Abstract:
A compressor for generating compressed air in a vehicle includes at least one piston, a cylinder, a crankshaft, a lubricant connection, a lubricant supply channel, and a clutch device by means of which the crankshaft can be connected to or disconnected from a drive device. The lubricant supply channel opens into at least one lubricant outlet in the interior of the compressor directed toward a piston running surface of the cylinder at least in particular rotational positions of the crankshaft.

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to a compressor for generating compressed air in a vehicle. The compressor is disconnectable from or connectable to a drive via a clutch device, for example a shut-off clutch. 
     BACKGROUND OF THE INVENTION 
     A compressor of the general type under consideration is described in DE 20 2006 019 190 U1. 
     The use of a known shut-off clutch on compressors has the advantage that, in order to save energy, the compressor can be disconnected from a drive, for example the drive engine of the vehicle, if compressed air generation is not required. Without such a shut-off clutch, it has been usual hitherto to let the compressor run constantly with the drive engine and merely to switch it to a pneumatically neutral state in phases in which compressed air generation is not required. The introduction of a shut-off clutch to engage and disengage the compressor has the consequence that, upon being connected, the compressor is subjected to greater wear than in constant operation. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the invention to improve the wear resistance and therefore the durability of the compressor even when a clutch device is used. 
     In accordance with a preferred embodiment of the present invention, a compressor for generating compressed air in a vehicle includes at least one piston; a cylinder; a crankshaft; a lubricant connection; a lubricant supply channel; and a, clutch device by which the crankshaft is one of connectable to and disconnectable from a drive arrangement. The lubricant supply channel opens into at least one lubricant outlet in an interior region of the compressor. The lubricant outlet is directed towards a piston running surface of the cylinder in at least one rotational position of the crankshaft. 
     Still other objects and advantages of the present invention will in part be obvious and will in part be apparent from the specification. 
     The present invention accordingly comprises the features of construction, combination of elements, and arrangement of parts all as exemplified in the constructions herein set forth, and the scope of the invention will be indicated in the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is explained in more detail below with reference to exemplary embodiments and to the appended drawings, in which: 
         FIG. 1  shows a twin-cylinder compressor in a schematic representation; 
         FIG. 2  shows a splash-type connecting rod in a sectional representation; 
         FIG. 3  shows the configuration of the lubricant supply on the inlet side; and 
         FIG. 4  shows a piston with piston rings. 
     
    
    
     In the figures, the same reference numerals are used for corresponding elements. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a compressor  1  with a compressor housing  2  and a clutch device  3  arranged on the compressor housing  2 . The clutch device  3  is in the form of a pneumatically actuatable shut-off clutch. For this purpose the clutch device  3  has a pneumatic actuating cylinder  19  by means of which, upon pneumatic pressurization thereof, a coupling  18 , for example clutch plates or clutch disks, can be pressed against or disengaged from one another. The clutch device  3  connects a crankshaft  12  of the compressor  1  to a drive shaft of a drive arrangement (not shown in detail) of a vehicle, for example the vehicle engine. 
     The compressor  1  has a first cylinder  8  and a second cylinder  9 . A first piston  6  is arranged in the first cylinder  8 . A second piston  7  is arranged in the second cylinder  9 . The first piston  6  is connected to the crankshaft  12  via a first connecting rod  10  and corresponding bearings. The second piston  7  is connected to the crankshaft  12  via a second connecting rod  11 , likewise via corresponding bearings. For the sake of simplicity, the mounting of the pistons  6 ,  7  and of the crankshaft  12  in the corresponding bearing eyes of the connecting rods  10 ,  11  is represented only schematically in  FIG. 1 . In practice, suitable sliding or rolling bearings are used for this purpose. The cylinders  8 ,  9  are arranged in a cylinder housing  4  of the compressor  1 . The cylinder housing  4  forms part of the housing  2 . 
     A valve and control block  5 , which contains, for example, the inlet and outlet valves for the aspiration of compressed air and the discharge thereof to units located downstream, such as compressed air reservoirs, is arranged on the cylinder housing  4 . The valve block  5  may be configured as described in DE 197 451 18 A1, for example. 
     In order to lubricate the pistons  6 ,  7  in the respective cylinders  8 ,  9 , the compressor  1  has a lubricant supply. Oil, for example the engine oil of the vehicle engine, can be used, for example, as the lubricant. The lubricant supply of the compressor  1  has a lubricant connection  14  that is connectable to the engine oil supply of the vehicle engine. From the lubricant connection  14  a first lubricant passage  15  leads through the housing  2  to a lubricant supply groove  16  running around the crankshaft  12 . The lubricant supply groove  16  is connected to a lubricant supply channel section  13  disposed inside the crankshaft  12  in the form of a hollow channel. The channel section  13  is connected to lubricant outlet points in the region of the connecting rods  10 ,  11 , which outlet points are explained in greater detail below with reference to  FIG. 2 . The use of the peripheral lubricant supply groove  16  has the advantage that the lubricant can be distributed around the circumference of the crankshaft  12  and can thereby be fed relatively quickly and uniformly into the lubricant channel section  13 . 
     The lubricant is usually pressurized and can be subjected to a pressure of approximately 3 to 4 bar. A lubricant supply that is independent of the movement of the compressor, that is, which also operates when the compressor is stationary, is thereby made possible. 
       FIG. 2  shows the connecting rod  11  in a sectional representation. The cylinder wall  19  of the cylinder  9  is additionally shown. The connecting rod  11  has a connecting rod eye  25  connected to the piston  7 . A further (lower) connecting rod eye surrounds the crankshaft  12 , which is also reproduced in a sectional representation in  FIG. 2 . A bearing, for example a ball bearing, is provided between the crankshaft  12  and the connecting rod eye surrounding the crankshaft, which bearing is not represented explicitly in  FIG. 2  for the sake of simplicity. As can be seen, the channel section  13  is connected to a radial lubricant section  20  in the crankshaft  12 , which serves to introduce lubricant into the connecting rod  11 . The connecting rod  11  has, in the region of the connecting rod eye that receives the crankshaft  12 , a segmentally widened section  21  that forms a channel between the crankshaft and the inner face of the connecting rod eye. The widened section  21  can advantageously be implemented as a recess within the connecting rod eye. Alternatively or additionally, the section  21  can be in the form of a groove in the crankshaft  12 . What is important is that a channel is formed for conducting the lubricant from the channel section  13  to lubricant outlets  22 ,  23 . The recess  21  conducts the lubricant to the lubricant outlets  22 ,  23 , which are provided on each side of the connecting rod  11 . A configuration with only one lubricant outlet  22  or  23  is also possible; however, increased lubricant throughput can be achieved with a plurality of lubricant outlets. The lubricant outlets  22 ,  23  are configured to taper inwardly in the direction of the lubricant outlet orifice and thus are in the form of nozzles. Because of the overpressure of the lubricant and the nozzle effect of the lubricant outlets  22 ,  23 , the lubricant is sprayed from the orifices and, as indicated by the arrow  24  in  FIG. 2 , impinges on the cylinder wall  19 . Early and good lubrication of the cylinder wall with respect to the piston is thereby ensured, even when the compressor  1  is temporarily shut off by means of the clutch device  3 . 
     The taper of the lubricant outlets  22 ,  23  may have a continuous or stepped configuration, with a linear or curved contour. 
       FIG. 3  shows the connection of the crankshaft  12  to the lubricant connection  14  on the inlet side. As can be seen, the lubricant channel section  13  is connected to the peripheral groove  16  of the crankshaft  12 . A connection to the lubricant passage  15  is thereby ensured in all rotation-angle positions of the crankshaft, so that a reliable and high throughput of lubricant through the passages  15 ,  13  is guaranteed. 
     In one embodiment of the present invention, the lubricant supply channel  13 ,  15 ,  16 ,  20 ,  21  additionally has a lubricant supply gallery with a plurality of lubricant nozzles arranged in a fixed manner in the crankshaft housing of the compressor  1 . The lubricant nozzles are set up to spray the cylinder bore with lubricant. For this purpose the outlet points of the lubricant nozzles can be aligned towards the cylinder bore or cylinder wall  19 . Lubrication of the compressor can thereby be further improved. 
       FIG. 4  shows a detail of the cylinder  9  with the piston  7 . The piston  7 , and optionally also the piston  6 , are provided with piston rings  40 ,  41 ,  42  arranged in circumferential grooves of the piston. The piston rings  40 ,  41  are in the form of compression rings and ensure an airtight seal of the compression chamber located above the piston  7  with respect to the crankshaft housing located below. Through the use of two compression rings increased airtightness can be achieved, as compared to the use of one compression ring. The piston ring  42  is in the form of an oil control ring. The oil control ring is intended to prevent oil from entering the compression chamber located above the piston  7 . As can be seen, all the piston rings  40 ,  41  and  42  move along the cylinder running surface  19  as the piston  7  moves in the cylinder  9 . In order to increase the durability of the compressor, the oil control ring  42  has a wear-reducing coating. The coating can advantageously contain chromium. In an advantageous configuration of the invention, the oil control ring  42  is configured to be chromium-plated on its outer face. 
     As is also apparent from  FIG. 1 , the clutch device  3  projects beyond the housing  2  of the compressor  1 ; that is, the clutch device is not integrated in the housing, as is known from DE 20 2006 019 190 U1. The clutch device  3  projects with at least a region containing the coupling  18 , for example the clutch disks or plates, from the housing  2  of the compressor  1 . The external arrangement of the clutch device offers the advantage of modularity. The inventive compressor having the same construction can therefore be used both with and without a clutch device. If required, the clutch device is merely screwed to the housing  2  of the compressor  1 . 
     In summary, the compressor according to embodiments of the present invention variously has the following features:
         use of compression and oil control rings with increased wear resistance;   pistons with additional bores in the second groove;   splash-type connecting rods for lubricating the bore, for example as previously explained with reference to  FIGS. 1 and 2 , with one or two outlet orifices and/or additional piston pin lubrication;   oil supply groove in upper part of connecting rod;   groove in the crankshaft or in a bearing bush to increase oil throughput;   oil supply gallery with nozzles for continuously spraying the cylinder bores   the oil supply groove in the connecting rod can be precast asymmetrically; and   the groove  16  in the crankshaft can be provided on only one side, for example on the non-drive side.       

     It will be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained, and since certain changes may be made without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. 
     It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention that, as a matter of language, might be said to fall therebetween.