Engine Braking Valve Fixing Mechanism
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Solution Overview
Problem
In engine braking mode, hydraulic valve clearance compensating elements in internal combustion engines can 'pump up' due to indifferent movement sequences and valve jumping, leading to unreliable closure of exhaust valves.
Innovation Solution
A device with a fixing mechanism, such as an electromagnet or friction brake, is introduced to control the actuating element, ensuring it is fixed during engine braking mode to prevent unwanted valve opening and maintain a reliable valve train operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hydraulic valve clearance compensating element (HVA) is used in engine braking mode, then valve clearance compensation is improved, but the HVA element pumps up due to indifferent movement sequences and valve jumping, causing unreliable valve closure
Solution Approach 1:
The patent applies a dynamic fixing device that can be activated and deactivated based on operating conditions. During engine braking mode, the fixing device is activated to prevent HVA element pumping up, and deactivated during normal operation to allow proper valve clearance compensation. This dynamic switching resolves the contradiction by adapting the system behavior to different operational states.
Solution Approach 2:
The fixing device acts as an intermediary between the cam and the actuating element, providing temporary fixation during engine braking mode. This intermediary mechanism prevents the harmful pumping up effect while allowing the HVA element to function normally during regular operation, thus resolving the stability-reliability contradiction.
2Reliability
If the actuating element is fixed continuously to prevent pumping up, then valve closure reliability is improved, but regular engine operation is impaired due to delayed fixation and loss of HVA adjustment effect
Solution Approach 1:
The fixing device is activated periodically only during engine braking mode when the cam base circle is traversed, and deactivated during normal operation. This periodic activation ensures that the fixing effect is applied only when needed, preventing pumping up during engine braking while maintaining full adaptability during regular engine operation.
Solution Approach 2:
The system changes its operational parameters based on the operating mode. During engine braking, the fixing device is activated to provide rigid fixation. During normal operation, the fixing device is deactivated to allow the HVA element to adjust valve clearance dynamically. This parameter change resolves the contradiction between reliability and adaptability.
3Reliability
If a fixing device is introduced to control the actuating element during engine braking, then valve closure reliability is improved, but device complexity increases
Solution Approach 1:
The patent employs an electromagnet as the fixing device, replacing a purely mechanical solution with an electromagnetic one. The electromagnet can be activated and deactivated electrically based on operating conditions, providing a relatively simple and reliable fixing mechanism that adds minimal complexity to the valve train system.
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 solution prevents the undesired pumping up of compensating elements, ensuring reliable valve closure and maintaining the function of engine braking without impairing regular engine operation.
Implementation Method 1
A device with a fixing mechanism, such as an electromagnet or friction brake, is introduced to control the actuating element
Implementation Method 2
A device with a fixing mechanism, such as an electromagnet or friction brake, is introduced to control the actuating element
Data Source
Figure 1
AI summary
Device and method for actuating at least one exhaust valve of an internal combustion engine, with an actuating element (6) driven by a camshaft, in particular a rocker arm as the actuating element, wherein a first, preferably hydraulically actuated, piston-cylinder unit (15) is included in the force flow between a cam (4) of the camshaft and at least one exhaust valve (2), by means of which at least one exhaust valve (2) can be held in an open intermediate position during engine braking with exhaust backpressure, and with a second piston-cylinder unit (11) which is designed as a, preferably hydraulic, valve lash compensating element (VFE).According to the invention, at least one fixing device (23; 24) for fixing the actuating element (6) is provided in the force flow between the cam (4) and the exhaust valve (2), wherein the fixing device (23; 24) is designed and/or can be controlled in such a way that it is activated during engine braking operation when passing through the cam base circle (4) and accordingly the actuating element (6) is fixed in position and that it is deactivated during engine braking operation when passing through the cam (4) and accordingly the position fixing of the actuating element (6) is removed.