GEAR-RING-YM 3940882 - Caterpillar

Illustration 1 g00501382
(1) Control valve with primary resolver (2) Secondary resolverEach control valve section in the implement hydraulic system has two resolvers. Each resolver compares two pressure signals. The higher signal of the two signals goes to the next resolver. One of the resolvers is called the primary resolver. The other resolver is called the secondary resolver.The primary resolver has an axial drilled passage with three cross-drilled holes that are located in the directional spool. The secondary resolver is a ball check valve that is installed at a perpendicular angle to the primary resolver. The check ball is not contained in a housing. A plug holds the check ball in the valve body.The primary resolver compares the pressure that is between the two ports in each control valve section. In other words, the primary resolver compares the head end pressure of the cylinder to the rod end pressure of the same cylinder.The highest pressure of the two cylinder ends moves the directional spool. This blocks the lower pressure port. The outlet line to the secondary resolver is opened. The higher cylinder pressure is the outlet pressure to the secondary resolver.The secondary resolver in each of the valve sections works similarly. The secondary resolver compares the pressure signal that is between two valve sections. This means that the higher primary pressure signal in the control valve of the secondary resolver is compared with the higher resolved signal of the previous secondary resolver.The highest resolved signal from the implement control valve goes to the compensator valve on the pump. The signal instructs the pump to vary pump output in order to meet the highest resolved load requirements. The pump compensator valve adds margin pressure to the load requirements. Note that the resolver network does not add various loads together. Instead, the single highest resolved load plus margin pressure governs the pump output. Therefore, the entire system is supplied with 2100 kPa (305 psi) higher than the necessary pressure for handling the single largest load. The pump will not change pump output until the resolver network identifies a different highest resolved signal.