Pulse Width Modulator

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aburani Associate Join Date: Jul 2008 Posts: 26	Pulse Width Modulator 07/25/2010 6:26 AM
	To CR4 Team What is the function of pulse width modulator in electronic fuel injection pump such as electronic unit injector , electronic unit pump and common rail system. Thanks aburani
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bob c Guru Join Date: Jul 2007 Location: Fort Lauderdale Florida Posts: 5708 Good Answers: 123	#1 Re: Pulse width modulator 07/25/2010 8:04 PM
	The injector is going to cycle, or fire once every time the engine reaches compression stroke. That is a given.But how does the injector compensate for the larger fuel load needed for higher power demands? The fuel pressure is constant. The answer is to make the injector remain open longer. At idle, it may only remain open for 5% of the revolution. At wide open throttle, it may remain open 25 to 30 % of the revolution. This is an exaggeration, as the fuel is delivered in a very narrow time period relative to crankshaft rotation. The duration of the injector is a very sensitive thing. Does this help you to understand? If not let me know. __________________ Bob
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aburani Associate Join Date: Jul 2008 Posts: 26	#3 In reply to #1 Re: Pulse width modulator 07/26/2010 3:25 PM
	Until now is ok but what is the function of pulse width modulator to give electric current to the injectornto open. Thanks
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LAA_Lucke Guru Join Date: Feb 2010 Posts: 1013 Good Answers: 36	#4 In reply to #3 Re: Pulse width modulator 07/26/2010 7:41 PM
	Pulse Width Modulation is what it says: Imagine a square wave of Amplitude = 1 and wave frequency of 50 Hz (cycles /second): the voltage remains = 0 V for 1/2 the cycle(100 milliseconds) then = 1V for the 2nd half (100 milliseconds) then repeats again. (200 ms x 50 = 1000 ms = 1second) Now, during this 200 ms cycle, if we vary the time when the Amplitude is 1V from 0 sec to 200 ms, we are modulating the pulse to keep the injector injecting for more or less time, thus supplying more or less fuel. This is simply what Pulse Width Modulation means. the rest is dependent on the use made of this principle to control different phenomenae...
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bob c Guru Join Date: Jul 2007 Location: Fort Lauderdale Florida Posts: 5708 Good Answers: 123	#5 In reply to #4 Re: Pulse width modulator 07/26/2010 10:19 PM
	Definately not off topic. __________________ Bob
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Gurnavemerno? Member Join Date: Jul 2010 Location: UK Posts: 6	#2 Re: Pulse Width Modulator 07/26/2010 7:42 AM
	The actuation of the Injector / Pump requires current regulated to the right ampage to operate correctly and without damage. Because the voltage is not varied the correct current must be achieved by pulsing it on and off. I.e. current control is achieved by varying the duration of the on/off pulses.
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