Fuel Pump Drive Upstream of VCT Actuators
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Solution Overview
Problem
In engines with direct fuel injection, the high pressure fuel pump is typically driven downstream of hydraulic actuators used for variable cam timing, causing significant resistance that decreases the shifting velocity of the cam timing actuator, leading to degraded engine performance, emissions, and fuel economy.
Innovation Solution
A fuel pump drive system is actuated upstream of the hydraulic actuators, using an intermediate power transfer mechanism like a drive shaft to position the fuel pump resistance torque upstream of the actuators, thereby allowing more accurate adjustment of variable camshafts without affecting shifting velocity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the fuel pump is driven downstream of the hydraulic actuators, then the fuel pump can be integrated into the camshaft structure, but the resistance torque significantly decreases the shifting velocity of the VCT actuator
Solution Approach 1:
The patent segments the power flow path by introducing an intermediate power transfer mechanism that separates the fuel pump drive from the hydraulic actuator drive. This segmentation allows the fuel pump to be driven independently from the VCT actuators, eliminating the negative impact of fuel pump resistance torque on actuator shifting velocity while maintaining integration benefits.
Solution Approach 2:
The intermediate power transfer mechanism acts as a mediator between the camshaft and the fuel pump. By positioning this intermediary component upstream of the hydraulic actuators, the system transfers power to the fuel pump without requiring the hydraulic actuators to overcome additional resistance torque, thus preserving fast shifting velocity.
2Volume of moving object
If the fuel pump is driven downstream of the hydraulic actuators, then the structure is compact, but the transient control of valve timing is adversely affected
Solution Approach 1:
The power flow is segmented into independent paths: one path drives the hydraulic actuators for VCT control, and another path drives the fuel pump. This segmentation ensures that fuel pump operation does not interfere with the transient response of the valve timing control, improving reliability while maintaining compactness through shared mounting space.
Solution Approach 2:
The intermediate power transfer mechanism serves as a mediator that decouples the fuel pump drive from the hydraulic actuator drive. This intermediary arrangement allows the system to maintain compact packaging while ensuring that fuel pump resistance torque does not adversely affect the transient control performance of the variable cam timing system.
3Ease of operation
If the fuel pump is driven by the camshaft downstream of VCT actuators, then the fuel pump actuation is simplified, but the resistance torque must be overcome during camshaft phasing adjustments
Solution Approach 1:
The system segments the load paths by introducing an intermediate power transfer mechanism upstream of the hydraulic actuators. This segmentation creates independent power flow paths, allowing the fuel pump to be actuated simply while preventing its resistance torque from opposing camshaft phasing adjustments, as the fuel pump is now driven from a different point in the power flow.
Solution Approach 2:
The intermediate power transfer mechanism acts as an intermediary that redirects the power flow to drive the fuel pump from upstream of the hydraulic actuators. This intermediary arrangement maintains simple fuel pump actuation while eliminating the problematic resistance torque effect during VCT actuator operation, as the fuel pump is no longer part of the same power flow path.
Data Source
AI summary
A fuel pump drive system is provided. A system for an engine driven by an engine crankshaft may include a first variable cam device including a first hydraulic actuator, and a second variable cam device including a second hydraulic actuator. The system may further include an intermediate power transfer mechanism coupled between the first variable cam device and the second variable cam device upstream, in a direction of power flow from the engine crankshaft, of the first hydraulic actuator and the second hydraulic actuator. The system may further include an auxiliary device coupled to and driven by the intermediate power transfer mechanism. In this way, because the auxiliary device is driven via the intermediate power transfer mechanism and thus derives its power from upstream of the hydraulic actuator of the variable cam device, the actuator can be adjusted without having to overcome resistance torque of the auxiliary device.