Wheel loader

Patent metadata

Field	Value
Publication number	US-11027775-B2
Application number	US-201916640363-A
Country	US
Kind code	B2
Filing date	Mar 5, 2019
Priority date	Mar 28, 2018
Publication date	Jun 8, 2021
Grant date	Jun 8, 2021

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.

First claim

The invention claimed is:

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.

2. 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.

3. 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.

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.

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 val

Assignees

• Hitachi Construction Mach Co

Inventors

• Tanaka Shinichiro
• Kodera Hiroyasu

Classifications

• E02F9/225 Primary

  Control of steering, e.g. for hydraulic motors driving the vehicle tracks (steering in general B62D) · CPC title

• E02F9/2267

  Valves or distributors (position of valves arrangements on upper-structures E02F9/0875) · CPC title

• E02F9/0841

  Articulated frame, i.e. having at least one pivot point between two travelling gear units (tractor-trailer combinations B62D53/00) · CPC title

• E02F9/2235

  including an electronic controller · CPC title

• E02F9/2246

  Control of prime movers, e.g. depending on the hydraulic load of work tools · CPC title