electronic throttle
in [Technical]
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From: Bill Putney on 10 Mar 2010 06:13 Rodan wrote: > Once upon a time there was a cable from the gas pedal to the > throttle that operated the throttle butterfly. The throttle > shaft had a position sensor that told the computer how much > power the driver was demanding. > > Someone figured they could save money by eliminating the > cable and attaching a position sensor to the gas pedal to tell > the computer the driver's gas pedal position. The throttle > shaft still had to have a position sensor to let the computer > know its state compared to the pedal position, so the cost > tradeoff was one less cable and one more position sensor. > > But there were more costs. The throttle butterfly no longer > had the driver's foot power to move it, so they had to add a > servo device to the throttle to provide power to the butterfly, > and controlling power transistors to drive the servo, plus > a reprogrammed computer to keep track of it. > > More complexity, added electromechanical hardware, higher > cost, multiple new interfaces, and more computer operations. > The whole thing sounds like a joke invented by Rube Goldberg. > > Rodan. And more otherwise good cars hauled off to the junk yard when the cost and bother of troubleshooting and repairing the problems created by the complexity far exceeding the dollar value of the vehicle. Perhaps that is part of the goal of the explosion in complexity. -- Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')
From: News on 10 Mar 2010 08:33 Rodan wrote: > clare(a)snyder.on.ca wrote: > > Toyota throttle has 2 hall effect sensors. The output of one tracks the > other but is offset. In other words, one starts at say, 0 volts, and the > other at, say 1 volt - and they increase in step with each other. That way > the CPU can tell if one has failed, and if the two outputs are shorted > together (one bypassed) If either accelerator sensor fails, the CEL comes on > and the vehicle is limited to 1/4 throttle. If both fail, the throttle > gets set to a fast idle position and the rpm is controlled to normal idle > speed by programmed [missfire] (injector cut) The throttle position sensor > (throttle feedback) also has 2 hall effect sensors 0 and they have > [different] "rates" - the primary gives a higher signal linear from closed > to open, while the secondary reads full by about half throttle. > If the CPU senses a single TPS failure the engine is reduced to a fast idle. > iF BOTH tps fail, it is returned to base idle - and if the ECU determines > that the throttle has NOT closed - the engine is shut off. The ECU has 2 > CPUs. the main monitors all sensors and [controlls] the entire power-train - > engine, transmission, cruise control, traction control, etc. The "sub" > monitors all sensors and all outputs - and monitors the main CPU via a > "watchdog" program. The sub ALSO controls the electronic throttle. Both > cpus control an output transistor that feeds power to the throttle control > motor - BOTH must be turned on in order to open the throttle. They are > series connected). If either CPU senses a problem and shuts down, there is > no throttle. Gets pretty darn difficult to envision any electronic error > that could cause uncontrolled [accelleration], particularly without > registering a code and turning on the CEL. > _________________________________________________________________________ > > Once upon a time there was a cable from the gas pedal to the > throttle that operated the throttle butterfly. The throttle > shaft had a position sensor that told the computer how much > power the driver was demanding. > > Someone figured they could save money by eliminating the > cable and attaching a position sensor to the gas pedal to tell > the computer the driver's gas pedal position. The throttle > shaft still had to have a position sensor to let the computer > know its state compared to the pedal position, so the cost > tradeoff was one less cable and one more position sensor. > > But there were more costs. The throttle butterfly no longer > had the driver's foot power to move it, so they had to add a > servo device to the throttle to provide power to the butterfly, > and controlling power transistors to drive the servo, plus > a reprogrammed computer to keep track of it. > > More complexity, added electromechanical hardware, higher > cost, multiple new interfaces, and more computer operations. > The whole thing sounds like a joke invented by Rube Goldberg. > > Rodan. > > > All to make it easier to meet emissions specs...
From: Bob Flumere on 10 Mar 2010 16:39 On Wed, 10 Mar 2010 09:52:49 -0600, "E. Meyer" <e.p.meyer(a)verizon.net> wrote: >On 3/9/10 8:34 PM, in article hn70gb$ea0$1(a)panix2.panix.com, "Scott Dorsey" ><kludge(a)panix.com> wrote: > >> Dave <hairy411(a)hotmail.com> wrote: >>> >>> You're imagining things. I made no comparisons. jim beam says that as long >>> as an engine is running, it's creating plenty of vacuum to run accessories. >>> Even at WOT. Absolutely not so with any naturally aspirated internal combustion engine. Manifold vacuum depends entirely on the air moving through the engine and being "throttled" by the butterfly in the intake. This vacuum or low pressure (below atmospheric) only exists because the engine is pumping out air that cannot be resupplied through the closed or partially closed throttle plate(s). Throttle open (stuck, actuated improperly, or opened wide by driver) always equals ZERO (or certainly very low) manifold vacuum. Low manifold vacuum means zero power assist from a vacuum assisted brake booster. There is a check valve to hold the (low) pressure in the booster housing during low manifold vacuum events. However, the booster housing holds only enough volume to fully assist only the first or second brake pedal application. This gives the driver a very hard brake pedal after only couple of strokes and causes a major reduction of the amount of brake line pressure that the average person can muster with only leg power. ie: the common feeling that the brakes have "failed". Unless there is some kind of a vacuum backup assist pump.. (some trucks and buses), not that I'm aware of on Toyotas, or the brakes are power boosted by some other means, hydroboost etc. there is going to be little or no power assistance to help the driver control the "runaway" vehicle if the throttle is in the opened position. Neutraling the runaway engine, allowing the RPM to rise until there is some other limiting factor STILL won't produce much, if any intake manifold vacuum. It would of course help the driver to regain control (if only with little or no power assist to the brakes). Switching "off" may stop the engine and if the still engaged transmission allows it to stop turning, there still won't be any brake assistance because there STILL won't be any vacuum as long as the throttle is (stuck?) open. Furthermore, if the engine should stop turning when switched "off", we now have the added element of no power steering asist, (if the steering is assisted by an engine driven hydraulic pump). Hope this somewhat basic expanation helps to explain what the driver of a "runaway" feels and experiences. Bob Flumere rflumere(a)comcast.net
From: clare on 10 Mar 2010 18:13 On Wed, 10 Mar 2010 06:15:09 +0000 (UTC), "Rodan" <Rodan(a)Verizon.NOT> wrote: >clare(a)snyder.on.ca wrote: > >Toyota throttle has 2 hall effect sensors. The output of one tracks the >other but is offset. In other words, one starts at say, 0 volts, and the >other at, say 1 volt - and they increase in step with each other. That way >the CPU can tell if one has failed, and if the two outputs are shorted >together (one bypassed) If either accelerator sensor fails, the CEL comes on >and the vehicle is limited to 1/4 throttle. If both fail, the throttle >gets set to a fast idle position and the rpm is controlled to normal idle >speed by programmed [missfire] (injector cut) The throttle position sensor >(throttle feedback) also has 2 hall effect sensors 0 and they have >[different] "rates" - the primary gives a higher signal linear from closed >to open, while the secondary reads full by about half throttle. >If the CPU senses a single TPS failure the engine is reduced to a fast idle. >iF BOTH tps fail, it is returned to base idle - and if the ECU determines >that the throttle has NOT closed - the engine is shut off. The ECU has 2 >CPUs. the main monitors all sensors and [controlls] the entire power-train - >engine, transmission, cruise control, traction control, etc. The "sub" >monitors all sensors and all outputs - and monitors the main CPU via a >"watchdog" program. The sub ALSO controls the electronic throttle. Both >cpus control an output transistor that feeds power to the throttle control >motor - BOTH must be turned on in order to open the throttle. They are >series connected). If either CPU senses a problem and shuts down, there is >no throttle. Gets pretty darn difficult to envision any electronic error >that could cause uncontrolled [accelleration], particularly without >registering a code and turning on the CEL. >_________________________________________________________________________ > >Once upon a time there was a cable from the gas pedal to the >throttle that operated the throttle butterfly. The throttle >shaft had a position sensor that told the computer how much >power the driver was demanding. > >Someone figured they could save money by eliminating the >cable and attaching a position sensor to the gas pedal to tell >the computer the driver's gas pedal position. The throttle >shaft still had to have a position sensor to let the computer >know its state compared to the pedal position, so the cost >tradeoff was one less cable and one more position sensor. > >But there were more costs. The throttle butterfly no longer >had the driver's foot power to move it, so they had to add a >servo device to the throttle to provide power to the butterfly, >and controlling power transistors to drive the servo, plus >a reprogrammed computer to keep track of it. > >More complexity, added electromechanical hardware, higher >cost, multiple new interfaces, and more computer operations. >The whole thing sounds like a joke invented by Rube Goldberg. > >Rodan. > Would be true, except it had NOTHING to do with saving money, and the throttle position sensor doesn't tell how much power is required - just how impatient the driver is!! >
From: Rodan on 10 Mar 2010 20:51
>clare(a)snyder.on.ca wrote: > >Toyota throttle has 2 hall effect sensors. The output of one tracks the >other but is offset. In other words, one starts at say, 0 volts, and the >other at, say 1 volt - and they increase in step with each other. That way >the CPU can tell if one has failed, and if the two outputs are shorted >together (one bypassed) If either accelerator sensor fails, the CEL comes >on >and the vehicle is limited to 1/4 throttle. If both fail, the throttle >gets set to a fast idle position and the rpm is controlled to normal idle >speed by programmed [missfire] (injector cut) The throttle position >sensor >(throttle feedback) also has 2 hall effect sensors 0 and they have >[different] "rates" - the primary gives a higher signal linear from closed >to open, while the secondary reads full by about half throttle. >If the CPU senses a single TPS failure the engine is reduced to a fast >idle. >iF BOTH tps fail, it is returned to base idle - and if the ECU determines >that the throttle has NOT closed - the engine is shut off. The ECU has 2 >CPUs. the main monitors all sensors and [controlls] the entire >power-train - >engine, transmission, cruise control, traction control, etc. The "sub" >monitors all sensors and all outputs - and monitors the main CPU via a >"watchdog" program. The sub ALSO controls the electronic throttle. >Both >cpus control an output transistor that feeds power to the throttle control >motor - BOTH must be turned on in order to open the throttle. They are >series connected). If either CPU senses a problem and shuts down, there >is >no throttle. Gets pretty darn difficult to envision any electronic error >that could cause uncontrolled [accelleration], particularly without >registering a code and turning on the CEL. >_________________________________________________________________________ > >Once upon a time there was a cable from the gas pedal to the >throttle that operated the throttle butterfly. The throttle >shaft had a position sensor that told the computer how much >power the driver was demanding. > >Someone figured they could save money by eliminating the >cable and attaching a position sensor to the gas pedal to tell >the computer the driver's gas pedal position. The throttle >shaft still had to have a position sensor to let the computer >know its state compared to the pedal position, so the cost >tradeoff was one less cable and one more position sensor. > >But there were more costs. The throttle butterfly no longer >had the driver's foot power to move it, so they had to add a >servo device to the throttle to provide power to the butterfly, >and controlling power transistors to drive the servo, plus >a reprogrammed computer to keep track of it. > >More complexity, added electromechanical hardware, higher >cost, multiple new interfaces, and more computer operations. >The whole thing sounds like a joke invented by Rube Goldberg. > >Rodan. ____________________________________________________________________ clare(a)snyder.on.ca wrote: Would be true, except it had NOTHING to do with saving money, and the throttle position sensor doesn't tell how much power is required - just how impatient the driver is!! ____________________________________________________________________ You're right, of course. It had nothing to do with saving money. It costs more, it's more complex, it adds more electromechanical hardware and increases electrical, mechanical, and computer interfaces. It introduces multiple new failure modes, while yielding no significant improvement in gas mileage or pollution control. It is a money pit, a maintenance nightmare and a death trap waiting for a victim. So why would anyone other than Rube Goldberg build such a useless (and dangerous) contraption? My guess is that the automakers are trying to develop a generic accelerator pedal that would work for any automotive power plant combination. A single pedal would indicate the driver's intention to a gas engine, electric motor, hybrid, steam engine, or rear-engine system, or an engine powered by tram cables. Unfortunately, in their zeal to prove the concept, they chose to dismantle and scrap the simple, proven, reliable gas pedal-to-cable mechanism for their experiment, resulting in more danger for conventional automobiles. Regarding the throttle position sensor - until fly-by-wire took throttle position control away from the driver it did indicate the driver's wishes for the power level to be applied. Stepping on a gas pedal to open the throttle is necessary to merge into traffic, to maneuver, and to maintain separation and safety in traffic conditions. Opening the throttle doesn't automatically prove that a driver is impatient. Rodan. |