Hybrid Hydraulic Pump Drive With Dual-Speed Transmission Paths
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Solution Overview
Problem
Hydraulic systems in working machines are inefficient when using hydraulic pressure for driving tires or crawlers, and existing hybrid systems face challenges in maintaining hydraulic pump operation at varying engine rotational speeds.
Innovation Solution
A hybrid system with a transmission mechanism that includes multiple transmission paths and clutches to maintain hydraulic pump operation by adjusting engine rotational speed, using a mode switch and controller to select optimal power transmission paths based on engine speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the engine rotational speed is reduced to optimize generator output, then energy efficiency is improved, but the hydraulic pump operates below its optimal rotational speed
Solution Approach 1:
The power transmission system is segmented into multiple transmission paths (first transmission path and second transmission path) with different speed change ratios. The first transmission path connects the engine directly to the hydraulic pump, while the second transmission path includes a speed increasing mechanism. This segmentation allows selective engagement based on engine speed to maintain optimal hydraulic pump operation.
Solution Approach 2:
The transmission mechanism dynamically switches between different transmission paths based on engine rotational speed. When engine speed is high, the first transmission path is engaged; when engine speed is low, the second transmission path is engaged. This dynamic adaptation ensures the hydraulic pump receives appropriate rotational speed regardless of engine operating conditions.
2Device complexity
If a single transmission path is used from engine to hydraulic pump, then device complexity is reduced, but the system cannot maintain hydraulic pump operation across varying engine speeds
Solution Approach 1:
The transmission mechanism is designed with multi-functionality to handle different operating conditions. It can operate in two distinct modes: direct transmission when engine speed is sufficient, and speed-increasing transmission when engine speed is low. This universal design allows a single system to adapt to varying engine speeds without requiring completely different transmission configurations.
Solution Approach 2:
A speed increasing mechanism acts as an intermediary in the second transmission path. This intermediary component enables the system to bridge the gap between low engine rotational speed and the higher rotational speed required by the hydraulic pump, allowing operation across a broader range of engine speeds.
3Use of energy by moving object
If the engine rotational speed changes frequently between modes, then energy efficiency is optimized, but hydraulic pump flow rate may decrease during mode switches
Solution Approach 1:
The system prepares for mode transitions by maintaining both transmission paths in a ready state. The clutches are designed to engage and disengage smoothly, and the speed increasing mechanism is pre-configured to immediately take over when needed. This preliminary preparation ensures that mode switches occur without interruption to hydraulic pump operation.
Solution Approach 2:
The dual transmission path design ensures continuous power delivery to the hydraulic pump during mode transitions. While one transmission path is disengaging, the other is already prepared to engage, maintaining uninterrupted power flow. This continuity prevents flow rate decreases and ensures stable hydraulic pump operation throughout mode switches.
Data Source
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AI summary
A hybrid system (25) includes an engine (7), a generator (9) to be driven by the engine (7), an electric actuator (26) to be driven by electricity generated by the generator (9), a transmission mechanism (27) to transmit power from the engine (7), a hydraulic pump (17) to receive power from the engine (7) through the transmission mechanism (27) to deliver hydraulic fluid, and a hydraulic actuator (28) to be driven by hydraulic fluid delivered by the hydraulic pump (17). The transmission mechanism (27) includes a first transmission path (39) to transmit power from the engine (7) to the hydraulic pump (17) when a rotational speed of the engine (7) is a first rotational speed (R1), and a second transmission path (40) to transmit power from the engine (7) to the hydraulic pump (17) at a speed change ratio at which rotational speed is increased to a greater degree than the first transmission path (39) when the rotational speed of the engine (7) is a second rotational speed (R2) lower than the first rotational speed (R1).