Negative-Pressure Pump Cleaning to Prevent Sliding-Member Sticking
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Solution Overview
Problem
The sliding members of negative pressure pumps in evaporative-fuel processing systems can become stuck due to the ingress of substances like salt, water, or abrasion powder, leading to misdiagnosis in on-board diagnostics.
Innovation Solution
A stuck-pump prevention device comprising a recovery-liquid generator, first and second on-off valves, and a control unit that executes cleaning control by opening the valves and driving the pump to intake a recovery liquid, which washes off accumulated substances when a predetermined condition is met, such as engine stoppage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pump operates continuously to maintain negative pressure for diagnostic purposes, then the diagnostic function is maintained, but the sliding member becomes stuck due to accumulation of salt, water, or abrasion powder
Solution Approach 1:
The system performs preliminary cleaning action by introducing recovery liquid into the pump before the sliding member becomes completely stuck. The control unit executes cleaning control at predetermined intervals or when sticking is detected, proactively removing accumulated substances before they cause diagnostic failures.
Solution Approach 2:
Recovery liquid serves as an intermediary substance that facilitates cleaning of the pump sliding member. The recovery liquid, generated by condensing low-boiling components from evaporative fuel, acts as a medium to wash off salt, water, and abrasion powder from the sliding member surfaces.
2Reliability
If cleaning control is executed frequently to prevent sticking, then the sliding member remains free of accumulated substances, but the canister load increases due to continuous removal of low-boiling components
Solution Approach 1:
The control unit monitors the operational state of the pump and executes cleaning control based on feedback conditions. Cleaning is triggered when predetermined conditions are met, such as detection of sticking or accumulation of substances, rather than continuously, thereby optimizing the balance between preventing sticking and minimizing canister load.
Solution Approach 2:
The system changes operational parameters by executing cleaning control only when necessary conditions are satisfied. The control unit adjusts the timing and frequency of cleaning operations based on monitored parameters, such as pump operation duration, detected sticking conditions, or accumulation levels, rather than maintaining fixed continuous cleaning.
3Use of energy by moving object
If the pump is stopped to reduce load, then energy consumption is reduced, but the sliding member becomes stuck due to lack of liquid flow for cleaning
Solution Approach 1:
The system performs preliminary cleaning action while the pump is still operating or immediately upon startup. By introducing recovery liquid at these critical moments, the system prevents sticking without requiring continuous pump operation, thereby reducing energy consumption while maintaining sliding member mobility.
Solution Approach 2:
Instead of continuous operation, the pump operates periodically with cleaning cycles interspersed between diagnostic operations. The control unit executes cleaning control at predetermined intervals or when sticking is detected, creating a periodic pattern that reduces overall energy consumption while preventing accumulation of harmful substances.
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
Prevents the sliding member of the pump from becoming stuck, thereby avoiding misdiagnosis and reducing the load on the canister by removing low-boiling components of evaporative fuel.
Implementation Method 1
cooling evaporative fuel generated in the fuel tank and condensing and recovering a low-boiling component of the fuel included in the evaporative fuel
Implementation Method 2
The pump is configured to generate negative pressure
Data Source
AI summary
A stuck-pump prevention device includes: a pump; a recovery-liquid generator coupled to a fuel tank and generating a recovery liquid by cooling evaporative fuel generated in the fuel tank and condensing and recovering a low-boiling component included in the evaporative fuel; a first pipe allowing a discharge port of the recovery-liquid generator and a recovery-liquid inlet of the pump to communicate with each other; a first on-off valve that opens and closes the discharge port of the recovery-liquid generator; a second on-off valve that opens and closes the recovery-liquid inlet of the pump; and a control unit that opens and closes the on-off valves and controls driving of the pump. When a predetermined cleaning-control execution condition is satisfied, the control unit executes cleaning control involving opening the on-off valves and driving the pump to cause the recovery liquid to be taken into the pump through the first pipe.