Abstract:
A valve having a housing and including a rotatable rotary spool that includes a conducting chamber. A first inlet communicates with the conducting chamber and with a plurality of outlets that are selectively individually connected with the conducting chamber as a function of the rotational position of the rotary spool within the valve housing. The conducting chamber communicates with a first pressure chamber through a first check valve carried by the rotary spool. A second check valve carried by the rotary spool provides communication between the first pressure chamber and a second pressure chamber that surrounds the rotary spool.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a valve having a rotary spool with a conducting chamber, a first inlet to the conducting chamber, and a plurality of outlets that are individually connectable to the conducting chamber as a function of the rotational position of the rotary spool. 
         [0003]    2. Description of the Related Art 
         [0004]    Valves having a rotary spool are known. They can be used to actuate a hydraulically operated transmission of a motor vehicle, for example. In hydraulically shifted transmissions, normally one of several hydraulic cylinders must be subjected to a hydraulic pressure while the other cylinders remain unpressurized. As a rule, the hydraulic cylinders are combined by pairs into double cylinders, so that the pistons can be moved into a middle position or to one of two end positions by pressurizing the cylinders alternately. 
         [0005]    An object of the present invention is to provide an improved valve, in particular a rotary spool valve having reduced leakage. 
       SUMMARY OF THE INVENTION 
       [0006]    The above-mentioned object is achieved with a valve that includes a rotatable spool and a conducting chamber to which a first inlet is connected, and to which a plurality of outlets are individually connectable. The outlets are connected based upon the rotational position of the rotary spool. The conducting chamber communicates with a first pressure chamber through a first check valve. Advantageously, a positive pressure existing in the conducting chamber can also be fed to the first pressure chamber. Also advantageously, pressure forces that develop in the pressure chamber when the conducting chamber is full of fluid can be utilized to supply a sealing force for the rotary spool. 
         [0007]    In addition, the object is achieved with a valve having a rotatable spool with a conducting chamber and a first inlet connected to the conducting chamber, and wherein a plurality of outlets are individually connectable to the conducting chamber as a function of the rotational position of the rotary spool. The valve includes a cylinder connected with the rotary spool, wherein the cylinder is received in a bore in the valve housing with a clearance fit. Because of the clearance fit, the cylinder can advantageously assume a slight angular displacement relative to the axis of the bore. That condition can be used advantageously to compensate for possibly existing tolerances. In addition, the rotary spool with the cylinder can likewise assume a slight angle and in so doing better match a sealing surface, whereby leakage that can possibly arise between the rotary spool and the sealing surface can be prevented or at least reduced to a minimum. 
         [0008]    Preferred exemplary embodiments of the valve are characterized in that an upper end face of the cylinder forms a first pressure surface, wherein the first pressure surface and the bore define the first pressure chamber. The pressure forces acting on the first pressure surface can be transmitted to the rotary spool via the end face of the cylinder, so that a sealing contact results between the rotary spool and the sealing surface. 
         [0009]    Additional preferred exemplary embodiments are characterized in that a second pressure chamber surrounding the rotary spool is connectable to the first pressure chamber and the first pressure surface through a second check valve. When the second pressure chamber is pressurized, the first pressure chamber can also be pressurized through the second check valve. Advantageously, that pressurization also results in a higher contact force of the rotary spool with the sealing surface, and thus a tighter seal. 
         [0010]    Additional preferred exemplary embodiments are characterized in that the valve has a second inlet associated with the second pressure chamber. The second pressure chamber can be pressurized via the second inlet. 
         [0011]    Additional preferred exemplary embodiments are characterized in that when the first inlet is pressurized and the second inlet is unpressurized, the first check valve is open and the second check valve is closed, and vice versa. The check valves advantageously constitute an OR function, where one of the check valves is always open, so that the first pressure chamber is always pressurizable with the greatest pressure present at the inlets. 
         [0012]    Additional preferred exemplary embodiments are characterized in that the cylinder has a peripheral groove to receive a sliding-seal ring that is associated with the bore and the cylinder to seal them. By way of the sliding-seal ring, which is received in the groove, the cylinder can be supported in the bore with a fluid-tight seal despite the clearance fit, and the pressure chambers can be separated from each other with a fluid-tight seal. 
         [0013]    Additional preferred exemplary embodiments are characterized in that the rotary spool has a sealing surface situated opposite the first pressure surface, wherein pressure forces acting on the first pressure surface bring about a contact force for the sealing surface on an intermediate plate of a housing of the valve. In particular, through the pressure forces operating in the first pressure chamber, a sealing contact can be effected between the sealing surface of the rotary spool and the intermediate plate of the housing. 
         [0014]    Additional preferred exemplary embodiments are characterized in that the intermediate plate bounds the conducting chamber of the rotary spool and includes the first inlet as well as the plurality of outlets. Advantageously, the rotary spool can associate one outlet of the plurality of outlets to the inlet by way of the conducting chamber. To that end, the intermediate plate that bounds the conducting chamber can be in sealing contact with the sealing surface of the rotary spool, and can have corresponding bores to achieve the plurality of outlets. The sealing surface can separate the conducting chamber and the second pressure chamber from each other with a fluid-tight seal. 
         [0015]    Additional preferred exemplary embodiments are characterized in that the intermediate plate includes a second inlet. The second inlet can be in the form of a corresponding bore, for example outside of a perimeter of the conducting chamber. That enables the second inlet to be associated with the second pressure chamber. 
         [0016]    Additional preferred exemplary embodiments are characterized in that the intermediate plate bounds the second pressure chamber. Advantageously, the intermediate plate can close the bore forming the second inlet, so that the closed bore results in the second pressure chamber. Situated inside the bore, or inside the second pressure chamber, is the rotary spool, and in it the conducting chamber. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The structure, operation, and advantages of the present invention will become further apparent upon consideration of the following description, taken in conjunction with the accompanying drawings in which: 
           [0018]      FIG. 1  is a longitudinal cross-sectional view through a known rotary valve when it is in a first pressure condition; 
           [0019]      FIG. 2  is a longitudinal cross-sectional view through the valve shown in  FIG. 1  when it is in a second pressure condition; 
           [0020]      FIG. 3  is a perspective view of a rotary spool in accordance with an embodiment of the present invention; 
           [0021]      FIG. 4  is a perspective view, partially in section, of the rotary spool shown in  FIG. 3  when it is in a first pressure condition; and 
           [0022]      FIG. 5  is a perspective view, partially in section, of the rotary spool shown in  FIG. 3  when it is in a second pressure condition. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0023]      FIG. 1  shows a known rotary valve  1 ′ in a longitudinal cross-sectional view and when it is in a first pressure condition.  FIG. 2  shows the valve  1 ′ of  FIG. 1  when it is in a second pressure condition. Valve  1 ′ includes a first inlet  3 , which leads into a conducting chamber  5  of valve  1 ′. Conducting chamber  5  is formed by a rotary spool  7  of valve  1 ′. More precisely, rotary spool  7  includes an essentially rectangular-shaped recess  9  that forms the conducting chamber  5 . 
         [0024]    Viewed in the orientation of  FIGS. 1 and 2 , conducting chamber  5  is bounded on the underside by an intermediate plate  11 , which is part of a housing  13  of valve  1 ′. Housing  13  includes a base plate  15  that is joined to intermediate plate  11 . Intermediate plate  11  includes a first inlet  3 , in the form of a bore, for example. In addition, intermediate plate  11  includes a plurality of outlets, of which a first outlet  17  is visible in the views shown in  FIGS. 1 and 2 . At times one of the outlets, outlet  17  in the views shown in  FIGS. 1 and 2 , can be connected to first inlet  3  through conducting chamber  5 . In  FIG. 1 , conducting chamber  5  is pressurized via first inlet  3 , as indicated by dashed line region  19 . 
         [0025]    It can be seen from  FIG. 1  that conducting chamber  5  of rotary spool  7  is connected to a first pressure chamber  23  by throughbores  21 . The throughbores  21  extend through a cylinder  25  at the upper part of rotary spool  7 , which cylinder is supported in a bore  27  in the base plate  15 . It can be seen in  FIG. 1  that there is a pressure present at an end face  31  of cylinder  25 , i.e., that a pressure force is being exerted, which is indicated in  FIG. 1  by means of two arrows  29 . The pressure force indicated by the arrows  29  is transmitted via cylinder  25  to rotary spool  7 , so that the latter can be pressed against intermediate plate  11  in a sealing contact arrangement. 
         [0026]    It is apparent that the pressure force  29  results in a fluid-tight conducting chamber  5 , provided that the forces acting on the end face  31  of the cylinder  25  are greater than the upwardly-directed forces acting on the conducting chamber, in an upward direction in the orientation shown in  FIG. 1 . To that end, the area relationships must be appropriately selected so that the end face  31  has a greater area than a horizontal inner surface of the conducting chamber  5 . 
         [0027]    It can be seen in  FIG. 2  that a second pressure chamber  33  exists, which is bounded by an outer surface of rotary spool  7 , an inner surface of housing  13  outwardly of bore  27 , and the intermediate plate  11 . Arrows  29  represent a pressure force that acts on an upper side of rotary spool  7 , in a downward direction as shown in  FIG. 2 . The second pressure chamber  33  of valve  1 ′ can be pressurized by means of a second inlet  35 , which is merely indicated schematically in  FIGS. 1 and 2 . 
         [0028]    To rotate the rotary spool  7 , cylinder  25  can be coupled through a shaft  39  to a drive  41 , which is merely suggested. 
         [0029]      FIG. 3  is a perspective view from above of a rotary spool  7  of a valve  1  in accordance with an embodiment of the present invention.  FIG. 4  shows the rotary spool  7  of  FIG. 3  in a perspective view, partially in cross section.  FIG. 5  shows another partial cross-sectional perspective view of the rotary spool  7  shown in  FIGS. 3 and 4 . The description below will only identify the differences from the known arrangement that is shown in  FIGS. 1 and 2 . Otherwise the description for  FIGS. 1 and 2  is applicable. 
         [0030]    Cylinder  25 , which is coupled with shaft  39  and rotary spool  7 , has a peripheral groove  43 . A sealing ring (not shown) can be placed in the groove  43 . The sealing ring can provide a sealing contact arrangement between groove  43  of cylinder  25  and a cylindrical inner wall of bore  27  of base plate  15 . Advantageously, it is therefore possible to place cylinder  25  within bore  27  as a clearance fit and to provide the seal by means of the sealing ring (not shown). A fluid-tight fit between the opposed surfaces of cylinder  25  and bore  27 , as in the known arrangement, is not required. That makes it possible to slightly tilt the rotary spool  7 , or the entire system including rotary spool  7 , cylinder  25 , and shaft  39 , within the bore  27 , which tilting is indicated in  FIG. 3  by a curved, double-headed arrow  45 . 
         [0031]    In that way, rotary spool  7 , or a sealing surface  47  of rotary spool  7 , can be placed more precisely in contact with the intermediate plate  11  of valve  1 , not shown in greater detail in  FIGS. 3 through 5 . Slight tolerances when fitting the base plate  15  together with the intermediate plate  11  and/or the bore  27  of the base plate  15  can thus be compensated for by the slight tilting of rotary spool  7  relative to the central axis of bore  27 . Therefore, a better-sealing contact arrangement of the sealing surface  47  of rotary spool  7  on the intermediate plate  11  results. 
         [0032]    In  FIG. 4 , arrows  29  indicate a pressure force acting on a first pressure surface  49  defined by the end face  31  of cylinder  25 . That pressure force is directed downward, and causes rotary spool  7  to be pressed against intermediate plate  11 . An opposing upward pressure force, which acts on a second pressure surface  53 , within conducting chamber  5 , is indicated by means of arrows  51 . First pressure surface  49  faces in an opposite direction from that of second pressure surface  53  and sealing surface  47 . When designing the valve  1 , the area of first pressure surface  49  must be made larger than the area of second pressure surface  53 . 
         [0033]    In contrast to the known structure shown in  FIGS. 1 and 2 , conducting chamber  5  is coupled with first pressure chamber  23  through a first bore  55  and a first check valve  57  provided in first bore  55 . To that end, the first bore  55  is executed as a stepped bore, where a step of the first bore  55  serves as the ball seat for a ball  59  of the first check valve  57 . Thus, the first check valve  57  is designed so that the ball  59  rises and thereby releases the first bore  55  as soon as a higher pressure exists in conducting chamber  5  than in first pressure chamber  23 . 
         [0034]    It is apparent that because of the connection by means of the first bore  55  and the first check valve  57 , the same pressure conditions result as in the known arrangement shown in  FIG. 1 . 
         [0035]      FIG. 5  shows rotary spool  7  in the second pressure situation, analogous to the representation of the known arrangement shown in  FIG. 2 . Here second pressure chamber  33  is pressurized via the second outlet  35 . Arrows  61  indicate that downward-directed pressure forces, as shown in  FIG. 5 , act on a top side or a third pressure surface  63  of rotary spool  7 . The downward pressure forces indicated by arrows  61  are counteracted by upward pressure forces indicated by arrows  65 , the latter of which act on an underside or a fourth pressure surface  67  of cylinder  25 . 
         [0036]    In principle it is desirable to design the area of third contact surface  63  larger than the area of fourth contact surface  67 , so that a net downward force results, as viewed in the orientation of  FIG. 5 , so that rotary spool  7  can reliably be pressed against the intermediate plate  11 . Advantageously however, in accordance with the representation in  FIG. 5  the second pressure chamber  33  is connected with the first pressure chamber  23  through a second bore  69  and a second check valve  71 . Second bore  69  is formed similar to first bore  55 , so that the pertinent description of bore  55  applies. Second check valve  71  likewise includes a ball  73 , and opens as soon as the pressure is higher in the second pressure chamber  33  than in the first pressure chamber  23 . 
         [0037]    Under the pressure conditions as represented in  FIG. 5 , advantageously second check valve  71  is open and first check valve  57  is closed. First check valve  57  thus prevents an unwanted inflow of fluid from second inlet  35  into conducting chamber  5 . It is apparent that by switching check valves  57  and  71 , the first pressure surface  49  can be additionally pressurized with the pressure supplied through second inlet  35 , so that an additional downwardly-directed force results to press rotary spool  7  against the intermediate plate  11 , as represented by the arrows  29  in  FIG. 5 . 
         [0038]    The two pressure conditions analogous to  FIGS. 4 and 5  can be adjusted by a direction-switching valve (not shown) that is connected ahead of rotary spool  7 . If the pressure is switched to the interior of rotary spool  7 , i.e., into the conducting chamber  5 —pressure conditions as represented in FIG.  4 —that simultaneously causes the second pressure chamber  33  to be switched to zero pressure. Because of first bore  55  and second bore  69 , the pressure is present at the first pressure surface  49  and the second pressure surface  53 . Those surfaces are so designed that the resulting force acts in the direction of intermediate plate  11 . To that end, the area of first pressure surface  49  must be designed to be larger than the area of second pressure surface  53 . 
         [0039]    Therefore rotary spool  7  itself provides for its own sealing, i.e., for the sealing surface  47  to be pressed against intermediate plate  11 . Under the pressure conditions illustrated in  FIG. 5 , the pressure is present on third pressure surface  63  and on fourth pressure surface  67 . In that case, the conducting chamber  5  is switched to zero pressure by the switching direction valve (not shown). Advantageously, through the interconnection by means of check valves  57  and  71  the pressure acting on the first pressure surface  49  can also be present, whereby the force pressing rotary spool  7  against intermediate plate  11  is increased. In particular, as a result it is also possible to enlarge the diameter of cylinder  25  without causing lifting of rotary spool  7  because of the similarly enlarged fourth pressure surface  67 . 
         [0040]    Advantageously, the check valves  57  and  71  constitute an OR element, where the first pressure surface  49  is pressurizable under both pressure conditions. That can improve the contact pressure of the rotary spool  7  against the intermediate plate  11 . In addition, the clearance fit of cylinder  25  in bore  27  can result in rotary spool  7  being enabled to tilt slightly in the guideway, in order to thus be able to compensate for a possible angularity error. 
         [0041]    Advantageously, the diameter of the cylinder  25  provided with the circumferential groove  43  can additionally be enlarged, whereby the first pressure surface  49  and therefore the resulting downward-acting pressure forces are also increased. Bores  55  and  69  are countersunk bores, which can receive the balls  59  and  73  to achieve the respective check valve functions. A sliding seal, not shown in  FIGS. 3 through 5 , can be inserted into the circumferential groove  43 . 
         [0042]    The end face  31  of cylinder  25  defines the first pressure surface  49 . As soon as pressure is applied to the conducting chamber  5  within rotary spool  7 , ball  59  of first check valve  57  rises and releases the oil pressure that is present at first pressure surface  49 . Ball  73  of second check valve  71 , on the other hand, is pressed into the ball seat by the existing pressure or by the pressure-free second pressure chamber  33 , and thereby closes second bore  69 . Advantageously, compared to the known arrangement shown in  FIGS. 1 and 2 , that results in a greater axial force, acting downward in the representations in  FIGS. 3 through 5 , to press rotary spool  7  against intermediate plate  11 . That increased axial force can be further increased by enlarging the diameter of cylinder  25 . 
         [0043]    Under the pressure conditions represented in  FIG. 5 , in the known arrangement as illustrated in  FIG. 2  heretofore only the third pressure surface  63  provided for the corresponding downward-acting pressure force. That pressure force is counteracted by the pressure forces acting on the fourth pressure surface  67 . Advantageously, because of the switching of check valves  57  and  71 , despite the enlarged diameter of cylinder  25 , a greater downward-acting pressure force can be achieved by the additional pressure force acting on the first pressure surface  49 . 
         [0044]    The valve function of check valves  57  and  71  represents an OR element, because one of the two bores  55  and  69  is always open when there is pressure present. Because of that OR element, the first pressure surface  49  of end face  31  of cylinder  25  can be used by both pressures as an effective area for pressing rotary spool  7  against the intermediate plate  11 . The higher pressure force guarantees better contact pressure, and thus lower leakage in both pressure positions. An additional measure, which provides for better sealing when there is a slight angular displacement of bore  27  that is designed to receive rotary spool  7 , cylinder  25 , and shaft  39 , is to use the sliding seal ring (not shown) in the circumferential groove  43 . 
         [0045]    In comparison to the known arrangement shown in  FIGS. 1 and 2 , cylinder  25  in accordance with the present invention, in contrast, is not configured to provide a close fit, but is smaller in diameter than the bore  27  by about 0.2 mm, for example. As a result, the rotary spool  7  has the possibility of minimal tilting in the bore  27 . That enables rotary spool  7  to compensate for any tilting of the bore  27  that can occur, and thus to always lie flat against the intermediate plate  11 . Since the periphery of cylinder  25  serves to separate first pressure chamber  23  and second pressure chamber  33 , i.e., it must assume a sealing function, the sliding seal ring (not shown) can be inserted into the groove  43 . The sliding seal ring advantageously guarantees sealing at the periphery of the cylinder  25  against the bore  27  in both pressure directions. 
         [0046]    Although particular embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit of the present invention. It is therefore intended to encompass within the appended claims all such changes and modifications that fall within the scope of the present invention.