2. Hydraulic Valve, Pump, Motors
(Mechanical Engineering for Mechatronics)
Lecture:2
G D Mistry
Lecturer
SPCE, Visnagar
Hydraulic Valve, Pump, Motors

3. Hydraulic Valves Valves can be divided into three major types:
Pressure Control Valves
Directional Control Valves
Volume Control Valves

4. Pressure Control valves
Limit system pressure
Reduce pressures
Set pressure at which oil enters a circuit
Unload a pump

5. Pressure Control Valves
Relief valves
Pressure reducing valves
Pressure sequencing valves
Unloader valves

6. Relief Valves
The purpose of any relief valve is to protect the hydraulic system and its component parts from excessive pressure or damage.

7. Relief Valves Types Direct Acting- open / closed valves
Pilot Operated- controls the main relief valve

8. Direct Acting Relief Valve
OUTLET
OUTLET
INLET
INLET
CLOSED
OPEN

9. Direct Acting Relief Valve
These valves are used mainly where volume is low, and for less frequent operations.
They have fast response, making them ideal for relieving shock pressure.
They are often used as safety valves to prevent damage to components.

10. Pilot Operated Relief Valve
Because these valves don’t start to open until almost full-flow pressure, the efficiency of the system is protected-less oil is released.
These valves are best for high-pressure, high volume systems.
Although slower to operate than direct acting valves, the pilot operated relief valve keeps system oil at a more constant pressure while releasing oil

11. Pressure Reducing Valves Types
Constant reduced pressure valve
Fixed amount reduction valve

12. Constant Reduced Pressure Valves
They supply a fixed pressure regardless of main circuit pressure. (So long as it is higher)

13. Constant Reduced Pressure Valve
VALVE OPEN, NOT OPERATING
VALVE PARTLY CLOSES
TO REDUCE PRESSURE
FROM MAIN CIRCUIT
TO SECONDARY CIRCUIT

14. Fixed Amount Reduction Valves
They supply a fixed amount of pressure reduction, which means that it varies with the main circuit pressure.
For example,the valve might be set to give a reduction of 500 PSI. If system pressure was 2000 PSI, the valve would reduce pressure to ________ PSI.

15. Fixed Amount Reduction Valve
FROM
MAIN
CIRCUIT TO
SECONDARY CIRCUIT

16. Pressure Sequence Valves
They are used to control the sequence of flow to various branches of a circuit.
Usually the valves allow flow to a second function only after a first has been fully satisfied.

17. Pressure Sequence Valve
INLET TO
PRIMARY
CIRCUIT
TO SECONDARY CIRCUIT
CLOSED
OPEN

18. Unloading Valve
This valve directs pump output oil back to the reservoir at low pressure after system pressure has been reached.
They may be installed in the pump outlet line with a tee connection.

19. Valve Types Pressure control valves Directional control valves
Volume control valves

20. Directional Control Valves
Direct the flow of oil in the system
Types of valves
- Check valves
- Rotary valves
- Spool valves
- Pilot controlled poppet valves
- Electro-hydraulic valves

21. Check Valves One way valves, only allow fluid to flow in one direction
The valve is open by system pressure
The valve closes when inlet pressure drops
Usually installed in oil line

22. Rotary Valve
To Reservoir
From Work
From Pump
To Work
This valve allows pressurized oil from the pump to enter one port, flow through the valve, and out another port to the work

23. Rotary Valve
This valve also allows oil from another working port to flow through the valve and return to the reservoir.
To Reservoir
From Work
From Pump
To Work

24. Rotary Valves Used as pilot valves to direct flow to other valves
Can be modified to operate as two, three, or four way valves
Done by relocating parts, altering passageways, or adding and removing oil routes

25. Spool Valves Most common is open center and closed center
Directs oil to start, operate, and stop actuating units
Dirt can cause these valves to stick or work erratically

26. Spool Valves
open center allows fluid to flow thru the center when in neutral and return to tank
Closed center stops the flow of oil in neutral
Used as a control valves

27. Spool Valve (Stacked)

28. Spool Valve (Unibody)

29. Pilot Controlled Poppet Valves
May be mounted close to the function it controls
Eliminates the need for routing hydraulic pipes and hoses over long distances for every control function
Reduces valve leakage (i.e. cylinder drift)
Adjustable to vary amount of oil flow

30. Electro-Hydraulic Valves
Actuated by an electric solenoid
+ BATTERY
ROCKER
SWITCH
SOLENOID TO
RESERVOIR
FROM
PUMP
+ BATTERY
ROCKER
SWITCH
SOLENOID TO
RESERVOIR
FROM
PUMP

31. Valve Types Directional control valves Pressure control valves
Volume control valves

32. Volume Control Valve Types
Flow control.
Flow divider.

33. Flow Control Valves
Restricts flow in or out of the component whose speed is being regulated.
These valves are noncompensated.

34. Bypass Flow Regulator
This valve works by diverting flow away from the component whose speed is being regulated.
These valve are usually compensated.
BYPASS
OUTLET
FULL FLOW TO BYPASS

35. Volume Control Valve Types
Flow control.
Flow divider.

36. Priority Flow Divider Allows oil to feed two different circuit.
Example,steering circuit and loader circuit.
Pump output 10 gpm.
Steering 2 gpm.
Loader 8 gpm.
PRIORITY
OUTLET
SECONDARY
FIXED ORIFICE
INLET
FROM
PUMP

37. Proportional Flow Divider
OUTLET #1
OUTLET #2
INLET
Divides a single flow of oil to two circuits.
Can divided oil flow in ratios from to

38. Hydraulic Pumps The pump is the heart of the hydraulic system.
The pump is the generating force of the hydraulic system, it creates the flow of fluid which supplies the whole circuit.
Pumps convert mechanical energy to hydraulic power

39. Pump Classification Two classifications of pumps Fixed Displacement
Variable Displacement

40. Types Displacement Fixed
-Moves the same volume of fluid with each cycle

41. Variable Displacement Pumps
Changing Displacement- this is accomplished by changing the angle of the swashplate.
Swash Plate Positioning - The position is controlled by one of two ways.
- A small hydraulic cylinder called a “servo”
- A spring loaded cylinder called a “pressure compensator”

42. Types Of Pumps
GEAR
VANE
PISTON

43. Types Of Pumps Gear (rotary) Vane (centrifugal) Piston (reciprocating)
Internal
External
Vane (centrifugal)
Balanced
Unbalanced
Piston (reciprocating)
Axial
Radial

44. Gear Pumps Simple Design. Economical. Fixed Displacement.
Used as charging pumps for larger system pumps.

45. Gear Pump Side Plates
Some gear pumps are equipped with pressurized plates on both side of the gears. These plates are used to prevent cavitation. The plates seal tightly when the pump is under a load and relax when there is no load.

46. Internal Gear Pumps
Pump Housing
Inlet
Outlet
Separator
(fixed)
Outer Ring
Gear
Internal Gear
The internal gear is the drive gear, which is meshed with the outer ring gear and traps fluid between the gear teeth on both gears and the separator, which is fixed.

47. External Gear Pump
Inlet
Outlet
Pump Housing
Drive Gear
Idle Gear
Oil is trapped between the gear teeth and flows around the outer perimeter of the pump housing, not through the middle of the meshing gears.

48. Gear Pump Advantages Most widely used. Easiest to manufacture.
Produces a large volume of oil for its size.
Tolerant to dirt.
Inexpensive to manufacture.

49. Gear Pump Disadvantages
Noisier than other types of pumps.
Fixed displacement only.

50. Vane Pumps Balanced Vane Pump - Fixed Displacement only.
- Equalized force increases bearing life.
Unbalanced Vane Pump
- Either Fixed or Variable Displacement.
- Frequent bearing failure.

51. Balanced Vane Pump
PRESSURE
HERE
INLET
ROTOR
OUTLET
PRESSURE
HERE
DRIVE
SHAFT
Balanced pumps are preferred because they allow an even load of oil around the circumference of the pump shaft, this reduces the wear on the pump.
PUMP HOUSING
VANE

52. Unbalanced Vane Pump
PRESSURE
UNBALANCED
HERE
OUTLET
VANE
As the name implies only one side of the pump forces oil through, causing the oil load to shift to one side of the pump.
INLET

53. Vane Pump Advantages
Quiet.
They are self compensating for wear.

54. Vane Pumps Disadvantages
Not as tolerable to dirt as gear pumps.
Low volume output.
Low pressure output.

55. Piston Pumps Radial piston pumps Axial piston pumps Rotating cam.
Rotating piston.
Axial piston pumps
Inline axial.
Bent-axis axial.

56. Radial Piston Pump (Rotating Cam)
Pistons are driven outward to discharge oil by the shaft cam, they move inward to take in oil by the force of their springs.
Normally designed as a 4 or 8 piston model.
SPRINGS

57. Radial Piston Pump (Rotating Piston)
INLET PORTS
As the cylinder rotates pistons are thrown out against the housing by centrifugal force. A partial vacuum is created in the piston bores and oil flows into the inlet ports to fill the bores.
ROTATING
CYLINDER
FIXED
SHAFT
PISTON
PISTON BORE
OUTLET PORTS

58. Radial Piston Pump (Rotating Piston)
CYLINDER
FIXED
SHAFT
INLET PORTS
PISTON
PISTON BORE
As the cylinder keeps turning, the pistons are pushed back into the bores and force the oil out the ports on the outlet side.
OUTLET PORTS

59. Axial Piston Pumps
The axial flow of fluid provides a more compact design and is the second most widely used pump in the industry next to the gear pump.
Inline axial piston pump.
Bent-axis axial piston pump

60. Axial Piston Pumps (Inline)
SWASH
PLATE
PISTON
DRIVE
SHAFT
INLET
ROTATING
CYLINDER
BLOCK
Pump can be variable displacement.
Swashplate directs the intake and discharge of flow.
Piston, draws and discharges the fluid.
Cylinder block, holds the piston and rotates them from inlet to outlet ports.
OUTLET

62. Axial Piston Pumps (Bent-axis)
INLET
OUTLET
PISTON
ROTATING DRIVE
MEMBER
ROTATING
CYLINDER
BLOCK
Fixed displacement.
Rotating drive member directs the intake and discharge of flow.
Piston, draws and discharges the fluid.
Cylinder block, holds the pistons and rotates them from inlet to outlet ports.
DRIVE
SHAFT

64. Piston Pumps Advantages
Able to withstand high pressure.
Capable of variable displacement.

65. Piston Pumps Disadvantages
Very low tolerance to dirt.
More difficult to manufacture.
Most expensive to manufacture.

66. Questions What are the three types of pumps? - Gear, Piston and Vane
What will change the displacement of the piston pump?
- Angle of the swashplate
What is the purpose of the side plates in the gear type pump ?
- These plates are used to prevent cavitation

67. HYDRAULIC MOTORS

68. Hydraulic Pump and Motor
Drive Gear
Motor Housing
Inlet
Outlet
Idle Gear
Inlet
Outlet
Pump Housing
Drive Gear
Idle Gear
A pump drives its fluid, while the motor is driven by its fluid.

70. Hydraulic Motors
A motor is a rotary actuator that rotates in a full circle.
The work output of a motor is called torque.
They convert hydraulic energy to mechanical energy.

71. Hydraulic Motors
Fixed displacement motors- have variable speed but fixed torque
Variable displacement motors- have variable speeds and torques

72. Hydraulic Motors (Types)
Gear motors.
Vane motors.
Piston motors.

73. Thank You