190303gB Flashcards
Tracked Equipment Steering Fundamentals and Service- Part B
what does a dual path hydrostatic system to control direction and speed of machines tracks consist of?
2 closed circuit hydrostatic drive systems that control speed and direction of each track
what kind of pumps are used on a hydrostatic steering system?
variable displacement reversible pumps
what kind of motors are used in a hydrostatic steering system?
variable displacement motors, mounted directly to the final drives
how can the operator vary track speed?
vary pump and motor displacement
what happens when one of the hydrostatic pumps is placed in neutral and the other still spins?
machine will perform a pivot turn
how can the machine counter-rotate?
rotate one track in forward direction and the other track in the reverse direction
advantages of a hydrostatic steering system?
- power is applied to both tracks when tractor is being turned
- infinitely variable track speed and counter rotation
- machine ground speed can be adjusted for optimum traction with infinite speed control
function of the charge pump?
keep closed circuit filled with oil so pump will not cavitate
supercharge the pump
keep system pressurized
provide lube
what does the neutral charge relief valve do?
limit pressure in charge circuit when hydrostatic pump is in neutral
where does the neutral charge relief valve oil dump to?
the hydrostatic pump case for pump cooling and lube
where is a charge filter located?
outlet line from charge pump, filters shit out before it can get to important steering system
what does the internal pump swashplate control?
pump displacement, flow direction
what controls the position of the pump swashplate?
pressure control pilot and pump displacement control valve
what happens when the swashplate is in neutral on the pump?
no piston stroke, no oil to motor.
what style are the hydrostatic motors?
bent axis variable displacement
how is the displacement of the motor controlled?
by servo pistons, change angle from 32” to 6”
greater angle of the cylinder block the greater the motor _______
displacement
as motor displacement increases, the speed of the output shaft ____ but torque generating capability _______
decreases, increases
what helps to charge the circuit when the hydrostatic pump is in neutral?
check valves
why are there 2 high pressure relief valves?
to limit pressure in both forward and reverse directions
what is the flushing valve for?
for filtering oil so that cool oil can be brought in
how is the flushing valve shifted open?
shifted open by high side, dumps from low side
what side does the operating charge pressure relief valve limit pressure on?
the low pressure side
what does the engine speed control sensor do?
send voltage signal to ecu indicating position of engine throttle
what does the left/right steer sensor do?
sends variable voltage signal to ecu indicating direction operator wishes to turn
what does the steering differential have?
power input from power shift tranny, determines ground speed and direction
power input from hyd steer motor, right and left turns,
2 power outputs, one to each final drive
the direction of rotation of the steering motor determines the direction of the turn, while the speed of the motor and speed of the tractor determines the _______ of the turn
radius
what is the function of the steering system hyd components?
control speed and direction of steering motor, controls direction and rate of machine turns
what are the two methods used to control steering motor speed and direction?
proportional dcv
closed circuit hydrostatic drive
