Hydraulic motors share several common design elements: a pressure-sensitive driving surface area, a mechanism for regulating the flow of pressure fluid to this surface for continuous rotation, and a mechanical link between the surface area and an output shaft.
The maximum performance of a Automotive Lift Repair Florida hydraulic motor—regarding pressure, flow, torque output, speed, volumetric and mechanical efficiencies, service life, and physical configuration—is influenced by the ability of the pressure surfaces to endure force, the leakage characteristics, and the efficiency of the linkage between the pressure surface and the output shaft.
Motor Displacement: The volume of fluid needed to complete one revolution of the Automotive Lift Repair Florida motor’s output shaft. It is usually measured in cubic inches (in³) or cubic centimeters (cm³) per revolution. Displacement can be fixed or variable. A fixed-displacement motor delivers constant torque, with speed varying based on input flow. A variable-displacement motor adjusts both torque and speed, allowing for a varying torque-speed ratio to match load requirements.
Torque Output: Measured in inch-pounds or foot-pounds, torque output depends on system pressure and motor displacement. Ratings are typically provided for specific pressure drops, reflecting the theoretical torque available, assuming no mechanical losses.
Breakaway Torque: The torque required to initiate movement of a stationary load, which is generally higher than the torque needed to keep it moving.
Running Torque: This can refer to the torque needed to keep a load turning or the actual torque a motor generates to maintain that rotation. It typically represents about 90% of theoretical torque.
Starting Torque: The amount of torque a motor can generate to start a load moving, which can be significantly less than running torque. It often ranges between 70% and 80% of theoretical torque.
Mechanical Efficiency: The ratio of the actual torque delivered to the theoretical torque.
Torque Ripple: The variation between the minimum and maximum torque delivered at a given pressure during one motor revolution.
Motor Speed: A function of motor displacement and the volume of fluid supplied to the motor.
Maximum Motor Speed: The highest speed a motor can sustain for a short period at a specific inlet pressure without damage.
Minimum Motor Speed: The slowest, continuous rotational speed achievable from the motor output shaft.
Slippage: The leakage through the motor where fluid passes without performing work.
Gear Motors
Automotive Lift Repair Florida External Gear Motors: These feature two matched gears within a single housing. One gear is connected to the output shaft, while the other is an idler. Pressure fluid enters at the gear mesh point, causing rotation. Close tolerances and wear plates help control leakage and improve efficiency.
Internal Gear Motors: Include direct-drive gerotor motors with inner and outer gears. The inner gear has fewer teeth than the outer, ensuring continuous contact and smooth fluid flow.
Automotive Lift Repair Florida Orbiting Gerotor Motors: Feature a stationary outer gear with more teeth than a rotating inner gear. A commutator or valve plate directs fluid to and from the motor, ensuring consistent pressure and efficient operation.
Roller-Vane Gerotor Motors: A variant of the orbiting gerotor motor, incorporating rolling vanes to reduce wear and enable use in high-pressure circuits.
Vane Motors
Vane Motors: Have a slotted rotor with vanes that move radially to seal against a cam ring. The fluid flow direction determines rotor movement, with vane motors offering good efficiency but not as high as piston motors.
Piston-Type Motors
Radial-Piston Motors: Feature a cylinder barrel with pistons that move radially. They offer high torque at low speeds and long service life but have limited high-speed capabilities.
Axial-Piston Motors: Use axial piston motion and can be either inline or bent-axis types. They excel at high speeds but have limited low-speed performance.
Other Designs
Rotary Abutment Motors: Utilize rotary abutments and a vane to transmit torque. Timing gears ensure proper alignment and minimal friction.
Screw Motors: Function as pumps in reverse, using meshing screws to create torque through differential pressure.
Selecting and Sizing a Hydraulic Motor
Automotive Lift Repair Florida Motor selection is based on application needs, considering factors such as reliability, life expectancy, and performance. Sizing involves calculations based on horsepower, speed, pressure, and efficiency to determine displacement and flow requirements. Efficiency factors and operating limits also play crucial roles in determining the motor’s overall effectiveness and longevity.
Hydraulic Motor Malfunctions
Common issues arise from improper fluid, poor maintenance, or incorrect operation. Ensuring clean fluid, correct installation, and adherence to operational limits can prevent many problems. Excessive pressure, speed, torque, load, or temperature can all contribute to motor failure.
Gear Pumps
Gear pumps have minimal moving parts, consisting of two interlocking gears. They provide a constant flow rate and operate at pressures typically ranging from 50 to 210 bar. These pumps can run at very high speeds, up to 3000-6000 rpm.
Advantages:
– Cost-effective
– Fixed displacement
Types of Gear Pumps:
1. External-Gear Pumps:
– One gear, the drive gear, is connected to the drive, while the other gear, the driven gear, rotates in the opposite direction. The gears interlock to move the fluid.
– Double External-Gear Pumps: These combine two gear pumps driven by the same shaft, offering two independent hydraulic circuits or increased flow to one circuit.
2. Internal-Gear Pumps:
– These feature an eccentric internal gear and an external gear (crown gear). As the external gear rotates, volume is created between the gear profiles and housing walls, drawing in the fluid as the gears disengage.
– Advantages: Quiet operation, constant flow.
Piston Pumps
Automotive Lift Repair Florida Piston pumps manage large flows at high pressures using pistons that move back and forth. They are known for their excellent sealing and low fluid leakage, making them suitable for high-pressure applications.
Advantages:
– Superior volumetric efficiency
– Capable of the highest pressures
– Reliable and high power density
– Available in both variable and fixed displacement models
Types of Automotive Lift Repair Florida Piston Pumps:
1. Axial Mounting:
– Swash Plate Design: Pistons are supported by a swash plate, which determines the piston stroke.
– Curved Shaft Design: The displacement volume changes with the swivel angle as the pistons move in the cylinders.
2. Radial Mounting:
– Eccentric Cylinder Block: Pistons move inside a rigid outer ring with the eccentricity setting the piston stroke.
– Eccentric Shaft: The eccentric shaft creates radial oscillations in the pistons.
Advantages:
– Multiple independent outputs available.