Abstract:
A pump, particularly to a vane-cell pump for a vacuum for brake boosters in motor vehicles or for drawing blow-by gas out of the crankcase of internal combustion engines, with a casing, a rotor and with at least one vane and a liquid cooling device, which is depicted by a simple, essentially cylindrical insertion bush for inserting inside the casing.

Description:
[0001]    The present invention relates to a pump, in particular to a vane-type pump for a vacuum for brake power assist units in motor vehicles or for evacuating blow-by gas from the crankcase of combustion engines, having a housing, a rotor and at least one vane and one liquid-cooling device. 
       BACKGROUND 
       [0002]    Under the related art, vacuum pumps powered directly by the combustion engine are operated as wet-running pumps. Engine oil is used for lubrication, sealing and cooling. When dry-running pumps are used, one encounters the problem of dissipating the heat generated by friction and compression, especially at high speeds. 
         [0003]    Also known from the related art are pumps, commonly referred to as scroll compressors, for example, which have costly cooling devices on the housing that require a large installation volume. 
       SUMMARY OF THE INVENTION 
       [0004]    An object of the present invention is to provide a pump which will overcome these disadvantages. 
         [0005]    The present invention provides a pump, in particular a vane-type pump for generating a vacuum for brake power assist units in motor vehicles or for evacuating blow-by gas from the crankcase of combustion engines, having a housing, a rotor and at least one vane and one liquid-cooling device, the cooling device including a simple, essentially cylindrical insert bushing that is placed inside of the housing. A pump is preferred where the insert bushing may form both a bearing bushing for the vane and the rotor, as well as one of the walls of the cooling device. 
         [0006]    A pump is also preferred where the insert bushing may have a helicoidal groove in its outer circumferential surface that, together with the inner circumferential surface of the housing, forms a cooling channel. Here, the advantage may be derived that the cooling channels are able to be produced by a simple external machining of the bushing, while the smooth inner circumferential surface does not require any machining. 
         [0007]    A pump according to the present invention may have the distinguishing feature that the insert bushing is manufactured in one piece of a material having good bearing surface/sliding properties, in particular low wear and low friction properties, for the vane and the rotor. This has the advantage that the insert bushing, not, however, the remaining housing of the pump, is to be manufactured of a high-grade material. 
         [0008]    A pump is also preferred where the housing may be made of a flange part, an essentially tubular intermediate part and an end cover part. Here the advantage is derived that, through the use of two tubular parts, namely that of the housing and that of the insert bushing, a simple design may be employed to produce the cooling device. 
         [0009]    In addition, a pump is preferred where the cooling fluid or the lubricating oil of the combustion engine may be used as coolant. 
         [0010]    A pump is also preferred where the pump, as what is commonly referred to as a dry-running pump, for example, without lubricating oil, may be combined with a wet-running vacuum pump, for example, a pump that is lubricated and cooled with lubricating oil. 
         [0011]    A pump according to the present invention may have the distinguishing feature that the insert bushing may have made from plastic. This has the advantage that the helicoidal cooling channels configured externally on the bushing may be produced as already preformed channels in the plastic injection molding process. 
         [0012]    A pump is also preferred where the vane may be made of plastic, optionally including caps fabricated from a low-wear, low-friction plastic. In addition, a pump is preferred in which the rotor may be made of plastic. 
         [0013]    Another pump according to the present invention may have the distinguishing feature that the housing may be manufactured from a metallic material, for example of sheet steel or of die-cast aluminum. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The present invention is described in the following with reference to the figures. 
           [0015]      FIG. 1  shows the insert bushing and the housing parts of a pump according to the present invention. 
           [0016]      FIG. 2  shows a cross section through a combination of a dry-running pump according to the present invention and a wet-running vacuum pump. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    The individual parts of the housing and the bushing-shaped insert of the cooling device are shown in  FIG. 1 . An approximately cylindrical or cup-shaped housing  1  that is produced from a metallic material such as die-cast aluminum, for example, has a smooth, cylindrical inner circumferential surface  3 . However, housing  1  may equally be made of a sheet steel material, for example, in a deep-drawing process, or of a plastic material. In addition, housing  1  has a flange side having mounting lugs  5  and may be flange-mounted on this side onto a wet-running vacuum pump according to the related art, using screws  7 , for example. An insert bushing  9 , which has helicoidal grooves  11  in its cylindrical outer surface, is inserted into housing  1 . Once insert bushing  9  is inserted into housing  1 , outer circumferential surface  13  of insert bushing  9  hermetically seals off insert bushing  9  against cylindrical inner surface  3  of housing  1 , so that only helicoidal grooves  11  within the now double-walled housing form a circumferentially extending channel. Through this channel, a suitable coolant may be externally introduced, for example, from the cooling-water circuit of the combustion engine or the lubricating-oil circuit of the combustion engine. Within insert bushing  9 , a rotor, which is eccentrically mounted relative to the housing and, for example, a vane disposed within a slot therein, are rotationally driven via a drive shaft or a coupling device. The now double-walled housing is sealed by an end cover  15  that is tightened by corresponding screws  17  against housing  1  and against insert bushing  9 . In this context, insert bushing  9  is preferably made of a high-grade, wear-resistant material having good sliding properties, since the vane slides by way of its end caps sealingly along the inner wall of bushing  9  within the same. A high-grade plastic is preferably selected for insert bushing  9  that is low-wear and also has good sliding properties and, moreover, is able to efficiently seal against inner wall  3  of housing  1  because of a certain elasticity relative to metallic materials. 
         [0018]    The pump according to the present invention is shown in  FIG. 2  in combination with what is generally known as a wet-running vacuum pump. The same components are denoted here by the same reference numerals as in  FIG. 1 . Discernible in cross section is housing  1  having inner wall  3  into which insert bushing  9  having helicoidal grooves  11  is inserted. By its surface  13 , insert bushing  9  seals against housing  1  having inner surface  3 . Housing  1  and insert bushing  9  are laterally sealed by cover  15 . In addition, seals  19  and  21  are disposed between cover  15 , housing  1  and insert bushing  9 , respectively. On the other side, the liquid-cooled vacuum pump is sealed by a flange  23 , which has seals  25  oriented toward housing  1  and seals  27  oriented toward the insert bushing. A rotor  29  shown in cross section and having two drive shaft ends  31  and  33  is eccentrically mounted within insert bushing  9 . Shaft ends  31  and  33  are supported, in turn, in two bearings  35  and  37 , bearing  35  being mounted in a recess of cover  15  and bearing  37  in flange  23 . In addition, the liquid-cooled vacuum pump is sealed by a shaft seal  39  against wet-running vacuum pump  41 . In this context, flange  23  forms the transition to wet-running vacuum pump  41  and, thus, at the same time constitutes part of the housing of this vacuum pump  41 . In addition, vacuum pump  41  includes a housing  43  and a rotor  45 . A vane  47  is discernible in cross section within rotor  45 . Rotor  45  is driven via a driving surface  49  and a coupling  51  by a drive, for example the shaft end of a camshaft projecting out of the combustion engine. On the side opposing coupling  51 , rotor  45  has a second coupling device  53  which constitutes the drive for shaft portion  33  of the liquid-cooled vacuum pump. While wet-running pump  41  is lubricated and cooled via lubricating-oil supply devices, represented here partially in cross section by channels  55 , this does not apply to the liquid-cooled vacuum pump. Therefore, to cool the dry-running vacuum pump, a coolant flow is introduced through an inlet  57  into helicoidal ring channels  11 , and the coolant flow is subsequently directed, in turn, through a corresponding outlet  59  into the other coolant circuit of the motor vehicle. Thus, the liquid cooling makes it possible for the heat that is generated in response to rotation of the dry-running vacuum pump to be dissipated, thereby preventing the pump from overheating. In this context, one area of application for the dry-running vacuum pump may be the evacuation of blow-by gas out of the crankcase space of the combustion engine. However, as an individual liquid-cooled pump, the vacuum pump may be used in the manner of the wet-running vacuum pump for brake power assist systems, if, for some other reasons, it is not feasible for oil to be supplied from the lubricating-oil circuit of the combustion engine. 
       LIST OF REFERENCE NUMERALS 
       [0000]    
       
           1  cup-shaped housing 
           3  cylindrical inner circumferential surface 
           5  mounting lugs 
           7  screws 
           9  insert bushing 
           11  helicoidal grooves 
           13  outer circumferential surface of insert bushing  9   
           15  end cover 
           17  screws 
           19  seal for housing 
           21  seal for insert bushing 
           23  flange 
           25  seal on housing 
           27  seal on insert bushing 
           29  rotor 
           31  drive shaft end 
           33  drive shaft end 
           35  bearing in cover  15   
           37  bearing in flange  23   
           39  shaft seal 
           41  wet-running vacuum pump 
           43  housing of vacuum pump  41   
           45  rotor of vacuum pump  41   
           47  vane of vacuum pump  41   
           49  drive surface of rotor  45   
           51  coupling 
           53  second coupling device 
           55  lubricating-oil channels 
           57  inlet for coolant flow 
           59  outlet for coolant flow