ENGINE AR 9Y7542 - Caterpillar

Control Valve And Resolver Check Valves
(1) Primary resolver check valve. (2) Secondary resolver check valve.Signal pressure from the backhoe control valve group enters the stabilizer valve group at the left cover end. That signal pressure is then compared to any signal pressure in the stabilizer control valve group. The highest resolved signal pressure (backhoe or stabilizer) is sent to the loader control valve group. That signal pressure is then compared to any signal pressure in the loader control valve group. The ball check valve in the priority valve then compares the highest resolved signal pressure from the loader valve group to any signal pressure from the hand metering unit. Finally, the highest signal pressure (implement or steering) is sent to the pump compensator valve.This signal now instructs the pump to vary its output to meet the highest resolved load requirements. The compensator valve adds margin pressure to the load requirements. The pump will not change its pressure until the resolver network identifies a different highest resolved signal. The resolver network does not add the various loads together. Instead, the single highest resolved load plus margin governs pump output pressure. Therefore, the entire hydraulic system is supplied with 2100 100 kPa (305 15 psi) more pressure than necessary to handle the single largest load.When the spool in a stabilizer or loader control valve is shifted, primary resolver check valve (1) compares the pressure between the two work ports in the control valve section. In other words, it compares the head end pressure of the cylinder to the rod end pressure of the same cylinder.In the above example, head end pressure in line (3) is greater than the rod end pressure in line (4). The head end pressure forces ball check (5) up. This blocks line (4). The pressure in line (3) is now the highest resolved primary pressure in this resolver. This pressure is sent to secondary resolver (2).Secondary resolver check valve (2) in each valve section works similarly. It compares the pressure signals between two control valves. Secondary resolver check valve (2) compares the highest primary pressure signal in its control valve [line (3)] to the highest resolved signal from the previous control valve [line (6)]. The highest resolved pressure (primary or secondary) is sent through line (7) to the next control valve.Hydraulic Cylinders
Cylinder Identification Right Side Of MachineThe backhoe and loader cylinders are the threaded gland design. The rod end assembly is called the gland. The gland is threaded into the expanded rod end of the cylinder. This keeps the gland threads bathed in oil to prevent them from corroding. The gland to rod seals include a urethane wiper, a urethane U-cup, a urethane buffer seal and a glass filled Nylon wear band. The cylinder piston seals include a glass filled Nylon wear band and a Teflon piston oil seal with a ring to preload the seal.
Basic Hydraulic CylinderThe piston is secured to the rod with a bolt and washer. The piston incorporates a wear