Synchronize PTO=power output shaft speed and tractor rear wheel running speed are strictly synchronized and linked in a fixed proportion
The tractor moves forward, and the PTO follows suit; The tractor stops and the PTO immediately stops running; The speed of the vehicle increases, and the PTO speed increases proportionally.
The most fundamental difference between it and the standard independent constant speed PTO is:
Ordinary PTO: The engine speed determines the PTO speed, and the speed of the vehicle does not affect the output speed;
Synchronous PTO: The rear wheel speed determines the PTO speed, and the throttle size does not change the synchronous transmission ratio.
Principles of Mechanical Transmission
Different sources of power take-off
Conventional independent PTO: Power is taken from the input shaft/engine end of the gearbox and is only controlled by throttle and engine speed;
Synchronous PTO: The power is directly taken from the tractor's rear axle final drive and rear wheel drive half axle front end, that is, the power of the wheels is branched out all the way to the PTO.
Gear ratio transmission
A set of fixed transmission gear pairs is designed inside the main transmission box of the rear axle, which transmits the rotation of the rear axle to the PTO output shaft according to the factory preset fixed speed ratio.
The speed ratio is accurately calculated to ensure:
The PTO rotates a fixed number of turns for every fixed distance the tractor advances.
Linkage logic
Clutch engagement → gearbox shifting → rear axle driving wheel rotation → synchronous power take-off gear following rear axle rotation → PTO shaft synchronous rotation;
Press the clutch to cut off the walking power, the wheels stop rotating, and the synchronous PTO stops synchronously.
Why is synchronous PTO necessary for sowing?
The seeding machine and planter rely on PTO to drive the seeding wheel for feeding:
If using a regular constant speed PTO: When the engine speed remains constant, the PTO speed remains constant. When the tractor runs slowly at low speeds, the seeding is dense, and when the speed increases, the seeding is sparse. The seeding amount is extremely uneven under the row spacing;
Synchronous PTO: Within a unit driving distance, the number of PTO rotations is always the same. Regardless of the speed, the number of seeds discharged per meter of land is exactly the same, achieving uniform and precise seeding.
The same applies to agricultural tools such as mulching and film laying machines, rice transplanters, and fertilizer spreaders that require matching with the distance traveled.
Two common implementation forms in terms of structure
Method 1: Directly apply force to the rear axle (the most mainstream)
At the input end of the rear differential, a gear pair is led out, and a power is distributed to the PTO shaft, completely following the wheel speed.
Method 2: Synchronized power take-off at the end of the gearbox
Taking force at the output end of the gearbox (the output shaft leading to the rear axle) essentially remains a branch of the rear axle's driving power, with the same effect.
Synchronized PTO switchable function (supported by most tractors)
The tractor control panel generally has gear shifting:
Independent gear (standard PTO): detached from the rear axle linkage, controlled by engine speed, used for rotary tillage, pesticide spraying, water pumping, and field returning;
Synchronous gear (synchronous PTO): connected to the rear axle power take-off circuit, rotates with the vehicle speed, used for sowing and transplanting;
Neutral: The PTO is completely disconnected and there is no output.
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