The hydraulic control devices of agricultural tractors mainly have the following control methods:
Machinery tractor for agriculture Manual control
Spool valve type manual control: The flow direction and volume of hydraulic oil are controlled by manually operating the spool valve, thereby controlling the action of actuating elements (such as cylinders and motors). This method has a simple structure and low cost, and is commonly found in some small agricultural tractors. For instance, when performing the lifting and flipping operations of a loader's bucket, the driver controls the bucket's movement by pulling the corresponding slide valve handle to allow the hydraulic oil to enter different oil circuits.
Rotary valve manual control: Rotary valve manual control changes the on-off state of the oil circuit and the flow direction of the oil by rotating the valve core. It is characterized by simple operation and compactness, and is often used in the hydraulic systems of some agricultural tractors with high space requirements. For example, when controlling the lifting and lowering of the suspension system of a tractor, the driver can turn the handle of the rotary valve to make the suspension device rise or fall, so as to meet different operation requirements.
Agricultural tractor Hydraulic pilot control
Pilot valve control: This method utilizes a pilot valve with a small flow rate to control the operation of the main valve. The driver operates the pilot valve to generate a small control pressure. This pressure acts on the control end of the main valve, causing it to open or close, thereby controlling a large flow of hydraulic oil towards the actuator. Pilot control can achieve remote operation and has a small operating force, which can reduce the labor intensity of the driver. For instance, the hydraulic suspension system and steering system of large agricultural tractors often adopt pilot control. The driver only needs to gently operate the pilot valve handle to easily control the lifting of the suspended farm tools and the steering of the tractor.
Proportional pilot control: Proportional pilot control, based on the pilot valve, can proportionally control the opening degree of the main valve according to the displacement or pressure of the driver's operating handle, thereby precisely controlling the movement speed and force of the actuator. This control method is widely used in agricultural tractors with high requirements for operation accuracy. For instance, when performing precise fertilization, sowing and other operations, the working speed and force of hydraulic-driven fertilizer applicators, seeders and other equipment can be precisely controlled through proportional pilot control, ensuring the operation quality.
Agriculture tractors Electronic control
Electro-hydraulic proportional control: Through an electronic control system, the opening degree of the electro-hydraulic proportional valve is controlled based on preset parameters and information fed back by sensors, thereby precisely controlling the flow and pressure of the hydraulic oil and achieving precise control of the actuating elements. For instance, on some advanced agricultural tractors, the electronic control unit (ECU) automatically adjusts the working parameters of the hydraulic-driven irrigation system and the spraying system based on sensor data such as soil moisture and crop growth conditions, achieving precise irrigation and spraying.
Computer control: The computer control system can comprehensively manage and coordinate the control of multiple hydraulic systems of the tractor. It can automatically optimize the working parameters of the hydraulic system according to different operation modes and working conditions, improving operation efficiency and economy. For instance, in a combine harvester, the computer control system automatically adjusts the working states of multiple hydraulic control components such as the lifting of the header, the rotational speed of the threshing wheel, and the speed of the conveyor chain based on factors like the type and yield of the harvested crops, achieving efficient and stable harvesting operations.
