Control system for integrating a work attachment to a work vehicle

• US 5,182,908 A
• Filed: 01/13/1992
• Issued: 02/02/1993
• Est. Priority Date: 01/13/1992
• Status: Expired due to Term

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Krone, John J., Lunzman, Stephen V., Devier, Lonnie J., Marsden, Howard A.
• Primary Examiner(s): Look, Edward K.
• Assistant Examiner(s): NGUYEN, HOANG M
• Application Number:
  US07/819,705
• Time in Patent Office: 386 Days
• Field of Search: 91/514, 91/516, 91/517, 91/518, 91/532, 91/459, 60/420, 60/459, 60/428, 60/420, 60/430, 60/422
• US Class Current: 60/420
• CPC Class Codes: E02F 9/2221 Control of flow rate; Load sensing arrangements E02F9/2203 take precedence over E02F9/2221
• CPC Class Codes: F15B 11/162 for giving priority to particular servomotors or users
• CPC Class Codes: F15B 11/165 for adjusting the pump output or bypass in response to demand
• CPC Class Codes: F15B 21/08 Servomotor systems incorporating electrically operated control means F15B21/02, F15B21/065 take precedence
• CPC Class Codes: F15B 2211/20546 variable capacity
• CPC Class Codes: F15B 2211/20576 with multiple pumps
• CPC Class Codes: F15B 2211/6309 the pressure being a pressure source supply pressure
• CPC Class Codes: F15B 2211/633 representing a state of the prime mover, e.g. torque or rotational speed
• CPC Class Codes: F15B 2211/6333 representing a state of the pressure source, e.g. swash plate angle
• CPC Class Codes: F15B 2211/6336 representing a state of the output member, e.g. position, speed or acceleration
• CPC Class Codes: F15B 2211/6346 representing a state of input means, e.g. joystick position
• CPC Class Codes: F15B 2211/6651 Control of the prime mover, e.g. control of the output torque or rotational speed
• CPC Class Codes: F15B 2211/6652 Control of the pressure source, e.g. control of the swash plate angle
• CPC Class Codes: F15B 2211/71 Multiple output members, e.g. multiple hydraulic motors or cylinders
• CPC Class Codes: F15B 2211/781 one or more output members having priority
• CPC Class Codes: F15B 2211/865 Prevention of failures
• CPC Class Codes: G05B 19/042 using digital processors G05B19/05 takes precedence
• CPC Class Codes: G05B 19/43 fluidic

Abstract

An apparatus controls a fluid system of a work vehicle. The work vehicle has an engine and at least one fluid circuit which has a pump driven by the engine. A plurality of control valves controllably pass fluid from the pump to a plurality of respective work elements. The control valves have movable valve stems. A work attachment which has a respective control valve is added to the fluid system. A plurality of operator control elements provide demand signals in response to selected settings. Each demand signal is indicative of a requested fluid flow to a respective work element or work attachment. A memory device stores select parameters of the fluid system. One of the select parameters is a predetermined priority value representing the precedence in which fluid is delivered from the pump to the control valve of the work attachment. A controller receives the predetermined priority value of the work attachment and the demand signals. The controller responsively determines the sequence in which fluid is distributed from the pump to the respective control valves. Then the controller delivers control signals to the rerspective control valves in response to the determination, selectively positioning the stem of the respective control valves.

Claims

1. An apparatus for controlling a fluid system of a work vehicle having an engine, at least one fluid circuit having a pump driven by the engine, a plurality of control valves for controllably passing fluid from the pump to a plurality of respective work elements, said control valves having movable valve stems, and a plurality of operator control elements, the apparatus comprising:

a work attachment having a respective control valve, said work attachment control valve being connected to said fluid system, said work attachment being removably attached to said work vehicle and adapted to perform a specific work function;

means for providing demand signals in response to selected settings of each respective operator control elements, each demand signal being indicative of a requested fluid flow to one of a respective work element and a respective work attachment;

memory means for storing select parameters of said fluid system, one of the select parameters being a predetermined priority value representing the order in which fluid is delivered from the pump to the control valve of said work attachment;

means for providing a plurality of work mode signals, each work mode signal representing a predetermined electrohydraulic circuit arrangement associated with the control valves of the work elements;

means for receiving the work mode signal, determining the sequence in which fluid is distributed from the pump to the control valves associated with the predetermined electrohydraulic circuit arrangement in response to receiving the work mode signal, and responsively assigning a priority value to each control valve associated with the predetermined electrohydraulic circuit arrangement;

means for receiving the predetermined priority value of said work attachment, responsively redetermining the sequence in which fluid is distributed from the pump to the control valves associated with the predetermined electrohydraulic circuit arrangement, and reassigning the priority values of the control valves associated with the predetermined electrohydraulic circuit arrangement in response to the redetermined sequence; and

means for receiving the demand signals, determining the total requested flow rates of the respective control valves in response to the demand signals, comparing the total requested flow rates of the respective control valves to the maximum flow capacity of the fluid system, calculating the valve stem displacements of the respective control valves in response to the demand signals, modifying the calculated valve stem displacements to limit the requested fluid flow to the lower priority control valves when the calculated valve stem displacement of the highest priority control valve yields less than the required fluid flow, delivering control signals to the respective control valves in response to the modified calculated valve stem displacements, and selectively positioning the stems of the respective control valves.

2. An apparatus, as set forth in claim 1, wherein the calculated valve stem displacements are modified proportional to the assigned priority value to limit the requested fluid flow to the respective control valves when the total requested flow exceeds the maximum flow capacity, causing the total requested flow to be reduced to the maximum flow capacity.

3. An apparatus, as set forth in claim 2, including a means for supplying information representing the selected parameters to the memory means.

4. An apparatus, as set forth in claim 1, wherein said memory means includes another select parameter which represents the maximum flow capacity of said pump.

5. An apparatus, as set forth in claim 4, wherein said control means receives the select parameters, calculates the total requested flow capacities of said pump in response to the demand signals, compares the total requested flow to the maximum flow capacity, delivers the control signals to the respective control valves in response to said comparison, selectively positions the stem of the respective valves, and limits the requested fluid flow to said respective work element and work attachment within the maximum flow capacity of said pump in response to the determined sequence.

6. An apparatus, as set forth in claim 5, wherein said pump includes a variable displacement pump and including a means for sensing the swashplate angle of said variable displacement pump and delivering a signal representative of the actual swashplate angle in response to said sensed swashplate angle.

7. An apparatus, as set forth in claim 6, including a means for sensing the engine speed of the engine and delivering a signal representative of the actual engine speed in response to said sensed speed.

8. An apparatus, as set forth in claim 7, wherein said control means receives said actual speed and swashplate angle signals, and responsively determines an actual flow rate of said pump.

9. An apparatus, as set forth in claim 8, wherein said control means compares the actual flow rate with the maximum pump displacement and alters the flow from the variable displacement pump.

10. An apparatus, as set forth in claim 9, including a means for sensing the discharge pressure of said variable displacement pump and producing a signal representative of the actual pressure in response to said sensed pressure.

11. An apparatus, as set forth in claim 10, wherein said control means receives the actual pressure signal and alters the flow of the variable displacement pump.

12. An apparatus, as set forth in claim 6, wherein said control means alters the flow from the variable displacement pump in response to priority of said work attachment.