can be increased further without further increasing the diameter or the rotational speed, where the flow conditions in the flow channels and in the impeller are optimized, and/or with where a lower power consumption of the drive can be provided while maintaining feed rates. An aspect of the present invention is also to provide a blower which is suitable for various applications and feed rates and which has a noise generation which is as low as possible. 
         [0012]    In an embodiment, the present invention provides a side-channel blower for an internal combustion engine which includes a flow housing, an impeller comprising a rotary axis and being configured to rotate in the flow housing, a housing wall configured to radially surround the impeller, a drive unit configured to drive the impeller, 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, two flow channels configured to connect the inlet to the outlet and to be fluidically connected to one another via intermediate spaces between the impeller blades, and an interruption zone arranged between the outlet and the inlet. 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 interruption zone is configured to interrupt the two flow channels in a peripheral direction. The impeller blades, as seen from a cross section of a plane on which the rotary axis lies, each comprise a V-shaped cross-section so that, in a direction of rotation of the impeller, the impeller blades extend at an angle from the rotary axis in a direction of the respective one of the two flow channel respectively arranged opposite to the impeller blades. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The present invention is described in greater detail below on the basis of embodiments and of the drawings in which: 
           [0014]      FIG. 1  shows a sectional side view of a side-channel blower according to the present invention; 
           [0015]      FIG. 2  shows a perspective view of a detail of the impeller of the side-channel blower in  FIG. 1 ; and 
           [0016]      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 
       [0017]    Contrary to expectations, such an optimization in conveying compressible media is achieved with a side-channel blower in which the impeller blades are formed in a V-shape, as seen in a 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. The impeller is at the same time formed to be open both in the axial and 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. Such a side-channel blower has a higher efficiency and covers a wide range of operating points. 
         [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 portion of the impeller blades adjoining the end region on the inner side. An additional acceleration is thereby generated as the medium is moved radially outward, whereby the efficiency is additionally improved. 
         [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 portion of the impeller blades can, for example, be inclined by 5° to 20° against the direction of rotation with respect to the radial direction. Optimized efficiencies of the blower are obtained with these pitch angles. 
         [0021]    In an embodiment of the present invention, the radial gap between the end region of the impeller blades and the housing wall radially surrounding the impeller can, for example, be 0.03 to 0.1 times the impeller diameter in the region of the flow channels. This means that the gap has been significantly reduced compared to known embodiments which, in combination with correspondingly shaped impeller blades, leads to improved results. This is contrary to expectations. 
         [0022]    In this embodiment of the impeller, 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, results in a good discharge of the feed flow and thus also results in high feed rates. 
         [0023]    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. 
         [0024]    A side-channel blower is thus provided in which, compared to known side-channel blowers for compressible media, the feed rate and/or the possible pressure increase are improved and/or the power consumption is reduced, while the feed rate is maintained, so that the efficiency is improved. A very wide performance range is at the same time covered by a single blower size and noise emissions are reduced. 
         [0025]    An embodiment of a side-channel blower according to the present invention is illustrated in the drawings and will be described below. 
         [0026]    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 . 
         [0027]    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 shaft, 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 . 
         [0028]    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. 
         [0029]    For a reliable suppression of a short-circuit flow against the direction of rotation Y of the impeller  16  from the inlet  18  to the outlet  30 , interruption zones  36 ,  38  are arranged at the housing cover  12  and at the bearing housing  10  that interrupt the two flow channels  20 ,  22  so that a gap as small as possible exists in the interruption zones  36 ,  38  axially opposite the impeller blades  32  of the impeller  16 . An interruption zone  40  acting in the radial direction Z is also formed on a radially delimiting housing wall  42  of the housing parts  10 ,  12  radially delimiting the two flow channels  20 ,  22 . 
         [0030]    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 across the circumference of the housing cover  12  and the bearing housing  10 , except for the interruption zones  36 ,  38 ,  40 . In the view of  FIG. 3 , the direction of rotation Y of the impeller  16  thus extends counter-clockwise from the beginning of the first flow channel  20  to the end of the first flow channel  20  or to the outlet  30  and then across the interruption zone  36  back to the beginning of the first flow channel  20  that is opposite the inlet  18 . 
         [0031]    A sealing from the two flow channels  20 ,  22  to the interior of the impeller  16  is obtained by circumferential corresponding webs  41  and grooves  43  in the housing parts  10 ,  12  and the disc-shaped central part  34  of the impeller  16 . 
         [0032]    The impeller blades  32  of the impeller  16  have a radially outer end region  44 , as well as a radially adjoining intermediate region  46  arranged between the disc-shaped central part  34  and the radially outer end region  44 . In this intermediate region  46 , the impeller blades  32  are divided by a radially extending partition wall  48  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  44  so that in this region an exchange of medium between the two flow channels  20 ,  22  is possible. 
         [0033]    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  50  of 3 to 6 mm in dimension is thus formed between the radially delimiting housing wall  42  and the radial end of the impeller  16 , where a correspondingly larger impeller  16  requires a correspondingly larger radial gap  50  as well. Pockets  52 , which are open radially outwards, are thus formed between the impeller blades  32 , in which pockets  52  the medium is accelerated so that the pressure of the medium is increased over the length of the two flow channels  20 ,  22 . 
         [0034]    The size of the radial gap  50  in particular results with regard to the design of the impeller blades  32  provided by the present invention. In the shown embodiment, the impeller blades  32  are inclined, with respect to the radial direction Z, in the intermediate region  46  by an angle of about 10° against the direction of rotation Y of the impeller  16 . In the adjoining radially outer end region  44 , the impeller blades  32  are inclined by an angle of 20° in the direction of rotation Y, compared to the intermediate region  46 , or the impeller blades  32  extend in this radially outer end region  44  by an angle of 10° in the direction of rotation Y with respect to the radial direction Z. This causes an additional acceleration of the medium during the rotation Y of the impeller  16  at a speed of about 12,000 to 24,000 rpm. 
         [0035]    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 of the impeller blades  32  is assigned to its opposite flow channel  20 ,  22  and the partition wall  48  is arranged between the legs in the intermediate region  46 . Compared to a vector extending in parallel with the rotary axis X, each leg is inclined by about 15° in the direction of rotation Y 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. 
         [0036]    When the impeller  16  is rotated by the drive unit  14 , the gas from the two flow channels  20 ,  22  enters the pockets  52  in the radially inner intermediate region  46 . 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 blade  32 . This accumulated gas is then accelerated outward via the axially central region, the inclination of the radially outer end region  44  generating an additional acceleration exceeding that caused by the normal rotational speed. The gas is accelerated with this pressure towards the radially limiting housing wall  42  which is arranged correspondingly at a greater distance so that a larger space is available for deflection towards the flow channels. The flow channels are then flowed through again from radially outside to the inside. A helical movement is thus obtained along each flow channel from the inlet  18  to the outlet  30 . The helical movement has a circular cross section, whereby the cross section available for outflow from a pocket gradually decreases during rotation. This results in low noise generation and only a small gas flow directed along the interruption zone, whereby the efficiency of the blower is improved. 
         [0037]    A side-channel blower for compressible media is thus provided which generates high differential pressures and volume flows without an increase in energy requirement so that efficiency is improved compared to known blowers. It is also possible, by merely changing the rotational speed, to reach a number of different operating points with a single blower without causing low efficiencies. 
         [0038]    It should be clear that different modifications can be made to the described embodiment of the side-channel blower without leaving the protective scope of the main claim. The drive, the inlet and the outlet, the interruption and outlet contours or the fastening and sealing structures can, for example, be modified. Further modifications are also conceivable. Reference should also be had to the appended claims.