5230B Excavator Hydraulic System Control Valve Spool Operation Caterpillar


Control Valve Spool Operation
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1.1. Operation of the Implement Control Valve Spools and Travel Control Valve Spools
2.1. Operation of the Bucket Bottom Dump Control Valve Spool
3.1. Operation of the Boom Head End Control Valve Spool

Operation of the Implement Control Valve Spools and Travel Control Valve Spools




Illustration 1g00937904

Cross section of typical control valve

(1) Load sensing signal pressure

(2) Load sensing signal pressure to margin relief valves and load sensing control valve in the control valves for the implement pump regulators

(3) True load signal from the other circuits

(4) Resolver valve

(5) Compensator piston

(6) Load check valve

(7) Orifices

(8) True load signal to the signal duplication valve and the resolver valves in the load signal network

(9) Control valve spool

(10) Supply passage

(11) Feeder passage

Note: There are no load check valves in the travel circuit.

The control valve spools in the front control valve and in the rear control valve operate in the same basic manner with the exception of the bucket bottom dump control valve spool and the boom head end control valve spool. When a control lever is moved for a stick, a boom, a bucket or a travel function, a pilot valve sends pressurized pilot oil to one end of control valve spool (9). In this example, the pressurized pilot oil is directed to the right end of the control valve spool (9). The pressurized pilot oil is also directed to the implement pressure switch. The implement pressure switch is located on the front control valve. The implement pressure switch opens and the implement pressure switch sends a signal to the Engine Control Module (ECM) indicating that a function has started. The ECM module communicates with the Vital Information Management System (VIMS) module over the Cat Data Link. The VIMS module de-energizes the warm-up solenoid valves on the front control valve and on the rear control valve. De-energizing the warm-up solenoid valves closes the return oil passages in the control valves. Pressurized pilot oil shifts control valve spool (9) to the left and the implement pump oil flow is directed to the control valve spool and to the bottom of compensator piston (5) and of load check valve (6) .

The pump oil flow into the area beneath load check valve (6) pushes the load check valve and the flow compensator piston (5) upward. The pump discharge oil flows through the orifices in the bottom of load check valve (6) to the feeder passage. The oil flows through the feeder passage and around the right end of control valve spool (9) to the cylinders. The highest true load signal pressure in the feeder passage also goes through resolver valve (4). True load signal (3) goes through the passage to the signal duplication valve. The signal duplication valve duplicates the true load signal pressure. The signal duplication valve sends load sensing signal pressure (2) to the load sensing control spools in the regulator control valves for the implement pumps in order to upstroke the pumps.

Oil flow in the implement hydraulic system is available on demand. The amount of movement of the implement spool or movement of the travel spool determines the amount of pump flow that goes to the hydraulic circuit.

Operation of the Bucket Bottom Dump Control Valve Spool




Illustration 2g00929841

Bucket bottom dump circuit with bucket open

(12) Left implement control lever

(13) Right implement control lever

(14) Solenoid valve for the bottom dump open

(15) Machine Control Module (MCM)

(16) Solenoid valve for the bottom dump close

(17) Bucket bottom dump cylinders

(18) Rear control valve

(19) Flow from hydraulic activation control selector valve

(20) Implement warm-up solenoid valves

(21) Flow to hydraulic activation control selector valve

(22) Implement pressure switch

(23) Engine control module

(24) Interface module "number 2" for the Vital Information Management System

(25) Front control valve

The bucket bottom dump function on the front shovel arrangement is operated with trigger switches instead of implement control levers. The trigger switch in left implement control lever (12) actuates the bucket bottom close function. The trigger switch in right implement control lever (13) actuates the bucket bottom open function.

When the right trigger switch is squeezed, the switch closes. This signals machine control module (15). Machine control module (15) energizes the solenoid valve (14) for the bottom dump open which is located on the pilot manifold. Pilot system oil is directed to implement pressure switch (22). Implement pressure switch (22) is located on the front control valve. Implement pressure switch (22) opens and the implement pressure switch sends a signal to Engine Control Module (ECM) (23) which indicates that the function of the bucket bottom dump open has been requested. ECM (23) communicates with the Vital Information Management System (VIMS) main module over the Cat Data Link. The VIMS main module communicates with VIMS interface module number 2 (24). VIMS interface module number 2 (24) de-energize warm-up solenoid valves (20) on rear control valve (18) and front control valve (25). De-energizing warm-up solenoid valves (20) closes the return oil passages in the control valves. Also, pilot system oil is directed to the end of the bucket bottom dump control valve spool for bucket bottom dump open. The force of the pilot pressure shifts the bucket bottom dump control valve spool which sends pump flow to the rod end of the front shovel bottom dump cylinders. The front shovel bottom dump cylinders retract and the cylinders open the two bucket halves.

When the left trigger switch is squeezed, the switch closes. This signals machine control module (15). Machine control module (15) energizes solenoid valve (16) for the bottom dump close which is located on the pilot manifold. Pilot system oil is directed to implement pressure switch (22). Implement pressure switch (22) opens and the implement pressure switch sends a signal to Engine Control Module (ECM) (23) which indicates that the function of the bottom dump close has been requested. ECM (23) communicates with the Vital Information Management System (VIMS) main module over the Cat Data Link. The VIMS main module communicates with VIMS interface module number 2 (24). VIMS interface module number 2 (24) de-energizes warm-up solenoid valves (20) on rear control valve (18) and front control valve (25). De-energizing warm-up solenoid valves (20) closes the return oil passages in the control valves. Pilot system oil is also directed to the end of the bucket bottom dump control valve spool for the bottom dump close. The force of the pilot pressure shifts the bucket bottom dump control valve spool which sends pump flow to the head end of the front shovel bottom dump cylinders. The front shovel bottom dump cylinders extend and the cylinders close the two bucket halves.

Operation of the Boom Head End Control Valve Spool




Illustration 3g00929844

Boom head end control valve spool circuit

(13) Right implement control lever

(17) Boom cylinders

(18) Rear control valve

(25) Front control valve

(26) Flow to automatic track tension circuit

(27) Control valve spool for the head end of the boom cylinder

(28) Pilot manifold

(29) Engine

(30) Flow to proportional reducing solenoid valves

(31) Flow to pilot system

(32) Implement high pressure screens

(33) Pilot hydraulic oil filters

(34) Implement piston pumps

(35) Pilot gear pump

(36) Implement piston pumps

Rear control valve (18) includes a spool (27) for the boom head end. Spool (27) provides an additional path for the main system oil flow during the boom up functions. Spool (27) provides an additional path for the return oil during the boom down functions.

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