Shift Control Actuator, Temp. Over-Ride.

I have two Gen2 Prius in my shop for repairs and this frequently requires they be transported or moved with out aux battery or HV battery. Or might have inactive ECU system, lack of Smart Key, etc.. This means the Park Pawl will remain engaged and so far the only way I have been able to move these cars is restore the batteries or remove one of the axles.
Since I expect this problem will recur again since I find these cars a new challenge for my "Auto Repair interests".
The overall is seen in The System Diagram and System Operstion has a good discription of the Park Pawl motor
Here are my thoughts on releasing the Parking Pawl. The motor operated pawl is controled by the Transmission Control ECU of the Shift Control Actuator Assembly and a Relay on the Eng. Rm. R/B and J/B.
Of course, the ECUs are not going to be of any help without the batteries or Smart Keys. The Pawl Control Relay could be jumpered but the Tranny Control ECU still controls the ground leg of the stepping motor in the Shift Control Actuator Assembly.
Access to mechanically release the Pawl would be difficult and I don't want to try over ride the ECU circuits for lack knowledge of the signal levels, etc.. If there is no power to the Tranny ECU then switching the Gnd signal to the stepping motor would be the biggest and most risky problem.
I'm thinking, unplug the connector that goes directly into the Actuator Assembly which will also completely isolate the sensor signals from the Tranny ECU.
Now, I may be getting in way over my head here and that is why I pose this idea here. I'm a retired Mfg Eng. (not an EE) but have some understanding of stepping motors and with a little help, might be able to figure this out by trial and (hopefully no harmful errors).
I do have the advantage of having a good spare transaxle in my shop. I have observed in a YouTube video that the Shift Actuator Assembly and Shift Pawl can be easily opened/exposed for examination.
I'm thinking that I might develop a 12 volt/dc switch w/indicator lites
on a pendent assembly that I can plugin when I need to move a car. The plug is accessable from the left rear side of the tranny.
I would really appreciate some thoughts, comments or suggestions.
Thanks
Steve

 

Yes, I see your point and recognize the complexity of the 3 phase motor. If we are to trust the "over simplification" the manual diagram, I would assume the Pos would be 12volt from the Aux battery and would guess the Neg from MWA, MVA and MUA of the Transmission Control ECU. Again, guessing, the frequency would be determined by the cycle rate between those three phases. So, for simplicity sake, I have a, say rotory switch with every third contact representing the neg of phase W,V,A leg. then I could spin the switch to step the motor. Noted, the Cycloid reduction mechanism rotates only a single tooth for each motor shaft revolution (10:1). Admitidly there will be a lot of torque on the pawl shaft and establishing the limit might be accomplished through the sense signal outputs from the Shift Control Actuator Assy.
Yes, I tend to over simplify things, lacking the knowledge of an EE, but veiwing this in the simplest of mechanical terms, I'm hoping to Cobble something to gether that will safely move and disengage that pawl. Again for a mechanical approach I know I could remove the motor or the pawl latch cover and manually lift the pawl but either of these choices are complicated with the transmition being in the car, where the shift control assy connector is much easier to remove and would prevent the system ECUs from detecting or interfering with the pawl over-ride.

I also agree with DogFriend and recognize that as a very easy process, if the smart key and other systems are operational. But in 50% of the cars (in my shop, 1 of 2) I can't get to the Ready stage and get it out of park and expect that might be typical in the future. Example, a Prius breaks down on the road or some other location and needs to be towed to shop, can't roll it onto a trailer or dolly, can't even push it into a parking space. Only recourse is an expensive tow truck with wheel lift, just to move it a few feet or a few miles. Or as I have done, removed one of the axles which means draining half the tranny oil or disassembling the inter tripod axle joint.

(didn't I once say "I look forward to the new chanlenges of the Prius", or word to that effect. I also enjoy the topics, comments and fellowship of this forum.)

Steve

 

I have a set of these wheel dollys but they are not usable on gravel, rough surfaces or of any assistance in getting a Prius on a roll-back truck, trailer or dolly. Since my movement at the shop usually involves moving it out of the shop bay to allow me to move another in, I would end up on gravel outside the shop.

I don't have the ability or the skills to observe the signal levels, etc.. My electrical education/skill developement ended in highschool shop/science class. Plus a little in learning the use of stepping motors and solinoids, etc.. in the manufacturing process. Know the difference between AC and DC and manage to wire my own shop 3 phase equipment without killing myself or any machines. Made it though nearly 70 yrs of automotive DIY repairs without much outside assistance. Again the, the Prius is a new Challenge! to keep the mind alert!

Steve

 

Johon, I agree that the phases of the shift control motor should follow that of another Pawl Motor, but definate;ly not the MG1 or MG2 since they are HV AC 3 phase while the Pawl motor is 12 volt DC.
Even though I do have the spare transmission available in the shop for this R&D of a Parking Pawl Dongle, I can't commit the spare pawl motor to this project beyond the R&D. Worth too much $$.

Thanks to all who are responding. All adeas are worth considering and of value in this process, with no disrespect intended in my above comments.

Steve

 

I do tend to agree that the Parking Pawl ECU would control the negative of each phase, in sequence. However, with all due respect (and maybe some ignorence), I don't see how this could shift the polarity of individual phase windings since the positive is being constantly or common center connection is supplied by the Aux battery. In other works we would never see the traditional 3 phase or even a single phase wave form so I don't see how it could be called AC.

If someone has a scope and could access the leads to the shift pawl connection, it would be interesting to find out what the wave form (or frequency) looks like.

I have watch a YouTube video of the Prius tanny tear down and the demonstate the MG1/MG2 reaction when interconnected to each other and rotated by hand. You can see the driven MG shift from pole to pole while the driver is rated slowly. Not sure of the difference between syncro and stepping motor reaction but the MG example seems like "Syncro". Again I could be wrong and often am.

Steve

 

I rolled out my spare Prius Gen2 transaxle and pulled a couple cover plates. The Toyota manual lacks details of the internal workings and I wasn't able to tell much more through these opening. I actually got more info from the YouTube video I had watched last week. What I did note was that there is only about 15 deg. of rotation of the internal pawl shaft between the two detents. Without removing the Shift Assembly motor, I removed the shift detent leaf spring and detent roller. The quadrant with the detent notched and rod link going inside the gear case to the Pawl. I could not view the Pawl from the area I had opened. I tried to move these components with my hand but there was too much resistance to shift the pawl. This was probably because of the cyloid gear reducer (1:10 rev.).
So, a mechanical solution might be to remove the motor and stick a special splined shaft and lever into the drive coupling of the cycloid gear reducer and crank it until the pawl is with drawn.. Sounds do-able on the in the shop but there isn't enough room to do this from under the car. (just barely enough room to pull the connector plug).

Steve (still learning @ 75)

 

Still looking at this problem of disengaging the Park Pawl. However, there is one question that I still should consider.
At what step or phase of the Smart Key/emobilizor process can the park release allowed. I realize it ain't going to happen if the the key FOB insn't inserted or proximity in the case of the Smart Key.

Right now of the two Gen2s in my shop, neither is operational electrically, only one having the key FOB. So if the key fob is available but the electical system has problems, either in the ECUs or battery faults Red Tiangle, no READY, etc..?? If the car is in Park already, at what "State" until READY will the Park button be effective??


To put it another way. If a Gen2 goes into an InOp mode due to problems, I have noted that you can't remove the FOB until it is returned to Park. Haven't been able to check this, but can the Park be released once the FOB is inserted, inspit of other Error problems??

If not, just how would a dealer be able to move a dead Gen2 or Gen3 into or out of the service bay??

Steve

 

Agree! At last! I'm more mechanical that electrical and my knowledge (very) limited is to Stepping motor, solinoids and relays in manufacturing processes. And what you porpose here goes along with my thoughts to set up a commutator/rotory switch that would allow me to rotate from pole to pole in sequence to cause the pawl lock motor to follow one phase coil at a time.
The cyloid torque muliplyer has a 10:1 ratio and the quadrant/lever arm only has to shift about 12-15 deg. to move from pawl locked to pawl fully disengaged (into the locked out detent). So the motor would have to rotate between 25 to 30 revolutions. Since we can't observe the location of the pawl linkage and the torque multiplyer having great advantage, it becomes necassary to monitor the open/latched postion. Therefore I must look into the signals of the position sensors Shift Control Actuator. In the electrical diagrams I see there are 5 connection that seem to be related to this sensor function.
Looking at the transmission ECU connector T4 (page 05-1150), we see pin16 E2 is Body GND, pin17 is VC-E2 Power Source (rotary angle sensor) 4.5 to 5.5 Vdc, pin4, pin5, pin6 are each rotary angle signals. From this and the shop spare tranny actuator, I hope to figure out what type of sensor device this is.

I truly think there is a fairly simple way to accomplish this but I must approach it carefully since I don't want to damage the spare Actuator I have. I don't have any test equipment beyond a Fluke digital meter and a simple logic probe. Since we now know that the sensor it basically 5vdc I suppose I can use a 5vdc power source to power the sensor circuit and then use the logic probe to see what activity there is static and then manually rotate the motor shaft with it out of the tranny. From that I think I could tell what the signal level combination would be in each extreme limit conditions. Lock or Unlocked. Then, maybe back to my old Bread Board and do some TTL logic circuits (seems like the '70s again).

Who know, maybe I will eventually develope a Dongle for this purpose.
BTW. I have found that the Transmission ECU connector is more easily eccessable from under the glove box than trying reaching the Actuator on the tranny.

Steve