Abstract:
Provided is a hydraulic control valve with a main stage, having a movable spool valve in a valve housing with at least four ports P, A, B, T to block or release the ports, and provided with control edges formed on piston collars, and with a hydraulic pilot stage provided to control the spool valve of the main stage. If the spool valve of a hydraulic control valve requires a control to release or block the valve housing ports, in addition to electromechanical pilot valves, hydraulically operating pilot stages are also known, in which a pilot valve, controlled by means of a connected drive, regulates a stream of hydraulic fluid acting upon the spool valve of the hydraulic main stage and therefore moving the spool valve between its control positions.

Description:
SUMMARY 
       [0001]    The invention concerns a hydraulic control valve with a main stage, having a movable spool valve in a valve housing with at least four ports P, A, B, T to block or release the ports, and provided with control edges formed on piston collars, and with a hydraulic pilot stage provided to control the spool valve of the main stage. 
         [0002]    If the spool valve of a hydraulic control valve requires a control to release or block the valve housing ports, in addition to electromechanical pilot valves, hydraulically operating pilot stages are also known, in which a pilot valve, controlled by means of a connected drive, regulates a stream of hydraulic fluid acting upon the spool valve of the hydraulic main stage and therefore moving the spool valve between its control positions. When a hydraulic pilot stage arranged separately from the valve housing of the main stage is provided, a corresponding large size is obtained for such a hydraulic control valve and therefore a correspondingly large space requirement. 
         [0003]    The underlying task of the invention is to provide a hydraulic control valve with a hydraulic pilot stage having limited space requirement. The solution to this task is obtained, including advantageous embodiments and modifications of the invention, from the content of the claims which follow this description. 
         [0004]    In its main idea, the invention proposes that the spool valve of the main stage be designed hollow to form the hydraulic pilot stage, and a pilot valve movable by an external drive with a diameter smaller than the cavity be arranged in the cavity formed in the spool valve and be movable relative to the spool valve, the wall of the hollow spool valve being provided with a central inflow opening and with an outer outflow opening on both sides of it, and in which piston collars forming control edges, cooperating with the inflow opening and the outflow openings, are arranged on the pilot valve, and that two thrust plates are arranged in the valve housing enclosing the spool valve on its front ends and creating a pressure chamber for the spool valve on the ends sealed off on the housing side and the corresponding pressure chamber is connected to the annular space connected to the inflow opening via an inflow path that bridges a piston collar of the pilot valve assigned to the outflow openings. 
         [0005]    The advantage that the pilot stage is moved into the main stage of the hydraulic control valve and the space requirements for the control valve overall are therefore reduced is initially connected with the invention. For this purpose, the invention exploits the hydraulic principle in a special way that the pilot stage with the pilot valve movable in both axial directions operates with four resistances, i.e., two resistances in each movement direction of the pilot valve. The hydraulic resistances consist, according to the invention, of the openings formed on the hollow spool valve in the form of at least one inflow opening and outflow openings, to which piston collars with control edges on them formed on the pilot valves are assigned, so that variable resistances are produced according to the position of the pilot valve within the spool valve. These resistances are set according to the use conditions for the hydraulic control valve, so that on the one hand, a displacement of the pilot valve as free of loss as possible by the connected drive is possible, but, on the other hand, sufficient control speeds of the control valve are attainable via a sufficiently large fluid flow. 
         [0006]    According to one embodiment of the invention, it can then be prescribed that the pilot valve have a piston collar that penetrates the pressure chamber and the corresponding thrust plate in a bearing opening, and that the outflow openings be formed in the spool valve as openings opened toward the tank port in its neutral position, which are blocked in the neutral position of the pilot valve within the spool valve by the corresponding piston collar of the pilot valve. During displacement of the pilot valve, starting from its neutral position, hydraulic fluid is introduced into the annular space from the inflow opening released by the corresponding piston collar, in which case the outflow opening of the spool valve opened toward the tank is released by the corresponding piston collar on the side situated in the movement direction of the pilot valve. 
         [0007]    If it is necessary in such an embodiment to connect the outer pressure chamber with the annular space separated from it by the piston collar, according to one practical example of the invention, it is prescribed that the inflow path be designed as a flat spot of the pilot valve forming a flow space between the pilot valve and the spool valve and the assigned outflow opening formed in the spool valve be arranged with an angle offset to the flat spot formed on the pilot valve, and that a torsion safeguard be provided for non-torsional guiding of the spool valve in the valve housing and the pilot valve relative to each other in all control positions. In order for the hydraulic fluid guided over the flat spots of the annular space into the pressure chamber not to flow out via the outflow openings covered by the piston collar, the offset arrangement of the flat spots and outflow openings is provided. This offset arrangement, however, also requires the provision of a torsion safeguard, so that the spool valve and pilot valve do not twist relative to each other during the control movements and the flat spots therefore can form an open flow path with the outflow openings. 
         [0008]    The provision of a torsion safeguard can drop out if, in an alternative variant of the invention, it is prescribed that the inflow path be formed as a hole which passes through the piston collar of the pilot valve assigned to the outflow openings and connects the pressure chamber with the annular space, since the holes running in the piston collars do not connect with the outflow openings assigned to the piston collars. 
         [0009]    With respect to an alterative embodiment of the inflow path, according to one practical example of the invention, it could be prescribed that the inflow path be designed as a hole running in the wall of the spool valve and connecting the pressure chamber with the annular space. The corresponding piston collar of the pilot valve can also be bridged in this way. 
         [0010]    In an alternative variant with respect to arrangement of the outflow opening and the piston collar on the pilot valve, it is prescribed that the outflow openings in the spool valve be assigned in its neutral position to the consumer ports A and B, and that two control edges for the piston collar forming the outflow edges be arranged on the pilot valve, which are blocked in the neutral position of the pilot valve within the spool valve by the assigned piston collar of the pilot valve. This variant exploits the fact that, in the corresponding control position of the spool valve produced by movement of the pilot valve in the spool valve, one of the consumer ports A or B is always connected to the tank port, so that during displacement of the spool valve hydraulic fluid displaced from the pressure chamber can flow out to the tank via the assigned consumer port. 
         [0011]    If it is also necessary in this practical example to bridge the piston collar situated between the annular space connected to the inflow opening and the pressure chamber, it can be prescribed according to the already described embodiment that the inflow path be designed as a hole passing through the piston collar assigned to the outflow openings and connecting the pressure chamber with the annular space. 
         [0012]    Accordingly, in an alternative variant, it can again be prescribed that the inflow path be designed as a flat spot formed on the piston collars assigned to the outflow openings of the pilot valve, that the assigned outflow openings formed in the spool valve be arranged with an angular offset relative to the flat spots formed on the piston collars of the pilot valve, and that a torsion safeguard be provided for non-torsional guiding in the valve housing of the spool valve and the pilot valve relative to each other in all control positions. 
         [0013]    It is prescribed according to a practical example of the invention that a plurality of inflow and outflow openings leading into the cavity of the spool valve be distributed in symmetric arrangement over the periphery of the spool valve. 
         [0014]    In order to create the pressure chamber required for axial displacement of the spool valve of the main stage of the hydraulic control valve, according to a practical example of the invention, it is prescribed that the thrust plate have a peripheral recess to accommodate an axial protrusion of the spool valve on the front as a stop for the end position of the spool valve, whose depth is chosen so that in the end position of the spool valve an intermediate space remains between the thrust plate and the front of the spool valve as pressure chamber. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    Practical examples of the invention, which is described below, are depicted in the drawings. In the drawing: 
           [0016]      FIG. 1  shows a hydraulic control valve with integrated pilot stage in cross-section without depicting the corresponding drive for the pilot stage and other safety devices to be provided on a control valve, which are not affected by the invention, 
           [0017]      FIG. 2  shows the object of  FIG. 1  in a view rotated by 90°, 
           [0018]      FIG. 3  shows another variant of a spool valve with a pilot valve situated in it in a merely schematic depiction for use in the control valve depicted in  FIGS. 1 and 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    On the valve housing  10  of a hydraulic control valve shown in  FIGS. 1 and 2 , four standard ports P, A, B, T are formed, as such ports are common, but of which only the ports A and B are visible in the drawing. In known fashion, annular spaces are assigned to the ports in the valve housing  10 , specifically an annular space  11  for the pump port P, an annular space  12  for the consumer port A and an annular space  13  for the consumer port B. Outer annular spaces  14  and  15  are also arranged in the depicted practical example, which are assigned to the tank port T, in which case the annular space  14  can be directly connected to the tank port T, whereas the annular space  15  is connected the annular space  14  via an internal bridge  16  and therefore to tank port T. 
         [0020]    In the context of the control valve design known to this extent, a spool valve  17  is arranged movable in valve housing  10 , on which two piston collars  18  with outer control edges are arranged, the piston collars  18  blocking annular spaces  12  and  13  in the neutral position of the control valve depicted in the drawing. During displacement of the spool valve  17 , port of the annular space  11  either to annular space  12  or  13  occurs, in which case the other annular space  12  or  13  is connected accordingly to one of the annular spaces  14  or  15 . In this way, the annular spaces  12 ,  13  of the consumer ports A, B are either acted upon with pump pressure or connected to the tank port. 
         [0021]    To form a hydraulic pilot valve, the spool valve  17  is designed hollow and has an internal cavity, in which the pilot valve  20  is arranged movable relative to the spool valve. The pilot valve  20  has a smaller diameter than the cavity of the spool valve  17 , so that an annular space  21  is produced for flow of a hydraulic fluid. A piston collar with outside control edges  22  is arranged on the pilot valve  20 , which has a peripheral groove  24  for pressure equalization in the center. The piston collar  22  of the pilot valve  20  cooperates with two oppositely arranged openings  25  of the spool valve in the depicted practical example, which are connected to the annular space  11  connected to pump port P, so that the hydraulic fluid supplied by the pump is present on the openings  25  of spool valve  17 . If a displacement of the pilot valve  20  to the left or right from the neutral position depicted in the drawing occurs, the connected control edge  23  of the piston collar  22  releases the corresponding opening  25 , so that hydraulic fluid flows into the annular space  20 , depending on the position of the pilot valve  20  in the cavity of spool valve  17 . 
         [0022]    The space penetrated by the spool valve  17  and traversed during its control movement is closed by the thrust plate  26  tightly arranged relative to the valve housing in valve housing  10 , so that a pressure chamber  30  is formed between the thrust plate  26  and the end of the spool valve  17 . The thrust plates  26  have a peripheral recess  34 , which is made to accommodate an axially protruding protrusion  35  arranged on the front of the spool valve  17 . The depth of the recess  34  relative to the axial extent of the protrusion  35  is dimensioned, so that in the end position of the spool valve  17 , in which its axial protrusion  35  has entered the recess  34  of thrust plate  26 , an intermediate space remains between the thrust plate  26  and the end of the spool valve  17  as pressure chamber  30 . 
         [0023]    The functional space  33  that accommodates the end of the pilot valve  20  is formed on the side of the thrust plate  26  in valve housing  10  facing away from the spool valve. Additional safety devices not necessary for understanding of the invention, like return springs, measurement systems or the like, can be arranged in the functional space. 
         [0024]    In the depicted practical example on the right end of the pilot valve  20 , an opening  38  is formed in the valve housing  10  for connection of an external, preferably electromechanical drive for the pilot valve  20 . 
         [0025]    As follows from examination of the two  FIGS. 1 and 2 , an outflow opening  27  open toward the corresponding tank port annular space  14  or  15  is formed on the spool valve  17 , to which a piston collar  28  is assigned on the pilot valve  20 , which, starting from the annular space  21 , extends through the thrust plate  26  over the axial length of the pilot valve  20 , so that the corresponding piston collar  28  simultaneously also forms a bearing and guide of the pilot valve  20  in the two outer thrust plates  26 . Each piston collar  28  is then laid out, so that it blocks the assigned outflow opening  27  in the spool valve  17  within spool valve  17  in the neutral position of the pilot valve  20  depicted in  FIGS. 1 and 2 . 
         [0026]    In order to create a flow path for inflow of hydraulic fluid from the annular space  21  into the pressure chamber  30 , opposite flat spots  29  ( FIG. 2 ) are formed on the corresponding piston collar  28  of the pilot valve  20 , which form a flow space between the piston collar  28  and the pilot valve  20  and the spool valve  17  and therefore create an inflow path for the pressure chamber  30 . 
         [0027]    In order for hydraulic fluid not to directly escape through the outflow openings  27  during corresponding action of this inflow path, the flat spots  29  on the pilot valve  20  and the arrangement of the outflow openings  27  on the spool valves  17  are offset by 90° relative to each other, so that an open flow path is not formed. 
         [0028]    In order to prevent torsion of the two parts relative to each other and therefore creation of an open flow path during the control movements of pilot valve  20  and spool valve  17 , a torsion safeguard of the two components is provided. If the pilot valve  20  is secured against torsion in the interior of spool valve  17 , because of its connection to an external drive (not shown), a separate torsion safeguard is formed in valve housing  10  for the spool valve  17 . For this purpose, the spool valve  17  is fastened by means of a pin  31  to the corresponding thrust plate  26 , in which case the thrust plate  26 , in turn, is fastened via an additional pin  32  in valve housing  10 , so that protection against torsion of the spool valve  17  of valve housing  10  is implemented via the two correspondingly provided pins  31 ,  32 . 
         [0029]    If the pilot valve  20  is displaced leftward by means of the drive (not shown) from the neutral position depicted in the drawing, the right control edge  23  (in the drawing depiction) of the piston collar  22  formed on pilot valve  20  releases the inflow opening  25  into the spool valve  17 , so that hydraulic fluid supplied by the pump flows rightward into annular space  21 . From here the hydraulic fluid flows into pressure chamber  30  via the flat spots  29  formed in the right piston collar  28  of the pilot valve  20 , so that a pressure builds up in pressure chamber  30  that also leads to displacement of the spool valve  17  leftward. On the opposite left side of pilot valve  20  and spool valve  17 , the fluid present there in pressure chamber  30  must be displaced according to the movement of the spool valve leftward. This fluid can flow back into annular space  21  via the flat spots  29  arranged in the left piston collar  28  of the pilot valve  20 . Since the corresponding control edge of the piston collar  28  has released the outflow opening  27 , because of the leftward offset position of the pilot valve  20  relative to spool valve  17 , the hydraulic fluid displaced from the left pressure chamber  30  can now flow out into the annular channel  15  via the flat spots  29 , annular space  21  and outflow opening  27  and into the tank via the internal bridge  16 . 
         [0030]    As not further shown, the flow paths produced by the flat spots  29  can also be replaced by holes arranged in the piston collars  28  of the pilot valve  20 , which directly connect the annular space  21  to pressure chamber  30 , in which case no connection is present between the holes and the outflow openings  27 . Inflow and outflow of hydraulic fluid occur as described; however, in this case, a special protection against torsion, especially of the spool valve  17  in valve housing  10 , is not necessary. 
         [0031]    According to an alternative also not shown, the flow paths produced by the flat spots  29  can also be shifted into the wall of the spool valve  17  by arranging there at least one hole that connects the pressure chamber  30  to annular space  21 . 
         [0032]    The practical example depicted in  FIG. 3  differs from the practical example described above for  FIGS. 1 and 2  in that the outflow openings  27  according to the invention in the spool valve  17  are now assigned to the annular spaces  12  and  13  corresponding to the consumer ports A and B of valve housing  10 . Since control edges on the pilot valve  20  are also assigned to these outflow openings  27 , the pilot valve  20  has a piston collar  36  assigned to the two outflow openings  27  of the spool valve  17 , which block the outflow opening  27  within spool valve  17  in the neutral position of the pilot valve  20  depicted in  FIG. 3 . Owing to the arrangement of these two piston collars  36 , an annular space  21  on the inflow side and an annular space  21   a  on the outflow side are produced, which are connected, in turn, to the pressure chamber  30  lying on the outside. In order to permit an inflow path from the annular space  21  on the inflow side into pressure chamber  30 , holes  37 , via which the fluid can flow, which pass through the piston collar  36 , are arranged in the practical example depicted in  FIG. 3 . 
         [0033]    The control movements occur in this practical example in the same manner as described for  FIGS. 1 and 2 . During corresponding adjustment of the pilot valve  20  within spool valve  17 , fluid is admitted into annular space  21  on the inflow side, which flows into the pressure chamber  30  on the pressure side via the holes  37 . On the other side, the hydraulic fluid displaced from the pressure chamber  30  there can flow into the annular space  21  via the holes  37  of the corresponding piston collar  36 , which is now open to corresponding outflow opening  27  in spool valve  17 , however, owing to the offset position of the pilot valve  20  relative to spool valve  17 , so that a connection is present between the annular space  21  and the assigned consumer port A or B. Since the corresponding consumer port is connected to the tank in the corresponding position of the spool valve  17 , a corresponding outflow of the fluid displaced from the pressure chamber  30  to the tank also occurs here. 
         [0034]    The features of the object of this document, disclosed in the preceding description, and the claims, summary and drawing, can be essential individually and in any combination with each other for implementation of the invention in its different variants.