08:12 Nov 28, 2018 |
English to Polish translations [PRO] Tech/Engineering - Agriculture / combine harvesters | |||||||
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3 | zawór elektromagnetyczny przekazujący ciśnienie sygnałowe do wylotu pompy//zawór sygnałowy |
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zawór elektromagnetyczny przekazujący ciśnienie sygnałowe do wylotu pompy//zawór sygnałowy Explanation: Jammer Solenoids and the Implications of Connecting the Pump Outlet to a Signal Network In Chapter 16, jammer solenoids were described in open-center hydraulic systems. Jammer solenoids are also used in LSPC variable-displacement systems. Even though the solenoids provide the same effect—placing the system on demand (maximum system pressure)—the jammer solenoid has an opposite design when used in LSPC variable-displacement pump systems. In an LSPC variable-displacement hydraulic system, anytime the pump outlet pressure is directly connected to the signal pressure, the pump will suddenly enter the stall mode. Why is this? The fl ow compensator has pump outlet oil pressure acting on the top of the spool while pump outlet oil pressure and the fl ow control spring pressure are acting on the bottom of the spool. Therefore, the fl ow control spool remains shifted upward, asking for more oil. As the pump attempts to upstroke, however, the PC spool senses the high system pressure and holds the pump destroked in the stall mode. A jammer solenoid in an LSPC variable-displacement pump is normally closed, which is the opposite of the design in an open-center system. See Figure 18-23. When the jammer solenoid valve is energized, it opens to connect pump outlet pressure to signal pressure. John Deere uses an LSPC jammer solenoid on their sprayers. Case IH uses LSPC jammer solenoids on their combines. AGCO uses LSPC jammer solenoids on their Massey Ferguson, Gleaner, Challenger, and Fendt combines. Case IH used the 12-volt diode assembly that was discussed in Chapter 16 on their 2100 and 2300 series combines. However, like most manufacturers, late-model machines have the jammer solenoid directly controlled by the ECM, allowing the manufacturer to eliminate an external diode module. The jammer solenoid is sometimes called a signal valve solenoid because it creates a false signal by connecting pump outlet pressure to signal pressure. Reasons to Use a Jammer Solenoid in an LSPC System Manufacturers typically use jammer solenoids in LSPC systems for two reasons. The fi rst reason is to force the hydraulic system to perform the same as a PC hydraulic system described in Chapter 17. Any time the jammer solenoid A John Deere 4630 sprayer uses a jammer solenoid that pressurizes the hydraulic system to a constant 3000 to 3100 psi (207 to 214 bar). In this application, the jammer solenoid is constantly energized. The sprayer takes advantage of the instantaneous response of the hydraulic system. One benefi t of this system over a true PC system is that the jammer solenoid can be disabled during engine startup. Jammer solenoids have the same effect whether a hydraulic system is open center or an LSPC variable-displacement system. Any time the jammer solenoid is energized, the hydraulic system exhibits the characteristics of a PC system: high system pressure, high noise, and responsive hydraulic controls. The second reason for using a jammer solenoid is to eliminate the need of a signal network with numerous shuttle valves (refer back to Figures 18-6). A simple closed-center DCV can easily be incorporated into a variabledisplacement LSPC system with the use of a jammer solenoid. This system design eliminates the use of a complex system of primary and secondary shuttle valves. When manufacturers use jammer solenoids, they sometimes use orifi ces in conjunction with the DCVs to control the cylinder speed. John Deere 4940 and 4730 sprayers use a jammer solenoid, but not for all of the system functions. The 4730 sprayer uses the jammer for everything except adjusting the tread and raising and lowering the boom. The 4940 sprayer uses the jammer solenoid for everything except adjusting the tread and tilt. Signal solenoid valve (jammer valve) Figure 18-23. A jammer solenoid valve used in an LSPC variable-displacement system is designed to connect p |
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