Actuators : Solenoid Valves

Introduction

The beginning of my career, Solenoid valves are my first work. My team was the Control unit development team, actually focused on sensors and actuators. At that time, Solenoid valves are hot potatoes so even though I was a freshman, I was in charge of this work. The reason that I am in charge of this work was crazy, the reason was that I majored in EECS(because the solenoid is about electrical stuff!). Anyway, I worked in this part for 1 year and a half, fortunately, I could get lots of experience and knowledge of actuators.

Solenoid Valves

Mechanism

As you know, it is an inductor. if you apply current on the solenoid, its plunger which is inside of solenoid is moving. The plunger pushes spool, the spool is on/off the hydraulic path. or making hydraulic pressure according to current. In automatic transmission use solenoid valves to shift. With solenoid valves, we can control the hydraulic system by the current. 

Core items in Hydraulic system

Variable force solenoid valves(VFS) is the core item in the hydraulic system. The control unit can control these actuators accurate and dynamic by VFS. Amount of current means Amount of hydraulic pressure in this system. For accurate control, we need to consider not only mechanical Processing tolerance(it causes hydraulic pressure change) but also control logic(you know temperature affects resistance, it causes current change according to Ohm's law).

Electric and electrical elements?

It cannot be an E/E system by itself. but the system level, it is in the E/E system as an actuator. The control unit system must monitor the actuator's signal, electrical status(i.e. short to ground or short to the battery).

Opinion

it looks simple but it is very complex. Have you ever heard about dither frequency? Have you ever seen a number of factors that are influent to current? because of this, test engineers test infinite to find adequate factors. 


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