# US 2021/0340731 A1 · Hydraulic Drive Apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0340731 A1 - Document ID: US20210340731A1 - Status: Published application - Kind: A1 - Application number: 16/330,407 - Filed: 2017-09-08 - Published: 2021-11-04 - Earliest claimed: 2017-09-08 - Assignees: Hitachi Construction Machinery Co., Ltd. - Applicants: Hitachi Construction Machinery Co., Ltd. - Inventors: Kiwamu TAKAHASHI; Kouji ISHIKAWA; Yasutaka TSURUGA; Masatoshi HOSHINO; Seiji HIJIKATA - Web page: https://patentgrep.com/patent/US20210340731A1 ## CPC - E02F 9/2296: {Systems with a variable displacement pump} - F15B 11/17: using two or more pumps - B62D 11/04: by means of separate power sources - E02F 9/22: Hydraulic or pneumatic drives {(for dipper or bucket arm position control E02F3/43, for blade position control for graders E02F3/844; for turntables E02F9/121; for fork-lift trucks B66F9/22)} - E02F 9/2235: {including an electronic controller} - E02F 9/2292: {Systems with two or more pumps} - F15B 2211/20523: Internal combustion engine - F15B 2211/20553: with pilot circuit, e.g. for controlling a swash plate - F15B 2211/20576: with multiple pumps - F15B 2211/2656: by control of the pumps - F15B 2211/6316: the pressure being a pilot pressure - F15B 2211/6346: representing a state of input means, e.g. joystick position - F15B 2211/6652: Control of the pressure source, e.g. control of the swash plate angle - F15B 2211/6654: Flow rate control - 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 2211/782: Concurrent control, e.g. synchronisation of two or more actuators - E02F: DREDGING; SOIL-SHIFTING (winning peat E21C49/00) - F15B: SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR - B62D: MOTOR VEHICLES; TRAILERS (steering, or guiding on a desired track, of agricultural machines or implements A01B69/00; wheels, castors, axles, increasing wheel adhesion B60B; vehicle tyres, tyre inflation or tyre changing B60C; connections between vehicles of a train or the like B60D; vehicles for use on rail and road, amphibious or convertible vehicles B60F; suspension arrangements B60G; heating, cooling, ventilating or other air treating devices B60H; windows, windscreens, non-fixed roofs, doors or similar devices, protective coverings for vehicles not in use B60J; propulsion plant arrangements, auxiliary drives, transmissions, controls, instrumentation or dashboards B60K; electric equipment or propulsion of electrically-propelled vehicles B60L; power supply for electrically-propelled vehicles B60M; passenger accommodation not otherwise provided for B60N; adaptations for load transportation or to carry special loads or objects B60P; arrangement of signalling or lighting devices, the mounting or supporting thereof or circuits therefor, for vehicles in general B60Q; vehicles, vehicle fittings or vehicle parts not otherwise provided for B60R; servicing, cleaning, repairing, supporting, lifting, or manoeuvring, not otherwise provided for, B60S; brake arrangements, brake control systems or parts thereof B60T; air-cushion vehicles B60V; motor-cycles, accessories therefor B62J, B62K; testing of vehicles G01M) ## Abstract A first torque control proportional electromagnetic valve (37) is connected through a first torque control line (41) to a third pressure receiving chamber (32D) in a first torque control regulator (32). A second torque control proportional electromagnetic valve (38) is connected through a second torque control line (42) to a third pressure receiving chamber (35D) in a second torque control regulator (35). The first and second torque control proportional electromagnetic valves (37, 38) are controlled by a controller 47. A switching valve (48) is provided between the first torque control line (41) and the second torque control line (42). The switching valve (48) supplies an output pressure of the first torque control proportional electromagnetic valve (37) to the third pressure receiving chamber (35D) in the second torque control regulator (35) at the time of driving hydraulic motors (2B, 2C) for left side and right side traveling. ## Claims ### Claim 1 A hydraulic drive apparatus comprising: a displacement variable first hydraulic pump that includes a first displacement variable part and delivers pressurized oil to a plurality of hydraulic actuators including one traveling hydraulic motor; a first tilting actuator that drives the first displacement variable part to increase/decrease a delivery amount of the pressurized oil to be delivered from the first hydraulic pump; a first regulator that variably controls a control pressure that is supplied to/discharged from the first tilting actuator; a first proportional electromagnetic valve that is connected through a first oil passage to a pressure receiving chamber of the first regulator and supplies an output pressure to the pressure receiving chamber of the first regulator; a displacement variable second hydraulic pump that includes a second displacement variable part and delivers pressurized oil to a plurality of hydraulic actuators including the other traveling hydraulic motor; a second tilting actuator that drives the second displacement variable part to increase/decrease a delivery amount of the pressurized oil to be delivered from the second hydraulic pump; a second regulator that variably controls a control pressure that is supplied to/discharged from the second tilting actuator; a second proportional electromagnetic valve that is connected through a second oil passage to a pressure receiving chamber of the second regulator and supplies an output pressure to the pressure receiving chamber of the second regulator; and a controller configured to control the first proportional electromagnetic valve and the second proportional electromagnetic valve, characterized in that: the hydraulic drive apparatus further comprising; a switching valve that supplies the output pressure of the first proportional electromagnetic valve to the pressure receiving chamber of the second regulator at the time of driving at least any one of the one traveling hydraulic motor and the other traveling hydraulic motor. ### Claim 2 (depends on 1) The hydraulic drive apparatus according to claim 1, wherein the first oil passage is provided between the first proportional electromagnetic valve and the pressure receiving chamber in the first regulator, the second oil passage is provided between the second proportional electromagnetic valve and the pressure receiving chamber in the second regulator, and the switching valve is provided between the first oil passage and the second oil passage. ### Claim 3 (depends on 1) The hydraulic drive apparatus according to claim 1, wherein when none of the one traveling hydraulic motor and the other traveling hydraulic motor are driven, the switching valve cuts off the connection between the first proportional electromagnetic valve and the pressure receiving chamber in the second regulator and establishes the connection between the second proportional electromagnetic valve and the pressure receiving chamber in the second regulator, and when at least any one of the one traveling hydraulic motor and the other traveling hydraulic motor is driven, the switching valve cuts off the connection between the second proportional electromagnetic valve and the pressure receiving chamber in the second regulator and connects the first proportional electromagnetic valve to both of the pressure receiving chamber in the first regulator and the pressure receiving chamber in the second regulator, the hydraulic drive apparatus further comprising: a drive detecting device that detects a drive of at least anyone of the one traveling hydraulic motor and the other traveling hydraulic motor, wherein when the drive of the traveling hydraulic motor is detected by the drive detecting device, the controller gives a command signal to at least the first proportional electromagnetic valve in such a manner as to supply the output pressure from the first proportional electromagnetic valve to both of the pressure receiving chamber in the first regulator and the pressure receiving chamber in the second regulator. ### Claim 4 (depends on 1) The hydraulic drive apparatus according to claim 1, wherein when none of the one traveling hydraulic motor and the other traveling hydraulic motor are driven, the switching valve cuts off the connection between the first oil passage and the second oil passage, when at least any one of the one traveling hydraulic motor and the other traveling hydraulic motor is driven, the switching valve establishes the connection between the first oil passage and the second oil passage, the hydraulic drive apparatus further comprising: a drive detecting device that detects a drive of at least any one of the one traveling hydraulic motor and the other traveling hydraulic motor, wherein when the drive of the traveling hydraulic motor is detected by the drive detecting device, the controller gives the same command signal to the first proportional electromagnetic valve and the second proportional electromagnetic valve in such a manner as to supply both of the output pressure of the first proportional electromagnetic valve and the output pressure of the second proportional electromagnetic valve to both of the pressure receiving chamber in the first regulator and the pressure receiving chamber in the second regulator.