190301d Flashcards
What do hydraulic motors convert hydraulic energy into?
rotary mechanical energy
Over time, internal clearances in a motor increase due to wear. What else does this increase?
leakage and oil flow through the drain line
Name three categories of hydraulic motors.
- Gear motors, including external gear motors and gerotor and geroller motors
- Vane motors
- Piston motors.
True or false: The construction between hydraulic pumps and hydraulic motors is significantly different.
False; In most cases, the construction of hydraulic motors is very similar to the construction of hydraulic pumps.
What does reversing oil flow through a hydraulic motor do?
Reversing the oil flow through the motor reverses output shaft rotation
Why are gear type motors not commonly used?
Their design makes them poor torque generators
Pressurized oil is allowed to flow past the ________ to the rod side of a ram type
cylinder
piston
What advantage do telescoping cylinders offer?
additional stroke length is gained from a relatively compact retracted package
Why are double-acting cylinders are often referred to as differential cylinders?
There is a difference in the speed and forces generated by extension versus retraction
What is the difference between a differential and non-differential cylinders?
nondifferential cylinders have equal piston area and equal volume on both sides of the cylinder.
What three things does a leaking piston seal in a differential cylinder result in?
- increased cylinder cycle times.
- cylinder drifting in the extension direction.
- pressure intensification when in the hold position.
What is the function of a cylinder rod wiper?
prevent contamination from entering the cylinder.
What is the purpose of a piston relief valve?
allow pump oil flow to bypass the piston when the piston reaches the end of its stroke, reducing heat generation
In reference to hydraulic cylinder operation, what does the term regeneration refers to?
supplementing pump oil flow to the base end of a double-acting cylinder with oil flow from the rod end which increases cylinder extension speed
The quick drop valve used on dozer cylinders provides regeneration when the operator selects ___________
the full lower position
The speed of a motor driveshaft depends upon which two factors?
- Inlet flow rate
- Motor displacement (capacity)
One factor that does not influence motor torque generation is: __________________
inlet flow rate
Most motors are equipped with a drain line. What does that line do?
carries leakage oil from the motor to the reservoir
Why are external gear motors such poor torque generators?
Due to counteracting forces, torque is generated by inlet pressure acting on the surface area of just one tooth
True or False: Gerotor motors are considered to be high-speed low torque motors.
False
What is the function of a spool valve in a gerotor motors?
direct the flow of oil to and from the valleys in the gerotor element.
Why are balanced vane motors good torque generators?
they can operate at higher pressures than other types of vane motors.
Why must some vane motors be equipped with spring-loaded vanes?
Spring-loaded vanes are used to ensure good vane-to-cam ring contact at start-up.
What is the main difference between variable and fixed displacement motors?
The speed and torque characteristics of a variable displacement motor will change as their displacement changes
Pressure compensated, variable displacement motors vary their displacement in response to changes in motor load.
As the load on the motor output shaft increases,
the motor displacement ______________
increases
Why are variable displacement motors prevented from reaching the zero displacement position?
The motor will hydrostatically lock and stall (freewheel) in the zero displacement position
In a piston motor the cylinder barrel and pistons are often referred to as?
Rotating group
Three types of piston motors?
- Axial
- Bent
- Radial
In a piston motor how is leakage oil returned to tank?
A drain port/line
What are the 2 most common set angles that can be set as swash plate displacement?
6.5 and 19
If a motors swash plate goes into a perpendicular position, what could happen?
The circuit would go into a hydrostatically locked situation allowing motor to freewheel (stall).
Pressure compensation allows for the motor to have what?
It allows the motor to have a swash plate that is automatically adjusted according to load on the motors output shaft.
How is maximum torque achieved in a piston pump?
With the swash plate at minimum flow angle.
Least speed. Maximum torque
True or False: A bent axis piston motor cannot be made to bend at 6.5 or 19 degrees?
False: A bent axis piston motor will use the rotating group as the swash plate.
How does a bent axis piston motor become a fixed displacement motor?
The motor housing holds the rotating group in a bent shape.
How does the bent axis piston motor become a variable displacement motor?
This is achieved by using the rotating block as a swash plate.
