Variable Valve Actuation Device with Mechanical Blocking Mechanism
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Solution Overview
Problem
Existing variable valve actuation devices for engines face challenges at high speeds due to short switching times and variability in response times, leading to potential damage and inconsistency in rocker arm mechanism operation, especially when the camshaft rotational speed is high, and errors in cam position sensing can cause switching failures.
Innovation Solution
The device incorporates a rocker arm mechanism with a widened roller mounting space, an actuation mechanism using a small compressed air cylinder, and a blocking mechanism with a control cam and blocking rod to ensure the rocker arm roller can only switch within a safe region, eliminating the need for precise timing control by the ECU and reducing the impact of response time variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the camshaft rotational speed is increased to improve engine productivity, then the switching time for the rocker arm roller becomes too short, causing incomplete switching and potential damage to the rocker arm mechanism
Solution Approach 1:
The control cam is designed to advance the blocking mechanism action before the rocker arm roller reaches the switching zone. By preemptively positioning the blocking rod to prevent premature switching attempts, the system ensures that switching can only occur when sufficient time is available, even at high engine speeds. This preliminary positioning of the blocking mechanism resolves the contradiction by ensuring reliable switching conditions are met before the switching event is attempted.
2Manufacturing precision
If ECU software logic is added to control solenoid valve timing based on camshaft position to improve switching precision, then device complexity increases and response time variability still affects performance
Solution Approach 1:
The invention replaces the complex electronic control system (ECU, cam position sensors, solenoid valves with variable response times) with a purely mechanical solution. The control cam mechanically controls the blocking rod to prevent switching in prohibited zones, while the permissive zone automatically allows switching when conditions are right. This mechanical substitution eliminates software complexity and removes sensitivity to electronic response time variations, as the control is inherent in the mechanical geometry of the control cam profile.
3Loss of time
If the solenoid valve response time is reduced to improve switching timing accuracy, then manufacturing consistency becomes more difficult due to part variability and environmental factors
Solution Approach 1:
The blocking mechanism is designed to be self-regulating based on the mechanical state of the system. The control cam automatically positions the blocking rod to prevent switching in prohibited zones without requiring timed activation. The system serves itself by using the inherent mechanical relationships between the control cam, blocking rod, and rocker arm roller to ensure proper timing, eliminating the need for precisely controlled actuator response times and reducing sensitivity to manufacturing variations.
Data Source
AI summary
A variable valve actuation device for an engine includes a rocker arm mechanism, a camshaft, an actuation mechanism and a blocking mechanism. The rocker arm roller can slide on a roller shaft so as to have two operating positions, a first cam and a second cam which are adjacent are provided on the camshaft, the rocker arm mechanism is actuated, based on the different operating positions of the rocker arm roller, by the first cam or the second cam, respectively, to enable the engine to have two valve lifts, a control cam is further provided on one side of the first cam or the second cam, the control cam can actuate the blocking mechanism, and the rocker arm roller is blocked from switching in a switching prohibited portion of the first cam and the second cam, and is allowed to switching in a non-switching prohibited portion.