Abstract:
A multi-vane hydraulic motor for accessory drive in which the vanes of a hydraulically balanced rotor are primarily urged into operative engagement with a surrounding cam by forces of the hydraulic fluid in undervane passage produced by an associated hydraulic pump to eliminate requirement for biasing springs and spring attachment of prior art motor. A high pressure chamber provided between the motor housing and a pressure plate mounted therein is hydraulically connected to the vane chambers of the rotor of the motor for the hydraulic drive thereof. An end cap closing the motor housing has the hydraulic input and output lines operatively connected thereto.

Description:
FIELD OF THE INVENTION  
         [0001]    This Invention relates to hydraulically powered motors for accessory drives and more particularly to a new and improved multi-vane hydraulic motor with a hydraulically balanced rotor for improved high pressure performance and advanced pressurization of the undervane for quick and effective motor priming and efficient motor operation.  
         DESCRIPTION OF RELATED ART  
         [0002]    Prior to the present invention a variety of hydraulic motors have been devised to provide improved drives in various systems such as the hydraulic accessory drive system in automotive vehicles. Many of such motors are multi-vane units that utilize a rotor with an arrangement of outwardly-extending and reciprocally-movable vanes that have cooperating springs for exerting a yieldable outward spring force on the vanes. This force fully maintains the vanes in good sealing and sliding contact with a surrounding outer cam for efficient motor operation. Some problems have been experienced with some motors with vane biasing springs in high cyclic and high speed operation. For example, the vane springs for engine cooling fan drive motors may fatigue and have shortened service life because of high speed and cycle actions during vehicle operation. Such spring fatigue may cause poor motor performance or break down.  
           [0003]    [0003]FIG. 7 of the drawings of this application illustrates one prior art motor with spring biased radial vanes. Other examples are illustrated and described in U.S. Pat. No. 5,470,215 issued Nov. 28, 1995 to Stephen Stone for Wear Resistant Vane-Type Fluid Power Converter and U.S. Pat. No. 5,702,243 issued Dec. 30, 1997 to C. Richard Gulach for Hydraulic Motor with Pressure Compensated End Plates.  
           [0004]    While such prior art hydraulic motors have generally met their objectives in providing improved operating characteristics, more economical and efficient motors are needed to meet requirements for a wider range of applications and to meet higher standards from an efficiency, service life and cost standpoints. Moreover, manufacture and assembly of prior art motors with their special vane and spring constructions are tedious, difficult and costly. New and improved motors are needed to alleviate such problems.  
           [0005]    In contrast to the prior art multi vane hydraulic motors exemplified above, the present invention provides a new and improved hydraulic motor of straight-forward construction with effective and efficient routing of hydraulic motor drive pressures for quickly stroking the vanes into operative sliding-sealing engagement with a surrounding cam surface for quick motor priming. With the hydraulic biasing of the vanes of this invention, wear is materially reduced. This invention furthermore advantageously utilizes a minimal number of components particularly as compared to the prior art constructions with spring biased vanes.  
           [0006]    This invention accordingly provides for the effective elimination of vane springs with the optimized employment of hydraulic forces instead of mechanical spring forces for yieldably stroking or urging the vanes into operative sealing engagement with an outer cam ring. Moreover with the quick stroking or “pop out” of vanes with high pressure hydraulics, initially fed at elevated points on the pressure grade curve to the undervane, the specialized prior art vanes and springs and their mechanical attachment are no longer required for quick and optimized motor priming. With the effective elimination of such springs and their attachment constructions, potential sources of motor wear and breakdown are eliminated.  
           [0007]    In this invention high pressure hydraulic fluid from a hydraulic pump feeds into the inlet port of the motor and then into the high pressure side chambers or balancing pockets formed on opposing sides of the rotor of the motor. These side chambers are interconnected by the undervane passages so that a hydraulic pressure on opposing sides of the rotor is the same and rotor balancing is achieved. With such balanced rotor, motor breakdowns such as from rotor seizure experienced by prior unbalance rotors is minimized. The undervane passages in the rotor are formed at the inner ends of outwardly extending slots in the rotor. The vanes are mounted for reciprocal movement in these slots and the outer tips thereof operatively engage the cam surface of a surrounding cam ring mounted in the motor housing. The porting of high pressure flow into the rotor balancing chambers and interconnecting undervane passages of the rotor further forces the vanes outwardly and the tips of the vanes against the interior contour of the outer cam ring to effect an optimized sliding fluid seal.  
           [0008]    In one preferred embodiment of this invention, an open ended housing is provided in which a specialized disk-like pressure plate is fixed at a predetermined distance from an internal end wall as determined by radial inner and outer o-ring seals to define a high pressure drive chamber therebetween located at one side of the rotor. The rotor is operatively mounted within the housing on an output shaft which extends axially therefrom for driving an accessory such as an engine cooling fan. The housing is closed by an end plate fixed thereto at the other side of the rotor which is formed with the inlet and outlet passages therein for the connection of hydraulic input and return lines thereto.  
           [0009]    As the rotor is rotatably driven by the feed of pressurized hydraulic fluid from the high pressure drive chamber through one or more routing passages in the pressure plate into the vane chambers, the vanes reciprocate in their slots to establish an endless series of sealed rotor-drive chambers between adjacent vanes. These chambers serially receive pressure fluid from the system pump via the internal passages in the motor including the rotor balancing pressure chambers and the connecting undervane passages that feed into the high pressure drive chamber through inner passages in the pressure plate. The vane chambers subsequently discharge such fluid into an exhaust passage system in the end or cover plate and then to the return line operatively connected thereto.  
           [0010]    The flow through the vane chambers with minimized leakage past the vane tip and cam seal effects rotation of the rotor and attached output shaft for accessory drive. Importantly in this invention the undervane passages receive pump pressure at high and optimum points on the pressure gradient for exerting an equal and outward force on each of the vanes optimizing and equalizing vane fluid sealing and wear. With improved vane-cam ring wear and sealing, pump operation is optimized.  
           [0011]    These and other features, objects and advantages of the invention will become more apparent from the following detailed description and drawings in which:  
           [0012]    [0012]FIG. 1 is a diagrammatic view of a hydraulic pump and motor system employed in a vehicle for driving accessories;  
           [0013]    [0013]FIG. 2 is an end view of the hydraulic motor of FIG. 1 sight arrow A of FIG. 1 but with the pressure inlet port rotated out of position;  
           [0014]    [0014]FIG. 3 is a cross sectional view of Fig. 2 but with some parts shown in full lines;  
           [0015]    [0015]FIG. 3 a  is an enlarged portion of the encircled part of FIG. 3 modified to illustrate an alternative structure of the invention;  
           [0016]    [0016]FIG. 4 is a sectional view taken generally along sight lines  4 - 4  of FIG. 3 but with some parts shown in full lines and broken away;  
           [0017]    [0017]FIG. 5 is a sectional view taken generally along sight lines  5 - 5  of Fig. 3  but with some parts shown in full lines and broken away;  
           [0018]    [0018]FIG. 6 is a view of the pressure plate of the motor taken generally along sight lines  6 - 6  of Fig.3; and  
           [0019]    [0019]FIG. 7 is a sectional view of a prior art spring-biased radial vane hydraulic motor. 
       
    
    
     DETAILED DESCRIPTION  
       [0020]    Turning now in greater detail to the drawing there is schematically shown in FIG. 1 a vehicle engine cooling fan drive system  10  that is operatively integrated into the hydraulic power steering gear drive  12 . The steering gear drive includes a hydraulic pump  14 , that may be common to both power steering and fan drives and is driven by the vehicle engine, not shown. In addition to powering the power steering gear, the pump  14  is operatively connected by supply line  22  and return line  24  to power a hydraulic motor  26 . The return line  24  connects back into the pump  14  via to a fluid cooling radiator  28  and reservoir  30  as schematically shown. Controls for controlling the flow to the motor are not shown. The motor  26  may be supplied with pressure fluid from a pump dedicated thereto if desired.  
         [0021]    The hydraulic motor  26  has an elongated, stepped-diameter output shaft  32  that rotatably drives a shrouded engine cooling fan  34  that effects the flow of air through an engine cooling radiator  36  operatively connected to a liquid cooled internal combustion engine, not shown, for engine cooling purposes. The hydraulic motor  26 , details of which are best shown in FIGS.  2 - 6 , comprises a generally cylindrical shell-like housing  38  which defines a cavity  40  in which a rotor  42  is operatively mounted. More particularly, the rotor is splined or otherwise mounted on the stepped diameter output shaft  32  that has it&#39;s innermost end rotatably mounted in bushing  43  or other suitable bearing supported in a mating cylindrical recess  41  in an end cover plate of the motor housing described hereinafter.  
         [0022]    The output shaft  32  is further rotatably supported in the housing by a suitable bearing unit  42  axially spaced in the housing from the bushing  43 . A main lip seal  45  is mounted in a cylindrical recess in an outer extending cylindrical neck portion of the housing for annular sealing contact with the outer surface the output shaft.  
         [0023]    The rotor, drivingly mounted by splines at its centralized inner bore to the output shaft  32 , is a generally cylindrical component formed with a circular periphery  44 . The periphery is of predetermined width matching the width of flattened, blade-like rotor vanes  46  associated with the rotor. The vanes  46  are operatively mounted in a plurality of generally linear slots  48  that preferably project radially in the rotor from a circular arrangement of inner and transversely extending undervane hydraulic passages  50 . Other slot arrangements, such as slots that are off center from the axis of rotor rotation may be used as desired.  
         [0024]    The passages  50  extend from one side of the rotor to the other to hydraulically connect rotor balancing chambers  51  and  53  formed on opposite sides of the rotor described below. With a hydraulically balanced rotor  42 , rotor seizing is reduced or eliminated and motor operating efficiency is increased. When these balancing chambers and the connecting undervane hydraulic passages  50  are pressurized, the pressurized fluid in the undervanes exerts an equal outward force on each of the vanes for effecting the equal operative engagement of each the vane tips with the interior surface  52  of a cam ring  54 . The cam ring is securely fixed in the housing by dowel pins  55  and surrounds the rotor.  
         [0025]    As best shown in FIGS. 3, 4 and  5 , the opposite sides of the rotor  42  are formed with preferably concentric inner and outer annular lands  56  and  58  and  56 ′ and  58 ′ that respectively cooperate with the flattened inner faces  60  of a disc-like pressure plate  62  mounted within the housing  38  by dowel pins  55  and the opposing flattened face  64  of a cover plate  66  that closes the housing. Threaded fasteners such as illustrated by reference numeral  62  in FIG. 2 secure the cover plate to the housing. While O-ring seal  69  provides fluid sealing between these two components. With the cover plate  66  secured to the housing  38 , the fluid pressure chambers  51 ,  53  are formed between the annular lands on opposite sides of the rotor for rotor balancing purposes. Pressure fluid for motor operation is supplied from pump  14  via supply line  22  which connects into a hydraulic fitting  88  on cover plate  66 . The fitting connects to the radial passage  90  and transverse leg  92  in the cover plate for feeding high pressure fluid into the rotor balancing chambers and the interconnecting undervane.  
         [0026]    The adjacent reciprocally movable vanes  46  further cooperate with the outer periphery of the rotor and the inner cam surface of the cam ring to define vane pressure chambers  74  in the motor so that the feed of high pressure hydraulic fluid thereto effects rotation of the rotor and thereby the drive of the fan. In FIG. 5 for instance, the high pressure of hydraulic fluid supplied to vane chambers  74  exerts a counter clockwise force on the rotor as it flows to the low pressure of the exhaust because of the area differential of adjacent vanes defining each vane chamber established by the cam surface as is well known in this art.  
         [0027]    Fluid for driving the rotor is fed from high pressure drive chamber  78  (FIG. 3) formed in housing  38  between the pressure plate  62  and the facing end wall of the housing. The radial outer and inner limits of the high pressure chamber  78  are provided by outer and inner seal rings  80  and  82  of elastomer or other suitable material. The high pressure chamber  78  is supplied with pressure fluid by a pair of radially inner passages  83  in the pressure plate  62  for the direct feed of hydraulic fluid from the side rotor balancing chamber  51  into the high pressure drive chamber  78 .  
         [0028]    As shown in FIG. 3, seal ring  82  is operatively mounted on an inner cylindrical neck  84  of the body of the housing and between the pressure plate and the facing inner wall of the housing. The outer sealing ring  80  is mounted between the pressure plate and the facing inner wall of the housing. With the high pressure drive chamber  78  established high pressure fluid is provided for feed through the vane chambers for the drive of the rotor.  
         [0029]    Pressure fluid in the high pressure drive chamber is forced through one or more outer radial passages  98  in the fixed pressure plate (FIG. 5) and into the vane chambers  74  as they turn and serially pass such passages. These vane chambers exhaust as they pass arcuate discharge ports  100  cut or otherwise formed in the inner face of the cover plate. Pressure fluid discharged into ports  100  will flow back into low pressure such as provided by the exhaust or return line  24  through the transverse passage  102  and connected radial passage  104  in the cover plate. Passage  104  is connected by fitting  108  to the end portion of the return line  24 .  
         [0030]    The radial bleed line  109  also formed in the cover plate connects the central opening  41  in the cover plate mounting the sleeve bearing  43  therein relieves the pressure in the opening for the output shaft  32  to provide relief and protection of the main seal  45  and for the circulating of the hydraulic fluid that act as a lubricating oil for the shaft and bearings.  
         [0031]    In FIG. 3A, a modification to the motor primarily involving changes to the pressure plate is disclosed. In this modification the pressure plate  62 ′ is provided with spring-biased check valves  112  in the radially inner passages  83 ′ leading to the high pressure rotor drive chamber This check valve construction opens from the force of a predetermined pressure acting on the ball valve element of the check valve for effecting the build up of high pressure in the pressure balancing chambers for improved rotor balancing. Also the increased undervane pressure optimizes “pop out” of the vanes  46  to operatively engage the cam before the high pressure drive chamber  78  is fully charged.  
         [0032]    In any event with this invention the motor vanes will be quickly “popped out” in response to the delivery of the high pressure from the pump  14  at a high point on the pressure gradient curve. With such response, the employment of spring devices such as vane springs  116  and their threaded rotor attachment fasteners  117  of FIG. 6 effecting the engagement of the vanes  11   8  with the cam  120  is not required. Moreover with the present invention, the force applied to each of the vanes is equal so that vane wear is equal for enhanced vane cam ring sealing and increased service life. With the prior vane spring and connections eliminated, unit build is simplified and motor performance is maintained at an optimized level with minimized breakdown.  
         [0033]    Having described and illustrated preferred embodiments of this invention, various changes and modifications to the embodiments or the inventive concepts disclosed therein may be apparent to those skilled in the art without departing from the spirit or scope of the invention.