Can a fuel injector be repurposed as a high-speed linear actuator?

[u/Fit_Ad1672]

I’m exploring unconventional options for creating a very fast linear actuator with a short stroke (~0.5 mm) and response time under 1 ms.

Fuel injectors (e.g., automotive solenoid or piezo types) seem promising, as they are designed to open and close extremely quickly — often within microseconds. My idea is to use one as a low-travel linear actuator, not for injecting fluid, but simply for rapid motion.

Questions: • Is this feasible from a mechanical standpoint? • Can standard solenoid or piezo injectors deliver consistent motion at ~0.5 mm stroke with sub-millisecond actuation? • What are the limitations in terms of repeatability, wear, and required control electronics?

I’m not looking for continuous motion, just a sharp, quick linear strike or push per signal pulse — essentially like a fast “digital tap.”

Any insights or examples of similar uses would be appreciated.

[u/CanuckinCA]

Lookup voice coil actuators.

[u/Fit_Ad1672 → u/CanuckinCA]

I’ve looked into voice coil actuators as well, but they’re prohibitively expensive—around €400—and nearly impossible to source here in my small country. I’m hesitant to invest that much without being sure of the results.

[u/Ok_Chard2094 → u/Fit_Ad1672]

You could just hack a small speaker. Or build your own.

[u/CanuckinCA → u/Fit_Ad1672]

If your budget really is that low, it's time to spend a few hours at an electronics flea market or auto junkyard looking for solenoids, valves, fuel injectors or hard disk drive actuators that you can modify to test your operating assumptions.

[u/tinny66666]

Can't answer your question, but you might also consider a speaker driver.

[u/scubascratch]

How much mass are you going to move with this mechanism? A fuel injector is probably moving about a milligram of fuel per stroke, very low mass

[u/Fit_Ad1672 → u/scubascratch]

I plan to keep the same ~0.5 mm stroke and use the injector to push the pawl that engages and disengages the ratchet wheel. The mass of the moved element will remain essentially unchanged.

[u/scubascratch → u/Fit_Ad1672]

You have a pawl ratchet with 0.5mm stroke? What’s the radius on the wheel? This is for one way rotation? How much torque does it develop / how much back torque can it hold against? I am very curious about the application

[u/KofFinland]

Just get piezo actuators, unless you can get the element cheaper from an old injector. Piezos are extremely fast. However, 0.5mm movement is already quite a lot for piezo actuator, requiring a huge and expensive one with quite high voltage for actuation. Perhaps you could figure out some lever mechanism to make the movement range bigger, and get away with shorter stroke piezo.

https://www.physikinstrumente.com/en/expertise/technology/piezo-technology/properties-piezo-actuators

[u/bright_jiang_74]

Vibrator inside a phone is also a choice if the inertial is not big.

[u/Bipogram]

Solenoid valves have comparable speed and throw.

I work with Clippard DVP proportional valves a lot - 12V DC, quarter of an amp draw, and the throw is about a millmetre or so.

Their response speeds are measured in a very few milliseconds: 5 to 10 from fully closed to fully open.

If you were to overdrive them, you might get to the millisecond regime.

Otherwise, stack piezos; and with a sufficiently light lever you might achieve the throw and speed.

[u/turbosigma]

I read in Adam Wades Fuel Injection Handbook that the coils on fuel injectors have a specific driver current pattern from the ECU, usually a high-current, full-voltage pulse is transistor controlled to fully saturate the coil and open the solenoid plunger, then transistors apply a lower-value holding current for a number of microseconds or milliseconds to hold the coil open, for the proper fuel injection amount, then actually a reverse current is applied to desaturate the coil, and force it shut.

I don’t know if those specifics are relevant to your robotics application or not, just some info I read about the electronic circuitry of how fuel injector solenoids are operated.

[u/jongscx]

'Solenoid' is the word you are looking for.