HYDRAULIC DRIVE SYSTEM

• US 20140366521A1
• Filed: 11/30/2012
• Published: 12/18/2014
• Est. Priority Date: 12/08/2011
• Status: Active Grant

• Current Assignee: Hitachi Construction Machinery Company Limited (Hitachi, Ltd.), Kabushiki Kaisha Kcm
• Original Assignee: Kabushiki Kaisha Kcm, Kawasaki Jukogyo Kabushiki Kaisha
• Inventors: Tanaka, Shinichiro, Kodera, Hiroyasu, Ito, Makoto
• Granted Patent: US 9,546,673 B2
• Time in Patent Office: Days
• US Class Current: 60/464
• CPC Class Codes: B62D 5/063 Pump driven by vehicle engine B62D5/065 takes precedence
• CPC Class Codes: E02F 9/2228 including an electronic controller
• CPC Class Codes: E02F 9/2246 Control of prime movers, e.g. depending on the hydraulic load of work tools
• CPC Class Codes: E02F 9/225 Control of steering, e.g. for hydraulic motors driving the vehicle tracks steering in general B62D
• CPC Class Codes: E02F 9/2285 Pilot-operated systems
• CPC Class Codes: F01N 2590/08 for heavy duty applications, e.g. trucks, buses, tractors, locomotives
• CPC Class Codes: F01N 3/023 using means for regenerating the filters, e.g. by burning trapped particles by electrically controlling the supply of combustible mixture or its constituents only F02D41/0235
• CPC Class Codes: F15B 1/26 Supply reservoir or sump assemblies
• CPC Class Codes: F15B 11/162 for giving priority to particular servomotors or users
• CPC Class Codes: F15B 21/001 Servomotor systems with fluidic control
• CPC Class Codes: F15B 2211/20523 Internal combustion engine
• CPC Class Codes: F15B 2211/252 Low pressure control
• CPC Class Codes: F15B 2211/4053 using valves
• CPC Class Codes: F15B 2211/428 actuated by fluid pressure
• CPC Class Codes: F15B 2211/6355 having valve means
• CPC Class Codes: F15B 2211/6658 Control using different modes, e.g. four-quadrant-operation, working mode and transportation mode
• CPC Class Codes: F15B 2211/67 Methods for controlling pilot pressure
• CPC Class Codes: F15B 2211/7135 Combinations of output members of different types, e.g. single-acting cylinders with rotary motors
• CPC Class Codes: F15B 2211/781 one or more output members having priority
• CPC Class Codes: F15B 2211/85 Control during special operating conditions
• CPC Class Codes: F16H 61/4017 : Control of high pressure, e.g. avoiding excess pressure by a relief valve

Abstract

A hydraulic drive system includes a pump, a steering actuator, a loading/unloading apparatus actuator, a drive device, a relief valve, and an input unit. The drive device: flows hydraulic oil from the pump to the loading/unloading apparatus actuator when an operating tool is operated; flows the hydraulic oil from the pump to the steering actuator when a steering has become an operated state from a non-operated state regardless of an operation of the operating tool; and causes the hydraulic oil from the pump to be discharged to a tank via the relief valve to increase the torque of an engine when an increase instruction is inputted to the input unit and the steering is in a non-operated state.

Claims

1. A hydraulic drive system to be applied to construction machinery, the construction machinery including:

a steering for steering a wheel;

a loading/unloading apparatus; and

an operating tool for operating the loading/unloading apparatus,

the hydraulic drive system comprising;

a pump configured to be driven by an engine and discharge hydraulic oil;

a steering actuator connected to the pump and configured to operate based on the hydraulic oil from the pump;

a loading/unloading apparatus actuator connected to the pump in parallel with the steering actuator and configured to operate based on the hydraulic oil from the pump;

a drive device configured to control a flow of the hydraulic oil from the pump in accordance with an operation of the operating tool and an operation of the steering;

a relief valve configured to discharge the hydraulic oil from the pump to a tank when a discharge pressure of the pump has become a predetermined pressure or higher; and

an input unit for inputting an increase instruction to increase a torque of the engine, wherein

the drive device;

flows the hydraulic oil from the pump to the loading/unloading apparatus actuator when the operating tool is operated;

flows the hydraulic oil from the pump to the steering actuator when the steering has become an operated state from a non-operated state regardless of an operation of the operating tool; and

causes the hydraulic oil from the pump to be discharged to the tank via the relief valve to increase the torque of the engine when the increase instruction is inputted to the input unit and the steering is in a non-operated state.

2. The hydraulic drive system according to claim 1, wherein

the drive device:

causes the hydraulic oil flowing from the pump to the steering actuator to be discharged to the tank via the relief valve when the increase instruction to increase the torque of the engine is inputted to the input unit and the steering is in a non-operated state; and

flows the hydraulic oil from the pump to the steering actuator preferentially when the increase instruction to increase the torque of the engine is inputted to the input unit and the steering is operated.

3. The hydraulic drive system according to claim 1, wherein

the drive device includes:

a priority valve configured to flow the hydraulic oil from the pump toward the loading/unloading apparatus actuator when the operating tool is operated, and flow the hydraulic oil from the pump toward the steering actuator preferentially when the steering is operated regardless of an operation of the operating tool;

a loading/unloading apparatus direction control valve configured to flow the hydraulic oil flowing toward the loading/unloading apparatus actuator to at least one of the loading/unloading apparatus actuator and the tank in accordance with an operation of the operating tool;

a steering direction control valve configured to flow the hydraulic oil toward the steering actuator or block a flow of the hydraulic oil in accordance with an operation of the steering; and

a direction switching valve provided downstream from the priority valve and configured to switch a flow direction of the hydraulic oil flowing from the pump toward the loading/unloading apparatus actuator, such that the hydraulic oil is directed to the relief valve.

4. The hydraulic drive system according to claim 3, wherein the direction switching valve is provided between the priority valve and the loading/unloading apparatus direction control valve.

5. The hydraulic drive system according to claim 3, wherein

the drive device includes the input unit for inputting the increase instruction to increase the torque of the engine,

the direction switching valve flows the hydraulic oil from the pump to the relief valve when the increase instruction to increase the torque of the engine is inputted to the input unit and the steering is in a non-operated state, and

the priority valve flows the hydraulic oil from the pump toward the steering actuator when the increase instruction to increase the torque of the engine is inputted and the steering is in an operated state regardless of an operation of the operating tool.

6. The hydraulic drive system according to claim 1, wherein

the drive device includes:

a first switching valve configured to flow the hydraulic oil from the pump toward the steering actuator when the steering is operated;

a second switching valve configured to flow the hydraulic oil from the pump toward the loading/unloading apparatus actuator, and blocks between the pump and the loading/unloading apparatus actuator when the steering is operated;

a loading/unloading apparatus direction control valve configured to flow the hydraulic oil flowing toward the loading/unloading apparatus actuator to at least one of the loading/unloading apparatus actuator and the tank in accordance with an operation of the operating tool;

a steering direction control valve configured to flow the hydraulic oil toward the steering actuator or block a flow of the hydraulic oil in accordance with a state of operation of the steering; and

a breaker configured to cause the second switching valve to block between the pump and the loading/unloading apparatus actuator regardless of an operation of the steering, and

the relief valve is configured to discharge the hydraulic oil flowing between the pump and the second switching valve to the tank.