Abstract:
The invention relates to an air conditioning compressor ( 1 ) for a vehicle ( 24 ), in particular a motor vehicle ( 25 ), having a compression chamber ( 18 ) having an inlet ( 7 ) for a cooling medium to be compressed and an outlet ( 8 ) for the compressed cooling medium, wherein a wall of the compression chamber ( 18 ) is formed at least in sections by a translationally displaceable piston ( 3 ). According to the invention, the end of the piston ( 3 ) facing away from the compression chamber forms at least one wall region of a control pressure chamber ( 19 ). The invention further relates to a vehicle having an air conditioning apparatus.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention relates to an air-conditioning compressor for a vehicle, in particular motor vehicle, having a compression chamber which has an inlet for a cooling medium to be compressed and an outlet for the compressed cooling medium, wherein a wall of the compression chamber is formed at least in regions by a piston which is displaceable in a translatory fashion. 
         [0002]    The invention also relates to a vehicle, in particular motor vehicle, having a drive device and having an air-conditioning device which has an air-conditioning compressor. 
         [0003]    Air-conditioning compressors and vehicles of the type in question here are known from the prior art. To increase comfort in vehicles, in particular with regard to the vehicle interior temperature, it is known to provide air-conditioning devices which serve for cooling the interior. For this purpose, air-conditioning devices of said type have at least one air-conditioning compressor which serves for the compression, which permits the air conditioning, of a gaseous and/or vaporous refrigerant in a circuit of the air-conditioning device. Here, air-conditioning compressors are known which are based on the principle of a piston pump and which, for this purpose, have a piston which is displaceable in a translatory fashion and which serves for compressing a gaseous and/or vaporous cooling medium situated in a compression chamber. Here, the piston forms at least one wall region of the compression chamber, such that as a result of a displacement of the piston, the volume of the compression chamber is reduced, and the cooling medium situated therein is compressed. 
         [0004]    Known air-conditioning compressors are designed so as to be mechanically driven by a crankshaft of an internal combustion engine via a belt or chain drive. In this way, however, energy is extracted from the drive device of a vehicle of said type, which energy is no longer available for providing propulsion and also becomes noticeable in terms of pollutant emissions (CO 2  emissions). 
       SUMMARY OF THE INVENTION 
       [0005]    The air-conditioning compressor according to the invention is driven in such a way as not to reduce the power of a drive device, and takes up a smaller amount of installation space than known air-conditioning compressors. Accordingly, the air-conditioning compressor is designed such that the piston forms, at its end facing away from the compression chamber, at least one wall region of a control pressure chamber. An air-conditioning compressor is thus provided which has an axially displaceable piston which interacts on one side, or with one end, with the compression chamber and on the other side, or with the other end, with the control pressure chamber. Here, as a result of the pressure difference between the control pressure chamber and compression chamber, the piston is displaced axially. The pressure in the control pressure chamber can, as the name suggests, be controlled, such that a compression process in the compression chamber can be adjusted by increasing and decreasing the pressure in the control pressure chamber. By increasing the pressure in the control chamber, the piston is moved into the compression chamber, and the volume of the compression chamber is reduced. By reducing the pressure in the control pressure chamber, the piston is moved out of the compression chamber, such that there is a follow-up flow, and possibly suction, of cooling medium into the compression chamber. The air-conditioning compressor according to the invention is thus driven not mechanically but rather preferably hydraulically. Here, the air-conditioning compressor may be connected to an existing hydraulic system. The advantageous air-conditioning compressor thus does not extract any energy required for drive/propulsion from a drive device of a motor vehicle. 
         [0006]    It is advantageous for the inlet and/or the outlet of the compression chamber to be arranged or formed at an end region, which is remote from the piston, of the compression chamber. In this way, it is ensured that the greatest possible volume of the compression chamber can be utilized for conveying and compressing cooling medium. In the simplest case, the inlet and/or the outlet are formed as a bore/as bores in a housing which forms the compression chamber. 
         [0007]    It is preferable for the inlet and/or the outlet to be assigned in each case one check valve. Here, the check valves are designed and/or arranged such that, when there is an elevated pressure in the compression chamber, the check valve assigned to the inlet closes and the check valve assigned to the outlet opens, such that cooling medium which has been compressed in the compression chamber is expelled from the compression chamber at high pressure when the piston is displaced into the compression chamber. If, owing to there being a relatively low pressure in the control pressure chamber, the piston moves in the opposite direction, the check valve assigned to the outlet thus closes the previously opened-up throughflow cross section and the check valve assigned to the inlet opens up a throughflow cross section, such that a follow-up flow of gaseous and/or vaporous cooling medium into the compression chamber can take place. The check valves thus ensure a pressure build-up in the compression chamber and a separation between a high-pressure portion and a low-pressure portion of a cooling circuit which conducts the cooling medium. 
         [0008]    The piston is expediently assigned at least one restoring spring, wherein here, the restoring action is to be understood to mean the displacement of the piston out of the compression chamber. In other words, the restoring spring serves to increase the volume of the compression chamber by displacing the piston. This has the advantage that the (negative) pressure to be set in the control pressure chamber can be reduced in order to displace the piston in the direction of the control pressure chamber. The restoring spring permanently ensures reliable operation of the air-conditioning compressor in that it exerts a spring force on the piston in the direction of the control pressure chamber. 
         [0009]    It is furthermore provided that the restoring spring is for this purpose formed as a helical spring and arranged in the compression chamber. The restoring spring thus acts as a compression spring and is situated, possibly in a preloaded state, between that end side of the piston which points toward the compression chamber and a housing wall, which faces said end side of the piston, of the compression chamber. 
         [0010]    It is furthermore provided that the control pressure chamber can be incorporated into a hydraulic circuit, in particular of a drive device of a motor vehicle. For this purpose, the control pressure chamber has corresponding ports which permit simple incorporation into a hydraulic circuit of said type. It is expedient for the material and material thickness of the housing which forms the control pressure chamber to also be selected in accordance with the high pressure requirements. This leads inter alia to the control pressure chamber being formed as a hydraulic chamber and the air-conditioning compressor being designed as a hydraulically controlled air-conditioning compressor. 
         [0011]    The control pressure chamber preferably has, for this purpose, a high-pressure port and a low-pressure port for the hydraulic circuit. Through the high-pressure port, hydraulic fluid is conducted into the control pressure chamber such that the piston is displaced into the compression chamber. For this purpose, a pressure must expediently prevail at the high-pressure port which is adequate to effect a displacement of the piston for compressing the gaseous and/or vaporous cooling medium situated in the compression chamber. 
         [0012]    It is finally provided that the low-pressure and/or the high-pressure port is assigned in each case one switchable valve. In this way, it is possible in a simple manner to adjust not only the working frequency of the air-conditioning compressor but also the compression pressure acting in the compression chamber. By opening the switchable valve assigned to the high-pressure port, hydraulic fluid flows at high pressure into the control pressure chamber. Here, the low-pressure valve is expediently closed. As a result of the high pressure of the hydraulic fluid, the piston is displaced into the compression chamber, and the cooling medium situated therein is compressed. At the latest when the pressure in the compression chamber corresponds to the pressure acting on the piston in the control chamber—that is to say including the spring force of the restoring spring—the valve assigned to the high-pressure port is closed and the valve assigned to the low pressure is opened, such that the hydraulic fluid flows out of the control pressure chamber and the piston is restored as a result of the loss of pressure in the control pressure chamber. 
         [0013]    The vehicle according to the invention is characterized by an air-conditioning compressor as described above. The air-conditioning compressor is expediently incorporated into a hydraulic circuit of the drive device, wherein it is advantageously the case that the low-pressure port is connected to a low-pressure portion of the hydraulic circuit and the high-pressure port is connected to a high-pressure portion of the hydraulic circuit. Through corresponding actuation of the switchable valves, it is now possible for the cooling power of the air-conditioning device to be controlled or regulated in a simple manner. Since a mechanical drive of the air-conditioning compressor is dispensed with, no energy required for propulsion is extracted from the drive device, such that firstly the power of the drive device can be used entirely for propulsion, and secondly pollutant emissions are reduced. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The invention shall be explained in more detail below on the basis of the drawing, in which: 
           [0015]      FIG. 1  shows an air-conditioning compressor in a simplified sectional illustration, and 
           [0016]      FIG. 2  shows a vehicle having an air-conditioning device. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]      FIG. 1  shows, in a simplified illustration, a longitudinal section through an air-conditioning compressor  1  for an air-conditioning device in particular of a vehicle or motor vehicle. The air-conditioning compressor  1  has a housing  2  which is preferably of at least substantially circular cylindrical form. A piston  3  is arranged in the housing  2  so as to be displaceable axially—that is to say in the direction of its longitudinal axis—in a translatory fashion. At its outer lateral surface, the piston  3  has arranged thereon two seal elements  4  in the form of O-rings  5  which sealingly close off the gap between the piston  3  and the inner side of the housing  2 . At the same time, the seal elements  4  may also serve for guiding the piston  3  in the housing  2 . For guidance, however, it is expedient for further means (not illustrated here) to be provided, for example in the form of guide ridges and/or grooves, which serve in particular for minimizing friction during the displacement of the piston  3  in the housing  2  and prevent the piston  3  from tilting and becoming jammed in the housing  2 . 
         [0018]    The housing  2  of the air-conditioning compressor  1  furthermore has, in a first region  6 , an inlet  7  and an outlet  8  which are formed in each case in the casing wall of the housing  2 . In the present case, the inlet  7  and the outlet  8  are aligned substantially radially with respect to the housing  2 . The inlet  7  has a first check valve  9  and the outlet  8  has a second check valve  10 . The design and function of check valves is generally known, such that the exact design of the check valves  9  and  10  shall not be discussed in any more detail here. 
         [0019]    At its end region  11  situated opposite the end region  6 , the housing  2  of the air-conditioning compressor  1  has a high-pressure port  12  and a low-pressure port  13 , which in the present case are likewise formed in the casing wall of the housing  2 . Here, the high-pressure port  12  and the low-pressure port  13  are assigned in each case one switchable valve  14  and  15  respectively. By means of the ports  12  and  13 , the air-conditioning compressor  1  can be incorporated into the hydraulic circuit of a drive device of the abovementioned motor vehicle. By means of the switchable valves  14  and  15 , it is possible at the respective port  12 ,  13  for a corresponding throughflow cross section to be closed or opened up. The throughflow cross sections can possibly be adjusted in a continuously variable fashion. The check valves  9 ,  10  and/or the valves  14 ,  15  may in each case, at least in regions, be formed integrally with the housing  2  or as separate attachment parts. 
         [0020]    The piston  3  which is displaceably mounted in the housing  2 , and which is sealed off with respect to the inner wall of the housing  2  by means of the sealing elements  4 , divides the housing  2  into two chambers  16  and  17 . The chamber on the side which has the inlet  7  and the outlet  8  forms a compression chamber  18  for a cooling medium of the air-conditioning device, which has the air-conditioning compressor  1 , of the motor vehicle. The chamber  17  which is situated on the opposite side of the piston  3  forms, together with the piston, a control pressure chamber  19  which, through the switching of the valves  14  and  15 , substantially controls the movement of the piston  3 . 
         [0021]    In the compression chamber  18  there is advantageously arranged a restoring spring  20  formed in the present case as a helical spring  21 . Here, the restoring spring  20  interacts with the free end side of the piston  3  and with the closed end side, which faces the piston, of the housing  2  in the end region  6 . The restoring spring  20  is possibly arranged between the piston  3  and the housing  2  with a preload, such that it always exerts a spring force on the piston  3  in the direction of the control pressure chamber  19 . In order that the piston  3  does not enter completely into the control pressure chamber  19 , stops are expediently provided in this case on the housing inner wall, which stops prevent the piston  3  from protruding too far into the control pressure chamber  19 . The control pressure chamber  19  and the compression chamber  18  are thus formed in each case by the walls of the housing  2  and by in each case one free end side of the piston  3 . 
         [0022]    The function of the air-conditioning compressor  1  shall be explained below: A gaseous and/or vaporous cooling medium of the cooling circuit of the air-conditioning device is supplied to the inlet  7 . The check valves  9  and  10  ensure that the cooling medium to be compressed can duly flow into the compression chamber  18  but cannot flow out of said compression chamber again for as long as the pressure in the compression chamber does not exceed a critical pressure. For a compression process, the valve  14  is firstly opened such that hydraulic fluid flows out of the hydraulic circuit of the drive device into the control pressure chamber  19 , while the valve  15  is closed. In this way, a pressure builds up in the control pressure chamber  19 , which pressure serves to move the piston  3  in the direction of the compression chamber  16  or in the direction of the end region  6 , as indicated by an arrow  22 . Here, the restoring spring  20  is stressed and the gaseous and/or vaporous cooling medium situated in the compression chamber  16  is compressed, with the pressure in the compression chamber  18  being increased. 
         [0023]    The remaining liquid phase is forced toward the check valve  10  of the outlet  8 , as a result of which said check valve opens when the critical pressure is reached, and the now liquid, compressed cooling medium is conveyed or pushed through the outlet  8  into the cooling circuit at least for as long as the pressure in the control pressure chamber is higher than the pressure in the compression chamber  18 . At the latest when pressure equalization between the compression chamber  18  and the control pressure chamber  19  has taken place, the valve  14  of the high-pressure port  12  is closed and the valve  15  of the low-pressure port  13  is opened. As a result, the hydraulic fluid in the control pressure chamber  19  expands and flows through the valve  15  and the low-pressure port  13  back into the hydraulic circuit of the drive device. The restoring spring  20  and the pressure difference which now prevails between the control pressure chamber  19  and the compression chamber  18  serve to displace the piston  3  back, as indicated by an arrow  23 , into its initial position. Here, the coolant remaining in the compression chamber  18  evaporates again, and as a result of the suction action generated, additional gaseous and/or vaporous cooling medium is sucked into the compression chamber  18  via the check valve  9 , while the check valve  10  is again closed. Here, the above-described process starts to repeat. It is possible here for the speed of the piston  3 , and the movement travel of the piston  3 , to be manipulated through corresponding adjustment of the valves  14  and  15 . 
         [0024]      FIG. 2  shows a simplified illustration of an advantageous exemplary embodiment of a vehicle  24  which is in the form of a motor vehicle  25  and which, for this purpose, comprises a drive device  26  which comprises an internal combustion engine and/or one or more electric machines. The drive device  26  is assigned a hydraulic unit  27  which has inter alia means for generating a pressure for a liquid hydraulic medium. The hydraulic unit is connected via a first hydraulic circuit  28  to components of the drive device  26  and via a second hydraulic circuit  29  to the above-described air-conditioning compressor  1 . Here, a high-pressure portion of the hydraulic circuit  29  is connected to the high-pressure port  12  of the control pressure chamber  19  and a low-pressure portion of the hydraulic circuit  29  is connected to the low-pressure port  13 . The compression chamber  18  is incorporated, by means of its inlet  7  and its outlet  8 , into a cooling circuit  30  of an air-conditioning device  31 , and is thus a constituent part of the air-conditioning device  31 . Also incorporated into the cooling circuit  30  is a condenser  32  through which ambient air flows, if appropriate with the aid of a fan  33 , as indicated by arrows  34 . The air-conditioning device  31  advantageously furthermore comprises—though these are not illustrated here—a collecting tank for the cooling medium, a temperature-regulated switch for the activation and deactivation of the air-conditioning compressor  1 , in particular in the form of a two-position controller, a temperature sensor assigned to the switch, an expansion valve and also an evaporator with a switchable evaporator fan for imparting the cooling power. 
         [0025]    Overall, the air-conditioning compressor  1  thus provides, in a particularly simple manner, a facility for compressing the cooling medium without the need for extracting power from a drive device  26  of the motor vehicle  25 . Furthermore, the present air-conditioning compressor  1  is of particularly compact and cheap design. Furthermore, air conditioning can easily be provided even when the engine is at a standstill, which in particular in modern hybrid drive concepts which, as drive components, have not only a classic internal combustion engine, such as a spark-ignition or diesel engine, but also one or more electric machines. 
         [0026]    To prevent contamination between the hydraulic fluid and the refrigeration medium in the air-conditioning compressor  1 , an “atmospheric intermediate part” is provided, in a further exemplary embodiment not illustrated here, between the compression chamber  18  and the control pressure chamber  19 . It is thus possible, for example, for one or more diaphragms to be provided in the housing  2  for the purpose of separating the various media. It is also conceivable for the compression chamber  18  and the control pressure chamber  19  to be provided in different, substantially mutually separate housing parts, with a component piston being displaceably mounted in each of the housing parts, and the component pistons in turn being connected to one another via a corresponding mechanism.