345C MHPU Mobile Hydraulic Power Unit Hydraulic System Combined Function Hydraulic System - System 17 Caterpillar

Illustration 1	g01626866
(1) Motor for rotation (2) Line relief valve for auxiliary control valve (medium pressure) (3) Auxiliary control valve (medium pressure) (4) Main relief valve (medium pressure) (5) PRV for the retraction of attachment stem 3 (6) PRV for the extension of attachment stem 3 (7) "(EC3)" Solenoid for one-way flow and two-way flow (8) Line for work tool (9) Line for work tool (10) Number two line relief valve (11) Number two solenoid valve "EC2" (12) Number one line relief valve (13) Number one solenoid valve "EC1" (14) Extend solenoid for the attachment stem 1 (15) Retract solenoid for the attachment stem 1 (16) Extend solenoid for attachment stem 2 (17) Retract solenoid for the attachment stem 2 (18) Proportional solenoid valve for negative flow control (19) Relief valve (line) (20) Auxiliary control valve (21) Attachment control valve (22) Machine ECM (23) Main control valve (24) Joystick (right) (25) Joystick (left) (26) Pilot manifold (27) Hydraulic tank (28) Auxiliary pump (29) Idler pump (30) Drive pump (31) Pilot pump

System 17 is designed to allow complete electronic control over the tool control system. The combined function hydraulic system combines the features of the one-way/two-way flow system with the features of the one pump/two pump flow system.

The one pump flow system allows flow from one pump to power a work tool. All of the load is placed on a single pump. One pump flow is used for work tools that require low flow rates for actuation.

The two pump flow system allows the combined flow from both pumps to power a work tool. Rather than placing all of the load on a single pump, the two pump flow system allows the two pumps to provide flow equally. A two pump flow is used for work tools that require high flow rates for actuation. A two pump flow distributes the load equally for work tools that are used extensively.

A medium pressure circuit is optional on the System 17 excavators. The medium pressure circuit for the work tool operates in the same manner for all machines. The descriptions refer to the operation of a rotating grapple. Other operations may be performed.

Refer to Table 1 for the appropriate work tool and "TOOL#".

Note: System 17 is controlled by one of the following: joystick thumbwheel, electric foot pedal, electric foot switch and joystick with four buttons. The following procedure is for a machine that is equipped with joystick thumbwheel controls. The operation of machines that are equipped with another device for activation of the work tool is accomplished in the same manner.

Note: Machines with a foot switch do not have two-way flow or proportional flow.

Two joysticks with thumb wheels are used to operate the work tool.

Illustration 2	g01195826
(32) Horn (33) Left joystick (34) Left joystick thumbwheel (35) Right joystick (36) Right joystick thumbwheel (37) Switch for one-way flow (38) One touch low idle

One-Way Flow from One Pump

Illustration 3	g01626884

Description

The default parameter values for one-way hydraulic oil flow from one main pump are shown in Table 1. A typical example is a hammer. Refer to Testing and Adjusting, "System 17: Default Value of Work Tool Parameters" for the Tool Control System.

Use the display monitor or ET in order to set the hydraulic flow to the work tool.

The work tool is operated by switch (37) that is located on the right joystick (35).

Operation

Pilot pump (31) supplies oil to pilot manifold (26). When the hydraulic activation lever is moved to the UNLOCK position, pilot oil flows from pilot manifold (26) to solenoid valves: (5), (6), (14), (15), (16) and (17) .

When switch (37) is pressed, the machine ECM sends a signal to the extend solenoid for attachment control valve (14). The machine ECM also sends a signal to the solenoid valve for one-way flow and two-way flow (7) in order to open the valve. Pilot oil flows to attachment control valve (21). The pilot oil will shift the spool in attachment control valve (21) to the DOWNWARD position. Shifting the spool allows oil from drive pump (30) to flow through the valve. The pump oil flows through the line for the work tool (9) to the work tool. Return oil flows through the line for the work tool (8), through the valve for one-way flow and two-way flow. The oil then flows back to hydraulic tank (27) .

During operation of the work tool, the machine ECM sends a signal to the proportional solenoid valve for negative flow control (18). Negative flow control pressure in the center bypass passage is blocked when the control valve spools shift DOWNWARD. The machines ECM has the following programmed parameter values: "A1 FLOW", "A1 MULTI ADD FLOW", "A1 NOMINAL PRES" and "COMBINER ENABLE". The parameters control the flow and pressure of the work tool. The machine ECM regulates the negative flow control pressure that will be supplied to the pump regulator. The negative flow control pressure forces the swashplate in the pump to the correct angle to limit the flow and pressure to the work tool.

One-Way Flow from Two Pumps

Illustration 4	g01626891

Description

The default parameter values for one-way hydraulic oil flow from two main pumps are shown in Table 1. A typical example is a hammer. Refer to Testing and Adjusting, "System 17: Default Value of Work Tool Parameters" for the Tool Control System.

Use the display monitor or ET in order to set the hydraulic flow to the work tool.

The work tool is operated by switch (37) that is located on right joystick (35) .

Operation

Pilot pump (31) supplies oil to pilot manifold (26). When the hydraulic activation lever is moved to the UNLOCK position, pilot oil flows from pilot manifold (26) to solenoid valves: (5), (6), (14), (15), (16) and (17) .

When switch (37) on the right joystick is pressed, the machine ECM sends a signal to the extend solenoid for the following: attachment control valve (14) and the extend solenoid for auxiliary control valve (16). The machine ECM also sends a signal to the solenoid valve for one-way flow (7) in order to open the valve.

Pilot oil flows to attachment control valve (21) and to auxiliary control valve (20). The pilot oil will shift the control valve spools DOWNWARD. Shifting the spool to DOWNWARD allows oil from drive pump (30) to flow through attachment control valve (21) .Oil from idler pump (29) will now flow through auxiliary control valve (20). Hydraulic oil from the two pumps combines after the oil passes through both valves. The pump oil flows through the line for the work tool (9) to the work tool. Return oil flows through the line for the work tool (8), through the valve for one-way flow and two-way flow (7). The oil then flows back to hydraulic tank (27) .

During operation of the work tool, the machine ECM sends a signal to the proportional solenoid valve for negative flow control (18). Negative flow control pressure in the center bypass passage is blocked when the control valve spools shift DOWNWARD. The machines ECM has the following programmed parameter values: "A1 FLOW", "A1 MULTI ADD FLOW", "A1 NOMINAL PRES" and "COMBINER ENABLE". The parameters control the flow and pressure for the work tool. The machine ECM regulates the negative flow control pressure that will be supplied to the pump regulator. The negative flow control pressure forces the swashplate in the pump to the correct angle to limit the flow and pressure to the work tool.

Two-Way Flow from One Pump

Illustration 5	g01626897

Illustration 6	g01626902

Description

The default parameter values for two-way hydraulic oil flow from one main pump are shown in Table 1. A typical example is a pulverizer. Refer to Testing and Adjusting, "System 17: Default Value of Work Tool Parameters" for the Tool Control System.

Use the display monitor or ET in order to set the hydraulic flow to the work tool.

The "TOOL#" determines the control device that operates the work tool. The work tool operates with modulated control from the right joystick thumbwheel. The work tool can be rotated by operating the left joystick thumbwheel.

Auxiliary pump (28) is mounted on machines that are equipped with System 17. The pump in order supplies hydraulic oil to the medium pressure circuit for rotation of the work tool. The left joystick thumbwheel is the only control device that controls the medium pressure circuit. Select the appropriate "TOOL#" for work tools that rotate.

Operation

When the hydraulic activation lever is moved to the UNLOCK position, pilot pump (31) supplies oil to solenoid valves: (5), (6), (14), (15), (16) and (17). When right joystick thumbwheel (36) is moved FORWARD, the machine ECM sends a signal to the extend solenoid for attachment control valve (14). The machine ECM also sends a signal to the solenoid for number one check valve "EC1" (13) in order to open the valve. The machine ECM also sends a signal to the solenoid for one-way flow and two-way flow "EC3" (7) in order to de-energize this valve. Pilot oil flows to the top of attachment control valve (21). The pilot oil will shift the spool to the DOWNWARD position. Shifting the spool to DOWNWARD allows oil from drive pump (30) to flow through attachment control valve (21). The pump oil flows through the line for the work tool (9) to the work tool. The working pressure for the work tool is limited by the line relief valve for the work tool (12) through number one check valve "EC1" (13) .

When right joystick thumbwheel (36) is moved BACKWARD, the machine ECM sends a signal to the retract solenoid for attachment control valve (15). The machine ECM sends a signal to the solenoid for number two check valve "EC2" (11) in order to open the valve. The machine ECM also sends a signal to the solenoid for one-way flow and two-way flow "EC3" (7) in order to de-energize this valve. Pilot oil flows to the bottom of attachment control valve (21). The pilot oil will shift the spool to the UPWARD position. Shifting the spool to UPWARD allows oil from drive pump (30) to flow through attachment control valve (21). The pump oil flows through the line for the work tool (8) to the work tool. The working pressure for the tool is limited by the line relief valve for the work tool (10), through number two check valve "EC2" (11) .

During operation of the work tool, the machine ECM sends a signal to the proportional solenoid valve for negative flow control (18). Negative flow control pressure in the center bypass passage is blocked when the control valve spools shift DOWNWARD. The machine ECM has the following programmed parameter values: "A1 FLOW", "A1 MULTI ADD FLOW", "A1 NOMINAL PRES" and "COMBINER ENABLE". The parameters control the flow and pressure for the work tool. The machine ECM regulates the negative flow control pressure that will be supplied to the pump regulator. The negative flow control pressure forces the swashplate in the pump to the correct angle to limit the flow and pressure to the work tool.

Two-Way Flow from Two Pumps

Illustration 7	g01626912

Illustration 8	g01626916

Description

The default parameter values for two-way hydraulic oil flow from two main pumps are shown in Table 1. A typical example is a pulverizer. Refer to Testing and Adjusting, "System 17: Default Value of Work Tool Parameters" for the Tool Control System.

The work tool is operated by right joystick slide control (36) .

Note: Refer to Testing and Adjusting, "System 17: Default Value of Work Tool Parameters" and Testing and Adjusting, "Work Tool Parameter - Program" for the Tool Control System.

Operation

Pilot pump (31) supplies oil to pilot manifold (26). When the hydraulic activation lever is moved to the UNLOCK position, pilot oil flows from pilot manifold (26) to the solenoid valves: (5), (6), (14), (15), (16) and (17) .

When right joystick thumbwheel (36) is moved FORWARD, the machine ECM sends a signal to the following: the extend solenoid for attachment control valve (14) and the extend solenoid for auxiliary control valve (16). The signal is proportional to the forward displacement of the joystick thumbwheel. The machine ECM also sends a signal to the solenoid for number one check valve "EC1" (13) in order to open the valve. Pilot oil flows to the top of attachment control valve (21) and auxiliary control valve (20). The pilot oil will shift the spool in each control valve DOWNWARD. Shift the spool DOWNWARD allows oil from drive pump (30) to flow through attachment control valve (21). Oil from idler pump (29) now flows through auxiliary control valve (20). The hydraulic oil from the two pumps combines after the oil passes through both valves. The pump oil flows through the line for the work tool (9) to the work tool. The working pressure for the work tool is limited by the line relief valve for the work tool (12) through number one check valve "EC1" (13) .

When right joystick thumbwheel (36) is moved BACKWARD, the machine ECM sends a signal to the following: the retract solenoid for attachment control valve (15) and the retract solenoid for auxiliary control valve (17). The machine ECM also sends a signal to number two check valve "EC2" (11) in order to open the valve. Pilot oil flows to the bottom of attachment control valve (21) and auxiliary control valve (20). The pilot oil will shift the spool in each control valve UPWARD. Shifting the spool UPWARD allows oil from drive pump (30) to flow through attachment control valve (21). Oil from idler pump (29) now flows through auxiliary control valve (20). The hydraulic oil from the two pumps combines after the oil passes through both valves. The pump oil flows through the line for the work tool (8) to the work tool. The working pressure for the work tool is limited by the line relief valve for the work tool (10) through the number two check valve "EC2" (11) .

During operation of the work tool, the machine ECM sends a signal to the proportional solenoid valve for negative flow control (18). Negative flow control pressure in the center bypass passage is blocked when the control valve spools shift Downward. The machine ECM has the following programmed parameter values: "A1 FLOW", "A1 MULTI ADD FLOW", "A1 NOMINAL PRES" and "COMBINER ENABLE". The parameters control the flow and pressure for the work tool. The machine ECM regulates the negative flow control pressure that will be supplied to the pump regulator. The negative flow control pressure forces the swashplate in the pump to the correct angle to limit the flow and pressure to the work tool.

Rotation

Illustration 9	g01538573

Note: The auxiliary control valve (medium pressure) does not influence the proportional solenoid valve for negative flow control.

Pilot pump (31) supplies oil to pilot manifold (26). When the hydraulic activation lever is moved to the UNLOCK position, pilot oil flows from pilot manifold (26) to solenoid valves: (5) and (6) .

When left joystick thumbwheel (34) is moved FORWARD, the machine ECM sends a signal to the retract solenoid for the auxiliary control valve (medium pressure) (5). Pilot oil flows to the top of the valve. The pilot oil will shift the control valve spool to the DOWNWARD position. Shifting the spool DOWNWARD allows oil from auxiliary pump (28) to flow through the auxiliary control valve (medium pressure) (3). The oil flows to the motor for clockwise rotation. The working pressure for rotation is limited by main relief valve (4) .

When left joystick thumbwheel (34) is moved BACKWARD, the machine ECM sends a signal to the extend solenoid for the auxiliary control valve (medium pressure) (6). Pilot oil flows to the bottom of the auxiliary control valve (medium pressure) (3). The pilot oil will shift the control valve spool to the DOWNWARD position. Shifting the spool DOWNWARD allows oil from auxiliary pump (28) to flow through the auxiliary control valve (medium pressure) (3). The oil flows to the motor for counterclockwise rotation. The working pressure for the work tool is limited by main relief valve (4) .