Abstract:
A hydraulic control apparatus having a master cylinder, a slave cylinder, and a conduit connecting the master cylinder to the slave cylinder is constituted as separate modular units interconnected by a quick connect coupling including a female coupler member and a male coupler member. In addition to providing part of the quick connect coupling between the modular units the female coupler member is provided with a bleed system to facilitate removal and addition of hydraulic fluid to the system as required in relation to initial manufacturer and installation and in relation to field maintenance.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to hydraulic control apparatus in general and more specifically to a hydraulic control apparatus comprising a hydraulic master cylinder and a hydraulic slave cylinder for operating a mechanism remotely located from the master cylinder such for example as the clutch of a motor vehicle. 
     It is known to prefill with hydraulic fluid a motor vehicle clutch control apparatus comprising a master cylinder, a reservoir of hydraulic fluid, and a slave cylinder for operating the throw-out bearing of a mechanical diaphragm spring clutch, as disclosed in British patent number 1,539,879 and in corresponding U.S. Pat. Nos. 4,407,125 and 4,599,860 assigned to the assignee of the present invention. In addition, U.S. Pat. Nos. 4,503,678, 4,516,507, 4,585,106, 4,585,107, 4,585,108 and 4,585,109, all assigned to the assignee of the present invention, also disclose diverse forms of prefilled hydraulic control apparatus for motor vehicle clutches. 
     Prefilling with hydraulic fluid and pretesting hydraulic apparatus for operating motor vehicle mechanisms such as mechanical clutches present the many advantages for the motor vehicle manufacturer of receiving a fully assembled mechanism comprising all of the components filled with hydraulic fluid and pretested for proper operation ready to install on a motor vehicle on the assembly line without requiring that the components be installed, separately connected by way of a rigid or flexible conduits, and filled after installation with hydraulic fluid while being purged of any atmospheric air contained in the apparatus. 
     To simplify the installation of a hydraulic control apparatus in a motor vehicle, and particularly in situations where the apparatus employs a concentric slave cylinder as the clutch actuating device, it is known to provide the control apparatus with a one way quick connect coupling or connector either at some point along the flexible conduit connecting the master cylinder to the slave cylinder or at the end of the conduit connected to the master cylinder or at the end of the conduit connected to the slave cylinder. The one-way quick connect coupling is arranged such that after the hydraulic control apparatus has been assembled, prefilled with hydraulic fluid, and pretested, the connection between the master cylinder and slave cylinder may be broken without loss of fluid, or negligible loss of fluid. The apparatus may thus be shipped to the motor vehicle manufacturer completely filled with hydraulic fluid but in two separate modules such that the concentric slave cylinder may be made a part of the clutch bell housing, or of the transmission casing. This allows the slave cylinder clutch bell housing assembly, or the slave cylinder transmission casing assembly, to be installed in the motor vehicle at whatever station on the assembly line that the clutch or transmission is installed and the master cylinder may be installed in the motor vehicle also at whatever appropriate station and the two cylinders connected together without any loss or negligible loss of fluid and without introduction of air into the apparatus. Whereas module systems of this type have proven to be generally satisfactory, there is still a need to provide a bleed system in the apparatus to facilitate initial filling of the apparatus and/or to facilitate field maintenance and, specifically, field maintenance where it is necessary to bleed the system and refill the system. Whereas the prior art control apparatus have typically included a bleed system in the apparatus, for example in association with the slave cylinder, the prior art bleed systems have complicated the structure of the apparatus and have added to the cost of the apparatus. 
     SUMMARY OF THE INVENTION 
     This invention is directed to the provision of improved hydraulic control apparatus for a motor vehicle clutch. 
     More specifically, this invention is directed to the provision of a hydraulic clutch control apparatus of the modular type incorporating a simplified and improved arrangement for bleeding and filling the system. 
     The hydraulic control system of the invention is of the type including a master cylinder having an outlet, a slave cylinder having an inlet; a bleed system to facilitate bleeding and filling of the control system; and a conduit assembly interconnecting the outlet of the master cylinder and the inlet of the slave cylinder and including a quick connect coupling including a male coupler member and a female coupler member. Each of the coupler members defines a hydraulic fluid passage and each includes a valve mechanism positioned in the respective fluid passage, means normally maintaining the respective valve mechanism in a closed position closing the respective passage, and means operative in response to coupling of the male and female members to move the valve mechanism to an open position allowing passage of hydraulic fluid through the conduit assembly from the master cylinder outlet to the slave cylinder inlet. 
     According to the invention, the bleed system includes means defining a bleed passage in one of the quick connect coupler members communicating at one end thereof with the hydraulic fluid passage in the coupler member and at its other end with atmosphere. This arrangement incorporates the bleed system into one of the coupler members of the quick connect coupler to simplify and reduce the cost of the hydraulic control system while yet retaining an effective bleed system for the system. 
     According to a further feature of the invention, the fluid passage in each coupler member extends through the respective coupler member from the passage inlet to a passage outlet; the conduit assembly includes conduit means extending from the outlet of the master cylinder to the inlet of the fluid passage in the first coupler member and further conduit means extending from the outlet of the fluid passage in the second coupler member to the input of the slave cylinder; the valve mechanism in the first coupler member is positioned in the respective fluid passage adjacent the passage outlet; the valve mechanism in the second coupling member is positioned in the respective fluid passage adjacent the passage inlet; and the bleed passage opens in the respective fluid passage at a location between the inlet and outlet of the fluid passage. This specific inter-relationship between the inlet and the outlet of the fluid passage and the bleed passage contributes importantly to the efficient operation of the bleed system. 
     According to a further feature of the invention, the means defining the bleed passage includes a threaded bleed bore in the coupler member and a bleed screw threadably positioned in the threaded bore and moveable in an unscrewing manner from a closed position closing the bleed passage to an open position opening the bleed passage. This specific bleed system construction facilitates the ready and efficient operation of the bleed system to facilitate bleeding and refilling of the system. 
     In the disclosed embodiment of the invention, the bleed system is provided in the female coupler member, although the invention envisions that the bleed system could also be provided in the male coupler member. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic view of a motor vehicle hydraulic clutch control apparatus according to the invention; 
     FIG. 2 is a detail cross-sectional view of a quick connect coupling utilized in the invention control apparatus; 
     FIG. 3 is a cross-sectional view taken on line  3 — 3  of FIG. 2; and 
     FIG. 4 is a perspective view of the quick connect coupling of FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The quick connect coupling of the invention is intended for use in association with a hydraulic clutch actuator for a motor vehicle. With reference to FIG. 1, the motor vehicle transmission is schematically illustrated as comprising a friction clutch assembly  11  and a gear box  12  enclosed in a casing or housing  15 . A drive shaft  13  drives the gear box  12  from the clutch assembly  11 . A bell housing  14  surrounding the clutch assembly  11  is bolted on the rear face of the motor vehicle engine E, and the rear face  16  of the bell housing  14  is bolted to the front face  17  of the gear box casing  15 . An annular concentric hydraulic slave cylinder  18  is disposed around the drive shaft  13  within the bell housing  14 . 
     Slave cylinder  18  is connected via a conduit assembly  24  to a master cylinder  26 . Master cylinder  26  is provided with an integral hydraulic fluid reservoir  29  and includes an input rod  30  pivotally connected to an end of a clutch control pedal  32  installed within the drivers compartment of the motor vehicle. Rod  30  is connected in known manner to a piston disposed in the master cylinder  26  that operates to displace hydraulic fluid through conduit assembly  24  to the slave cylinder  18  when the clutch pedal is depressed. 
     Slave cylinder  18  is adapted in known manner to displace a throw-out bearing  36  engaged with the end of clutch release fingers  38  so that clutch  11  is released when hydraulic fluid is introduced into the slave cylinder  18  from the master cylinder  26  through the conduit assembly  24 . 
     Conduit assembly  24  includes a quick connect coupling assembly  42  including a female coupler member  44  and a male coupler member  46 ; a conduit  48  interconnecting the outlet of the master cylinder  26  and the inlet of male coupler member  46 ; and a conduit  50  interconnecting the outlet of female coupler member  44  and a connector fitting  52  at the hydraulic inlet of the slave cylinder. 
     Female coupler member  44  (FIGS. 2,  3  and  4 ) includes a body  54 ; a disc  56 ; a valve stem  58 ; a retainer ring  60 ; a valve head  62 ; a valve sleeve  64 ; a spring  66 ; a retainer clip  68 ; and a bleed screw  70 . 
     Body  54  may be formed, for example, as a casting or forging and may be formed of an aluminum material. Body  54  includes a main body generally cylindrical portion  54   a  and a block portion  54   b  extending radially from main body cylindrical portion  54   a . A central axial hydraulic fluid passage  54   c  is defined in main body portion  54   a  and the outlet end  54   d  of the main body portion  54   a  is suitably formed to provide a fitting  54   e  for suitable connection to conduit  50 . The inlet end  54   f  of main body portion  54   a  is provided with a circular opening  54   g  sized to pass male coupler member  46  and further defines a circular spring seat  54   h  sized to seat retainer clip  68  and having a diameter greater than opening  54   g  and passage  54   c . Body  54  further defines a bleed passage  54   i  communicating at its inboard end with central passage  54   c  and opening at its outboard end in the outer face  54   j  of block portion  54   b . Passage  54   i  includes a threaded outboard portion  54   k  opening in face  54   j  and a reduced diameter port portion  54   l  communicating with the inboard end of portion  54   k  and opening in central bore  54   c.    
     Disc  56  has a perforated circular configuration and is fixedly positioned against a shoulder  54   m  formed at the outlet end of the main body portion  54   a , by a retainer ring  60 . 
     Valve stem  58  is fixedly secured at one end  58   a  to disc  56  and extends axially and centrally within fluid passage  54   c.    
     Valve head  62  is fixedly secured to the upstream free end  58   b  of stem  58  for coaction with valve sleeve  64 , which is slidably and sealingly received in bore  54   c  and biased into a closed position with respect to valve head  62  by coil spring  66 . 
     Retainer clip  68  is positioned in seat  54   h  and includes a plurality of circumferentially spaced spring fingers  68   a  for locking coaction with the male coupler member. Retainer clip  68  may, for example, be of the type disclosed in U.S. Pat. No. 4,936,345 assigned to the assignee of the present invention. 
     Bleed screw  70  is threadably received in threaded bore  54   k  and includes a central bleed passage  70   a  communicating with port  54   l  via a bleed screw port  70   b  in a reduced diameter inboard end of the screw when the bleed screw is unscrewed to lift the conical seat  70   c  of the screw off of the conical seat  54   n  defined by the body  54  at the juncture of threaded bore  54   k  and port  54   l.    
     Male coupler member  46  includes a body  72 , a valve member  74 , and a spring  76 . Body  72  may be formed of an aluminum material in a casting or forging operation. Body  72  is cylindrical and defines a central passage  72   a , a fitting  72   b  at the inlet end of the coupler member for coaction with conduit  48 , and an external annular ridge  72   c  for coaction with retainer clip spring fingers  68   a  in response to insertion of the male coupler member into the female coupler member. 
     Valve member  74  includes a main body portion  74   a  slidably received in bore  72   a  and a nose portion  74   b  positioned in a circular opening  72   d  defined within the annulus  72   e  at the outlet end of the coupler member. Nose portion  74   b  has a cross-sectional configuration corresponding generally to the cross-sectional configuration of valve head  62 . 
     Spring  76  functions to maintain valve member  74  in a closed position in which the outlet end of passage  72   a  is closed. Circumferentially spaced axial grooves  74   c  allow the passage of hydraulic fluid through the male coupling member when valve member  74  is moved to an open position. 
     It will be understood that, in the assembly of the invention control apparatus, a module comprising the female coupler member  44  (with bleed screw  70  in a closed position) the conduit  50 , and the slave cylinder  18  is evacuated and filled with a suitable hydraulic fluid; a separate module comprising the male coupler member  46 , the conduit  48  and the master cylinder  26  is evacuated and filled with hydraulic fluid; the modules are delivered as two separate modules to the motor vehicle manufacturer; the master cylinder module is installed in the vehicle at a convenient location on the vehicle assembly line; the slave cylinder module is installed on the vehicle at a convenient location on the vehicle assembly line; and the male coupler member  46  is inserted into the female coupler member  44  to move the valve mechanisms in both the male and female coupler members to an open position and provide fluid communication between central passage  72   a  and central passage  54   c.    
     Specifically, as the male member is inserted into the female member the annulus  72   e  of the male member engages valve sleeve  64  and moves the valve sleeve  64  away from valve head  62  to open passage  54   c  while valve head  62  engages nose  74   b  of valve member  74  to move the valve member away from the valve seat defined by the coaction of valve member  74  and opening  72   d  and open up passage  72   a  via axial grooves  74   c  so that a continuous fluid passage is now established through the coupled coupler members extending from fitting  72   b  to fitting  54   e . As the male member arrives at its coupled position within the female member, spring fingers  68   a  engage the annular shoulder  72   f  defined by ridge  72   c  to lock the male member in its inserted position and preclude inadvertent withdrawal of the male member from the female member. 
     The control apparatus now functions normally in response to depression of the clutch pedal to deliver pressurized fluid from the master cylinder to the slave cylinder and actuate the vehicle clutch in known manner. In the event that field maintenance is required, bleed screw  70  may be selectively turned in an unscrewing manner to open a passage through port  54   l , port  70   b , and passage  70   a  to the atmosphere to allow hydraulic fluid to be added to the system or removed from the system as required to perform the field maintenance, whereafter the bleed screw is moved in a tightening direction to reseat the bleed screw nose  70   c  on the seat  54   h  and return the control apparatus to a sealed, normal operating condition. 
     The invention will be seen to simplify the construction of the clutch control apparatus by incorporating the bleed function in the female member of the quick connect coupler. 
     Whereas a preferred embodiment of the invention has been illustrated and described in detail, it will be apparent that various changes may be made in the disclosed embodiment without departing from the scope or spirit of the invention. For example, the invention envisions that the bleed system could alternatively be provided in the male member of the quick connect coupling.