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Join Date: Jul 2008
Posts: 29

How Do Piezo-Inline Injectors Work?

08/16/2008 11:06 PM

I want to knowthe piezo-inline injector work in common rail system andwhat is piezo material

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Australia - Member - New Member

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Location: Newcastle NSW Australia
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Re: How Do Piezo-Inline Injectors Work?

08/17/2008 11:26 PM

Piezo material is a type of crystal (I believe in the quartz family). This crystal will emit a small voltage when vibrated or struck (hence its use in record player needles to convert the vibrations of the record into electrical signals).

Conversely, if you apply a voltage to piezo material it changes its shape ever so slightly.

A piezo injector has many, wafer like (very thin) slices of peizo material placed together in the fuel orifice. They are jammed against each so that no fuel can pass through (a bit like squeezing the neck of a balloon with your fingers). When a voltage is applied, the change in shape of the crystals produces gaps between the wafers of piezo material and fuel can flow. This allows you to meter the diesel fuel to the engine with an electric signal, generated by a computer chip.

A diesel engine normally uses a mechanical injector pump to force fuel into the engine, metered at the right quantity and time.

The fuel system of a common-rail diesel engine works like a fuel-injected petrol engine. It has a high pressure diesel pump (approx 2000psi?) that delivers constant pressure diesel into a fuel pipe (or rail). All the injectors are connected to the rail with diesel available all the time that the engine is running. The fuel is then delivered to each cylinder by the injector when required as described above.

The piezo injector was developed to solve the extreme pressures required for diesel injection (petrol injectors only deliver fuel at approx 40psi!). This enabled the development of an electronic computer controlled injection system for diesel engines.

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Popular Science - Weaponology - Scapolie, new member.

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In reply to #1

Re: How Do Piezo-Inline Injectors Work?

08/18/2008 4:36 AM

Tourmaline is another piezo material, it is often used in micro-scales to weigh extremely small amounts. It is in fact a much better piezo material than quartz, but nobody has yet produced it artificially ie, Synthetically because it is a very difficult material to synthesise with a much more complicated chemical composition.

It has to be noted that both quartz and tourmaline belong to the trigonal (rhombohedral) system of crystalography, and that several minerals of this system have piezo quality.


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Anonymous Poster
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Re: How Do Piezo-Inline Injectors Work?

01/08/2010 8:03 PM

Latest common rail systems are around 2000 BAR (29000 psi). 4th generation systems are decreasing the pump pressure while employing a pressure multiplier in the piezo injectors to achieve 2500 BAR (36000 psi).

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Join Date: Feb 2008
Posts: 49
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Re: How Do Piezo-Inline Injectors Work?

08/18/2008 8:21 PM

The primary strength of the piezo-electric valve is not only the resistance to high pressure, when turned off, it is the capacity to precisely meter exactly the right amount of fuel to create combustion, and not a bit more. This cuts down on unburnt fuel, therefore it cuts down the tailpipe emissions of harmful pollutants. The vehicles which have diesel engines in them must meet very tight standards in 2010. That is the year you will see many automakers introducing diesel powered autos here in the U.S.

This may possibly be responsible for some of the downturn in the sales of cars this year. It's certainly not a secret that these cars will be sold soon. The advantage is quite dramatic. Fuel economy, compared to the same auto using a gas engine which delivers approximately the same performance, can be as much as 40% better with the diesel. These new engines eliminate the smell normally associated with diesel engines, so more auto buyers will be attracted to them.


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Join Date: Sep 2008
Posts: 93
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Re: How Do Piezo-Inline Injectors Work?

09/04/2008 1:58 PM

In addition to the advantages of piezo injectors mentioned by the other commentators, you should also consider the speed of the injector's response. When European auto manufacturers switched predominately to diesel engines in the last decade (because of their greater fuel economy) they insisted their engineers design a system that was quieter at idle. After a great deal of research, Bosch and other injector manufacturers designed a very high pressure, common rail, direct injection system that used piezo injectors. The engineers discovered they could quiet the idle, improve fuel economy and reduce emissions if the injector made multiple small injections during the 3 millisecond injection cycle. An electric coil can not respond that rapidly but piezos can and many of the most modern injection systems have up to ten separate injections in that three millisecond interval.

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Anonymous Poster

Re: How Do Piezo-Inline Injectors Work?

03/05/2010 11:08 AM

I drive a Jaguar S-type diesel with a 6cyl V engine using Siemens piezo-electric actuated injectors. I can assure you that this engine is very fuel efficient (31.5mpg IMP. in urban use) and the quietest diesel engine I've not heard. It sounds like a petrol engine (Jag. of course).

The actuation principle is different from solenoid injectors. The solenoid has a finite mass requiring the drive current to have a strong initial 'peak' during it's rise-time. This is normal with solenoid drive circuits, intended to at least partially overcome the inertia of the solenoid core which has to be of a magnetc material, usually steel -- hence the inertia due to the mass. This is also a rapidly oscillating component.

The stack of piezo-electric elements is quite different. The length of the stack changes slightly if a voltage of about 400volt is put across the ends, the response being EXTREMELY rapid. The effective inertia of the stack is very much lower than a metal such as iron or steel. There is no 'actual' moving part, just the length of the stack changing. The stack itself does not oscillate in and out like a solenoid. There are piezo-ceramic transducers that can create sound waves vastly beyond hearing, even for dogs. I believe 150KHz is easy. This speed means that the fuel injection may be controlled by the drive module to limits far more precise than solenoid actuation. Also up to 7 separate injections per power-stroke is possible.

I should say the advantages of piezo over solenoid are:-

Lower diesel consumption per horse produced.

Less wear in the actuator, therefore longer life.

Less combustion noise with good design.

Less particulates, and other pollutants.

Cheers, Fred.

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Anonymous Poster

Re: How Do Piezo-Inline Injectors Work?

04/05/2010 1:18 PM

Thanks a lot for the valuable informations...What I understand is that the principle used here is same as what is used in Squiggle motor...Voltage to linear motion conversion...

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