Hydraulic Pump Flow Control for Hybrid Work Machine High Load
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Solution Overview
Problem
Hybrid work machines with small-sized engines face depletion of electric power in heavy load work, leading to continuous electric discharge from the storage device, which can cause unusual operational feelings for the operator and limit machine performance.
Innovation Solution
A hybrid work machine with a pump flow rate control device that gradually decreases the hydraulic pump's delivery flow rate when in a high load operation state for an extended period, preventing continuous electric discharge from the storage device without causing operational discomfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a small-sized engine is used to reduce fuel consumption, then fuel efficiency is improved, but the engine cannot provide sufficient power for heavy load work
Solution Approach 1:
The patent combines a small-sized engine with an assist motor to create a hybrid power system. The assist motor supplements the engine's output power during heavy load work, enabling the use of a smaller engine while maintaining sufficient total power output for both light and heavy load conditions.
Solution Approach 2:
The system dynamically changes the operating parameters by switching between engine-only operation for light load work and hybrid operation (engine + assist motor) for heavy load work. This allows optimization of fuel consumption during light load while providing sufficient power during heavy load.
2Power
If the assist motor operates continuously during heavy load work to supplement engine power, then sufficient power output is maintained, but the electric storage device becomes depleted
Solution Approach 1:
The control device operates the assist motor in periodic cycles rather than continuously. During heavy load work, the assist motor operates intermittently to supplement engine power when needed, then stops to allow the electric storage device to recharge, preventing complete depletion while maintaining sufficient average power output.
Solution Approach 2:
The control device monitors the charge level of the electric storage device and adjusts assist motor operation accordingly. When the storage device approaches depletion, the control device reduces or stops assist motor operation to prevent complete depletion, using feedback from the storage device's state to modulate power assistance.
3Productivity
If the pump operates at high flow rate during heavy load work, then work capability is improved, but electric power is depleted faster
Solution Approach 1:
The hydraulic pump's delivery flow rate is made dynamic rather than fixed. The control device adjusts the flow rate based on actual work requirements and the charge level of the electric storage device, allowing high flow rate when work capability is needed and reducing flow rate when electric power is low, optimizing both productivity and energy usage.
4Quantity of substance
If the assist motor operates during light load work to charge the storage device, then electric power is accumulated, but fuel consumption increases
Solution Approach 1:
The assist motor operates partially during light load work rather than continuously. The control device determines optimal moments to operate the assist motor for charging the storage device, using it only when beneficial for accumulating electric power without significantly increasing fuel consumption, rather than excessive continuous operation.
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 solution effectively suppresses continuous electric discharge during high load pressure operations, ensuring the hybrid work machine can perform heavy load tasks without depleting the electric storage device and maintaining operational comfort.
Implementation Method 1
an assist motor (3), a hydraulic pump (41a, 41b) driven by a total torque of the engine (22) and the assist motor (23), and an electric storage device (24) that accumulates electric power generated by the assist motor (23)
Data Source
Figure 1
Figure 2
Figure 3
AI summary
In a hybrid work machine including an engine, an assist motor, a hydraulic pump which is driven by total torque of the engine and the assist motor, and an electric storage device which accumulates electric power generated by the assist motor and supplies the electric power when the assist motor performs electric discharge, the continuous electric discharge from the electric storage device due to continuous operation at high load pressure can be suppressed without causing an unusual operational feeling for the operator. To this end, a pump flow rate control unit 82 of a controller 80 includes a pump flow rate correction control unit 82b which judges whether each hydraulic pump 41a, 41b is in a high load operation state or not based on the output horsepower of at least one of the hydraulic pumps 41a and 41b and/or the delivery pressure of each hydraulic pump and performs control such that the delivery flow rate of the hydraulic pump 41a or 41b gradually decreases when the hydraulic pump 41a or 41b is in the high load operation state and the high load operation state continues beyond a predetermined time.