# US 2014/0190153 A1 · Drive control method and system for operating a hydraulic driven work machine > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0190153 A1 - Document ID: US20140190153A1 - Status: Published application - Kind: A1 - Application number: 14/239,553 - Filed: 2011-08-26 - Published: 2014-07-10 - Earliest claimed: 2011-08-26 - Assignees: Volvo Construction Equipment AB - Inventors: Judith Britten; Daniel Müller; Thomas Schaefer; Bernd Faber - Web page: https://patentgrep.com/patent/US20140190153A1 ## CPC - E02F 9/2228: {including an electronic controller} - E02F 9/2246: {Control of prime movers, e.g. depending on the hydraulic load of work tools} - E02F 9/2253: {Controlling the travelling speed of vehicles, e.g. adjusting travelling speed according to implement loads, control of hydrostatic transmission} - E02F 9/2278: {Hydraulic circuits} - E02F 9/2285: {Pilot-operated systems} - E02F 9/2296: {Systems with a variable displacement pump} - F16H 61/421: Motor capacity control by electro-hydraulic control means, e.g. using solenoid valves - F16H 61/433: Pump capacity control by fluid pressure control means - F16H 61/478: for preventing overload, e.g. high pressure limitation - F16H 61/47: for achieving a target output speed - F16H 2059/465: {Detecting slip, e.g. clutch slip ratio} - E02F: DREDGING; SOIL-SHIFTING (winning peat E21C49/00) - F16H: GEARING ## Abstract A system and a method for operating a hydraulic driven work machine including a hydraulic travel motor having a variable displacement is provided, wherein a flow of hydraulic fluid generated by a hydraulic pump is provided to the travel motor and wherein a control valve is provided for controlling the flow of hydraulic fluid from the hydraulic pump to the travel motor. The hydraulic pump is provided with a hydraulic control depending on a load signal generated by the travel control valve and the travel motor is provided with an electric control according to a desired driving behaviour. ## Claims ### Claim 1 A method for operating a hydraulic driven work machine comprising a hydraulic travel motor having a variable displacement, wherein a flow of hydraulic fluid generated by a hydraulic pump is provided to the travel motor and wherein a control valve is provided for controlling the flow of hydraulic fluid from the hydraulic pump to the travel motor in an open loop, closed centre load sensing hydraulic system, wherein the hydraulic pump is hydraulically controlled depending on a load signal generated by the travel control valve and the travel motor is electrically controlled according to a desired driving behaviour of the work machine. ### Claim 2 (depends on 1) The method according to claim 1, wherein the displacement of the travel motor is adjusted by an electrically controlled travel motor displacement control valve. ### Claim 3 (depends on 1) The method according to claim 1, wherein the flow of hydraulic fluid in at least one pilot pressure line of the travel control valve is selectively generated by an independent travel flow valve or a travel actuator depending on a selected control state of the work machine, the flow of hydraulic fluid in the at least one pilot pressure line of the travel control valve in a first control state is generated by a travel actuator and in a second control state is generated by an independent travel flow valve. ### Claim 4 (depends on 3) The method according to claim 3, wherein an electrically controlled valve selects between the flow of hydraulic fluid generated by the independent travel flow valve or generated by the travel actuator depending on the selected control state of the work machine. ### Claim 5 (depends on 1) The method according to claim 1, wherein the displacement of the travel motor is continuously adjustable between a maximum displacement and a minimum displacement. ### Claim 6 (depends on 1) The method according to claim 1, wherein in a travel mode of downhill driving the displacement of the travel motor is increased to a larger displacement when the machine exceeds its maximum allowed speed and/or that in an operational mode of uphill driving the travel motor is shifted to a bigger displacement when a defined value for a travel high pressure is exceeded, and/or wherein a speed decrease exceeds a defined maximum value. ### Claim 7 (depends on 1) The method according to claim 1, wherein a pressure difference between a pump side and a load side of the travel control valve is reduced for reducing the flow of hydraulic fluid applied to the travel motor. ### Claim 8 (depends on 1) The method according to claim 1, wherein a pilot pressure in travel pilot lines is reduced for reducing the flow of hydraulic fluid applied to the travel motor. ### Claim 9 (depends on 1) The method according to claim 1, wherein a pressure difference between pump side and load side of the control valve is adjusted to a preset value. ### Claim 10 (depends on 8) The method according to claim 8, wherein in a work mode of the machine the displacement of the travel motor is decreased parallel to the reduction of the flow of hydraulic fluid to the travel motor. ### Claim 11 (depends on 1) The method according to claim 1, wherein in a travel mode of the machine a speed of the prime mover is set to a predetermined fuel economic speed and/or that the pressure in the travel motor is increased by reducing the flow of hydraulic fluid from the hydraulic pump. ### Claim 12 (depends on 1) The method according to claim 1, wherein, when driving on a flat ground in the travel mode, when the travel actuator is activated, thus generating a hydraulic pilot pressure in a hydraulic fluid depending on the stroke of the travel actuator and moving the spool of the travel control valve thus sending the flow of hydraulic fluid to the travel motor, the displacement of the travel motor is changed to a displacement between maximum and minimum displacement depending on a travel high pressure and a travel speed of the machine. ### Claim 13 A travel system for operating a work machine having an open loop, closed centre load sensing hydraulic system, the work machine comprising a hydraulic pump driven by a prime mover, and a hydraulic travel motor having a variable displacement and being drivable by a hydraulic fluid supplied from the hydraulic pump, wherein the travel motor is provided with a travel motor control valve which is electrically controlled and the hydraulic pump is provided with a hydraulic pump controller controlling the hydraulic pump depending on a load signal generated by a travel control valve. ### Claim 14 (depends on 13) The system according to claim 13, wherein a valve is provided for operationally connecting pilot lines of the travel control valve alternately either to a pilot-pressure generating travel actuator or to a pilot-pressure generating independent travel flow valve depending on a selected control state of the work machine. ### Claim 15 (depends on 13) The system according to claim 13, wherein the hydraulic pump controller includes a pressure reduction valve. ### Claim 16 (depends on 13) A vehicle comprising a travel system according to claim 13. ### Claim 17 (depends on 16) The vehicle according to claim 16, comprising at least one of an electro-hydraulic control system including at least one joystick and or pedal and/or main control valve communicating with a control unit via electric signals. ### Claim 18 (depends on 1) Microcomputer comprising a computer program comprising a computer program code adapted to perform a method or for use in a method according to claim 1. ### Claim 19 (depends on 1) Computer comprising a computer program comprising a computer program code adapted to perform a method or for use in a method according to claim 1 adapted to be downloadable to a control unit or one of its components. ### Claim 20 (depends on 1) Computer program product stored on a nontransitory computer readable medium, comprising a program code for use in a method according to claim 1.