专业英语3Word文档格式.docx

1、 Note the bronze female cone insert frictional face is not smooth, but consists of a series of tramline grooves which assist in cutting away the oil film so that a much larger synchronizing torque will be generated to speed up the process. 3.3.2 Positive baulk ring synchromesh unit （Fig. 36（a, b and

2、 c） The gearbox mainshaft rotates at propellor shaft speed and, with the clutch disengaged, the first motion shaft gear, layshaft cluster gears, and mainshaft gears rotate freely. Drive torque will be transmitted when a gear wheel is positively locked to the mainshaft. This is achieved by means of t

3、he outer synchromesh hub internal teeth which slide over the inner synchromesh hub splines （Fig. 36（a） until they engage with dog teeth formed on the constant mesh gear wheel being selected. When selecting and engaging a particular gear ratio, the gear stick slides the synchromesh outer hub in the d

4、irection of the chosen gear （towards the left）. Because the shift plate is held radially outwards by the two energizing ring type springs and the raised middle hump of the plate rests in the groove formed on the inside of the hub, the end of the shift plate contacts the baulking ring and pushes it t

5、owards and over the conical surface, forming part of the constant mesh gear wheel （Fig. 36（b）. The frictional grip between the male and female conical members of the gear wheel and baulking ring and the difference in speed will cause the baulking ring to be dragged around relative to the inner hub a

6、nd shift plate within the limits of the clearance between the shift plate width and that of the recessed slot in the baulking ring. Owing to the designed width of the shift plate slot in the baulking ring, the teeth on the baulking ring are now out of alignment with those on the outer hub by approxi

7、mately half a tooth width, so that the chamfered faces of the teeth of the baulking ring and outer hub bear upon each other. As the baulking ring is in contact with the gear cone and the outer hub, the force exerted by the driver on the gear stick presses the baulking ring female cone hard against t

8、he male cone of the gear. Frictional torque between the two surfaces will eventually cause these two members to equalize their speeds. Until this takes place, full engagement of the gear and outer hub dog teeth is prevented by the out of alignment position of the baulking ring teeth. When the gear w

9、heel and main shaft have unified their speeds, the synchronizing torque will have fallen to zero so that the baulking ring is no longer dragged out of alignment. Therefore the outer hub can now overcome the baulk and follow through to make a positive engagement between hub and gear （Fig. 36（c）. It s

10、hould be understood that the function of the shift plate and springs is to transmit just sufficient axial load to ensure a rapid bringing together of the mating cones so that the baulking ring dog teeth immediately misalign with their corresponding outer hub teeth. Once the cone faces contact, they

11、generate their own friction torque which is sufficient to flick the baulking ring over, relative to the outer hub. Thus the chamfers of both sets of teeth contact and oppose further outer hub axial movement towards the gear dog teeth. 3.3.3 Positive baulk pin synebromesh unit （Fig. 37（a, b, c and d）

12、 Movement of the selector fork synchronizing sleeve to the left （Fig. 37（a and b） forces the female （internal） cone to move into contact with the male （external） cone on the drive gear. Frictional torque will then synchronize （unify） the input and output speeds. Until speed equalization is achieved,

13、 the collars on the three thrust pins （only one shown） will be pressed hard into the enlarged position of the slots （Fig. 3 5（c） in the synchronizing sleeve owing to the frictional drag when the speeds are dissimilar. Under these conditions, unless extreme pressure is exerted, the dog teeth cannot b

14、e crushed by forcing the collars into the narrow portion of the slots. However, when the speeds of the synchromesh hub and drive gear are equal （synchronized） the collars tend to float in the enlarged portion of the slots, there is only the pressure of the spring loaded balls to be overcome. The col

15、lars will then slide easily into the narrow portion of the slots （Fig. 35（d） allowing the synchronizer hub dog teeth to shift in to mesh with the dog teeth on the driving gear. 3.3.4 Split baulk pin synebromesh unit .（Fig. 38（a, b, c and d） The synchronizing assembly is composed of two thick bronze

16、synchronizing rings with tapered female conical bores, and situated between them is a hardened steel drive hub internally splined with external dog teeth at each end （Fig. 38（a）. Three shouldered pins, each with a groove around its centre, hold the bronze synchronizing cone rings apart. Alternating

17、with the shouldered pins on the same pitch circle are diametrically split pins, the ends of which fit into blind bores machined in the synchronizing cone rings. The pin halves are sprung apart, so that a chamfered groove around the middle of each half pin registers with a chamfered hole in the drive

18、 hub. If the gearbox is in the neutral position, both sets of shouldered and split pins are situated with their grooves aligned with the central drive hub （Fig. 38（a and b）. When an axial load is applied to the drive hub by the gear stick, it moves over （in this case to the left） until the synchroni

19、zing ring is forced against the adjacent first motion gear cone. The friction （synchronizing） torque generated between the rubbing tapered surfaces drags the bronze synchronizing ring relative to the mainshaft and drive hub until the grooves in the shouldered pins are wedged against the chamfered ed

20、ges of the drive hub （Fig. 38（c） so that further axial movement is baulked. Immediately the input and output shaft speeds are similar, that is, synchronization has been achieved, the springs in the split pins are able to expand and centralize the shouldered pins relative to the chamfered holes in th

21、e drive hub. The drive hub can now ride out of the grooves fomed around the split pins, thus permitting the drive hub to shift further over until the internal and external dog teeth of both gear wheel hub mesh and fully engage （Fig. 38（d）. 3.3.5 Split ring synebromesh unit （Fig. 3.9（a, b, c and d） I

22、n the neutral position the sliding sleeve sits centrally over the drive hub （Fig. 39（a）. This permits the synchronizing ring expander band and thrust block to float within the constraints of the recess machine in the side of the gear facing the drive hub （Fig. 39（b）. For gear engagement to take plac

23、e, the sliding sleeve is moved towards the gear wheel selected （to the left） until the inside chamfer of the sliding sleeve contacts the bevelled portion of the synchronizing ring. As a result, the synchronizing ring will be slightly compressed and the friction generated between the two members then

24、 drags the synchronizing ring round in the direction of whichever member is rotating fastest, be it the gear or driven hub. At the same time, the thrust block is pulled round so that it applies a load to one end of the expander band, whilst the other end is restrained from moving by the anchor block

25、 （Fig. 3.9（c）. Whilst this is happening the expander is also pushed radially outwards. Consequently, there will be a tendency to expand the synchronizing slit ring, but this will be opposed by the chamfered mouth of the sliding sleeve. This energizing action attempting to expand the synchronizing ri

26、ng prevents the sliding sleeve from completely moving over and engaging the dog teeth of the selected gear wheel until both the drive hub and constant mesh gear wheel are revolving at the same speed. When both input and output members are unified, that is, rotating as one, there cannot be any more f

27、riction torque because there is no relative speed to create the frictional drag. Therefore the expander band immediately stops exerting radial force on the inside of the synchronizing ring. The axial thrust applied by the gear stick to the sliding sleeve will now be sufficient to compress the split

28、synchronizing ring and subsequently permits the slee曹操曹操曹操非凡方法ve to slide over the gear wheel dog teeth for full engagement （Fig. 39（d）. 3.4 Remote controlled gear selection and engagement mechanisms Gear selection and engagement is achieved by two distinct movements: 1 The selection of the required gear shift gate and the positioning of the engagement gate lever. 2 The shifting of the chosen selector gate rod into the engagement gear position. These two operations are generally performed through the media of the g