Abstract:
A fluid controller ( 17 ) to control flow to a steering cylinder ( 19 ) is modified to include a selector valve assembly ( 41,73 ) having two operating positions. In a first position (“R” in FIG.  1 ), the selector valve ( 73 ) permits fluid flow though the main fluid path ( 53 ) in the normal manner, as would be used when the vehicle is in a “roading” mode. In a second position (“W” in FIG.  1  and in FIG.  3 ), the selector valve ( 73 ) blocks flow through the fluid meter ( 43 ) which normally provides the follow-up movement ( 51 ) to the controller valving ( 31,33 ), and bypasses the fluid meter in a “working” mode. Thus, the normal flow rate can be achieved by merely rotating the steering wheel ( 27 ) an amount which corresponds to the desired deflection of the controller valving ( 31,33 ), without the need for the continuous rotation of the steering wheel, as required during normal steering.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     MICROFICHE APPENDIX 
     Not Applicable 
     BACKGROUND OF THE DISCLOSURE 
     The present invention relates to fluid controllers of the type used to control the flow of fluid from a source of pressurized fluid to a fluid pressure actuated device, such as a steering cylinder for steering a vehicle. More particularly, the present invention relates to such a fluid controller having at least two different modes of operation, in terms of the relationship between the manual input to the fluid controller and the rate of fluid flow out of the controller. 
     Although the present invention may be used in connection with fluid controllers of many types, and having various constructions and applications, it is especially advantageous when used in conjunction with a full-fluid-linked steering controller, for use on a vehicle of primarily the “off highway” type, and will be described in connection therewith. 
     A conventional fluid controller of the type to which the present invention relates includes a housing which defines various fluid ports, and further includes a fluid meter, a valve means defining a main fluid path, and an arrangement for imparting follow-up movement to the valve means, in response to the flow of fluid through the fluid meter. The flow through the controller valve means is directly proportional to the areas of the variable flow control orifices in the main fluid path. As is well know to those skilled in the art, the area of each flow control orifice is, in turn, typically proportional to the rate at which the steering wheel is rotated. 
     A typical application for a full-fluid-linked steering controller of the type to which the present invention relates would be a vehicle such as is used on a work site, and such a vehicle would be used in one of two operating modes. First, the vehicle may be operated in a “roading” mode, i.e., it is driven on the road, at normal roading speeds, in order to reach a work site. Second, the vehicle may be operated in a “working” mode, at the work site and is performing work related operations, such as moving a pile of dirt, etc., during which the vehicle is moving at relatively slow speeds. 
     The roading and working modes of operation described above present very different steering requirements, as is now well know to those skilled in the art. When roading the vehicle, a relatively low gain rate would be desirable, whereas, when operating in the working mode, a relatively high gain rate would be desirable. As used herein, the term “gain rate” refers to the rate of change of steered wheel position for a given amount of steering input (such as, but not limited to, rotation of a vehicle steering wheel). With a conventional full-fluid-linked steering controller, however, the gain rate is actually a constant, and as a result, the amount of steering motion by the vehicle operator while roading is typically acceptable, but the amount of steering motion required at the work site, over the course of a typical workday, can cause excessive operator fatigue. 
     One approach to providing a steering system which gives the operator separate reading and working modes of operation has been to provide the vehicle operator with a steering wheel for use when the vehicle needs to be in the roading mode, and with a joy stick for use when the vehicle needs to be in the working mode. The steering wheel gives the operator somewhat the same feel as driving an automobile, which is desirable for the roading mode, while the joy stick may be used to provide relatively large steering changes with relatively little operator input (a large gain rate), which is desirable for use in the working mode. 
     Unfortunately, the provision of a steering wheel/joy stick system adds substantially to the overall expense and complication of the system, in terms of the hardware involved, and also results in substantial complication and expense in order to coordinate the portion of the system operated by the steering wheel with the portion of the system operated by the joy stick. 
     BRIEF SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide an improved fluid controller for use in a vehicle steering system which can provide both a roading mode and a working mode of operation, but which overcomes the disadvantages of the prior art described above. 
     It is a more specific object of the present invention to provide such an improved fluid controller which can accomplish the above-stated object, while requiring only a single steering input device, thus overcoming the prior art disadvantage of the need to coordinate between two different steering inputs. 
     It is still another object of the present invention to provide an improved steering system for a vehicle wherein both the roading mode and the working mode may be accomplished in a single fluid controller, thus overcoming the prior art disadvantage of excessive and complicated hardware. 
     It is still a further object of the present invention to provide an improved fluid controller for use in a vehicle steering system, which greatly reduces the amount of operator steering motion when operating in the working mode. 
     The above and other objects of the invention are accomplished by the provision of an improved fluid controller operable to control the flow of fluid from a source of pressurized fluid to a fluid pressure operated device. The controller includes housing means defining an inlet port for connection to the source of fluid, and first and second control fluid ports for connection to the fluid pressure operated device. Controller valve means is disposed in the housing means and defines a neutral position, and at least one operating position in which the housing means and the controller valve means cooperate to define a main fluid path providing fluid communication from the inlet port to the first control fluid port and including a fluid actuated means for imparting follow-up movement to the controller valve means generally proportional to the volume of fluid flow through the main fluid path when the controller valve means is in the operating position. The fluid actuated means includes a rotatable measuring member providing the follow-up movement. 
     The improved fluid controller is characterized by selector valve means disposed in series flow relationship in the main fluid path, between the fluid inlet port and the fluid actuated means and operable, in a first position to permit normal flow through the main fluid path. The selector valve means is operable in a second position to block fluid flow through the fluid actuated means while bypassing the fluid actuated means, thus permitting flow through the main fluid path, but preventing the follow-up movement to the controller valve means. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a somewhat simplified hydraulic schematic of a hydrostatic power steering system including a fluid controller made in accordance with the present invention. 
     FIG. 2 is a fragmentary, axial cross-section of one portion of the fluid controller shown schematically in FIG.  1 . 
     FIG. 3 is a transverse cross-section, taken on line  3 — 3  of FIG. 2, and on a smaller scale than FIG.  2 . 
     FIG. 4 is a transverse cross-section, taken on line  4 — 4  of FIG. 2, and on a somewhat smaller scale than FIG.  3 . 
     FIG. 5 is a transverse cross-section, taken on line  5 — 5  of FIG. 2, and on the same scale as FIG.  4 . 
     FIG. 6 is a graph of Flow, as a percent of maximum possible flow, versus Steering Wheel Rotation (in degrees) to accomplish the particular flow in one second, comparing the two operating modes of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, which are not intended to limit the invention, FIG. 1 is a somewhat simplified hydraulic schematic of a vehicle hydrostatic power steering system including a fluid controller made in accordance with the teachings of the present invention. The system includes a fluid pump  11 , shown herein as a fixed displacement pump, having its inlet connected to a system reservoir  13 . The output of the pump  11  is communicated to an inlet port  15  of a fluid controller, generally designated  17 . 
     Referring still to FIG. 1, the fluid controller  17  controls the flow of fluid from the pump  11  to a steering cylinder  19 , or some other suitable fluid pressure operated steering actuator or device. The fluid controller  17  includes a pair of control (cylinder) fluid ports  21  and  23  which are connected to the opposite ends of the steering cylinder  19 . The fluid controller  17  also includes a return port  25  which returns fluid to the reservoir  13 . 
     The fluid controller  17  is preferably made in accordance with the teachings of U.S. Pat. Nos. 4,759,182 and 5,080,135, both of which are assigned to the assignee of the present invention and incorporated herein by reference. In accordance with one important aspect of the present invention, the fluid controller  17  is operated by means of only a single steering input, shown herein schematically in FIG. 1 as being a conventional steering wheel  27 , although it should be understood by those skilled in the art that the invention is not limited to use with a steering wheel, and the steering input device could take various other forms, all of which would be within the scope of the present invention. However, the present invention makes it possible, and it is quite desirable to use only a single steering input device, and avoid the complication and expense of multiple steering input devices. 
     Referring now to FIG. 2, in conjunction with FIG. 1, the fluid controller  17  includes a valve housing  29 , and disposed therein is the controller valving. In the subject embodiment, and by way of example only, the controller valving includes a primary valve member  31 , also referred to hereinafter as the “spool valve”, and a follow-up valve member  33 , also referred to hereinafter as the “sleeve valve”. The valve housing  29  defines a plurality of meter passages  35 , the function of which is well know to those skilled in the art, but which will be described briefly subsequently. Disposed adjacent the valve housing  29  is port plate  37  which defines a plurality of ports  39 , with one port  39  being disposed at the end of, and in open communication with, each of the meter passages  35 . Preferably, the spool valve  31  and the sleeve valve  33  incorporate the “wide angle” feature of the above-incorporated U.S. Pat. No. 5,080,135. By wide angle, it is meant that the various flow control orifices defined by the spool valve and sleeve valve do not reach their maximum orifice areas until the relative displacement (deflection) between the spool valve and sleeve valve is on the order of about thirty-five to forty-five or fifty degrees, rather than the ten to twenty degree maximum deflection conventional in many fluid controllers. 
     Disposed rearwardly of the port plate  37  is a selector valve section, generally designated  41 , which will be described in greater detail subsequently. The selector valve section  41  is shown schematically in FIG. 1 as a two-position, three-way, pressure pilot operated flow control valve. 
     Disposed rearwardly (to the left in FIG. 2) of the selector valve section  41  is a fluid meter, generally designated  43  (also shown schematically in FIG.  1 ). As is well known in the art, the fluid meter  43  includes an internally toothed ring member  45 , and disposed eccentrically within the ring member  45  is an externally toothed star member  47 . The internal and external teeth of the ring member  45  and star member  47 , respectively, cooperate to define a plurality of expanding and contracting fluid volume chambers  49  (shown best in FIG.  5 ). As is also well known in the art, as unmetered fluid is communicated to the expanding volume chambers, the star  47  orbits and rotates within the ring  45 , and as a result of such orbital and rotational movement, metered fluid is then communicated from the contracting volume chambers. In this way, the fluid meter  43  measures (or “meters”) the fluid which flows therethrough, and in addition, provides an output motion (i.e., the orbital and rotational motion of the star  47 ) which is proportional to the fluid flow through the fluid meter  43 . 
     As is also well know to those skilled in the fluid controller art, the output motion of the star  47  is communicated by means of a drive shaft  51  and is transmitted, in a manner not shown herein, but shown in the above-incorporated patents, into follow-up movement. This follow-up movement is transmitted to the follow-up valve member  33 , tending to return the valve member  33  to a neutral position, relative to the primary valve member  31  at the completion of a steering operation. What has been described above is part of the operation when the fluid controller  17  is operating in its normal, roading mode, which occurs when the selector valve section  41  is in the condition, designated “R” shown schematically in FIG.  1 . 
     In a conventional manner, the fluid meter  43  and the selector valve section  41  are held in tight, sealing engagement with the valve housing  29  and port plate  37  by means of a plurality of bolts B, only one of which is shown in FIG. 2, but all of which are shown in transverse cross-section in FIGS. 3,  4 , and  5 . 
     Referring again primarily to FIG. 1, when the fluid controller  17  is operating in the normal, roading mode, rotation of the steering wheel  27  by the vehicle operator displaces the spool valve  31 , relative to the sleeve valve  33 . This displacement of spool valve  31  relative to the sleeve valve  33 , opens up a main fluid path, generally designated  53  which provides communication from the inlet port  15  through the fluid meter  43  to the control fluid port  21 . The main fluid path  53  includes a series of flow control orifices, and in the subject embodiment, some are fixed orifices, and some are variable orifices (i.e., the flow area through the orifice varies in proportion to the relative displacement of the spool  31  and sleeve  33 ). These orifices are well know to those skilled in the art, are not in and of themselves essential features of the invention, and therefore will not be described in detail. These flow control orifices are conventionally designated A 1 ; A 2 ; A 3 ; A 4 ; and A 5 . It should be noted in FIG. 1 that the A 5  orifice is not actually part of what has been described as the main fluid path  53 , but instead, is part of the return path communicating between the control fluid port  23  on the “return” side of the steering cylinder  19 , and the return port  25 . Thus, references herein, and in the appended claims, to the “main fluid path” will be understood to mean and include either the path designated “ 53 ” in FIG. 1, or the path  53  plus the return path from the port  23  to the return port  25 . 
     In accordance with one important feature of the subject embodiment, the fluid controller  17  is preferably of the type having, in parallel with the main fluid path  53 , an amplification fluid path  55 , including a variable amplification orifice  57 . As is now well know to those skilled in the art, both the amplification fluid path  55  and the variable amplification orifice  57  are defined primarily by the spool valve  31  and the sleeve valve  33 , in accordance with the teachings of the above-incorporated U.S. Pat. No. 4,759,182. Although not essential to the present invention, the amplification fluid path  55  communicates with (receives fluid from) the main fluid path  53  just downstream of the main flow control orifice A 1 , and then again communicates with (flows into) the main fluid path  53  just upstream of the flow control orifice A 4 . The main purpose of the amplification fluid path  55  is to “amplify” the flow through the fluid meter  43 , i.e., communicate a greater total flow to the steering cylinder  19  than the size of the fluid meter  43  would, in and of itself permit. 
     Referring now primarily to FIGS. 2,  3  and  4 , the selector valve section  41  includes a selector valve housing  61 , and on either axial end of the housing  61 , a spacer plate  63 . The spacer plate  63  disposed adjacent the port plate  37  will be referred to hereinafter as the forward spacer plate, while the spacer plate  63  adjacent the fluid meter  43  will be referred to hereinafter as the rearward spacer plate. Preferably, the two spacer plates  63  are substantially identical, thus reducing the total part count of the controller and simplifying assembly thereof. As will be understood by those skilled in the fluid controller art, each of the meter passages  35  and ports  39  would, in a conventional fluid controller, be aligned with the respective fluid volume chamber  49 . The selector valve section  41  is interposed between the port plate  37  and the fluid meter  43 , both physically and in terms of fluid flow relationship. Therefore, the function of the spacer plates  63  is to “transport” fluid from the meter passages  35  and ports  37  radially inward to the selector valving (to be described subsequently), and then from the selector valving radially outward to the volume chambers  49 . 
     Referring now primarily to FIG. 4, each spacer plate defines a plurality of through bores  65 , and communicating with each bore  65  is an angled recess  67 , formed in an axial end surface  69  of the spacer plate  63 . The forward spacer plate  63  has the radially outer end of each recess  67  in communication with its respective port  39 , whereas the rearward spacer plate  63  has the radially outer end of each recess  67  in communication with its respective volume chamber  49 . 
     Referring now primarily to FIG. 3, in which the drive shaft  51  is omitted from the view, the selector valve housing  61  defines a generally cylindrical valve chamber  71 , and disposed within the chamber  71  is a rotatable, generally cylindrical selector valve  73 . The valving action accomplished by the selector valve  73  will be described subsequently in detail. The selector valve housing  61  also defines a transverse bore  75 , the left end of the bore  75  being provided with a fitting  77 , and the right end of the bore  75  being provided with a fitting  79 . As will be understood by those skilled in the art of hydraulic controls (pilot controls), the fittings  77  and  79  are shown in the schematic of FIG. 1 as the hydraulic means by which the selector valve  73  is piloted or shifted between its two, discrete operating positions shown in FIG.  1  and to be described in greater detail subsequently. Disposed within the transverse bore  75  is a pair of pilot pistons  81  and  83 , and disposed axially between the pistons  81  and  83  is a lever member  85  which is received within a bore  87  (see FIG. 2) formed in the selector valve  73 . 
     Thus, when pilot pressure is communicated through the fitting  77 , and drained from the fitting  79 , the pilot piston  81  shifts to the right to the position shown in FIG.  3 . Subsequently, if the pilot pressure in the fitting  77  is drained, and a pilot pressure is communicated through the fitting  79 , the pilot piston  83  will be biased from the position shown in FIG. 3, rotating the selector valve  73  counter-clockwise about twenty degrees from the FIG. 3 position. 
     Referring now primarily to FIGS. 2 and 3, the selector valve  73  defines a plurality of axial bores  91 , the number of axial bores  91  being equal to the number of volume chambers  49 , and also equal to the number of through bores  65  and recesses  67  in each spacer plate  63 . Disposed adjacent each axial bore  91 , the forward end surface of the selector valve  73  defines a shallow, radial recess  93 . With the selector valve  73  in the rotational position shown in FIG. 3, each recess  93  is in communication with a shallow radial recess  95  formed in a forward axial face of the selector valve housing  61 . The radial recesses  95  are each in open communication with an annular chamber  97 , the function of which will be described subsequently. 
     Operation 
     When the vehicle operator wishes to be able to steer the vehicle in the normal roading mode, it is necessary to direct pilot pressure through the fitting  79 , rotating the selector valve  73  from the position shown in FIG. 3 in a counter-clockwise direction such that each axial bore  91  is moved counter-clockwise to the position occupied in FIG. 3 by the radially inner end of the adjacent recess  93 . The position of the selector valve  73  just described corresponds to that shown schematically in FIG. 1, and designated “R”. By comparing the shifted position of the selector valve  73  described above with FIG. 4, it may be seen that, in the normal, roading mode, each through bore  65  in the forward spacer plate  63  is in communication with its respective axial bore  91 . At the same time, each bore  91  is also in communication with its respective through bore  65  in the rearward spacer plate  63 . 
     Thus, with the selector valve  73  shifted from the position shown in FIG. 3 to the normal, roading mode, unmetered fluid is communicated through certain of the meter passages  35 , through the axial bores  91  to the expanding volume chambers  49 , while at the same time, metered fluid is being communicated from the contracting volume chambers  49  through the respective axial bores  91 , and to other of the meter passages  35 . It should be understood that in the roading mode, the operation of the fluid controller  17  of the present invention is the same as if the entire selector valve section  41  were removed, and the fluid meter  43  were disposed immediately adjacent the port plate  37 . 
     As is understood by those skilled in the art, in the normal steering mode “R”, the deflection angle refers to the displacement between the spool valve  31  and sleeve valve  33  which, in turn, is a function of the rate of rotation of the steering wheel  27 . As may best be seen in FIG. 1, in the normal, roading mode of operation, fluid flows through the main fluid path  53  in the same manner as in any conventional fluid controller. At the same time, there is the flow through the amplification flow path  55 , such that the total flow to the steering cylinder  19  is the sum of the flows in the flow paths  53  and  55 , as is well known already in the fluid controller art. 
     When the vehicle operator wishes to steer the vehicle in the working mode, it is necessary to communicate pilot pressure through the fitting  77  to rotate the selector valve  73  in a clockwise direction from that described previously, back to the working mode position shown in FIG. 3, i.e., the position designated “W” in FIG.  1 . With the selector valve  73  in the working mode position, each of the through bores  65  in the forward spacer plate  63  is in open communication with its respective radial recess  93 , and in turn, each recess  93  communicates through its respective radial recess  95  with the annular chamber  97 . Note that in FIG. 1, the annular chamber  97  is shown schematically as a bypass path around the fluid meter  43 . 
     With the selector valve  73  in the working mode position “W” of FIG. 3, each axial bore  91  is out of communication with its respective through bores  65  in both the forward and rearward spacer plates  63 , such that fluid in the axial bores  91  is simply trapped therein. At the same time, each of the through bores  65  in the rearward spacer plate  63  has flow therethrough blocked by the adjacent axial end surface of the selector valve  73 . While the fluid controller is operating in the working mode, fluid in each of the volume chambers  49 , as well as fluid in each of the recesses  67  in the rearward spacer plate  63  is trapped. As a result, the star member  47  does not engage in its normal orbital and rotational movement, but instead, is effectively “fluid locked” and remains stationary. Thus, there is no follow-up movement transmitted from the star member  47  by the drive shaft  51  to the follow-up valve member  33 . 
     Therefore, when the fluid controller  17  is operating in the working mode “W”, the size of each of the flow control orifices A 1  through A 5  is determined solely by the angle of deflection of the steering wheel  27  from its neutral position. It will be understood by those skilled in the art that the same torque is required to rotate the steering wheel  27  in either mode “R” or “W”, but when operating in the working mode, much less movement of the steering wheel is required, as is illustrated in the graph of FIG. 6, because of the absence of any follow-up movement back to the follow-up valve member  33 . Instead, the unit operates in the manner of what is known as a “jerk-steer” controller having no fluid meter, in which rotation of the steering wheel merely opens up the valving orifices A 1  through A 5 . 
     By way of example only, and referring now also to FIG. 6, in the subject embodiment of the invention, when the fluid controller is in the working mode “W”, a steering wheel displacement of about 50 degrees results in about the same flow rate (100 percent of maximum possible flow in FIG. 6) to the steering cylinder  19  as occurs when the fluid controller is in the roading mode, and the steering wheel is being rotated at about 120 rpm, to keep the spool valve  31  at the 50 degree deflection, relative to the sleeve valve  33 . Thus, with a typical, prior art fluid controller having about four turns (lock-to-lock) capability, the operator must turn the steering wheel two turns (720 degrees) from the centered (neutral) position, and at a high rate of rotation (120 rpm), every time it is desired to make a major steering correction on a work site. However, with the arrangement of the present invention, the operator merely rotates the steering wheel by an angle equal to the desired spool-sleeve deflection (e.g., 50 degrees), and hold the wheel in that position until the desired movement of the steering cylinder  19  has occurred, then releases the steering wheel allowing it to re-center under the influence of the centering springs, shown in the above-incorporated patents. 
     As will be understood by those skilled in the art, in either mode of operation, the torque required to rotate the steering wheel is the same, because the torque to rotate the wheel is a function of the spring rate of the centering springs. However, with the invention, operation in the working mode “W” requires so much less arm motion by the operator (less rotation of the steering wheel) than was required with the prior art fluid controller (represented by the roading mode “R” in FIG.  6 ), resulting in much less fatigue for the operator, and enhanced operating efficiency. The decrease in operator effort may best be seen in FIG. 6, which is a graph of Flow (as a percent of maximum flow) versus Steering Wheel Rotation (in degrees) in one second to achieve the corresponding flow. The significance of the graph of FIG. 6 is that it illustrates, pictorially, the decreased operator effort when operating in the working mode “W”, as compared to the roading mode “R”. In the graph of FIG. 6, the area under each of the graphs is representative of the steering effort required by the operator to achieve the particular flow, in one second. 
     The invention has been described in great detail in the foregoing specification, and it is believed that various alterations and modifications of the invention will become apparent to those skilled in the art from a reading and understanding of the specification. It is intended that all such alterations and modifications are included in the invention, insofar as they come within the scope of the appended claims.