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  Work vehicle steering system with flow-metering curve selection and associated methodUSPTO Application #: 20070219689Title: Work vehicle steering system with flow-metering curve selection and associated method Abstract: A steering system for a work vehicle adjusts the steering ratio in response to changes in the speed of the work vehicle. (end of abstract) Agent: Deere & Company - Moline, IL, US Inventors: Michael T. Gacioch, Alvaro Jose Forero, Lars Althof USPTO Applicaton #: 20070219689 - Class: 701 41 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20070219689. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001]This application claims the benefit under 35 U.S.C. .sctn. 119(e) of U.S. Provisional Patent Application 60/782,111, which was filed 14 Mar. 2006 and is hereby incorporated by reference herein. FIELD OF THE DISCLOSURE [0002]The present disclosure relates to steering systems for work vehicles. BACKGROUND OF THE DISCLOSURE [0003]As used in this application, the steering ratio is defined as steering output/steering input. The steering input may be, for example, displacement of a joystick or a steering wheel. The steering output may be, for example, change in the steered position of one or more steerable elements (e.g., an articulated section of the vehicle and/or traction elements, such as wheels, of the vehicle), and/or change in the actuator(s) (e.g., hydraulic cylinder(s)) for effecting such change in the steered position of the one or more steerable elements. A larger steering ratio represents a steering system in which a given steering input results in a relatively large steering output whereas a smaller steering ratio represents a steering system in which the given steering input results in a relatively small steering output. Thus, the steering output of a steering system with a larger steering ratio is more "sensitive" to the steering input than a steering system with a smaller steering ratio. Such sensitivity could be particularly noticeable in vehicles set at a higher steering ratio and traveling at relatively high speed. SUMMARY OF THE DISCLOSURE [0004]According to the present disclosure, there is provided a steering system for a work vehicle. The steering ratio of the steering system is automatically adjustable in response to vehicle speed. [0005]In an aspect, the steering system comprises a steering input device for receiving a steering input and generating a steering input signal representative thereof, a speed sensor for sensing a speed of the work vehicle and generating a speed signal representative thereof, a steering valve, and a controller unit. The controller unit is adapted to: receive the steering input signal and the speed signal, select a flow-metering curve among a plurality of flow-metering curves representing different steering ratios using the speed signal and generate a selected flow-metering curve signal representative of the selected flow-metering curve, determine a desired valve position setting for the steering valve using the steering input signal and the selected flow-metering curve signal, and output a position setting signal so as to command that the steering valve assume the desired valve position setting to effect a corresponding steering output. [0006]Further, the controller unit is adapted to determine a target flow-metering curve among the plurality of flow-metering curves and transition from an initial flow-metering curve of the plurality of flow-metering curves to the target flow-metering curve in response to a change in the vehicle speed. The plurality of flow-metering curves comprises a number of intermediate curves between the initial flow-metering curve and the target flow-metering curve. The controller unit is adapted to step sequentially through each intermediate curve during the transition from the initial flow-metering curve to the target flow-metering curve, thereby providing a smooth transition therebetween. An associated method is disclosed. [0007]The controller unit selects a flow-metering curve that will establish an appropriate steering ratio for the current speed of the work vehicle. Exemplarily, the plurality of flow-metering curves comprises first, second, and third base curves representing, in order, decreasing steering ratios. The controller unit selects the first base curve if the vehicle speed is less than a predetermined first speed threshold (e.g., the work vehicle is operating in a "working mode"), the second base curve if the vehicle speed is between the predetermined first speed threshold and a second speed threshold greater than the predetermined first speed threshold (e.g., the work vehicle is operating in an "intermediate mode"), and the third base curve if the vehicle speed exceeds the second speed threshold (e.g. the work vehicle is operating in a "roading or transport mode"). [0008]Further exemplarily, the plurality of flow-metering curves comprises a number of intermediate curves between the first and second base curves and a number of intermediate curves between the second and third base curves. The controller unit steps sequentially through each intermediate curve between the first and second base curves when there is a transition between the first and second base curves, through each intermediate curve between the second and third base curves when there is a transition between the second and third base curves, and through each intermediate curve between the first and second base curves, the second base curve, and each intermediate curve between the second and third base curves when there is a transition between the first and third base curves. The controller unit pauses for a predetermined period of time (e.g., 1 second) between each step. [0009]Such a steering system is particularly useful to effect electrohydraulic joystick steering. In such a case, the steering input device has a joystick which can be manipulated by an operator to produce a joystick steering input and a representative joystick steering input signal. [0010]The above and other features will become apparent from the following description and the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0011]The detailed description of the drawings refers to the accompanying figures in which: [0012]FIG. 1 is a simplified block diagram of a steering system of a work vehicle; [0013]FIG. 2 is a flow chart of control routine for operating the steering system; [0014]FIG. 2a is an expanded flow chart of an act of the control routine shown in FIG. 2; [0015]FIG. 3 is a graph relating vehicle ground speed and a maximum hydraulic flow limit; [0016]FIG. 4 is a graph illustrating flow-metering curves; [0017]FIG. 5 is a graph relating time and curve selection; and [0018]FIG. 6 is a side elevation view of a work vehicle in the form of, for example, a loader on which the steering system may be implemented. DETAILED DESCRIPTION OF THE DRAWINGS [0019]A work vehicle 11 having a steering system 12 is shown in FIG. 1, and a control routine 100 for control of the steering system 12 is shown in FIG. 2. The work vehicle 11 may be configured in a variety of ways. For example, it may be configured as a construction vehicle, a forestry vehicle, or an agricultural vehicle. The steering system 12 is particularly useful with a four-wheel loader, as shown in FIG. 6. Continue reading... Full patent description for Work vehicle steering system with flow-metering curve selection and associated method Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Work vehicle steering system with flow-metering curve selection and associated method patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Work vehicle steering system with flow-metering curve selection and associated method or other areas of interest. ### Previous Patent Application: Vehicle motion control system Next Patent Application: Steering apparatus for vehicle Industry Class: Data processing: vehicles, navigation, and relative location ### FreshPatents.com Support Thank you for viewing the Work vehicle steering system with flow-metering curve selection and associated method patent info. IP-related news and info Results in 0.75497 seconds Other interesting Feshpatents.com categories: Medical: Surgery , Surgery(2) , Surgery(3) , Drug , Drug(2) , Prosthesis , Dentistry |
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