Open-center steering control unit with flow amplification

• US RE34,746 E
• Filed: 01/17/1992
• Issued: 10/04/1994
• Est. Priority Date: 10/06/1988
• Status: Expired due to Term

• Current Assignee: Eaton Corp. (Wisconsin) (Eaton Corporation PLC.)
• Original Assignee: Eaton Corp. (Wisconsin) (Eaton Corporation PLC.)
• Inventors: Schutten, Herman P., Stephenson, Dwight B., Haarstad, Donald M.
• Primary Examiner(s): Look, Edward K.
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US07/822,245
• Time in Patent Office: 991 Days
• Field of Search: 60/384, 91/370, 91/375 R, 91/467, 137/596.13, 137/625.21, 137/625.24, 180/132
• US Class Current: 60/384
• CPC Class Codes: B62D 5/097 gerotor type
• CPC Class Codes: B62D 5/32 for telemotor systems
• CPC Class Codes: Y10T 137/86662 Axial and radial flow
• CPC Class Codes: Y10T 137/87185 Controlled by supply or exhaust valve

Abstract

An open-center fluid controller (15) is disclosed for controlling the flow of fluid to a steering cylinder (25). The controller includes a fluid meter (29) and valving arrangement (27), including a valve spool (43) and a sleeve (45), which define a main fluid path. The main path includes a fixed flow control orifice (86), a variable flow control orifice (87), the fluid meter (29), and a variable flow control orifice (89). In accordance with the invention, the spool and sleeve define an amplification fluid path (101), including a variable amplification orifice (99), in parallel with the main fluid path, and disposed to amplify the flow of fluid through the meter (29). In order to facilitate manual steering, the amplification orifice (99) reaches its maximum flow area when the spool and sleeve are in a normal operating position (FIG. 6). The amplification orifice then decreases and closes as the displacement between the spool and sleeve reach a maximum displacement (FIG. 7). As a result, the amplification fluid path (101) is closed at maximum valve displacement, thus making it possible to manually steer the vehicle.

Claims

1. An open-center controller operable to control the flow of fluid from a source of fluid to a fluid pressure operated device;

said controller being of the type including housing means defining a fluid inlet port for connection to the source of fluid, a returna port for connection to a reservoir, and first and second control fluid ports for connection to the fluid pressure operated device;

valve means disposed in said housing means and defining a neutral position and a first operating position;

said housing means and said valve means cooperating to define a neutral fluid path communicating between said inlet port and said return port, and including a variable neutral orifice having its maximum flow area when said valve means is in said neutral position, and a decreasing flow area as said valve means is displaced from said neutral position toward said first operating position;

said housing means and said valve means cooperating to define a main fluid path communicating between said inlet port and said first control fluid port, and between said second control fluid port and said return port when said valve means is in said first operating position;

fluid actuated means for imparting follow-up movement to said valve means proportional to the volume of fluid flow through said fluid actuated means, said fluid actuated means being disposed in series flow relationship in said main fluid path between said inlet port and said first control fluid port;

said main fluid path including a first, .[.fixed.]. flow control orifice disposed between said inlet port and said fluid actuated means, a second, variable flow control orifice disposed between said first flow control orifice and said fluid actuated means, and a third, variable flow control orifice disposed between said fluid actuated means and said first control fluid port, said second and third flow control orifices having minimum flow areas when said valve means is in said neutral position, and increasing flow areas as said valve means is displaced from said neutral position toward said first operating position;

characterized by;

(a) said housing means and said valve means cooperating to define an amplification fluid path in parallel with said main fluid path, said amplification fluid path being in fluid communication with said main fluid path at a first location disposed between said fluid inlet port and said first.[., fixed.]. flow control orifice, and at a second location disposed between said third, variable flow control orifice and said first control fluid port;

(b) said amplification fluid path including a variable amplification orifice having its minimum flow area when said valve means is in said neutral position, and an increasing flow area as said valve means is displaced from said neutral position toward said first operating position; and

(c) said variable amplification orifice begins to open at substantially the same time as said second and third, variable flow control orifices begin to open.

2. An open-center controller as claimed in claim 1 characterized by said valve means comprising a primary, rotatable valve member and a cooperating, relatively rotatable, follow-up valve member, said primary and follow-up valve members defining said neutral position relative to each other.

3. An open-center controller as claimed in claim 2 characterized by said primary and follow-up valve members cooperating to define said first, second, and third flow control orifices, the flow areas of said second and third flow control orifices varying in response to relative rotation of said primary and follow-up valve members.

4. An open-center controller as claimed in claim 2 characterized by said amplification fluid path and said variable amplification orifice being wholly defined by said primary and follow-up valve members.

5. An open-center controller as claimed in claim 1 characterized by said main fluid path including a fourth, variable flow control orifice disposed between said third, variable flow control orifice and said first control fluid port.

6. An open-center controller as claimed in claim 5 characterized by said amplification fluid path being in fluid communication with said main fluid path at a second location disposed between said third and fourth variable flow control orifices.

7. An open-center controller as claimed in claim 2 characterized by said fluid actuated means comprises a fluid meter including a metering member movable to measure the volume of fluid flowing through said main fluid path, said controller further comprising means coupling said metering member to said follow-up member.

8. An open-center controller as claimed in claim 1 characterized by said controller having a generally constant amplification ratio as said valve means is displaced from said neutral position to said first operating position, and a decreasing amplification ratio as said valve means moves from said first operating position toward a maximum displacement.

9. An open-center controller as claimed in claim 1 characterized by said variable amplification orifice having its maximum flow area when said valve means is in said first operating position, and a decreasing flow area as said valve means is displaced from said first operating position toward a maximum displacement position.

10. An open-center controller as claimed in claim 1 characterized by said housing means and said valve means cooperating to define a second main fluid path communicating between said inlet port and said second control fluid port, and between said first control fluid port and said return port when said valve means is in a second operating position.

11. An open-center controller as claimed in claim 10 characterized by said housing means and said valve means cooperating to define a second amplification fluid path in parallel with said second main fluid path, said amplification fluid path being in fluid communication with said second main fluid path at a first location disposed between said fluid inlet port and said first, .[.fixed.]. flow control orifice, and at a second location disposed between a third, variable flow control orifice and said second control fluid port.

12. An open-center controller as claimed in claim 11 characterized by said second amplification fluid path including a second variable amplification orifice having its minimum flow area when said valve means is in said neutral position, and an increasing flow area as said valve means is displaced from said neutral position toward said second operating position, said second variable amplification orifice begins to open at substantially the same time as said third, variable flow control orifice begins to open.

16. An open-center controller as claimed in claim 14 characterized by said amplification fluid path and said variable amplification orifice being wholly defined by said primary and follow-up valve members. .Iadd.17. An open-center controller as claimed in claim 1, characterized by said first flow control orifice comprising a fixed flow control orifice..Iaddend. .Iadd.18. An open-center controller as claimed in claim 13, characterized by said first flow control orifice comprising a fixed flow control orifice..Iaddend.

13. An open-center controller operable to control the flow of fluid from a source of fluid to a fluid pressure operated device;

said controller being of the type including housing means defining a fluid inlet port for connection to the source of fluid, a return port for connection to a reservoir, and first and second control fluid ports for connection to the fluid pressure operated device;

valve means disposed in said housing means and defining a neutral position and a first operating position;

said housing means and said valve means cooperating to define a neutral fluid path communicating between said inlet port and said return port, and including a variable neutral orifice having its maximum flow area when said valve means is in said neutral position, and a decreasing flow area as said valve means is displaced from said neutral position toward said first operating position;

said housing means and said valve means cooperating to define a main fluid path communicating between said inlet port and said first control fluid port, and between said second control fluid port and said retuen port when said valve means is in said first operating position;

fluid actuated means for imparting follow-up movement to said valve means proportional to the volume of fluid flow through said fluid actuated means, said fluid actuated means being disposed in series flow relationship in said main fluid path between said inlet port and said first control fluid port;

said main fluid path including a first, .[.fixed.]. flow control orifice disposed between said inlet port and said fluid actuated means, and a variable flow control orifice disposed between said fluid actuated means and said first control flow port, said variable flow control orifice having its minimum flow area when said valve means is in said neutral position, .[.at.]. .Iadd.and .Iaddend.an increasing flow area as said valve means is displaced from said neutral position toward said first operating position;

characterized by;

(a) said housing means and said valve means cooperating to define an amplification fluid path in parallel with said main fluid path, said amplification fluid path being in fluid communication with said main fluid path at a first location disposed between said fluid inlet port and said first.[., fixed.]. flow control orifice, and at a second location disposed upstream of said variable flow control orifice;

(b) said amplification fluid path including a variable amplification orifice having its minimum flow area when said valve means is in said neutral position and an increasing flow area as said valve means is displaced from said neutral position toward said first operating position; and

(c) said variable amplification orifice begins to open before said variable flow control orifice begins to open, said variable amplification orifice having its maximum flow area when said valve means is in said first operating position, and a decreasing flow area as said valve means is displaced from said first operating position toward a maximum displacement position, said variable amplification orifice being closed before said valve means reaches said maximum displacement position.

14. An open-center controller as claimed in claim 13 characterized by said valve means comprising a primary, rotatable valve member and a cooperating, relatively rotatable, follow-up valve member, said primary and follow-up valve members defining said neutral position relative to each other.

15. An open-center controller as claimed in claim 14 characterized by said primary and follow-up valve members cooperating to define said variable, neutral orifice, said first.[., fixed.]. flow control orifice, and said variable flow control orifice, the flow areas of said variable orifices varying in response to relative rotation of said primary and follow-up valve members.