Hydraulic Steering Pump for Hybrid Forklift Idling Stop
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Solution Overview
Problem
Conventional hybrid forklifts face challenges in performing steering operations during idling stop without using complex mechanisms like planetary gears and clutches, as the existing configuration is insufficient to supply sufficient pressure oil to the steering hydraulic system when the engine is stopped.
Innovation Solution
The hybrid industrial vehicle incorporates a third electric motor to drive the second hydraulic pump, allowing for steering operation during idling stop, and a shared hydraulic line merges pressure oil from both hydraulic pumps to supply the cargo-handling and steering systems, enabling simultaneous operation without complex mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single hydraulic pump supplies both cargo-handling and steering systems, then device complexity is reduced, but steering operation during idling stop becomes impossible due to insufficient pressure oil supply
Solution Approach 1:
The hydraulic system is segmented into two independent pumps: a first hydraulic pump for cargo-handling operations and a second hydraulic pump for steering operations. This segmentation allows each pump to be independently controlled and sized for its specific function, enabling steering operation during idling stop while maintaining overall system manageability
Solution Approach 2:
The first hydraulic pump is designed with multi-functionality to supply pressure oil to both the cargo-handling hydraulic system and the steering hydraulic system. This universal pump can operate independently for cargo handling or in conjunction with the second pump for steering, providing flexible system operation modes
2Device complexity
If the first hydraulic pump supplies pressure oil to both cargo-handling and steering systems, then device complexity is reduced, but the pump cannot provide sufficient pressure oil for steering during engine stop
Solution Approach 1:
The hydraulic power supply is segmented between two pumps with the second hydraulic pump dedicated exclusively to steering operations. This ensures sufficient pressure oil supply for steering during idling stop while the first pump handles cargo-handling requirements
Solution Approach 2:
The second hydraulic pump is pre-configured and ready to supply pressure oil to the steering hydraulic system during idling stop conditions. This preliminary preparation ensures immediate steering capability when the engine stops, without waiting for alternative power sources
3Reliability
If a third electric motor is added to drive the second hydraulic pump, then steering operation during idling stop is enabled, but device complexity increases
Solution Approach 1:
The third electric motor replaces the need for mechanical power transmission from the engine to the second hydraulic pump during idling stop. This substitution of mechanical drive with electric drive enables steering operation independent of engine operation, achieving reliability without complex mechanical coupling mechanisms
4Adaptability or versatility
If pressure oil from both hydraulic pumps is merged on a shared hydraulic line, then system versatility is improved, but pressure oil flow control becomes more complex
Solution Approach 1:
The discharge sides of both hydraulic pumps are merged into a shared hydraulic line that supplies both cargo-handling and steering systems. This merging allows flexible operation modes where either pump can independently supply its designated system or both pumps can operate simultaneously to provide enhanced capability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enables steering and engine starting without complex mechanisms, ensures continuous vehicle operation even with gear train issues, and improves energy efficiency by reducing the need for frequent actuation of the second hydraulic pump.
Implementation Method 1
a first hydraulic pump supplying pressure oil to a cargo-handling hydraulic system
Implementation Method 2
a second hydraulic pump supplying pressure oil to a steering hydraulic system
Implementation Method 3
the pressure oil discharged from the first hydraulic pump and the pressure oil discharged from the second hydraulic pump are merged on a hydraulic line shared by the first hydraulic pump and the second hydraulic pump
Data Source
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AI summary
An object of the present invention is to provide a hybrid industrial vehicle which can perform steering operation and the like during idling stop, without using a complicated mechanism. To achieve the object, for example, the hybrid industrial vehicle configured to transmit power of a first electric motor (23) and power of an engine (21) to a drive wheel (34) through a first gear train (32) comprises: a second electric motor (24) actuated when supplied with electric power from a battery (22) ; a first hydraulic pump (26) supplying pressure oil to a cargo handling hydraulic system; a second gear train (28) interposed among the engine and the second electric motor and the first hydraulic pump and capable of mutual power transmission among the engine, the second electric motor and the first hydraulic pump; a second hydraulic pump (27) supplying pressure oil to a steering hydraulic system; and a third electric motor (25) actuated to drive the second hydraulic pump when supplied with electric power from the battery.