Profiling solenoids

In Rostra’s hydraulic testing laboratory, valve body environments are reproduced within specially designed test fixtures. Control signals are measured on test vehicles and accurately reproduced using our custom electronic drivers. Data is collected on solenoid performance under all conditions to guarantee the solenoid will always work.
Illustration profiling solenoids

Profiling Solenoids: A Normally Closed solenoid

  • Response time-how long does it take solenoid to operate? ( in milliseconds)
    Measured by the current rise of coil (light blue). The dip in the light blue curve is when the armature bounces off the stop. ( Some vehicle computer measure this inductive spike to indicate solenoid operation.)
  • Source Pressure – Oil pressure value from pump (dark blue)
  • Feed Pressure – The pressure feeding the solenoid before the orifice restriction in the valve body separator plate.
  • Control pressure – The pressure measured between separator plate orifice, and solenoid port. This is the pressure that controls the shift valve. (pink)

Sequence of events:

  1. Solenoid is off. Feed pressure and control pressure are the same as the source pressure.
  2. Solenoid is turned on. Once the armature moves, as seen in the coil rise (light blue), the control pressure pressure falls.
  3. When solenoid is shut off, the control pressure builds back up
  4. .

Notice the problem here?
This solenoid had reduced stroke due to contamination, ball never fully off seat., all of the pressure could not bleed off.

Profiling solenoids: A Normally Open 3 way shift solenoid AX4S
Top Left Rostra sample:

  • Electrical response time (light blue)
  • Source from pump (dark blue)
  • Feed pressure to solenoid (TV pressure axode) (pink)
  • Control pressure to shift valve (red)
  • Sequence of events:
    1. Source Feed and control pressures are all the same.
    2. Solenoid is energized, and the control pressure bleeds to exhaust allowing shift valve to move.
    3. When solenoid is shut off feed pressure and control pressure rise simultaneously as the hydraulic circuit is re-charged with oil pressure

Top right: OE sample
Bottom right: Other after-market solenoid

Explore posts in the same categories: how a solenoid works, solenoid components, solenoid terms, solenoids, testing solenoids

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