Abstract:
An electro-hydraulic power steering system having a motor, a pump, and a control module all formed as an integral unit. The motor is shaft coupled to the pump and the pump housing and the motor housing are sealingly attached to prevent any fluid leakage. The control module is sealingly attached to the pump housing to prevent any fluid leakage. The control module is in electrical communication with the motor in order to drive a motor shaft and operate the hydraulic pump. The entire unit is submersible and can operate when submersed.

Description:
TECHNICAL FIELD 
     The present invention relates generally to electro-hydraulic power packs for use in automotive applications. More specifically, the present invention relates to a submersible electro-hydraulic power pack for use in automotive power steering applications. 
     BACKGROUND ART 
     The use of hydraulic pumps, such as power steering pumps, is well known in the automotive industry. The use of an electro-hydraulic power steering system having an individual hydraulic pump shaft-coupled to a separate electric motor has also become well known in the automotive industry. These power steering systems typically have a combined electronic control unit and power module functionally connected to the motor such as through a wiring harness or the like. In current systems, the control unit and module are often mounted remotely from the motor and pump and often at some considerable distance away. 
     Such a motor, pump, module arrangement is relatively costly to manufacture and assemble because each of the components is separate and discrete requiring that they be manufactured and sold individually. Further, because they are separate units that are typically mounted at least some distance from one another, they require the usage of a large space envelope underneath the hood of a vehicle. Additionally, the more parts required to operate the system, the heavier and the more expensive the system becomes. 
     Further, these prior systems are all configured such that they are shielded from direct splash, such as through the inclusion of a splash guard. This is to prevent the components from being damaged due to a direct splash of water from underneath the vehicle. However, if the undercarriage of a vehicle into which a typical power steering system (pump, motor, and module) is installed, were to become submerged in water or other fluid, it would typically leak and most likely damage one or more components of the system rendering them inoperable for at least a short period of time. This is because current power steering systems are not designed to be submersible when operating. For example, typical electrical connections between the module and the motor have rubber seals which are insufficient to prevent water from leaking into the pump/motor housing. Additionally, typical pump/motor modules have drain holes to allow water to drain out in the event any finds its way into the housing. Those drain holes would allow water direct access to the interior of the pump/motor module in the event the module was submerged. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide an electro-hydraulic power steering system having all necessary components assembled as an integrated unit that is submersible when operating without any resultant water damage. 
     It is a further object of the present invention to provide an integrated electro-hydraulic power steering system having all necessary components assembled as an integrated unit allowing for the components of the system to share functions, resulting in the usage of less parts and therefore a cost and weight savings. 
     It is another object of the present invention to provide an integrated electro-hydraulic power steering system having a shaft bearing retention that allows for easy non-destructive removal of the shaft and bearing for service. 
     In accordance with the objects of the present invention, an electro-hydraulic power steering system is provided. The system includes a power pack having an electric motor with a rotatable drive shaft and a hydraulic pump having a gear drive in rotatable communication with the drive shaft. The electric motor is disposed in a motor housing having a closed end and an open end. The open end of the motor housing is in communication with the motor drive shaft such that the drive shaft can extend therethrough. The open end of the motor housing is secured to one end of a pump housing. The other end of the pump housing is secured to a pump reservoir. The pump reservoir is in fluid communication with the pump in order to provide fluid thereto such that the pump can pass the fluid to a steering gear as required. 
     An electronic control module which controls the operation of the motor is disposed on the pump housing and in thermal communication with the pump reservoir such that the power pack and the electronic control module are constructed as a single modular unit. The modular unit is constructed such that it can be submerged in liquid while operating without leakage, which would affect the operation. 
     Other objects and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and independent claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of an electro-hydraulic power steering system in accordance with a preferred embodiment of the present invention; 
     FIG. 2 is a cross-sectional view of an electro-hydraulic power steering system as viewed from one side in accordance with a preferred embodiment of the present invention; 
     FIG. 3 is a cross-sectional view of an electro-hydraulic power steering system as viewed from another side from the other side of the system; and 
     FIG. 4 is an enlarged illustration of a bearing snap ring arrangement for a motor housing for communicating with a motor drive shaft in accordance with a preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIGS. 1 through 3, which illustrate an electro-hydraulic power steering system  10 , in accordance with the present invention. The system  10  includes a motor  12  having a rotatable drive shaft  14 . The motor  12  is disposed in a motor housing  16  having a closed end  18  and an open end  20 . The rotatable drive shaft  14  of the motor  12  preferably extends through the open end  20  of the motor housing  16 . The disclosed motor  12  may be any commercially available DC motor or any other asynchronous device. 
     The system  10  also includes a hydraulic pump or gear pump  22  having a drive gear  24  which is in rotational communication with the drive shaft  14 . The hydraulic pump  22  is preferably disposed within a pump housing  26 . The pump housing  26  is preferably in communication at one end with the motor housing  16  and at the other end with a pump reservoir  28 . Alternatively, the pump  20  may be disposed entirely within the pump reservoir  28 . The hydraulic pump  22  is preferably a positive displacement pump, such as a gear pump or a vane pump, however any other dispositive displacement pump may be utilized. The pump housing  26  is preferably secured to the motor housing  16  by fasteners  30  such as conventional screws, bolts or the like. A seal  32  such as an o-ring or the like is preferably disposed at the junction between the pump housing  26  and the motor housing  16  to prevent egress of fluid from outside the housings and into contact with the components contained therein. 
     The pump reservoir  28  is preferably secured to the pump housing  26  by fasteners  33  or other conventional securing mechanism. A pump reservoir seal  34  is preferably disposed at the junction between the pump housing  26  and the pump reservoir  28  to prevent egress of fluid into or out of the pump reservoir  28  from outside the pump housing  26  or reservoir  28 . 
     An electronic control unit  36 , preferably including a power module, is disposed on an outer surface  38  of the reservoir housing  38 . The electronic control unit  36  includes an input electrical interconnect  40  to provide power to the control unit  36 . The input electrical interconnect  40  includes a plurality of connection terminals  41  that are disposed within a housing  43 , preferably made of plastic or the like. When a male portion (not shown) engages the terminals  41 , a seal is formed to prevent the terminals  41  from being contacted by fluid. At the opposing end of a control unit  36 , is an output electrical interconnect  42 . The output electrical interconnect  42  is in communication with the input electrical interconnect  40  for control purposes. The power to drive the motor is provided to the electrical output interconnect  42  from a specific electrical connector (not shown). The output electrical interconnect  42  is in communication with the motor  12  via a sealed motor/module connector  44  that passes through a sealed motor connector  45  that allows current to be transferred to the motor without providing any leak paths. 
     The electronic control unit  36  is preferably secured to an outer surface  46  of the pump reservoir  28 . Alternatively, the electronic control unit  36  can be integrally formed such as by casting with the outer surface  46  of the pump reservoir  28 . The junction where the electronic control unit  36  is secured to the pump reservoir  26  has a modular seal  48  located thereat preventing any leakage of fluid therethrough. The electronic control module  36  is disposed over the pump reservoir  28  such that the electronic control module  36  is in thermal communication with the pump reservoir  28  such that the pump reservoir acts as a heat sink to absorb any excess heat generated by the electronic control unit  36  during use and protect the components thereof. 
     The electronic control unit  36  is in electrical communication with a plurality of windings  50  which are part of the motor  12  through the motor module power connector which includes the terminals  44  and the plug  45  The plug  45  also acts to seal the interior of the motor housing from the outside. Current is applied from electronic control module  36  to the windings  50  to cause the drive shaft  14  to rotate. The drive shaft  14  has a first end  52  in proximity to the closed end  18  of the motor housing  16  and a second end  54  which extends into communication with the drive gear  24  of the hydraulic pump  22 . As the drive shaft  14  rotates, it draws fluid from the fluid reservoir  28  into the pump and out an exit passageway  53  to a steering gear (not shown), as is known in the art. 
     As shown specifically in FIG. 4, the first end  52  of the drive shaft  14  is in communication with a bearing  56 . The bearing  56  is located in an annular recess  58  or bearing bore formed in the closed end  18  of the motor housing  16 . The annular recess  58  has an annular groove  60  formed therein for receipt of a snap ring  62 . The snap ring  62  is retained within the annular groove  60  formed in the annular recess  58  of the motor housing  16 . The snap ring  62  has an inner diameter that is slightly smaller than the outer diameter of the bearing  56 . For example, in the preferred embodiment, the inner diameter of the snap ring  62 , may be only one millimeter smaller than the outer diameter of the bearing  56 . As the bearing  56  is slid or pressed into the annular recess  58 , the radius at the intersection of the bearing face outer diameter and the snap ring  62  presses against the rounded side of the snap ring  62 . This produces a wedging action and opens the inner diameter of the snap ring  62 . The snap ring  62  is caused to expand into the annular groove  60  of the annular recess  58  and allows the outer diameter of the bearing  56  to pass therethrough. When the bearing snap ring groove  64  reaches the inner diameter of the snap ring  62 , the inner diameter of the snap ring  62  reduces to the new diameter of the bearing groove  64 . The bearing groove  64  preferably has a square corner to maintain the snap ring  62  therein. 
     When the square corner of the bearing snap ring groove  64  contacts the round cross-section snap ring  62 , the wedging forces to expand the snap ring inner diameter versus the rounded radius of the bearing face are tremendously higher. Because of this, the bearing  56  becomes locked into place until a considerably larger axial load is applied to the bearing  56 . Thus, in accordance with the present invention, when a large enough load is applied too the bearing  56 , it can be removed from the snap ring  62  for service. Therefore, in accordance with the present invention, the bearing  56  can be retained in a blind hole that locks into place without a second operation of applying snap rings. Additionally, the snap ring  62  cannot be installed after the bearing  56  is in place. The snap ring  62  must be installed before the bearing  56  is installed. The disclosed invention thus allows for the non-destructive removal of the bearing  56  and connected drive shaft  14  for service. 
     The axial retention forces are determined by the shape of the cross-sectional area of the snap ring  62  and/or size of the circular cross-section to the width and depth of the groove  64  in the bearing  56 . Alternatively, a lighter axial retention force can be obtained by utilizing a groove having the same configuration, but by utilizing a larger circular cross-section snap ring  62 . Further, a larger axial retention force can be obtained by utilizing a smaller diameter snap ring  62 . In accordance with another embodiment, the radius of the snap ring cross-section and the depth of the bearing groove  64  are the same and are both one-half of the groove width, then the bearing  56  will be permanently locked into place. Also, a square or rectangular cross-sectional snap ring  62  can be used, resulting in a design that would be a one-time permanent assembly requiring a destructive method of disassembly. 
     It should be understood that other cross-sectional shapes could be used for the snap ring  62  such as a curve or angle on one side and a square on the other would allow for easy removal and with permanent retention and no ability for disassembly. Alternatively, the annular groove  60  for the snap ring  62  to expand could also be located on the outer diameter of the shaft in or the inner diameter of the bearing  56 . With this configuration, the snap ring  62  would then compress to a smaller diameter, but the same concept as described above would apply. 
     Having now fully described the invention, it will be apparent to one of ordinary skill in the art that many changes and modifications can be made thereto without departing from the spirit or scope of the invention as set forth herein.