车辆与动力工程学院毕业设计说明书Power takeoff shaftThe power takeoff shaft usually called simply the power takeoff ,provides a means to drive the machine that are being towed by the tractor .the engine power of the tractor is being used not only to pull or carry the machine ,but also to operate it .typical exampled of machines that are power driven are mowers .,balers ,combine.potato harvests ,and manure spreader .the PTO provides a very useful source of power .and the alternative would be to fit an engine to each of these machine .this is ,of course done where the power required to drive the machine may be greater than the tractor can be supply. Generally most machines can be powered by the tractor . Power take off shaft are calssifily according to their location of the tractor,type of the drive .rotation speed ,and method of control . Most tractor are equipped with a rear PTO.some of them have a front PTO ,ROW-tractor use both a rear and a side PTO . AS to the type of drive, power take off shaft are classed as transmission drive .live ,semi-independent ,and ground-speed type ,the transmission drive PTO IS driven from the tractor transmission and so it will stop rotating whenever the engine clutch is disengage .The live PTO is driven from the engine crankshaft through the clutch driving member irrespective of the position of the clutch .the semi-independent PTO WILL continue to operate while the driver is shifting gears , but is incapable of being engaged or disengaged while the tractor is moving .the ground-speed PTO has its speed proportional to the ground speed of the tractor .such A PTO finds application on row-crop tractors to operate machine .such as mounted drills .whose working rate must be in synchronism with the ground speed of the tractor .The power takeoff are standardized at 540 and 1000rpm (AT nominal engine speed )the spined ends of PTO shaft of all tractor are of one and same size and are arranged at one and the same level relative to the tractor support surface .when the PTO Shaft is not used ,its end is covered by a guard stamped from sheet steel. Power takeoff shaft may be control by either mechanical or hydraulic means Live PTO shaft can be engage or disengage on the run by hydraulic or complex mechanical means.When the PTO is disengage , sun gear brake is released and planet carrier is applied. In this case ,PTO shaft is held stationary and the planet gear transmit rotation from the internal gear to the sun gear .When the PTO is engaged. sun gear brake is applied and planet carrier is released. The planet gears now have to walk around the sun gear .as the planet gears roll around the sun gear.they carry the planet carrier around with them .thus driving the PTO shaft which is rigidly connected the planer carrier.When the PTO is not used the PTO control lever is placed into its neutral (central) position. In this case.both the sun gear and the planet carrier brakes are released.Toothed clutch 1 inserted into the PTO driving line makes it possible to have either independent or ground-speed power takeoff. The clutch is operated by a control lever and can be placed into three different positions. When the clutch is shifted all the way forward (to the left .as shown in Fig.165a), drive shaft 9(see Fig.164) of the PTO nit is connected to the transmission main(output) shaft to obtain ground-speed power takeoff. If the clutch is moved all the way backward (to the right .as shown in Fig.165b). the drive shaft of the PTO unit will be connected to the engine crankshaft, and so power takeoff will be independent. With the clutch in its neutral (central) position . no drive is transmitted to the PTO unit.To place the clutch into the “GROUND-SPEED PTO”position, one should disengage the engine clutch, whereas placing it into the “LIVE PTO”position required that the engine should be stopped.THE HYDRAULICALLY CONTROLLED PTO UNIT (Fig.166) includes a planetary gear set and a self-contained hydraulic system. The unit is contained in a case that is attached to the rear axle housing of the tractor.The reduction gear set of the PTO unit comprises drive gear 3 carried on shaft 1 and driven gear 9 and hydraulic clutch 10 that are mounted on PTO shaft 5. The shafts are supported by ball bearings housed in bores in the PTO case. Drive gear shaft 1 is driven from the engine crankshaft, and so the unit provides splined to its shaft and is in constant mesh with a hub that is freely supported by ball bearings on the PTO shaft.The connection between the driven gear and the PTO shaft is effected by hydraulic clutch 10 similar to those described in Section 11.4. The clutch comprises a series of driving and driven discs accommodated in a drum that is splined to the PTO shaft. The clutch driving discs are made of steel and equipped with cermet linings. These discs are splined on to the drive gear hub. The clutch driven discs of plain steel are arranged alternately between the driving discs and