Energy Recovering Method and System in Hydraulic Lift Device of Battery Operated Industrial Trucks
First Claim
1. An energy recovering method in a hydraulic lift device of a battery operated industrial truck which is provided with a lift cylinder for lifting a lift means, an electric motor driven by a battery power source, a hydraulic pump for supplying pressurized working fluid to said lift cylinder to lift said lift means, and a control valve disposed between said lift cylinder and said hydraulic pump, whereby said electric motor is allowed to function as an electric generator driven by said hydraulic pump which is allowed to work as a hydraulic motor driven by pressurized working fluid returning from said lift cylinder to the hydraulic pump when a load on said lift means is lowered, and potential energy of the load is recovered as electric power to the battery, wherein lowering speed of said lift means is controlled by controlling the amount of opening of said control valve for controlling the flow rate of the pressurized working fluid returning to the hydraulic pump and rotation speed of said electric motor.
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Accused Products
Abstract
An energy recovering system in a hydraulic lift device of a battery operated industrial truck. With the system, working oil can be supplied to other hydraulic actuators while energy recovering operation is performed by the hydraulic lift device, occurrence of pressure pulsation in the working oil can be prevented, and energy recovering efficiency is increased. The hydraulic lift device comprises a lift cylinder (1) for lifting a fork F, an electric motor (4) rotated by power supply from a battery (5), a hydraulic pump (3) for supplying pressurized oil to the lift cylinder (1), a control valve (14) disposed in a pressurized oil supply path (23), and a controller (17). The controller (17) controls the opening of the control valve (14) and rotation speed of the electric motor (4) which functions as an electric generator driven by the hydraulic pump (3) rotated by the action of the pressurized oil returning from the lift cylinder (1) when a load is lowered so that the generated electricity charges the battery (5) to recover the potential energy of the load.
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Citations
14 Claims
- 1. An energy recovering method in a hydraulic lift device of a battery operated industrial truck which is provided with a lift cylinder for lifting a lift means, an electric motor driven by a battery power source, a hydraulic pump for supplying pressurized working fluid to said lift cylinder to lift said lift means, and a control valve disposed between said lift cylinder and said hydraulic pump, whereby said electric motor is allowed to function as an electric generator driven by said hydraulic pump which is allowed to work as a hydraulic motor driven by pressurized working fluid returning from said lift cylinder to the hydraulic pump when a load on said lift means is lowered, and potential energy of the load is recovered as electric power to the battery, wherein lowering speed of said lift means is controlled by controlling the amount of opening of said control valve for controlling the flow rate of the pressurized working fluid returning to the hydraulic pump and rotation speed of said electric motor.
- 5. An energy recovering system in a hydraulic lift device of a battery operated industrial truck which is provided with a lift cylinder for lifting a lift means, an electric motor driven by a battery power source, a hydraulic pump for supplying pressurized working fluid to said lift cylinder to lift said lift means, and a control valve disposed between said lift cylinder and said hydraulic pump, whereby said electric motor is allowed to function as an electric generator driven by said hydraulic pump which is allowed to work as a hydraulic motor driven by pressurized working fluid returning from said lift cylinder to the hydraulic pump when a load on said lift means is lowered, and potential energy of the load is recovered as electric power to the battery, wherein are provided a controller which controls lowering speed of said lift means by controlling the amount of opening of said control valve for controlling the flow rate of the pressurized working fluid returning to said hydraulic pump and the rotation speed of said electric motor.
Specification