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OK, please be nice to me this is my first post. I’m sure someone out in the world has done this, but I couldn’t find it (High performance cars maybe? Big diesel engines?)
The idea here is to use electronic linear actuators (electronic motors that move in a straight line, not round and round) to
open and close the valves. The motors would be computer controlled based on the gas pedal position, whether or not the car is towing something, stop and go traffic vs. freeway, some stupid nut with a 454 parks next to you at a red light and wants to race, etc. I believe this would also reduce emissions and dramatically lower the fuel usage.
Another way to do this would be to use hydraulic actuators on the push rods. This would allow everything to be tucked neatly into the block to minimize the “under-hood clutter.” I hate under-hood clutter.
Linear Actuator
http://www.thomsoni...rue&IT=Descrip&GI=1
We used something like this to control throttle position on CAT engines at a place I used to work [Katt, Oct 04 2004]
Underdrive Cam Sprockets
http://www.halfbake...e_20Cam_20Sprockets
Not the same idea, but annotations turned towards your idea. [Cedar Park, Oct 04 2004]
Solenoids Described
http://www.detroitcoil.com/whatis.htm
An alternative to linear actuators. [Laughs Last, Oct 04 2004]
Camless Electronic Valve Internal Combustion Engine
http://rbowes1.11net.com/dbowes/
One Cylinder and now two cylinder working engine! You can even buy plans to build your own [fark, Oct 04 2004]
Servo valve example
http://www.omegavalve.com/
300Hz -3dB [Ling, Oct 04 2004]
free pistion engine
https://tec.grc.nas...stirling-convertor/
a type of stirling engine without a cam shaft. [travbm, Oct 29 2015]
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This idea was talked about in an idea a few weeks back. Seems that Cadillac and BMW are looking to bake this idea. |
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Wouldn't the actuators need to fire 133 times per second (at 8000rpm)..? |
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OK, 133 times per second.... |
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Correct me if I'm wrong (it's 6am here and I haven't slept in 2 days because I'm out of meds) but it don't think that's right.... |
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8000rpms = 2000open/close cycles of each valve per minute (8000/4=2000) |
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2000o/cpm=33.33 open/close cycles per second (2000/60=33.33) |
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So 8000rpms = 33.33 open/close per second |
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But what are you driving that redlines at 8k? |
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My Chevy Beretta shifts at 5500rpms at wide open throttle. I typicaly shift a standard between 3 to 4k. |
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Besides, most cars experience "valve float" before reaching 8krpms. Valve float is when the valves don't have time to close before the cam forces them to open again (really bad for HP and torque). |
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Thanks for the welcome CP |
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Well, I guess in a 4-stroke engine the valves would actuate once ever other revolution, so it would really be 4000/60 = 66 fires per seconds (at 8000rpm). And you have to synchronize at least 8 of these with very high precision. Let's just say for sake of argument that you drive a Honda and rev at close to 7-8k consistently. 66 fires per seconds * 60 seconds in a minute * 60 minutes in an hour = 237600 fires per hour. Let's say you drive on average an hour a day. 237600 * 365 hours per year = 86 million fires per year. All I know is that electro-mechanical components usually have a pretty low MTBF. I'm not saying it wouldn't work, I'm just wondering what the advantage would be over mechanical VVT systems..? |
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Well, I'm not saying it will work, at least not with current technology in linear actuators. But the main benefit over a mechanical cam is that the timing, open length, close, open-time, could all be controlled by the computer in real time. This would allow the computer to change the virtual "cam" while the car was running to provide horsepower and torque curves that match the current operating conditions. |
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Let's say you have a stock pick-up, pulling a 12-foot box trailer, and your tying to go over the Rockies. Your going to go really slow pulling that trailer with a stock cam that isn't designed for low-end torque. Now if the cam was designed for low-end torque, you could make it over the Rockies, but the fuel performance will be pretty poor one you reach the flat lands. The computer controlled "virtual cam" could make the changes required to provide HP and torque going over the Rockies and then readjust when you hit the flat lands. It's like having and infinite number of cams loaded in your engine for every operating condition. |
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It could give you lots of low-end torque for pulling out with the trailer, then switch to an economical mode when you reach freeway speeds. |
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I like it. A cam-less engine would have infinitely variable timing (IVT). This would be at least marginally better than a VVT in a conventional engine. The real opportunity for this idea to shine comes in pairing with a much more complicated cylinder arrangement. For example, a cylinder with variable stroke, or an engine block with cylinders of a variety of bores that are fired on demand. Radial engines could also benefit from the elimination of rocker arms and cam ring. |
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Maybe what we need here is a dual-acting solenoid (see link) for a long life of fast switching. The tough part will be keeping the solenoid cool. |
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Another thought I had about this, the computer could also be programmed to close the intake valves during braking (Engine braking, very minor fuel gains) |
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http://www.me.sc.edu/research/
AARG/history.htm |
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This was first thought up back in
1899. A mechanical connection to
control valves is still favourable on
multi valve installations for
reliability. VVt systems have
proven that although there are
gains to be had with alteration to
valve timing, the big leaps are to
be made with programmable
fuelling/timing via electronics. |
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//Cams usually counter-rotate, relative to the crankshaft.// |
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They do? Hmmm... doesn't chain, belt, or idler gear drive generally lead to a similar rotational direction? |
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Lotus are developing this and have patents for solenoid actuated valves with infinitle variable electronic timing. So there! |
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Infantile electronic timing sounds about right coming from Lotus. |
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Indy cars, formula 1, etc. have used pneumatic valves to allow their tiny little 3L engines pump out around 800 HP at upwards of 18,000 RPM. (HP is a direct result of RPM) |
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Although not variable, Ducatti allow their motorcycles to easily rev to 14,000 RPM with their Desmodromic system (no springs, but would mechanically open AND close the valves - so no floating and steep open and close profiles) |
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The F1 pneumatics are only for valve closing I believe, to reduce valve float. Valve opening is still effected by a camshaft. |
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there are camless engines. some racing motor bikes use rotary disk valves.they work great but have wear problems. |
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there are a few huge problems with this set up which many companys are researching right now.
firstly the energy to power the solinoids in not free it comes out of your alternater, so power loss is not avoided.alternaters and soliniods may be 70% efficient at best so is this better than a normal head i dont know.secondly the solniods have to be quite large bigger and heavier than normal valve setups.thirdly if the electrical system fails big big problems could occur. |
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But rotary disc valves are for 2 stroke engines! |
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If you can get injectors in EFI systems to deliver fuel with such precision, and Ducatti can actuate their valves at 14,000 revs, there's no reason that this couldn't work with a system of electromagnets and similar. The benefits of IVT would have to be huge in terms of efficiency of petrol engines. |
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The argument against electricty (not "free" energy) is ridiculous in light of how much power it takes to drive a cam. And as far as "what happens if there's a fault in the electrics" BMW are using "throttle by wire" and "steer by wire" so they're obviously confident that it won't happen very often. |
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to Skinup - In WW2 the Germans (Felix Wankel) tried to develope a long range high speed torpedo powered by a v8 engine. This engine was a 4s with disk type rotary valves. This type of valve was employed to allow ohv configuration for high power and still keep the height down so it would fit in the torpedo. A long service life was not important for this application. |
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Automobile (not Diesel) fuel injectors are electrically operated valves. |
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For maximum braking [Katt] the valves should act like a "Jake Brake". A Jake Brake opens the exhaust valve at the end of the compression stroke -- in effect making the engine an air compressor. A Jake Brake works best with wide open throttle as in a Diesel. . |
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With a 4 stroke engine, exhaust and intake valves cycle once per every two crank rotations or half the engine RPM. The first crank rotation deals with intake, then compression (one intake valve cycle). The second crank rotation deals with power, then exhaust (one exhaust valve cycle). Therefore: |
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8000 RPM = 4000 CPM (per valve) |
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4000 CPM/60 seconds = 66.67 CPS |
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It's hard to imagine that a pneumatic or hydraulic or even an eltromagnetic (solenoid) arrangement would be able to cycle a typical valve that fast. Even though 8000 RPM is a bit unrealistic for normal street use, even 4000 PRM (33.33 CPS) sounds a bit much for a scheme like this. |
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First: I can't see how a hydraulic system would be fast enough with it's inherent slowness due to the inertia of the fluid flow (first into a cylinder/piston arrangement to move the valve, then out again when the vlave is to receed). A pneumatic system would have to operate at extremely high pressures to help overcome the time delay in building up pressure to move the valve. |
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Second: I would imagine that the support components (pumps & plumbing for hydraulic/pneumatic and solenoids, wiring & large alternator for electromagnetic) would increase weight and consume more space. |
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Third: A solenoid would have to be extremely powerful for an exhaust valve which has to overcome combustion pressures upon opening. This would require a large winding and a heavy current draw. |
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Other miscellaneous comments: |
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·HP is not a direct result of RPM. HP is directly related to torque which does not necessarily relate to RPM. |
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·Most camshafts rotate in the same direction as the crankshaft. Some smaller engines may use a counter-rotating arrangement (as mentioned in another post), but often, another system of separate counter-rotating shafts are used to offset vibration. This was popular with many 4 cylinder Chrysler engines. |
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·Most types of fuel injectors are indeed electronic valves (as mentioned in another post). However, in contrast to an intake or exhaust valve, these types valves travel very short distances and are not required to open in direct mechanical opposition against a high pressure like an exhaust valve does. Therefore, fuel injectors require little power to operate. |
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Perhaps a servo valve or cylinder might help. We have servo cylinders where I work that can follow a step response within 5mS, and move a 12 ton oscillation platform. Accumulators must be positioned very close to the servo on the pressure and drain side and high pressure is required. There is a servo motor which rotates a screw in the cylinder. The screw "unbalances" the servo cylinder, and the piston moves to re-balance it. The oscillator is continuously moving at 3 to 4 cycles per second, all day, every day, and the speed of operation is required to ensure a perfect sinusoidal response (cancelling out resonances in the mechanical structure).
See omega link for a taste of what is available. |
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I believe that this will be the future.
Especially since you can gain so much more flexibility when you do not have mechanically fixed valve timing. |
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If you'd use this in combination with a Diesel, you could make a Diesel/pneumatic hybrid. The engine could then run as a 2-stroke engine and be used as an air compressor or an air motor.
Besides Diesel engines run slower. |
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Also when you accelerate at full throttle, you wouldn't need any power from the crankshaft to run the cams. In addition there's no rotational mass to be turned. The car would at this point only draw electricity from the battery to run the valves. Which would mean that can get more torque out of the same engine.
(New cars have alternator that turn off at full throttle). |
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Keep in mind car manufacturers will soon switch from 12V to 42V, to be able to provide the car with more electricity. |
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Now I get it! Linear induction, as used in mag-lev trains, roller-coasters & so on. Cool idea. |
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[Katt]: //But the main benefit over a mechanical cam is that the timing, open length, close, open-time, could all be controlled by the computer in real time.// |
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There is no advantage to opening the exhaust valve at any time other than BDC, nor to closing it at any time other than TDC. There is no advantage to opening the intake valve at any time other than TDC. Varying the intake valve closing time is useful, but it's generally best to use cams to set the other three times even if one uses electronics to time the valve closing. |
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//Another thought I had about this, the computer could also be programmed to close the intake valves during braking (Engine braking, very minor fuel gains)// |
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Jake brakes work by converting mechanical energy into audio noise. They are mechanically complicated by the requirement to open valves against high pressure (generally valves are opened under low-pressure conditions). Diesels use them because they cannot significantly throttle the air flow. Gasoline engines can use the throttle effectively without the disadvantages of jake brakes. |
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[MutantLifeForm] ·HP is not a direct result of RPM. HP is directly related to torque which does not necessarily relate to RPM. |
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Power is equal to rotational speed times torque. To be precise (if I got my units right), 3600rpm at one pound-foot of torque is 0.685hp. |
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i ahd a friend who was working on this for GM several years ago. the two problems he was always whining about was heating of the solenoids and cracking of the valves because they couldn't get the electronics to close the valves smoothly & gently like a cam does |
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To add to Supercat's statement, |
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Double the speed at which a given torque is produced and you double hp. |
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This faster rpm allows a lower gear for torque multiplication.
Torque = rotational force, hp = actual work in a given time. |
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With a perfectly flat torque output, you get a constantly rising hp curve.
The hp will always be lower than torque below 5252 rpm, and always higher than torque above 5252 rpm. |
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From the Ducati Tech FAQ: |
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2)What is electromechanical (or camless) timing, how does it work and what advantages does it offer over traditional timing?
Electromechanical timing is one of the possible modern alternatives to the traditional, and today, obsolete, mechanical valve control. As is known, the most common "valve control" system in automotive engines is by mechanical drive chain: the camshaft (1) and then, the valves (2), are rigorously driven in this order. Notwithstanding the special type of coupling 1 and 2 chosen (1: chain, gears, toothed belt; 2: rocker arms, face rocker arms, springs, desmodromic), all these are "fixed" systems, in other words, they are NOT adjustable in real time: the final result, i.e. the valve motion, is unequivocally determined in the design phase and unequivocally linked with the drive shaft motion. The electromechanical control system design is simple: no camshafts or chains are used; each valve is controlled by a double solenoid (or electric magnet), coaxial with the valve: by electrically energising the upper or lower part, an up-stroke (closing) or down-stoke (opening) of the valve is obtained. The evolution of these components and the increased availability of the required electronic control systems have opened the way for this new system. Let's take a look at its pros (+) and cons (-), with respect to the traditional system: |
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+ less friction among mechanical parts, fewer dynamic effects caused by inertia (better mechanical efficiency) |
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+ total operation control: the timing diagram can be modified according to the field of use; valves and cylinders can even be by-passed; this clever engine management results in dramatically lower consumption and emissions. |
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+ quicker valve movement, which ensures improved fluid-dynamic efficiency (valves can close and open almost instantly, without any risk of valve bouncing) |
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+ simpler design (hence, cost-effective construction) |
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- low inherent system reliability (one faulty solenoid is enough to severely affect the entire engine operation) |
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- solenoids are designed to require an idle time between one opening and the next: this causes low system speed (max 5 to 6 thousand RPM), which makes it impossible to use this system on sports machines |
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- heavy weight of the solenoid assembly |
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I am a fan of simplicity and my most favourite but is the delete key --- so my inclination is to delete the cam shaft (we need the valves)... |
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So what is left --- automatic valves on the intake side and something that doesnt work on the exhaust side. |
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So lets say we put the cam back on the exahust side -- all done (no need to a solenoid).... |
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It is possible. Even speakers move upwards of 30,000 times pers second, with a great amount of precision and power. If you simply use the same idea as a speaker, it could work. The only problem being the weight. You'd have to control movement of more mass effectively, which wouldn't be easy unless you had some real light poppet valves. Also, getting them to seat gently would be almost impossible electrically. I think. |
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[supercat]"There is no advantage to opening the exhaust valve at any time other than BDC, nor to closing it at any time other than TDC. There is no advantage to opening the intake valve at any time other than TDC. Varying the intake valve closing time is useful, but it's generally best to use cams to set the other three times even if one uses electronics to time the valve closing." |
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Not true. Opening the inlet early allows a small ram effect due to intrinsic resonances in the inlet manifold. Closing late also allows these resonances to cram in more charge as the piston begins to move back up the cylinder (piston velocity is very low at this point remember). |
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Also, opening the exhaust valve early allows the exhaust gas to exit the cyclinder under it's own pressure, reducing the amount of work required to move the piston back up on the exhaust stoke, thus reducing pumping losses. |
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Leaving the EVO past TDC means the vacuum created by the exhaust gases exiting through the manifold can actively draw in fresh charge. |
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I will be starting a research project on this type of technology over the summer and continuing through my university course. |
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I believe Suzuki have solenoid-driven valves on this year's Moto-GP bikes. It's brought them right up from the back of the pack, even though I believe it's only used to get the valves open fast and early, and closed fast and late. |
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On a road-going engine, the timings can be mapped to offer efficiency, smoothness and power, depending on the situation. The ECU can the advance or retard the valve timing (on both sides) *and* the spark. Nice. But done. |
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Baked. BMW has a throttleless IC engine.
By controlling the valves electronically, the
timing precision is sufficient to eliminate
the need to meter air into a plenum. |
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Cam less engines are in use in maritime industry. These are huge engines, 2 stroke Diesel engines with power rating more than 100,000 KW. These engines are running with computer hardware controlling, both fuel, exhaust valve operation and the Cylinder Lubrication. Engines made by MAN B&W, Mitsubhishi, and New Sulzer. |
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The only reason that F1 engines use pressure to close the valves is that mechanical springs are unable to react quick enough above 17000 or so rpm. |
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If all you want to do is vary the timing, you could just use a small cam shaft for each valve and power it from a motor rather than directly from the engine. |
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