Patent Publication Number: US-2009223581-A1

Title: Power steering gear housing with balanced flow pressure port

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Provisional Patent Application Ser. No. 61/068,200, filed on Mar. 2, 2008, the disclosure of which is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The subject invention generally relates to a power steering system for a vehicle, and more specifically to a gear housing of the power steering system. 
     2. Description of the Prior Art 
     Generally, vehicular power steering systems include a pump in fluid communication with a gear housing. The gear housing defines a valve bore and supports a steering valve within the valve bore. The gear housing further defines a pressure port. A fluid line is attached to the pressure port and interconnects the pump and the gear housing. A passageway interconnects the pressure port and valve bore in fluid communication, with the passageway defining an orifice into the valve bore. The pump pressurizes and circulates a power steering fluid to the gear housing, and more specifically, the pump circulates the power steering fluid through the fluid line to the pressure port, and through the passageway into the valve bore. 
     A typical gear housing is shown in Prior Art  FIG. 1 , in which the gear housing defines a single passageway, having a single orifice, interconnecting the pressure port and the valve bore. The entire volume of the power steering fluid enters the valve bore through the orifice via the passageway. Design constraints of the typical gear housings limit the area of the orifice permitting entry of the power steering fluid into the valve bore. At high fluid velocities, having the entire volume of the power steering fluid enter through the single orifice creates an unbalanced or uneven flow of the power steering fluid through the valve bore. The unbalance flow of the power steering fluid causes undesirable vibrations in the steering valve, which produces an undesirable “hissing” noise noticeable by the occupants of the vehicle. 
     SUMMARY OF THE INVENTION AND ADVANTAGES 
     The subject invention provides a power steering system for a vehicle. The power steering system comprises a reservoir for storing a supply of a fluid. A pump is in fluid communication with the reservoir. The pump pressurizes and circulates the fluid. A gear housing defines a valve bore, a pressure port and a plurality of orifices into the valve bore. The pressure port is in fluid communication with the pump, and receives the pressurized fluid from the pump. The plurality of orifices is in fluid communication with the valve bore and the pressure port. The plurality of orifices direct the fluid into the valve bore at multiple locations about the valve bore. 
     Accordingly, the subject invention directs the power steering fluid into the valve bore through a plurality of orifices. By increasing the number of orifices through which the fluid enters the valve bore, the flow area through which the fluid flows is increased, which decreases the velocity of the fluid through the orifices. The decreased velocity reduces vibration in the steering valve and thereby reduces the undesirable “hissing” noise. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings. 
         FIG. 2  is a schematic view of a power steering system. 
         FIG. 3  is a cross sectional view of a first embodiment of a gear housing of the power steering system. 
         FIG. 4  is a cross sectional view of a second embodiment of a gear housing of the power steering system. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, a power steering system is shown at  20  in  FIG. 2 . The power steering system  20  described herein is commonly referred to as a rack and pinion steering system  20 . However, it should be appreciated that the subject invention may be incorporated into and used with other types of power steering systems  20 . 
     Referring to  FIG. 2 , the power steering system  20  includes a pump  22 , a steering gear  24  and a reservoir  26 . The reservoir  26  stores a supply of a power steering fluid. The pump  22  is in fluid communication with the reservoir  26  and in fluid communication with the steering gear  24 . The steering gear  24  is in fluid communication with the reservoir  26 . The fluid circulates from the pump  22 , through the steering gear  24 , and back to the reservoir  26 . The pump  22  pressurizes the power steering fluid and circulates the power steering fluid through the power steering system  20 , i.e., from the reservoir  26  to the steering gear  24 , and from the steering gear  24  back to the reservoir  26 . 
     The steering gear  24  includes a gear housing  28 . The gear housing  28  defines a pressure port  30 , a valve bore  32 , a plurality of orifices  34 ,  36  and a plurality of passageways  38 ,  40 . The pressure port  30  is in fluid communication with the pump  22 . The pressure port  30  receives the pressurize fluid from the pump  22 . A first fluid line  42  connects the pump  22  with the gear housing  28  of the steering gear  24 , and is attached to the steering gear  24  at the pressure port  30 . A second fluid line  43  connects the gear housing  28  with the reservoir  26 . 
     The valve bore  32  extends along a bore axis  44 . A steering valve  46  is disposed within the valve bore  32 . The steering valve  46  directs the power steering fluid to one of a first chamber and a second chamber of a power piston disposed within or adjacent to the gear housing  28  to assist in moving the rack as is known in the art. 
     The plurality of orifices  34 ,  36  is in fluid communication with and open into the valve bore  32 . The plurality of passageways  38 ,  40  interconnect the plurality of orifices  34 ,  36  and the pressure port  30 . Accordingly, the plurality of orifices  34 ,  36  are also in fluid communication with the pressure port  30 . The plurality of orifices  34 ,  36  direct the power steering fluid into the valve bore  32  at multiple locations about the valve bore  32 . Each of the plurality of orifices  34 ,  36  is disposed angularly about the bore axis  44  relative to all other of the plurality of orifices  34 ,  36 . By having the plurality of orifices  34 ,  36  introduce the power steering fluid, i.e., permit flow of the power steering fluid into, the valve bore  32 , the flow of the power steering fluid is balanced, thereby reducing vibration of the steering valve  46  at high flows of the power steering fluid. The reduced vibration of the steering valve  46  reduces or eliminates the undesirable “hissing” noise heard by the occupants of the vehicle. 
     It should be appreciated that the gear housing  28  may define any number of orifices  34 ,  36  opening into the valve bore  32 , and that the plurality of orifices  34 ,  36  may be disposed at any desirable location about the bore axis  44 . For example, the plurality of orifices  34 ,  36  may include four orifices  34 ,  36  equally spaced about the bore axis  44 , i.e., spaced ninety degrees apart from each other. Alternatively, the plurality of orifices  34 ,  36  need not be spaced equidistant from each other, and may be randomly spaced about the bore axis  44 . 
     The gear housing  28  may include a valve housing  48 . The valve housing  48  may define the valve bore  32 , the pressure port  30 , the plurality of orifices  34 ,  36  and the plurality of passageways  38 ,  40 . The valve housing  48  may be integrally formed with the gear housing  28 . Alternatively, the valve housing  48  may be a separate component rigidly connected to the gear housing  28 . 
     As shown, the plurality of passageways  38 ,  40  includes a first passageway  38  and a second passageway  40 , and the plurality of orifices  34 ,  36  includes a first orifice  34  and a second orifice  36 . The first orifice  34  is in fluid communication with the first passageway  38 , and the second orifice  36  is in fluid communication with the second passageway  40 . 
     It should be appreciated that the pressure port  30  is an opening that extends into the gear housing  28 . Accordingly, the pressure port  30  extends along a port axis  50 . It should be appreciated that the port axis  50  may be disposed in any desirable orientation to accommodate differing design and space restraints. It should be further appreciated that the orientation of the port axis  50  is not related to the bore axis  44 . 
     Referring to  FIG. 3 , a first embodiment of the gear housing is shown. The first embodiment of the gear housing  28  includes the pressure port  30 , and thereby the port axis  50 , extending into the gear housing  28  in a direction generally transverse to the valve bore  32 . In the first embodiment of the gear housing  28 , at least one of the plurality of passageways  38 ,  40 , i.e., at least one of the first passageway  38  and the second passageway  40 , is co-planar with the port axis  50 . As shown, both the first passageway  38  and the second passageway  40  are coplanar with the port axis  50 . The first passageway  38  extends along a first axis  52 , and the second passageway  40  extends along a second axis  54 . The first axis  52  intersects the second axis  54 . Accordingly, the first passageway  38  and the second passageway  40  are angled relative to each other, and form an acute angle therebetween. 
     It should be appreciated that the power steering fluid enters the gear housing  28  through the pressure port  30 , flows through the first passageway  38  and the second passageway  40  to the first orifice  34  and the second orifice  36  respectively, and into the valve bore  32 . Once the power steering fluid enters the valve bore  32 , the steering valve  46  directs the power steering fluid to one of the first chamber and the second chamber of the power piston as is well known. 
     In manufacture of the first embodiment of the gear housing  28 , the pressure port  30  is machined into the gear housing  28  first. After which, the first passageway  38  and the second passageway  40  are machined into the gear housing  28  via the pressure port  30 , and into the valve bore  32 . 
     Referring to  FIG. 4 , a second embodiment of the gear housing is shown. The second embodiment of the gear housing  28  includes the port axis  50  being disposed in a generally parallel relationship relative to the valve bore  32 . At least one of the first passageway  38  and the second passageway  40  are disposed along a plane intersecting the port axis  50 . As shown, the plane is perpendicular to the port axis  50 . However, it should be appreciated that the plane need only be substantially perpendicular to the port axis  50 , i.e., the plane may be disposed at an approximate, but not quite, perpendicular angle relative to the port axis  50 . 
     As shown in the second embodiment of the gear housing  28 , the first passageway  38  and the second passageway  40  are co-planar. Additionally, the first passageway  38  and the second passageway  40  are parallel. A first plug  56  and a second plug  58  are disposed at a distal end of the first passageway  38  and the second passageway  40  respectively. 
     In manufacture, the pressure port  30  is machined into the gear housing  28 . After which, the first passageway  38  and the second passageway  40  are machined into the gear housing  28 , and at least partially intersect the pressure port  30 . The first passageway  38  and the second passageway  40  are machined past the pressure port  30  and into the valve bore  32 . The first plug  56  and the second plug  58  seal the first passageway  38  and the second passageway  40  respectively, so that the power steering fluid does not leak from the gear housing  28 . Accordingly, it should be appreciated that the power steering fluid flows into the pressure port  30 , through the first passageway  38  and the second passageway  40  to and through the first orifice  34  and the second orifice  36  respectively. The first plug  56  and the second plug  58  prevent the power steering fluid from flowing through the first passageway  38  and the second passageway  40  in a direction away from the first orifice  34  and the second orifice  36  respectively. 
     It should be appreciated that the gear housing  28  may also define a plurality of pressure ports  30 , with one of the plurality of passageways  38 ,  40  interconnecting each of the plurality of pressure ports  30  with one of the plurality of orifices  34 ,  36 . 
     The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. As is now apparent to those skilled in the art, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, wherein reference numerals are merely for convenience and are not to be in any way limiting, the invention may be practiced otherwise than as specifically described.