Mobile crane

Patent metadata

Field	Value
Publication number	US-10287145-B2
Application number	US-201615212619-A
Country	US
Kind code	B2
Filing date	Jul 18, 2016
Priority date	Jul 23, 2015
Publication date	May 14, 2019
Grant date	May 14, 2019

Abstract

A mobile crane includes a crane main body including a control valve which controls a supply flow rate of hydraulic oil to a main-body driving motor and a pilot-pressure control device which controls a pilot pressure supplied to the control valve. The pilot-pressure control device increases the pilot pressure at a first ratio according to an increase in an operation amount of an operation section when a counterweight carrier is an uncoupled state, increases the pilot pressure at a second ratio lower than the first ratio according to the increase in the operation amount when the counterweight carrier is a coupled state and a grounded state, and increases the pilot pressure at a third ratio higher than the second ratio and equal to or lower than the first ratio according to the increase in the operation amount when the counterweight carrier is the coupled state and an afloat state.

First claim

The invention claimed is:

1. A mobile crane comprising:
a crane main body including a lower traveling body capable of self-traveling and an upper swing body mounted on the lower traveling body to be capable of swinging around a vertical axis, the upper swing body including a work device adapted to perform hoisting work;
a counterweight carrier configured to be capable of being switched to a coupled state in which the counterweight carrier is coupled to the upper swing body and an uncoupled state in which the counterweight carrier is disconnected from the upper swing body, in the coupled state, the counterweight carrier being movable according to a movement of the crane main body in a state in which a counterweight is mounted on the counterweight carrier and being capable of taking a grounded state and an afloat state, the grounded state being a state in which the counterweight carrier is in contact with a ground, the afloat state being a state in which the counterweight carrier is afloat above the ground with a load transmitted from the work device;
a coupled-state deriving section configured to derive a state taken by the counterweight carrier out of the coupled state and the uncoupled state; and
an afloat-state detecting section configured to detect a state taken by the counterweight carrier out of the grounded state and the afloat state, wherein
the crane main body includes:
an operation section configured to be operated to instruct an operation of the crane main body;
a hydraulic pump configured to discharge hydraulic oil;
a main-body driving motor configured to generate power for causing the crane main body to operate by being supplied with the hydraulic oil discharged from the hydraulic pump;
a control valve provided in a supply route of the hydraulic oil between the hydraulic pump and the main-body driving motor and configured to control a supply flow rate of the hydraulic oil such that the supply flow rate of the hydraulic oil to the main-body driving motor increases as a pilot pressure supplied to the control valve increases;
a pilot pressure source configured to supply the pilot pressure to the control valve; and
a pilot-pressure control device configured to control the pilot pressure supplied from the pilot pressure source to the control valve,

the counterweight carrier includes a carrier driving motor configured to generate power for moving the counterweight carrier according to a movement of the crane main body, and
the pilot-pressure control device is configured to increase the pilot pressure supplied to the control valve at a first ratio according to an increase in an operation amount of the operation section when the state derived by the coupled-state deriving section is the uncoupled state, increase the pilot pressure supplied to the control valve at a second ratio lower than the first ratio according to the increase in the operation amount of the operation section when the state derived by the coupled-state deriving section is the coupled state and the state detected by the afloat-state detecting section is the grounded state, and increase the pilot pressure supplied to the control valve at a third ratio higher than the second ratio and equal to or lower than the first ratio according to the increase in the operation amount of the operation section when the state derived by the coupled-state deriving section is the coupled state and the state detected by the afloat-state detecting section is the afloat state.

2. The mobile crane according to claim 1 , wherein
the pilot-pressure control device includes:
a proportional solenoid valve provided in a supply route of the pilot pressure between the pilot pressure source and the control valve and configured to adjust the pilot pressure such that the pilot pressure supplied to the control valve increases as an input electric current increases; and
a controller configured to control the electric current input to the proportional solenoid valve according to operation of the operation section to thereby control the proportional solenoid valve, and

the controller is configured to increase the electric current input to the proportional solenoid valve at the first ratio according to the increase in the operation amount of the operation section when the state derived by the coupled-state deriving section is the uncoupled state, increase the electric current input to the proportional solenoid valve at the second ratio according to the increase in the operation amount of the operation section when the state derived by the coupled-state deriving section is the coupled state and the state detected by the afloat-state detecting section is the grounded state, and increase the electric current input to the proportional solenoid valve at the third ratio according to the increase in the operation amount of the operation section when the state derived by the coupled-state deriving section is the coupled state and the state detected by the afloat-state detecting section is the afloat state.

3. The mobile crane according to claim 2 , wherein
the counterweight carrier includes wheels rotated by the carrier driving motor during the movement of the counterweight carrier, the wheels are configured to be capable of being steered to take a traveling posture in which the wheels face a traveling direction of the lower traveling body during traveling of the crane main body by the lower traveling body and take a swing posture in which the wheels face a direction along a swing direction of the upper swing body during swinging of the upper swing body,
the hydraulic pump is a variable displacement pump capable of changing a discharge flow rate of the hydraulic oil discharged by the hydraulic pump,
the crane main body includes:
an engine configured to cause the hydraulic pump to operate; and
a discharge-flow-rate changing device configured to cause the hydraulic pump to change the discharge flow rate of the hydraulic oil, and

when the state derived by the coupled-state deriving section is the uncoupled state, the controller causes the discharge-flow-rate changing device to change the discharge flow rate of the hydraulic oil of the hydraulic pump such that the discharge flow rate of the hydraulic oil of the hydraulic pump increases as the number of revolutions of the engine increases from a minimum number of revolutions, and, when the state derived by the coupled-state deriving section is the coupled state, the state detected by the afloat-state detecting section is the grounded state, and the wheels of the counterweight carrier is in the swing posture, the controller causes the discharge-flow-rate changing device to set the discharge flow rate of the hydraulic oil of the hydraulic pump such that, in a range of the number of revolutions of the engine between the minimum number of revolutions and a predetermined number of revolutions higher than the minimum number of revolutions, the discharge flow rate of the hydraulic oil of the hydraulic pump is larger than the discharge flow rate of the hydraulic oil of the hydraulic pump obtained when the state derived by the coupled-state deriving section is the uncoupled state.

Assignees

• Kobelco Constr Mach Co Ltd
• Kobelco Construction Mechinery Co Ltd

Inventors

• Iwazawa Takahiro

Classifications

• B66C13/20

  for non-electric drives (transmitting control pulses B66C13/40) · CPC title

• B66C23/74 Primary

  separate from jib · CPC title