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Power Transmission, Brakes and Cooling Systems
Published in Iqbal Husain, Electric and Hybrid Vehicles, 2021
The manual transmission is a gear train with several shafts, countershafts, spur gears, synchronizers and safety devices to facilitate multiple gear ratios for power transmission from engine to the drive shaft. Different gear meshes lock and unlock through the use of clutch, gear lever, synchronizer and the lock/unlock mechanisms in the transmission [3]. The simplified schematic of a four-speed manual transmission is shown in Figure 14.15. The transmission has the input shaft, output shaft, one countershaft, eight gears, an idler and two synchronizers. The functions of the synchronizer are to ensure that the driving gear and the shaft are rotating at the same speed prior to engagement, and then to lock the gear to the shaft after engagement. The synchronizer eliminates the need for double clutches.
Getting Power to the Pavement
Published in Patrick Hossay, Automotive Innovation, 2019
The basic design of a manual transmission itself is defined by three shafts: an input shaft connected to the clutch; an output shaft, also called a main shaft; and what is called a layshaft or countershaft (since it counter rotates). Gears are mounted to the layshaft and rotate as one unit (Image 3.9). The gears on the output shaft rotate independently but are always meshed with the layshaft gears. The output shaft is splined, and between each gear is a ring, called a collar, that incorporates a cone-shaped clutch mechanism, called a synchronizer and dogteeth. As the collar slides toward a selected gear, initial engagement of the synchronizer allows a smooth friction contact so both gear and shaft are rotating at the same speed prior to engagement of the teeth that lock the gear to the shaft. This gear now defines the driving gear ratio, as other gears on the output shaft spin freely. Placing an additional gear, called an idler gear, between a layshaft gear and reverse gear on the output shaft, enables reverse.
Automotive Transmissions and Drive Trains
Published in Don M. Pirro, Martin Webster, Ekkehard Daschner, Lubrication Fundamentals, 2017
Don M. Pirro, Martin Webster, Ekkehard Daschner
Sliding element transmissions are typically used in only low speed applications, such as tractors. In this application, the clutch must be disengaged and the vehicle must be at a complete stop before the gears can be engaged or the gear ratio changed. For other applications, syncromesh or synchronized transmissions are used. In this type of transmission, all gears are always in mesh, except the reverse gear. One of each pair of gears is free to revolve on its shaft unless locked to it by a clutching mechanism called a synchronizer as shown in Figure 11.2. The synchronizer, which is keyed or splined to the shaft, consists of a friction clutch and a dog clutch. As the shift fork moves the synchronizer toward the gear, the friction cones make contact first to bring the shaft to the same rotational speed as the gear. The outer rim of the clutch gear then slides over its hub, causing a set of internal teeth to engage with a set of teeth (dogs) on the side of the gear. This then provides a positive mechanical connection between the gear and shaft.
Performance improvement of a transmission synchronizer via sensitivity analysis and Pareto optimization
Published in Cogent Engineering, 2018
Muhammad Irfan, Viktor Berbyuk, Håkan Johansson
A prominent problem in synchronizer design is the case of transmission vibrations. To study the effect of transmission vibration on synchronizer performance it is assumed that the sleeve rotational speed is subject to periodic excitation. Therefore, we here study the effect of a periodic variation of the master rotational speed as follows: