Fluid Pressure Circuit Pump Load Reduction
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Solution Overview
Problem
Conventional hydraulic static transmission (HST) circuits for vehicles, particularly wheel loaders, face high durability requirements due to frequent use and high loads, and the accumulator-based systems have limited oil accumulation and pressure, restricting continuous high-load operation of the hydraulic motor.
Innovation Solution
A fluid pressure circuit with a variable capacity pump, motor, accumulator, and switching valve configuration that allows pressure fluid accumulation in a separate accumulator and timely supply to the motor, reducing the load on the pump and enhancing energy efficiency by minimizing the tilting amount of the swash plate during accumulator-driven operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If the hydraulic pump operates continuously to drive the hydraulic motor during high-load conditions, then the motor can maintain operation, but the pump durability deteriorates due to repeated high loads
Solution Approach 1:
The accumulator stores high-pressure oil in advance during low-load periods, so that when high-load conditions occur, the stored oil can be immediately supplied to the hydraulic motor without requiring the pump to operate at high load. This preliminary accumulation of energy allows the pump to remain idle or operate at low load during critical high-demand periods, extending pump life while maintaining continuous motor operation.
2Reliability
If an accumulator is used to store high-pressure oil, then the pump load can be reduced, but the accumulation capacity and pressure are limited by vehicle traveling state
Solution Approach 1:
A switching valve is introduced as an intermediary component to control the connection between the accumulator, pump, and motor. This valve enables flexible routing of oil flow, allowing the system to switch between pump-driven mode and accumulator-driven mode based on operational requirements. The switching mechanism resolves the limitation of fixed accumulation capacity by enabling dynamic supplementation from the pump while maintaining the pressure-reduction benefit during accumulator discharge phases.
3Power
If the switching valve connects the accumulator to the hydraulic motor, then the pump load is reduced, but the pump cannot supplement the accumulator during this period
Solution Approach 1:
The switching valve dynamically changes connection configurations based on real-time operational needs. When the motor requires high power, the valve connects the accumulator to the motor and isolates the pump. When the accumulator needs replenishment, the valve reconfigures to connect the pump to the accumulator. This dynamic switching enables the system to optimize between immediate power delivery and energy accumulation, resolving the contradiction between reducing pump load and maintaining accumulation 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
The solution reduces the load on the fluid pressure pump, improves durability, and enhances energy efficiency by allowing the hydraulic motor to operate with accumulated pressure fluid, especially during high-load conditions, such as when dirt enters the wheel loader bucket.
Implementation Method 1
an accumulator pump (11) to accumulate pressure fluid in the accumulator (10)
Implementation Method 2
a variable capacity fluid pressure pump (1) to be driven by a mechanism to perform forward-reverse rotation, a fluid pressure motor (4) to be driven by fluid discharged from the fluid pressure pump (1)
Data Source
Figure 1
Figure 2
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AI summary
Provided is a fluid pressure circuit capable of reducing a load on a fluid pressure pump. A fluid pressure circuit 120 includes an HST circuit 121 having a variable capacity fluid pressure pump 1 to be driven by a mechanism 110 to perform forward-reverse rotation, a fluid pressure motor 4 to be driven by fluid discharged from the fluid pressure pump 1 to perform forward-reverse rotation, a first line 3 configured to connect a first port of the fluid pressure pump 1 and a first port of the fluid pressure motor 4, and a second line 5 configured to connect a second port of the fluid pressure pump 1 and a second port of the fluid pressure motor 4; an accumulator 10 connected in parallel with the fluid pressure pump 1; an accumulator pump 11 configured to accumulate pressure fluid in the accumulator 10; and an accumulator switching valve 14, 20, 25 configured to switch connection between the fluid pressure motor 1 and the accumulator 10.