SERVO VALVE
1.1. ServServo vo valve alve asseassemblmbly (y (No. No. 1 f1 fronront)t)
P1
P1 :M ain pump pressure IN port 1.C O+NC valve PE
PE : TVC valve output pressure front, rear interconnection port
2. Servo valve PCO
PCO : CO selector pilot port PD
PD : Jet sensor downstream pressure IN port PT
PT : Jet sensor upstream pressure IN port PAC
PAC : Servo actuator port PDR
PDR : Servo valve drain OUT port PPO
PPO : Servo basic pressure IN port PECN
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STRRUCUCTUTURERE, , FUFUNCNCTITION ON ANAND D MAMAININTETENANANCNCE SE STTAANDNDARARDD HYHYDDRARAULULIC IC PUPUMMP (P (PIPISTSTON ON PUPUMPMP))
2.
2. SerServo vo valvalve ve (N(No. o. 1 f1 frorontnt))
P2
P2 : Main pump pressure OUT port PDR
PDR : CO+NC valve drain IN port PECN
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STRURUCTCTUURERE, , FUFUNCNCTITIOON N ANAND D MAMAININTETENNANANCE CE STSTAANDNDARARDD HHYDYDRARAULULIC IC PUPUMP MP (P(PISISTTON ON PUPUMPMP))
3.
3. SerServo vvo valvalve asse assememblbly (Ny (No. 1 reo. 1 re arar))
P1
P1 :M ain pump pressure IN port 1.T VC valve P2
P2 :M ain pump pressure IN port 2.C O+NC valve PCO
PCO : CO selector pilot port 3.C onnector PAC
PAC : Servo actuator port 4. Servo valve PDR
PDR : Servo valve drain OUT port PPO
PPO : Servo basic pressure IN port PD
PD : Jet sensor downstream pressure IN port PE
PE : TVC valve output pressure front, rear interconnection port
PT
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STRRUCUCTUTURERE, , FUFUNCNCTITION ON ANAND D MAMAININTETENANANCNCE SE STTAANDNDARARDD HYHYDDRARAULULIC IC PUPUMMP (P (PIPISTSTON ON PUPUMPMP))
4.
4. SerServo vo valvalve ve (N(No. o. 1 r1 rearear))
P1
P1 : Main pump pressure OUT port P2
P2 : Main pump pressure OUT port PDR
PDR : CO+NC valve drain IN port PPO
PPO : Servo basic pressure OUT port PECN
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STRURUCTCTUURERE, , FUFUNCNCTITIOON N ANAND D MAMAININTETENNANANCE CE STSTAANDNDARARDD HHYDYDRARAULULIC IC PUPUMP MP (P(PISISTTON ON PUPUMPMP))
Structure Structure
(The following illustration shows the servo valve for No. 1 rear.)
Function Function
Discharge amounts Q1Q1 and Q2Q2 of main pumps P1P1 and P2P2 are controlled individually by the respective servo valves. The relationship between pump dis- charge amount QQ and input signal PECNPECN to the servo valve is as shown in the graph on the right. QQ varies in proportion to PECN.PECN.
1. Locknut 7. Pin 13. Sleeve 2. Cover 8. Piston 14. Piston 3. Plug 9. Locknut 15. Spring 4. Spring 10. Plug 16. Plug 5. Valve body 11. Locknut 17. Cover 6. Arm 12. Cover 18. Locknut
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STRRUCUCTUTURERE, , FUFUNCNCTITION ON ANAND D MAMAININTETENANANCNCE SE STTAANDNDARARDD HYHYDDRARAULULIC IC PUPUMMP (P (PIPISTSTON ON PUPUMPMP))
1)
1) OperatiOperation in dion in direction rection of incrof increase of puease of pump dischmp discharge amouarge amount (maxnt (max. angle). angle)
Operation Operation
• The control pump pressure PPOPPO is taken to port a
a.
• Signal pressure PECNPECN from the NC valve is tak- en from port bb to chamber cc.
• When signal pressure PECNPECN rises, piston (8) is pushed to the right by the pressure in chamber cc, and stops at a point where it balances the pres- sure of springs (4) and (4A).
• At the same time, arm (6) uses servo piston (19) as a fulcrum and sways to the right in the same way as piston (8). This moves guide spool (13) to the right.
• When guide spool (13) moves, port aa and port dd are closed and port dd is connected to drain chamber ee. As a result, servo piston chamber f f is also interconnected with drain chamber ee through port gg and port dd.
• At the same time, port aa is interconnected with port hh, so the pressure oil flows through port ii to servo piston chamber j j, pushes servo piston (19) to the right, increases the swash plate angle in the main piston pump and increases the pump discharge amount.
• When servo piston (19) moves, arm (6) rotates counterclockwise with its center at pin (7) and moves guide spool (13) to the left. Port aa, port dd and port hh close, so the discharge increases by an amount that matches signal pressure PECNPECN.
ST
STRURUCTCTUURERE, , FUFUNCNCTITIOON N ANAND D MAMAININTETENNANANCE CE STSTAANDNDARARDD HHYDYDRARAULULIC IC PUPUMP MP (P(PISISTTON ON PUPUMPMP))
2)
2) OperatiOperation in dion in direction rection of decreof decrease of puase of pump dischmp discharge amouarge amount (minnt (min. angle). angle)
Operation Operation
• When signal pressure PECNPECN goes down, piston (8) moves to the left and stops at a point where the pressure in chamber cc balances the pressure of springs (4) and (4A).
• At the same time, arm (6) uses servo piston (19) as a fulcrum and sways to the left in the same way as piston (8). This moves guide spool (13) to the left.
• When guide spool (13) moves, port aa and port hh are closed and port hh is connected to drain chamber ee. As a result, servo piston chamber j j is also interconnected with drain chamber ee through port i i and port hh.
• At the same time, port aa is interconnected with port dd, so the oil flows through port gg to servo pis- ton chamber f f , pushes servo piston (19) to the left, decreases the swash plate angle in the main piston pump and decreases the pump discharge amount.
• When servo piston (19) moves, arm (6) rotates counterclockwise with its center at pin (7). Guide spool (13) is moved to the right and closes port a
a, port dd and port hh, so the discharge decreases by an amount that matches signal pressure PECN
ST
STRRUCUCTUTURERE, , FUFUNCNCTITION ON ANAND D MAMAININTETENANANCNCE SE STTAANDNDARARDD HYHYDDRARAULULIC IC PUPUMMP (P (PIPISTSTON ON PUPUMPMP))