| 1. |
- Holgerson, Mikael, et al.
(författare)
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Engagement behaviour of a paper-based wet clutch Part 1: Influence of drive torque
- 1999
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Ingår i: Proceedings of the Institution of mechanical engineers. Part D, journal of automobile engineering. - : SAGE Publications. - 0954-4070 .- 2041-2991. ; 213:4, s. 341-348
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Tidskriftsartikel (refereegranskat)abstract
- Owing to increasing demands when designing wet clutches for automatic transmissions, more knowledge about their behaviour is needed. In cars with power shifting automatic transmissions, an engine torque is continuously transmitted through the gear box. Most experimental and theoretical work concerning investigations of wet clutches today uses the inertia type of test apparatus, e.g. the SAE test machine 2. However, this type of test machine has no possibility of investigating the influence of a drive torque from the power supply. In order to investigate the influence of drive torque on wet clutch engagements, a new type of apparatus was built, which can operate with different combinations of inertia and drive torque. This apparatus can perform engagements more similar to those in automatic transmissions. The aim of this paper was to compare experimental outputs obtained using these principles of testing, concerning the influence of drive torque. It was found that the friction characteristics of wet clutches are independent of how the input energy is produced. This means that friction can be investigated with both principles. It was also found that an apparatus using only inertia gives shorter engagement times and higher temperatures than an apparatus including a drive torque at the same level of input energy. This can be explained by different power characteristics. Therefore, when investigating temperatures of wet clutch engagements, one must be careful when translating the results into reality.
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| 2. |
- Holgerson, Mikael, et al.
(författare)
-
Engagement behaviour of a paper-based wet clutch Part 2: Influence of temperature
- 1999
-
Ingår i: Proceedings of the Institution of mechanical engineers. Part D, journal of automobile engineering. - : SAGE Publications. - 0954-4070 .- 2041-2991. ; 213:5, s. 449-455
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Tidskriftsartikel (refereegranskat)abstract
- To increase comfort, performance and fuel economy, a more careful optimization of automatic transmissions is needed. Of special interest is how the temperature influences the engagement characteristics. In order to increase the level of knowledge in this area, a wet clutch test rig including a drive torque and inertia was used. The temperature and the developed energy were varied in order to investigate their influence on the characteristics of an engagement. As a consequence the influence of instant temperature, maximum temperature and instant normal force was also studied. Some of the most important conclusions of the investigation are that both the dynamic and static friction coefficients slightly decrease and the engagement time increases with increasing temperature. It was also found that the static and dynamic friction coefficients are not influenced by energy if the instant temperature is the same. An important parameter that describes the risk of stick-slip is the quotient between the static and dynamic friction. It was found that this quotient decreases with increasing temperature, and thus the risk of stick-slip is also supposed to decrease.
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