Wrong. MG1 is always turning in the "negative" direction when the car is moving forward at any speed and ICE is stopped. I don't think you understand that this is what I have been saying. Furthermore, MG1 needs to be slowed down from a near max negative speed to a less negative speed in this scenario with a constant wheel speed, in order to spin up the ICE. The ICE does not want to turn, and the wheels/MG2 are nearly free spinning (in this scenario where there is adequate vehicle inertia - the spin-up only takes a second or so - and/or a bit of downhill). With nearly no power to or from the wheels, the friction/pumping losses in the ICE is the source of power input to MG1 (driving MG1 in the negative direction). Resisting the ICE force means SLOWING down MG1, which allows it to act as a generator.

With the ICE stopped, forward wheel motion is negative MG1 rotation. For any given wheel speed, increasing the ICE speed, increases MG1's speed. MG1 has to decrease it's negative speed to increase the rotational speed of the ICE. (At high wheel speeds, both MG1 and the ICE are rotating positively -- as the ICE always does.) The vehicle needs to be accelerating from external forces (including the battery driving MG2, or going downhill) before MG1 will sink power to spin up the ICE.

There is no if, ands, or buts about this, MG1 is generating current when the ICE is spun up in this case. Only if external forces are accelerating the vehicle (such as a steep downhill) can the wheel force be greater than the resistance of the ICE such that there would there be a force great enough to drive MG1 in the positive direction such that it would take additional power to slow it down enough to speed up the ICE. The gear ratios are irrelevant to the argument (even if they are critically important to getting exact values as may be used to determine how much of an decline would be needed at 40 miles per hour to cause MG1 to become an energy sink rather than a generator.) When all of the forces/speeds/etc. are in the appropriate direction, the gear rations will only give the magnitude, and cannot change the sign of the answer. We are describing a scenario where the power is generated by MG1 to cause it to slow down faster than it would if it were free spinning, and the magnitude is not an issue.

I am too tired to discuss the non-applicability of most of the patent sections you quoted earlier, and remember that the patent does not prove the implementation. It says how it can be done, perhaps how it was originally done, but not necessarily how it is done.

-- Alan

Some of the problem is our (own) tendancy to think we are in one "mode" or another. I think in an acutal cruise state over reasonably level, but somewhat undulating terrain, the computer is constantly switching modes. The frequent switching on and off of the battery to wheels portion of the display and less frequently the switching off and on the ICE to wheels indication prove this. In the 45-55 miles per hour speed range on this terrain with indications of 40-59 MPG, I strongly suspect that MG1 is operating on and near its reversal point and on both sides of it, switching back and forth as road conditions change. Likewise, the ICE may be switching between fuel-cut and slow RPM operation under power. When the discussed steady state of ICE and battery to wheel indication pops up and stays -- it is really saying that somehow we have managed to optimize the ratio between the ICE and the axle through the computer's manipulation of MG1. The computer will not let the driver "lug" the engine, but we have convinced it to enter a high ratio overdrive-like sustainible state somehow.

Since I have added the fuel flow transducer I have made some interestng observations. For the most part, unless at freeway speeds a 60 MPG indication means nothing because you could either be in fuel-cut or have the ICE turning and burning at something near idle. It seems that the ambient manifold pressure in fuel-cut with the egnine turning but not lit equates in the computers mind to "60 MPG" or so. The reverse situation is also true. I have not seen a fuel-cut (zero fuel flow) indication with the MPG in an extended-period range of less than 60 MPG, (say 55-50 MPG indication).

If I hit a hill with these indications, it may well be that the computer is adjusting the field controls of MG1 to slightly lower the effective "gear ratio" between the ICE and the axle. It may even be reversing it sometimes across what we call "modes".

I have acquired a triple tach from a Bell 212 and hope to get it installed if I can figure out how to interface it. I don't like the idea of a ScanGuage as it blocks my other instumentation and is too distracting.

It is the ignorant among us that will eventually destroy us all.

What type of information will this provide?

-Ed

Shaft RPM for Axle, ICE and MG1 -- if I can figure out how to get a drive on them that will drive a 70 Hz signals tach generator OR I can get a 0-5 vdc signal via CanBus to Analog convertors.

http://www.inscousa.com/products/6520.htm

It is the ignorant among us that will eventually destroy us all.

Are you sure you have proper RPM range? Those heli shafts turn very slow compared to MG1 and ICE. I also think TCH computer has to know ICE and both MG RPM's , therefore it would be a question of getting proper scanner to intercept that data from the data bus. I think I've seen some program running on the laptop, that can be programmed to display different parameters and by now maybe they had enough time to figure things out for TCH as well. I need to find the links I saved somewhere. You could also record data for future analysis, since it would be difficult to drive and observe all 3 parameters at the same time to get some meaningful conclusions. I think you would have to install tiny magnets on the shaft and pick up coil to read pulses from them, it may require some heavy duty disassembly of the transmission housing to get to MG1. Let us know how it goes.

True, heli ROTOR turns slow, but turbine Heli N1 shafts turn very, very fast. Shaft speed really doesn't matter as you match the equation to the pulse rate.

Besides, not to worry, I can use a box my company builds to divide the pulse train from the Tach Generator if I need to. I would prefer to breadboard up a small D/A CanBus to square wave converter if I can because its cleaner than using tach generators. It only requires a few PALs or similar logic that can be hidden under the steering column.

As far as the guage readings, I will simply use %RPM. For AC tach generator the gauge goes from 0-115% for 0-70 Hz and has a beta indication if the rotation is in the reverse direction (out of phase). If I wind up using DC from a convertor it is simply 0-5 vdc and the beta discrete for reverse.

It is the ignorant among us that will eventually destroy us all.

Clearly there's a major disagreement between alan_in_tempe and me regarding the operation of the TCH when in fuel-cut mode. Judging by the number of views, there also appears to be significant interest in this thread, so others also may be interested in what I am about to show. In the hope that I can shed some light on this issue for all readers, I have produced some formulas and computed some numbers and tables for the TCH, and a set of diagrams to illustrate various driving scenarios. I didn't have the time to produce "professional-grade" diagrams and tables, but these should do. They are in the .zip file attached to this post. Included are:

1. CH-02to03.pdf from the TCH "New Car Features Guide" — page CH-3 gives the tooth ratios of the two planetary gear sets, the counter gear, and the final drive gear in the transaxle, and thus also for the reduction ratio of the MG2 drive to the ring-gear of the "power-split" planetary gear set. From this we can derive formulas for the "torque-split," "speed-split," and "power split" occurring in the transaxle.
2. AP-02.pdf from the TCH "New Car Features Guide" gives the ICE’s and the car’s maximum speed ratings.
3. Formulas.gif gives the derived formulas linking the various quantities that are relevant to understanding how the Hybrid Synergy Drive of the TCH works. It also contains conversion formulas between US and metric measurements, in case you wish to convert the data, since I have calculated everything basically in metric units for simplicity and universality. I have adopted Toyota's notation, for consistency with their US Patent #5 914 575, that I posted earlier in this thread.
4. Table.gif contains my computed parameter values for a variety of different driving situations. The first column of this table references the corresponding diagram.
5. Figs A & B.gif through Figs I & J.gif are 10 figures illustrating some of the different cases shown in the Table.

I am assuming a familiarity with the Toyota Hybrid Synergy Drive system, with the physics involved, and also with the use of nomograms to illustrate the linear relationship between the planetary gears’ speeds and the engine’s torque split between them. The engine’s total torque, Te, applied at the planetary-gear carrier (the ICE’s drive shaft), is split in the ratio of 28% to 72% between the portion, Tes, that appears at the sun-gear (MG1's shaft), and the portion, Ter, that appears at the ring-gear (the output of the "power-split" planetary gear set, and also MG2's input thereto via the second planetary-gear set acting as a reduction gear for MG2): Te = Tes + Ter. Knowing any two of the three shaft speeds Ns (rpm of the sun-gear), Ne (rpm of the ICE), and Nr (rpm of the ring-gear, from which we can compute the shaft speed of MG2 via the equation relating Nr to MG2's rpm), the third shaft speed can be computed. In turn, Nr can be related to the car's road speed RS by the given formula. The second factor on the right-hand side of the formula for RS represents the combined effect of the counter-gear and final-gear ratios. The third factor is the circumference of the 333-mm radius tires. The fourth factor converts from rpm to km/h. MG1 and MG2 exert torques Tm1 and Tm2 at the sun- and ring-gears respectively, and Tr denotes the resultant of all the torques exerted at the ring gear. These facts let us construct diagrams for different driving scenarios, and so illustrate what's going on internally in the TCH. Note that, in the units used, power = torque ´ rpm, and that, if an MG's power is positive (i.e., rpm and torque arrow both of the same sign), then it is acting as a motor; if it's negative (i.e., rpm and torque arrow of opposite signs), then it is behaving as a generator.

Here are brief descriptions of the different cases illustrated:

• Fig A shows the car stationary with the ICE "on" and charging the NiMH battery (Pm1 < 0, Pm2 = 0).
• Figs B and C show the situations when driving in "Normal" mode and "Heretical" mode respectively at a road speed of 120 km/h. In "Normal" mode with the ICE's speed at say typically 3000 rpm, MG1 acts as a generator and MG2 as a motor. In "Heretical" mode with the ICE's speed now forced down to say 2000 rpm, MG1’s direction of rotation has reversed, and now MG2 acts as a generator and MG1 as a motor. [Indeed, as the Table shows, at 120 km/h, MG1's rotation direction reverses at an ICE speed of 2446 rpm.]
• Fig D shows the car coasting (say downhill) at 65 km/h with the ICE "off" and MG1 spinning freely. [This is about the highest speed at which the ICE can remain stationary.] MG2 is providing regenerative braking, and charging the battery in the process. MG1 spins negatively. The next two lines of the Table and Fig E illustrate why Toyota don't allow the ICE to remain stationary at higher speeds, because the spin rate of MG1 becomes excessive. [I have labelled 10 000 rpm on the diagrams as the nominal maximum allowed MG rpm, although I believe that 14 000 rpm is the design limit.] Note that Fig E corresponds to a speed of 185 km/h, the nominal governor-limited top speed of the TCH. Above 64 km/h Toyota have taken a decision to start the ICE spinning in "fuel-cut" mode if necessary, as discussed earlier in this thread, in order to lower the spin rate of MG1 to safe values.
• Fig F shows fuel-cut coasting in ‘D’ at 120 km/h with no fuel being sent to the ICE, but with the latter being spun at ~1000 rpm. Note that all the ICE torque arrows (Te, Tes, and Ter) have reversed, since now the car is applying the torque to the ICE, which provides mild engine braking. The ICE is being spun because of a retarding torque applied by MG1 to protect the latter from over-revving. In this situation, MG1 is spinning backwards and generates electrical power, which is used to charge the battery. MG2 can spin freely and plays no role here.
• Figs G, H1 and H2 again show fuel-cut coasting in ‘D’ at speeds of 120, 65, and 49 km/h respectively, with no fuel being sent to the ICE, which is being spun at a constant ~1000 rpm (a value measured using my ScanGaugeII), but this time without the need for any battery involvement (although it could be involved). [As pointed out by me earlier in this thread, the battery’s finite capacity means that it cannot be used during prolonged fuel-cut coasting (as, say, when descending a long hill).] So, the power generated by MG1 while spinning the ICE is shuttled to MG2 to provide a controllable amount of propulsive torque. MG1 is still spinning backwards. The net engine braking, Tr, in this mode is adjustable. Fig G (= Fig H1) shows it at a speed of 120 km/h as being less than that shown in Fig F (Tr is smaller). The next line of the Table shows the situation at a speed of 65 km/h in ‘D’, the speed below which the car changes from fuel-cut ICE spinning to pure-EV mode with the ICE stationary. Fig H2 shows a hypothetical fuel-cut situation at 49 km/h, at which speed MG1 would reverse its spin direction from negative to positive, and so couldn’t be used as a generator any longer. We see that electrical power flows from MG1 to MG2 in all these cases.
• Figs I, J, and H3 illustrate fuel-cut engine braking, in ‘B’ this time, and at realistic road speeds of 100, 65, and 40 km/h, with corresponding engine speeds of 3000, 3000, and 1000 rpm respectively (again, measured with ScanGauge). Here, MG1 always spins forwards, and so acts as a motor, with MG2 acting as the generator now. Electrical power flows from MG2 to MG1. Much greater engine braking is exerted now by spinning the ICE at speeds greater than in the case of ‘D’ engine braking already illustrated. Again, the battery is not involved here (although it could be).
• For interest, the Table also shows the shaft speeds and directions when the car is travelling at its governor-limited top speed of nominally 185 km/h. Starting with the engine running flat-out at its rated top speed of 6000 rpm, I show progressively lower ICE speeds all the way down to 1000 rpm. (Consider that the car was initially propelled at its top speed on a horizontal section of road, and that a steepening decline then started, so that less accelerator pressure was needed to maintain this top speed.) Notice how MG1 initially spins forwards at near its positive rpm limit, but that, as the ICE slows down, it reverses its direction of rotation at an ICE speed of 3770 rpm, and then begins to spin backwards, reaching its negative rpm limit at the ICE’s idling speed of ~1000 rpm. Clearly, Toyota have chosen the gear ratios very carefully!
• Finally, the situation of the car coasting with the ICE "on" but idling at 900 rpm is shown in the Table. Here MG1 is spinning freely backwards, while MG2 is applying regenerative braking and charging the battery at the same time.

So, what can we conclude from all these numbers? First, that both alan_in_tempe and I were each partially correct in our statements about the TCH’s behavior in fuel-cut mode. Second, I find the interplay of the numbers and their effects on the operation of MG1 and MG2 illuminating. I certainly have a better understanding of the TCH’s operation after going through this exercise. I hope that others will find it useful too.

Some concluding comments (for now?):

alan_in_tempe — I feel that I must respond to your repeated comment that the fact that a patent mentions certain implementations does not mean that they are in fact being used. Agreed. But, conversely, it also does not mean that they are not being used! By the way, the only vehicle-braking method that the Toyota patent cites as being "prior art" is the one using only MG2 (as a generator charging the battery). Since the patent was granted, it would seem that the methods using only MG1, or both MG1 and MG2 were considered to be new. I’m sure that all three methods are in fact used in the TCH under appropriate circumstances.

FastMover — If the ScanGauge is mounted on the top of the steering column it does not obscure the TCH’s displays at all. I believe that the display shows arrows from/to the battery only when current is indeed flowing from/to the battery. ScanGauge’s fuel-usage readings are wrong during fuel-cut mode, but the open-/closed-loop indications and ICE rpm readings are nevertheless correct. On metric TCHs, when the FE gauge reads precisely 0 L/100 km no fuel is flowing but the ICE is being spun. In US TCHs, this bottom tick mark appears to be labelled 60 mpg. If the calibration of the US FE gauge is similar to that of the metric FE gauge, a reading of precisely 60 mpg should likewise indicate fuel-cut operation. Does your FE gauge behave the same way as mine? As the Formulas show, you can deduce MG2’s rpm from the car’s road speed. Knowing the ICE’s rpm [from ScanGauge or by reading it off the CAN bus (it’s a standardized data item)], one can then deduce MG1’s rpm from the appropriate formula. Thus if you can read road speed and ICE rpm from the CAN bus into a portable PC, you can deduce MG1’s rpm in software without needing any further instrumentation. Have you considered doing this?

Stan

P.S. In post #34 I have placed an updated version of this post. The changes consist of new versions of the Figures with more accurately drawn lengths for the torque vectors, and detailed improvements in this covering document. They are all bundled in a new attachment Heretical_v2.zip.

Attached Files

Heretical.zip (637.3 KB, 28 views)

I think I agree with your supposition except for one case. Since the installation of the fuel flow transducer, I have seen a situation where the MPG indication is 60MPG and a very small fuel flow of 25 GPH/1000 (0.025 GPH) or so is present. If you do the math, this equates to a powered fuel burn of about 40 miles per hour based on 40 MPG. I cannot explain what is happening, but I speculate that the TCH computer has a state wherein the ICE is working at its minimum RPM much like the earlier observations I made about operation in the 55-45 MPG zone, and ICE shutdown has not quite been reached yet. Thus my earlier statement that the 60 MPG indication MAY be an indication of fuel-cut, but it is not a absolute one.

Regarding the Scan Guage, I concede your mounting location. But I also found the instument distracting as it takes some visual scan time to acquire the desired value and intrepret it. They would have a hot product if the "Gauges" were graphics, either round gauges or bar instruments with digital values below Since I have cheap (free) access to CanBus guages, I am looking into other ways to make a more efficient presentation of what the powertrain is doing. I am still looking into it, but right now I am considering 1" round gauges in a housing in front of (and below) the center "eyebrow" panel containing the clock and annunciators for the alarm and passenger seatbelt.

Your point about RPM for MG1 is valid, but the data recorder I am planning to use (also free) is remote mounted and records to a PCM-CIA card, so it cannot drive a display. Besides, I think it will be very cool to be able to directly observe the drive ratio on a single gauge. If it is set up correctly, the split in the needles should provide a direct indication of the actual drivetrain power ratio at any point in time, and also what the computer is doing to change it.

It is the ignorant among us that will eventually destroy us all.

I dunno 'bout the rest of you, but I think that I need to go back to school for some engineering classes to understand this thread.

Stan,
Excellent work! Very nicely, throughly, and competently done. THANKS!!!!

If I may suggest, we were not so much disagreeing, as not talking exactly about the same thing. I was repeatedly referring to a very narrow, specific scenario. Your data, and most of your posts go well beyond this scenario, around all sides of it. My original comment only intended to correct a very minor point you made, only in reference to this single scenario where MG1 will act as a generator, not a motor, in order to spin up the ICE from 0 RPM to idling speed, which is now confirmed by your data in Figs F, G & H. You had earlier suggested (in a much broader sense) that this can never happen. In nearly all other cases, I have been in complete agreement with your analysis and comments.

-- Alan