# US 10,767,668 B2 · Hydraulic control system for construction machine > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,767,668 B2 - Document ID: US10767668B2 - Status: Granted - Kind: B2 - Application number: 16/346,765 - Filed: 2016-11-02 - Published: 2019-10-31 - Granted: 2020-09-08 - Earliest claimed: 2016-11-02 - Assignees: Volvo Construction Equipment AB - Applicants: Volvo Construction Equipment AB - Inventors: Youngjin Son; Sewan An - Web page: https://patentgrep.com/patent/US10767668B2 ## CPC - F15B 11/17: using two or more pumps - E02F 9/2242: {including an electronic controller} - E02F 9/2267: {Valves or distributors (position of valves arrangements on upper-structures E02F9/0875)} - E02F 9/2285: {Pilot-operated systems} - E02F 9/2292: {Systems with two or more pumps} - F15B 11/10: in which the servomotor position is a function of the pressure {; Pressure regulators as operating means therefor} - F15B 11/166: {Controlling a pilot pressure in response to the load, i.e. supply to at least one user is regulated by adjusting either the system pilot pressure or one or more of the individual pilot command pressures} - F15B 13/0402: {for linearly sliding valves, e.g. spool valves} - F15B 13/043: with electrically-controlled pilot valves - F15B 2211/20576: with multiple pumps - F15B 2211/30595: with additional valves between the groups of valves for multiple output members - F15B 2211/329: actuated by fluid pressure - F15B 2211/355: Pilot pressure control - F15B 2211/40576: Assemblies of multiple valves - F15B 2211/428: actuated by fluid pressure - F15B 2211/6355: having valve means - F15B 2211/67: Methods for controlling pilot pressure - F15B 2211/7135: Combinations of output members of different types, e.g. single-acting cylinders with rotary motors - F15B 2211/7142: the output members being arranged in multiple groups - F15B: SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR - E02F: DREDGING; SOIL-SHIFTING (winning peat E21C49/00) ## Abstract A hydraulic control system for a construction machine includes a hydraulic pump group including a first hydraulic pump, a second hydraulic pump and a third hydraulic pump; a main control valve including a first spool group that controls a flow of pressurised fluid from the first hydraulic pump and the second hydraulic pump and that includes an operation apparatus spool, a driving spool and a merging spool, a second spool group that controls a flow of pressurised fluid from the third hydraulic pump and that includes a rotating spool, and a straight driving valve between the first spool group and the second spool group; a first pilot signal line connected to the operation apparatus spool that provides a supply path for a pilot pressurised fluid that is applied to switch the operation apparatus spool; a second pilot signal line connected to the driving spool that provides a supply path for a pilot pressurised fluid that is applied to switch the driving spool; and a direction changing valve on the second pilot signal line connecting the driving spool and a tank, that is connected to the first pilot signal line, and that is switched when the operation apparatus spool is switched so as to cut off the flow of a pilot pressurised fluid that is returning to the tank. ## Claims ### Claim 1 A hydraulic control system for a construction machine, the hydraulic control system comprising: a hydraulic pump group comprising a first hydraulic pump, a second hydraulic pump and a third hydraulic pump; a main control valve (MCV) comprising: a first spool group configured to control flow rates and flows of pressurized oils to be supplied from the first hydraulic pump and the second hydraulic pump and comprising a spool for a working device, a spool for traveling and a spool for confluence, a second spool group configured to control a flow rate and flow of pressurized oil to be supplied from the third hydraulic pump and comprising a spool for swing, and a straight traveling valve equipped between the first spool group and the second spool group; a first pilot signal line connected to the spool fora working device and configured to provide a supply passage of pilot pressurized oil to be applied so as to switch the spool for a working device; a second pilot signal line connected to the spool for traveling and configured to provide a supply passage of pilot pressurized oil to be applied so as to switch the spool for traveling, and a direction changing valve equipped on the second pilot signal line configured to interconnect the spool for traveling and a tank, connected to the first pilot signal line, and configured to be switched upon switching of the spool for a working device, thereby cutting off flow of pilot pressurized oil returning to the tank. ### Claim 2 (depends on 1) The hydraulic control system according to claim 1, wherein the straight traveling valve is switched by a pressure that is formed by the pilot pressurized oil of which returning flow to the tank is cut off by the switching of the spool for a working device and the pilot pressurized oil of which returning flow to the tank is cut off by the direction changing valve, upon the switching of the spool for a working device. ### Claim 3 (depends on 2) The hydraulic control system according to claim 2, wherein the pressurized oil that is discharged from the third hydraulic pump is supplied to the first spool group in accordance with the switching of the straight traveling valve and joins the pressurized oils that are discharged from the first hydraulic pump and the second hydraulic pump and pass through the spool for a working device and the spool for confluence. ### Claim 4 (depends on 1) The hydraulic control system according to claim 1, further comprising a remote control valve (RCV) configured to apply a pilot signal pressure to the first spool group and the second spool group by a driver's manipulation thereon. ### Claim 5 (depends on 4) The hydraulic control system according to claim 4, wherein the direction changing valve cuts off the flow of the pilot pressurized oil returning to the tank when an operating amount of the RCV is a predetermined amount or larger in a state when the spool for a working device is switched. ### Claim 6 (depends on 1) The hydraulic control system according to claim 1, wherein the direction changing valve is a solenoid valve. ### Claim 7 (depends on 6) The hydraulic control system according to claim 6, further comprising a changeover switch electrically connected to the direction changing valve and configured to actuate the direction changing valve by a driver's on/off manipulation. ### Claim 8 (depends on 7) The hydraulic control system according to claim 7, wherein the direction changing valve cuts off the flow of the pilot pressurized oil returning to the tank when the changeover switch is on in a state where the spool for a working device is switched. ### Claim 9 (depends on 1) The hydraulic control system according to claim 1, wherein the direction changing valve is arranged inside the MCV. ### Claim 10 (depends on 1) The hydraulic control system according to claim 1, wherein the direction changing valve is arranged outside the MCV.