Abstract:
A switchable device for supplying at least one consumer of an internal combustion engine with pressure, comprising: a cavity formed inside a camshaft; a first displacement element arranged in the cavity having a first pressure surface which at least partially delimits a first accumulator chamber together with the wall of the cavity; a first energy accumulator which interacts with the first displacement element; a locking mechanism by which the first displacement element can be locked in the second end position; a switching mechanism which can be actuated by an actuator, having a switch element that can be brought into at least two switching positions; a second displacement element arranged in the cavity having a second pressure surface which at least partially delimits a second accumulator chamber together with the wall of the cavity; a second energy accumulator which interacts with the second displacement element; the first accumulator chamber and the second accumulator chamber communicating with each other and being connectible to a pressure source in a fluid-conducting manner.

Description:
FIELD OF THE INVENTION 
     The invention lies in the technical field of internal combustion engines and relates to a switchable device integrated in a cavity of a camshaft for supplying pressure to loads of an internal combustion engine. 
     BACKGROUND 
     From Patent No. EP 1197641 A2, a pressure accumulator for supporting a hydraulically adjustable camshaft is known in which the flow of hydraulic fluid into or out of the pressure accumulator is controlled by the use of different solenoid valves. 
     A pressure accumulator with a separate housing is further known from the German Laid Open Patent Application DE 102007056684 A1 of the applicant. 
     SUMMARY 
     Accordingly, the objective of the present invention is to improve conventional pressure accumulators for supplying pressure to loads in an internal combustion engine in an advantageous manner. 
     This and other objects are met according to the invention by a switchable device for supplying pressure with the features of the main claim. Advantageous constructions of the invention are specified by the features of the subordinate claims. 
     According to the invention, a switchable device for supplying pressure to at least one load of an internal combustion engine is shown. The load can involve, in particular, a hydraulic camshaft adjuster for adjusting the phase position between the crankshaft and camshaft. It is also conceivable, however, that the device is used, for example, in an electrohydraulic valve actuation device of an internal combustion engine. 
     The device for supplying pressure comprises an active (switchable) pressure accumulator and a passive (non-switchable) pressure accumulator, each of which are integrated in a cavity of a camshaft. 
     The active pressure accumulator comprises a first displacement element that is arranged in the cavity and can be displaced between a first end position and a second end position. The first displacement element has a first pressure surface that at least partially bounds, together with a wall of the cavity, a first storage space that can be connected or is connected in a fluid-conducting manner to the load. The displacement element can be constructed, for example, in the form of a piston with an end-side pressure surface. 
     The active pressure accumulator further comprises a first force accumulator that interacts with the first displacement element so that the first displacement element can be displaced by pressurization of the first storage space against the force of the first force accumulator from the first end position into the second end position. The first force accumulator is constructed, for example, as a spring element, in particular, in the form of a compression spring, wherein any other suitable spring type could also be used. 
     The active pressure accumulator further comprises a locking mechanism through which the first displacement element can be locked detachably in the second end position in which the first force accumulator is clamped. 
     The active pressure accumulator further comprises a switching mechanism with a switch element, wherein this switching mechanism is actuated by an actuator and can be brought into at least two switch positions, wherein the switch element interacts with the locking mechanism so that the locking of the first displacement element is maintained in a first switch position and is released in a second switch position. Advantageously, the switching element can be displaced between the two switch positions by an actuator rotationally decoupled from the camshaft. 
     The passive pressure accumulator comprises a second displacement element that is arranged in the cavity and can be displaced between a first end position and a second end position. Here, the second displacement element is provided with a second pressure surface that at least partially bounds, together with the wall of the cavity, a second storage space. 
     The passive pressure accumulator further comprises a second force accumulator that interacts with the second displacement element, wherein the second displacement element can be displaced by the pressurization of the second storage space against the force of the second force accumulator from the first end position into the second end position. 
     In the device according to the invention, the first storage space and the second storage space communicate with each other, i.e., are in constant fluid-conducting connection and can be connected or are connected in a fluid-conducting manner to a pressure source or pressurized medium source. For example, the two storage spaces are connected to the lubricating oil circuit of the internal combustion engine, wherein an oil pump acts as a pressure source and oil of the lubricating oil circuit is used as the pressurized medium. 
     For relatively low installation space requirements, the device according to the invention allows a more reliable and more secure supply of pressure to the loads of an internal combustion engine that is provided independent of the pressure in the lubricating circuit of the internal combustion engine. Here, a relatively large pressurized medium volume can be provided by the two storage spaces. One special advantage of the device according to the invention is produced in that the passive pressure accumulator is used for supplying pressure to loads while the internal combustion engine is running, while the active pressure accumulator can be used only for starting the internal combustion engine and is charged for the next start while the internal combustion engine is running. 
     In one advantageous construction of the device according to the invention for supplying pressure, the second storage space is arranged between the first storage space and the load, so that the load, for example, a hydraulic camshaft adjuster, can be easily supplied with pressurized medium when the internal combustion engine is running. 
     In another advantageous construction of the device according to the invention, the second storage space can be connected or is connected in a fluid-conducting manner to the pressure source and to the load with at least one leakage prevention device provided in-between. The leakage prevention device is constructed so that it allows the through flow of pressurized medium, while it blocks the through flow of non-pressurized medium merely at the hydrostatic pressure. Thus, the leakage prevention device can prevent leakage from the storage space if insufficient pressure is supplied by the pressure source, for example, in the case of insufficient output from the oil pump. The leakage prevention device can be used as a limit for the second storage space and can form, in particular, a stop for the second displacement element in the first end position. The construction of such a leakage prevention device is known to someone skilled in the art and is described in the patent literature, for example, in DE 19615076. 
     In another advantageous construction of the device according to the invention, there is a support element that is connected rigidly to the camshaft and on which the second force accumulator of the second displacement element is supported. Here it can be advantageous if the support element is used as a stop for the first displacement element in the first end position. 
     In another advantageous construction of the device according to the invention, a hollow guide element guiding the second displacement element is held in a passage opening of the support element. The two storage spaces communicate with each other via the cavity of this guide element. The provision of a support element, in particular, with a guide element, allows an especially simple technical realization of the device for supplying pressure. 
     In another advantageous construction of the device according to the invention, the active accumulator comprises a ball carrier that is connected rigidly to the camshaft and surrounds the switch element. The ball carrier has a plurality of openings in each of which a ball is held so that it can move freely in the radial direction. Here, the balls are supported in the radial direction by a support surface formed by the switch element. In this construction of the device, it further comprises a locking element that is connected rigidly to the first displacement element and is provided with a locking section that is led into engagement with the balls in the second end position of the first displacement element, for example, in that it engages behind these balls, in order to lock the first displacement element on the camshaft. On the other side, the locking element is not led into engagement with the balls in the first end position of the first displacement body, so that the first displacement element is not locked. In this construction of the device, a first non-return element is also provided that is arranged so that the switch element can be displaced by the actuator relative to the ball carrier against the force of the first non-return element from the first switch position into the second switch position. The first non-return element is constructed, for example, as a spring element, in particular, in the form of a compression spring, wherein any other suitable spring type could also be used. In this construction of the device, the support surface of the switch element is provided with at least one recess that is allocated to the balls and is constructed and arranged so that the balls can be held at least partially in the recess in the second switch position of the switch element, so that the locking section is led out of engagement with the balls and the locking of the first displacement element is released. On the other side, the balls are not held by the recess of the support surface in the first switch position of the switch element, so that the locking of the first displacement element is maintained. 
     These measures allow a technically especially simple realization of the locking and switch mechanism of the active pressure accumulator, wherein the device for supplying pressure is distinguished by an especially good response behavior. 
     In the above construction of the invention, it can also be advantageous if a sliding element is provided that can be displaced by the first displacement element against the force of a second restoring element, wherein the sliding element is constructed so that it slides around the balls for securing them in their radial position in the first end position of the first displacement element and releases these balls in the second end position. Thus the sliding element forms a captive securing device for the balls when these are not in engagement with the locking section of the first locking element. The second restoring element is constructed, for example, as a spring element, in particular, in the form of a compression spring, wherein any other suitable type of spring could also be used. 
     In another advantageous construction of the device according to the invention for supplying pressure, this is provided with a sealing element that seals the camshaft to the outside and on which the first force accumulator of the first displacement element is supported. The sealing element can be used here especially for securing the position of the force accumulator. 
     In another advantageous construction of the device according to the invention, the pressure source can be connected or is connected in a fluid-conducting manner via a non-return valve that forms a block in the direction toward the pressure source to the load and to the two storage spaces. 
     In the device according to the invention, it can be advantageous when it is connected to the lubricating oil circuit of the internal combustion engine, so that oil from the lubricating oil circuit is used as the pressurized medium. 
     The invention further extends to an internal combustion engine that is equipped with at least one device that can be switched as described above for supplying pressure to at least one load. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be explained in more detail with reference to an embodiment, wherein reference is made to the accompanying drawings. Elements that are identical or have identical actions are designated in the drawings with the same reference symbols. Shown are: 
         FIG. 1  is a schematic overview diagram, with reference to which the connection of the device for supplying pressure from  FIG. 1  to the lubricating oil circuit of an internal combustion engine is illustrated, 
         FIG. 2  is a schematic axial section diagram of an embodiment of the device according to the invention for supplying pressure, 
         FIG. 3  is an enlarged section from  FIG. 2  for illustrating the active pressure accumulator of the device for supplying pressure with a locked switch element, 
         FIG. 4  is an enlarged section from  FIG. 2  for illustrating the active pressure accumulator of the device for supplying pressure with a released switch element, 
         FIG. 5  is an enlarged section from  FIG. 2  for illustrating the passive pressure accumulator of the device for supplying pressure with a released switch element. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the figures, an embodiment of the device according to the invention for supplying pressure to loads of an internal combustion engine is shown. The device designated overall with the reference number  1  comprises a camshaft  2  that is built-up as an example here and has a plurality of cams  69  and is supported so that it can be rotated about a central rotational axis  7  on the bearing points  70 . The same would also be conceivable, however, if the camshaft  2  was produced in a foundry process. 
     An active (switchable) pressure accumulator  85  and a passive pressure accumulator  86  are integrated in the camshaft  2 . The active pressure accumulator  85  is shown enlarged in  FIG. 3  and  FIG. 4 , wherein  FIG. 3  corresponds to a charged (tensioned) state and  FIG. 4  shows the torque absorbed during the pressure-release process. In  FIG. 5 , the passive pressure accumulator  86  is shown enlarged in a charged state. A cavity  3  is left open in the camshaft  2  for integrating the two pressure accumulators  85 ,  86 . 
     For forming the active pressure accumulator  85 , a first displacement element constructed in the form of a first piston  4  is held in the cavity  3  so that it can be displaced in the axial direction. In addition, a sealing body  5  constructed in the form of a stepped cylinder can be pressed into the cavity  3  of the camshaft  2  that extends from one end of the camshaft  2  into the cavity  3 . In this way, the sealing body  5  can be divided into a terminal first section  8  with larger diameter and an adjacent second section  9  with smaller diameter, wherein a ring stage  10  is produced. A first force accumulator spring (helical compression spring)  11  used as a first force accumulator is supported with one of its ends on the ring stage  10  of the sealing body  5 . With its other end, this first force accumulator contacts the first piston  4 . 
     The sealing body  5  connected rigidly to the camshaft  2  is further provided with a central axial bore  6  in which a switch rod  12  is held so that it can be displaced in the axial direction. The switch rod  12  can be actuated by an electromagnetic actuator  17  that is arranged on one end of the camshaft  2 , wherein a tappet  19  engages an end-side impact surface  18  of the switch rod  12  for this purpose. The switch rod  12  is part of a switch mechanism for releasing a locking mechanism for the first piston  4  that will be explained in more detail farther below. 
     For forming the passive pressure accumulator  86 , a second displacement element constructed in the form of a second piston  76  is held in the cavity  3  of the camshaft  2  so that it can be displaced in the axial direction. In addition, a support body  71  constructed in the form of a stepped cylinder is pressed into the cavity  3  of the camshaft  2 . It can be divided into a first section  72  with larger diameter and an adjacent second section  73  with smaller diameter, wherein a ring stage  74  is produced. A second force accumulator spring (helical compression spring)  76  used as a second force accumulator is supported on the ring stage  74  of the support body  71 . With its other end, the second force accumulator spring contacts the second piston  76 . In a central passage bore  77  of the support body  71 , a hollow tube  78  is held on which the second piston  76  is supported so that it can be displaced in the axial direction. By means of a sealing element  84 , the second piston  76  forms a low-friction contact with the wall  14  of the cavity  3  of the camshaft  2 , wherein the sealing element  84  provides an oil-tight connection between the second piston  76  and the wall  14 . A ring seal  29  is further provided between the first section  72  of the support body  71  and the wall  14 . 
     The piston  4  has an end-side first pressure surface  13  that defines a first storage space  15  for pressurized oil  28  together with an (inner) wall  14  of the hollow space  3  of the camshaft  2  and an end surface  80  of the support body  71  facing the first piston  4 . Through a plurality of ring seals  29 , the first storage space  15  is sealed oil-tight to the outside. On the other hand, the second piston  76  has an end-side second pressure surface  82  that defines a second storage space  83  for pressurized oil  28  together with the wall  14  of the cavity  3  of the camshaft  2  and a leakage prevention device  16 . Here, the first storage space  15  communicates with the second storage space  83  via the cavity  79  of the hollow tube  78 . 
     Opposite the actuator  17 , a hydraulic camshaft adjuster  21  is attached, for example, by means of a (not shown) central screw to the end side of the camshaft  2 . As usual, the hydraulic camshaft adjuster  21  comprises a drive part in drive connection with the crankshaft via a drive wheel and a camshaft-fixed driven part, as well as a hydraulic actuating drive that is switched between a drive part and a driven part and transfers the torque from the drive part to the driven part and allows an adjustment and fixing of the rotational position between these parts. The hydraulic actuating drive is provided with at least one pressure chamber pair that act against each other and can be selectively pressurized with pressurized oil, in order to generate a change in the rotational position between the drive part and driven part by generating a pressure drop across the two pressure chambers. 
     Hydraulic camshaft adjusters as such are well known to someone skilled in the art and described in detail, for example, in publications DE 202005008264 U1, EP 1596040 A2, DE 102005013141 A1, DE 19908934 A1, and WO 2006/039966 of the applicant, so that more exact details do not need to be discussed here. 
     In the central screw for fastening the camshaft adjuster  21  to the camshaft  2 , a control valve not shown in more detail is arranged for controlling the oil flows. This control valve can connect the pressure chambers of the camshaft adjuster  21  in a fluid-conducting manner via oil paths  26  selectively with a pressure source or pressurized medium source constructed in the form of an oil pump  22  or with an oil tank  23 . Such control valves are well known as such to someone skilled in the art and described in detail, for example, in the German Patent DE 19727180 C2, the German Patent DE 19616973 C2, the European Patent Application EP 1 596 041 A2, and the German Laid Open Patent Application DE 102 39 207 A1 of the applicant, so that more exact details do not have to be discussed here. 
     As can be taken from  FIG. 2 , the second storage space  83  is connected in a fluid-conducting manner to the oil pump  22  via a pressure line  24 . The pressure line  24  here opens upstream of the leakage prevention device  16  into pressure channels  68  that are in fluid-conducting connection to the oil paths  26  via the control valve and to the second storage space  83 . Thus, both the two storage spaces  15 ,  83  and also the hydraulic camshaft adjuster  21  are connected in a fluid-conducting manner to the oil pump  22  via the pressure line  24 . A non-return valve  25  that is arranged in the pressure line  24  and forms a block in the direction toward the oil pump  22  prevents a return flow of pressurized oil in the case of reduced or insufficient output from the oil pump  22 . 
     In the internal combustion engine, additional loads are connected upstream of the non-return valve  25  to the pressure line  24 , such as support elements  27  and the bearing points  70  of the camshaft  2  that must be supplied with pressurized oil  28 . 
     If the first storage space  15  and the second storage space  83  that can communicate with each other via the hollow tube  78  are now loaded with pressurized oil via the pressure line  24 , the first piston  4  can be pushed against the spring force of the first force accumulator spring  11  by pressurization of the first storage space  15  and the second piston  76  can be pushed against the spring force of the second force accumulator spring  76  by pressurization of the second storage space  83 . Here, the pressurized oil  28  passes through the leakage prevention device  16  that is transmissible for pressurized pressurized oil  28 . Here, the second piston  76  is pushed from a first end position in which it contacts the leakage prevention device  16  into a second end position in which the second force accumulator spring  76  is tensioned or is more strongly tensioned in the presence of a biasing tension. Furthermore, the first piston  4  is pushed from a first end position in which it contacts the support body  71  into a second end position in which the first force accumulator spring  11  is tensioned or is more strongly tensioned in the presence of a biasing tension. 
     The spring force of the first force accumulator spring  11  is greater than the spring force of the second force accumulator spring  76 , so that when the communicating storage spaces  15 ,  83  are pressurized, the second force accumulator spring  76  is compressed preferentially before the first force accumulator spring  11 . The spring force of the first force accumulator spring  11  can be designed, for example, with reference to a maximum oil pressure in the cylinder head, while the spring force of the second force accumulator spring  76  can be given from the characteristic map of the hydraulic camshaft adjuster  21 . 
     In contrast to the second piston  76 , in the second end position, the first piston  4  can be locked by a locking mechanism. The locking mechanism thus comprises a sleeve-shaped ball carrier  31  that is pressed into a sleeve-shaped end section  30  of the sealing body  5  and has a plurality of radial bores  32  arranged distributed in the peripheral direction. A ball  33  is held in each of these bores. Here, the bores  32  each have a larger diameter than the balls  33 , so that these are freely moveable in the radial direction in the bores  32 . The ball carrier  31  is provided with an end surface  58  on its side facing away from the sealing body  5 . 
     Furthermore, a sleeve body  36  is pressed into a hollow space  35  of the ball carrier  31 , wherein this sleeve body contacts a shoulder  39  of the sealing body  5  with a first end surface  59  facing away from the first piston  4 , and wherein oil tightness is ensured by an intermediary ring seal  29 . An opposite second end surface  60  of the sleeve body  36  forms an end stop for a switch pin  37  connected rigidly to the switch rod  12 . 
     An outer lateral surface  41  of the switch pin  37  is provided with a ring groove  38  whose axial section has a ball-shell shape and is allocated to the balls  33 . On its end facing away from the sleeve body  36 , the switch pin  37  is provided with a sleeve-shaped end section  42  in which a restoring spring  43  is held. The restoring spring  43  is supported with its one end on a ring stage  46  shaped by the switch pin  37  and is supported with its other end on a punch  44 . In the locked position of the first piston  4  shown in  FIG. 3 , the punch  44  contacts an inner surface  34  of the first piston  4 . The punch  44  is secured by a snap ring  45  against falling out from the end section  42  of the switch pin  37 . 
     Furthermore, on an outer lateral surface  40  of the ball carrier  31 , an at least approximately sleeve-shaped sliding body  47  is arranged so that it can move in the axial direction relative to the ball carrier  31 . The sliding body  47  is loaded by a sliding spring  49  that is constructed here, for example, as a compression spring. For this purpose, the sliding spring  49  is supported with one end on an end surface  62  of the sealing body  5  and with its other end on a ring stage  48  of the sliding body  47 , so that the sliding body  47  is loaded by the spring force of the sliding spring  49  in the direction of the switch pin  37 . The sliding body  47  made, for example, from sheet steel is provided with a sliding section  50  that slides into the locked position shown in  FIG. 3  over the balls  33  and thus acts as a captive securing device. In contrast, in the non-locked position of the piston  4  shown in  FIG. 4 , the sliding section  50  releases the balls  33 . 
     The first piston  4  is connected to a sleeve-shaped locking body  53 . The locking body  53  is provided with a radially projecting collar  54  that is provided for this purpose and is pressed by the first force accumulator  11  against a shoulder  52  of the first piston  4 , so that the locking body  53  is connected by a non-positive fit to the first piston  4 . The locking body  53  has a locking section  55  with a radially inward directed ring bead  56  that forms a recess  57 . 
     Now if the two storage spaces  15 ,  83  are loaded with pressurized oil  28 , the second piston  76  is displaced by means of its second pressure surface  82  against the spring force of the second force accumulator spring  76  until the second piston  76  is finally led into contact against the second end surface  81  of the support body  71  that is used as a stop for the second piston  76 . In addition, the first piston  4  is displaced by means of its pressure surface  13  against the spring force of the first force accumulator spring  11 . Here, an end surface  61  of the locking body  53  comes into contact with a first end surface  63  of the sliding body  47  and displaces this body against the spring force of the sliding spring  49  up to the balls  33  in the region of the recess  57 . In addition, the inner surface  34  of the first piston  4  comes into contact with an end surface  65  of the punch  44 , wherein the switch pin  37  is displaced in the same direction as the piston  4 . Here, the balls  33  are pressed out from the ring groove  38  of the switch pin  37  into the recess  57 . This movement of the balls  33  is supported by centrifugal force of the rotating camshaft  2 . The balls  33  then contact the outer lateral surface  41  of the switch pin  37 , wherein the ring bead  56  engages behind the balls  33 . An end surface  66  of the switch pin  37  facing away from the punch  44  is here led into contact with the second end surface  60  of the sleeve body  36  that thus acts as a stop for the switch pin  37 . By means of the switch pin  37 , the switch rod  12  is displaced in the central axial bore  6  of the sealing piece  5 . Finally, the inner surface  34  of the first piston  4  is led into contact with the end surface  58  of the ball carrier  31  that thus acts as a stop for the first piston  4 . 
     If the pressure in the lubricating circuit drops when the internal combustion engine is running, the camshaft adjuster  21  can be provided with pressure by the passive pressure accumulator  86 , wherein the second piston  76  is displaced by the spring force of the second force accumulator spring  76  and pressurized oil  28  of the second storage space  83  is pressed through the leakage prevention device  16  into the camshaft adjuster  21 . If the oil pump  22  supplies sufficient pressurized oil  28 , the passive pressure accumulator  86  is recharged in that the second piston  76  is displaced against the spring force of the second force accumulator spring  76 . The leakage prevention device  16  here comprises, for example, three disks  51  that are locked in rotation with each other and are each provided with an eccentric bore, wherein the three bores are each offset relative to each other by 120°. Between the disks  51  there are cavities that allow transport of the pressurized oil  28 . This allows pressurized oil  28  to pass the leakage prevention device  16  and blocks the passage of pressurized oil  28  merely at atmospheric or hydrostatic pressure. 
     Additionally or alternatively, the charged active pressure accumulator  85  can be discharged when the internal combustion engine is running or when the internal combustion engine is started. For this purpose, the locked first piston  4  can be released by a switch mechanism explained in more detail. The first piston  4  can be unlocked in that the switch rod  12  is moved by the tappet  19  contacting the impact surface  18  against the force of the restoring spring  43 . The tappet  19  is attached rigidly to a magnetic armature of an electromagnet  20  of the actuator  17  and can be displaced in the axial direction by energizing the magnetic armature. If the magnetic armature is not energized, the switch rod  12  is restored by the spring force of the restoring spring  43 . For releasing the lock, the switch rod  12  and the switch pin  37  that contacts the switch rod  12  are displaced by the action of the tappet  19  until the ring groove is aligned with the bores  32  of the ball carrier  31 . This has the result that the balls  33  enter into the ring groove  38 , so that the ring bead  56  no longer engages behind the balls  33  or the balls  33  come out from the recess  57 . The locking section  53  of the locking element  53  thus loses its engagement with the balls  33 , wherein the locking of the piston  4  is released. 
     The first piston  4  is then displaced by the spring force of the first force accumulator spring  11  and the pressurized oil  28  contained in the first storage space  15  is discharged to the camshaft adjuster  21  via the hollow tube  78  and the leakage prevention device  16 . The non-return valve  25  prevents pressurized oil  28  from reaching the oil pump  22  and the other loads. Simultaneously, the sliding body  47  is displaced by the spring force of the sliding spring  49 , wherein the sliding section  50  slides over the balls  33 . When the first piston  4  is displaced by the first force accumulator spring  11 , the first end surface  80  of the sliding body  71  forms a stop for the first piston  4 . 
     The device according to the invention thus allows a reliable supply of pressure medium to loads of an internal combustion engine, wherein pressurized oil is provided independent of the oil supply of the internal combustion engine through the active (switchable) pressure accumulator integrated in the camshaft and the passive pressure accumulator. Thus, loads, like the hydraulic camshaft adjuster shown in the exemplary embodiment, can then also be supplied with pressurized oil, when the engine-side oil supply is not sufficient. When the oil pressure drops when the internal combustion engine is running, for example, in the state of hot idling, in the typical way, very hot pressurized oil in connection with a low output of the oil pump leads to a drop in the oil pressure, loads, like the hydraulic camshaft adjuster, can be easily and reliably provided with pressurized oil via the passive pressure accumulator. This can also contribute to improving the adjustment rate of the camshaft adjuster. Because the oil pump needs, on one hand, a certain amount of time after the internal combustion engine starts to build up the necessary oil pressure, an adjustment of the camshaft adjuster into a base position (retarded, middle, advanced position) can take place through the charged active pressure accumulator immediately after the internal combustion engine starts, which is especially suitable in connection with start/stop systems. When the internal combustion engine is running, the passive pressure accumulator can thus be used primarily to compensate oil pressure fluctuations in loads, such as the hydraulic camshaft adjuster. The active pressure accumulator is charged when the internal combustion engine is running and can be discharged when the internal combustion engine starts, in order to supply the hydraulic camshaft adjuster with oil pressure and to shorten the time interval for adjusting the camshaft adjuster by the oil pump. Simultaneously, however, it is also possible that the active pressure accumulator is used when the internal combustion engine is running. The arrangement of the active and passive pressure accumulators in a cavity of the camshaft produces an advantage in terms of installation space compared with external pressure accumulators. 
     List Of Reference Symbols
       1  Device     2  Camshaft     3  Cavity of the camshaft     4  First piston     5  Sealing body     6  Axial bore     7  Rotational axis     8  First section of the sealing body     9  Second section of the sealing body     10  Ring step of the sealing body     11  First force accumulator spring     12  Switch rod     13  First pressure surface     14  Wall     15  Storage room     16  Leakage prevention device     17  Actuator     18  Impact surface     19  Tappet     20  Electromagnet     21  Camshaft adjuster     22  Oil pump     23  Oil tank     24  Pressure line     25  Non-return valve     26  Oil path     27  Support element     28  Pressurized oil     29  Ring seal     30  End section of the sealing body     31  Ball carrier     32  Bore     33  Ball     34  Inner surface     35  Cavity of the ball carrier     36  Sleeve body     37  Switch pin     38  Ring groove     39  Shoulder of the sealing body     40  Outer lateral surface of the ball carrier     41  Outer lateral surface of the switch pin     42  End section of the switch pin     43  Restoring spring     44  Punch     45  Snap ring     46  Ring stage of the switch pin     47  Sliding body     48  Ring stage of the sliding body     49  Sliding spring     50  Sliding section     51  Disk     52  Shoulder of the piston     53  Locking body     54  Collar     55  Locking section     56  Ring bead     57  Recess     58  End surface of the ball carrier     59  First end surface of the sleeve body     60  Second end surface of the sleeve body     61  End surface of the locking body     62  End surface of the sealing body     63  First end surface of the sliding body     64  Second end surface of the sliding body     65  End surface of the punch     66  End surface of the switch pin     67  Connecting space     68  Pressure channel     69  Cams     70  Bearing point     71  Support body     72  First section of the support body     73  Second section of the support body     74  Ring stage of the support body     75  Second force accumulator spring     76  Second piston     77  Passage bore     78  Hollow tube     79  Cavity of the hollow tube     80  First end surface of the support body     81  Second end surface of the support body     82  Second pressure surface     83  Second storage space     84  Sealing element     85  Active pressure accumulator     86  Passive pressure accumulator