Abstract:
A control valve for a device for the variable adjustment of the valve timing of gas exchange valves of an internal combustion engine. The control valve has a substantially hollow-cylindrical valve box, a control piston and a securing ring. The valve box is arranged in a receptacle inside the device, the securing ring projects over the valve box in the radial direction and the control piston is arranged so as to be axially displaceable inside the valve box.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a 371 of PCT/EP2010/061009 filed Jul. 29, 2010, which in turn claims the priority of DE 10 2009 039 385,4 filed Aug. 29, 2009. The priority of both applications is hereby claimed and both applications are incorporated by reference herein. 
     FIELD OF THE INVENTION 
     The invention relates to a control valve for a device for variably setting the control times of gas exchange valves of an internal combustion engine with an essentially hollow-cylindrically designed valve housing, a control piston and a securing ring. The valve housing is arranged in a receptacle inside the device, the securing ring projects beyond the valve housing in the radical direction, and the control piston is arranged displaceably inside the valve housing. 
     BACKGROUND OF THE INVENTION 
     In modern internal combustion engines, devices for variably setting the control times of gas exchange valves are used in order to be able to variably configure the phase relation between crankshaft and camshaft within a defined angular range between a maximum advance position and a maximum retard position. The device is connected fixedly in terms of rotation to a camshaft and has a plurality of pressure chambers, by means of which a phase relation between the crankshaft and the camshaft can be varied in a directed way by the supply or discharge of pressure medium. The supply of pressure medium to and discharge of pressure medium from the pressure chambers are controlled by means of a control valve. 
     A device and a control valve are known, for example, from DE 102 11 468 A1. The device comprises a driven element which is arranged rotatably with respect to a drive element and which is connected fixedly in terms of rotation to a camshaft. The drive element is drive-connected to a crankshaft. Inside the device, a plurality of pressure chambers acting opposite to one another are provided, by means of which the phase position of the driven element in relation to the drive element can be set in a directed way within a defined angular range. Directed rotation of the camshaft in relation to the crankshaft can thus be brought about. In DE 102 11 468 A1, the device is of vane type design. However, other forms of construction, such as axial piston adjusters from DE 42 18 082 A1, are also known. 
     The camshaft is mounted in a cylinder head of the internal combustion engine by means of a plurality of camshaft bearings. Pressure medium is supplied via one of the camshaft bearings to a pressure medium duct formed in the camshaft and can be conducted into the pressure chambers via a control valve which is arranged in a receptacle of the camshaft. The control valve is composed of a valve housing and of a control piston received axially displaceably in the valve housing. The control piston can be positioned in relation to the valve housing in the axial direction, counter to the force of a spring element, by means of an electromagnetic actuating unit and the pressure medium streams are thus controlled. 
     SUMMARY OF THE INVENTION 
     The object on which the present invention is based is to specify a control valve, of which the outlay in terms of assembly is to be reduced. 
     The object is achieved, according to the invention, in that an annular groove is formed on an inner circumferential face of the receptacle, into which annular groove the securing ring can engage. The securing ring bears against an axial side face of the valve housing, and at least one positively locking element is formed on the valve housing. The securing ring is fastened to the valve housing by the positively locking element. Moreover, the positively locking element is formed on the axial side face of the valve housing against which the securing ring bears. 
     The securing ring serves for fastening the control valve in the receptacle which can be formed, for example, within the camshaft or the inner rotor. The control valve is therefore positioned radially within the device. The securing ring is configured as an elastically deformable component which can be compressed and extended elastically in the radial direction, with the result that its diameter can he reduced and increased from the rest state under the action of force. If the force ceases, the securing ring returns into its original state. 
     During the mounting of the control valve in the receptacle, the diameter of the securing ring is compressed in the radial direction upon entry into the receptacle by the wall of the latter. When the securing ring passes into the region of the annular groove of the receptacle, it latches into the annular groove. At the same time, said securing ring bears in the axial direction against the valve housing, for example against an axial side face of the valve housing, with the result that the axial position of the valve housing and therefore of the control valve in the receptacle is fixed. 
     As a result of the positively locking connection of the securing ring with the valve housing, the control valve including securing ring can be supplied to the assembly line as one module. During the mounting of the control valve in the receptacle, only one module has to be mounted, and not two separate components. Moreover, it is ensured that the securing ring is installed during the mounting. 
     In one development of the invention, it can be provided that two hook-shaped positively locking elements which are spaced apart in the circumferential direction are formed in the region of that side face of the valve housing, against which the securing ring bears, which positively locking elements are configured so as to be open radially to the outside and engage behind the securing ring in the axial direction, with the result that the securing ring bears both against the axial side face of the valve housing and against radially extending sections of the hook-shaped positively locking elements. The radial movability of the securing ring is therefore ensured, as a result of which the mounting is simplified further. The hook-shaped structures hold the securing ring in its predefined position, radial compression being made possible during the mounting. The mounting of the securing ring on the valve housing takes place by virtue of the fact that the securing ring is first of all bent open elastically in the radial direction with an increase in its diameter and is inserted into the hooks. Subsequently, the action of force which has led to the increase in the diameter is ended and the securing ring returns into its original state, with the result that said securing ring is received captively in the hooks. 
     In one advantageous development of the invention, it is provided that the securing ring has a radially inwardly extending section which serves as an axial stop for the control piston. As a result, the components which are arranged within the valve housing, such as the control piston, spring element and sleeves which are possibly arranged between the valve housing and the control piston, are secured captively, with the result that the entire control valve can be supplied to the assembly line and installed as one module. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features of the invention may be gathered from the following description and from the drawings which illustrate exemplary embodiments of the invention in simplified form and in which: 
         FIG. 1  shows an internal combustion engine only highly diagrammatically, 
         FIG. 2  shows a longitudinal section through a device for variably setting the control times of gas exchange valves of an internal combustion engine by means of a control valve according to the invention, 
         FIG. 3  shows a cross section through the device from  FIG. 2  along the line III-III, 
         FIG. 4  shows an enlarged view of  FIG. 2 , only the camshaft and control valve being illustrated and the sectional plane having been tilted through 45° in the circumferential direction, 
         FIG. 5  shows the control valve from  FIG. 4  in an exploded illustration, 
         FIG. 6  shows a top view of the control valve according to the arrow VI in  FIG. 4 , 
         FIG. 7  shows a further embodiment according to the invention of a control valve in an illustration similar to that of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An internal combustion engine  1  is sketched in  FIG. 1 . A piston  3  seated on a crankshaft  2  is indicated in a cylinder  4 . In the embodiment illustrated, the crankshaft  2  is connected to an inlet camshaft  6  and an outlet camshaft  7  via a traction mechanism  5 . A first and a second device  11  for variably setting the control times of gas exchange valves  9 ,  10  of an internal combustion engine  1  are capable of ensuring relative rotation between the crankshaft  2  and camshafts  6 ,  7 . Cams  8  of the camshafts  6 ,  7  actuate one or more inlet gas exchange valves  9  and one or more outlet gas exchange valves  10  respectively. There may also be provision for equipping only one of the camshafts  6 ,  7  with a device  11  or for providing only one camshaft  6 ,  7  which is equipped with a device  11 . 
       FIGS. 2 and 3  show a device  11  in longitudinal section and in cross-section respectively. A camshaft  6 ,  7  and a control valve  12  according to the invention are additionally illustrated in  FIG. 2 . 
     The device  11  comprises a drive element  14  and a driven element  16 . The drive element  14  is composed of a housing  15  with two side covers  17 ,  18  which are arranged on the axial side faces of the housing  15  and are fastened to the latter by means of screws. The driven element  16  is designed in the form of an impeller and has an essentially cylindrically designed hub element  19 , from the outer cylindrical surface area of which five vanes  20  extend outward in the radial direction in the embodiment illustrated. 
     Starting from an outer circumferential wall  21  of the housing  15 , five projections  22  extend radially inward. In the embodiment illustrated, the projections  22  and the vanes  20  are formed in one part with the circumferential wall  21  and with the hub element  19  respectively. Embodiments will likewise be envisaged in which the vanes  20  and/or the projections  22  are designed as separately manufactured components which are subsequently mounted on the corresponding component. The drive element  14  is mounted on the driven element  16  rotatably in relation to the latter by means of radially inner circumferential walls of the projections  22 . 
     Formed on an outer surface area of the first housing  15  is a chain wheel  23 , via which torque can be transmitted from the crankshaft  2  to the drive element  14  by means of a chain mechanism, not illustrated. The driven element  16  has a central orifice  13  which is pierced by the camshaft  6 ,  7 . In this case, the driven element  16  is fastened fixedly in terms of rotation to the camshaft  6 ,  7  by means of a press fit. 
     A pressure space  28  is formed inside the device  11  in each case between two projections  22  adjacent in the circumferential direction. Each of the pressure spaces  28  is delimited in the circumferential direction by mutually opposite projections  22  adjacent to essentially radially running boundary walls, in the axial direction, by the side covers  17 ,  18 , radially inward by the hub element  19  and radially outward by the circumferential wall  21 . A vane  20  projects into each of the pressure spaces  28 . The vanes  20  are designed in such a way that they bear both against the side covers  17 ,  18  and against the circumferential wall  21 . Each vane  20  thus divides the respective pressure space  28  into two pressure chambers  29 ,  30  acting opposite to one another. 
     By the action of pressure upon one group of pressure chambers  29 ,  30  and by the relief of pressure from the other group, the face position of the drive element  14  in relation to the driven element  16  and consequently the phase position of the camshaft  6 ,  7  in relation to the crankshaft  2  can be varied. By the action of pressure upon both groups of pressure chambers  29 ,  30 , the phase position can be kept constant. 
     Pressure medium is supplied to the device  11  via the interior of the camshaft  6 ,  7  which is of hollow form in the embodiment illustrated, and via a control valve  12  arranged in the receptacle  31  of the camshaft  6 ,  7 . 
       FIG. 4  shows the control valve  12  inside the camshaft  6 ,  7  in an enlarged illustration. The control valve  12  has an essentially hollow-cylindrically designed valve housing  34 , a cylindrical sleeve  35  and an essentially hollow-cylindrical control piston  36 . 
     One radial inflow connection P, two radial working connections A, B and one axial outflow connection T are formed on the valve housing  34 . The outflow connection T is designed as an axial orifice on the valve housing  34 . The working connections A, B are designed as radial orifices on the surface area of the valve housing  34 , each of the working connections A, B communicating with a group of pressure chambers  29 ,  30  via pressure medium ducts  46  formed in the driven element  16 . The inflow connection P is likewise designed as a radial orifice on the surface area of the valve housing  34 , said inflow connection being arranged so as to be offset in the circumferential direction to the working connections A, B and being designed as a long hole ( FIG. 5 ). The inflow connection P extends in the axial direction as far as a nonreturn valve receptacle  32  which communicates via an axial orifice, not illustrated, with the interior of the camshaft  6 ,  7 . Arranged in the nonreturn valve receptacle  32  is a spring plate  33  which is prestressed against the axial orifice, not illustrated, so as to implement a nonreturn valve which permits a flow of pressure medium from the camshaft  6 ,  7  to the inflow connection P and which shuts off an opposite flow of pressure medium. Upstream of the nonreturn valve, a pot-shaped filter element  47  is fastened to the valve housing  34 . 
     The valve housing  34  is arranged inside the camshaft  6 ,  7 , the axial position of which valve housing is defined by a shoulder, formed on the inner surface area of the camshaft  6 ,  7  and the outer surface area of the valve housing  34 , and a securing ring  42 . The securing ring  42  projects beyond the valve housing  34  in the radial direction, is arranged in an annular groove  44  formed on the inner surface area of the camshaft  6 ,  7  and bears against an axial side face  43  of the valve housing  34 . 
     Inside the valve housing  34  is arranged the sleeve  35 , the outside diameter of which is adapted to the inside diameter of the valve housing  34 . The sleeve  35  has a plurality of orifices  37 , each of the orifices  37  communicating with one of the working connections A, B or with the inflow connection P. 
     The control piston  36  is received axially displaceably inside the sleeve  35 . The control piston  36  has two control sections  38 , the outside diameters of which are adapted to the inside diameter of the sleeve  35 . A groove  39  running annularly around the control piston  36  is provided between the control sections  38 . 
     The control piston  36  can be positioned in relation to the valve housing  34  in the axial direction, counter to the force of a spring element  40 , by means of an electromagnetic actuating unit, not illustrated, which acts on that end of the control piston  36  which faces away from the camshaft  6 ,  7 . The spring element  40  is arranged in a spring receptacle  41  formed on the valve housing  34  and is supported, on the one hand, on the spring receptacle  41  and, on the other hand, on the control piston  36 . In this case, the travel of the control piston  36  in the axial direction is limited, on the one hand, by the spring receptacle  41 , and, on the other hand, by radially inward-extending sections  45  of the securing ring  42  ( FIGS. 4-6 ). 
     Depending on the position of the control piston  36  in relation to the valve housing  34 , one of the working connections A, B is connected to the inflow connection P, while at the same time the other working connection A, B is connected directly or via the interior of the control piston  36  to the outflow connection T. In this case, control edges, by means of which the streams of pressure medium are controlled, are formed on the control sections  38  of the control piston  36  and the orifices  37  of the sleeve  35 . 
     When the internal combustion engine  1  is in operation, pressure medium is supplied to the interior of the camshaft  6 ,  7  via camshaft orifices  48  by a pressure medium pump, not illustrated. The pressure medium passes through the filter element  47 , via the axial orifice, not illustrated, in the valve housing  34  and the spring plate  33  to the inflow connection P and, from there, into an annular space which is delimited by the groove  39  formed on the control piston  36  and by the sleeve  35 . 
     Depending on the position of the control piston  36  in relation to the valve housing  34 , the pressure medium is conducted to the first or to the second pressure chambers  29 ,  30 . At the same time, pressure medium passes from the other pressure chambers  29 ,  30  via the outflow connection T to a pressure medium reservoir, not illustrated, of the internal combustion engine  1 . A variation in the phase position of the driven element  16  in relation to the drive element  14  and consequently of the camshaft  6 ,  7  in relation to the crankshaft  2  thereby takes place. When the desired phase position is reached, the electromagnetic actuating unit, not illustrated, displaces the control piston  36  into a neutral position in which pressure medium is supplied to both groups of pressure chambers  29 ,  30 , so that the relative phase position is kept constant. 
     Two hook-shaped formfit elements  49  which are spaced apart in the circumferential direction are formed on the axial side face  43  against which the securing ring  42  bears, which formfit elements  49  are designed to be open radially outward. Each of the formfit elements  49 , starting from the side face  43 , first extends in the axial direction and has an adjoining radial section  50 . The formfit elements  49  engage behind the securing ring  42  in the axial direction, so that the latter is received captively between the axial side face  43  and the radial sections  50 . When the control valve  12  is being mounted, first, the sleeve  35 , spring element  40  and control piston  36  are positioned inside the valve housing  34 . The slotted securing ring  42  is thereafter bent open elastically by means of a circumferentially directed force, and is positioned on the side face  43 . The action of force is thereafter terminated so that the securing ring  42  resumes its original shape with a smaller diameter and is thus fastened to the valve housing  34 . On account of the radially inward-extending sections  45 , both the sleeve  35  and the control piston  36  and consequently the spring element  40  are received captively in the valve housing  34 , so that the entire control valve  12  can be delivered as a subassembly to the assembly line, without the fear that components may be lost. 
     When the control valve  12  is being mounted in the camshaft  6 ,  7 , the control valve  12  is pushed into the latter until the shoulder of the valve housing  34  comes to bear against the shoulder of the camshaft  6 ,  7 . In this case, the securing ring  42 , when it enters the camshaft  6 ,  7 , is compressed elastically. In the region of the annular groove  44 , the securing ring  42  expands and automatically engages into the latter, so that the axial position of the control valve  12  inside the camshaft  6 ,  7  is defined. As well as the simple mounting of the control valve  12  in the camshaft  6 ,  7 , one advantage of the control valve  12  according to the invention in the plug-in type of construction is that it can be delivered as a module to the assembly line, without the fear that one of the components, namely the control piston  36 , spring element  40 , securing ring  42  or sleeve  35 , may be lost. 
       FIG. 7  shows a further embodiment of a control valve  12  according to the invention similar to the illustration in  FIG. 4 . In contrast to the first embodiment, the fastening of the securing ring  42  to the valve housing  34  is realized by means of a clip connection. For this purpose, the securing ring  42  has a through opening  51 , through which an axially extending positively locking element  49  reaches which is provided with barbs and is formed on the valve housing  34 . 
     The valve housings  34  which are introduced can be configured in one piece or multiple pieces. In the case of valve housings  34  which are formed from a plurality of axially extending part sections with open ends which lie opposite one another in the circumferential direction, a positively locking element  49  is preferably formed on each of the part sections, with the result that the part sections are likewise secured relative to one another by the securing ring  42 . 
     The valve housings  34  may be manufactured, for example, from steel, aluminum or plastic. 
     REFERENCE SYMBOLS 
     
         
           1  Internal Combustion Engine 
           2  Crankshaft 
           3  Piston 
           4  Cylinder 
           5  Traction Mechanism 
           6  Inlet Camshaft 
           7  Outlet Camshaft 
           8  Cam 
           9  Inlet Gas Exchange Valve 
           10  Outlet Gas Exchange Valve 
           11  Device 
           12  Control Valve 
           13  Central Orifice 
           14  Drive Element 
           15  Housing 
           16  Driven Element 
           17  Side Cover 
           18  Side Cover 
           19  Hub Element 
           20  Vane 
           21  Circumferential Wall 
           22  Projection 
           23  Chain Wheel 
           24  - 
           25  - 
           26  - 
           27  - 
           28  Pressure Space 
           29  First Pressure Chamber 
           30  Second Pressure Chamber 
           31  Receptacle 
           32  Nonreturn Valve Receptacle 
           33  Spring Plate 
           34  Valve Housing 
           35  Sleeve 
           36  Control Piston 
           37  Orifice 
           38  Control Section 
           39  Groove 
           40  Spring Element 
           41  Spring Receptacle 
           42  Securing Ring 
           43  Side Face 
           44  Annular Groove 
           45  Section 
           46  Pressure Medium Duct 
           47  Filter Element 
           48  Camshaft Orifices 
           49  Formfit Element 
           50  Radial Section 
           51  Through Orifice 
         A First Working Connection 
         B Second Working Connection 
         P Inflow Connection 
         T Outflow Connection