Reduce Shock with Solenoid Soft-Shift Option

Sun's economical soft-shift option is designed to extend response time and, as a result, minimize hydraulic shock in the system when shifting a valve or unloading a main stage valve.
  • All of Sun's solenoid tubes utilize a wetted armature design. By placing an orifice in the armature, the displaced oil can be metered as it moves from one position to another. By dampening the armature movement, the hydraulic response is in turn also dampened, thus reducing hydraulic shock in decompression applications.
  • Sun's soft shift option is available for all DL**, DM**, DN**, DT**, DW**, DAAL, and DBAL models.
  • In some applications, expensive proportional valves are used to reduce system shock due to abrupt valve shift. In many of these applications, soft shift valves can provide a more economical solution.
Soft Shift Cross Section
  • Spool valves utilizing Sun's precision spool/sleeve design are available for 2-, 3-, 4-, and 6-way applications. A poppet style valve is also available in the 2- and 3-way configuration when lower leakage is a requirement.
  • Soft shift solenoid operated directional valves can be used in conjunction with other pressure control functions. For example, Sun's vented relief valves (models RV*A, RV*D, RV*S, and RV*T) can be controlled via a soft-shift pilot switching valve. Below is an example showing RVEA with DAALS.
Soft Shift Schematic

Applying Soft-Shift Solenoid Operated Valves


  • When using soft-shift solenoids, it is recommended that inlet flow be routed to port one. If port one is routed to tank, then a check valve is required to keep the oil from draining out of the solenoid tube. (Please note that oil must be maintained in the solenoid tube for the soft shift effect to occur.)

Valve Selection

  • Before choosing between the poppet- or spool-style valve, acceptable leakage rates must be considered.

- Full-flow poppet-style valves have low leakage rates, typically less than 10 drops per minute at 5000 psi (350 bar). They can be used in load-holding applications.
- Full-flow spool-style valves can have leakage rates of 10 in³ (160 cc) per minute at 3000 psi (210 bar).
- Pilot-capacity spool valves also have low leakage rates, less that 10 drops per minute at 5000 psi (350 bar).
- Please note that soft-shift solenoid operated cartridges operate at a reduced capacity when compared with the standard versions.

Performance characteristics and response time

  • Response time is defined as the time elapsed between energizing the valve and when pressure can be sensed.
Soft Shift Response
  • Response times will vary depending on fluid temperatures and viscosity, system capacitance, and rates of pressure rise. Unless coil current is controlled, solenoid force will vary based on coil temperature. It is important to consider these variables when specifying valves for a particular application.
  • Despite these variations in measured times, users can be sure the valves will have a softer shift and the performance advantages this offers.

For more information on Sun's soft-shift valves, please contact your local Sun Hydraulics distributor.