# US 11,027,775 B2 · Wheel loader > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,027,775 B2 - Document ID: US11027775B2 - Status: Granted - Kind: B2 - Application number: 16/640,363 - Filed: 2019-03-05 - Published: 2020-06-04 - Granted: 2021-06-08 - Earliest claimed: 2018-03-28 - Assignees: Hitachi Construction Machinery Co., Ltd. - Applicants: Hitachi Construction Machinery Co., Ltd. - Inventors: Shinichiro Tanaka; Hiroyasu Kodera - Web page: https://patentgrep.com/patent/US11027775B2 ## CPC - B62D 5/07: Supply of pressurised fluid for steering also supplying other consumers {; control thereof} - E02F 9/2235: {including an electronic controller} - E02F 9/2246: {Control of prime movers, e.g. depending on the hydraulic load of work tools} - E02F 9/225: {Control of steering, e.g. for hydraulic motors driving the vehicle tracks (steering in general B62D)} - E02F 9/2296: {Systems with a variable displacement pump} - E02F 9/0841: {Articulated frame, i.e. having at least one pivot point between two travelling gear units (tractor-trailer combinations B62D53/00)} - E02F 9/2267: {Valves or distributors (position of valves arrangements on upper-structures E02F9/0875)} - 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) - E02F: DREDGING; SOIL-SHIFTING (winning peat E21C49/00) ## Abstract The operability can be improved when the rotational speed of the engine is low and the working device actuator and the steering actuator are operated in a combined manner, while the configuration of prioritizing the operation of the steering actuator is maintained. A control device (70) included in a wheel loader (1) determines whether a working device (4) is in load lifting operation or not based on the pressure that is between a working device directional switching valve (44) and an orifice (45) and is detected by a pressure sensor (71), and reduces the opening area of a steering control valve (37) when determining that the rotational speed of an engine (14) detected by a rotational speed sensor (72) is equal to or less than a predetermined threshold (Ns) and a working device is in the load lifting operation. ## Claims ### Claim 1 A wheel loader, comprising: a vehicle body; a steering actuator that steers the vehicle body; a working device attached to a front of the vehicle body; a working device actuator that operates the working device; a hydraulic pump that supplies pressure oil to the steering actuator and the working device actuator; an engine that drives the hydraulic pump; a steering directional switching valve that is provided between the steering actuator and the hydraulic pump, and switches a direction of pressure oil supplied to the steering actuator; a steering control valve that is provided between the steering directional switching valve and the hydraulic pump, and controls a flow rate of the pressure oil supplied to the steering actuator; a working device directional switching valve that is provided between the working device actuator and the hydraulic pump, and switches the direction of the pressure oil supplied to the working device actuator; a working device control valve that is provided between the working device directional switching valve and the hydraulic pump, and controls the flow rate of the pressure oil to the working device actuator; an orifice provided downstream of the working device directional switching valve; a rotational speed sensor that detects the rotational speed of the engine; a pressure sensor that detects a pressure between the working device directional switching valve and the orifice; and a control device that controls the steering control valve, wherein in a case where the rotational speed of the engine detected by the rotational speed sensor is equal to or less than a predetermined threshold, and the pressure detected by the pressure sensor is equal to or higher than a predetermined pressure, an opening area of the steering control valve is reduced. ### Claim 2 (depends on 1) The wheel loader according to claim 1, further comprising: a path that allows one of both pressure receivers of the steering control valve and a tank to communicate with each other; and a directional solenoid valve provided on the path, wherein the steering control valve is configured to be operated according to a differential pressure before and after the steering directional switching valve, by the pressure oil on an outlet side of the steering directional switching valve being guided to the one pressure receiver of the steering control valve, and by the pressure oil on an inlet side of the steering directional switching valve being guided to another pressure receiver of the steering control valve, and in a case where the rotational speed of the engine detected by the rotational speed sensor is equal to or less than the predetermined threshold and the pressure detected by the pressure sensor is equal to or higher than the predetermined pressure, the control device opens the directional solenoid valve and allows the one pressure receiver and the tank to communicate with each other, to reduce the opening area of the steering control valve by returning the pressure oil applied on the one pressure receiver to the tank via the path. ### Claim 3 (depends on 1) The wheel loader according to claim 1, further comprising: a path that allows one of both pressure receivers of the steering control valve and a hydraulic pressure source to communicate with each other; and a directional solenoid valve provided on the path, wherein the steering control valve is configured to be operated according to a differential pressure before and after the steering directional switching valve, by the pressure oil on an inlet side of the steering directional switching valve being guided to the one pressure receiver of the steering control valve, and by the pressure oil on an outlet side of the steering directional switching valve being guided to another pressure receiver of the steering control valve, and in a case where the rotational speed of the engine detected by the rotational speed sensor is equal to or less than the predetermined threshold and the pressure detected by the pressure sensor is equal to or higher than the predetermined pressure, the control device opens the directional solenoid valve and allows the one pressure receiver and the hydraulic pressure source to communicate with each other, to reduce the opening area of the steering control valve by supplying the pressure oil from the hydraulic pressure source to the one pressure receiver via the path. ### Claim 4 A wheel loader, comprising: a vehicle body; a steering actuator that steers the vehicle body; a working device attached to a front of the vehicle body; a working device actuator that operates the working device; a hydraulic pump that supplies pressure oil to the steering actuator and the working device actuator; an engine that drives the hydraulic pump; a steering directional switching valve that is provided between the steering actuator and the hydraulic pump, and switches a direction of pressure oil supplied to the steering actuator; a steering control valve that is provided between the steering directional switching valve and the hydraulic pump, and controls a flow rate of the pressure oil supplied to the steering actuator; a working device directional switching valve that is provided between the working device actuator and the hydraulic pump, and switches the direction of the pressure oil supplied to the working device actuator; a working device control valve that is provided between the working device directional switching valve and the hydraulic pump, and controls the flow rate of the pressure oil to the working device actuator; and an orifice provided downstream of the working device directional switching valve; the wheel loader further comprising: a path that allows one of both pressure receivers of the steering control valve and a tank to communicate with each other; and a hydraulic switching valve that is provided on the path, and is operated by application of a pressure between the working device directional switching valve and the orifice onto a pressure receiver, wherein the steering control valve is configured to be operated according to a differential pressure before and after the steering directional switching valve, by the pressure oil on an outlet side of the steering directional switching valve being guided to the one pressure receiver of the steering control valve, and by the pressure oil on an inlet side of the steering directional switching valve being guided to another pressure receiver of the steering control valve, and the one pressure receiver and the tank are allowed to communicate with each other by operation of the hydraulic switching valve, to reduce an opening area of the steering control valve by returning the pressure oil applied onto the one pressure receiver to the tank via the path. ### Claim 5 A wheel loader, comprising: a vehicle body; a steering actuator that steers the vehicle body; a working device attached to a front of the vehicle body; a working device actuator that operates the working device; a hydraulic pump that supplies pressure oil to the steering actuator and the working device actuator; an engine that drives the hydraulic pump; a steering directional switching valve that is provided between the steering actuator and the hydraulic pump, and switches a direction of pressure oil supplied to the steering actuator; a steering control valve that is provided between the steering directional switching valve and the hydraulic pump, and controls a flow rate of the pressure oil supplied to the steering actuator; a working device directional switching valve that is provided between the working device actuator and the hydraulic pump, and switches the direction of the pressure oil supplied to the working device actuator; a working device control valve that is provided between the working device directional switching valve and the hydraulic pump, and controls the flow rate of the pressure oil to the working device actuator; and an orifice provided downstream of the working device directional switching valve; the wheel loader further comprising: a path that allows one of both pressure receivers of the steering control valve and a hydraulic pressure source to communicate with each other; and a hydraulic switching valve that is provided on the path, and is operated by application of a pressure between the working device directional switching valve and the orifice onto a pressure receiver, wherein the steering control valve is configured to be operated according to a differential pressure before and after the steering directional switching valve, by the pressure oil on an inlet side of the steering directional switching valve being guided to the one pressure receiver of the steering control valve, and by the pressure oil on an outlet side of the steering directional switching valve being guided to another pressure receiver of the steering control valve, and the one pressure receiver and the hydraulic pressure source are allowed to communicate with each other by operation of the hydraulic switching valve, to reduce an opening area of the steering control valve by supplying the pressure oil from the hydraulic pressure source to the one pressure receiver via the path.