How many power take-off shafts are there? What are their characteristics?
Tractor power take-off
The tractor outputs part of the power to drive the working mechanism of supporting agricultural implements. According to the different installation positions on the tractor, the power take-off can be divided into two types: rear type and front type; According to the speed characteristics, it can be divided into constant speed type and synchronous speed type. The speed of the constant speed PTO is in a fixed proportion to the engine speed. According to transmission, operation and working characteristics, it can be divided into three types: independent type, semi-independent type and non-independent type.
The speed of the constant speed PTO is in a fixed proportion to the engine speed. According to transmission, operation and working characteristics, it can be divided into three types: independent type, semi-independent type and non-independent type.
The shaft extension size and speed type of the power take-off shaft are standard:
Type I 35mm 6-tooth rectangular spline with standard speed of 540 rpm; Type II 35mm 21-tooth involute spline and type III 45mm 20-tooth involute spline, with standard speed of 1000 rpm.
The maximum power output at standard speed is:
Type I 48 kW; Type II 92 kW; Type III 185 kW. The engine speed corresponding to the standard speed is generally not less than 80% of the rated speed. The three types of constant speed PTO can be distinguished by their functional characteristics:
① The independent PTO does not affect the normal operation of the driven agricultural implements when the tractor starts, runs, shifts and stops; The starting and stopping of the working mechanism of agricultural machinery and tools have nothing to do with the starting, running and stopping of the tractor mechanism.
② When the tractor starts, runs, shifts and stops, the semi-independent PTO does not affect the normal operation of the driven agricultural implements; The starting, running and stopping of the working mechanism of agricultural implements can not occur simultaneously with the starting and stopping of the tractor, but when the tractor unit is working, the agricultural implements must be started first, and then the tractor can be started; Only after the tractor is stopped can the agricultural machinery stop, that is, the tractor is in the stop state before starting and when the working mechanism of the agricultural machinery stops.
③ The operation and stop of the non-independent PTO are completely restricted by the operation and stop of the tractor, that is, the PTO can only be started after the tractor starts running; When the tractor stops, the PTO stops immediately. The constant speed power output shaft is used to drive the harvester, rotary tiller and fixed work tools.
Figure 1 Structure of double-shaft power take-off
The speed of the synchronous speed PTO is in a fixed proportion to the tractor speed. The power output shaft is used to drive the driving axle of the seeder, fertilizer applicator, planter and other machines and trailers.
On tractors with large power, the PTO shaft has two standard rotational speeds. For this reason, two corresponding shaft heads are set (Figure 1), or the structure of replaceable shaft heads is set (Figure 2). The upper half of the power output shaft in Figure 2 is a 1000 rpm shaft head, and the lower half is a 540 rpm shaft head.
Figure 2 Structure of shaft-changing power take-off
Some tractors have a 2~4 speed variable power output shaft, which is suitable for rotary tillage operation and to save fuel consumption with a high grade small throttle under partial load.
The position of the PTO shaft on the tractor and its relative position with the hitch and the tractor are specified in the standard. During operation, the driven implement drive shaft is allowed to swing within a certain range. In order to ensure normal operation and personal safety, the power output shaft shall be equipped with protective devices. The shape and size of the protective device shall conform to the standard.
