Teach you how to choose tractor hydraulic cylinder

Hydraulic cylinders for tractors

Hydraulic cylinders for tractors serve as the core actuators in tractor hydraulic systems, primarily categorized into single-acting and double-acting types. These are suited for unidirectional motion applications and bidirectional force output scenarios, respectively. Below is a detailed introduction to tractor hydraulic cylinders:

First, Types and Characteristics of hydraulic cylinders for tractors

1. Single-Acting Hydraulic Cylinder

Principle: Extends under hydraulic pressure, relying on gravity or spring force for retraction.

Applications: Suitable for single-direction operations, such as tractor lift arms and sprayer folding brackets.

Advantages: Simple structure and lower cost.

Limitations: Return speed is significantly affected by load, limiting applicability in scenarios requiring precise control. Failure rate is 15% higher than double-acting cylinders (primarily due to return seal wear).

2. Double-Acting Hydraulic Cylinder

Principle: Utilizes dual oil circuits to control extension/retraction, enabling bidirectional force output and speed regulation.

Applications: Dominates heavy-duty scenarios requiring bidirectional force, such as corn harvester ear-removal roller adjustment and depth control in large seeders.

Advantages: High control precision enables centimeter-level adjustments, ensuring consistent operational quality. For example, Bosch Rexroth's CDT3 series double-acting cylinders achieve ±1 mm control accuracy in combine harvester header elevation, guaranteeing uniform cutting height and reducing loss rates by 2%.

Market: Penetration exceeds 90% in large tractors. For instance, the John Deere S780 harvester uses Parker Hannifin double-acting cylinders with 40-ton single-cylinder thrust, maintaining header stability in lodged crops.

Second, Selection Criteria

1. Determine System Pressure

Pressure selection depends on load magnitude and equipment type. At a fixed load, low working pressure increases actuator structural dimensions, compromising cost-effectiveness. Excessively high pressure demands superior materials, seals, and manufacturing precision for pumps, cylinders, valves, etc., raising equipment costs.

Generally, lower pressures suit equipment with less dimensional constraints. For mobile machinery (e.g., tractors) where equipment durability is paramount, higher pressures are preferable.

2. Determining Stroke Allowance

Stroke allowance must account for manufacturing tolerances in system structure and installation dimensions, plus potential stroke requirements at both the start and end points during actual operation. Note that when buffering functionality is required, stroke allowance directly impacts buffering performance; minimizing it is recommended.

3. Selecting Mounting Methods

Hydraulic cylinder mounting methods include flange, pin, lug, and tie-rod types. Selection should ensure the cylinder is not subjected to compound forces while considering alignment ease, rigidity, cost, and maintainability.

Flange mounting is suitable for fixed installations where forces act along the same axis as the support center during operation.

Hinge mounting includes single/double tail-end lug mounting and end/mid-section/tail-end pivot mounting. It is suitable for applications where the applied force causes the moved machine component to follow a curved path within the same plane of motion during cylinder operation.

Foot mounting is suitable for fixed installations where the mounting plane is not coplanar with the cylinder's central axis during operation.

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