PAGO - PLAZOS (*):

CO+NC VALVE

1. CO+CO+NC NC valvalve ve (N(No. o. 1 f1 frorontnt))

P

P : Main pump pressure IN port PDPD : Jet sensor downstream pressure IN port PEFR

PEFR : TVC valve output pressure front, rear in ter- connection port

PT

PT : Jet sensor upstream pressure IN port PDR

PDR : CO+NC valve drain OUT port PE

PE : TVC valve output pres sure detection port PECNPECN : CO+NC valve output pressure OUT port PCO

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STRRUCUCTUTURERE, , FUFUNCNCTITION ON ANAND D MAMAININTETENANANCNCE SE STTAANDNDARARDD HYHYDDRARAULULIC IC PUPUMMP (P (PIPISTSTON ON PUPUMPMP))

2.

2. COCO+N+NC vC valalve ve (N(No. o. 1 r1 reaear)r)

P1I

P1I : Main pump pressure IN port (front) PDPD : Jet sensor downstream pressure IN port P1O

P1O : Main pump pressure OUT port PTPT : Jet sensor upstream pressure IN port P2I

P2I : Main pump pressure IN port (rear) PDRIPDRI : TVC valve drain IN port P2O

P2O : Main pump pressure OUT port PDROPDRO : CO+NC valve drain OUT port PEFR

PEFR : TVC valve output pressure front, rear inter- connection port

PPOI

PPOI : Servo basic pressure IN port PPOO

PPOO : Servo basic pressure OUT port PEI

PEI : TVC valve output pressure IN port PECNPECN : CO+NC valve output pressure OUT port PCO

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STRURUCTCTUURERE, , FUFUNCNCTITIOON N ANAND D MAMAININTETENNANANCE CE STSTAANDNDARARDD HHYDYDRARAULULIC IC PUPUMP MP (P(PISISTTON ON PUPUMPMP))

C CO O vvaallvvee NNC C vvaallvvee 1. Plug 7. Plug 2. Piston 8. Sleeve 3. Spring 9. Piston 4. Spool 10. Spool 5. Piston 11. Spring 6. Plug 12. Plug

ST

STRRUCUCTUTURERE, , FUFUNCNCTITION ON ANAND D MAMAININTETENANANCNCE SE STTAANDNDARARDD HYHYDDRARAULULIC IC PUPUMMP (P (PIPISTSTON ON PUPUMPMP))

3

3.. CCO O vvaallvvee

Function Function

• When the load becomes large during operations and the main pump discharge pressure rises to a point close to relief pressure, the cut-off function of the CO valve acts to reduce the pump dis- charge in order to reduce relief loss.

• At the same time, it has a cut-off cancel function actuated by the pilot pressure from the heavy-lift solenoid valve.

• The CO valve is controlled by balancing the spring with the total of main pump discharge pressure PP and CO valve output pressure PECPEC.

1)

1) When mWhen main ain pump pump dischargdischarge pree pressure ssure is lois lower twer than rehan relief lief pressurepressure

Operation Operation

• Spool (4) is pressed down by spring (3). As a re- sult, ports "aa" and "bb" are opened fully, and TVC valve output pressure PEPE is equal to CO valve output pressure PECPEC . Accordingly, CO valve output pressure PECPEC , signal pressure PECNPECN , and pump discharge amount become maximum.

ST

STRURUCTCTUURERE, , FUFUNCNCTITIOON N ANAND D MAMAININTETENNANANCE CE STSTAANDNDARARDD HHYDYDRARAULULIC IC PUPUMP MP (P(PISISTTON ON PUPUMPMP))

2)

2) When maWhen main pump in pump dischardischarge presge pressure bsure becomes ecomes close close to relto relief preief pressuressure

Operation Operation

• If the load increases and main pump discharge pressure PP increases near to the relief pressure, main pump discharge pressure PP presses piston (5). At the same time, CO valve output pressure PEC

PEC presses piston (5) and spool (4) moves up. • As a result, oil flow from port " aa" to port "bb" is re- duced by the notch of the spool and the open ar- eas of port "bb" and port "cc" (drain port) increase. Accordingly, CO valve output pressure PECPEC and signal pressure PECNPECN lower and the pump dis- charge amount becomes minimum.

ST

STRRUCUCTUTURERE, , FUFUNCNCTITION ON ANAND D MAMAININTETENANANCNCE SE STTAANDNDARARDD HYHYDDRARAULULIC IC PUPUMMP (P (PIPISTSTON ON PUPUMPMP))

3)

3) When When cut-off cut-off function function is cais canceled nceled by heaby heavy-lift vy-lift solenoid solenoid valvevalve

Operation Operation

• If the heavy lift solenoid valve is turned ON, its pi- lot pressure PCOPCO is lead in the port and piston (2) is pressed down. Accordingly, seat (6) touches seat (7) and locks spool (4).

• As a result, even if main pump discharge pres- sure PP increases to the relief pressure, spool (4) does not operate. Accordingly, CO valve output pressure PECPEC keeps maximum and the pump discharge amount does not decrease.

ST

STRURUCTCTUURERE, , FUFUNCNCTITIOON N ANAND D MAMAININTETENNANANCE CE STSTAANDNDARARDD HHYDYDRARAULULIC IC PUPUMP MP (P(PISISTTON ON PUPUMPMP))

4

4.. NNC C vvaallvvee

Function Function

• The NC valve controls the main pump discharge amount to reduce the neutral loss and fine con- trol loss according to the moving distance of the control valve spool.

• The main pump discharge amount is controlled by balance of the sum of jet sensor upstream pressure PTPT and NC valve output pressure PECN

PECN and the sum of the force of NC valve spring (12) and jet sensor downstream pressure PD

PD.

• The jet sensor senses the flow of the oil returning through the control valve to the tank and use it as PT

PT and PDPD of the NC valve. 1)

1) WheWhen conn controtrol val valvlve is ae is at net neutrutralal

Operation Operation

• When the control valve is at neutral, jet sensor differential pressure ( PTPT – PDPD) becomes the maximum, and the force of jet sensor output pressure PTPT pushing piston (10) becomes larger than the total of the force of spring (12) and the force of jet sensor output pressure PDPD pushing the bottom of spool (11).

• As a result, spool (11) is pushed down, so the flow from port cc to port bb is throttled, and the area of the opening of port bb and port aa (drain port) be- comes larger. In this way, NC valve output pres- sure PECNPECN becomes the minimum, and the main pump discharge amount also becomes the mini- mum.

ST

STRRUCUCTUTURERE, , FUFUNCNCTITION ON ANAND D MAMAININTETENANANCNCE SE STTAANDNDARARDD HYHYDDRARAULULIC IC PUPUMMP (P (PIPISTSTON ON PUPUMPMP))

2)

2) When When contcontrol rol levelever ir is os operaperatedted

Operation Operation

• When the control lever is moved, the jet sensor differential pressure (PTPT – PDPD) goes down in ac- cordance with the movement of the control lever. Spool (11) is pushed up, and the area of the opening of port cc and port bb becomes larger. In this way, NC valve output pressure PECNPECN be- comes larger and the discharge amount from the main pump increases. In other words, the pump discharge amount increases according to the amount that the control lever is operated.

ST

STRURUCTCTUURERE, , FUFUNCNCTITIOON N ANAND D MAMAININTETENNANANCE CE STSTAANDNDARARDD HHYDYDRARAULULIC IC PUPUMP MP (P(PISISTTON ON PUPUMPMP))