Variable Capacity Oil Pump Speed Control
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Solution Overview
Problem
Conventional oil pressure systems experience significant loss of engine horsepower due to excessive pressure oil being fed to low-pressure circuits, leading to inefficiencies and increased relief pressure, especially at varying engine rotational speeds.
Innovation Solution
An oil pressure system with a flow passage changeover valve and a relief pressure changeover unit that adjusts the relief pressure based on engine speed, switching between merging and branching states to optimize oil distribution and reduce relief pressure, incorporating a pilot pressure control system to manage the relief valve's operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a fixed-capacity pump is used to supply pressure oil to the high-pressure circuit, then the required oil quantity can be supplied at low-idle rotational speed, but excessive pressure oil is fed to the low-pressure circuit via the relief valve, causing significant engine horsepower loss
Solution Approach 1:
The patent applies a variable-capacity pump instead of a fixed-capacity pump, allowing the discharge quantity to be dynamically adjusted according to engine rotational speed. At low-idle speeds, the pump supplies the required minimum oil quantity, while at higher speeds, it automatically reduces the discharge quantity to match actual demand, preventing excessive oil from being diverted through the relief valve and reducing horsepower loss.
Solution Approach 2:
The patent changes the operational parameters of the oil pump by using a variable-capacity design that adjusts discharge volume based on rotational speed. This parameter change allows the system to optimize oil supply quantity across different operating conditions, ensuring sufficient lubrication at low speeds while avoiding over-suppression at high speeds that would cause relief valve activation and energy loss.
2Reliability
If the relief valve is set to a high relief pressure to maintain high-pressure circuit pressure, then the high-pressure circuit can operate reliably, but the loss of engine horsepower increases due to excessive pressure oil being fed to the low-pressure circuit
Solution Approach 1:
The variable-capacity pump dynamically adjusts its discharge quantity to match the actual demand of the high-pressure circuit. By reducing the pump's discharge at higher rotational speeds, the system maintains adequate pressure for reliable high-pressure circuit operation while preventing the over-pressurization that would force excessive oil through the relief valve, thereby reducing horsepower loss.
Solution Approach 2:
The patent converts the potential harm of over-supplying pressure oil into a benefit by using the variable-capacity pump to intentionally limit discharge quantity. This prevents the relief valve from needing to operate at high flow rates, transforming what would be a harmful energy loss into a controlled, minimal-pressure relief scenario that maintains reliability while reducing horsepower loss.
3Quantity of substance
If a low-capacity high-pressure pump and a high-capacity low-pressure pump are used, then the required oil quantity can be supplied at various rotational speeds, but the system complexity increases due to the need for a flow passage changeover valve and relief pressure changeover unit
Solution Approach 1:
The patent uses a single variable-capacity pump that performs multiple functions: it supplies pressure oil to both the high-pressure circuit and the low-pressure circuit as needed. This eliminates the need for separate high-pressure and low-pressure pumps, thereby reducing system complexity while maintaining the ability to supply appropriate oil quantities to both circuits across various rotational speeds.
Solution Approach 2:
The patent extracts and eliminates the unnecessary low-pressure pump from the system. By using a variable-capacity high-pressure pump that can directly supply both circuits, the design removes the complex flow passage changeover valve and relief pressure changeover unit that would be required to coordinate two separate pumps, thereby simplifying the overall system while maintaining adequate oil supply.
4Stress or pressure
If the relief valve constantly operates at high relief pressure, then the high-pressure circuit pressure is maintained, but the durability of the system decreases due to increased horsepower loss and excessive pressure oil delivery
Solution Approach 1:
The variable-capacity pump dynamically adjusts discharge quantity to match actual circuit demands, preventing the constant over-pressurization that would force the relief valve to operate continuously at high pressure. This reduces the mechanical stress and thermal load on the relief valve and surrounding components, thereby improving system durability while maintaining adequate high-pressure circuit pressure when needed.
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 reduces engine horsepower loss by optimizing oil flow and pressure distribution, suppressing excessive pressure oil delivery to high-pressure circuits and adjusting relief pressure accordingly, enhancing system efficiency and durability.
Implementation Method 1
The relief valve 205 closes the relief flow passage 204 when the pressure of the pressure oil that flows through the first flow passage 203 is at a predetermined relief pressure or less, and opens the relief flow passage 204 when the pressure of the pressure oil that flows through the first flow passage 203 is greater than the relief pressure
Implementation Method 2
a pilot pressure control unit 22 that supplies or releases pressure oil to or from the pilot flow passage 19
Implementation Method 3
the pressing member 42 presses the urging member 35 of the relief valve 8 when a predetermined pilot pressure is produced in the pilot flow passage 19, thereby changing the relief pressure from low relief pressure to high relief pressure
Data Source
AI summary
In the oil pressure system, a control unit sets a flow passage changeover valve to be in a merging state, and sets a relief pressure to a low relief pressure via a relief pressure changeover unit in the case that the rotational speed of the engine is lower than a predetermined threshold level. Also, the control unit sets the flow passage changeover valve to be in a branching state, and sets the relief pressure to a high relief pressure via the relief pressure changeover unit in the case that the rotational speed of the engine is the predetermined threshold level or higher.