Controlling arrangement for travelling work vehicle

• US 5,295,353 A
• Filed: 10/23/1992
• Issued: 03/22/1994
• Est. Priority Date: 06/06/1990
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Komatsu Seisakusho, Komatsu Mec Kabushiki Kaisha
• Original Assignee: Kabushiki Kaisha Komatsu Seisakusho, Komatsu Mec Kabushiki Kaisha
• Inventors: Ikari, Masanori
• Primary Examiner(s): Look, Edward K.
• Assistant Examiner(s): NGUYEN, HOANG M
• Application Number:
  US07/941,440
• Time in Patent Office: 515 Days
• Field of Search: 60/431, 60/420, 60/422, 60/426, 60/428, 60/429, 60/430, 60/468, 60/452, 91/511, 91/518, 417/34
• US Class Current: 60/431
• CPC Class Codes: E02F 9/2246 Control of prime movers, e.g. depending on the hydraulic load of work tools

Abstract

A device for controlling a vehicle for loading work and equipped with a plurality of hydraulic pumps of fixed capacity for loading work and a torque converter driven from an engine, an electronic control governor for optionally selecting output characteristic in steps for controlling output of the engine, changeover valves disposed in the circuit on the downstream side of one pump for changing over the flow of pressure oil to a drain circuit in response to working oil pressure or an electric signal, a selection switch for selecting the output characteristics, a governor controller for controlling engine the output characteristic as selected by the switch, and control circuits for actuating the changeover valves in response to the position of the selection switch.

Claims

1. A control system for a vehicle having an engine which simultaneously supplies power to a drive system and a hydraulic working system via an output shaft, said control system comprising:

an electronic governor coupled to said engine for selectively controlling output characteristics thereof;

a governor controller coupled to said governor for controlling the governor in accordance with a plurality of input signals;

first and second fixed capacity hydraulic pumps mechanically coupled to said output shaft for supplying pressurized hydraulic oil to said hydraulic working system;

a torque converter for mechanically coupling said output shaft to said drive system;

a user operable selection switch means cooperating with said controller for manually selecting first, second and third operational modes which respectively represent desired engine output characteristics;

a pilot-type pressure relief valve means serially coupled between a discharge side of said first pump and a sump;

a first changeover valve means coupled to a pilot line of said pressure relief valve means for permitting said pressure relief valve means to communicate said discharge side of said first pump with said sump when said pressurized hydraulic oil at a discharge side of said second pump exceeds a predetermined value;

a second changeover valve means coupled to said pilot line of said pressure relief valve means for permitting said pressure relief valve means to communicate said discharge side of said first pump with said sump when said second changeover valve means is activated;

speed selection switch means defining first and second speed positions;

controlling means responsive to signals received from said governor controller and said speed selection switch means for sending signals to and effecting activation of said second changeover valve means, said controlling means effecting activation of said second changeover valve means upon receiving a signal from the governor controller that the selection switch means is in said third mode, and said controlling means sending a signal to said second changeover valve means to cause activation thereof upon receiving both a signal from said governor controller that the selection switch means is in said second mode and a signal from the speed selection switch means that the latter is in a selected said speed position.

2. In a travelling working vehicle having a working apparatus including a movable boom controlled by first pressure cylinder means and a working element movably supported on the boom and controlled by a second pressure cylinder means, the first and second pressure cylinder means being respectively controlled by first and second valve means, the vehicle having an engine and a torque converter coupled to the output of the engine for controlling travelling of the vehicle, and first and second hydraulic fixed-capacity pumps driven by the output of the engine at the same time as the torque converter, said pumps supplying pressure fluid to the first and second valve means;

unload valve means operated by a pilot pressure fluid for causing, when activated, the pressure fluid discharged from solely said first pump to be returned to a sump;

controller means for controlling the operational characteristics of the engine, and mode selector means coupled to the controller means for permitting selection of first, second and third operating modes;

first control valve means for controlling pilot pressure to said unload valve means, said first control valve means being responsive to and activated by a pilot pressure from said second pump for causing activation of said unload valve means only when said first control valve means is activated by a predetermined pressure from said second pump, said unload valve means being activated solely by said first control valve means when said mode selector means is in said first mode;

second control valve means for controlling pilot pressure to said unload valve means for permitting activation of said unload valve means when said second control valve means is activated;

valve control means for receiving signals from said controller means and for activating said second control valve means when said mode selector is in said third mode;

speed selection switch means for defining first and second speed positions and for transmitting a signal to said valve controller means only when in one of said first and second speed condition; and

said valve control means activating said second control valve means to activate said unload valve means when said mode selector means is in said second mode and upon receipt of said signal from said speed selection switch means.

3. In a tavelling work vehicle having a swingable boom and a working element movably mounted on the boom, first pressure cylinder means coupled to the boom for controlling movement thereof, second pressure cylinder means coupled to the working element for controlling movement thereof relative to the boom, an engine having an output, a torque converter coupled to the output of the engine for effecting travelling of the vehicle, first and second fixed capacity hydraulic pumps driven from the output of the engine, and a control arrangement for controlling the supply of pressure fluid from the pumps to the first and second pressure cylinder means, said control arrangement including first and second valve means for respectively controlling flow of pressure fluid to the first and second cylinder means, comprising the improvement wherein said control arrangement includes:

unloading valve means coupled to the output of said first pump for permitting, when activated, flow of pressure fluid from said first pump back to a sump;

changeover valve means coupled to pilot pressure of said unloading valve means for controlling activation of said unload valve means;

governor controller means for controlling output of said engine;

mode selecting means for permitting selection of first, second and third operating modes and for inputting the selected mode to the governor controller means, said first mode permitting both of said first and second pumps to be operational for supplying pressure fluid to said first and second valve means, said second mode permitting said first pump to be coupled to the sump when in a first forward speed condition, and said third mode causing said first pump to be continually coupled to sump;

forward speed switch means operable between first and second forward speed positions and for outputting a signal when moved from the second forward condition to the first forward speed condition;

valve control means for sending signals to and receiving signals from said governor controller means and for controlling activation of said changeover valve means, said valve controller means causing activation of said changeover valve means so as to in turn cause activation of said unloading valve means when said valve controller means receives said signal from said forward speed switch means and said mode selection means is in said second operating mode, and said valve control means causing activation of said changeover valve means to activate said unloading valve means whenever said mode selection means is in said third operating mode.

4. A vehicle according to claim 3, including second changeover valve means coupled to the pilot pressure of the unloading valve means for causing activation of said unloading valve means whenever said second changeover valve means is activated, said second changeover valve means being activated in response to the pressure from said second pump reaching a predetermined value.

5. A vehicle according to claim 3, wherein said forward speed selection means is provided at a pilot valve which controls operation of said first valve means.