Hydrodynamic Retarder Clutch Wear Reduction via Controlled Emptying
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Solution Overview
Problem
The frequent switching of hydrodynamic retarders in motor vehicles leads to high wear in the separating clutch, resulting in increased maintenance efforts due to incomplete emptying of the working chamber during transitions between braking and non-braking operations.
Innovation Solution
A method that ensures the hydrodynamic retarder's working chamber is completely or largely emptied before reconnecting the separating clutch during transitions from non-braking to braking operations by maintaining the clutch closed for a predetermined period, varying based on rotor speed, outlet pressure, degree of filling, temperature, and braking torque, to minimize wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the separating clutch is opened immediately upon detecting a retarder switch-off request, then the response time is reduced and the retarder is deactivated quickly, but the clutch wear increases due to frequent switching operations
Solution Approach 1:
The patent applies preliminary action by keeping the separating clutch closed for a predetermined time period after detecting a switch-off request, before actually opening it. This preliminary waiting period allows the working chamber to empty completely, ensuring that when the clutch does open, there is no residual working medium causing frictional slip bridging and excessive wear. The predetermined time is determined based on rotor speed and other parameters to optimize the balance between response time and clutch protection.
2Loss of time
If the working chamber is emptied quickly by reducing the predetermined time, then the switching response is faster, but the clutch wear increases due to incomplete emptying and frictional slip bridging
Solution Approach 1:
The patent applies dynamics by making the predetermined time period variable rather than fixed. The control device adjusts the predetermined time based on the current rotor speed and other operating parameters. When rotor speed is high, the predetermined time can be shorter because the pumping action empties the working chamber faster. When rotor speed is low, the predetermined time is extended to ensure complete emptying. This dynamic adjustment optimizes the balance between switching speed and clutch wear prevention.
3Reliability
If the separating clutch is kept closed for a longer predetermined period to ensure complete emptying, then clutch wear is reduced, but the retarder activation time increases
Solution Approach 1:
The patent applies parameter changes by adjusting the predetermined time period based on multiple parameters including rotor speed, temperature, and degree of filling of the working chamber. By monitoring these parameters in real-time, the control device can dynamically determine the optimal predetermined time that ensures complete emptying while minimizing activation time. This parameter-based adjustment resolves the contradiction by adapting the timing to actual operating conditions rather than using a fixed conservative value.
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 approach significantly reduces clutch wear by ensuring complete emptying of the working chamber, thereby extending the lifespan of the clutch and reducing maintenance needs.
Implementation Method 1
the emptying is effected partially or exclusively by means of the pumping action of the retarder or the rotor of the retarder
Data Source
Figure 1~2
AI summary
The invention relates to a method for controlling a hydrodynamic retarder in a motor vehicle. Said hydrodynamic retarder, which can be mechanically disengaged by a disconnect clutch, comprises a revolving bladed rotor and a bladed stator or a revolving bladed rotor and a counter-rotating bladed twin rotor which jointly form a working chamber that is filled with a working medium in a decelerating mode and is purged of the working medium in a non-decelerating mode. The rotor is driven via a drive train including an engaged disconnect clutch in the decelerating mode, and the working chamber is purged and the disconnect clutch is disengaged during the transition from the decelerating mode to the non-decelerating mode, said transition being initiated by having a driver assistance system request that the retarder be switched off or having a driver of the vehicle actuate an input device. The invention is characterized in that once it has been determined that there is a request to switch off the retarder, the disconnect clutch is kept in the engaged state over a predefined time period and the working chamber of the retarder is purged of the working medium by continuing to drive the rotor and interrupting the supply of working medium into the working chamber, said predefined time period being varied according to at least one of the following parameters or at least one parameter correlated with one of said parameters when and/or after determining that there is a request to switch off the retarder: - the rotor speed; - an outlet pressure against which the working medium is purged from the working chamber; - the fill level of the working medium in the working chamber; - the temperature of the working medium; - the deceleration moment of the hydrodynamic retarder.