Abstract:
A hydraulic block ( 24 ), in particular for an automatic transmission of a motor vehicle, includes at least one valve socket ( 44 ) for accommodating a pressure control valve or switching valve ( 10 ) and a hydraulic medium at an inlet pressure on an inlet side ( 30 ). The hydraulic block ( 24 ) includes at least one annular seal ( 52, 54 ) encompassing a valve body ( 20, 66 ) in the region of the at least one valve socket ( 44 ).

Description:
CROSS-REFERENCE 
     The invention described and claimed hereinbelow is also described in PCT/EP2007/058860, filed on Aug. 27, 2007 and DE 10 2006 045 162.7, filed on Sep. 25, 2006. This German Patent Application, whose subject matter is incorporated here by reference, provides the basis for a claim of priority of invention under 35 U.S.C. 119 (a)-(d). 
     BACKGROUND OF THE INVENTION 
     In transmissions for motor vehicles, in particular automatic transmissions, hydraulically actuated clutches are used to shift gears. Electromagnetically actuated pressure control valves and switching valves are used to hydraulically control the shifting procedures. The need to improve transmission efficiency and driving comfort has caused the function of automatic transmissions to become continuously more complex in recent years. As a result, the number of pressure control valves and switching valves used in automatic transmissions has increased drastically. Modern automatic transmissions for motor vehicles usually contain a number of pressure control valves or switching valves, e.g. approximately eight of them. 
     In the manufacture of transmissions, assembly complexity dictated by the large number of valves has resulted in a trend toward integrating the pressure control valves and switching valves into an installation module. This means that the valve manufacturer mounts the valves in a shared hydraulic block and they are electrically contacted to a central plug connector by means of a pressed screen or the like. The transmission manufacturer thus has the advantage of only having to install one component, namely the hydraulic block, and hydraulically contacting it. The electrical contacting is also reduced to the contacting of the central plug connector. In order to reduce the manufacturing costs of hydraulic blocks, it is customary to embody them of plastic, preferably in the form of an injection molded plastic component. 
     To seal the pressure control valve and switching valve in relation to the hydraulic block, it is possible to use O-rings that are accommodated in correspondingly configured grooves in the housing of the pressure control valve or switching valve. In addition, it is possible to provide gap seals. This means that both the fitting diameter of the corresponding pressure control valve or switching valve and the receiving diameter in the hydraulic block are produced with high precision. The resulting diametrical difference is so slight that the hydraulic flow resistance in the resulting gap is sufficient to produce the seal. In addition, it is also possible to hydraulically seal the pressure control valves or switching valves by means of a production process, e.g. by means of ultrasonic welding, caulking, press-fitting, or the like. But these produce nondetachable connections, thus rendering it impossible to carry out refinishing work during production or a replacement of pressure valves and switching valves that are attached to the hydraulic block in this way. 
     There are also design approaches in which elastic regions, preferably made of plastic, are provided on the pressure control/switching valve and seal the connection of the pressure control valve or switching valve in relation to the hydraulic block. 
     DE 198 27 281 C1 has disclosed an externally actuatable directional control valve. It is provided with specially embodied sealing devices for the external or reciprocal sealing of its pressure fluid-conveying conduits. These sealing devices are inexpensive to manufacture, can be integrally formed onto the valve unit, and have particularly good elastic properties. This makes it possible to largely rule out temperature- and pressure-induced excessive strains on the sealing device and to eliminate components that require separate assembly. 
     DE 199 55 887 A1 relates to a solenoid valve equipped with a check valve. The solenoid valve is particularly used in slip-controlled hydraulic brake systems of motor vehicles and includes a sealing lip and elastic regions on the hydraulic connection. 
     DE 196 35 693 A1 has disclosed a solenoid valve for a slip-controlled hydraulic vehicle brake system. To produce a simple seal, this design proposes using a plastic end piece, which is placed onto the end surface of the valve body protruding into the receiving bore and produces a seal in relation to both the receiving bore and the valve seat part. 
     In the designs outlined above according to DE 198 27 281 C1 and DE 199 55 887 A1 as well as the design according to DE 196 35 693 A1, it is disadvantageous that in order to achieve a sufficient elasticity, the corresponding components must either be very thin-walled or very long. In particular, the thin-walled production makes them very difficult to manufacture. Between the elastic regions, i.e. the sealing points, a hydraulic connection in the form of a transverse conduit for the working pressure must be provided, which leads to a valve closure member. In a plastic part, the transverse conduit is implemented in the injection mold by means of a transverse slider. This transverse slider cannot be provided in the region of the elastic elements since otherwise, a demolding there is not possible. Also, an overlapping of the elastic regions in order to reduce overall length can only be implemented with difficulty. Such designs, therefore, are generally rejected when there is a small amount of available space, particularly a limited length. 
     SUMMARY OF THE INVENTION 
     The present invention proposes a hydraulic block in the wall of which at least one annularly embodied seal is provided. Preferably, the hydraulic block according to the present invention includes at least one annular seal, for example sealing lips embodied in cascading sequence with one another in the wall of the hydraulic block. The hydraulic block proposed according to the invention is preferably produced using the plastic injection molding process; its wall is embodied so that downstream of the at least one seal extending an annular fashion, a cavity, i.e. a distance from the wall of the hydraulic block, remains, which lends the at least one annular seal a high degree of elasticity. By contrast with the designs known from the prior art, the at least one annular, elastically embodied seal is no longer embodied directly on a pressure control valve or switching valve to be installed in at least one valve socket of the hydraulic block, but is instead now integrated into the wall of the hydraulic block in the region of the valve socket. Since the elastically embodied seals no longer have to be embodied on the circumference of the valve body or on the circumference of a hydraulic part of a pressure control valve or switching valve, there are no longer conflicts with regard to the production of a working pressure conduit that must be embodied transverse to the symmetry axis of the pressure control valve or switching valve, which conduit is manufactured in the injection mold by means of a transverse slider in the mold. Following the embodiment proposed according to the present invention, the at least one annular seal embodied in the wall of the hydraulic block and a transverse conduit required for conveying the working pressure of the hydraulic medium can be produced so as to enable a trouble-free demolding of the hydraulic block from the injection mold. 
     Another advantage that can be achieved with the embodiment for a hydraulic block proposed according to the present invention lies in the fact that the transverse conduit required for conveying the working pressure inside the hydraulic block extends in a region of the valve socket, opens into the vicinity of the at least one annular seal on the valve socket and, because of this circumstance, can be embodied as significantly larger, thus assuring a sufficient flow cross section for the hydraulic medium at working pressure. It is also advantageous that the elasticity of the at least one annular seal in the wall of the hydraulic block is provided by the material of the hydraulic block itself, which permits the reduction of the sealing diameter, i.e. a reduction of the valve socket containing the pressure control valve or switching valve. Due to this circumstance, in turn, the hydraulic forces produced, which act on the pressure control/switching valve in the axial direction and must be absorbed by a correspondingly dimensioned valve attachment, are significantly less powerful. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a valve socket of a hydraulic block according to the prior art, with sealing regions embodied on the pressure valve or switching valve, 
         FIG. 2  shows a shortened design of a hydraulic block according to the prior art, 
         FIG. 3  shows an embodiment variant of the hydraulic block proposed according to the invention, equipped with annular seals embodied in its wall, and 
         FIG. 4  is a perspective depiction of a section through a hydraulic block. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a pressure control valve or switching valve  10 , which includes a valve closure member  12  equipped with a plunger  14  via which it acts on a closure element  16  that is embodied as ball-shaped in the depiction in  FIG. 1 . The closure element  16  closes a closure seat  18  of a valve body  20  of the pressure control valve or switching valve  10 . The valve body  20  of the pressure control valve or switching valve  10  also contains a conduit  22  that leads to a tank outlet. A hydraulic block  24  contains a valve socket  44 . A first elastic sealing region  26  and a second elastic sealing region  28  are embodied on the circumference of the valve body  20  of the pressure control valve or switching valve  10 . The first sealing region  26  embodied on the valve body  20  seals a working connection  36 , while the second elastic sealing region  28  on the circumference of the valve body  20  seals an inlet side  30  containing a hydraulic medium at an inlet pressure. When the closure element  16  opens, hydraulic medium at the inlet pressure p Zu  flows past from the inlet side  30  through the open closure seat  18 , and into a transverse conduit  32 , from which it travels into the working connection  36 . The valve socket  44  in the hydraulic block  24  according to  FIG. 1  is embodied in a first diameter  38 . The outlet pressure of the hydraulic medium is labeled p Ab  and the working pressure of the hydraulic medium is labeled p R . 
     The depiction in  FIG. 2  shows a modified embodiment of a valve socket of a hydraulic block according to the prior art, which is reduced in length. 
     The embodiment variant of the hydraulic block  24  known from the prior art shown in  FIG. 2  is shortened in comparison to the embodiment variant shown in  FIG. 1 . The plunger  14  in the exemplary embodiment shown in  FIG. 2  is significantly shorter than the plunger  14  in the depiction according to  FIG. 1 . The quick succession of the first elastic sealing region  26  and the second elastic sealing region  28  on the valve body  20  of the pressure control valve or switching valve  10  results in a relatively narrow transverse conduit  40  in the region of the valve socket  44  so that the hydraulic medium at working pressure flowing out through this transverse conduit travels at a high flow speed due to the narrow cross section. In addition, the embodiment variant according to  FIG. 2  has the decisive disadvantage that a transverse conduit  42  in the valve body  20  of the pressure control/switching valve  10  is either impossible to demold or can only be demolded with great difficulty. 
       FIG. 3  schematically depicts the hydraulic block  24  proposed according to the present invention. 
     The schematic depiction in  FIG. 3  shows that the valve body  20  of the pressure control valve or switching valve  10  has been placed into the valve socket  44 , which by contrast with the embodiments known from the prior art shown in  FIGS. 1 and 2 , has a significantly reduced diameter  56  so that the resulting hydraulic forces to which the pressure control valve or switching valve  10  in the hydraulic block  24  is subjected are significantly less powerful. The symmetry axis of the pressure control valve or switching valve  10  schematically depicted in  FIG. 3  is labeled with the reference numeral  34 ; the valve closure member is labeled with the reference numeral  12  and, via the plunger  14  that is embodied with a reduced length, acts on the closure element  16  embodied here in the form of a ball, which closes a closure seat  18  embodied in the valve body  20  of the pressure control valve or switching valve  10 .  FIG. 3  shows that the valve socket  44  is embodied with a reduced length  50  that essentially corresponds to a length of an annularly embodied second annular chamber  62  inside the hydraulic block  24 . On its end surface, the hydraulic block  24  has a first annular seal  52  that has a greater degree of elasticity since it is backed by a first annular chamber  60  situated in the wall of the hydraulic block  24 . The same is true for a second smaller-diameter, likewise annular seal  54  that is likewise embodied in the wall of the hydraulic block  24  and, inside the valve socket  44 , is separated from the boundary wall of the valve socket  44  by a second annular chamber  62  extending axially inside the reduced length  50 . 
     It is also clear from the depiction in  FIG. 3  that the transverse conduit  40  for the working connection  36 , which conduit is very narrow in the exemplary embodiment according to the prior art shown in  FIG. 2 , can be embodied with an enlarged cross section in the hydraulic block  24  proposed according to the present invention and preferably opens into the vicinity of one of the two annular seals  52 ,  54  shown in  FIG. 3 ; in the exemplary embodiment according to  FIG. 3 , it opens into the vicinity of the second, inner annular seal  54 . 
     The inlet side  30  of the valve body  20  of the pressure control valve or switching valve  10 , embodied with a reduced diameter  56 , is acted on by a hydraulic medium at the inlet pressure p Zu , which is prevented from passing through into a demoldably embodied transverse conduit  58  in the valve body  20  by the closure element  16 —which is embodied for example in the form of a ball—that has been moved into the closure seat  18 . If the plunger  14  is actuated through a supply of electrical current to an electromagnet, not shown in  FIG. 3 , of the pressure control valve or switching valve  10 , then the ball-shaped closure element  16  is moved out of the closure seat  18  so that hydraulic medium at the inlet pressure p Zu  flows from the inlet side  30 , through the opened closure seat  18 , into the demoldable transverse conduit  58  and from there, overflows into the working connection  36  in accordance with the set regulating pressure. The pressure in the working connection  36  is labeled p R . 
       FIG. 4  is a perspective view of a section through the hydraulic block proposed according to the present invention. 
     The perspective depiction in  FIG. 4  shows that a hydraulic part  64  of the pressure control valve or switching valve  10  is inserted with its housing  66  into the valve socket  44  of the hydraulic block  24 . The hydraulic block  24  is preferably produced using the plastic injection molding technique and has a socket plate  68  from which a wall  70  extends, which is adapted to the geometry of the pressure control valve or switching valve  10 . The first annular seal  52  is embodied in the region of an inside  72  of the wall  70  of the hydraulic block  24 . The first annular seal  52  is separated from the wall  70  of the hydraulic block  24  by the first annular chamber  60 . An additional, second annular seal  54  is embodied analogously in the wall  70  of the hydraulic block  24  and is likewise separated from the wall  70  of the hydraulic block  24  by a second annular chamber  62 . The two annular chambers  60 ,  62  lend the annular seals  52 ,  54  a high degree of elasticity. 
     The depiction according to  FIG. 4  shows that the housing  66  of the hydraulic part  64  of the pressure control valve or switching valve  10  forms a first sealing surface  74  with the first annular seal  52  and forms a second sealing surface  76  with the second likewise annular seal  54 . The perspective depiction according to  FIG. 4  also shows that in the housing  66  of the hydraulic part  64  of the pressure control valve or switching valve  10 , a ball-shaped captive retainer  78  is provided on the inlet side and prevents a loss of the ball-shaped closure element  16  situated opposite the closure seat  18 . 
     In addition,  FIG. 4  shows that the pressure control valve or switching valve  10  includes the plunger  14  that is attached to the cylindrically embodied valve closure member  12  and that extends through the closure seat  18  to act on the closure element  16 —which is depicted as ball-shaped in FIG.  4 —of the pressure control valve or switching valve  10 . 
     While the first sealing surface  74  between the first annular sealing ring  52  and the circumference of the housing  66  of the hydraulic part  64  seals the working connection  36 , the second sealing surface  76  between the second annular seal  54  and the circumference of the housing  66  of the hydraulic part  64  produces a seal of the inlet side  30  of the hydraulic module  40  with regard to the prevailing inlet pressure p Zu  of the hydraulic medium contained therein. 
     The hydraulic block  24  shown in  FIGS. 3 and 4  advantageously permits the production of the seal by means of elastic sealing regions—in this case embodied in the form of annular seals  52 ,  54 —without requiring an increased length and with the advantage that the diameter  56  serving as the seal is significantly reduced in comparison to the embodiment variants according to the prior art shown in  FIGS. 1 and 2 . Viewed as a whole, this results in a significantly lower hydraulic force acting on the pressure control valve or switching valve  10 , which on the one hand, has a positive influence on its service life and on the other hand, simplifies the mechanical fastening of the pressure control valve or switching valve  10  since it permits the valve to be designed in accordance with the reduced hydraulic forces. In addition, the reduced hydraulic force acting on the pressure control valve or switching valve  10  reduces the force acting on the seal, which has a positive influence on the service life and sealing action of the seal and permits the use of less expensive sealing materials.